Powdered lithium transition metal oxide having doped interface layer and outer layer and method for preparation of the same

1. A powdered lithium transition metal oxide comprising a lithium transition metal oxide particle, a cation doped interface layer formed near the surface of the particle, and a thermodynamically and mechanically stable outer layer, wherein the cation doped interface layer is a reaction product of (i) the lithium transition metal oxide and (ii) a lithium acceptor compound supplying the cation, and the lithium transition metal oxide is LiCoO 2 having a layered crystal structure, or a mixed Li—Mn—Ni—Co-oxide having a layered crystal structure.

2. The powdered lithium transition metal oxide according to claim 1 , wherein the lithium transition metal oxide further contain cationic dopants.

3. The powdered lithium transition metal oxide according to claim 1 , wherein the dopant cation is Al or Al/Mg.

4. The powdered lithium transition metal oxide according to claim 3 , wherein the dopant cation is Al.

5. The powdered lithium transition metal oxide according to claim 1 , wherein the lithium acceptor is phosphate and/or fluorine anions, and the concentration of fluorine anion is 0.5˜5% by atoms F per transition metal cation, and the concentration of phosphate anion is 0.2˜2% by atoms per transition metal cation.

6. The powdered lithium transition metal oxide according to claim 1 , wherein the outer layer is a surface film which is mechanically stable and also has thermodynamic stability under cathodic conditions to at least 5V versus Li/Li + .

7. The powdered lithium transition metal oxide according to claim 1 , wherein the lithium acceptor is lithium cryolite Li 3 AlF 6 and the cation is aluminum, in which the concentration of fluorine is 0.5-5% by atoms per metal cation.

8. The powdered lithium transition metal oxide according to claim 1 , wherein the lithium acceptor has a low melting point below 800° C.

9. A method of preparing the powdered lithium transition metal oxide according to claim 1 , comprising the steps of:

(a) coating the surface of a powdered lithium transition metal oxide with a primary salt containing a dopant cation and being a strong lithium acceptor; and

(b) subjecting the salt-coated metal oxide to heat treatment at a temperature of not less than 700° C.

10. The method according to claim 9 , wherein the primary salt is of a single salt phase or a mixture of two or more salt phases.

11. The method according to claim 9 , wherein the lithium acceptor is one or more selected from the group consisting of F − and PO 4 − , and the dopant cation is one or more selected from the group consisting of Al 3+ , Ca 2+ , Mg 2+ and Ba 2+ .

12. The method according to claim 9 , wherein the primary salt contains 0.1˜5% by atoms of dopant cation per transition metal cation.

13. The method according to claim 9 , wherein the primary salt contains at least 30% by weight of Li 3 AlF 6 and the total amount of the aluminum dopant cation per transition metal is in the range of 0.1 to 2% by atoms.

14. The method according to claim 13 , wherein the primary salt contains at least 50% by weight of Li 3 AlF 6 and the total amount of the aluminum dopant cation per transition metal is in the range of 0.2 to 1.5% by atoms.

15. The method according to claim 9 , wherein the primary salt further includes other lithium salts of Li 2 CO 3 , LiPO 3 and/or LiOH in the range of 1˜60% by weight based upon the total weight of salts including the primary salt.

16. The method according to claim 9 , wherein the primary salt is a mixture of Li 3 AlF 6 and Li 2 CO 3 in which the content of Li 3 AlF 6 is at least 30% by weight.

17. The method according to claim 9 , wherein the heat treatment temperature is in the range of 700° C.˜1020° C.

18. A cathode active material for rechargeable lithium ion battery, comprising the powdered lithium transition metal oxide according to claim 1 .

19. The powdered lithium transition metal oxide according to claim 1 , wherein the cationic dopants are one or more selected from the group consisting of Mg, Al, Ti, Cu, Fe, Zn, Ta, Cr, B, and Ga.