Positive electrode active material for lithium secondary battery including lithium cobalt oxide having core-shell structure, method for producing the same, and positive electrode and secondary battery including the positive electrode active material

Patent metadata

Field	Value
Publication number	US-11038159-B2
Application number	US-201816097049-A
Country	US
Kind code	B2
Filing date	Jan 26, 2018
Priority date	Jan 31, 2017
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery including a lithium cobalt oxide having a core-shell structure, wherein the lithium cobalt-doped oxide of the core and the lithium cobalt-doped oxide of the shell include each independently three kinds of dopants and satisfy specific conditions, a method for producing the same, and a positive electrode and a secondary battery containing the positive electrode active material.

First claim

The invention claimed is:

1. A positive electrode active material for a lithium secondary battery comprising a lithium cobalt-doped oxide having a core-shell structure,
wherein the lithium cobalt-doped oxide of a core has a composition of the following Chemical Formula (1) and the lithium cobalt-doped oxide of a shell has a composition of the following Chemical Formula (2):
Li a Co 1-x-y-z M1 x M2 y M3 z O 2   (1)

wherein in Chemical Formula 1,
M1, M2 and M3 are each independently one element selected from the group consisting of Ti, Mg, Al, Zr, Ba, Ca, Ta, Nb, Mo, Zn, Si, and V;
0.95≤a≤1.05;
0<x≤0.04, 0<y≤0.04, and 0<z≤0.04
Li b Co 1-s-t-w M1′ s M2′ t M3′ w O 2   (2)

wherein in Chemical Formula 2,
M1′, M2′ and M3′ are each independently one element selected from the group consisting of Ti, Mg, Al, Zr, Ba, Ca, Ta, Nb, Mo, Zn, Si, and V;
0.95≤b≤1.05;
0<s≤0.04, 0<t≤0.04, and 0<w≤0.04,
wherein the lithium cobalt-doped oxide of the core and the lithium cobalt-doped oxide of the shell include each independently three kinds of dopants and satisfy the following (a) or (b):
(a) a ratio between the average oxidation number of the dopants present in the core and the average oxidation number of the dopants present in the shell satisfies the following condition (1);
0.7 ≤t (molar ratio)= OC/OS< 0.95  (1)

wherein, OC is the average oxidation number of the dopants present in the core, and OS is the average oxidation number of the dopants present in the shell, or
(b) the dopants of the core are a metal (M1) having an oxidation number of +2, a metal (M2) having an oxidation number of 1-3 and a metal (M3) having a oxidation number of +4, and a content of M1 M2 and M3 satisfy the following condition (2) based on the molar ratio; the dopants of the shell are a metal(M1′) having an oxidation number of +2, a metal(M2′) having an oxidation number of +3 and a metal(M3′) having a oxidation number of +4, and a content of M1′, M2′ and M3′ satisfy the following condition (3) based on the molar ratio:
2≤ r (molar ratio)= CM 1/( CM 2+ CM 3)≤3  (2)

0.5 ≤r ′(molar ratio)= CM 1′( CM 2′+ CM 3′)<2  (3)

wherein CM1 is the content of M1, CM2 is the content of M2, CM3 is the content of M3, CM1′ is the content of M1′, CM2′ is the content of M2′, and CM3′ is the content of M3′.

2. The positive electrode active material according to claim 1 , wherein in (a), t (molar ratio) satisfies the condition of 0.8≤t<0.95.

3. The positive electrode active material according to claim 1 , wherein in (b), r(molar ratio) satisfies the condition of 2≤r≤2.5, and r′ (molar ratio) satisfies the condition of 0.5≤r′≤1.5.

4. The positive electrode active material according to claim 1 , wherein the lithium cobalt-doped oxide having a core-shell structure maintains the crystal structure without phase change in a range where the positive electrode potential during full charge is higher than 4.5 V on the basis of a Li potential.

5. The positive electrode active material according to claim 1 , wherein
the M1 and M1′ are each independently one element selected from the group consisting of Mg, Ca, and Ba;
the M2 and M2′ are each independently one element selected from the group consisting of Ti, Al, Ta and Nb; and
the M3 and M3′ are each independently selected from the group consisting of Ta, Nb, and Mo and are elements different from M2 and M2′.

