CN-122000431-A - Secondary battery and electronic device

Abstract

The application discloses a secondary battery and electronic equipment, wherein a first negative electrode material layer is provided with a first groove, and a part of a negative electrode tab is electrically connected with a negative electrode current collector in the first groove. The surface of the first positive electrode material layer facing the first groove is provided with a second groove, and a part of the first positive electrode material layer between the positive electrode current collector and the second groove forms a thinning area. The thinning area comprises a first section and a second section, and the second section and the first section are sequentially arranged along the second direction. In the first direction, the first section has an average thickness of T 1 μm and the second section has an average thickness of T 2 μm,T 1 <T 2 . The first insulating layer is arranged in the second groove, and in the first direction, in the projection range of the first positive electrode section, the orthogonal projection of the first groove is positioned in the orthogonal projection range of the first insulating layer. The risk of lithium precipitation of the second anode material layer and the risk of lithium precipitation near the first recess can be reduced.

Inventors

• ZHANG WEICHAO

Assignees

• 宁德新能源科技有限公司

Dates

Publication Date

20260508

Application Date

20260213

Claims (18)

1. 1. The secondary battery comprises a negative electrode tab, a positive electrode tab, a separation film and a negative electrode tab, wherein the positive electrode tab, the separation film and the negative electrode tab are stacked and wound, the positive electrode tab comprises a first positive electrode section and a second negative electrode section, the first negative electrode section and the second negative electrode section are respectively positioned at two sides of the thickness direction of the first positive electrode section, the positive electrode tab comprises a positive electrode current collector and a first positive electrode material layer arranged on the surface of the positive electrode current collector, the negative electrode tab comprises a negative electrode current collector and a first negative electrode material layer, the first negative electrode material layer is arranged on the surface of the negative electrode current collector facing the first positive electrode material layer, a first groove is arranged on the first negative electrode section, the first groove enables the negative electrode current collector to be exposed, one part of the negative electrode tab is electrically connected with the negative electrode current collector in the first groove, and the other part of the negative electrode tab extends out of the negative electrode tab; the first positive electrode material layer comprises a thinning area, and a part of the first positive electrode material layer, which is positioned between the positive electrode current collector and the second groove, forms the thinning area along a first direction, wherein the first direction is the thickness direction of the first positive electrode section, which is positioned at the second groove; The thinning area comprises a first section and a second section, wherein the second section and the first section are sequentially arranged along a second direction, the average thickness of the first section is T 1 mu m along the first direction, the average thickness of the second section is T 2 μm,T 1 <T 2 , and the second direction is the direction in which the negative electrode tab extends out of the negative electrode plate; The secondary battery further comprises a first insulating layer, wherein the first insulating layer is arranged in the second groove, and in the first direction, in the projection range of the first positive electrode section, the orthographic projection of the first groove is positioned in the orthographic projection range of the first insulating layer.
2. 2. The secondary battery according to claim 1, wherein the thickness of the thinned region gradually decreases in the second direction.
3. 3. The secondary battery according to claim 1, wherein the first positive electrode material layer includes a first edge to which the thinned region extends in the second direction, and wherein the thinned region has a thickness T a μm,0.5≤T a ≤5 at the first edge.
4. 4. The secondary battery according to claim 3, wherein 1≤T a ≤4.
5. 5. The secondary battery according to claim 3, further comprising a second insulating layer provided to the first anode material layer, the second insulating layer covering the first groove in the first direction; Along a second direction, at one end far away from the first edge, the length of the first insulating layer beyond the second insulating layer is W a mm,2≤W a less than or equal to 5; The length of the first insulating layer exceeding the second insulating layer is L 1 mm,2≤L 1 or less along the third direction, and the length of the first insulating layer exceeding the second insulating layer is L 2 mm,2≤L 2 or less along the third direction; The first direction, the second direction and the third direction are perpendicular to each other.
6. 6. The secondary battery according to any one of claims 3 to 5, wherein, Along the second direction, the second groove comprises a second edge which is opposite to the first edge, and along the second direction, the distance between the first insulating layer and the second edge is W 1 mm,0.5≤W 1 less than or equal to 1; The second groove comprises a third edge and a fourth edge which are oppositely arranged, the distance between the first insulating layer and the third edge is L 3 mm along the third direction, the distance between the first insulating layer and the fourth edge is L 4 mm;0.5≤L 3 less than or equal to 1.5, and/or L 4 less than or equal to 0.5 less than or equal to 1.5; The first direction, the second direction and the third direction are perpendicular to each other.
7. 7. The secondary battery according to claim 3, wherein the first insulating layer further includes a first extension portion protruding from the first edge by a length L a mm,0.5≤L a +.1.5 from the first edge.
8. 8. The secondary battery according to claim 1, wherein, The thickness of the first positive electrode material layer is H [ mu ] m along the first direction; at one end of the second direction opposite to the first direction, the first insulating layer includes a fifth edge, and along the first direction, the thinned region includes a first position overlapping with orthogonal projection of the fifth edge; And along the first direction, the thinning area comprises a first area covered by the first insulating layer, the maximum thickness of the first area comprises the first position, and the thickness of the thinning area at the first position is H 1 μm,0.25≤H 1 /H less than or equal to 0.75.
9. 9. The secondary battery according to claim 8, wherein the first positive electrode material layer includes a first surface facing the first negative electrode material layer, and the first insulating layer does not protrude from the first surface.
10. 10. The secondary battery according to claim 1, wherein the thinned region has a surface roughness of R μm, 2≤r≤15.
11. 11. The secondary battery according to claim 1, wherein the first negative electrode material layer includes a first portion, wherein the first negative electrode material layer includes a sixth edge in the second direction, and wherein a portion of the first negative electrode material layer between the sixth edge and the first recess forms the first portion; along the first direction, the negative electrode tab covers at least part of the first portion.
12. 12. The secondary battery according to claim 1, further comprising a positive electrode tab and a third insulating layer; The first positive electrode material layer is provided with a third groove, the third groove enables the positive electrode current collector to be exposed, one part of the positive electrode lug is electrically connected with the positive electrode current collector in the third groove, and the other part of the positive electrode lug extends out of the positive electrode plate; The first positive electrode material layer further comprises a first coverage area covered by the third insulating layer, and the thickness of the first coverage area is sequentially reduced along the second direction.
13. 13. The secondary battery according to claim 1, further comprising a first adhesive layer disposed between the negative electrode tab and the negative electrode current collector; the first negative electrode section further comprises a second negative electrode material layer which is arranged on the surface of the negative electrode current collector, which is away from the first negative electrode material layer; The second negative electrode material layer comprises a second portion, and an orthogonal projection of the second portion overlaps an orthogonal projection of the first groove along the first direction.
14. 14. The secondary battery according to claim 1, further comprising an electrolyte comprising a first component selected from at least one of 2, 2-difluoroethyl acetate, ethyl difluoroacetate, 2-fluoroacetate; Based on the total mass of the electrolyte, the mass percentage of the first component is A, and A is more than or equal to 10 and less than or equal to 60.
15. 15. The secondary battery according to claim 14, wherein the electrolyte further comprises a second component selected from at least one of ethylene carbonate, propylene carbonate; Based on the total mass of the electrolyte, the mass percentage of the first component is B≤A/B≤5.
16. 16. The secondary battery according to any one of claims 1 to 15, wherein the electrolyte further comprises a third component selected from at least one of the following compounds of formulae I-1 to I-6; based on the total mass of the electrolyte, the mass percentage of the third component is C≤C≤5.
17. 17. The secondary battery according to any one of claims 1 to 16, wherein a charge cut-off voltage of the secondary battery is G V, and G is 4.55+.4.65.
18. 18. An electronic device comprising the secondary battery according to any one of claims 1 to 17.

