Two-Dimensional VSe₂@Polypyrrole Heterostructure Enables Stable High-Rate Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation high-energy-density storage systems. However, their practical application is limited by the poor conductivity of sulfur and its discharge products (Li₂S₂/Li₂S) and the polysulfide shuttle effect. This work presents a two-dimensional sheet-like nanocomposite of polypyrrole-coated VSe₂ (VSe₂@PPy) as an advanced sulfur host for high-performance Li-S battery cathodes. The design integrates the high conductivity and intrinsic catalytic activity of metallic VSe₂ for polysulfide conversion with the excellent conductive network, adsorption capacity, and mechanical flexibility offered by the PPy coating. A functional interface was established through the interface electronic coupling effect between VSe₂ and PPy, thereby constructing an "adsorption-enrichment-fast interfacial conversion" pathway. Their synergy comprehensively enhances the overall conductivity of the electrode, ensures strong polysulfide adsorption, accelerates redox kinetics, and alleviates volume changes during cycling. Consequently, the VSe₂@PPy/S cathode delivers a high initial capacity of 1243 mAh g^-1 at 0.5 C and remarkable cycling stability with a low decay rate of 0.06% per cycle over 1000 cycles at 3 C. It also maintains good performance under challenging conditions, including high sulfur loading and a wide temperature range from -25 to 55 °C.