Mechanically and Conductively Adaptive Interface for High-Rate Si-Based All-Solid-State Pouch Cell

Si-based all-solid-state batteries are promising candidates for achieving high-energy density but are hampered by sluggish kinetics and deleterious stress accumulation at the rigid solid–solid interfaces within Si anodes. Herein, we report a mechanically and conductively adaptive interface that transforms the rigid solid–solid interfaces in Si anodes into soft, highly conductive ones through its deformation capability during cycling, enabling high-rate and long-cycle-life batteries. The interfacial phase in the lithiated state exhibits a lower Young’s modulus and higher mixed-conductivity than Si and its alloys, facilitating a uniform and low-stress field within the Si electrode that effectively stabilizes the interfacial transport. Upon delithiation, it spontaneously heals stress-induced interfacial damage, preserving a robust three-dimensional adaptive network throughout cycling. The dynamically adaptive interface enables a pouch cell to cycle stably over 150 cycles at 1C, with 94% capacity retention. Our work provides valuable insights into the stability of solid–solid interfaces that are crucial in practical all-solid-state-batteries.