An inner core, a battery cell and a method of manufacture

Abstract

The application discloses an inner core, a battery monomer and a preparation method, and belongs to the technical field of batteries. The inner core comprises an inner core body and a plurality of tabs connected with the inner core body; the plurality of tabs are overlapped, and the plurality of tabs are integrally connected in the overlapped area and form an integrated overlapping structure; the integrated overlapping structure has a cutting surface, and the cutting surface is covered with a protective piece. By connecting the overlapped area of the plurality of tabs to form an integrated overlapping structure and cutting the part where the tabs are misaligned, and by covering the cutting surface with the protective piece, on the one hand, the assembly process of the tabs is simplified to a certain extent, and the risk of connection loosening or damage caused by relative displacement between the tabs during use is reduced; on the other hand, the cutting surface is effectively protected from external environmental factors, short circuit, corrosion and other problems at the cutting surface are avoided, the risk of damage to other components caused by burrs at the edge of the cutting surface is reduced, and the safety and reliability of the inner core are improved.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an inner core, a battery cell, and a preparation method thereof. Background Technology

[0002] Currently, during the preparation of the inner core, after the tabs are gathered, there will be misalignment of different sizes between the tabs of different layers. The misaligned areas of the tabs cannot be effectively utilized, and cutting off the misaligned areas of the tabs will affect the safety and reliability of the inner core. Summary of the Invention

[0003] Purpose of the invention: The embodiments of this application provide an inner core, which aims to overcome the technical problem that cutting the misaligned area of ​​the electrode affects the safety and reliability of the battery cell; another purpose of the embodiments of this application is to provide an inner core preparation method.

[0004] Technical solution: The inner core in this application embodiment includes an inner core body and a plurality of tabs connected to the inner core body; the plurality of tabs overlap, and the plurality of tabs are integrally connected in the overlapping area to form an integral overlapping structure; the integral overlapping structure has a cut surface, and the cut surface is covered with a protective member.

[0005] In some embodiments, the tab includes a retractable portion and a connecting portion connected together, the retractable portion being connected to the inner core body, and the connecting portion being connected to the end of the retractable portion away from the inner core body;

[0006] The connecting portions of the multiple electrodes overlap.

[0007] In some embodiments, the integral connection includes fusion welding.

[0008] This application also discloses a battery cell, comprising:

[0009] case,

[0010] pole assembly,

[0011] Multiple inner cores as described in the above embodiments, wherein the integral overlapping structure of the multiple inner cores is connected to the pole post assembly.

[0012] In some embodiments, the protective element is multiple, and each protective element covers at least one of the cut surfaces.

[0013] In some embodiments, the plurality of protective elements are an integral structure.

[0014] In some embodiments, the pole assembly has a groove on the side facing the inner core body, the cut surface is located at the opening of the groove, and the protective member is at least partially filled in the groove.

[0015] In some embodiments, the pole assembly has a plurality of grooves on the side facing the inner core body, and each groove corresponds to at least one cut surface.

[0016] In some embodiments, the protective member has at least a partial connection to the side of the integral overlapping structure opposite to the inner core body.

[0017] This application also discloses a method for preparing an inner core, comprising:

[0018] The multiple tabs of the inner core are brought together, and the overlapping areas of the multiple tabs are connected in one piece to form an integrated overlapping structure.

[0019] The end of the integrated overlapping structure away from the inner core body is cut to form a cut surface;

[0020] A protective element is wrapped around the cut surface.

[0021] Beneficial Effects: The inner core in this embodiment includes an inner core body and multiple tabs connected to the inner core body; the multiple tabs overlap and are integrally connected in the overlapping area to form an integral overlapping structure; the integral overlapping structure has a cut surface, and the cut surface is covered with a protective component. By connecting the overlapping areas of multiple tabs to form an integral overlapping structure and cutting off the misaligned parts of the tabs, and using a protective component to cover the cut surface, on the one hand, the assembly process of the tabs is simplified to a certain extent, reducing the risk of loosening or damage to the connection that may occur due to relative displacement between the tabs during use; on the other hand, it effectively protects the cut surface from the influence of external environmental factors, avoids problems such as short circuits and corrosion at the cut surface, reduces the risk of damage to other components from burrs on the cut surface edge, and improves the safety and reliability of the inner core.

