Ternary Ni–Cu–OH and Ni–Co–OH electrodes for electrochemical energy storage

Abstract

In this project, Ni–Cu–OH and Ni–Co–OH ternary electrodes have been prepared. Different Ni:Cu and Ni:Co ratios were deposited by chemical bath deposition (CBD) at room temperature on carbon microfibers. Since Ni(OH)2 is notorious for poor cycling stability, the goal of the work was to determine if doping with Cu or Co could improve Ni(OH)2 cycling stability performance and conductivity against reaction with electrolyte. It is observed that the electrodes with Ni:Cu and Ni:Co composition ratio of 100:10 result in the optimum capacitance and cycling stability in both Ni–Cu–OH and Ni–Co–OH electrodes. This improvement in cycling stability can be attributed to the higher redox reversibility as indicated by the smaller CV redox peak separation. In addition, it is found that decreasing Cu and Co ratios, with fixed CBD time, enhances nanoflakes formation, and hence increases electrode capacitance. For the optimum composition (Ni:Co = 100:10), composites of the ternary electrodes with graphene and carbon nanofibers were also tested, with resultant improvement in potential window, equivalent series resistance, areal capacitance and cycling stability.