Secondary battery

Abstract

Some embodiments of this utility model provide a secondary battery, comprising: a core, formed by winding a positive electrode sheet, a negative electrode sheet, and a separator between the positive and negative electrode sheets; the negative electrode sheet including a first negative electrode corner segment and a second negative electrode corner segment arranged sequentially along the winding direction of the core, the first negative electrode corner segment being connected to the starting end of the negative electrode sheet; and support members respectively disposed on the inner sides of the first and second negative electrode corner segments of the negative electrode sheet. The above technical solution can at least improve the electrode contact at the corners, thereby improving the lithium plating problem at the corners.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, provides a secondary battery. Background Technology

[0002] In the field of new energy power batteries, the application of rechargeable batteries is becoming increasingly widespread. These batteries (such as lithium-ion batteries) can be used in vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, e-cigarettes, digital products, power tools, power units, and other electronic devices. Currently, there are generally two methods for assembling electrode sheets in rechargeable batteries: winding and stacking. While the winding process has high production efficiency, the large gaps and poor contact between the electrodes at the inner corners of the winding layer can easily lead to lithium plating, a problem that urgently needs to be addressed. Utility Model Content

[0003] To address the aforementioned problems in the prior art, this application provides a secondary battery that can at least improve the electrode contact at the corner, thereby improving the lithium plating problem at the corner.

[0004] According to one aspect of this application, a secondary battery is provided, comprising: a core formed by winding a positive electrode sheet, a negative electrode sheet, and a separator between the positive and negative electrode sheets; the negative electrode sheet including a first negative electrode corner segment and a second negative electrode corner segment sequentially arranged along the winding direction of the core, the first negative electrode corner segment being connected to the starting end of the negative electrode sheet; and support members respectively disposed inside the first and second negative electrode corner segments of the negative electrode sheet.

[0005] In some embodiments, the secondary battery further includes a flat support member, which is connected along the winding direction between the support member inside the first negative electrode corner segment and the support member inside the second negative electrode corner segment.

[0006] In some embodiments, the support includes a substrate and an adhesive layer, the adhesive layer being located between the substrate and the negative electrode sheet and attached to the surface of the first negative electrode corner segment and the second negative electrode corner segment of the negative electrode sheet.

[0007] In some embodiments, the starting end of the negative electrode extends beyond the starting end of the support in the opposite direction to the winding direction.

[0008] In some embodiments, the starting end of the negative electrode sheet extends 2mm-30mm beyond the starting end of the support in the opposite direction to the winding direction.

[0009] In some embodiments, along the winding direction, the negative electrode sheet further includes a first negative electrode straight section connecting the first negative electrode corner section and the second negative electrode corner section, and the positive electrode sheet includes a first positive electrode corner section connected to the starting end of the positive electrode sheet. The starting end of the positive electrode sheet is located outside the first negative electrode straight section of the negative electrode sheet, wherein the first negative electrode corner section extends beyond the starting end of the positive electrode sheet in the opposite direction of the winding direction, and the second negative electrode corner section is located inside the first positive electrode corner section.

[0010] In some embodiments, the thickness of the support is greater than 30 micrometers.

[0011] In some embodiments, along the winding direction, the diaphragm includes a first diaphragm corner segment and a second diaphragm corner segment arranged sequentially, the first diaphragm corner segment being located inside the first negative electrode corner segment and the second diaphragm corner segment being located inside the second negative electrode corner segment; wherein, the support member is respectively arranged inside or outside the first diaphragm corner segment and the second diaphragm corner segment.

[0012] In some embodiments, in a first direction, the negative electrode sheet includes an electrode body and a negative electrode tab extending from the electrode body, wherein the first direction is parallel to the axial direction of the center hole of the core; in the first direction, the opposite ends of the support member extend beyond the opposite ends of the electrode body of the negative electrode sheet.

[0013] In some embodiments, in the first direction, the opposite ends of the support extend 1 mm to 5 mm beyond the opposite ends of the electrode body.

[0014] In some embodiments, the support is an adhesive tape attached to the negative electrode or diaphragm.

