Battery cell, battery monomer, method for preparing battery cell and method for preparing battery monomer

Abstract

The invention provides a battery cell, a battery monomer, a method for preparing the battery cell and a method for preparing the battery monomer. The battery cell comprises a first pole piece and a second pole piece, the isolating membrane is arranged between the first pole piece and the second pole piece so as to isolate the first pole piece from the second pole piece, and the isolating membrane, the first pole piece and the second pole piece form a winding structure; the innermost ring of the battery cell is provided with N layers of isolating membranes along the winding direction of the battery cell, the N layers of isolating membranes are wound to form a cylindrical structure with a through hole inside, and the end parts, positioned in the through hole, of the isolating membranes are provided with extension parts and pressing parts which are connected with each other; observed in the axial direction of the through hole, the extending part divides the through hole into two parts. The abutting part abuts against the inner wall of the through hole and is bent towards one side along the inner wall of the through hole. The isolating membrane is wound to form a cylindrical structure, and the cylindrical structure directly abuts against the tab during welding to replace an ejector pin.

Description

Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular, to a battery cell, a battery monomer, a method for manufacturing a battery cell, and a method for manufacturing a battery monomer. Background Art

[0002] The manufacturing process of a battery includes processes such as coating, sheet making, winding, assembly, and welding. Currently, in the process of welding a tab to a battery case and / or a lid, a thimble needs to pass through a through hole formed by winding a separator film and abut against the tab to support the tab in a suitable position during welding so that the tab can be effectively welded to the case and the lid.

[0003] To accommodate the passage of the thimble, the through hole formed by winding the separator film needs to have a relatively large inner diameter. However, the through hole with a relatively large inner diameter also occupies a relatively large amount of space in the middle of the battery cell, which in turn results in a relatively low energy density of the battery cell. Therefore, how to improve the energy density of the battery cell has become a technical problem to be solved urgently. Summary of the Invention

[0004] To solve at least one technical problem in the prior art and other aspects, the present disclosure provides a battery cell, a battery monomer, a method for manufacturing a battery cell, and a method for manufacturing a battery monomer, which are beneficial to improving the energy density of the battery cell.

[0005] An embodiment of the present disclosure provides a battery cell, including: a first electrode plate and a second electrode plate; a separator film disposed between the first electrode plate and the second electrode plate to isolate the first electrode plate and the second electrode plate and form a wound structure with the first electrode plate and the second electrode plate; along the winding direction of the battery cell, N layers of separator film are provided in the innermost layer of the battery cell, N≥2, and the N layers of separator film are wound to form a tubular structure with a through hole inside. The end of the separator film located inside the through hole has a sequentially arranged extension part and a pressing part; wherein, when observed along the axial direction of the through hole, the extension part divides the through hole into at least two parts; the pressing part presses against the inner wall of the through hole.

[0006] The wound tubular structure formed by the separator film with at least two layers has relatively high structural strength. When welding the battery cell to an external case and / or lid, the tubular structure can directly abut against the tab to replace the thimble. Since there is no need to insert a thimble into the through hole for support during welding, the inner diameter of the through hole of the tubular structure formed by winding the separator film does not need to consider the size of the thimble. Correspondingly, the outer diameter of the tubular structure can also be wound smaller to reduce the space occupied by the tubular structure in the middle of the battery cell, thereby improving the energy density of the battery cell.

[0007] Based on the feature that the inside of the cylindrical structure has a through hole, the part of the separator film located inside the through hole further forms an extension part and a pressing part. The extension part extends from one side of the inner wall of the through hole to the other side, and is suitable for providing support in the radial direction of the cylindrical structure to compensate for the structural strength of the cylindrical structure. Moreover, when the cylindrical structure supports the tab, the extension part also abuts against the tab. Therefore, the force in the axial direction of the cylindrical structure can be dispersed, which is beneficial to preventing the cylindrical structure from collapsing due to excessive force. The pressing part abuts against the inner wall of the through hole, and the friction between the pressing part and the inner wall of the through hole can be used to limit the extension part from approaching the inner wall on one side of the through hole, so that the extension part is maintained at a position approximately in the middle of the cylindrical structure.

[0008] According to an embodiment of the present disclosure, the extension part and the pressing part are respectively formed by at least one layer of separator film. Based on different arrangement methods of the separator film before winding, the extension part and the pressing part can be formed by one layer of separator film, or can be formed by two or more layers of stacked separator films. The more layers of the separator film forming the extension part and the pressing part, the greater the radial support force that the extension part can provide to the cylindrical structure.

[0009] According to an embodiment of the present disclosure, when observed along the axial direction of the through hole, the extension part is arranged in an S shape.

[0010] The extension part has an S structure and can be directly formed by a winding pin during the manufacturing process without adding other processes.

[0011] According to an embodiment of the present disclosure, the diameter of the through hole is configured to be greater than or equal to 0.6 mm and less than or equal to 2.3 mm. The diameter of this through hole is small, so it does not occupy too much middle space, and thus the design requirement of improving the energy density of the battery cell can be achieved.

[0012] According to an embodiment of the present disclosure, the diameter of the through hole is less than 2.0 mm. In the prior art, the battery cell is welded by a thimble. Currently, the thimbles with smaller diameters used are mostly 2 mm. And to reserve the insertion space for the thimble, the distance between the through holes formed in the middle of the existing battery cells needs to be greater than 2 mm and it is difficult to design it smaller. Therefore, the energy density of the battery cell is limited.

[0013] According to an embodiment of the present disclosure, 8≥N≥3. The cylindrical structure formed by winding the separator film is welded with a supporting tab. The more layers of the cylindrical structure, the higher the strength, but it will also occupy a larger middle space of the battery cell. The cylindrical structure within this layer number range not only has a higher strength but also does not occupy too much space, and thus the design requirement of improving the energy density of the battery cell can be achieved.

[0014] According to an embodiment of the present disclosure, the thickness of the cylindrical structure is configured to be greater than or equal to 0.06 mm and less than or equal to 0.5 mm. If the thickness is set too thin, the cylindrical structure may deform axially when supporting the tab, and it cannot effectively support the tab. If the thickness is set too thick, the outer diameter of the cylindrical structure may be too large, which instead increases the space occupied by the cylindrical structure.

[0015] According to an embodiment of the present disclosure, the thickness of the cylindrical structure is further configured to be greater than or equal to 0.1 mm and less than or equal to 0.2 mm. Based on the same principle as the embodiment, the cylindrical structure within this thickness range can achieve a better balance between the supporting effect and the occupied space.

