Density functional theory studies on tuning TaXTi(1−X)S2 for insoluble Li2S2–Li2S conversion in lithium–sulfur batteries†

Abstract

Due to the complexity of insoluble Li₂S₂–Li₂S conversion, few descriptors exist to correlate the catalytic performance and the underlying electronic structures of a given catalyst, which inhibits the development of lithium–sulfur catalysts. In this article, we employ the cluster expansion method to select 17 optimal structures for Ta_XTi_(1−X)S₂ (0 ≤ X ≤ 1) and apply density functional theory calculations to probe the relationship between electronic structures and the conversion of Li₂S₂ to Li₂S across different doping concentrations. Five possible reaction pathways were proposed, and we found that the simultaneous pathway is the most possible among the proposed five possible reaction pathways. Notably, we identify Ta_0.38Ti_0.62S₂ as a promising candidate for electrocatalytic applications in the conversion from Li₂S₂ to Li₂S. Furthermore, our study analyzes the charge transfer of Li₂S₂ (Q_Li2S2), the electronegative difference (ΔX), the adsorption energy of Li₂S (E_aLi2S), and work function (WF) as machine learning descriptors to investigate their significant influence on the Gibbs free energy (ΔG), which is negative on the simultaneous pathway. This research contributes to a deeper theoretical understanding of the complex mechanisms underlying the Li₂S₂–Li₂S conversion and provides valuable insights into the rational design of sulfur redox catalysts.