WO2024120551A1

WO2024120551A1 - Electrode sheet and battery cell

Info

Publication number: WO2024120551A1
Application number: PCT/CN2024/075669
Authority: WO
Inventors: 青峻毅; 李习新; 何世聪
Original assignee: 惠州亿纬锂能股份有限公司
Priority date: 2023-02-08
Filing date: 2024-02-04
Publication date: 2024-06-13
Also published as: CN219286442U

Abstract

An electrode sheet and a battery cell are provided. The electrode sheet comprises a current collector and active substance layers; the active substance layers are arranged on two opposing side faces of the current collector; a first groove is formed on the active substance layer at one side, and a second groove is formed on the active substance layer at the other side, where the bottoms of first groove and the second groove penetrate to the current collector; tabs are separately inserted into the first groove and the second groove; the two tabs are both connected to the current collector, and the two tabs are connected to each other.

Description

Electrode and battery cell

This application claims priority to the Chinese patent application filed with the China Patent Office on February 8, 2023, with application number 2023201893728, the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the technical field of battery cells, for example, to a pole piece and a battery cell.

Background technique

With the rapid development of battery technology, people have put forward higher requirements on the energy density, discharge rate and discharge temperature rise of lithium-ion batteries.

At present, the electrode production technology commonly used is to weld a single pole ear to one side of the current collector. The battery cell is formed by winding two pole pieces with opposite polarities and a diaphragm. The relevant technology has the following technical defects: the internal resistance of the battery cell in the form of a single pole ear is very large, and the heat generated during fast charging is high, which affects the service life and safety performance of the battery cell.

Summary of the invention

The present application provides a pole piece with a simple structure and good safety performance.

The present application provides a battery cell with a simple structure and a relatively thin thickness.

The embodiments of the present application adopt the following technical solutions:

In the first aspect, an embodiment of the present application provides a pole piece, comprising a current collector and an active material layer, wherein the active material layer is arranged on two opposite side surfaces of the current collector, a first groove is opened on the active material layer on one side, and a second groove is opened on the active material layer on the other side, the bottoms of the first groove and the second groove both penetrate into the current collector, a pole ear is inserted in the first groove and the second groove respectively, the two pole ears are connected to the current collector, and the two pole ears are connected to each other.

In one embodiment, the two tabs are connected via a current collecting sheet.

In one embodiment, the pole ear includes a metal sheet and an insulating glue arranged on the periphery of the metal sheet, the two metal sheets are respectively inserted into the first groove and the second groove, and the two metal sheets are connected through the current collecting sheet, and the two insulating glues are arranged side by side along a first direction, and the first direction is the length direction of the pole sheet when it is unfolded.

In one embodiment, the first groove and the second groove are arranged opposite to each other, and the size of the first groove and the second groove along the first direction is greater than or equal to twice the size of the insulating glue along the first direction; or,

The projections of the first groove and the second groove on the current collector are arranged side by side along the first direction, and the sizes of the first groove and the second groove along the first direction are greater than the size of the insulating glue along the first direction.

In one embodiment, the dimensions of the pole piece satisfy at least one of the following: the thickness of the active material layer ranges from 0.05 to 0.2 mm; the thickness of the pole tab ranges from 0.1 to 0.7 mm; and the thickness of the insulating glue ranges from 0.05 to 0.3 mm.

In one embodiment, the first groove and the second groove at least penetrate one end of the active material layer along the width direction of the pole piece.

In one embodiment, the first groove and the second groove are located at non-end positions in the unfolded length direction of the pole piece.

In a second aspect, an embodiment of the present application provides a battery cell, which is formed by winding a separator and a positive electrode sheet and a negative electrode sheet located on both sides of the separator, and the positive electrode sheet and the negative electrode sheet are the above-mentioned electrode sheets.

In one embodiment, one of the positive electrode sheet and the negative electrode sheet is provided with a first groove of the electrode sheet and a second groove of the electrode sheet, and the other of the positive electrode sheet and the negative electrode sheet is provided with a first avoidance groove and a second avoidance groove respectively relative to the first groove position and the second groove position, and an accommodating space for accommodating the pole ear of the electrode sheet is formed between the first avoidance groove and the first groove, and between the second avoidance groove and the second groove, which are opposite to each other after the battery cell is wound.

