A core-shell structured nanocomposite of NiO with carbon nanotubes as positive electrode material of high capacitance for supercapacitors

A nanocomposite of carbon nanotubes coated with nickel oxide was prepared by a simple hydrothermal method. The structure, morphology and electrochemical performance of the nanocomposite were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, electrochemical tests including cyclic voltammogram, galvanostatic charge-discharge and electrochemical impedance spectroscopy, respectively. It presents the highest specific capacitance of 1844 F g^-1 at 1 A g^-1 and 1145 F g^-1 at current density of 10 A g^-1 with 88.9% (at 1 A g^-1) capacitance retention after 1000 cycles. The specific capacitance of the nanocomposite is almost double of that of the virginal NiO (972 F g^-1 at 1 A g^-1). Its cycling behavior is also very good. When combined with activated carbon as the negative electrode, the energy density can be up to 52.6 Wh kg^-1. Such good electrochemical behavior indicates that the nanocomposite is a promising electrode material for supercapacitors.