Stress-Lensed Electrochemical Sintering Enables Fast and Stable Lithium-Silicon Alloy Chemistry in All-Solid-State Batteries.

The fundamental challenge in all-solid-state batteries (ASSBs) lies in regulating the dynamic reconstruction of solid-solid interfaces under electro-chemo-mechanical conditions. Currently, no mechanism exists to reconcile the conflicting requirements of structural stability and rapid ion transport for high-capacity silicon (Si) anodes: expansion-accommodated encapsulation strategies preserve integrity but block interparticle ionic contact, while intrinsic electrochemical sintering restores conduction but creates excessive agglomeration that fractures the electrode. Here, we propose a stress-lensed electrochemical sintering (SLES) strategy to guide selective interfacial bonding by depositing Si conformally into a porous carbon host, specifically utilizing its high-curvature pore entrances as geometric constrictions. During cycling, these constrictions act as "stress lenses", concentrating the volumetric expansion stress of Si precisely at interparticle contacts. This focused mechanical energy locally lowers the atomic diffusion barrier, guiding the formation of a robust, percolating Si network while preserving internal voids to buffer volume changes. The resulting Si-SLES anode resolves the stability-transport conflict, achieving ∼100% capacity retention after 100 cycles with superior rate capability and demonstrating practical viability in full cells over 700 cycles.