Impact of Ambient Air Contamination on the Performance of Argyrodite-Based All-Solid-State Lithium–Sulfur Batteries

Sulfide-based Li-argyrodites (Li5.5PS4.5Cl1.5) are considered as promising solid-state electrolytes for all-solid-state Li–S batteries (ASSLSBs) due to their high ionic conductivity and suitable mechanical properties. However, their hygroscopic nature and intense decomposition behavior when combined with conductive additives at the sulfur cathode introduce many variables that can affect cell performance. This study demonstrates that an optimized amount of ambient air contamination during cycling can enhance cell performance. Multiple spectroscopic analyses reveal that the hydrolysis of Li5.5PS4.5Cl1.5 can incorporate oxygen into the argyrodite structure, thereby increasing the oxidative stability and generating additional redox active sulfur species. Methods, such as monitoring cell impedance growth, open-circuit voltage changes, and 31P NMR spectroscopic analysis, are proposed to determine the air-tightness of cell configurations. The research findings suggest that verifying the air-tightness of cell configurations is critical for ASSLSBs research to prevent misleading results.