CN219917514U

CN219917514U - Battery cell, cylindrical battery and battery module

Info

Publication number: CN219917514U
Application number: CN202321332959.6U
Authority: CN
Inventors: 赖永芳
Original assignee: Weilai Battery Technology Anhui Co ltd
Current assignee: Weilai Battery Technology Anhui Co ltd
Priority date: 2023-05-25
Filing date: 2023-05-25
Publication date: 2023-10-27
Anticipated expiration: 2033-05-25

Abstract

The utility model relates to the technical field of batteries, in particular to a battery cell, a cylindrical battery and a battery module, and aims to solve the problem of uneven temperature rise distribution in the existing full-tab battery cell. The battery cell is formed by winding a pole piece unit, wherein the pole piece unit comprises a pole piece and a diaphragm, the pole piece comprises a plurality of pole lugs, the pole lugs are provided with middle parts which are formed by extending along a first direction, and end parts which are connected with the middle parts and are obliquely arranged relative to the first direction; after two adjacent tab groups are bent, the end part of each tab in one tab group can be partially connected with the other tab group. The end parts can conduct adjacent tab groups, so that current can be conducted through the middle part along the radial direction and also can be conducted through the end parts along the tangential direction, the uniformity of current collection can be effectively improved, and therefore the consistency of temperature rise of the battery cell is improved, and the reliability and durability of the battery cell are improved.

Description

Battery cell, cylindrical battery and battery module

Technical Field

The utility model relates to the technical field of batteries, and particularly provides an electric core, a cylindrical battery and a battery module.

Background

The power battery is an important component of the new energy automobile, and comprises a plurality of sequentially arranged battery cells, wherein the battery cells are divided into cylindrical battery cells and square battery cells according to the shape. The battery core of the cylindrical battery is formed by laminating and winding a positive plate, a diaphragm and a negative plate, wherein the diaphragm is used for isolating the positive plate and the negative plate. The positive plate is connected with a negative electrode lug which is connected with the negative electrode of the cylindrical battery cell. The negative plate is connected with a positive electrode lug, and the positive electrode lug is connected with the positive electrode of the cylindrical battery cell. In the working process of the battery cell, the positive plate, the negative plate and the electrolyte react chemically, and electric energy is output from the positive electrode and the negative electrode of the battery cell.

In the structure of the traditional cylindrical battery cell, after the bare battery cell is wound, the negative electrode lug and the positive electrode lug are aligned along the radial arrangement of the bare battery cell so as to connect the electrode lug with the current collector for electronic transmission.

At present, the full-lug cylindrical battery cell comprises a current collector and a bare battery cell. The lugs connected with the pole pieces are uniformly arranged at a smaller interval, and the positive pole piece, the diaphragm and the negative pole piece are laminated and wound to form a bare cell. After the bare cell is wound, the lugs are lodged along the radial direction of the bare cell, so that the lugs of the single poles are overlapped with each other, then the overlapped lugs are welded with a current collector, and the current collector is connected with the negative electrode or the positive electrode of the cylindrical cell. Compared with the traditional cylindrical battery cell, the full-lug cylindrical battery cell has the advantages that the electron transmission distance is greatly reduced and the internal resistance is obviously reduced due to denser arrangement of the lugs.

The electrode tabs are stacked with each other along the radial direction, only part of the electrode tabs are welded with the current collector in the welding process of the electrode tabs and the current collector, and electron transmission between the electrode tabs which are not welded with the current collector only depends on stacked contact with each other, but the stacked compactness between the electrode tabs is different. The transmission resistance between the lugs is determined by the compactness of lamination between the lugs, so that uneven current distribution in the cylindrical battery cell can be caused, uneven temperature rise distribution of the battery cell can be caused, and the reliability of the battery cell can be reduced.

Therefore, a battery cell, a cylindrical battery and a battery module are needed to solve the problem of nonuniform temperature rise distribution in the existing full-tab battery cell.

Disclosure of Invention

The utility model aims to solve the technical problems, namely the problem of uneven temperature rise distribution in the existing battery cell.

In a first aspect, the utility model provides a battery cell, which is formed by winding a pole piece unit, wherein the pole piece unit comprises a pole piece and a diaphragm, the pole piece comprises a plurality of pole lugs, the pole lugs are provided with middle parts formed by extending along a first direction, and end parts which are connected with the middle parts and are obliquely arranged relative to the first direction; after two adjacent tab groups are bent, the end part of each tab in one tab group can be partially connected with the other tab group.

In the specific embodiment of the battery cell, the tab group satisfies that the projection length of the end part in the first direction is larger than the distance between two adjacent tab groups.

