Cylindrical battery including a jelly-roll structure for improving performance of a cylindrical battery

Abstract

The application discloses a cylindrical battery comprising a winding core structure for improving the performance of a cylindrical battery roller, and relates to the battery field.The cylindrical battery comprises a winding core structure and an organic electrolyte, and the winding core structure is wound by a positive electrode sheet and a negative electrode sheet.The positive electrode sheet comprises a positive electrode current collector, a positive electrode coating and a first empty foil area; the first empty foil area is provided with a separated positive electrode tab; the positive electrode tab extends from the first end of the positive electrode sheet; the negative electrode sheet comprises a negative electrode current collector, a negative electrode coating and a second empty foil area; the second empty foil area is provided with two separated negative electrode tabs; the negative electrode tabs extend from the second end of the negative electrode sheet; the winding core structure is externally provided with a first insulating layer close to the first end and a second insulating layer close to the second end; the first insulating layer can swell after being in contact with the organic electrolyte; the second insulating layer does not swell after being in contact with the organic electrolyte, or the swelling rate of the second insulating layer is smaller than that of the first insulating layer.The cylindrical battery can inhibit the shaking of the winding core structure in the steel shell, and further improve the performance of the cylindrical battery roller.

Description

Technical Field

[0001] This specification relates to the field of battery technology, and more particularly to a cylindrical battery including a core structure for improving the performance of a cylindrical battery drum. Background Technology

[0002] Cylindrical lithium batteries often employ a "single positive, double negative" tab design (i.e., one tab on the positive electrode and two or more tabs on the negative electrode) to reduce negative electrode impedance. This design increases the thickness of the negative electrode current collector at the bottom of the cell, resulting in an asymmetrical "stepped" structure with a smaller diameter at the top and a larger diameter at the bottom. In subsequent drum tests, the adhesive on the outside of the cell is prone to cracking and peeling due to stress concentration, thus losing its fixing and insulation function for the cell. This leads to the cell becoming loose and short-circuiting within the battery box, causing test failure. Summary of the Invention

[0003] In view of the shortcomings of the prior art, one object of this specification is to provide a cylindrical battery including a core structure for improving the performance of the cylindrical battery drum, which can suppress the shaking of the core structure within the steel casing, thereby improving the drum performance of the cylindrical battery.

[0004] To achieve the above objectives, this specification provides a cylindrical battery, including a core structure for improving the performance of the cylindrical battery drum and an organic electrolyte, wherein the core structure is formed by winding a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector, a positive electrode coating, and a first empty foil region; the positive electrode coating is applied to the surface of the positive current collector; the first empty foil region is the area on the surface of the positive current collector that is not coated with the positive electrode coating; a separate positive electrode tab is provided on the first empty foil region; the positive electrode tab extends from the first end of the positive electrode sheet. The negative electrode sheet includes a negative electrode current collector, a negative electrode coating, and a second empty foil area; the negative electrode coating is applied to the surface of the negative electrode current collector; the second empty foil area is the region on the surface of the negative electrode current collector where the negative electrode coating is not applied; two separate negative electrode tabs are provided on the second empty foil area; the negative electrode tabs extend from the second end of the negative electrode sheet; the first end and the second end are opposite ends; a first insulating layer and a second insulating layer are provided outside the core structure, the first insulating layer is located near the first end, and the second insulating layer is located near the second end; the first insulating layer can expand after contacting the organic electrolyte; the second insulating layer does not expand after contacting the organic electrolyte, or its expansion rate is less than that of the first insulating layer.

[0005] In a preferred embodiment, the first empty foil area is located in the middle region along the length direction of the positive electrode sheet, which is perpendicular to the axial direction of the core structure.

[0006] In a preferred embodiment, there are two second empty foil regions, and each second empty foil region is provided with one negative electrode tab; the two second empty foil regions are respectively located on both sides of the negative electrode sheet along its length.

[0007] In a preferred embodiment, the expansion rate of the first insulating layer after contact with the organic electrolyte is greater than 150%; the expansion rate of the second insulating layer after contact with the organic electrolyte is less than 5%.

[0008] In a preferred embodiment, the first insulating layer is made of expanding tape; preferably, the first insulating layer is made of polyurethane expanding tape.

[0009] In a preferred embodiment, the second insulating layer is made of non-expanding tape; preferably, the second insulating layer is made of any one of PI tape, PP tape, and PET tape.

[0010] In a preferred embodiment, the first insulating layer and the second insulating layer do not overlap, and the sum of the axial lengths of the first insulating layer and the second insulating layer is less than the axial length of the core structure.

[0011] In a preferred embodiment, the distance between the first insulating layer and the first end is 1mm to 3mm; the distance between the second insulating layer and the second end is 1mm to 3mm.

[0012] In a preferred embodiment, the length of the first insulating layer in the axial direction is 5mm to 40mm, or the length of the first insulating layer is ~ of the length of the core structure.

[0013] In a preferred embodiment, the length of the first insulating layer in the axial direction is 10mm to 30mm, or the length of the first insulating layer is ~ of the length of the core structure.

[0014] In a preferred embodiment, in the circumferential direction, the length of the first insulating layer is 1mm to 2mm smaller than the circumference of the core structure, and the length of the second insulating layer is 1mm to 2mm smaller than the circumference of the core structure.

