High Capacity Li<sub>2</sub>S–Li<sub>2</sub>O–LiI Positive Electrodes with Nanoscale Ion‐Conduction Pathways for All‐Solid‐State Li/S Batteries
Yushi Fujita, Atsushi Sakuda, Yuki Hasegawa, Minako Deguchi, Kota Motohashi, Jiong Ding, Hirofumi Tsukasaki, Shigeo Mori, Masahiro Tatsumisago, Akitoshi Hayashi
Abstract
Abstract 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 Li 2 S active material used in the positive electrode has a high theoretical capacity; consequently, nanocomposites composed of Li 2 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 Li 2 S–Li 2 O–LiI positive electrode is developed in which the active material is dispersed in an amorphous matrix. Li 2 S–Li 2 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 Li 2 O–LiI provides nanoscale ion‐conduction pathways during cycling that activate Li 2 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 Li 2 S–Li 2 O–LiI positive electrode. This study represents a major step toward the commercialization of all‐solid‐state Li/S batteries.