In the specific embodiment of the foregoing electrical cell, the angle between the middle portion and the end portion is 120 ° to 165 °.

In a specific embodiment of the foregoing electrical cell, the length of the intermediate portion in the first direction is 5mm to 10mm.

In a specific embodiment of the above cell, the length of the end portion in the oblique direction is 3mm to 8mm.

In the specific embodiment of the battery cell, the interval between two adjacent middle parts is 0.05mm to 5mm.

In the specific embodiment of the battery cell, the tab groups are uniformly spaced along the circumferential direction of the battery cell.

In a specific embodiment of the above battery cell, the end portion of the battery cell is provided with a plurality of tab groups, and the tab groups include at least 10 middle portions that are bent and stacked.

In a second aspect, the present utility model provides a cylindrical battery comprising the above-described cell.

In a third aspect, the present utility model provides a battery module comprising a case and the above-described cylindrical battery disposed in the case.

Compared with the prior art, the utility model has the following beneficial effects:

the battery cell provided by the utility model is formed by winding a pole piece unit, wherein the pole piece unit comprises a pole piece and a diaphragm, the pole piece comprises a plurality of pole lugs, and the pole lugs are provided with middle parts formed by extending along a first direction and end parts which are connected with the middle parts and are obliquely arranged relative to the first direction; after two adjacent tab groups are bent, the end part of each tab in one tab group can be partially connected with the other tab group. The end part can conduct the adjacent tab group, even if a part of tabs in a single tab group are poor in contact tightness and cause resistance to rise, electrons flowing through the tab group can flow to the adjacent tab group through the end part, so that current can be conducted through the middle part in the radial direction or the end part in the tangential direction, the uniformity of current collection can be effectively improved, and the consistency of temperature rise of the battery core is improved, so that the reliability and the durability of the battery core are improved.

Drawings

Preferred embodiments of the present utility model are described below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a cell provided by the present utility model;

FIG. 2 is a cross-sectional view of a pole piece unit provided by the present utility model;

FIG. 3 is a schematic view of the pole piece of the present utility model after being unfolded;

fig. 4 is a schematic view of a single-row tab stack provided by the present utility model.

Reference numerals illustrate:

2. a tab; 21. an intermediate portion; 22. an end portion; 3. a battery cell; 31. a positive plate; 32. a first diaphragm; 33. a negative electrode sheet; 34. a second diaphragm; d. a welding area; z, a first direction; y, second direction.

Detailed Description

Preferred embodiments of the present utility model are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present utility model, and are not intended to limit the scope of the present utility model.

It should be noted that, in the description of the present utility model, terms such as "upper," "lower," "left," "right," "inner," "outer," and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Furthermore, it should be noted that, in the description of the present utility model, unless explicitly specified and limited otherwise, the terms "mounted," "configured," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected, can be indirectly connected through an intermediate medium, and can also be communicated with the inside of two elements. The specific meaning of the above terms in the present utility model can be understood by those skilled in the art according to the specific circumstances.

In order to solve the problem of uneven temperature rise distribution in the existing battery cell, the utility model provides a battery, which is particularly a cylindrical battery. The negative electrode current collector, the battery cell and the positive electrode current collector are sequentially arranged in the shell from top to bottom, and electrolyte is injected into the shell to enable the battery cell to be soaked in the electrolyte.

As shown in fig. 1 and 2, the battery cell 3 is wound by a pole piece unit, the pole piece unit includes a positive pole piece 31, a first diaphragm 32, a negative pole piece 33, and a second diaphragm 34 that are sequentially stacked, the first diaphragm 32 can isolate the positive pole piece 31 and the negative pole piece 33 to avoid short circuit, and after the pole piece unit is wound, the second diaphragm 34 can isolate the positive pole piece 31 of the pole piece unit and the negative pole piece 33 of an adjacent pole piece unit to avoid short circuit.

The pole piece units are unfolded to form a first direction Z and a second direction Y, wherein the first direction Z is the width direction of the pole piece units, the second direction Y is the length direction of the pole piece units, and the first direction Z and the second direction Y are mutually perpendicular. After the pole piece units are wound, the first direction Z is the height direction of the battery cell 3, and the second direction Y is the circumferential direction of the battery cell 3.

The positive plate 31 includes a plurality of positive tabs, and the positive tabs are located at one side of the positive plate 31 along the first direction Z; the negative electrode tab 33 includes a plurality of negative electrode tabs, the negative electrode tabs are located at one side of the negative electrode tab 33 along the first direction Z, and the positive electrode tabs and the negative electrode tabs are located at two sides of the electrode tab unit along the first direction Z, respectively. The positive electrode tab and the negative electrode tab are collectively referred to as tab 2.