[0015] Beneficial effects:

[0016] The cylindrical battery provided in this embodiment includes a core structure for improving the performance of the cylindrical battery drum and an organic electrolyte. The core structure has a positive electrode tab extending from a first end on the positive electrode sheet and two positive electrode tabs extending from a second end on the negative electrode sheet, resulting in a diameter at the first end being smaller than the diameter at the second end. By providing a first insulating layer near the first end and a second insulating layer near the second end on the outside of the core structure, the first and second insulating layers can fix and insulate the core structure, preventing it from disintegrating or making electrical contact with the steel casing. Simultaneously, since the first insulating layer expands upon contact with the organic electrolyte, it can undergo controllable expansion after electrolyte injection, compensating for the diameter of the first end and effectively filling the gap between the core structure and the inner wall of the battery steel casing at the first end. This provides support to the first end, suppresses the shaking of the core structure within the steel casing, and thus improves the drum performance of the cylindrical battery. After the core structure is installed in the steel shell and the battery is filled with electrolyte, the first insulating layer expands, which can ultimately compensate for the smaller core diameter at the first end. The second end, on the other hand, has a slightly larger diameter when the battery cell is installed. This design ensures that the second end of the core has a good match with the steel shell when the core is installed, ultimately achieving a good dimensional match between the overall core structure (especially at the first and second ends) and the steel shell.

[0017] Specific embodiments of the present invention are disclosed in detail with reference to the following description and accompanying drawings, indicating how the principles of the invention can be employed. It should be understood that the embodiments of the present invention are not limited in scope as a result.

[0018] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0019] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a core structure for improving the performance of a cylindrical battery drum provided in this embodiment; Figure 2 for Figure 1 A structural diagram from another perspective; Figure 3 This is a schematic diagram of the unfolded structure of a core structure provided in this embodiment. Figure 4 This is a schematic diagram of a cylindrical battery including the winding structure provided in this embodiment. Figure 5 for Figure 4 A schematic diagram of the cross-sectional structure of the AA surface in the middle; Figure 6 for Figure 5 Enlarged structural diagram at point B; Figure 7 for Figure 5 Enlarged structural diagram at point C; Figure 8 This is a schematic diagram of the broken positive electrode tab in Comparative Example 1.

[0022] Explanation of reference numerals in the attached figures: 100. Cylindrical battery; 10. Core structure; 101. Center hole; 20. Steel casing; 30. First current collector; 40. Second current collector; 50. Cap; 1. Positive electrode sheet; 11. Positive current collector; 12. Positive electrode coating; 13. First empty foil area; 2. Negative electrode sheet; 21. Negative current collector; 22. Negative electrode coating; 23. Second empty foil area; 3. Positive electrode tab; 4. Negative electrode tab; 5. First insulating layer; 6. Second insulating layer; 7. First end; 8. Second end; X, axial direction; Y, length direction. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0024] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or may be interposed with another element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or may be interposed with another element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Please see Figures 1 to 7 This application provides a core structure 10 and a cylindrical battery 100 for improving the performance of the cylindrical battery 100 roller. The cylindrical battery 100 includes the core structure 10 and an organic electrolyte.

[0027] Specifically, such as Figure 4 As shown, the cylindrical battery 100 further includes a steel shell 20, a wound core structure 10, a first current collector 30, a second current collector 40, and a cap 50. The wound core structure 10 is disposed inside the steel shell 20 and has a central hole 101. One side of the first current collector 30 is connected to the bottom of the steel shell 20, and the other side is connected to the end face of the wound core structure 10 at the second end 8. The second current collector 40 is connected to the end face of the wound core structure 10 at the first end 7. The first end 7 and the second end 8 are the two opposite ends of the wound core structure 10. The cap 50 is disposed on the side of the second current collector 40 facing away from the wound core structure 10.

[0028] It should be noted that the steel casing 20, first current collector 30, second current collector 40, and cap 50 of the cylindrical battery provided in this embodiment can be any suitable existing structure. To clearly and concisely illustrate the technical solution provided in this embodiment, the above-mentioned parts will not be repeated here, and the accompanying drawings have also been simplified accordingly. However, it should be understood that this embodiment is not limited in scope as a result.

[0029] This application does not limit the size of the core structure 10. Preferably, the core structure 10 of the 18650 or 21700 type cylindrical battery 100 can be selected.

[0030] Please see Figure 3 The core structure 10 is formed by winding a positive electrode 1 and a negative electrode 2. A separator (not shown) may be provided between the positive electrode 1 and the negative electrode 2.

[0031] The positive electrode 1 includes a positive current collector 11, a positive electrode coating 12, and a first empty foil region 13. The positive electrode coating 12 is coated on the surface of the positive current collector 11 (including...). Figure 3 (The upper and lower surfaces of the positive current collector 11). The first empty foil region 13 is the area on the surface of the positive current collector 11 that is not coated with the positive electrode coating 12. A separate positive electrode tab 3 is provided on the first empty foil region 13. The positive electrode tab 3 extends out of the positive electrode plate 1 from the first end 7.

