High Capacity Li₂ S-Li₂ O-LiI Positive Electrodes with Nanoscale Ion-Conduction Pathways for All-Solid-State Li/S...

All-solid-state lithium-sulfur (Li/S) batteries are promising next-generation energy-storage devices owing to their high capacities and long cycle lives. The Li₂ S active material used in the positive electrode has a high theoretical capacity; consequently, nanocomposites composed of Li₂ S, solid electrolytes, and conductive carbon can be used to fabricate high-energy-density batteries. Moreover, the active material should be constructed with both micro- and nanoscale ion-conduction pathways to ensure high power. Herein, a Li₂ S-Li₂ O-LiI positive electrode is developed in which the active material is dispersed in an amorphous matrix. Li₂ S-Li₂ O-LiI exhibits high charge-discharge capacities and a high specific capacity of 998 mAh g^-1 at a 2 C rate and 25 °C. X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy observation suggest that Li₂ O-LiI provides nanoscale ion-conduction pathways during cycling that activate Li₂ S and deliver large capacities; it also exhibits an appropriate onset oxidation voltage for high capacity. Furthermore, a cell with a high areal capacity of 10.6 mAh cm^-2 is demonstrated to successfully operate at 25 °C using a Li₂ S-Li₂ O-LiI positive electrode. This study represents a major step toward the commercialization of all-solid-state Li/S batteries.