Battery cell and battery

Abstract

This application discloses a battery cell and a battery. The battery cell includes a cathode sheet, a separator, and an anode sheet. Both opposite sides of the cathode sheet are coated with a cathode active material layer, and the cathode sheet includes a cathode termination section. The separator is located on one side of the cathode sheet. The anode sheet is located on the side of the separator facing away from the cathode sheet, and the anode sheet includes an anode termination section that covers the cathode termination section. The anode termination section includes an anode termination section base layer, and the side of the anode termination section base layer facing the cathode termination section is coated with an anode active material layer. The cathode sheet, separator, and anode sheet are jointly wound to form a battery cell with a central region, and the anode termination section is located on the side of the cathode termination section facing away from the central region. The battery includes the aforementioned battery cell. The battery cell and battery of this application can improve the consistency of battery cell capacity.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell and a battery. Background Technology

[0002] Current battery cell structures typically employ a stacked arrangement of anode plates, separators, and cathode plates, wound together. In this structure, the active material layers on the cathode and anode plates are arranged opposite each other, and the outer electrode section is typically single-layer coated to ensure the volumetric energy density of the cell. However, since the cathode is usually used as the outer electrode and serves as the primary source of lithium ions in the cell, a single-layer coating on the outer electrode section leads to poor capacity consistency within the cell. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a battery cell that can improve the consistency of battery cell capacity.

[0004] This application also proposes a battery having the above-mentioned cells.

[0005] The battery cell according to an embodiment of this application includes a cathode sheet, a separator, and an anode sheet; Both sides of the cathode sheet are coated with a cathode active material layer, and the cathode sheet includes a cathode termination section; The diaphragm is located on one side of the cathode plate; The anode plate is located on the side of the diaphragm away from the cathode plate. The anode plate includes an anode termination section, which covers the cathode termination section. The anode termination section includes an anode termination section base layer, and the side of the anode termination section base layer facing the cathode termination section is coated with an anode active material layer. The cathode plate, diaphragm, and anode plate are used to jointly wind together to form a battery cell with a central region, and the anode end section is located on the side of the cathode end section away from the central region.

[0006] The battery cell according to the embodiments of this application has at least the following beneficial effects: the anode end section is located on the side of the cathode end section away from the central region, so that the battery cell in this application has a structure in which the anode sheet is wrapped with a cathode sheet. Based on this, the cathode sheet can be coated with a cathode active material layer on both opposite sides, so that the active material on the cathode sheet is continuously coated. Compared with intermittent coating, the continuous coating of the active material on the cathode sheet can make the active material thickness more uniform in all places. Therefore, during charging and discharging, lithium ions can be provided more uniformly in all places of the battery cell, which is beneficial to improving the consistency of the battery cell capacity.

[0007] According to some embodiments of this application, the side of the anode termination layer away from the central region is coated with an insulating coating.

[0008] According to some embodiments of this application, the thickness of the insulating coating is from 2µm to 10µm. According to some embodiments of this application, along the winding direction, the tail end of the anode tail section extends beyond the tail end of the cathode tail section, and the insulating coating includes an insulating head end. Along the thickness direction, the insulating head end is located on the side of the anode tail section base layer facing the cathode tail section, and the insulating head end is stacked with the tail end of the anode tail section.

[0009] According to some embodiments of this application, the length of the overlapping area between the insulating start end and the anode end end along the winding direction is 0 to 3 mm.

[0010] According to some embodiments of this application, the cathode sheet includes a first straight section, a corner section, and a second straight section, which are connected sequentially. The first straight section includes the starting end of the winding of the cathode sheet. The anode sheet includes a third straight section, which includes the starting end of the winding of the anode sheet. Along the thickness direction, the third straight section is located between the first straight section and the second straight section, and along the winding direction, the connection between the corner section and the second straight section extends beyond the starting end of the winding of the anode sheet.

[0011] According to some embodiments of this application, the anode sheet includes a winding start end and a winding end end, and the cathode sheet includes a winding end end. The projections of the three sheets on a plane perpendicular to the thickness direction are arranged at intervals along the thickness direction.