[0032] Continue to refer to Figure 3 The negative electrode 2 includes a negative electrode current collector 21, a negative electrode coating 22, and a second empty foil region 23. The negative electrode coating 22 is coated on the surface of the negative electrode current collector 21 (including...). Figure 3 The upper and lower surfaces of the negative electrode current collector 21. The second empty foil region 23 is the area on the surface of the negative electrode current collector 21 where the negative electrode coating 22 is not applied. Two separate negative electrode tabs 4 are provided on the second empty foil region 23. The negative electrode tabs 4 extend from the second end 8 of the negative electrode sheet 2. (e.g., ...) Figure 1 As shown, the core structure 10 is provided with a first insulating layer 5 and a second insulating layer 6. The first insulating layer 5 is disposed near the first end 7, and the second insulating layer 6 is disposed near the second end 8. The first insulating layer 5 can expand after contacting the organic electrolyte.

[0033] In this embodiment, the second insulating layer 6 does not expand upon contact with the organic electrolyte, or its expansion rate is less than that of the first insulating layer 5. The second insulating layer 6 primarily needs to fix and insulate the core structure 10 near the second end 8, preventing the second end 8 of the core structure 10 from disintegrating or making electrical contact with the steel shell 20. The second insulating layer 6 only needs to achieve the effects of fixation and insulation; it does not need to have expansion properties. To reduce costs, the material of the second insulating layer 6 can be chosen to be one that does not expand upon contact with the organic electrolyte.

[0034] The core structure 10 provided in this embodiment for improving the performance of the cylindrical battery 100 roller has a positive electrode tab 3 extending from the first end 7 on the positive electrode sheet 1 and two positive electrode tabs 3 extending from the second end 8 on the negative electrode sheet 2. After the core is wound, since there is only one positive electrode tab 3 at the upper end (first end 7) of the core structure 10 and two negative electrode tabs 4 at the lower end (second end 8), this difference will not cause an excessive core size problem. However, since the dimensions of the core structure 10 and the steel shell 20 are often precisely designed, after the core structure 10 is placed into the steel shell 20, this small diameter difference will be amplified between the upper end of the core structure 10 and the inner wall of the steel shell 20. This gap can easily cause the upper end of the battery 100 to shake violently in subsequent roller tests, especially in roller tests, which can lead to the breakage of the positive current collector 11 on the upper cap 50 and ultimately cause the battery 100 to fail.

[0035] By providing a first insulating layer 5 near the first end 7 on the outside of the core structure 10, and a second insulating layer 6 near the second end 8 on the outside of the core structure 10, the first insulating layer 5 and the second insulating layer 6 can fix and insulate the core structure 10, preventing the core structure 10 from falling apart or making electrical contact with the steel shell 20. At the same time, since the first insulating layer 5 can expand after contact with the organic electrolyte, the first insulating layer 5 can expand controllably after the battery is filled with electrolyte, compensating for the diameter of the first end 7, effectively filling the gap between the core structure 10 and the inner wall of the battery steel shell 20 at the first end 7, increasing support for the first end 7, suppressing the shaking of the core structure 10 inside the steel shell 20, and thus improving the roller performance of the cylindrical battery 100. After the core structure 10 is installed into the steel shell 20 and the battery is filled with electrolyte, the first insulating layer 5 expands, which can ultimately compensate for the smaller core diameter at the first end 7. The second end 8 has a slightly larger diameter when the battery cell is installed. This design ensures that the second end 8 of the core has a good match with the steel shell 20 when the core is installed into the shell, and ultimately achieves a good size match between the overall diameter of the core structure 10 (especially at the first end 7 and the second end 8) and the steel shell 20.

[0036] In this embodiment, such as Figure 3 As shown, the first empty foil area 13 is located in the middle region along the length Y of the positive electrode sheet 1, and the length Y is perpendicular to the axial direction X of the core structure 10. The positive electrode tab 3 is generally connected to the first empty foil area 13 by welding. The separate positive electrode tab 3 extends out of the positive electrode sheet 1 from the first end 7. Along the axial direction X, the length of the positive electrode sheet 1 is greater than the length of the positive electrode tab 3 within the positive electrode sheet 1. Depending on the specific cell design, the length of the positive electrode tab 3 within the positive electrode sheet 1 is approximately half the axial length X of the positive electrode sheet 1, which is within a certain range.

[0037] Continue to refer to Figure 3 There are two second empty foil areas 23, each with a negative electrode tab 4. The two second empty foil areas 23 are located on opposite sides of the negative electrode sheet 2 along its length Y. The negative electrode tabs 4 are generally connected to the second empty foil areas 23 by welding. The two separate negative electrode tabs 4 extend from the second end 8 of the negative electrode sheet 2. In the axial direction X, the length of the negative electrode sheet 2 is greater than the length of the negative electrode tab 4 within the negative electrode sheet 2. Depending on the specific cell design, the length of the negative electrode tab 4 within the negative electrode sheet 2 is approximately half the axial length X of the negative electrode sheet 2, falling within a certain range.

[0038] In this embodiment, since the first end 7 is provided with one positive electrode tab 3 and the second end 8 is provided with two negative electrode tabs 4, forming a "one positive and two negative" tab distribution, and the root of all tabs (i.e., the part where the tab connects to the electrode sheet) does not exceed half the width of the electrode sheet, the average diameter of the second end 8 is larger than the average diameter of the first end 7. Therefore, the core structure 10 is not an ideal cylinder of equal diameter. Although this difference is small, since the process of inserting the core structure 10 into the steel shell 20 is precisely designed, if the diameter of the core structure 10 is slightly smaller, there will be a gap between the core structure 10 and the steel shell 20, causing shaking, which will greatly increase the probability of failure in the roller test. If the diameter of the core structure 10 is slightly larger, it will cause difficulty in inserting into the shell, or even make it impossible to insert into the steel shell 20.

