High Capacity Li2S-Li2O-LiI Positive Electrodes with Nanoscale Ion-Conduction Pathways for All-Solid-State Li/S Batteries

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 Li2S active material used in the positive electrode has a high theoretical capacity; consequently, nanocomposites composed of Li2S, 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 Li2S-Li2O-LiI positive electrode is developed in which the active material is dispersed in an amorphous matrix. Li2S-Li2O-LiI exhibits high charge-discharge capacities and a high specific capacity of 998 mAh g(-1) at a 2 C rate and 25 degrees C. X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy observation suggest that Li2O-LiI provides nanoscale ion-conduction pathways during cycling that activate Li2S 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 degrees C using a Li2S-Li2O-LiI positive electrode. This study represents a major step toward the commercialization of all-solid-state Li/S batteries.