Gradient-Interlocked Solid Electrolyte Interphase via Spatial Reconfiguration for Stable Silicon Anodes in Solid-State Batteries

Silicon (Si) anodes are highly promising for high-energy-density solid-state batteries (SSBs), but substantial volume changes during cycling cause persistent solid electrolyte interphase (SEI) fracture and an unstable electrode interface. This challenge is exacerbated in solid-state batteries, where rigid, immobile interfaces present poor mechanical buffering. Herein, an ingenious "mortise-tenon" structural SEI is built by introducing the cyclotetrasiloxane into polymer electrolytes to promote the precise spatial reconfiguration of SEI, achieving an interlock between the cyclotetrasiloxane and LiF-rich inorganic phase, which ensures robust adhesion and structural stability of the SEI under large volume changes. The resulting Si||Li half cells deliver a high capacity of 1553.6 mAh g^-1 at a high current density of 12 A g^-1. The NCM811||Si full cells achieve a high-capacity retention of 97.6% at 0.5 C, showing only 0.12% capacity decay per cycle over 300 cycles. The LFP||Si full cells also show a low decay rate of 0.07‰ per cycle across 700 cycles. This strategy provides stable SEI engineering for the practical application of high-energy-density Si-based SSBs.