[0039] For different models of cylindrical battery 100, the difference between the diameter of the second end 8 and the diameter of the first end 7 varies. Generally, the difference between the diameter of the second end 8 and the diameter of the first end 7 is 0.1mm to 0.5mm. More specifically, the difference between the diameter of the second end 8 and the diameter of the first end 7 is 0.3mm to 0.45mm.

[0040] The core structure 10 provided by this invention is suitable for cylindrical battery cells with traditional welded tabs. For such asymmetrical battery cells with different diameters at both ends, if uniform tape is still used for external insulation and fixation, it is difficult to simultaneously meet the different functional requirements of both ends: the larger diameter of the second end 8 requires robust insulation and fixation, while the smaller diameter of the first end 7 requires providing volume expansion filling space to improve roller test performance. This is a key improvement mechanism.

[0041] To address the issue of different diameters at both ends of the core structure 10 caused by the aforementioned tab arrangement, the key improvement of this invention lies in a differentiated adhesive application scheme. A first insulating layer 5 is attached to the outer surface of the core structure 10 near the first end 7 (i.e., the end with fewer tabs and a relatively smaller diameter), and the first insulating layer 5 is made of a material that can expand upon contact with a liquid.

[0042] Specifically, the first insulating layer 5 can be made of expandable tape. In this invention, expandable tape is defined as tape capable of controlled expansion after the battery is filled with electrolyte. This application does not impose any particular restrictions on the material or performance of the expandable tape; commercially available expandable tapes are acceptable.

[0043] This invention can use commercially available expansion tape, which needs to have an expansion rate greater than 150% after electrolyte injection. Preferably, the expansion rate of the first insulating layer 5 is greater than 200%.

[0044] Preferably, the first insulating layer 5 is made of polyurethane-based expanding tape, which expands after absorbing electrolyte, and the expansion rate can generally reach about 280%.

[0045] Compared to traditional termination tape (ordinary insulating tape), expansion tape is significantly more expensive, with a cost difference of about 10 times for the same size, and can significantly affect the final cost of a cylindrical battery cell by 3% to 5%. Therefore, making the final cost of cylindrical battery cells more competitive has become a more pressing issue.

[0046] If both the first insulating layer 5 and the second insulating layer 6 use ordinary terminating tape, the cost advantage can obviously be greatly increased, but the roller test will not pass; if both the first insulating layer 5 and the second insulating layer 6 use expanding tape, the cost will obviously be higher.

[0047] To balance safety and product cost, the second insulating layer 6 in this application is made of a material that does not expand upon contact with liquid. Preferably, the second insulating layer 6 is made of non-expanding adhesive tape, i.e., ordinary adhesive tape. More preferably, the second insulating layer 6 is made of any one of PI tape, PP tape, or PET tape. In this application, ordinary adhesive tape is defined as commercially available general adhesive tape, and relatively common PET tape can be selected. Generally, this type of tape does not expand or expands very little after contact with electrolyte in the battery cell, and can be understood as a non-expanding tape.

[0048] The second insulating layer 6 hardly expands after absorbing the electrolyte. This lack of expansion can be considered as an expansion rate of less than 5%, and further, it can be considered as an expansion rate of less than 2%.

[0049] In this embodiment, the first insulating layer 5 and the second insulating layer 6 do not overlap, which avoids increasing the diameter of the core structure 10. The sum of the lengths of the first insulating layer 5 and the second insulating layer 6 in the axial direction X is less than the length of the core structure 10 in the axial direction X.

[0050] Specifically, the distance between the first insulating layer 5 and the first end 7 is 1mm to 3mm, and the distance between the second insulating layer 6 and the second end 8 is 1mm to 3mm. This ensures that the first insulating layer 5 and the second insulating layer 6 can effectively cover the area that needs support or fixation, without interfering or curling when inserted into the shell due to being too close to the edge. Preferably, the distance between the first insulating layer 5 and the first end 7 is 2mm, and the distance between the second insulating layer 6 and the second end 8 is 2mm.

[0051] like Figure 2As shown, in the circumferential direction, the length of the first insulating layer 5 is 1mm to 2mm smaller than the circumference of the core structure 10, and the length of the second insulating layer 6 is 1mm to 2mm smaller than the circumference of the core structure 10. That is, the first insulating layer 5 and the second insulating layer 6 do not completely cover the entire circumference of the core structure 10 when they are attached, but a gap of 1mm to 2mm is deliberately reserved. This gap design helps the electrolyte to more smoothly penetrate the interior of the core structure 10 after the battery is filled with electrolyte, while taking into account the binding and fixing functions of the first insulating layer 5 and the second insulating layer 6 on the core structure 10.

[0052] Through the precise dimensional and process control described above, this embodiment successfully achieved effective filling of the gap near the first end 7 of the core structure 10 and reinforcement of the overall structure.

[0053] In this embodiment, the length of the first insulating layer 5 in the axial direction X cannot be too small. As the length of the first insulating layer 5 in the axial direction X decreases, its resistance to the roller test weakens. Therefore, the length of the first insulating layer 5 in the axial direction X is 5mm to 40mm, or the length of the first insulating layer 5 is 1 / 10 to 2 / 3 of the length of the core structure 10. Preferably, the length of the first insulating layer 5 in the axial direction X is 10mm to 30mm, or the length of the first insulating layer 5 is 1 / 5 to 1 / 2 of the length of the core structure 10.

