An all-solid-state lithium–sulfur battery using two solid electrolytes having different functions

•Ionic conductivity of Li1.5PS3.3 is increased by addition of LiI.•The positive electrode included two SEs that have different functions.•Improving sulfur reactivity and ionic conductivity using two kinds of SEs.•The cell using the positive electrode was estimated to be 540 W h kg−1 at cell level.

All-solid-state lithium–sulfur batteries are expected to be valuable next generation batteries. To improve the performance of all-solid-state lithium–sulfur batteries, it is essential to raise both the reactivity of sulfur and the ionic conductivity of the positive composite electrode. For achieving this, we investigate a positive composite electrode prepared using P2S5 and a solid electrolyte with a high ionic conductivity. As a result, we have found that the lithium–sulfur cell exhibits a relatively low activation energy together with high ionic conductivity. The positive composite electrode exhibits an extremely high capacity of 1550 mA h g−1 (sulfur) at 1.3 mA cm−2 and 25 °C. Moreover, when using the positive electrode, the energy densities at the cell level (18650) are 540 W h kg−1 and 990 W h L−1, estimated from the equivalent structure of a current lithium-ion battery.