High Charge Storage of Amorphous Ni-Doped VO<i><sub>x</sub></i>-Modified Ni(OH)<sub>2</sub> Substrate on a Ni Foam Cathode in a Base Solution
Hairus Abdullah, Siang-Jhih Jhuang, Hardy Shuwanto, Dong–Hau Kuo
Abstract
Green energy of solar light has been harnessed to overcome the energy and environment crisis. However, solar energy is an intermittent power source. This work demonstrates a promising amorphous Ni-doped VO x /Ni(OH) 2 (a-NVO- x )-layered Ni foam with different contents of VO x as the energy material to store the intermittent energy. a-NVO- x is electrodeposited on Ni(OH) 2 lamellar-grown Ni foam and used as a cathode material in a supercapacitor cell. The as-prepared a-NVO- x cathode materials with different electrodeposition times are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Simultaneously, the electrochemical properties are examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) analyses. a-NVO-5 achieves the highest specific capacitance of about 7500 F/g or 3000 C/g at 1 A/g, with energy and power densities of about 167 Wh/kg and 199 W/kg, respectively, in a 3 M KOH solution. The capacity retention can reach >90% after 10k cycles at 20 A/g. A full-cell supercapacitor is also built by coupling the a-NVO-5 cathode with an active carbon anode, and it can deliver energy and power densities of 286.5 Wh/kg and 1150 W/kg at 1 A/g, respectively. The excellent performance of the a-NVO- x electrode accommodates the pseudocapacitive charge balance in the a-VO x structure during charge–discharge processes.