Ju Li

The development of high‐energy‐density and high‐safety lithium‐ion batteries requires advancements in electrolytes. This study proposes a high‐entropy ionic liquid/ether composite electrolyte, which is composed of N‐propyl‐N‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMP–TFSI) ionic liquid, dimethoxymethane (DME), lithium difluoro(oxalato)borate (LiDFOB), fluoroethylene carbonate (FEC), and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether (TTE). In this electrolyte, a unique coordination structure forms, where Li⁺ is surrounded by a highly complex environment consisting of DME, FEC, TTE, TFSI⁻, DFOB⁻, and PMP⁺. The effects of this solution structure on the solid‐electrolyte interphase chemistry and Li⁺ desolvation kinetics are examined. The proposed electrolyte has low flammability, high thermal stability, negligible corrosivity toward an Al current collector, and the ability to withstand a high potential of up to 5 V. Importantly, this electrolyte is highly compatible with graphite and SiO_x anodes, as well as a high‐nickel LiNi_0.8Co_0.1Mn_0.1O₂ cathode. Operando X‐ray diffraction data confirm that the co‐intercalation of DME and PMP⁺ into the graphite lattice, a long‐standing challenge, is eliminated with this electrolyte. A 4.5‐V LiNi_0.8Co_0.1Mn_0.1O₂//graphite full cell with the proposed high‐entropy electrolyte is shown to have superior specific capacity, rate capability, and cycling stability, demonstrating the great potential of the proposed electrolyte for practical applications.

Electrocatalysis exhibits certain benefits for water purification, but the low performance of electrodes severely hampers its utility. Here, we report a general strategy for fabricating high-performance three-dimensional (3D) porous electrodes with ultrahigh electrochemical active surface area and single-atom catalysts from earth-abundant elements. We demonstrate a binder-free dual electrospinning-electrospraying (DESP) strategy to densely distribute single atomic Ti and titanium oxycarbide (TiO _x C _y ) sub–3-nm clusters throughout interconnected carbon nanofibers (CNs). The composite offers ultrahigh conductivity and mechanical robustness (ultrasonication resistant). The resulting TiO _x C _y filtration membrane exhibits record-high water purification capability with excellent permeability (~8370 liter m ⁻²  hour ⁻¹  bar ⁻¹ ), energy efficiency (e.g., >99% removal of toxins within 1.25 s at 0.022 kWh·m ⁻³ per order), and erosion resistance. The hierarchical design of the TiO _x C _y membrane facilitates rapid and energy-efficient electrocatalysis through both direct electron transfer and indirect reactive oxygen species ( ¹ O ₂ , · OH, and O ₂ · ⁻ , etc.) oxidations. The electric field–confined DESP strategy provides a general platform for making high-performance 3D electrodes.

Electrocatalysis exhibits certain benefits for water purification, but the low performance of electrodes severely hampers its utility. Here, we report a general strategy for fabricating high-performance three-dimensional (3D) porous electrodes with ultrahigh electrochemical active surface area and single-atom catalysts from earth-abundant elements. We demonstrate a binder-free dual electrospinning-electrospraying (DESP) strategy to densely distribute single atomic Ti and titanium oxycarbide (TiO _x C _y ) sub–3-nm clusters throughout interconnected carbon nanofibers (CNs). The composite offers ultrahigh conductivity and mechanical robustness (ultrasonication resistant). The resulting TiO _x C _y filtration membrane exhibits record-high water purification capability with excellent permeability (~8370 liter m ⁻²  hour ⁻¹  bar ⁻¹ ), energy efficiency (e.g., >99% removal of toxins within 1.25 s at 0.022 kWh·m ⁻³ per order), and erosion resistance. The hierarchical design of the TiO _x C _y membrane facilitates rapid and energy-efficient electrocatalysis through both direct electron transfer and indirect reactive oxygen species ( ¹ O ₂ , · OH, and O ₂ · ⁻ , etc.) oxidations. The electric field–confined DESP strategy provides a general platform for making high-performance 3D electrodes.

Programmable synaptic devices that can achieve timing‐dependent weight updates are key components to implementing energy‐efficient spiking neural networks (SNNs). Electrochemical ionic synapses (EIS) enable the programming of weight updates with very low energy consumption and low variability. Here, the strongly nonlinear kinetics of EIS, arising from nonlinear dynamics of ions and charge transfer reactions in solids, are leveraged to implement various forms of spike‐timing‐dependent plasticity (STDP). In particular, protons are used as the working ion. Different forms of the STDP function are deterministically predicted and emulated by a linear superposition of appropriately designed pre‐ and post‐synaptic neuron signals. Heterogeneous STDP is also demonstrated within the array to capture different learning rules in the same system. STDP timescales are controllable, ranging from milliseconds to nanoseconds. The STDP resulting from EIS has lower variability than other hardware STDP implementations, due to the deterministic and uniform insertion of charge in the tunable channel material. The results indicate that the ion and charge transfer dynamics in EIS can enable bio‐plausible synapses for SNN hardware with high energy efficiency, reliability, and throughput.

Understanding topological defects-controlled structural degradation of layered oxides—a key cathode material for high-performance lithium-ion batteries—plays a critical role in developing next-generation cathode materials. Here, by constructing a nanobattery in an electron microscope enabling atomic-scale monitoring of electrochemcial reactions, we captured the electrochemically driven atomistic dynamics and evolution of dislocations—a most important topological defect in material. We deciphered how dislocations nucleate, move, and annihilate within layered cathodes at the atomic scale. Specifically, we found two types of dislocation configurations, i.e., single dislocations and dislocation dipoles. Both pure dislocation glide/climb and mixed motions were captured, and the dislocation glide and climb velocities were first experimentally measured. Moreover, dislocation activity-mediated structural degradation such as crack nucleation, phase transformation, and lattice reorientation was unraveled. Our work provides deep insights into the atomistic dynamics of electrochemically driven dislocation activities in layered oxides.

All-solid-state batteries (ASSBs) are pursued due to their potential for better safety and high energy density. However, the energy density of the cathode for ASSBs does not seem to be satisfactory due to the low utilization of active materials (AMs) at high loading. With small amount of solid electrolyte (SE) powder in the cathode, poor electrochemical performance is often observed due to contact loss and non-homogeneous distribution of AMs and SEs, leading to high tortuosity and limitation of lithium and electron transport pathways. Here, we propose a novel cathode design that can achieve high volumetric energy density of 1258 Wh L⁻¹ at high AM content of 85 wt% by synergizing the merits of AM@SE core–shell composite particles with conformally coated thin SE shell prepared from mechanofusion process and small SE particles. The core–shell structure with an intimate and thin SE shell guarantees high ionic conduction pathway while unharming the electronic conduction. In addition, small SE particles play the role of a filler that reduces the packing porosity in the cathode composite electrode as well as between the cathode and the SE separator layer. The systematic demonstration of the optimization process may provide understanding and guidance on the design of electrodes for ASSBs with high electrode density, capacity, and ultimately energy density.

As the key component in solid‐state batteries, Li superionic conductors ought to exhibit high ionic conductivities (>10⁻⁴ S cm⁻¹) at room temperature (σ_RT). However, identifying such materials is a grand challenge due to the limited number of known candidates and the difficulty of predicting σ_RT with both efficiency and accuracy. Herein, a high‐throughput screening model is developed that requires only two easily accessible parameters: the diameter of Li‐ion diffusion path (D_path) and the dimension of Li‐ion network (D_Li). This model successfully identifies Li superionic conductors from 132 experimentally available Li‐ion conductors. Using this approach, 13 new candidates are screened out of the 21 686 Li‐containing materials from the Materials Project, and their Li superionic conductivity is confirmed by first‐principle molecular dynamics simulations. Notably, two N‐containing materials (i.e., Li_6.5Ta_0.5W_0.5N₄ and Li_6.5Nb_0.5W_0.5N₄) are identified, enriching the rare N‐based Li superionic conductor family, while Li₂Mo₃S₄ achieves the highest conductivity of 6.24 × 10⁻² S cm⁻¹ due to its unique structure of interconnected Mo₆O₈ clusters, providing a robust and optimal diffusion path. Li_6.5Ta_0.5W_0.5N₄, Li_6.5Nb_0.5W_0.5N₄, and Li₇PSe₆ have been identified as promising solid‐state electrolytes for use at the anode interface for the solid‐state Li‐ion batteries, while Li₁₀X(PS₆)₂ (X = Si, Ge, or Sn), Li₂Mn_0.75Ta_0.5Sn_0.5S₄, and Li₂Zn_0.5TaS₄ are suitable for the cathode interface. This work not only proposes a highly effective and accurate screening model for exploring Li superionic conductors but also provides several new frameworks for designing systems with ultrahigh σ_RT values.

Extracting hydrogen from metallic components can open up a new pathway for preventing hydrogen embrittlement.

A novel liquified-salts-assisted upcycling strategy achieves compositional and morphological upgrading of spent cathodes, offering a scalable pathway for high-performance cathode regeneration with reduced process energy and material waste.

The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb_1−xO_1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al_1−xO_1−x and Ti_1−xO_1−x (λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc_1−xO_1−x and Nb_1−xO_1−x show significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti_1−x(O_1−xHx) and Nb_1−x(O_1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure.

The highest ambient‐pressure Tc among binary compounds is 40 K (MgB2). Higher Tc is achieved in high‐pressure hydrides or multielement cuprates. Alternatively, are explored superconducting properties of binary, metastable sub‐oxides, that may emerge under extremely low oxygen partial pressure. The emphasis is on the rock‐salt structure, which is known to promote superconductivity, and exploring AlO, ScO, TiO, and NbO. Dynamic lattice stability is achieved by introducing metal and oxygen vacancies in the fashion of Nb_1−xO_1−x‐type structure (x = ¼). The electron‐phonon (e‐ph) coupling is remarkably large in Al_1−xO_1−x and Ti_1−xO_1−x (λ ≈ 2 at x = ¼), with Tc ≈ 35 K according to the Allen–Dynes equation. Significantly, the coupling strength is comparable to that in high‐pressure hydrides, yet, in contrast to hydrides and MgB2, the coupling is largely driven by low frequency phonons. Sc_1−xO_1−x and Nb_1−xO_1−x show significantly smaller λ and Tc. Further, hydrogen intercalation to boost λ and Tc is investigated. Only Ti_1−x(O_1−xHx) and Nb_1−x(O_1−xHx) are dynamically stable upon intercalation, where H, respectively, decreases and increases Tc. The effect of H doping on electronic structure and Tc is discussed. Altogether, the study suggests that metal sub‐oxides are promising compounds to achieve strong e‐ph coupling at ambient pressure.

The advent of artificial intelligence (AI) has enabled a comprehensive exploration of materials for various applications. However, AI models often prioritize frequently encountered material examples in the scientific literature, limiting the selection of suitable candidates based on inherent physical and chemical attributes. To address this imbalance, we generated a dataset consisting of 1,453,493 natural language-material narratives from OQMD, Materials Project, JARVIS, and AFLOW2 databases based on ab initio calculation results that are more evenly distributed across the periodic table. The generated text narratives were then scored by both human experts and GPT-4, based on three rubrics: technical accuracy, language and structure, and relevance and depth of content, showing similar scores but with human-scored depth of content being the most lagging. The integration of multimodal data sources and large language models holds immense potential for AI frameworks to aid the exploration and discovery of solid-state materials for specific applications of interest.

Lithium-ion battery recycling is pivotal for resource conservation and environmental sustainability. Direct recycling, while offering a promising avenue for battery recovery with reduced waste compared to pyrometallurgy and hydrometallurgy, often involves intricate and long processes. This study introduces a novel and energy-efficient water electrolysis-induced gas separation approach, utilizing H₂ or O₂ microbubbles to efficiently separate electrode materials from current collectors. The process achieves 99.5% material recycling with metal impurities below 40 ppm within 35 seconds for LiFePO₄ and 3 seconds for graphite at 10 mA h cm^–2, and can be expedited at higher current density, with minimal energy consumption of 11 and 1.1 kJ (kg cell)⁻¹. Moreover, this approach accommodates various electrode types, encompassing cathodes, and anodes from spent batteries or manufacturing scraps. Leveraging effective mixing of active materials and conductive agents, the recycled powders are directly refabricated into dry electrodes, showcasing electrochemical performances comparable to commercial counterparts. The elimination of N-methyl pyrrolidone (NMP) usage enhances environmental friendliness. An Everbatt analysis underscores a remarkable reduction in energy consumption and waste generation compared to industrial-adopted recycling methods. This approach is an efficient and sustainable solution for LIB recycling, ensuring environmental responsibility and high-quality materials production.

To enhance Li storage properties, nitrogenation methods are developed for Si anodes. First, melamine, urea, and nitric oxide (NO) precursors are used to nitrogenize carbon‐coated Si particles. The properties of the obtained particles are compared. It is found that the NO process can maximize the graphitic nitrogen (N) content and electronic conductivity of a sample. In addition, optimized N functional groups and O─C species on the electrode surface increase electrolyte wettability. However, with a carbon barrier layer, NO hardly nitrogenizes the Si cores. Therefore, bare Si particles are reacted with NO. Core‐shell Si@amorphous SiN_x particles are produced using a facile and scalable NO treatment route. The effects of the NO reaction time on the physicochemical properties and charge–discharge performance of the obtained materials are systematically examined. Finally, the Si@SiN_x particles are coated with N‐doped carbon. Superior capacities of 2435 and 1280 mAh g⁻¹ are achieved at 0.2 and 5 A g⁻¹, respectively. After 300 cycles, 90% of the initial capacity is retained. In addition, differential scanning calorimetry data indicate that the multiple nitrogenation layers formed by NO significantly suppress electrode exothermic reactions during thermal runaway.

To enhance Li storage properties, nitrogenation methods are developed for Si anodes. First, melamine, urea, and nitric oxide (NO) precursors are used to nitrogenize carbon‐coated Si particles. The properties of the obtained particles are compared. It is found that the NO process can maximize the graphitic nitrogen (N) content and electronic conductivity of a sample. In addition, optimized N functional groups and O─C species on the electrode surface increase electrolyte wettability. However, with a carbon barrier layer, NO hardly nitrogenizes the Si cores. Therefore, bare Si particles are reacted with NO. Core‐shell Si@amorphous SiN_x particles are produced using a facile and scalable NO treatment route. The effects of the NO reaction time on the physicochemical properties and charge–discharge performance of the obtained materials are systematically examined. Finally, the Si@SiN_x particles are coated with N‐doped carbon. Superior capacities of 2435 and 1280 mAh g⁻¹ are achieved at 0.2 and 5 A g⁻¹, respectively. After 300 cycles, 90% of the initial capacity is retained. In addition, differential scanning calorimetry data indicate that the multiple nitrogenation layers formed by NO significantly suppress electrode exothermic reactions during thermal runaway.

Dynamic doping by electrochemical ion intercalation is a promising mechanism for modulating electronic conductivity, allowing for energy‐efficient, brain‐inspired computing hardware. While proton‐based devices have achieved success in terms of speed and efficiency, the volatility and environmental pervasiveness of hydrogen (H) might limit the robustness of devices during fabrication, as well as the long‐term retention of devices after programming. This motivates the search for alternative working ions. In this work, a proof‐of‐concept is demonstrated for electrochemical ionic synapses (EIS) based on intercalation of Mg²⁺ions. The reported device has a symmetric design, with Mg_xWO₃used as both the gate and channel material. Increasing the Mg fraction,x, in WO₃increases the electronic conductance in a continuum over a large range (80 nS − 2 mS). Ex situ characterization of the channel confirms that modulation of channel conductance is due to Mg²⁺intercalation. Unlike H‐EIS which rapidly loses programmed conductance states over a few seconds when exposed to air, Mg‐EIS can be operated and has good retention in air, with no sign of degradation after 1 h. Mg²⁺as a working ion with WO₃as the channel is a promising material system for EIS with long‐term retention and low energy consumption.

Dynamic doping by electrochemical ion intercalation is a promising mechanism for modulating electronic conductivity, allowing for energy‐efficient, brain‐inspired computing hardware. While proton‐based devices have achieved success in terms of speed and efficiency, the volatility and environmental pervasiveness of hydrogen (H) might limit the robustness of devices during fabrication, as well as the long‐term retention of devices after programming. This motivates the search for alternative working ions. In this work, a proof‐of‐concept is demonstrated for electrochemical ionic synapses (EIS) based on intercalation of Mg²⁺ions. The reported device has a symmetric design, with Mg_xWO₃used as both the gate and channel material. Increasing the Mg fraction,x, in WO₃increases the electronic conductance in a continuum over a large range (80 nS − 2 mS). Ex situ characterization of the channel confirms that modulation of channel conductance is due to Mg²⁺intercalation. Unlike H‐EIS which rapidly loses programmed conductance states over a few seconds when exposed to air, Mg‐EIS can be operated and has good retention in air, with no sign of degradation after 1 h. Mg²⁺as a working ion with WO₃as the channel is a promising material system for EIS with long‐term retention and low energy consumption.

Solid‐state batteries have the potential to replace the current generation of liquid electrolyte batteries. However, the major limitation resulting from their solid‐state architecture is the gradual loss of ionic conductivity due to the loss of physical contact between the individual battery components during charging/discharging. This is mainly due to mechanical stresses caused by volume changes in the cathode and anode during lithiation and delithiation. To date, limited research has been devoted to understanding the spatio‐temporal distribution of stresses during battery operation. Here, operando scanning high‐energy X‐ray diffraction to quantify cross‐sectional axial stresses with a spatial resolution of 10 µm is used. It is shown how a non‐monotonous stress distribution evolves over time during the cycling of the solid‐state battery. In addition, degradation of the solid‐state electrolyte in the vicinity of the lithium anode is observed and tracked periodic changes in the unit cell volume in the cathode. The presented methodology of tracking the chemo‐mechanically induced stresses and interface morphology in real time in correlation with other battery parameters is believed, can provide a valuable platform for the future optimization of solid‐state batteries.

Newly discovered opto‐ionic effects in metal oxides provide unique opportunities for functional ceramic applications. The authors generalize the recently demonstrated grain boundary opto‐ionic effect observed in solid electrolyte thin films under ultraviolet (UV) irradiation to a radiation‐ionic effect that can be applied to bulk materials and used for gamma‐rays (γ‐rays) detection. Near room temperature, lightly doped Gd‐doped CeO₂, a polycrystalline ion conducting ceramic, exhibits a resistance ratio change ≈10³ and reversible response in ionic current when exposed to ⁶⁰Co γ‐ray (1.1 and 1.3 MeV). This is attributed to the steady state passivation of space charge barriers at grain boundaries, that act as virtual electrodes, capturing radiation‐induced electrons, in turn lowering space charge barrier heights, and thereby exclusively modulating the ionic carrier flow within the ceramic electrolytes. Such behavior allows significant electrical response under low fields, that is, < 2 V cm⁻¹, paving the way to inexpensive, sensitive, low‐power, and miniaturizable solid‐state devices, uniquely suited for operating in harsh (high temperature, pressure, and corrosive) environments. This discovery presents opportunities for portable and/or scalable radiation detectors benefiting geothermal drilling, small modular reactors, nuclear security, and waste management.

Newly discovered opto‐ionic effects in metal oxides provide unique opportunities for functional ceramic applications. The authors generalize the recently demonstrated grain boundary opto‐ionic effect observed in solid electrolyte thin films under ultraviolet (UV) irradiation to a radiation‐ionic effect that can be applied to bulk materials and used for gamma‐rays (γ‐rays) detection. Near room temperature, lightly doped Gd‐doped CeO₂, a polycrystalline ion conducting ceramic, exhibits a resistance ratio change ≈10³ and reversible response in ionic current when exposed to ⁶⁰Co γ‐ray (1.1 and 1.3 MeV). This is attributed to the steady state passivation of space charge barriers at grain boundaries, that act as virtual electrodes, capturing radiation‐induced electrons, in turn lowering space charge barrier heights, and thereby exclusively modulating the ionic carrier flow within the ceramic electrolytes. Such behavior allows significant electrical response under low fields, that is, < 2 V cm⁻¹, paving the way to inexpensive, sensitive, low‐power, and miniaturizable solid‐state devices, uniquely suited for operating in harsh (high temperature, pressure, and corrosive) environments. This discovery presents opportunities for portable and/or scalable radiation detectors benefiting geothermal drilling, small modular reactors, nuclear security, and waste management.