Specifically, the plurality of tabs 2 are arranged on the pole piece at intervals, after the pole piece is wound, the plurality of tabs 2 are distributed on the same or different turns, and a plurality of tabs which are positioned on different turns and are mutually laminated are defined as tab groups. The negative electrode side is a negative electrode lug group, the negative electrode lug group is composed of negative electrode lugs, the positive electrode side is a positive electrode lug group, and the positive electrode lug group is composed of positive electrode lugs. The number of negative electrode tab groups and the number of positive electrode tab groups may be different or the same. Specifically, the number of negative electrode tab groups is the same as the number of positive electrode tab groups, and is twelve. The plurality of positive tab groups or the plurality of negative tab groups are arranged at intervals along the circumferential direction of the battery cell 3, and are preferably uniformly arranged along the circumferential direction of the battery cell 3 in this embodiment. The tab 2 is bent inward or outward along the radial direction of the cell, and is preferably bent inward in this embodiment. Any two adjacent tabs 2 of the tab group are stacked and connected together.

The tab group is welded with the current collector so as to facilitate electron transmission through the current collector; specifically, the tab group on the negative electrode side is welded with the negative electrode current collector, and the tab group on the positive electrode side is welded with the positive electrode current collector. The battery cell with the structure is called a full-tab battery cell, electrons can be transmitted through the current collector and the densely arranged tabs 2 in the process of electrochemical reaction of the positive electrode plate 31 and the negative electrode plate 33 in the electrolyte, so that the transmission path of the electrons on the pole piece is shortened, the transmission path of the electrons is shortened, the internal resistance of the battery cell 3 is reduced, and the performance of the battery cell 3 is improved.

As shown in fig. 3, the tab 2 has an intermediate portion 21 extending in the first direction Z, and an end portion 22 connected to the intermediate portion 21 and disposed obliquely to the first direction Z. After the pole piece units are wound, the root part, connected with the middle part 21, of the pole piece is bent along the radial direction of the battery core 3, generally inwards, and after bending, the middle parts 21 of the pole lugs 2 in each pole lug group are arranged in a stacked manner, and the end parts 22 of each pole lug 2 can be connected with the pole lugs 2 in the adjacent pole lug group. Specifically, after two adjacent tab groups are bent, the end 22 of the tab 2 in one tab group can be partially connected with the other tab group, so that the end 22 can conduct the two tab groups. After the end part 22 conducts two adjacent tab groups, even if the resistance rises due to poor contact tightness between a part of tabs 2 in a single tab group, electrons flowing through the tab group can be shunted to the adjacent tab group through the end part 22, so that current can be conducted through the middle part 21 in the radial direction or the end part 22 in the tangential direction, the uniformity of current collection can be effectively improved, and the consistency of the temperature rise of the battery core is improved, so that the reliability and the durability of the battery core are improved.

Specifically, the length of the projection of the end 22 in the first direction Z is greater than the spacing between two adjacent tab groups, so that the end 22 can be connected to the adjacent tab groups.

The welding position of the current collector and the tab 2 is preferably the intersection area of the end 22 and the adjacent tab group so as to improve the contact stability of the end 22 and the adjacent tab group.

After the pole piece is unfolded, the end parts 22 on the pole lugs 2 are arranged in parallel, so that the shapes of the pole lugs 2 are more regular and orderly, and a die for die cutting is convenient to design so as to carry out mass production.

Wherein the end portion 22 and the intermediate portion 21 are arranged in an L-shape, i.e. the end portion of the end portion 22 is connected to the second end of the intermediate portion 21. Of course, in other examples, the end portion 22 and the intermediate portion 21 may be provided in a T-shaped arrangement, i.e., the second end of the intermediate portion 21 may be connected to the intermediate portion of the end portion 22, without departing from the principles of the present utility model.

The middle portion 21 is generally bent radially inward, and the number of layers stacked in the middle portion 21 in the tab group decreases as the middle portion approaches the outer side of the cell 3. After the middle portions 21 in each tab group are laminated, the lamination number of the outermost middle portions 21 is 1, and the lamination number of the innermost middle portions 21 is the largest. The greater the length of the intermediate portion 21, the greater the number of lamination layers of the innermost intermediate portion 21 in the tab group, and in a limit case, the number of lamination layers thereof may be the same as the number of tabs 2 in the tab group. Of course, in most cases, the number of lamination layers of the innermost middle portion 21 is smaller than the number of tabs 2 in the tab group, and specifically, when the length of the tab 2 is smaller than the radius of the cell 3, the number of the innermost tabs 2 is smaller than the number of tabs 2 in the tab group.

