Cycle stability of La0.7Mg0.3Ni2.55-xCo0.45Cux (x=0-0.4) electrode alloys

The La0.7Mg0.3Ni2.55-xCo0.45Cux (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and rapid quenching. Ni in the alloy was partially substituted by Cu in order to improve the cycle stability of La-Mg-Ni system (PuNi3-type) hydrogen storage alloy. The effects of substituting Ni with Cu on the microstructures and cycle stability of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the substitution of Cu for Ni is favourable for the formation of an amorphous in the as-quenched alloy, and this leads to an obvious refinement of the as-quenched alloy gains and a growth of the lattice constants and cell volumes of the as-cast and quenched alloys. The results obtained by the electrochemical measurement indicate that the cycle stability of the alloys significantly rises with the incremental variety of Cu content. When Cu content changes from 0 to 0.4, the cycle lives of the as-cast and quenched (30 m/s) alloys are enhanced from 72 to 88 cycles and from 100 to 121 cycles, respectively.