Nanoflakes-Assembled 3D Flower-Like Nickel Oxide/Nickel Composites as Supercapacitor Electrode Materials

A 3D flower-like NiO/Ni composite was prepared by a facile, template-free, hydrothermal method followed by calcination in N-2 atmosphere in the presence of glucose. The particles are assembled from porous nanoflakes. XRD, SEM, TEM, and X-ray photoelectron spectroscopy were performed to characterize the morphology and composition of the material. This revealed that during the calcination process NiO was partially transformed into Ni and consequently an NiO/Ni composite was obtained. Cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy were conducted in 6 m KOH electrolyte solution. This showed that the NiO/Ni composite exhibits a higher specific capacitance (363.7 F/g at 0.5 A/g) and better cycling stability than the as-prepared NiO. The superior performance of the composite is attributed to the interconnected network of the 3D structure, which provides more channels for electrolyte transport and electrochemically active sites for faradaic reaction. The modified Ni metal forms a conductive network on the surface and improves the conductivity of the material, which favors effective electron transport from the surface to the current collector. The results indicate application potential of the NiO/Ni composite in electrode materials for supercapacitors.