Influence of Temperature on Discharge Process of Misch Metal-Based Hydrogen Storage Alloy Electrodes

Abstract

For the purpose of clarifying the reason why the discharge capacity of a misch metal (Mm)-based hydrogen storage alloy negative electrode in nickel-metal hydride battery drastically decreases at relatively low temperatures, the activation energies for hydrogen diffusion in the alloy bulk, charge-transfer reaction on the electrode surface and the electric conductivity of KOH solution were evaluated in the temperature range of 25°C to −40°C. By comparing the activation energies with one another, it was clarified that both the hydrogen diffusion and the charge-transfer reaction significantly influenced the discharge process at relatively low temperatures. The addition of Mo to the MmNi_3.6Mn_0.4Al_0.3Co_0.7 alloy was found to be effective for the improvement of the high-rate dischargeability at relatively low temperatures.