Composite positive active material, method of preparing the same, positive electrode including the composite positive active material, and lithium battery including the positive electrode

1. A composite positive active material comprising:

a composite comprising:

a first metal oxide that is a compound represented by Formula 1 and having a layered structure, and

a second metal oxide having a crystal structure that is a layered structure, a perovskite structure, a rock salt structure, or a spinel structure;

wherein a content of the second metal oxide is greater than 0 and equal to or less than 0.2 moles per mole of the composite, and

wherein the composite positive active material has an amount of residual lithium between 5,000 parts per million by weight to 14,6000 parts per million by weight, based on a total weight of the composite positive active material,

LiNi x M 1 1-x O 2-e M a e   Formula 1

wherein, in Formula 1,

M 1 is a Group 4 to Group 14 element of the Periodic Table of the Elements, or a combination thereof;

M a is F, S, Cl, Br, or a combination thereof;

0.7≤x<1; and

0≤e<1.

2. The composite positive active material of claim 1 , wherein the amount of residual lithium in the composite positive active material is 9,810 parts per million by weight to 14,571 parts per million by weight, based on a total weight of the composite positive active material.

3. The composite positive active material of claim 1 , wherein M 1 in Formula 1 is manganese, vanadium, chromium, iron, cobalt, nickel, zirconium, rhenium, aluminum, boron, germanium, ruthenium, tin, titanium, niobium, molybdenum, platinum, or a combination thereof.

4. The composite positive active material of claim 1 , wherein the first metal oxide is a compound represented by Formula 2,

LiNi x Co y Mn z M 3 c O 2-e M a c   Formula 2

wherein, in Formula 2, 0.7≤x≤0.99; 0≤y<1; 0<z<1; 0≤c<1, 0<x+y+z+c≤1; 0≤e<1;

M 3 is a Group 4 to Group 14 element of the Periodic Table of the Elements, or a combination thereof; and

M a is F, S, Cl, Br, or a combination thereof.

5. The composite positive active material of claim 1 , wherein the first meal oxide is a compound represented by Formula 3:

LiNi x Co y Mn z O 2   Formula 3

wherein, in Formula 3, 0.7≤x≤0.99; 0<y<1; 0<z<1; and 0<x+y+z+c≤1.

6. The composite positive active material of claim 1 , wherein the second metal oxide is a compound represented by Formula 4, a compound represented by Formula 5, a compound represented by Formula 6, or a compound represented by Formula 7,

A 2 M 2 O 3 ,  Formula 4

AM 2 O 3 ,  Formula 5

(A b M 2 1-b )O, or  Formula 6

AM 2 2 O 4 ,  Formula 7

wherein, in Formulae 4 to 7,

A is a Group 1 to Group 3 element of the Periodic Table of the Elements, or a combination thereof;

M 2 is a Group to Group 16 element of the Periodic Table of the Elements, a rare earth element, or a combination thereof; and

0≤b≤1.

7. The composite positive active material of claim 6 , wherein, in Formulae 4 to 7, A is Li, Na, Sr, Ba, H, K, Ca, Y, or a combination thereof; and M 2 is Al, Ga, Ge, Mg, Nb, Zn, Cd, Ti, Co, Ni, Mn, Ca, Si, Fe, Cu, Sn, V, B, P, Se, Bi, As, Zr, Re, Ru, Cr, Sr, Sc, Y, or a combination thereof.

8. The composite positive active material of claim 6 , wherein the compound represented by Formula 4 is Li 2 MnO 3 , Li 2 TiO 3 , Li 2 SnO 3 , Li 2 ZrO 3 , Li 2 MoO 3 , or Li 2 RuO 3 .

9. The composite positive active material of claim 6 , wherein the compound represented by Formula 5 is a compound represented by Formula 8,

(A 1 1-a A 2 a )M 1 O 3   Formula 8

wherein, in Formula 8,

A 1 is La, Sr, Ba, Ce, Y, Se, or a combination thereof;

A 2 is Li, Na, Ca, Ag, K, Mg, Cu, or a combination thereof;

M 1 is Mn, V, Cr, Fe, Co, Ni, Zr, Ti, Mg, Cu, Nb, Ta, Ru, W, Sn, or a combination thereof; and

0<a≤0.3.

