To provide a
lithium /
nickel /
cobalt /
manganese-containing
composite oxide powder which has a
high weight capacity density, a high packing property, an excellent cycle property, an excellent
discharge rate property and an excellent safety, and which has little content of free alkalis and is free from gelation at a time of producing a
slurry.A
lithium /
nickel /
cobalt /
manganese-containing
composite oxide powder represented by the formula LipNixCoyMnzMqO2-aFa (wherein M is at least one element selected from the group consisting of Al, Ge, Sn,
alkaline earth metal elements and
transition metal elements other than Co, Mn and Ni, 0.9≦p≦1.1, 0.2≦x≦0.5, 0.2≦y≦0.5, 0.1≦z≦0.4, 0≦q≦0.05, 1.9≦2-a≦2.1, p+x+y+z+q=2, and 0≦a≦0.02), characterized in that when the
powder is classified into
small particle size-classified particles with an average particle size of 2 μm≦D50≦8 μm and
large particle size-classified particles with an average particle size of 10 μm≦D50≦25 μm, the ratio of (% by weight of the
small particle size-classified particles) / (% by weight of the
large particle size-classified particles) is from 15 / 85 to 40 / 60, the
molar ratio (ps) of
lithium to the total of
nickel,
cobalt,
manganese and the M element contained in the
small particle size-classified particles is smaller than the
molar ratio (pl) of lithium to the total of nickel, cobalt, manganese and the M element contained in the
large particle size-classified particles.