Y<sub>2</sub>S<sub>3</sub>-Doped Li<sub>2</sub>S Active Cathode Materials for All-Solid-State Li–S Batteries
Kazuhiro Hikima, Ryo Fujii, Hirotada Gamo, Hirofumi Tsukasaki, Shigeo Mori, Toshiki Watanabe, Kentaro Yamamoto, Yoshiharu Uchimoto, Hiroyuki Muto, Atsunori Matsuda
Abstract
All-solid-state Li–S batteries with sulfur-based cathodes have attracted attention, because of their high theoretical energy density. However, it is difficult to transfer electrons and ions and activate redox reaction of Li 2 S because Li 2 S and S are insulators. In this study, the Y 2 S 3 doping of Li 2 S active cathode materials was performed to enhance their properties while minimizing the dopant amount. As a result, the 99Li 2 S–1Y 2 S 3 (mol %) active cathode material exhibited the highest reversible capacities of 953 mAh g –1 that exceeded those of intrinsic Li 2 S, although its Y 2 S 3 content (1 mol % = 5.7 wt %) was lower than that reported in a previous work. Transmission electron microscopy observations indicated that Y atoms aggregated on the Li 2 S surface in the form of P-doped LiYS 2 species, and their morphology did not change after the charge–discharge process. This result indicated that the P-doped LiYS 2 at the Li 2 S surface served as a catalyst. In addition, the full cell of the 99Li 2 S–1Y 2 S 3 (mol %) with Si anode shows high capacity of 605 mAh g –1 . These findings of this study enable the material design of Li 2 S-based cathode active materials for use in high-energy-density Li–S batteries.