Rare earth metal-nickel-based hydrogen storage alloy, method for producing the same, and negative electrode for nickel-metal hydride secondary battery

摘要

A rare earth metal-nickel-base hydrogen absorbing alloy having a composition represented by the following formula (1): (R1-xLx)(Ni1-yMy)z wherein R represents La, Ce, Pr, or Nd; L represents Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Mg, or Ca; M represents Co, Al, Mn, Fe, Cu, Zr, Ti, Mo, Si, V, Cr, Nb, Hf, Ta, W, B, or C; 0.05/=x/=0.4, 0/=y/=0.5, and 3.0/=z4.5. The alloy contains at least 30 to less than 95 % by volume of crystal grains wherein the reverse phase boundary present in a direction perpendicular to the C axis of the crystal grain of the alloy is 5 to 25 per 20 nm in the direction of the C axis. 60 to less than 95 % of the amount of the element added and represented by L in the formula (1) is disposed in the reverse phase region.