Effects of Al on Cycling Stability of a New Rare-Earth Mg-Based Hydrogen Storage Alloy

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In order to improve the cycling stability of a new rare-earth Mg-based hydrogen storage alloys, La0.7Mg0.3Ni2.65-xMn0.1Co0.75Alx (x=0.0-0.4) alloys were prepared to investigate the structure and electrochemical properties of these alloys. XRD and Rietveld analyses reveal that the alloys consist of a (La,Mg)Ni3 phase with rhombohedral PuNi3-type structure and a LaNi5 phase with hexagonal CaCu5-type structure. Electrochemical studies on these alloys indicate that their maximum discharge capacities were decreased from 400.7 mAh/g (x=0.0) to 335.6 mAh/g (x=0.4). However, the cycling stability of the alloy electrodes was significantly improved after Ni was partially replaced by Al. After 100 charge/discharge cycles, the discharge capacity retention was increased from 32.0% (x=0.0) to 73.8 % (x=0.3), which can be attributed to the formation of a dense oxide film on the alloy surface. Moreover, the high rate dischargeability measurements indicate that the electrochemical kinetic properties were deteriorated with increasing Al content owing to the presence of a dense oxide film of Al.

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Periodical:

Materials Science Forum (Volumes 475-479)

Main Theme:

Edited by:

Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie

Pages:

2457-2462

DOI:

10.4028/www.scientific.net/MSF.475-479.2457

Citation:

Y.F. Liu et al., "Effects of Al on Cycling Stability of a New Rare-Earth Mg-Based Hydrogen Storage Alloy", Materials Science Forum, Vols. 475-479, pp. 2457-2462, 2005

Online since:

January 2005

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$35.00

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