[0015] The above-described technical solution of this application provides a support member on the inner side of the first and second negative electrode corner sections within the core. This support member provides support and prevents the electrode from collapsing inwards, reduces the distance between the negative and positive electrode sections at the corner, and improves the contact between the positive and negative electrode sections at the corner, thereby mitigating the lithium plating problem at the corner. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It is worth noting that, according to industry standard practice, the components are not drawn to scale and are only used for illustrative purposes. In fact, for clarity of discussion, the dimensions of the components can be arbitrarily increased or decreased.

[0017] Figure 1The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0018] Figure 2 This is an exploded schematic diagram of a secondary battery cell provided in some embodiments of this application.

[0019] Figures 3 to 8 The diagram shows the structure of the core provided in different embodiments of this application.

[0020] Figure 9 This is a partial schematic diagram of the core in one embodiment of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0022] The following disclosure provides numerous different embodiments or instances for implementing various features of the provided subject matter. Specific examples of elements and arrangements will be described below to simplify the present invention. These are merely examples and are not intended to limit the present invention. For example, in the following description, forming a first component above or on a second component may include embodiments where the first and second components are in direct contact, or embodiments where an additional component is formed between the first and second components such that the first and second components are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in various instances of the present invention. Such repetition is merely for brevity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0023] Furthermore, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific structures shown in the figures are merely illustrative and are not intended to limit the scope of this application. Other structures not described in the figures may be provided according to actual needs when describing specific figures, and are not intended to limit the scope of this application.

[0024] Currently, there are generally two methods for assembling electrodes in rechargeable batteries: winding and stacking. The winding process involves controlling factors such as electrode speed, tension, size, and deviation to slit matching electrodes, separators, and tapes, and then winding them into a core according to the specified dimensions. The stacking process involves alternately stacking electrodes and separators to create multiple layers. From a battery form factor perspective, pouch cells and blade batteries are typically designed and manufactured using the stacking process. Stacking produces cells with higher energy density but lower production efficiency, while prismatic batteries can use either stacking or winding. The winding process has high production efficiency. However, the winding process has a drawback: at the inner corners of the wound core, the electrodes tend to collapse inwards, resulting in larger gaps between the positive and negative electrodes and poor electrode contact, which easily leads to lithium plating. Especially with the increasing market demand for fast charging, lithium plating at the corners of the wound core is even more likely to occur.

[0025] Existing technologies propose creating pores at the innermost corner of the negative electrode to insert lithium into the active sites on the side of the negative electrode not aligned with the positive electrode, thereby increasing the available active sites and reducing the risk of lithium plating. However, in this method, poor contact at the corner leads to increased impedance, and the risk of lithium plating is not completely eliminated. Therefore, although the winding process is highly efficient, it suffers from poor contact at the innermost corner of the negative electrode. Current methods of creating pores at the inner corner of the negative electrode cannot completely solve this problem. To fundamentally solve the problem, it is still necessary to address the issue of poor contact between the positive and negative electrode sheets at the corner.

[0026] This application provides a secondary battery and an electronic device using the secondary battery, which provides electrical energy to the electronic device. The electronic device can be a vehicle, mobile phone, portable device, laptop, ship, spacecraft, electric toy, or power tool, etc. In one embodiment of this invention, the vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle; the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electronic devices.

[0027] Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. In this embodiment, the electronic device is vehicle 1000. Figure 1As shown, a battery pack 1002 is installed inside the vehicle 1000. The battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle 1000; for example, the battery pack 1002 can serve as the operating power source for the vehicle 1000. The working part of the vehicle 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part can be the vehicle body 1001, and the battery pack 1002 is located at the bottom of the vehicle body 1001, providing electrical power support for the vehicle's operation or the operation of its internal electrical components. The battery pack 1002 can include multiple secondary batteries.

[0028] Figure 2 This is an exploded view of a single secondary battery cell provided in some embodiments of this application. For example... Figure 2 As shown, the secondary battery 100 includes a casing 10 and a winding core 120 disposed within the casing 10. This invention does not limit the type and shape of the secondary battery 100; for example, it can be a pouch battery or a prismatic battery, or a sodium-ion secondary battery or a lithium-ion secondary battery. In this embodiment, a prismatic battery is used as an example for description.

