Preparation of Vanadium-based Sulfide-MXene Hetero-Catalysts and Comparative Study of Catalytic Mechanism of Lithium-sulfur Batteries

Because of high theoretical specific capacity and energy density, lithium-sulfur batteries (LSBs) are regarded as one of the most promising energy storage batteries. However, the low conductivity of the active sulfur and the Li₂S discharge product, the shuttle effect of intermediate products produced by the charging and discharging process, and serious capacity degradation caused by the slow sulfur redox kinetics, limits the practical application of LSB. Herein, three different vanadium sulfide@MXene hetero-structure catalysts were synthesized by one-step hydrothermal method and applied to the cathode host in LSBs. Compared with VS₄@MXene and V₅S₈@MXene, VS₂@MXene has the largest specific surface area and electrochemical active surface area, which provides more active sites in LSBs, thereby improving the electrochemical reaction kinetics. Meanwhile, the experimental and Density Functional Theory(DFT) theoretical calculation results show that the VS₂@MXene has the strongest polysulfide adsorption ability and electronic conductivity, which effectively alleviates the shuttle effect of polysulfides and improves the utilization of sulfur. LSBs with S/VS₂@MXene as the cathode achieve an initial discharge specific capacity of 815.4 mAh·g⁻¹ and still maintain a reversible specific capacity of 645.4 mAh·g⁻¹ after 400 cycles at 1 C. This research provides some insights for the selection of vanadium-based sulfide as the catalytic materials and hosts in lithium-sulfur batteries.