Battery

Abstract

A battery, comprising a battery cell (1) and a housing. The battery cell (1) comprises a first electrode sheet (8), an isolation layer (7), a second electrode sheet (9), a first tab (2), and a second tab (4) which are sequentially stacked or wound; the first tab (2) is provided with a first welding mark (3), and the second tab (4) is provided with a second welding mark (5); the metal material of the first tab (2) is the same as that of the housing; the first welding mark (3) protrudes out of the surface of the first tab (2) and faces the housing, and the first welding mark (3) is not covered with an adhesive tape (6); and the second welding mark (5) is covered with the adhesive tape (6). According to the battery provided by the present application, by means of the structural arrangement, on the basis of not causing any safety hazard, the adhesive tape (6) does not need to be adhered to the first tab (2), so that the volume ratio of a charging / discharging component of the battery is increased, improving the energy density of the battery.

Description

A battery Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery.

[0002] Background of the Invention

[0003] With the continuous advancement of science and technology, people expect mobile phones, computers, tablets and other electronic products to become lighter and thinner, that is, lighter in weight, thinner in thickness, and easier to carry. Therefore, higher requirements are placed on batteries. While ensuring fast charging, energy density must also be improved.

[0004] Summary of the Invention

[0005] In view of this, the embodiments of the present application are dedicated to providing a battery that does not require adhesive tape to be adhered to the first pole ear without creating a safety hazard, thereby increasing the volume ratio of the battery's discharge and collection components, that is, increasing the volume of the discharge and collection components per unit area, thereby improving the energy density of the battery.

[0006] The present application provides a battery, comprising a battery cell and a shell wrapping the battery cell, wherein the battery cell comprises a first electrode sheet, an isolation layer, a second electrode sheet, a first electrode tab and a second electrode tab, wherein the first electrode tab has a first weld mark, and the second electrode tab has a second weld mark; wherein the metal material of the first electrode tab is the same as the metal material of the shell, the first weld mark protrudes from the surface of the first electrode tab and faces the shell, and the first weld mark is not covered with adhesive tape.

[0007] In a possible implementation, the shell includes a first resin layer, a metal layer, and a second resin layer in sequence along a thickness direction, and a protruding height of the first weld mark is less than the sum of the thicknesses of the second resin layer and the metal layer.

[0008] In a possible implementation, both the first surface and the second surface of the second electrode tab have protruding second weld marks, and both are provided with adhesive tape covering the second weld marks.

[0009] In a possible implementation manner, the adhesive tape covering the second weld mark and the first electrode tab are arranged side by side in the width direction of the battery cell.

[0010] In a possible implementation, a protruding height of the second weld mark on the second surface is smaller than a protruding height of the second weld mark on the first surface.

[0011] In a possible implementation, the thickness of the adhesive tape on the second surface is greater than or equal to the thickness of the adhesive tape on the first surface.

[0012] In a possible implementation, the thickness of the adhesive tape on the first surface is 10-100 microns, and the thickness of the adhesive tape on the second surface is 10-100 microns.

[0013] In a possible implementation, a projection of the adhesive tape in the thickness direction does not overlap with a projection of the electrode of the battery cell in the thickness direction.

[0014] In one possible embodiment, the first pole piece, the isolation layer and the second pole piece are wound together, and along the winding direction, the outermost circle of the battery cell is a section of the first pole piece, and the tail end of the first pole piece is covered with a finishing glue; wherein, the tail end edge of the finishing glue is located on the bent section of the battery cell closest to the tail end edge of the first pole piece.

[0015] In one possible embodiment, the first pole piece, the isolation layer and the second pole piece are wound together, the outermost circle of the battery cell along the winding direction is a section of the first pole piece, and the isolation layer has an extension section that exceeds the tail edge of the second pole piece; the tail edge of the extension section is located on the bent section of the battery cell closest to the tail edge of the first pole piece.

[0016] In a possible implementation manner, the length of the extension section is 5-20 mm.

