Degradation mechanism of all-solid-state lithium-ion batteries with argyrodite Li7-xPS6-xClx sulfide through high-temperature cycling test

Sulfide-based all-solid-state lithium-ion batteries (LIBs) are promising replacements for conventional liquid electrolyte LIBs. However, their degradation mechanisms and analysis methods are poorly understood. Herein, the degradation mechanism of an argyrodite-type sulfide-based all-solid-state prototype LIB cell is reported. Furthermore, an analysis method for all-solid-state batteries using charge/discharge cycle tests at 100 degrees C followed by the disassembly analysis of cells before and after accelerated degradation tests is reported. Based on the findings of this study, the degradation of the prototype cell is classified as follows: (i) solid electrolyte (SE) oxidation in the positive electrode, which recovers battery capacity and increases resistance; (ii) SE reduction in the negative electrode, which decreases capacity; (iii) lithium deposition on/in the negative electrode, which decreases capacity; and (iv) capacity loss of the positive electrode, which decreases capacity. These degradation reactions appear to occur simultaneously. These findings are expected to aid the development of sulfide-based solid-electrolyte LIBs with improved safety and energy densities.