Positive electrode active material precursor for secondary battery, positive electrode active material, and lithium secondary battery including the positive electrode active material

A positive electrode active material precursor for a secondary battery, the positive electrode active material precursor which is a secondary particle in which primary particles are aggregated,

• wherein the secondary particle comprises a core portion including nickel (Ni), cobalt (Co), and manganese (Mn);
• and
• a shell portion surrounding a surface of the core portion and including nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al),
• wherein the core portion and the shell portion comprises rod-shaped primary particles, and an average major axis length of the primary particles in the shell portion is smaller than an average major axis length of the primary particles in the core portion,
• wherein the average major axis length of the primary particles of the core portion is in a range of 300 nm to 1 μm, and
• wherein the average major axis length of the primary particles of the shell portion is in a range of 100 nm to 250 nm.