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

1. A positive electrode sheet, comprising:

a positive electrode current collector; and

a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises an inner active material layer stacked on a surface of the positive electrode current collector and an outer active material layer stacked on a surface of the inner active material layer;

wherein:

the inner active material layer has a three-level pore size distribution: an inner primary pore size distribution from 3 nm to 10 nm, an inner secondary pore size distribution from 10 nm to 100 nm, and an inner tertiary pore size distribution from 0.1 μm to 2 μm; and

the outer active material layer has a three-level pore size distribution: an outer primary pore size distribution from 0.5 nm to 3 nm, an outer secondary pore size distribution from 10 nm to 100 nm, and an outer tertiary pore size distribution from 0.1 μm to 2 μm.

2. The positive electrode sheet according to claim 1 , wherein:

the inner active material layer comprises an inner conductive agent and an inner active material, and a specific surface area of the inner conductive agent is from 300 m 2 /g to 1,000 m 2 /g; and/or

the outer active material layer comprises an outer conductive agent and an outer active material, and a specific surface area of the outer conductive agent is from 1,000 m 2 /g to 2,500 m 2 /g.

3. The positive electrode sheet according to claim 2 , wherein:

a mass ratio of the inner conductive agent to the inner active material is (0.3-2):100; and/or

a mass ratio of the outer conductive agent to the outer active material is (0.3-3):100.

4. The positive electrode sheet according to claim 2 , wherein the inner conductive agent and the outer conductive agent are each independently selected from activated carbon or carbon nanotube.

5. The positive electrode sheet according to claim 1 , wherein:

the inner active material layer comprises an inner first active material and an inner second active material, a particle size distribution of the inner first active material is from 24 nm to 600 nm, and a particle size distribution of the inner second active material is from 0.25 μm to 13 μm; and/or

the outer active material layer comprises an outer first active material and an outer second active material, a particle size distribution of the outer first active material is from 24 nm to 600 nm, and a particle size distribution of the outer second active material is from 0.25 μm to 13 μm.

6. The positive electrode sheet according to claim 5 , wherein:

a particle size of the inner first active material does not overlap with the inner tertiary pore size; and/or

a particle size of the outer first active material does not overlap with the outer tertiary pore size.

7. The positive electrode sheet according to claim 5 , wherein:

a mass ratio of the inner first active material to the inner second active material is (0.3-3):1; and/or

a mass ratio of the outer first active material to the outer second active material is (0.3-3):1.

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

9. A battery module, comprising the secondary battery according to claim 8 .

10. A battery pack, comprising the secondary battery according to claim 8 .

11. An electrical apparatus, comprising the secondary battery according to claim 8 .