Lithium‐Rich Li2TiS3 Cathode Enables High‐Energy Sulfide All‐Solid‐State Lithium Batteries

Abstract

AbstractOutstanding interfacial issues exist between oxide cathodes and sulfide electrolytes in all‐solid‐state lithium batteries (ASSLBs), while high‐capacity Li‐rich sulfide cathodes are gaining attention for application. Herein, a sulfide cathode active material Li2TiS3 (LTS) that is chemically compatible with sulfide solid electrolytes, is used in high‐performance Li6PS5Cl‐based ASSLBs at room temperature. The batteries demonstrate a maximum discharge capacity of 423.2 mAh g−1 (910 Wh kg−1 based on Li2TiS3) with 95% capacity retention after 100 cycles at 0.1 C (0.33 mA cm−2). Traces of elemental sulfur on the surface of LTS are mainly responsible for the excessive Li‐intercalation and the capacity exceedance. The Li6PS5Cl is also found to offer a nonnegligible capacity (at least 27% of excess capacity) by comparing the Li6PS5Cl‐based and Li3YCl6‐based cells using Li2TiS3 as cathode active material. During long cycling, the amorphization and degradation of Li2TiS3 and Li6PS5Cl cause capacity decay. The electrochemical kinetics of Li6PS5Cl‐based cells are evaluated as a reference to further exploit the potential of Li2TiS3 material for practical applications in ASSLBs. Overall, this superior Li‐rich sulfide material is an attractive alternative to oxide cathodes for the development of high‐performance ASSLBs.