[0012] According to some embodiments of this application, the distance L between two adjacent projections is ≥1mm.

[0013] According to some embodiments of this application, the density of the cathode active material layer is greater than the density of the anode active material layer, the starting end of the diaphragm winding is flush with or extends beyond the starting end of the cathode sheet winding in the winding direction, and the diaphragm covers the cathode sheet.

[0014] The battery according to the embodiments of this application includes the battery cell in any of the above embodiments.

[0015] The battery according to the embodiments of this application has at least the following beneficial effects: the consistency of cell capacity is improved, making the ability of each part of the battery to store and release electricity more consistent during charging and discharging, thereby making the overall capacity of the battery closer to the theoretical design value and reducing energy waste caused by local capacity differences.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the battery cell structure according to an embodiment of this application; Figure 2 for Figure 1 A magnified view of a portion of point A in the middle; Reference numerals: cathode sheet 100, cathode active material layer 110, cathode termination section 120, first straight section 130, corner section 140, second straight section 150; Diaphragm 200; Anode plate 300, anode end section 310, anode end section base layer 320, anode active material layer 330, insulating coating 340, insulating start end 341, third straight section 350. Detailed Implementation

[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0019] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0020] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0021] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0022] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] The embodiments of this application are described below with reference to the accompanying drawings: refer to Figure 1 and Figure 2 According to an embodiment of this application, a battery cell includes a cathode plate 100, a separator 200, and an anode plate 300. Both opposite sides of the cathode plate 100 are coated with a cathode active material layer 110. The cathode plate 100 includes a cathode termination section 120. The separator 200 is located on one side of the cathode plate 100, and the anode plate 300 is located on the side of the separator 200 facing away from the cathode plate 100. The anode plate 300 includes an anode termination section 310, which covers the cathode termination section 120. The anode termination section 310 includes an anode termination section base layer 320. The side of the anode termination section base layer 320 facing the cathode termination section 120 is coated with an anode active material layer 330. The cathode plate 100, separator 200, and... The anode sheet 300 is used to co-wind to form a cell with a central region. The anode tail section 310 is located on the side of the cathode tail section 120 away from the central region. Thus, the cell of this application forms a structure in which the anode sheet 300 is wrapped around the cathode sheet 100, so that the cathode active material layer 110 is continuously coated on both sides of the cathode sheet base layer. Compared with the method of coating the cathode active material layer 110 intermittently on the cathode sheet base layer, it can avoid the problem of inconsistent thickness of the edge thinning area at the transition between the active material coated area and the uncoated area on the cathode sheet 100, thereby improving the capacity consistency of the cell.

[0024] Specifically, the cathode sheet 100 includes a cathode sheet base layer, and both sides of the cathode sheet base layer are coated with cathode active material layers 110. During the production of the cathode sheet 100, based on the structure that both sides of the cathode sheet base layer need to be coated with active material layers, a continuous coating process can be used. This process can reduce the coating gap areas caused by discontinuous coating (such as intermittent coating), avoiding the problem of thinning or uneven distribution of the cathode active material layers 110 at the edges, thus making the thickness of the cathode active material layers 110 more uniform throughout the cathode sheet 100. The cathode active material layers 110 can be lithium compounds such as lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, and lithium nickel cobalt manganese oxide. These materials can provide a carrier for energy storage and release in the battery cell by inserting and deintercalating lithium ions during charging and discharging. Therefore, the uniform distribution of the cathode active material layers 110 helps to make the degree of participation in electrochemical reactions in different areas of the cathode sheet 100 more consistent during battery cell operation, thereby improving the capacity consistency of the battery cell.

