Electronic structure engineering of Zn-based catalysts via anionic regulation for polysulfide adsorption-catalysis in Li-S batteries

Abstract

Sluggish sulfur redox kinetics and polysulfide shuttling significantly compromise the cycling stability and sulfur utilization of lithium-sulfur batteries (LSBs). Efficient catalytic conversion of polysulfides is a pivotal strategy to address these issues, yet remains challenged by ambiguous electronic structure-performance relationships and limited catalytic efficacy. We rationally designed zinc-based compounds encapsulated in N-doped porous carbon (ZnX@PC, X=O/S/Se) to modulate the orbital electronic structure of zinc centers, serving as catalysts for accelerating sulfur redox kinetics and suppressing polysulfide migration in LSBs. The battery performance with these zinc-based catalysts was systematically evaluated, with a particular focus on how p-band characteristics of anions (O/S/Se) govern d-p orbital hybridization between Zn center and S in polysulfides. Compared to O and S, the Se anion optimizes the Zn d-band center closer to the Fermi level in ZnSe compounds. The ZnSe@PC catalyst exhibits balanced polysulfide adsorption and the most favorable d-band proximity to the Fermi level, demonstrating optimal adsorption-catalysis synergy for polysulfides. Electrochemical testing revealed an initial specific capacity of 1526 mAh g-1 at 0.1C for ZnSe@PC-based cells, confirming high sulfur utilization efficiency. Under challenging conditions (E/S ratio = 4.0 μL mg-1, sulfur loading = 7.0 mg cm-2), the pouch cell system delivered an exceptional capacity of 953.3 mAh g-1 at 0.1C, representing one of the best performances reported for high loading sulfur cathodes. Consequently, this work deepens the mechanistic understanding of LSBs and offers empirical validation for the conventional theory regarding the influence of the d-band center on battery performance.