Hydrogen storage alloy, hydrogen storage alloy powder, production method thereof, and negative electrode for nickel metal hydride secondary battery

摘要

A hydrogen-occluding alloy which is reduced in cobalt content, has a satisfactory balance among activity, corrosion resistance, and life characteristics, and has excellent suitability for recycling. The hydrogen-occluding alloy has a composition represented by the formula (1), is constituted substantially of a single phase, and has an average crystal grain diameter of 15 microm or smaller and a major axis/minor axis ratio in each crystal of 3 or higher. RNiaCobAlcMndMe (1) (R is any of rare earth elements including yttrium, etc.; M is magnesium, iron, copper, zirconium, etc.; and 3.30a=5.15, 0.10=b=0.50, 0.15=c0.35, 0.10=d=0.45, 0=e=0.50, 5.10=a+b+c+d+e=5.50, and 0.1=c/d=5.0.)