Long-cycle stability for Li-S batteries by carbon nanofibers/reduced graphene oxide as host cathode material

3D network structure of carbon nanofibers (CNF) chemically cross-linked with reduced graphene oxide (RGO) sheet was successfully prepared by electrospinning a dispersion of polyacrylonitrile (PAN) and graphene oxide (GO) sheets in dimethylformamide followed by heat treatment. Cathodes made with such composites after infused with sulfur (CNF-RGO/S) were able to deliver an initial reversible capacity of 730 mAh/g and 378 mAh/g after 500 cycles at 0.1 C. Even at a high rate of 5 C, the CNF-RGO/S experienced the capacity of 227 mAh/g and no capacity fade after 400 cycles. In contrast, the capacity of an electrode without adding RGO decayed dramatically. The CNF matrix provides stable mechanical stability and shortens diffusion paths. The addition of RGO sheets increase the contact area with the electrolyte and speed up the reaction rate. These results demonstrate that the 3D network structure is of great potential as the cathode for long-cycle and high-rate rechargeable Li-S batteries.