VS2/graphene heterostructures as cathode materials for sodium-sulfur batteries: A first-principles study

Sodium-sulfur batteries have garnered significant attention recently due to their high energy density. Nevertheless, the dissolution of sodium polysulfides in the electrolyte results in the shuttle effect, severely impacting the cycling efficiency of these batteries and limiting their widespread application. In this study, a novel two-dimensional VS₂/ graphene heterostructure was designed. This material is used as an anchoring material for the anode of sodium-sulfur battery to suppress the shuttle effect. This van der Waals heterostructure is composed of graphene and VS₂ stacked, and retains their inherent electronic structures. Graphene not only enhances the conductivity of sulfur cathode, but also improves the polarity of VS₂ thin film. Adsorption simulations of sodium polysulfide showed that the VS₂/graphene heterostructures possessed suitable adsorption energies in the range of 1.63 ∼ 3.47 eV, which were able to effectively anchor the polysulfide. In addition, the lower Na₂S decomposition energy barriers and sodium ion migration energy barriers show the potential of the heterostructures in catalyzing the reaction kinetics. Therefore, the VS₂/graphene heterostructure is anticipated to be an optimal anchoring material for sodium-sulfur batteries.