The invention claimed is:
1 . A positive electrode active material for a secondary battery comprising a lithium composite transition metal oxide represented by Formula 1 below, and
the lithium composite transition metal oxide is in a form of particles having a crystallite size of 170 nm to 300 nm:
Li p Ni 1−(x1+y1+z1+w1) Co x1 Mn y1 M a z1 M b w1 O 2+δ [Formula 1]
wherein M a is at least two elements selected from the group consisting of Zr, Al, V, and Mg, M b is at least two element selected from the group consisting of Ti, Y, Sr, Nb, Ba, and Ca, and 1≤p≤1.5, 0<x1<0.5, 0<y1≤0.5, 0<z1≤0.025, 0<w1≤0.015, and −0.1≤δ≤1.
2 . The positive electrode active material of claim 1 , wherein an average number of primary particles in secondary particles on a cross-section is 20 or less, wherein the average number is calculated by etching the particles of the lithium composite transition metal oxide into the cross-section using a focused ion beam (FIB) device, and calculating the average number when 20 or more secondary particle cross-sections are observed using a scanning electron microscope (FE-SEM).
3 . The positive electrode active material of claim 1 , wherein the elements of M a are contained in a total content of 2,000 ppm to 6,000 ppm.
4 . The positive electrode active material of claim 1 , wherein the elements of M b are contained in a total content of 500 ppm to 3,000 ppm.
5 . The positive electrode active material of claim 1 , wherein the particles of the lithium composite transition metal oxide have a specific surface area of 0.2 m 2 /g to 0.7 m 2 /g.
6 . The positive electrode active material of claim 2 , wherein the particles of the lithium composite transition metal oxide have an average number of primary particles in secondary particles on a cross-section of 10 or less.
7 . The positive electrode active material of claim 1 , wherein the lithium composite transition metal oxide has a nickel (Ni) content of 60 mol % or greater in a total content of metals excluding Li (lithium).
8 . The positive electrode active material of claim 1 , wherein the lithium composite transition metal oxide has a nickel (Ni) content of less than 60 mol % in the total content of metals excluding Li (lithium).
9 . A positive electrode comprising the positive electrode active material according to claim 1 .
10 . A lithium secondary battery comprising the positive electrode according claim 9 .