Round battery cell winding structure and secondary battery

Abstract

The utility model belongs to the technical field of batteries, and mainly relates to a circular battery cell winding structure which is formed by winding a positive plate, an isolating membrane and a negative plate which are sequentially attached, wherein the positive plate comprises a first current collector, first active material layers coated on the two surfaces of the first current collector in the thickness direction, and a first empty foil section which is not coated with the first active material layers and is positioned at the winding starting end of the first current collector; the length of the first empty foil section is greater than the perimeter of a winding needle for a winding process, so that the end part of the first empty foil section is correspondingly contacted with the first empty foil section after being wound; through the improvement of winding of the pole piece in the battery cell structure, the problem of risks such as short circuit caused by the fact that burrs on the end face of the positive pole piece easily pierce an isolating membrane to be in contact with the negative pole piece is solved; in addition, the utility model also discloses a secondary battery comprising the circular battery cell winding structure.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and in particular relates to a round battery core winding structure and a secondary battery. Background Art

[0002] In the professional field of battery manufacturing technology, square wound batteries use a specific stacking method, where the positive and negative electrodes and the separator are stacked in a predetermined order, and the production process of circular wound cells involves the positive and negative electrodes and the separator being wound onto the negative electrode column to form a compact core package structure. Therefore, during the winding process of circular wound batteries, the positive and negative electrodes cannot avoid direct contact between the positive and negative electrodes, resulting in a short circuit.

[0003] In the existing circular battery cell winding technology, most of them adopt the method of inserting the negative electrode sheet first and then inserting the positive electrode sheet. The advantage of this method is that it can improve the winding efficiency, but there are also some problems. This not only affects the safety of the battery, but may also affect the performance and service life of the battery. In addition, the winding method of this structure also increases the manufacturing difficulty and cost of the battery. Therefore, how to improve the circular battery cell winding structure to avoid the end face of the positive electrode sheet piercing the isolation membrane and contacting the negative electrode sheet is a problem that needs to be solved urgently in the field of battery manufacturing technology. Utility Model Content

[0004] One of the purposes of the utility model is to provide a circular battery cell winding structure that can prevent the end face of the positive electrode sheet from piercing the separator and contacting the negative electrode sheet to cause a short circuit inside the battery cell in response to the shortcomings of the prior art.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A circular battery cell winding structure, comprising a positive electrode sheet, a separator and a negative electrode sheet which are laminated in sequence and wound together, wherein the positive electrode sheet comprises a first current collector, a first active material layer coated on both sides of the first current collector in a thickness direction, and a first empty foil section which is not coated with the first active material layer and is located at the starting end of the first current collector winding;

[0007] The length of the first empty foil segment is greater than the circumference of the winding needle used in the winding process, so that the ends of the first empty foil segment contact themselves respectively after winding.

[0008] The circular battery core winding structure proposed by the utility model has the following technical effects:

[0009] By improving the circular battery cell winding structure, the utility model successfully avoids the risk of the end face of the positive electrode sheet piercing the separator and contacting the negative electrode sheet, thereby significantly improving the safety and performance of the battery. Specifically, the positive electrode sheet in the battery cell winding structure includes a first empty foil segment, the length of which is greater than the circumference of the winding needle used in the winding process, so that during the winding process, the end of the first empty foil segment can contact itself correspondingly, thereby avoiding the possibility of the end face of the positive electrode sheet directly contacting the negative electrode sheet.

[0010] As an improvement to the circular battery core winding structure of the utility model, the length of the first empty foil segment is greater than 1.2-2 times the circumference of the winding needle used in the winding process, and the length of the first empty foil segment is 3-100 mm.

[0011] As an improvement to the circular battery winding structure of the utility model, the first hollow foil segment is bonded with a first protective adhesive on both sides in the thickness direction, and the first protective adhesive extends to cover the end of the first active material layer, and the length L1 of the covering portion is 0.5-2 mm.

[0012] As an improvement on the circular battery cell winding structure of the utility model, the negative electrode sheet includes a second current collector, a second active material layer coated on both sides of the second current collector in the thickness direction, and a second empty foil segment that is not coated with the second active material layer and is located at the starting end of the second current collector winding. The end of the second empty foil segment corresponds to the position of the first protective glue after winding.

[0013] As an improvement to the circular battery core winding structure of the utility model, the length of the second empty foil segment is 0.1-3 mm, and the length of the first empty foil segment is 4-40 times the length of the second empty foil segment.

