DEGRADATION MECHANISM OF ZRCRNILA0.05 ELECTRODES IN 30-WT-PERCENT KOH SOLUTIONS

The change of discharge capacity of a ZrCrNiLa0.05 metal hydride electrode with a number of cycles of repeated charging-discharging has been investigated in alkaline solution. After 500 cycles, the discharge capacity of this electrode decreases to about 11 % of the initial one. To illustrate the good durability of this electrode for repeated charge-discharge cycling, the surfaces of air-exposed, activated and cycled ZrCrNiLa0.05 electrodes are examined by Auger electron spectroscopy (AES), respectively. It is found that nickel and lanthanum hydroxide are enriched at the surface for the prolonged cycling and the high resistance to degradation of this electrode is due to the presence of immune nickel and lanthanum hydroxide. The degradation process of this electrode is discussed on the basis of the observed experimental results.