CN114975864A

CN114975864A - Pole piece, electric core structure, lithium battery and electronic equipment

Info

Publication number: CN114975864A
Application number: CN202110204795.8A
Authority: CN
Inventors: 杜思红
Original assignee: Beijing Xiaomi Mobile Software Co Ltd
Current assignee: Beijing Xiaomi Mobile Software Co Ltd
Priority date: 2021-02-23
Filing date: 2021-02-23
Publication date: 2022-08-30

Abstract

The disclosure relates to the technical field of lithium batteries, and particularly provides a pole piece, a battery cell structure, a lithium battery and electronic equipment. A pole piece is applied to a wound cell, the pole piece comprising: the current collector is coated with active substances, one end of the current collector along a first direction is provided with at least two first lugs, and the at least two first lugs are sequentially arranged at intervals along a second direction of the current collector; the first direction is parallel to a width direction of the current collector, and the second direction is parallel to a length direction of the current collector; the first length of the first tab in the first direction is smaller than the second length of the first tab in the second direction. The pole piece disclosed by the invention enables the energy density of the battery to be higher, and improves the reliability and the electrochemical performance of the battery.

Description

Pole piece, electric core structure, lithium battery and electronic equipment

Technical Field

The disclosure relates to the technical field of lithium batteries, in particular to a pole piece, a battery cell structure, a lithium battery and electronic equipment.

Background

The lithium battery is taken as an energy storage device capable of being charged and discharged circularly, and is widely applied to the fields of electronic products, new energy automobiles and the like at present. For electronic equipment such as mobile phones and the like, the utilization rate of the internal space approaches to the limit, so that how to improve the energy density of a lithium battery in the limited space and further improve the endurance of the equipment is an important research direction.

Disclosure of Invention

In order to improve the energy density of a lithium battery, the embodiment of the disclosure provides a pole piece, a battery cell structure, a lithium battery and an electronic device.

In a first aspect, an embodiment of the present disclosure provides a pole piece, which is applied to a winding type battery cell, where the pole piece includes:

the current collector is coated with active substances, one end of the current collector along a first direction is provided with at least two first lugs, and the at least two first lugs are sequentially arranged at intervals along a second direction of the current collector; the first direction is parallel to a width direction of the current collector, and the second direction is parallel to a length direction of the current collector;

the first length of the first tab in the first direction is smaller than the second length of the first tab in the second direction.

In some embodiments, the ratio of the second length to the first length is 50: 1-2: 1.

in some embodiments, the at least two first tabs are die cut from the current collector.

In some embodiments, the at least two first tabs are welded to the current collector as one piece.

In some embodiments, in the second direction, the interval between two adjacent first tabs gradually increases from the winding head end to the winding tail end of the pole piece.

In some embodiments, the first length of the first tab in the first direction is 2mm to 10mm, and the second length of the first tab in the second direction is 20mm to 100 mm.

In a second aspect, an embodiment of the present disclosure provides a cell structure, including:

the battery cell structure comprises a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece are pole pieces according to any embodiment of the first aspect, the polarities of the first pole piece and the second pole piece are opposite, and the first pole piece and the second pole piece are stacked and wound to form the battery cell structure;

the second utmost point ear, the second utmost point ear includes first polarity utmost point ear and second polarity utmost point ear, first polarity utmost point ear with each first utmost point ear of first pole piece is connected, second polarity utmost point ear with each first utmost point ear of second pole piece is connected.

In some embodiments, the second tab includes a first connection portion connected with the first tab and a second connection portion adapted to be connected with an external electrode terminal; a third length of the first connection portion in the second direction is greater than a fourth length of the second connection portion in the second direction.

In some embodiments, the first polarity tab is welded to each first tab of the first pole piece and the second polarity tab is welded to each first tab of the second pole piece.

In some embodiments, the disclosed embodiments provide a lithium battery comprising:

the cell structure according to any of the embodiments of the second aspect; and

the battery cell protection plate is characterized in that the first polarity tab is connected with the first polarity terminal of the battery cell protection plate, and the second polarity tab is connected with the second polarity terminal of the battery cell protection plate.

