Ni-Doped Cobalt–Cobalt Nitride Heterostructure Arrays for High-Power Supercapacitors

Metal nitrides are widely recognized as a class of desirable supercapacitor electrode materials owing to their high electrical conductivity and structural stability. Embedding metal nanoparticles in nitrides can further enhance the conductivity for electron transport. Herein, a heterostructure consisting of Ni-doped Co–Co2N is synthesized by simple thermal annealing of metal–organic framework (MOF)-derived NiCo2O4 in ammonia atmosphere, in the process of which the MOF-derived two-dimensional (2D) nanoflake arrays were well retained, and the metal–metal nitride heterostructure was well established when annealed at 350 °C. Benefiting from the MOF-derived 2D nanoflake morphology and the metal-metal nitride heterostructure, the Ni-doped Co–Co2N delivers a specific capacity of 361.93 C/g. A full cell test has been conducted using Ni-doped Co–Co2N as the positive electrode and porous carbon as the negative electrode, and it shows an energy density of 20.4 Wh/kg at the power density of 9.85 kW/kg with 82.4% of initial energy density being retained after 5000 cycles.