Recent studies have reported the experimental discovery that nanoscale specimens of even a natural material, such as diamond, can be deformed elastically to as much as 10% tensile elastic strain at room temperature without the onset of permanent damage or fracture. Computational work combining ab initio calculations and machine learning (ML) algorithms has further demonstrated that the bandgap of diamond can be altered significantly purely by reversible elastic straining. These findings open up unprecedented possibilities for designing materials and devices with extreme physical properties and performance characteristics for a variety of technological applications. However, a general scientific framework to guide the design of engineering materials through such elastic strain engineering (ESE) has not yet been developed. By combining first-principles calculations with ML, we present here a general approach to map out the entire phonon stability boundary in six-dimensional strain space, which can guide the ESE of a material without phase transitions. We focus on ESE of vibrational properties, including harmonic phonon dispersions, nonlinear phonon scattering, and thermal conductivity. While the framework presented here can be applied to any material, we show as an example demonstration that the room-temperature lattice thermal conductivity of diamond can be increased by more than 100% or reduced by more than 95% purely by ESE, without triggering phonon instabilities. Such a framework opens the door for tailoring of thermal-barrier, thermoelectric, and electro-optical properties of materials and devices through the purposeful design of homogeneous or inhomogeneous strains.

Aqueous Zn‐ion batteries (AZIBs) are promising for grid‐scale energy storage. However, conventional AZIBs face challenges including hydrogen evolution reaction (HER), leading to high local pH, and by‐product formation on the anode. Hereby the hydrogen bonds in the aqueous electrolyte are reconstructed by using a deep eutectic co‐solvent (DES) made of acetamide (H‐bond donor) and caprolactam (H‐bond acceptor), which effectively suppresses the reactivity of water and broadens the electrochemical voltage stability window. The coordination between Zn²⁺ and acetamide‐caprolactam in DES‐based electrolytes produces a unique solvation structure that promotes the preferential growth of Zn crystals along the (002) plane. This will inhibit the formation of Zn dendrites and ensure the uniform deposition of Zn‐ions on the anode surface. In addition, it is found that this DES‐based electrolyte can form a protective membrane on the anode surface, reducing the risks of Zn corrosion. Compared to conventional electrolytes, the DES‐based electrolyte shows a long‐term stable plating/stripping performance with a significantly improved Coulombic efficiency from 78.18% to 98.37%. It is further demonstrated that a Zn||VS₂ full‐cell with the DES‐based electrolyte exhibits enhanced stability after 500 cycles with 85.4% capacity retention at 0.5 A g⁻¹.

Aqueous Zn‐ion batteries (AZIBs) are promising for grid‐scale energy storage. However, conventional AZIBs face challenges including hydrogen evolution reaction (HER), leading to high local pH, and by‐product formation on the anode. Hereby the hydrogen bonds in the aqueous electrolyte are reconstructed by using a deep eutectic co‐solvent (DES) made of acetamide (H‐bond donor) and caprolactam (H‐bond acceptor), which effectively suppresses the reactivity of water and broadens the electrochemical voltage stability window. The coordination between Zn²⁺ and acetamide‐caprolactam in DES‐based electrolytes produces a unique solvation structure that promotes the preferential growth of Zn crystals along the (002) plane. This will inhibit the formation of Zn dendrites and ensure the uniform deposition of Zn‐ions on the anode surface. In addition, it is found that this DES‐based electrolyte can form a protective membrane on the anode surface, reducing the risks of Zn corrosion. Compared to conventional electrolytes, the DES‐based electrolyte shows a long‐term stable plating/stripping performance with a significantly improved Coulombic efficiency from 78.18% to 98.37%. It is further demonstrated that a Zn||VS₂ full‐cell with the DES‐based electrolyte exhibits enhanced stability after 500 cycles with 85.4% capacity retention at 0.5 A g⁻¹.

Diffusion in alloys is an important class of atomic processes. However, atomistic simulations of diffusion in chemically complex solids are confronted with the timescale problem: the accessible simulation time is usually far shorter than that of experimental interest. In this work, long‐timescale simulation methods are developed using reinforcement learning (RL) that extends simulation capability to match the duration of experimental interest. Two special limits, RL transition kinetics simulator (TKS) and RL low‐energy states sampler (LSS), are implemented and explained in detail, while the meaning of general RL are also discussed. As a testbed, hydrogen diffusivity is computed using RL TKS in pure metals and a medium entropy alloy, CrCoNi, and compared with experiments. The algorithm can produce counter‐intuitive hydrogen‐vacancy cooperative motion. We also demonstrate that RL LSS can accelerate the sampling of low‐energy configurations compared to the Metropolis–Hastings algorithm, using hydrogen migration to copper (111) surface as an example.

Diffusion in alloys is an important class of atomic processes. However, atomistic simulations of diffusion in chemically complex solids are confronted with the timescale problem: the accessible simulation time is usually far shorter than that of experimental interest. In this work, long‐timescale simulation methods are developed using reinforcement learning (RL) that extends simulation capability to match the duration of experimental interest. Two special limits, RL transition kinetics simulator (TKS) and RL low‐energy states sampler (LSS), are implemented and explained in detail, while the meaning of general RL are also discussed. As a testbed, hydrogen diffusivity is computed using RL TKS in pure metals and a medium entropy alloy, CrCoNi, and compared with experiments. The algorithm can produce counter‐intuitive hydrogen‐vacancy cooperative motion. We also demonstrate that RL LSS can accelerate the sampling of low‐energy configurations compared to the Metropolis–Hastings algorithm, using hydrogen migration to copper (111) surface as an example.

Lithium substitution suppresses Fe migration in Fe-containing Na layered oxide cathodes by occupying migration sites without structural damage, significantly increasing the activation energy for Fe migration and enhancing the material's stability.

Lithium metal (Li⁰) solid‐state batteries encounter implementation challenges due to dendrite formation, side reactions, and movement of the electrode–electrolyte interface in cycling. Notably, voids and cracks formed during battery fabrication/operation are hot spots for failure. Here, a self‐healing, flowable yet solid electrolyte composed of mobile ceramic crystals embedded in a reconfigurable polymer network is reported. This electrolyte can auto‐repair voids and cracks through a two‐step self‐healing process that occurs at a fast rate of 5.6 µm h⁻¹. A dynamical phase diagram is generated, showing the material can switch between liquid and solid forms in response to external strain rates. The flowability of the electrolyte allows it to accommodate the electrode volume change during Li⁰ stripping. Simultaneously, the electrolyte maintains a solid form with high tensile strength (0.28 MPa), facilitating the regulation of mossy Li⁰ deposition. The chemistries and kinetics are studied by operando synchrotron X‐ray and in situ transmission electron microscopy (TEM). Solid‐state NMR reveals a dual‐phase ion conduction pathway and rapid Li⁺ diffusion through the stable polymer‐ceramic interphase. This designed electrolyte exhibits extended cycling life in Li⁰–Li⁰ cells, reaching 12 000 h at 0.2 mA cm⁻² and 5000 h at 0.5 mA cm⁻². Furthermore, owing to its high critical current density of 9 mA cm⁻², the Li⁰–LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) full cell demonstrates stable cycling at 5 mA cm⁻² for 1100 cycles, retaining 88% of its capacity, even under near‐zero stack pressure conditions.

An electrochemical indentation (ECI) theory was proposed to explain the LCO cycling decay. A CNT-cocooned LCO cathode was developed to maximize the electrical contact area for LCO, which greatly eliminated ECI and stabilized the high-voltage cycling.

An electrochemical indentation (ECI) theory was proposed to explain the LCO cycling decay. A CNT-cocooned LCO cathode was developed to maximize the electrical contact area for LCO, which greatly eliminated ECI and stabilized the high-voltage cycling.

Metal nanoparticles have extraordinary properties, but their integration into mesostructures has been challenging. Producing uniformly dispersed nanoparticles attached to substrates in industrial quantities is difficult. Herein, a “plasmashock” method was developed to synthesize metal nanoparticles anchored on different types of carbonaceous substrates using liquid salt solution precursors. These self-supporting, nanoparticle-loaded carbon fabrics are mechanically robust and have been tested as antibacterial substrates and electrocatalysts for reducing carbon dioxide and nitrite. A piece of silver–carbon nanotube paper with a silver loading of ~0.13 mg cm⁻² treated after a few-second plasmashock presents good antibacterial and electrocatalytic properties in wastewater, even after 20 bactericidal immersion cycles, due to the strong bonding of the nanoparticles to the substrate. The results prove the effectiveness of this plasmashock method in creating free-standing functional composite films or membranes.

A controllable and sustainable lithium replenishment strategy was developed to achieve high-energy-density and long-lifespan lithium-ion batteries.

A supercritical carbon dioxide (SCCO₂) fluid, characterized by gas‐like diffusivity, near‐zero surface tension, and excellent mass transfer properties, is used as a precursor to produce silicon oxycarbide (SiOC) coating. SCCO₂ disperses and reacts with Si particles to form an interfacial layer consisting of Si, O, and C. After an 850 °C annealing process, a conformal SiOC coating layer forms, resulting in core‐shell Si@SiOC particles. High‐resolution transmission electron microscopy and its X‐ray line‐scan spectroscopy, X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, and Raman spectroscopy, are used to examine the SiOC formation mechanism. Effects of SCCO₂ interaction time on the SiOC properties are investigated. The SiOC layer connects the Si@SiOC particles, improving electron and Li⁺ transport. Cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy are employed to examine the role of SiOC during charging/discharging. Operando X‐ray diffraction data reveal that the SiOC coating reduces crystal size of the formed Li₁₅Si₄ and increases its formation/elimination reversibility during cycling. The Si@SiOC electrode shows a capacitiy of 2250 mAh g⁻¹ at 0.2 A g⁻¹. After 500 cycles, the capacity retention is 72% with Coulombic efficiency above 99.8%. A full cell consisting of Si@SiOC anode and LiNi_0.8Co_0.1Mn_0.1O₂ cathode is constructed, and its performance is evaluated.

A supercritical carbon dioxide (SCCO₂) fluid, characterized by gas‐like diffusivity, near‐zero surface tension, and excellent mass transfer properties, is used as a precursor to produce silicon oxycarbide (SiOC) coating. SCCO₂ disperses and reacts with Si particles to form an interfacial layer consisting of Si, O, and C. After an 850 °C annealing process, a conformal SiOC coating layer forms, resulting in core‐shell Si@SiOC particles. High‐resolution transmission electron microscopy and its X‐ray line‐scan spectroscopy, X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, and Raman spectroscopy, are used to examine the SiOC formation mechanism. Effects of SCCO₂ interaction time on the SiOC properties are investigated. The SiOC layer connects the Si@SiOC particles, improving electron and Li⁺ transport. Cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy are employed to examine the role of SiOC during charging/discharging. Operando X‐ray diffraction data reveal that the SiOC coating reduces crystal size of the formed Li₁₅Si₄ and increases its formation/elimination reversibility during cycling. The Si@SiOC electrode shows a capacitiy of 2250 mAh g⁻¹ at 0.2 A g⁻¹. After 500 cycles, the capacity retention is 72% with Coulombic efficiency above 99.8%. A full cell consisting of Si@SiOC anode and LiNi_0.8Co_0.1Mn_0.1O₂ cathode is constructed, and its performance is evaluated.

The precise and reversible detection of hydrogen sulfide (H₂S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self‐assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H₂S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H₂S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe‐doped CuO hollow spheres as H₂S gas‐sensing materials via spray pyrolysis. 4 at.% of Fe‐doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H₂S under high humidity (relative humidity 80%) at 175 °C. The effect of multi‐valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti‐ or Nb ions into CuO sensors. Mechanistic details of these excellent H₂S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe‐doped CuO sensing materials. The selective and reversible detection of H₂S using the Fe‐doped CuO sensor suggested in this work opens a new possibility for halitosis self‐monitoring.

In the absence of externally applied mechanical loading, it would seem counterintuitive that a solid particle sitting on the surface of another solid could not only sink into the latter, but also continue its rigid-body motion towards the interior, reaching a depth as distant as thousands of times the particle diameter. Here, we demonstrate such a case using in situ microscopic as well as bulk experiments, in which diamond nanoparticles ~100 nm in size move into iron up to millimeter depth, at a temperature about half of the melting point of iron. Each diamond nanoparticle is nudged as a whole, in a displacive motion towards the iron interior, due to a local stress induced by the accumulation of iron atoms diffusing around the particle via a short and easy interfacial channel. Our discovery underscores an unusual mass transport mode in solids, in addition to the familiar diffusion of individual atoms.

Rare‐earth borides have become very popular in recent decades with high mechanical strength, melting point, good corrosion, wear, and magnetic behavior. However, the production of these borides is very challenging and unique. The production of ErB₄ and NdB₄ nanopowders via mechanochemical synthesis (MCS) is reported in this study first time in the literature. Er₂O₃ or Nd₂O₃, B₂O₃, and Mg initial powders are mechanically alloyed for different milling times to optimize the process. Rare‐earth borides with MgO phases are synthesized, then MgO is removed with HCl acid. The nanostructured rare‐earth tetraboride powders are analyzed using X‐ray diffraction (XRD). Based on the XRD, ErB₄ powders are produced successfully at the end of the 5 h milling. However, the NdB₄ phase does not occur as the stoichiometric ratio, so the B₂O₃ amount is decreased to nearly 35 wt%. When the amount of B₂O₃ is decreased to 20 wt%, NdB₄ and NdB₆ phases are 50:50 according to the Rietveld analysis. However, a homogenous NdB₄ phase is obtained with 30 wt% loss of B₂O₃. The average particle sizes of ErB₄ and NdB₄ powders are nearly 100.4 and 85.6 nm, respectively. The rare‐earth tetraborides exhibit antiferromagnetic‐to‐paramagnetic‐like phase transitions at 18 and 8.53 K, respectively.

The precise controllability of the Fermi level is a critical aspect of quantum materials. For topological Weyl semimetals, there is a pressing need to fine-tune the Fermi level to the Weyl nodes and unlock exotic electronic and optoelectronic effects associated with the divergent Berry curvature. However, in contrast to two-dimensional materials, where the Fermi level can be controlled through various techniques, the situation for bulk crystals beyond laborious chemical doping poses significant challenges. Here, we report the milli-electron-volt (meV) level ultra-fine-tuning of the Fermi level of bulk topological Weyl semimetal tantalum phosphide using accelerator-based high-energy hydrogen implantation and theory-driven planning. By calculating the desired carrier density and controlling the accelerator profiles, the Fermi level can be experimentally fine-tuned from 5 meV below, to 3.8 meV below, to 3.2 meV above the Weyl nodes. High-resolution transmission electron microscopy reveals the crystalline structure is largely maintained under irradiation, while electrical transport indicates that Weyl nodes are preserved and carrier mobility is also largely retained. Our work demonstrates the viability of this generic approach to tune the Fermi level in semimetal systems and could serve to achieve property fine-tuning for other bulk quantum materials with ultrahigh precision.

Ferrimagnetic oxide thin films are important material platforms for spintronic devices. Films grown on low symmetry orientations such as (110) exhibit complex anisotropy landscapes that can provide insight into novel phenomena such as spin‐torque auto‐oscillation and spin superfluidity. Using spin‐Hall magnetoresistance measurements, the in‐plane (IP) and out‐of‐plane (OOP) uniaxial anisotropy energies are determined for a thickness series (5–50 nm) of europium iron garnet (EuIG) and thulium iron garnet (TmIG) films epitaxially grown on a gadolinium gallium substrate with (110) orientation and capped with Pt. Pt/EuIG/GGG exhibits an (001) easy plane of magnetization perpendicular to the substrate, whereas Pt/TmIG/GGG exhibits an (001) hard plane of magnetization perpendicular to the substrate with an IP easy axis. Both IP and OOP surface anisotropy energies comparable in magnitude to the bulk anisotropy are observed. The temperature dependence of the surface anisotropies is consistent with first‐order predictions of a simplified Néel surface anisotropy model. By taking advantage of the thickness and temperature dependence demonstrated in these ferrimagnetic oxides grown on the low symmetry (110) orientations, the complex anisotropy landscapes can be tuned to act as a platform to explore rich spin textures and dynamics.

Although numerous efforts are made to synthesize active electrocatalysts for green hydrogen production; catalyst stability, and facile synthesis to scale up the production are still challenging. Herein, the production of novel non‐PGM catalysts for the oxygen reduction reaction (OER) in an alkaline aqueous medium is reported, which is based on the synthesis of a trimetallic metal–organic framework (MOF) precursors. Fine‐tuning of the composition of the metal centers (Ni, Co, and Fe) shows a great effect on OER activity after the MOF undergoes dynamic chemical and structural transformations under OER conditions. In situ characterization reveals the origin of OER activity enhancement as metals’ oxidation state increases, inducing compressive mechanical strain on metal centers, enhancing the electronic conductivity through the formation of oxygen vacancies, and stronger metal–oxygen covalency. Catalysts are used in membrane electrode assembly (MEA) setup within an industrial full‐cell anion exchange membrane electrolyzer (AEMEC), showing a stable performance for 550 h without noticeable decay at 750 and 1000 mA cm⁻² industrial level current densities.

Cation lattice flexibility and covalent bond lengths serve as good physical descriptors of proton conduction in solid acids and enable the discovery of promising proton conductors beyond traditional chemistries.

This review provides a comprehensive overview of liquid fuel oxidation electrocatalysts, from fundamental principles to state-of-the-art materials in an effort to unify design principles for future materials.

Autonomous laboratories were previously controlled mainly by scripting languages such as Python, limiting their usage among experimentalists. The recent release of OpenAI's ChatGPT API's function calling feature has enabled seamless integration and execution of Python subroutines in experimental workflows using voice commands. We have developed a system of Copilot for Real-world Experimental Scientist (CRESt) system, with a demonstration shown on YouTube. Large language models (LLMs) empower all research group members, regardless of coding experience, to leverage the robotic platform for their own projects, simply by talking with CRESt.

Self‐discharge, which is associated with energy efficiency loss, is a critical issue that hinders practical applications of rechargeable aluminum batteries (RABs). The self‐discharge properties of two commonly‐used RAB positive electrode materials, namely natural graphite (NG) and expanded graphite (EG), are investigated in this work. EG, which has a wider spacing between graphitic layers and a larger surface area, has a higher self‐discharge rate than that of NG. After 12 h of rest, NG and EG electrodes retain 74% and 63% of their initial capacities, respectively, after charging up to 2.4 V at 0.3 A g⁻¹. Operando X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy are employed to study the self‐discharge mechanism. The self‐discharge loss is related to the spontaneous deintercalation of AlCl₄⁻ anions from the graphite lattice charge‐compensated by Cl₂ gas evolution at the same electrode and can be restored (i.e., no permanent damage is caused to the electrodes) in the next charge‐discharge cycle. It is found that the charging rate and depth of charge also affect the self‐discharge properties. In addition, the self‐discharge rates of NG in 1‐ethyl‐3‐methylimidazolium chloride–AlCl₃ and urea–AlCl₃ electrolytes are compared.

Self‐discharge, which is associated with energy efficiency loss, is a critical issue that hinders practical applications of rechargeable aluminum batteries (RABs). The self‐discharge properties of two commonly‐used RAB positive electrode materials, namely natural graphite (NG) and expanded graphite (EG), are investigated in this work. EG, which has a wider spacing between graphitic layers and a larger surface area, has a higher self‐discharge rate than that of NG. After 12 h of rest, NG and EG electrodes retain 74% and 63% of their initial capacities, respectively, after charging up to 2.4 V at 0.3 A g⁻¹. Operando X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy are employed to study the self‐discharge mechanism. The self‐discharge loss is related to the spontaneous deintercalation of AlCl₄⁻ anions from the graphite lattice charge‐compensated by Cl₂ gas evolution at the same electrode and can be restored (i.e., no permanent damage is caused to the electrodes) in the next charge‐discharge cycle. It is found that the charging rate and depth of charge also affect the self‐discharge properties. In addition, the self‐discharge rates of NG in 1‐ethyl‐3‐methylimidazolium chloride–AlCl₃ and urea–AlCl₃ electrolytes are compared.

