Effect of temperature on the discharge capacity of the Laves phase alloy used in nickel/metal-hydride batteries

The discharge capacity, the high-rate dischargeability and the self-discharge characteristics of negative electrodes consisting of the Zr-based, modified AB2 type alloys of ZrV0.1Mn0.7Ni1.2 alloy and ZrV0.1Mn0.5Mo0.2Ni1.2 alloy, the latter having the form of partially substituted Mo for Mn sites in the former alloy, are investigated in 6 M KOH solution at 30, 40 and 60°C. It is found that the discharge capacities obtained at 30 and 40°C are almost the same in both alloys, but they decrease at 60°C. The activation process becomes faster in both alloys with increasing temperature. The high-rate dischargeability increases slightly from 85% at 30°C to 90% at 60°C. At the very high discharge current of 5 A g−1, however, the discharge capacity at 60°C was increased by 7× and 17× more than that at 30°C in ZrV0.1Mn0.7Ni1.2 alloy and ZrV0.1Mn0.5Mo0.2Ni1.2 alloy, respectively. The addition of Mo improved the self-discharge characteristics, especially at 60°C.