Nickel-containing composite hydroxide and production process thereof

A nickel-containing composite hydroxide that is expressed by

• the general formula:
• Ni1-x-yCoxAlyMt(OH)2+α, where, 0≤x≤0.20, 0≤y≤0.15, 0≤t≤0.10, 0≤α≤0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y, or
• the general formula:
• Ni1-x-zCoxMnzMt(OH)2+α, where 0≤x≤0.50, 0≤z≤0.50, x+z≤0.70, 0≤t≤0.10, 0≤α≤0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y,
• the nickel-containing composite hydroxide comprising secondary particles, each of the secondary particles being formed from an aggregation of a plurality of primary particles,
• wherein the shape of each of the secondary particles is spherical or ellipsoidal,
• wherein the average particle size of the secondary particles is 20 μm to 50 μm, and the average particle size of the primary particles is 0.01 μm to 0.40 μm, and the BET value after roasting the nickel-containing composite hydroxide in air for 2 hours at 800° C. is 12 m2/g to 50 m2/g.