RAPE EARTH-NICKEL HYDROGEN STORAGE ALLOY AND NEGATIVE ELECTRODE FOR ALKALI STORAGE BATTERY

摘要

PROBLEM TO BE SOLVED: To obtain a hydrogen storage alloy for an inexpensive nickel-hydrogen battery having a long service life by allowing rare earths, Ni, Fe and Mn in a rare earth hydrogen storage alloy having a CaCu5 type crystal structure to have specified compositional contg. relation to reduce expensive Co without reducing the amt. of hydrogen to be occluded. SOLUTION: This rare earth hydrogen storage alloy is expressed by formula I [R denotes a mixture of rate earth elements, (a), (b) and (c) denote the atomic ratio of each element to R, and 3.0=a=4.4, 0. 8=b1.5, 0c=0.7, and 4.8=a+b+c=5.2 are satisfied). Moreover, the alloy of formula II (the items are the same as those in the formula I except (d), M denotes either or both of Co and Al, and 0d=0.5 and 4.8=a+b+c+d=5.2 are satisfied] is suitable as well. A prescribed amt. of each component is melted in a vacuum or in an inert gas atmosphere to obtain alloy molten metal, which is cooled and cast. Furthermore, it is subjected to heat treatment at 800 to 1,200 deg.C for 5 to 20 hr in a vacuum or in an inert gas atmosphere and is thereafter cracked to obtain alloy powder of 5 to 50 m. In the case it is used as the negative electrode, its characteristics are extremely exhibited.