Roll core, cylindrical battery and battery pack

Abstract

The invention provides a roll core, a cylindrical battery and a battery pack, and belongs to the technical field of batteries, the roll core is formed by sequentially superposing and winding a positive plate, a first diaphragm, a negative plate and a second diaphragm, the roll core further comprises a winding adhesive tape, the winding adhesive tape is pasted on the second diaphragm, and the winding adhesive tape is pasted on the second diaphragm from a winding terminal of the negative plate as a starting point to a winding terminal of the second diaphragm as a terminal point; an elastic area is arranged on the winding adhesive tape and is arranged on one side, far away from the negative plate, of the winding adhesive tape. The battery has the beneficial effects that the elastic area is arranged on one side, far away from the negative plate, of the winding adhesive tape, so that the non-uniform stress on the outermost layer of the winding core can be buffered, the non-uniform strain generated when the winding core is in contact with a battery shell is reduced, and the performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a roll core, a cylindrical battery and a battery pack. Background Art

[0002] With the rapid development of lithium-ion batteries in the fields of power and energy storage systems, the demand for high-energy lithium-ion batteries has shown a continuous growth trend. At the level of single cells, the energy density of lithium-ion batteries is mainly determined by the positive and negative electrode materials. At present, the energy density of ternary positive electrode materials has reached its limit. Therefore, in order to continue to improve the energy density of lithium-ion batteries, researchers and engineers have begun to turn their attention to the improvement of negative electrode materials.

[0003] In recent years, silicon negative electrodes have attracted much attention due to their higher theoretical specific capacity than traditional carbon negative electrodes. However, silicon negative electrodes are prone to volume expansion during the charging and discharging process, which is specifically manifested in: the lithium-silicon alloy formed by the alloying reaction causes the electrode volume to expand, resulting in an increase in the internal stress of the core; and lithium ions are embedded back into the positive electrode, causing the negative electrode structure to collapse. These phenomena cause the core to expand and collapse as a whole, causing damage to the electrode structure, leading to battery capacity decline, and thus affecting the battery's cycle life.

[0004] To address the stress problem caused by core expansion, the industry currently uses the following three solutions:

[0005] One is to improve the center hole structure. For example, Chinese patent CN218887283U9 discloses a cylindrical battery, which defines the range of the center hole diameter of the cylindrical battery as r / cell diameter R, 7% ≤ r / R ≤ 33%, 40mm ≤ R ≤ 80mm. This solution can avoid the risk of active material shedding or pole piece breakage under high stress, and the winding center hole can provide a buffer for the expansion of the battery cell, further reducing the risk of pole piece breakage.

[0006] The second is the core partition design, which adjusts the stress of the inner layer of the core through the partition design. For example, Chinese patent CN116826142A discloses a core and its preparation method and cylindrical battery, which involves a core layered nesting design, that is, the core is sequentially sleeved with n (n≥2) core units from the inside to the outside, and each core unit is composed of a first diaphragm, a negative electrode sheet, a second diaphragm and a positive electrode sheet wound in sequence, and the electrode formula and thickness in each unit are specified. This solution can buffer the excessive stress in the inner circle of the core, significantly improve the phenomenon of electrode breakage and material drop, and at the same time, improve the energy density of the battery while ensuring battery performance.

[0007] The third is to optimize the design of the positive electrode sheet, design a stress buffer layer between the current collector and the tab to prevent the aluminum foil from breaking due to the shearing effect of the tab. For example, Chinese patent CN108281609A discloses a positive electrode sheet with a tab, a preparation method thereof, and a lithium-ion battery comprising the positive electrode sheet, which involves a positive electrode sheet including a current collector, a stress buffer conductive layer with holes, a tab, and a tape. The surface of the current collector is provided with a positive electrode slurry layer and a blank area, and the stress buffer conductive layer, the tab, and the tape are sequentially arranged from bottom to top in the blank area. The stress buffer conductive layer is an elastic double-sided conductive tape with a thickness of 30μm-50μm, and the material is a composite material of an elastic binder and any one or at least two of carbon powder, graphene or carbon nanotubes, and the surface structure is a pyramid or pyramid-like structure. This solution can release the shear stress of the positive electrode tab on the aluminum foil, avoid cracking of the aluminum foil during the cycle, and improve the cycle performance.