[0025] Furthermore, the outermost edge of the battery cell in this application is covered by an anode sheet 300. The anode sheet 300 is provided with an anode termination section 310. This anode termination section 310 can adopt a single-layer coating design, that is, the anode active material layer 330 is coated only on the side facing the cathode sheet 100, while the outermost edge of the battery cell (the side away from the central area) is not coated. This helps to reduce the amount of anode active material 330 material used and avoids excess material occupying the internal space of the battery cell, thereby optimizing the space utilization of the battery cell and improving the volumetric energy density of the battery cell. The anode active material layer 330 can be made of carbon materials such as graphite. After the battery cell is formed by winding the cathode sheet 100, the separator 200 and the anode sheet 300 together, the anode active material layer 330 can cover the outside of the cathode active material layer 110. Under the action of the separator 200 separating the anode sheet 300 and the cathode sheet 100, the two work together to realize the directional movement of lithium ions during the charging and discharging process, completing the storage and release of electrical energy.

[0026] refer to Figure 1 and Figure 2 In some embodiments, the side of the anode end section base layer 320 away from the central region is coated with an insulating coating 340. The insulating coating 340 may be made of a material with insulating properties, such as a ceramic coating, to block the conduction between the anode end section base layer 320 and the aluminum foil layer of the aluminum-plastic film, so as to avoid short circuit of the battery cell and improve the safety of the battery cell.

[0027] Specifically, the anode termination layer 320 is made of copper foil, and the aluminum-plastic film is used to wrap the battery cell. The aluminum-plastic film consists of an outer nylon layer, a middle aluminum foil layer, and an inner PP (polypropylene) layer. The PP layer is relatively thin and is easily damaged during battery production or transportation due to external forces (such as dust burrs, mechanical compression, etc.), causing the inner aluminum foil layer to be exposed and in contact with the electrolyte, or directly connected to the anode termination layer 320 (copper foil). When the PP layer is damaged, the anode termination layer 320 and the aluminum foil layer will form an electrochemical reaction circuit in the electrolyte. Due to the difference in standard electrode potentials between aluminum and copper, aluminum will act as the anode and be oxidized, causing corrosion of the aluminum-plastic film, resulting in a short circuit in the battery cell and affecting its safety. In this application, by providing an insulating coating 340 on the outside of the anode end section base layer 320, the direct contact between the anode end section base layer 320 and the aluminum foil layer can be effectively blocked, thereby reducing the risk of internal short circuit caused by damage to the aluminum-plastic film and improving the side voltage problem, which is beneficial to improving the safety of the battery cell.

[0028] In addition, the thickness of the insulating coating 340 can be set to be the same as the thickness of the single-sided anode active material layer 330, or slightly less than the thickness of the single-sided anode active material layer 330. This design ensures that after the cell is wound and formed, the overall thickness of the anode tail section 310 area remains uniform with other areas, avoiding stress concentration or unreasonable space occupation inside the cell due to local thickness differences, thereby helping to ensure the volumetric energy density of the cell.

[0029] refer to Figure 1 and Figure 2 In some embodiments, the thickness of the insulating coating 340 is 2µm to 10µm, for example, it can be 2µm, 4µm, 6µm, 8µm or 10µm, or any two of the above values ​​can be used as an interval value (such as 4µm to 8µm) to limit the lower limit of the thickness of the insulating coating 340, so as to ensure the insulating performance of the insulating coating 340, so as to effectively block the direct contact between the copper base layer of the anode sheet 300 and the aluminum foil layer, and limit the upper limit of the thickness of the insulating coating 340, so as to avoid causing additional space occupation inside the cell, affecting the overall thickness uniformity and volumetric energy density of the cell.

[0030] Furthermore, referring to the table below, in the embodiment of serial number 1, the insulating coating 340 has a low thickness and a high side voltage and external short circuit ratio; In embodiment number 2, the thickness of the insulating coating 340 is too low, resulting in poor edge voltage. In the embodiment of serial number 3, the insulating coating 340 has a moderate thickness and no adverse phenomena, and is recommended for use; In embodiment number 4, the insulating coating 340 is thicker, increasing the cell thickness by 20 μm; In embodiment number 5, the insulating coating 340 is thicker, increasing the cell thickness by 30 μm.