[0054] The core structure 10 provided in this application for improving the performance of the cylindrical battery 100 has the following advantages: 1. Compared with traditional termination tape, the present invention introduces expansion tape at the first end 7, which solves the problem of roller failure; 2. Compared with the full-coverage expansion tape solution, the present invention uses ordinary tape at the second end 8, which does not significantly weaken the roller failure, thus greatly reducing manufacturing costs and increasing product competitiveness. 3. After repeated verification, applying expansion tape to end 7 of the first end significantly improved the performance of the roller compared to applying expansion tape to end 8 of the second end; conversely, applying ordinary tape to end 7 of the first end and expansion tape to end 8 of the second end resulted in the roller failing the performance test.

[0055] To verify the technical effect of the core structure 10 provided in this application for improving the performance of the cylindrical battery 100 roller, this application provides the following three embodiments and three comparative examples. The following embodiments and comparative examples all use 18650 type battery cells for demonstration. The height of the core structure 10 (i.e., the length of the core structure 10 in the axial direction X) is uniformly 61mm~62mm, and all adopt a one-positive-two-negative tab layout structure. The root of all tabs (i.e., the part where the tab connects to the electrode sheet) is strictly controlled within half the width of the electrode sheet to ensure the regularity of the winding process.

[0056] Example 1

[0057] Before expansion, the average diameter of the second end 8 is 17.64 mm, and the average diameter of the first end 7 is 17.22 mm, with a difference of 0.42 mm. The length of the first insulating layer 5 (expanding tape) in the axial direction X is 18 mm, and the length of the second insulating layer 6 (ordinary tape) in the axial direction X is 18 mm.

[0058] Specifically, after the winding process, due to the uneven distribution of the tabs, the core structure 10 exhibits a non-strict cylindrical shape. Precise measurements revealed significant differences in the diameter at different locations of the core structure 10: the average diameter of the first end 7 is 17.22 mm, while the average diameter of the second end 8 is 17.64 mm. To specifically compensate for this gap and enhance structural stability, this embodiment implements a differentiated adhesive application scheme. The total height of the core structure 10 (its length along its axial direction X) is 61 mm.

[0059] In a preferred embodiment, such as Figure 5 The image shown is a front cross-sectional view of the cylindrical battery 100 in this embodiment, clearly showing the internal structure of the core structure 10 after it is inserted into the casing and sealed. Figure 6 for Figure 5 The enlarged view of the adhesive application near the first end 7 (point B) shows the application state of the expansion tape near the first end 7, where the expansion tape fills the gap between the core structure 10 and the inner wall of the steel shell 20. Figure 7 for Figure 5 The enlarged view of the adhesive application near the second end 8 (point C) specifically shows the application state of the ordinary termination tape near the second end 8, clarifying the fixing and insulating functions of the ordinary termination tape near the second end 8. In this embodiment, a specific width of expansion tape is applied to the outside of the core structure 10 near the first end 7, while an ordinary termination tape of the same width is applied to the outside of the core structure 10 near the second end 8. The width (length in the axial direction X) of both tapes is set to 18 mm, and the length (unfolded length in the circumferential direction) of both tapes is set to 54 mm (1 mm to 2 mm smaller than the circumferential length of the core structure 10).

[0060] Example 2

[0061] The difference from Example 1 is that, before expansion, the average diameter of the second end 8 differs from the average diameter of the first end 7 by 0.40 mm. The length of the first insulating layer 5 (expanding tape) in the axial direction X is 30 mm, and the length of the second insulating layer 6 (ordinary tape) in the axial direction X is 30 mm.

[0062] Example 3

[0063] The difference from Example 1 is that, before expansion, the average diameter of the second end 8 differs from the average diameter of the first end 7 by 0.41 mm. The length of the first insulating layer 5 (expanding tape) in the axial direction X is 10 mm, and the length of the second insulating layer 6 (ordinary tape) in the axial direction X is 20 mm.

[0064] Comparative Example 1: The difference from Example 1 is that a single piece of ordinary tape is used instead of the first insulating layer 5 and the second insulating layer 6. The length of the ordinary tape in the axial direction X is 60 mm.

[0065] Specifically, unlike Example 1, Comparative Example 1 uses a conventional adhesive application method: a standard termination tape with a width (length in the axial X direction) of 60 mm is applied along the entire cylindrical surface of the core structure 10 (i.e., "full application"), and the tape's length (circumferential unfolded length) is 54 mm. This application method cannot compensate for the internal gaps caused by the difference in diameter at both ends. When the core is installed into the battery steel casing 20, the lower part of the negative electrode side with the largest diameter (near the second end 8) has the closest contact with the inner wall of the casing, which effectively becomes the mechanical fulcrum for the entire core within the steel casing 20.

[0066] During the roller test, the core will wobble around this fulcrum. Because the upper part of the positive electrode side (closest to the first end 7) has the smallest diameter and the largest gap with the shell wall, the wobbling amplitude is most intense at this location. This continuous, unrestrained mechanical wobbling causes stress concentration at the root of the positive electrode tab 3 (i.e., the connection between the positive electrode tab 3 and the first empty foil area 13), ultimately leading to the breakage of the positive electrode tab 3 at its root. Figure 8 As shown.