[0016] According to an embodiment of the present disclosure, the thickness of the separator is configured to be less than or equal to 11 μm. The thickness of at least three layers of the separator and the separator can generally meet the structural strength requirements of various separators when wound into a cylindrical structure. It should be understood that the number of layers of the separator formed by winding the separator and the thickness of the separator should be designed as a whole. For example, if the thickness of the separator is relatively thick, the number of layers of the separator can be correspondingly less; if the thickness of the separator is relatively thin, the number of layers of the separator can be correspondingly more.

[0017] According to an embodiment of the present disclosure, the separator includes a substrate; alternatively, the separator includes a substrate and a coating attached to at least one surface of the substrate.

[0018] According to an embodiment of the present disclosure, the separator includes one of a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator.

[0019] According to an embodiment of the present disclosure, the coating includes at least one of a ceramic coating, a nano - coating, and a silicone coating.

[0020] Based on the supporting effect of the cylindrical structure formed by the separator, it should have strong structural strength to prevent deformation when abutting against the tab. To this end, based on the substrate, or based on the substrate and the coating attached to the substrate, higher structural strength can be provided, which is beneficial to preventing the cylindrical structure from being deformed under pressure.

[0021] According to an embodiment of the present disclosure, the first electrode tab has a first current collector and a first active material layer disposed on the surface of the first current collector; the second electrode tab has a second current collector and a first active material layer disposed on the surface of the second current collector; the battery cell further includes at least one first tab and at least one second tab, the first tab is electrically connected to the first current collector, and the second tab is electrically connected to the second current collector. One of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab. The first active material or the second active material can be coated on both sides of the current collector, which is beneficial to reducing the number of coating method changes during the manufacturing process of the electrode tab, so as to improve production efficiency. According to an embodiment of the present disclosure, in the height direction of the battery cell, the first tab abuts against one end of the cylindrical structure; and / or, the second tab abuts against the other end of the cylindrical structure. The first tab and / or the second tab abuts against the end of the cylindrical structure. Therefore, the cylindrical mechanism can support the tab in the axial direction, and without cooperating with a thimble, the tab can also form an effective weld with the housing and / or the cover.

[0022] According to an embodiment of the present disclosure, in the projection in the height direction of the battery cell, the projection of the cylindrical structure is configured to be one of a circular ring, an elliptical ring, and a polygonal ring. Among them, the cylindrical structure configured to have a circular ring, an elliptical ring, and a penetrating ring in cross-section is beneficial to forming a smaller space in the middle of the battery cell; the cylindrical structure configured to be a polygonal ring is also beneficial to preventing the separator from deforming under stress.

[0023] An embodiment of the present disclosure further provides a battery module, including a battery cell; a housing having an opening, and an accommodation cavity is defined within the opening, and the battery cell is disposed within the accommodation cavity; a cover disposed at the opening to close the accommodation cavity; wherein, one of the housing and the cover is welded to the first tab of the battery cell and forms an electrical connection, and the other of the housing and the cover is welded to the second tab of the battery cell and forms an electrical connection. The battery module includes a battery cell. When welding the housing and / or the cover to the tab, it is also not necessary to insert a thimble into the through hole formed by winding the separator for support. Therefore, a battery module with a higher energy density of the battery cell can be formed.

[0024] According to an embodiment of the present disclosure, a method for preparing an electrode core is further provided, including: clamping a first electrode sheet and a separator by a winding pin, in the length direction of the electrode sheet, a third winding starting section of the separator extends out from a first winding starting section of the first electrode sheet; feeding a second electrode sheet; winding the first electrode sheet and the separator so that the third winding starting section is wound to form a cylindrical structure with a through hole inside, an extending portion of the separator located inside the through hole extends from one side of the inner wall of the through hole to the opposite side, a pressing portion of the separator presses against the inner wall of the through hole and bends along the inner wall of the through hole to one side, and in the winding direction, a second winding starting section of the second electrode sheet extends beyond the first winding starting section to form an electrode assembly; welding the electrode assembly to a first electrode tab and a second electrode tab to form an electrode core. Based on the electrode core, a method for preparing the electrode core is correspondingly provided. For the electrode core prepared by this preparation method, in the process of welding the electrode tab to the housing and / or the cover, there is no need to insert and extract a thimble. Therefore, the preparation process of the electrode core is simplified.

[0025] According to an embodiment of the present disclosure, the wound separator protrudes from the first electrode sheet in the width direction of the first electrode sheet. The part of the separator protruding from the first electrode sheet outside the cylindrical structure is subjected to heat ironing treatment.

[0026] According to an embodiment of the present disclosure, winding the third winding starting section to form a cylindrical structure with a through hole includes: winding the third winding starting section to form a cylindrical structure with at least two layers of separator.

[0027] According to an embodiment of the present disclosure, winding the third winding starting section to form a multi-layer cylindrical structure includes: winding the third winding starting section to form a cylindrical structure with a thickness of at least 0.06 mm and less than or equal to 0.5 mm.

[0028] According to an embodiment of the present disclosure, the method for preparing the electrode core further includes: removing the winding pin and hot pressing the electrode assembly so that the cross section of the electrode assembly in a first plane is substantially circular, and the first plane is perpendicular to the winding axis of the electrode assembly.

[0029] According to an embodiment of the present disclosure, welding the electrode assembly to the first electrode tab and the second electrode tab includes: welding one end of the first electrode tab to the first current collector of the first electrode sheet to form an electrical connection; welding one end of the second electrode tab to the second current collector of the second electrode sheet to form an electrical connection.

[0030] The present disclosure also provides a method for preparing a battery cell, comprising: placing a battery cell in a receiving cavity formed by a shell; making the cylindrical structure formed by the battery cell abut against the end face of the second pole tab of the battery cell facing away from the shell, and welding the second pole tab to the shell; assembling the shell cover to the opening of the shell to close the receiving cavity; and welding the first pole tab of the battery cell to the shell cover. The isolation film of the battery cell is wound to form a cylindrical structure. When welding the battery cell to the shell and / or shell cover, the cylindrical structure can be used to abut against the pole tab to replace the ejector pin, which is conducive to simplifying the welding process. Moreover, since an ejector pin is not required during welding, the outer diameter of the corresponding cylindrical structure can also be wound smaller, thereby reducing the space occupied by the cylindrical structure in the middle of the battery cell, thereby improving the energy density of the battery cell having the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a partial cross-sectional schematic diagram of a battery cell according to an exemplary embodiment of the present disclosure;

[0032] Figure 2 is a schematic diagram of a cylindrical structure according to an exemplary embodiment of the present disclosure;

[0033] Figure 3 yes Figure 1 The exploded view of the battery cell shown;

[0034] Figure 4 is an exploded view of a battery cell according to an exemplary embodiment of the present disclosure;

[0035] Figure 5 is a flow chart of a method for preparing a battery cell according to an exemplary embodiment of the present disclosure;

[0036] Figure 6 is a flow chart of a method for preparing a battery cell according to an exemplary embodiment of the present disclosure.

