Vanadium dioxide nanorods/carbon nanofibers as functional separator coatings for capturing polysulfides in superior-performance lithium-sulfur batteries

Lithium-sulfur batteries have the advantages of abundant raw materials, high theoretical specific capacity, high energy density and low cost, making them one of the most promising batteries. However, the severe “shuttle effect” and sluggish conversion kinetics have led to rapid capacity degradation. Here, we have manufactured a nanomaterial of carbon nanofibers (CNFs) and vanadium dioxide (VO2) nanorods interwoven together coated on the other side of the separator. In the design, VO2/CNFs with a large number of active sites can not only immobilise polysulfides through chemisorption and three-dimensional network structure, but also promote the conversion of polysulfides during charging and discharging, Meanwhile, the conductive CNFs provided a good conductive network and stabilised the VO2 structure during cycling, thus simultaneously improving the kinetics and efficiency of the electrochemical conversion. As a result, the batteries with VO2/CNFs separators achieve a superior cycling capacity (682.7 mAh/g at 0.1 C after 200 cycles), after 400 cycles at 1 C, the decay rate per cycle was only 0.011 %. Even employed with a high sulfur loading of 2 mg/cm2, the capacity reaches 615.9 mAh/g at 0.1C after 100 cycles, which provided a new approach for designing high-performance lithium-sulfur battery separator materials. •Three-dimensional interconnected networks of VO2 nanorods/CNFs were successfully prepared.•The interconnected CNFS provide a continuous conductive network.•The polar VO2 nanorods provide strong binding sites for the adsorption of polysulfides.•The VO2/CNFs separators demonstrates excellent cycling performance.