The effect of Nd content on the electrochemical properties of low-Co La-Mg-Ni-based hydrogen storage alloys

The low-Co content La0.80-xNdxMg0.20Ni3.20CO0.20Al0.20 (x=0.20,0.30, 0.40, 0.50, 0.60) alloys were prepared by inductive melting and the effect of Nd content on the electrochemical properties was investigated. XRD shows that the alloys consist mainly of LaNi5 phase, La2Ni7 phase and minor LaNi3 phase. The electrochemical P-C-T test shows hydrogen storage capacity increases first and then decreases with increasing x, which is also testified by the electrochemical measurement that the maximum discharge capacity increases from 290 mAh/g (x = 0.20) to 374 mAh/g (x = 0.30), and then decreases to 338 mAh/g (x = 0.60). The electrochemical kinetics test shows exchange current density I-0 increases with x increasing from 0.20 to 0.50 followed by a decrease for x = 0.60, and hydrogen diffusion coefficient D increases with increasing x. Accordingly high rate dischargeability increases with a slight decrease at x = 0.60 and the low temperature dischargeability increases with increase in Nd content. When x is 0.50, the alloy exhibits a better cycling stability. (c) 2007 Elsevier B.V. All rights reserved.