[0017] In one possible embodiment, the two surfaces of the first pole piece have a first paste layer and a second paste layer, respectively, the two surfaces of the second pole piece have a third paste layer and a fourth paste layer, the first outer paste layer of the first pole piece and the third paste layer of the second pole piece are opposite, and the second paste layer of the first pole piece and the fourth paste layer of the second pole piece are opposite.

[0018] In a possible implementation, at the tail end of the second pole piece, the tail end of the fourth paste layer exceeds the tail end edge of the second paste layer opposite thereto, and the excess length is ≥1 mm.

[0019] In a possible implementation manner, the tail end of the third pasting layer exceeds the edge of the tail end of the first pasting layer opposite thereto, and the exceeding length is ≥1 mm.

[0020] In a possible implementation, along the thickness direction, the first pole piece, the isolation layer, and the second pole piece are stacked in sequence.

[0021] In a possible embodiment, an insulating layer is provided in an area of ​​the first pole piece close to the first pole tab, and the edge of the paste layer of the second pole piece close to the second pole tab has its projection in the thickness direction located within the projection area of ​​the insulating layer in the thickness direction.

[0022] The battery provided herein has weld marks on both the first and second tabs. However, the metal material of the first tab is the same as that of the outer shell. For example, if the outer shell is made of aluminum-plastic film, the first tab is made of aluminum foil. Because the first tab and the outer shell are made of the same metal, contact between them does not generate a potential difference, nor does it lead to electrochemical corrosion. Therefore, the first tab and the outer shell can contact each other without posing a safety hazard. Furthermore, the first weld mark of the first tab protrudes from the surface of the first tab and faces the outer shell. Therefore, even if the first weld mark is not covered with adhesive tape, it will not puncture the isolation layer of the battery cell, eliminating the safety issue of short-circuiting the positive and negative electrode sheets of the battery cell. If the protruding height of the first weld mark is less than the thickness of the outer shell, it will not puncture the outer shell either. Compared to batteries with adhesive tape applied to the first tab in the prior art, the battery provided herein does not have adhesive tape applied to the first tab. This reduces the overall thickness while maintaining the same current collection capacity, thereby increasing the volume ratio of the battery's discharge and collection components. This increases the volume of the discharge and collection components per unit area, thereby improving the battery's energy density.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic diagram of a battery cell in an embodiment of the present application.

[0025] FIG2 is a cross-sectional schematic diagram showing a battery cell having a roll core structure in an embodiment of the present application.

[0026] FIG3 is a cross-sectional schematic diagram showing a stacked core structure of a battery cell in an embodiment of the present application.

[0027] In Figure 1-3:

[0028] 1. Battery cell; 2. First tab; 3. First weld mark; 4. Second tab; 5. Second weld mark; 6. Adhesive tape; 7. Isolation layer; 8. First pole piece; 9. Second pole piece; 10. Finishing glue; 11. Insulation layer.

