The phase structures and electrochemical properties of (La, Mg)(Ni, Co)3.7M0.1 (M = Zr, Cr, Al, Mn, Ni) hydrogen storage alloys

Abstract

A5B19 phase were obtained by using the La-Ni and Mg-La precursors instead of La, Mg and Ni pure metal to prepare the La0.85Mg0.15Ni2.65Co1.05M0.1 alloys (M = Ni, Zr, Cr, Al, Mn). Rietveld refinement of XRD shows that there are (La, Mg)5Ni19 (Ce5Co19 + Pr5Co19), and LaNi5 phases in the La0.85Mg0.15Ni2.65Co1.05M0.1 alloys, and the elements of Mn or Cr and Al or Zr can respectively promote the formation of Pr5Co19 phase and (La, Mg)2Ni7 phase. Electrochemical tests reveals that the maximum discharge capacity (Cmax) of the alloys correspondingly change with the abundance of A5B19 phase which possesses higher hydrogen storage capacity. The elements of Al and Zr can improve the cycling stability, but decrease the high-rate dischargeability. This result can be due to the properties of the surface oxide film which can reduce corrosion and decrease the surface catalytic activity. The kinetics analysis revealed that the kinetics performance of alloy of M = Al is mainly affected by I0, and that of the other alloys benefits from both I0 and D.