NICKEL-BASED ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, METHOD OF PREPARING THE SAME, AND LITHIUM SECONDARY BATTERY INCLUDING POSITIVE ELECTRODE INCLUDING THE NICKEL-BASED ACTIVE MATERIAL

Provided are a nickel-based active material, a method of preparing the same, and a lithium secondary battery including a positive electrode including the nickel-based active material. The nickel-based active material includes at least one secondary particle including an aggregate of two or more primary particles, wherein at least a portion of the secondary particle has a radial array structure, and a hetero-element compound is positioned between the primary particles.