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

摘要

A hydrogen storage alloy having a good balance of activity, corrosion resistance and life characteristics with a small amount of cobalt, and excellent recyclability, a method for producing the same, and a negative electrode for a nickel metal hydride secondary battery, The composition has the composition of formula (1), is substantially single phase, has an average crystal grain size of 15 μm or less, and the ratio of the major axis to the minor axis of each crystal is 3 or more. RNiaCobAlcMndMe (1) (R: rare earth elements including Y, M: Mg, Fe, Cu, Zr, etc. 3.30 a ≦ 5.15, 0.10 ≦ b ≦ 0.50,. 15 ≦ c 0.35, 0.10 ≦ d ≦ 0.45, 0 ≦ e ≦ 0.50, 5.10 ≦ a + b + c + d + e ≦ 5.50, c / d = 0.1 to 5.0)