Study on kinetics and electrochemical properties of Ml0.70Mg0.30(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 Ml0.70Mg0.30(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).