PEG-VN modified PP separator for high-stability and high-efficiency lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising candidates for next generation energy storage systems due to their high theoretical energy density. However, the practical application of Li-S batteries is limited by the low lithium ion (Li + ) transport efficiency and the rapid capacity decay caused by the shuttle effect. Herein, we report a composite comprising Polyethylene glycol (PEG) and vanadium nitride (VN) nanosheets coated onto a commercial polypropylene (PP) separator, called PEG-VN@PP separator. The supercatalytic effect and adsorption properties exhibited by the VN nanosheets significantly enhance the conversion of polysulfides, thereby improving both the capacity and stability of Li-S batteries. Due to the coating of PEG, Li + are attracted to the polar functional groups, enabling selective transport, which improves the transport efficiency of Li + and the rate capability of Li-S batteries. The Li-S battery assembled with PEG-VN@PP exhibits a high specific capacity of 782.0 mAh·g −1 and an average capacity decay of 0.048% per cycle at 1 C (1675 ​mA·g −1 ) for 700 cycles, using the carbon nanotubes/sulfur cathode with a sulfur mass loading of 1.2 ​mg·cm −2 . Through the synergistic effect of the selective transport of Li + by PEG and the catalytic adsorption performance of VN on LiPSs, the shuttle effect of Li–S batteries was inhibited and the transport of Li + was enhanced.