[0029] Modes for Carrying Out the Invention

[0030] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] Referring to Figures 1-3, an embodiment of the present application provides a battery comprising a cell 1 and a casing enclosing the cell 1. The cell 1 comprises a first electrode sheet 8, a separator 7, a second electrode sheet 9, a first electrode tab 2, and a second electrode tab 4, which are stacked or wound in sequence. The separator 7 may be a diaphragm or other insulating material layer. The first electrode tab 2 is disposed on the first electrode sheet 8, and the second electrode tab 4 is disposed on the second electrode sheet 9. A first weld mark 3 is formed on the surface of the first electrode tab 2, and a second weld mark 5 is formed on the surface of the second electrode tab 4. Weld marks refer to weld marks formed by welding. For example, the first pole ear 2 includes a first soft pole ear and a first hard pole ear, the first soft pole ear is connected to the first pole piece 8, the end of the first soft pole ear facing away from the first pole piece 8 is welded to the first hard pole ear, and the first soft pole ear and the first hard pole ear are welded to form a first weld mark 3, multiple first soft pole ears are bent upward to form a bending section, the first weld mark 3 is located on the bending section, and the part of the first hard pole ear facing away from the first weld mark 3 is bent twice to extend out of the shell; the second pole ear 4 includes a second soft pole ear and a second hard pole ear, the second soft pole ear is connected to the second pole piece 9, the end of the second soft pole ear facing away from the second pole piece 9 is welded to the second hard pole ear, and the second soft pole ear and the second hard pole ear are welded to form a second weld mark 5, multiple second soft pole ears are bent upward to form a bending section, the second weld mark 5 is located on the bending section, and the part of the second hard pole ear facing away from the second weld mark 5 is bent twice to extend out of the shell. The metal material of the first pole lug 2 is the same as the metal material of the outer shell. For example, when the outer shell is an aluminum-plastic film, the material of the first pole lug 2 is aluminum foil. In this way, since the metal material of the first pole lug 2 and the outer shell is the same, no potential difference will be generated when the two are in contact, and no electrochemical corrosion will occur. Therefore, the first pole lug 2 and the outer shell can be in contact without causing safety hazards. At the same time, the first weld mark 3 of the first pole lug 2 is protruding from the surface of the first pole lug 2 and facing the outer shell. Even if the first weld mark 3 is not covered with adhesive tape 6, it will not puncture the isolation layer 7 on the battery cell 1, and there will be no safety problem of short-circuiting the positive and negative electrodes of the battery cell 1. If the protruding height of the first weld mark 3 is less than the thickness of the outer shell, it will not puncture the outer shell. Therefore, through the structural setting, in this application, no adhesive tape 6 covering the first weld mark 3 is provided on the first pole lug 2, and no safety problem will arise.

[0032] Compared to batteries with adhesive tape 6 applied to the first tab 2 in the prior art, the battery provided in this application does not have adhesive tape 6 applied to the first tab 2. This reduces the overall thickness while maintaining the same current collection capacity, increasing the volume ratio of the battery's discharge and collection components. This increases the volume of the discharge and collection components per unit area, increasing the unit current collection capacity and thus improving the battery's energy density. Furthermore, the reduced overall thickness of the battery facilitates a thin and lightweight design, making it easier to use. Furthermore, the absence of adhesive tape 6 on the first tab 2 prevents the adhesive tape 6 on the first tab 2 from adhering to the outermost layer of the battery cell 1, thereby improving the flatness of the battery cell 1 soft pack.

[0033] The metal material of the second electrode tab 4 can be different from the metal material of the first electrode tab 2. Therefore, a tape 6 can be provided on the second electrode tab 4 to cover the second weld mark 5 to avoid the second electrode tab 4 from contacting the shell and generating a potential difference, and to avoid the problem of burrs on the second weld mark 5 that may puncture the diaphragm or the shell.

[0034] The outer shell used to encase the battery cell 1 can be an aluminum-plastic film. In some embodiments, the aluminum-plastic film comprises three composite layers along the thickness direction: a first resin layer, a metal layer, and a second resin layer. The protrusion height of the first weld mark 3 (i.e., the height protruding from the surface of the first tab 2) is less than the sum of the thicknesses of the second resin layer and the metal layer. This ensures that even if burrs are present on the first weld mark 3, they will not puncture the outer shell.

[0035] As shown in FIG1 , the second tab 4 is in the form of a thin sheet, with two surfaces of the sheet being designated as the first surface and the second surface. Both the first surface and the second surface have protruding second weld marks 5 and are provided with adhesive tape 6 covering the second weld marks 5. This provides comprehensive protection.

[0036] Typically, the hard tab is located on one side of the soft tab, so there is a height difference between the weld marks on the first surface and the second surface. For example, the protruding height of the second weld mark 5 on the second surface is greater than the protruding height of the second weld mark 5 on the first surface. Therefore, in some embodiments, the thickness of the adhesive tape 6 on the second surface is equal to or greater than the thickness of the adhesive tape 6 on the first surface. In other words, the thickness of the adhesive tape 6 on the first surface is less than the thickness of the adhesive tape 6 on the second surface. Because the protruding height of the weld mark on the first surface is smaller, the adhesive tape 6 applied to the first surface can be thinner. In this way, there is no safety risk, and the overall thickness of the battery cell 1 can be further reduced, the total proportion of the current collecting material is increased, and the volume of the current collecting material per unit area is increased, that is, the current collecting capacity and the energy density of the battery are increased.

