Function of Al on the cycling behavior of the La-Mg-Ni-Co-type alloy electrodes

The cycling behavior of the La0.7Mg0.3Ni2.65-xCo0.75Mn0.1Alx (x=0, 0.3) alloy electrodes was systematically investigated by XRD, SEM, EIS, XPS and AES measurements, and the function of Al in the La-Mg-Ni-based alloys and the reasons for the improvement of the cycling stability of the alloy electrode with Al were discussed. Results show that the cycling behavior of the La0.7Mg0.3Ni2.35Co0.75Mn0.1Al0.3 alloy electrode can be divided into three stages, i.e., the pulverization and Mg oxidation stage, the Mg oxidation and La and/or Al oxidation stage, and the La and Al oxidation and Al oxide film protection stage. The improvement of the cycling stability of the alloy electrode with Al can be ascribed to two factors. One is the decrease in the pulverization of the alloy particles during charge/discharge cycling due to the alloy with Al undergoes a smaller cell volume expansion and contraction. The other is the increase in the anti-oxidation/corrosion due to the formation of a dense Al oxide film during cycling, which is believed to be the most important reason for the improvement of the cycling stability of the La-Mg-Ni-Co-Mn-Al-type alloy electrodes. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.