Optimizing Electrocatalysis and Domain Effects of Graphene on Li₂S Cathodes for High-Efficient-Stable Li─S Batteries

Reducing the initial activation barrier of Li₂S is crucial for enhancing the coulomb efficiency and cycle life of Li─S batteries. Herein two Li₂S-graphene cathode architectures are constructed and investigated the electrocatalytic and domain effects of two graphene on Li₂S. Systematic studies reveal an unprecedented relevancy between Li₂S activation and graphene electrocatalysis, as well as an intrinsic relationship between Li₂S stability and the graphene domain. A dramatically reduced initial activation potential of 2.8 V is achieved via the S─C bonding electrocatalysis of Li₂S-graphene structure, much lower than the initial activation potential of 3.68 V triggered by two-phase electrocatalysis of Li₂S/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 Li₂S@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 Li₂S-graphene cathode materials.