[0014] As an improvement to the circular battery winding structure of the utility model, the second hollow foil segment is bonded with a second protective adhesive on both sides in the thickness direction, and the second protective adhesive extends to cover the end of the second active material layer, and the length L2 of the covering portion is 0.5-2mm.

[0015] As an improvement to the circular battery core winding structure of the utility model, the coating area of ​​the first active material layer is smaller than the coating area of ​​the second active material layer.

[0016] As an improvement to the circular battery core winding structure of the utility model, the first active material layer includes a first layer and a second layer coated on both sides of the first current collector in the thickness direction, and the ends of the second layer and the first layer are aligned or staggered.

[0017] As an improvement to the circular battery core winding structure of the utility model, the second active material layer includes a third layer coated on both sides of the second current collector in the thickness direction and aligned with the fourth layer, and the ends of the fourth layer and the third layer are arranged.

[0018] The second purpose of the utility model is to provide a secondary battery that can avoid the end face of the positive electrode sheet piercing the isolation membrane and contacting the negative electrode sheet to cause a short circuit inside the battery cell in response to the shortcomings of the prior art.

[0019] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0020] A secondary battery comprises any of the above-mentioned circular battery cell winding structures.

[0021] The secondary battery proposed by the utility model has the following technical effects:

[0022] By adopting the circular cell winding structure, the secondary battery of the utility model effectively avoids the risk of the end face of the internal cell positive electrode sheet piercing the separator and contacting the negative electrode sheet, thereby significantly improving the safety and performance of the battery. This improvement not only reduces the difficulty and cost of the battery manufacturing process, but also improves the reliability and service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic implementation of the present invention and its description are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0024] Figure 1 This is a schematic diagram of the circular battery cell winding structure of implementation mode 1 of the present utility model;

[0025] Figure 2 This is a schematic diagram of the positive electrode structure of implementation mode 2-3 of the present utility model;

[0026] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0027] Figure 4 The negative electrode sheet structure of the fourth embodiment of the present invention is shown;

[0028] Figure 5 for Figure 4 Enlarged view of point B in the middle;

[0029] Figure 6 This is a schematic diagram of the positive electrode structure of implementation modes 1-5 of the present invention;

[0030] Figure 7 This is a schematic diagram of the structure of the negative electrode sheet of implementation modes 1-6 of the present utility model;

[0031] in:

[0032] 100-round battery cell winding structure;

[0033] 1- positive electrode;

[0034] 11- first empty foil section;

[0035] 111 - first protective glue;

[0036] 12- first fluid collector;

[0037] 121- first active material layer;

[0038] 1211-1st floor;

[0039] 1212-Second floor;

[0040] 13- positive electrode tab;

[0041] 2-Isolation film;

[0042] 3- negative electrode;

[0043] 31- second empty foil section;

[0044] 311-Second protective glue;

[0045] 32- second fluid collector;

[0046] 321 - second active material layer;

[0047] 3211-Third floor;

[0048] 3212-Fourth Floor

[0049] 33-Negative electrode tab. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model. Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as those commonly understood by technicians in the technical field of the utility model. The terms used in this article in the specification of the utility model are only for the purpose of describing specific embodiments and are not intended to limit the utility model.

[0051] In the description of the present utility model, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances. Although the present utility model is disclosed as above in the preferred embodiment, it is not used to limit the claims. Any technical personnel in this field can make several possible changes and modifications without departing from the concept of the present utility model. Therefore, the scope of protection of the present utility model should be based on the scope defined by the claims of the present utility model. The following content is a specific description of the principle of the present utility model:

[0052] The wound battery, especially the improved circular wound structure battery in the utility model, has a pole piece composed of a positive pole piece, a negative pole piece and a separator. The positive pole piece is usually made of aluminum foil, and the surface is coated with a positive active material (such as lithium cobalt oxide); the negative pole piece is made of copper foil, and the surface is coated with a negative active material (such as graphite). During the charging process, the current provided by the charger flows into the battery through the positive electrode tab, passes through the positive electrode active material, the electrolyte, the negative electrode active material, and finally flows out of the battery through the negative electrode tab. In this process, lithium ions are deintercalated from the positive electrode and migrate to the negative electrode, combining with the negative electrode active material, thereby realizing the storage of electrical energy.

