La-Mg-Ni alloys were prepared by melt-spinning with different cooling rates and followed by annealing. Elevation of the cooling rate leads to refinement of the grains size and increasing of the abundance of LaNi5. Annealing is favorable to formation of the A2B7-type phase and promotes the discharge capacity, cycling stability and high rate discharge ability of the as-spun alloys. Phase constitution of the annealed alloys is found to be closely related to the microstructure of the as-spun alloys. A single phase A2B7-type microstructure is obtained in the annealed alloy which is attributed to the lower abundance of the LaNi5 of the original alloy spun with lower cooling rate. Formation of the single phase A2B7-type microstructure is also ascribed to the isolated and homogeneous distribution of the morphology of the as-spun alloy. The single phase alloy presents higher discharge capacity and better cycling stability compared with other annealed alloys.
