High‐Performance Li–SeS x All‐Solid‐State Lithium Batteries

Abstract All‐solid‐state Li–S batteries are promising candidates for next‐generation energy‐storage systems considering their high energy density and high safety. However, their development is hindered by the sluggish electrochemical kinetics and low S utilization due to high interfacial resistance and the electronic insulating nature of S. Herein, Se is introduced into S cathodes by forming SeS x solid solutions to modify the electronic and ionic conductivities and ultimately enhance cathode utilization in all‐solid‐state lithium batteries (ASSLBs). Theoretical calculations confirm the redistribution of electron densities after introducing Se. The interfacial ionic conductivities of all achieved SeS x –Li 3 PS 4 ( x = 3, 2, 1, and 0.33) composites are 10 −6 S cm −1 . Stable and highly reversible SeS x cathodes for sulfide‐based ASSLBs can be developed. Surprisingly, the SeS 2 /Li 10 GeP 2 S 12 –Li 3 PS 4 /Li solid‐state cells exhibit excellent performance and deliver a high capacity over 1100 mAh g −1 (98.5% of its theoretical capacity) at 50 mA g −1 and remained highly stable for 100 cycles. Moreover, high loading cells can achieve high areal capacities up to 12.6 mAh cm −2 . This research deepens the understanding of Se–S solid solution chemistry in ASSLB systems and offers a new strategy to achieve high‐performance S‐based cathodes for application in ASSLBs.