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 3.68V 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.