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

Luo, Jin; Yang, Moon Young; Mu, Yuhe; Yang, Zhongjiu; Merinov, Boris V; Goddard, William A; Zhou, Yue · ACS Nano · 2025

basic_science · Level V

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Abstract

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 W<sub>2</sub>N-WO<sub>3</sub> metal-insulator interface is developed to address these issues systematically. By precisely controlling the coating process, W<sub>2</sub>N and WO<sub>3</sub> 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 W<sub>2</sub>N-WO<sub>3</sub> heterostructure improves the redox kinetics of liquid-solid conversion and enhances the absorption of long-chain LiPSs. Li-S cells employing W<sub>2</sub>N-WO<sub>3</sub>/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.