Battery cell, separator and preparation method therefor, battery, and electric device

Abstract

A battery cell, a separator and a preparation method therefor, a battery, and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet, the negative electrode sheet, and the separator are wound to form a wound structure, the wound structure comprising corner regions at two ends and a flat region connecting the corner regions. The separator comprises a substrate and an adhesive layer, the adhesive layer being disposed on at least one surface of the substrate. The adhesive layer comprises a plurality of dot-shaped protrusions disposed at predetermined intervals, wherein the height of the dot-shaped protrusions in the corner regions ranges from 5 μm to 35 μm, and the center-to-center spacing between two adjacent dot-shaped protrusions ranges from 360 μm to 650 μm. The expansion space in the corner regions of the wound battery cell is increased, thereby improving the cycle performance of the battery cell.

Description

Battery cells, separators and their preparation methods, batteries, and electrical devices Cross-reference of related applications

[0001] This patent document claims priority and benefit to Chinese Patent Application No. 202510205640.4, filed on February 24, 2025, entitled "Separator Membrane, Secondary Battery Cell and Electrical Device". The entire contents of the aforementioned patent application are incorporated herein by reference as a part of the disclosure of this patent document. Technical Field

[0002] This application relates to the field of batteries, and more specifically, to a battery cell, a separator and its preparation method, a battery, and an electrical device. Background Technology

[0003] The new energy industry is attracting increasing attention. Within this industry, battery technology is a crucial factor in its development.

[0004] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, capacity, and reliability. Improving the capacity of individual battery cells has always been a key focus of research in the battery field. However, as battery capacity increases, the expansion space in the corner areas of wound battery cells needs to be increased accordingly to improve cycle performance. Therefore, improving the expansion space in the corner areas of wound battery cells to enhance their cycle performance is a pressing issue that needs to be addressed. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell that increases the expansion space in the corner area of ​​the wound battery cell and improves the cycle performance of the battery cell.

[0006] To achieve the above objectives, this application provides a battery cell, a separator, a method for preparing the same, a battery, and an electrical device.

[0007] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, a negative electrode sheet, and a separator; the positive electrode sheet, the negative electrode sheet, and the separator are wound to form a wound structure, the wound structure including corner regions at both ends and a planar region connecting the corner regions; the separator includes a substrate and an adhesive layer, the adhesive layer being disposed on at least one surface of the substrate, the adhesive layer including a plurality of dot-shaped protrusions arranged at predetermined intervals, wherein the height of the dot-shaped protrusions in the corner regions is 5 μm to 35 μm; the center-to-center distance between two adjacent dot-shaped protrusions is 350 μm to 650 μm.

[0008] In this embodiment, by setting multiple dot-shaped protrusions at predetermined intervals in the separator adhesive layer, wherein the dot-shaped protrusions are evenly distributed and have relatively uniform heights, the consistency of the adhesive layer thickness is improved, and the contact between the electrode and the separator is more uniform and tighter, reducing local stress concentration during cycling and improving cycle stability. Furthermore, when the height of the dot-shaped protrusions in the corner area is greater than or equal to 5 μm, a larger gap can be formed between the separator and the electrode, providing more space for electrode expansion during cyclic charging and discharging, buffering the cyclic expansion force of the battery cell, and improving the wetting of the electrode assembly by the electrolyte. When the height of the dot-shaped protrusions in the corner area is less than or equal to 35 μm, the ionic conductivity of the separator can be taken into account, so that the gap formed between the dot-shaped protrusions and the electrode is not too large, and the transport path of ions between the positive and negative electrodes is as short as possible, thus better balancing the cycle life and kinetic performance of the battery cell. Furthermore, when the center distance between two adjacent dot-shaped protrusions is greater than or equal to 350 μm, it is beneficial to improve the air permeability of the separator. At the same time, keeping the center distance between two adjacent dot-shaped protrusions less than or equal to 650 μm can increase the expansion space in the corner area and improve cycle performance.

[0009] In one possible implementation, the height of the dot-like protrusions in the corner area is 8μm to 30μm.

[0010] In this embodiment, when the height of the dot-shaped protrusions in the corner area is greater than or equal to 8 μm, the adhesive layer formed by the dot-shaped protrusions can be more tightly bonded to the electrode, and the expansion space in the corner area is increased, thus improving the cycle performance. When the height of the dot-shaped protrusions in the corner area is less than or equal to 30 μm, excessive use of adhesive material can be avoided, which would increase the cost. At the same time, sufficient expansion space in the corner area can be provided while taking into account ion transport efficiency, further improving the cycle performance.

[0011] In one possible implementation, the planar region includes a first region and a second region disposed adjacent to each other along the width direction of the separator. The first region is the projection region of the positive electrode sheet in the separator along a direction perpendicular to the separator. The height of the dot-shaped protrusions in the first region is 0.5 μm to 2 μm. The height of the dot-shaped protrusions in the second region is 8 μm to 40 μm.