[0029] The outer casing 10 may include a housing 11 and a cover plate 12. The cover plate 12 is used to seal the opening of the housing 11 to define a receiving space for accommodating the core 120. The shape of the outer casing 10 matches the shape of the core 120, and the material of the housing 11 is, for example, a rigid housing such as an aluminum or steel shell. The cover plate 12 may include a first electrode 22, a second electrode 24, and an explosion-proof valve 28. The core 120 is electrically connected to the first electrode 22 and the second electrode 24. The first electrode 22 and the second electrode 24 have opposite polarities. The first electrode 22 and the second electrode 24 are either positive or negative electrodes, and this invention does not limit the specific polarity categories of the first and second electrodes. The first electrode 22 and the second electrode 24 are electrically connected to tabs of the same polarity on the core 120. By placing the first electrode 22 and the second electrode 24 on the same side of the casing, the space utilization within the casing can be improved, while simplifying the battery structure and facilitating the connection of multiple cell structures in a battery module.

[0030] In some embodiments, the explosion-proof valve 28 can be disposed between the first electrode 22 and the second electrode 24, and is respectively at a preset distance from the first electrode 22 and the second electrode 24. The explosion-proof valve can function as a venting valve when the battery is operating normally, allowing airflow inside and outside the battery. When the battery experiences thermal runaway and the pressure difference between the inside and outside of the battery reaches a preset explosion-proof value, the explosion-proof valve 28 can open, allowing gas and solids to be discharged from inside the battery to the outside, thus improving battery safety performance.

[0031] Figure 3 This is a schematic diagram of the structure of the core 120 provided in one embodiment of this application. Figure 3 As shown, the core 120 may include a positive electrode 122, a negative electrode 124, and a separator 128, with the separator 128 disposed between the positive electrode 122 and the negative electrode 124. The positive electrode 122 and the negative electrode 124 are wound along the winding direction Dr to form the core 120 with a wound structure. In some embodiments, the separator 128 may include a polypropylene (PP) separator and a polyethylene (PE) separator, etc. The core 120 may be, for example, a rounded rectangle. The core 120 may have a length in the X direction, a width in the Z direction, and a thickness in the Y direction. The core 120 may have a central hole 129. The axial direction of the central hole 129 is parallel to the Z direction. The Z direction may be the height direction of the secondary battery 100. The negative electrode 124 is closer to the central hole 129 than the positive electrode 122.

[0032] Along the winding direction Dr of the core 120, the negative electrode sheet 124 includes a plurality of negative electrode corner segments arranged sequentially, and adjacent negative electrode corner segments are connected by negative electrode straight segments. For example, along the winding direction Dr, a first negative electrode corner segment 124a and a second negative electrode corner segment 124c are shown, with the first negative electrode corner segment 124a connected to the starting end 124s of the negative electrode sheet 124. A first negative electrode straight segment 124b is connected between the first negative electrode corner segment 124a and the second negative electrode segment 124c.

[0033] In some embodiments, two support members 200 are respectively disposed inside the first negative electrode corner segment 124a and the second negative electrode corner segment 124c. In this embodiment, the support members 200 are adjacent to the first negative electrode corner segment 124a and the second negative electrode corner segment 124c, respectively. By providing support members 200 inside the first negative electrode corner segment 124a and the second negative electrode corner segment 124c within the core 120, the support members 200 can provide support. The supporting effect of the support members 200 can prevent the electrode sheet from easily collapsing inward, reduce the distance between the negative electrode sheet and the positive electrode sheet at the corner, improve the contact between the positive and negative electrode sheets at the corner, and thus improve the lithium plating problem at the corner.

[0034] In some embodiments, the support member 200 is an adhesive tape attached to the negative electrode sheet 124. Specifically, the support member 200 may include a substrate and an adhesive layer, the adhesive layer being located between the substrate and the negative electrode sheet 124 and attached to the surfaces of the first negative electrode corner segment 124a and the second negative electrode corner segment 124c. By implementing the support member 200 as an adhesive tape, it is easier to fix and attach the support member 200 to the negative electrode sheet 124, thereby improving the supporting effect. The support member 200 can be set by a simple adhesive application process, which is low in process difficulty and can greatly improve the contact between the positive and negative electrode sheets at the corners, thus improving the lithium plating problem at the corners.