In a fourth aspect, the disclosed embodiments provide an electronic device comprising the lithium battery according to any one of the embodiments of the third aspect.

The pole piece of the embodiment of the disclosure is applied to a winding type battery core, and the pole piece comprises a current collector, wherein an active material is coated on the current collector, the current collector is provided with at least two first tabs along one end of a first direction, and the plurality of first tabs are arranged at intervals along a second direction of the current collector. The winding type pole piece with multiple tabs can effectively reduce the internal resistance of the pole piece during charging and discharging, improve the high-rate charging capability of the lithium battery and realize the quick charging of the battery. Moreover, the first length of first utmost point ear along first direction is less than the second length along the second direction, also each first utmost point ear is great along the ascending width of pole piece length direction to when the pole piece was convoluteed, it is bigger to the dislocation error fault-tolerance of a plurality of first utmost point ears, avoids because the rosin joint problem that the utmost point ear dislocation leads to, improves electric core reliability. Meanwhile, the length of each first tab in the width direction of the pole piece is smaller, namely the length of the tab extending out of the pole piece is smaller, so that the occupation of the battery space by the head of the battery cell caused by the length of the tab is reduced, and the energy density of the battery is effectively improved.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic diagram of a pole piece structure in the related art.

Fig. 2 is a cross-sectional view of a cell structure in the related art.

FIG. 3 is a schematic illustration of a pole piece structure according to some embodiments of the present disclosure.

FIG. 4 is a schematic illustration of a pole piece structure according to some embodiments of the present disclosure.

Fig. 5 is a front view of a cell structure according to some embodiments of the present disclosure.

Fig. 6 is a schematic diagram of a second structure in accordance with some embodiments of the present disclosure.

Fig. 7 is a front view of a cell structure according to some embodiments of the present disclosure.

Detailed Description

The technical solutions of the present disclosure will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only some embodiments of the present disclosure, but not all embodiments. All other embodiments, which can be derived by one of ordinary skill in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure. In addition, technical features involved in different embodiments of the present disclosure described below may be combined with each other as long as they do not conflict with each other.

With the development of the intelligent consumer product market, the demand of more products for quick charging is more and more strong, such as electronic products, new energy vehicles, and the like. Taking a smart phone as an example, a fast charging (abbreviated as "fast charging") technology of a lithium battery is one of the key research directions of various manufacturers.

Traditional lithium battery cell structure includes coiling formula and lamination formula, because lamination formula electricity core stacks up positive negative pole piece and diaphragm counterpoint and forms, and the process is complicated, consuming time long, consequently often more adoption coiling formula electricity core in intelligent electronic product. For the winding type cell structure, the positive pole piece and the negative pole piece are a whole piece of winding type pole piece, the number of the pole lugs of the pole pieces is increased, the pole pieces among all the pole lugs can be connected in parallel, the internal resistance of the battery is greatly reduced, the high-rate charging capability of the battery is improved, the large-current constant-current charging time is obviously reduced, and the winding type cell structure is one of necessary technical schemes for realizing quick charging.

For example, fig. 1 shows a structure of a multi-tab pole piece in the related art, and as shown in fig. 1, the pole piece is exemplified by a positive pole piece 10, and a negative pole piece is similar thereto, and will not be separately described. The electrode plate 10 includes a current collector, the current collector of the positive electrode plate is generally aluminum foil, the current collector can be coated with active material on one side or both sides, the active material coated on the positive electrode plate can be lithium cobaltate LiCoO ₂ Lithium manganate LiMn ₂ O ₄ Lithium iron phosphate LiFePO ₄ And the like. It can be understood by those skilled in the art that if the electrode sheet is a negative electrode sheet, the current collector may generally adopt copper foil, the current collector may also be coated with active material on one side or both sides as required, and the active material coated on the negative electrode sheet may generally be graphite or lithium titanate Li ₂ TiO ₃ And the like.

With reference to fig. 1, the pole piece 10 is a winding type pole piece, and therefore the length direction (x direction) is greater than the width direction (y direction), so that after being laminated with the negative pole piece and the separator, the pole piece can be wound along the length direction to form a multilayer cell structure.

