Degradation behavior of Cu-coated Ti-Zr-V-Mn-Ni metal hydride electrodes

In order to improve the durability and elucidate the degradation mechanism of Ti-Zr-V-Mn-Ni metal hydride electrodes which have a poor cycling property in KOH electrolyte, the cycling behavior of these electrodes has been investigated after Cu-coating treatment. It was observed that the cycle life of these electrodes was improved with increasing amounts of Cu-coating. However, these electrodes still degraded with further cycling, To examine the reasons for the abrupt degradation of these electrodes, surface morphologies, concentration depth profiles and polarization resistance of the degraded Cu-coated electrodes were investigated. 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 surface of the degraded Cu-coated electrode and the polarization resistance 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 and the degradation mechanism of these electrodes can be clarified. (C) 1998 Elsevier Science S.A.