Lithium metal serves as an outstanding anode material, providing a high theoretical capacity of 3860 mA h g-1 and a low reduction potential of-3.04 V vs. Li+ /Li relative to the typical hydrogen electrode. All-solid-state lithium-metal batteries demonstrate exceptionally high energy density within power battery technology. The existing inorganic solid-state electrolytes (SSEs), including oxides, sulfides, and halides, demonstrate particular interactions with lithium metal. This study categorizes nine inorganic solid-state electrolytes (SSEs) according to their electrochemical behavior with lithium metal electrodes during the deposition and stripping cycles of lithium-symmetric cells into three classifications: (1) unrestricted reaction and failure, (2) dendritic growth and short circuit, (3) self-limiting decomposition and passivation. Concentrating on the third category of solid-state electrolytes (SSEs), we investigate the complex Li|Li(3-5x-3y)TaxLayCl3|Li system, particularly examining the performance of the Li|Li0.233Ta0.217La0.559Cl3(LTLC)|Li cell, which demonstrates stable cycling for more than 7000 h at a current density of 0.2 mA cm-2/0.2 mA h cm-2 after a pre-fabrication resting period of 60 h. In situ X-ray photoelectron spectroscopy analysis semi-quantitatively elucidates the interfacial redox hierarchy in LTLC, indicating amore rapid reduction rate of Ta5+ with lithium metal compared to La3+. The byproducts at the interaction are identified as well. X-ray Computed Tomography research revealed that the interfacial layer created during the pre-fabrication process is homogeneous, unlike that produced during a 6-h fabrication time, underscoring the importance of pre-fabrication in interfacial layer development. This technology enables the discovery of halide solid-state electrolytes that demonstrate advantageous interactions with lithium metal and the selection of interfacial products that enhance the stabilization of the battery system. This study serves as a significant reference for examining the compatibility of solid-state electrolytes with lithium metal and offers insights to inform future research. (c) 2025 Published by Elsevier B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Solid-state batteries with Li alloy anodes offer enhanced safety and energy density. However, many studies still rely on high stack pressures, while low stack pressure operation is essential for practical application. This work establishes a general electro-chemo-mechanical framework that enables rational pairing of alloy anodes and solid electrolytes by predicting the critical stack pressure required for interfacial stability under practical operating conditions. Based on thermodynamic and mechanical factors, our findings identified three design principles for achieving low stack pressure: (1) applying highly conductive and mechanically compliant solid electrolytes; (2) using Li-rich and hard alloy anodes; and (3) optimizing external conditions through smooth interfaces, low applied current densities, and elevated temperatures. Experimental results demonstrate that the LiAl alloy paired with Li6PS5Cl electrolyte exhibits stable cycling performance and smooth interfacial morphology above the critical stack pressure, while poor performance with rough morphology has been observed below it. These findings provide key principles for achieving low stack pressure in solid-state batteries.

ABSTRACT Solid‐state batteries with Li alloy anodes offer enhanced safety and energy density. However, many studies still rely on high stack pressures, while low stack pressure operation is essential for practical application. This work establishes a general electro‐chemo‐mechanical framework that enables rational pairing of alloy anodes and solid electrolytes by predicting the critical stack pressure required for interfacial stability under practical operating conditions. Based on thermodynamic and mechanical factors, our findings identified three design principles for achieving low stack pressure: (1) applying highly conductive and mechanically compliant solid electrolytes; (2) using Li‐rich and hard alloy anodes; and (3) optimizing external conditions through smooth interfaces, low applied current densities, and elevated temperatures. Experimental results demonstrate that the LiAl alloy paired with Li 6 PS 5 Cl electrolyte exhibits stable cycling performance and smooth interfacial morphology above the critical stack pressure, while poor performance with rough morphology has been observed below it. These findings provide key principles for achieving low stack pressure in solid‐state batteries.

Atomistic modeling of solid-solid battery interfaces is essential for understanding electro-chemo-mechanical coupling, but the complex interfacial chemistry and heterogeneous environments pose major challenges for quantum-accurate, data-efficient modeling. Herein, we propose an approach of fine-tuning with integrated replay and efficiency (FIRE), a general framework for universal machine-learning interatomic potentials by combining efficient configurational sampling with a replay-argumented continual strategy, achieving quantum-level accuracy at moderate cost. Across six solid-solid battery interface systems, FIRE consistently achieves root-mean-square errors in energy below 1 meV/atom and in force near 20 meV/angstrom, marking an order-of-magnitude improvement over existing models while requiring only 10% of the original datasets. In addition, the fine-tuned model successfully reproduces key mechanical and electrochemical properties of the materials, in close agreement with experimental data. The FIRE offers a generalizable and data-efficient approach for developing accurate interatomic potentials across diverse materials, enabling predictive simulations beyond the reach of first-principles methods.

