Atomic-Level Asymmetric Regulation of Co–N3S1 Catalysts Accelerates Polysulfide Trapping and Conversion in Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries are severely limited by the shuttling behavior of soluble lithium polysulfides (LiPSs) and slow catalytic conversion kinetics. Herein, a single-atom catalyst featuring asymmetric S–Co–N₃ coordination (Co_SA-SNC) supported by hollow carbon nanoboxes is designed to act as an efficient host catalyst of the Li–S battery. Experimental and theoretical calculations reveal that the introduction of S into the Co single-atom catalyst induces asymmetric local charge distribution around Co centers and more unpaired electrons. The tailored electronic structure with optimized d-orbital energy levels accelerates charge transfer and further enhances adsorption energy and conversion kinetics for LiPSs. The hollow nanostructure of Co_SA-SNC confines and suppresses polysulfide shuttling for high sulfur loadings and fast charge/mass transfer. The resultant Li–S batteries incorporated with Co_SA-SNC deliver a high initial specific capacity of 1408 mAh g^–1, and ultralow capacity decay of 0.027% per cycle over 900 cycles. This investigation provides insights into the design of advanced cathode catalysts of Li–S batteries.