Artificial neural networks based on crossbar arrays of analog programmable resistors can address the high energy challenge of conventional hardware in artificial intelligence applications. However, state‐of‐the‐art two‐terminal resistive switching devices based on conductive filament formation suffer from high variability and poor controllability. Electrochemical ionic synapses are three‐terminal devices that operate by electrochemical and dynamic insertion/extraction of ions that control the electronic conductivity of a channel in a single solid‐solution phase. They are promising candidates for programmable resistors in crossbar arrays because they have shown uniform and deterministic control of electronic conductivity based on ion doping, with very low energy consumption. Here, the desirable specifications of these programmable resistors are presented. Then, an overview of the current progress of devices based on Li⁺, O²⁻, and H⁺ ions and material systems is provided. Achieving nanosecond speed, low operation voltage (≈1 V), low energy consumption, with complementary metal–oxide–semiconductor compatibility all simultaneously remains a challenge. Toward this goal, a physical model of the device is constructed to provide guidelines for the desired material properties to overcome the remaining challenges. Finally, an outlook is provided, including strategies to advance materials toward the desirable properties and the future opportunities for electrochemical ionic synapses.

Solid-state defects are attractive platforms for quantum sensing and simulation, e.g., in exploring many-body physics and quantum hydrodynamics. However, many interesting properties can be revealed only upon changes in the density of defects, which instead is usually fixed in material systems. Increasing the interaction strength by creating denser defect ensembles also brings more decoherence. Ideally one would like to control the spin concentration at will while keeping fixed decoherence effects. Here, we show that by exploiting charge transport, we can take some steps in this direction, while at the same time characterizing charge transport and its capture by defects. By exploiting the cycling process of ionization and recombination of NV centers in diamond, we pump electrons from the valence band to the conduction band. These charges are then transported to modulate the spin concentration by changing the charge state of material defects. By developing a wide-field imaging setup integrated with a fast single photon detector array, we achieve a direct and efficient characterization of the charge redistribution process by measuring the complete spectrum of the spin bath with micrometer-scale spatial resolution. We demonstrate a two-fold concentration increase of the dominant spin defects while keeping the T ₂ of the NV center relatively unchanged, which also provides a potential experimental demonstration of the suppression of spin flip-flops via hyperfine interactions. Our work paves the way to studying many-body dynamics with temporally and spatially tunable interaction strengths in hybrid charge–spin systems.

The US global leadership in science and technology has greatly benefitted from immigrants from other countries, most notably from China in the recent decades. However, feeling the pressure of potential federal investigations since the 2018 launch of the China Initiative, scientists of Chinese descent in the United States now face higher incentives to leave the United States and lower incentives to apply for federal grants. Analyzing data pertaining to institutional affiliations of more than 200 million scientific papers, we find a steady increase in the return migration of scientists of Chinese descent from the United States to China. We also conducted a survey of scientists of Chinese descent employed by US universities in tenured or tenure-track positions (n = 1,304), with results revealing general feelings of fear and anxiety that lead them to consider leaving the United States and/or stop applying for federal grants. If the situation is not corrected, American science will likely suffer the loss of scientific talent to China and other countries.

The US global leadership in science and technology has greatly benefitted from immigrants from other countries, most notably from China in the recent decades. However, feeling the pressure of potential federal investigations since the 2018 launch of the China Initiative, scientists of Chinese descent in the United States now face higher incentives to leave the United States and lower incentives to apply for federal grants. Analyzing data pertaining to institutional affiliations of more than 200 million scientific papers, we find a steady increase in the return migration of scientists of Chinese descent from the United States to China. We also conducted a survey of scientists of Chinese descent employed by US universities in tenured or tenure-track positions (n = 1,304), with results revealing general feelings of fear and anxiety that lead them to consider leaving the United States and/or stop applying for federal grants. If the situation is not corrected, American science will likely suffer the loss of scientific talent to China and other countries.

Aqueous zinc‐ion batteries (ZIBs) are promising energy storage solutions with low cost and superior safety, but they suffer from chemical and electrochemical degradations closely related to the electrolyte. Here, a new zinc salt design and a drop‐in solution for long cycle‐life aqueous ZIBs are reported. The salt Zn(BBI)₂ with a rationally designed anion group, N‐(benzenesulfonyl)benzenesulfonamide (BBI⁻), has a special amphiphilic molecular structure, which combines the benefits of hydrophilic and hydrophobic groups to properly tune the solubility and interfacial condition. This new zinc salt does not contain fluorine and is synthesized via a high‐yield and low‐cost method. It is shown that 1 m Zn(BBI)₂ aqueous electrolyte with a widened cathodic stability window effectively stabilizes Zn metal/H₂O interface, mitigates chemical and electrochemical degradations, and enables both symmetric and full cells using a zinc‐metal electrode.

Aqueous zinc‐ion batteries (ZIBs) are promising energy storage solutions with low cost and superior safety, but they suffer from chemical and electrochemical degradations closely related to the electrolyte. Here, a new zinc salt design and a drop‐in solution for long cycle‐life aqueous ZIBs are reported. The salt Zn(BBI)₂ with a rationally designed anion group, N‐(benzenesulfonyl)benzenesulfonamide (BBI⁻), has a special amphiphilic molecular structure, which combines the benefits of hydrophilic and hydrophobic groups to properly tune the solubility and interfacial condition. This new zinc salt does not contain fluorine and is synthesized via a high‐yield and low‐cost method. It is shown that 1 m Zn(BBI)₂ aqueous electrolyte with a widened cathodic stability window effectively stabilizes Zn metal/H₂O interface, mitigates chemical and electrochemical degradations, and enables both symmetric and full cells using a zinc‐metal electrode.

Ion concentration polarization (CP, current‐induced concentration gradient adjacent to a charge‐selective interface) has been well studied for single‐phase mixed conductors (e.g., liquid electrolyte), but multiphase CP has been rarely addressed in literature. In our recent publication, we proposed that CP above certain threshold currents can flip the phase distribution in multiphase ion‐intercalation nanofilms sandwiched by ion‐blocking electrodes. This phenomenon is known as multiphase polarization (MP). It is then proposed that MP can further lead to nonvolatile interfacial resistive switching (RS) for asymmetric electrodes with ion‐modulated electron transfer, which theory can reproduce the experimental results of LTO memristors. In this study, a comprehensive 2D phase‐field model is derived for coupled ion‐electron transport in ion‐intercalation materials, with surface effects including electron transfer kinetics, non‐neutral wetting, energy relaxation, and surface charge. Then, the model is used to study MP. Time evolution of phase boundaries is presented, and analyze the switching time, current, energy, and cyclic voltammetry, for various boundary conditions. It is found that the switching performance can be improved significantly by manipulating surface conditions and mean concentration. Finally, the prospects of MP‐based memories and possible extensions of the current model is discussed.

Ion concentration polarization (CP, current‐induced concentration gradient adjacent to a charge‐selective interface) has been well studied for single‐phase mixed conductors (e.g., liquid electrolyte), but multiphase CP has been rarely addressed in literature. In our recent publication, we proposed that CP above certain threshold currents can flip the phase distribution in multiphase ion‐intercalation nanofilms sandwiched by ion‐blocking electrodes. This phenomenon is known as multiphase polarization (MP). It is then proposed that MP can further lead to nonvolatile interfacial resistive switching (RS) for asymmetric electrodes with ion‐modulated electron transfer, which theory can reproduce the experimental results of LTO memristors. In this study, a comprehensive 2D phase‐field model is derived for coupled ion‐electron transport in ion‐intercalation materials, with surface effects including electron transfer kinetics, non‐neutral wetting, energy relaxation, and surface charge. Then, the model is used to study MP. Time evolution of phase boundaries is presented, and analyze the switching time, current, energy, and cyclic voltammetry, for various boundary conditions. It is found that the switching performance can be improved significantly by manipulating surface conditions and mean concentration. Finally, the prospects of MP‐based memories and possible extensions of the current model is discussed.

The ability to synthesize compositionally complex nanostructures rapidly is a key to high‐throughput functional materials discovery. In addition to being time‐consuming, a majority of conventional materials synthesis processes closely follow thermodynamics equilibria, which limit the discovery of new classes of metastable phases such as high entropy oxides (HEO). Herein, a photonic flash synthesis of HEO nanoparticles at timescales of milliseconds is demonstrated. By leveraging the abrupt heating and cooling cycles induced by a high‐power‐density xenon pulsed light, mixed transition metal salt precursors undergo rapid chemical transformations. Hence, nanoparticles form within milliseconds with a strong affinity to bind to the carbon substrate. Oxygen evolution reaction (OER) activity measurements of the synthesized nanoparticles demonstrate two orders of magnitude prolonged stability at high current densities, without noticeable decay in performance, compared to commercial IrO₂ catalyst. This superior catalytic activity originates from the synergistic effect of different alloying elements mixed at a high entropic state. It is found that Cr addition influences surface activity the most by promoting higher oxidation states, favoring optimal interaction with OER intermediates. The proposed high‐throughput method opens new pathways toward developing next‐generation functional materials for various electronics, sensing, and environmental applications, in addition to renewable energy conversion.

All‐solid‐state batteries with metallic lithium (Li_BCC) anode and solid electrolyte (SE) are under active development. However, an unstable SE/Li_BCC interface due to electrochemical and mechanical instabilities hinders their operation. Herein, an ultra‐thin nanoporous mixed ionic and electronic conductor (MIEC) interlayer (≈3.25 µm), which regulates Li_BCC deposition and stripping, serving as a 3D scaffold for Li⁰ ad‐atom formation, Li_BCC nucleation, and long‐range transport of ions and electrons at SE/Li_BCC interface is demonstrated. Consisting of lithium silicide and carbon nanotubes, the MIEC interlayer is thermodynamically stable against Li_BCC and highly lithiophilic. Moreover, its nanopores (<100 nm) confine the deposited Li_BCC to the size regime where Li_BCC exhibits “smaller is much softer” size‐dependent plasticity governed by diffusive deformation mechanisms. The Li_BCC thus remains soft enough not to mechanically penetrate SE in contact. Upon further plating, Li_BCC grows in between the current collector and the MIEC interlayer, not directly contacting the SE. As a result, a full‐cell having Li_3.75Si‐CNT/Li_BCC foil as an anode and LiNi_0.8Co_0.1Mn_0.1O₂ as a cathode displays a high specific capacity of 207.8 mAh g⁻¹, 92.0% initial Coulombic efficiency, 88.9% capacity retention after 200 cycles (Coulombic efficiency reaches 99.9% after tens of cycles), and excellent rate capability (76% at 5 C).

All‐solid‐state batteries with metallic lithium (Li_BCC) anode and solid electrolyte (SE) are under active development. However, an unstable SE/Li_BCC interface due to electrochemical and mechanical instabilities hinders their operation. Herein, an ultra‐thin nanoporous mixed ionic and electronic conductor (MIEC) interlayer (≈3.25 µm), which regulates Li_BCC deposition and stripping, serving as a 3D scaffold for Li⁰ ad‐atom formation, Li_BCC nucleation, and long‐range transport of ions and electrons at SE/Li_BCC interface is demonstrated. Consisting of lithium silicide and carbon nanotubes, the MIEC interlayer is thermodynamically stable against Li_BCC and highly lithiophilic. Moreover, its nanopores (<100 nm) confine the deposited Li_BCC to the size regime where Li_BCC exhibits “smaller is much softer” size‐dependent plasticity governed by diffusive deformation mechanisms. The Li_BCC thus remains soft enough not to mechanically penetrate SE in contact. Upon further plating, Li_BCC grows in between the current collector and the MIEC interlayer, not directly contacting the SE. As a result, a full‐cell having Li_3.75Si‐CNT/Li_BCC foil as an anode and LiNi_0.8Co_0.1Mn_0.1O₂ as a cathode displays a high specific capacity of 207.8 mAh g⁻¹, 92.0% initial Coulombic efficiency, 88.9% capacity retention after 200 cycles (Coulombic efficiency reaches 99.9% after tens of cycles), and excellent rate capability (76% at 5 C).

The use of strong acids and low atom efficiency in conventional hydrometallurgical recycling of spent lithium-ion batteries (LIBs) results in significant secondary wastes and CO ₂ emissions. Herein, we utilize the waste metal current collectors in spent LIBs to promote atom economy and reduce chemicals consumption in a conversion process of spent Li _{1- x} CoO ₂ (LCO) → new LiNi _0.80 Co _0.15 Al _0.05 O ₂ (NCA) cathode. Mechanochemical activation is employed to achieve moderate valence reduction of transition metal oxides (Co ³⁺ →Co ^2+,3+ ) and efficient oxidation of current collector fragments (Al ⁰ →Al ³⁺ , Cu ⁰ →Cu ^1+,2+ ), and then due to stored internal energy from ball-milling, the leaching rates of Li, Co, Al, and Cu in the ≤4 mm crushed products uniformly approach 100% with just weak acetic acid. Instead of corrosive precipitation reagents, larger Al fragments (≥4 mm) are used to control the oxidation/reduction potential (ORP) in the aqueous leachate and induce the targeted removal of impurity ions (Cu, Fe). After the upcycling of NCA precursor solution to NCA cathode powders, we demonstrate excellent electrochemical performance of the regenerated NCA cathode and improved environmental impact. Through life cycle assessments, the profit margin of this green upcycling path reaches about 18%, while reducing greenhouse gas emissions by 45%.

The use of strong acids and low atom efficiency in conventional hydrometallurgical recycling of spent lithium-ion batteries (LIBs) results in significant secondary wastes and CO ₂ emissions. Herein, we utilize the waste metal current collectors in spent LIBs to promote atom economy and reduce chemicals consumption in a conversion process of spent Li _{1- x} CoO ₂ (LCO) → new LiNi _0.80 Co _0.15 Al _0.05 O ₂ (NCA) cathode. Mechanochemical activation is employed to achieve moderate valence reduction of transition metal oxides (Co ³⁺ →Co ^2+,3+ ) and efficient oxidation of current collector fragments (Al ⁰ →Al ³⁺ , Cu ⁰ →Cu ^1+,2+ ), and then due to stored internal energy from ball-milling, the leaching rates of Li, Co, Al, and Cu in the ≤4 mm crushed products uniformly approach 100% with just weak acetic acid. Instead of corrosive precipitation reagents, larger Al fragments (≥4 mm) are used to control the oxidation/reduction potential (ORP) in the aqueous leachate and induce the targeted removal of impurity ions (Cu, Fe). After the upcycling of NCA precursor solution to NCA cathode powders, we demonstrate excellent electrochemical performance of the regenerated NCA cathode and improved environmental impact. Through life cycle assessments, the profit margin of this green upcycling path reaches about 18%, while reducing greenhouse gas emissions by 45%.

Designing stable Li metal and supporting solid structures (SSS) is of fundamental importance in rechargeable Li‐metal batteries. Yet, the stripping kinetics of Li metal and its mechanical effect on the supporting solids (including solid electrolyte interface) remain mysterious to date. Here, through nanoscale in situ observations of a solid‐state Li‐metal battery in an electron microscope, two distinct cavitation‐mediated Li stripping modes controlled by the ratio of the SSS thickness (t) to the Li deposit's radius (r) are discovered. A quantitative criterion is established to understand the damage tolerance of SSS on the Li‐metal stripping pathways. For mechanically unstable SSS (t/r < 0.21), the stripping proceeds via tension‐induced multisite cavitation accompanied by severe SSS buckling and necking, ultimately leading to Li “trapping” or “dead Li” formation; for mechanically stable SSS (t/r > 0.21), the Li metal undergoes nearly planar stripping from the root via single cavitation, showing negligible buckling. This work proves the existence of an electronically conductive precursor film coated on the interior of solid electrolytes that however can be mechanically damaged, and it is of potential importance to the design of delicate Li‐metal supporting structures to high‐performance solid‐state Li‐metal batteries.

Designing stable Li metal and supporting solid structures (SSS) is of fundamental importance in rechargeable Li‐metal batteries. Yet, the stripping kinetics of Li metal and its mechanical effect on the supporting solids (including solid electrolyte interface) remain mysterious to date. Here, through nanoscale in situ observations of a solid‐state Li‐metal battery in an electron microscope, two distinct cavitation‐mediated Li stripping modes controlled by the ratio of the SSS thickness (t) to the Li deposit's radius (r) are discovered. A quantitative criterion is established to understand the damage tolerance of SSS on the Li‐metal stripping pathways. For mechanically unstable SSS (t/r < 0.21), the stripping proceeds via tension‐induced multisite cavitation accompanied by severe SSS buckling and necking, ultimately leading to Li “trapping” or “dead Li” formation; for mechanically stable SSS (t/r > 0.21), the Li metal undergoes nearly planar stripping from the root via single cavitation, showing negligible buckling. This work proves the existence of an electronically conductive precursor film coated on the interior of solid electrolytes that however can be mechanically damaged, and it is of potential importance to the design of delicate Li‐metal supporting structures to high‐performance solid‐state Li‐metal batteries.

An ultra-lightweight Li-CNT film was developed as a high-capacity anode prelithiation material, offering exceptional mechanical properties. This innovation holds great potential for precise prelithiation applications in lithium-ion batteries.

An ultra-lightweight Li-CNT film was developed as a high-capacity anode prelithiation material, offering exceptional mechanical properties. This innovation holds great potential for precise prelithiation applications in lithium-ion batteries.

Na‐ion batteries (NIBs) are promising for grid‐scale energy storage applications. However, the lack of Co, Ni‐free cathode materials has made them less cost‐effective. In this work, Mg²⁺ is successfully utilized to activate the oxygen redox reaction in earth‐abundant Fe/Mn‐based layered cathodes to achieve reversible hybrid anionic and cationic redox capacities. A high first charge capacity of ≈210 mAh g⁻¹ with balanced charge–discharge efficiency is achieved without O‐loss, showing a promising energy cost of $2.02 kWh⁻¹. Full cell against hard carbon anode without pre‐sodiation shows energy density exceeding ≈280 Wh kg⁻¹ with a decent capacity retention of 85.6% after 100 cycles. A comprehensive analysis of the charge compensation mechanisms and structural evolution is conducted. Voltage and capacity loss resulting from partially reversible Fe³⁺ migration to the Na layer is confirmed, shedding light on further improvements for low‐cost NIB cathodes in application scenarios.

Nonlinear optical materials possess wide applications, ranging from terahertz and mid-infrared detection to energy harvesting. Recently, the correlations between nonlinear optical responses and certain topological properties, such as the Berry curvature and the quantum metric tensor, have attracted considerable interest. Here, we report giant room-temperature nonlinearities in non-centrosymmetric two-dimensional topological materials—the Janus transition metal dichalcogenides in the 1 T’ phase, synthesized by an advanced atomic-layer substitution method. High harmonic generation, terahertz emission spectroscopy, and second harmonic generation measurements consistently show orders-of-the-magnitude enhancement in terahertz-frequency nonlinearities in 1 T’ MoSSe (e.g., > 50 times higher than 2H MoS₂ for 18^th order harmonic generation; > 20 times higher than 2H MoS₂ for terahertz emission). We link this giant nonlinear optical response to topological band mixing and strong inversion symmetry breaking due to the Janus structure. Our work defines general protocols for designing materials with large nonlinearities and heralds the applications of topological materials in optoelectronics down to the monolayer limit.

The lithiation/delithiation properties of α‐Si₃N₄ and β‐Si₃N₄ are compared and the carbon coating effects are examined. Then, β‐Si₃N₄ at various fractions is used as the secondary phase in a Si anode to modify the electrode properties. The incorporated β‐Si₃N₄ decreases the crystal size of Si and introduces a new NSiO species at the β‐Si₃N₄/Si interface. The nitrogen from the milled β‐Si₃N₄ diffuses into the surface carbon coating during the carbonization heat treatment, forming pyrrolic nitrogen and CNO species. The synergistic effects of combining β‐Si₃N₄ and Si phases on the specific capacity are confirmed. The operando X‐ray diffraction and X‐ray photoelectron spectroscopy data indicate that β‐Si₃N₄ is partially consumed during lithiation to form a favorable Li₃N species at the electrode. However, the crystalline structure of the hexagonal β‐Si₃N₄ is preserved after prolonged cycling, which prevents electrode agglomeration and performance deterioration. The carbon‐coated β‐Si₃N₄/Si composite anode shows specific capacities of 1068 and 480 mAh g⁻¹ at 0.2 and 5 A g⁻¹, respectively. A full cell consisting of the carbon‐coated β‐Si₃N₄/Si anode and a LiNi_0.8Co_0.1Mn_0.1O₂ cathode is constructed and its properties are evaluated. The potential of the proposed composite anodes for Li‐ion battery applications is demonstrated.