[0022] The battery cell in this application embodiment includes the core as described in the above embodiments. Therefore, it can have all the technical features and effects of the core described above, which will not be repeated here.

[0023] The method for preparing the inner core in this embodiment has all the technical features and effects of the aforementioned inner core, and will not be repeated here. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0025] Figure 1This is a schematic diagram of the external structure of a single battery cell according to an embodiment of this application;

[0026] Figure 2 for Figure 1 Cross-sectional view along the AA direction;

[0027] Figure 3 For another embodiment of this application Figure 1 Cross-sectional view along the AA direction;

[0028] Figure 4 This is yet another embodiment of the present application. Figure 1 A cross-sectional view along the AA direction, showing only one protective component;

[0029] Figure 5 This is a schematic diagram of a battery cell during the cell assembly process according to an embodiment of this application. The protective components are shown in the diagram.

[0030] Figure 6 This is a schematic diagram showing the interconnection of multiple inner cores in the inner core preparation method of this application embodiment;

[0031] Figure 7 This is a schematic diagram illustrating the truncation of misaligned regions of multiple inner cores in the preparation method of the inner core according to an embodiment of this application;

[0032] Figure 8 This is a schematic flowchart of the method for preparing the core according to an embodiment of this application;

[0033] Reference numerals: 1. Inner core; 11. Inner core body; 12. Electrode; 121. Integrated overlapping structure; 1210. Cut surface; 2. Protective component; 1211. Connecting part; 1212. Closing part; 3. Housing; 4. Electrode assembly; 41. Groove. Detailed Implementation

[0034] 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 a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] In the description of this application, it should be understood that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. In the description of this application, "multiple" means two or more, and "at least one" can refer to one, two, or more, unless otherwise explicitly specified. The terms "first," "second," and "third," etc., are only for the convenience of description and are used to name parts or embodiments by number, and do not imply any order of importance between the parts or embodiments.

[0036] As a preamble to the embodiments of this application, during the battery manufacturing process, after the tabs are gathered, there will be misalignments of different sizes between the tabs of different layers. The misaligned areas of the tabs cannot be effectively utilized, and cutting off the misaligned areas of the tabs will affect the safety of the battery. In addition, as the thickness of the battery increases, the misalignment between the tabs located on the top layer and the bottom layer will become larger, which can easily cause interference during the battery assembly process and reduce assembly efficiency.

[0037] In view of this, embodiments of this application provide an inner core 1, which aims to solve at least one of the above-mentioned technical problems.

[0038] Please see Figures 1 to 7 As shown, the inner core 1 in this embodiment includes an inner core body 11 and a plurality of tabs 12 connected to the inner core body 11; the plurality of tabs 12 overlap and are integrally connected in the overlapping area to form an integral overlapping structure 121; the integral overlapping structure 121 has a cut surface 1210, and the cut surface 1210 is covered with a protective member 2. It is important to understand that by connecting the overlapping areas of multiple tabs 12 to form an integrated overlapping structure 121, and cutting off the misaligned parts of the tabs 12, and using the protective component 2 to cover the cut-off surface, on the one hand, the assembly process of the tabs 12 is simplified to a certain extent, reducing the risk of loosening or damage to the connection that may occur due to relative displacement between the tabs 12 during use. On the other hand, it effectively protects the cut-off surface 1210 from external environmental factors (such as moisture, oxidation, mechanical damage, etc.), avoiding problems such as short circuits and corrosion at the cut-off surface 1210, reducing the risk of damage to other components from burrs on the edge of the cut-off surface 1210, extending the service life of the inner core 1, and improving the safety and reliability of the inner core 1. The stable tab 12 connection structure and the protected cut-off surface 1210 help ensure the electrical connection performance of the inner core 1, reduce problems such as resistance changes and poor contact, thereby improving the charging and discharging performance and overall electrical performance of the inner core 1, which is conducive to improving the user experience and performance of the product.

