Study on kinetics and electrochemical properties of Ml 0.70Mg 0.30(Ni 3.95Co 0.75Mn 0.15Al 0.15) x ( x = 0.60, 0.64, 0.68, 0.70, 0.76) alloys

Abstract

In our endeavor to obtain hydrogen storage alloys with high discharge capacity and good cycling stability, the Ml 0.70Mg 0.30(Ni 3.95Co 0.75Mn 0.15Al 0.15) 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 LaNi 5 phase and LaNi 3 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).