Positive active material for rechargeable lithium battery, preparing method thereof, and rechargeable lithium battery including the same

Patent metadata

Field	Value
Publication number	US-2023074190-A1
Application number	US-202217746684-A
Country	US
Kind code	A1
Filing date	May 17, 2022
Priority date	Aug 17, 2021
Publication date	Mar 9, 2023
Grant date	—

Abstract

A method of preparing a positive active material for a rechargeable lithium battery is provided. The method includes preparing a first aqueous solution that includes a cobalt salt and composite particles including a lithium nickel-based composite oxide and in the form of secondary particles in which a plurality of primary particles are aggregated, the first aqueous solution having a pH of about 6 to about 8, adding an alkali material into the first aqueous solution to obtain a second aqueous solution, obtaining a pre-positive active material including the composite particles and a cobalt coating layer formed on a surface thereof in the second aqueous solution, and heat-treating the pre-positive active material to obtain a final positive active material.

First claim

What is claimed is:

1 . A positive active material for a rechargeable lithium battery, the positive active material comprising:
a first positive active material that comprises a lithium nickel-based composite oxide having a nickel content of greater than or equal to about 90 mol % based on a total amount of metals excluding lithium, wherein the first positive active material comprises secondary particles in which a plurality of primary particles are aggregated, and comprises a cobalt coating layer on a surface of a secondary particle from among the secondary particles, and wherein the secondary particles have a particle diameter of about 10 μm to about 25 μm; and a second positive active material that comprises a lithium nickel-based composite oxide having a nickel content of greater than or equal to about 90 mol % based on a total amount of metals excluding lithium, wherein the second positive active material comprises secondary particles in which a plurality of primary particles are aggregated, and comprises a cobalt coating layer on a surface of a secondary particle from among the secondary particles, and wherein the secondary particles have a particle diameter of about 1 μm to about 9 μm, wherein a ratio (X/Y) of a cobalt atomic content (X) based on a total amount of transition metals excluding lithium on the surface of the secondary particle of the first positive active material to a cobalt atomic content (Y) based on a total amount of transition metals excluding lithium on the surface of the secondary particle of the second positive active material is greater than 1.

2 . The positive active material of claim 1 , wherein the cobalt atomic content (X) based on the total amount of transition metals excluding lithium on the surface of the secondary particle of the first positive active material is about 25 atomic % to about 60 atomic %, and
wherein the cobalt atomic content (Y) based on the total amount of transition metals excluding lithium on the surface of the secondary particle of the second positive active material is about 15 atomic % to about 45 atomic %.

3 . The positive active material of claim 1 , wherein on an entire surface of the positive active material comprising the first positive active material and the second positive active material, a cobalt content based on the total amount of transition metals excluding lithium is about 20 atomic % to about 55 atomic %.

4 . The positive active material of claim 1 , wherein in the first positive active material, the cobalt coating layer on the surface of the secondary particle is a first coating portion,
wherein the first positive active material further comprises a second coating portion that is a cobalt coating layer on the surface of the primary particles in an inner portion of the secondary particles, and wherein a ratio (C1/(C1+D1)) of a cobalt content (C1) of the first coating portion to a sum of the cobalt content (C1) of the first coating portion and a cobalt content (D1) of the second coating portion is about 0.20 to about 0.49.

5 . The positive active material of claim 4 , wherein the second coating portion has a thickness of about 1 nm to about 250 nm.

6 . The positive active material of claim 1 , wherein in the second positive active material, the cobalt coating layer on the surface of the secondary particle is a first coating portion,
wherein the second positive active material further comprises a second coating portion that is a cobalt coating layer on the surface of the primary particles in an inner portion of the secondary particles, and wherein a ratio (C2/(C2+D2)) of a cobalt content (C2) of the first coating portion to a sum of the cobalt content (C2) of the first coating portion and a cobalt content (D2) of the second coating portion is about 0.20 to about 0.49.

7 . The positive active material of claim 6 , wherein the second coating portion has a thickness of about 1 nm to about 250 nm.

8 . The positive active material of claim 1 , wherein the first positive active material is comprised in an amount of about 50 wt % to 90 wt % and the second positive active material is comprised in an amount of about 10 wt % to about 50 wt % based on the total amount of the first positive active material and the second positive active material.

9 . A rechargeable lithium battery comprising a positive electrode comprising the positive active material of claim 1 , a negative electrode, and an electrolyte.

10 . A method of preparing a positive active material for a rechargeable lithium battery, the method comprising
preparing a first aqueous solution that comprises a cobalt salt and composite particles comprising a lithium nickel-based composite oxide and said composite particles are in the form of secondary particles in which a plurality of primary particles are aggregated, the first aqueous solution having a pH of about 6 to about 8; adding an alkali material into the first aqueous solution to obtain a second aqueous solution, wherein the second aqueous solution has a pH of about 12 to about 14; obtaining a pre-positive active material comprising the composite particles and a cobalt coating layer formed on a surface thereof in the second aqueous solution; and heat-treating the pre-positive active material to obtain a final positive active material.

11 . The method of claim 10 , wherein on the surface of the pre-positive active material, a cobalt content (A) based on a total amount of transition metals excluding lithium is about 56 atomic % to about 90 atomic %.

12 . The method of claim 10 , wherein on a surface of the final positive active material, a cobalt content (B) based on a total amount of transition metals excluding lithium is about 15 atomic % to about 55 atomic %.

13 . The method of claim 10 , wherein a ratio (B/A) of a cobalt atomic content (B) based on a total amount of transition metals excluding lithium on a surface of the final positive active material to a cobalt atomic content (B) based on a total amount of transition metals excluding lithium on the surface of the pre-positive active material is about 0.3 to about 0.49.

14 . The method of claim 10 , wherein the final positive active material comprises secondary particles in which a plurality of primary particles are aggregated and the final positive active material comprises a first coating portion that is a cobalt coating layer on a surface of a secondary particle among the secondary particles and further comprises a second coating portion that is a cobalt coating layer on a surface of the primary particles in an inner portion of the secondary particle, and wherein a ratio (C/(C+D)) of a cobalt content (C) of the first coating portion based on a sum of a cobalt content (C) of the first coating portion and a cobalt content (D) of the second coating portion in the final positive active material is about 0.30 to about 0.49.

15 . The method of claim 10 , wherein in the lithium nickel-based composite oxide, a nickel content is greater than or equal to about 90 mol % based on a total amount of metals excluding lithium.

16 . The method of claim 10 , wherein the composite particles are a mixture of about 50 wt % to about 90 wt % of large particles having a particle diameter of about 10 μm to about 25 pm and about 10 wt % to about 50 wt % of small particles having a particle diameter of about 1 μm to about 9 μm, and wherein the final positive active material is a mixture of a first positive active material having a particle diameter of about 10 μm to about 25 μm and a second positive active material having a particle diameter of about 1 μm to about

Assignees

• Samsung Sdi Co Ltd

Inventors

• Kim Hyunjeong
• Kang Gwiwoon
• Song Jayhyok
• Shin Dongwook
• Hong Soonkie

Classifications

• H01M10/052

  Li-accumulators · CPC title

• H01M10/0525

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

• H01M4/1391

  of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M4/525 Primary

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title