Method of fabricating cathode active material of lithium secondary battery

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

disposing a lithium transition metal oxide and a washing liquid into a reaction chamber;

contacting the lithium transition metal oxide with the washing liquid to wash the lithium transition metal oxide and form a washed lithium transition metal oxide;

disposing a layered double hydroxide into the reaction chamber to form a coating of the layered double hydroxide on a surface of the washed lithium transition metal oxide to provide a coated lithium transition metal oxide; and

heat treating the coated lithium transition metal oxide to form a cathode active material, wherein the cathode active material comprises a layered double oxide coated lithium transition metal oxide,

wherein the contacting the lithium transition metal oxide with the washing liquid and the forming of the coated lithium transition metal oxide are consecutively performed in a single space.

2. The method of claim 1 , further comprising contacting the lithium transition metal oxide and the washing liquid before the disposing to form a slurry, and

wherein the disposing of the lithium transition metal oxide in the washing liquid comprises disposing the slurry, which comprises the lithium transition metal oxide and the washing liquid, into the reaction chamber.

3. The method of claim 2 , wherein the content of Ni in the lithium transition metal oxide is in a range from 80 atomic percent to 93 atomic percent, based on a total transition metal content of the lithium transition metal oxide.

4. The method of claim 1 , wherein a content of the washing liquid is about 1.5 to 5 times a total weight of the lithium transition metal oxide.

5. The method of claim 1 , wherein the reaction chamber is a Couette-Taylor Reactor.

6. The method of claim 5 , wherein the layered double hydroxide is supplied to the reaction chamber through a surface treatment agent supply port, which is disposed within 10% of a flow length of the reaction chamber of a middle point of the flow length of the reaction chamber.

7. The method of claim 6 , wherein a content of the layered double hydroxide is 0.5 weight percent to 5 weight percent of a total weight of the lithium transition metal oxide.

8. The method of claim 6 , wherein the layered double hydroxide is expressed as Chemical Formula 1:

[M 2+ 1-x M 3+ x (OH) 2 ] x+ [A n− ] x/n .y H 2 O  Chemical Formula 1

wherein, in Chemical Formula 1,

0.1≤x≤0.4,

0<y,

M 2+ comprises Co 2+ , Mg 2+ , Ni 2+ , Cu 2+ , zn 2+ , or a combination thereof,

M 3+ comprises Al 3+ , Fe 3+ , V 3+ , Ti 3+ , Ga 3+ , or a combination thereof, and

A is an anion and comprises NO 3 2− , SO 4 2− , CO 3 2− , PO 4 2− , Cl − , or a combination thereof, and

n is a valence of the anion.

9. The method of claim 5 ,

wherein the Couette-Taylor Reactor comprises an outer fixed cylinder and an inner rotation cylinder disposed inside the outer fixed cylinder, and

wherein the inner rotation cylinder is rotated at a rotation speed of 1200 revolutions per minute to 1400 revolutions per minute during the contacting the lithium transition metal oxide with the washing liquid and during the disposing of the layered double hydroxide into the reaction chamber to form the layered double hydroxide coating.

10. The method of claim 1 , wherein the layered double hydroxide coating has a thickness in a range from 5 nanometers to 20 nanometers.

11. The method of claim 1 , wherein the heat treating is performed for about 1 to about 5 hours at a temperature in a range from about 600° C. to about 800° C.

12. The method of claim 1 , further comprising selectively filtering the coated lithium transition metal oxide prior to the heat treating.

13. A cathode active material comprising:

a lithium transition metal oxide; and

a layered double hydroxide disposed on a surface of the lithium transition metal oxide,

wherein a content of residual lithium is less than about 750 parts per million.

14. The cathode active material of claim 13 , wherein the residual lithium is in a form of LiOH, Li 2 CO 3 , or a combination thereof.

15. The cathode active material of claim 13 , wherein the content of residual lithium is between about 100 parts per million and about 750 parts per million.

16. A cathode active material, comprising:

a lithium transition metal oxide; and

a coating comprising a layered double oxide, a layered double hydroxide, or a combination thereof, on a surface of the lithium transition metal oxide,

wherein the coating has a thickness of about 5 nanometers to about 20 nanometers.

17. The cathode active material of claim 16 , wherein a content of the layered double hydroxide is 0.5 weight percent to 5 weight percent of a total weight of the lithium transition metal oxide.

18. The cathode active material of claim 16 , wherein the layered double hydroxide is expressed as Chemical Formula 1:

[M 2+ 1-x M 3+ x (OH) 2 ] x+ [A n− ] x/n .y H 2 O  Chemical Formula 1

wherein, in Chemical Formula 1,

0.1≤x≤0.4,

0<y,

M 2+ comprises Co 2+ , Mg 2+ , Ni 2+ , Cu 2+ , zn 2+ , or a combination thereof,

M 3+ comprises Al 3+ , Fe 3+ , V 3+ , Ti 3+ , Ga 3+ , or a combination thereof, and

A is an anion and comprises NO 3 2− , SO 4 2− , CO 3 2− , PO 4 2− , Cl − , or a combination thereof, and

n is a valence of the anion.

19. The cathode active material of claim 16 , wherein a content of Ni in the lithium transition metal oxide is in a range from 80 atomic percent to 93 atomic percent, based on a total transition metal content of the lithium transition metal oxide.

20. The cathode active material of claim 19 ,

wherein a content of residual lithium is less than about 750 parts per million, and

wherein the residual lithium comprises LiOH, Li 2 CO 3 , or a combination thereof.