A plurality of tabs 20 extending out of the pole piece are disposed on one side of the pole piece 10 in the width direction, and the tabs 20 are sequentially disposed at intervals in the length direction. Because pole piece 10 length is longer, if adopt unipolar ear structure, the position internal resistance that is farther away from utmost point ear is bigger, and it is bigger that generate heat during the electric core charges to limit the charge rate of battery. And the structure of the multi-pole lug enables different pole piece positions to form a parallel structure, so that the internal resistance of the battery is greatly reduced, the charging rate of the battery cell is improved, and the quick charging with higher multiplying power is realized. As shown in fig. 1, in order to ensure the overcurrent capability of each tab, the tab 20 often needs to extend out of the tab by a long length, that is, the length h of the tab 20 in the y direction is often greater than the length w in the x direction.

After the pole piece shown in fig. 1 is wound and packaged, the cross-sectional structure of the pole piece is as shown in fig. 2, a plurality of tabs 20 of the pole piece 10 need to be welded with a positive tab 30 after being bent for a second time, the positive tab 30 extends out of the cell structure after the cell structure is packaged by an aluminum-plastic film 40, the positive tab 30 serves as a positive electrode of the cell, and is welded with a positive terminal on a battery protection board, for example, and a complete lithium battery can be formed after being packaged again. It will be understood by those skilled in the art that the present disclosure is not described in detail.

It can be seen that the bent structure of the tabs 20 at the head of the pole piece 10 greatly occupies the head space of the battery core, so that an inert space without active materials is formed in the head space, and the energy density of the battery is greatly reduced.

In addition, the inventor also finds that the reliability and the electrochemical performance of the cell structure in the related art are poor. It has been found through research that, since the plurality of tabs 20 are limited by the machining and winding processes during the winding process, the plurality of tabs 20 are prone to be misaligned in the x direction (the direction perpendicular to the y axis and the z axis in fig. 2), that is, the plurality of tabs 20 cannot be perfectly aligned. Therefore, when the tabs 20 are bent and welded for the second time, the cold joint condition easily occurs on part of the tabs 20, and especially under the condition that the battery cell is impacted or falls, the welding connection structure of part of the tabs 20 fails, so that the internal resistance of the battery cell is increased, and the reliability and the electrochemical performance of the battery are affected.

According to the multi-tab pole piece structure in the related art, the head space of the battery cell is largely occupied by the small tabs, the space of active substances is greatly reduced, and the energy density of the battery is low. Moreover, after the pole piece is wound, the pole piece is limited by processing and winding processes, and dislocation errors are easy to occur among the small pole lugs, so that partial small pole lugs are subjected to insufficient welding during welding, and the reliability and the electrochemical performance of the battery are influenced.

Based on the defects in the related art, the embodiments of the present disclosure provide a pole piece, a cell structure, a lithium battery, and an electronic device, so as to improve the energy density, reliability, and electrochemical performance of the battery.

In a first aspect, the present disclosure provides a pole piece, which is applied to a winding type cell structure. It is to be understood that the pole piece of the embodiments of the present disclosure may be a positive pole piece, and may also be a negative pole piece, which is not limited by the present disclosure.

The pole piece comprises a current collector, and active substances are coated on the current collector. For example, in one example, the electrode sheet is a positive electrode sheet, the current collector of the electrode sheet can be an aluminum foil, which can be coated with an active material on one or both sides, and the active material can be lithium cobaltate LiCoO ₂ Lithium manganate LiMn ₂ O ₄ Lithium iron phosphate LiFePO ₄ And the like. For another example, in another example, the electrode sheet is a negative electrode sheet, the current collector of the electrode sheet may be a copper foil, which may be coated with an active material on one or both sides, and the active material may be graphite or lithium titanate Li ₂ TiO ₃ And the like.

The mass flow body is equipped with two at least first utmost point ears along the one end of first direction, and the first direction is on a parallel with the width direction of the mass flow body, also is provided with a plurality of first utmost point ears in one of them side of mass flow body width direction both sides promptly to first utmost point ear stretches out along the width direction of the mass flow body. Moreover, a plurality of first utmost point ears are setting up along the second direction interval in proper order, and the second direction is on a parallel with the length direction of mass flow body, also means a plurality of first utmost point ears set up along mass flow body length direction interval in proper order.

