| abstract |
[Problem] To provide a positive electrode active material which, when used in a lithium ion secondary battery, is capable of better reducing positive electrode resistance and achieving more favorable output characteristics. [Solution] This positive electrode active material comprises: lithium transition-metal-containing complex oxide particles that include an additive element M1; and a coating layer that comprises a metal complex oxide containing Li and a metal element M2 and that is provided to at least a part of the surface of the particles. The particles have a d50 of 3.0-7.0 μm, a BET specific surface area of 2.0-5.0 m2 /g, a tapped bulk density of 1.0-2.0 g/cm3, and an oil absorption amount of 30-60 ml/100g. Among primary particles, each of a plurality of primary particles having a primary particle diameter in a range of 0.1-1.0 μm has: a coefficient of variation of M1 concentration which is not greater than 1.5; and an amount of M2 which is 0.1-1.5 at% with respect to the total number of atoms of Ni, Mn, and Co contained in the complex oxide particle. |