Dual-Atom Doping Carbon Materials as Highly Efficient Electrocatalysts for Lithium–Sulfur Batteries: Bimetallic Cooperation Mechanism

Abstract

Due to the low sulfur utilization, slow battery kinetics, and shuttle effect of lithium polysulfides (LiPSs), the practical application of lithium–sulfur (Li–S) batteries is severely limited. Understanding the reaction mechanism is very important for the design and application of high-performance batteries. Herein, the adsorption mechanism of LiPSs, the reaction mechanism of a battery electrode, and the catalytic decomposition of LiPSs on pristine, single-atom, and dual-atom doping C9N4 (C9N4, M/C9N4, and M1–M2/C9N4) nanosheets are comprehensively considered for the first time. Through bond length analysis, charge analysis, and energy analysis, the doping of metal atoms, especially co-doping of V and Zn atoms (Zn–V/C9N4), can greatly improve the adsorption performance of material C9N4. More importantly, Zn–V/C9N4 can significantly reduce the reaction energy barrier of the battery electrode (0.144 eV) and the decomposition energy barrier of Li2S (0.661 eV). The simulation results show that high catalytic activity depends on the unique d-orbital coupling and the ″pull″ effect of metal co-doping. These findings are crucial to understanding the role of dual-atom doping carbon materials in the design of cathode materials to cope with the performance constraints in lithium–sulfur batteries. We hope that this research idea can also be applied to other dual-atom systems.