Interfacial Evolution, Failure Mechanisms, and Multiscale Stabilization Strategies for Silicon Anodes in Sulfide‐Based All‐Solid‐State Batteries

Silicon anodes offer exceptionally high theoretical capacity and low lithiation potential, making them attractive for high‐energy‐density all‐solid‐state batteries using sulfide solid‐state electrolytes. However, Si undergoes substantial structural reconstruction and volume variation during cycling, while deeply lithiated Li x Si strongly reduces sulfide solid‐state electrolytes. The resulting interphase growth, loss of active lithium, particle fracture, interfacial delamination, contact loss, and heterogeneous ionic/electronic transport produce tightly coupled electrochemical–chemical–mechanical degradation. This Review summarizes the alloying‐type Li‐storage mechanism and room‐temperature phase evolution of Si, emphasizing low‐potential interfacial instability, volume‐strain‐induced fracture, solid–solid contact loss, and pressure‐dependent failure. Stabilization strategies based on structural regulation, carbon hybridization, conductive‐network construction, prelithiation, Li–Si alloying, elemental doping, surface modification, protective interlayers, functional binders, electrode processing, and pressure management are critically assessed. Advanced characterization and modeling methods are discussed for resolving interfacial reactions and failure pathways. Future progress requires chemically stable and mechanically compliant interfaces, low‐pressure architectures, controllable prelithiation, scalable manufacturing, artificial‐intelligence‐assisted design, standardized full‐cell evaluation, and coordinated optimization of transport, stress accommodation, Li inventory, and manufacturability.