CATHODE ACTIVE MATERIAL, METHOD FOR PREPARING THE SAME, AND LITHIUM SECONDARY BATTERIES INCLUDING THE SAME

• US 20140162127A1
• Filed: 12/03/2013
• Published: 06/12/2014
• Est. Priority Date: 12/06/2012
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung Fine Chemicals Company Limited (Lotte Chemical Corporation)
• Inventors: Kim, Kitae, Kim, Jiyoon, Shin, Dongwook, Shim, Hyung Cheoul, Lee, Hayeon, Jo, SungNim, Cho, Haein
• Granted Patent: US 9,368,791 B2
• Time in Patent Office: Days
• US Class Current: 429/224
• CPC Class Codes: H01M 4/366 as layered products
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/582 Halogenides
• CPC Class Codes: H01M 4/5825 Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

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_aCo_bMn_c)_1-x]O_2-yF_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.

Claims

1. A cathode active material comprising:

a lithium manganese-excess layered structure composite oxide represented by Formula Li[Li_x-z(Ni_aCo_bMn_c)_1-x]O_2-yF_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.

2. The cathode active material of claim 1, further comprising:

a lithium manganese oxide (LiMn₂O₄) having a cubic spinel structure, which is formed by a change in a part of a monoclinic Li₂MnO₃ 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 LiMO₂ (here, M is Ni, Co, and Mn) and a monoclinic Li₂MnO₃.

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 AlF₃, MgF₂, CoF₃, 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 AlPO₄, Mg₃(PO₄)₂, Co₃(PO₄)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 %.

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.

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_aCo_bMn_c)_1-x]O_2-yF_y (here, a+b+c=1, 0.05≦

x≦

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 Li₂MnO₃ region in the composite oxide with the metal fluoride coating layer; and

changing a part of Li₂MnO₃ in the monoclinic Li₂MnO₃ region into LiMn₂O₄ 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 AlF₃, MgF₂, CoF₃, NaF, and a mixture thereof.

19. The method of claim 11, wherein the metal phosphate is one selected from the group consisting of AlPO₄, Mg₃(PO₄)₂, Co₃(PO₄)₂, and a mixture thereof.