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

Outstanding 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 Li 2 TiS 3 (LTS) that is chemically compatible with sulfide solid electrolytes, is used in high-performance Li 6 PS 5 Cl-based ASSLBs at room temperature. The batteries demonstrate a maximum discharge capacity of 423.2 mAh g −1 (910 Wh kg −1 based on Li 2 TiS 3 ) 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 Li 6 PS 5 Cl is also found to offer a nonnegligible capacity (at least 27% of excess capacity) by comparing the Li 6 PS 5 Cl-based and Li 3 YCl 6 -based cells using Li 2 TiS 3 as cathode active material. During long cycling, the amorphization and degradation of Li 2 TiS 3 and Li 6 PS 5 Cl cause capacity decay. The electrochemical kinetics of Li 6 PS 5 Cl-based cells are evaluated as a reference to further exploit the potential of Li 2 TiS 3 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.