Positive electrode active material for secondary battery and method for preparing the same

1. A positive electrode active material for a secondary battery, comprising:

a core comprising a lithium composite metal oxide; and

a surface treatment layer located on a surface of the core and comprising an amorphous oxide;

wherein the amorphous oxide including silicon (Si), nitrogen (N) and at least one metal element selected from the group consisting of a Group 1A element, a Group 2A element, and a Group 3B element.

2. The positive electrode active material of claim 1 , wherein the surface treatment layer comprises silicon oxide (SiO 2 ), a nitride including at least one metal or semi-metal element selected from the group consisting of a Group 3A element and a Group 4A element, and a metal oxide including at least one metal element selected from the group consisting of a Group 1A element, a Group 2A element, and a Group 3B element.

3. The positive electrode active material of claim 2 , wherein a molar ratio of the silicon oxide, the nitride, and the metal oxide is (0.5 to 1.5):(0.5 to 1.5):(0.5 to 1.5).

4. The positive electrode active material of claim 2 , wherein the nitride is at least one selected from the group consisting of silicon nitride (Si 3 N 4 ) and aluminum nitride (AlN).

5. The positive electrode active material of claim 2 , wherein the metal oxide is at least one selected from the group consisting of sodium oxide (Na 2 O), magnesium oxide (MgO), calcium oxide (CaO), and yttrium oxide (Y 2 O 3 ).

6. The positive electrode active material of claim 1 , wherein an average thickness of the surface treatment layer is 0.01 to 0.1 times an average radius of the core.

7. The positive electrode active material of claim 1 , wherein the lithium composite metal compound is represented by Chemical Formula 1:

Li a Ni x Co y M1 z M2 w O 2   <Chemical Formula 1>

wherein,

M1 is at least one selected from the group consisting of Mn and Al,

M2 is at least one element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb, and

0.8≤a≤1.5, 0.3≤x<1, 0<y≤0.5, 0<z≤0.5, 0≤w≤0.02 and x+y+z+w=1.

8. A positive electrode for a secondary battery comprising the positive electrode active material for a secondary battery of claim 1 .

9. A secondary battery comprising the positive electrode for a secondary battery of claim 8 .

10. A method for preparing a positive electrode active material for a secondary battery, comprising:

a first process of forming an amorphous oxide using a first raw material including silicon, a second raw material including nitrogen, and a third raw material including at least one metal element selected from the group consisting of a Group 1A element, a Group 2A element, and a Group 3B element; and

a second process of forming a surface treatment layer including the amorphous oxide on a lithium composite metal oxide by mixing the amorphous oxide and the lithium composite metal oxide and performing heat treatment.

11. The method of claim 10 , wherein the first process is a process of forming an amorphous oxide by mixing the first raw material, the second raw material, and the third raw material, and melting the mixture at 900° C. to 1,800° C. followed by cooling.

12. The method of claim 11 , wherein the mixing is performed by mixing the first raw material, the second raw material, and the third raw material at a molar ratio of (0.5 to 1.5):(0.5 to 1.5):(0.5 to 1.5).

13. The method of claim 10 , further comprising a process of pulverizing the amorphous oxide so that an average particle diameter thereof is in a range of 1 to 1,000 nm, after the first process is performed.

14. The method of claim 10 , wherein the heat treatment is performed at a temperature of 300° C. to 700° C. in the second process.