Lithium cobalt-based positive electrode active material, preparation method thereof, positive electrode and secondary battery including the same

Patent metadata

Field	Value
Publication number	US-11476456-B2
Application number	US-201816756073-A
Country	US
Kind code	B2
Filing date	Nov 13, 2018
Priority date	Nov 13, 2017
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

A lithium cobalt-based positive electrode active material is provided. The lithium cobalt-based positive electrode active material includes a core portion including a lithium cobalt-based oxide represented by Formula 1 and a shell portion including a lithium cobalt-based oxide represented by Formula 2, wherein the lithium cobalt-based positive electrode active material includes 2500 ppm or more, preferably 3000 ppm or more of a doping element M based on the total weight of the positive electrode active material. An inflection point does not appear in a voltage profile measured during charging/discharging a secondary battery including the lithium cobalt-based positive electrode active material.

First claim

The invention claimed is:

1. A lithium cobalt-based positive electrode active material comprising:
a core portion including a lithium cobalt-based oxide represented by Formula 1 below; and
a shell portion including a lithium cobalt-based oxide represented by Formula 2 below, wherein the lithium cobalt-based positive electrode active material comprises 2500 ppm or more of a doping element M based on a total weight of the lithium cobalt-based positive electrode active material:
Li a Co 1-b M b O 2   [Formula 1]

in Formula 1, M includes Al and optionally includes one or more selected from the group consisting of Mg, W, Mo, Zr, Ti, Fe, V, Cr, Ba, Ca, Sr and Nb, and 1≤a≤1.2 and 0.005≤b≤0.05, and
Li x Co 1-y M y O 2   [Formula 2]

in Formula 2, M is one or more selected from the group consisting of Mg, W, Mo, Zr, Ti, Fe, V, Cr, Ba, Ca, Sr and Nb, and 0.5≤x≤1 and 0≤y≤0.01.

2. The lithium cobalt-based positive electrode active material of claim 1 , wherein the doping element M is one or more selected from the group consisting of Al, Mg, Ca, Sr, Ba, Ti, and Zr.

3. The lithium cobalt-based positive electrode active material of claim 1 , wherein the doping element M comprises a first doping element selected from the group consisting of Al, Mg, Ca, Sr, and Ba, and a combination thereof, and a second doping element selected from the group consisting of Ti, and Zr, and a combination thereof.

4. The lithium cobalt-based positive electrode active material of claim 1 , wherein Al and Mg are present in the core portion.

5. The lithium cobalt-based positive electrode active material of claim 1 , wherein the lithium cobalt-based oxide represented by Formula 1 above has a layered crystal structure, and
the lithium cobalt-based oxide represented by Formula 2 above has a spinel-like crystal structure.

6. The lithium cobalt-based positive electrode active material of claim 1 , wherein the lithium cobalt-based positive electrode active material comprises 3000 ppm or more of the doping element M based on the total weight of the lithium cobalt-based positive electrode active material.

7. A method for preparing a lithium cobalt-based positive electrode active material, comprising:
a first step in which a core portion including a lithium cobalt-based oxide represented by Formula 1 below is formed by mixing a first cobalt raw material, a first lithium raw material, and a doping element M raw material to obtain a first mixture, and then subjecting the first mixture to a first heat treatment; and
a second step in which a shell portion including a lithium cobalt-based oxide represented by Formula 2 below is formed by mixing the lithium cobalt-based oxide represented by Formula 1 and a second cobalt raw material to obtain a second mixture, and then subjecting the second mixture to a second heat treatment, wherein
the doping element M raw material comprises one or more selected from the group consisting of Al, Mg, W, Mo, Zr, Ti, Fe, V, Cr, Ba, Ca, Sr, and Nb, and is mixed in an amount of 2500 ppm or more based on a total weight of the lithium cobalt-based positive electrode active material:
Li a Co 1-b M b O 2   [Formula 1]

in Formula 1, M includes Al and optionally includes one or more selected from the group consisting of Mg, W, Mo, Zr, Ti, Fe, V, Cr, Ba, Ca, Sr and Nb, and 1≤a≤1.2 and 0.005≤b≤0.05, and
Li x Co 1-y M y O 2   [Formula 2]

in Formula 2, M is one or more selected from the group consisting of Mg, W, Mo, Zr, Ti, Fe, V, Cr, Ba, Ca, Sr and Nb, and 0.5≤x≤1 and 0≤y≤0.01.

8. The method of claim 7 , wherein, in the first step, the first cobalt raw material, the first lithium raw material, and the doping element M raw material are mixed in an amount such that the atomic ratio of Li/(Co+M) of the core portion is 1 to 1.2.

9. The method of claim 7 , wherein the second step further comprises mixing a second lithium raw material.

10. The method of claim 9 , wherein, in the second step, the second cobalt raw material and the second lithium raw material are mixed in an amount such that the atomic ratio of Li/(Co+M) of the shell portion is 0.50 to less than 1.

11. A positive electrode comprising the positive electrode active material according to claim 1 .

12. A lithium secondary battery comprising the positive electrode of claim 11 .

13. The lithium secondary battery of claim 12 , wherein the driving voltage of the lithium secondary battery is 4.45 V or greater.

14. The lithium cobalt-based positive electrode active material of claim 1 , wherein the cobalt-based positive electrode active material comprises 3000 ppm to 5000 ppm of the doping element M based on the total weight of the positive electrode active material.

15. The method of claim 7 , wherein the doping element M raw material is mixed in an amount of 3000 ppm to 5000 ppm based on the total weight of the lithium cobalt-based positive electrode active material.

16. The method of claim 7 , wherein Al and Mg are present in the core portion.

17. The lithium secondary battery of claim 12 , wherein, when charging and discharging the secondary battery at room temperature and 0.2 C, an inflection point does not appear in a measured voltage profile.

Assignees

• Lg Chemical Ltd
• Lg Energy Solution Ltd

Inventors

• Jo Chi Ho
• You Min Kyu
• Park Sung Bin
• Hur Hyuck
• Hwang Jin Tae
• Jung Wang Mo

Classifications

• C01P2004/84

  one phase coated with the other · CPC title

• H01M10/052

  Li-accumulators · CPC title

• C01G51/66

  containing alkaline earth metals, e.g. SrCoO3 · CPC title

• H01M4/366 Primary

  as layered products · CPC title

• C01P2002/52

  containing elements as dopants · CPC title