Nanocarved vanadium nitride nanowires encapsulated in lamellar graphene layers as supercapacitor electrodes

Supercapacitors have the characteristics of high specific capacitance, long cycle life and fast charging ability, which have shown extremely valuable applications in energy storage fields. Improving the electrode materials is a crucial approach to achieve high capacity. Vanadium nitride (VN) has higher theoretical capacitance than noble metal oxides, as well as better chemical stability and good electrical conductivity. Herein, a composite of VN nanowires with multiple cavities encapsulated in N-doped reduced graphene oxide lamellar layers (VNNWs@rGO) has been synthesized by facile freeze-casting and subsequent nitridation technique. The hierarchical VNNWs@rGO composite exhibited excellent supercapacitor performance: high capacitances of 222 and 65 F g −1 were achieved at current densities of 0.5 and 10 A g −1 , respectively. The improved electrochemical performance is associated with the unique structural design: the N-doped rGO sheets endowed enhanced electric conductivity and chemical stability for VN, the interconnected laminar network of VNNWs@rGO are crucial for electrolyte penetration and charge transfer, and the cavities and nanoparticles inside the VN nanowires can provide abundant active sites for electric double-layer capacitor and pseudocapacitance.