DEGRADATION BEHAVIOR OF CU-COATED TI-ZR-V-MN-NI METAL HYDRIDE ELECTRODES

In order to improve the durability and elucidate the degradation mecha nism of Ti-Zr-V-Mn-Ni metal hydride electrodes which have a poor cycli ng property in KOH electrolyte, the cycling behavior of these electrod es has been investigated after Cu-coating treatment. It was observed t hat the cycle life of these electrodes was improved with increasing am ounts of Cu-coating. However, these electrodes still degraded with fur ther cycling, To examine the reasons for the abrupt degradation of the se electrodes, surface morphologies, concentration depth profiles and polarization resistance of the degraded Cu-coated electrodes were inve stigated. It was found that the Ti oxide film, which has been reported as a main reason of degradation in our previous work, formed on the s urface of the degraded Cu-coated electrode and the polarization resist ance of these electrodes increased greatly. From these results, it is suggested that eventually the problem of degradation behavior of these electrodes is not overcome perfectly through the Cu-coating process a nd the degradation mechanism of these electrodes can be clarified. (C) 1998 Elsevier Science S.A.