Corrosion is a ubiquitous failure mode of materials. Often, the progression of localized corrosion is accompanied by the evolution of porosity in materials previously reported to be either three-dimensional or two-dimensional. However, using new tools and analysis techniques, we have realized that a more localized form of corrosion, which we call 1D wormhole corrosion, has previously been miscategorized in some situations. Using electron tomography, we show multiple examples of this 1D and percolating morphology. To understand the origin of this mechanism in a Ni-Cr alloy corroded by molten salt, we combined energy-filtered four-dimensional scanning transmission electron microscopy and ab initio density functional theory calculations to develop a vacancy mapping method with nanometer-resolution, identifying a remarkably high vacancy concentration in the diffusion-induced grain boundary migration zone, up to 100 times the equilibrium value at the melting point. Deciphering the origins of 1D corrosion is an important step towards designing structural materials with enhanced corrosion resistance.

New physical insights and a robust approach are provided to develop super-MIEC anodes for high-rate batteries, which would bridge two materials families—nanoporous framework materials and conductive oxides.

High entropy oxide (HEO) has emerged as a new class of anode material for Li‐ion batteries (LIBs) by offering infinite possibilities to tailor the charge–discharge properties. While the advantages of single‐phase HEO anodes are realized, the effects of a secondary phase are overlooked. In this study, two kinds of Co‐free HEOs are prepared, containing Cr, Mn, Fe, Ni, and Zn, for use as LIB anodes. One is a plain cubic‐structure high entropy spinel oxide HESO (C) prepared using a solvothermal method. The other HESO (C+T) contains an extra secondary phase of tetragonal spinel oxide and is prepared using a hydrothermal method. It is demonstrated that the secondary tetragonal spinel phase introduces phase boundaries and defects/oxygen vacancies within HESO (C+T), which improve the redox kinetics and reversibility during electrode lithiation/delithiation. Density functional theory calculation is performed to assess the phase stability of cubic spinel, tetragonal spinel, and rock‐salt structures, and validate the cycling stability of the electrodes upon charging–discharging. The secondary‐phase‐induced rate capability and cyclability enhancement of HEO electrodes are for the first time demonstrated. A HESO (C+T)||LiNi_0.8Co_0.1Mn_0.1O₂ full cell is assembled and evaluated, showing a promising gravimetric energy density of ≈610 Wh kg⁻¹ based on electrode‐active materials.

A rapid transition in the energy infrastructure is crucial when irreversible damages are happening quickly in the next decade due to global climate change. It is believed that a practical strategy for decarbonization would be 8 h of lithium‐ion battery (LIB) electrical energy storage paired with wind/solar energy generation, and using existing fossil fuels facilities as backup. To reach the hundred terawatt‐hour scale LIB storage, it is argued that the key challenges are fire safety and recycling, instead of capital cost, battery cycle life, or mining/manufacturing challenges. A short overview of the ongoing innovations in these two directions is provided.

A rapid transition in the energy infrastructure is crucial when irreversible damages are happening quickly in the next decade due to global climate change. It is believed that a practical strategy for decarbonization would be 8 h of lithium‐ion battery (LIB) electrical energy storage paired with wind/solar energy generation, and using existing fossil fuels facilities as backup. To reach the hundred terawatt‐hour scale LIB storage, it is argued that the key challenges are fire safety and recycling, instead of capital cost, battery cycle life, or mining/manufacturing challenges. A short overview of the ongoing innovations in these two directions is provided.

Civilian fusion demands structural materials that can withstand the harsh environments imposed inside fusion plasma reactors. The structural materials often transmute under 14.1 MeV fast neutrons, producing helium (He), which embrittles the grain boundary (GB) network. Here, it is shown that neutron‐friendly and mechanically strong nano‐phases with atomic‐scale free volume can have low He‐embedding energy and >10 at.% He‐absorbing capacity, and can be especially advantageous for soaking up He on top of resisting radiation damage and creep, provided they have thermodynamic compatibility with the matrix phase, satisfactory equilibrium wetting angle, as well as a high enough melting point. The preliminary experimental demonstration proves that is a good ab initio predictor of He shielding potency in nano‐heterophase materials, and thus, is used as a key feature for computational screening. In this context, a list of viable compounds expected to be good He‐absorbing nano‐phases is presented, taking into account , the neutron absorption and activation cross‐sections, the elastic moduli, melting temperature, the thermodynamic compatibility, and the equilbrium wetting angle of the nano‐phases with the Fe matrix as an example.

Civilian fusion demands structural materials that can withstand the harsh environments imposed inside fusion plasma reactors. The structural materials often transmute under 14.1 MeV fast neutrons, producing helium (He), which embrittles the grain boundary (GB) network. Here, it is shown that neutron‐friendly and mechanically strong nano‐phases with atomic‐scale free volume can have low He‐embedding energy and >10 at.% He‐absorbing capacity, and can be especially advantageous for soaking up He on top of resisting radiation damage and creep, provided they have thermodynamic compatibility with the matrix phase, satisfactory equilibrium wetting angle, as well as a high enough melting point. The preliminary experimental demonstration proves that is a good ab initio predictor of He shielding potency in nano‐heterophase materials, and thus, is used as a key feature for computational screening. In this context, a list of viable compounds expected to be good He‐absorbing nano‐phases is presented, taking into account , the neutron absorption and activation cross‐sections, the elastic moduli, melting temperature, the thermodynamic compatibility, and the equilbrium wetting angle of the nano‐phases with the Fe matrix as an example.

Mixed transition‐metals (TM) based catalysts have shown huge promise for water splitting. Conventional synthesis of nanomaterials is strongly constrained by room‐temperature equilibria and Ostwald ripening. Ultra‐fast temperature cycling enables the synthesis of metastable metallic phases of high entropy alloy nanoparticles, which later transform to oxide/hydroxide nanoparticles upon use in aqueous electrolytes. Herein, an in situ synthesis of non‐noble metal high entropy oxide (HEO) catalysts on carbon fibers by rapid Joule heating and quenching is reported. Different compositions of ternary to senary (FeNiCoCrMnV) HEO nanoparticles show higher activity towards catalyzing the oxygen evolution reaction (OER) compared to a noble metal IrO₂ catalyst. The synthesized HEO also show two orders of magnitude higher stability than IrO₂, due to stronger carbide‐mediated intimacy with the substrate, activated through the OER process. Alloying elements Cr, Mn and V affect OER activity by promoting different oxidation states of the catalytically active TM (Fe, Ni and Co). Dissolution of less stable elements (Mn, V and Cr) leads to enhancements of OER activity. Dynamic structural and chemical perturbations of HEO oxide nanoparticles activate under OER conditions, leading to enlargement in ECSA by forming mixed single atom catalysts and ultra‐fine oxyhydroxide nanoparticles HEOs.

With full knowledge of a material’s atomistic structure, it is possible to predict any macroscopic property of interest. In practice, this is hindered by limitations of the chosen characterization techniques. For example, electron microscopy is unable to detect the smallest and most numerous defects in irradiated materials. Instead of spatial characterization, we propose to detect and quantify defects through their excess energy. Differential scanning calorimetry of irradiated Ti measures defect densities five times greater than those determined using transmission electron microscopy. Our experiments also reveal two energetically distinct processes where the established annealing model predicts one. Molecular dynamics simulations discover the defects responsible and inform a new mechanism for the recovery of irradiation-induced defects. The combination of annealing experiments and simulations can reveal defects hidden to other characterization techniques and has the potential to uncover new mechanisms behind the evolution of defects in materials.

Nanoscale ionic programmable resistors for analog deep learning are 1000 times smaller than biological cells, but it is not yet clear how much faster they can be relative to neurons and synapses. Scaling analyses of ionic transport and charge-transfer reaction rates point to operation in the nonlinear regime, where extreme electric fields are present within the solid electrolyte and its interfaces. In this work, we generated silicon-compatible nanoscale protonic programmable resistors with highly desirable characteristics under extreme electric fields. This operation regime enabled controlled shuttling and intercalation of protons in nanoseconds at room temperature in an energy-efficient manner. The devices showed symmetric, linear, and reversible modulation characteristics with many conductance states covering a 20× dynamic range. Thus, the space-time-energy performance of the all–solid-state artificial synapses can greatly exceed that of their biological counterparts.

Porous electrodes that conduct electrons, protons, and oxygen ions with dramatically expanded catalytic active sites can replace conventional electrodes with sluggish kinetics in protonic ceramic electrochemical cells. In this work, a strategy is utilized to promote triple conduction by facilitating proton conduction in praseodymium cobaltite perovskite through engineering non‐equivalent B‐site Ni/Co occupancy. Surface infrared spectroscopy is used to study the dehydration behavior, which proves the existence of protons in the perovskite lattice. The proton mobility and proton stability are investigated by hydrogen/deuterium (H/D) isotope exchange and temperature‐programmed desorption. It is observed that the increased nickel replacement on the B‐site has a positive impact on proton defect stability, catalytic activity, and electrochemical performance. This doping strategy is demonstrated to be a promising pathway to increase catalytic activity toward the oxygen reduction and water splitting reactions. The chosen PrNi_0.7Co_0.3O_3−δ oxygen electrode demonstrates excellent full‐cell performance with high electrolysis current density of −1.48 A cm⁻² at 1.3 V and a peak fuel‐cell power density of 0.95 W cm⁻² at 600 °C and also enables lower‐temperature operations down to 350 °C, and superior long‐term durability.

Porous electrodes that conduct electrons, protons, and oxygen ions with dramatically expanded catalytic active sites can replace conventional electrodes with sluggish kinetics in protonic ceramic electrochemical cells. In this work, a strategy is utilized to promote triple conduction by facilitating proton conduction in praseodymium cobaltite perovskite through engineering non‐equivalent B‐site Ni/Co occupancy. Surface infrared spectroscopy is used to study the dehydration behavior, which proves the existence of protons in the perovskite lattice. The proton mobility and proton stability are investigated by hydrogen/deuterium (H/D) isotope exchange and temperature‐programmed desorption. It is observed that the increased nickel replacement on the B‐site has a positive impact on proton defect stability, catalytic activity, and electrochemical performance. This doping strategy is demonstrated to be a promising pathway to increase catalytic activity toward the oxygen reduction and water splitting reactions. The chosen PrNi_0.7Co_0.3O_3−δ oxygen electrode demonstrates excellent full‐cell performance with high electrolysis current density of −1.48 A cm⁻² at 1.3 V and a peak fuel‐cell power density of 0.95 W cm⁻² at 600 °C and also enables lower‐temperature operations down to 350 °C, and superior long‐term durability.

Nonlinear light–matter interaction, as the core of ultrafast optics, bulk photovoltaics, nonlinear optical sensing and imaging, and efficient generation of entangled photons, has been traditionally studied by first-principles theoretical methods with the sum-over-states approach. However, this indirect method often suffers from the divergence at band degeneracy and optical zeros as well as convergence issues and high computation costs when summing over the states. Here, using shift vector and shift current conductivity tensor as an example, we present a gauge-invariant generalized approach for efficient and direct calculations of nonlinear optical responses by representing interband Berry curvature, quantum metric, and shift vector in a generalized Wilson loop. This generalized Wilson loop method avoids the above cumbersome challenges and allows for easy implementation and efficient calculations. More importantly, the Wilson loop representation provides a succinct geometric interpretation of nonlinear optical processes and responses based on quantum geometric tensors and quantum geometric potentials and can be readily applied to studying other excited-state responses.

The nonlinear optical (NLO) responses of topological materials are under active research. Most previous works studied the surface and bulk NLO responses separately. Here we develop a generic Green’s function framework to investigate the surface and bulk NLO responses together. We reveal that the topological surface can behave disparately from the bulk under light illumination. Remarkably, the photocurrents on the surface can flow in opposite directions to those in the bulk interior, and the light-induced spin current on the surface can be orders of magnitude stronger than its bulk counterpart on a per-volume basis. We also study the responses under inhomogeneous field and higher-order NLO effect, which are all distinct on the surface. These anomalous surface responses suggest that light can be a valuable tool for probing the surface states of topological materials. Besides, the surface effects should be prudently considered when investigating the optical properties of topological materials.

The 3D nanocomposite structure of plated lithium (Li_Metal) and solid electrolyte interphases (SEI), including a polymer‐rich surficial passivation layer (SEI exoskeleton) and inorganic SEI “fossils” buried inside amorphous Li matrix, is resolved using cryogenic transmission electron microscopy. With ether‐based DOLDME‐LiTFSI electrolyte, LiF and Li₂O nanocrystals are formed and embedded in a thin but tough amorphous polymer in the SEI exoskeleton. The fast Li‐stripping directions are along or , which produces eight exposed {111} planes at halfway charging. Full Li stripping produces completely sagging, empty SEI husks that can sustain large bending and buckling, with the smallest bending radius of curvature observed approaching tens of nanometers without apparent damage. In the 2nd round of Li plating, a thin Li_BCC sheet first nucleates at the current collector, extends to the top end of the deflated SEI husk, and then expands its thickness. The apparent zero wetting angle between Li_BCC and the SEI interior means that the heterogeneous nucleation energy barrier is zero. Due to its complete‐wetting property and chemo‐mechanical stability, the SEI largely prevents further reactions between the Li metal and the electrolyte, which explains the superior performance of Li‐metal batteries with ether‐based electrolytes. However, uneven refilling of the SEI husks results in dendrite protrusions and some new SEI formation during the 2nd plating. A strategy to form bigger SEI capsules during the initial cycle with higher energy density than the following cycles enables further enhanced Coulombic efficiency to above 99%.

The 3D nanocomposite structure of plated lithium (Li_Metal) and solid electrolyte interphases (SEI), including a polymer‐rich surficial passivation layer (SEI exoskeleton) and inorganic SEI “fossils” buried inside amorphous Li matrix, is resolved using cryogenic transmission electron microscopy. With ether‐based DOLDME‐LiTFSI electrolyte, LiF and Li₂O nanocrystals are formed and embedded in a thin but tough amorphous polymer in the SEI exoskeleton. The fast Li‐stripping directions are along or , which produces eight exposed {111} planes at halfway charging. Full Li stripping produces completely sagging, empty SEI husks that can sustain large bending and buckling, with the smallest bending radius of curvature observed approaching tens of nanometers without apparent damage. In the 2nd round of Li plating, a thin Li_BCC sheet first nucleates at the current collector, extends to the top end of the deflated SEI husk, and then expands its thickness. The apparent zero wetting angle between Li_BCC and the SEI interior means that the heterogeneous nucleation energy barrier is zero. Due to its complete‐wetting property and chemo‐mechanical stability, the SEI largely prevents further reactions between the Li metal and the electrolyte, which explains the superior performance of Li‐metal batteries with ether‐based electrolytes. However, uneven refilling of the SEI husks results in dendrite protrusions and some new SEI formation during the 2nd plating. A strategy to form bigger SEI capsules during the initial cycle with higher energy density than the following cycles enables further enhanced Coulombic efficiency to above 99%.

High entropy oxide (HEO) is a new class of lithium‐ion battery anode with high specific capacity and excellent cyclability. The beauty of HEO lies in the unique tailorable properties with respect to tunable chemical composition, which enables the use of infinite element combinations to develop new electrode materials. This study synthesizes a series of Co‐free spinel‐type HEOs via a facile hydrothermal method. Based on quaternary medium‐entropy (CrNiMnFe)₃O₄, the fifth elements of V, Mg, and Cu are added, and their ability to form single‐phase HEOs is investigated. It is demonstrated that the chemical composition of HEOs is critical to the phase purity and corresponding charge–discharge performance. The oxygen vacancy concentration seems to be decisive for the rate capability and reversibility of the HEO electrodes. An inactive spectator element is not necessary for achieving high cyclability, given that the phase purity of the HEO is wisely controlled. The single‐phase (CrNiMnFeCu)₃O₄ shows a great high‐rate capacity of 480 mAh g⁻¹ at 2000 mA g⁻¹ and almost no capacity decay after 400 cycles. Its phase transition behavior during the lithiation/delithiation process is characterized with operando X‐ray diffraction. A (CrNiMnFeCu)₃O₄||LiNi_0.8Co_0.1Mn_0.1O₂ cell is constructed with 590 Wh kg⁻¹ (based on electrode materials) gravimetric energy density.

Magnesium, the lightest structural metal, usually exhibits limited ambient plasticity when compressed along its crystallographic c-axis (the “hard” orientation of magnesium). Here we report large plasticity in c-axis compression of submicron magnesium single crystal achieved by a dual-stage deformation. We show that when the plastic flow gradually strain-hardens the magnesium crystal to gigapascal level, at which point dislocation mediated plasticity is nearly exhausted, the sample instantly pancakes without fracture, accompanying a conversion of the initial single crystal into multiple grains that roughly share a common rotation axis. Atomic-scale characterization, crystallographic analyses and molecular dynamics simulations indicate that the new grains can form via transformation of pyramidal to basal planes. We categorize this grain formation as “deformation graining”. The formation of new grains rejuvenates massive dislocation slip and deformation twinning to enable large plastic strains.

Proton conduction underlies many important electrochemical technologies. A family of new proton electrolytes is reported: acid‐in‐clay electrolyte (AiCE) prepared by integrating fast proton carriers in a natural phyllosilicate clay network, which can be made into thin‐film (tens of micrometers) fluid‐impervious membranes. The chosen example systems (sepiolite–phosphoric acid) rank top among the solid proton conductors in terms of proton conductivities (15 mS cm⁻¹ at 25 °C, 0.023 mS cm⁻¹ at −82 °C), electrochemical stability window (3.35 V), and reduced chemical reactivity. A proton battery is assembled using AiCE as the solid electrolyte membrane. Benefitting from the wider electrochemical stability window, reduced corrosivity, and excellent ionic selectivity of AiCE, the two main problems (gassing and cyclability) of proton batteries are successfully solved. This work draws attention to the element cross‐over problem in proton batteries and the generic “acid‐in‐clay” solid electrolyte approach with superfast proton transport, outstanding selectivity, and improved stability for room‐ to cryogenic‐temperature protonic applications.

Transition metal high‐entropy oxides (HEOs) are an attractive class of anode materials for high‐performance lithium‐ion batteries (LIBs). However, owing to the multiple electroactive centers of HEOs, the Li⁺ storage mechanism is complex and debated in the literature. In this work, operando quick‐scanning X‐ray absorption spectroscopy (XAS) is used to study the lithiation/delithiation mechanism of the Cobalt‐free spinel (CrMnFeNiCu)₃O₄ HEO. A monochromator oscillation frequency of 2 Hz is used and 240 spectra are integrated to achieve a 2 min time resolution. High‐photon‐flux synchrotron radiation is employed to increase the XAS sensitivity. The results indicate that the Cu²⁺ and Ni²⁺ cations are reduced to their metallic states during lithiation but their oxidation reactions are less favorable compared to the other elements upon delithiation. The Mn^2+/3+ and Fe^2+/3+ cations undergo two‐step conversion reactions to form metallic phases, with MnO and FeO as the intermediate species, respectively. During delithiation, the oxidation of Mn occurs prior to that of Fe. The Cr³⁺ cations are reduced to CrO and then Cr⁰ during lithiation. A relatively large overpotential is required to activate the Cr reoxidation reaction. The Cr³⁺ cations are found after delithiation. These results can guide the material design of HEOs for improving LIB performance.

Aqueous electrolytes are considered as an alternative to flammable and toxic organic electrolytes, whose broad applications in electrochemical energy storage (EES) devices unfortunately suffer from low electrochemical stability due to the easy electrolysis of water. Here, by performing in situ transmission electron microscope electrochemical characterizations at atomic resolution during charging/discharging, an anti‐electrolytic strategy is revealed in aqueous electrolytes via physical zwitterionic waterproofing. It is found that the zwitterionic molecules can be directionally adsorbed to the negative electrode's surface under the applied electric field, forming strings of zwitterionic molecules that extract water out from the electrode. More zwitterionic molecules further aggregate at the outer end of the strings through intermolecular electrostatic interactions, forming a waterproof layer that successfully expels water from the electrode's surface. Meanwhile, the self‐aggregation of zwitterionic additives in the bulk liquid successfully minimizes the influence on ion transport. Being intrinsically distinct from the solid electrolyte interphase concept associated with certain electrochemical reactions in organic or super‐concentrated electrolytes, the strategy is effective in improving the electrochemical stability while maintaining high ionic conductivity in various aqueous electrolytes even with a dilute concentration, shedding light on developing sustainable EES devices with high performance.

