Search

CN-120674563-B - Secondary battery and electronic device

CN120674563BCN 120674563 BCN120674563 BCN 120674563BCN-120674563-B

Abstract

The application provides a secondary battery and an electronic device, wherein the secondary battery comprises a positive electrode plate and a negative electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer, the negative electrode material layer comprises a first negative electrode material layer and a second negative electrode material layer, 1/2 of the width difference value of the first negative electrode material layer and the second negative electrode material layer is W mm, 1/2 of the width difference value of the first negative electrode material layer and the positive electrode material layer is L mm, and W/L is more than or equal to 0.2 and less than or equal to 4. The first negative electrode active material comprises a first graphite material, the second negative electrode active material comprises a second graphite material and a silicon-based material, the average particle size of the particles of the first negative electrode active material is D1 mu m, and the average particle size of the particles of the second negative electrode active material is D2 mu m, wherein D2/D1 is more than or equal to 1.1 and less than or equal to 1.8. Through the arrangement, side reactions at the edge area of the pole piece are reduced, and the cycle performance of the secondary battery is improved.

Inventors

  • WANG YING
  • LI CHUNHUA
  • HAN XIANGLONG

Assignees

  • 厦门新能安科技有限公司

Dates

Publication Date
20260508
Application Date
20250623

Claims (19)

  1. 1. A secondary battery comprising a positive electrode tab including a positive electrode current collector and a positive electrode material layer on at least one surface of the positive electrode current collector, and a negative electrode tab including a negative electrode current collector and a negative electrode material layer on at least one surface of the negative electrode current collector, the negative electrode material layer including a first negative electrode material layer and a second negative electrode material layer, the first negative electrode material layer being located between the negative electrode current collector and the second negative electrode material layer in a thickness direction of the negative electrode tab; Along the width direction of the unfolded cathode electrode plate, the width of the first cathode material layer is larger than that of the second cathode material layer, 1/2 of the width difference value between the first cathode material layer and the second cathode material layer is W mm, the width of the first cathode material layer is larger than that of the anode material layer, 1/2 of the width difference value between the first cathode material layer and the anode material layer is L mm, and W/L is more than or equal to 0.2 and less than or equal to 4; The first anode material layer comprises a first anode active material, the first anode active material comprises a first graphite material, the second anode material layer comprises a second anode active material, the second anode active material comprises a second graphite material and a silicon-based material, the average particle size of particles of the first anode active material is D1 mu m, the average particle size of particles of the second anode active material is D2 mu m, and D2/D1 is less than or equal to 1.1 and less than or equal to 1.8.
  2. 2. The secondary battery according to claim 1, wherein 0.2≤L≤5, and/or 7≤D1≤15.
  3. 3. The secondary battery according to claim 1, wherein 1≤W/L≤3, and/or 1.3≤D2/D1≤1.6.
  4. 4. The secondary battery according to claim 1, wherein a mass percentage of Si element in the second anode material layer is a,1% +.a≤50%, based on the mass of the second anode material layer.
  5. 5. The secondary battery according to claim 4, wherein 15.5% or more and 30% or less of A.
  6. 6. The secondary battery according to any one of claims 1 to 5, wherein a compacted density of a region of a first anode material layer beyond the second anode material layer in a width direction of the anode tab after being developed is PD1 g/cm 3 , and a compacted density of the second anode material layer is PD2 g/cm 3 , 0.8 ∈pd2/pd1 ∈1.6.
  7. 7. The secondary battery according to claim 6, wherein 1.0≤PD 2/PD 1≤1.4.
  8. 8. The secondary battery according to claim 6, wherein 0.8≤Pd1≤1.5, and/or 1.3≤Pd2≤1.65.
  9. 9. The secondary battery according to claim 1, wherein the first graphite material, the second graphite material are each independently selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, or hard carbon, and the silicon-based material comprises at least one of elemental silicon, a silicon oxygen compound, a silicon carbon compound, or a silicon alloy.
  10. 10. The secondary battery according to any one of claims 1 to 9, wherein the first graphite material is 95 to 99% by mass based on the mass of the first negative electrode material layer, the second graphite material is 28 to 95% by mass based on the mass of the second negative electrode material layer, and the silicon-based material is 1 to 70% by mass.
  11. 11. The secondary battery according to any one of claims 1 to 10, wherein the first anode material layer includes opposite first and second edges in a width direction of the anode tab after being developed, the second anode material layer includes opposite third and fourth edges, an edge of the second anode material layer near the first edge is the third edge, a region of the first anode material layer from the first edge to the third edge is a first single-layer region, and a region of the first anode material layer from the second edge to the fourth edge is a second single-layer region; The first single-layer region and/or the second single-layer region are/is provided with a plurality of grooves, and the grooves extend along the width direction of the unfolded negative electrode plate and are arranged at intervals along the length direction of the unfolded negative electrode plate.
  12. 12. The secondary battery according to claim 11, wherein the width of each groove is W 'μm,20 +.w' +.400, along the length direction of the negative electrode tab after being developed.
  13. 13. The secondary battery according to claim 12, wherein 90≤w'. Ltoreq.150.
  14. 14. The secondary battery according to claim 11, wherein a ratio of a length of the single groove to a width of the first single layer region or the second single layer region in a width direction of the negative electrode tab after being developed is P, 0.2≤p≤1.
  15. 15. The secondary battery according to claim 14, wherein 0.4≤p≤1.
  16. 16. The secondary battery according to claim 11, wherein the thickness of the first single layer region or the second single layer region is H μm in the thickness direction of the negative electrode tab, and the average depth of the plurality of grooves is H 'μm, 2≤h'. Ltoreq.0.8H.
  17. 17. The secondary battery according to claim 16, wherein 2≤H'≤0.6H, and/or 15≤H≤35.
  18. 18. The secondary battery according to claim 11, wherein a distance between two adjacent grooves in a length direction of the developed negative electrode tab is N mm, 1≤n≤5.
  19. 19. An electronic device comprising the secondary battery according to any one of claims 1 to 18.