[0035] In some embodiments, such as when the support member 200 is an adhesive tape, the thickness of the support member 200 can be greater than 30 micrometers. This greater thickness can result in better support from the support member 200. For example, in embodiments where the support member 200 is an adhesive tape, a thicker tape can provide better support.

[0036] Figure 4 A schematic diagram of the structure of the core 120 provided in another embodiment of this application. See also... Figure 4 As shown, along the winding direction Dr, the diaphragm 128 includes a first diaphragm corner segment 128a and a second diaphragm corner segment 128c arranged sequentially. The first diaphragm corner segment 128a is located inside the first negative electrode corner segment 124a, and the second diaphragm corner segment 128c is located inside the second negative electrode corner segment 124c. In this embodiment, the support member 200 is respectively disposed inside the first diaphragm corner segment 128a and the second diaphragm corner segment 128c, and is adjacent to the diaphragm 128. Thus, the support member 200 is respectively located inside the first negative electrode corner segment 124a and the second negative electrode corner segment 124c. By disposing the support member 200 inside the first diaphragm corner segment 128a and the second diaphragm corner segment 128c, it can also serve to support the positive and negative electrode sheets at the corners. Therefore, the supporting component 200 can prevent the electrode from collapsing inward, reduce the distance between the negative electrode and the positive electrode at the corner, improve the contact between the positive and negative electrodes at the corner, and thus improve the lithium plating problem at the corner.

[0037] exist Figure 4 In the illustrated embodiment, a support member 200 is provided inside the inner diaphragm 128 of the two diaphragms 128. In other embodiments, the support member 200 may be provided inside either or both of the two diaphragms 128 and the corner. In some embodiments, the support member 200 may also be provided outside either or both of the first diaphragm corner segment 128a and the second diaphragm corner segment 128c.

[0038] Figure 5 A schematic diagram of the structure of the core 120 provided in another embodiment of this application. See also... Figure 5As shown, this embodiment is similar to Figure 4 The difference in the illustrated embodiment is that the support member 200 is respectively disposed on the inner and outer sides of the first separator corner segment 128a and the second separator corner segment 128c. In some embodiments, the support member 200 can be disposed on the inner and outer sides of either of the two separators 128 and / or both of the first separator corner segments 128a and 128c. By disposing the support member 200 on both the inner and outer sides of the separator 128, the supporting effect can be improved, thereby more effectively reducing the spacing between the positive and negative electrodes at the corner, improving electrode contact, and avoiding lithium plating problems at the corner.

[0039] Figure 6 A schematic diagram of the structure of the core 120 provided in another embodiment of this application. See also... Figure 6 As shown, several aspects of this embodiment can be related to Figure 3 The illustrated embodiment is the same, except that a straight support member 202 can be provided. This straight support member 202 is connected along the winding direction Dr between the support member 200 inside the first negative electrode corner segment 124a and the support member 200 inside the second negative electrode corner segment 124c. The straight support member 202 can extend along the first negative electrode straight segment 124b. The straight support member 202 can be attached to the first negative electrode straight segment 124b. In some embodiments, the straight support member 202 can be an adhesive tape. In some embodiments, the straight support member 202 and the support member 200 to which it is connected can be integral. In some embodiments, the straight support member 202 and the two support members 200 are continuous adhesive tape. By providing a straight support member 202 connecting the two support members 200, the straight support member 202 and the two support members 200 can jointly provide better support at the corner, thereby more effectively improving electrode contact and preventing lithium deposition at the corner.

[0040] Furthermore, according to embodiments of this application, the extension length of the support member 200 along the winding direction Dr is not greater than the extension length of the corresponding first negative electrode corner segment 124a or second negative electrode corner segment 124c. In the opposite direction of the winding direction Dr, the starting end 124s of the negative electrode sheet 124 extends beyond the starting end 200s of the support member 200. By configuring the starting end 124s of the negative electrode sheet 124 to extend beyond the starting end 200s of the support member 200, it is easier to configure the support member 200 in the processing technology. For example, in an embodiment where the support member 200 is an adhesive tape, configuring the starting end 124s of the negative electrode sheet 124 to extend beyond the starting end 200s of the support member 200 makes it easier to attach the support member 200 to the first negative electrode corner segment 124a of the negative electrode sheet 124.

