Active Regulation Volume Change of Micrometer‐Size Li<sub>2</sub>S Cathode with High Materials Utilization for All‐Solid‐State Li/S Batteries through an Interfacial Redox Mediator
Peiwen Yu, Shaorui Sun, Chunhao Sun, Chaoyuan Zeng, Ze Hua, Niaz Ahmad, Ruiwen Shao, Wen Yang
Abstract
Abstract 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 Li 2 S‐Li x In 2 S 3 cathode is designed whereby In 2 S 3 reacts with Li 2 S under high‐energy ball milling. In situ electron diffraction and ex situ XPS are implanted to probe the reaction mechanism of Li 2 S‐Li x In 2 S 3 in ASSLSBs. The results indicate that Li x In 2 S 3 serves as a mobility mediator for both charge‐carriers (Li + and e − ) and redox mediator for Li 2 S 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 Li 2 S‐Li x In 2 S 3 cathode delivers an initial areal capacity of 3.47 mAh cm −2 at 4.0 mg Li2S cm −2 with 78% utilization of Li 2 S. A solid‐state cell with Li 2 S‐Li x In 2 S 3 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, Li 2 S‐Li x In 2 S 3 exhibits the highest initial areal capacity of 4.08 mAh cm −2 with ≈74.01% capacity retention over 50 cycles versus 6.6 mg Li2S 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.