[0012] In this embodiment, the height of the dot-shaped protrusions in the first region of the planar area is within the above-mentioned range. This can provide ample corner space without significantly thickening the planar area of ​​the electrode assembly, maintaining a high group margin, which is beneficial to improving the energy density of the battery cell.

[0013] In one possible implementation, the center-to-center distance between two adjacent point protrusions is 480 μm to 580 μm.

[0014] In this embodiment of the application, by controlling the center-to-center distance between two adjacent dot-shaped protrusions within the above-mentioned range, the adhesion between the separator and the electrode and the ion transport capability of the separator can be better balanced.

[0015] In one possible implementation, the diameter of the dot-shaped protrusion is 210 μm to 310 μm, and optionally, the diameter of the dot-shaped protrusion is 240 μm to 280 μm.

[0016] In this embodiment, when the diameter of the dot-shaped protrusions in the corner area is within the above-mentioned range, it can provide more bonding sites to meet the bonding requirements, while also helping to maintain the air permeability of the separator, reduce internal resistance, and improve cycle performance.

[0017] In one possible implementation, the area coverage of the adhesive layer on one side of the substrate is 12% to 28%, and optionally, the area coverage is 16% to 23%.

[0018] In the embodiments of this application, the coverage of the adhesive layer is within the above range, which can provide high adhesion while taking into account the air permeability of the separator, improving ion transport efficiency and enhancing cycle performance.

[0019] In one possible implementation, the dot-like protrusions include organic particles, which include at least one of non-fluorinated organic particles and fluorinated organic particles.

[0020] In one possible implementation, the non-fluorinated organic particles satisfy one or more of the following conditions: the non-fluorinated organic particles have a first glass transition temperature Tg1 and a second glass transition temperature Tg2, and 100°C > Tg1 > Tg2; optionally, Tg1 is 26°C to 54°C, and / or Tg2 is 0°C to 25°C; the non-fluorinated organic particles include at least two types of monomer units selected from acrylate monomer units, acrylic monomer units, vinyl monomer units, unsaturated nitrile monomer units, and amide monomer units; the non-fluorinated organic particles include a first polymer and a second polymer, wherein the first polymer and / or the second polymer includes one or more of copolymers containing acrylate monomer units, copolymers containing acrylic monomer units, and copolymers containing vinyl monomer units; optionally, the first polymer and / or the second polymer includes at least one of carboxyl groups, amide groups, and cyano groups.

[0021] In this embodiment, during cold pressing, non-fluorinated organic particles with relatively low glass transition temperatures can enhance the adhesion of the adhesive layer to the positive and negative electrodes. As the battery charges and discharges and the temperature rises, the adhesion of non-fluorinated organic particles with high glass transition temperatures to the positive and negative electrodes increases, thereby effectively controlling the shrinkage of the separator during thermal runaway, maintaining a stable structure, and achieving the function of isolating the positive and negative electrodes. When the non-fluorinated organic particles include the types described above, the adhesion requirements can be met, and the aforementioned non-fluorinated organic particles also have high electrochemical stability, resisting the corrosion of the adhesive layer by the electrolyte.

[0022] In one possible implementation, the dot-like protrusions comprise fluorinated organic particles that satisfy one or more of the following conditions: the melting point temperature of the polymer comprised in the fluorinated organic particles is 139°C to 154°C; the number average molecular weight of the polymer comprised in the fluorinated organic particles is 400,000 to 650,000; the fluorinated organic particles comprise a fluorinated polymer, wherein the fluorinated polymer comprises polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorinated alkenyl monomer units, copolymers of fluorinated alkenyl monomer units and vinyl monomer units, copolymers of fluorinated alkenyl monomer units and acrylic monomer units, copolymers of fluorinated alkenyl monomer units and acrylate monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0023] In one possible implementation, the volume average particle size Dv50 of the organic particles is 5 μm to 25 μm.

[0024] In the embodiments of this application, when the volume average particle size Dv50 of the organic particles is greater than or equal to 5 μm, the height requirement of the dot-shaped protrusions can be met, the expansion space in the corner area can be increased, and the cycle performance can be improved; when the volume average particle size Dv50 of the organic particles is less than or equal to 25 μm, the risk of separator blockage can be reduced, which is beneficial to improving the capacity utilization and cycle life of the battery cells.

[0025] In one possible implementation, the volume average particle size Dv50 of the organic particles is 7 μm to 20 μm.

[0026] In the embodiments of this application, when the volume average particle size Dv50 of the organic particles is greater than or equal to 7 μm, it helps to form dot-like protrusions with a frustum shape, increasing the number of bonding sites and thus improving the bonding force; when the volume average particle size Dv50 of the organic particles is less than or equal to 20 μm, it can further reduce the risk of separator blockage, improve the air permeability of the separator, and help improve the cycle performance of the battery cell.

[0027] In one possible implementation, the dot-like protrusion includes a platform area and an edge area surrounding the platform area, wherein the minimum height of the platform area is not less than the maximum height of the edge area.

