Positive electrode active material for secondary batteries and lithium secondary batteries, which includes the positive electrode active material

Abstract

Positive electrode active material for a secondary battery, wherein the positive electrode active material comprises a first positive electrode active material and a second positive electrode active material, wherein an average particle diameter (D50) of the first positive electrode active material is twice or more the average particle diameter (D50) of the second positive electrode active material; the second positive electrode active material has a crystallite size, calculated according to the Scherrer equation using X-ray diffraction (XRD) data, of 200 nm or more; and the second positive electrode active material is a lithium composite transition metal oxide in which the nickel content (Ni) is 60 mol% or more, based on the total amount of the other metal elements besides lithium in the lithium composite transition metal oxide.