Electrochemical deposition of NiO/NiCo₂O₄ nanostructures for high-performance supercapacitors

NiO is widely used in supercapacitors because of its low toxicity, low price and environmental friendliness. In this study, NiO/NiCo₂O₄ composites were prepared on nickel foam substrates using a simple electrochemical deposition technique. By adjusting the deposition time in the electrochemical parameters, the optimum conditions for the deposition process can be fine-tuned. Characterization techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) confirmed the synthesis of NiO/NiCo₂O₄ composites. The electrochemical properties of the composite electrode NiO/NiCo₂O₄/NF were evaluated by cyclic voltammetry (CV), electrostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance (Cs) of the prepared composite electrode NiO/NiCo₂O₄/NF electrode was 717.8 mF/cm² at 2 mA/cm² with a capacitance retention of 74.8 %. In addition, Aqueous symmetric supercapacitors (SSCs) and all-solid symmetric supercapacitors were assembled based on the composite NiO/NiCo₂O₄/NF electrode, respectively. The aqueous SSCs have a power density of 880 μW/cm² and an energy density of 123.0 μWh/cm², the all-solid symmetric supercapacitors have a power density of 960 μW/cm² and an energy density of 24.27 μWh/cm². The series connection of two identical capacitors can light up light-emitting diodes (LEDs). This research presents a promising technique for producing Ni-based electrode material for supercapacitors.