For the wound pole piece, the spacing distance between two adjacent tabs should be increased in sequence, because the wound perimeter of the pole piece is larger and larger when the pole piece is wound, and the spacing distance should be gradually increased in order to ensure that the tabs can be aligned. It will be appreciated by those skilled in the art that the present disclosure is not described in detail herein.

In an embodiment of the present disclosure, a first length of the first tab in the first direction is less than a second length of the second tab in the second direction. That is, to each first utmost point ear of pole piece, it stretches out in the length of pole piece width direction shorter, and electric core structure need not both to carry out the secondary to a plurality of first utmost point ears when the encapsulation like this and buckles, simplifies the encapsulation technology, can effectively reduce again first utmost point ear to the occupation of electric core head space, improves the energy density of battery. Meanwhile, for each first tab of the pole piece, the length of the first tab along the length direction of the pole piece is longer, so that the flow area of the first tab can still meet the design requirement although the extension length of the first tab is reduced. And because the length of the first pole lug along the length direction of the pole piece is longer, when the battery cell structure is packaged, the plurality of first pole lugs have larger overlapping fault-tolerant areas, and under the same process and winding errors, the first pole lugs can have larger welding areas, so that the rosin joint risk is greatly reduced, and the reliability and the electrochemical performance of the battery cell are improved.

Therefore, the pole piece of the embodiment of the present disclosure adopts a winding pole piece structure with multiple tabs, so that the internal resistance of the pole piece during charging and discharging can be effectively reduced, the high-rate charging capability of the lithium battery is improved, and the rapid charging of the battery is realized. And moreover, the occupation of the lug on the head space of the battery cell is reduced, the energy density of the battery is improved, and the reliability and the electrochemical performance of the battery are improved.

Fig. 3 illustrates a pole piece structure in some embodiments of the present disclosure, which is further described below in conjunction with fig. 3.

As shown in fig. 3, in the present embodiment, the pole piece 100 includes a current collector and a tab 200. The mass flow body can be copper foil or aluminium foil, and to coiling formula electric core, the mass flow body often is rectangle sheet structure, and its length direction is greater than width direction to can follow the length direction and coil into the multilayer.

For convenience of description and understanding, the "first direction" according to the present disclosure is defined hereinafter as a width direction of the current collector, i.e., a y direction shown in fig. 3; defining the "second direction" described in the present disclosure as the length direction of the current collector, i.e., the x direction shown in fig. 3; defining a "first length" of the first tab 200 as a length h of the first tab 200; the "second length" of the first tab 200 is defined as the width w of the first tab 200. This will be explained in the following embodiments.

With continued reference to fig. 3, it can be seen that a plurality of first tabs 200 are disposed on one side of the pole piece 100 in the width direction (y direction), and the plurality of first tabs 200 are sequentially disposed at intervals along the length direction (x direction) of the pole piece 100. In the example of fig. 2, four first tabs 200 are shown, and those skilled in the art will appreciate that the pole pieces of the disclosed embodiments do not limit the number of first tabs 200, but may be any other number suitable for implementation.

In some embodiments, as shown in fig. 4 (a), the first tab 200 may be integrally die-cut with the current collector 110. That is, an integrated aluminum foil or copper foil is punched in the shape shown in fig. 4 (a), and the current collector 110 is formed at the main body portion thereof and the first tab 200 is formed at the protruding portion thereof. Then, only one side or both sides of the current collector 110 are coated with active materials, and the first tabs 200 are not coated with active materials, so that a complete pole piece can be formed.

In other embodiments, as shown in fig. 4 (b), the first tab 200 may be formed by welding separately from the current collector 110. That is, the current collector 110 is formed by punching an aluminum foil or a copper foil, and each of the first tabs 200 is fixedly disposed at one side of the current collector 110 by a welding process or the like. Then, only one side or both sides of the current collector 110 are coated with active materials, and the first tabs 200 are not coated with active materials, so that a complete pole piece can be formed.

