Promoting reaction kinetics in lithium-sulfur batteries: A study of bifunctional UIO-66-NH2-HSO3@rGO for Li+ transport and polysulfide adsorption

Abstract

Lithium-sulfur batteries (LSBs) are recognized for their high energy density; however, challenges such as the lithium polysulfide (LiPS) shuttle effect and sluggish reaction kinetics remain unresolved. To mitigate these issues, a dual-functional metal–organic framework material integrated with graphene (UIO-66-NH₂-HSO₃@rGO) has been developed, with its Li⁺ transport and LiPS anchoring capabilities systematically investigated. Through density functional theory (DFT) calculations, it was demonstrated that the –HSO₃ group in UIO-66-NH₂-HSO₃ facilitates LiPS adsorption via strong electrostatic interactions while repelling polysulfide anions, whereas the –NH₂ group chemically anchors these anions, thereby enhancing Li⁺ transport and LiPS trapping. Furthermore, the incorporation of reduced graphene oxide (rGO) has been shown to enhance conductivity, mechanical stability, and LiPS adsorption, attributed to its unique two-dimensional structure. Electrochemical evaluations have revealed that separators coated with this composite exhibit superior long-term cycling stability and rate performance when compared to those with single-functional groups. In situ UV–vis spectroscopy and electrochemical impedance spectroscopy have confirmed that the coating promotes uniform Li⁺ transport and effectively suppresses the LiPS shuttle effect, significantly improving LSBs performance. Important insights are provided into the practical application of multifunctional material structure design in the field of LSBs technology by this study.