Strengthened d-p Orbital-Hybridization of Single Atoms with Sulfur Species Induced Bidirectional Catalysis for Lithium-Sulfur Batteries

Single-atom catalysts (SACs) have been widely explored as additives to improve the performance of lithium-sulfur (Li-S) batteries, however, the design of highly catalytic and in-depth knowledge of the structure-activity relationship of SACs remains a huge challenge. Herein, electron redistribution of the Co site by introducing the S atom to replace the N atom in the first coordination shell is theoretically predicted to enhance the anchoring capability of lithium polysulfides (LiPSs) and simultaneously facilitate the redox process of Li-S batteries, due to the strengthened d-p orbital hybridization between sulfur species and SACs compared with the traditional CoN4 architecture. Enlightened by theoretical analysis, asymmetric (N, S) coordinated Co single atoms embedded on N, S-doped hierarchically porous carbon (S-Co-SACs/NSC) is precisely designed and constructed as a high-efficiency fixity and catalyst for Li-S batteries. Therefore, the battery with S@S-Co-SACs/NSC cathode exhibits high areal capacity and cycling stability. This work highlights the vital function of the electronic structures of SACs in promoting the practical application of Li-S batteries.