Water-based anti-corrosion coatings, which are environmentally-friendly replacements for organic solvent-based coatings, do not perform well enough for use in the most challenging corrosion environments. The high water absorption capacity of water-based latex films may reduce barrier performance by contributing to corrosive reactant/product transport. We seek to understand the coupled effects of water absorption and ion transport in hydrated latex films, and to propose mechanisms explaining these effects. Water absorption and ion transport in films immersed in deionized (DI) water were monitored by mass gain and electrical conductivity measurements, respectively. Despite very similar polymer compositions between films, large differences in water absorption and ion transport rates were observed and explained by percolating networks at latex particle boundaries which facilitate transport. A semi-continuum model with three-component diffusion and convection-like elastic relaxation supported the assumptions of the physical mechanisms governing water absorption and ion transport. The evidence of the coupled processes of water absorption and ion transport in hydrated latex films revealed in this study are useful for designing water-based coatings that provide high levels of corrosion resistance.

The formation of hydrides challenges the integrity of zirconium (Zr) fuel cladding in nuclear reactors. The dynamics of hydride precipitation are complex. Especially, the formation of the butterfly or bird‐nest configurations of dislocation structures around hydride is rather intriguing. By in‐situ transmission electron microscopy experiments and density functional theory simulations, it is discovered that hydride growth is a hybrid displacive‐diffusive process, which is regulated by intermittent dislocation emissions. A strong tensile stress field around the hydride tip increases the solubility of hydrogen in Zr matrix, which prevents hydride growth. Punching‐out dislocations reduces the tensile stress surrounding the hydride, decreases hydrogen solubility, reboots the hydride precipitation and accelerates the growth of the hydride. The emission of dislocations mediates hydride growth, and finally, the consecutively emitted dislocations evolve into a butterfly or bird‐nest configuration around the hydride.

A highly deformable separator/current collector composite is designed for Li-ion batteries to mitigate mechanical abuse-induced short-circuiting.

Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface‐area adsorbents functionalized with high‐selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen‐rich polymer, is reported, giving rise to PAN‐S nanoparticles with cyclic π‐conjugated backbone and electronic conductivity. PAN‐S can be coated on ultra‐robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N‐ and S‐containing soft Lewis bases have strong binding to Hg²⁺, Pb²⁺, Cu²⁺, and Cd²⁺, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter‐electrode as metallic Hg⁰, Pb⁰, Cu⁰, and Cd⁰, and the PAN‐S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN‐S@ML filter can be fabricated cheaply and holds promise for scale‐up applications.

Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface‐area adsorbents functionalized with high‐selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen‐rich polymer, is reported, giving rise to PAN‐S nanoparticles with cyclic π‐conjugated backbone and electronic conductivity. PAN‐S can be coated on ultra‐robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N‐ and S‐containing soft Lewis bases have strong binding to Hg²⁺, Pb²⁺, Cu²⁺, and Cd²⁺, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter‐electrode as metallic Hg⁰, Pb⁰, Cu⁰, and Cd⁰, and the PAN‐S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN‐S@ML filter can be fabricated cheaply and holds promise for scale‐up applications.

Hydrogen embrittlement jeopardizes the use of high-strength steels as critical load-bearing components in energy, transportation, and infrastructure applications. However, our understanding of hydrogen embrittlement mechanism is still obstructed by the uncertain knowledge of how hydrogen affects dislocation motion, due to the lack of quantitative experimental evidence. Here, by studying the well-controlled, cyclic, bow-out movements of individual screw dislocations, the key to plastic deformation in α-iron, we find that the critical stress for initiating dislocation motion in a 2 Pa electron-beam-excited H₂ atmosphere is 27~43% lower than that under vacuum conditions, proving that hydrogen lubricates screw dislocation motion. Moreover, we find that aside from vacuum degassing, dislocation motion facilitates the de-trapping of hydrogen, allowing the dislocation to regain its hydrogen-free behavior. Atomistic simulations reveal that the observed hydrogen-enhanced dislocation motion arises from the hydrogen-reduced kink nucleation barrier. These findings at individual dislocation level can help hydrogen embrittlement modelling in steels.

Ex-situ Arrhenius analyses and calculations reveal the activation mechanism of halide salts for molybdenum disulfide growth.

Ex-situ Arrhenius analyses and calculations reveal the activation mechanism of halide salts for molybdenum disulfide growth.

Supercritical CO₂ (SCCO₂), characterized by gas‐like diffusivity, low surface tension, and excellent mass transfer properties, is applied to create a SiO_x/carbon multi‐layer coating on Si particles. Interaction of SCCO₂ with Si produces a continuous SiO_x layer, which can buffer Si volume change during lithiation/delithiation. In addition, a conformal carbon film is deposited around the Si@SiO_x core. Compared to the carbon film produced via a conventional wet‐chemical method, the SCCO₂‐deposited carbon has significantly fewer oxygen‐containing functional groups and thus higher electronic conductivity. Three types of carbon precursors, namely, glucose, sucrose, and citric acid, in the SCCO₂ syntheses are compared. An eco‐friendly, cost‐effective, and scalable SCCO₂ process is thus developed for the single‐step production of a unique Si@SiO_x@C anode for Li‐ion batteries. The sample prepared using the glucose precursor shows the highest tap density, the lowest charge transfer resistance, and the best Li⁺ transport kinetics among the electrodes, resulting in a high specific capacity of 918 mAh g⁻¹ at 5 A g⁻¹. After 300 charge–discharge cycles, the electrode retains its integrity and the accumulation of the solid electrolyte interphase is low. The great potential of the proposed SCCO₂ synthesis and composite anode for Li‐ion battery applications is demonstrated.

Supercritical CO₂ (SCCO₂), characterized by gas‐like diffusivity, low surface tension, and excellent mass transfer properties, is applied to create a SiO_x/carbon multi‐layer coating on Si particles. Interaction of SCCO₂ with Si produces a continuous SiO_x layer, which can buffer Si volume change during lithiation/delithiation. In addition, a conformal carbon film is deposited around the Si@SiO_x core. Compared to the carbon film produced via a conventional wet‐chemical method, the SCCO₂‐deposited carbon has significantly fewer oxygen‐containing functional groups and thus higher electronic conductivity. Three types of carbon precursors, namely, glucose, sucrose, and citric acid, in the SCCO₂ syntheses are compared. An eco‐friendly, cost‐effective, and scalable SCCO₂ process is thus developed for the single‐step production of a unique Si@SiO_x@C anode for Li‐ion batteries. The sample prepared using the glucose precursor shows the highest tap density, the lowest charge transfer resistance, and the best Li⁺ transport kinetics among the electrodes, resulting in a high specific capacity of 918 mAh g⁻¹ at 5 A g⁻¹. After 300 charge–discharge cycles, the electrode retains its integrity and the accumulation of the solid electrolyte interphase is low. The great potential of the proposed SCCO₂ synthesis and composite anode for Li‐ion battery applications is demonstrated.

Quantum anomalous Hall (QAH) effect generates quantized electric charge Hall conductance without external magnetic field. It requires both nontrivial band topology and time‐reversal symmetry (TRS) breaking. In most cases, one can break the TRS of time‐reversal invariant topological materials to yield QAH effect, which is essentially a topological phase transition. However, conventional topological phase transition induced by external field/stimulus usually needs a route along which the bandgap closes and reopens. Hence, the transition occurs only when the magnitude of field/stimulus is larger than a critical value. In this work the authors propose that using gapless systems, the transition can happen at an arbitrarily weak (but finite) external field strength. For such an unconventional topological phase transition, the bandgap closing is guaranteed by bulk‐edge correspondence and symmetries, while the bandgap reopening is induced by external fields. This concept is demonstrated on the 2D surface states of 3D topological insulators like Bi₂Se₃, which become 2D QAH insulators once a circularly polarized light is turned on, according to the Floquet time crystal theory. The sign of quantized Chern number can be controlled via the chirality of the light. This provides a convenient and dynamic approach to trigger topological phase transitions and create QAH insulators.

Quantum anomalous Hall (QAH) effect generates quantized electric charge Hall conductance without external magnetic field. It requires both nontrivial band topology and time‐reversal symmetry (TRS) breaking. In most cases, one can break the TRS of time‐reversal invariant topological materials to yield QAH effect, which is essentially a topological phase transition. However, conventional topological phase transition induced by external field/stimulus usually needs a route along which the bandgap closes and reopens. Hence, the transition occurs only when the magnitude of field/stimulus is larger than a critical value. In this work the authors propose that using gapless systems, the transition can happen at an arbitrarily weak (but finite) external field strength. For such an unconventional topological phase transition, the bandgap closing is guaranteed by bulk‐edge correspondence and symmetries, while the bandgap reopening is induced by external fields. This concept is demonstrated on the 2D surface states of 3D topological insulators like Bi₂Se₃, which become 2D QAH insulators once a circularly polarized light is turned on, according to the Floquet time crystal theory. The sign of quantized Chern number can be controlled via the chirality of the light. This provides a convenient and dynamic approach to trigger topological phase transitions and create QAH insulators.

Spin current generators are critical components for spintronics-based information processing. In this work, we theoretically and computationally investigate the bulk spin photovoltaic (BSPV) effect for creating DC spin current under light illumination. The only requirement for BSPV is inversion symmetry breaking, thus it applies to a broad range of materials and can be readily integrated with existing semiconductor technologies. The BSPV effect is a cousin of the bulk photovoltaic (BPV) effect, whereby a DC charge current is generated under light. Thanks to the different selection rules on spin and charge currents, a pure spin current can be realized if the system possesses mirror symmetry or inversion-mirror symmetry. The mechanism of BSPV and the role of the electronic relaxation time $$\tau$$ τ are also elucidated. We apply our theory to several distinct materials, including monolayer transition metal dichalcogenides, anti-ferromagnetic bilayer MnBi₂Te₄, and the surface of topological crystalline insulator cubic SnTe.

The development of Li‐excess disordered‐rocksalt (DRX) cathodes for Li‐ion batteries and interpretation through the framework of percolation theory of Li diffusion have steered researchers to consider “Li‐excess” (x > 1.1 in Li_xTM_2−xO₂; TM = transition metal) as being critical to achieving high performance. It is shown that this is not necessary for Mn‐rich DRX‐cathodes demonstrated by Li_1.05Mn_0.90Nb_0.05O₂ and Li_1.20Mn_0.60Nb_0.20O₂, which both deliver high capacity (>250 mAh g⁻¹) regardless of their Li‐excess level. By contextualizing this finding within the broader space of DRX chemistries and confirming with first‐principles calculations, it is revealed that the percolation effect is not crucial at the nanoparticle scale. Instead, Li‐excess is necessary to lower the charging voltage (through the formation of condensed oxygen species upon oxygen oxidation) of certain DRX cathodes, which otherwise would experience difficulties in charging due to their very high TM‐redox potential. The findings reveal the dual roles of Li‐excess – modifying the cathode voltage in addition to promoting Li diffusion through percolation – that must be simultaneously considered to determine the criticality of Li‐excess for high‐capacity DRX cathodes.

The development of Li‐excess disordered‐rocksalt (DRX) cathodes for Li‐ion batteries and interpretation through the framework of percolation theory of Li diffusion have steered researchers to consider “Li‐excess” (x > 1.1 in Li_xTM_2−xO₂; TM = transition metal) as being critical to achieving high performance. It is shown that this is not necessary for Mn‐rich DRX‐cathodes demonstrated by Li_1.05Mn_0.90Nb_0.05O₂ and Li_1.20Mn_0.60Nb_0.20O₂, which both deliver high capacity (>250 mAh g⁻¹) regardless of their Li‐excess level. By contextualizing this finding within the broader space of DRX chemistries and confirming with first‐principles calculations, it is revealed that the percolation effect is not crucial at the nanoparticle scale. Instead, Li‐excess is necessary to lower the charging voltage (through the formation of condensed oxygen species upon oxygen oxidation) of certain DRX cathodes, which otherwise would experience difficulties in charging due to their very high TM‐redox potential. The findings reveal the dual roles of Li‐excess – modifying the cathode voltage in addition to promoting Li diffusion through percolation – that must be simultaneously considered to determine the criticality of Li‐excess for high‐capacity DRX cathodes.

The solid electrolyte interphase (SEI) dictates the cycling stability of lithium‐metal batteries. Here, direct atomic imaging of the SEI's phase components and their spatial arrangement is achieved, using ultralow‐dosage cryogenic transmission electron microscopy. The results show that, surprisingly, a lot of the deposited Li metal has amorphous atomic structure, likely due to carbon and oxygen impurities, and that crystalline lithium carbonate is not stable and readily decomposes when contacting the lithium metal. Lithium carbonate distributed in the outer SEI also continuously reacts with the electrolyte to produce gas, resulting in a dynamically evolving and porous SEI. Sulfur‐containing additives cause the SEI to preferentially generate Li₂SO₄ and overlithiated lithium sulfate and lithium oxide, which encapsulate lithium carbonate in the middle, limiting SEI thickening and enhancing battery life by a factor of ten. The spatial mapping of the SEI gradient amorphous (polymeric → inorganic → metallic) and crystalline phase components provides guidance for designing electrolyte additives.

The solid electrolyte interphase (SEI) dictates the cycling stability of lithium‐metal batteries. Here, direct atomic imaging of the SEI's phase components and their spatial arrangement is achieved, using ultralow‐dosage cryogenic transmission electron microscopy. The results show that, surprisingly, a lot of the deposited Li metal has amorphous atomic structure, likely due to carbon and oxygen impurities, and that crystalline lithium carbonate is not stable and readily decomposes when contacting the lithium metal. Lithium carbonate distributed in the outer SEI also continuously reacts with the electrolyte to produce gas, resulting in a dynamically evolving and porous SEI. Sulfur‐containing additives cause the SEI to preferentially generate Li₂SO₄ and overlithiated lithium sulfate and lithium oxide, which encapsulate lithium carbonate in the middle, limiting SEI thickening and enhancing battery life by a factor of ten. The spatial mapping of the SEI gradient amorphous (polymeric → inorganic → metallic) and crystalline phase components provides guidance for designing electrolyte additives.

This paper shows how terahertz light can drive ultrafast topological phase transitions in monolayer transition metal dichalcogenides (TMDs). The phase transition is induced by the light interaction with both electron and phonon subsystems in the material. The mechanism of such a phase transition is formulated by thermodynamics theory: the Gibbs free energy landscape can be effectively modulated under light, and the relative stability between different (meta‐)stable phases can be switched. This mechanism is applied to TMDs and reversible phase transitions between the topologically trivial 2H and nontrivial 1T′ phases are predicted, providing appropriate light frequency, polarization, and intensity are applied. The large energy barrier on the martensitic transformation path can be significantly reduced, yielding a small energy barrier phase transition with fast kinetics. Compared with other phase transition schemes, light illumination has great advantages, such as its non‐contact nature and easy tunability. The reversible topological phase transition can be applicable in high‐resolution fast data storage and in‐memory computing devices.

The controlled introduction of elastic strains is an appealing strategy for modulating the physical properties of semiconductor materials. With the recent discovery of large elastic deformation in nanoscale specimens as diverse as silicon and diamond, employing this strategy to improve device performance necessitates first-principles computations of the fundamental electronic band structure and target figures-of-merit, through the design of an optimal straining pathway. Such simulations, however, call for approaches that combine deep learning algorithms and physics of deformation with band structure calculations to custom-design electronic and optical properties. Motivated by this challenge, we present here details of a machine learning framework involving convolutional neural networks to represent the topology and curvature of band structures in k-space. These calculations enable us to identify ways in which the physical properties can be altered through “deep” elastic strain engineering up to a large fraction of the ideal strain. Algorithms capable of active learning and informed by the underlying physics were presented here for predicting the bandgap and the band structure. By training a surrogate model with ab initio computational data, our method can identify the most efficient strain energy pathway to realize physical property changes. The power of this method is further demonstrated with results from the prediction of strain states that influence the effective electron mass. We illustrate the applications of the method with specific results for diamonds, although the general deep learning technique presented here is potentially useful for optimizing the physical properties of a wide variety of semiconductor materials.

Nonlinear optical properties, such as bulk photovoltaic effects, possess great potential in energy harvesting, photodetection, rectification, etc. To enable efficient light–current conversion, materials with strong photo-responsivity are highly desirable. In this work, we predict that monolayer Janus transition metal dichalcogenides (JTMDs) in the 1T′ phase possess colossal nonlinear photoconductivity owing to their topological band mixing, strong inversion symmetry breaking, and small electronic bandgap. 1T′ JTMDs have inverted bandgaps on the order of 10 meV and are exceptionally responsive to light in the terahertz (THz) range. By first-principles calculations, we reveal that 1T′ JTMDs possess shift current (SC) conductivity as large as 2300 nm μA V⁻², equivalent to a photo-responsivity of 2800 mA/W. The circular current (CC) conductivity of 1T′ JTMDs is as large as ∼10⁴ nm μA V⁻². These remarkable photo-responsivities indicate that the 1T′ JTMDs can serve as efficient photodetectors in the THz range. We also find that external stimuli such as the in-plane strain and out-of-plane electric field can induce topological phase transitions in 1T′ JTMDs and that the SC can abruptly flip their directions. The abrupt change of the nonlinear photocurrent can be used to characterize the topological transition and has potential applications in 2D optomechanics and nonlinear optoelectronics.

The COVID-19 pandemic has led to widespread shortages of personal protective equipment (PPE) for healthcare workers, including of N95 masks (filtering facepiece respirators; FFRs). These masks are intended for single use but their sterilization and subsequent reuse has the potential to substantially mitigate shortages. Here we investigate PPE sterilization using ionized hydrogen peroxide (iHP), generated by SteraMist equipment (TOMI; Frederick, MD), in a sealed environment chamber. The efficacy of sterilization by iHP was assessed using bacterial spores in biological indicator assemblies. After one or more iHP treatments, five models of N95 masks from three manufacturers were assessed for retention of function based on their ability to form an airtight seal (measured using a quantitative fit test) and filter aerosolized particles. Filtration testing was performed at a university lab and at a National Institute for Occupational Safety and Health (NIOSH) pre-certification laboratory. The data demonstrate that N95 masks sterilized using SteraMist iHP technology retain filtration efficiency up to ten cycles, the maximum number tested to date. A typical iHP environment chamber with a volume of ~ 80 m³ can treat ~ 7000 masks and other items (e.g. other PPE, iPADs), making this an effective approach for a busy medical center.

Spinel LiMn₂O₄, whose electrochemical activity was first reported by Prof. John B. Goodenough's group at Oxford in 1983, is an important cathode material for lithium‐ion batteries that has attracted continuous academic and industrial interest. It is cheap and environmentally friendly, and has excellent rate performance with 3D Li⁺ diffusion channels. However, it suffers from severe degradation, especially under extreme voltages and during high‐temperature operation. Here, the current understanding and future trends of the spinel cathode and its derivatives with cubic lattice symmetry (LiNi_0.5Mn_1.5O₄ that shows high‐voltage stability, and Li‐rich spinels that show reversible hybrid anion‐ and cation‐redox activities) are discussed. Special attention is given to the degradation mechanisms and further development of spinel cathodes, as well as concepts of utilizing the cubic spinel structure to stabilize high‐capacity layered cathodes and as robust framework for high‐rate electrodes. “Good spinel” surface phases like LiNi_0.5Mn_1.5O₄ are distinguished from “bad spinel” surface phases like Mn₃O₄.

Spinel LiMn₂O₄, whose electrochemical activity was first reported by Prof. John B. Goodenough's group at Oxford in 1983, is an important cathode material for lithium‐ion batteries that has attracted continuous academic and industrial interest. It is cheap and environmentally friendly, and has excellent rate performance with 3D Li⁺ diffusion channels. However, it suffers from severe degradation, especially under extreme voltages and during high‐temperature operation. Here, the current understanding and future trends of the spinel cathode and its derivatives with cubic lattice symmetry (LiNi_0.5Mn_1.5O₄ that shows high‐voltage stability, and Li‐rich spinels that show reversible hybrid anion‐ and cation‐redox activities) are discussed. Special attention is given to the degradation mechanisms and further development of spinel cathodes, as well as concepts of utilizing the cubic spinel structure to stabilize high‐capacity layered cathodes and as robust framework for high‐rate electrodes. “Good spinel” surface phases like LiNi_0.5Mn_1.5O₄ are distinguished from “bad spinel” surface phases like Mn₃O₄.

