Different ammonium fluoride induced nickel cobalt layered double hydroxides nanostructure on nickel foam as high-performance supercapacitor electrodes

Abstract

Supercapacitors are electrochemical energy storage devices lying between secondary batteries and general physical capacitors in terms of their electrochemical properties. In recent years, supercapacitors attracted tremendous interests in electrochemical energy storage applications because of its high-power density and better cycling property. Nickel cobalt layered double hydroxide (Ni Co-LDH) made from metal hydroxide electrode material was recently examined for its potential as a battery-type hybrid supercapacitor. This interest is due to its unique spatial structure, excellent electrochemical activity, and good electrical conductivity. However, the main disadvantage that restricts the application of Ni Co-LDH is low electronic conductivity, which results in low capacitance. To address this problem, we used different concentrations of ammonium fluoride to control the surface morphology of Ni Co-LDH and allow its direct growth on the nickel foam (NF). We created a different morphological structure of Ni Co-LDH composite electrode material with a large surface area, high conductivity, and high electrochemical performance. Results showed that the sample prepared with an ammonium fluoride additive reveals a higher specific capacitance, about 1445 Fg-1 at a current density of 2 Ag-1, a good specific capacitance rate, about 59.5 % from 2 Ag-1 to 40 Ag-1, and good capacity retention, up to 99 % when the current density is enhanced to 30 A g-1. These suggest the promising applications of Ni Co-LDH in the future.