Pole group and battery cell
By optimizing the electrode group structure and using a pole ear assembly stacked with multiple conductive parts, the problem of inadequate bending caused by high hardness of the pole ear is solved, the risk of short circuit and welding defect rate is reduced, and the production efficiency of the battery cell is improved.
Patent Information
- Application Number
- CN202510492264.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-18
- Publication Date
- 2025-07-08
AI Technical Summary
The number of electrode ears is too large and the hardness is large, which leads to inadequate bending of the electrode ears, which increases the risk of overlapping short circuit between the electrode ears and the shell, and the welding defect rate between the cover plate and the shell increases, affecting the production efficiency of the battery cell.
The electrode assembly is adopted, wherein the electrode ear assembly includes a plurality of conductive parts stacked in the arrangement direction, and a predetermined number of electrode ears replaces a single electrode ear with a larger thickness, reduces the hardness of the electrode ears, and optimizes the bent parts and connection methods of the electrode ears to ensure stable overlap between the electrode ears and the shell and good welding of the cover plate to the shell.
It reduces the risk of inadequate bending of the electrode ear, reduces the possibility of short-circuiting of the electrode ear and the shell, reduces the defective rate of welding between the cover plate and the shell, and improves the production efficiency of the battery cell.
Smart Images
Figure CN120280531A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and particularly to a pole group and a battery cell. Background Art
[0002] Lithium-ion batteries have been widely used in various fields of life and production such as consumer electronics, electric vehicles, aerospace, medical equipment, and energy storage due to their advantages of high working voltage, high energy density, fast charging speed, and good environmental performance.
[0003] A battery cell generally includes a pole group, an electrolyte, a cover plate, a housing, an end plate, an insulating structure, etc. Among them, the cover plate and the housing are usually fixed by laser welding to form a sealed space with a certain structural strength to protect the pole group. The cover plate is generally integrated with functional areas such as a pole column, an explosion-proof valve, a liquid injection hole, etc. The pole group is fixed by laser welding the pole ear to the pole column base of the cover plate to realize the electrical connection between the pole group and the pole column, thereby leading the current inside the battery cell to the outside of the housing. The pole ear is formed by bonding multiple layers of foil materials together through ultrasonic welding.
[0004] With the continuous increase in the capacity of single batteries, especially in the energy storage field, single batteries with capacities of 660Ah, 730Ah, or 770Ah and charge rates that can reach 5C or 6C have begun to appear. This poses very high requirements for the overcurrent of the internal structure of the battery cell. The number of foil layers included in the pole ear reaches 80 layers, 90 layers, 100 layers or even more layers. At this time, the thickness of the pole ear can usually reach more than 1.3mm, which poses great challenges to the bending of the pole ear and the assembly of the cover plate during the manufacturing process of the battery cell. Due to the large number of layers and high hardness of the pole ear, the pole ear cannot be bent in place, which increases the risk of short circuit between the pole ear and the housing. At the same time, the pole ear not being bent in place makes it difficult to align the cover plate with the housing during the assembly process, which will lead to an increase in the welding defect rate between the cover plate and the housing, seriously affecting the production efficiency of the battery cell. Summary of the Invention
[0005] In view of this, this application provides a pole group and a battery cell to solve the problems that the number of layers of the pole ear is too large, the hardness is high, and the pole ear cannot be bent in place, which increases the risk of short circuit between the pole ear and the housing. At the same time, the pole ear not being bent in place makes it difficult to align the cover plate with the housing during the assembly process, which will lead to an increase in the welding defect rate between the cover plate and the housing, seriously affecting the production efficiency of the battery cell.
[0006] According to one aspect of this application, a pole group is provided. The pole group includes a pole group body and a pole ear assembly. The pole group body includes two connection ends that face away from each other in the length direction of the pole group. The pole ear assembly includes a predetermined number of pole ears. The predetermined number is greater than or equal to two. Each pole ear includes a plurality of conductive members stacked along the arrangement direction, and adjacent conductive members are connected. The predetermined number of the tabs in the tab assembly are connected to the same connection end, and the predetermined number of the tabs in the tab assembly are used to be connected to the same pole.
[0007] Preferably, the pole lug includes a first connecting portion and a second connecting portion connected to each other, the first connecting portion is connected to the pole group body, the predetermined number of the first connecting portions in the predetermined number of the pole lugs are arranged at intervals along the thickness direction of the pole group, and the predetermined number of the second connecting portions in the predetermined number of the pole lugs are connected.
