Electrochemical impedance and cyclic voltammetry characterization of a metal hydride electrode in alkaline electrolytes

The electrochemical characterization of a MmNi3.55Co0.75Al0.2Mn0.5 metal hydride electrode in two alkaline electrolytes (NaOH or KOH) is reported. The results from both electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) show that absorption/desorption of H atoms at the metal–electrolyte interface is markedly suppressed by using a NaOH electrolyte instead of a KOH electrolyte. This results in a significant reduction of the self-decomposition rate of the negative active material and thus leads to an improvement in the self-discharge performance of nickel–metal hydride (Ni–MH) batteries.