Convergence structure of laminated battery cell

Abstract

The utility model discloses a confluence structure of a laminated battery cell. The confluence structure comprises a confluence sheet, at least two pole pieces and at least two pole lugs, wherein the pole pieces and the pole lugs are arranged in the vertical direction. The confluence sheet is arranged along the vertical direction and is provided with a first connecting surface; the at least two pole pieces are arranged in the vertical direction, each pole piece comprises a pole piece main body, one end, close to the bus piece, of each pole piece main body is connected with a connecting lug, one end, close to the bus piece, of each connecting lug is bent to form a first piece connecting part, the first piece connecting parts are arranged in the vertical direction, and each first piece connecting part is connected with the first connecting surface; and the tabs are electrically connected with the bus sheets. The first connecting piece portions of the connecting lugs of the pole pieces are connected with the first connecting faces of the confluence pieces in an attached mode, the confluence pieces are electrically connected with the pole pieces, the confluence effect is prevented from being affected by pseudo soldering between the connecting lugs, the connecting lugs are not connected in an overlapped mode any more, the length of the confluence structure can be shortened, and the service life of the confluence structure is prolonged. Therefore, the length of the laminated cell adopting the confluence structure can be reduced.

Description

Technical Field

[0001] The utility model relates to the field of laminated battery cores, in particular to a busbar structure of laminated battery cores. Background Art

[0002] Existing laminated battery cells have multiple parallel electrode plates with a separator between adjacent electrode plates. The electrode plates include a main body and a connecting lug. The connecting lugs of multiple electrode plates of the same polarity are gradually brought together by a long inclined section and welded together to form an intermediate connecting lug. The intermediate connecting lug is partially bent and connected to the electrode lugs and welded together to form the laminated battery cell's busbar structure. However, this busbar structure of laminated battery cells is prone to cold solder joints between the connecting lugs, and the busbar structure is relatively long, which increases the length of laminated battery cells using this busbar structure. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a busbar structure for laminated battery cells that can reduce cold solder joints between connecting ears and shorten the length of the busbar structure, thereby reducing the length of laminated battery cells using the busbar structure.

[0004] The bus structure of a laminated battery cell according to an embodiment of the present invention includes a busbar, at least two pole pieces arranged in a vertical direction, and a pole lug. The busbar is arranged in a vertical direction and is provided with a first connection surface; at least two pole pieces arranged in a vertical direction, each pole piece includes a pole piece body, and the pole piece body is connected to a connection lug at one end near the busbar. The connection lug is bent at the end near the busbar to form a first contact portion, the first contact portion is arranged in a vertical direction, and each first contact portion is connected to the first connection surface; the pole lug is electrically connected to the busbar.

[0005] The busbar structure of the laminated battery cell according to the embodiment of the present invention has at least the following beneficial effects: the first contact portion of the connecting ear of each pole piece is respectively fitted and connected with the first connecting surface of the busbar, and the busbar is electrically connected to the pole ear, thereby avoiding the occurrence of cold solder joints between the connecting ears and affecting the busbar effect, and the connecting ears are no longer overlapped and connected, which can shorten the length of the busbar structure, so that the length of the laminated battery cell using this busbar structure can be shortened.

[0006] According to some embodiments of the present invention, the busbar is provided with clearance holes corresponding to all the connecting ears in the up and down directions, the first connecting surface is located on the side of the busbar away from the pole piece body, and one end of each connecting ear is passed through the corresponding clearance hole and bent to form the first connecting piece portion.

[0007] According to some embodiments of the present invention, the busbar includes a first insulating layer and a conductive layer, the first insulating layer is located on a side of the conductive layer close to the pole piece body, and the first connecting surface is located on a side of the conductive layer away from the first insulating layer.

[0008] According to some embodiments of the present invention, the thickness of the connecting ear is A, and the size of the clearance hole in the up-down direction is B, satisfying A+2μm≤B≤A+4μm.

