High Charge Storage of Amorphous Ni-Doped VOx-Modified Ni(OH)2 Substrate on a Ni Foam Cathode in a Base Solution

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 VOx/Ni(OH)2 (a-NVO-x)-layered Ni foam with different contents of VOx 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-VOx structure during charge–discharge processes.