Fabricating self-standing argyrodite electrolyte sheets containing SiO2 fibers for all-solid-state batteries

Due to their high ionic conductivities, sulfide-based solid electrolytes (SEs)—such as argyrodite Li₆PS₅Cl—are good candidates for all-solid-state lithium-ion batteries (ASSLIBs). For adequate energy density, the thinner SE layers of ASSLIBs, the better, but it must also be durable to avoid short circuits. Using SiO₂ fibers in the SE layer as a support, we used a liquid process to produce all-inorganic, self-standing-sheet argyrodite-SEs with a thickness of approximately 60 μm, without resorting to organofluorine compounds such as polytetrafluoroethylene (PTFE) or polyvinylidene difluoride (PVDF). The ionic conductivity of a sheet containing 20 % SiO₂ fibers was 4.2 × 10⁻⁴ S cm⁻¹ at 25 °C. We also prepared graphite composites as anodes using argyrodite SE containing SiO₂ fibers. In addition, we fabricated ASSLIB cells using these SE sheets, Ni_1/3Mn_1/3Co_1/3O₂-composite positive, and graphite-composite negative electrodes and evaluated their charge–discharge characteristics.