CN112687831B

CN112687831B - Electrode assembly and secondary battery

Info

Publication number: CN112687831B
Application number: CN202011545982.4A
Authority: CN
Inventors: 黄少军; 赖仕斌; 朱奥生; 何世峰
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2022-03-22
Anticipated expiration: 2040-12-24
Also published as: CN112687831A

Abstract

The present disclosure provides an electrode assembly, including a first pole piece and a second pole piece which are alternately arranged, wherein the first pole piece includes a first current collector, and the electrode assembly includes a first region, a second region and a third region from outside to inside in the thickness direction of the electrode assembly; the thicknesses of the first current collectors in the first, second, and third regions are sequentially reduced. The thickness of the first current collector in the first area of the electrode assembly is the largest, so that the overall mechanical performance of the battery can be improved, the short circuit failure of the battery when the battery is impacted is effectively reduced, and meanwhile, the deformation of the battery in the circulating process can be inhibited; the second area adopts a first current collector with medium thickness, plays a role in buffer transition, improves the mechanical property of the battery when the battery is impacted, and provides a thickness space for improving the energy density of the battery; the third area adopts the thinner first current collector, and more thickness space is provided for improving the energy density of the battery.

Description

Electrode assembly and secondary battery

Technical Field

The present disclosure relates to a secondary battery, and more particularly, to an electrode assembly and a secondary battery.

Background

The negative current collector material in the secondary battery is usually copper foil, and the thickness of the copper foil has a great influence on the performance of the battery when the battery is impacted. If the secondary battery adopts thicker copper foil, the battery can have better mechanical strength, and when the battery is impacted, the thick copper foil effectively reduces the short circuit failure caused by the generation of fragments. If short circuit occurs, the thick copper foil can enable current to be shunted more, voltage drops rapidly, heat generation of the battery is reduced, and thermal runaway of the battery is prevented.

Although the thick copper foil can effectively improve the passing rate when the battery is impacted, the improvement of the energy density of the battery is greatly influenced.

Disclosure of Invention

In view of the defects of the prior art, the present disclosure is directed to an electrode assembly and a secondary battery, which can effectively increase the energy density of the battery, increase the pass rate when the battery is impacted, and improve the cycle deformation of the battery.

In order to achieve the above object, an embodiment of the present disclosure provides an electrode assembly, which includes a first pole piece and a second pole piece alternately arranged, where the first pole piece includes a first current collector, and the electrode assembly includes, from outside to inside in a thickness direction of the electrode assembly, a first region, a second region, and a third region; the thicknesses of the first current collectors in the first, second, and third regions are sequentially reduced.

In some embodiments, the pole pieces of the electrode assembly are symmetrically arranged in the thickness direction, i.e., such that the electrode assembly exhibits a substantially symmetrical structure in the thickness direction thereof, to reduce the likelihood of the electrode assembly shorting when impacted in any of the major planes.

According to another embodiment of the present application, in the first region, the first current collector has a thickness of 12 μm to 25 μm; in the second region, the first current collector has a thickness of 8 μm to 10 μm; in the third region, the thickness of the first current collector is less than 6 μm.

In some embodiments, the electrode assembly further comprises a separator separating the first and second pole pieces; the diaphragm thickness of the first region, the second region and the third region decreases in the thickness direction in this order.

In some embodiments, the septum is a high-bond septum; the diaphragms are symmetrically arranged in the thickness direction; that is, it is further ensured that the electrode assembly assumes a substantially symmetrical structure in the thickness direction thereof.

According to another embodiment of the present application, in the first region, the thickness of the separator is 9 μm to 15 μm; in the second region, the thickness of the separator is 7 μm to 9 μm; in the third region, the thickness of the membrane is less than 7 μm.

In some embodiments, the first, second, and third regions are separated by a membrane; the thickness of the diaphragm between the first region and the second region is the same as the thickness of the diaphragm in the first region, and the thickness of the diaphragm between the second region and the third region is the same as the thickness of the diaphragm in the second region.

In some embodiments, the first pole piece is a negative pole piece and the second pole piece is a positive pole piece; the outermost side of the electrode assembly in the thickness direction is a positive pole piece, so that the situation that the outermost pole piece and a shell (usually an aluminum-plastic film) of the battery are subjected to galvanic corrosion is avoided.