[0039] In some embodiments, the protective element 2 is made of insulating rubber and is tightly wrapped around the cut surface 1210 by compression molding. Rubber has good elasticity and insulation properties, which can effectively buffer external impact forces and prevent the cut surface 1210 from contacting external conductive materials.

[0040] In some embodiments, multiple tabs 12 are integrally connected in overlapping areas by welding, such as laser welding. Laser welding can achieve a strong connection between tabs 12, and the weld points are small with a small heat-affected zone, which can reduce the impact on the material properties of tabs 12. In some inner cores 1 with high requirements for connection accuracy and reliability, the integral overlapping structure 121 formed by laser welding can better guarantee the performance of the inner core 1.

[0041] In some embodiments, the tabs 12 are formed into an integral overlapping structure 121 by pressing in the overlapping area. Conductive adhesive can be added between the tabs 12 during the pressing process to enhance the conductivity and stability of the connection. This method is suitable for the production of inner cores 1 that are cost-sensitive and have certain requirements for connection performance. The pressing process is relatively simple, and the use of conductive adhesive can further optimize the connection performance between the tabs 12.

[0042] Please see Figures 2 to 4 , Figure 6 and Figure 7 As shown, in some embodiments, the tab 12 includes a connected folding portion 1212 and a connecting portion 1211. The folding portion 1212 is connected to the inner core body 11, and the connecting portion 1211 is connected to the end of the folding portion 1212 away from the inner core body 11; the connecting portions 1211 of multiple tabs 12 overlap. It should be understood that by folding and bending multiple tabs 12 to form the folding portion 1212 and the connecting portion 1211, wherein the folding portion 1212 is connected to the inner core body 11, the folding portion 1212 can be adapted to the shape and size of the inner core body 11, and the connecting portion 1211 is concentrated at the end of the folding portion 1212 away from the inner core body 11 and overlaps, it is convenient to connect to external circuits or other components in the future, simplifying the assembly process and improving assembly efficiency. The overlapping of the connection parts 1211 of multiple tabs 12 enhances the connection stability between the tabs 12 and other components, reduces resistance, reduces heat generation, improves electrical performance, and ensures a reliable connection between the inner core 1 and the external circuit. At the same time, it facilitates the optimized management of the electrical connections of the tabs 12, makes the design and layout of electrical connections easier, reduces the length and complexity of connection lines, and makes more effective use of the space around the inner core 1. It avoids the cluttered distribution of the tabs 12 in space, making the overall structure of the inner core 1 more compact, which is conducive to the miniaturization and lightweight design of the product and adapts to the space requirements of different application scenarios.

[0043] In some embodiments, the integrated connection includes welding. It should be understood that during the welding process, strong chemical bonds are formed between the metal atoms at the connection portions 1211 of the multiple tabs 12, achieving molecular-level bonding between the tabs 12 and thus obtaining extremely high connection strength. This high-strength connection can effectively resist various external forces during use, such as pulling and vibration, ensuring the stability of the tab 12 connection under complex operating conditions and reducing the risk of performance degradation or failure due to loose connections. The welded connection surface has almost no gaps or contact resistance. Compared with other connection methods (such as mechanical connections), it can significantly reduce the resistance between the tabs 12, improve the charging and discharging efficiency and overall electrical performance of the core 1, and extend the service life of the core 1. It is particularly suitable for applications with high requirements for power transmission efficiency, such as the core 1 of the power battery in new energy vehicles. During the welding process, the tab 12 materials fuse together to form a continuous whole, effectively preventing external moisture, corrosive gases, etc., from entering the connection portion 1211, providing good sealing protection for the cut surface 1210 and the connection area. Furthermore, the welding process makes the integrated overlapping structure 121 of the tab 12 highly efficient and consistent in production, which is conducive to large-scale production and reduces the product defect rate.

