6. The transition metal composite hydroxide according to claim 1, wherein the average particle size of the secondary particles is within a range of 1 μm to 15 μm to, and the value of [(d90−d10)/average particle size], which is an index that represents the spread of the particle size distribution of the secondary particles, is 0.65 or less.
the secondary particles
average particle size
1 μm to 15 μm
μm
the secondary particles
particle size distribution
0.65 or less