In one embodiment, the thickness of the tab is less than or equal to the dimension of the accommodation space along the second direction.

The beneficial effects of the present application are as follows: by opening a groove respectively on the active material layer on two opposite sides of the current collector, a pole ear is welded in each of the two grooves, the two pole ears are connected to the current collector and the two pole ears are connected to each other, so as to form a pole piece with a bipolar ear structure in which pole ears are welded on both sides of the current collector. The pole piece with a bipolar ear structure is conducive to the conduction of current, thereby effectively reducing the internal resistance of the battery cell, reducing the heat generated during fast charging of the battery cell, and effectively improving the service life and safety performance of the battery cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a pole piece according to an embodiment of the present application;

FIG2 is a schematic diagram of the coordination between the current collector and the active material layer in an embodiment of the present application;

FIG3 is a schematic diagram of the structure of a battery cell according to an embodiment of the present application;

FIG4 is a schematic diagram of the coordination of the positive electrode sheet, the negative electrode sheet and the separator according to an embodiment of the present application;

In the figure:

1. Current collector; 2. Active material layer; 21. First groove; 22. Second groove; 23. First air-avoiding groove; 24. Second air-avoiding groove; 3. Pole ear; 31. Metal sheet; 32. Insulating glue; 4. Current collector; 5. Diaphragm; 6. Positive electrode sheet; 7. Negative electrode sheet.

Detailed ways

In the description of this application, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the meanings of the above terms in this application can be understood according to the circumstances.

In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

As shown in Figures 1 and 2, the pole piece of the embodiment of the present application includes a current collector 1 and an active material layer 2, the active material layer 2 is arranged on two opposite sides of the current collector 1, a first groove 21 is provided on the active material layer 2 on one side, and a second groove 22 is provided on the active material layer 2 on the other side, the groove bottoms of the first groove 21 and the second groove 22 are both penetrated to the current collector 1, and a pole ear 3 is inserted in the first groove 21 and the second groove 22 respectively, and the pole ear 3 can be welded to the current collector 1 by laser welding, and the two pole ears 3 are connected to the current collector 1, and the two pole ears 3 are connected to each other. By welding a pole ear 3 on each side of the two opposite sides of the current collector 1, and the two pole ears 3 are connected to each other, a pole piece with a bipolar ear structure in which pole ears are welded on both sides of the current collector 1 is formed, and the pole piece with a bipolar ear structure is conducive to the conduction of current, thereby effectively reducing the internal resistance of the battery cell, reducing the heat generated when the battery cell is quickly charged, and effectively improving the service life and safety performance of the battery cell.

It is worth noting that, as shown in FIG1 , the first groove 21 and the second groove 22 are located at non-end positions in the length direction of the pole piece (the length direction of the pole piece is the X direction in FIG1 ), that is, the first groove 21 and the second groove 22 are located at positions other than the two ends of the active material layer 2, which may be 1/15, 1/5, 1/3, 1/2 or other non-end positions of the active material layer along the X direction, without making too many restrictions here.

In this embodiment, as shown in FIG1 , the two pole tabs 3 are connected to each other through a current collector 4. The current collector 4 increases the contact area of the two pole tabs 3 and improves the connection strength of the two pole tabs 3, thereby improving the conductivity of the current at the connection between the two pole tabs 3 and reducing the heat generated when the pole tabs 3 are quickly charged and discharged.

Optionally, as shown in FIG1 , the first groove 21 and the second groove 22 at least penetrate one end of the active material layer 2 along the width direction of the pole piece (the width direction of the pole piece is the Y direction in FIG1 ), and the cleaning method of the first groove 21 and the second groove 22 can be laser cleaning, mechanical cleaning, or foam cleaning, etc., and no excessive restrictions are made here. In this embodiment, the first groove 21 and the second groove 22 only penetrate one end of the active material layer 2 along the Y direction, and the pole ear 3 inserted in the first groove 21 and the second groove 22 extends from the through end of the groove to the outside of the groove, and the parts of the two pole ears 3 extending outside the groove are connected by the current collector 4. At the same time, the end of the first groove 21 and the second groove 22 that does not completely penetrate the Y direction can provide support for the pole ear 3 during welding, thereby improving the stability of the welding of the pole ear 3. In other embodiments, the first groove 21 and the second groove 22 can also completely penetrate both ends of the active material layer 2 along the Y direction.

