Dicyandiamide (C 3 N 4 or Melamine)-Assistance Preparation of Cobalt-Doped Vanadium Nitride/Carbon Nanocomposite Electrodes for Supercapacitors

Vanadium nitride (VN) is considered to be one of the negative electrode candidates for supercapacitors; however, the dissolution and oxidation of nanosized VN particles lead to its poor cycle stability. In addition, the preparation process requires the use of ammonia gas. We proposed a heat treatment mixture of cobalt-doped vanadium-based metal–organic frameworks (MOFs) and different materials (C 3 N 4, melamine (ML), and dicyandiamide (DCD)) to prepare a carbon/cobalt/VN (C DCD /Co/VN-X) nanosheet composite. The optimized nanocomposite materials presented a prominent specific capacitance of 405 F g –1 at a pressure of 0.5 A g –1 . Additionally, the C DCD /Co/VN-DCD nanocomposite was chosen as the negative electrode, as-prepared Ni(OH) 2 as the positive electrode, and KOH as an electrolyte to assemble an asymmetric supercapacitor device. This device could achieve a superior capacitance of 151.3 F g –1 and an energy density of 47.3 Wh kg –1 at a power density of 375 W kg –1 . Moreover, there remained a high capacitance retention of 96% after 10,000 cycles.