Composite positive electrode active material for lithium secondary battery, preparation method thereof, and lithium secondary battery including positive electrode including the same

Patent metadata

Field	Value
Publication number	US-12107268-B2
Application number	US-202117192711-A
Country	US
Kind code	B2
Filing date	Mar 4, 2021
Priority date	Mar 5, 2020
Publication date	Oct 1, 2024
Grant date	Oct 1, 2024

Abstract

This application relates to a composite positive electrode active material for a lithium secondary battery. The composite positive electrode active material includes a nickel-based active material and a cobalt-boron compound-containing coating layer formed on a surface of the nickel-based active material. The application also relates to a method of preparation of the composite positive electrode active material. The application further relates to a lithium secondary battery including a positive electrode containing the composite positive electrode active material.

First claim

What is claimed is:

1. A composite positive electrode active material for a lithium secondary battery, comprising:
a nickel-based active material; and
a cobalt-boron compound-containing coating layer formed on a surface of the nickel-based active material,
wherein the cobalt-boron compound-containing coating layer comprises an amorphous cobalt-boron compound,
wherein the oxidation number of cobalt in the cobalt-boron compound-containing coating layer is +2+α (−1<α<1).

2. The composite positive electrode active material of claim 1 , wherein the cobalt-boron compound-containing coating layer comprises a compound represented by Formula 1:
Co x B y ,  [Formula 1]

wherein x is a number of 1 to 3, and y is a number of 0.05 to 3.

3. The composite positive electrode active material of claim 2 , wherein in Formula 1, x/y is 0.5 to 2.5.

4. The composite positive electrode active material of claim 1 , wherein the nickel-based active material comprises secondary particles, and the secondary particles comprise aggregates of primary particles.

5. The composite positive electrode active material of claim 4 , wherein the cobalt-boron compound-containing coating layer is present within voids between the secondary particles.

6. The composite positive electrode active material of claim 1 , wherein the content of the cobalt-boron compound is 0.001 parts by weight to 10 parts by weight based on 100 parts by weight of the nickel-based active material.

7. The composite positive electrode active material of claim 1 , wherein the nickel-based active material comprises a compound represented by Formula 2:
Li a (Ni 1-x-y-z CO x M y M′ z )O 2-δ   [Formula 2]

wherein M is at least one element selected from Mn and Al, M′ is at least one element selected from boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), and aluminum (Al), except when M and M′ are both aluminum (Al), and
0.95≤a≤1.3, x≤(1-x-y-z), y≤(1-x-y-z), z≤(1-x-y-z), 0<x<1, 0≤y<1, 0≤z<1, and 1.98≤2−δ≤2 are satisfied.

8. The composite positive electrode active material of claim 1 , wherein, in an X-ray photoelectron spectroscopy of the composite positive active material:
a first peak corresponding to Co 2p1/2 appears at a binding energy of 793 eV to 796 eV; and
a second peak corresponding to Co 2p3/2 appears at a binding energy of 778 eV to 781 eV,
wherein an intensity ratio of the first peak and the second peak is 1:1.18 to 1:1.26.

9. The composite positive electrode active material of claim 1 , wherein the cobalt-boron compound has a nanoflake shape.

10. The composite positive electrode active material of claim 1 , wherein the composite positive electrode active material comprises mesopores having an average diameter of 10 nm to 30 nm.

11. The composite positive electrode active material of claim 1 , wherein the cobalt-boron compound-containing coating layer has a thickness of 100 nm or less.

12. The composite positive electrode active material of claim 1 , wherein the cobalt-boron compound-containing coating layer comprises uniformly-distributed mesopores configured for ion transfer at an interface between the composite positive electrode active material and electrolyte.

13. A lithium secondary battery comprising:
a positive electrode comprising the composite positive electrode active material of claim 1 ;
a negative electrode; and
an electrolyte interposed between the positive electrode and the negative electrode.

14. The lithium secondary battery of claim 13 , the cobalt-boron compound-containing coating layer of the composite positive electrode active material comprises a compound represented by Formula 1:
Co x B y ,  [Formula 1]

wherein x is a number of 1 to 3, and y is a number of 0.05 to 3, and wherein the cobalt-boron compound-containing coating layer is present within voids between the secondary particles.

15. A method of preparing a composite positive electrode active material for a lithium secondary battery according to claim 1 , the method comprising:
mixing a nickel-based active material, a cobalt precursor, and a first solvent to prepare a mixture;
adding a boron reducing agent and a second solvent to the mixture; and
performing a reaction at room temperature under an inert gas atmosphere.

16. The method of claim 15 , wherein the boron reducing agent is sodium borohydride (NaBH 4 ), sodium cyanoborohydride (NaCNBH 3 ), sodium acetoxyborohydride (NaBH 3 OAc), or a mixture thereof, and wherein the cobalt precursor is cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxide, cobalt carbonate, cobalt citrate, cobalt acetate, or a combination thereof.

17. The method of claim 15 , wherein the nickel-based active material is a compound represented by Formula 2-1:
Li a (Ni 1-x-y-z CO x Mn y M′ z )O 2-δ ,  [Formula 2-1]

wherein M′ is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), Zirconium (Zr), aluminum (Al), or a combination thereof and
0.95≤a≤1.3, x≤(1-x-y-z), y≤(1-x-y-z), z≤(1-x-y-z), 0<x<1, 0≤y<1, 0≤z<1, and 1.998≤2−δ≤2.000 are satisfied.

18. The method of claim 15 , wherein each of the first solvent and the second solvent is distilled water, ethanol, methanol, isopropanol, butanol, pentanol, or a combination thereof.

Assignees

• Samsung Sdi Co Ltd
• Ulsan Nat Inst Science & Tech Unist

Inventors

• Cho Kwanghwan
• Yoon Moonsu
• Cho Jaephil

Classifications

• H01M2004/028

  Positive electrodes · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/505

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

• H01M4/04

  Processes of manufacture in general · CPC title

• C01P2006/40

  Electric properties · CPC title