(100-x)Li3PS4-xLil solid electrolytes are successfully prepared using a simple process proposed in this study. The results show that the heat-treatment process plays a crucial role in the formation of the final product. In the case of x = 33.3%, 2Li(3)PS(4)-1Lil, a nearly pure crystalline phase of Li7P2S8I (LPSI), is obtained. The cyclic voltammogram result and DC polarization curves indicate that the interfacial layer between LPSI and the Li metal is stable. Li2S, Lil, Li5P, Li4P2S6, and some unknown substances were detected in the interfacial layer by XRD. (C) 2017 Elsevier B.V. All rights reserved.