Electrochemical studies on the Ti-Zr-V-Mn-Cr-Ni hydrogen storage electrode alloys

In this paper, the electrochemical properties of the (Ti_0.8Zr_0.2)(V_0.533Mn_0.107Cr_{0.1 6}Ni_0.2)_x (x = 2,3,4,5,6) hydrogen storage electrode alloys have been studied. X-ray powder diffraction analysis showed that all alloys mainly consisted of a C14 Laves phase with hexagonal structure and a V-based solid solution phase with BCC structure. The lattice parameters and the unit cell volumes of the two phases decrease when x is increased. The electrochemical performances of the alloy electrodes, including the cycle life, the linear polarization, the anodic polarization, the Tafel polarization and the electrochemical impedance spectra, have been investigated systematically. After considering the global effect of the non-stoichiometry of B-side elements on the performances of the alloy electrodes, the optimum composition was found to lie in x = 5. Consequently, we believe that the non-stoichiometry is an effective way to improve the overall electrochemical properties of the Ti-based Laves phase hydrogen storage alloys used for the negative electrodes of Ni-MH secondary batteries.