Polyvinylidene fluoride-assisted construction of anion-doped two-dimensional cobalt selenide modified Janus...

Despite promise, monocomponent catalysts suffer from the slow reaction kinetics and polysulfide shuttling in lithium-sulfur (LiS) 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-CoSe₂/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-CoSe₂/NC. Additionally, the introduction of F doping further modulates the d-band center of CoSe₂, enhancing its ability to interact with lithium polysulfides (LiPSs) and imparting high catalytic activity. The ordered pore structure and excellent conductivity of F-CoSe₂/NC can guide uniform lithium deposition. Benefiting from synergistic effects, LiS batteries with F-CoSe₂/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.