Analysis of Hydrogen Storage Alloy Negative Electrodes by Potential Step Method
Shinya MORISHITA*, Yutaka OHYA, Shin-ichi TOWATA and Katsushi ABE
Toyota Central Research and Development Laboratories, Inc.; 41-1 Yokomichi, Nagakute, Aichi 480-1192 Japan
Large decrease in discharge capacity of hydrogen storage alloy negative electrodes was observed by assembling with nickel hydroxide positive electrodes containing cadmium. From the relationship between discharge rate and discharge capacity of the negative electrode, and analysis by potential step method, the mechanism of this phenomenon was presumed to be as follows:
1) Cadmium in the positive electrodes dissolves into an electrolyte, and then transfers on the surface of the hydrogen storage alloy particles.
2) Transferred cadmium impedes hydrogen diffusion between the inside of the alloy and the surface reaction sites where charge/discharge reaction takes place. Therefore, remarkable decrease in the discharge capacity of the negative electrode is observed.
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