CATHODE ACTIVE MATERIAL FOR SECONDARY BATTERY, MANUFACTURING METHOD THEREFOR, AND LITHIUM SECONDARY BATTERY COMPRISING SAME

The present invention relates to a positive electrode active material for a secondary battery which is a lithium composite transition metal oxide including nickel (Ni), cobalt (Co), and manganese (Mn), wherein the lithium composite transition metal oxide includes the nickel (Ni) in an amount of 65 mol% or more and the manganese (Mn) in an amount of 5 mol% or more based on a total amount of transition metals, and wherein the electrode positive active material is composed of a single particle, and has a crystallite size of 180 nm or more.