[0009] According to some embodiments of the present invention, a dimension B of the clearance hole in the vertical direction satisfies: 5 μm≤B≤20 μm.

[0010] According to some embodiments of the present invention, the distance between two adjacent clearance holes is C, which satisfies 0.5 mm ≤ C ≤ 1 mm.

[0011] According to some embodiments of the present invention, the tab is provided with a protruding piece portion and a second contact piece portion, the second contact piece portion and the bus bar are arranged side by side, the first contact piece portion is located between the second contact piece portion and the bus bar, the second contact piece portion is connected to the first contact piece portion, and the protruding piece portion and the second contact piece portion are perpendicular to each other.

[0012] According to some embodiments of the present invention, all of the first connecting pieces are staggered with each other.

[0013] According to some embodiments of the present invention, the first tab portion and the first connecting surface are welded together by at least two connecting welds; the first tab portion and the second tab portion are welded together by at least two of the connecting welds; and the protruding tab portion and the first connecting surface are welded together by at least two of the connecting welds.

[0014] According to some embodiments of the present invention, the width of the connecting weld is X, satisfying: 0.01mm≤X≤0.1mm, and / or the upper and lower dimensions of the connecting weld are Y, satisfying: 0.01mm≤Y≤0.08mm, and / or the distance between two adjacent connecting welds is Z, satisfying: 0.01mm≤Z≤0.05mm.

[0015] According to some embodiments of the present invention, the electrode sheet includes a positive electrode sheet, the positive electrode sheet includes a positive electrode sheet body, the positive electrode sheet body is connected to a positive electrode connection ear at one end close to the bus bar, and a second insulating layer is provided on the edge of one side of the positive electrode sheet body close to the positive electrode connection ear, and the length D of the second insulating layer satisfies: 0.1mm≤D≤3mm.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 A side view schematic diagram of a busbar structure of a laminated battery cell according to an embodiment of the present utility model;

[0019] Figure 2 For the embodiment of the utility model Figure 1 SS direction cross-sectional schematic diagram;

[0020] Figure 3 This is a front view schematic diagram of a busbar according to an embodiment of the present invention;

[0021] Figure 4 A schematic side view of a pole piece according to an embodiment of the present invention;

[0022] Figure 5 A schematic side view of a positive electrode sheet with a second insulating layer according to an embodiment of the present invention;

[0023] Figure 6 It is a front view schematic diagram of the busbar and the first connecting piece portion of an embodiment of the present utility model.

[0024] Reference numerals:

[0025] Busbar 100, clearance hole 110, first insulating layer 120, conductive layer 130;

[0026] Pole piece 200, pole piece body 210, connecting ear 220, first contact portion 221, positive pole piece 230, positive pole piece body 231, positive connecting ear 232, second insulating layer 233;

[0027] Tab 300, extended piece portion 310, second contact piece portion 320;

[0028] Connect the solder joint 400 . DETAILED DESCRIPTION

[0029] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0030] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] In the description of this utility model, "a plurality" means more than two. The use of "first" or "second" is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0032] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0033] Existing laminated battery cells have multiple parallel pole pieces 200, with a diaphragm disposed between adjacent pole pieces 200. The pole pieces 200 include a pole piece body 210 and a connecting lug 220. The connecting lugs 220 of multiple pole pieces 200 of the same polarity are gradually brought together through a long inclined section and stacked and welded to form an intermediate connecting lug 220. The intermediate connecting lug 220 is partially bent and connected to the pole lug 300 and welded to form the busbar structure of the laminated battery cell. However, the busbar structure of the laminated battery cell described above is prone to cold solder joints between the connecting lugs 220, and the busbar structure is relatively long, resulting in a longer laminated battery cell using this busbar structure.