[0037] In the drawings, the meanings of the reference numerals are as follows:

[0038] 1. Battery cell; 11. First pole piece; 111. First winding start section; 12. Second pole piece; 121. Second winding start section; 13. Separator; 131. First separator; 132. Second separator; 133. Third winding start section; 1331. Winding portion; 1332. Extension portion; 1333. Pressing portion; 14. First tab; 15. Second tab;

[0039] 2. Shell cover;

[0040] 3. Shell; 31. Liquid filling plug. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the present disclosure more clear and understandable, the present disclosure will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0042] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0043] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0044] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc. In the case of using expressions such as "at least one of A, B, or C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.

[0045] Figure 1 is a cross-sectional schematic view of a battery cell according to an exemplary embodiment of the present disclosure.

[0046] According to the battery cell 1 provided by the present disclosure, as Figure 1 shown, it includes a first electrode tab 11, a second electrode tab 12, and a separator 13. The separator 13 is disposed between the first electrode tab 11 and the second electrode tab 12 to isolate the first electrode tab 11 and the second electrode tab 12, and the separator 13 and the first electrode tab 11 and the second electrode tab 12 form a wound structure. Along the winding direction of the battery cell 1, N layers of separators 13 are provided in the innermost circle of the battery cell 1, N≥2, and the N layers of separators 13 are wound to form a cylindrical structure with a through hole inside. The end of the separator located inside the through hole has a connected extension portion 1332 and a pressing portion 1333. (That is, it can be understood that there are multiple layers of separators 13 in the innermost circle of the battery cell.) Among them, the extension portion 1332 extends from one side of the inner wall of the through hole to the opposite side, and along the axial direction of the through hole (such as Figure 1The extending portion 1332 divides the through hole into at least two parts. The pressing portion 1333 presses against the inner wall of the through hole.

[0047] In the above solution, the extension portion 1332 and the pressing portion 1333 do not necessarily constitute the starting point of the isolation film 13 . It is possible that the extension portion 1332 and the pressing portion 1333 are still some distance away from the winding starting point of the isolation film 13 .

[0048] The following explanation is made using the case of being divided into two parts as an example. It can be understood that being divided into multiple parts can also have the effect of strengthening the cylindrical structure.

[0049] At present, the electrode assembly (including the first electrode plate 11, the second electrode plate 12 and the isolation membrane 13) needs to be wound with a winding needle. For this reason, a through hole will inevitably be formed in the middle of the cylindrical structure after the winding is completed. When the internal hollow cylindrical structure abuts the electrode ear, if the force is too large, it is easy to collapse.

[0050] In this embodiment, the third winding starting section 133 includes, in addition to the winding portion 1331 for forming a cylindrical structure, an extension portion 1332 and a pressing portion 1333 sequentially arranged along the length direction of the battery core. The extension portion 1332 extends from one side of the inner wall of the through hole to the other side (e.g., Figure 1 The extension portion 1332 is adapted to provide support in the radial direction of the cylindrical structure to compensate for the structural strength of the cylindrical structure. Furthermore, since the extension portion 1332 also passes through the through hole in the axial direction of the through hole, when the cylindrical structure supports the tab, the force on the cylindrical structure in the axial direction can also be dispersed, which helps prevent the collapse of the cylindrical structure due to excessive force. The pressing portion 1333 abuts against the inner wall of the through hole. For this purpose, the extension portion 1332 can be limited to a certain side of the through hole (such as Figure 1 The inner wall of the cylindrical structure (upper or lower side as shown) is close to each other so that the extension 1332 is maintained in a position approximately in the middle of the cylindrical structure.

[0051] The length direction of the battery cell 1 is the winding center (i.e. Figure 1 The O point shown in the figure is the end point along the winding direction (i.e. Figure 1 The D direction shown is the direction of spiral extension; the thickness direction is the direction tangent to a certain position along the length of the battery cell 1; and the height direction is the direction orthogonal to both the length and thickness directions. Unless otherwise specified, the length, thickness, and height directions of the battery cells described below refer to this section.

[0052] In some exemplary embodiments, Figure 1As shown, when observing along the axial direction of the through-hole, the extension portion 1332 and the pressing portion 1333 form a substantially S-shaped structure.

[0053] Among them, the extension portion 1332 divides the through-hole into a first part and a second part. Based on the process of winding the battery core with a winding needle, two clamp-like parts formed by branching from the main body of the winding needle are respectively located in the first part or the second part. On this basis, the substantially S-shaped structure formed by the extension portion 1332 and the pressing portion 1333 can be understood as follows: during the winding process, the opposite surfaces of the extension portion 1332 are respectively in misaligned contact with one clamp-like part of the winding needle, and are deformed along the pressure direction under the pressure provided by the winding needle during winding. Further, when observing along the axial direction of the through-hole, it can be seen that recessed parts are formed in a misaligned manner on both sides of the extension portion 1332. The two recessed parts form a continuous and smooth transition, and since the pressing portion 1333 and the extension portion 1332 are integral, therefore, it will also bend along the extending direction of the inner wall of the through-hole. It should be noted that the two recessed parts are not necessarily centrosymmetric about the center of the through-hole, and there may be a situation where the recessed degree of one recessed part is different from that of the other recessed part.

[0054] According to an embodiment of the present disclosure, the extension portion 1332 and the pressing portion 1333 are respectively formed by at least one layer of separator film.

[0055] In some exemplary embodiments, as Figure 1 shown, the extension portion 1332 and the pressing portion 1333 have two layers of separator film. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0056] For example, the extension portion 1332 and the pressing portion 1333 may have one layer, two layers, three layers, four layers or any other number of layers of separator film. Specifically, it should be configured according to the number of layers of the separator film 13 provided in the battery core and whether the third winding start segment 133 of the separator film 13 is aligned.

