Corrosion in Nickel-Metal Hydride (Ni-MH) Batteries—Recent Developments

Ni-MH batteries are a family of alkaline storage batteries featuring a positive nickel hydroxide electrode and a negative electrode based on an intermetallic compound able to reversibly absorb hydrogen at ambient conditions of pressure and temperature. This chapter focuses on the corrosion encountered for negative electrode materials. First, the different intermetallic families able to be used as negative electrode materials are presented, then for each case the corrosion mechanisms are described. It is evidenced that the corrosion mechanisms are mainly driven by the anodic oxidation of the elements more electropositive than nickel—such as rare earth (RE) but also vanadium or titanium—which are strongly oxidized by the KOH solution and form hydroxides or oxides at the surface, their morphology depending on their chemical composition. Nickel and partially substituting late transition metals form on the cathodic side a catalytic layer that promotes water reduction. To conclude, main prospects to overcome corrosion issues are presented.