[0053] During the discharge process, the lithium ions inside the battery are deintercalated from the negative electrode active material, move to the positive electrode through the electrolyte, and combine with the positive electrode active material. The electrons generated in this process flow to the load through the external circuit, thereby releasing electrical energy. If the positive and negative electrodes are in direct contact during the above battery charging and discharging process, a short circuit will occur inside the battery, causing the current inside the battery to flow directly through the short circuit point, and the battery temperature will rise. In severe cases, it may cause the battery to catch fire or explode.

[0054] In the existing production process of wound batteries, the negative electrode sheet is usually wound first, and then the positive electrode sheet is accurately matched and bonded to the wound negative electrode sheet and the separator. The structure of the wound battery cell mainly includes two types: square and round. During the winding process of the square wound battery cell, effective stress is easily formed on both sides. When the two sides of the battery cell are subjected to a certain degree of external force, it is possible to cause the positive and negative electrodes to break, thereby causing a short circuit in the battery cell. Therefore, many battery module products that specialize in protecting both sides of the square wound battery cell structure have emerged on the market.

[0055] At the same time, the two sides of the circular battery cell winding structure have a certain curvature, which can just solve the problem of possible breakage of the square wound battery cell when subjected to force. Therefore, batteries with circular wound battery cell structures occupy a considerable share in the market. However, the structural characteristics of the circular battery cell also bring some new technical problems. Because when the positive electrode sheet is subjected to external force, this structure will exert a force on the isolation membrane in contact with the negative electrode sheet. If the end of the positive electrode sheet or the positive electrode sheet itself has more burrs, it will often cause the positive electrode sheet to puncture the isolation membrane and contact the negative electrode sheet.

[0056] As mentioned above, the positive electrode sheet of the commonly used wound battery is usually made of aluminum foil. In the process of making aluminum foil, mechanical processing methods such as rolling and stamping may be used, which may produce tiny burrs on the surface of the aluminum foil. During storage and transportation, the aluminum foil may also be scratched or collided by external objects, further causing the generation of burrs. To make it more complicated, after the battery cell is encapsulated, the reaction between the aluminum foil and the electrolyte will form a layer of aluminum oxide film, and the uneven growth of this film may also cause the appearance of burrs. Therefore, based on the above reasons, the terminal of the positive electrode sheet is very easy to pierce the isolation membrane due to burrs in the circular structure of the battery cell winding. Once the empty foil segment at the end of the positive electrode sheet pierces the isolation membrane and connects to the negative electrode sheet, a conductive channel will be formed between the positive and negative electrodes, resulting in the passage of short-circuit current. This short circuit will cause a lot of heat to be generated inside the battery, and in extreme cases, it may cause the battery to catch fire or even explode. Therefore, in the design and manufacturing process of the battery, these potential risk factors must be strictly controlled to ensure the safety and stability of the battery.

[0057] The utility model understands the problems in the existing round battery core winding structure, so it improves the existing prototype battery core winding structure. The utility model will be further described in detail below in conjunction with specific implementation methods, but the implementation methods of the utility model are not limited thereto.

[0058] Implementation Method 1

[0059] like Figure 1 As shown, the circular battery cell winding structure in this embodiment includes a positive electrode sheet 1, a separator 2 and a negative electrode sheet 3 that are sequentially bonded and wound together; wherein the positive electrode sheet 1 includes a first current collector 12, a first active material layer 121 coated on both sides of the first current collector 12 in a thickness direction, and a first empty foil segment 11 that is not coated with the first active material layer 121 and is located at the starting end of the winding of the first current collector 12; wherein the length of the first empty foil segment 11 is greater than the circumference of the winding needle used in the winding process, so that the end of the first empty foil segment 11 contacts itself correspondingly after winding.

[0060] On the one hand, by providing a first empty foil segment 11 not coated with the first active material layer 121 in the positive electrode sheet 1, and making the end of the first empty foil segment 11 contact itself after winding, the structure inside the circular wound battery cell is improved. Among them, in order to enable the first empty foil segment 11 to contact itself, the length of the first empty foil segment 11 is designed to be greater than the circumference of the winding needle used in the winding process. During the winding process, the negative electrode sheet 3 can only be wound through the separator 2 and the positive electrode sheet 1 at a distance behind the first empty foil segment 11 due to the obstruction of the first empty foil segment 11. Therefore, during the winding process, the end of the first empty foil segment 11 will naturally form contact without additional fixing or connecting operations, which not only simplifies the production process, but also effectively avoids the risk of the end face of the positive electrode sheet 1 piercing the separator 2 and contacting the negative electrode sheet 3, thereby improving the safety and performance of the battery. At the same time, since the coating area of ​​the active material layer is reduced, the material cost is reduced, and the problem of the active material layer falling off or being damaged during the winding process is reduced, the reliability and service life of the battery are improved.