[0044] Please see Figures 2 to 7 As shown in the embodiments of this application, a battery cell is also disclosed, including: a housing 3, a terminal assembly 4, and multiple inner cores 1 as described in the above embodiments; wherein, the housing 3 mainly serves to house, protect, and provide mechanical support, effectively resisting the erosion and physical damage of the multiple inner cores 1 by the external environment, ensuring that the inner cores 1 can work normally under various complex working conditions. The terminal assembly 4 is used to electrically connect the inner cores 1 to external devices to realize the current transmission of the battery cell. The integrated overlapping structure 121 of the multiple inner cores 1 is connected to the terminal assembly 4. The integrated overlapping structure 121 of the multiple inner cores 1 connected to the terminal assembly 4 can reasonably distribute the current, improve the charging and discharging efficiency of the battery cell, and meet the needs of different application scenarios for high power output or long-term stable power supply. At the same time, when it is necessary to inspect or replace the inner cores 1, since the structure of each component is relatively independent, it can be operated more conveniently, reducing maintenance costs and difficulties. The reasonable layout and connection method of the multiple inner cores 1 improves the energy storage capacity of the battery cell within a limited space, thereby increasing the energy density. Meanwhile, stable connection and good current transmission performance help improve the charging and discharging performance of individual battery cells and extend battery life.

[0045] Please see Figure 2 and Figure 4As shown, in some embodiments, there are multiple protective elements 2, each of which covers at least one cut surface 1210. It should be understood that by having each protective element 2 cover at least one cut surface, precise protection of the cut surface is achieved. When each protective element 2 corresponds to only one cut surface, the independent protection of the cut surface by the protective element 2 minimizes the impact on other cut surfaces and the overall performance of the core 1. The arrangement of multiple protective elements 2 makes battery cell maintenance or troubleshooting more convenient, reducing maintenance workload and time costs. If it is necessary to replace a protective element 2 on a certain cut surface 1210, it will not affect the protection status of other cut surfaces 1210, reducing the interference of maintenance operations on the normal operation of the battery cell.

[0046] Please see Figure 3 As shown, in some embodiments, the multiple protective components 2 are an integral structure. It should be understood that by setting the multiple protective components 2 as an integral structure, a continuous and complete protective layer can be formed without seams, which can more effectively prevent external moisture, dust, corrosive substances, etc., from entering the cut surface 1210 area, providing all-round protection for the cut surface 1210 of the inner core 1. Compared with multiple independent protective components 2, the integral structure reduces the possibility of external factors intruding through the gaps between the protective components 2, greatly improving the protection capability of the cut surface 1210 and enhancing the reliability and stability of the battery cell. During installation, the multiple protective components 2 of the integral structure can cover multiple cut surfaces 1210 in a single operation, reducing the cumbersome steps and time costs of installing multiple independent protective components 2, and improving the production efficiency of the battery cell. At the same time, it also reduces the probability of problems such as improper or misaligned installation of the protective components 2 due to multiple installations, ensuring the installation quality and consistency of the protective components 2. The multiple protective components 2 are integrated into a single structure, which provides better structural strength and integrity. When the battery cell is subjected to external mechanical impact or vibration, it can distribute stress more evenly, preventing the protective effect on the cut surface 1210 from being affected by local damage to the protective components 2. In addition, the fit between the integrated protective components 2 and the integrated overlapping structure 121 of the inner core 1 is tighter, which helps to improve the overall stability of the inner core 1.

[0047] In some embodiments, the protective component 2 is manufactured using an injection molding process, and the material is a high-strength engineering plastic, such as polycarbonate (PC). Polycarbonate has good mechanical properties, insulation properties, and chemical corrosion resistance. Through injection molding, the integrated protective component 2 can be precisely manufactured according to the shape and position of the cut surface 1210 of the inner core 1, so that it fits tightly to the cut surface 1210 and provides reliable protection.

[0048] In some embodiments, a one-piece protective component 2 is fabricated using 3D printing technology. The material selected is a composite material with special properties, such as reinforced plastic containing nanoparticles. 3D printing can realize the fabrication of protective components 2 with complex shapes, which can better adapt to the irregular shape of the inner core 1 cut surface 1210, and the addition of nanoparticles can further improve the strength, wear resistance and aging resistance of the protective component 2.