[0031]

[0032] refer to Figure 1 and Figure 2 In some embodiments, along the winding direction, the end of the anode termination section 310 (i.e., the winding termination section of the anode sheet 300) extends beyond the end of the cathode termination section 120 (i.e., the winding termination section of the cathode sheet 100). This is to ensure that during the charging and discharging process of the battery cell, the anode termination section 310 has a sufficient anode active material layer 330 covering the end of the cathode termination section 120, thereby providing sufficient insertion sites for lithium ions, alleviating the lithium plating phenomenon caused by insufficient lithium ion insertion sites, and improving the cycle stability and safety of the battery cell.

[0033] Furthermore, the insulating coating 340 includes an insulating beginning end 341. Along the thickness direction, the insulating beginning end 341 is located on the side of the anode termination layer 320 facing the cathode termination section 120, and the insulating beginning end 341 is stacked with the end of the anode termination section 310. Specifically, along the winding direction, the insulating beginning end 341 is connected to the anode active material layer 330. In the transition region between the anode active material layer 330 and the insulating coating 340, the insulating beginning end 341 can be partially stacked with the anode active material layer 330, effectively avoiding gaps that may occur in the transition region, so as to prevent electrolyte or metal ions from contacting the substrate of the anode sheet 300 through the gaps and causing a short circuit. Moreover, the stacked arrangement of the insulating beginning end 341 with the end of the anode termination section 310 (stacked beyond the end of the cathode termination section 120) avoids additional thickness increase of the battery cell, which is beneficial to balancing the safety and volumetric energy density of the battery cell.

[0034] refer to Figure 1 and Figure 2 In some embodiments, along the winding direction, the length of the stacked region between the insulating start end 341 and the anode end end 310 is 0 to 3 mm, for example, it can be 0, 1 mm, 2 mm or 3 mm, or it can be any two of the above values ​​as the endpoint values ​​(such as 1 mm to 2 mm). When the stacked length is 0, the insulating start end 341 and the anode end end 310 are flush. At this time, the end end of the anode end end 310 exceeds the end end of the cathode end end 120. While taking into account the cell thickness, lithium plating can be avoided. Limiting the upper limit of the stacked length is equivalent to limiting the distribution of the transition region between the insulating start end 341 and the anode active material layer 330, which is beneficial to reducing the space occupied by the cell.

[0035] refer to Figure 1 and Figure 2In some embodiments, the cathode sheet 100 includes a first straight section 130, a corner section 140, and a second straight section 150, which are connected sequentially. The first straight section 130 includes the starting end of the winding of the cathode sheet 100. The anode sheet 300 includes a third straight section 350, which includes the starting end of the winding of the anode sheet 300. Along the thickness direction, the third straight section 350 is located between the first straight section 130 and the second straight section 150. Along the winding direction, the connection between the corner section 140 and the second straight section 150 extends beyond the starting end of the winding of the anode sheet 300 (i.e., the starting position of the third straight section 350). Therefore, the third straight section 350 of the anode sheet 300 is positioned between the first straight section 130 and the second straight section 150 in the thickness direction. The anode active material layer 330 can be coated on both sides of the third straight section 350, and the cathode active material layer 110 on the first straight section 130 and the second straight section 150 corresponds to it. Thus, the anode sheet 300 only needs to adopt a single-layer coating structure of the anode active material layer 330 at the anode end section 310 to meet the charging and discharging requirements of the battery cell, without having to set a single-sided coating structure at both ends of the winding of the anode sheet 300, which is more beneficial to the bonding coating process.

[0036] Specifically, current coating processes typically employ a method of first coating the longer film side (the side with a larger active material coverage area) and then coating the shorter film side (the side with a smaller active material coverage area). Therefore, when coating the shorter film side, an active material layer provides support on the back of the electrode, resulting in a relatively uniform overall thickness of the active material on the shorter film side. If a single-sided coating structure is applied to both ends of the anode sheet 300, the areas without an active material layer will lack support, leading to uneven coating amounts (such as excessively thick coating in certain areas). This embodiment, however, avoids the process difficulties of single-sided coating at both ends of the electrode sheet by distributing the single-sided coating of the anode sheet 300 only to the anode termination section 310. This eliminates the need for additional optimization of coating equipment or process parameters, making it easier to manufacture.

