13. A positive electrode active material for a non-aqueous electrolyte secondary battery which includes secondary particles formed by aggregates of a plurality of primary particles and having a tap density of 1.5 g/cm3or more and a surface roughness index which is a value in which the measured specific surface area of the secondary particles is divided by the geometric surface area of the secondary particles when the secondary particles are assumed to be true sphere is within a range of 3.6 to 10.
plurality of primary particles
tap density
1.5 g/cm3
g/cm3