Structures and electrochemical performances of La_(0.75-x)Zr_xMg_(0.25)Ni_(3.2)Co_(0.2)Al_(0.1) (x=0-0.2) electrode alloys prepared by melt spinning

The La-Mg-Ni system A2B7-type electrode alloys with nominal composition La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x=0, 0.05, 0.1, 0.15, 0.2) were prepared by casting and melt-spinning. The influences of melt spinning on the electrochemical performances as well as the structures of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the as-cast and spun alloys have a multiphase structure, consisting of two main phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The melt spinning leads to an obvious increase of the LaNi5 phase and a decrease of the (La, Mg)Ni3 phase in the alloys. The results of the electrochemical measurement indicate that the discharge capacity of the alloys (x≤0.1) first increases and then decreases with the increase of spinning rate, whereas for x＞0.1, the discharge capacity of the alloys monotonously falls. The melt spinning slightly impairs the activation capability of the alloys, but it significantly enhances the cycle stability of the alloys.