[0037] refer to Figure 1 and Figure 2 In some embodiments, the anode sheet 300 includes a winding start end and a winding end end, and the cathode sheet 100 includes a winding end end. The projections of the three on the plane perpendicular to the thickness direction are arranged at intervals along the thickness direction, that is, the three are arranged at intervals along the width direction of the battery cell. The width direction of the battery cell is perpendicular to the thickness direction of the battery cell, which effectively improves the problem of uneven thickness caused by edge defects in traditional battery cells, thereby improving the uniformity of battery cell thickness.

[0038] Specifically, during the production process, the ends of the electrode are cut to form the electrode. At the cut edges, there are often burrs, edge protrusions, and other abnormal increases in thickness. In this application, the starting end of the winding of the anode sheet 300, the ending end of the winding of the anode sheet 300, and the ending end of the winding of the cathode sheet 100 are arranged alternately along the width direction. This prevents the protrusions at the cut edges of each electrode sheet from overlapping in the thickness direction, thus avoiding local thickening of the battery cell. As a result, the thickness of the battery cell is more even.

[0039] It should be noted that improving the overall uniformity of cell thickness helps reduce the risk of internal stress concentration and reduce electrode structure damage caused by local pressure differences, thereby extending the cell's cycle life. Secondly, the flat outer surface structure of the cell effectively avoids appearance defects such as bulges and wrinkles that may occur after aluminum-plastic film coating, improving the product yield. Furthermore, the uniform thickness distribution of the cell also helps optimize the assembly compatibility between the cell and the battery casing, reducing assembly difficulties or structural loosening problems caused by dimensional deviations, and facilitating the integrated assembly of battery modules.

[0040] refer to Figure 1 In some embodiments, the distance L between two adjacent projections is greater than or equal to 1 mm. For example, the value of L can be 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm or 6 mm, which is beneficial to improve the flatness of the battery cell and avoid the battery cell from bulging due to the overlap of the electrode ends.

[0041] Specifically, along the width direction of the battery cell, the projections of the starting end of the winding of the anode plate 300, the ending end of the winding of the cathode plate 100, and the ending end of the winding of the anode plate 300 are spaced apart in sequence. The projection interval between the starting end of the winding of the anode plate 300 and the ending end of the winding of the cathode plate 100 is at least 1 mm, and the projection interval between the ending end of the winding of the cathode plate 100 and the ending end of the winding of the anode plate 300 is at least 1 mm.

[0042] It should be noted that there is an upper limit to the distance between two adjacent projections. For example, the maximum distance between two adjacent projections is 10mm. The upper limit can be adjusted according to the size of the battery cell. Therefore, the maximum distance between two adjacent projections is not limited to 10mm.

[0043] refer to Figure 1 and Figure 2 In some embodiments, the density of the cathode active material layer 110 is greater than the density of the anode active material layer 330. The starting end of the winding of the diaphragm 200 is flush with or extends beyond the starting end of the winding of the cathode sheet 100 along the winding direction, and the diaphragm 200 covers the cathode sheet 100 to improve the composite effect between the diaphragm 200 and the cathode sheet 100. This allows the diaphragm 200 to fit more tightly against the cathode sheet 100, which is beneficial to reduce the internal resistance of the battery cell and reduce the risk of the electrode edge or burr piercing the diaphragm 200, thereby improving the safety of the battery cell.

