Exploring the Optimal Binder Content of Composite Cathode and Anode for Sulfide-Based All-Solid-State Batteries

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All-solid-state batteries (ASSBs) using solid electrolytes (SEs) are promising candidates for next-generation batteries due to their enhanced safety and high energy density compared to conventional lithium-ion batteries using flammable liquid electrolytes. Among various SEs, sulfide-based SEs exhibit high ionic conductivity comparable with liquid electrolytes, and their ductile properties allow them to be processed without high-temperature sintering. Despite these advantages, interfacial contact issues cause the performance degradation of ASSBs. The use of an appropriate polymer binder can maintain good interfacial contact among the electrode components (active material, SE, and conducting carbon) during the repeated cycles. However, using an excessive polymer binder increases the resistance and causes a reduction in energy density because of the decrease of the active material loading in the electrode. Moreover, cathode and anode exhibit different tendencies depending on binder content at the same areal capacity. In this study, we explore the optimal binder content in the composite electrode by evaluating the mechanical and electrochemical properties. Furthermore, we investigate the factors contributing to the disparate behaviors observed between the cathode and anode, and the electrodes that exert a more significant influence on the full cell performance will be ascertained.