[0008] However, although these technical solutions have alleviated the core expansion and stress problems caused by silicon negative electrodes to a certain extent, the core of lithium-ion batteries will expand during the charge and discharge process and will be constrained by the rigid outer shell, resulting in point contact between the outer layer of the core and the inner wall of the steel shell at the beginning of the cycle. This point contact will pull other areas of the core, resulting in uneven strain on the core as a whole. As the cycle continues, the stress between the pole pieces will continue to increase, and due to the constraints of the steel shell, the scaling ability of the core will become weaker, resulting in the largest radial stress in the outermost layer of the core and the largest circumferential stress in the center, which will eventually cause uneven distribution of electrolyte in the core and uneven overall stress. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a winding core for buffering battery stress; on the other hand, it also provides a cylindrical battery; on the other hand, it also provides a battery pack.

[0010] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0011] A winding core, wherein the positive electrode sheet, the first separator, the negative electrode sheet and the second separator are stacked and wound in sequence, and the winding core further comprises:

[0012] A winding tape, the winding tape is attached to the second separator and starts from the winding terminal of the negative electrode sheet and ends at the winding terminal of the second separator;

[0013] The winding tape is provided with an elastic area, and the elastic area is arranged on a side of the winding tape away from the negative electrode sheet.

[0014] Preferably, the winding tape further comprises a base layer and discontinuous regions, wherein the discontinuous regions and the elastic regions are alternately arranged on the base layer.

[0015] Preferably, the elastic zone comprises:

[0016] A first elastic region is disposed near a winding terminal of the negative electrode sheet; and / or

[0017] The second elastic region and the third elastic region are located between the winding terminal of the negative electrode sheet and the outermost circumference of the winding core; and / or

[0018] The fourth elastic zone is located on the outermost circumference of the winding core.

[0019] Preferably, the length of the fourth elastic zone is respectively greater than the lengths of the first elastic zone, the second elastic zone and the third elastic zone.

[0020] Preferably, the length of the first elastic region is 10 mm-15 mm; and / or

[0021] The length of the second elastic zone is 10 mm to 15 mm; and / or

[0022] The length of the third elastic zone is 10mm-15mm; and / or

[0023] The length of the fourth elastic zone is 130mm-140mm.

[0024] Preferably, a current collector is provided on the positive electrode sheet, and a plurality of flexible areas are provided on the current collector, and the plurality of flexible areas are distributed at intervals along the circumferential direction.

[0025] Preferably, the flexible zone comprises:

[0026] A first flexible zone is located in the inner layer of the winding core; and / or

[0027] A second flexible zone is located in the middle layer of the winding core; and / or

[0028] The third flexible zone is located on the outer layer of the winding core.

[0029] Preferably, the flexible region is a porous conductive carbon layer.

[0030] A second aspect of the present invention is to provide a cylindrical battery, which includes a battery housing, in which the winding core as described above is installed.

[0031] A third aspect of the present invention is to provide a battery pack comprising a plurality of cylindrical batteries as described above.

[0032] The advantages or beneficial effects of the technical solution of the present invention are:

[0033] The present invention provides an elastic area on the side of the winding tape away from the negative electrode sheet, which can buffer the uneven stress of the outermost layer of the winding core and reduce the uneven strain generated when the winding core contacts the battery shell, thereby improving the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a tape reel in a preferred embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a current collector in a preferred embodiment of the present invention; Figure 1 and Figure 2 In the figure, D1 indicates the terminal direction of the negative electrode sheet, and D2 indicates the outermost circumferential direction of the winding core;

[0036] Figure 3 A schematic diagram of a current collector in a preferred embodiment of the present invention;

[0037] Figure 4 A schematic diagram of a current collector in a preferred embodiment of the present invention;

[0038] Figure 5 A schematic diagram of a current collector in a preferred embodiment of the present invention;

[0039] Figure 6 Schematic diagram of the current collector in a preferred embodiment of the present invention; wherein D3 represents the inner layer direction of the winding core, and D4 represents the outer layer direction of the winding core.

