Pressure-resistant positive active material and electrochemical energy storage apparatus

Patent metadata

Field	Value
Publication number	US-2022045324-A1
Application number	US-201917416122-A
Country	US
Kind code	A1
Filing date	Nov 25, 2019
Priority date	Dec 27, 2018
Publication date	Feb 10, 2022
Grant date	—

Abstract

This application relates to the field of battery technologies, and in particular, to a pressure-resistant positive active material and an electrochemical energy storage apparatus. The positive active material includes secondary particles composed of primary particles, and a quantity σ of primary particles per unit sphere area in a SEM graph of the secondary particles is 5/μm2 to 30/μm2. A single-particle pressure-resistant strength of the secondary particles is 60 MPa to 300 MPa. A molecular formula of the positive active material is LixNiyCozMkMepOrAm, where 0.95≤x≤1.05, 0≤y≤1, ≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤2, 0≤m≤2, and m+r≤2. The positive active material in this application has a compact particle structure and a high single-particle pressure-resistant strength.

First claim

1 . A positive active material, wherein the positive active material comprises secondary particles composed of primary particles, a quantity σ of primary particles per unit sphere surface area in a SEM profile of the secondary particles is 5/μm 2 to 30/μm 2 , and a single-particle pressure-resistant strength of the secondary particles is 60 MPa to 300 MPa; and
a molecular formula of the positive active material is Li x Ni y Co z M k Me p O r A m , wherein 0.95≤x≤1.05, 0≤y≤1, 0≤z≤1, 0≤k≤1, 0≤p≤0.1, 1≤r≤2, 0≤m≤2, and m+r≤2, M is selected from Mn and/or Al, Me is selected from any one or a combination of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, and Nb, and A is selected from any one or a combination of N, F, S, and Cl.

2 . The positive active material according to claim 1 , wherein in the molecular formula of the positive active material, 0.70≤y≤0.95, 0≤z≤0.2, 0≤k≤0.2, and 0≤p≤0.05.

3 . The positive active material according to claim 1 , wherein a powder compacted density of the positive active material is not less than 3.3 g/cm 3 .

4 . The positive active material according to claim 1 , wherein the secondary particles have D v 10 of 2 μm to 8 μm, D v 50 of 5 μm to 18 μm, and D v 90 of 10 μm to 30 μm.

5 . The positive active material according to claim 4 , wherein the secondary particles are obtained by stacking the primary particles in an extension direction of the primary particles; the primary particles are rod-shaped, cone-shaped, or needle-shaped; the primary particles are 100 nm to 1000 nm in length; the primary particles is 50 nm to 400 nm in radial cross-sectional width.

6 . The positive active material according to claim 1 , wherein the secondary particles have a BET of 0.3 m 2 /g to 0.8 m 2 /g.

7 . The positive active material according to claim 1 , wherein an inner coating layer is provided on the surface of at least a portion of the primary particles at non-outermost positions of the secondary particles, the inner coating layer comprises a coating element, and the coating element of the inner coating layer is selected from any one or a combination of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, and P.

8 . A positive electrode material, comprising the positive active material according to claim 1 , wherein an outer coating layer is provided on the surface of the positive active material, the outer coating layer comprises a coating element, and the coating element of the outer coating layer is selected from any one or a combination of Al, Ba, Zn, Ti, Co, W, Y, Si, Sn, B, and P.

9 . The positive electrode material according to claim 8 , wherein the outer coating layer is a continuous and/or discontinuous coating layer.

