Insight into the Anchoring Effect of Two-Dimensional TiX2 (X = S, Se) Materials for Sodium-Sulfur Batteries: A First-Principles Study

In this paper, a monolayer of TiX2 (X = S, Se) is used to suppress the shuttle effect of polysulfides, thereby accelerating the kinetic process of lower-order polysulfides. The results show that the adsorption energies of the studied TiX2 for Na2Sn are all better than those of common electrolytes, and the effect of adsorption on the structure of Na2Sn is negligible. The calculated results show that the anchoring behavior of TiX2 to Na2Sn has no effect on the metallic properties of pristine TiX2. On the other hand, the introduction of this material can reduce the diffusion barrier energy of Na2S and improve the utilization rate of sulfur more effectively. In conclusion, TiX2 has suitable adsorption strength, enhances electrical conductivity, and promotes the oxidative decomposition process of polysulfides. It can be theoretically demonstrated that TiS2 is better than TiSe2 in improving the performance of sodium-sulfur batteries and is more suitable as an anchoring material (AM) for sodium-sulfur batteries.