[0040] Description of reference numerals:

[0041] 1. Winding core; 2. First separator; 3. Negative electrode sheet; 4. Positive electrode sheet; 40. Current collector; 41. Positive electrode slurry area; 421. First flexible area; 422. Second flexible area; 423. Third flexible area; 5. Winding tape; 50. Base layer; 51. First elastic area; 52. First discontinuous area; 53. Second elastic area; 54. Second discontinuous area; 55. Third elastic area; 56. Third discontinuous area; 57. Fourth elastic area; 6. Second separator. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0045] See also Figure 1 In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a winding core is provided, wherein the winding core 1 is formed by stacking and winding a positive electrode sheet 4, a first separator 2, a negative electrode sheet 3, and a second separator 6 in sequence, and the winding core 1 also includes:

[0046] The winding tape 5 is attached to the second separator 6 and has a winding terminal of the negative electrode sheet 3 as a starting point and a winding terminal of the second separator 6 as an end point;

[0047] An elastic area is provided on the winding tape 5 , and the elastic area is provided on a side of the winding tape 5 away from the negative electrode sheet 3 .

[0048] Specifically, in order to solve the problem of core expansion caused by the silicon negative electrode, the embodiment of the present invention provides elastic areas arranged at intervals on the side of the winding tape 5 away from the negative electrode sheet 3. The elastic effect of the elastic areas at different stages buffers the uneven stress on the outermost layer of the core, thereby reducing the uneven strain generated when the core contacts the battery casing.

[0049] As a preferred embodiment, the winding tape 5 further includes a base layer 50 and intermittent regions, and the intermittent regions and the elastic regions are alternately arranged on the base layer 50 .

[0050] In this embodiment, the base layer 50 is made of PI or PET.

[0051] Intermittent areas are provided between the elastic areas. The intermittent areas may be blank areas or left blank areas, or may be other materials that can promote wetting, such as but not limited to polar materials, perfluorophenyl azide compounds PFPA, and surface-treated tape films.

[0052] During the high-rate charge and discharge process, the blank area retained on the tape can promote the circulation, infiltration and backflow of the electrolyte in the core, solving the problem that the electrolyte is difficult to exist in the center hole and difficult to flow back to the electrode layers, thereby improving the performance and efficiency of the battery.

[0053] The elastic area is made of thermoplastic polyurethane (TPU), which has excellent elasticity and chemical corrosion resistance as well as good mechanical properties, and can be compounded with PI or PET materials.

[0054] As a preferred embodiment, the number of the elastic regions does not exceed four.

[0055] In this embodiment, the winding tape 5 is attached to the outermost second separator 6 , with the winding terminal of the negative electrode sheet 3 as the starting point and the winding terminal of the second separator 6 as the end point.

[0056] The winding tape 5 is provided with a base layer 50, elastic regions, and discontinuous regions, and the number of the elastic regions is ≤ 4. The discontinuous regions are arranged between the elastic regions, and the number of the elastic regions is one more than the number of the discontinuous regions.

[0057] As a preferred embodiment, the elastic region includes:

[0058] The first elastic region 51 is disposed close to the winding terminal of the negative electrode sheet 3; and / or

[0059] The second elastic region 53 and the third elastic region 55 are located between the winding end of the negative electrode sheet 3 and the outermost circumference of the winding core 1; and / or

[0060] The fourth elastic region 57 is located on the outermost circumference of the winding core 1 .

[0061] The embodiment of the present invention takes the arrangement of four elastic regions as an example, such as a first elastic region 51 , a second elastic region 53 , a third elastic region 55 and a fourth elastic region 57 .

[0062] The first elastic region 51 is close to the winding end of the negative electrode sheet 3 .

[0063] The second elastic region 53 and the third elastic region 55 are located between the circumference of the outermost circle and the winding terminal of the negative electrode sheet.

[0064] The fourth elastic zone 57 is arranged on the outermost circumference, that is, the fourth elastic zone 57 is on the last circumference of the winding core. The fourth elastic zone 57 is used as an elastic layer between the outermost circle of the winding core and the steel shell. When the outermost layer of the winding core contacts the steel shell, the elastic layer can reduce the uneven strain caused by the contact between the winding core and the steel shell.

[0065] As a preferred embodiment, the length of the fourth elastic region 57 is greater than the lengths of the first elastic region 51 , the second elastic region 53 and the third elastic region 55 .