10. The composite positive active material of claim 6 , wherein the compound represented by Formula 6 is (Li b Ni 1-b )O, (Li b Co 1-b )O, (Li b Fe 1-b )O, (Li b Cu 1-b )O, (Li b Zn 1-b )O, (Li b Ca 1-b )O, (Li b Sr 1-b )O, (Li b Mg 1-b )O, or (Li b Cr 1-b )O), wherein each b is independently selected and is 0≤b≤1.

11. The composite positive active material of claim 6 , wherein the compound represented by Formula 7 is LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiCo 0.5 Mn 1.5 O 4 , Li[Co f Ni g Mn h ] 2 O 4 , or Li[Cu c Mn 2-c ] 2 O 4 , wherein 0<c≤2, 0<f≤2, 0<g≤2, 0<h≤2, and f+g+h=2.

12. The composite positive active material of claim 1 , wherein the composite positive active material is a compound represented by Formulae 9 to 12, or a combination thereof,

(1−a)LiNi x M 1 1-x O 2 .aA 2 M 2 O 3 ,  Formula 9

(1−a)LiNi x M 1 1-x O 2 .aAM 2 O 3 ,  Formula 10

(1−a)LiNi x M 1 1-x O 2 .a(A b M 2 1-b )O, and  Formula 11

(1−a)LiNi x M 1 1-x O 2 .aAM 2 2 O 4 ,  Formula 12

wherein, in Formulae 9 to 12,

A is Li, Na, La, Sr, Ba, H, K, Ca, Y, or a combination thereof;

M 2 is Al, Ga, Ge, Mg, Nb, Zn, Cd, Ti, Co, Ni, Mn, Ca, Si, Fe, Cu, Sn, V, B, P, Se, Bi, As, Zr, Re, Ru, Cr, Sr, Sc, Y, a rare earth element, or a combination thereof; 0<a≤0.2; and 0<b≤1.

13. The composite positive active material of claim 1 , wherein the composite positive active material is a compound represented by Formulae 9-1 to 12-1, or a combination thereof,

(1−a)LiNi x Co y Mn z O 2 .aLi 2 MnO 3 ,  Formula 9-1

(1−a)LiNi x Co y Mn z O 2 .aLiMnO 3 ,  Formula 10-1

(1−a)LiNi x Co y Mn z O 2 .a(Li b La 1-b )MnO 3 ,  Formula 10-2

(1−a)LiNi x Co y Mn z O 2 .a(Li b La 1-b )O, Formula 11-1

(1−a)LiNi x Co y Mn z O 2 .aLiMn 2 O 4 ,  Formula 12-1

wherein, in Formulae 9-1 to 12-2, 0.7≤x≤0.99, 0<y≤0.3, 0<z≤0.3, x+y+z=1, 0<b≤1, and 0<a≤0.2.

14. The composite positive active material of claim 13 , wherein, in Formulae 9-1 to 12-1, LiNi x Co y Mn z O 2 is LiNi 0.85 Co 0.10 Mn 0.05 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.75 Co 0.20 Mn 0.05 O 2 , or LiNi 0.9 Co 0.05 O 2 , or a combination thereof.

15. The composite positive active material of claim 1 , wherein the second metal oxide is intermixed in the layered structure of the first metal oxide.

