Secondary battery, and battery module, battery pack and apparatus comprising the same
The embodiments of this application provide a secondary battery, and a battery module, a battery pack and an apparatus including the same. Specifically, this application provides a secondary battery, which includes a negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector. The negative electrode film includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material includes SiOx (0<x<2) and graphite. An average particle diameter Dv50 of the negative electrode active material is from 8 μm to 14 μm. The conductive agent includes carbon nanotubes whose aspect ratio is greater than or equal to 2500:1. The secondary battery can have both good rate performance and cycle performance under the premise of a relatively high energy density.
1. A secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, and the negative electrode film comprises a negative electrode active material, a conductive agent and a binder,
the negative electrode active material comprises particles comprising particles of SiOx (0<x<2) and particles of graphite, wherein the particles of SiOx and the particles of graphite are physically mixed together;
the average particle diameter Dv50 of the particles of SiOx is from 5 μm to 8 μm;
the average particle diameter Dv50 of the particles of graphite is from 10 μm to 20 μm;
the average particle diameter Dv50 of the particles of the negative electrode active material is from 8 μm to 14 μm;
and the conductive agent comprises carbon nanotubes whose aspect ratio is greater than (3000:1) and less than or equal to (20000:1).
2. The secondary battery according to claim 1 , wherein the carbon nanotubes are single-walled carbon nanotubes (SWCNTs).
3. The secondary battery according to claim 1 , wherein a mass proportion of the carbon nanotubes in the negative electrode film is 0.3% to 1%.
4. The secondary battery according to claim 1 , wherein the binder comprises polyacrylate.
5. The secondary battery according to claim 1 , wherein a weight content of the binder in the negative electrode film is from 3% to 9%.
6. The secondary battery according to claim 1 , wherein a mass percentage content W of the SiOx (0<x<2) in the negative electrode active material is 15%≤W≤40%.
7. The secondary battery according to claim 1 , wherein the graphite comprises artificial graphite.
8. The secondary battery according to claim 1 , wherein a thickness of the negative electrode current collector is from 4 μm to 10 μm.
9. The secondary battery according to claim 1 , wherein a range of surface roughness Ra of the negative electrode current collector is 1.6 μm≤Ra≤3.2 μm.
10. The secondary battery according to claim 1 , wherein an adhesion F between the negative electrode film and the negative electrode current collector is 10 N/m≤F≤90 N/m.
11. The secondary battery according to claim 1 , wherein a thickness of the negative electrode current collector is from 4 μm to 10 μm;
a range of surface roughness Ra of the negative electrode current collector is 1.6 μm≤Ra≤3.2 μm;
and an adhesion F between the negative electrode film and the negative electrode current collector is 10 N/m≤F≤90 N/m.
12. The secondary battery according to claim 1 , wherein a compacted density PD of the negative electrode film is 1.6 g/cm 3 ≤PD≤2.0 g/cm 3 .
13. The secondary battery according to claim 1 , wherein a coating weight CW of the negative electrode film is 0.045 mg/mm 2 ≤CW≤0.09 mg/mm 2 .
14. The secondary battery according to claim 1 , wherein the secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material, the positive electrode active material comprises Li 1+y Ni a Co b M c O 2−z A z , wherein −0.2≤y≤0.2, 0.5≤a<1, 0<b≤0.3, 0<c≤0.2, 0≤z<0.2, and M is selected from the group consisting of one or more of Mn and Al, and A is selected from the group consisting of one or more of S, N, F, Cl, Br and I.
15. The secondary battery according to claim 1 , wherein the carbon nanotubes whose aspect ratio is greater than (2800:1) and less than or equal to (10000:1).
16. The secondary battery according to claim 1 , wherein an adhesion F between the negative electrode film and the negative electrode current collector is 30 N/m≤F≤80 N/m.
17. The secondary battery according to claim 16 , wherein an adhesion F between the negative electrode film and the negative electrode current collector is 30 N/m≤F≤50 N/m.
18. A battery module, comprising:
a secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, and the negative electrode film comprises a negative electrode active material, a conductive agent and a binder,
the negative electrode active material comprises particles comprising particles of SiOx (0<x<2) and particles of graphite, wherein the particles of SiOx and the particles of graphite are physically mixed together;
the average particle diameter Dv50 of the particles of SiOx is from 5 μm to 8 μm;
the average particle diameter Dv50 of the particles of graphite is from 10 μm to 20 μm;
the average particle diameter Dv50 of the particles of the negative electrode active material is from 8 μm to 14 μm;
and the conductive agent comprises carbon nanotubes whose aspect ratio is greater than (3000:1) and less than or equal to (20000:1).
19. An apparatus, comprising:
a secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, and the negative electrode film comprises a negative electrode active material, a conductive agent and a binder,
the negative electrode active material comprises particles comprising particles of SiOx (0<x<2) and particles of graphite, wherein the particles of SiOx and the particles of graphite are physically mixed together;
the average particle diameter Dv50 of the particles of SiOx is from 5 μm to 8 μm;
the average particle diameter Dv50 of the particles of graphite is from 10 μm to 20 μm;
the average particle diameter Dv50 of the particles of the negative electrode active material is from 8 μm to 14 μm;
and the conductive agent comprises carbon nanotubes whose aspect ratio is greater than (3000:1) and less than or equal to (20000:1).