1. A transition metal mixed hydroxide consisting of primary particles and approximately spherical secondary particles formed by aggregation of primary particles, wherein the transition metal mixed hydroxide has an average particle diameter of from 1 μm to 20 μm and contains Mn, Ni, Fe and Co in a molar ratio of a:b:c:d, wherein a is from 0.3 to 0.7, b is from 0.4 to 0.7, c is more than 0 and not more than 0.1, d is from 0 to 0.2, and a+b+c+d=1.
the transition metal mixed hydroxide
average particle diameter
from 1 μm to 20 μm
μm