Two-Dimensional VSe ₂ @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 (Li 2 S 2 /Li 2 S) and the polysulfide shuttle effect. This work presents a two-dimensional sheet-like nanocomposite of polypyrrole-coated VSe 2 (VSe 2 @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 VSe 2 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 VSe 2 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 VSe 2 @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.