Crack Suppression by Downsizing Sulfide‐Electrolyte Particles for High‐Current‐Density Operation of Metal/Alloy Anodes

Abstract Stable physical contact between lithium metal/alloy anodes and the solid electrolyte layer is crucial for the durable operation of all‐solid‐state batteries. Herein, we have attempted to control the mechanical properties of a Li 10.35 Ge 1.35 P 1.65 S 12 (LGPS) solid electrolyte layer by the grain size and examined the mechanical strength against stresses originating from volumetric changes of an In‐Li anode layer. The submicron‐sized LGPS electrolyte ( d 50 : 0.51 μm) with a uniform particle size distribution was successfully fabricated by a wet‐milling process. The crystallinity of LGPS negligibly changes on pulverization. In‐Li symmetric cells with the wet‐milled LGPS exhibit higher cycle stability than those constructed with micro‐sized LGPS ( d 50 : 1.32 μm), not well‐controlled by particle size, owing to greater suppression of overvoltage generation and growth. Microstructural analyses have revealed that the small and uniform LGPS particles are less prone to physical degradation (cracking) owing to volume changes of In‐Li. Downsizing of solid electrolytes is a good strategy for developing physically stable electrode/solid electrolyte interfaces even at high current density operation.