[0037] In some embodiments, the thickness of the adhesive tape 6 on the first surface of the second tab 4 is 10-100 μm, for example, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm. The thickness of the adhesive tape 6 on the second surface is 10-100 μm, for example, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0038] The adhesive tape 6 on the second tab 4, whether it is the adhesive tape 6 on the first surface or the adhesive tape 6 on the second surface, can extend to the electrode, such as the tail end is pasted on the electrode of the outermost layer of the battery cell 1, or it can not extend to the electrode, for example, the projection of the adhesive tape 6 in the thickness direction does not overlap with the projection of the electrode in the thickness direction.

[0039] The first electrode sheet 8 includes a first current collector, a first paste layer located on both surfaces of the first current collector, and a second paste layer. The second electrode sheet 9 includes a second current collector, a third paste layer located on both surfaces of the second current collector, and a fourth paste layer. The battery cell 1 can have a stacked core structure, such as by stacking the first electrode sheet 8, the isolation layer 7, and the second electrode sheet 9 in sequence, or a wound core structure, such as by winding the first electrode sheet 8, the isolation layer 7, and the second electrode sheet 9 together.

[0040] When the battery cell 1 is a wound core structure, the two surfaces of the current collector include a surface facing the center of the battery cell 1 and a surface facing the outside of the battery cell 1. The second paste layer of the first pole piece 8 can be a paste layer on the current collector surface facing or closer to the center of the battery cell 1 on the same current collector section, that is, a paste layer closer to the center of the battery cell 1, and the first paste layer is a paste layer on the current collector surface facing the outside of the battery cell on the same current collector section, that is, a paste layer farther away from the center of the battery cell 1. Similarly, on the second pole piece 9, the third paste layer refers to the paste layer on the same current collector section that is closer to the center of the battery cell 1, and the fourth paste layer refers to the paste layer on the same current collector section that is farther away from the center of the battery cell 1. The first paste layer of the first pole piece 8 and the third paste layer of the second pole piece 9 are opposite and separated by the isolation layer 7, and the second paste layer of the first pole piece 8 and the fourth paste layer of the second pole piece 9 are opposite and separated by the isolation layer 7.

[0041] In some embodiments, as shown in FIG2 , on the first pole piece 8, the second paste layer extends from the head edge of the first current collector to the tail edge of the first current collector on one side surface of the first current collector, which can also be said to be fully coated, and the side surface of the first current collector is completely covered, and there is no uncoated area. The first paste layer extends from the head edge of the first current collector to the tail end on the other side surface of the first current collector, and has a distance from the tail end edge. In other words, the other side surface of the first current collector is not completely covered, and the other side surface of the first current collector has an uncoated uncoated area at the tail end. In this way, in the wound battery cell 1, as shown in FIG2 , the tail end of the first pole piece 8 is used for finishing, and the uncoated area forms the outer surface of the entire battery cell 1. There is no uncoated area at the head end of the first pole piece 8. Such a setting can increase the proportion of the collector material and increase the energy density of the battery.

[0042] When the battery cell 1 is a roll core structure, it includes multiple annular segments along the winding direction, and the first pole piece 8 and the second pole piece 9 also include multiple annular segments. In some embodiments, the tail end of the first pole piece 8 forms the outermost circle of the battery cell 1, that is, the outermost circle of the battery cell 1 is the segment of the first pole piece 8, or it can be said that the tail end of the first pole piece 8 is used as the end of the battery cell 1. The head end of the second pole piece 9 serves as the innermost circle of the battery cell 1. Along the winding direction, the annular segment of the outermost circle of the battery cell 1 is formed by the tail end of the first pole piece 8, or it can be said that the tail end of the first pole piece 8 completely wraps the tail end of the second pole piece 9, or the last annular segment of the first pole piece 8 covers the last annular segment of the second pole piece 9.

