In Situ Formation of 3D Cross-Linked Binders in Silicon–Graphite Composite Anodes for All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) with sulfide-based solid electrolytes offer improved safety compared to conventional lithium-ion batteries. Silicon-based anode materials enable an increase in the energy density of ASSLBs. However, the substantial volume change during cycling induces interfacial degradation, leading to significant capacity loss. In this study, the composite silicon-graphite (Si-C) anodes were fabricated via an in situ cross-linking reaction between polybutadiene (PBD) and n-butyl acrylate monomer. The resulting three-dimensional cross-linked polymer binder significantly improved interfacial adhesion and cycling stability of the composite anode. Furthermore, the influence of PBD isomeric structure on cross-linking selectivity was investigated to optimize the electrochemical performance and mechanical properties of the composite anode. As a result, the composite anode employing solid electrolyte (Li₆PS₅Cl_0.5Br_0.5) and highly cross-linked binder based on cis-PBD delivered a high initial discharge capacity of 1056.3 mAh g^-1 (areal capacity: 3.8 mAh cm^-2) and exhibited superior capacity retention at 0.3 C and 30 °C.