A Dual-Functional Sulfur-rich Copolymers for Stable Anchoring and Enhanced Conversion of Polysulfide in Lithium-Sulfur Batteries.

Sulfur-rich copolymers have gained a great deal of attention as promising cathode materials in Li-S batteries due to their low cost and naturally uniform sulfur dispersion. However, the poor electrical conductivity and shuttle effect cause rapid capacity decay and low sulfur utilization especially under high sulfur loading and low electrolyte/sulfur ratio. Herein, the Fe1-xS/C dispersed and Se-containing sulfur-rich polymer (FSP) was synthesized by one-pot reaction of ferrocene, trithioiynuric acid with SexSy. In such process, the trithioiynuric acid reacts with SexSy to form Se-containing sulfur-rich copolymers. Simultaneously, ferrocene reacts with sulfur to form highly dispersed Fe1-xS/C within sulfur-rich copolymers. The covalent chemical binding of sulfur in the FSP effectively suppress the shuttle effect of polysulfides by chemical binding. Meanwhile, the Se improves the conductivity of FSP, which enhances the reaction kinetics. Moreover, the highly dispersed Fe1-xS/C in the FSP is able to effectively catalyze polysulfide conversion and inhibit the shuttle effect. As a result, the optimized FSP electrode exhibits a high capacity of 1330 mAh g-1 at 0.2 C. Even under high sulfur loading (4.08 mg cm-2) and low E/S ratio (6 μL mg-1), the FSP cathode demonstrates a remarkable capacity of 734.7 mAh g-1 at 0.2 C.