[0008] Preferably, the tab further includes a connecting portion, two ends of which are respectively connected to the first connecting portion and the second connecting portion, the connecting portion is bent, and an extending direction of the first connecting portion intersects with an extending direction of the second connecting portion.
[0009] Preferably, the pole ear also includes a first bending portion, a second bending portion and a transition portion connected to each other, the first bending portion, the transition portion and the second bending portion are connected in sequence, the end of the first bending portion away from the transition portion is connected to the first connection portion, the end of the second bending portion away from the transition portion is connected to the second connection portion, the middle portion of the first bending portion protrudes relative to the two ends of the first bending portion, and the middle portion of the second bending portion protrudes relative to the two ends of the second bending portion.
[0010] Preferably, a plane perpendicular to the width direction of the pole group is defined as a reference plane; The angle between the surface of the transition part facing the pole group body and the reference plane is 25 degrees to 75 degrees; and / or the angle between the surface of the transition part facing away from the pole group body and the reference plane is 25 degrees to 75 degrees.
[0011] Preferably, in one of the pole lug assemblies, the predetermined number of the second connecting portions in the predetermined number of the pole lugs are stacked along the length direction of the pole group.
[0012] Preferably, the pole group includes two pole lug assemblies, the two pole lug assemblies are respectively connected to two ends of the pole group body in the length direction, and the pole lugs in the two pole lug assemblies are respectively connected to two pole posts.
[0013] Preferably, the dimension of the tab in the arrangement direction is less than or equal to 0.5 mm.
[0014] According to another aspect of the present application, a battery cell is provided, the battery cell comprising the above-mentioned electrode group.
[0015] Preferably, the battery cell further includes a cover plate, the cover plate includes a plate body and a pole column, the pole column includes a bottom plate and a pole column body, the pole column body is fixed on a side of the bottom plate facing away from the pole group body, the bottom plate is located on a side of the plate body facing the pole group body, and the pole column body penetrates through the plate body; Two adjacent ones of the predetermined number of pole tabs are attached to each other, and the first one of the predetermined number of pole tabs close to the bottom plate is attached to the bottom plate.
[0016] In the pole group of the present application, the pole group includes a pole group body and a pole tab assembly. The pole group body includes two connection ends facing away from each other in the length direction of the pole group. The pole tab assembly includes a predetermined number of pole tabs, the predetermined number being greater than or equal to two. The pole tab includes a plurality of conductive members stacked along the arrangement direction, and adjacent conductive members are connected. A predetermined number of pole tabs in the pole tab assembly are connected to the same connection end, and a predetermined number of pole tabs in the pole tab assembly are used to be connected to the same pole column. In this way, by using a predetermined number of pole tabs to replace a relatively thick pole tab, the number of layers of a single pole tab is reduced, the hardness of the pole tab is decreased, the risk of incomplete bending of the pole tab is reduced, thereby reducing the risk of short circuit between the pole tab and the housing. At the same time, the defective rate of welding between the cover plate and the housing is reduced, and the production efficiency of the battery cell is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and thus should not be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.
[0018] Figure 1 Showing a schematic plan view of a pole group; Figure 2 Showing a schematic plan view of Embodiment 1 of a pole tab; Figure 3 Showing a schematic three-dimensional view of Embodiment 1 of a pole tab; Figure 4 Showing a schematic plan view of Embodiment 2 of a pole tab; Figure 5 Showing a schematic three-dimensional view of Embodiment 2 of a pole tab; Figure 6 Showing a partial enlarged view of the location where the welding mark is located.
[0019] Icons: 1-pole group body; 2-pole ear assembly; 21-pole ear; 211-first connecting part; 212-second connecting part; 213-connecting part; 214-first bending part; 215-second bending part; 216-transition part; 3-cover plate; 31-plate body; 32-pole column; 4-weld mark; L1-length direction; L2-width direction; L3-thickness direction. DETAILED DESCRIPTION
[0020] The following specific embodiments are provided to help the reader obtain a comprehensive understanding of the methods, devices and / or systems described herein. However, after understanding the disclosure of the present application, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be apparent. For example, the order of operations described herein is merely an example, and is not limited to the order set forth herein, but in addition to the operations that must occur in a particular order, changes that will be apparent after understanding the disclosure of the present application may be made. In addition, in order to improve clarity and brevity, descriptions of features known in the art may be omitted.