[0034] Reference Figures 1 to 6 , is a busbar structure of a laminated battery cell according to an embodiment of the present invention, comprising a busbar 100, at least two pole pieces 200 arranged in the vertical direction, and a pole tab 300. The busbar 100 is arranged in the vertical direction and is provided with a first connection surface; the at least two pole pieces 200 arranged in the vertical direction each include a pole piece body 210, the pole piece body 210 having a connection tab 220 connected to the end thereof close to the busbar 100, and the connection tab 220 is bent at the end close to the busbar 100 to form a first contact portion 221, the first contact portion 221 being arranged in the vertical direction, and each first contact portion 221 being connected to the first connection surface; the pole tab 300 is electrically connected to the busbar 100.

[0035] The first contact portion 221 of the connecting ear 220 of each pole piece 200 is respectively fitted and connected with the first connecting surface of the busbar 100, and the busbar 100 is electrically connected to the pole ear 300, so as to avoid the occurrence of cold solder joints between the connecting ears 220 and affect the busbar effect, and the connecting ears 220 are no longer overlapped and connected, which can reduce the length of the busbar structure, so that the length of the laminated battery cell using this busbar structure can be reduced; when the size of the laminated battery cell remains unchanged, the busbar structure occupies less space in the laminated battery cell, and the pole piece body 210 can be made larger, thereby improving the energy density of the laminated battery cell.

[0036] Specifically, the aforementioned bus structure refers to a bus structure used by electrode sheets 200 of the same polarity, such as a bus structure used by two or more positive electrode sheets 230, or a bus structure used by two or more negative electrode sheets 200. The aforementioned bus structure is generally not used between electrode sheets 200 of different polarities to avoid risks such as short circuits between electrode sheets 200 of different polarities.

[0037] In this embodiment, the busbar 100 is provided with clearance holes 110 arranged in the vertical direction, corresponding one-to-one with all the connecting ears 220. The first connection surface is located on the side of the busbar 100 away from the pole piece body 210. One end of each connecting ear 220 is inserted into the corresponding clearance hole 110 and bent to form a first contact portion 221. This structure makes the connection between the connecting ears 220 and the busbar 100 more secure, and can reduce the risk of the connecting ears 220 and the busbar 100 loosening due to tension.

[0038] Specifically, the laminated battery cell may include two, three, four or more pole pieces 200 with the same polarity, and the connecting ears 220 correspond one-to-one to the pole pieces 200. At this time, the busbar 100 should also have two, three, four or more clearance holes 110, and each connecting ear 220 passes through a clearance hole 110. Those skilled in the art can make specific configurations according to actual needs.

[0039] Specifically, the connecting ear 220 is an empty foil area on the pole piece 200. The pole piece 200 includes a current collector layer and an active material layer. Usually, the active material layer is connected to opposite sides of the current collector layer. The area of ​​the current collector layer not covering the active material layer is the empty foil area.

[0040] In an embodiment, the busbar 100 includes a first insulating layer 120 and a conductive layer 130. The first insulating layer 120 is located on a side of the conductive layer 130 close to the electrode body 210, and the first connecting surface is located on a side of the conductive layer 130 away from the first insulating layer 120. Since there is a risk of safety issues when the tab 300 is directly connected to the electrode body 210, the busbar 100 includes the first insulating layer 120 and the conductive layer 130. Even when the busbar 100 is in contact with the electrode body 210, the tab 300 will not be directly connected to the electrode body 210 through the busbar 100. Instead, the tab 300 is indirectly connected to the electrode body 210 through the busbar 100 and the connecting tab 220, thereby reducing the risks of laminated cells using this busbar structure.

[0041] Specifically, the clearance hole 110 passes through the first insulating layer 120 and the conductive layer 130. The connecting ear 220 horizontally passes through the first insulating layer 120 and the conductive layer 130. The end of the connecting ear 220 away from the electrode body 210 is bent to form a first contact portion 221 arranged in a vertical direction. The first contact portion 221 is in contact with the side of the conductive layer 130 away from the first insulating layer 120. The rest of the connecting ear 220 is arranged in a horizontal direction and is substantially perpendicular to the first contact portion 221.

