Lithium-rich Li${}_2$TiS${}_3$ 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. (© 2022 Wiley‐VCH GmbH)