A self-growing “Polysulfide-Phobic” interface constructed by in-situ gelation of organic bentonite interlayer to suppress shuttle effect in lithium-sulfur batteries

Abstract

The shuttle effect of polysulfides hinders the long-term operation of lithium-sulfur batteries (LSBs). As the secondary current collector, the conductive interlayer can achieve induced fixation of polysulfide within a certain range, but the mechanism of action is limited by bearing saturation of the interlayer on polysulfide. In this work, the limited gelation of organic bentonite (OB) in the electrolyte is utilized to construct an in-situ gel-type physical barrier. During the initial discharge activation stage, the gel layer gradually evolves into a "Polysulfide-Phobic" repulsive layer by trapping free Lithium-polysulfides (LiPSs). Due to the strong repulsion between the "Polysulfide-Phobic" layer and free polysulfide anions, the spatial distribution of LiPSs in the positive electrode region is changed. In addition, the physical barrier effect of the gel interlayer and the chemisorbed action on LiPSs ensure the stability of the "Polysulfide-Phobic" layer during the discharge stage, while the low electronic conductivity avoids the risk of oxidation decomposition of the interface during the charging stage, which is verified by in-situ Raman. The Cells with OB interlayers show excellent cycle stability (515.5 mAh g−1 after 300 cycles) under high loading conditions (5 mg cm−2, E/S≈7.5 μL mg−1). This strategy of sacrificing initial efficiency to build an electrostatic repulsion layer in exchange for long-term stability is profitable, providing a new approach to addressing the shuttle effect.