[0021] The features described herein may be implemented in different forms and should not be interpreted as being limited to the examples described herein. Rather, the examples described herein have been provided only to illustrate some of the many possible ways of implementing the methods, devices and / or systems described herein that will be apparent after understanding the disclosure of the present application.
[0022] Throughout the specification, when an element (such as a layer, a region, or a substrate) is described as being “on”, “connected to”, “bound to”, “over”, or “covering” another element, it may be directly “on”, “connected to”, “bound to”, “over”, or “covering” another element, or one or more other elements may be present between them. In contrast, when an element is described as being “directly on”, “directly connected to”, “directly bound to”, “directly over”, or “directly covering” another element, there may be no other elements present between them.
[0023] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more items.
[0024] Although terms such as "first", "second", and "third" may be used herein to describe various components, elements, regions, layers, or sections, these components, elements, regions, layers, or sections are not limited by these terms. Rather, these terms are only used to distinguish one component, element, region, layer, or section from another. Thus, a first component, element, region, layer, or section referred to in the examples described herein may also be termed a second component, element, region, layer, or section without departing from the teachings of the examples.
[0025] For ease of description, spatial relationship terms such as "above", "upper", "below", and "lower" may be used herein to describe the relationship of one element to another as shown in the figures. Such spatial relationship terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as "above" or "upper" relative to another element will then be "below" or "lower" relative to the other element. Thus, the term "above" includes both the orientation of "above" and "below" depending on the spatial orientation of the device. The device may also be positioned in other ways (e.g., rotated 90 degrees or at other orientations), and the spatial relationship terms used herein will be interpreted accordingly.
[0026] The terms used herein are for the purpose of describing various examples only and are not intended to limit the disclosure. Unless the context clearly dictates otherwise, the singular forms are also intended to include the plural forms. The terms "comprises", "comprising", and "having" list the stated features, quantities, operations, components, elements, and / or combinations thereof that exist, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.
[0027] Due to manufacturing techniques and / or tolerances, variations in the shapes shown in the figures may occur. Thus, the examples described herein are not limited to the specific shapes shown in the figures, but include changes in shape that occur during manufacturing.
[0028] The features of the examples described herein may be combined in various ways that will be apparent after understanding the disclosure of the present application. In addition, although the examples described herein have a variety of configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application.
[0029] According to one aspect of the present application, there is provided a cell stack, as Figures 1 to 5As shown in the figure, the electrode group includes an electrode group body 1 and an electrode tab assembly 2. The electrode group body 1 includes two connection ends facing away from each other in the length direction L1 of the electrode group. The electrode tab assembly 2 includes a predetermined number of electrode tabs 21, and the predetermined number is greater than or equal to two. The electrode tab 21 includes a plurality of conductive members stacked along the arrangement direction, and adjacent conductive members are connected. The predetermined number of electrode tabs 21 in the electrode tab assembly 2 are connected to the same connection end, and the predetermined number of electrode tabs 21 in the electrode tab assembly 2 are used to be connected to the same electrode post 32. In this way, by using a predetermined number of electrode tabs 21 to replace one electrode tab 21 with a larger thickness, the number of layers of a single electrode tab 21 is reduced, the hardness of the electrode tab 21 is decreased, the risk of incomplete bending of the electrode tab 21 is reduced, thereby reducing the risk of short circuit due to the overlap of the electrode tab 21 and the housing. At the same time, the defective rate of welding between the cover plate 3 and the housing is reduced, and the production efficiency of the battery cell is improved.
[0030] Preferably, the length direction L1 of the electrode group is perpendicular to the width direction L2 and the thickness direction L3 of the following electrode group in pairs.