[0042] Specifically, the first insulating layer 120 may be made of insulating plastic or ceramic, and the insulating plastic may be made of plastic such as polyethylene, polyvinyl chloride, etc. Those skilled in the art may configure the first insulating layer 120 according to actual needs.

[0043] Specifically, the conductive layer 130 can be made of a conductive metal material, such as silver, copper or aluminum; or a conductive non-metal material, such as graphite. Those skilled in the art can make specific configurations according to actual needs.

[0044] In this embodiment, the thickness of the connecting lug 220 is A, and the vertical dimension of the clearance hole 110 is B, satisfying the condition A+2μm≤B≤A+4μm. If the vertical dimension of the clearance hole 110 is too large, the gap between the hole wall of the clearance hole 110 and the connecting lug 220 is large, causing the vertical dimension of the busbar 100 to be too large, making the busbar 100 less compact and affecting the size of the laminated battery cell. If the vertical dimension of the clearance hole 110 is too small, the connecting lug 220 may have difficulty passing through the clearance hole 110, affecting the smooth assembly of the connecting lug 220 and the busbar 100. When the vertical dimension of the clearance hole 110 is 2μm to 4μm larger than the thickness of the connecting lug 220, the connecting lug 220 can pass through the clearance hole 110 relatively easily, facilitating assembly. Furthermore, the busbar 100 becomes relatively compact and compatible with the size of existing laminated battery cells. Specifically, the size of the clearance hole 110 in the up and down directions can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, etc. larger than the thickness of the connecting ear 220, or other values ​​within the range can be used. Those skilled in the art can make specific configurations according to actual needs.

[0045] In an embodiment, the dimension B of the clearance hole 110 in the vertical direction satisfies: 5μm≤B≤20μm. The above dimensions meet the thickness requirements of the foil material of the commonly used pole piece 200. Specifically, the dimension of the clearance hole 110 in the vertical direction can be selected from values ​​such as 5μm, 10μm, 15μm or 20μm, or other values ​​within the range. Those skilled in the art can adopt it according to actual needs. Specifically, the commonly used collector foil materials of the pole piece 200 include aluminum foil or copper foil, etc. Those skilled in the art can configure it according to actual needs.

[0046] In an embodiment, the distance between two adjacent clearance holes 110 is C, which satisfies 0.5mm≤C≤1mm. When the distance between two adjacent clearance holes 110 is too small, the connection size between the first contact portion 221 and the first connection surface is insufficient, which may result in an insufficiently firm connection; when the distance between two adjacent clearance holes 110 is too large, the overall size of the busbar 100 is larger, affecting the size of the laminated battery cell. The above-mentioned size between two adjacent clearance holes 110 meets the connection strength requirements between the first contact portion 221 and the first connection surface, and can also make the busbar 100 structure more compact, meeting the size requirements of existing laminated battery cells. Specifically, the distance between two adjacent clearance holes 110 can be selected from sizes such as 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, or any other value within the range can be selected. Those skilled in the art can make specific configurations according to actual needs.

[0047] In the embodiment, the tab 300 is provided with an extension portion 310 and a second tab portion 320. The second tab portion 320 is arranged side by side with the busbar 100, the first tab portion 221 is located between the second tab portion 320 and the busbar 100, the second tab portion 320 is connected to the first tab portion 221, and the extension portion 310 and the second tab portion 320 are perpendicular to each other. The above structure makes the tab 300 substantially L-shaped, making the structure between the busbar 100, the tab 300 and the connecting tab 220 relatively compact, further reducing the length of the busbar structure; at the same time, it can directly connect the tab 300 to the connecting tab 220, with high connection strength, further reducing the risk of false contact of the connecting tab 220.

[0048] Furthermore, in other embodiments, the dimensions of different first joining pieces 221 along the up and down directions may be different. For example, from top to bottom, the dimensions of different first joining pieces 221 along the up and down directions may gradually increase or decrease, so that the first joining piece 221 can have stronger contact with the second joining piece 320 and better connection strength.

