Maintaining Intimate Contact of Graphite-Silicon Composite Electrodes via Morphological Design for High Performance All-Solid-State Batteries

Abstract While the exploration of all-solid-state batteries has gained attention as post Li-ion batteries owing to their superior safety, the relatively high density and ratio of solid electrolytes for the ion conductive matrix in the electrodes undermine the energy density of cells, requiring electrode materials with higher specific capacities. In this study, we comparatively investigate the performances of two graphite-silicon composites with distinct morphologies in sulfide-based solid-state batteries: physically mixed graphite-silicon (Gr-Si) composite and silicon-coated graphite (Si-coated Gr), exhibiting a high specific capacity of approximately 500 mAh/g. While the Gr-Si composite exhibited severe mechanical degradation due to the volume expansion of Si particles, the Si-coated Gr maintained intimate contact with solid electrolytes after repeated cycling, exhibiting improved cycle performances. This study highlights the importance of intimate solid-solid interfaces within the electrode and proposes the principles of structural designs for high-capacity electrode materials.