Abstract: The segregation and dissolution of Mn at the electrodes of hydrogen storage alloys, LaMmMnCoNi and AlMmMnCoNi (Mm-alloy of rare earth rich in lanthanum), have been studied in cycling course using XPS and electron probe techniques. It was observed that Mn inside the electrodes dispersed rapidly to the electrode surfaces in the active stage, forming MnO₂. Both the capacities of the electrodes and the Mn content on the electrode surfaces gave maximum values in the cycling course, The segregation and dissolution of Mn in the hydrogen storage alloy electrode containing Al were slower than that in the alloy electrode without Al, The alloy electrode with and without Al in 80% discharge showed a cycling life of 520 and 350 times, respectively. It is concluded that Al may inhibit the segregation and dissolution of Mn and extend the cycling life of the eletrode.

Key words: hydride electrode, segregation, Mn