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

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–N 3 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.