Alkaline alloy anodes present a promising alternative to pure Li or Na anodes for solid-state batteries. However, identifying optimal cycling intervals (e.g., LixAl -> LiyAl) and atomic-scale mechanisms for driving multiperformance synergy remains challenging. This study employed high-throughput calculations and machine learning to screen Li/Na alloys, focusing on dendrite free and high reversibility. The cycling intervals for alloys (Li-Al, Li-Ga, and Li-In) containing Group 13 elements are cycled in the Li/Na-poor region, those for alloys (Li-Si, Li-Ge, and Na-Sn) containing Group 14 elements in the Li/Na-moderate region, and for alloys (Li-Mg) containing Group 2 element in the Li/Na-rich region. Through machine learning analysis, the atomic-scale mechanisms for achieving multi-performance synergy are a decrease in BCM (Bader charge of alloying element M) for Li alloys and an increase in VPA (volume per atom) for Na alloys. Experimental validation confirms that LiAl is optimal phase for Li-Al alloy, with the best cycling interval in the Li/Na-poor region, both aligning with computational results. These findings highlight the optimization of cycling intervals and atomic-scale mechanisms for improved Li/Na alloy performance, providing valuable guidance for their application in commercial solid-state batteries.

Most solid-state electrochemical reactions, such as those in lithium-ion batteries, are described well using thermodynamics under ambient conditions. In this work, we show that the microscopic stress in the composite cathode of solid-state batteries is highly heterogeneous and can exceed several hundreds of MPa via quasi in situ confocal Raman spectroscopy, making expansion work (p Delta V) no longer negligible. We observed a strong correlation between the state of charge of cathode particles with their state of stress. By building a nonambient thermodynamics framework to describe cathode reactions in solid-state batteries, we identified the substantial mechanical potential (up to tens of mV) as a primary cause of capacity loss upon electrochemical cycling. Pairing a cathode and solid electrolyte of similar partial molar volumes is suggested to mitigate this issue. This work highlights the importance of considering expansion work in solid-state batteries and suggests new materials' design rules for improved electrochemical performance.

All-solid-state batteries frequently encounter mechanical instability due to the inherent brittleness and low elasticity of inorganic ceramic electrolytes, such as sulfides, oxides, and halides. These electrolytes struggle to accommodate the volumetric fluctuations of positive electrode materials during cycling, potentially leading to performance degradation and premature failure. To address this challenge, we propose a defect-based toughening approach for resilient halide solid electrolytes. By meticulously controlling the cooling rate during synthesis, we successfully increase the defect density within the electrolyte, enhancing its mechanical properties and mitigating the risk of mechanical failure. Mechanical property testing, high-resolution transmission electron microscopy characterization, and synchrotron radiation diffraction analysis reveal that the quenched material exhibit not only a higher Young's modulus, rendering it less susceptible to deformation under stress and a higher capacity for energy absorption before plastic deformation or fracture due to its increased dispersed defect density. Consequently, it demonstrates better adaptability to the volumetric changes associated with the positive electrode material during battery cycling, effectively mitigating strain-induced material behavior. Here we show the effectiveness of defect-enhanced toughening strategies in optimizing the mechanical properties and microstructure of electrolyte materials, thereby enhancing the overall integrity of solid-state batteries without requiring modifications to their chemical composition.

Sulfone-based electrolytes offer unusually high anodic and thermal stability that in principle makes them promising candidates for fabricating energy-dense lithium metal batteries (LMBs). Their uses in practical batteries are currently limited by their inability to sustain long-term Li metal plating/stripping processes due to their high reactivity toward the Li metal. Here, we report on the design and synthesis of a unique family of fluorosulfonyl group-based (FSO2-) molecules, modified with ethyl (FSE)/N,N-dimethyl (FSNDM)/N,N-diethyl (FSNDE)/N-pyrrolidine (FSNP) end groups to create exceptionally stable single-salt single-solvent electrolytes. The flammability, solvation structure, ion transport, Li metal deposition kinetics, and high-voltage stability of the electrolytes are systematically studied. It is shown that the electrolytes are nonflammable, possess weak solvation characteristics, yet manifest high room-temperature ionic conductivities (1.6-6.1 mS cm-1) and low solution viscosities. In comparison to FSE, the FSNDM-, FSNDE-, and FSNP-based electrolytes exhibit an exceptionally reversible Coulombic efficiency for Li metal plating/stripping (>99.71% over 800 cycles) and exhibit typical oxidative stability at voltages exceeding 4.6 V. Deployed as electrolytes in Li metal batteries (20 μm Li anode and 3 g A h-1 electrolyte) with high-loading (18.5 mg cm-2) LiNi0.8Co0.1Mn0.1O2 cathodes, 329 cycles have been achieved before 80% capacity retention. Six Ah Li metal pouch cells based on the designed electrolytes also exhibit high stability and high energy density (496 W h kg-1) for over 150 cycles with at most 2.7% volume expansion. Our findings demonstrate that through an intentional molecular design, sulfone electrolytes provide a robust route toward nonflammable Li metal compatible electrolytes with practical high-voltage cathodes.