[0028] In this embodiment, the dot-shaped protrusions have a frustum shape, and the organic particles are medium-sized particles that are randomly distributed within the dot-shaped protrusions, increasing the number of bonding sites and improving the bonding force.

[0029] In one possible implementation, the adhesive layer further includes invalid protrusions with a height of less than 100 μm; the ratio of the number of invalid protrusions to the number of dot-like protrusions is less than or equal to 5:95.

[0030] In this embodiment, the ratio of invalid protrusions to dot-like protrusions in the adhesive layer is within the above-mentioned range, indicating that there are fewer invalid protrusions and the adhesive layer is mostly composed of uniformly distributed and highly consistent dot-like protrusions. This reduces the risk of invalid protrusions clogging the separator, improves the air permeability of the separator, improves ion transport efficiency, and enhances the cycle performance of the battery cell.

[0031] In one possible implementation, the positive electrode sheet includes a positive active material, and the negative electrode sheet includes a negative active material; the positive active material is a lithium phosphate, and the compaction density of the positive electrode sheet is 2.6 g / cm³. 3 ~2.8g / cm 3 Alternatively, the positive electrode active material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 ; and / or, the negative electrode active material includes silicon-based materials.

[0032] In the embodiments of this application, when a battery cell meets one or more of the above conditions, the volume change of the electrode in the high expansion system battery cell is more significant, and the expansion space requirement in the corner area is high. When the height of the dotted protrusion is increased, a larger gap can be formed between the separator and the electrode, which provides more space for the electrode expansion during the cyclic charging and discharging process, buffers the cyclic expansion force of the battery cell, and improves the cycle performance of the battery cell.

[0033] In one possible implementation, the release membrane includes a first adhesive layer and a second adhesive layer respectively disposed on two surfaces of the substrate. The first adhesive layer includes a plurality of first dot-shaped protrusions disposed at a first predetermined interval, and the second adhesive layer includes a plurality of second dot-shaped protrusions disposed at a second predetermined interval.

[0034] In this embodiment, dotted protrusions are provided on both sides of the separator, which can further improve the adhesion and increase the expansion space in the corner area, thereby improving the cycle performance.

[0035] In one possible implementation, the first dot-shaped protrusion includes a first organic particle, and the second dot-shaped protrusion includes a second organic particle, wherein the first organic particle and the second organic particle are made of different materials.

[0036] In this embodiment, the first dot-shaped protrusion and the second dot-shaped protrusion are made of different materials, and the adhesive layers on both sides can be set to have an adhesive gradient, reducing the risk of self-adhesion of the release film during the winding process.

[0037] In one possible implementation, the first predetermined interval is different from the second predetermined interval.

[0038] In this embodiment, the spacing between adjacent dots of the dotted protrusions in the first adhesive layer and the dotted protrusions in the second adhesive layer is different. On the side with a larger spacing, there are fewer dotted protrusions, resulting in higher air permeability of the separator and improved ion transport efficiency. On the side with a smaller spacing, there are more dotted protrusions, improving the adhesion of the separator. At the same time, the different adhesion on both sides of the separator reduces self-adhesion of the separator and improves processing performance during the unpressurized separator preparation and winding process.

[0039] In one possible implementation, in a direction perpendicular to the separating membrane, the center of the first dot-shaped protrusion in the first adhesive layer coincides with the center of at least a portion of the second dot-shaped protrusion in the second adhesive layer.

[0040] In this embodiment, the overlapping of at least some of the dot-shaped protrusions on both sides can further increase the expansion space in the corner area, while also ensuring the air permeability of the separator while satisfying the adhesion, reducing blockage of the separator and improving the cycle performance of the battery cell.

[0041] In one possible implementation, the first adhesive layer includes a plurality of adjacent first repeating units, each first repeating unit including a plurality of first dot-shaped protrusions, the plurality of first dot-shaped protrusions being arranged at a third predetermined interval in a first direction and at a fourth predetermined interval in a second direction, the third predetermined interval being different from the fourth predetermined interval, and the first direction being perpendicular to the second direction; the second adhesive layer includes a plurality of adjacent second repeating units, each second repeating unit including a plurality of second dot-shaped protrusions, the plurality of second dot-shaped protrusions being arranged at a fourth predetermined interval in a first direction and at a third predetermined interval in a second direction.

[0042] In this embodiment, by setting the dot-shaped protrusions on one side to have the same spacing in the first direction as the dot-shaped protrusions on the other side in the second direction, the effect of constructing repeating units is achieved. The repeating unit includes multiple at least partially overlapping dot-shaped protrusions. In the separator adhesive layer, the repeating units are adjacent to each other. In this way, the dot-shaped protrusions on both sides are not misaligned, which increases the overlap rate of the dot-shaped protrusions on both sides. This avoids the misalignment problem caused by inconsistent thickness during the winding of the multilayer battery module. At the same time, the increased overlap rate can increase the expansion space in the corner area and improve the cycle performance of the battery cell.

