Lithium complex oxide for lithium secondary battery positive active material and method of preparing the same

1. A lithium complex oxide secondary particle formed by coagulation of a plurality of primary particles, wherein Co concentration at a boundary of the primary particle is higher than Co concentration in an internal part of the primary particle,

wherein the secondary particle has a bound energy (P1) of spin-orbit-spit 2p3/2 peak and a bound energy (P2) of 2p1/2 peak in a Co 2p core-level spectrometry obtained through XPS measurement,

wherein the P1 and the P2 are ranged respectively in 779 eV≤P1≤780 eV and 794 eV≤P2≤795 eV, and

wherein a primary particle located at a surface part of the secondary particle has a Co concentration gradient reduced by 0.05 to 0.07 mol % per nm toward a center of the primary particle from a surface of the primary particle.

2. The lithium complex oxide secondary particle of claim 1 , wherein the Co concentration of the primary particle located at the surface part of the secondary particle, at a part which is in contact with the surface of the secondary particle, is higher than at a part that is in noncontact with the surface of the secondary particle.

3. The lithium complex oxide secondary particle of claim 1 , wherein Co ion concentration is graded, in the primary particle located at the surface of the secondary particle, toward a center of the particle from the surface of the particle.

4. The lithium complex oxide secondary particle of claim 1 , wherein the primary particle located at the surface part of the secondary particle is configured to satisfy that dc/dh is 2 to 10, where the dc is a length toward the center and the dh is a length vertical to the center.

5. The lithium complex oxide secondary particle of claim 1 , wherein the secondary particle has at least one peak at positions (104), (110), (113), (101), (102), and (003) during XRD analysis.

6. The lithium complex oxide secondary particle of claim 1 , wherein the secondary particle has a ratio of peak intensity (I 531 ) around 531 eV and peak intensity (I 528 ) around 528.5 eV during an O 1s core-level spectrometry that is obtained through XPS measurement, and

wherein the ratio is I 531 /I 528 ≤2.

7. The lithium complex oxide secondary particle of claim 1 , wherein the secondary particle has a ratio between peak intensity (I 289 ) around 289 eV and peak intensity (I 284 ) around 284.5 eV during a C 1s core-level spectrometry that is obtained through XPS measurement, and

wherein the ratio is I 289 /I 284 ≤0.9.

8. The lithium complex oxide secondary particle of claim 1 , wherein the secondary particle is given by the following Formula 1,

Li x Ni 1-(a1+b1+c1) Co a1 M1 b1 M2 c1 M3 d O y ,  [Formula 1]

wherein, in the Formula 1, M1 is Mn or Al, and M2 and M3 are metals selected from a group of Al, Ba, B, Co, Ce, Cr, F, Li, Mg, Mn, Mo, P, Sr, Ti, and Zr, and

wherein 0.95≤x≤1.05, 1.50≤y≤2.1, 0.02≤a1≤0.25, 0.01≤b1≤0.20, 0≤c1≤0.20, and 0≤d≤0.20.

9. A lithium secondary battery comprising a lithium complex oxide secondary particle of claim 1 .

10. The lithium secondary battery of claim 9 , wherein the lithium secondary battery is configured to have residual lithium equal to or smaller than 6,000 ppm.

11. A method of preparing a lithium complex oxide secondary particle by claim 1 , the method comprising:

manufacturing precursors of lithium secondary battery positive active materials given by the following Formula 2,

Ni 1−(x2+y2+z2) Co x2 M1 y2 M2 z2 (OH) 2 ,  [Formula 2]

wherein, in Formula 2, M1 is Mn or Al, and M2 is a metal selected from a group of Al, Ba, B, Co, Ce, Cr, F, Li, Mg, Mn, Mo, P, Sr, Ti, and Zr, and wherein 0≤2≤0.25, 0≤y2≤0.20, and 0≤z2≤0.20;

reacting precursors of lithium secondary battery positive active materials with a lithium compound and manufacturing a positive active material by first thermal treating the reactant;

washing the positive active material with distilled water or an alkaline solution;

reactively coating the washed positive active material with a solution containing M2 that is a metal selected from the group of Al, Ba, B, Co, Ce, Cr, F, Li, Mg, Mn, Mo, P, Sr, Ti, and Zr;

drying particles of the positive active material; and

mixing the dried positive active material with M3 that is a metal selected from the group of Al, Ba, B, Co, Ce, Cr, F, Li, Mg, Mn, Mo, P, Sr, Ti, and Zr and doping the metal M3 into the particles by second thermal treating the mixture.

12. The method of claim 11 , wherein the reactively coating comprises:

reactively coating the washed positive active material with the solution containing Co.

13. The method of claim 11 , wherein, in the reactively coating, the solution containing Co ion has concentration of 1 to 10 mol %.