The propagation of physicochemical heterogeneity from particles to electrodes under galvanostatic cycling conditions largely determines battery performance but is often computationally unreachable. We formulate a Real 2D (R2D) full-battery model via an electrode-adaptive mathematical framework that addresses the electrochemically correlated nonlinear current-potential responses of the electrodes. This allows us to quantify the impact of multiphysics coupling on cycling performance in emerging solid-state batteries. R2D advances the modeling efficiency and can be generally applied to heterogeneous battery systems, providing a new pathway for accurate full battery simulations.

The electrochemical plating of lithium metal is known to be nonuniform and complex, which can ultimately lead to short circuits and capacity degradation in lithium-metal batteries. These detrimental phenomena are extremely challenging to both predict and manage. Herein, we develop a fast photoacoustic imaging system based on microelectromechanical systems and can thus achieve a high temporal resolution of 0.45 ms per pixel. This system enables operando monitoring of the lithium-plating process under practical current densities, with a lateral resolution of 7.8 μm. We monitor a millimeter-scale region and simultaneously follow the height evolution of lithium metal across 1000 subregions using grid-based tracking. Careful statistical analysis of these growth patterns reveals that the lithium plating begins as a diffusion-controlled process but subsequently diverges into explosive, steady, and diminishing patterns at different locations. This variation likely arises from the spatially dependent lithium-ion diffusivity of the solid-electrolyte interphase formed at the lithium metal-liquid electrolyte interface, which ultimately leads to uneven lithium plating. These findings significantly advance our understanding of lithium-plating dynamics and motivate the development of strategies to mitigate the associated risks in lithium-metal batteries.

Our prior focus on interfacial electrochemical processes has been on homogeneous interfaces like solid-liquid. However, solid-state batteries present a new challenge: heterogeneous solid-solid interfaces under mechanical constraints. In this talk, I will discuss the development of ultrafast XCT, photoacoustic microscopy, and confocal Raman spectroscopy to directly visualize the dynamic evolution of physicochemical solid-state batteries. I will also introduce an electrode-adaptive heterogeneous solid-state battery modeling strategy, Real 2D (R2D). These lead to innovative ways to manage and control heterogeneity, thus improving the electrochemical performance of solid-state batteries.

Halide solid-state electrolytes are promising for next-generation all-solid-state lithium-ion batteries due to their high ionic conductivity and wide electrochemical windows. While most research focuses on close-packed crystal structures, nonclose-packed frameworks─exemplified by UCl3-type structures─offer unique advantages in enhancing lithium-ion transport via reduced diffusion barriers. Here, we report a new family of UCl3-type crystalline oxychloride electrolytes, Li0.388+xLa0.475Ta0.238Cl3-xOx (0 ≤ x ≤ 0.388, LLTCO), synthesized via rapid high-energy shake milling. The material with an optimized composition (x = 0.15) exhibits high ionic conductivity above 2 mS cm-1 at 30 °C, oxidative stability exceeding 5 V vs Li/Li+, and excellent mechanical compressibility. Moreover, the LLTCO-based Li-Li symmetric cells show a long cycle life, indicating their strong capacity to suppress lithium dendrite formation. Spectroscopy analyses reveal the successful incorporation of oxygen, which preferentially substitutes Cl- around Ta5+ sites without compromising crystallinity, even at a high oxygen content. The oxygen incorporation further promotes the formation of Li environments with fast dynamics, accounting for the enhanced conductivity. All-solid-state batteries utilizing the optimized oxychloride electrolyte in conjunction with Ni-rich cathodes demonstrate enhanced reversible capacities compared to their undoped counterparts. This work highlights the benefits of nonclose-packed UCl3-type oxychloride electrolytes, offering new design strategies for high-performance all-solid-state batteries.

