Electrochemical characterization of LaNi5−xAlx (x = 0.1–0.5) in the absence of additives

The electrochemical performance of LaNi5−xAlx (x = 0.1–0.5) hydrogen storage alloys was quickly and systematically evaluated by powder microelectrode (PME) technique. X-ray diffraction (XRD) and X-ray photo-electron spectroscopy (XPS) studies were also carried out for a better understanding of the effect of Al partial substitution for Ni on the alloy's performance. PME study results show that Al partial substitution for Ni improves both the cycling performance and the anti-electro-oxidation ability of the alloys; however, it prolongs the alloy activation process, decreases the maximum discharge ability and enhances the polarization of the alloy electrode. The alloy decay mainly behaves as the capacity reduction with the time, but the maximum discharge ability almost keeps constant during the service life. The changes of both the physical and the chemical properties of the alloys resulted from Al partial substitution for Ni are the main factors which lead to the changes of the electrochemical performance of the alloys.