[0067] Comparative Example 2: The difference from Example 1 is that the first insulating layer 5 is made of ordinary tape, and the second insulating layer 6 is made of expanding tape; the length of the ordinary tape in the axial direction X is 18mm, and the length of the expanding tape in the axial direction X is 18mm.

[0068] Specifically, to further clarify the necessity of the synergistic effect of tape type and application position in this invention, Comparative Example 2 provides an adhesive application scheme that is the opposite of that in Example 1. The basic configuration of the core structure 10 is consistent with that of this invention, also adopting a tab layout structure with one positive and two negative tabs. The root of all tabs (i.e., the part where the tab connects to the electrode sheet) is strictly controlled within half the width of the electrode sheet to ensure the initial consistency of the core structure 10.

[0069] However, in the adhesive application scheme of Comparative Example 2, a setup contrary to the core concept of this invention was adopted. Specifically, at the position near the first end 7, where the diameter is smaller and the structural support is relatively weaker, a conventional termination tape was applied. This termination tape is 18 mm wide (length in the axial direction X) and 54 mm long (circumferential unfolded length). It is applied approximately 2 mm away from the first end 7 and does not completely cover the circumference of the cylindrical surface, leaving a gap of approximately 1 mm. At the position near the second end 8, where the structure is more stable and the diameter is larger, an expansion tape was applied. This expansion tape is exactly the same in size and application method as the termination tape at the other end, i.e., 18 mm wide, 54 mm long, 82 mm away from the second end, and with a 1 mm gap around the circumference of the cylindrical surface.

[0070] After assembling the battery using this method and conducting a roller test, the battery still failed, exhibiting the same failure mode as Comparative Example 1, namely, breakage at the root of the positive electrode tab 3. Analysis after the test indicated that although the expansion tape on the lower end face expanded after liquid injection, further reinforcing the fixation of the lower part of the core within the steel casing 20, this did not solve the fundamental problem. Because the average diameter of the first end 7 was still relatively small (approximately 17.22 mm), and only a non-expanding terminating tape was applied, this tape could not effectively fill the inherent gap between the first end 7 and the inner wall of the steel casing 20.

[0071] Therefore, under the mechanical stress simulated by the roller test, there is still significant sway space near the first end 7. The failure mechanism can be explained as follows: after the second end 8 is firmly supported by the expansion tape, the fulcrum of the entire core's swaying essentially moves towards the second end 8 and becomes more stable. This may, in turn, cause the bending moment and stress generated by the free swaying of the first end 7 to act more concentratedly on the only weak point—the root of the positive electrode tab 3. The aluminum positive electrode tab 3 is subjected to high-frequency bending stress at its root, and the local deformation accumulates rapidly until it reaches the fatigue limit of its metallic material, ultimately leading to fracture.

[0072] The results of Comparative Example 2 strongly demonstrate that simply using expanding tape cannot guarantee improved roller performance; it must be applied to the upper part of the core (near the first end 7), where the diameter is smaller and the need for mechanical support is more urgent, in order to specifically solve the wobbling problem. Comparative Example 2, through a reverse experiment, highlights the non-obviousness and technical contribution of the specific positional relationship of "expanding tape on the upper part and ordinary termination tape on the lower part" in this invention.

[0073] Comparative Example 3: The difference from Example 1 is that an integral expanding tape is used instead of the first insulating layer 5 and the second insulating layer 6, and the length of the expanding tape in the axial direction X is 60mm.

[0074] Specifically, Comparative Example 3 aims to further explore the impact of the adhesive area on the technical effect and economy. The basic configuration of the core structure 10 is consistent with that of the present invention, also adopting a one-positive-two-negative tab layout structure, and the root of all tabs (i.e. the part where the tab connects to the electrode sheet) is strictly controlled within half the width of the electrode sheet.

[0075] In Comparative Example 3, the adhesive application method was adjusted as follows: an expansion tape with a width (length in the axial direction X) of 60 mm and a length (unfolded length in the circumferential direction) of 54 mm was used to fully cover the entire cylindrical surface of the core structure 10 (i.e., "full coverage"). After the battery was filled with electrolyte, the expansion tape underwent controlled expansion. The tape located near the first end 7 effectively filled the gap between the upper part of the core and the inner wall of the steel shell 20 caused by the small diameter (average of about 17.22 mm), thereby increasing support and suppressing shaking. Its mechanism of action is the same as that of the expansion tape attached near the first end 7 in Embodiment 1 of the present invention. At the same time, the tape near the second end 8 and the middle also expanded. However, since the lower part of the core (second end 8) has a large diameter (average of about 17.64 mm) due to the large number of tabs, the structure is relatively stable. The filling and support of the expansion tape at this point is a redundant reinforcement. It does not produce any additional beneficial effects beyond the solution of this invention (applying expansion tape only near the first end 7) in solving the most critical problem of upper shaking in the roller test.

[0076] The roller test results show that the pass rate of Comparative Example 3 is comparable to that of Example 1 of this invention, and both achieve equivalent technical effects in suppressing the breakage of the positive electrode tab 3 and improving roller performance. However, the area of ​​expanding tape required by Comparative Example 3 is much larger than that of the present invention, which only applies the tape locally near the first end 7. As a functional special tape, expanding tape has a significantly higher unit cost than ordinary termination tape.

