CERIUM CONTENT AND CYCLE LIFE OF MULTICOMPONENT AB(5) HYDRIDE ELECTRODES

Multicomponent AB(5) hydrides are attractive replacements for the cadmium electrode in nickel-cadmium batteries. The archetype compound of the AB(5) alloy class is LaNi5, but in a typical battery electrode mischmetal is substituted for La and Ni is substituted in part by various metals. While the effects of Ni substitution have been widely studied, relatively little effort has been focused on the effect of La substitution. Cerium is the predominant rare earth in normal mischmetal, and this paper deals with the effect on cycle life and storage capacity due to the increasing presence of Ce in the alloy series La1-xCexNi3.55Co0.75Mn0.4Al0.3. Alloys were characterized by the determination of pressure-composition relationships, molar volume of H in the hydride phase and electrode cycle life. The effects due to lattice expansion are taken into account. It was concluded that the rate of loss of electrochemical capacity per charge-discharge cycle due to electrode corrosion was significantly decreased by the presence of Ce.