Rechargeable solid-state batteries (SSBs) have emerged as the next-generation energy storage device based on lowered fire hazard and the potential of realizing advanced battery chemistries, such as alkali metal anodes. However, ceramic solid electrolytes (SEs) generally have limited capability in relieving mechanical stress and are not chemically stable against body-centered cubic alkali metals or their alloys with minor solute elements ( β -phase). Swelling-then-retreating of β -phase often causes instabilities such as SE fracture and corrosion as well as the loss of electronic/ionic contact, which leads to high charge-transfer resistance, short-circuiting, etc. These challenges have called for the cooperation from other classes of materials and novel nanocomposite architectures in relieving stress and preserving essential contacts while minimizing detrimental disruptions. In this review, we summarize recent progress in addressing these issues by incorporating other classes of materials such as mixed ion-electron conductor (MIEC) porous interlayers and ion-electron insulator (IEI) binders, in addition to SE and metals (e.g., β -phase and current collectors) that are the traditional SSB components. In particular, we focus on providing theoretical interpretations on how open nanoporous MIEC interlayers manipulate β -phase deposition and stripping behavior and thereby suppress such instabilities, referring to the fundamental thermodynamics and kinetics governing the nucleation and growth of the β -phase. The review concludes by describing avenues for the future design of porous MIEC interlayers for SSBs.

Nanocrystalline materials with superior properties are of great interest. Much is discussed about obtaining nanograins, but little is known about maintaining grain‐size uniformity that is critical for reliability. An especially intriguing question is whether it is possible to achieve a size distribution narrower than what Hillert theoretically predicted for normal grain growth, a possibility suggested—for growth with a higher growth exponent—by the generalized mean‐field theory of Lifshitz, Slyozov, Wagner (LSW), and Hillert but never realized in practice. Following a rationally designed two‐step sintering route, it has been made possible in bulk materials by taking advantage of the large growth exponent in the intermediate sintering stage to form a uniform microstructure despite residual porosity, and freezing the grain growth thereafter while continuing densification to reach full density. The bulk dense Al₂O₃ ceramic thus obtained has an average grain size of 34 nm and a size distribution much narrower than Hillert's prediction. Bulk Al₂O₃ with a grain‐size distribution narrower than the particle‐size distribution of starting powders is also demonstrated, as are highly uniform bulk engineering metals (refractory Mo and W‐Re alloy) and complex functional ceramics (BaTiO₃‐based alloys with superior dielectric strength and energy capacity).

Nanocrystalline materials with superior properties are of great interest. Much is discussed about obtaining nanograins, but little is known about maintaining grain‐size uniformity that is critical for reliability. An especially intriguing question is whether it is possible to achieve a size distribution narrower than what Hillert theoretically predicted for normal grain growth, a possibility suggested—for growth with a higher growth exponent—by the generalized mean‐field theory of Lifshitz, Slyozov, Wagner (LSW), and Hillert but never realized in practice. Following a rationally designed two‐step sintering route, it has been made possible in bulk materials by taking advantage of the large growth exponent in the intermediate sintering stage to form a uniform microstructure despite residual porosity, and freezing the grain growth thereafter while continuing densification to reach full density. The bulk dense Al₂O₃ ceramic thus obtained has an average grain size of 34 nm and a size distribution much narrower than Hillert's prediction. Bulk Al₂O₃ with a grain‐size distribution narrower than the particle‐size distribution of starting powders is also demonstrated, as are highly uniform bulk engineering metals (refractory Mo and W‐Re alloy) and complex functional ceramics (BaTiO₃‐based alloys with superior dielectric strength and energy capacity).

Diamond is thought of as being unbendable, but thin samples can actually deform elastically. Applying relatively large amounts of strain to diamond may shift its electronic properties, which is of interest for a number of applications. Dang et al. elastically stretched micrometer-sized plates of diamond along different crystallographic directions. These relatively large samples show that deep-strain engineering can be accomplished in more uniform diamond specimens and may have a large impact on the electronic properties.

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Cryo-electron microscopy study finds that EC-based electrolyte can exfoliate the graphite surface and destabilize the SEI. Useful additives including FEC, DTD, TPP, and VC can form a stable SEI to protect the graphite anode.

A self‐supporting Al foil anode should be attractive to the lithium‐ion battery (LIB) industry. However, initial attempts at using thin Al foil directly as a LIB anode ends up with extremely large initial Coulombic inefficiency and gross mechanical failures in just a few cycles. This feels incongruent with the expectation that face‐centered cubic Al should have good ductility. In this study, the discrepancy between “electrochemical ductility” and “mechanical ductility” is explained. Unlike “mechanical ductility” based on dislocation slip inside each grain, here it is proposed that “electrochemical ductility” of such high‐capacity alloy foil electrodes should be related to grain boundaries (GB) activities. It is found that after reducing the grain size D > 50 µm of the starting Al foil by shot‐peening treatment, higher GB density (e.g., smaller initial grain size D < 20 µm) greatly alleviates the initial porosity damage after the roll‐to‐roll mechanical prelithiation and significantly improves electrochemical ductility thereafter, with enhanced cycle life in various kinds of full cells. Li_xAl foil also demonstrates surprising air stability with negligible capacity loss even after several hours’ exposure to air. Such thin prelithiated metallic foil anodes are therefore highly competitive against pure Li metal foils.

Space radiation is one of the main concerns in planning long‐term human space missions. There are two main types of hazardous radiation: solar energetic particles (SEP) and galactic cosmic rays (GCR). The intensity and evolution of both depends on solar activity. GCR activity is most enhanced during solar minimum and lowest during solar maximum. The reduction of GCRs is alagging behind solar activity only by 6–12 month. SEP probability and intensity are maximized during solar maximum and are minimized during solar minimum. In this study, we combine models of the particle environment arising due to SEP and GCR with Monte Carlo simulations of radiation propagation inside a spacecraft and phantom. We include 28 fully ionized GCR elements from hydrogen to nickel and consider protons and nine ion species to model the SEP irradiation. Our calculations demonstrate that the optimal time for a flight to Mars would be launching the mission at solar maximum, and that the flight duration should not exceed approximately 4 years.

Solar-driven hydrogen production from water using particulate photocatalysts is considered the most economical and effective approach to produce hydrogen fuel with little environmental concern. However, the efficiency of hydrogen production from water in particulate photocatalysis systems is still low. Here, we propose an efficient biphase photocatalytic system composed of integrated photothermal–photocatalytic materials that use charred wood substrates to convert liquid water to water steam, simultaneously splitting hydrogen under light illumination without additional energy. The photothermal–photocatalytic system exhibits biphase interfaces of photothermally-generated steam/photocatalyst/hydrogen, which significantly reduce the interface barrier and drastically lower the transport resistance of the hydrogen gas by nearly two orders of magnitude. In this work, an impressive hydrogen production rate up to 220.74 μmol h⁻¹ cm⁻² in the particulate photocatalytic systems has been achieved based on the wood/CoO system, demonstrating that the photothermal–photocatalytic biphase system is cost-effective and greatly advantageous for practical applications.

The rapid spread of COVID-19 and disruption of normal supply chains has resulted in severe shortages of personal protective equipment (PPE), particularly devices with few suppliers such as powered air-purifying respirators (PAPRs). A scarcity of information describing design and performance criteria for PAPRs represents a substantial barrier to mitigating shortages. We sought to apply open-source product development (OSPD) to PAPRs to enable alternative sources of supply and further innovation. We describe the design, prototyping, validation, and user testing of locally manufactured, modular, PAPR components, including filter cartridges and blower units, developed by the Greater Boston Pandemic Fabrication Team (PanFab). Two designs, one with a fully custom-made filter and blower unit housing, and the other with commercially available variants (the “Custom” and “Commercial” designs, respectively) were developed; the components in the Custom design are interchangeable with those in Commercial design, although the form factor differs. The engineering performance of the prototypes was measured and safety validated using National Institutes for Occupational Safety and Health (NIOSH)-equivalent tests on apparatus available under pandemic conditions at university laboratories. Feedback was obtained from four individuals; two clinicians working in ambulatory clinical care and two research technical staff for whom PAPR use is standard occupational PPE; these individuals were asked to compare PanFab prototypes to commercial PAPRs from the perspective of usability and suggest areas for improvement. Respondents rated the PanFab Custom PAPR a 4 to 5 on a 5 Likert-scale 1) as compared to current PPE options, 2) for the sense of security with use in a clinical setting, and 3) for comfort compared to standard, commercially available PAPRs. The three other versions of the designs (with a Commercial blower unit, filter, or both) performed favorably, with survey responses consisting of scores ranging from 3 to 5. Engineering testing and clinical feedback demonstrate that the PanFab designs represent favorable alternatives to traditional PAPRs in terms of user comfort, mobility, and sense of security. A nonrestrictive license promotes innovation in respiratory protection for current and future medical emergencies.

The energy density presents the core competitiveness of lithium (Li)‐ion batteries. In conventional Li‐ion batteries, the utilization of the gravimetric/volumetric energy density at the electrode level is unsatisfactory (<84 wt% and <62 vol%, respectively) due to the existence of non‐electrochemical active parts among the 3D porous electrodes, including electrolytes, binders, and carbon additives. These are regarded as indispensable and irreducible components of the electronic and ionic transport network. Here, a dense “all‐electrochem‐active” (AEA) electrode for all‐solid‐state Li batteries is proposed, which is entirely constructed from a family of superior mixed electronic–ionic‐conducting cathodes, to minimize the energy density gap between the accessible and theoretical energy density at the electrode level. Furthermore, with the ionic–electronic‐conductive network self‐supported from the AEA cathode, the dense hybrid sulfur (S)‐based AEA electrode exhibits a high compacted filling rate of 91.8%, which indicates a high energy density of 777 W h kg⁻¹ and 1945 W h L⁻¹ at the electrode level based on the total cathodes and anodes when at 70 °C.

Manipulating materials with atomic-scale precision is essential for the development of a next-generation material design toolbox. Tremendous efforts have been made to advance the compositional, structural, and spatial accuracy of material deposition and patterning. Here, we presented a new reaction pathway to implement the conversions of two-dimensional materials within the atomic-layer thickness at room temperature for electrical dipole manipulation. Not only could various Janus monolayer transition metal dichalcogenides with vertical dipole be realized, but also some heterostructures, including the dipole-nondipole heterostructures (MoS₂-MoSSe) and multiheterostructures (MoS₂-MoSSe-MoSeS-MoSe₂) within the same monolayer host structure are developed, in which the dipoles can be selectively patterned to be zero (MoS₂, MoSe₂), positive (MoSSe), and negative (MoSeS).

Ultrathin and flexible layers containing BaTiO₃ (BTO) nanoparticles, graphene oxide (GO) sheets, and carbon nanotube (CNT) films (BTO/GO@CNT) are used to trap solvated polysulfides and alleviate the shuttle effect in lithium–sulfur (Li–S) batteries.

Ultrathin and flexible layers containing BaTiO₃ (BTO) nanoparticles, graphene oxide (GO) sheets, and carbon nanotube (CNT) films (BTO/GO@CNT) are used to trap solvated polysulfides and alleviate the shuttle effect in lithium–sulfur (Li–S) batteries.

Electrospinning is a popular technique to prepare 1D tubular/fibrous nanomaterials that assemble into 2D/3D architectures. When combined with other material processing techniques such as chemical vapor deposition and hydrothermal treatment, electrospinning enables powerful synthesis strategies that can tailor structural and compositional features of energy storage materials. Herein, a simple description is given of the basic electrospinning technique and its combination with other synthetic approaches. Then its employment in the preparation of frameworks and scaffolds with various functions is introduced, e.g., a graphitic tubular network to enhance the electronic conductivity and structural integrity of the electrodes. Current developments in 3D scaffold structures as a host for Li metal anodes, sulfur cathodes, membrane separators, or as a 3D matrix for polymeric solid‐state electrolytes for rechargeable batteries are presented. The use of 1D electrospun nanomaterials as a nanoreactor for in situ transmission electron microscopy (TEM) observations of the mechanisms of materials synthesis and electrochemical reactions is summarized, which has gained popularity due to easy mechanical manipulation, electron transparency, electronic conductivity, and the easy prepositioning of complex chemical ingredients by liquid‐solution processing. Finally, an outlook on industrial production and future challenges for energy storage materials is given.

A sulfonamide-based electrolyte can greatly improve the cycling stability of the commercial LiCoO₂ cathode at high cut-off voltages in Li metal||LCO batteries by stabilizing the electrode–electrolyte interfaces on both the anode and cathode.

We report here two new semiconducting two-dimensional lead iodide organic–inorganic hybrid compounds with broadband emission and strong photocurrent response.

In molten fluoride salt systems, the chemistry and transport of hydrogen are coupled to its valence state, which controls the balance of tritium leakage and corrosion.

Personal protective equipment (PPE) is crucially important to the safety of both patients and medical personnel, particularly in the event of an infectious pandemic. As the incidence of Coronavirus Disease 2019 (COVID-19) increases exponentially in the United States and many parts of the world, healthcare provider demand for these necessities is currently outpacing supply. In the midst of the current pandemic, there has been a concerted effort to identify viable ways to conserve PPE, including decontamination after use. In this study, we outline a procedure by which PPE may be decontaminated using ultraviolet (UV) radiation in biosafety cabinets (BSCs), a common element of many academic, public health, and hospital laboratories. According to the literature, effective decontamination of N95 respirator masks or surgical masks requires UV-C doses of greater than 1 Jcm⁻², which was achieved after 4.3 hours per side when placing the N95 at the bottom of the BSCs tested in this study. We then demonstrated complete inactivation of the human coronavirus NL63 on N95 mask material after 15 minutes of UV-C exposure at 61 cm (232 μWcm⁻²). Our results provide support to healthcare organizations looking for methods to extend their reserves of PPE.

Airborne particulate matters (PM) pose serious health threats to the population, and efficient filtration is needed for indoor and vehicular environments. However, there is an intrinsic conflict between filtration efficiency, air resistance, and service life. In this study, a two‐stage electrostatically assisted air (EAA) filtration device is designed and the efficiency‐air resistance‐filter life envelope is significantly improved by a thin coating of polydopamine (PDA) on the polyethylene terephthalate (PET) coarse filter by in situ dopamine polymerization. The 8 mm thick EAA PDA‐140@PET filter has a high filtration efficiency of 99.48% for 0.3 µm particles, low air resistance of 9.5 Pa at a filtration velocity of 0.4 m s⁻¹, and steady performance up to 30 d. Compared with the bare PET filter, the penetration rate for 0.3 µm particles is lowered by 20×. The coated PDA is of submicron thickness, 10⁻³ × the gap distance between filter fibers, so low air resistance could be maintained. The filter shows steadily high filtration efficiency and an acceptable increase of air resistance and holds nearly as many particles as its own weight in a 30 day long‐term test. The working mechanism of the EAA coarse filter is investigated, and the materials design criteria are proposed.

Nuclear fission produces 400 GWe which represents 11% of the global electricity output. Uranium is the essential element as both fission fuel and radioactive waste. Therefore, the recovery of uranium is of great importance. Here, an in situ electrolytic deposition method to extract uranium from aqueous solution is reported. A functionalized reduced graphene oxide foam (3D‐FrGOF) is used as the working electrode, which acts as both a hydrogen evolution reaction catalyst and a uranium deposition substrate. The specific electrolytic deposition capacity for U(VI) ions with the 3D‐FrGOF is 4560 mg g⁻¹ without reaching saturation, and the Coulombic efficiency can reach 54%. Moreover, reduction of the uranium concentration in spiked seawater from 3 ppm to 19.9 ppb is achieved, which is lower than the US Environmental Protection Agency uranium limits for drinking water (30 ppb). Furthermore, the collection electrode can be efficiently regenerated and recycled at least nine times without much efficiency fading, by ejecting into 2000 ppm concentrated uranium solution in a second bath with reverse voltage bias. All these findings open new opportunities in using free‐standing 3D‐FrGOF electrode as an advanced separation technique for water treatment.

Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional (3D) perovskites like methylammonium lead iodide (MAPI), which have demonstrated efficient solar cells and photodetectors, are determined to be ferroelastic. Apart from 3D perovskites, Ruddlesden-popper layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain as well as ferroelasticity in 2D layered perovskites is still lacking. Here，using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the existence of ferroelasticity in layered perovskites with layer number more than one, while the 2D perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in 2D perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. Additionally, the absence of methylammonium cations in single layer perovskite is consistent with the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield appreciably, indicating the glissile ferroelastic twin boundaries are benign defects. Our findings provide scientific insights in understanding strain-dependent material properties in 2D perovskites and lead to new potential flexible electronics controlled by strain engineering.

Ferroelasticity represents material domains possessing spontaneous strain that can be switched by external stress. Three-dimensional perovskites like methylammonium lead iodide are determined to be ferroelastic. Layered perovskites have been applied in optoelectronic devices with outstanding performance. However, the understanding of lattice strain and ferroelasticity in layered perovskites is still lacking. Here, using the in-situ observation of switching domains in layered perovskite single crystals under external strain, we discover the evidence of ferroelasticity in layered perovskites with layer number more than one, while the perovskites with single octahedra layer do not show ferroelasticity. Density functional theory calculation shows that ferroelasticity in layered perovskites originates from the distortion of inorganic octahedra resulting from the rotation of aspherical methylammonium cations. The absence of methylammonium cations in single layer perovskite accounts for the lack of ferroelasticity. These ferroelastic domains do not induce non-radiative recombination or reduce the photoluminescence quantum yield.

Identifying the conditions for complete metallization of diamond solely through mechanical strain is an important scientific objective and technological demonstration. Through quantum mechanical calculations, continuum mechanics simulations validated by experiments, and machine learning, we show here that reversible metallization can be achieved in diamond deformed below threshold elastic strain levels for failure or phase transformation. The general method outlined here for deep elastic strain engineering is also applicable to map the strain conditions for indirect-to-direct bandgap transitions. Our method and findings enable extreme alterations of semiconductor properties via strain engineering for possible applications in power electronics, optoelectronics, and quantum sensing.

Li‐rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g⁻¹. However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well‐known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full‐cell performance degradation. Herein, an artificial surface prereconstruction (ASR) for Li_1.2Mn_0.6Ni_0.2O₂ particles with a molten‐molybdate leaching is conducted, which creates a crystal‐dense anion‐redox‐free LiMn_1.5Ni_0.5O₄ shell that completely encloses the LXMO lattice (ASR‐LXMO). Differential electrochemical mass spectroscopy and soft X‐ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR‐LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR‐LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g⁻¹ with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full‐cell matched with a commercial graphite anode and lean (2 g A⁻¹ h⁻¹) electrolyte, ASR‐LXMO shows high capacity retention of 76% after 125 cycles in full‐cell cycling.

Li‐rich metal oxide (LXMO) cathodes have attracted intense interest for rechargeable batteries because of their high capacity above 250 mAh g⁻¹. However, the side effects of hybrid anion and cation redox (HACR) reactions, such as oxygen release and phase collapse that result from global oxygen migration (GOM), have prohibited the commercialization of LXMO. GOM not only destabilizes the oxygen sublattice in cycling, aggravating the well‐known voltage fading, but also intensifies electrolyte decomposition and Mn dissolution, causing severe full‐cell performance degradation. Herein, an artificial surface prereconstruction (ASR) for Li_1.2Mn_0.6Ni_0.2O₂ particles with a molten‐molybdate leaching is conducted, which creates a crystal‐dense anion‐redox‐free LiMn_1.5Ni_0.5O₄ shell that completely encloses the LXMO lattice (ASR‐LXMO). Differential electrochemical mass spectroscopy and soft X‐ray absorption spectroscopy analyses demonstrate that GOM is shut down in cycling, which not only stabilizes HACR in ASR‐LXMO, but also mitigates the electrolyte decomposition and Mn dissolution. ASR‐LXMO displays greatly stabilized cycling performance as it retains 237.4 mAh g⁻¹ with an average discharge voltage of 3.30 V after 200 cycles. More crucially, while the pristine LXMO cycling cannot survive 90 cycles in a pouch full‐cell matched with a commercial graphite anode and lean (2 g A⁻¹ h⁻¹) electrolyte, ASR‐LXMO shows high capacity retention of 76% after 125 cycles in full‐cell cycling.

Hydrogen segregation at grain boundaries induces micrometer-scale dislocation motion.

