Studies of electrochemical properties of Ti0.35Zr0.65NixV2-x-yMny alloys with C14 laves phase for nickel/metal hydride batteries

Electrochemical properties of Ti0.35Zr0.65NixV2-x-9Mny alloys used as metal hydride electrode material have been investigated. In the cathodic charging process, alloy B (Ti0.35Zr0.65Ni1.0V0.6Mn0.4) has the largest reduction current followed by alloy C (Ti0.35Zr0.65Ni1.2V0.6Mn0.2) and alloy D (Ti0.35Zr0.65Ni1.2V0.4Mn0.4). On the other hand, hydrogen evolution reaction occurs when the electrode potentials of alloy B to D reach -0.946, -0.941, and -0.932 V vs. Hg/HgO, respectively. In the anodic process, the discharge capacities were measured. The activation overpotential and concentration overpotential of electrode can be separately calculated from the anodic polarization data. At low discharge current density, the charge-transfer process is the dominant electrode reaction, whereas at high discharge current density, hydrogen diffusion within the bulk of: alloy is the rate-determining step. Finally, some electrochemical parameters concerning the electrode kinetics of hydrogen-absorbing alloy such as exchange current density, limiting current density, and transfer coefficient are estimated.