Positive electrode active material for lithium secondary battery, method of preparing the same and lithium secondary battery including the same
The present invention provided a positive electrode active material for a lithium secondary battery including lithium cobalt oxide particles. The lithium cobalt oxide particles include lithium deficient lithium cobalt oxide having Li/Co molar ratio of less than 1, belongs to an Fd-3m space group, and having a cubic crystal structure, in surface of the particle and in a region corresponding to a distance from 0% to less than 100% from the surface of the particle relative to a distance (r) from the surface to the center of the particle. In the positive electrode active material for a lithium secondary battery according to the present invention, the intercalation and deintercalation of lithium at the surface of a particle may be easy, and the output property and rate characteristic may be improved when applied to a battery.
1. A method of preparing a positive electrode active material for a lithium secondary battery including lithium cobalt oxide particles having a core-shell structure comprising a core part and a shell part provided on a surface of the core part, the method comprising:
preparing initial lithium cobalt oxide particles by mixing a first amount of a cobalt raw material and a first amount of a lithium raw material in amounts satisfying a molar ratio of 1≤Li/Co≤1.2, and first heating under an air or oxygen atmosphere, so that a surface of the initial lithium cobalt oxide particles is exposed to the air or oxygen atmosphere during the first heating; and
preparing the lithium cobalt oxide particles by second heating the initial lithium cobalt oxide particles to produce the shell part comprising the lithium deficient lithium cobalt oxide having the Li/Co molar ratio of less than 1, belonging to an Fd-3m space group and having a cubic crystal structure, wherein the second heating is conducted more than once,
wherein the second heating is conducted under an air or oxygen atmosphere, so that the surface of the initial lithium cobalt oxide particles is exposed to the air or oxygen atmosphere during the second heating,
wherein the second heating can comprise: further adding a raw material consisting of a second amount of the cobalt raw material, a second amount of the lithium raw material, or a combination therein, and
wherein, when the second heating comprises further adding the raw material, the raw material is added in amounts satisfying a molar ratio of 0≤Li/Co<1.
2. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , wherein a metal-containing raw material comprising at least one metal element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb is further included during mixing the cobalt raw material and the lithium raw material in the preparing of the initial lithium cobalt oxide particles.
3. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , wherein the first heating is conducted by heating at a temperature from 800° C. to 1,100° C. in the atmosphere or an oxygen atmosphere.
4. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , wherein the second heating is conducted by heating at a temperature from 800° C. to 1,100° C. in the atmosphere or an oxygen atmosphere.
5. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , wherein the second heating is conducted twice at a temperature from 800° C. to 1,100° C., and the temperature during each heating is the same or different.
6. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , further comprising adding a cobalt raw material and a lithium raw material in amounts satisfying the following relation of 0.95<Li/Co molar ratio<1 during the second heating.
7. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , further comprising adding a metal-containing raw material including at least one metal element selected from the group consisting of W, Mo, Zr, Ti, Mg, Ta, Al, Fe, V, Cr, Ba, Ca, and Nb during the second heating.
8. The method of preparing the positive electrode active material for a lithium secondary battery of claim 1 , wherein the method is a dry method not using a solvent.