Hidemi Kato

All-solid-state lithium metal batteries (ASSLMBs) promise enhanced safety and high energy density, yet their solid–solid interfaces create mechanical constraints absent from conventional liquid-electrolyte cells. Electrochemical reactions, ion transport, and interfacial reactions generate lattice strain, volume change, and heterogeneous stress; in turn, stress redistributes ionic and electronic transport, reaction kinetics, and local current density. This bidirectional electro-chemo-mechanical coupling drives particle cracking, interfacial debonding, contact loss, void formation, lithium-filament penetration, and ultimately capacity decay or short circuiting. In this review, we establish a multiscale framework connecting the origins of stress to electrochemical consequences and failure across the crystal, particle, electrode, interface, and cell levels. We critically examine cathode deformation, lithium plating and stripping, stack-pressure evolution, thermal mismatch, and defect-assisted fracture, together with operando imaging, stress sensing, and multiphysics modeling approaches used to resolve these processes. We further assess mitigation strategies based on low-strain electrodes, mechanically compatible composite cathodes, defect-tolerant solid electrolytes, adaptive interphases, regulated stack pressure, and cell architecture. Finally, we identify the need for quantitative failure criteria, multimodal operando characterization, and standardized testing under practical conditions to accelerate durable, high-energy ASSLMBs.

As a part of a systematic study on the structural changes of Gd-transition metal (TM) alloy glasses induced by cryogenic rejuvenation, high-energy x-ray diffraction (HEXRD) and anomalous x-ray scattering (AXS) measurements were performed on a Gd 65 Cu 35 metallic glass (MG) possessing minimal elastic heterogeneity, as indicated by dynamical mechanical analysis. Significant structural changes were observed in this MG as a result of temperature cyclings between liquid N 2 and room temperatures 40 times. (1) HEXRD revealed minor changes in the first nearest neighbour range of the pair distribution function, g ( r ) , consistent with observations in other Gd 65 TM 35 glasses. (2) The partial structural information obtained from HEXRD and AXS showed that Gd–Cu and Cu–Cu partial correlations dominate the first peak region of the total g ( r ) , whereas Gd–Gd correlations contribute mainly to the second peak. (3) Additionally, some of the Gd–Cu and Cu–Cu correlations extend to the second peak of the total g ( r ) , unlike in Gd 65 Co 35 and Gd 65 Ni 35 MGs. (4) Futhermore, Cu atoms shift farther from each other by cryogenic rejuvenation. (5) Heterogeneities in the Cu elemental composition and the total number density at nm length scale increase by cryogenic rejuvenation, similar to the Gd 65 Co 35 MG but opposite to the trend observed in the Gd 65 Ni 35 MG. Accordingly, these findings suggest that structural heterogeneity in MGs is not systematically related to the extent of elastic heterogeneity.

1. High-pressure inelastic neutron scattering (INS) is a powerful spectroscopic technique [1–3] that directly probes elementary excitations driven by pressures across a broad range of momentum and ...

Solid‐state batteries (SSBs) are widely regarded as promising next‐generation energy storage technology due to their potential for enhanced safety and higher energy density compared to conventional Li‐ion batteries. Among the various oxide solid electrolytes, garnet Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) is considered one of the most promising, yet the Li–LLZO solid–solid interface remains a major bottleneck. Both LLZO and the relatively stiff Li metal anode rapidly accumulate Li ₂ CO ₃ surface impurities and form limited contact, leading to large interfacial resistance. Here, we demonstrate that ultrasonic welding (USW) provides a rapid, mechanically driven route to establish intimate Li–LLZO contact within seconds. A preliminary ambient‐air experiment confirms the basic feasibility of the technique, while all controlled welding experiments performed in Ar yield Li/LLZO interfaces with resistances on the order of several hundred Ω cm ² . Systematic comparison of pyramidal and flat horn geometries reveals that uniform pressure delivery is essential for stable interfacial formation, with the flat horn reducing the resistance to approximately 225 Ω cm ² . Furthermore, introducing a sputtered Au interlayer significantly enhances mechanical conformity and wetting by compensating LLZO surface roughness and enabling Li to more effectively accommodate LLZO surface asperities. As a result, the interfacial resistance decreases to as low as 1.5 Ω cm ² , among the lowest values reported for garnet–Li interfaces processed at room temperature. This study demonstrates USW as an effective mechanical strategy for constructing low‐resistance Li–garnet interfaces suitable for next‐generation SSBs.