Suppression of H₂S gas generation from the 75Li₂S·25P₂S₅ glass electrolyte by additives

Abstract

Solid electrolytes in the system Li₂S–P₂S₅ are attractive for all-solid-state lithium batteries since the electrolytes have high lithium ion conductivities and wide electrochemical windows. In particular, the 75Li₂S·25P₂S₅ (mol%) glass showed the highest stability to moisture in the system Li₂S–P₂S₅ because the amount of H₂S gas generated from the glass was the smallest in the system Li₂S–P₂S₅. In this study, several additives such as metal sulfides and metal oxides (FeS, CuO, etc.) were mixed with the 75Li₂S·25P₂S₅ glass in order to suppress H₂S gas generation from the sulfide glasses in air. The addition of more than 30 mol% FeS greatly decreased H₂S gas generation from the sulfide glass in air. In the case of the FeS addition, sulfur crystal was precipitated and the 75Li₂S·25P₂S₅ glass changed to Li₃PO₄ crystal after a reaction with water. On the other hand, the addition of 30 mol% CuO dramatically decreased H₂S gas generation from the sulfide glass in air. In the case of the CuO addition, Cu₃PS₄ crystal was precipitated after the reaction with water. Furthermore, the 75Li₂S·25P₂S₅ glass added with 30 mol% FeS or CuO showed relatively high conductivities of more than 10⁻⁴ S cm⁻¹ at room temperature. Therefore, the 75Li₂S·25P₂S₅ glass added with FeS or CuO was expected to be a suitable solid electrolyte material for all-solid-state batteries.