Composite cathode active material, lithium battery including the same, and preparation method thereof

1. A composite cathode active material comprising:

a core comprising a composite oxide capable of intercalation and deintercalation of lithium, wherein the composite oxide comprises a lithium transition metal oxide represented by

x Li[Li 1/3 Me 2/3 ]O 2 -(1 −x )LiMe′O 2   Formula 1

wherein in Formula 1, x is 0<x≤0.8, Me is Mn, Mo, W, V, Ti, Zr, Ru, Rh, Pd, Os, Ir, Pt, or a combination thereof, and Me′ is Ni, Mn, Co, or a combination thereof,

y Li[Li 1/3 ((M1) a (M2) b (M n ) c ) 2/3 ]O 2 -(1 −y )LiMe′O 2   Formula 2

wherein in Formula 2, a is 0≤a≤⅓, b is 0≤b≤⅓, and a+b+c=1, y is 0<y≤0.8, M1 is Ni, Cu, Zn, Co, Cr, Fe, Mg, or a combination thereof, and M2 is Mo, W, V, Ti, Zr, Ru, Rh, Pd, Os, Ir, Pt, or a combination thereof,

Li d Co 1-e-g Ni e (M3) g O 2-j (X1) j   Formula 3

wherein in Formula 3, d is 0.9≤d≤1.6, e is 0≤e≤1, g is 0≤g≤0.6, j is 0≤j≤1, M3 is Mn, Ni, Co, Cu, Mg, Na, Ca, Ti, Zn, Ga, Ge, Al, Cr, Sr, Mo, W, V, Zr, Ru, Rh, Pd, Os, Ir, Ag, Au, Hf, Sn, Pt, or a combination thereof, and X1 is O, F, S, P, or a combination thereof,

Li p Mn 2-q (M4) q O 4-t (X2) t   Formula 4

wherein in Formula 4, p is 0.9≤p≤1.6, q is 0≤q≤1, t is 0≤t≤1, M4 is Mn, Ni, Co, Cu, Mg, Na, Ca, Ti, Zn, Ga, Ge, Al, Cr, Mg, Sr, Mo, W, V, Zr, Ru, Rh, Pd, Os, Ir, Ag, Au, Hf, Sn, Pt, or a combination thereof; and X2 is O, F, S, P, or a combination thereof;

a carbon nanostructure disposed directly on an outer surface of the core; and

a particle of a material which is chemically inert to lithium also disposed directly on an outer surface of the core,

wherein the contents of the carbon nanostructure and the material which is chemically inert to lithium is about 0.001 parts by weight to about 10 parts by weight based on 100 parts by weight of a composite oxide capable of intercalation/deintercalation of lithium, and

wherein the material which is chemically inert to lithium consists of an inorganic material represented by Formula 5:

(M5)O x   Formula 5

wherein, in Formula 5, M5 is Al, V, Nb, Mo, W, Mn, Cr, Zr, Si, Mg, Ca, Y, Ba, B, Ta, In, Ag, Ti, Fe, Co, Ni, Cu, Zn, Sn, La, or a combination thereof, and x is 0<x≤6.

2. The composite cathode active material according to claim 1 , wherein the carbon nanostructure and the material which is chemically inert lithium are in the form of a shell, which is on the core.

3. The composite cathode active material according to claim 2 , wherein a thickness of the shell is from about 1 nanometer to about 10 micrometer.

4. The composite cathode active material according to claim 1 , wherein the composite oxide capable of intercalation/deintercalation of lithium includes at least one selected from an over-lithiated layered oxide, a lithium manganese oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium manganese oxide doped with a nonmetal element, a lithium nickel manganese oxide doped with a nonmetal element, a lithium nickel cobalt manganese oxide doped with a nonmetal element, and combinations thereof.

5. The composite cathode active material according to claim 1 , wherein the carbon nanostructure comprises a carbon nanocone, a carbon nanohorn, a carbon nanotube, or a combination thereof.

6. The composite cathode active material according to claim 1 , wherein the carbon nanostructure comprises a single-walled carbon nanotube, a multi-walled carbon nanotube, or combination thereof.

7. The composite cathode active material according to claim 1 , wherein the material which is chemically inert to lithium has an average particle size from about 1 nanometer to about 900 nanometers.

8. The composite cathode active material according to claim 1 , wherein a weight ratio between the carbon nanostructure and the material which is chemically inert to lithium is from 1:1 to 10:1.

9. A lithium battery comprising

a cathode;

electrolyte; and

an anode;

wherein the cathode includes the composite cathode active material according to claim 1 .

10. The lithium battery according to claim 9 , wherein an operational voltage of the composite cathode active material is equal to or greater than 4.3 volts versus lithium.

11. A method of manufacturing a composite cathode active material, the method comprising:

providing a composite oxide core capable of intercalation and deintercalation of lithium; and

surface treating the composite oxide core to manufacture the composite cathode active material of claim 1 .

12. The method of manufacturing a composite cathode active material according to claim 11 , wherein the surface treatment comprises a dry process comprising ball milling, hybridization, or mechanofusion.

13. The method of manufacturing a composite cathode active material according to claim 11 , wherein the surface treatment comprises a wet process comprising spraying, co-precipitation, or dipping.

14. The method of manufacturing a composite cathode active material according to claim 11 , wherein the content of the carbon nanostructure and the content of the material which is chemically inert to lithium are each independently from about 0.001 parts by weight to about 10 parts by weight, based on 100 parts by weight of the composite oxide capable of intercalation and deintercalation of lithium.

15. The method of manufacturing a composite cathode active material according to claim 11 , wherein a weight ratio between the carbon nanostructure and the material which is chemically inert to lithium is from about 1:1 to about 5:1.

16. The composite cathode active material according to claim 1 , wherein the carbon nanostructure and the particle of a material which is chemically inert to lithium partially cover the outer surface of the core.

17. A composite cathode active material comprising:

a core comprising a composite oxide capable of intercalation and deintercalation of lithium; and

a shell comprising a carbon nanostructure and a particle of a material which is chemically inert to lithium on the core, wherein the carbon nanostructure comprises a single-walled carbon nanotube, a multi-walled carbon nanotube, or a combination thereof,

wherein the shell is disposed directly on an outer surface of the core,

wherein the shell partially covers the outer surface of the core,

wherein the material which is chemically inert to lithium comprises an inorganic material represented by Formula 5, Formula 6, or a combination thereof:

(M5)O x   Formula 5

wherein, in Formula 5, M5 is Al, V, Nb, Mo, W, Mn, Cr, Zr, Si, Mg, Ca, Y, Ba, B, Ta, In, Ag, Ti, Fe, Co, Ni, Cu, Zn, Sn, La, or a combination thereof, and x is 0<x≤6; and

(M6)F y   Formula 6

wherein, in Formula 6, M6 is Al, V, Nb, Mo, W, Mn, Cr, Zr, Si, Mg, Ca, Y, Ba, B, Ta, In, Ag, Ti, Fe, Co, Ni, Cu, Zn, Sn, La, or a combination thereof, and y is 0<y≤6, and

wherein a weight ratio between the carbon nanostructure and the inorganic material represented by Formula 5, Formula 6, or a combination thereof is from 1.3:1 to 6.5:1.