Study of decrepitation and corrosion effects of AB(5) alloys used in Ni/MHbatteries by X-ray diffraction, step potential electrochemical spectroscopy and impedance spectroscopy

The effects of decrepitation and corrosion on AB, alloys used in Ni/MH batt eries have been evaluated by several methods. Alloys exhibiting different r esistances to corrosion and capacities evolution upon cycling due to decrep itation phenomena have been selected. The X-ray diffraction patterns showed the formation of corrosion products due to electrochemical cycling in alka line medium, and the decrease of the mean crystallite size and of the latti ce microstrains produced by cracking of the particles during cycling. The r elaxation currents measured during potential steps and impedance spectra we re used to study in situ the decrepitation. Capacities evolution during cyc ling, corrosion rate determined by analysis of Al trapped in the positive e lectrode and micrographs of cycled electrodes were compared to the Impedanc e Spectroscopy results. This technique has shown to be a valid method to de termine in situ the corrosion resistance.