As shown in fig. 3, in the disclosed embodiment, the width w of each first tab 200 is greater than the protrusion length h. In some embodiments, the ratio w/h of the width w to the length h of the first tab 200 is 50: 1-2: 1.

for example, in some examples, taking a conventional smartphone battery as an example, the width w of the first tab of the pole piece may range from 20mm to 100mm, and the protrusion length h may range from 2mm to 10 mm.

In some embodiments, the spacing between adjacent tabs increases gradually in the direction from the winding head end to the winding tail end of the pole piece 100.

As shown in fig. 3, the winding direction of the pole piece 100 is the longitudinal direction x. The winding head end refers to the end of the pole piece 100 that is on the inner core when wound, i.e., the left end in fig. 3. The winding end refers to the end of the pole piece 100 that is located on the outer layer when wound, i.e., the end on the right in fig. 3. Since the winding radius of the pole piece 100 is gradually increased during the winding process, in order to ensure that the first tabs 200 can be aligned in the x direction after the winding process, the distance d between two adjacent first tabs 200 is set ₁ 、d ₂ 、d ₃ It should also be gradually increased.

In some embodiments, the cell structure may be a full tab structure, that is, for a single positive plate or negative plate, one tab is provided for each layer of winding, that is, each winding structure includes two tabs.

In other embodiments, the cell structure may be a half-tab structure, that is, for a single positive electrode sheet or negative electrode sheet, one tab is disposed for each winding.

For the tab spacing arrangement of the winding structure in the above embodiment, the technology in the art can be understood and fully implemented in combination with the related technology, and the detailed description of the disclosure is omitted.

In a second aspect, an embodiment of the present disclosure provides an electrical core structure, where the electrical core structure includes a first pole piece and a second pole piece, and both the first pole piece and the second pole piece adopt the pole piece structure in any one of the embodiments of the first aspect.

In some embodiments, the first and second pole pieces are of opposite polarity. For example, in one example, the first pole piece is a positive pole piece and the second pole piece is a negative pole piece. For another example, in another example, the first pole piece is a negative pole piece and the second pole piece is a positive pole piece. The present disclosure is not so limited.

The first pole piece and the second pole piece are wound in a stacked mode to form a wound battery cell structure. Of course, those skilled in the art can understand that a diaphragm is further disposed between the first pole piece and the second pole piece, and the battery cell structure may be packaged by an aluminum plastic film and then filled with an electrolyte, which is not described in detail in this disclosure.

Fig. 5 shows a front view of the cell structure after the first pole piece and the second pole piece are wound. As shown in fig. 5, after the first and second pole pieces are wound, the head of the cell structure includes a plurality of positive first tabs 210 and a plurality of negative first tabs 220 respectively located at the left and right sides of the cell. During subsequent packaging, the plurality of positive first tabs 210 are used for being welded with the positive tabs, and the plurality of negative first tabs 220 are used for being welded with the negative tabs.

It can be seen that each first utmost point ear in this disclosed embodiment, because width w is great, even consequently there is certain dislocation error between each first utmost point ear, still can guarantee to have great welding area, the risk of rosin joint appears in the follow-up welding process of greatly reduced, improves battery reliability and electrochemical performance.

The electric core structure of the present disclosure further includes a second tab, the second tab includes a first polarity tab and a second polarity tab, that is, a positive tab and a negative tab, the positive tab is welded with the plurality of positive first tabs 210, and the negative tab is welded with the plurality of negative first tabs 220. Thus, after the cell is packaged, the positive electrode tab and the negative electrode tab serve as positive and negative terminals for connecting the cell with the outside.

In some embodiments, the second tab has a T-shaped configuration. As shown in fig. 6, the second tab includes a first connection portion 310 and a second connection portion 320, and a third length L of the first connection portion 310 in the second direction ₁ Is greater than the fourth length L of the second connection part 320 along the second direction ₂ That is, the first connection part 310 and the second connection part 320 form a second tab of a T-shaped structure.

In the embodiment of the present disclosure, the third length L of the first connection portion 310 of the T-shaped structure ₁ Substantially the same as the width w of the first tab, so that the second tab is weld-coupled to each first tab by the first coupling portion 310. The second connecting portion 320 is used to connect with an external electrode, for example, when a lithium battery is packaged, a battery protection board is often required to be disposed, and the second tab can be connected with the positive and negative terminals on the protection board by welding through the second connecting portion 320.

