High-molecular-weight ethylene-vinyl acetate binder enables uniform electrode architecture and stable silicon-graphite composite anodes for practical sulfide all-solid-state batteries

초록

Sulfide-based all-solid-state batteries (ASSBs) are recognized as promising next-generation energy storage systems owing to their high energy density and intrinsic safety. Among various anode candidates for ASSBs, silicon–graphite (Si–Gr) composites offer high specific capacity and favorable cycling stability; however, their large volume changes during cycling lead to interfacial degradation, limiting practical applicability. Herein, we report a scalable wet slurry-processed composite anode composed of Si–Gr active material, sulfide solid electrolyte (Li6PS5Cl), and highly adhesive ethylene-vinyl acetate (EVA) copolymer binder. By optimizing the vinyl acetate content, the EVA binder provides a balanced combination of elasticity and adhesion, effectively preserving intimate interfacial contact within the anode during prolonged cycling. In addition, using high-molecular-weight EVA markedly suppresses binder migration during high-temperature drying, enabling a homogeneous binder distribution throughout the anode. As a result, a pouch-type ASSB employing Si–Gr composite anode, Li6PS5Cl-based sheet electrolyte, and LiNi0.90Co0.05Mn0.05O2 cathode delivers a high initial discharge capacity of 199.6 mA h g−1 (3.0 mA h cm−2) at 0.05C and retains 85.6% of its initial capacity after 100 cycles at 0.2C and 30 °C. These results demonstrate that high-molecular-weight EVA effectively enhances interfacial stability in sulfide-based composite electrodes while enabling scalable manufacturing and robust electrochemical performance under practical operating conditions.

키워드