First-Principles Investigation of Anchoring Behavior of WS2 and WSe2 for Lithium-Sulfur Batteries

The commercial realization of lithium-sulfur (Li-S) batteries is obstructed because of rapid capacity fading due to lithium polysulfides (LiPSs) dissolution into the electrolyte. In order to enhance the efficiency and performance of the Li-S batteries, the transition metal dichalcogenides are reported as promising anchoring materials (AMs) as they could strongly adsorb and effectively suppress the migration of the polysulfides species. Herein, we used first-principles based density functional theory (DFT) calculations to investigate the interactions between AMs such as tungsten dichalcogenides, WX2 (X=S and Se) and the LiPSs. The LiPSs binding behavior of WS2 and WSe2 are found to be quite similar. The calculated adsorption energies of LiPS species indicate that the WX2 possesses moderate binding strength and the binding is facilitated via charge transfer from the polysulfides to the AM. We observe elongation of intramolecular Li-S bonds in LiPS upon their adsorption onto the WX2, however, chemical structures of LiPSs are preserved without decomposition. The calculated density of states indicates the LiPS adsorbed WX2 systems exhibits semiconducting behavior with a slightly lower bandgap compared to the pristine WX2. Overall, our simulation results provide detailed insight into the behavior of WX2 as AMs to suppress the LiPSs migration and henceforth paves the way towards the development of high-performance Li-S batteries.