Alloy anodes hold promise for achieving dendrite-free all-solid-state lithium batteries (ASSLBs) by regulating lithium deposition behavior, leading to enhanced critical current density (CCD) and cycling stability. However, existing alloy anodes in ASSLBs fall short of practical requirements (CCD > 10 mA cm-2), and key factors determining CCD remain unclear. Here, we propose a diffusion-controlled Li deposition model in which CCD critically depends on the competition between surface attachment and diffusion of incoming atoms. Multimodal characterizations validate that Li atomic diffusivity in the alloy anode is a key descriptor for the CCD and cycling stability of ASSLBs. Leveraging this insight, LiGa is chosen as the optimized alloy anode due to its high Li atomic diffusivity (∼3 × 10-7 cm2 s-1), which enables a record-high CCD exceeding 50 mA cm-2 and stable solid electrolyte-anode interface at a high current density of 3 mA cm-2. ASSLBs pairing the LiGa anode with the LiNi0.8Co0.1Mn0.1O2 cathode and using Li6PS5Cl (LPSCl) solid electrolyte exhibit remarkable long-term cycling stability of 1000 cycles with 80% capacity retention under 25 °C and a stacking pressure of 1 MPa, outperforming state-of-the-art alloy anode-based counterparts. This work establishes a unified descriptor for the control of Li deposition, advancing practical ASSLB development.

Several tens of MPa stacking pressure is usually necessary to fully utilize the capacity of energy-dense silicon anode in solid-state batteries, presenting significant hurdles for real applications. It is thus critical to establish the link between the macroscopic stacking pressure and the microscopic electrochemical processes. In this work, we used titration gas chromatography to quantify the capacity-loss processes of silicon anodes under different stacking pressures. Furthermore, time-of-flight secondary ion mass spectrometry, electron microscopy, and phase-field modeling techniques were used to map the spatial distribution of chemical species (e.g., LixSi alloys), stress, and electrochemical overpotential upon (de)lithiation processes of the silicon anode. High stacking pressure was observed to significantly increase the extent that a Si anode can be lithiated because of the increased reaction homogeneity resulting from the strong electro-mechanical coupling, while its impact over lithium loss during the first cycle is rather limited. Our work provides a basis to unlock the full potential of Si-anode based solid-state batteries at near-ambient stacking pressure and calls for innovative strategies to minimize or compensate for the lithium loss at the first cycle.

Magnesium-sulfur (Mg-S) batteries have attracted considerable attention because of their high volumetric energy density and safety as well as the earth abundance of Mg and S. However, the high porosity of the conventional cathode composed of porous carbon mixed with sulfur requires a large amount of liquid electrolyte to fill the pores, decreasing the practical energy density. In this study, Mo6S8 or Cu2Mo6S8 materials with high density and high electronic conductivity were used to largely replace the lightweight carbon materials. This results in substantially decreased porosity and improved specific capacity of the S-Mo6S8 and S-CuMo6S8 composite cathodes compared with those of the S-C cathode. Ex situ X-ray diffraction and X-ray photoelectron spectroscopy analyses revealed that the S-Mo6S8 and S-CuMo6S8 composite cathodes undergo intercalation-conversion and displacement-conversion reactions, respectively, with the changed extent of sulfur redox processes. Our work offers important insight into cathode design strategies for Mg-S batteries, which can lead to improved electrochemical performance.

Alloy anodes present promising alternatives to alkali metals in solid-state batteries but still face morphological instability upon cycling. Unlike conventional batteries using liquid electrolytes, interfacial evolution between solid-state electrolytes and alloy anodes is determined by interfacial electrochemistry and mechanics. Here, we adapt a classical chemomechanical model for Li metal to apply to alloy anodes. This allows generalizing a principle, namely, the hard and soft electrolytes and alloy anodes pairing principle, to guide improving morphological stability. Specifically, "hard" (high-shear-modulus) ceramic electrolytes should be paired with "harder" alloys, while "soft" (low-shear-modulus) polymer electrolytes favor "softer" alloys. We examine the chemomechanical properties of several Li-M alloys (M = Al, Mg, In, Sn, and Sb). Consistent with the principle, the "harder" Li-Sn anode exhibits a flattened morphology with the "hard" Li6PS5Cl electrolyte after cycling. Conversely, the "softer" Li-In anode evolves extremely rough, indicating Li-In dendrite formation. Our work underscores the significance of tuning alloy anode mechanical properties, incorporating well-established rules in traditional metallurgy.

