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

Low 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 In(2)S(3)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 LixIn(2)S(3) 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 approximate to 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 mgLi(2)S 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 approximate to 74.01% capacity retention over 50 cycles versus 6.6 mgLi(2)S 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.