[0061] On the other hand, the applicant also considers that there may be a situation in the prior art where the positive electrode sheet 1 is preferentially wound in the inner circle, but the length of the positive electrode empty foil segment is not enough to achieve the contact between the end of the empty foil segment of the positive electrode sheet 1 and itself. Because, when the positive electrode active material contacts the positive electrode empty foil segment, the positive electrode active material has a higher potential, and the positive electrode empty foil segment is not coated with any active material, so the potential is lower. Due to the existence of the potential difference, a conductive path will be formed, resulting in a short circuit inside the battery. In this case, the battery may be at risk of overheating, fire or even explosion. By adjusting the positive electrode empty foil segment in this embodiment, after the positive electrode empty foil segment pierces the isolation membrane, the positive electrode empty foil segment contacts the positive electrode empty foil segment. Since the positive electrode empty foil segment contacts the positive electrode empty foil segment, since both have the same potential, no potential difference will be formed, and no current will be generated, thereby avoiding the occurrence of a short circuit.

[0062] In addition, this embodiment can also be combined with other technical solutions to further improve the performance and safety of the battery. For example, a protective adhesive or pressure-sensitive adhesive or other bonding material can be provided at the end of the first empty foil segment 11 to enhance the stability and reliability of its contact. Other functional layers or structures can also be provided between the positive electrode sheet 1, the negative electrode sheet 3 and the separator 2 to improve the conductivity, thermal stability and other properties of the battery.

[0063] It should be noted that, although only the structural improvement of the positive electrode sheet 1 is described in this embodiment, the negative electrode sheet 3 can also be designed similarly, for example, a second empty foil segment 31 not coated with the second active material layer 321 is provided, and the end of the second empty foil segment 31 is in contact with itself after winding. This can further improve the safety and performance of the battery.

[0064] In summary, the circular battery cell winding structure in this embodiment effectively avoids the risk of the end face of the positive electrode sheet 1 piercing the isolation membrane 2 and contacting the negative electrode sheet 3 by optimizing the internal structure, thereby improving the safety and performance of the battery, reducing production costs, and improving the reliability and service life of the battery.

[0065] Implementation Method 2

[0066] like Figure 1-2 As shown, the difference from the first embodiment is that in order to further realize the contact between the first empty foil segment 11 and itself, the length of the first empty foil segment 11 is greater than 1.2-2 times the circumference of the winding needle used in the winding process, and the length of the first empty foil segment 11 is 3-100 mm.

[0067] In the second embodiment, the length of the first empty foil segment 11 is more accurately defined, so that its length is greater than 1.2-2 times the circumference of the winding needle used in the winding process, and the length of the first empty foil segment 11 is specifically proposed to be in the range of 3-100 mm. In the specific embodiment, the length of the first empty foil segment 11 can be any one of 3 mm, 5 mm, 10 mm, 20 mm, 30 mm, 50 mm, 70 mm and 90 mm. Among them, the length of the first empty foil segment 11 mainly depends on the circumference of the winding needle. If it is applied to a battery cell with a smaller thickness, the limit value of the circumference of the winding core can reach 3 mm or less. The first empty foil segment 11 of this embodiment is greater than 3 mm or equal to 3 mm to maintain a circumference greater than the circumference of the winding core. The selected design further ensures that the end of the first empty foil segment 11 can contact itself correspondingly after winding, thereby effectively avoiding the risk of the end face of the positive electrode sheet 1 piercing the separator 2 and contacting the negative electrode sheet 3. At the same time, by limiting the length range of the first empty foil segment 11, the internal structure and performance of the battery can be better controlled, and the safety and reliability of the battery can be improved.

[0068] It should be noted that in Embodiment 2, the length of the first empty foil segment 11 is not necessarily the larger the better. If the length is too large, the volume and weight of the battery may increase, which is not conducive to the energy density and lightweight design of the battery. Therefore, in practical applications, it is necessary to reasonably select the length of the first empty foil segment 11 according to the specific requirements and specifications of the battery to achieve the best performance and safety effect.