Dendrite formation, contact loss, and continuous formation of the solid electrolyte interphase (SEI) preclude the practical use of the energy-dense lithium (Li) metal. Li–Ag alloys have the potential to address these issues due to their exceptional lithiophilicity, outstanding mechanical stability, and moderate chemical stability. This study evaluates all phases in the Li–Ag phase diagram based on lithiation capacity, Li insertion, mechanical property, and chemical stability. Our findings suggest that Li4Ag is the most promising phase, and the Gibbs free energy of nucleation (∆Gnucle) for Li–Ag alloys is 3 to 5 orders of magnitude smaller compared to pure Li, resulting in uniform nucleation and deposition behavior. We proposed practical applications within the Li4Ag phases or from the Li9Ag4 to the Li4Ag phases, which may provide a usable capacity of 409 to 696 mAh/g, respectively. Experiments indicate that Li4Ag exhibits not only the smallest impedance but also the highest capacity retention compared to Li9Ag4 and pure Li. The study provides valuable guidance for the selection and application of Li-containing alloys in future battery development.

Although hard carbon anodes are known to outperform alloys in conventional sodium-ion batteries, this trend is reversed in solid-state sodium batteries due to the different underlying sodiation processes. Whereas the sodiation of hard carbon is triggered by Na cation (Na+) adsorption onto electrochemically active sites, that of alloys is driven by solid-state diffusion of Na+ and successive Na-alloy phase transformations. Thus, sodiation processes critically depend upon the chemical nature of Na+, which is solvated in liquids but is bonded at lattice sites in solid electrolytes. In addition, elucidating charge-transport and charge-transfer processes as well as electromechanical coupling at solid/solid interfaces (for solid-state batteries) remains an unresolved challenge. The transition in knowledge from well-investigated solid/liquid interfaces to solid-state sodium batteries is not straightforward. The exploration of hard carbon, alloys, and their composites requires further advancement. This perspective aids in streamlining the research efforts of battery communities, thereby accelerating the development of solid-state sodium batteries.

Lithium (Li) metal batteries though with high energy density are still facing issues like Li dendrite growth, dead Li formation, and thick solid electrolyte interphase (SEI) formation, hindering their long-term stability. Recently, Li-Ag alloys have been reported to potentially address these challenges possibly due to their superior conductivity, lithiophilicity, and mechanical stability. In the pursuit of high-energy-density batteries, Li-Ag alloys typically employ a high Li content phase (γ1). In this study, we applied density functional theory (DFT) calculations to compare the thermodynamic stability, Li adsorption, and Li diffusion of Ag-rich Li-Ag alloy within the γ1 phase (AR-γ1), Ag-poor Li-Ag alloy within the γ1 phase (AP-γ1), and pure Li. AR-γ1 showed better thermodynamic stability and improved Li adsorption and diffusion properties compared to AP-γ1 and pure Li. Electrochemical tests further confirmed the advantages of AR-γ1 in terms of electrode kinetics and cell stability compared to AP-γ1 and pure Li. Our study offers guidance for the selection of the most suitable Li-Ag alloys that can be utilized in high-energy-density lithium batteries.

Solid polymer electrolytes (SPE) have attracted a great deal of interest; however, their poor room temperature ionic conductivities still impede their practical application in lithium-ion batteries. Although the polymer blend is considered to be an effective strategy to improve ionic conductivity of SPEs, no quantitative model describing the ion conduction mechanism in polymer blends has yet been identified, and the interplay between the components has not been well elucidated. In this work, we focus on poly(ethylene oxide) (PEO)-based electrolytes blended with poly(methyl methacrylate) (PMMA) or poly(vinylidene fluoride) (PVDF) with systematically changed component ratios. A maximum ionic conductivity of 1.4 x 10(-4) S/cm at 30 degrees C is achieved by accelerated interfacial and segmental dynamics, together with decreased charge-concentrated layers, which promote ion concentration. We demonstrate that both segmental motion and interfacial polarization quantitatively determine ion conduction in polymer blends. Flory-Huggins interaction parameters unveil the thermodynamic interaction between the components and are directly related to the ionic conductivity of polymer blend electrolytes. Furthermore, the polymer blend enables viable applications of the SPE with fairly good ionic conductivity and allows the LFP||Li cell to deliver a discharge-specific capacity of similar to 113.5 mAh/g at 1 C and a capacity retention of similar to 70% after 100 cycles.