[0057] In some exemplary embodiments, as Figure 1 shown, the first electrode tab 11, the separator film 13 and the second electrode tab 12 are sequentially stacked and wound to form a wound electrode assembly. Specifically, the electrode assembly has a winding center perpendicular to the paper surface (i.e., the point O as Figure 1 shown). Further, the winding start segments of the first electrode tab 11, the separator film 13 and the second electrode tab 12 surround the winding center along the winding direction (such as Figure 1The winding direction D shown (i.e., the counterclockwise direction) winds from the inside to the outside to form a substantially cylindrical electrode assembly. Among them, the substantially cylindrical shape is characterized in that when observing the cross-section (or top view) of the wound electrode assembly in the radial direction, its outer periphery forms a continuous curved surface. Although in the actual manufacturing process, due to the thickness of the first electrode sheet, the second electrode sheet, and the separator film, there will be a slight difference in the distance from each part of the outer periphery to the center, but this difference is negligible compared to the approximately constant diameter. It should be understood that the embodiments of the present disclosure are not limited to this.

[0058] For example, the electrode assembly can also be configured to wind in the clockwise winding direction.

[0059] In some exemplary embodiments, as Figure 1 shown, the third winding start segment 133 includes a pressing portion 1333, an extending portion 1332, and a winding portion 1331 arranged in sequence along the length direction of the battery cell. Specifically, when winding the third winding start segment 133, an external winding needle can be cooperated with the extending portion 1332 and then wound along the winding direction. During winding, the pressing portion 1333 and the extending portion 1332 form a complete winding cycle, while the winding portion 1331 winds layer by layer around the winding center in a winding cycle, so that the part of the separator film 13 located in the battery cell 1 forms a cylindrical structure.

[0060] According to the embodiments of the present disclosure, as Figure 1 shown, the diameter of the through hole (i.e., Figure 1 D shown) includes but is not limited to being configured to be greater than or equal to 0.6 mm and less than or equal to 2.3 mm. That is, 2.3 mm ≥ D ≥ 0.6 mm.

[0061] According to the embodiments of the present disclosure, as Figure 1 shown, the diameter of the through hole is less than 2.0 mm. That is, 2.0 mm ≥ D.

[0062] In such an implementation manner, the through hole is formed based on the characteristics of the winding process (i.e., winding the battery cell through a winding needle). Based on the through hole with the above diameter parameters, the diameter of the through hole can be made smaller. Therefore, it does not occupy too much space in the middle of the battery cell, and thus the design requirement of improving the energy density of the battery cell can be achieved. In the prior art, the battery cell is welded through a thimble. Currently, the diameter of the thimble with a smaller diameter used is mostly 2 mm. And to reserve the insertion space for the thimble, the distance between the through holes formed in the middle of the existing battery cell needs to be greater than 2 mm and it is difficult to design it smaller. Therefore, the energy density of the battery cell is limited. It should be understood that the embodiments of the present disclosure are not limited to this.

[0063] For example, the diameter of the above through-hole can be configured as 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm;

[0064] Alternatively, the diameter of the above through-hole can also be configured to be less than 0.6 mm, such as 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm;

[0065] Alternatively, the diameter of the above through-hole can also be configured to be more than 3 mm, such as 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm and any other diameter, which should be set as small as possible on the basis of meeting the tape measure size.

[0066] In such an embodiment, the third winding starting section 133 of the isolation film 13 is wound to form a multi-layer cylindrical structure with high structural strength. When welding the tab of the battery cell 1 to the external housing and / or the cover, the tab can be directly abutted through the cylindrical structure to support the tab for welding. Since there is no need to insert a thimble (which can also be called a pressure rod or a punch pin) into the through-hole during welding, therefore, the inner diameter of the through-hole formed by winding the isolation film 13 does not need to consider the size of the thimble. Furthermore, the outer diameter of the cylindrical structure formed by winding the isolation film 13 (such as Figure 1 the D shown) can be designed to be smaller to improve the energy density of the battery cell 1.

[0067] Taking the method of supporting the tab for welding by a thimble in the prior art as an example, limited by the size of the thimble (mainly the radial size), in order to make the through-hole formed by winding the isolation film 13 accommodate the thimble to penetrate, enough inner diameter needs to be reserved. Therefore, the outer diameter of the cylindrical structure formed by winding the isolation film 13 is also correspondingly limited. And for the cylindrical structure in the embodiment as Figure 1 shown, since it is not limited by the size of the thimble, therefore, its outer diameter can be correspondingly reduced.

[0068] Assume that the first outer diameter of the cylindrical structure formed in the middle of the battery cell 1 using the prior art is configured as 2.3 mm, that is, D1 = 2.3 mm; and the second outer diameter of the cylindrical structure using the above embodiment is reduced to 1.2 mm, that is, D2 = 1.2 mm. Then, the difference N in the occupancy rate of the two for the central space of the battery cell 1 (that is, the space formed by the outer diameter of the cylindrical structure formed by winding the isolation film 13) can be calculated by the following formula 1.

[0069] Formula 1

[0070] In Formula 1, N represents the difference in the occupancy rate of the central space between the battery cell of the present application and that of the prior art, D1 represents the first outer diameter (the outer diameter of the cylindrical structure in the prior art), D2 represents the second outer diameter (the outer diameter of the cylindrical structure of the present application), and H represents the height of the battery cell.

[0071] Through the calculation of Formula 1, it can be seen that the utilization rate of the central space of the battery cell using the above-mentioned embodiment is increased by 72.78% compared with the prior art. Therefore, the cylindrical structure using the above-mentioned embodiment occupies a smaller volume of the central space of the battery cell. The total volume of the battery cell is limited by the internal space of the housing of the battery module and can be regarded as constant. Since the cylindrical structure occupies a smaller volume, more active materials can be configured in the battery cell to improve the energy density of the battery cell.

[0072] According to the embodiments of the present disclosure, N layers of separator films 13 are provided in the innermost layer of the battery cell, where 8 ≥ N ≥ 5. That is, the cylindrical structure with three layers of separator films can be formed by winding the third winding starting section 133 of the single-layer separator film 13 around the winding center (such as Figure 1 the O shown) three times.

[0073] In some exemplary embodiments, the cylindrical structure includes, but is not limited to, having at least five layers of separator films (i.e., N = 5). It should be understood that the embodiments of the present disclosure are not limited thereto.

[0074] For example, the cylindrical structure may include 1 layer, 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers, and any other number of layers of separator films.

