The effect of growth potential on the self-discharge behavior of Cu-Ni based alloy electrodes

Recently, the increasing demand for sustainable clean energy from non-fossil sources motivated the researchers in energy storage devices and supercapacitors are one of the most promising energy storage systems. In this study, flexible copper and nickel coated electrodes are fabricated for supercapacitor applications from Ethaline deep eutectic solvent media. Copper and nickel-based materials were potentiostatically electrodeposited on flexible graphite substrates from Ethaline ionic liquid containing copper and nickel ions. Cu-Ni coated graphite films were scanned in 1 M KOH from -0.7 V to 0.4 V at different scan rates ranging between 5 mV s-1 and 100 mV s-1. Fabricated Cu-Ni electrodes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Copper and nickel formation ratios on graphite films at different deposition voltages were determined by EDX analysis. Cu-Ni coated graphite films applying -1.8 V deposition potential exhibited a maximum areal capacitance of 47.3 mF cm-2 at 5 mV s-1 scan rate. Galvanostatic charge-discharge curves of the electrodes obtained at different applied voltages confirms the supercapacitor behaviour of Cu-Ni coated films. One of the biggest issues regarding the use of supercapacitors in daily life is their self-discharge behaviour. Self-discharge curves of the Cu-Ni modified electrodes were illustrated that decreasing deposition potentials can decrease self-discharge problem. This research determines that Ethaline ionic liquid is a potential media for alloy-based electrodes in the usage of supercapacitor applications.