Electrochemical study of the cobalt-containing and non-cobalt-containing AB5 alloys used as negative electrodes in nickel-metal hydride batteries

Abstract

The thermodynamic parameters of LaNi3.55Mn0.4Al0.3Co0.75 andLaNi3.55Mn0.4Al0.3Fe0.75 alloys have been evaluated from the electrochemical isothermsdetermined by OCV method. A comparative study has been done betweenthe parameter values deduced from the electrochemical OCV method and the solid-gas method. It was found that the difference can be explained by the electrochemicalcorrosion of these alloys in aqueous KOH electrolyte. The corrosion behaviorof the LaNi3.55Mn0.4Al0.3Co0.75 and LaNi3.55Mn0.4Al0.3Fe0.75 electrodes after activationwas investigated using the method of the potentiodynamic polarization. Theevolution of corrosion current density and potential values as function of the state ofcharge (SOC), show that the total substitution of cobalt by iron leads to accentuatethe corrosion process.