[0066] Specifically, in this embodiment, at least one elastic region is located on the outermost circumference, and other elastic regions are located between the outermost circumference and the terminal of the negative electrode sheet 3. The length of the elastic region on the outermost circumference is greater than the length of other elastic regions between the outermost circumference and the terminal of the negative electrode sheet 3. When the outermost layer of the winding core contacts the steel shell, the elastic layer can reduce the uneven strain caused by the contact between the winding core and the steel shell.

[0067] For the sake of clarity, the length in the present invention refers to the size of the winding core in its winding direction (or circumferential direction), and the width refers to the size of the winding core in the axial direction.

[0068] As a preferred embodiment, the length of the first elastic region 51 is 10 mm-15 mm; and / or

[0069] The length of the second elastic region 53 is 10 mm to 15 mm; and / or

[0070] The length of the third elastic region 55 is 10 mm to 15 mm; and / or

[0071] The length of the fourth elastic zone 57 is 130 mm-140 mm.

[0072] In this embodiment, the total length of the winding tape 1 is 130 mm-230 mm, the width is 60 mm-70 mm, and the thickness is 40 μm-50 μm.

[0073] In this embodiment, the width of the elastic area is the same as the width of the winding tape 1 .

[0074] The first elastic region 51 , the second elastic region 53 and the third elastic region 55 are all the same in length, width and thickness.

[0075] Specifically, the lengths of the first elastic region 51 , the second elastic region 53 and the third elastic region 55 are 10 mm to 15 mm, the widths are 60 mm to 70 mm, and the thicknesses are 5 μm to 10 μm, respectively.

[0076] The fourth elastic zone has a length of 130 mm to 140 mm, a width of 60 mm to 70 mm, and a thickness of 5 μm to 10 μm.

[0077] Furthermore, the discontinuity zone includes:

[0078] A first discontinuous area 52, located between the first elastic area 51 and the second elastic area 53;

[0079] A second discontinuous area 54, located between the second elastic area 53 and the third elastic area 55;

[0080] The third discontinuous zone 56 is located between the third elastic zone 55 and the fourth elastic zone 57 .

[0081] Specifically, the elastic areas and the discontinuous areas are spaced apart, and discontinuous areas are provided between the four elastic areas, and the discontinuous areas are blank areas of the base layer. For example, a first discontinuous area 52 is provided between the first elastic area 51 and the second elastic area 53, a second discontinuous area 54 is provided between the second elastic area 53 and the third elastic area 55, and a third discontinuous area 56 is provided between the third elastic area 55 and the fourth elastic area 57.

[0082] During high-rate charge and discharge, it is difficult for the electrolyte to remain in the central hole and to flow back between the electrode layers. At this time, a blank area is set on the outermost layer of the winding core to facilitate the circulation, infiltration or reflux of the electrolyte.

[0083] Specifically, the lengths of the first intermittent zone 52, the second intermittent zone 54 and the third intermittent zone 56 are 10 mm to 15 mm, and the widths are 55 mm to 65 mm, respectively.

[0084] As a preferred embodiment, a current collector 40 is provided on the positive electrode sheet 4 , and a plurality of flexible areas are provided on the current collector 40 , and the plurality of flexible areas are distributed at intervals along the circumferential direction.

[0085] Specifically, the current collector 40 is a positive electrode current collector. From the perspective of the battery cell pole piece design, the N / P ratio (the margin of the negative electrode capacity to the positive electrode capacity) is usually greater than 1, in order to ensure that the negative electrode can accommodate the lithium ions released from the positive electrode and avoid lithium precipitation caused by excessive lithium ions during charging. From the perspective of the negative electrode material of the lithium-ion battery, a high-energy-density silicon negative electrode (silicon-carbon or silicon-oxygen material) is usually used to improve the energy density of the entire battery, but the silicon negative electrode produces a large volume expansion during the charging and discharging process, resulting in the electrolyte between the positive and negative electrodes being squeezed out, and the liquid-solid-liquid interface contact between the electrode and the electrolyte deteriorates, affecting the battery cycle performance.

[0086] Considering the above two aspects, the flexible area is arranged on the positive electrode current collector.

[0087] In this embodiment, flexible areas are arranged at intervals along the circumferential direction on the current collector 40 , and the flexible areas are used as buffers to relieve stress on the outer layer, middle layer and inner layer of the winding core.

[0088] In this embodiment, the core 1 is a jelly-like core. For a cylindrical lithium ion jelly-like core, the flexible area is located on the upper layer of the positive electrode current collector.

