Electrode stabilities of copper-containing misch metal-nickel-based hydride forming alloys

Abstract

Electrochemical charge-discharge cycling measurements were conducted on electrode samples prepared from alloy powders of a series of Cu-containing Ce- and La-rich misch metal (Mm and Ml, respectively)-Ni-based stoichiometric multicomponent alloys. A severe decrease in the electrochemical capacity was observed for Mm-Ni-Al electrodes, which was believed to be related to the deterioration of electrical contact within the electrodes, in addition to the decomposition of the active materials. Although the addition of cobalt powders to these electrodes improved the electrical contact within the electrodes, it had no effect on retarding the decomposition of the active materials. The substitution of copper into the Mm-Ni-Al composition improved the stability of this electrode material, but brought about a decrease in its electrochemical capacity. As a compromise, partial substitutions of copper for cobalt in Mm-Ni-Co-Al, Mm-Ni-Co-Mn-Al as well as Ml-Ni-Co-Al alloys were proved to be possible without remarkable changes in electrode properties, but too much of this substitution brought about decreases in material stability, which was observed to be accompanied by an increase in tendency of the materials to pulverize during electrochemical cycling.