The intermediate portions 21 in the tab groups have a certain gap between adjacent intermediate portions 21 before lamination. As shown in fig. 4, after the middle portions 21 in the tab group are laminated, due to a certain gap between adjacent middle portions 21, the thickness of the laminated middle portions 21 in the tab group gradually increases along the bending direction, then tends to be stable, and finally gradually decreases. The thickness of the middle part 21 is equal to the thickness of the single-layer middle part 21 at the initial end and the final end of the tab group, the number of the middle part 21 layers can be stabilized above a certain number in the region of the middle part of the tab group, and the thickness of the region of the middle part of the tab group is not less than a preset value on the premise that the thickness of the middle part 21 is certain. The current collector is welded in the area (namely, the area of the middle part of the tab group) where the thickness of the tab group is not smaller than a set value, so that the tab group cannot be burnt through during welding, and the stability of current conduction can be guaranteed. The region of the middle portion of the tab group is referred to as a welding region d. At least a part of the intermediate portion 21 is laminated in the welding zone d in a number of layers not smaller than the set value, that is, the intermediate portion 21 is laminated in a number of layers not smaller than the set value at any point in the welding zone d. On the premise that the thickness of the intermediate portion 21 is constant, the number of layers stacked in the intermediate portion 21 is not smaller than the set value in the land d, which means that the thickness of the land d is not smaller than the set value.

The length of the middle portion 21 in the first direction Z should not be too large, otherwise, the middle portion 21 is easy to deform during bending, such as folding, reverse insertion, and the like, which affects the performance of the battery cell 3. Of course, the height of the intermediate portion 21 should not be too short, which would otherwise affect the length of the weld zone d. Specifically, the length of the intermediate portion 21 in the first direction Z is 5mm to 10mm, specifically 7mm in the example of the present utility model, and the length of the land d is 6mm.

The longer the length of the end 22 in the oblique direction, the more conducive it is to connect two adjacent tab groups, but at the same time, the more easily it is deformed, and the more folded or inverted. Of course, the length of the end 22 cannot be too short, otherwise, the end 22 is difficult to connect to the adjacent tab group after the tab 2 is bent. The length of the end portion 22 in the oblique direction is related to the pitch of the adjacent tab groups and the angle between the end portion 22 and the intermediate portion 21. The pitch of the adjacent tab groups is related to the arrangement rule of the tabs 2, and the smaller the pitch of the adjacent tab groups is, the shorter the length of the end portion 22 in the oblique direction can be set. The closer the angle between the end portion 22 and the intermediate portion 21 is to 90 ° - α/2, the shorter the length of the end portion 22 in the oblique direction can be set, assuming that the angle between the two tab groups is α. It should be noted that, in the case that the length of the end portion 22 in the oblique direction and the angle between the end portion 22 and the middle portion 21 are set reasonably, for two adjacent tabs 2 after the pole piece is unfolded, the end portion 22 of one tab 2 can be directly connected with the middle portion 21 of the other tab 2. Of course, in other embodiments, two adjacent tabs 2 cannot be directly connected after the pole piece is unfolded, and the end 22 of one tab 2 can be connected to another tab 2 in the adjacent tab group.

Specifically, the length of the end 22 in the oblique direction is 3mm to 8mm, in particular 5mm in the example of the utility model. The angle between the end portions 22 and the intermediate portion 21 is 120 ° to 165 °, in particular 150 ° in the example of the utility model.

The number of layers of the middle part 21 in the tab group needs to meet certain requirements, specifically, the tab group comprises at least 10 middle parts 21 which are bent and stacked, so as to ensure that the thickness of the middle parts 21 stacked along the radial direction of the battery core 3 meets the welding requirements. If the thickness of the intermediate portion 21 stacked in the radial direction is thin, the heat insulation effect thereof is poor, and the high temperature generated during the welding process of the current collector and the tab 2 may deform the first diaphragm 32 or the second diaphragm 34 in the pole piece unit, thereby affecting the performance and safety of the battery cell 3.