[0049] In some cases, two adjacent first tabs 221 may overlap, thereby affecting the length of the busbar structure occupied by the laminated core, as well as the contact and connection strength between the first tab 221 and the tab 300. Therefore, the following improvements are made:

[0050] In the embodiment, all the first contact portions 221 are staggered. When the first contact portions 221 are staggered, the first contact portions 221 do not overlap with each other, which can minimize the length of the bus structure occupied by the laminated battery core, thereby improving the energy density of the laminated battery core. It can also ensure that all the first contact portions 221 are connected one by one to the second contact portion 320 of the tab 300, reducing the risk of false contact and increasing the connection strength.

[0051] In the embodiment, the first tab portion 221 is welded to the first connection surface via three connection welds 400; the first tab portion 221 is welded to the second tab portion 320 via three connection welds 400; and the extension portion 310 is welded to the first connection surface via three connection welds 400. Spot welding provides a secure connection with good connection strength, a relatively suitable spot welding connection area, and low internal resistance.

[0052] In this embodiment, the width of the connection solder joint 400 is X, which satisfies: 0.01mm≤X≤0.1mm; the vertical dimension of the connection solder joint 400 is Y, which satisfies: 0.01mm≤Y≤0.08mm; and the distance between two adjacent connection solder joints 400 is Z, which satisfies: 0.01mm≤Z≤0.05mm. The above structure ensures that the area of ​​the connection solder joint 400 is relatively appropriate, and the welding strength is good, and the welding internal resistance is low.

[0053] Preferably, the three connecting welding points 400 are arranged along a straight line to form a welding mark, and the welding mark size is J, which satisfies 0.1mm≤J≤5mm. The welding strength is good and the existing spot welding mechanism can be used for welding.

[0054] It is conceivable that, in other embodiments, the first tab portion 221 and the first connection surface can be connected via two or more connection welds 400; the first tab portion 221 and the second tab portion 320 can be connected via two or more connection welds 400; and the protruding tab portion 310 and the first connection surface can be connected via two or more connection welds 400.

[0055] In an embodiment, the electrode sheet 200 includes a positive electrode sheet 230, which includes a positive electrode sheet body 231. A positive electrode connection ear 232 is connected to the end of the positive electrode sheet body 231 near the busbar 100. A second insulating layer 233 is provided on the edge of the positive electrode sheet body 231 near the positive electrode connection ear 232. The length D of the second insulating layer 233 satisfies the following conditions: 0.1mm≤D≤3mm. The second insulating layer 233 can be formed by mixing inorganic particles such as ceramics with an adhesive. Since the positive electrode connection ear 232 is formed from a positive electrode foil, which is relatively soft, providing a second insulating layer 233 of the aforementioned size at the edge of the positive electrode sheet body 231 can facilitate the insertion of the positive electrode connection ear 232 into the corresponding clearance hole 110 of the busbar 100.

[0056] Specifically, the positive electrode sheet 230 with the second insulating layer 233 is located at the outermost layers on both sides of the laminated battery core.

[0057] Specifically, the necessary length of the above-mentioned bus structure is E, the thickness of the bus bar 100 is F, the thickness of the first contact portion 221 is G, and the thickness of the second contact portion 320 is H. Then the necessary length of the bus structure satisfies E=F+G+H. Compared with the bus structure of the existing laminated battery cell, when the number of bus pole sheets 200 reaches 25 layers, the length of the bus structure of this technical solution is reduced by about 0.4 mm.

[0058] It is understandable that since the positive electrode sheets 230 and the negative electrode sheets 200 are arranged alternately inside the laminated battery cell, one laminated battery cell needs to adopt two of the above-mentioned bus structures, one bus structure for busing the positive electrode sheets 230 and the other bus structure for busing the negative electrode sheets 200.

[0059] Specifically, tab glue is provided on the tab 300 to provide surface protection, insulation and fixation for the tab 300 .

