Cathode active material, method for preparing the same, and lithium secondary batteries including the same

Patent metadata

Field	Value
Publication number	US-9368791-B2
Application number	US-201314095764-A
Country	US
Kind code	B2
Filing date	Dec 3, 2013
Priority date	Dec 6, 2012
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, a method for preparing the same, and a lithium secondary battery including the same, and provides a cathode active material including: a lithium manganese-excess layered structure composite oxide represented by Formula Li[Li x-z (Ni a Co b Mn c ) 1-x ]O 2-y F y (here, a+b+c=1, 0.05≦x≦0.33, 0≦y≦0.08, and 0<z≦0.05); a metal fluoride coating layer coated on a surface of the composite oxide; and a metal phosphate coating layer coated on the metal fluoride coating layer.

First claim

What is claimed is:

1. A cathode active material comprising:
a lithium manganese-excess layered structure composite oxide represented by Formula Li[Li x-z (Ni a Co b Mn c ) 1-x ]O 2-y F y (here, a+b+c=1, 0.05<×<0.33, 0<y<0.08, and 0<z<0.05);
a metal fluoride coating layer coated on a surface of the composite oxide; and
a metal phosphate coating layer coated on the metal fluoride coating layer.

2. The cathode active material of claim 1 , further comprising:
a lithium manganese oxide (LiMn 2 O 4 ) having a cubic spinel structure, which is formed by a change in a part of a monoclinic Li 2 MnO 3 in the composite oxide in a vicinity of a surface of the composite oxide.

3. The cathode active material of claim 2 , wherein the lithium manganese oxide having a cubic spinel structure performs a reduction reaction at 2.8 V to 3.0 V.

4. The cathode active material of claim 1 , wherein the composite oxide comprises a rhombohedral LiMO 2 (here, M is Ni, Co, and Mn) and a monoclinic Li 2 MnO 3 .

5. The cathode active material of claim 1 , wherein a total content of the metal fluoride coating layer and the metal phosphate coating layer is 0.5 wt% to 2.0 wt% based on a content of the cathode active material.

6. The cathode active material of claim 5 , wherein a weight ratio of the metal fluoride coating layer and the metal phosphate coating layer is within a range of 1.0 <the metal fluoride coating layer/the metal phosphate coating layer <5.0.

7. The cathode active material of claim 1 , wherein the metal fluoride is one selected from the group consisting of AlF 3 , MgF 2 , CoF 3 , NaF, and a mixture thereof.

8. The cathode active material of claim 1 , wherein the metal phosphate is one selected from the group consisting of AlPO 4 , Mg 3 (PO 4 ) 2 , Co 3 (PO 4 ) 2 , and a mixture thereof.

9. The cathode active material of claim 1 , wherein a content of the metal phosphate coating layer is 1.0 wt % or less.

10. The cathode active material of claim 9 , wherein a content of the metal phosphate coating layer is 0.2 wt % to 0.4 wt %.

11. A method for preparing a cathode active material comprising:
preparing a lithium manganese-excess layered structure composite oxide represented by Formula Li[Li x-z (Ni a Co b Mn c ) 1-x ]O 2-y F y (here, a+b+c=1, 0.05 <×<0.33, 0<y<0.08, and 0<z<0.05);
performing a primary coating on a surface of the composite oxide with a metal fluoride; and
performing a secondary coating on the metal fluoride coating layer with a metal phosphide.

12. The method of claim 11 , further comprising:
forming a lithium manganese oxide having a cubic spinel structure between the composite oxide and the metal fluoride coating layer.

13. The method of claim 12 , wherein the forming comprises:
forming a lithium-metal-fluoride (Li-M-F) composite by reacting lithium in a monoclinic Li 2 MnO 3 region in the composite oxide with the metal fluoride coating layer; and
changing a part of Li 2 MnO 3 in the monoclinic Li 2 MnO 3 region into LiMn 2 O 4 having a cubic spinel structure.

14. The method of claim 11 , further comprising:
heat-treating the cathode active material under an inert atmosphere.

15. The method of claim 11 , wherein the primary coating and the secondary coating are continuously performed.

16. The method of claim 11 , wherein a total content of the coating layer coated through the primary coating and the secondary coating is 0.5 wt % to 2.0 wt % based on the content of the cathode active material.

17. The method of claim 11 , wherein a weight ratio of the metal fluoride coating layer coated through the primary coating and the metal phosphate coating layer coated through the secondary coating is within a range of 1.0<the metal fluoride coating layer/the metal phosphate coating layer <5.0.

18. The method of claim 11 , wherein the metal fluoride is one selected from the group consisting of AlF 3 , MgF 2 , CoF 3 , NaF, and a mixture thereof.

19. The method of claim 11 , wherein the metal phosphate is one selected from the group consisting of AlPO 4 , Mg 3 (PO 4 ) 2 , Co 3 (PO 4 ) 2 , and a mixture thereof.

20. A lithium secondary battery comprising:
a cathode comprising the cathode active material of claim 1 ;
an anode comprising an anode active material; and
an electrolyte present between the cathode and the anode.

21. The lithium secondary battery of claim 20 , wherein a nominal voltage of a discharge curve (1 C and 4.6 V to 2.5 V) is 3.6 V or more.

Assignees

• Samsung Sdi Co Ltd

Inventors

• Kim Jiyoon
• Kim Kitae
• Shin Dongwook
• Shim Hyung Cheoul
• Lee Hayeon
• Jo Sungnim
• Cho Haein

Classifications

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• Y02E60/122

  Cross-Sectional Technologies · mapped topic

• H01M4/582

  Halogenides · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• H01M4/5825

  Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines · CPC title