Abstract:As the loss of active material Mg may affect electrode's discharge capacity and the cycling stability, a more refined mechanism study on cycling capacity de gradation should be made. The present investigation is based on the supposition that the capacity degradation of the binary Mg50Ni50 alloy and ternary Mg45Cu5Ni50 alloy electrodes is solely due to the corrosion of Mg, the active hydrogen storage element. That means amount of capacity degradation is determined by the corrosion current time, which is also the time of operation. The corrosion current J_corr dependence on cycling time was deduced. A mathematic relation between the cycling capacity retention C_N/C₁ (%) and the duration of operation was also deduced. The data calculated from the equations deduced agree well with those of the experiment result. The loss of the active hydrogen-absorbing element Mg is proved to be the main cause for cycling capacity deterioration in the present investigation.

Key words: mechanism of degradation; cycling capacity degradation; corrosion current; MgNi-based alloys