Nickel-cobalt oxide coated CNTs as additives of activated carbon electrode for high-performance supercapacitors

Nanocomposites of carbon nanotubes (CNTs) coated with nickel-cobalt (Ni-Co) oxide nanoparticles were synthesized using electroless plating. Their morphology and microstructure were investigated by transmission electron microscope (TEM) and X-ray diffraction (XRD), showing that the Ni-Co oxide nanoparticles were uniformly distributed on the outer surface of CNTs and formed nanocrystals. The Ni-Co oxides modified CNTs were added into activated carbon (AC) electrodes of supercapacitors to improve their performance. The electrochemical properties of the supercapacitors were investigated by cyclic voltammetry (CV), alternating current impedance techniques, and charge-discharge curve. A maximum specific capacitance of 215 F·g^-1 was achieved, which is ca. 23% higher than that without the addition of the composite, and the electrode resistance is lower than that of other electrodes. The enhanced performance of the supercapacitor is attributed to the modified microstructure and the increase of electrical conductivity of the electrode due to the addition of the nanocomposite. Supercapacitors with such kind of electrode materials have potentials for microelectronic and energy storage devices and systems.