[0077] Therefore, compared to the full application of expansion tape, this invention significantly reduces battery manufacturing costs by precisely applying expansion tape to the critical support areas near the first end 7 and using inexpensive ordinary termination tape near the second end 8, while ensuring equally excellent vibration resistance. This design demonstrates superior technical insight and cost control, significantly enhancing the product's market competitiveness and highlighting the advanced nature and economic efficiency of this invention in industrial applications.

[0078] To more clearly illustrate the advantages of this application, some key experimental data from the above embodiments 1-3 and comparative examples 1-3 are summarized in the following table 1: Table 1 Example 1 The first insulation layer uses 18mm of expansion tape; the second insulation layer uses 18mm of ordinary tape. 100% 67% Example 2 The first insulation layer uses 30mm of expansion tape; the second insulation layer uses 30mm of ordinary tape. 100% 45% Example 3 The first insulation layer uses 10mm of expansion tape; the second insulation layer uses 20mm of ordinary tape. 99.5% 80% Comparative Example 1 A single piece of regular tape, 60mm thick. 80% 90% Comparative Example 2 The first insulation layer uses 18mm of ordinary adhesive tape; the second insulation layer uses 18mm of expanding adhesive tape. 83% 67% Comparative Example 3 A single piece of expansion tape, 60mm in diameter. 100% 0% In Table 1, the single-tape cost reduction rate is calculated based on fully expanded tape, with the cost of ordinary tape being 1 / 10 of that of expanded tape. Roller throughput is tested using a set of 200 samples.

[0079] As can be seen from Examples 1-3, with the increase of the amount of expanding tape used, the roller throughput increased from 99.5% for 10mm to 100% for 18mm and beyond. It can be seen that the above specifications can meet the actual requirements of the present invention.

[0080] As can be seen from Examples 1 and 2, the roller throughput is 100% in both examples. However, the cost reduction rate of Example 1 is 67% (greater than the 45% of Example 2). Therefore, the optimal width (length in the axial direction X) of the first insulating layer 5 and the optimal width (length in the axial direction X) of the second insulating layer 6 in this invention are 18mm.

[0081] While using a narrow expansion tape, regular tape must be used near the second end 8 for fit. Without regular tape, the structure of the core structure 10 near the second end 8 will easily fall apart. Therefore, the regular tape used for fit near the second end 8 is essential and indispensable.

[0082] The half of the core structure 10 closest to the first end 7 (occupying 1 / 2 of the core structure 10) is defined as the upper half of the core structure 10, and the half of the core structure 10 closest to the second end 8 (occupying 1 / 2 of the core structure 10) is defined as the lower half of the core structure 10. The average diameter of the lower half is larger than that of the upper half. While ensuring smooth insertion into the shell, a larger gap will inevitably be formed between the upper half and the steel shell 20, which needs to be filled with expansion tape.

[0083] It can be further understood that, since the diameter of the lower part is closely matched with that of the steel shell 20, and after the use of ordinary tape, it can form a good support effect with the steel shell 20 with almost no gap. Therefore, through this design, the half of the core structure 10 near the second end 8 can pass the roller test smoothly without the need for expansion tape.

[0084] It can also be understood that if the lower part uses expansion tape when it fits perfectly with the steel shell 20, the expansion tape has the technical effect of expansion, but there is no extra space to accommodate the expansion of the expansion tape. Therefore, an inward squeezing force will inevitably be generated. At this time, this extra squeezing is not needed by the core structure 10, which may further cause undesirable capacity decay and cycle decline in the cell design, making it difficult for cell manufacturing and design.

[0085] As for the upper part, there is a certain gap between it and the steel shell 20. This gap is caused by the one positive tab at the top and the two negative tabs at the bottom. If ordinary tape is still used in the upper part, the upper part will continue to vibrate during the roller test and will not pass the test at all. Therefore, it is necessary to limit the upper part. The introduction of expansion tape fills the gap between the upper part and the steel shell 20 and forms a suitable compressive force between the core structure 10 and the steel shell 20. The vibration resistance makes the upper part more stable, and the core structure 10 is also more stable.

[0086] Overall, the use of expanding tape in the upper part and ordinary tape in the lower part perfectly achieves the design goal of this invention.

[0087] In Comparative Example 1, no expanding tape was used; only ordinary tape was employed. According to the data in Table 1 of Comparative Example 1, without expanding tape, the roller pass rate of the product was only 80%, resulting in product defects.

[0088] In Comparative Example 2, the placement of the expanding tape and the ordinary tape was interchanged with that in Example 1. According to the data in Table 1 of Comparative Example 2, even with the introduction of some expanding tape, the increase in roller throughput was extremely limited, only increasing from 80% to 83%, and the product still failed to meet standards.

[0089] In Comparative Example 3, expansion tape was used exclusively. According to the data in Table 1 for Comparative Example 3, although the roller throughput met the requirements, its high price significantly weakened the product's competitiveness.

[0090] Compared to Comparative Example 3, this invention achieves a throughput of over 99.5% without compromising battery performance, particularly the crucial roller throughput. The cost of this invention is reduced by 45% to 80% or more compared to Comparative Example 3, thereby reducing the total cost of the entire cylindrical battery 100 by 3% to 5%.

[0091] In Examples 1-3, the upper part has a larger diameter due to the application of expansion tape, while the lower part has a slightly larger diameter due to the addition of an extra tab. This tape application design can complement the diameters of the upper and lower parts. This structure is an original discovery of the present invention, which can still achieve the effect of full application of expansion tape while greatly reducing the amount of expansion tape.

