Lithium ion conducting solid electrolytes prepared from Li2S, elemental P and S

Glassy electrolyte of 80Li2S·20P2S5 (mol%) was prepared by mechanical milling of Li2S and the mixture of elemental phosphorus and sulfur, which was mechanically milled in advance (two-step process). The glass showed relatively low conductivity of 3.9 × 10− 5 S cm− 1 at room temperature, while the glass–ceramic obtained by crystallization exhibited higher conductivity of 4.3 × 10− 4 S cm− 1 than the pristine glass. Raman spectroscopy revealed that the glass was mainly composed of the PS43− ions and slightly contained homo bonds such as P–P and S–S bonds. The mechanochemical synthesis using the two-step process was effective in reducing the homo bonds in the glassy electrolytes. The glass–ceramic, in which a highly ion-conductive thio-LISICON analog was precipitated, was mainly composed of the PS43− ions and very small amounts of S–S bonds. Cyclic voltammmetry demonstrated that the Li2S–P–S glass–ceramic had wide electrochemical window of 5 V.