Fabrication of a vanadium nitride/N-doped carbon hollow nanosphere composite as an efficient electrode material for asymmetric supercapacitors

Low-cost materials and facile processes to obtain novel electrode materials for assembling asymmetric supercapacitors (ASCs) are urgently needed. Herein, a vanadium nitride/nitrogen-doped carbon nanosphere (VN/NCS) composite composed of VN nanoparticles and N-doped carbon (NC) covering the surface of VN has been prepared by the nitridation of a V₂O₃/C nanocomposite. The hollow VN/NCS composite with a mesoporous structure and the dispersion of VN NPs in N-doped carbon result in a VN/NCS composite with good electrochemical behavior. Moreover, the N-doped carbon layer on the surface of VN effectively inhibits the oxidation of VN during cycling in an alkaline electrolyte. With the VN/NC composite utilized as a novel active electrode material for SCs, good rate capability, specific capacitance, and cycling stability are exhibited. Strikingly, using the VN/NCS composite as a negative electrode and its precursor, the V₂O₃/C composite, as a positive electrode, an asymmetric supercapacitor (ASC) device, with a good energy density of 19.8 W h kg^-1 at 801 W kg^-1 and a short charging time of 89 s, was assembled.