[0031] In the embodiment of the present application, the electrode group may include two electrode tab assemblies 2. The two electrode tab assemblies 2 are respectively connected to the two connection ends of the electrode group body 1. The electrode tabs 21 in the two electrode tab assemblies 2 have opposite polarities. The electrode tabs 21 in the first electrode tab assembly 2 are connected to the first electrode post 32, and the electrode tabs 21 in the second electrode tab assembly 2 are connected to the second electrode post 32. Specifically, the electrode group body 1 may be formed by winding or stacking electrode plates. The electrode tabs 21 in one of the electrode tab assemblies 2 are all used as positive electrode tabs, and the electrode tabs 21 in the other electrode tab assembly 2 are all used as negative electrode tabs. The conductive members in the electrode tab 21 used as the positive electrode tab are connected to the positive electrode plate, and the conductive members in the electrode tab 21 used as the negative electrode tab are connected to the negative electrode plate. The electrode tab 21 used as the positive electrode tab and the electrode tab 21 used as the negative electrode tab are respectively connected to the electrode posts 32 on the two cover plates 3.
[0032] Optionally, the conductive member may be a foil material. The electrode tab 21 is formed by stacking a plurality of conductive members along the arrangement direction and bonding them together by ultrasonic welding. The arrangement direction is the thickness direction of the conductive member.
[0033] Further, the conductive members located on the same side of the electrode group body 1 in the length direction L1 are divided into multiple groups, and the conductive members within each group are bonded together by ultrasonic welding to form the tab 21 in the shape of a sheet. The size of each tab 21 in the arrangement direction is less than or equal to 0.5 mm. That is to say, the thickness of the tab 21 is less than or equal to 0.5 mm. For example, the thickness of the tab 21 can be 0.3 mm, 0.32 mm, 0.35 mm, 0.38 mm, 0.4 mm, 0.42 mm, 0.45 mm, 0.48 mm or 0.5 mm, etc. Setting the thickness of the tab 21 to the above thickness ensures that the tab 21 can be bent in place, reduces the risk of short circuit due to the overlap of the tab 21 and the housing of the battery cell, and also reduces the risk of poor welding between the cover plate 3 and the housing of the battery cell.
[0034] As Figures 2 to 6 shown, the tab 21 includes a first connecting portion 211 and a second connecting portion 212 connected to each other. The first connecting portion 211 is connected to the electrode group body 1. A predetermined number of the first connecting portions 211 among the predetermined number of tabs 21 are arranged at intervals in the thickness direction L3 of the electrode group, and a predetermined number of the second connecting portions 212 among the predetermined number of tabs 21 are connected. When welding the second connecting portions 212 of the predetermined number of tabs 21 to the electrode post 32, the predetermined number of the second connecting portions 212 are stacked together at the welding mark 4.
[0035] Optionally, the shape of the tab 21 can be selected according to requirements. The shape of the tab 21 will be described below in combination with Embodiment 1 and Embodiment 2.
[0036] Embodiment 1 As Figure 2 and Figure 3 shown, the tab 21 includes a first connecting portion 211, a second connecting portion 212 and a connecting portion 213. The two ends of the connecting portion 213 are respectively connected to the first connecting portion 211 and the second connecting portion 212. The first connecting portion 211, the second connecting portion 212 and the connecting portion 213 are all in the shape of a sheet. The connecting portion 213 is in a bent shape, and the extending direction of the first connecting portion 211 intersects with the extending direction of the second connecting portion 212. Preferably, the first connecting portion 211 is perpendicular to the thickness direction L3, and the second connecting portion 212 is perpendicular to the length direction L1.
[0037] In this embodiment, a predetermined number of the first connecting portions 211 among the predetermined number of tabs 21 are parallel, and a predetermined number of the second connecting portions 212 are stacked along the length direction L1.
[0038] Optionally, the number of tabs 21 in the tab assembly 2 can be two, three, four or more. Taking the number of tabs 21 being two as an example, as Figure 2 and Figure 3As shown, the two first connection parts 211 are parallel. The size of the second connection part 212 in one tab 21 in the thickness direction L3 is larger than that of the second connection part 212 in the other tab 21 in the thickness direction L3. The second connection part 212 with the larger size in the thickness direction L3 is attached to the side of the second connection part 212 with the smaller size in the thickness direction L3 facing away from the electrode group body 1. The second connection part 212 with the larger size in the thickness direction L3 can be attached to the pole post 32 on the cover plate 3.
