Atomic-Level Asymmetric Regulation of Co-NS 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 coordination (Co-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-SNC confines and suppresses polysulfide shuttling for high sulfur loadings and fast charge/mass transfer. The resultant Li-S batteries incorporated with Co-SNC deliver a high initial specific capacity of 1408 mAh g, 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.