[0043] In a second aspect, a separation membrane is provided, comprising a substrate and an adhesive layer, wherein the adhesive layer is disposed on at least one surface of the substrate; the adhesive layer includes a plurality of dot-shaped protrusions disposed at predetermined intervals; the height of the dot-shaped protrusions is 8 μm to 40 μm, optionally, the height of the dot-shaped protrusions is 15 μm to 35 μm; the center-to-center distance between two adjacent dot-shaped protrusions is 360 μm to 650 μm.

[0044] In this embodiment, the adhesive layer is obtained by dot coating. The height of the multiple dot-shaped protrusions on the surface of the separator is within the above-mentioned range, which can provide a suitable space between the electrode and the separator, while providing good adhesion.

[0045] In one possible implementation, the separator membrane satisfies one or more of the following conditions: the diameter of the dot-shaped protrusions is 210 μm to 310 μm, optionally, the diameter of the dot-shaped protrusions is 240 μm to 280 μm; the center-to-center distance between two adjacent dot-shaped protrusions is 480 μm to 580 μm; the dot-shaped protrusions include at least one of non-fluorinated organic particles and fluorinated organic particles; and the adhesive forces of the adhesive layers on both sides of the substrate are different.

[0046] Thirdly, a method for preparing a release liner is provided, comprising applying a slurry to the surface of a substrate by a dotting roller and drying it to form an adhesive layer including a plurality of dot-shaped protrusions to obtain a release liner, wherein the solid content of the slurry is 15% to 22%, and optionally, the solid content of the slurry is 16% to 20%.

[0047] In this embodiment, the adhesive layer slurry is applied to the release membrane by a dotting roller. When the solid content of the slurry is greater than or equal to 15%, the transferability of a single slurry dot can be increased, thus improving the height of the dotted protrusions in a simple and efficient manner. When the solid content of the slurry is less than or equal to 22%, the fluidity of the slurry can be maintained, allowing the slurry to adhere evenly to the surface of the release membrane and form uniformly arranged dotted protrusions.

[0048] In one possible implementation, the dispensing roller includes a dispensing roller with a plurality of raised structures arranged at predetermined intervals along the axial and circumferential directions of the dispensing roller.

[0049] In this embodiment, the dispensing roller applies slurry to the surface of the release liner through the raised structure on its surface. The raised structure is arranged at a predetermined interval, so that dot-shaped protrusions arranged at predetermined intervals can be formed on the surface of the release liner, thereby improving the thickness uniformity of the release liner.

[0050] In one possible implementation, the contact angle between the protruding structural material and the slurry is 65° to 75°; the Shore hardness of the protruding structural material is 70 to 75.

[0051] In the embodiments of this application, when the Shore hardness of the material of the protruding structure is 70 to 75, it is beneficial to the transfer of slurry and helps to form dot-shaped protrusions with consistent morphology. When the contact angle between the protruding structure and the slurry is within the above range, it is beneficial for the protruding structure to adsorb sufficient slurry, and the slurry can be spread out on the protruding structure to be transferred to the surface of the separating membrane, forming higher dot-shaped protrusions.

[0052] In one possible implementation, the protrusion is shaped like a frustum.

[0053] In this embodiment, the raised structure on the surface of the dispensing roller is frustum-shaped. The frustum-shaped raised structure is beneficial to increasing the height of the slurry dispensing and forming higher dot-shaped raised structures.

[0054] In one possible implementation, the dotting roller further includes a gravure roller, the surface of which includes a plurality of protrusions arranged in a honeycomb hexagonal structure along the axial and circumferential directions of the gravure roller.

[0055] In this embodiment, the bumps on the surface of the gravure roller are arranged in a honeycomb hexagonal pattern, which is conducive to the adhesion of more paste, thereby transferring sufficient paste to the dispensing roller and increasing the height of the bumps.

[0056] In one possible implementation, the gravure roller has a line count of 40 lines / inch to 100 lines / inch.

[0057] In one possible implementation, the extrusion depth of the gravure roller toward the dispensing roller is 10μm to 30μm.

[0058] In this embodiment, the state where the gravure roller and the dispensing roller are just in contact but not under force is taken as 0 displacement. When the extrusion depth from the gravure roller to the dispensing roller is greater than or equal to 10 μm, the amount of paste transfer meets the requirements and can maintain a high dot protrusion height. When the extrusion depth is less than or equal to 30 μm, the amount of paste adhesion can be controlled more precisely, and the uniformity of dotting can be improved.

[0059] In one possible implementation, during the preparation of the adhesive layer, the substrate moving speed is 60 m / min to 150 m / min, optionally 80 m / min to 120 m / min.

[0060] In the embodiments of this application, the moving speed of the substrate is within the above-mentioned range, which can improve the integrity of the slurry points and reduce the occurrence of tailing and connecting points while meeting production efficiency.

[0061] Fourthly, a battery is provided, comprising a battery cell as described in the first aspect and any of the possible implementations thereof, and / or a separator as described in the second aspect and any of the possible implementations thereof, and / or a separator prepared by a method as described in the third aspect and any of the possible implementations thereof.

