Influence of Substituting Ni with Fe on Cycle Stabilities of as-Cast and as-Quenched La0.7Mg0.3Co0.45Ni2.55-xFex (x=0-0.4) Electrode Alloys

The electrode alloys La0.7Mg0.3Co0.45Ni2.55-xFex (x = 0, 0. 1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The influences of the substitution of Fe for Ni on their cycle stabilities as well as their structures were investigated in detail. The results indicate that the substitution of Fe for Ni significantly improves the cycle stability of the alloys, and the positive impact of such a substitution on the cycle stability of the as-quenched alloy is much larger than that of the as-cast. All of the alloys have multiphase structures composed of two major phases, (La, Mg)Ni-3 and LaNi5, and a residual phase LaNi2. The substitution of Fe for Ni helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grains in the as-quenched alloy arc significantly refined, and the lattice constants and the cell volumes of the alloys are obviously enlarged.