[0039] Embodiment 2 As Figure 4 and Figure 5 As shown, the tab 21 includes a first connection part 211, a second connection part 212, a first bending part 214, a second bending part 215 and a transition part 216. The first connection part 211, the first bending part 214, the transition part 216, the second bending part 215 and the second connection part 212 are connected in sequence. The first connection part 211, the second connection part 212, the transition part 216, the first bending part 214 and the second bending part 215 are all sheet-shaped. The first connection part 211 extends upward from the electrode group body 1. Both the first bending part 214 and the second bending part 215 are curved. The middle part of the first bending part 214 protrudes relative to the two ends of the first bending part 214. The middle part of the second bending part 215 protrudes relative to the two ends of the second bending part 215. The protruding direction of the middle part of the first bending part 214 is opposite to the protruding direction of the middle part of the second bending part 215. The extending direction of the first connection part 211 intersects with the extending direction of the second connection part 212. Preferably, the second connection part 212 is perpendicular to the length direction L1.
[0040] Furthermore, a plane perpendicular to the width direction L2 of the pole group is defined as a reference plane; an angle α between the surface of the adapter 216 facing the pole group body 1 and the reference plane is 25 degrees to 75 degrees; an angle β between the surface of the adapter 216 facing away from the pole group body 1 and the reference plane is 25 degrees to 75 degrees. As can be seen from the following table, when the angle α between the surface of the adapter 216 facing the pole group body 1 and the reference plane is less than 25 degrees, and the angle β between the surface of the adapter 216 facing away from the pole group body 1 and the reference plane is less than 25 degrees, there is a risk of the pole ear 21 being invertedly inserted into the pole group body 1, causing an internal short circuit; when the angle α between the surface of the adapter 216 facing the pole group body 1 and the reference plane is greater than 75 degrees, and the angle β between the surface of the adapter 216 facing away from the pole group body 1 and the reference plane is greater than 75 degrees, the shape of the pole ear 21 It is irregular, and there is a risk that the pole ear 21 exceeds the pole group body 1 in the thickness direction L3 after being bent, and the pole ear and the shell are overlapped abnormally and short-circuited when the pole group is put into the shell; when the angle α between the surface of the adapter 216 facing the pole group body 1 and the reference plane is 25 degrees to 75 degrees; when the angle β between the surface of the adapter 216 facing away from the pole group body 1 and the reference plane is 25 degrees to 75 degrees, the bending shape of the pole ear 21 is regular, the pole ear 21 is "S"-shaped, the bending shape of the pole ear 21 is regular, and the pole ear 21 has no abnormal short-circuit problem.
[0041]
[0042] Optionally, the predetermined number may be two, three, four or more. Taking the number of tabs 21 as two as an example, Figure 4 and Figure 5 As shown, the first connection portion 211 extends upward from the pole group body 1, the middle portion of the first bending portion 214 protrudes upward relative to the two ends of the first bending portion 214, and the middle portion of the second bending needle portion protrudes downward relative to the two ends of the second bending portion 215. The size of the second connection portion 212 in one pole ear 21 in the thickness direction L3 is larger than the size of the second connection portion 212 in the other pole ear 21 in the thickness direction L3. The second connection portion 212 with a smaller size in the thickness direction L3 is fitted with the side of the second connection portion 212 with a larger size in the thickness direction L3 facing the pole group body 1, and the second connection portion 212 with a larger size in the thickness direction L3 can be fitted with the pole 32 on the cover plate 3 on the side facing away from the second connection portion 212 with a larger size in the thickness direction L3.
[0043] Optionally, in the same electrode group, the shapes of the pole lugs 21 in the two pole lug assemblies 2 may be the same or different. For example, the pole lugs 21 in one pole lug assembly 2 all adopt the pole lugs 21 in the first embodiment, and the pole lugs 21 in the other pole lug assembly 2 all adopt the pole lugs 21 in the second embodiment; for another example, the pole lugs 21 in the two pole lug assemblies 2 all adopt the pole lugs 21 in the first embodiment; for another example, the pole lugs 21 in the two pole lug assemblies 2 all adopt the pole lugs 21 in the second embodiment.
[0044] In the electrode group of the present application, a predetermined number of tabs 21 are used to replace a tab 21 with a larger thickness. The number of layers of a single tab 21 is reduced, and the hardness of the tab 21 is decreased, reducing the risk that the tab 21 is not bent in place, thereby reducing the risk of short circuit due to the overlap of the tab 21 and the housing. At the same time, the defective rate of welding between the cover plate 3 and the housing is reduced, improving the production efficiency of the battery cell.