[0062] Fifthly, an electrical device is provided, including the battery of the fourth aspect. Attached Figure Description

[0063] Figure 1 is a schematic diagram of an electrode assembly with a wound structure inside a battery cell according to an embodiment of this application.

[0064] Figure 2 is a schematic diagram of the structure of the isolation membrane according to an embodiment of this application.

[0065] Figure 3 is a schematic diagram of the structure of the isolation membrane according to another embodiment of this application.

[0066] Figure 4 is a schematic diagram of the structure of the isolation membrane according to another embodiment of this application.

[0067] Figure 5 is a schematic diagram of a battery cell according to an embodiment of this application.

[0068] Figure 6 is a schematic diagram of the structure of a battery device according to an embodiment of this application.

[0069] Figure 7 is a schematic diagram of an electrical device according to an embodiment of this application.

[0070] Figure 8 is a SEM image of the separator membrane according to an embodiment of this application.

[0071] Figure 9 is a SEM image of the separator membrane according to another embodiment of this application.

[0072] Explanation of reference numerals in the attached drawings: 10 Corner area; 100 Separator; 101 Substrate; 1011 Second region; 1012 First region; 102 Adhesive layer; 103 Dotted protrusions; 110 Positive electrode sheet; 120 Negative electrode sheet; 20 Planar region; 3 Battery cell; 31 Housing; 32 End cap assembly; 33 Electrode assembly; 34 Connecting member; 322 Electrode terminal; 330 Electrode assembly body; 331 Tab; 4 Battery device; 5 Electrical device. Detailed Implementation

[0073] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its manufacturing method, the battery, and the power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0074] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0075] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0076] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0077] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0078] In recent years, rechargeable batteries have been widely used in many fields such as power tools, electronic products, electric vehicles, and aerospace due to their high energy density and long service life, thus achieving significant development.

[0079] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, fast charging capability, reliability, and initial charge capacity. With the widespread use of batteries, the requirements for battery capacity are gradually increasing. Improving the capacity of wound batteries mainly involves using high-density electrodes, increasing the number of winding turns in the battery assembly, or increasing the volume of the individual battery cells. However, with the increase in battery capacity, the battery is prone to high expansion during charging and discharging. This poses a risk of unreleased local stress in the corner areas of the wound battery, leading to continuous compression between the electrodes and the separator. The electrolyte transport space becomes increasingly smaller, hindering electrolyte transport in the corner areas of the separator. This results in insufficient lithium insertion and lithium plating in the corner areas of the wound battery cells, reducing cycle performance. Severe unreleased local stress in the corner areas of wound batteries can lead to electrode cracking, affecting the safety performance of the individual battery cells.

[0080] Currently, in some implementations, spin coating is used to prepare the adhesive layer of the separator, which can provide a high adhesive layer thickness. However, due to process limitations, it is difficult to control the coating density, slurry dot distribution uniformity, and area coverage. In contrast, dot coating can obtain a more uniform and controllable adhesive layer, which is beneficial for better regulation and optimization of the separator properties. However, the existing dot coating process can only achieve a relatively small adhesive layer height, which cannot meet the expansion space requirements of the corner area of ​​the wound battery.

[0081] In view of this, in one embodiment of this application, a battery cell is provided, comprising: a positive electrode sheet, a negative electrode sheet, and a separator; the positive electrode sheet, the negative electrode sheet, and the separator are wound to form a wound structure, the wound structure including corner regions at both ends and a planar region connecting the corner regions; the separator includes a substrate and an adhesive layer, the adhesive layer is disposed on at least one surface of the substrate, the adhesive layer includes a plurality of dot-shaped protrusions arranged at predetermined intervals, wherein the height of the dot-shaped protrusions in the corner regions is 5μm to 35μm; the center-to-center distance between two adjacent dot-shaped protrusions is 360μm to 650μm.

[0082] By setting multiple dot-shaped protrusions at predetermined intervals on the surface of the separator in a wound battery, a separator adhesive layer with high uniformity of thickness can be formed, improving the adhesion between the separator and the electrode. This prevents adverse situations such as separator-electrode separation, electrode tab misalignment, and electrode wrinkling during operation, thereby enhancing the structural strength and stability of the electrode assembly and improving the electrical performance of the battery cell. Furthermore, when the height of the dot-shaped protrusions in the corner area is greater than or equal to 5μm, the protrusions can support a larger gap between the separator and the electrode. This allows for more space in the corner area while ensuring effective adhesion, buffering the cyclic expansion force of the battery cell and ensuring... Maintaining sufficient space for electrolyte transport improves cycle performance and enhances safety. When the height of the dotted protrusions in the corner area is less than or equal to 35 μm, it avoids excessive gaps between the separator and the electrode, which could affect ion transport and better balance the cycle life and kinetic performance of the battery cells. Simultaneously, maintaining a center-to-center distance of less than or equal to 650 μm between adjacent dotted protrusions further increases the expansion space in the corner area. A center-to-center distance of greater than or equal to 360 μm improves the gas permeability of the separator, preventing excessively dense dotted protrusions from clogging the separator's pores and improving both cycle and kinetic performance.

