Tailored ZnO-ZnS heterostructure enables a rational balancing of strong adsorption and high catalytic activity of polysulfides for Li-S batteries

Abstract

Electrocatalytic conversion of polysulfides is an effective strategy to alleviate shuttle effects for Li-S batteries, but achieving the synergistic effects between strong adsorption and high catalytic activity with a single catalyst is still challenging. Herein, we report the rational balancing of strong adsorption and high catalytic activity on the tailored ZnO-ZnS/reduced graphene oxide (rGO) heterostructure to achieve significantly enhanced conversion of polysulfides. By integrating the merits of adsorptive ZnO, catalytic ZnS and conductive rGO, the ZnO-ZnS/rGO heterostructures could enable an unrestricted adsorption-diffusion-conversion of polysulfides. Moreover, by controlling the sulfurization degree, the ZnO-ZnS/rGO heterostructure with ZnO/ZnS ratio of 7:3 performs the optimized overall performance, indicative of a trade-off between adsorption and catalytic activity. When served as functional coatings onto the separators, the ZnO-ZnS/rGO heterostructures could greatly promote the redox kinetics and retrain the polysulfides shuttling. The pure sulfur cathode with the 7ZnO-3ZnS/rGO modified separator delivers a high initial specific capacity of 1186 mAh g −1 at 0.5 C and a low capacity fading of 0.06% per cycle over 500 cycles at 1 C. Even with high sulfur loading of 7.6 mg cm −2 , a high reversible specific capacity of 671 mAh g −1 at 1 C can still be retained. This work presents a rational method to tailor the heterostructure catalysts for boosting electrocatalytic conversion of polysulfides towards high-performance Li-S batteries.