Materials Chemistry and Physics, Vol.108, No.1, 92-96, 2008
Study on kinetics and electrochemical properties of Ml(0.70)Mg(0.30)(Ni3.95Co0.75Mn0.15Al0.15)(x) (x=0.60, 0.64, 0.68, 0.70, 0.76) alloys
In our endeavor to obtain hydrogen storage alloys with high discharge capacity and good cycling stability, the Ml(0.70)Mg(0.30)(Ni3.95Co0.75Mn0.15Al0.15)(x) (x = 0.60, 0.64, 0.68, 0.70, 0.76) (where Ml denotes La-rich misch metal) alloys with Ml substitution for La and B-side multi-alloying have been prepared by inductive melting, and the effect of stoichiometry x on the electrochemical properties has been investigated systematically. XRD analysis shows that the alloys are mainly composed of LaNi5 phase and LaNi3 phase. The electrochemical test shows that the maximum discharge capacity, kinetics, high rate dischargeability (HRD) and low temperature dischargeability (LTD) all increase and then decrease with increasing x. The alloy with x=0.64 has larger maximum discharge capacity, 372 mAh g(-1). As the case of x=0.70, the alloy exhibits better kinetics, HRD and LTD. The testing alloys exhibit good cycling stability, and the capacity retention of the alloys at the 100th cycles increases from 78.0% (x=0.60) to 90.3% (x=0.76). (C) 2007 Elsevier B.V. All rights reserved.