The repair of damaged Ni‐based superalloy single‐crystal turbine blades has been a long‐standing challenge. Additive manufacturing by an electron beam is promising to this end, but there is a formidable obstacle: either the residual stress and γ/γ  ′ microstructure in the single‐crystalline fusion zone after e‐beam melting are unacceptable (e.g., prone to cracking), or, after solutionizing heat treatment, recrystallization occurs, bringing forth new grains that degrade the high‐temperature creep properties. Here, a post‐3D printing recovery protocol is designed that eliminates the driving force for recrystallization, namely, the stored energy associated with the high retained dislocation density, prior to standard solution treatment and aging. The post‐electron‐beam‐melting, pre‐solutionizing recovery via sub‐solvus annealing is rendered possible by the rafting (i.e., directional coarsening) of γ  ′ particles that facilitates dislocation rearrangement and annihilation. The rafted microstructure is removed in subsequent solution treatment, leaving behind a damage‐free and residual‐stress‐free single crystal with uniform γ  ′ precipitates indistinguishable from the rest of the turbine blade. This discovery offers a practical means to keep 3D‐printed single crystals from cracking due to unrelieved residual stress, or stress‐relieved but recrystallizing into a polycrystalline microstructure, paving the way for additive manufacturing to repair, restore, and reshape any superalloy single‐crystal product.

The repair of damaged Ni‐based superalloy single‐crystal turbine blades has been a long‐standing challenge. Additive manufacturing by an electron beam is promising to this end, but there is a formidable obstacle: either the residual stress and γ/γ  ′ microstructure in the single‐crystalline fusion zone after e‐beam melting are unacceptable (e.g., prone to cracking), or, after solutionizing heat treatment, recrystallization occurs, bringing forth new grains that degrade the high‐temperature creep properties. Here, a post‐3D printing recovery protocol is designed that eliminates the driving force for recrystallization, namely, the stored energy associated with the high retained dislocation density, prior to standard solution treatment and aging. The post‐electron‐beam‐melting, pre‐solutionizing recovery via sub‐solvus annealing is rendered possible by the rafting (i.e., directional coarsening) of γ  ′ particles that facilitates dislocation rearrangement and annihilation. The rafted microstructure is removed in subsequent solution treatment, leaving behind a damage‐free and residual‐stress‐free single crystal with uniform γ  ′ precipitates indistinguishable from the rest of the turbine blade. This discovery offers a practical means to keep 3D‐printed single crystals from cracking due to unrelieved residual stress, or stress‐relieved but recrystallizing into a polycrystalline microstructure, paving the way for additive manufacturing to repair, restore, and reshape any superalloy single‐crystal product.

Rechargeable aluminum batteries (RABs) are extensively developed due to their cost‐effectiveness, eco‐friendliness, and low flammability and the earth abundance of their electrode materials. However, the commonly used RAB ionic liquid (IL) electrolyte is highly moisture‐sensitive and corrosive. To address these problems, a 4‐ethylpyridine/AlCl₃ IL is proposed. The effects of the AlCl₃ to 4‐ethylpyridine molar ratio on the electrode charge–discharge properties are systematically examined. A maximum graphite capacity of 95 mAh g⁻¹ is obtained at 25 mA g⁻¹. After 1000 charge–discharge cycles, ≈85% of the initial capacity can be retained. In situ synchrotron X‐ray diffraction is employed to examine the electrode reaction mechanism. In addition, low corrosion rates of Al, Cu, Ni, and carbon‐fiber paper electrodes are confirmed in the 4‐ethylpyridine/AlCl₃ IL. When opened to the ambient atmosphere, the measured capacity of the graphite cathode is only slightly lower than that found in a N₂‐filled glove box; moreover, the capacity retention upon 100 cycles is as high as 75%. The results clearly indicate the great potential of this electrolyte for practical RAB applications.

Cycling LiCoO₂ to above 4.5 V for higher capacity is enticing; however, hybrid O anion‐ and Co cation‐redox (HACR) at high voltages facilitates intrinsic O^α− (α < 2) migration, causing oxygen loss, phase collapse, and electrolyte decomposition that severely degrade the battery cyclability. Hereby, commercial LiCoO₂ particles are operando treated with selenium, a well‐known anti‐aging element to capture oxygen‐radicals in the human body, showing an “anti‐aging” effect in high‐voltage battery cycling and successfully stopping the escape of oxygen from LiCoO₂ even when the cathode is cycled to 4.62 V. Ab initio calculation and soft X‐ray absorption spectroscopy analysis suggest that during deep charging, the precoated Se will initially substitute some mobile O^α− at the charged LiCoO₂ surface, transplanting the pumped charges from O^α− and reducing it back to O²⁻ to stabilize the oxygen lattice in prolonged cycling. As a result, the material retains 80% and 77% of its capacity after 450 and 550 cycles under 100 mA g⁻¹ in 4.57 V pouch full‐cells matched with a graphite anode and an ultralean electrolyte (2 g Ah⁻¹).

A new “full fluorosulfonyl” (FFS) electrolyte is developed for highly reversible 4 V class lithium-metal batteries (LMBs).

An integral LiMn_1.5Ni_0.5O₄ shell completely wets ∼10 μm LiCoO₂ single crystals to cut off global oxygen migration and enables >4.6 V cycling.

Graphite and lithium metal are two classic anode materials and their composite has shown promising performance for rechargeable batteries. However, it is generally accepted that Li metal wets graphite poorly, causing its spreading and infiltration difficult. Here we show that graphite can either appear superlithiophilic or lithiophobic, depending on the local redox potential. By comparing the wetting performance of highly ordered pyrolytic graphite, porous carbon paper (PCP), lithiated PCP and graphite powder, we demonstrate that the surface contaminants that pin the contact-line motion and cause contact-angle hysteresis have their own electrochemical-stability windows. The surface contaminants can be either removed or reinforced in a time-dependent manner, depending on whether the reducing agents (C6→LiC6) or the oxidizing agents (air, moisture) dominate in the ambient environment, leading to bifurcating dynamics of either superfast or superslow wetting. Our findings enable new fabrication technology for Li–graphite composite with a controllable Li-metal/graphite ratio and present great promise for the mass production of Li-based anodes for use in high-energy-density batteries.

A material potentially exhibiting multiple crystalline phases with distinct optoelectronic properties can serve as a phase-change memory material. The sensitivity and kinetics can be enhanced when the two competing phases have large electronic structure contrast and the phase change process is diffusionless and martensitic. In this work, we theoretically and computationally illustrate that such a phase transition could occur in the group-IV monochalcogenide SnSe compound, which can exist in the quantum topologically trivial Pnma-SnSe and nontrivial $$Fm\bar 3m$$ F m 3 ¯ m -SnSe phases. Furthermore, owing to the electronic band structure differences of these phases, a large contrast in the optical responses in the THz region is revealed. According to the thermodynamic theory for a driven dielectric medium, optomechanical control to trigger a topological phase transition using a linearly polarized laser with selected frequency, power and pulse duration is proposed. We further estimate the critical optical electric field to drive a barrierless transition that can occur on the picosecond timescale. This light actuation strategy does not require fabrication of mechanical contacts or electrical leads and only requires transparency. We predict that an optically driven phase transition accompanied by a large entropy difference can be used in an “optocaloric” cooling device.

Self‐assembled membranes with periodic wrinkled patterns are the critical building blocks of various flexible electronics, where the wrinkles are usually designed and fabricated to provide distinct functionalities. These membranes are typically metallic and organic materials with good ductility that are tolerant of complex deformation. However, the preparation of oxide membranes, especially those with intricate wrinkle patterns, is challenging due to their inherently strong covalent or ionic bonding, which usually leads to material crazing and brittle fracture. Here, wrinkle‐patterned BaTiO₃ (BTO)/poly(dimethylsiloxane) membranes with finely controlled parallel, zigzag, and mosaic patterns are prepared. The BTO layers show excellent flexibility and can form well‐ordered and periodic wrinkles under compressive in‐plane stress. Enhanced piezoelectricity is observed at the sites of peaks and valleys of the wrinkles where the largest strain gradient is generated. Atomistic simulations further reveal that the excellent elasticity and the correlated coupling between polarization and strain/strain gradient are strongly associated with ferroelectric domain switching and continuous dipole rotation. The out‐of‐plane polarization is primarily generated at compressive regions, while the in‐plane polarization dominates at the tensile regions. The wrinkled ferroelectric oxides with differently strained regions and correlated polarization distributions would pave a way toward novel flexible electronics.

Physical neural networks made of analog resistive switching processors are promising platforms for analog computing. State-of-the-art resistive switches rely on either conductive filament formation or phase change. These processes suffer from poor reproducibility or high energy consumption, respectively. Herein, we demonstrate the behavior of an alternative synapse design that relies on a deterministic charge-controlled mechanism, modulated electrochemically in solid-state. The device operates by shuffling the smallest cation, the proton, in a three-terminal configuration. It has a channel of active material, WO₃. A solid proton reservoir layer, PdH_x, also serves as the gate terminal. A proton conducting solid electrolyte separates the channel and the reservoir. By protonation/deprotonation, we modulate the electronic conductivity of the channel over seven orders of magnitude, obtaining a continuum of resistance states. Proton intercalation increases the electronic conductivity of WO₃ by increasing both the carrier density and mobility. This switching mechanism offers low energy dissipation, good reversibility, and high symmetry in programming.

Capture and storage of volatile radionuclides that result from processing of used nuclear fuel is a major challenge. Solid adsorbents, in particular ultra-microporous metal-organic frameworks, could be effective in capturing these volatile radionuclides, including ⁸⁵Kr. However, metal-organic frameworks are found to have higher affinity for xenon than for krypton, and have comparable affinity for Kr and N₂. Also, the adsorbent needs to have high radiation stability. To address these challenges, here we evaluate a series of ultra-microporous metal-organic frameworks, SIFSIX-3-M (M = Zn, Cu, Ni, Co, or Fe) for their capability in ⁸⁵Kr separation and storage using a two-bed breakthrough method. These materials were found to have higher Kr/N₂ selectivity than current benchmark materials, which leads to a notable decrease in the nuclear waste volume. The materials were systematically studied for gamma and beta irradiation stability, and SIFSIX-3-Cu is found to be the most radiation resistant.

Accelerator-based ion-beam irradiation has been widely used to mimic the effects of neutron radiation damage in nuclear reactors. However, ion radiation is most often monodisperse in the incoming ions’ momentum direction, leading to excessive polarization in defect distribution, while the scattering under neutron irradiation is often more isotropic and has less radiation-induced polarization. Mitigation of the excess-polarization as well as the damage non-uniformity artifact might be crucial for making the simulation of neutron radiation by ion-beam radiation more realistic. In this work, a general radiation polarization theory in treating radiation as external polar stimuli is established to understand the natural material responses in different contexts, and the possibility to correct the defect polarization artifact in ion-beam irradiation. Inspired by Magic Angle Spinning in Nuclear Magnetic Resonance, we present a precise sample spinning strategy to reduce the point-defect imbalance effect in ion-beam irradiation. It can be seen that with optimized surface inclination angle and the axis of sample rotation, the vacancy-interstitial population imbalance, as well as the damage profile non-uniformity in a designated region in the target are both reduced. It is estimated that sample spinning frequency on the order of kHz should be sufficient to scramble the ion momentum monodispersity for commonly taken ion fluxes and dose rates, which is experimentally feasible.

Lean electrolyte (small E/S ratio) is urgently needed to achieve high practical energy densities in Li–S batteries, but there is a distinction between the cathode's absorbed electrolyte (AE) which is cathode‐intrinsic and total added electrolyte (E) which depends on cell geometry. While total pore volume in sulfur cathodes affects AE/S and performance, it is shown here that pore morphology, size, connectivity, and fill factor all matter. Compared to conventional thermally dried sulfur cathodes that usually render “open lakes” and closed pores, a freeze‐dried and compressed (FDS‐C) sulfur cathode is developed with a canal‐capillary pore structure, which exhibits high mean performance and greatly reduces cell‐to‐cell variation, even at high sulfur loading (14.2 mg cm⁻²) and ultralean electrolyte condition (AE/S = 1.2 µL mg⁻¹). Interestingly, as AE/S is swept from 2 to 1.2 µL mg⁻¹, the electrode pores go from fully flooded to semi‐flooded, and the coin cell still maintains function until (AE/S)_min ≈ 1.2 µL mg⁻¹ is reached. When scaled up to Ah‐level pouch cells, the full‐cell energy density can reach 481 Wh kg⁻¹ as its E/S ≈ AE/S ratio can be reduced to 1.2 µL mg⁻¹, proving high‐performance pouch cells can actually be working in the ultralean, semi‐flooded regime.

A practical solution is presented to increase the stability of 4.45 V LiCoO₂ via high‐temperature Ni doping, without adding any extra synthesis step or cost. How a putative uniform bulk doping with highly soluble elements can profoundly modify the surface chemistry and structural stability is identified from systematic chemical and microstructural analyses. This modification has an electronic origin, where surface‐oxygen‐loss induced Co reduction that favors the tetrahedral site and causes damaging spinel phase formation is replaced by Ni reduction that favors octahedral site and creates a better cation‐mixed structure. The findings of this study point to previously unspecified surface effects on the electrochemical performance of battery electrode materials hidden behind an extensively practiced bulk doping strategy. The new understanding of complex surface chemistry is expected to help develop higher‐energy‐density cathode materials for rechargeable batteries.

Self‐supporting Sn foil is a promising high‐volumetric‐capacity anode for lithium ion batteries (LIBs), but it suffers from low initial Coulombic efficiency (ICE). Here, mechanical prelithiation is adopted to improve ICE, and it is found that Sn foils with coarser grains are prone to cause electrode damage. To mitigate damage and prepare thinner lithiated electrodes, 3Ag0.5Cu96.5Sn foil is used that has more refined grains (5–10 µm) instead of Sn (50–100 µm), where the abundant grain boundaries (GBs) offer more sliding systems to release stress and reduce deep fractures. Thus, the thickness of Li_x3Ag0.5Cu96.5Sn can be reduced to 50 µm, compared to 100 µm Li_xSn. When the foils contact open air, the Sn‐Li‐O(H) products are more stable than Li‐O(H), thus Li_x3Ag0.5Cu96.5Sn shows outstanding air stability. The as‐prepared 50 µm foil anode achieves stable 200 cycles in LiFePO₄//Li_x3Ag0.5Cu96.5Sn full cell (≈2.65 mAh cm⁻²) and the capacity retention is 95%. Even at 5C, the capacity of Li_x3Ag0.5Cu96.5Sn is still up to ≈1.8 mAh cm⁻². The cycle life of NCM523//Li_x3Ag0.5Cu96.5Sn full cell exceeds that of NCM523//Li. Furthermore, 70 µm Li_x3Ag0.5Cu96.5Sn is used as double‐sided anode for a 3 cm × 2.8 cm pouch cell and its actual volumetric capacity density is 674 mAh cm⁻³ after 50 cycles.

Self‐supporting Sn foil is a promising high‐volumetric‐capacity anode for lithium ion batteries (LIBs), but it suffers from low initial Coulombic efficiency (ICE). Here, mechanical prelithiation is adopted to improve ICE, and it is found that Sn foils with coarser grains are prone to cause electrode damage. To mitigate damage and prepare thinner lithiated electrodes, 3Ag0.5Cu96.5Sn foil is used that has more refined grains (5–10 µm) instead of Sn (50–100 µm), where the abundant grain boundaries (GBs) offer more sliding systems to release stress and reduce deep fractures. Thus, the thickness of Li_x3Ag0.5Cu96.5Sn can be reduced to 50 µm, compared to 100 µm Li_xSn. When the foils contact open air, the Sn‐Li‐O(H) products are more stable than Li‐O(H), thus Li_x3Ag0.5Cu96.5Sn shows outstanding air stability. The as‐prepared 50 µm foil anode achieves stable 200 cycles in LiFePO₄//Li_x3Ag0.5Cu96.5Sn full cell (≈2.65 mAh cm⁻²) and the capacity retention is 95%. Even at 5C, the capacity of Li_x3Ag0.5Cu96.5Sn is still up to ≈1.8 mAh cm⁻². The cycle life of NCM523//Li_x3Ag0.5Cu96.5Sn full cell exceeds that of NCM523//Li. Furthermore, 70 µm Li_x3Ag0.5Cu96.5Sn is used as double‐sided anode for a 3 cm × 2.8 cm pouch cell and its actual volumetric capacity density is 674 mAh cm⁻³ after 50 cycles.

Mass transport driven by temperature gradient is commonly seen in fluids. However, here we demonstrate that when drawing a cold nano-tip off a hot solid substrate, thermomigration can be so rampant that it can be exploited for producing single-crystalline aluminum, copper, silver and tin nanowires. This demonstrates that in nanoscale objects, solids can mimic liquids in rapid morphological changes, by virtue of fast surface diffusion across short distances. During uniform growth, a thin neck-shaped ligament containing a grain boundary (GB) usually forms between the hot and the cold ends, sustaining an extremely high temperature gradient that should have driven even larger mass flux, if not counteracted by the relative sluggishness of plating into the GB and the resulting back stress. This GB-containing ligament is quite robust and can adapt to varying drawing directions and velocities, imparting good controllability to the nanowire growth in a manner akin to Czochralski crystal growth.

Poor ductility is one limiting factor in widespread use of strong but lightweight magnesium alloys in cars, trains, and planes. The usual way to try to circumvent this poor ductility is by adding other elements, which can be costly. Liu et al. show that very small samples of pure magnesium are much more ductile than previously believed (see the Perspective by Proust). The small samples suppress the deformation twinning that causes fractures in larger samples. Avoiding this mechanism should allow development of high-ductility magnesium and other metal alloys.

Science , this issue p. 73 ; see also p. 30

Traditional semiconductor fabrication methods, such as lithography and etching, have been sufficient for the needs of integrated circuits over past decades. Their applicability has also been demonstrated in emerging 2D materials, which offers facile processing over large lateral dimensions, while unique and remarkable properties due to the confinement within atomic thicknesses. Nevertheless, each fabrication step adds cost to the manufacturing and increases the possibility of quality degradation. Here, we developed a method to directly synthesize arbitrary monolayer molybdenum disulfide patterns with high spatial resolution, excellent homogeneity, and electrical performance on insulating SiO ₂ /Si. Significantly, our on-demand method allows for the repeated growth of patterned 2D materials with preserved structural integrity and material qualities, paving the way for simpler and cost-effective fabrication.

A lithium metal anode suffers from a short cycle life, and the parasitic reactions of lithium with electrolytes are widely observed.

ZnS (short arms)–ZnSe (long arms)/ZnS shell nanorod couple heterostructures was prepared and over-coated by a CdS layer to generate blue emission.

Deforming a material to a large extent without inelastic relaxation can result in unprecedented properties. However, the optimal deformation state is buried within the vast continua of choices available in the strain space. Here we advance a unique and powerful strategy to circumvent conventional trial-and-error methods, and adopt artificial intelligence techniques for rationally designing the most energy-efficient pathway to achieve a desirable material property such as the electronic bandgap. The broad framework for tailoring any target figure of merit, for any material using machine learning, opens up opportunities to adapt elastic strain engineering of properties and performance in devices and systems in a controllable and efficient manner, for potential applications in microelectronics, optoelectronics, photonics, and energy technologies.

Fluid‐like sliding graphenes but with solid‐like out‐of‐plane compressive rigidity offer unique opportunities for achieving unusual physical and chemical properties for next‐generation interfacial technologies. Of particular interest in the present study are graphenes with specific chemical functionalization that can predictably promote adhesion and wetting to substrate and ultralow frictional sliding structures. Lubricity between stainless steel (SS) and diamond‐like carbon (DLC) is experimentally demonstrated with densely functionalized graphenes displaying dynamic intersheet bonds that mechanically transform into stable tribolayers. The macroscopic lubricity evolves through the formation of a thin film of an interconnected graphene matrix that provides a coefficient of friction (COF) of 0.01. Mechanical sliding generates complex folded graphene structures wherein equilibrated covalent chemical linkages impart rigidity and stability to the films examined in macroscopic friction tests. This new approach to frictional reduction has broad implications for manufacturing, transportation, and aerospace.

A vector-space formalism is developed for optimizing single-atom manipulation outcomes under focused electron irradiation.

SIB with hard carbon anode is getting competitive vs. LIB, but one needs to be careful in assessing capacity and cycle life with conventional half-cell tests. New guidelines are provided for half-cell and full-cell tests and understanding the results.

The 5 V electrolyte shows great compatibility with LiNi_0.5Mn_1.5O₄ and graphite electrodes, high thermal stability, and good wettability toward commercial separators.

The 5 V electrolyte shows great compatibility with LiNi_0.5Mn_1.5O₄ and graphite electrodes, high thermal stability, and good wettability toward commercial separators.

A random Li₄Mn₅O₁₂-like nanoparticulate cathode demonstrates a high reversible capacity (212 mA h g⁻¹) with a hybrid cation-redox capacity (108 mA h g⁻¹) and anion-redox capacity (103 mA h g⁻¹).