In some embodiments, the first pole piece further comprises a first active material layer disposed on a surface of the first current collector; the second pole piece includes a second current collector and a second active material layer disposed on a surface of the second current collector.

In some embodiments, the pole pieces located outermost in the electrode assembly are provided with an active material layer only on one side thereof facing the inside of the electrode assembly.

In some embodiments, the present disclosure provides a secondary battery including the electrode assembly described above.

In some embodiments, the secondary battery further comprises a case comprising a protective layer, a metal layer, and a fusing layer; the metal layer and the current collector of the outermost pole piece in the thickness direction of the electrode assembly are configured so as not to cause galvanic corrosion. That is, according to one embodiment of the present application, the material of the case may be an aluminum composite film, the metal layer of which is aluminum, and the current collector of the outermost pole piece is a cathode current collector tail in the thickness direction of the electrode assembly, for example, the cathode current collector may be an aluminum foil. According to another embodiment of the present application, the material of the case may be a steel case or a steel composite film, and the current collector of the outermost pole piece is an anode current collector tail along the thickness direction of the electrode assembly, for example, the anode current collector may be a copper foil.

The beneficial effects of this disclosure are as follows: the thickness of the first current collector in the first area of the electrode assembly is maximum, so that the overall mechanical performance of the battery can be improved, the short circuit failure of the battery when the battery is impacted can be effectively reduced, even if the short circuit occurs, the current can be more shunted, the voltage is rapidly reduced, the heat generation of the battery is reduced, the thermal runaway of the battery is prevented, and meanwhile, the deformation of the battery in the circulating process can be inhibited; the second area adopts a first current collector with medium thickness, plays a role in buffer transition, improves the mechanical property of the battery when the battery is impacted, and provides a thickness space for improving the energy density of the battery; the third area adopts the thinner first current collector, and more thickness space is provided for improving the energy density of the battery.

Drawings

Fig. 1 is a schematic diagram of a pole piece structure of an embodiment of an electrode assembly according to the present disclosure.

Fig. 2 is a perspective view schematically illustrating an electrode assembly according to the present disclosure.

Fig. 3 is a schematic structural view of a secondary battery according to the present disclosure.

Wherein the reference numerals are as follows:

100 secondary battery

1 electrode Assembly

11 first pole piece

111 first current collector

112 first active material layer

12 second pole piece

121 second current collector

122 second active material layer

13 first tab

14 second ear

S-shaped diaphragm

A1 first region

A2 second region

A3 third region

D thickness direction

2 casing

21 protective layer

22 metal layer

23 fused layer

3 lead wire

Detailed Description

The accompanying drawings illustrate embodiments of the present disclosure and it is to be understood that the disclosed embodiments are merely examples of the disclosure, which can be embodied in various forms, and therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

An electrode assembly and a secondary battery according to the present disclosure will be described in detail below with reference to the accompanying drawings.

Referring to fig. 1, the electrode assembly 1 includes first and

second electrode tabs

11 and 12 alternately arranged, the first electrode tab 11 includes a first current collector 111, and the electrode assembly 1 includes, from the outside to the inside in a thickness direction D of the electrode assembly 1, a first region a1, a second region a2, and a third region A3; the thicknesses of the first current collectors 111 in the first, second, and third regions a1, a2, and A3 are sequentially reduced.

The thickness of the first current collector 111 in the first area a1 of the electrode assembly 1 is the largest, so that the overall mechanical performance of the battery can be improved, the short circuit failure of the battery when the battery is impacted can be effectively reduced, even if the short circuit occurs, the current can be more shunted, the voltage is rapidly reduced, the heat generation of the battery is reduced, the thermal runaway of the battery is prevented, and the deformation of the battery in the circulating process can be inhibited; the second area A2 adopts the first current collector 111 with medium thickness, which plays a role in buffer transition, and provides a thickness space for improving the energy density of the battery while improving the mechanical property of the battery when the battery is impacted; the third region a3 uses the thinner first current collector 111, providing more space for the thickness to increase the energy density of the battery.

