Modulating the d-band center of single-atom catalysts for efficient Li 2 S 2-Li 2 S conversion in durable lithium-sulfur batteries

Enhancing the conversion of insoluble Li 2 S 2 -Li 2 S to improve sulfur utilization has become an essential strategy for Lithium-Sulfur (Li-S) batteries. The proposed approach employs single-atom catalysts (SACs) known for their high atomic usage efficiency to enable in -situ reactions with Li 2 S 2 . However, the origin and mechanisms of various SACs involved in the Li 2 S 2 to Li 2 S reduction reaction are not fully elucidated. Herein, we reveal the underlying mechanism of Li 2 S 2 -Li 2 S reduction catalysis on Mn atoms by examining the electronic structure of d orbitals. Theoretical calculations indicate that substituting a S atom for N in the first coordination structure of Mn SACs elevates the Mn d -band center and simultaneously enhances the hybridization between the Mn d orbitals and the p orbitals of sulfur species. This alteration not only improves the anchoring of lithium polysulfides, leading to better adsorption but also accelerates the conversion kinetics of Li 2 S 2 to Li 2 S due to the improved intrinsic catalytic activity of SACs. As a result, the Li-S batteries equipped with the SAMn-based cathode deliver an impressive initial capacity of 1343.9 mAh g - 1 at 0.1 C, exceptional rate capability of 782.4 mAh g - 1 at 3 C, and maintain a low degradation rate of approximately 0.025% per cycle over 1000 cycles at 1.0 C. Furthermore, with a sulfur loading of 6 mg cm -2 , the S/SAMn@NSC cathode achieves a reversible areal capacity of 4.4 mAh cm -2 at 0.1 C. This study significantly advances the kinetics of solid-solid transformation in Li-S battery cathodes through catalysis facilitated by single-atom d -band regulation.