First-principles study of sulfur-host materials utilizing single-atom catalysts embedded within g-C3N4

The performance of lithium-sulfur batteries (LSBs) is limited by the shuttle effect and the conversion between lithium polysulfides (LiPSs). In this study, based on first-principles calculations, we thoroughly investigated the anchoring and catalytic effects of transition metal atom-embedded g-C3N4 (TM@g-C3N4, TM = Fe, Co, Ni) as sulfur host materials for LSBs. COHP calculation results demonstrate that TM@g-C3N4 effectively anchors LiPSs by forming Li-N and TM-S bonds, suppressing the shuttle effect, and enhancing the electrochemical performance. The density of states (DOS) results indicate that the introduction of transition metal atoms improves the conductivity, rendering the entire adsorption system metallic, which helps maintain good conductivity of sulfur-loaded cathode materials during charge and discharge processes. Among them, Ni@g-C3N4 exhibits superior performance by effectively anchoring LiPSs (1.98-4.21 eV) and significantly reducing the free energy of sulfur reduction reaction (0.07 eV). This study provides new insights into the development of sulfur host materials with strong anchoring capability and excellent catalytic activity, and serves as a reference for g-C3N4 loaded with transition metal atoms as high-quality cathode materials.