The electrode plates of the electrode assembly 1 are symmetrically arranged in the thickness direction D, that is, the first electrode plate 11 and the second electrode plate 12 are symmetrically distributed in the thickness direction D, and the symmetrical structure makes the battery not prone to bending deformation biased to one side after the battery is cycled. In some embodiments, in the first region a1, the thickness of the first current collector 111 is 12 μm to 25 μm for improving the mechanical properties of the battery; in the second region a2, the thickness of the first current collector 111 is 8 μm to 10 μm, which plays a role of buffering excessive; in the third region a3, the thickness of the first current collector is less than 6 μm for improving the energy density of the battery.

Referring to fig. 1, the electrode assembly 1 further includes a separator S separating the first and

second pole pieces

11 and 12; in the thickness direction, the thicknesses of the diaphragm S in the first region a1, the second region a2, and the third region A3 decrease in order. The thickness of the diaphragm S in the first area A1 in the electrode assembly 1 is the largest, so that the overall mechanical performance of the battery can be improved, and the short circuit failure of the battery when the battery is impacted can be effectively reduced; the second area A2 adopts a diaphragm S with medium thickness, plays a role in buffer transition, improves the mechanical property of the battery when the battery is impacted, and provides a thickness space for improving the energy density of the battery; the third region a3 uses a thinner separator S to provide more space for the thickness to increase the energy density of the battery.

The separators S of the electrode assembly 1 are also symmetrically arranged in the thickness direction D, and in some embodiments, the separators have a thickness of 9 μm to 15 μm in the first region for improving the overall mechanical properties of the battery; in the second area, the thickness of the diaphragm is 7-9 μm, which plays a role of buffering excessive; in the third region, the thickness of the separator is less than 7 μm for improving the energy density of the battery.

In some embodiments, septum S is a high bond septum. The first region a1, the second region a2 and the third region A3 are separated by a diaphragm S; the membrane S between the first region a1 and the second region a2 is the same thickness as the membrane S in the first region a1, and the membrane S between the second region a2 and the third region A3 is the same thickness as the membrane S in the second region a 2.

Referring to fig. 2, the electrode assembly 1 further includes a first tab 13 connected to the first current collector 111, and a second tab 14 connected to the second current collector 121, and in some embodiments, the first current collector 111 and the first tab 13 are integrally formed, and the second current collector 121 and the second tab 14 are integrally formed, so that welding is not required, and the process flow is simplified. In some embodiments, the first tabs 13 are symmetrically arranged in the thickness direction D of the electrode assembly 1, and the second tabs 14 are also symmetrically arranged in the thickness direction D of the electrode assembly 1, improving the resistance of the electrode assembly 1 against deformation.

In some embodiments, the first pole piece 11 is a negative pole piece, and the second pole piece 12 is a positive pole piece; the outermost side of the electrode assembly 1 in the thickness direction D is a positive electrode plate, and considering that the casing of the conventional battery is basically an aluminum plastic film, and the material of the positive current collector in the positive electrode plate is basically an aluminum foil, the arrangement mode can avoid the occurrence of corrosion of the primary battery. The length and the width of the positive pole piece are both smaller than those of the negative pole piece, and the length and the width of the negative pole piece are both smaller than that of the diaphragm S.

In some embodiments, the first electrode plate 11 is a negative electrode plate, the material of the negative current collector in the negative electrode plate is copper foil, the second electrode plate 12 is a positive electrode plate, and the material of the positive current collector in the positive electrode plate is aluminum foil. The thicknesses of the copper foil and the diaphragm S are sequentially reduced from the first region a1 to the third region A3, and the thickness of the aluminum foil is maintained to be uniform. The copper foil and the diaphragm S are of a combined structure with different thicknesses, and specifically, in the first area A1, the copper foil with the thickness of 12-25 microns and the high-adhesion diaphragm S with the thickness of 9-15 microns are adopted as negative current collectors; in the second area A2, the negative current collector adopts copper foil with the thickness of 8-10 μm and a high-adhesion diaphragm S with the thickness of 7-9 μm; in the third region a3, a copper foil having a thickness of 6 μm or less and a highly adhesive separator S having a thickness of 7 μm or less were used as the negative electrode current collector.

