Pressure-resistant positive active material and electrochemical energy storage apparatus
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.
1. A positive active material, wherein the positive active material comprises secondary particles composed of primary particles, 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, the primary particles are rod-shaped, cone-shaped, or needle-shaped and have an average length of 200 nm to 1000 nm and an average radial cross-sectional width of 150 nm to 400 nm, an average 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 150 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, wherein an outer coating layer is provided on a surface of the positive active material, and 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,
wherein the inner coating layer comprises a coating element selected from any one or a combination of Ba, Zn, W, Y, and P, and the inner coating layer is 0.01% to 0.5% by weight of the positive active material,
wherein the outer coating layer is a composite form of a continuous first coating layer and a discontinuous second coating layer, wherein the continuous first coating layer comprises an oxide of a coating element selected from any one or a combination of W, Y, Si, B, P and Sn, and wherein the discontinuous second coating layer comprises an oxide of a coating element selected from any one or a combination of Zn, and Co, and the outer coating layer is 0.01% to 0.5% by weight of the positive active material;
wherein a powder compacted density of the positive active material is not less than 3.3 g/cm 3 .
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 the secondary particles are obtained by stacking the primary particles in an extension direction of the primary particles.
4. 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.
5. An electrochemical energy storage apparatus, comprising the positive active material according to claim 1 .
6. The positive active material according to claim 1 , wherein a ratio of a length to a radial cross-sectional width of the primary particles is 2 to 10.
7. The positive active material according to claim 1 , wherein a substance of the discontinuous second coating layer is different from a substance of the continuous first coating layer.
8. The positive active material according to claim 1 , wherein the length of the primary particles is 300 nm to 1000 nm.
9. The positive active material according to claim 1 , wherein the length of the primary particles is 500 nm to 1000 nm.
10. The positive active material according to claim 1 , wherein the radial cross-sectional width of the primary particles is 200 nm to 400 nm.
11. The positive active material according to claim 1 , wherein a ratio of the length to the radial cross-sectional width of the primary particles is 2-5.
12. A method comprising:
preparing a positive active material, wherein the positive active material comprises secondary particles composed of primary particles, 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, the primary particles are rod-shaped, cone-shaped, or needle-shaped and have an average length of 200 nm to 1000 nm and an average radial cross-sectional width of 150 nm to 400 nm, an average 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 , a single-particle pressure-resistant strength of the secondary particles is 150 MPa to 300 MPa, the secondary particles have a BET of 0.3 m 2 /g to 0.8 m 2 /g, 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, and a powder compacted density of the positive active material is not less than 3.3 g/cm 3 ,
forming, on a surface of at least a portion of the primary particles at non-outermost positions of the secondary particles, an inner coating layer, wherein the inner coating layer comprises a coating element selected from any one or a combination of Ba, Zn, W, Y, and P, and the inner coating layer is 0.01% to 0.5% by weight of the positive active material, and
forming, on a surface of the positive active material, an outer coating layer, wherein the outer coating layer is a composite form of a continuous first coating layer and a discontinuous second coating layer, wherein the continuous first coating layer comprises an oxide of a coating element selected from any one or a combination of W, Y, Si, B, P and Sn, and
wherein the discontinuous second coating layer comprises an oxide of a coating element selected from any one or a combination of Zn, and Co, and the outer coating layer is 0.01% to 0.5% by weight of the positive active material.
13. The positive active material according to claim 1 , wherein the average length of the primary particles is of 500 nm to 1000 nm, and the average radial cross-sectional width of the primary particles is of 350 nm to 400 nm.