Polyoxometalates/Active Carbon Thin Separator for Improving Cycle Performance of Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries have great potential for the next generation of energy-storage devices owing to their high theoretical energy density. However, the polysulfides' shuttling effect seriously degraded the cycle stability and capacity and hindered their commercial applications. Here, we design and fabricate a bifunctional composite separator including a polypropylene (PP) matrix layer and Keggin polyoxometalate [PW12O40]3-/Super P composite retarding layer by utilizing the Coulombic repulsion between polyanion and polysulfides. Such a binary composite separator shows the effects in enhancing the Coulombic efficiency and cycling stability. Compared with the polypropylene (PP) matrix separator, the capacity is improved by 41% after 120 cycles when using the PW12/Super P separator. It is the first time that the polyoxometalate (POM) matrix is used as a bifunctional separator for lithium-sulfur batteries, demonstrating the promise of POM-based separators in reducing the shuttling effect of Li-S battery.