Anchoring enhancement of Graphdiyne by doping and molecular intercalation for Lithium−sulfur batteries

Abstract

Lithium−sulfur (Li − S) batteries are the most promising next-generation energy storage devices due to the high energy density, low cost, and environmental friendliness. The shuttle effect of lithium polysulfides (LiPSs) have hindered the commercialization of Li − S batteries owing to the remarkable deteriorations to the Coulombic efficiency, capacity retention and cycle life. Herein, we propose a method of B element doping combining with methylbenzene molecular intercalation to modify graphdiyne (GDY) as the cathode of Li − S batteries, which strengthens the anchoring to LiPSs. First-principle calculations are performed to explore the adsorption configurations, energies, charge transfers and diffusion coefficients of S₈ and LiPSs. Pure GDY can only adsorbed S₈ and LiPSs weakly, resulting in the LiPSs can freely diffuse and dissolve into the electrolyte and then self-discharge. Then, GDY with B element doping (B@GDY), facilitates the charge exchange between adsorbates and substrate by enabling S gaining extra electrons from B elements, which further enhances the absorption energies. The molecular intercalation to B@GDY (B_Ben@GDY) induce a steric hindrance to restrict the diffusion of S₈ and larger LiPSs, making the anchoring effect significantly enhanced. Last, the comparison between adsorption energies and the binding energy between LiPSs and solvent molecules, further supports the anchoring effects of B@GDY and B_Ben@GDY to LiPSs. Our study serves as a guide for the design of the cathode free from the shuttle effect for Li − S batteries.