Patent ID: 7078126

Claim:
A method for production of a hydrogen storage alloy, for use in alkaline storage batteries, including: a first step of preparing alloy particles having a CaCu 5 -type crystal structure and represented by the compositional formula MmNi x CO y Mn z M 1-z , wherein N represents at least one element selected from the group consisting of aluminum (Al) and copper (Cu), x is a nickel (Ni) stoichiometry and satisfies 3.0≦x≦5.2, y is a cobalt (Co) stoichiometry and satisfies 0≦y≦1.2, z is a manganese (Mn) stoichiometry and satisfies 0.1≦z≦0.9, and the sum of x, y and z satisfies 4.4≦x+y+z≦5.4; and a second step of immersing said alloy particles in an acid treating solution containing a cobalt compound and a copper compound, each in an amount of 0.1–5.0% by weight based on the weight of said alloy particles, and an organic additive to thereby remove oxide films on alloy particle surfaces of said alloy particles and also reductively deposit cobalt and copper so as to form surface regions at said alloy particle surfaces; wherein each said surface region respectively surrounds a bulk region of a respective one of said alloy particles having a CaCu 5 -type crystal structure and wherein, when the sum of percentages by number of cobalt (Co) atoms and copper (Cu) atoms present in said surface region is given by a and the sum of percentages by number of cobalt (Co) atoms and copper (Cu) atoms present in said bulk region is given by b, the relationship a/b≧1.3 is satisfied.