rGO/VNTs as Cathodes for High Performance Sodium Ion Batteries with Good Cycling Performance

Using the ex-situ composite method, we have prepared grapheme coating vanadium oxide nanotubes (VNT) by using vanadium oxide nanotubes, cationic surfactant cetyltrimethylammonium bromide (CTAB) and graphene oxide (GO) aqueous solution. The surface of the vanadium oxide nanotube was modified by CTAB, so that vanadium oxide nanotubes were combined with graphene oxide via electrostatic interaction. The introduction of graphene provides an effective protective layer for vanadium oxide nanotubes, alleviates the volume change caused by sodium ion insertion and extraction during charge and discharge process, and enhances the stability of vanadium oxide nanotube structure. The electrochemical test show that the capacity retention of VNTs after 50 cycles was only 18%, while the capacity retention rate of VNTs/rGO was as high as 74%. In addition, we made a detailed analysis of the morphology, structure and formation mechanism of the materials.