[0044] Specifically, during the preparation of the cathode sheet 100, the cathode active material layer 110 is more fully compacted, resulting in a higher density compared to the anode active material layer 330. Consequently, the surface of the cathode active material layer 110 is smoother and flatter. The starting end of the winding of the separator 200 extends beyond or is flush with the starting end of the winding of the cathode sheet 100, ensuring that the separator 200 can cover the cathode sheet 100. Therefore, during winding, the separator 200 and the cathode sheet 100 can be composited, and the separator 200 can have a larger effective contact area with the smoother surface of the cathode active material layer 110, reducing the air gap and micro-gap between them. This enhances the composite effect between the separator 200 and the cathode sheet 100, thereby reducing the interfacial impedance between the separator 200 and the cathode sheet 100, reducing the migration resistance of lithium ions at the interface, and improving the charge and discharge efficiency of the battery cell. In addition, the good composite effect can also prevent the relative displacement of the diaphragm 200 and the cathode plate 100 during the charging and discharging process of the cell, and prevent the risk of internal short circuit due to structural loosening; and the cell as a whole is flatter.

[0045] refer to Figure 1 and Figure 2 The battery in this application embodiment includes the battery cell from any of the above embodiments, and the battery cell is coated with an aluminum-plastic film. The battery cell has a structure in which active material layers are continuously coated on both sides of the cathode sheet 100, and the anode sheet 300 is wrapped around the cathode sheet 100, thus improving the capacity consistency of the battery cell. Based on this, since the overall performance of the battery depends on the internal battery cells, the improved capacity consistency of the battery cells makes the ability of each part of the battery to store and release electricity more consistent during charging and discharging, which is beneficial to making the overall capacity of the battery more stable and reducing energy loss caused by local capacity differences.

[0046] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. An electric cell having a thickness direction, characterized by, include: The cathode sheet has a cathode active material layer coated on both opposite sides, and the cathode sheet includes a cathode termination section. A diaphragm is located on one side of the cathode plate; An anode sheet is located on the side of the diaphragm opposite to the cathode sheet. The anode sheet includes an anode termination section that covers the cathode termination section. The anode termination section includes an anode termination section base layer, and the side of the anode termination section base layer facing the cathode termination section is coated with an anode active material layer. The cathode sheet, the diaphragm, and the anode sheet are used to jointly wind together to form the battery cell with a central region, and the anode tail section is located on the side of the cathode tail section away from the central region.

2. The electric cell of claim 1, wherein, An insulating coating is applied to the side of the anode tail section base layer that is away from the central region.

3. The electric cell of claim 2, wherein, The thickness of the insulating coating is 2µm to 10µm.

4. The electric cell of claim 2, wherein, Along the winding direction, the tail end of the anode termination section extends beyond the tail end of the cathode termination section. The insulating coating includes an insulating head end. Along the thickness direction, the insulating head end is located on the side of the anode termination section base layer facing the cathode termination section, and the insulating head end is stacked with the tail end of the anode termination section.

5. The electric cell of claim 4, wherein, Along the winding direction, the length of the overlapping area between the insulating start end and the anode finish end is 0 to 3 mm.

6. The battery cell according to claim 1, characterized in that, The cathode sheet includes a first straight section, a corner section, and a second straight section, which are connected sequentially. The first straight section includes the starting end of the winding of the cathode sheet. The anode sheet includes a third straight section, which includes the starting end of the winding of the anode sheet. Along the thickness direction, the third straight section is located between the first straight section and the second straight section, and along the winding direction, the connection point between the corner section and the second straight section extends beyond the starting end of the winding of the anode sheet.

7. The battery cell according to claim 1, characterized in that, The anode sheet includes a winding start end and a winding end end, and the cathode sheet includes a winding end end. The projections of the three sheets onto a plane perpendicular to the thickness direction are arranged at intervals along the thickness direction.

8. The battery cell according to claim 7, characterized in that, The distance L between two adjacent projections is ≥1mm.

9. The battery cell according to claim 1, characterized in that, The density of the cathode active material layer is greater than that of the anode active material layer. The starting end of the winding of the diaphragm is flush with or extends beyond the starting end of the winding of the cathode sheet along the winding direction, and the diaphragm covers the cathode sheet.

10. A battery, characterized in that, The battery cell includes any one of claims 1 to 9.

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