Corrosion of AB5 alloy during the storage on the performance of nickel-metal-hydride battery

The deposition of corrosion products of MmNi3.55Co0.75Al0.2Mn0.5 (where Mm is mischmetal) alloy in the positive electrodes during the storage of nickel-metal-hydride (Ni-MH) batteries at 60 °C under open-circuit condition is studied by inductively-coupled plasma spectroscopy and X-ray diffraction. It is shown that (i) the deposition amount is independent with the state-of-charge of the batteries during the storage; (ii) the deposition results in no structure change on both active materials of the positive and negative electrodes; (iii) the deposition is not a main cause of capacity loss of the batteries. Thus, it is beneficial to keep the open-circuit voltage of Ni-MH batteries above 1.0 V by periodically charging during the storage.