[0069] In summary, the circular battery cell winding structure in Implementation 2 further optimizes the internal structure of the battery, improves the safety and performance of the battery, and provides a more reliable and effective solution for the design and manufacture of the battery by precisely controlling the length of the first empty foil segment 11.

[0070] The rest of the structure is the same as that of Implementation 1 and will not be described in detail in this implementation.

[0071] Implementation 3

[0072] like Figure 1-3 As shown, the difference from Implementation Example 1 is that: in order to further ensure that the first empty foil segment 11 does not contact the positive electrode sheet 1, the first empty foil segment 11 is bonded with a first protective glue 111 on both sides of its thickness direction, and the first protective glue 111 extends to cover the end of the first active material layer 121, and the length L1 of the covering part is 0.5-2mm.

[0073] In Embodiment 3, the structure of the first empty foil segment 11 is further improved, and the first protective glue 111 is bonded to both sides of the first empty foil segment 11, and the first protective glue 111 also extends to cover the end of the first active material layer 121. Such a design not only enhances the contact stability and reliability between the first empty foil segment 11 and the positive electrode sheet 1, but also effectively prevents the first active material layer 121 from falling off or being damaged during the winding process. At the same time, by covering the end of the first active material layer 121, the risk of the end face of the positive electrode sheet 1 piercing the separator 2 and contacting the negative electrode sheet 3 can also be avoided, further improving the safety and performance of the battery.

[0074] In addition, the covering length L1 of the first protective glue 111 is specifically limited to 0.5-2 mm. Specifically, the length L1 of the first protective glue 111 covering the first active material layer 121 can be any one of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.75 mm and 2 mm. Selecting these lengths can ensure that the first protective glue 111 can play an effective protective role without increasing the volume and weight of the battery too much. It should also be noted that the specific value of the length L1 covering the first active material layer 121 can be selected according to the specific specifications and requirements of the battery.

[0075] In summary, the circular battery cell winding structure in embodiment 3 further enhances the safety and performance of the battery by setting the first protective glue 111 on both sides of the first empty foil segment 11 and covering the end of the first active material layer 121, providing a more comprehensive and reliable solution for the design and manufacture of the battery.

[0076] The rest of the structure is the same as that of Implementation 1 and will not be described in detail in this implementation.

[0077] Implementation 4

[0078] like Figure 1-4 , which is different from Embodiment 1, the negative electrode sheet 3 of this embodiment includes a second current collector 32, a second active material layer 321 coated on both sides of the second current collector 32 in the thickness direction, and a second empty foil segment 31 which is not coated with the second active material layer 321 and is located at the starting end of the winding of the second current collector 32, and the end of the second empty foil segment 31 corresponds to the position of the first protective glue 111 after winding.

[0079] In Embodiment 4, the structure of the negative electrode sheet 3 is improved, a second empty foil segment 31 is added, and the end of the second empty foil segment 31 corresponds to the position of the first protective glue 111 after winding. This design enables the first protective glue 111 to form effective contact with the second empty foil segment 31 after winding, thereby further preventing the risk of the end face of the positive electrode sheet 1 piercing the separator 2 and contacting the negative electrode sheet 3, thereby improving the safety of the battery. At the same time, the presence of the second empty foil segment 31 also helps to maintain the stability and consistency of the negative electrode sheet 3, and improve the reliability and performance of the battery.

[0080] In addition, the circular battery cell winding structure in Embodiment 4 can also be combined with other technical solutions to further improve the performance and safety of the battery. For example, a separation layer can be provided between the first empty foil segment 11 and the second empty foil segment 31 to prevent the two from contacting each other during the winding process. Other functional layers or structures can also be provided between the positive electrode sheet 1, the negative electrode sheet 3 and the separator 2 to improve the conductivity, thermal stability and other properties of the battery.

[0081] In summary, the circular battery cell winding structure in Embodiment 4 further improves the safety and performance of the battery by adding the second empty foil segment 31 and making it correspond to the first protective glue 111, and provides a more effective solution for the design and manufacture of the battery.