[0083] During the charging process of a lithium-ion secondary battery, lithium ions are released from the positive electrode active material, move and embed into the negative electrode active material; while during the discharging process, lithium ions are released from the negative electrode active material, move and embed into the positive electrode active material.

[0084] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated into the positive electrode active material or the negative electrode due to an electrochemical reaction, and the “extraction” and “deintercalation” processes described in this application refer to the process by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0085] In this application's embodiments, a single battery cell can refer to the smallest structural unit of a battery. Multiple battery cells can first be assembled into a battery module, and then the battery module can be assembled into a battery; multiple battery cells can also be directly assembled into a battery.

[0086] In this application's embodiments, the battery cell refers to a lithium-ion secondary battery, that is, a lithium-ion battery cell that can be reversibly charged and discharged.

[0087] [Battery cell]

[0088] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0089] In one embodiment of this application, a battery cell is provided, the battery cell including a positive electrode, a negative electrode and a separator.

[0090] Figure 1 is a schematic diagram of an electrode assembly with a wound structure inside a battery cell according to an embodiment of this application. For example, as shown in Figure 1, the positive electrode 110, the negative electrode 120, and the separator 100 are wound to form a wound structure, which includes corner regions 10 at both ends and a planar region 20 connecting the corner regions 10.

[0091] Figure 2 is a schematic diagram of the structure of a separator membrane according to an embodiment of this application. The separator membrane 100 includes a substrate 101 and an adhesive layer 102 disposed on at least one surface of the substrate 101. The substrate 101 has two opposing surfaces along its own thickness direction. The adhesive layer 102 may be disposed on one surface of the substrate 101 or on both surfaces of the substrate 101. As an example, as shown in Figure 2, the adhesive layer 102 is disposed on both surfaces of the substrate 101. The substrate 101 may include only a base film, or it may include a base film and a functional coating disposed on at least one surface of the base film. This functional coating can be used to improve the thermal stability, flame retardancy, and overall mechanical properties of the separator membrane, wherein the functional coating may be a ceramic coating.

[0092] Figure 3 is a structural example diagram of the isolation membrane according to another embodiment of this application. The adhesive layer 102 includes a plurality of dot-shaped protrusions 103 arranged at predetermined intervals, wherein the height of the dot-shaped protrusions 103 in the corner area 10 is 5μm to 35μm; the center-to-center distance between two adjacent dot-shaped protrusions is 360μm to 650μm.

[0093] The height of the dot-like protrusions can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm or any value within the above range.

[0094] The center-to-center distance between two adjacent point protrusions can be 360μm, 370μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm or any value within the above range.

[0095] In some embodiments, the height of the dot-shaped protrusions 103 in the corner area 10 is optionally 8 μm to 30 μm.

[0096] The height of the dot-like protrusions can be 8μm, 9μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 30μm or any value within the above range.

[0097] The height of the dot-like protrusions can be represented by dividing the difference between the gap between the positive and negative electrode plates and the thickness of the substrate (including the ceramic coating) of the separator by 2. The gap between the positive and negative electrode plates refers to the distance between the positive and negative electrode plates.

[0098] The gap between the positive and negative electrode sheets located at the corner of the electrode assembly can be determined by the following measurement method: First, the negative electrode sheet, separator, and positive electrode sheet are stacked sequentially to form an electrode assembly and then wound up (the outermost layer of the electrode assembly ends with the convex surface of the positive electrode sheet). The electrode assembly is placed in a square aluminum shell, vacuum dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained. Then, a CT device (Zeiss METROTOM 1500CT system) is used to scan the negative electrode sheet at the corner of the wound electrode assembly in the battery cell at a distance of 15±1mm downwards from the edge. Samples are taken along the horizontal and oblique angles (30°~45°) in the obtained CT image, and lines are drawn in the direction of the maximum gap. The sampling position for the inner 5 folds is from the convex surface of the innermost positive electrode sheet to the convex surface of the 5th positive electrode sheet, and the average value of 4 folds is taken. After 6 folds, the sampling position is from the convex surface of the inner positive electrode sheet to the convex surface of the outer positive electrode sheet, and the value is taken every 5 folds.