Exemplarily, as shown in FIG1 , the pole tab 3 includes a metal sheet 31 and an insulating glue 32 arranged on the periphery of the metal sheet 31 , two metal sheets 31 are respectively inserted into the first groove 21 and the second groove 22 , and the two metal sheets 31 are connected by the current collector 4 , and the two insulating glues 32 are arranged side by side along the first direction, and the first direction is the X direction. In this embodiment, the first groove 21 and the second groove 22 are arranged opposite to each other, and the first groove 21 and the second groove 22 are arranged symmetrically about the current collector 1 , so that the first groove 21 and the second groove 22 are formed at one time during the production process, and the production is convenient. The size of the first groove 21 and the second groove 22 along the X direction is greater than or equal to twice the size of the insulating glue 32 along the X direction, so that the insulating glue 32 of the two pole tabs 3 is arranged side by side along the X direction, and the two insulating glues 32 are prevented from interfering with each other when the metal sheets 31 of the two pole tabs 3 are respectively inserted into the first groove 21 and the second groove 22 , thereby ensuring the welding strength between the metal sheet 31 and the current collector 1 and the connection strength between the metal sheet 31 and the current collector 4. In other embodiments, the first groove 21 and the second groove 22 are arranged side by side along the X direction of the projection of the current collector 1, and the size of the first groove 21 and the second groove 22 along the X direction is slightly larger than the size of the insulating glue 32 along the X direction, which can also avoid the interference of the two insulating glues 32 when the two metal sheets 31 are welded to the current collector 1. Of course, when the thickness of the insulating glue 32 of the two tabs 3 is relatively thin, that is, when the projections of the two insulating glues 32 on the current collector 1 overlap, the two insulating glues 32 located at the overlapping part of the projection are still arranged at intervals, and the first groove 21 and the second groove 22 slightly larger than the size of the metal sheet 31 along the X direction can be directly arranged.

For example, as shown in Figures 1 and 2, the thickness of the active material layer 2 is in the range of 0.05 to 0.2 mm; the thickness of the pole ear 3 is in the range of 0.1 to 0.7 mm; and the thickness of the insulating glue 32 is in the range of 0.05 to 0.3 mm. It should be noted that the above thickness directions are all the thickness directions of the unfolded pole piece (the thickness direction of the unfolded pole piece is the Z direction in Figure 1).

The embodiment of the present application also provides a battery cell, as shown in FIG3 , the battery cell is formed by winding a separator 5 and a positive electrode sheet 6 and a negative electrode sheet 7 located on both sides of the separator 5 , and the positive electrode sheet 6 and the negative electrode sheet 7 are the electrode sheets of any of the above embodiments.

Optionally, as shown in FIG. 4 , a first groove 21 and a second groove 22 are provided on the positive electrode sheet 6, and a pole ear 3 is provided in each of the first groove 21 and the second groove 22, and the two pole ears 3 are connected to form a positive total pole ear. At this time, the active material layer 2 on the opposite sides of the negative electrode sheet 7 is provided with a first avoidance groove 23 and a second avoidance groove 24 at the positions of the first groove 21 and the second groove 22, respectively. After winding, a storage space that can accommodate the pole ear 3 of the positive electrode sheet 6 is formed between the first avoidance groove 23 and the first groove 21, and between the second avoidance groove 24 and the second groove 22. By providing the first avoidance groove 23 and the second avoidance groove 24 on the negative electrode sheet 7, the pole ear 3 of the positive electrode sheet 6 protruding from the first groove 21 and the second groove 22 can be avoided when the positive electrode sheet 6 and the negative electrode sheet 7 are wound into a battery cell, which can reduce the thickness increase caused by the pole ear 3, thereby reducing the thickness of the battery cell and improving the overall energy density of the battery cell. In addition, when the first groove 21 and the second groove 22 are formed on the negative electrode sheet 7, the first avoidance groove 23 and the second avoidance groove 24 are formed on the positive electrode sheet 6 to avoid the tab 3 on the negative electrode sheet 7, thereby preventing the tab 3 from protruding from the active material layer 2 and causing a thickness difference problem, thereby improving the flatness of the battery cell.