[0075] In some exemplary embodiments, as Figure 1 shown, it includes a first separator film 131 and a second separator film 132. The first electrode sheet 11, the first separator film 131, the second electrode sheet 12, and the second separator film 132 are sequentially stacked in the thickness direction of the battery cell. Specifically, one end of the first electrode sheet 11 close to the winding center is used as the first winding starting section 111, one end of the second electrode 12 close to the winding center is used as the second winding starting section 121, and one end of the first separator film 131 and the second separator film 132 close to the winding center is used as the third winding starting section 133. Among them, the third winding starting section 133 of the first separator film 131 and the second separator film 132 is located upstream of the first winding starting section 111 of the first electrode sheet 11 and the second winding starting section 121 of the second electrode sheet 12, that is, the third winding starting end 133 is closer to the winding center than the first winding starting section 111 and the second winding starting section 121.

[0076] In some exemplary embodiments, the third winding starting segment 133 of the first separator 131 and the third winding starting segment 133 of the second separator 132 may be configured to be offset along the length direction of the battery cell 1. Further, the cylindrical structure is formed only by winding the longer first separator 131. Wherein, the number of layers of the separator forming the cylindrical structure by winding the first separator 131 may be either an even number or an odd number.

[0077] In some other exemplary embodiments, the third winding starting segment 133 of the first separator 131 and the third winding starting segment 133 of the second separator 132 may be configured to be substantially aligned along the length direction of the battery cell 1. Further, the cylindrical structure is formed by co-winding the stacked first separator 131 and second separator 132. Wherein, the number of layers of the separator forming the cylindrical structure by co-winding the stacked first separator 131 and second separator 132 is an even number.

[0078] In some other exemplary embodiments, the third winding starting segment 133 of the first separator 131 and the third winding starting segment 133 of the second separator 132 may be configured to be offset along the length direction of the battery cell 1, and the offset distance is approximately one winding period. Wherein, the first separator 131 is wound before the second separator 132. After the portion where the first separator 131 and the second separator 132 are stacked is wound, they are co-wound to form a cylindrical structure, so that the number of layers of the separator of the cylindrical structure is an odd number. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0079] For example, the above-mentioned first separator 131 and second separator 132 may be two parts of the same separator. Specifically, the separator 13 includes a first part and a second part arranged in sequence along the length direction of the battery cell 1. The first part and the second part are folded in half along the thickness direction of the battery cell 1 to form a double-layer separator, that is, the winding end of the first part is connected to the winding end of the second part.

[0080] In such an embodiment, the number of layers of the separator of the cylindrical structure can be configured according to the structural strength required to provide effective support for the tab. If the number of layers of the separator structure is too large, it is easy to cause a large outer diameter of the cylindrical structure. If the number of layers of the separator is too small, it is difficult to maintain the structural strength of the cylindrical structure. Therefore, the number of layers of the separator should be set as small as possible while meeting the requirements for supporting the tab.

[0081] According to the embodiment of the present disclosure, as Figure 1 shown, the thickness of the cylindrical structure (i.e., as Figure 1 shown X) is configured to be greater than or equal to 0.06 mm and less than or equal to 0.5 mm. That is, 0.5mm ≥ X ≥ 0.06mm.

[0082] According to the embodiment of the present disclosure, as Figure 1As shown, the thickness of the cylindrical structure is further configured to be greater than or equal to 0.1 mm and less than or equal to 0.2 mm. That is, 0.2 mm ≥ X ≥ 0.1 mm.

[0083] In some exemplary embodiments, the thickness of the cylindrical structure includes, but is not limited to, being configured to be from 0.1 mm to 0.2 mm. That is, 0.2 mm ≥ X ≥ 0.1 mm. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0084] For example, the thickness of the cylindrical structure can be configured to be 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, and any value of other thicknesses.

[0085] In such an embodiment, the cylindrical structure formed by winding the separator 13 is suitable for making the axial end of the cylindrical structure abut against the tab when welding the housing and / or the lid to the tab. For this purpose, the thimble can be replaced to support the tab so that the tab is tightly pressed against the housing or the lid and welded.

[0086] According to an embodiment of the present disclosure, the thickness of the separator 13 is less than or equal to 11 μm.

[0087] In some exemplary embodiments, the thickness of the separator 13 includes, but is not limited to, being configured to be greater than or equal to 5 μm and less than or equal to 11 μm. That is, 11 μm ≥ δ ≥ 5 μm. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0088] For example, the thickness of the separator 13 includes, but is not limited to, being configured to be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, and any other arbitrary thickness value.

[0089] Limiting the thickness of the separator 13 to 11 μm ≥ δ ≥ 5 μm takes into account both safety performance and lithium-ion transmission performance. On the other hand, if the thickness of the separator 13 is too large, it is not easy to control the thickness of the cylindrical structure.

[0090] According to an embodiment of the present disclosure, the separator 13 includes a base material. Alternatively, the separator 13 includes a base material and a coating attached to at least one surface of the base material.

[0091] According to an embodiment of the present disclosure, the separator 13 includes one of a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator.

[0092] According to an embodiment of the present disclosure, the coating includes at least one of a ceramic coating, a nano - coating, and a silicone coating.

[0093] In a schematic embodiment, the separator 13 includes a substrate. Specifically, the substrate includes, but is not limited to, polyethylene (PE), polypropylene (PP), composite materials (such as a three - layer composite diaphragm of PE / PP / PE), and any other membrane material suitable for separating the first electrode and the second electrode.

[0094] In some other schematic embodiments, in addition to the substrate, the separator 13 may also have a coating on at least one surface (i.e., one surface or both surfaces) of the substrate. Specifically, the coating includes, but is not limited to, at least one of a ceramic coating, a nano - coating, and a silicone coating. That is to say, the coating can be a composite coating formed by any two of the above coatings. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0095] The above - mentioned coating can further increase the mechanical strength of the separator 13, so that the strength of the cylindrical structure is higher.

[0096] For example, the coating can also be a conductive coating, a flame - retardant coating, a functional coating (such as an ion - transport promoter, an electrolyte adsorbent, etc.), and any other coating suitable for improving the mechanical properties, thermal stability, and ionic conductivity of the separator 13.

[0097] In such an embodiment, when the material of the separator 13 is constant, it can be considered that the thicker the separator 13, or the more layers of the wound separator, the stronger the structural strength of the wound cylindrical structure. However, the thicker the separator 13, or the more layers of the wound separator, the larger the outer diameter of the formed cylindrical structure. Therefore, an overall design should be carried out for the thickness of the separator 13 and the number of layers of the wound separator. For example, if the separator 13 has a relatively thick thickness, the number of layers of the separator can be reduced; if the separator 13 has a relatively thin thickness, the number of layers of the separator can be increased. Specifically, it should be appropriate to meet the thickness requirements of the cylindrical structure and the structural strength requirements of the cylindrical structure.