6. The positive electrode active material according to claim 1 , wherein the thickness of the shell is 50 to 2000 nm.

7. The positive electrode active material according to claim 1 , wherein Al 2 O 3 having a thickness of 50 nm to 100 nm is coated onto the surface of the shell.

8. A method for producing a lithium cobalt-doped oxide having a core-shell structure of the positive electrode active material according to claim 1 , the method comprising:
(i) preparing a doped cobalt precursor containing three kinds of dopants by co-precipitation;
(ii) mixing the doped cobalt precursor and a lithium precursor, and subjecting them to a primary calcination to prepare core particles; and
(iii) mixing the core particles, the cobalt precursor, the lithium precursor, and the three kinds of dopant precursors, and subjecting them to a secondary calcination to form a shell on the core particle surface, thereby preparing a lithium cobalt-doped oxide having a core-shell structure.

9. The method according to claim 8 , wherein in the preparing a doped cobalt precursor, dopant element-containing salts and cobalt salts are dissolved in water to obtain a solution, and then the solution is converted to a basic atmosphere and subjected to a co-precipitation to prepare a doped cobalt oxide as the doped cobalt precursor.

10. A method for producing a lithium cobalt-doped oxide having a core-shell structure of the positive electrode active material according to claim 1 , the method comprising:
(i) mixing a cobalt precursor, a lithium precursor, and three kinds of dopant precursors and subjecting them to a primary calcination to prepare core particles; and
(ii) mixing the core particles, the cobalt precursor, the lithium precursor, and the three kinds of dopant precursors independently of the primary calcination, and subjecting them to a secondary calcination to form a shell on core particle surface, thereby preparing a lithium cobalt-doped oxide having a core-shell structure.

11. The method according to claim 8 , wherein the dopants of the three kinds of dopant precursors have different oxidation numbers.

12. The method according to claim 8 , wherein the lithium cobalt-doped oxide having a core-shell structure satisfies the following conditions (a) and (b):
(a) the ratio between the average oxidation number of the dopants present in the core and the average oxidation number of the dopants present in the shell satisfies the following condition (1);
0.7≤ t (molar ratio)= OC/OS< 0.95  (1)

wherein, OC is the average oxidation number of the dopants present in the core, and OS is the average oxidation number of the dopants present in the shell, or
(b) the dopants of the core are a metal (M1) having an oxidation number of +2, a metal (M2) having an oxidation number of +3 and a metal (M3) having a oxidation number of +4, the contents of M1, M2, and M3 satisfy the following condition (2) based on the molar ratio; the dopants of the shell are a metal(M1′) having an oxidation number of +2, a metal(M2′) having an oxidation number of +3 and a metal(M3′) having a oxidation number of +4, and the contents of M1′, M2′ and M3′ satisfy the following condition (3) based on the molar ratio:
2≤ r (molar ratio)= CM 1/( CM 2+ CM 3)≤3  (2)

0.5≤ r ′(molar ratio)= CM 1′/( CM 2′+ CM 3′)<2  (3)

wherein CM1 is the content of M1, CM2 is the content of M2, CM3 is the content of M3, CM1′ is the content of M1′, CM2′ is the content of M2′, and CM3′ is the content of M3′.

13. The method according to claim 8 , wherein the primary calcination is performed at a temperature of 850° C. to 1100° C. for 8 to 12 hours, and the secondary calcination is performed at a temperature of 700° C. to 1100° C. for 5 to 12 hours.

14. A positive electrode in which a positive electrode mixture containing the positive electrode active material according to any one of claim 1 , a conductive material, and a binder is applied to a current collector.

15. A secondary battery comprising the positive electrode according to claim 14 .

Assignees

• Lg Chemical Ltd

Inventors

• Jo Chi Ho
• Park Sungbin
• Park Jiyoung
• Lee Bo Ram
• Han Jungmin
• Hur Hyuck
• Jung Wang Mo

Classifications

• C01G51/82

  Compounds containing cobalt, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• C01G51/42 Primary

  containing alkali metals, e.g. LiCoO2 · CPC title

• C01P2006/40

  Electric properties · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title