[0082] Preferably, in order to ensure the consistency of the positive electrode sheet 1 and the negative electrode sheet 3, the length of the second empty foil segment 31 is 0.1-3mm, and the length of the first empty foil segment 11 is 4-40 times the length of the second empty foil segment 31. In a specific embodiment, the length of the second empty foil segment 31 can be 0.1mm, 0.2mm, 0.5mm, 0.75mm, 1mm, 1.2mm, 1.5mm, 2mm or 3mm. The selection of this length range not only ensures that the second empty foil segment 31 can play its due role, but also avoids unnecessary volume and weight increase due to excessive length. At the same time, the length of the first empty foil segment 11 should be 4-40 times the length of the second empty foil segment 31. That is, the length of the first empty foil segment 11 exemplified in Embodiment 1 is designed according to a certain ratio, not a simple design. The setting of this proportional relationship ensures the coordination of the positive electrode sheet 1 and the negative electrode sheet 3 during the winding process, which helps to improve the overall performance of the battery.

[0083] In addition, such a design also helps to control the manufacturing cost of the battery. By reasonably controlling the length of the second empty foil segment 31, we can effectively reduce the waste of raw materials, thereby reducing the manufacturing cost of the battery. At the same time, since the length relationship between the first empty foil segment 11 and the second empty foil segment 31 is optimized, the winding process of the battery will also be smoother, which helps to improve production efficiency.

[0084] In summary, the circular battery cell winding structure in Implementation 4 further improves the consistency and performance of the battery by optimizing the length of the second empty foil segment 31 and stipulating the length relationship between the first empty foil segment 11 and the second empty foil segment 31, thereby providing a more optimized solution for battery design and manufacturing.

[0085] It should be noted that the above implementation is only a description of a specific implementation of the utility model, and is not a limitation of the technical solution of the utility model. Without departing from the technical concept of the utility model, those skilled in the art can make various modifications and variations to the above implementation, and these modifications and variations should be included in the protection scope of the utility model.

[0086] Preferably, in order to further improve the safety of the winding structure of the utility model, the second empty foil segment 31 is bonded with a second protective adhesive 311 on both sides in the thickness direction, and the second protective adhesive 311 extends to cover the end of the second active material layer 321, and the length L12 of the covering portion is 0.5-2mm.

[0087] The second protective glue 311 is arranged on both sides of the second empty foil segment 31, and is extended to cover the end of the second active material layer 321. Such a design further enhances the safety and performance of the battery. The presence of the second protective glue 311 can effectively prevent the second active material layer 321 from falling off or being damaged during the winding process, thereby improving the reliability of the battery. At the same time, by covering the end of the second active material layer 321, the second protective glue 311 can also avoid the risk of the end face of the negative electrode sheet 3 piercing the isolation membrane and contacting the positive electrode sheet 1, further improving the safety of the battery.

[0088] In addition, the length L of the second protective glue 311 covering the second active material layer 321 is 2 Specifically limited to 0.5-2mm, the selection of this length range not only ensures that the second protective glue 311 can play an effective protective role, but also avoids unnecessary volume and weight increase due to excessive coverage. In a specific embodiment, the coverage length L2 of the second protective glue 311 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.5mm, 1.75mm or 2mm, etc. The selection of specific values ​​should be determined according to the specific specifications and requirements of the battery. By arranging the second protective glue 311 on both sides of the second empty foil segment 31 and controlling its coverage length L2 within a suitable range, the circular battery cell winding structure in embodiment 4 further improves the safety and reliability of the battery while maintaining the battery performance, providing a more comprehensive and effective solution for the design and manufacture of the battery.

[0089] Therefore, although the above embodiments have described the technical solutions of the present invention in detail, it does not mean that these descriptions are exclusive or restrictive. On the contrary, the protection scope of the present invention shall be based on the content defined in the claims, and any modifications and variations that meet these requirements shall be deemed to be included in the protection scope of the present invention.

[0090] The rest of the structure is the same as that of Implementation 1 and will not be described in detail in this implementation.

[0091] Implementation method 5

[0092] like Figure 1-7 The difference from Implementation 1 is that in order to further improve the safety of the battery, the coating area of ​​the first active material layer 121 in this implementation is smaller than the coating area of ​​the second active material layer 321. It is known that a smaller coating area of ​​the first active material layer 121 can reduce the heat generation of the battery under abnormal conditions such as overcharging or short circuit, thereby improving the safety of the battery.

