Li2S–V2S3–LiI Bifunctional Material as the Positive Electrode in the All-Solid-State Li/S Battery

All-solid-state batteries with sulfur-based positive electrode active materials have been attracting global attention, owing to their safety and long cycle life. Li2S and S are promising positive electrode active materials for high energy density in these batteries because of high theoretical capacities. All-solid-state batteries with these active materials generally require the addition of solid electrolytes (SEs) and conductive carbons to the positive electrode layer to form ionic and electronic conducting pathways due to their insulating nature. In this study, we developed electrode–electrolyte bifunctional materials in the system Li2S–V2S3–LiI with high ionic and electronic conductivity. All-solid-state batteries with Li2S–V2S3–LiI in the positive electrode layer work without SEs and conductive carbons. In particular, an all-solid-state battery with 90(0.75Li2S·0.25V2S3)·10LiI (mol %) showed a high capacity of 370 mA h g–1 at 25 °C and retained 83% of the initial discharge capacity even after 100 cycles. 90(0.75Li2S·0.25V2S3)·10LiI were composed of LiVS2 and Li2S–LiI nanoparticles embedded in the amorphous matrix. Both LiVS2 and Li2S–LiI solid solution showed electrode activity, which contribute to the high reversible capacity. Our findings offer new solutions for increasing the energy density of all-solid-state batteries.