Theoretical study on the role of solvents in lithium polysulfide anchoring on vanadium disulfide facets for lithium-sulfur batteries

The shuttle effects by lithium polysulfides (LiPSs) and the sluggish reaction kinetics are crucial obstacles in the commercialization of Li-S batteries. Hence, effectively trapping and promoting the conversion of LiPSs is of prime importance. However, the fundamental kinetics of the electrocatalytic charging and discharging of Li-S batteries have not been sufficiently explored yet. Therefore, by taking VS₂ as a model, we conducted a density functional theory-based study to investigate the ability of dominant exposed crystal planes of VS₂ to trap LiPSs from leaching into electrolytes and to act as an electrocatalyst to increase the sulfur reduction reaction (SRR) kinetics. To reflect a realistic environment of a battery, the effect of solvents on the electrocatalytic activity was further investigated. Our calculations show that VS₂ has moderate binding energy toward LiPSs; therefore, it can effectively inhibit LiPS shuttling and leaching. However, there was no consistent pattern for binding energies under different VS₂ facets. Furthermore, VS₂ (001) facets exhibit excellent electrocatalytic activity for the SRR and Li₂S decomposition reaction compared to other dominant crystal planes, which significantly lowers the energy barriers of LiPS conversion during the charging and discharging process, ensuring high-rate performance and longer cycle life. Beyond the VS₂ systems explored in the current study, the same approach can apply to other potential electrocatalysts as a promising pathway to improve the sluggish reaction kinetics of Li-S batteries.