[0049] Please see Figure 3 and Figure 4 As shown, in some embodiments, the pole post assembly 4 has a groove 41 on the side facing the inner core body 11, and the cut surface 1210 is located at the opening of the groove 41. The protective member 2 is at least partially filled in the groove 41. It should be understood that by opening the groove 41 on the pole post assembly 4, and by having at least a portion of the protective member 2 partially filled in the groove 41, the protective member 2 provides more adequate protection for the cut surface. The groove 41 itself can provide a certain degree of physical protection for the cut surface 1210, reducing the direct impact and friction of the external environment on the cut surface 1210. The protective component 2 further isolates the cut surface 1210 from external environmental factors (such as humid air and corrosive substances), preventing oxidation, short circuits, and other problems, thus effectively extending the service life of the inner core 1 and improving the reliability of the battery cell. Simultaneously, it prevents loosening or poor contact between the cut surface 1210 and the terminal assembly 4 due to external factors, ensuring smooth current transmission between the inner core 1 and the terminal assembly 4, reducing resistance, and improving the charging and discharging performance and overall electrical performance of the battery cell. Furthermore, the groove 41 serves a positioning function, helping to fix the position of the inner core 1, further improving assembly accuracy and stability, and contributing to increased production efficiency and product quality. At the same time, it improves the utilization rate of the internal space of the battery cell, making the structure more compact while ensuring connection reliability, thus contributing to the miniaturization and lightweight design of the battery cell.

[0050] Please see Figure 4As shown, in some embodiments, the terminal assembly 4 has multiple grooves 41 on the side facing the inner core body 11, and each groove 41 corresponds to at least one cut surface 1210. It should be understood that by setting multiple grooves 41, each corresponding to at least one cut surface, precise positioning and independent protection of each cut surface can be achieved. This adapts to the different working environments or stresses that different cut surfaces may experience, ensuring the protective performance of each cut surface 1210, effectively reducing the risk of damage to the cut surface 1210 due to external factors, and improving the reliability and stability of the battery cell. Furthermore, the connection between each cut surface 1210 and its corresponding groove 41 allows for better planning of the current path, avoiding electrical interference between different cut surfaces 1210. Simultaneously, it facilitates individual inspection and maintenance of each connection point. When a problem occurs at a connection point, it can be quickly located and repaired without affecting the normal operation of other cut surfaces 1210, ensuring the overall electrical performance of the battery cell. Multiple grooves 41 are provided one-to-one with multiple cut surfaces 1210, which helps to disperse the stress between the inner core 1 and the terminal assembly 4. When the battery cell is subjected to external mechanical force, the stress can be evenly transmitted and dispersed through the multiple grooves 41, avoiding damage to the connection part 1211 or deformation of the inner core 1 caused by local stress concentration, thereby enhancing the overall structural stability of the battery cell and extending its service life.

[0051] Please see Figure 3 and Figure 4 As shown, in some embodiments, the protective member 2 has at least a partial connection to the side of the integrated overlapping structure 121 opposite to the inner core body 11. It should be understood that the protective member 2, connected to the side of the integrated overlapping structure 121 opposite to the inner core body 11, can provide more comprehensive coverage and protection for the cut surface 1210. In addition to direct protection of the cut surface 1210 itself, it can also prevent external factors from intruding from the side or top of the cut surface 1210, further reducing the risk of corrosion, wear, electrical short circuits, etc., ensuring the electrical performance and structural integrity of the inner core 1, thereby improving the reliability and service life of the battery cell. The connection between the protective member 2 and the integrated overlapping structure 121 can, to a certain extent, enhance the overall structural stability of the inner core 1. When the battery cell is subjected to external mechanical forces (such as vibration, impact, etc.), the protective member 2 can play a certain buffering and supporting role, dispersing stress, reducing the deformation or damage to the integrated overlapping structure 121 caused by force, helping to maintain the relative positional stability between the components of the inner core 1, and ensuring the normal operation of the battery cell. The protective component 2 is typically made of insulating material and is connected to the side of the integrated overlapping structure 121 opposite to the inner core body 11. It can effectively isolate possible conductive objects from the outside and improve the electrical insulation performance of the inner core 1. At the same time, the protective component 2 can also encapsulate foreign objects generated by the processing cut surface, preventing them from flowing into other parts of the single cell and causing short circuit problems.