[0089] There is no filler or slurry between the flexible area and the positive electrode current collector.

[0090] In this embodiment, the flexible region does not contain positive electrode active material.

[0091] In this embodiment, the flexible region also does not contain negative electrode active material.

[0092] The flexible area and the positive electrode slurry area 41 (composed of positive electrode active material, binder, conductive agent, solvent, etc.) are adjacent to each other and are spaced apart from each other.

[0093] The flexible areas are distributed at intervals along the circumference of the jelly-like roll core.

[0094] As a preferred embodiment, the number of flexible zones is not less than 3, that is, ≥3.

[0095] In the core design, the number of flexible areas can be determined by the total pole piece length and the desired design energy density. Since the flexible area does not contain positive and negative active materials, it can avoid stress from adjacent pole piece layers, thereby enhancing the structural stability of the entire core. However, the presence of the flexible area will also reduce the proportion of active materials accordingly, which will have a certain impact on the energy density of the core. Therefore, in actual design, the number of flexible areas can be adjusted according to specific design requirements.

[0096] In order to achieve the best performance, it is necessary to comprehensively consider the balance between the number of flexible areas and the structural performance and energy density of the core. If the number is too large, the energy density of the battery will be low.

[0097] As a preferred embodiment, the flexible zone includes:

[0098] The first flexible area 421 is located in the inner layer of the winding core 1;

[0099] The second flexible area 422 is located in the middle layer of the winding core 1;

[0100] The third flexible zone 423 is located on the outer layer of the winding core 1 .

[0101] The embodiment of the present invention is explained by taking the setting of three flexible zones as an example, such as the first flexible zone 421, the second flexible zone 422 and the third flexible zone 423, which are respectively located in the inner layer (Inner Layer), the middle layer (Middle Layer) and the outer layer (Outer Layer) of the jelly-like roll core to achieve a balance between structural stability and energy density.

[0102] As a preferred embodiment, the flexible region is a porous conductive carbon layer.

[0103] In lithium-ion batteries, the current collector 40 mainly refers to metal foil, such as copper foil, aluminum foil, and may also include a tab.

[0104] In the embodiment of the present invention, a porous conductive carbon layer is coated on the surface of the current collector 40 . The flexible area is the coating area of ​​the conductive carbon layer. The conductive carbon layer is porously distributed, thereby further improving the conductive properties and electrochemical properties of the current collector 40 .

[0105] The porous conductive carbon layer has excellent conductivity and good pore structure, which can not only effectively improve the charge and discharge efficiency of the battery, but also promote the penetration of the electrolyte and the transmission of ions.

[0106] Furthermore, the thickness of the porous conductive carbon layer is 1 μm to 5 μm.

[0107] Specifically, in this embodiment, only a porous conductive carbon layer is coated on the current collector 40 , and the thickness of the conductive carbon layer is in the range of several microns.

[0108] The thickness of the conductive carbon layer is preferably 1 to 5 μm to ensure the best balance between conductivity and mechanical strength, to avoid increased battery internal resistance and decreased energy density due to excessive thickness, or poor conductivity and structural fragility due to excessive thinness.

[0109] By way of example and not limitation, the thickness of the conductive carbon layer may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0110] In this embodiment, the length of the conductive carbon layer is the same as the width of the positive electrode sheet; the width of the conductive carbon layer is the circumferential length of the positive electrode sheet, which is several millimeters.

[0111] In this embodiment, the width of the third flexible zone 423 is much larger than the width of the first flexible zone 421 and the width of the second flexible zone 432 ; the width of the second flexible zone 432 is larger than the width of the first flexible zone 431 , thereby increasing the conductivity.

[0112] Preferably, the width WI of the first flexible zone 431 is 1 mm to 2 mm. By way of example and not limitation, WI may be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.

[0113] The width WM of the second flexible zone 432 is 3 mm to 10 mm. By way of example and not limitation, WM may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc.

[0114] The width WO of the third flexible zone 433 is 10 mm to 18 mm. By way of example and not limitation, WO can be 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, etc.

[0115] As a preferred embodiment, the porous conductive carbon layer is made of carbon fiber material.

