To effectively drive the conversion of sulfur with electroactive niobium tungsten oxide microspheres for lithium-sulfur battery

摘要

Realizing high energy density is the desirable target of the research and development for lithium-sulfur battery. However, the demands of high sulfur content in composite, high sulfur loading in electrode, and low electrolyte usage are likely excessive for reaching both high gravimetric and volumetric capacities of sulfur cathode with conventional inactive hosts of sulfur. Herein, in order to effectively drive the conversion of sulfur, niobium tungsten oxide (Nb18W16O93) microspheres are adopted as electroactive host in the similiar electrochemical window to sulfur. As expected, Nb18W16O93 shows good electrochemical activity for lithium storage, and strong adsorption toward polysulfides. In particular, the in-situ electrochemically lithiated oxide in the discharge process can serve as good electrocatalyst and lithium-transfer bridge, facilitating the conversion of both the solid sulfur and soluble polysulfides. Correspondingly, the new lithium-transfer mechanism on Nb18W16O93 endows the sulfur cathode a high areal capacity (19.19 mAh cm(-2)) under both high sulfur loading (16.94 mg cm(-2)) and low electrolyte/sulfur ratio (4.5 mu L mg(-1)). In addition, the sulfur-based composite with high tap density (1.56 g cm(-3)) shows a desired volumetric capacity (1605.3 mAh cm(-composite)(-3)), almost 1.9 times of that for the conventional S/carbon composite. This work provides a new perspective for understanding the electroactive hosts in lithium-sulfur battery.