[0092] It should be noted that in the description of this specification, the terms "first," "second," etc., are used only for descriptive purposes and to distinguish similar objects; there is no order between them, nor should they be construed as indicating or implying relative importance. Furthermore, in the description of this specification, unless otherwise stated, "a plurality of" means two or more.

[0093] Any numerical values ​​cited herein include all values ​​ranging from a lower limit to an upper limit, increasing by one unit, with at least two units between any lower and any higher value. For example, if the quantity of a component or the value of a process variable (e.g., temperature, pressure, time, etc.) is described as being from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, the purpose is to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also explicitly listed in this specification. For values ​​less than 1, a unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1, etc. These are merely examples intended for explicit expression, and it can be assumed that all possible combinations of values ​​listed between the minimum and maximum values ​​are explicitly described in this specification in a similar manner.

[0094] Unless otherwise stated, all ranges include the endpoints and all numbers between them. The terms "approximately" or "about" used with ranges apply to both endpoints of the range. Thus, "approximately 20 to 30" is intended to cover "approximately 20 to approximately 30," including at least the specified endpoints.

[0095] All articles and references disclosed herein, including patent applications and publications, are incorporated herein by reference for various purposes. The term “substantially constitutes…” used to describe a combination should include the identified elements, components, parts, or steps, as well as other elements, components, parts, or steps that do not substantially affect the essential novelty of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, components, parts, or steps herein also contemplates embodiments substantially constituted by such elements, components, parts, or steps. The use of the term “may” herein is intended to indicate that any described attribute included by “may” is optional.

[0096] Multiple elements, components, parts, or steps can be provided by a single integrated element, component, part, or step. Alternatively, a single integrated element, component, part, or step can be divided into multiple separate elements, components, parts, or steps. The use of "a" or "an" to describe an element, component, part, or step does not imply the exclusion of other elements, components, parts, or steps.

[0097] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the appended claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the inventors have not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A cylindrical battery, comprising a core structure for improving the performance of the cylindrical battery drum and an organic electrolyte, wherein the core structure is formed by winding a positive electrode sheet and a negative electrode sheet, characterized in that: The positive electrode sheet includes a positive current collector, a positive electrode coating, and a first empty foil region; the positive electrode coating is applied to the surface of the positive current collector; the first empty foil region is the area on the surface of the positive current collector that is not coated with the positive electrode coating; a separate positive electrode tab is provided on the first empty foil region; the positive electrode tab extends from the first end of the positive electrode sheet. The negative electrode sheet includes a negative electrode current collector, a negative electrode coating, and a second empty foil area; the negative electrode coating is applied to the surface of the negative electrode current collector; the second empty foil area is the region on the surface of the negative electrode current collector that is not coated with the negative electrode coating; two separate negative electrode tabs are provided on the second empty foil area; the negative electrode tabs extend from the second end of the negative electrode sheet; the first end and the second end are opposite ends; The core structure is provided with a first insulating layer and a second insulating layer. The first insulating layer is disposed near the first end, and the second insulating layer is disposed near the second end. The first insulating layer can expand after contacting the organic electrolyte. The second insulating layer does not expand after contacting the organic electrolyte, or its expansion rate is less than that of the first insulating layer.

2. The cylindrical battery according to claim 1, characterized in that, The first empty foil area is located in the middle region along the length of the positive electrode sheet, which is perpendicular to the axial direction of the core structure.

3. The cylindrical battery according to claim 2, characterized in that, There are two second empty foil regions, and each second empty foil region is provided with a negative electrode tab; the two second empty foil regions are respectively located on both sides of the negative electrode sheet along its length.

4. The cylindrical battery according to claim 1, characterized in that, The expansion rate of the first insulating layer after contact with the organic electrolyte is greater than 150%; the expansion rate of the second insulating layer after contact with the organic electrolyte is less than 5%.

5. The cylindrical battery according to claim 1, characterized in that, The first insulating layer is made of expanding tape.

6. The cylindrical battery according to claim 1, characterized in that, The first insulating layer is made of polyurethane-based expanding tape.

7. The cylindrical battery according to claim 5, characterized in that, The second insulating layer is made of non-expanding tape.

8. The cylindrical battery according to claim 5, characterized in that, The second insulating layer is made of any one of PI tape, PP tape, or PET tape.

9. The cylindrical battery according to claim 1, characterized in that, The first insulating layer and the second insulating layer do not overlap, and the sum of the axial lengths of the first insulating layer and the second insulating layer is less than the axial length of the core structure.

10. The cylindrical battery according to claim 9, characterized in that, The distance between the first insulating layer and the first end is 1mm to 3mm; the distance between the second insulating layer and the second end is 1mm to 3mm.

11. The cylindrical battery according to claim 9, characterized in that, In the axial direction, the length of the first insulating layer is 5mm to 40mm, or the length of the first insulating layer is 1 / 10 to 2 / 3 of the length of the core structure.

12. The cylindrical battery according to claim 9, characterized in that, In the axial direction, the length of the first insulating layer is 10mm to 30mm, or the length of the first insulating layer is 1 / 5 to 1 / 2 of the length of the core structure.

13. The cylindrical battery according to claim 1, characterized in that, In the circumferential direction, the length of the first insulating layer is 1mm to 2mm smaller than the circumference of the core structure, and the length of the second insulating layer is 1mm to 2mm smaller than the circumference of the core structure.

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