Accelerating Polysulfide Redox Kinetics via the Metal-Insulator Interface in a Binder-Free Separator for Long-Life...

The sluggish bidirectional reaction kinetics of lithium polysulfides (LiPSs) and the severe shuttle effect continue to impede the commercialization of lithium-sulfur (Li-S) batteries. Herein, a binder-free separator featuring an in situ formed W₂N-WO₃ metal-insulator interface is developed to address these issues systematically. By precisely controlling the coating process, W₂N and WO₃ are codeposited on a carbon-coated glass fiber (C/GF) substrate to produce a robust and uniform film. The heterojunction generates an internal electric field at the interface, facilitating spontaneous electron transfer and accelerating sulfur redox reactions. Theoretical calculations further validate that the W₂N-WO₃ heterostructure improves the redox kinetics of liquid-solid conversion and enhances the absorption of long-chain LiPSs. Li-S cells employing W₂N-WO₃/C/GF binder-free separators exhibit an excellent rate capability and cycling stability. The Li-S pouch cell also maintains reversible capacity under bending conditions, demonstrating reliable mechanical integrity. These results illustrate the effectiveness of heterojunction engineering in regulating LiPS adsorption and catalysis for binder-free separators in high-performance Li-S batteries.