Zinc‐Doping‐Induced Electronic States Modulation of Molybdenum Carbide: Expediting Rate‐Determining Steps of Sulfur Conversion in Lithium‐Sulfur Batteries
Bin Qin, Yanmei Li, Qun Wang, Si Zhang, Jinglin Zhang, Bin Wang, Peijia Wang, Yuhan Chen, Weiqi Yao, Fang Wang
Abstract
Abstract Enhancing Li 2 S deposition and oxidation kinetics in lithium‐sulfur batteries, especially the potential‐limiting step under lean electrolyte, can be effectively achieved by developing conductive catalysts. In this study, by using ZnMoO 4 as precursors, Zn‐doped molybdenum carbide microflowers (Zn‐Mo 2 C) composed of speared porous sheets are fabricated with a hierarchically ordered structure. Density functional theory calculations indicate that Zn doping shifts the d‐band center on Mo atoms in Mo 2 C upward, promotes the elevation of certain antibonding orbitals in Mo─S bonds above the Fermi level, enhances d‐p interaction between lithium polysulfides (LiPSs) and catalysts, weakens both S─S and Li─S bonds of LiPSs. Incorporating Zn significantly reduces the Gibbs free energy barrier for the rate‐limiting step of the Li 2 S 2 → Li 2 S conversion, from 0.52 eV for Mo 2 C to just 0.05 eV for Zn‐doped Mo 2 C. Thus, the synthesized Zn‐Mo 2 C demonstrates impressive bifunctional electrocatalytic performance, significantly advancing sulfur reduction and Li 2 S decomposition. Moreover, this modification enhances charge transfer within the Zn‐Mo 2 C/LiPSs system, synergistically accelerating the kinetics of Li 2 S 4 to Li 2 S reduction and Li 2 S oxidation. The Zn‐Mo 2 C/S cathode demonstrates impressive electrochemical performance, achieves remarkable cycling stability with a minimal capacity decay of 0.021% per cycle over 1000 cycles at 5 C, underscoring its potential for high‐energy applications.