[0098] It is a schematic diagram of a cylindrical structure according to a schematic embodiment of the present disclosure.

[0099] According to an embodiment of the present disclosure, as Figure 2 shown, in the projection in the height direction of the battery cell (such as Figure 2 the direction facing the paper surface shown), the projection of the cylindrical structure is configured as a circular ring (such as Figure 2 a shown), an elliptical ring (such as Figure 2 b shown), or a polygonal ring (such as Figure 2 the triangular ring of c shown).

[0100] In such an embodiment, as Figure 2 shown, during the process of forming the winding part 1331 of the separator 13 by the winding needle, or by a shaping device (such as an extrusion forming device), the winding part 1331 can be wound to form at least one of a circular cylindrical structure, an elliptical cylindrical structure, and a polygonal cylindrical structure. Among them, the cylindrical structure configured with a circular ring cross-section, an elliptical ring, and a permeable ring cross-section is beneficial to forming a structure that occupies less space in the middle of the battery cell; the cylindrical structure configured with a polygonal ring is also beneficial to preventing the separator from deforming under stress. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0101] For example, in the projection in the height direction of the battery cell, the projection of the cylindrical structure can also be a racetrack-shaped ring, a quadrilateral ring, a pentagon ring, a horseshoe-shaped ring, or other irregular ring structures.

[0102] Figure 2 Yes Figure 3 is the exploded view of the parts of the battery cell shown.

[0103] According to an embodiment of the present disclosure, the first electrode tab 11 has a first current collector and a first active material layer provided on the surface of the first current collector. The second electrode tab 12 has a second current collector and a first active material layer provided on the surface of the second current collector. As Figure 1 shown, the battery cell further includes at least one first tab 14 and at least one second tab 15. The first tab 14 is electrically connected to the first current collector, and the second tab 15 is electrically connected to the second current collector. In the height direction of the battery cell 1, the first tab 14 abuts against one end of the cylindrical structure (such as Figure 3 the upper end shown); and / or, the second tab 15 abuts against the other end of the cylindrical structure (such as Figure 3 the lower end shown).

[0104] In some illustrative embodiments, the first electrode tab 11 can be a negative electrode tab, and the second electrode tab 12 can be a positive electrode tab. In the length direction of the battery cell, the second winding start segment 121 of the second electrode tab 12 (i.e., the negative electrode tab) can be arranged downstream of the first winding start segment 111 of the first electrode tab 11 (i.e., the positive electrode tab). Specifically, the distance between the second winding start segment 121 and the first winding start segment 111 includes but is not limited to being configured to be greater than or equal to half a winding period and less than or equal to one winding period. In this way, it is beneficial to avoid lithium plating and also beneficial to avoid waste of negative electrode material caused by an overly long negative electrode tab.

[0105] In a schematic embodiment, the first current collector of the first electrode tab 11 (i.e., the positive electrode tab) includes, but is not limited to, aluminum foil, and the first active material layer disposed on the first current collector includes, but is not limited to, lithium transition metal oxides, such as lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium iron phosphate oxide, and lithium nickel cobalt aluminum oxide, etc. Further, the second current collector of the second electrode tab 12 (i.e., the negative electrode tab) includes, but is not limited to, copper foil, and the second active material layer disposed on the second current collector includes, but is not limited to, graphite. Of course, silicon-based materials and lithium metal can also be used.

[0106] In a schematic embodiment, as Figure 3 shown, in the height direction of the battery cell (such as Figure 3 the up and down direction shown), the first tab 14 abuts against one end of the cylindrical structure (such as Figure 3 the upper end shown); and / or, the second tab 15 abuts against the other end of the cylindrical structure (such as Figure 3 the lower end shown).

[0107] In some schematic implementations, as Figure 3 shown, one end of the first tab 14 (such as Figure 3 the lower end shown) is configured to extend into the electrode assembly and be welded to the first current collector. Among them, the first tab 14 includes, but is not limited to, the part of the first current collector welded upstream of the first active material layer, or the part of the first current collector welded in the middle of the first active material layer and exposed to the first active material layer (such as a groove structure is provided in the first active material layer to expose the first current collector at the bottom of the groove). Similarly, one end of the second tab 15 (such as Figure 3 the upper end shown) is configured to extend into the electrode assembly and be welded to the second current collector. Of course, the first electrode tab 11 can also be used as the positive electrode tab, and correspondingly, the second electrode tab 12 can also be the negative electrode tab. It should be understood that the embodiments of the present disclosure are not limited thereto.

[0108] For example, the battery cell can be configured with multiple first tabs 14 and / or multiple second tabs 15, which is beneficial to improving the current collection effect.

[0109] In some schematic embodiments, the height of the cylindrical structure protruding from the abutting part of the first electrode tab 11 and the second electrode tab 12 is configured to be less than or equal to 0.6 mm and greater than 0.3 mm, and the other part of the separator 13 outside the cylindrical structure is configured to protrude from the first electrode tab 11 and the second electrode tab 12 by a height of less than or equal to 0.3 mm. That is, the cylindrical structure is higher than the other part of the separator 13, and this height difference can be formed by heat stamping with devices such as a heat stamping machine.

[0110] In such an embodiment, the cylindrical structure is configured to be slightly higher than other parts in order to make it closely abut against the tab during welding, thereby restricting the welding position of the tab. During the welding process, due to the reaction force exerted by the tab, therefore, a part of the cylindrical structure may be compressed and deformed in the direction close to the battery cell 1, and further reduce the height difference between the cylindrical structure and other parts of the separator 13, or even make them substantially flush.

[0111] On this basis, the present disclosure has carried out corresponding comparative experiments on the cylindrical structure with an abutting portion, and given a comparative experiment table of the cylindrical structure parameters based on the comparative experiments, as shown in Table 1 below:

[0112]

[0113] Note: The cylindrical structure with through holes formed by winding the separator, wherein the pressing portion pressing against the inner wall of the through hole and the connected extension portion are called the support structure.

[0114] Referring to Table 1 above, by comparing Comparative Example 1-1 with Example 1-4, and Comparative Example 1-2 with Example 1-3, it can be seen that setting the above support structure can reduce the welding defect rate.