Description

Secondary battery and electronic device Technical Field The present application relates to the field of electrochemical technology, and more particularly, to a secondary battery and an electronic device. Background Secondary batteries, such as lithium ion batteries, have the characteristics of large specific energy, high operating voltage, low self-discharge rate, small volume, light weight and the like, and have wide application in the consumer electronics field. At present, the lithium ion battery adopts a full tab design, namely, a positive electrode tab and a negative electrode tab extend out from opposite directions, and is prepared by adopting a full tab cutting and stacking or flattening technology. However, the full-lug rubbing structure can bring about the problem of pole piece infiltration, especially the pole piece edge, and electrolyte can be piled up on both sides of the material layer and continuously take place side reaction to cause capacity loss, and cycle performance declines. Disclosure of Invention The application aims to provide a secondary battery and an electronic device, which are used for reducing side reactions at the edge area of a pole piece and improving the cycle performance of the secondary battery. In the present application, a lithium ion battery is used as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium ion battery. The specific technical scheme is as follows: The first aspect of the application provides a secondary battery, which comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer positioned on at least one surface of the positive electrode current collector, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer positioned on at least one surface of the negative electrode current collector, the negative electrode material layer comprises a first negative electrode material layer and a second negative electrode material layer, the first negative electrode material layer is positioned between the negative electrode current collector and the second negative electrode material layer along the thickness direction of the negative electrode plate, the width of the first negative electrode material layer is larger than the width of the second negative electrode material layer along the width direction of the negative electrode plate after being unfolded, 1/2 of the width difference value between the first negative electrode material layer and the second negative electrode material layer is W mm, the width of the first negative electrode material layer is larger than the width of the positive electrode material layer, 1/2 of the width difference value between the first negative electrode material layer and the positive electrode material layer is L mm, 0.2W/L4, and optionally 1W/L3. The first anode material layer comprises a first anode active material, the first anode active material comprises a first graphite material, the second anode material layer comprises a second anode active material, the second anode active material comprises a second graphite material and a silicon-based material, the average particle size of particles of the first anode active material is D1 mu m, the average particle size of particles of the second anode active material is D2 mu m, D2/D1 is less than or equal to 1.1 and less than or equal to 1.8, and optionally, D2/D1 is less than or equal to 1.3 and less than or equal to 1.6. By setting a double-layer coating mode, the value of the regulating W/L is within the range of the application, and the wider first negative electrode material layer plays a certain physical blocking role, so that the diffusion of lithium ions to the edge area of the negative electrode plate is reduced, and the occurrence of side reactions at the edge of the plate is effectively reduced. And the value of D2/D1 is regulated and controlled to be within the range of the application, particles in the first negative electrode material layer and the second negative electrode material layer are mutually matched, so that the compaction density of the negative electrode plate is improved, the risk that the electrolyte is enriched on two sides of the negative electrode plate to generate side reaction is reduced, a channel which is more beneficial to lithium ion transmission is formed, and the cycle performance of the secondary battery is improved. In one or more embodiments of the application, 0.2≤L≤5, and/or 7≤D1≤15. By the arrangement, the energy density of the secondary battery is considered, and the occurrence of side reactions is reduced. And the particles in the first and second anode material layers may be matched with each other, thereby improving the cycle performance of the secondary battery. In one or more em