Composite cathode active material for lithium battery, cathode for lithium battery including the same, and lithium battery including the cathode

1. A composite cathode active material for a lithium battery comprising:

a lithium composite oxide;

a coating layer comprising a metal oxide and a lithium fluoride, wherein the coating layer is disposed on at least a portion of a surface of the lithium composite oxide; and

a spinel phase between the lithium composite oxide and the coating layer,

wherein a total amount of the metal oxide and the lithium fluoride is in a range of about 3 parts by weight to about 10 parts by weight, based on 100 parts by weight of the composite cathode active material,

wherein the lithium composite oxide is a layered oxide,

wherein a mole ratio of the metal oxide to the lithium fluoride in the coating layer is in a range of about 1:1.5 to about 1.2, and

wherein the coating layer is in the form of a continuous layer.

2. The composite cathode active material of claim 1 , wherein the coating layer is a single layer comprising a composite comprising the metal oxide and the lithium fluoride or a mixture comprising the metal oxide and the lithium fluoride.

3. The composite cathode active material of claim 1 , wherein the metal oxide is at least one of Al 2 O 3 , Bi 2 O 3 , B 2 O 3 , ZrO 2 , MgO, Cr 2 O 3 , MgAl 2 O 4 , Ga 2 O 3 , SiO 2 , SnO 2 , CaO, SrO, BaO, Y 2 O 3 , TiO 2 , Fe 2 O 3 , MoO 3 , MoO 2 , CeO 2 , La 2 O 3 , ZnO, or LiAlO 2 .

4. The composite cathode active material of claim 1 , wherein the composite cathode active material does not have a peak between about 23 degrees two-theta to about 27 degrees two-theta, when analyzed by X-ray powder diffraction.

5. The composite cathode active material of claim 1 , wherein the coating layer does not comprise AlF 3 .

6. The composite cathode active material of claim 1 , wherein the coating layer consists of the metal oxide and the lithium fluoride.

7. The composite cathode active material of claim 1 , wherein the composite cathode active material has a peak between about 72 electron volts to about 75 electron volts, and has a peak between about 683 electron volts to about 688 electron volts, when analyzed by X-ray photoelectron spectroscopy.

8. The composite cathode active material of claim 1 , wherein a total amount of the metal oxide and the lithium fluoride is in a range of 3 parts by weight to about 10 parts by weight, based on 100 parts by weight of the composite cathode active material.

9. The composite cathode active material of claim 1 , wherein the lithium composite oxide comprising the layered oxide comprises at least one compound represented by Formulae 1 to 3:

Li a Ni x Co y Mn z M c O 2-e A e   Formula 1

wherein, in Formula 1,

1.0<a≤1.4, 0<x<1, 0≤y<1, 0<z<1, 0≤c<1, 0<x+y+z+c<1, and 0≤e<1;

M is at least one of V, Mg, Ga, Si, W, Mo, Fe, Cr, Cu, Zn, Ti, Al, or B; and

A is at least one anion element of F, S, Cl, or Br,

Li[Co 1-x M x ]O 2-a A a   Formula 2

wherein, in Formula 2,

0≤a≤0.1 and 0≤x≤0.1;

M is at least one metal of Mg, Al, Ni, Mn, Zn, Fe, Cr, Ga, Mo, or W; and

A is at least one anion element of F, S, Cl, or Br,

Li 1+a [Ni 1-x M x ]O 2-b A b   Formula 3

wherein, in Formula 3,

0.01≤a≤0.2, 0≤b≤0.1, and 0.01≤x≤0.5;

M is at least one metal of Mg, Al, Co, Mn, Zn, Fe, Cr, Ga, Mo, or W; and

A is at least one anion element of F, S, Cl, or Br.

10. The composite cathode active material of claim 1 , wherein the lithium composite oxide comprising the layered oxide comprises at least one compound represented by Formula 7:

Li a Ni x Co y Mn z M c O 2-b A b   Formula 7

wherein, in Formula 7,

1.0<a≤1.4, 0<x<1, 0≤y<1, 0<z<1, 0≤c<1, 0<x+y+z+c<1, and 0≤b≤0.1;

M is at least one of V, Mg, Ga, Si, W, Mo, Fe, Cr, Cu, Zn, Ti, Al, or B; and

A is at least one anion element of F, S, Cl, or Br.

11. The composite cathode active material of claim 1 , wherein a thickness of the coating layer is in a range of about 1 nanometer to about 1 micrometer.