[0052] Please see Figures 6 to 8 As shown in the embodiment of this application, a method for preparing an inner core 1 is also disclosed, including: gathering a plurality of tabs 12 of the inner core 1 together and integrally connecting the overlapping areas of the plurality of tabs 12 to form an integral overlapping structure 121; cutting off one end of the integral overlapping structure 121 away from the inner core body 11 to form a cut surface 1210; and covering the cut surface 1210 with a protective member 2. It is important to understand that during the process of bringing together the multiple tabs 12 of the inner core 1, the tabs 12 will form a gathering part 1212 and a connecting part 1211. The overlapping area of ​​the connecting parts 1211 of the multiple tabs 12 is integrally connected. By cutting off the misaligned area of ​​the tabs 12 formed after the multiple tabs 12 are fused together, considering the cutting efficiency, the end of the integral overlapping structure 121 away from the gathering end is generally selected for cutting to ensure that the misaligned area of ​​the tabs 12 is not retained. The cut surface is wrapped and protected by the protective component 2 to prevent the cut surface 1210 from being affected by external environmental factors (such as moisture, oxidation, mechanical damage, etc.), avoid short circuits, corrosion and other problems at the cut surface 1210, extend the service life of the inner core 1, and at the same time reduce the risk of damage to other components by burrs on the edge of the cut surface 1210, thereby improving the safety and reliability of the entire inner core 1.

[0053] It is also important to understand that the integrated connection and precise cutting process allow for better control of the amount of material used in the tab 12, avoiding material waste caused by individual connection or over-cutting, thus improving material utilization and reducing production costs. In the above embodiments, the descriptions of each embodiment have their own emphasis; for parts not detailed in a particular embodiment, please refer to the relevant descriptions in other embodiments.

[0054] The core, battery cell, and preparation method provided in the embodiments of this application have been described in detail above, and specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A battery cell, characterized in that, include: Shell (3); pole assembly (4); Multiple inner cores (1), each inner core (1) comprising an inner core body (11) and multiple tabs (12) connected to the inner core body (11); the multiple tabs (12) overlap and are integrally connected in the overlapping area to form an integral overlapping structure (121); the integral overlapping structure (121) has a cut surface (1210) covered by a protective member (2); An integral overlapping structure (121) of multiple inner cores (1) is connected to the pole assembly (4); the pole assembly (4) has a groove (41) on the side facing the inner core body (11), the cut surface (1210) is located at the opening of the groove (41), and the protective member (2) is at least partially filled in the groove (41).

2. The battery cell according to claim 1, characterized in that, The tab (12) includes a closed portion (1212) and a connecting portion (1211) connected together. The closed portion (1212) is connected to the inner core body (11), and the connecting portion (1211) is connected to the end of the closed portion (1212) away from the inner core body (11). The connecting portions (1211) of the plurality of said tabs (12) overlap.

3. The battery cell according to claim 1, characterized in that, The integrated connection includes welding.

4. The battery cell according to claim 1, characterized in that, The protective element (2) has a plurality of components, and each protective element (2) covers at least one of the cut surfaces (1210).

5. The battery cell according to claim 4, characterized in that, The multiple protective components (2) are an integral structure.

6. The battery cell according to claim 1, characterized in that, The pole assembly (4) has a plurality of grooves (41) on the side facing the inner core body (11), and each groove (41) corresponds to at least one cut surface (1210).

7. The battery cell according to claim 1, characterized in that, The protective element (2) has at least a partial connection to the side of the integral overlapping structure (121) opposite to the inner core body (11).

8. A method for preparing a battery cell, used to prepare a battery cell as described in any one of claims 1 to 7, characterized in that, include: The multiple tabs (12) of the inner core (1) are brought together, and the overlapping areas of the multiple tabs (12) are connected in one piece to form an integrated overlapping structure (121). The end of the integrated overlapping structure (121) away from the inner core body (11) is cut to form a cut surface (1210); A protective element (2) is covered on the cut surface (1210).

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