Electrochemical Impedance Analysis of Hydrogen Storage Alloy Negative Electrodes Based on the Porous Electrode Model

Shinya MORISHITA*, Yoshihiro ISOGAI, Yutaka OHYA, Shin-ichi TOWATA and Katsushi ABE

Toyota Central Research and Development Laboratories, Inc.; 41-1 Yokomichi, Nagakute, Aichi 480-1192 Japan
Toyoda Automatic Loom Works, Ltd.; 2-1 Toyoda-cho, Kariya-shi 448-8671 Japan

Electrochemical impedance method was applied to pasted-type negative electrodes (current collector: metal core sheet) of Ni-MH batteries. The following information was obtained during a charge-discharge cycle test without disassembling the batteries; 1) solution resistance, 2) contact resistance between particles of the active material, 3) impedance of the corrosion product, 4) charge transfer resistance and capacitance of the electric double layer at the interface between the electrolyte and the active material, 5) Warburg impedance caused by hydrogen diffusion in the active material.
It was also clarified that the porosity of the electrode was very important to analyze impedance spectra measured by the pasted-type electrodes.

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