[0116] Specifically, in this embodiment, carbon fiber is used as the material of the conductive carbon layer. The carbon fiber material has a high elastic modulus, which can relieve the interlayer stress between the pole pieces caused by the charging and discharging process, and is suitable for high curvature electrodes of jelly-like winding cores. At the same time, carbon fiber has excellent conductivity, which can improve the overall electron transmission efficiency of the winding core and ensure a continuous electron transmission path between the flexible area and the adjacent positive electrode slurry layer.

[0117] The present invention also provides a cylindrical battery, which includes a battery shell (such as the steel shell mentioned above), and a winding core for buffering battery stress as mentioned above is installed in the battery shell.

[0118] Preferably, the cylindrical battery is a lithium-ion cylindrical battery.

[0119] Specifically, for the outer layer of the winding core, the winding tape is used as the object, and elastic areas and discontinuous areas are designed in stages on the winding tape 10. Among them, the elastic area can resist the uneven strain generated by the winding core during the charge and discharge cycle. The discontinuous area is set between the elastic areas to facilitate the flow of electrolyte, ensure the uniform penetration of the electrolyte in the winding core, and further improve the performance of the battery.

[0120] For the outer layer, inner layer and middle layer of the winding core, a flexible area is set on the current collector 40 to increase the conductivity; at the same time, the expansion stress generated by the interlayer pole pieces due to the charging and discharging process is relieved, and the potential damage between the pole pieces is reduced, thereby extending the service life of the battery.

[0121] The embodiment of the present invention does not need to add an additional external structure to the cylindrical battery, thereby ensuring the integrity of the electrode structure and the superiority of the battery performance.

[0122] The advantages or beneficial effects of adopting the above technical solution are: the present invention arranges elastic areas and discontinuous areas on the tape at intervals and alternately. Due to the setting of the elastic areas, the uneven strain generated when the winding core contacts the battery casing can be reduced; at the same time, during the high-rate charging and discharging process, the setting of the discontinuous areas promotes the circulation, infiltration and reflux of the electrolyte, solves the problem that the electrolyte is difficult to exist in the center hole and difficult to reflux to the electrode layers, thereby improving the performance and efficiency of the battery.

[0123] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A winding core, characterized in that: The winding core is formed by stacking and winding a positive electrode sheet, a first separator, a negative electrode sheet, and a second separator in sequence, and the winding core also includes: A winding tape, the winding tape is attached to the second separator and starts from the winding terminal of the negative electrode sheet and ends at the winding terminal of the second separator; The winding tape is provided with an elastic area, and the elastic area is arranged on a side of the winding tape away from the negative electrode sheet.

2. The winding core according to claim 1, characterized in that: The winding tape further comprises a base layer and discontinuous regions, wherein the discontinuous regions and the elastic regions are alternately arranged on the base layer.

3. The winding core according to claim 1, characterized in that: The elastic zone comprises: A first elastic region is disposed near a winding terminal of the negative electrode sheet; and / or The second elastic region and the third elastic region are located between the winding terminal of the negative electrode sheet and the outermost circumference of the winding core; and / or The fourth elastic zone is located on the outermost circumference of the winding core.

4. The winding core according to claim 3, characterized in that: The length of the fourth elastic zone is greater than the lengths of the first elastic zone, the second elastic zone, and the third elastic zone, respectively.

5. The winding core according to claim 3, characterized in that: The length of the first elastic region is 10 mm to 15 mm; and / or The length of the second elastic zone is 10 mm to 15 mm; and / or The length of the third elastic zone is 10mm-15mm; and / or The length of the fourth elastic zone is 130mm-140mm.

6. The winding core according to claim 1, characterized in that: A current collector is arranged on the positive electrode sheet, and a plurality of flexible areas are arranged on the current collector. The plurality of flexible areas are distributed at intervals along the circumferential direction.

7. The winding core according to claim 6, characterized in that: The flexible zone comprises: A first flexible zone is located in the inner layer of the winding core; and / or A second flexible zone is located in the middle layer of the winding core; and / or The third flexible zone is located on the outer layer of the winding core.

8. The winding core according to claim 6, characterized in that: The flexible region is a porous conductive carbon layer.

9. A cylindrical battery, characterized in that: The cylindrical battery comprises a battery housing, in which the winding core according to any one of claims 1 to 8 is installed.

10. A battery pack, characterized in that: The invention comprises a plurality of cylindrical batteries as claimed in claim 9.

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