Effect of the cerium content on the structural and electrochemical properties of the La0.7-xCexMg0.3Ni2.875Mn0.1Co0.525 (x=0-0.5) hydrogen storage alloys

In this paper, the effect of the cerium content on the structural and electrochemical properties of the La0.7-xCexMg0.3Ni2.875Mn0.1Co0.525 (x = 0-0.5) hydrogen storage alloys has been studied systematically. It is found by XRD Rietveld analysis that all these alloys mainly consist of two phases: the La(La,Mg)(2)Ni-9 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCu5-type structure. The abundance of the La(La,Mg)(2)Ni-9 phase increases with increasing cerium content. The P-C isotherms curves show that with increasing Cc content in the alloys, the plateau pressure of the hydrogen absorption and desorption increases steeply and the plateau region becomes narrower and steeper. It is found that with increasing Ce content the discharge capacity decreases and the cycling life can be gradually improved. The high rate dischargeability (HRD), the exchange current density I-0, and the limiting current density I-L of the alloy electrodes increases from x = 0 to 0.3 and then decreases with the increase of Ce content. (C) 2003 Elsevier B.V. All rights reserved.