As shown in fig. 5 and 6, the second tab includes a positive tab and a negative tab, and the positive tab and the negative tab are both T-shaped structures as shown in fig. 6, so that the positive tab and the negative tab are respectively welded to the positive first tab 210 and the negative first tab 220 on the left and right sides, and the welded structure is shown in fig. 7. After the cell structure is packaged, the positive electrode tab and the negative electrode tab extend out of the cell structure, so that the positive electrode tab and the negative electrode tab can be respectively connected with positive and negative terminals on a battery protection plate in a welding mode.

According to the battery core structure disclosed by the embodiment of the invention, the winding type pole piece structure with multiple lugs is adopted, so that the pole piece internal resistance during charging and discharging can be effectively reduced, the high-rate charging capability of the lithium battery is improved, and the quick charging of the battery is realized. In addition, secondary bending of the tabs is not needed in the packaging process, occupation of the tabs on the head space of the battery cell is reduced, the energy density of the battery is improved, and the reliability and the electrochemical performance of the battery are improved.

In a third aspect, an embodiment of the present disclosure provides a lithium battery, which includes the battery cell structure and the battery cell protection board described in any of the above embodiments, where positive and negative electrode tabs of the battery cell structure are respectively connected to positive and negative electrode terminals on the protection board.

For the lithium battery of the present disclosure, details are not given, and those skilled in the art can understand and fully realize the lithium battery by referring to the above description and the related art, and the detailed description of the disclosure is omitted.

In a fourth aspect, the embodiments of the present disclosure provide an electronic device, which includes the lithium battery described in any of the above embodiments. The disclosed electronic device may be any device type suitable for implementation, such as a smartphone, a tablet, a laptop, a wearable device, and so on, to which the present disclosure is not limited.

Therefore, the lithium battery and the electronic device with the lithium battery in the embodiment of the disclosure adopt a winding type pole piece structure with multiple tabs, so that the pole piece internal resistance during charging and discharging can be effectively reduced, the high-rate charging capability of the lithium battery is improved, and the quick charging of the battery is realized. And moreover, the occupation of the lug on the head space of the battery cell is reduced, the energy density of the battery is improved, and the reliability and the electrochemical performance of the battery are improved.

It should be understood that the above embodiments are only examples for clearly illustrating the present invention, and are not intended to limit the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications of the present disclosure may be made without departing from the scope of the present disclosure.

Claims

1. The utility model provides a pole piece, its characterized in that is applied to coiling formula electricity core, the pole piece includes:

2. The pole piece of claim 1,

a ratio of the second length to the first length is 50: 1-2: 1.

3. the pole piece of claim 1,

the at least two first tabs are formed by punching the current collector;

alternatively, the first and second electrodes may be,

the at least two first tabs and the current collector are welded into a whole.

4. The pole piece of claim 1,

and in the second direction, the interval between every two adjacent first tabs is gradually increased from the winding head end to the winding tail end of the pole piece.

5. The pole piece of claim 1,

the first length of the first tab along the first direction is 2 mm-10 mm, and the second length of the first tab along the second direction is 20 mm-100 mm.

6. A cell structure, comprising:

a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece are the pole pieces according to any one of claims 1 to 5, the polarity of the first pole piece is opposite to that of the second pole piece, and the first pole piece and the second pole piece are wound in a stacked manner to form the cell structure;

7. The cell structure of claim 6,

the second tab comprises a first connection part and a second connection part, the first connection part is connected with the first tab, and the second connection part is suitable for being connected with an external electrode terminal; a third length of the first connection portion in the second direction is greater than a fourth length of the second connection portion in the second direction.

8. The cell structure of claim 6,

the first polar lugs are connected with the first polar lugs of the first pole piece in a welded mode, and the second polar lugs are connected with the first polar lugs of the second pole piece in a welded mode.

9. A lithium battery, comprising:

the cell structure of any of claims 6 to 8; and

10. An electronic device characterized by comprising the lithium battery according to claim 9.