The electrochemical performance of a La-Mg-Ni-Co-Mn metal hydride electrode alloy in the temperature range of -20 to 30 °C

The effect of temperature on the overall electrochemical properties of La0.7Mg0.3Ni2.875Co0.525Mn0.1 hydrogen storage alloy has been studied systematically. The results show that temperature has a striking effect on the overall electrochemical properties, especially the electrochemical kinetic performance. The maximum discharge capacity and the high rate dischargeability (HRD) of La0.7Mg0.3M2.875Co0.525Mn0.1 alloy electrode both decrease with decreasing test temperature, mainly due to the slower hydrogen transfer in the bulk of the alloy and the lower electrocatalytic activity at lower temperatures. Detailed studies on the temperature effect on the polarization resistance (R-D), the exchange current density (I-0), the limiting current density (I-L) and the hydrogen diffusion coefficient (D), indicate that the diffusion of hydrogen in the bulk for La-Mg-Ni-Co system hydrogen storage alloy electrodes is the rate-determining factor for the discharge process of the alloy electrode for the temperature over 10 degreesC and the charge-transfer reaction is rate-determining step at lower temperature. (C) 2003 Elsevier Ltd. All rights reserved.