Interfacially Reinforced Crosslinked Binder with Structural Integrity for Stable Micro‐Sized Silicon Anodes in All‐solid‐state Batteries

All-solid-state batteries (ASSBs) have attracted considerable attention as next-generation energy storage systems owing to their high energy density and safety. However, their performance is critically limited by insufficient solid-solid interfacial contact and severe chemomechanical degradation, particularly for micro-sized silicon (µSi) anodes that undergo large volume changes during cycling. In this study, we report an interfacially reinforced crosslinked binder (IRCB) designed to stabilize µSi anodes in ASSBs by simultaneously addressing mechanical integrity and interfacial stability. The IRCB is synthesized via a facile crosslinking reaction between 1,4-butanediol diglycidyl ether and ethylenediamine, forming a robust 3D polymer network. This crosslinked structure enhances mechanical constraint, maintains interparticle contact, and provides ether-rich domains that facilitate Li⁺ transport, while strong hydrogen bonding improves adhesion to µSi surfaces. As a result, carbon-free µSi anodes employing IRCB exhibit markedly improved electrochemical stability, delivering 90% capacity retention after 300 cycles at 1 C, compared with only 16% for conventional PVDF-based electrodes. Structural and interfacial analyses reveal that IRCB effectively mitigates particle displacement and suppresses interfacial degradation with sulfide solid electrolytes. This work demonstrates that rational binder engineering is a key enabler for achieving stable and high-performance µSi anodes in ASSBs.