Stable Cyclability Caused by Highly Dispersed Nanoporous Si Composite Anodes with Sulfide-based Solid Electrolyte

All-solid-state lithium-ion batteries (ASSLIBs) without organic liquid electrolytes have attracted considerable attention as a solution to existing safety issues. Si is the most promising anode active material for increasing the energy density of such batteries owing to its high theoretical capacity. However, the stress relaxation of Si with large structural fluctuations is a major challenge to its practical use. In the present study, nanoporous Si particles and a sulfide-based solid electrolyte are composited to accommodate the volumetric expansion. To the best of our knowledge, this is a novel approach in the case of ASSLIBs. We find that the capacity retention of highly dispersed Si composite anodes is 80% up to 150 cycles. Such excellent cyclability is explained by our results, which suggest the following microstructural behavior. The pores in the Si particles act as buffer regions for large volume changes. In addition, the strains arising from the slightly expanded Si particles are relieved by the elasticity of the surrounding sulfide-based solid electrolyte. In summary, this study is a significant step toward the development of high-performance ASSLIBs for various applications.