ELECTROCHEMICAL PROPERTIES OF LANI5-XGEX ALLOYS IN NI-MH BATTERIES

Electrochemical studies were performed on LaNi5-xGex metal hydride all oys with 0 less than or equal to x less than or equal to 0.5. We carri ed out single-electrode studies to understand the effects of the Ge su bstituent on the hydrogen absorption characteristics, the electrochemi cal capacity, and the electrochemical kinetics of hydrogen absorption and desorption. The electrochemical characteristics of the Ge-substitu ted alloys are compared to those of the Sn-substituted alloys reported earlier. LaNi5-xGex alloys show compositional trends similar to LaNi5 -xSnx alloys, but unlike the Sn-substituted alloys, Ge-substituted all oys continue to exhibit facile kinetics for hydrogen absorption/desorp tion at high solute concentrations. Cycle lives of LaNi5-xGex electrod es were measured in 300 mAh laboratory test cells and were found to be superior to the Sn-substituted LaNi5 and comparable to a Mm(Ni, Co, M n, Al)(5) alloy. The optimum Ge content for LaNi5-xGex metal hydride a lloys in alkaline rechargeable cells is in the range 0.4 less than or equal to x less than or equal to 0.5.