[0041] In some embodiments, the extension length of the starting end 124s of the negative electrode 124 beyond the starting end 200s of the support member 200 in the opposite direction to the winding direction Dr is 2mm-30mm. This range allows for easy processing and setting of the support member 200 without excessive waste of negative electrode material.

[0042] In some embodiments, the starting end 122s of the positive electrode 122 is located outside the first negative electrode straight section 124b of the negative electrode 124. The starting end 122s of the positive electrode 122 and the first negative electrode straight section 124b are separated by a separator 128. Thus, the first negative electrode corner section 124a extends beyond the starting end 122s of the positive electrode 122 in the opposite direction of the winding direction Dr, and the second negative electrode corner section 124c is located inside the first positive electrode corner section 122a connected to the starting end 122s of the positive electrode 122. That is, the first negative electrode corner section 124a and the second negative electrode corner section 124c are the innermost electrode corner sections at the two corners, respectively. With the above configuration, since the starting end 122s of the positive electrode 122 avoids the first negative electrode corner segment 124a, lithium intercalation can be prevented at the first negative electrode corner segment 124a. At the same time, it can also be ensured that the negative electrode 124 can exceed the starting end 122s of the positive electrode 122 by a sufficiently long length to avoid lithium plating problems.

[0043] Figure 7 A schematic diagram of the structure of the core 120 provided in another embodiment of this application. See also... Figure 7 As shown, several aspects of this embodiment can be related to Figure 4 The embodiment shown is the same, except that a straight support member 202 can be provided, which is connected between the two supports 200 along the winding direction Dr. The straight support member 202 and the two supports 200 can work together to provide better support at the corner, thereby more effectively improving electrode contact and avoiding lithium deposition at the corner.

[0044] Figure 8 A schematic diagram of the structure of the core 120 provided in another embodiment of this application. See also... Figure 8 As shown, several aspects of this embodiment can be related to Figure 7The illustrated embodiment is the same, except that the support member 200 and the straight support member 202 are respectively disposed on the inner and outer sides of the first diaphragm corner segment 128a and the second diaphragm corner segment 128c. In some embodiments, the support member 200 and the straight support member 202 can be disposed on the inner and outer sides of either of the two diaphragms 128 and the first diaphragm corner segment 128a and the second diaphragm corner segment 128c. By disposing the support member 200 and the straight support member 202 on both the inner and outer sides of the diaphragm 128, the supporting effect can be improved, so as to more effectively reduce the spacing between the positive and negative electrodes at the corner, improve the electrode contact, and avoid lithium plating problems at the corner.

[0045] Figure 9 This is a partial schematic diagram of the core 120 in one embodiment of this application. (See reference) Figure 9 As shown, in direction Z, the positive electrode 122 may include a positive electrode body 122m and a positive electrode tab 122r extending from the positive electrode body 122m, and the negative electrode 124 may include a negative electrode body 124m and a negative electrode tab 124r extending from the negative electrode body 124m. The positive electrode tab 122r and the negative electrode 124 can be respectively connected to a reference... Figure 2 The first electrode 22 and the second electrode 24 are electrically connected as described.

[0046] In some embodiments, the opposite ends of the support member 200 and / or the straight support member 202 in the Z direction can extend beyond the opposite ends of the negative electrode body 124m of the negative electrode sheet 124. This ensures that the support member 200 and / or the straight support member 202 can effectively support both the positive and negative electrodes at the corners along the Z direction.

[0047] In some embodiments, in direction Z, the opposite ends of the support member 200 and / or the straight support member 202 extend 1 mm to 5 mm beyond the opposite ends of the negative electrode body 124m. This range of values ​​ensures effective support without adversely affecting battery performance.

