Effect of electrodeposition potential and time for nickel film generation from ionic liquid electrolytes for asymmetric supercapacitor production

The electrochemical performance of nickel-based modified electrodes deposited on stainless steel from ionic liquid was studied in the positive potential regions of alkaline solution to combine with graphite in the negative potential regions for asymmetric supercapacitor applications. Nickel-based electrodes were electroplated, separately, from an ionic liquid solution containing Ni2+ ions and an aqueous solution (Watts solution). The films obtained from the non-aqueous solutions (ionic liquid) were more stable and had better electrochemical performance than those from Watts solutions. The electrochemical performance, including capacitance, power and stability of electrodes were optimized depending on the deposition conditions, specifically, the electrolyte, deposition potential and deposition times. The performance of electrode may be regulated by altering material structure via the deposition conditions. The rate limiting reaction of nickel electrodes deposited from the ionic liquids was not dependent on deposition potentials and time. It was noted to be the mixture of surface and diffusional control mechanisms. As nickel-based coatings electrodeposited from ionic liquid had high surface area, they may be more suitable for energy storage electrodes than the electrodes obtained from Watts solution. The highest specific capacitance of the prepared nickel electrodes was found to be 1690 F g(-1) for the electrode electrodeposited from ionic liquid by the application of -0.7 V for 300 s. Ion transfer reactions between nickel electrodes of porous nanostructures and alkaline electrolyte were fast as a direct result of the greater surface areas.