Modulating the Coordination Environment of Co Single-Atom Catalysts: Impact on Lithium-Sulfur Battery Performance

The coordination environment is crucial to the electrocatalytic activity of single-atom catalysts (SACs). Although substituting N atoms in traditional transition metal-nitrogen (TM-N₄) configuration with other non-metal atoms has been reported, its specific role in sulfur electrochemical reactions has not been sufficiently investigated. Herein, a Co-P₂N₂ SACs configuration is fabricated to investigate the mechanistic differences compared to Co-N₄ in sulfur reduction/oxidation. This configuration enhances the electron transfer with Li₂S₆, where the electrons tend to aggregate between P and Li atoms as two separate parts rather than a single merged zone as observed in symmetric Co-N₄ SACs. This process facilitates polysulfide decomposition and promotes Li₂S nucleation/oxidation. Furthermore, the CoPNC interlayer effectively suppresses cell self-discharge and Li anode corrosion due to polysulfide shuttling. Li-Li symmetrical cell incorporated with the CoPNC interlayer achieves a prolonged lifespan exceeding 1000 h, and Li-S full cell delivers a discharge capacity of more than 1500 mAh g⁻¹. This research provides insights into how the geometric configuration of SACs influences the performance of conversion-type batteries.