10 . A method for determining a quantity of primary particles per unit sphere surface area of secondary particles in the positive active material according to claim 1 , comprising the steps of:
(1) selecting a positive active material sample whose particle size is an average secondary-particle size D v 50±20%, and conducting SEM-based testing on the sample, to obtain a 10K-times magnified SEM graph; (2) based on the SEM graph obtained in step (1), calculating the quantity σ of primary particles per unit sphere surface area in the positive active material by using the following formula:
σ=( x 1 +x 2)/2*( y 1 +y 2)/2/( A/C*B/C )

wherein
x1 represents a quantity of primary particles in a horizontal direction on a lower edge of the 10K-times magnified SEM image of the secondary particles;
x2 represents a quantity of primary particles in a horizontal direction on an upper edge of the 10K-times magnified SEM image of the secondary particles;
y1 represents a quantity of primary particles in a longitudinal direction on a left edge of the 10K-times magnified SEM image of the secondary particles;
y2 represents a quantity of primary particles in a longitudinal direction on a right edge of the 10K-times magnified SEM image of the secondary particles;
A represents an actual measured horizontal length of the 10K-times magnified SEM image of the secondary particles, measured in mm;
B represents an actual measured longitudinal length of the 10K-times magnified SEM image of the secondary particles, measured in mm; and
C represents an actual measured length of the 10K-times magnified SEM image of the secondary particles, corresponding to a scale of 1 μm and measured in mm/μm; wherein
during calculation of the quantity of primary particles in the 10K-times magnified SEM image of the secondary particles, a primary particle with presence of a portion is counted as one primary particle.

11 . An electrochemical energy storage apparatus, comprising the positive active material according to claim 1 .

12 . The positive active material according to claim 4 , wherein the secondary particles are obtained by stacking the primary particles in an extension direction of the primary particles; the primary particles are rod-shaped, cone-shaped, or needle-shaped; and a ratio of a length to a radial cross-sectional width of the primary particles is 2 to 10.

13 . The positive electrode material according to claim 9 , wherein the outer coating layer is a composite form of a continuous first coating layer and a discontinuous second coating layer.

14 . The positive electrode material according to claim 9 , wherein a substance of the discontinuous coating layer is different from a substance of the continuous coating layer.

15 . A method for determining a quantity of primary particles per unit sphere surface area of secondary particles in the positive electrode material according to claim 8 , comprising the steps of:
(1) selecting a positive active material sample whose particle size is an average secondary-particle size D v 50±20%, and conducting SEM-based testing on the sample, to obtain a 10K-times magnified SEM graph; (2) based on the SEM graph obtained in step (1), calculating the quantity σ of primary particles per unit sphere surface area in the positive active material by using the following formula:
σ=( x 1 +x 2)/2*( y 1 +y 2)/2/( A/C*B/C )

wherein
x1 represents a quantity of primary particles in a horizontal direction on a lower edge of the 10K-times magnified SEM image of the secondary particles;
x2 represents a quantity of primary particles in a horizontal direction on an upper edge of the 10K-times magnified SEM image of the secondary particles;
y 1 represents a quantity of primary particles in a longitudinal direction on a left edge of the 10K-times magnified SEM image of the secondary particles;
y2 represents a quantity of primary particles in a longitudinal direction on a right edge of the 10K-times magnified SEM image of the secondary particles;
A represents an actual measured horizontal length of the 10K-times magnified SEM image of the secondary particles, measured in mm;
B represents an actual measured longitudinal length of the 10K-times magnified SEM image of the secondary particles, measured in mm; and
C represents an actual measured length of the 10K-times magnified SEM image of the secondary particles, corresponding to a scale of 1 μm and measured in mm/μm; wherein
during calculation of the quantity of primary particles in the 10K-times magnified SEM image of the secondary particles, a primary particle with presence of a portion is counted as one primary particle.

16 . An electrochemical energy storage apparatus, comprising the positive electrode material according to claim 8 .

Assignees

• Contemporary Amperex Technology Co Ltd

Inventors

• Du Rui
• Liu Yongchao
• Zhao Deyu
• Wang Sihui
• Shen Chongheng
• Liu Na

Classifications

• H01M2004/028

  Positive electrodes · 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

• 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

• H01M2004/021

  Physical characteristics, e.g. porosity, surface area · CPC title