Hydrogen absorption characteristics and electrochemical properties of Ti substituted Zr-based AB2 alloys

The hydrogen absorption characteristics of Zr1−xTixCrNi alloys, with x ranging between 0.1 and 0.4, were studied by volumetric and electrochemical techniques in order to determine their possible application as the negative electrode in nickel/metal–hydride rechargeable batteries. Electrodes of alloy powders mixed with different compacting additives were tested with respect to charge and discharge cycles in KOH solution. The effects of the electrode-compacting additive, discharge rate and temperature on the electrode discharge capacity were also investigated. The results obtained show that: (i) at 80°C the equilibrium pressures of Zr1−xTixCrNi alloys with x=0.1 are 2.6 times higher than those for the unsubstituted ZrCrNi alloy, while maintaining a good hydrogen storage capacity; (ii) the Zr0.9Ti0.1CrNi alloy electrodes exhibit the highest discharge capacities and the best performances during fast charge–discharge cycling; (iii) the Ti substituted alloy electrodes using copper powder as compacting material show faster activation, while carbon–Teflon compacted electrodes exhibit the best cycle life behavior; (iv) for all Ti substituted alloy electrodes the discharge capacities increase with temperature.