Graphene oxide wrapped Na3V2(PO4)3/C nanocomposite as superior cathode material for sodium-ion batteries

Na3V2(PO4)3 is one of the most promising cathode materials for rechargeable sodium-ion batteries, which can deliver two Na+ ions extraction/insertion from/into the crystal structure. To further improve the electrochemical performance of the carbon-coated Na3V2(PO4)3 electrode, the conducting graphene has been adopted. In this paper, graphene-wrapped Na3V2(PO4)3/C nanocomposite has been successfully synthesized through a hydrothermal-assisted sol–gel method. X-ray diffraction (XRD) results demonstrate that the obtained nanocomposite is well crystallized with NASICON-type structure. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the modification of Na3V2(PO4)3/C with graphene could construct an effective conducting network, which significantly enhances the electronic conductivity of Na3V2(PO4)3/C based sample. Thus, the graphene-wrapped Na3V2(PO4)3/C exhibits superior high-rate capacity and excellent cycling stability. It shows an initial charge capacity of 113 mA h g−1 and a discharge capacity of 106.5 mA h g−1 at 0.1 C, and retains stable discharge capacities of 104.3, 101.1, 96.4 and 93 mA h g−1 at current rates of 0.2 C, 0.5 C, 1 C and 2 C, respectively. Even at higher rate of 5 C, it can still deliver a discharge capacity of 88.7 mA h g−1 with remarkable capacity retention of 92.5% after 200 cycles. This synthetic strategy should be helpful for the design of other conducting network structured electrodes with high-performances.