Description

Secondary battery and electronic device Technical Field The present application relates to the field of battery technologies, and in particular, to a secondary battery and an electronic device. Background The lithium ion secondary battery is widely applied to products such as mobile phones, notebook computers, electric vehicles and the like by virtue of the advantages of high energy density, low pollution and the like. With the rapid development of industries such as consumer electronics and new energy automobiles, the requirements of the market for the cycle performance of lithium ion secondary batteries are increasingly increasing. However, the problem of lithium precipitation of the negative electrode tab restricts the cycle performance of the lithium ion secondary battery. Disclosure of Invention The application aims to provide a secondary battery and electronic equipment, so as to reduce the lithium precipitation risk of the secondary battery. In a first aspect, the present application provides a secondary battery, including a negative electrode tab, and a positive electrode tab, a separator, and a negative electrode tab that are stacked and wound. The positive pole piece comprises a first positive pole section, the negative pole piece comprises a first negative pole section and a second negative pole section, and the first negative pole section and the second negative pole section are respectively positioned at two sides of the thickness direction of the first positive pole section. The positive pole piece comprises a positive current collector and a first positive material layer arranged on the surface of the positive current collector. The negative electrode plate comprises a negative electrode current collector and a first negative electrode material layer, and the first negative electrode material layer is arranged on the surface of the negative electrode current collector facing the first positive electrode material layer. In the first negative electrode section, the first negative electrode material layer is provided with a first groove, and the first groove exposes the negative electrode current collector. One part of the negative electrode tab is electrically connected with the negative electrode current collector in the first groove, and the other part of the negative electrode tab extends out of the negative electrode pole piece. In the first positive electrode section, a second groove is formed in the surface of the first positive electrode material layer facing the first groove. The first positive electrode material layer includes a thinned region, and a portion of the first positive electrode material layer between the positive electrode current collector and the second groove forms the thinned region in the first direction. The first direction is the thickness direction of the first positive electrode section at the second groove. The thinning area comprises a first section and a second section, and the second section and the first section are sequentially arranged along the second direction. Along the first direction, the average thickness of the first section is T 1 mu m, the average thickness of the second section is T 2μm,T1<T2, and the second direction is the direction in which the negative electrode tab extends out of the negative electrode plate. The secondary battery also comprises a first insulating layer which is arranged in the second groove, and in the first direction, in the projection range of the first positive electrode section, the orthogonal projection of the first groove is positioned in the orthogonal projection range of the first insulating layer. According to the technical scheme, the thickness gradient design is adopted in the thinning area, the larger thickness T 2 is arranged in the second section far away from the first edge, so that sufficient anode materials can be reserved, the energy density of the secondary battery can be effectively improved, the smaller thickness T 1 is adopted in the first section close to the first edge, the lithium ion stripping amount close to the first edge area is reduced, the phenomenon that lithium ions cross the anode current collector to migrate to the second anode material layer and are enriched at the edge of the anode current collector is relieved, and the risk of lithium precipitation of the second anode material layer is reduced. Meanwhile, in the projection range of the first positive electrode section, the orthogonal projection of the first groove is in the orthogonal projection range of the first insulating layer, so that the lithium ion release amount of the first positive electrode material layer to the first groove region can be reduced, and the lithium precipitation risk near the first groove is further reduced. In addition, the first insulating layer is arranged in the second groove, so that the occupation of the first insulating layer to the thickness space of the first positive electrode section can be reduced, an