[0099] Average gap between the inner 5 layers = [CT measurement distance - 4 × thickness of negative electrode sheet after cold pressing × (1 + negative electrode sheet rebound rate) - 4 × thickness of positive electrode sheet after cold pressing × (1 + positive electrode sheet rebound rate) - 8 × substrate thickness of separator] / 8;

[0100] The average gap after the inner 6-10 layers = [CT measurement distance - 5 × thickness of negative electrode sheet after cold pressing × (1 + negative electrode sheet rebound rate) - 5 × thickness of positive electrode sheet after cold pressing × (1 + positive electrode sheet rebound rate) - 10 × substrate thickness of separator] / 10;

[0101] Wherein, negative electrode rebound rate = (thickness of negative electrode before entering the casing - thickness of negative electrode after cold pressing) / thickness of negative electrode after cold pressing;

[0102] Positive electrode rebound rate = (positive electrode thickness before casing - positive electrode thickness after cold pressing) / positive electrode thickness after cold pressing;

[0103] The gap G between the positive and negative electrode plates in the corner region is calculated as (average gap of the inner 5 layers + average gap after the inner 6th to 10th layers) / 2, in μm. It represents the space available for buffering the volume expansion of the electrode plates in the corner region of the electrode assembly during cycling, essentially indicating the height of the dotted protrusion. To improve the accuracy of the measurement results, at least 5 samples should be measured, and the average value should be calculated.

[0104] By setting a dotted protrusion adhesive layer at predetermined intervals on the surface of the separator, a more uniform and controllable adhesive layer can be obtained through a dot coating process, which is beneficial for better control and optimization of the separator properties. In this application, the adhesive layer of the separator includes multiple dotted protrusions and has at least the following two characteristics: First, the dotted protrusions are set at predetermined intervals along the length direction (substrate feeding direction) and / or the width direction of the separator to form a non-full-coverage adhesive layer, which can form a separator with high thickness uniformity, improve the adhesion between the separator and the electrode, and enable the separator and the electrode to be bonded evenly and tightly. This avoids adverse situations such as separator separation, electrode tab misalignment, and electrode wrinkling in the electrode assembly during assembly and cycling processes, thereby enhancing the structural strength and stability of the electrode assembly and improving the cycle performance of the secondary battery cell; Second, when the height of the dotted protrusions is greater than or equal to 5 μm, it is greater than that of the dot coating process in the prior art. The achieved dotted protrusion height creates a larger gap between the separator and the electrode, providing more space for electrode expansion during cyclic charging and discharging to release stress in the battery cell and avoid excessive local stress. Simultaneously, when the height of the dotted protrusion is less than or equal to 35 μm, the ionic conductivity of the separator can be considered, ensuring the gap between the separator and the electrode is not too large. This minimizes the ion transport path between the positive and negative electrodes, reduces internal resistance, and prevents the adhesive layer from occupying too much space and compressing the space of other electrode components, thus better balancing the cycle life and energy density of the battery cell. Furthermore, with adjacent dotted protrusions within the aforementioned range, sufficient expansion space is provided, and the gas permeability of the separator is improved.

[0105] The height of the aforementioned dot-like protrusions can be 8μm to 30μm. While providing support and creating a suitable gap, the height consistency is good, which is beneficial for obtaining a more uniform bonding effect. Figure 4 is a structural example diagram of the separator membrane according to another embodiment of this application. The planar region 20 includes a first region 1012 and a second region 1011 adjacent to each other along the width direction (y) of the separator membrane 100. The first region 1012 is the projection area of ​​the positive electrode sheet 110 in the separator membrane along a direction perpendicular to the separator membrane 100.

[0106] The second region includes the overhang region, which is the portion of the negative electrode active material that extends beyond the edge of the positive electrode active material.

[0107] In some embodiments, the height of the dot-shaped protrusions 103 in the first region 1012 is 0.5 μm to 2 μm.

[0108] The height of the dot-like protrusions in the first region can be 0.5μm, 0.8μm, 1μm, 1.5μm, 1.8μm, 2μm or any value within the above range.

[0109] In some embodiments, the height of the dot-like protrusions in the second region is 8 μm to 40 μm.

[0110] The height of the dot-like protrusions in the second region can be 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm or any value within the above range.

[0111] The first region of the planar area is pressed relative to the second region, so that the dotted protrusions in the first region of the planar area are within the above-mentioned range. This can provide expansion space in the corner area while avoiding compression of the space of battery components such as active materials and electrolytes in the first region of the planar area, which is beneficial to improving the energy density of the battery cell.