Optionally, as shown in FIG3 , the thickness of the pole ear 3 is less than or equal to the dimension of the accommodation space along the second direction (the second direction is the thickness direction of the unfolded pole piece, i.e., the Z direction in FIG1 ), and the Z direction is perpendicular to the X direction, i.e., the pole ear 3 can be completely accommodated in the accommodation space, effectively improving the thickness difference of the battery cell at this position and improving the flatness of the battery cell.

Exemplarily, the pole piece also includes adhesive tape, and the exposed part of the pole ear 3 after welding is covered with adhesive tape, which can prevent the burrs of the pole ear 3 from piercing the diaphragm 5 and causing a short circuit inside the battery cell, enhance the insulation between the pole pieces, and thus ensure the service life and safety performance of the battery cell.

In the description of this article, it should be understood that the terms "upper", "lower", etc., and the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

Claims

A pole piece comprises a current collector (1) and an active material layer (2), wherein the active material layer (2) is arranged on two opposite side surfaces of the current collector (1), a first groove (21) is provided on the active material layer (2) on one side, and a second groove (22) is provided on the active material layer (2) on the other side, the groove bottoms of the first groove (21) and the second groove (22) both penetrate the current collector (1), a pole ear (3) is inserted in each of the first groove (21) and the second groove (22), and the two pole ears (3) are both connected to the current collector (1), and the two pole ears (3) are connected to each other.
The pole piece according to claim 1, wherein the two pole tabs (3) are connected via a current collecting sheet (4).
The pole piece according to claim 2, wherein the pole lug (3) comprises a metal sheet (31) and an insulating glue (32) arranged on the periphery of the metal sheet (31), two of the metal sheets (31) are respectively inserted into the first groove (21) and the second groove (22), and the two metal sheets (31) are connected through the current collecting sheet (4), and the two insulating glues (32) are arranged side by side along a first direction (X), and the first direction (X) is the length direction of the pole piece when it is unfolded.
The pole piece according to claim 3, wherein the first groove (21) and the second groove (22) are arranged opposite to each other, and the size of the first groove (21) and the second groove (22) along the first direction (X) is greater than or equal to twice the size of the insulating glue (32) along the first direction (X); or,

The projections of the first groove (21) and the second groove (22) on the current collector (1) are arranged side by side along the first direction (X), and the dimensions of the first groove (21) and the second groove (22) along the first direction (X) are greater than the dimension of the insulating glue (32) along the first direction (X).
The pole piece according to claim 3 or 4, wherein the size of the pole piece satisfies at least one of the following:

The thickness of the active material layer (2) is in the range of 0.05 to 0.2 mm;

The thickness of the tab (3) is in the range of 0.1 to 0.7 mm;

The thickness of the insulating glue (32) ranges from 0.05 to 0.3 mm.
The pole piece according to any one of claims 1 to 4, wherein the first groove (21) and the second groove (22) at least penetrate one end of the active material layer (2) along the unfolded width direction of the pole piece.
The pole piece according to any one of claims 1 to 4, wherein the first groove (21) and the second groove (22) are located at non-end positions in the unfolded length direction of the pole piece.
A battery cell, the battery cell being formed by winding a diaphragm (5) and a positive electrode sheet (6) and a negative electrode sheet (7) located on both sides of the diaphragm (5), wherein the positive electrode sheet (6) and the negative electrode sheet (7) are the electrode sheets according to any one of claims 1 to 7.
The battery cell according to claim 8, wherein one of the positive electrode sheet (6) and the negative electrode sheet (7) is provided with a first groove (21) and a second groove (22) of the electrode sheet, and the other of the positive electrode sheet (6) and the negative electrode sheet (7) is provided with a first avoidance groove (23) and a second avoidance groove (24) at positions opposite to the first groove (21) and the second groove (22), respectively, and an accommodation space capable of accommodating a pole ear (3) of the pole sheet is formed between the first avoidance groove (23) and the first groove (21), and between the second avoidance groove (24) and the second groove (22) when the battery cell is wound.
The battery cell according to claim 9, wherein the thickness of the tab (3) is less than or equal to the size of the accommodation space along the second direction (Z).