Electrochemical redox reaction of zinc ions at a Ni electrode in ZnCl2-based aqueous solutions

Abstract

The electrochemical redox reaction of zinc ions on a nickel electrode was investigated in aqueous solutions containing different concentrations of zinc chloride (ZnCl2). A relatively good cycle efficiency was obtained from the high-concentration solution. The charge and discharge of the nickel electrode exhibited a high cycle efficiency of 92% in the fiftieth cycle in a 2 mol dm−3 (M) solution, and a low cycle efficiency of ~43% in the 0.02-M solution. Atomic force microscopy revealed that the dendritic zinc formed on Ni produced different morphologies as the electrolyte concentration increased, resulting in the changes in cycle efficiency. Moreover, the sizes of the zinc particles deposited on the nickel electrode were dependent on the electrolyte concentration. After five cycles, the zinc particles generated in the 0.02-M solution were smaller than those generated in the 2-M solution; however, after fifty cycles, the former particles were larger than the latter.