[0115] It can be seen from Example 1-1 to Example 1-8 that when the thickness of the cylindrical structure is constant, the larger the aperture of the cylindrical structure, the larger the occupied space, and the smaller the energy density of the battery. However, the higher the breakage rate of the winding needle when the cylindrical structure is smaller.

[0116] It can be seen from Example 2-1 to Example 2-6 that the thickness of the cylindrical structure will also affect the welding defect rate. Within the protection scope of the present disclosure, the energy density and welding defect rate of the battery cell are reasonably controlled.

[0117] Figure 3 It is an exploded view of the parts of a battery cell according to a schematic embodiment of the present disclosure.

[0118] The present disclosure also provides a battery cell, as Figure 4 shown, including a battery cell 1, a housing 3 and a housing cover 2. The housing 3 has an opening, and an accommodation cavity is defined within the opening, and the battery cell 1 is disposed within the accommodation cavity. The housing cover 2 is disposed at the opening to close the accommodation cavity. Among them, one of the housing 3 and the housing cover 2 is welded to the first tab of the battery cell and forms an electrical connection, and the other of the housing 3 and the housing cover 2 is welded to the second tab of the battery cell and forms an electrical connection. Among them, the housing 3 is provided with a through liquid injection port to add electrolyte, such as lithium salt like lithium hexafluorophosphate, into the housing; a liquid injection plug 31 is disposed within the liquid injection port to close the liquid injection port after the electrolyte is filled.

[0119] In some schematic embodiments, such as Figure 4 and Figure 3As shown, the end portions of the first tab 14 and / or the second tab 15 extending from the electrode assembly are configured to be bent toward the electrode assembly. Specifically, the end portions of the first tab 14 and the second tab 15 extending from the electrode assembly closely abut against one axial end and the other axial end of the cylindrical structure and cover the cylindrical structure.

[0120] In such an embodiment, when welding the tab (i.e., the first tab 14 or the second tab 15) to the housing 3 or the housing cover 2, since the cylindrical structure plays a role in supporting and pressing the tab, therefore, the thimble used in the prior art can be replaced so that the tab is closely abutted against the housing 3 or the housing cover 2 for welding. The through-hole formed by winding the separator 13 in the middle of the battery cell is no longer limited by the size of the thimble, and the space in the middle of the battery cell occupied by the cylindrical structure is reduced. Therefore, more active materials can be arranged in the battery cell to form a battery cell with a higher energy density.

[0121] Other technical features of the battery cell have been described in detail in the above embodiments related to the battery cell, and the battery cell has technical effects similar to those of the battery cell. Therefore, it will not be elaborated here.

[0122] Figure 4 It is a flowchart of a method for manufacturing a battery cell according to an exemplary embodiment of the present disclosure.

[0123] The present disclosure also provides a method for manufacturing a battery cell, which is applicable to manufacturing a battery cell as described in the above embodiments, including:

[0124] Step S110: Clamp the first electrode sheet 11 and the separator 13 by a winding needle. In the length direction of the electrode sheet, the third winding starting section of the separator 13 extends from the first winding starting section of the first electrode sheet 11;

[0125] Step S120: Feed the second electrode sheet 12;

[0126] Step S130: Wind the first electrode sheet 11 and the separator 13 so that the third winding starting section is wound to form a cylindrical structure with a through-hole. The extending portion 1332 of the separator 13 located in the through-hole extends from one side of the inner wall of the through-hole to the other side facing it. The pressing portion 1333 of the separator 13 presses against the inner wall of the through-hole and bends toward one side along the inner wall of the through-hole. Along the winding direction, the second winding starting section of the second electrode sheet 12 extends beyond the first winding starting section to form an electrode assembly;

[0127] Step S140: Weld the electrode assembly to the first tab 14 and the second tab 15 to form the battery cell 1.

[0128] In such an embodiment, in the process of welding the tab (i.e., the first tab 14 and / or the second tab 15) to the housing and / or the lid of the battery cell, there is no need to insert and extract the ejector pin. Therefore, the manufacturing process of the battery cell is simplified.

[0129] According to an embodiment of the present disclosure, the method for manufacturing a battery cell further includes:

[0130] In step S160, the wound separator film protrudes from the first electrode sheet in the width direction of the first electrode sheet, and the part of the separator film protruding from the first electrode sheet outside the cylindrical structure is thermally treated.

[0131] According to an embodiment of the present disclosure, in step S130, winding the third winding starting section to form a multi-layer cylindrical structure includes: winding the third winding starting section to form a cylindrical structure having a three-layer to eight-layer separator film 13 structure.

[0132] According to an embodiment of the present disclosure, in step S130, winding the third winding starting section to form a multi-layer cylindrical structure includes: winding the third winding starting section to form a cylindrical structure with a thickness of at least 0.06 mm and less than or equal to 0.5 mm.

[0133] According to an embodiment of the present disclosure, the method for manufacturing a battery cell further includes:

[0134] Step S150: Remove the winding needle and hot-press the electrode assembly so that the cross-section of the electrode assembly in the first plane is substantially circular, and the first plane is perpendicular to the winding axis of the electrode assembly.

[0135] Among them, the cross-section of the electrode assembly in the first plane being substantially circular can be understood as that, visually, the above cross-section of the electrode assembly substantially presents a continuous and relatively uniform curve, and there are no obvious corners or protruding parts, so that the observer believes that it is basically a circle.

[0136] In such an embodiment, through step S150, when the winding needle winds the third winding starting section, the external winding needle can be wound along the winding direction in cooperation with the extension part 1332. During winding, the pressing part 1333 and the extension part 1332 form a complete winding cycle, and the winding part 1331 winds layer by layer around the winding center in a winding cycle to form a cylindrical structure having a multi-layer separator film 13 structure.

[0137] According to an embodiment of the present disclosure, step S140 of welding the electrode assembly to the first tab 14 and the second tab 15 includes:

[0138] Step S141: Weld one end of the first tab 14 to the first current collector of the first electrode sheet to form an electrical connection; and

[0139] Step S142 : welding one end of the second electrode tab 15 to the second current collector of the second electrode sheet 12 to form an electrical connection.

[0140] Figure 5 Figure 6 is a flow chart of a method for preparing a battery cell according to an exemplary embodiment of the present disclosure.

[0141] The present disclosure also provides a method for preparing a battery cell, which is suitable for preparing the battery cell according to the above embodiment, comprising:

[0142] Step S210: placing the battery cell in the receiving cavity formed by the shell;

[0143] Step S220: making the cylindrical structure formed by the battery cell abut against the end surface of the second tab of the battery cell facing away from the housing, and welding the second tab to the housing;

[0144] Step S230: Assembling the shell cover to the opening of the shell to close the accommodating cavity;

[0145] Step S240: welding the first tab of the battery cell to the shell cover.

