CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, PREPARATION METHOD THEREFOR, AND LITHIUM SECONDARY BATTERY COMPRISING SAME

1 . A cathode active material for a lithium secondary battery, comprising

a lithium nickel cobalt manganese-based oxide represented by Chemical Formula 1 including secondary particles obtained by agglomerating at least one primary particle; and

metal oxide particles having a nano-sized average diameter (D50) and disposed inside the secondary particles,

Li a [Ni x Co y Mn z ] t M 1-t O 2-p X p   [Chemical Formula 1]

wherein, in Chemical Formula 1,

M is any one element selected from Al, Mg, Sn, Ca, Ge, Ga, B, Ti, Mo, Nb, and W

X is any one element selected from F, N, and P,

0.8≤a≤1.3,

0.60≤x≤0.95, 0<y≤0.2, 0<z≤0.2, x+y+z=1, 0≤t≤1, and 0≤p≤0.1.

2 . The cathode active material of claim 1 , wherein in Chemical Formula 1, 0.8≤x≤0.95, 0<y≤0.1, and 0<z≤0.1.

3 . The cathode active material of claim 1 , wherein the metal oxide comprises at least one selected from ZrO 2 , WO 3 , CeO 2 , TiO 2 , HfO 2 , Co 3 O 4 , La 2 O 3 , BaO, SrO, and a combination thereof.

4 . The cathode active material of claim 1 , wherein the metal oxide has an average particle diameter (D50) of 50 nm to 800 nm.

5 . The cathode active material of claim 1 , wherein a metal content of the metal oxide is 0.1 wt % to 0.7 wt % based on 100 wt % of the cathode active material.

6 . The cathode active material of claim 1 , wherein the secondary particles comprise a core portion in which a nickel molar content is constant and a shell portion which surrounds the outer surface of the core portion and has a concentration gradient in which a nickel molar content gradually decreases in a direction from the interface with the core portion to the outermost surface.

7 . The cathode active material of claim 1 , which further comprises a coating layer disposed on the surface of the secondary particles.

8 . A method of preparing a cathode active material for a lithium secondary battery, comprising

preparing a hydroxide precursor particle including nickel, cobalt, and manganese;

subjecting the hydroxide precursor particles to first firing to prepare porous oxide precursor particles;

mixing the oxide precursor particles and a metal oxide to prepare a first mixture;

mixing the first mixture and a lithium raw material to prepare a second mixture; and

subjecting the second mixture to second firing.

9 . The method of claim 8 , wherein the first firing is performed by increasing a temperature up to 400° C. to 800° C. at 1.0° C./min to 5.0° C./min, and maintaining for 3 hours to 20 hours.

10 . The method of claim 8 , wherein the first firing is performed while blowing air or oxygen at a rate of 10 mL/min to 50 L/min.

11 . The method of claim 8 , wherein in the mixing the oxide precursor particles and a metal oxide to prepare a first mixture, a doping raw material is further included.

12 . The method of claim 8 , wherein

the preparing of the hydroxide precursor particle including nickel, cobalt, and manganese comprises

preparing a first metal salt solution and a second metal salt solution each including a nickel raw material, a cobalt raw material, a manganese raw material, and a solvent, and having different molar concentrations of the nickel raw material;

a first co-precipitating in which a core portion is formed by supplying the first metal salt solution at a constant concentration to a reactor in which the pH is maintained constant and a chelating agent;

second co-precipitating in which a product forming a shell portion surrounding the outer surface of the core portion is formed by gradually decreasing a feed rate of the first metal salt aqueous solution and at the same time gradually increasing a feed rate of the second metal salt aqueous solution after the first co-precipitating; and

drying the product.

13 . A lithium secondary battery comprising

the cathode including a cathode active material of claim 1 ;

an anode; and

a non-aqueous electrolyte.