Functional separators prepared via in-situ growth of hollow CoSO4 hydrate arrays on pristine polypropylene membrane for high performance lithium-Sulfur batteries

Abstract Lithium-sulfur (Li-S) batteries are considered as one kind of advanced rechargeable energy storage systems due to their remarkably low cost and high theoretical energy density. However, the severe shuttle effect of soluble polysulfide hinders the practical application for the lithium-sulfur batteries. Herein, different from the traditional coating method, a novel separator-modifying method is employed by in-situ growing polar CoSO4 hydrate nano-architecture on polypropylene (PP) membrane under different hydrothermal time (donated as CS/PP-x, x = 4, 6, 8 h). The catalytic effect of CoSO4 hydrate can effectively promote the conversion of polysulfide during charging and discharging and thus greatly improve the utilization of sulfur. The optimal modified separator (CS/PP-6) has larger pore volume and specific surface area to provide a rich adsorption site and a suitable thickness of the modified layer to ensure the transport of sufficient lithium-ions while inhibiting the shuttle effect. Even cooperated with a pure sulfur cathode, the CS/PP-6 exhibits a high discharge capacity of 1410.3 mAh g−1 at 0.1 C, and provides an excellent rate capability of 873.7 mAh g−1 even at 2 C. This work may present a new guidance to modify separator for high-performance Li-S battery.