Abstract
In this study, various LaNi5-based alloys were used as the negative electrode materials to study their electrochemical performances. From the cyclic test of two electrodes, LaNi4.25Al0.15Co0.5V0.1 and LaNi4.75Al0.15V0.1, it is observed that partial substitution of Ni with Co improves the cyclic stability of the electrode, although the maximum capacity decreases. In the case of high rate charge/discharge test, the addition of Co seems to be quite beneficial. This is ascribed to the lower pulverization rate of the alloy with substitution of Co. When 10% Ni powder was mixed with the alloy powder as a compacting agent, no significant improvement in both capacity and cycle life is observed. Several new compositions with Nb, Zr, Mn, or Cr partially substituting for Ni in the Co-free LaNi5-based alloys were also tested. The electrochemical performances of these new alloys are not satisfactory. As for the nonstoichiometric MmNi5-based alloys, Mm (Co0.13Mn0.07Fe0.01Ni0.71)5.10 and Mm(Co0.14Al0.06Mn0.08Ni0.72)5.7, supplied by Rhone-Poulenc Inc., they show smaller capacities but extremely good cyclic stability.