12. The composite cathode active material of claim 1 , wherein the lithium composite oxide comprising the layered oxide is at least one of Li 1.167 Ni 0.542 Co 0.083 Mn 0.208 O 2 , Li 1.130 Ni 0.565 Co 0.088 Mn 0.217 O 2 , Li 1.167 Ni 0.5 Co 0.125 Mn 0.208 O 2 , Li 1.130 Ni 0.522 Co 0.130 Mn 0.217 O 2 , Li 1.167 Ni 0.5 Co 0.1665 Mn 0.1665 O 2 , Li 1.130 Ni 0.522 Co 0.174 Mn 0.174 O 2 , Li 1.167 Ni 0.458 Co 0.083 Mn 0.292 O 2 , Li 1.130 Ni 0.478 Co 0.087 Mn 0.305 O 2 , Li 1.167 Ni 0.542 Co 0.083 Mn 0.208 O 1.99 F 0.01 , Li 1.130 Ni 0.565 Co 0.088 Mn 0.21701.99 F 0.01 , or Li 1.167 Ni 0.5 Co 0.125 Mn 0.208 O 1.99 F 0.01 .

13. The composite cathode active material of claim 1 , wherein the coating layer comprises a composite that includes Al 2 O 3 and LiF.

14. A method of preparing a composite cathode active material for a lithium battery, the method comprising:

mixing a metal oxide precursor, a lithium composite oxide, a fluoride precursor, and a solvent to prepare a reaction product;

drying the reaction product; and

heat-treating the dried reaction product to prepare the composite cathode active material,

wherein the composite cathode active material comprises

a lithium composite oxide,

a coating layer comprising a metal oxide and a lithium fluoride, wherein the coating layer is disposed on at least a portion of a surface of the lithium composite oxide, and

a spinel phase between the lithium composite oxide and the coating layer,

wherein a total amount of the metal oxide and the lithium fluoride is in a range of about 3 parts by weight to about 10 parts by weight, based on 100 parts by weight of the composite cathode active material,

wherein a mole ratio of the metal oxide to the lithium fluoride is in a range of about 1:1.5 to 1:2, and

wherein the coating layer is in the form of a continuous layer.

15. The method of claim 14 , wherein the drying is performed at a temperature in a range of about 50° C. to about 100° C.

16. The method of claim 14 , wherein the heat-treating is performed at a temperature in a range of about 400° C. to about 700° C. and in an inert gas atmosphere or in an oxidative gas atmosphere.

17. The method of claim 14 , wherein the heat-treating is performed at a temperature in a range of about 450° C. to about 700° C. and in an inert gas atmosphere or in an oxidative gas atmosphere.

18. The method of claim 14 , wherein the metal oxide precursor comprises at least one selected from an alkoxide, a sulfate, a nitrate, an acetate, a chloride, and a phosphate of at least one selected from aluminum, bismuth, boron, zirconium, magnesium, chrome, gallium, silicon, tin, calcium, strontium, barium, yttrium, titanium, iron, molybdenum, cerium, lanthanum, and zinc.

19. The method of claim 14 , wherein the fluoride precursor comprises at least one selected from ammonium fluoride, ammonium hydrogen fluoride, cesium fluoride, potassium fluoride, and sodium fluoride.

20. The method of claim 14 , wherein a washing process is not performed before the drying of the reacted product.

21. The method of claim 14 , wherein the mixing of the metal oxide precursor, the lithium composite oxide, the fluoride precursor, and the solvent comprises

mixing the metal oxide precursor, the fluoride precursor, and the solvent and then adding the lithium composite oxide to the mixture of the metal oxide precursor and the fluoride precursor, and the solvent; or

mixing the metal oxide precursor, the lithium composite oxide, and the solvent, and then adding the fluoride precursor to the mixture of the metal oxide precursor and the lithium composite oxide, and the solvent.

22. A cathode for a lithium battery comprising the composite cathode active material of claim 1 .

23. A lithium battery comprising the cathode of claim 22 .

24. The composite cathode active material of claim 1 , wherein the metal oxide comprises aluminum.

25. A composite cathode active material for a lithium battery comprising:

a lithium composite oxide;

a coating layer comprising a metal oxide and a lithium fluoride, wherein the coating layer is disposed on at least a portion of a surface of the lithium composite oxide, and

a spinel phase between the lithium composite oxide and the coating layer,

wherein a total amount of the metal oxide and the lithium fluoride is in a range of about 3 parts by weight to about 10 parts by weight, based on 100 parts by weight of the composite cathode active material,

wherein the lithium composite oxide is a layered oxide,

wherein a mole ratio of the metal oxide to the lithium fluoride in the coating layer is in a range of about 1:1.5 to about 1:1.15, and

wherein the coating layer is in the form of a continuous layer.

26. The composite cathode active material of claim 25 , wherein the metal oxide comprises aluminum.