[0043] The tail end of the first pole piece 8 is covered with a finishing glue 10, which can be a tape. The finishing glue 10 is applied to the tail edge of the first pole piece 8 to stick it in place and prevent it from unwinding. The annular ring segment includes a straight segment and a bent segment. In some embodiments, as shown in FIG2 , the tail edge of the finishing glue 10 is located on the bent segment of the battery cell 1 that is closest to the tail edge of the first pole piece 8 (along the winding direction, the bent segment that is closest to the tail edge of the first pole piece 8 can also be said to be an arcuate surface, the same below). In this way, the finishing glue 10 does not need to be too long, and will not extend to the straight section of the battery cell 1, which can reduce the proportion of non-current collecting materials and improve the energy density of the battery.

[0044] The isolation layer 7 can be a diaphragm. Along the winding direction, at the trailing end, the diaphragm extends beyond the trailing end of the second pole piece 9. That is, the diaphragm has an extension extending beyond the trailing edge of the second pole piece 9 (as shown at L1 in FIG. 2 , where L1 does not represent the length of the extension but is merely used to indicate the extension). This prevents short circuiting between the second pole piece 9 and the first pole piece 8. As shown in FIG. 2 , in some embodiments, the trailing edge of the diaphragm extension is located on the bend of the battery cell 1 closest to the trailing edge of the first pole piece 8. This can also improve the energy density of the battery.

[0045] The natural length of the extended section of the diaphragm is at least 5 mm, and may be 5-20 mm, preferably 8-10 mm, such as 8 mm, 9 mm, 10 mm.

[0046] When the tail end of the first electrode 8 serves as the end of the battery cell 1, at the tail end of the second electrode 9, the tail end of the fourth paste layer of the second electrode 9 exceeds the tail end edge of the second paste layer of the first electrode 8 (as shown by L2 in Figure 2), and the tail end of the third paste layer of the second electrode 9 exceeds the tail end edge of the first paste layer of the first electrode 8 (as shown by L3 in Figure 2). In this way, it can be ensured that the paste layer of the second electrode 9 exceeds the paste layer of the first electrode 8, preventing lithium deposition.

[0047] In some embodiments, in the winding direction, the trailing edge of the fourth paste layer of the second pole piece 9 extends beyond the trailing edge of the second paste layer of the first pole piece 8 opposite thereto, and the extending length is ≥1 mm. The trailing edge of the third paste layer of the second pole piece 9 extends beyond the trailing edge of the first paste layer of the first pole piece 8 opposite thereto, and the extending length is ≥1 mm.

[0048] When the battery cell 1 has a stacked core structure, the first electrode sheet 8, the isolation layer 7, and the second electrode sheet 9 are stacked sequentially along the thickness direction, as shown in Figure 3. An insulating layer 11 is provided in the area of ​​the first electrode sheet 8 near the first electrode tab 2. Specifically, the insulating layer is located on the first soft electrode tab in the first electrode tab 2. The material of the insulating layer includes, but is not limited to, at least one of aluminum oxide, polyimide, or boehmite. The insulating layer is used to prevent burrs from being generated when cutting the electrode tab. At the same time, the edge of the paste layer of the second electrode sheet 9 near the second electrode tab 4 is projected in the thickness direction within the projected area of ​​the insulating layer 11 in the thickness direction, thereby preventing the edge of the second electrode sheet 9 from contacting the current collector on the first electrode sheet 8, thereby causing a short circuit. In the width direction of the battery cell, the edge of the adhesive tape covering the second weld print near the battery cell extends beyond the edge of the insulating layer near the battery cell. The thickness of the adhesive tape is close to that of the insulating layer, thereby ensuring a smooth side interface of the battery cell.

[0049] The basic principles of this application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and non-restrictive, and should not be construed as necessarily possessed by each embodiment of this application. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, not for limitation. These details do not necessarily limit this application to the specific details employed.

[0050] The components and devices involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the accompanying drawings. As will be appreciated by those skilled in the art, these components and devices can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0051] It should also be noted that in the devices and equipment of the present application, the components can be decomposed and / or reassembled, and such decompositions and / or reassemblies should be regarded as equivalent solutions of the present application.

