A high rate performance positive composite electrode using a high P/S ratio and LiI composite solid electrolyte for an all-solid-state Li–S battery

Abstract

All-solid-state lithium–sulfur batteries are believed to have sufficient energy density to be next-generation batteries. In manufacturing the batteries, it is necessary to improve the sulfur reactivity and ion conductivity in the positive electrode. In this study, we investigated (100− x) (Li1.6PS2)·x (LiI) as a composite solid electrolyte with a high P/S ratio solid electrolyte and LiI to provide the dual functions of high sulfur activated property and high ionic conductivity. This solid electrolyte showed high ionic conductivity of over 0.5 mS cm−1 at over x = 35. The positive composite electrode using 65Li1.6PS2·35LiI exhibited a good high rate capacity of over 1260 mA h g−1 (sulfur) at 6.4 mA cm−2 (0.8 C) and 25 °C. Furthermore, it showed excellent battery performance at 45 °C. The high rate capacity was 25.5 mA cm−2 (3.2 C) over 1000 mA h g−1, and the 1 C cycle capacity was over 1230 mA h g−1 after 100 cycles.