In addition, the tensile capacity of the tab 2 should be greater than 13.8N/mm ² The transverse tensile strength is more than 230MPa. Meanwhile, the reliability of impact resistance and the fatigue resistance of vibration are ensured after the battery cell 3 is assembled. The first direction Z is the height direction of the battery cell 3, and the third direction m and the fourth direction n are two radial directions of the battery cell 3 perpendicular to each other. Specifically, at 25 ℃, and with the battery cell 3 at 100% soc (state of charge), the positive and negative directions Z direction are respectively impacted 5 times by the parameters of 15ms for the standard pulse time and 50G for the standard pulse peak acceleration, and then the positive and negative directions m direction and the positive and negative direction n direction are respectively impacted 3 times by the parameters of 6ms for the standard pulse time and 50G for the standard pulse peak acceleration; after standing for 30 minutes, the parameters of the standard pulse time of 6ms and the standard pulse peak acceleration of 50G are continuously impacted 7 times along the positive direction and the negative direction of the m direction and the positive direction and the negative direction of the n direction, and if the tab 2 is not broken, the impact resistance reliability of the battery cell 3 is proved to meet the requirement. And under the condition of 25 ℃, and the battery cell 3 is in 100% SOC (state of charge), the battery cell 3 is subjected to vibration test, the test directions are Z direction, n direction and m direction in sequence, the test time is 21 hours, and if the tab 2 has no plastic deformation, the fatigue resistance of the battery cell 3 in vibration is proved to meet the requirements.

The smaller the interval between two adjacent lugs 2 is, the denser the arrangement of the lugs 2 is, but the larger the occupied area of the lugs 2 after bending is, so that the flow channel of the electrolyte is reduced, and the liquid injection time is prolonged. Therefore, the distance between two adjacent lugs 2 should be designed reasonably to ensure that the liquid injection time is less than 20min. Specifically, taking the positive plate as an example, after the positive plate is unfolded, the thickness of a single tab 2 is about 12 μm, the distance between two adjacent tabs 2 is 0.05mm to 5mm, and in the example of the utility model, the distance between two adjacent tabs 2 is 1mm.

The working principle of the utility model is as follows: the pole piece units are wound to form a column shape, the negative pole lugs are inwards bent and laminated to form a lug group at the negative side, and the positive pole lugs are inwards bent and laminated to form a lug group at the positive pole lug. The end 22 of each tab 2 in a tab set is capable of contacting a tab 2 in an adjacent tab set. The end 22 can conduct adjacent tab groups, even if the resistance rises due to poor contact tightness between a part of tabs 2 in a single tab group, electrons flowing through the tab groups can be shunted to the adjacent tab groups through the end 22, so that current can be conducted through the middle part 21 in the radial direction or the end 22 in the tangential direction, the uniformity of current collection can be effectively improved, and the consistency of the temperature rise of the battery core is improved, so that the reliability and the durability of the battery core are improved.

The embodiment also discloses a battery module, which comprises a box body and a plurality of cylindrical batteries arranged in the box body. The battery module can be applied to a vehicle, is arranged on a vehicle body, can be a fuel vehicle, supplies power for starting and electricity utilization facilities of the vehicle, and is used as a power source of the vehicle except for supplying power for the electricity utilization facilities if the battery module is a plug-in hybrid vehicle, a fuel-electric hybrid vehicle or an electric vehicle.

Thus far, the technical solution of the present utility model has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present utility model is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present utility model, and such modifications and substitutions will fall within the scope of the present utility model.

Claims

1. A battery cell wound from a pole piece unit comprising a pole piece and a diaphragm, characterized in that the pole piece comprises a plurality of tabs (2), the tabs (2) having an intermediate portion (21) formed to extend in a first direction, and an end portion (22) connected to the intermediate portion (21) and disposed obliquely with respect to the first direction; after two adjacent tab groups are bent, one tab group can be partially connected with the other tab group at the end part (22) of the tab (2).

2. The cell of claim 1, wherein the tab sets satisfy a projection length of the end portion (22) in the first direction that is greater than a pitch of adjacent two of the tab sets.

3. The cell according to claim 1, characterized in that the angle between the intermediate portion (21) and the end portions (22) is 120 ° to 165 °.

4. A cell according to claim 1, characterized in that the length of the intermediate portion (21) in the first direction is 5-10 mm.

5. A cell according to claim 1, characterized in that the length of the end portion (22) in the oblique direction is 3-8 mm.

6. A cell according to claim 1, characterized in that the spacing between adjacent two of the intermediate portions (21) is 0.05mm to 5mm.

7. The cell of claim 1, wherein the tab groups are uniformly spaced apart along the circumference of the cell.

8. The cell according to claim 7, wherein an end portion of the cell is provided with a plurality of the tab groups including not less than 10 middle portions (21) which are folded and laminated.

9. A cylindrical battery comprising a cell as claimed in any one of claims 1 to 8.

10. A battery module comprising a case and the cylindrical battery according to claim 9 disposed in the case.