Accelerating Sulfur Redox Chemistry by Atomically Dispersed Zn‐N₄ Sites Coupled with Pyridine‐N Defects on Porous Carbon Sheets

Abstract

Abstract Single‐atom catalysts (SACs) with specific N‐coordinated configurations immobilized on the carbon substrates have recently been verified to effectively alleviate the shuttle effect of lithium polysulfides (LiPSs) in lithium–sulfur (Li─S) batteries. Herein, a versatile molten salt (KCl/ZnCl 2 )‐mediated pyrolysis strategy is demonstrated to fabricate Zn SACs composed of well‐defined Zn‐N 4 sites embedded into porous carbon sheets with rich pyridine‐N defects (Zn─N/CS). The electrochemical kinetic analysis and theoretical calculations reveal the critical roles of Zn‐N 4 active sites and surrounding pyridine‐N defects in enhancing adsorption toward LiPS intermediates and catalyzing their liquid–solid conversion. It is confirmed by reducing the overpotential of the rate‐determining step of Li 2 S 2 to Li 2 S and the energy barrier for Li 2 S decomposition, thus the Zn─N/CS guarantees fast redox kinetics between LiPSs and Li 2 S products. As a proof of concept demonstration, the assembled Li─S batteries with the Zn─N/CS‐based sulfur cathode deliver a high specific capacity of 1132 mAh g −1 at 0.1 C and remarkable capacity retention of 72.2% over 800 cycles at 2 C. Furthermore, a considerable areal capacity of 6.14 mAh cm −2 at 0.2 C can still be released with a high sulfur loading of 7.0 mg cm −2 , highlighting the practical applications of the as‐obtained Zn─N/CS cathode in Li─S batteries.