[0093] At the same time, since the coating area of ​​the first active material layer 121 is small, the corresponding amount of positive electrode material is also reduced accordingly, which helps to reduce the manufacturing cost of the battery. However, while reducing the coating area of ​​the first active material layer 121, the utility model also ensures that the performance of the battery is not affected. Specifically, the utility model optimizes the design of the positive electrode tab 13 and the negative electrode tab 33 of the battery so that they can better adapt to the positive and negative active material layers with different coating areas. (For example, the shape of the tab is changed so that the coating area can be fine-tuned without changing the length of the positive electrode sheet 1 or the negative electrode sheet 3)

[0094] In summary, the circular battery cell winding structure in Embodiment 5 reduces the coating area of ​​the first active material layer 121 and optimizes the battery structure and material ratio, thereby maintaining or even improving the battery performance while improving the battery safety.

[0095] In order to further improve the safety performance of the battery core winding structure, the first active material layer 121 includes a first layer 1211 and a second layer 1212 coated on both sides of the first current collector 12 in the thickness direction, and the ends of the second layer 1212 and the first layer 1211 are aligned or staggered. Figure 6 The first layer 1211 and the second layer 1212 are staggered along the dotted line in the figure.

[0096] By setting two different coating structures in the first active material layer 121, namely the first layer 1211 and the second layer 1212, and controlling their end alignment or misalignment, the safety performance of the battery cell winding structure can be further improved. When the ends of the second layer 1212 and the first layer 1211 are aligned, the uniform distribution of the positive electrode active material during the winding process can be ensured, avoiding the situation where the local thickness is too large or too small, thereby improving the capacity and stability of the battery. When the ends of the second layer 1212 and the first layer 1211 are misaligned, a certain misalignment buffer zone can be formed to reduce the stress concentration and damage that may occur during the winding process, further improving the safety and life of the battery.

[0097] In addition, the design of the double-layer coating structure can be flexibly adjusted according to actual needs. For example, the coating area, thickness, material and other parameters of the first layer 1211 and the second layer 1212 can be adjusted according to factors such as battery specifications, performance requirements and safety indicators to achieve optimal battery performance and safety performance.

[0098] In summary, the circular battery winding structure in Embodiment 5 reduces the coating area of ​​the first active material layer 121 and combines the design of the double-layer coating structure to improve battery safety while maintaining or even improving battery performance. This design provides a more comprehensive and effective solution for battery design and manufacturing, and helps promote the further development and application of battery technology.

[0099] Further references Figure 7 As a corresponding adjustment of the negative electrode sheet 3, the second active material layer 321 includes a third layer 3211 and a fourth layer 3212 coated on both sides of the second current collector 32 in the thickness direction, and the ends of the fourth layer 3212 and the third layer 3211 are aligned. By also adopting a double-layer coating structure in the second active material layer 321, that is, the third layer 3211 and the fourth layer 3212, and controlling their end alignment, the stability and safety of the battery core winding structure can be further improved. The design of this double-layer coating structure can ensure the uniform distribution of the negative electrode active material during the winding process, avoid the situation where the local thickness is too large or too small, thereby improving the capacity and stability of the battery. At the same time, due to the large coating area of ​​the negative electrode active material layer, this double-layer coating structure can also effectively alleviate the stress concentration and damage that may occur during the winding process, and improve the reliability and life of the battery.

[0100] Further, if Figure 7The second protective glue 311 of the negative electrode sheet 3 shown has also been adjusted accordingly, wherein the length of the second protective glue 311 in contact with the third layer 3211 is greater than the length of the second protective glue 311 in contact with the fourth layer 3212. Since the third layer 3211 is located on one side of the negative electrode sheet 3, it may be more susceptible to interference from external factors. Therefore, increasing the length of the second protective glue 311 in contact with it can further improve the stability and safety of the negative electrode sheet 3. For the second protective glue 311 in contact with the fourth layer 3212, although its length is relatively short, it can still play a certain protective role. At the same time, the shorter length of the second protective glue 311 can also reduce the occupation of the internal space of the battery, which is conducive to the miniaturization and lightweight of the battery.

[0101] In summary, by combining the double-layer coating structure of the second active material layer 321 with the double-layer coating structure of the first active material layer 121, a good match in structure and performance between the positive and negative active material layers can be achieved. This match can ensure that the battery can maintain stable performance output during the charge and discharge process, while reducing the risk of abnormal reactions and failures that may occur inside the battery.

[0102] The rest of the structure is the same as that of Implementation 1 and will not be described in detail in this implementation.