[0045] According to another aspect of the present application, a battery cell is provided. The battery cell includes a cover plate 3 and the above-mentioned electrode group. The cover plate 3 includes a terminal 32 and a plate body 31. The terminal 32 includes a bottom plate and a terminal body. The terminal body is fixed to one side of the bottom plate. The terminal body is located on one side of the plate body 31, and the terminal body passes through the plate body 31. A predetermined number of tabs 21 are all welded to the side of the bottom plate facing away from the terminal body, thereby realizing the connection between the terminal 32 and a predetermined number of tabs 21.
[0046] Further, a predetermined number of second connection portions 212 among the predetermined number of tabs 21 are stacked on the bottom plate and welded to the bottom plate, and the predetermined number of second connection portions 212 are stacked together at the weld mark 4.
[0047] In the battery cell of the present application, a predetermined number of tabs 21 are connected to the same terminal 32. The thickness of a single tab 21 is reduced, reducing the risk that the tab 21 is not bent in place, reducing the risk of short circuit due to the overlap of the tab 21 and the housing. At the same time, the defective rate of welding between the cover plate 3 and the housing is reduced, improving the production efficiency of the battery cell.
[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A battery electrode group, characterized in that, The pole group includes a pole group body and a pole lug assembly, wherein the pole group body includes two connection ends facing each other in the length direction of the pole group, the pole lug assembly includes a predetermined number of pole lugs, the predetermined number is greater than or equal to two, and the pole lug includes a plurality of conductive members stacked along an arrangement direction, and adjacent conductive members are connected; The predetermined number of the tabs in the tab assembly are connected to the same connection end, and the predetermined number of the tabs in the tab assembly are used to be connected to the same pole.
2. The electrode group according to claim 1, wherein The pole lug includes a first connection portion and a second connection portion connected to each other, the first connection portion is connected to the pole group body, the predetermined number of the first connection portions in the predetermined number of the pole lugs are arranged at intervals along the thickness direction of the pole group, and the predetermined number of the second connection portions in the predetermined number of the pole lugs are connected.
3. The electrode group according to claim 2, characterized in that, The electrode tab further includes a connecting portion, two ends of which are respectively connected to the first connecting portion and the second connecting portion, the connecting portion is bent, and an extending direction of the first connecting portion intersects with an extending direction of the second connecting portion.
4. The electrode group according to claim 2, characterized in that, The pole ear also includes a first bending portion, a second bending portion and a transition portion connected to each other, the first bending portion, the transition portion and the second bending portion are connected in sequence, one end of the first bending portion away from the transition portion is connected to the first connection portion, one end of the second bending portion away from the transition portion is connected to the second connection portion, the middle portion of the first bending portion protrudes relative to the two ends of the first bending portion, and the middle portion of the second bending portion protrudes relative to the two ends of the second bending portion.
5. The electrode group according to claim 4, wherein defining a plane perpendicular to the width direction of the pole group as a reference plane; The angle between the surface of the transition portion facing the pole group body and the reference plane is 25 degrees to 75 degrees; and / or, An angle between a surface of the transition portion facing away from the pole group body and the reference plane is 25 degrees to 75 degrees.
6. The electrode group according to any one of claims 3 to 5, characterized in that, In one of the electrode tab assemblies, the predetermined number of the second connecting portions in the predetermined number of the electrode tabs are stacked along the length direction of the electrode group.
7. The electrode group according to claim 1, wherein The pole group includes two pole lug assemblies, and the two pole lug assemblies are respectively connected to the two connection ends, wherein the predetermined number of pole lugs in one pole lug assembly is connected to the first pole, and the predetermined number of pole lugs in the other pole lug assembly is connected to the second pole.
8. The electrode group according to claim 1 or 7, wherein The dimension of the tab in the arrangement direction is less than or equal to 0.5 mm.
9. A battery cell, characterized in that, The battery core comprises the electrode group according to any one of claims 1 to 8.
10. The battery cell according to claim 9, characterized in that, The battery cell further comprises a cover plate, the cover plate comprises a plate body and a pole, the pole comprises a bottom plate and a pole body, the pole body is fixed on a side of the bottom plate facing away from the pole group body, the bottom plate is located on a side of the plate body facing the pole group body, and the pole body passes through the plate body; Two adjacent pole lugs among the predetermined number of pole lugs are fitted together, and a first pole lug among the predetermined number of pole lugs close to the bottom plate is fitted together with the bottom plate.