Effect of Ti substitution on electrochemical properties of ZrNi alloy electrode for use in nickel-metal hydride batteries

Crystal structure and electrochemical properties of the Zr1−xTixNi (0.05 ≤ x ≤ 0.5) alloys were investigated. X-ray diffraction spectra showed that the primary phase of all Zr1−xTixNi alloys had the B33-type orthorhombic crystal structure, which was characteristic of ZrNi, and the unit cell volume of the primary phase linearly decreased with an increase in the x value. In the charge-discharge tests with the Zr1−xTixNi alloy negative electrodes, the initial discharge curves for the alloys with x ≥ 0.3 had two plateaus. Both plateau potentials negatively shifted with an increase in the x value. The initial discharge capacity for the Zr0.6Ti0.4Ni alloy negative electrode was 349 mAh g−1 at 25 mA g−1 and 333 K, which was the highest in this study. The high-rate dischargeability and cycle performance were also improved by the partial replacement of Zr by Ti.