Optimizing Electrocatalysis and Domain Effects of Graphene on LiS Cathodes for High-Efficient-Stable Li─S Batteries.

Reducing the initial activation barrier of LiS is crucial for enhancing the coulomb efficiency and cycle life of Li─S batteries. Herein two LiS-graphene cathode architectures are constructed and investigated the electrocatalytic and domain effects of two graphene on LiS. Systematic studies reveal an unprecedented relevancy between LiS activation and graphene electrocatalysis, as well as an intrinsic relationship between LiS stability and the graphene domain. A dramatically reduced initial activation potential of 2.8 V is achieved via the S─C bonding electrocatalysis of LiS-graphene structure, much lower than the initial activation potential of 3.68V triggered by two-phase electrocatalysis of LiS/graphene composite. Density functional theory calculations offer mechanism insights into the electrocatalytic effect of S─C bonding on reduced overpotential, and in situ NMR provides solid evidence for the confinement effect of core-shell structure on enhanced cyclability. Notably, a specially designed LiS@graphene cathode with core-shell structure and S─C interactions exhibit both superior electrocatalytic activation and electrochemical reversibility, enabling Li─S battery promising electrochemical properties, including low charge-discharge overpotential, high specific capacity, and excellent cycling performance. More importantly, it demonstrates excellent chemical compatibility within various electrolytes. This study provides valuable theoretical insights for the development of high-performance LiS-graphene cathode materials.