Tungsten oxide nanowire clusters anchored on porous carbon fibers as a sulfur redox mediator for lithium–sulfur batteries†

Abstract

Addressing the sluggish redox kinetics of sulfur electrodes and mitigating the shuttle effect of intermediate lithium polysulfides (LiPS) are crucial for the advancement of high-energy lithium–sulfur batteries. Here, we introduce a pioneering flexible self-supporting composite scaffold that incorporates tungsten oxide nanowire clusters anchored on core–shell porous carbon fibers (WO₃/PCF) for sulfur accommodation. The core of PCF serves as a robust electrode supporting scaffold, whereas the porous shell of PCF provides a 3D interconnected conductive network to accommodate sulfur, restrain polysulfide diffusion and buffer electrode expansion. The WO₃ nanowire clusters not only entrap polysulfides but also function as a redox mediator to promote sulfur conversion, thus greatly mitigating the shuttle effect and boosting redox kinetics. The unique core–shell porous structure of PCF and the dual functionality of WO₃ for LiPS capture and conversion contribute to the high capacity, exceptional cycling stability, and superior rate capability of the WO₃/PCF/S cathode. Impressively, at a sulfur loading of 3.0 mg cm⁻², it achieves an initial capacity of 1082 mA h·g⁻¹ at 1 C with an ultralow decay rate of 0.039% over 1000 cycles. Even under a high sulfur loading of 6.1 mg cm⁻², it maintains a reversible capacity of 536 mA h·g⁻¹ after 1000 cycles with a decay rate of only 0.043% at 0.5 C.