Influence of the rare earth composition on the properties of Ni-MH electrodes

Lattice parameters, hydrogen absorption properties and electrochemical cycling properties up to 240 cycles have been measured as a function of the Ce content for alloys of composition La0.82-xCexNd0.15Pr0.03Ni3.55Mn0.4Al0.3Co0.75 (0≤x≤0.82). The results show the strong increase of the plateau pressure correlated to the cell volume decrease as a function of x. On the other hand, the hydrogen capacity measured in solid-gas reaction as well as the electrochemical capacity decreases slightly. The results show that both La and Ce have to be present to achieve a good cycle life, the cycling degradation being almost independent of their relative quantities in a broad range of concentrations