[0060] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative use of the above terms does not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0061] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A busbar structure of a laminated battery cell, characterized in that: include: A busbar (100) is arranged in an up-down direction, and the busbar (100) is provided with a first connection surface; At least two pole pieces (200) arranged in the vertical direction, each pole piece (200) comprising a pole piece body (210), one end of the pole piece body (210) close to the bus bar (100) being connected to a connecting ear (220), one end of the connecting ear (220) close to the bus bar (100) being bent to form a first connecting piece portion (221), the first connecting piece portion (221) being arranged in the vertical direction, and each first connecting piece portion (221) being connected to the first connecting surface; The tab (300) is electrically connected to the busbar (100).

2. The bus structure of the laminated battery cell according to claim 1, characterized in that: The busbar (100) is provided with clearance holes (110) arranged in an up-down direction and corresponding to all the connecting ears (220), the first connecting surface is located on the side of the busbar (100) away from the pole piece body (210), and one end of each connecting ear (220) is passed through the corresponding clearance hole (110) and bent to form the first connecting piece portion (221).

3. The bus structure of the laminated battery cell according to claim 2, characterized in that: The busbar (100) comprises a first insulating layer (120) and a conductive layer (130), wherein the first insulating layer (120) is located on a side of the conductive layer (130) close to the pole piece body (210), and the first connecting surface is located on a side of the conductive layer (130) away from the first insulating layer (120).

4. The bus structure of the laminated battery cell according to claim 2, characterized in that: The thickness of the connecting ear (220) is A, and the dimension of the clearance hole (110) in the vertical direction is B, satisfying A+2μm≤B≤A+4μm.

5. The bus structure of the laminated battery cell according to claim 4, characterized in that: The dimension B of the clearance hole (110) in the up-down direction satisfies: 5 μm≤B≤20 μm.

6. The bus structure of the laminated battery cell according to claim 2, characterized in that: The distance between two adjacent clearance holes (110) is C, which satisfies 0.5 mm ≤ C ≤ 1 mm.

7. The bus structure of the laminated battery cell according to claim 2, characterized in that: The tab (300) is provided with a protruding piece portion (310) and a second contact piece portion (320); the second contact piece portion (320) and the busbar (100) are arranged side by side; the first contact piece portion (221) is located between the second contact piece portion (320) and the busbar (100); the second contact piece portion (320) is connected to the first contact piece portion (221); and the protruding piece portion (310) and the second contact piece portion (320) are perpendicular to each other.

8. The bus structure of the laminated battery cell according to claim 7, characterized in that: All of the first connecting pieces (221) are staggered with each other.

9. The bus structure of the laminated battery cell according to claim 7, characterized in that: The first connecting piece (221) and the first connecting surface are welded together via at least two connecting welding points (400); the first connecting piece (221) and the second connecting piece (320) are welded together via at least two connecting welding points (400); and the extending piece (310) and the first connecting surface are welded together via at least two connecting welding points (400).

10. The bus structure of the laminated battery cell according to claim 9, characterized in that: The width of the connection welding spot (400) is X, which satisfies: 0.01mm≤X≤0.1mm, and / or the upper and lower dimensions of the connection welding spot (400) are Y, which satisfies: 0.01mm≤Y≤0.08mm, and / or the distance between two adjacent connection welding spots (400) is Z, which satisfies: 0.01mm≤Z≤0.05mm.

11. The bus structure of the laminated battery cell according to claim 2, characterized in that: The electrode sheet (200) comprises a positive electrode sheet (230), the positive electrode sheet (230) comprises a positive electrode sheet main body (231), one end of the positive electrode sheet main body (231) close to the busbar (100) is connected to a positive electrode connection ear (232), a second insulating layer (233) is provided on one side edge of the positive electrode sheet main body (231) close to the positive electrode connection ear (232), and a length D of the second insulating layer (233) satisfies: 0.1 mm≤D≤3 mm.

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