Preparation of ambient air-stable electrolyte Li4SnS4 by aqueous ion-exchange process

Sulfide-based solid electrolytes (SEs) are promising as an application in all-solid-state lithium batteries due to their high ionic conductivities and suitable plasticity in forming good contact with electrode active materials. In addition, stability in ambient air is one of the most important requirements for these electrolytes. Recently, there have been many studies about Li4SnS4 because of its good stability against H2O in ambient air. This paper reports our development of a unique preparation process of Li4SnS4 in aqueous solution, namely, ion-exchange (IE). The crystalline structure of Li4SnS4 obtained via this process was confirmed by XRD patterns. The residual amount of Na ions in the Li4SnS4 after the IE process was found to be less than a few percent of the atomic ratio compared to Li ions obtained by ion chromatography. The ionic conductivity of the Li4SnS4 was 1.0 × 10−4 Scm−1 at room temperature.