Performance of an AB, alloy in sealed Ni-MH batteries for electric vehicles: quantification of corrosion rate and consequences on the battery performance

The purpose of this study is to evaluate the corrosion rate of a Laves phas e alloy, with the C15 crystallographic structure, in 22 Ah sealed Ni-MN bat teries for electric vehicle applications. At the end of life, measurements of the capacities of negative and positive electrodes show that the battery capacity is limited by the negative polarity. Negative electrodes exhibit a capacity loss of 60% which is attributed to kinetics problems due to the corrosion layers and to a loss of the active material. A model allowing the determination of the alloy corrosion hits been developed by taking into ac count the solubilities and the oxidation state of the corrosion products an d the amount of oxygen in corroded alloy. Although the corrosion rate of th e AB(2) alloy is equivalent to what has been observed using AB(5) alloys, i ts consequences on battery performance are more severe due to the high oxid ation state of V and Zr. (C) 1999 Elsevier Science S.A. All rights reserved .