Rare earth metal-nickel metal hydride alloy, process for producing the same, and negative electrode for nickel metal hydride secondary battery

摘要

A rare earth metal-nickel hydrogen-occlusion alloy which has the following composition (1): RNix-yMy (wherein R represents La, Ce, Pr, Nd or a mixture thereof; M represents Co, Al, Mn, Fe, Cu, Zr, Ti, Mo, Si, V, Cr, Nb, Hf, Ta, W, B, C or a mixture thereof; and 3.5 x 5 and 0 y 2), in which crystals have each anLaNi5-type single-phase structure, and which contains from 5 vol. % to less than 95 vol. % of crystals containing from two to less than seventeen antiphase boundaries, per 20 nm in the direction of the C-axis of the crystal grains in the alloy, present at right angles with the C-axis. The negative electrode of a nickel-hydrogen secondary battery contains the above hydrogen-occlusion alloy and a conductive agent as the electrode material, and can be improved in initial activity, battery capacity and service life at the same time.