Cathode active material precursor, cathode active material formed therefrom, method of preparing the cathode active material, and cathode and lithium battery each including the cathode active material

A cathode active material includes a secondary particle including an aggregate of a plurality of primary particles, wherein the secondary particle includes a nickel-containing lithium transition metal oxide having a layered crystal structure, wherein the plurality of primary particles includes a first primary particle having a size greater than about 400 nanometers, a second primary particle having a size less than about 150 nanometers, and a third primary particle having a size of about 150 nanometers to about 400 nanometers, wherein the third primary particle has a area of greater than or equal to about 80% of a total area of the plurality of primary particles, and wherein the secondary particle has a porosity of less than or equal to about 10% of a total area of the cathode active material.