Active Regulation Volume Change of Micrometer‐Size Li2S Cathode with High Materials Utilization for All‐Solid‐State Li/S Batteries through an Interfacial Redox Mediator

Abstract

AbstractLow electronic and ionic transport, limited cathode active material utilization, and significant volume change have pledged the practical application of all‐solid‐state Li/S batteries (ASSLSBs). Herein, an unprecedented Li2S‐LixIn2S3 cathode is designed whereby In2S3 reacts with Li2S under high‐energy ball milling. In situ electron diffraction and ex situ XPS are implanted to probe the reaction mechanism of Li2S‐LixIn2S3 in ASSLSBs. The results indicate that LixIn2S3 serves as a mobility mediator for both charge‐carriers (Li+ and e−) and redox mediator for Li2S activation, ensuring efficient electronic and ionic transportation at the cathode interface and inhibiting ≈ 70% relative volumetric change in the cathode, as confirmed by in situ TEM. Thus, the Li2S‐LixIn2S3 cathode delivers an initial areal capacity of 3.47 mAh cm−2 at 4.0 mgLi2S cm−2 with 78% utilization of Li2S. A solid‐state cell with Li2S‐LixIn2S3 cathode carries 82.35% capacity retention over 200 cycles at 0.192 mA cm−2 and a remarkable rate capability up to 0.64 mA cm−2 at RT. Besides, Li2S‐LixIn2S3 exhibits the highest initial areal capacity of 4.08 mAh cm−2 with ≈74.01% capacity retention over 50 cycles versus 6.6 mgLi2S cm−2 at 0.192 mA cm−2 at RT. The proposed strategy of the redox mediator minimized volumetric change and realized outstanding electrochemical performance for ASSLSBs.