[0103] Implementation 6

[0104] like Figure 1-7 As shown, in order to solve the problem that none of the prior arts can solve the problem that the positive electrode sheet 1 and the negative electrode sheet 3 are in direct contact after the internal separator of the circular wound battery cell is pierced, the utility model also designs a secondary battery, including the circular battery cell winding structure 100 in any of the above embodiments.

[0105] By applying the circular battery cell winding structure 100 in Embodiment 4 to a secondary battery, this embodiment provides a battery design solution with higher safety and reliability. Since the circular battery cell winding structure 100 effectively improves the safety of the battery by providing the second protective glue 311 and controlling its coverage length while maintaining the battery performance, applying this structure to a secondary battery can significantly improve the overall safety performance of the battery.

[0106] In addition, since the circular battery winding structure 100 can be combined with other embodiments to further optimize the performance and safety of the battery, other functional layers or structures can be introduced into the secondary battery of embodiment 6 to improve the key performance indicators such as the conductivity and thermal stability of the battery. At the same time, by optimizing the design and manufacturing process of the battery, the comprehensive performance of the battery can be further improved to meet the needs of different application scenarios.

[0107] In summary, the secondary battery in Embodiment 6 adopts an optimized circular cell winding structure 100, which improves the safety and reliability of the battery and provides a more reliable and efficient solution for the application of the battery. This battery design is not only suitable for various consumer electronic products, but can also be widely used in electric vehicles, energy storage systems and other fields, promoting the further development and application of battery technology.

[0108] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may be modified and varied in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A circular battery core winding structure, comprising a positive electrode sheet (1), a separator (2) and a negative electrode sheet (3) which are laminated in sequence and wound together, characterized in that: The positive electrode sheet (1) comprises a first current collector (12), a first active material layer (121) coated on both sides of the first current collector (12) in the thickness direction, and a first empty foil section (11) not coated with the first active material layer (121) and located at the starting end of the winding of the first current collector (12); The length of the first empty foil segment (11) is greater than the circumference of a winding needle used in the winding process, so that the ends of the first empty foil segment (11) contact themselves correspondingly after winding.

2. The circular battery core winding structure according to claim 1, characterized in that: The length of the first empty foil segment (11) is greater than 1.2-2 times the circumference of the winding needle used in the winding process, and the length of the first empty foil segment (11) is 3-100 mm.

3. The circular battery core winding structure according to claim 1, characterized in that: The first hollow foil segment (11) is bonded with a first protective adhesive (111) on both sides in the thickness direction thereof, and the first protective adhesive (111) extends to cover the end of the first active material layer (121), and the length L1 of the covered portion is 0.5-2 mm.

4. The circular battery core winding structure as claimed in claim 3, characterized in that: The negative electrode sheet (3) comprises a second current collector (32), a second active material layer (321) coated on both sides of the second current collector (32) in the thickness direction, and a second empty foil segment (31) not coated with the second active material layer (321) and located at the starting end of the winding of the second current collector (32), wherein the end of the second empty foil segment (31) corresponds to the position of the first protective glue (111) after winding.

5. The circular battery core winding structure as claimed in claim 4, characterized in that: The length of the second empty foil segment (31) is 0.1-3 mm, and the length of the first empty foil segment (11) is 4-40 times the length of the second empty foil segment (31).

6. The circular battery core winding structure as claimed in claim 4, characterized in that: The second hollow foil segment (31) is bonded with a second protective adhesive (311) on both sides in the thickness direction thereof, and the second protective adhesive (311) extends to cover the end of the second active material layer (321), and the length L2 of the covered portion is 0.5-2 mm.

7. The circular battery core winding structure as claimed in claim 4, characterized in that: The coating area of ​​the first active material layer (121) is smaller than the coating area of ​​the second active material layer (321).

8. The circular battery core winding structure as claimed in claim 1, characterized in that: The first active material layer (121) comprises a first layer (1211) and a second layer (1212) coated on both sides of the first current collector (12) in the thickness direction, and the ends of the second layer (1212) and the first layer (1211) are aligned or staggered.

9. The circular battery core winding structure as claimed in claim 4, characterized in that: The second active material layer (321) includes a third layer (3211) and a fourth layer (3212) coated on both sides of the second current collector (32) in the thickness direction, and the ends of the fourth layer (3212) and the third layer (3211) are aligned.

10. A secondary battery, characterized in that: It comprises the circular battery core winding structure (100) as described in any one of claims 1 to 9.

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