Metal-doped cobalt precursor for preparing positive electrode active material for secondary battery

A lithium cobalt oxide having a layered structure for a positive electrode active material, wherein the lithium cobalt oxide is represented by the following Formula 1, and doped with, as dopants, magnesium (Mg) and M′;

• and
• the dopants have an average oxidation number of more than +2 to +2.5 or less in the lithium cobalt oxide:
• Lia(CoxMgyM′z)O2 (1)
• wherein a satisfies 0.95≤a≤1.05;
• x, y, and z satisfy the following weight ratio conditions:
• a content of x is in the range of 99 wt % to 99.8 wt % and a total content of y and z is in the range of 0.2 wt % to 1 wt %, when the sum of x, y, and z is regarded as 100 wt %;
• and
• M′ is one or more selected from the group consisting of Al, Ti, Mn, Zr, Ba, B, Ca, Ta, Mo, Nb, W, Sr, and PO4,
• wherein the positive electrode active material is in the form of particles, and the surface of the particle is coated with Al2O3, and
• wherein the Al2O3 is applied at a thickness of 0.2% to 5% of a diameter of the positive electrode active material particle.