Positive electrode sheet for secondary battery, secondary battery, battery module, battery pack, and apparatus

1. A positive electrode sheet for a secondary battery, the positive electrode sheet comprising: a positive electrode current collector and a positive electrode active material layer on a surface of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, the positive electrode active material comprises a first lithium nickel transition metal oxide and a second lithium nickel transition metal oxide, the first lithium nickel transition metal oxide comprises a first substrate and a first coating layer on a surface of the first substrate, the first substrate is secondary particles, and a chemical formula of the first substrate is represented by Formula I:

Li 1+a1 Ni x1 Co y1 Mn z1 M b1 O 2-e1 X e1   (Formula I)

in Formula I, −0.1<a1<0.1, 0.5<x1<0.95, 0.05<y1<0.2, 0.03<z1<0.4, 0<b1<0.05, 0<e1<0.1, and x1+y1+z1+b1=1; wherein M is one or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, and Mn, and X is F and/or Cl;

the first coating layer is a metal oxide and/or a non-metal oxide;

the second lithium nickel transition metal oxide is a single crystal or single-crystal-like morphological particles;

a particle size distribution of the positive electrode active material satisfies: 40<D v 90/D v 10*D v 50<80, unit: μm; and

when the positive electrode sheet has a compaction density of 3.3 g/cm 3 ˜3.5 g/cm 3 , orientation index (OI) of the positive electrode sheet is 10˜40.

2. The positive electrode sheet according to claim 1 , wherein the second lithium nickel transition metal oxide comprises a second substrate, and a chemical formula of the second substrate is represented by Formula II:

Li 1+a2 Ni x2 Co y2 Mn z2 M′ b2 O 2-e2 X′ e2   (Formula II)

in Formula II, −0.1<a2<0.1, 0.5≤x2≤0.95, 0.05≤y2≤0.2, 0.03≤z2≤0.4, 0≤b2≤0.05, 0≤e2≤0.1, and x2+y2+z2+b2=1, where M′ is one or more of Al, Ti, Zr, Nb, Sr, Sc, Sb, Y, Ba, B, Co, and Mn, and X′ is F and/or Cl; and

relative contents x1 and x2 of Ni elements in the first substrate and the second substrate satisfy:

0.8≤x1≤0.95, 0.8≤x2≤0.95, and |x1−x2|≤0.1.

3. The positive electrode sheet according to claim 1 , wherein when the positive electrode sheet has a compaction density of 3.3 g/cm 3 ˜3.5 g/cm 3 , the OI of the positive electrode sheet is 10˜20.

4. The positive electrode sheet according to claim 1 , wherein the positive electrode active material satisfies: 4.4<(D v 90−D v 10)/TD<8,

wherein units of D v 10 and D v 90 are μm; tap density (TD) is tap density of the positive electrode active material (unit: g/cm 3 ).

5. The positive electrode sheet according to claim 4 , wherein the positive electrode active material has a tap density TD of 2.2 g/cm 3 ˜2.8 g/cm 3 .

6. The positive electrode sheet according to claim 1 , wherein the first lithium nickel transition metal oxide is spherical particles, and the first lithium nickel transition metal oxide has a sphericity degree γ of 0.7˜1.

7. The positive electrode sheet according to claim 1 , wherein a size ratio of a longest diameter L max to a shortest diameter L min of the second lithium nickel translation metal oxide satisfies: 1≤L max /L min ≤3.

8. The positive electrode sheet according to claim 1 , wherein the first lithium nickel transition metal oxide has a D v 50 (L) of 5 μm˜18 μm, the second lithium nickel transition metal oxide has a D v 50 (S) of 1 μm˜5 μm;

the D v 50(L) and the D v 50(S) satisfies: 2≤D v 50(L)/D v 50(S)≤7.

9. The positive electrode sheet according to claim 1 , wherein the first lithium nickel transition metal oxide has a weight percentage content of 50%˜90% in the positive electrode active material; and

the second lithium nickel transition metal oxide has a weight percentage content of 10%˜50%.

10. The positive electrode sheet according to claim 2 , wherein the second lithium nickel transition metal oxide also comprises a second coating layer on a surface of the second substrate, the second coating layer is a metal oxide and/or a non-metal oxide.

11. A secondary battery comprising the positive electrode sheet according to claim 1 .

12. An apparatus, comprising the secondary battery according to claim 11 , wherein the secondary battery is used as a power supply for the apparatus, and the apparatus comprises an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, an electric ship, and an energy storage system.

13. The positive electrode sheet according to claim 1 , wherein the single crystal comprises a primary particle larger than 1 μm and with no obvious agglomeration; and the single-crystal-like comprises a primary particle larger than 1 μm with a certain agglomeration between the primary particles.

14. The positive electrode sheet according to claim 1 , wherein the OI of the positive electrode sheet is a ratio of diffraction peak areas corresponding to a first crystal plane and a second crystal plane of a positive electrode active material in X-Ray Diffraction (XRD) diffraction spectrum of the positive electrode sheet.

15. The positive electrode sheet according to claim 2 , wherein the content x1 of Ni element of the first lithium nickel transition metal oxide is higher than the content x2 of Ni element of the second lithium nickel transition metal oxide.

16. The positive electrode sheet according to claim 2 , wherein the contents x1 and the content x2 satisfy: 0<x1−x2<0.1.

17. The positive electrode sheet according to claim 1 , wherein, when compared with the second lithium nickel transition metal oxide, the first lithium nickel transition metal oxide has a larger particle size distribution.