[0146] In such an embodiment, the isolation membrane of the battery cell is wound to form a cylindrical structure. When the battery cell is welded to the shell and / or shell cover, the cylindrical structure can be used to abut the pole ear to replace the ejector pin, which is conducive to simplifying the welding process. Moreover, since there is no need to configure an ejector pin during welding, the outer diameter of the corresponding cylindrical structure can also be wound smaller, thereby reducing the space occupied by the cylindrical structure in the middle of the battery cell, thereby improving the energy density of the battery cell having the battery cell.

[0147] It should also be noted that directional terms such as "upper," "lower," "front," "back," "left," and "right" mentioned in the embodiments are merely references to the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Conventional structures or configurations will be omitted where they may cause confusion in understanding the present disclosure.

[0148] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A battery cell, characterized in that, Comprising: A first electrode tab and a second electrode tab; A separator disposed between the first electrode tab and the second electrode tab to isolate the first electrode tab and the second electrode tab, and form a winding structure with the first electrode tab and the second electrode tab; Along the winding direction of the battery cell, N layers of separators are provided on the innermost layer of the battery cell, N≥2, and the N layers of separators are wound to form a cylindrical structure with a through hole inside. The end of the separator located inside the through hole has a connected extension portion and a pressing portion; Wherein, and viewed along the axial direction of the through hole, the extension portion divides the through hole into at least two parts; the pressing portion presses against the inner wall of the through hole.

2. The battery cell according to claim 1, characterized in that, The extension portion and the pressing portion are respectively formed by at least one layer of separator.

3. The battery cell according to claim 1, characterized in that Viewed along the axial direction of the through hole, the extension portion is arranged in an S shape.

4. The battery cell according to claim 1, characterized in that, The diameter of the through hole is configured to be greater than or equal to 0.6 mm and less than or equal to 2.3 mm.

5. The battery cell according to claim 4, wherein The diameter of the through hole is less than 2.0 mm.

6. The battery cell according to claim 1, characterized in that 8≥N≥5。 7. The battery cell according to claim 1, wherein The thickness of the cylindrical structure is configured to be greater than or equal to 0.06 mm and less than or equal to 0.5 mm.

8. The battery cell according to claim 7, characterized in that, The thickness of the cylindrical structure is configured to be greater than or equal to 0.1 mm and less than or equal to 0.2 mm.

9. The battery cell according to claim 1, wherein, The thickness of the separator is configured to be less than or equal to 11 μm.

10. The battery cell according to claim 1, wherein The separator includes a substrate and a coating attached to at least one surface of the substrate; The substrate includes one of polyethylene, polypropylene, and polyvinylidene fluoride; The coating includes at least one of a ceramic coating, a nano - coating, and a silicone coating.

11. The battery cell according to claim 1, characterized in that, The first electrode tab has a first current collector and a first active material layer provided on the surface of the first current collector; The second electrode tab has a second current collector and a first active material layer provided on the surface of the second current collector; The battery cell further includes at least one first electrode tab and at least one second electrode tab. The first electrode tab is electrically connected to the first current collector, and the second electrode tab is electrically connected to the second current collector. In the height direction of the battery cell, the first electrode tab abuts against one end of the cylindrical structure; And / or, the second electrode tab abuts against the other end of the cylindrical structure.

12. The battery cell according to claim 1, wherein, Taking the bottom surface of the battery cell as the projection plane, in the projection along the height direction of the battery cell, the projection of the cylindrical structure is configured to be one of a circular ring, an elliptical ring, and a polygonal ring.

13. A battery cell, characterized in that, Comprising: A battery cell as described in any one of claims 1 to 12; A housing having an opening, and a receiving cavity is defined inside the opening, and the battery cell is disposed inside the receiving cavity; A cover disposed at the opening to close the receiving cavity; Wherein, one of the housing and the cover is welded to the first electrode tab of the battery cell and forms an electrical connection, and the other of the housing and the cover is welded to the second electrode tab of the battery cell and forms an electrical connection.

14. A method for preparing an electric core, characterized in that, Comprising: Clamping the first electrode tab and the separator with a winding needle. In the length direction of the first electrode tab, the third winding starting section of the separator extends out from the first winding starting section of the first electrode tab; Feeding the second electrode tab; Wind the first pole piece and the separator film so that the third winding starting section is wound to form a cylindrical structure with a through hole inside. The extending portion of the separator film located inside the through hole extends from one side of the inner wall of the through hole to the opposite side. The pressing portion of the separator film presses against the inner wall of the through hole and bends along the inner wall of the through hole to one side. Along the winding direction, the second winding starting section of the second pole piece extends beyond the first winding starting section to form an electrode assembly. Weld the electrode assembly to the first pole tab and the second pole tab to form an electric core.

15. The method according to claim 14, wherein It further includes: The wound separator film protrudes from the first pole piece in the width direction of the first pole piece. Thermally iron the part of the separator film protruding from the first pole piece outside the cylindrical structure.

16. The method according to claim 14, wherein The step of winding the third winding starting section to form a cylindrical structure with a through hole includes: Winding the third winding starting section to form a cylindrical structure with at least two layers of separator film.

17. The method according to claim 16, wherein The step of winding the third winding starting section to form a multi-layer cylindrical structure includes: Winding the third winding starting section to form a cylindrical structure with a thickness of at least 0.06 mm and less than or equal to 0.5 mm.

18. The method according to any one of claims 15 to 17, characterized in that, It further includes: Remove the winding needle and hot press the electrode assembly so that the cross-section of the electrode assembly along the first plane is substantially circular, and the first plane is perpendicular to the winding axis of the electrode assembly.

19. The method according to claim 18, wherein The step of welding the electrode assembly to the first pole tab and the second pole tab includes: Weld one end of the first pole tab to the first current collector of the first pole piece to form an electrical connection; weld one end of the second pole tab to the second current collector of the second pole piece to form an electrical connection.

20. A method for preparing a battery cell as described in claim 13, characterized in that, It includes: Place the electric core in the accommodation cavity formed by the housing. Make the cylindrical structure formed by the electric core abut against the end face of the second pole tab of the electric core facing away from the housing, and weld the second pole tab to the housing. Assemble the housing cover to the opening of the housing to close the accommodation cavity. Weld the first pole tab of the electric core to the housing cover.

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