Polyvinylidene fluoride–assisted construction of anion-doped two–dimensional cobalt selenide modified Janus separators for lithium-sulfur batteries

Despite promise, monocomponent catalysts suffer from the slow reaction kinetics and polysulfide shuttling in lithium–sulfur (Li S) batteries. The introduction of anion doping can offer a promising approach to modify the inherent electronic structure and enhance catalytic activity. Hereby, polyvinylidene fluoride (PVDF)–assisted high–temperature selenization method of the two–dimensional (2D) ZIF–67 precursor was designed to prepare fluorine–doped cobalt selenide embedded in nitrogen–doped carbon nanosheets (F–CoSe 2 /NC) as a novel catalyst. PVDF plays a crucial role in preserving the structural integrity of 2D ZIF–67, resulting in abundant active catalytic sites in the final product F–CoSe 2 /NC. Additionally, the introduction of F doping further modulates the d–band center of CoSe 2 , enhancing its ability to interact with lithium polysulfides (LiPSs) and imparting high catalytic activity. The ordered pore structure and excellent conductivity of F–CoSe 2 /NC can guide uniform lithium deposition. Benefiting from synergistic effects, Li S batteries with F–CoSe 2 /NC modified Janus separators demonstrate excellent rate performance of 816.5 mAh g −1 at 2C, long cycling stability (0.033 % decay/cycle at 5C over 800 cycles) and high areal capacity even under high sulfur loading. This strategy provides a feasible solution to enhance the catalytic efficiency of metal compounds.