Comparison of the electrochemical properties of cast and melt-spun MLN4.3-xCoxMn0.4Al0.3 (ML: La-rich Mischmetal) hydrogen-storage alloys

A series of hydrogen-storage alloys of composition MLNi4.3-xCoxMn0.4Al0.3 (ML denotes Lanthanum-rich Mischmetal and, x=0.2, 0.4, 0.5, 0.6, 0.7 and 0.9) were prepared with two methods, conventional casting and melt-spinning. The electrochemical properties of these alloys were measured and compared. It was found that rapid quenching by melt-spinning could very effectively improve the cycle stability of the AB(5)-type alloy, especially the cycle stability of the alloy with a low content of cobalt. Melt-spinning had some disadvantages in that it slowed down the initial activation rate and narrowed the width of the discharge voltage plateau and therefore led to a decrease in capacity. The phase structure of the investigated alloys was also measured by X-ray diffraction technique showing that all alloys were the same AB(5) phase with CaCu5 structure. (C) 1999 Elsevier Science S.A. All rights reserved.