A random Li₄Mn₅O₁₂-like nanoparticulate cathode demonstrates a high reversible capacity (212 mA h g⁻¹) with a hybrid cation-redox capacity (108 mA h g⁻¹) and anion-redox capacity (103 mA h g⁻¹).

A design to achieve unprecedented mechanical properties for ferroelastic smart materials by regulating martensitic transformations through concentration modulation by spinodal decomposition and pre-straining is described.

Tunable photoluminescent nitrogen-doped graphene and graphitic carbon nitride (g-C₃N₄) quantum dots are synthesized via a facile solid-phase microwave-assisted (SPMA) technique utilizing the pyrolysis of citric acid and urea precursors.

The development of photonic integrated circuits would benefit from a wider selection of materials that can strongly control near-infrared (NIR) light. Transition metal dichalcogenides (TMDs) have been explored extensively for visible spectrum optoelectronics; the NIR properties of these layered materials have been less-studied. The measurement of optical constants is the foremost step to qualify TMDs for use in NIR photonics. Here, we measure the complex optical constants for select sulfide TMDs (bulk crystals of MoS2, TiS2, and ZrS2) via spectroscopic ellipsometry in the visible-to-NIR range. We find that the presence of native oxide layers (measured by transmission electron microscopy) significantly modifies the observed optical constants and need to be modeled to extract actual optical constants. We support our measurements with density functional theory calculations and further predict large refractive index contrast between different phases. We further propose that TMDs could find use as photonic phase-change materials, by designing alloys that are thermodynamically adjacent to phase boundaries between competing crystal structures, to realize martensitic (i.e., displacive, order–order) switching.

A new group of two-dimensional layered materials with intrinsic ferroelectricity and antiferroelectricity are identified through first-principles calculations.

A new group of two-dimensional layered materials with intrinsic ferroelectricity and antiferroelectricity are identified through first-principles calculations.

Li_xSn foil anode prepared by mechanical prelithiation suppresses gassing and achieves stable full-cell cycling in lithium ion batteries.

High-quality ferroelectric materials, which polarize in response to an electric field, are usually oxides that crack when bent. Dong et al. found that high-quality membranes of barium titanate are surprisingly flexible and super-elastic. These films accommodate large strains through dynamic evolution of nanodomains during deformation. This discovery is important for developing more robust flexible devices.

Science , this issue p. 475

A family of strong yet removable 1- to 2-nm-thick ultrathin monolayer is developed as a corrosion inhibitor for 2-dimensional materials that significantly prolong lifetime while protecting optoelectronic properties in both ambient and harsh chemical or thermal environments. This method is low in toxicity and can be applied to arbitrary substrate with no size limit.

SnO₂@CMK‐8 composite, a highly promising anode for Na‐ion batteries (NIBs), was incorporated with polyvinylidene difluoride (PVDF), sodium carboxymethylcellulose (NaCMC), sodium polyacrylate (NaPAA), and NaCMC/NaPAA mixed binders to optimize the electrode sodiation/desodiation properties. Synergistic effects between NaCMC and NaPAA led to the formation of an effective protective film on the electrode. This coating layer not only increased the charge–discharge Coulombic efficiency, suppressing the accumulation of solid–electrolyte interphases, but also kept the SnO₂ nanoparticles in the CMK‐8 matrix, preventing the agglomeration and removal of oxide upon cycling. The adhesion strength and stability towards the electrolyte of the binders were evaluated. In addition, the charge–transfer resistance and apparent Na⁺ diffusion of the SnO₂@CMK‐8 electrodes with various binders were examined and post‐mortem analyses were conducted. With NaCMC/NaPAA binder, exceptional electrode capacities of 850 and 425 mAh g⁻¹ were obtained at charge–discharge rates of 20 and 2000 mA g⁻¹, respectively. After 300 cycles, 90 % capacity retention was achieved. The thermal reactivity of the sodiated electrodes was studied by using differential scanning calorimetry. The binder effects on NIB safety, in terms of thermal runaway, are discussed.

SnO₂@CMK‐8 composite, a highly promising anode for Na‐ion batteries (NIBs), was incorporated with polyvinylidene difluoride (PVDF), sodium carboxymethylcellulose (NaCMC), sodium polyacrylate (NaPAA), and NaCMC/NaPAA mixed binders to optimize the electrode sodiation/desodiation properties. Synergistic effects between NaCMC and NaPAA led to the formation of an effective protective film on the electrode. This coating layer not only increased the charge–discharge Coulombic efficiency, suppressing the accumulation of solid–electrolyte interphases, but also kept the SnO₂ nanoparticles in the CMK‐8 matrix, preventing the agglomeration and removal of oxide upon cycling. The adhesion strength and stability towards the electrolyte of the binders were evaluated. In addition, the charge–transfer resistance and apparent Na⁺ diffusion of the SnO₂@CMK‐8 electrodes with various binders were examined and post‐mortem analyses were conducted. With NaCMC/NaPAA binder, exceptional electrode capacities of 850 and 425 mAh g⁻¹ were obtained at charge–discharge rates of 20 and 2000 mA g⁻¹, respectively. After 300 cycles, 90 % capacity retention was achieved. The thermal reactivity of the sodiated electrodes was studied by using differential scanning calorimetry. The binder effects on NIB safety, in terms of thermal runaway, are discussed.

The removal of highly toxic, ultra-dilute contaminants of concern has been a primary challenge for clean water technologies. Chromium and arsenic are among the most prevalent heavy metal pollutants in urban and agricultural waters, with current separation processes having severe limitations due to lack of molecular selectivity. Here, we report redox-active metallopolymer electrodes for the selective electrochemical removal of chromium and arsenic. An uptake greater than 100 mg Cr/g adsorbent can be achieved electrochemically, with a 99% reversible working capacity, with the bound chromium ions released in the less harmful trivalent form. Furthermore, we study the metallopolymer response during electrochemical modulation by in situ transmission electron microscopy. The underlying mechanisms for molecular selectivity are investigated through electronic structure calculations, indicating a strong charge transfer to the heavy metal oxyanions. Finally, chromium and arsenic are remediated efficiently at concentrations as low as 100 ppb, in the presence of over 200-fold excess competing salts.

Despite their energy-efficient merits as promising light-weight structural materials, magnesium (Mg) based alloys suffer from inadequate corrosion resistance. One primary reason is that the native surface film on Mg formed in air mainly consists of Mg(OH)₂ and MgO, which is porous and unprotective, especially in humid environments. Here, we demonstrate an environmentally benign method to grow a protective film on the surface of Mg/Mg alloy samples at room temperature, via a direct reaction of already-existing surface film with excited CO_2. Moreover, for samples that have been corroded obviously on surface, the corrosion products can be converted directly to create a new protective surface. Mechanical tests show that compared with untreated samples, the protective layer can elevate the yield stress, suppress plastic instability and prolong compressive strains without peeling off from the metal surface. This environmentally friendly surface treatment method is promising to protect Mg alloys, including those already-corroded on the surface.

Despite their energy-efficient merits as promising light-weight structural materials, magnesium (Mg) based alloys suffer from inadequate corrosion resistance. One primary reason is that the native surface film on Mg formed in air mainly consists of Mg(OH)₂ and MgO, which is porous and unprotective, especially in humid environments. Here, we demonstrate an environmentally benign method to grow a protective film on the surface of Mg/Mg alloy samples at room temperature, via a direct reaction of already-existing surface film with excited CO_2. Moreover, for samples that have been corroded obviously on surface, the corrosion products can be converted directly to create a new protective surface. Mechanical tests show that compared with untreated samples, the protective layer can elevate the yield stress, suppress plastic instability and prolong compressive strains without peeling off from the metal surface. This environmentally friendly surface treatment method is promising to protect Mg alloys, including those already-corroded on the surface.

Vanadium‐based fluorophosphates are promising sodium‐ion battery cathode materials. Different phases of NaVPO₄F and Na₃V₂(PO₄)₂F₃ are reported in the literature. However, experiments in this work suggest that there could be confusions about the single‐phase NaVPO₄F in solid‐state synthesis. Here, systematic investigation of the mechanism underlying structural and compositional evolution of solid‐state synthesis (NaF:VPO₄ = 1:1) is determined by in situ and ex situ X‐ray diffraction and electrochemical measurements. Three reactions—3NaF + 3VPO₄ → Na₃V₂(PO₄)₂F₃ + VPO₄ (up to 500 °C), Na₃V₂(PO₄)₂F₃ + VPO₄ → Na₃V₂(PO₄)₃ + VF₃↑ (600–800 °C), and 2Na₃V₂(PO₄)₃ → 2(VO)₂P₂O₇ + Na₄P₂O₇ + amorphous products (above 800 °C)—are validated by in situ XRD and thermogravimetric analysis/differential scanning calorimetry. None of the products reported in this work is consistent with single‐phase NaVPO₄F at any temperature. It is speculated that the assignments of I4/mmm and C₂/c NaVPO₄F from solid‐state synthesis are incorrect, which are instead multiphase mixtures of Le Meins' Na₃V₂(PO₄)₂F₃, unreacted VPO₄, and hexagonal Na₃V₂(PO₄)₃. Liquid‐electrolyte‐based electrochemical ion exchange of LiVPO₄F produces a tavorite NaVPO₄F structure, which is very different from Le Meins' family of Na₃Al₂(PO₄)₂F₃ polymorphs.

Vanadium‐based fluorophosphates are promising sodium‐ion battery cathode materials. Different phases of NaVPO₄F and Na₃V₂(PO₄)₂F₃ are reported in the literature. However, experiments in this work suggest that there could be confusions about the single‐phase NaVPO₄F in solid‐state synthesis. Here, systematic investigation of the mechanism underlying structural and compositional evolution of solid‐state synthesis (NaF:VPO₄ = 1:1) is determined by in situ and ex situ X‐ray diffraction and electrochemical measurements. Three reactions—3NaF + 3VPO₄ → Na₃V₂(PO₄)₂F₃ + VPO₄ (up to 500 °C), Na₃V₂(PO₄)₂F₃ + VPO₄ → Na₃V₂(PO₄)₃ + VF₃↑ (600–800 °C), and 2Na₃V₂(PO₄)₃ → 2(VO)₂P₂O₇ + Na₄P₂O₇ + amorphous products (above 800 °C)—are validated by in situ XRD and thermogravimetric analysis/differential scanning calorimetry. None of the products reported in this work is consistent with single‐phase NaVPO₄F at any temperature. It is speculated that the assignments of I4/mmm and C₂/c NaVPO₄F from solid‐state synthesis are incorrect, which are instead multiphase mixtures of Le Meins' Na₃V₂(PO₄)₂F₃, unreacted VPO₄, and hexagonal Na₃V₂(PO₄)₃. Liquid‐electrolyte‐based electrochemical ion exchange of LiVPO₄F produces a tavorite NaVPO₄F structure, which is very different from Le Meins' family of Na₃Al₂(PO₄)₂F₃ polymorphs.

Manganese oxide (MnO₂) has long been investigated as a pseudo-capacitive material for fabricating fiber-shaped supercapacitors but its poor electrical conductivity and its brittleness are clear drawbacks. Here we electrochemically insert nanostructured MnO₂domains into continuously interconnected carbon nanotube (CNT) networks, thus imparting both electrical conductivity and mechanical durability to MnO₂. In particular, we synthesize a fiber-shaped coaxial electrode with a nickel fiber as the current collector (Ni/CNT/MnO₂); the thickness of the CNT/MnO₂hybrid nanostructured shell is approximately 150 μm and the electrode displays specific capacitances of 231 mF cm⁻¹. When assembling symmetric devices featuring Ni/CNT/MnO₂coaxial electrodes as cathode and anode together with a 1.0 M Na₂SO₄aqueous solution as electrolyte, we find energy densities of 10.97 μWh cm⁻¹. These values indicate that our hybrid systems have clear potential as wearable energy storage and harvesting devices.

Lithium metal anodes are potentially key for next‐generation energy‐dense batteries because of the extremely high capacity and the ultralow redox potential. However, notorious safety concerns of Li metal in liquid electrolytes have significantly retarded its commercialization: on one hand, lithium metal morphological instabilities (LMI) can cause cell shorting and even explosion; on the other hand, breaking of the grown Li arms induces the so‐called “dead Li”; furthermore, the continuous consumption of the liquid electrolyte and cycleable lithium also shortens cell life. The research community has been seeking new strategies to protect Li metal anodes and significant progress has been made in the last decade. Here, an overview of the fundamental understandings of solid electrolyte interphase (SEI) formation, conceptual models, and advanced real‐time characterizations of LMI are presented. Instructed by the conceptual models, strategies including increasing the donatable fluorine concentration (DFC) in liquid to enrich LiF component in SEI, increasing salt concentration (ionic strength) and sacrificial electrolyte additives, building artificial SEI to boost self‐healing of natural SEI, and 3D electrode frameworks to reduce current density and delay Sand's extinction are summarized. Practical challenges in competing with graphite and silicon anodes are outlined.

Lithium metal anodes are potentially key for next‐generation energy‐dense batteries because of the extremely high capacity and the ultralow redox potential. However, notorious safety concerns of Li metal in liquid electrolytes have significantly retarded its commercialization: on one hand, lithium metal morphological instabilities (LMI) can cause cell shorting and even explosion; on the other hand, breaking of the grown Li arms induces the so‐called “dead Li”; furthermore, the continuous consumption of the liquid electrolyte and cycleable lithium also shortens cell life. The research community has been seeking new strategies to protect Li metal anodes and significant progress has been made in the last decade. Here, an overview of the fundamental understandings of solid electrolyte interphase (SEI) formation, conceptual models, and advanced real‐time characterizations of LMI are presented. Instructed by the conceptual models, strategies including increasing the donatable fluorine concentration (DFC) in liquid to enrich LiF component in SEI, increasing salt concentration (ionic strength) and sacrificial electrolyte additives, building artificial SEI to boost self‐healing of natural SEI, and 3D electrode frameworks to reduce current density and delay Sand's extinction are summarized. Practical challenges in competing with graphite and silicon anodes are outlined.

When secondary domains nucleate and grow on the surface of monolayer MoS₂, they can extend across grain boundaries in the underlying monolayer MoS₂ and form overlapping sections.

When secondary domains nucleate and grow on the surface of monolayer MoS₂, they can extend across grain boundaries in the underlying monolayer MoS₂ and form overlapping sections.

Nanoparticles are useful in a wide range of applications such as catalysis, imaging, and energy storage. Yaoet al.developed a method for making nanoparticles with up to eight different elements (see the Perspective by Skrabalak). The method relies on shocking metal salt-covered carbon nanofibers, followed by rapid quenching. The “carbothermal shock synthesis” can be tuned to select for nanoparticle size as well. The authors successfully created PtPdRhRuCe nanoparticles to catalyze ammonia oxidation.

Science, this issue p.1489; see also p.1467

Rechargeable lithium metal battery (RLMB) is the holy grail of high-energy-density batteries. If lithium metal anode (LMA) could be combined with 5-V LiNi_0.5Mn_1.5O₄cathode, energy density could exceed 600 Wh/kg based on the cathode and anode electrode mass. Despite such promises, 5-V RLMB is still a vacant research space so far due to the unavailability of electrolytes which simultaneously satisfy a wide enough electrochemical stability window, good compatibility with LiNi_0.5Mn_1.5O₄, and superior reversibility of LMA. In this work, a class of full-fluoride (FF) electrolyte is invented for 5-V RLMB which not only has good compatibility with cathode and a wide stability window but also possesses the capability to make LMA more stable and reversible.

The room‐temperature tensile strength, toughness, and high‐temperature creep strength of 2000, 6000, and 7000 series aluminum alloys can be improved significantly by dispersing up to 1 wt% carbon nanotubes (CNTs) into the alloys without sacrificing tensile ductility, electrical conductivity, or thermal conductivity. CNTs act like forest dislocations, except mobile dislocations cannot annihilate with them. Dislocations cannot climb over 1D CNTs unlike 0D dispersoids/precipitates. Also, unlike 2D grain boundaries, even if some debonding happens along 1D CNT/alloy interface, it will be less damaging because fracture intrinsically favors 2D percolating flaws. Good intragranular dispersion of these 1D strengtheners is critical for comprehensive enhancement of composite properties, which entails change of wetting properties and encapsulation of CNTs inside Al grains via surface diffusion‐driven cold welding. In situ transmission electron microscopy demonstrates liquid‐like envelopment of CNTs into Al nanoparticles by cold welding.

We quantify effects of nanoscale ion-beam irradiation, and irradiation of nanoscale targets, setting guidelines for the use of full-3D simulations.

Embedded SnOx#C composite, with excellent structural robustness, exhibits stable full-cell performance and enhanced gravimetric/volumetric capacity.

Embedded SnOx#C composite, with excellent structural robustness, exhibits stable full-cell performance and enhanced gravimetric/volumetric capacity.

Ultra-stretchable lithium-ion battery electrodes were fabricated by coating carbon nanotube films and electrode materials on a biaxially pre-strained polydimethylsiloxane substrate and forming wrinkled structures. The composite electrodes demonstrated ultra-stretchability, high durability, and excellent electrochemical properties.

Coherent twin boundaries (CTBs) are internal interfaces that can play a key role in markedly enhancing the strength of metallic materials while preserving their ductility. They are known to accommodate plastic deformation primarily through their migration, while experimental evidence documenting large-scale sliding of CTBs to facilitate deformation has thus far not been reported. We show here that CTB sliding is possible whenever the loading orientation enables the Schmid factors of leading and trailing partial dislocations to be comparable to each other. This theoretical prediction is confirmed by real-time transmission electron microscope experimental observations during uniaxial deformation of copper pillars with different orientations and is further validated at the atomic scale by recourse to molecular dynamics simulations. Our findings provide mechanistic insights into the evolution of plasticity in heavily twinned face-centered cubic metals, with the potential for optimizing mechanical properties with nanoscale CTBs in material design.

The phase-field microelasticity theory has exhibited great capacities in studying elasticity and its effects on microstructure evolution due to various structural and chemical non-uniformities (impurities and defects) in solids. However, the usually adopted linear and/or collinear coupling between eigen transformation strain tensors and order parameters in phase-field microelasticity have excluded many nonlinear transformation pathways that have been revealed in many atomistic calculations. Here we extend phase-field microelasticity by adopting general nonlinear and noncollinear eigen transformation strain paths, which allows for the incorporation of complex transformation pathways and provides a multiscale modeling scheme linking atomistic mechanisms with overall kinetics to better describe solid-state phase transformations. Our case study on a generic cubic to tetragonal martensitic transformation shows that nonlinear transformation pathways can significantly alter the nucleation and growth rates, as well as the configuration and activation energy of the critical nuclei. It is also found that for a pure-shear martensitic transformation, depending on the actual transformation pathway, the nuclei and austenite/martensite interfaces can have nonzero far-field hydrostatic stress and may thus interact with other crystalline defects such as point defects and/or background tension/compression field in a more profound way than what is expected from a linear transformation pathway. Further significance is discussed on the implication of vacancy clustering at austenite/martensite interfaces and segregation at coherent precipitate/matrix interfaces.

Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

While lithium metal anodes have the highest theoretical capacity for rechargeable batteries, they are plagued by the growth of lithium dendrites, side reactions, and a moving contact interface with the electrolyte during cycling.

While lithium metal anodes have the highest theoretical capacity for rechargeable batteries, they are plagued by the growth of lithium dendrites, side reactions, and a moving contact interface with the electrolyte during cycling.

While lithium metal anodes have the highest theoretical capacity for rechargeable batteries, they are plagued by the growth of lithium dendrites, side reactions, and a moving contact interface with the electrolyte during cycling.

The separator has an electrocatalytic effect for polysulfide transformation, and can confine the polysulfides within the cathode and block the dendritic lithium in the anode.

The in situ polymerized solid barrier stops sulfur transport while still allowing bidirectional Li⁺ transport, alleviating the shuttle effect and increasing the cycling performance.

The in situ polymerized solid barrier stops sulfur transport while still allowing bidirectional Li⁺ transport, alleviating the shuttle effect and increasing the cycling performance.

Simulations demonstrate the critical roles of π-conjugation and large magnetic anisotropy in realizing high-temperature ferromagnetic 2D metal–organic framework, which is also half-metallic.

Simulations demonstrate the critical roles of π-conjugation and large magnetic anisotropy in realizing high-temperature ferromagnetic 2D metal–organic framework, which is also half-metallic.

Simulations demonstrate the critical roles of π-conjugation and large magnetic anisotropy in realizing high-temperature ferromagnetic 2D metal–organic framework, which is also half-metallic.