A Multi-Functional Separator for Li-S Batteries: WS2@C Nanoflowers Catalyze the Rapid Recycling of Lithium Polysulfides by Polar Attraction

Abstract

Featuring high theoretical capacity, environmental friendliness and low cost, lithium-sulfur (Li-S) batteries become promising alternatives to satisfy the growing demand for energy storage. To boost their energy density for practical application, modified separators are needed to suppress shuttle effects resulting from the solubility of lithium polysulfides (LiPSs). Herein, we modified traditional polypropylene (PP) separators with functional WS2@C nanoflower composites (WS2@C-PP). They can effectively adsorb LiPSs and catalyze their conversion on the edge sites of the WS2. Also, the unique construction of a carbon layer coating on the WS2 nanoflowers combines active sites and conducting properties. The material benefits the reversibility of redox reactions and reutilization of active materials. With the WS2@C-PP separator, the cell displays improved cycling stability and rate performance. When cycling at 0.1 C, the cell discharges a capacity of up to 1475 mAh g−1, and it contributes 943 mAh g−1 originally at 1 C, with a decay rate of only 0.07 % after 500 cycles. Our work highlights the potential of functional separators to advance the properties of Li-S batteries.