SnS2 monolayer and SnS2/graphene heterostructure as promising anchoring materials for lithium-sulfur batteries: A computational study

Highlights: • Interactions between polysulfides and SnS₂ were studied by DFT calculations. • SnS₂/G heterostructure was considered to improve electrical conductivity. • Both SnS₂ and SnS₂/G are promising anchoring materials for Li-S batteries. Lithium-sulfur (Li-S) batteries have attracted widespread attention as high energy storage systems. However, the shuttle of intermediate polysulfides is still one of the unresolved obstacles for their practical application. In this work, the potential of SnS₂ monolayer as polysulfides anchoring material for suppressing the "shuttle effect" were investigated through density functional theory (DFT) calculations. We found that SnS₂ monolayer can immobilize polysulfides with moderate binding strength and preserve their structural integrity well. The low diffusion barriers of long-chain polysulfides on SnS₂ surface suggest the improved electrode reaction efficiency. Furthermore, SnS₂/graphene heterostructure with improved electrical conductivity was selected to analyze the applicability, which also shows outstanding anchoring performance and good diffusion property for polysulfides. Combined with the small reduction free energies of S₈ to Li₂S and low decomposition barriers of Li₂S during the discharge/charge process, we can conclude that SnS₂-based composites are promising anchoring materials for advanced Li-S batteries.