16. The composite positive active material of claim 1 , wherein the composite positive active material is

0.98LiNi 0.85 Co 0.10 Mn 0.05 O 2 .0.02Li 2 MnO 3 , 0.95LiNi 0.85 Co 0.10 Mn 0.05 O 2 .0.05Li 2 MnO 3 ,

0.9LiNi 0.85 Co 0.10 Mn 0.05 O 2 .0.1Li 2 MnO 3 , 0.8LiNi 0.85 Co 0.10 Mn 0.05 O 2 .0.2Li 2 MnO 3 ,

0.98LiNi 0.8 Co 0.1 Mn 0.1 O 2 .0.02Li 2 MnO 3 , 0.95LiNi 0.8 Co 0.1 Mn 0.1 O 2 .0.05Li 2 MnO 3 ,

0.9Li Ni 0.8 Co 0.1 Mn 0.1 O 2 .0.1Li 2 MnO 3 , 0.8LiNi 0.8 Co 0.1 Mn 0.1 O 2 .0.2Li 2 MnO 3 ,

0.98LiNi 0.75 Co 0.20 Mn 0.05 O 2 .0.02Li 2 MnO 3 , 0.95LiNi 0.75 Co 0.20 Mn 0.05 O 2 .0.05Li 2 MnO 3 ,

0.9Li Ni 0.75 Co 0.20 Mn 0.05 O 2 .0.1Li 2 MnO 3 , 0.8LiNi 0.75 Co 0.20 Mn 0.05 O 2 .0.2Li 2 MnO 3 ,

0.98LiNi 0.9 Co 0.05 Mn 0.05 O 2 .0.02Li 2 MnO 3 , 0.95LiNi 0.9 Co 0.05 Mn 0.05 O 2 .0.05Li 2 MnO 3 ,

0.9Li Ni 0.9 Co 0.05 Mn 0.05 O 2 .0.1Li 2 MnO 3 , or 0.8LiNi 0.8 Co 0.05 Mn 0.05 O 2 .0.2Li 2 MnO 3 .

17. The composite positive active material of claim 1 , wherein, when evaluated by X-ray diffraction analysis with Cu—Kα radiation, a diffraction peak measured at a 2 theta value of 18.5° to 19.0° has a full width at half maximum of 0.1968° to 0.2362°.

18. The composite positive active material of claim 1 , wherein a half cell having a positive element including the composite positive active material and lithium metal as a counter electrode has an average discharge voltage of 92.5% to 99.95% after a 50 th charging and discharging cycle, with respect to the average discharge voltage after a 1 st charging and discharging cycle.

19. The composite positive active material of claim 1 , wherein the composite positive active material has a surface comprising the second metal oxide.

20. The composite positive active material of claim 1 , wherein the composite positive active material further comprises a coating layer on a surface thereof, and wherein the coating layer is a conductive material, a metal oxide, an inorganic fluoride, or a combination thereof.

21. The composite positive active material of claim 20 , wherein the conductive material is a carbonaceous material, indium tin oxide, RuO 2 , ZnO, or a combination thereof.

22. The composite positive active material of claim 20 , wherein the metal oxide is silica, alumina, zirconium oxide, titanium oxide, or a combination thereof.

23. The composite positive active material of claim 20 , wherein the coating layer comprises an inorganic fluoride, and wherein the inorganic fluoride is AlF 3 CsF, KF, LiF, NaF, RbF, TiF, AgF, AgF 2 , BaF 2 , CaF 2 , CuF 2 , CdF 2 , FeF 2 , HgF 2 , Hg 2 F 2 , MnF 2 , MgF 2 , NiF 2 , PbF 2 , SnF 2 , SrF 2 , XeF 2 , ZuF 2 , AlF 3 , BF 3 , BiF 3 , CeF 3 , CrF 3 , DyF 3 , EuF 3 , GaF 3 , GdF 3 , FeF 3 , HoF 3 , InF 3 , LaF 3 , LuF 3 , MnF 3 , NdF 3 , VOF 3 , PrF 3 , SbF 3 , ScF 3 , SmF 3 , TbF 3 , TiF 3 , TmF 3 , YF 3 , YbF 3 , CeF 4 , GeF 4 , HfF 4 , SiF 4 , TiF 4 , VF 4 , ZrF 4 , NbF 5 , SbF 5 , TaF 5 , BiF 5 , MoF 6 , ReF 6 , SF 6 , WF 6 , or a combination thereof.

24. A positive electrode comprising the composite positive active material of claim 1 .

25. A lithium battery comprising the positive electrode of claim 24 .