Referring to fig. 1 and 2, the first electrode sheet 11 further includes a first active material layer 112 disposed on a surface of the first current collector 111; the second electrode sheet 12 includes a second current collector 121 and a second active material layer 122 disposed on a surface of the second current collector 121. The pole piece located at the outermost side of the electrode assembly 1 is provided with an active material layer only at one side thereof facing the inside of the electrode assembly 1.

The first pole piece 11, the second pole piece 12 and the diaphragm S located between the first pole piece and the second pole piece form a lamination unit, the number of layers of the lamination unit in the first region a1 is N1, the number of layers of the lamination unit in the second region a2 is N2, the number of layers of the lamination unit in the third region A3 is N3, the total number of layers of the electrode assembly 1 is N1+ N2+ N3, in some embodiments, the total number of layers N of the electrode assembly 1 is not less than 5, N1 is not less than N2 but not more than N3, wherein N1 is not less than 2, N2 is not less than 2, and N1 is not less than 1. Thereby further improving the overall mechanical performance of the battery and improving the volume energy density of the battery.

Referring to fig. 3, the present disclosure provides a secondary battery 100 including the electrode assembly 1 of any one of the above.

In some embodiments, the secondary battery 100 further includes a case 2, the case 2 including a protective layer 21, a metal layer 22, and a fusion layer 23; the metal layer 22 and the current collector of the outermost pole piece in the thickness direction D of the electrode assembly 1 are arranged so as not to cause galvanic corrosion. In some embodiments, secondary battery 100 further includes a lead 3 connected to the consumer.

In some embodiments, when the case 2 of the secondary battery 100 is an aluminum plastic film, the outermost side in the thickness direction D of the electrode assembly 1 is set to be a positive electrode sheet, wherein the material of the positive electrode current collector is an aluminum foil; when the case 2 of the secondary battery 100 is a plastic-steel film, the outermost side of the electrode assembly 1 in the thickness direction D is a negative electrode plate, wherein the negative electrode current collector is made of copper foil, thereby preventing the current collector and the case 2 from being corroded by the primary battery.

The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. An electrode assembly comprising first and second alternately arranged pole pieces, said first pole piece comprising a first current collector,

the stacking direction in which the first and second pole pieces are alternately arranged is the thickness direction of the electrode assembly,

the electrode assembly comprises a first region, a second region and a third region from outside to inside in the thickness direction of the electrode assembly;

the first region, the second region, and the third region each include the first current collector, and thicknesses of the first current collector in the first region, the second region, and the third region are sequentially reduced in a thickness direction of the electrode assembly.

2. The electrode assembly of claim 1, wherein the electrode assembly has pole pieces symmetrically arranged in a thickness direction.

3. The electrode assembly of claim 1, further comprising a separator separating the first and second pole pieces;

the first region, the second region and the third region include the diaphragm, and the thicknesses of the diaphragm in the first region, the second region and the third region are sequentially reduced in the thickness direction.

4. The electrode assembly according to claim 3, wherein the separator is a high-adhesion separator, and the separator is symmetrically disposed in the thickness direction.

5. The electrode assembly of claim 3,

the first area, the second area and the third area are separated by the diaphragm;

the thickness of the diaphragm between the first region and the second region is the same as the thickness of the diaphragm in the first region, and the thickness of the diaphragm between the second region and the third region is the same as the thickness of the diaphragm in the second region.

6. The electrode assembly of claim 1, wherein the first pole piece is a negative pole piece and the second pole piece is a positive pole piece;

and the outermost side of the electrode assembly in the thickness direction is a positive pole piece.

7. The electrode assembly of claim 1, wherein the first pole piece further comprises a first active material layer disposed on a surface of the first current collector;

the second pole piece includes a second current collector and a second active material layer disposed on a surface of the second current collector.

8. The electrode assembly according to claim 7, wherein the pole piece located at the outermost side of the electrode assembly is provided with the active material layer only at one side thereof facing the inside of the electrode assembly.

9. A secondary battery comprising the electrode assembly according to any one of claims 1 to 8.

10. The secondary battery according to claim 9,

the secondary battery further comprises a case, wherein the case comprises a protective layer, a metal layer and a fusion layer;

the metal layer and a current collector of the outermost pole piece in the thickness direction of the electrode assembly are configured not to form galvanic corrosion.