Density Functional Theory Studies on Tuning p-Band Electronic Structures of TiS2-Based Single-Atom Catalysts for Polysulfide Conversion in Lithium–Sulfur Batteries

Despite extensive investigation, the utilization of sulfur and the cycling stability of lithium–sulfur (Li–S) batteries are significantly impeded by the polysulfide shuttle effect and sluggish sulfur reaction kinetics. In this study, aimed at enhancing the performance of Li–S batteries, we focus on the implementation of single metal atom (Be, Mg, Ca, V, Nb, and Ta)-doped TiS2 monolayers as cathode catalysts. Our findings reveal that Be-TiS2, Mg-TiS2, and Ca-TiS2 exhibit superior polysulfide adsorption capabilities and lower values for the rate-determining step in terms of Gibbs free energy. Electronic structure analysis further elucidates that the enhanced anchoring and electrocatalytic activities stem from the upward displacement of the p-band center and the narrowing of the gap within the Δd-p-band, respectively. Moreover, Be-TiS2 and Ca-TiS2 monolayers facilitate the acceleration of the Li2S decomposition reaction and Li-ion migration on their surfaces. This investigation effectively advances our understanding of the role of TiS2 in the polysulfide conversion process and offers valuable insights into the design of cathodes in Li–S batteries.