Theoretical Investigation of Nonmetallic Single-Atom Catalysts for Polysulfide Immobilization and Kinetic Enhancement in Lithium–Sulfur Batteries

Abstract

With the increasing interest in tackling the "shuttle effect" of lithium−sulfur (Li−S) batteries, there is a growing emphasis on investigating effective catalysts to improve redox kinetics and understand the associated reaction pathways. In this study, a series of nonmetal (B, N, Si, P, S, F, and Cl) single-atomdoped graphenes were theoretically investigated as the catalysts for the multistep reduction of S 8 and the kinetic conversion of the ratelimiting step. Analysis of the Gibbs free energy for the S 8 reduction process on these catalysts confirms that the rate-limiting step is the conversion of Li 2 S 2 to Li 2 S. Subsequently, six kinetic reaction paths transforming Li 2 S 2 to Li 2 S were constructed. Based on the optimal reaction path with LiS as the intermediate product, a volcano plot was built with the excellent descriptor, −ΔG ad (LiS). The peak catalytic efficiency corresponds to a −ΔG ad (LiS) value of 1.72 eV. Consequently, pyrrolic N-and Cl-doped graphene are identified as superior catalysts with energy barriers of 0.61 and 0.47 eV for the reversible conversion of Li 2 S 2 to Li 2 S. Furthermore, the strong correlation between ΔG ad (LiS) and ΔG ad (Li 2 S) also enables the prediction of catalytic performance using ΔG ad (Li 2 S). These findings have significant implications for future catalyst design and understanding of kinetic reaction pathways in Li−S batteries.