d-p Hybridization-Induced Trapping-Coupling-Conversion Enables High-Efficiency Nb Single-Atom Catalysis for Li-S Batteries

Single-atom catalysts have been paid more attention to improving sluggish reaction kinetics and anchoring polysulfide for lithium-sulfur (Li-S) batteries. It has been demonstrated that d-block single-atom elements in the fourth period can chemically interact with the local environment, leading to effective adsorption and catalytic activity toward lithium polysulfides. Enlightened by theoretical screening, for the first time, we design novel single-atom Nb catalysts toward improved sulfur immobilization and catalyzation. Calculations reveal that Nb-N4 active moiety possesses abundant unfilled antibonding orbitals, which promotes d-p hybridization and enhances anchoring capability toward lithium polysulfides via a trapping-coupling-conversion mech-anism. The Nb-SAs@NC cell exhibits a high capacity retention of over 85% after 1000 cycles, a superior rate performance of 740 mA h g-1 at 7 C, and a competitive areal capacity of 5.2 mAh cm-2 (5.6 mg cm-2). Our work provides a new perspective to extend cathodes enabling high-energy-density Li-S batteries.

Automated summary

Single-atom catalysts are important for improving the performance of lithium-sulfur batteries. In this study, novel single-atom Nb catalysts were designed to enhance sulfur immobilization and catalysis. The Nb-N4 active moiety possessed unfilled antibonding orbitals, promoting hybridization and anchoring of lithium polysulfides. The Nb-SAs@NC cell exhibited high capacity retention, superior rate performance, and competitive areal capacity, providing new possibilities for high-energy-density Li-S batteries.