[0052] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0053] It should be understood that the qualifiers "first" and "second" used in the description of the embodiments of the present application are only used to more clearly illustrate the technical solution and cannot be used to limit the scope of protection of the present application.

[0054] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0055] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A battery, characterized in that: The invention comprises a battery cell and a shell wrapping the battery cell, wherein the battery cell comprises a first pole piece, an isolation layer and a second pole piece stacked in sequence, and a first pole ear connected to the first pole piece and a second pole ear connected to the second pole piece, wherein the first pole ear has a first welding mark, and the second pole ear has a second welding mark; Wherein, the metal material of the first pole ear is the same as the metal material of the shell, The first weld mark protrudes from the surface of the first electrode ear and faces the shell, and the first weld mark is not covered with adhesive tape.

2. The battery according to claim 1, characterized in that The shell includes a first resin layer, a metal layer and a second resin layer in sequence along the thickness direction, and a protruding height of the first weld mark is less than the sum of the thicknesses of the second resin layer and the metal layer.

3. The battery according to claim 1 or 2, characterized in that The second welding mark is protruded from the first surface and the second surface of the second electrode tab, and adhesive tape covering the second welding mark is provided on both surfaces.

4. The battery according to claim 3, characterized in that The adhesive tape covering the second weld mark and the first electrode tab are arranged side by side in the width direction of the battery cell.

5. The battery according to claim 3 or 4, characterized in that A protruding height of the second weld mark on the second surface is greater than a protruding height of the second weld mark on the first surface.

6. The battery according to any one of claims 3 to 5, characterized in that The thickness of the adhesive tape on the second surface is greater than or equal to the thickness of the adhesive tape on the first surface.

7. The battery according to any one of claims 3 to 6, characterized in that The thickness of the adhesive tape on the first surface is 10-100 microns, and the thickness of the adhesive tape on the second surface is 10-100 microns.

8. The battery according to any one of claims 3 to 7, characterized in that The projection of the adhesive tape in the thickness direction does not overlap with the projection of the electrode of the battery cell in the thickness direction.

9. The battery according to any one of claims 1 to 8, characterized in that The first pole piece, the isolation layer and the second pole piece are wound together, the outermost circle of the battery cell along the winding direction is a section of the first pole piece, and the tail end of the first pole piece is covered with a finishing glue; The tail end edge of the finishing glue is located on the bending section of the battery cell that is closest to the tail end edge of the first pole piece.

10. The battery according to any one of claims 1 to 9, characterized in that The first pole piece, the isolation layer and the second pole piece are wound together, the outermost circle of the battery cell along the winding direction is a section of the first pole piece, and the isolation layer has an extension section exceeding the trailing edge of the second pole piece; The tail end edge of the extension section is located on the bending section of the battery cell that is closest to the tail end edge of the first pole piece.

11. The battery according to claim 10, characterized in that The length of the extension section is 5-20 mm.

12. The battery according to any one of claims 1 to 11, characterized in that The two surfaces of the first pole piece have a first paste layer and a second paste layer respectively, and the two surfaces of the second pole piece have a third paste layer and a fourth paste layer respectively. The first paste layer of the first pole piece and the third paste layer of the second pole piece are opposite to each other, and the second paste layer and the fourth paste layer of the second pole piece are opposite to each other.

13. The battery according to claim 12, characterized in that At the tail end of the second pole piece, the tail end of the fourth paste layer exceeds the tail end edge of the second paste layer opposite thereto, and the exceeding length is ≥1 mm.

14. The battery according to claim 12 or 13, characterized in that: The tail end of the third paste layer exceeds the tail end edge of the first paste layer opposite thereto, and the exceeding length is ≥1 mm.

15. The battery according to any one of claims 1 to 8, characterized in that Along the thickness direction, the first pole piece, the isolation layer and the second pole piece are stacked in sequence.

16. The battery according to claim 15, characterized in that An insulating layer is provided in a region of the first pole piece close to the first pole lug, and a projection in the thickness direction of an edge of the paste layer of the second pole piece close to the second pole lug is located within a projection region of the insulating layer in the thickness direction.

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