[0048] In one example, the width of the negative electrode 124 in the winding core is 50 mm in the Z direction. The support 200 and support 202 are integral continuous tapes with a width of 54 mm in the Z direction, extending 2 mm beyond the ends of the negative electrode body 124m at both ends. In this example, the tape thickness is 50 μm. Along the opposite direction of the winding direction Dr, the starting end 124s of the negative electrode 124 extends 10 mm beyond the first negative electrode corner segment 124a. The starting end 122s of the positive electrode 122 is 5 mm away from the first negative electrode corner segment 124a.

[0049] In another example, the width of the negative electrode 124 in the core along the Z direction is 70 mm. The support 200 and support 202 are integral continuous tapes with a width of 76 mm along the Z direction, extending 3 mm beyond the ends of the negative electrode body 124m. In this example, the tape thickness is 35 μm. Along the opposite direction of the winding direction Dr, the starting end 124s of the negative electrode 124 extends 6 mm beyond the first negative electrode corner segment 124a. The starting end 122s of the positive electrode 122 is 3 mm away from the first negative electrode corner segment 124a.

[0050] It should be understood that the various features of the embodiments of this application can be replaced and combined. The above are merely preferred embodiments of this application and are not intended to limit this application. Any combination of embodiments within the spirit and principles of this application, as well as any modifications, equivalent substitutions, improvements, etc., made to the embodiments, should be included within the protection scope of this application.

Claims

1. A secondary battery characterized by comprising: include: The core is formed by winding a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet. Along the winding direction of the core, the negative electrode sheet includes a first negative electrode corner segment and a second negative electrode corner segment arranged in sequence. The first negative electrode corner segment is connected to the starting end of the negative electrode sheet. Support members are respectively disposed on the inner side of the first negative electrode corner section and the second negative electrode corner section of the negative electrode sheet.

2. The secondary battery according to claim 1, characterized by Also includes: A straight support member is connected along the winding direction between the support member inside the first negative electrode corner segment and the support member inside the second negative electrode corner segment.

3. The secondary battery according to claim 1, characterized in that, The support includes a substrate and an adhesive layer. The adhesive layer is located between the substrate and the negative electrode sheet and is attached to the surfaces of the first negative electrode corner segment and the second negative electrode corner segment of the negative electrode sheet.

4. The secondary battery according to claim 3, characterized in that, In the opposite direction to the winding direction, the starting end of the negative electrode sheet extends beyond the starting end of the support.

5. The secondary battery according to claim 4, characterized in that, In the opposite direction to the winding direction, the starting end of the negative electrode sheet extends 2mm-30mm beyond the starting end of the support member.

6. The secondary battery according to claim 3, characterized in that, Along the winding direction, the negative electrode sheet further includes a first straight negative electrode section connecting the first negative electrode corner section and the second negative electrode corner section, and the positive electrode sheet includes a first positive electrode corner section connected to the starting end of the positive electrode sheet. The starting end of the positive electrode is located outside the first straight negative electrode section of the negative electrode, wherein the first negative electrode corner section extends beyond the starting end of the positive electrode in the opposite direction of the winding direction, and the second negative electrode corner section is located inside the first positive electrode corner section.

7. The secondary battery according to claim 3, characterized in that, The thickness of the support is greater than 30 micrometers.

8. The secondary battery according to claim 1, characterized in that, Along the winding direction, the diaphragm includes a first diaphragm corner section and a second diaphragm corner section arranged sequentially, wherein the first diaphragm corner section is located inside the first negative electrode corner section and the second diaphragm corner section is located inside the second negative electrode corner section. The support members are respectively disposed on the inner or outer side of the first diaphragm corner section and the second diaphragm corner section.

9. The secondary battery according to claim 1, characterized in that, In a first direction, the negative electrode sheet includes an electrode sheet body and a negative electrode tab extending from the electrode sheet body, wherein the first direction is parallel to the axial direction of the center hole of the winding core; In the first direction, the opposite ends of the support member extend beyond the opposite ends of the electrode body of the negative electrode sheet.

10. The secondary battery according to claim 9, characterized in that, In the first direction, the opposite ends of the support member extend 1 mm to 5 mm beyond the opposite ends of the electrode body.

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