[0112] The height of the dot-like protrusions of the separator in the first and second regions of the planar area can be obtained using CT and SEM equipment. Specifically, after the battery cell is disassembled, separators with flat surfaces and no peeling of the adhesive layer in the planar area of ​​the cell are selected. They are first soaked and cleaned with DMC and then dried to ensure that the electrolyte is clean. The first and second regions of the separator were cut as samples. The first region was the central area of ​​the separator, and the second region was the overhang area. The samples (approximately 6mm x 6mm) were fixed to the sample stage using conductive double-sided tape, ensuring the pre-cut flat surface protruded approximately 1mm from the edge of the sample stage. The sample stage was then installed into the sample holder and locked securely, ensuring no gaps between the sample surface and the baffle, and the distance of the sample protruding from the baffle was controlled within 100μm. The instrument used was an IM5000. The vacuum pump and gas valve were turned on, and the instrument was powered on. The AIR button was pressed and held to release the vacuum, the sample chamber was opened, and the cross-section cryogenic grinding was switched to the C processing position. The instrument was then powered off, and the CTC cold conduction unit was connected. The instrument was powered on again, and the CTC mode was selected in MODE. The operating voltage was set to 4KV, and the argon flow rate to 0.18m. 3 / min, grinding time 3h, swing mode C4, grinding temperature -80℃, click EVAC; the parameter confirmation interface will be entered automatically, click OK; grinding: the system will process automatically, no operation is required; when the grinding is finished, click ROOM to heat up; press and hold AIR to release vacuum, press the power button at the front to turn off; disconnect the CTC cable and sample holder, and take out the sample. Then open the SmartSEM user interface software, click Control Panel Status, click Vacuum, and click Vent to release the vacuum. After the vacuum is released, open the chamber door. Align the sample stage with the protruding area on the stage and insert it securely. Close the chamber door. Click Control Panel Status again and click Pump to evacuate the vacuum. Click EHT and then EHT ON to turn on the high voltage of 3kV. Move the sample stage by clicking its position on the sample navigation stage. Adjust the magnification on the control key and focus until a clear image is visible. Click Camera on the control panel to switch to the CCD camera mode. Adjust the joystick on the control key to adjust the working distance. Click Camera to switch to detector mode. In Rudecud / small window mode, adjust Focus, Stigmator, and Wobble until a clear image is visible. Adjust the Magnification on the control key to 3000x. Use the scale bar to measure the height of the protrusions. Measure the height of the point protrusions in the first and second regions of at least 5 separator samples. Calculate the average value as the height of the point protrusions in the first and second regions of the planar area, respectively. In some embodiments, the center-to-center distance between two adjacent dot-shaped protrusions is 480 μm to 580 μm.

[0113] The center-to-center distance between two adjacent point protrusions can be 480μm, 500μm, 520μm, 540μm, 560μm, 570μm, 580μm or any value within the above range.

[0114] The center of a dot-shaped protrusion refers to the center of the smallest circumcircle of the dot-shaped protrusion, and the distance between the centers of two adjacent dot-shaped protrusions is the distance between the two centers.

[0115] In some embodiments, two adjacent dot-shaped protrusions include the spacing between two dot-shaped protrusions along the length direction of the separator (i.e., the direction of the separator substrate's tape travel) and the spacing between two adjacent dot-shaped protrusions along the width direction of the separator (i.e., perpendicular to the direction of the separator substrate's tape travel). The center-to-center spacing between two adjacent dot-shaped protrusions along the length direction (MD) of the separator is 480 μm to 520 μm; optionally, the center-to-center spacing between two adjacent dot-shaped protrusions along the MD direction is 500 μm. The center-to-center spacing between two adjacent dot-shaped protrusions along the width direction (TD) of the separator is 530 μm to 580 μm; optionally, the center-to-center spacing between two adjacent dot-shaped protrusions along the TD direction is 550 μm.

[0116] When the center-to-center distance between two adjacent dot-shaped protrusions is greater than or equal to 480 μm, the air permeability requirements of the separator membrane can be met, ion transport efficiency can be maintained, and cycle performance can be improved. When the center-to-center distance between two adjacent dot-shaped protrusions is less than or equal to 580 μm, the adhesion of the separator membrane can be taken into account, and the coverage requirements of the separator membrane adhesive layer can be met.

[0117] In some embodiments, the diameter of the dot-like protrusions is 210 μm to 310 μm.

[0118] The diameter of the dot-like protrusions can be 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm or any value within the above range.

[0119] In some embodiments, the diameter of the dot-like protrusions is optionally 240 μm to 280 μm.

[0120] The diameter of the dot-like protrusions in the corner area can be 240μm, 250μm, 260μm, 270μm, 280μm or any value within the above range.

[0121] The diameter of the dot-shaped protrusion is the diameter of the smallest circumcircle of the dot-shaped protrusion.

[0122] The diameter of the dot-like protrusion can be determined by photographing it using a 3D laser measuring microscope (Olympus). After disassembling the battery cell, select a separator with a smooth surface and no peeling adhesive layer. First, soak and clean it with DMC, then dry it to ensure the electrolyte is completely removed. Then, sample the separator, cutting a piece at least 4cm x 4cm in size, with the test side facing up. Tighten it with a pressure block, turn on the device, and begin testing. Focus, select an appropriate lens magnification, locate the target protrusion, and then begin 3D acquisition at 50x magnification. After acquisition, the diameter of the dot-like protrusion can be determined by photographing it using a 3D laser measuring microscope (Olympus). After disassembling the battery cells, select separators with smooth surfaces and no peeling adhesive layers. First, soak and clean them with DMC, then dry them to ensure the electrolyte is thoroughly cleaned. Next, sample the separator, cutting pieces at least 4cm x 4cm in size, with the test side facing up. Tighten the sample with a pressure block, turn on the equipment, and begin testing. Focus, select an appropriate lens magnification, locate the target protrusion, and begin 3D acquisition at 50x magnification. After acquisition, use image analysis software (such as ImageJ) to open the acquired image, click the "Auto" function, and perform preprocessing operations such as noise removal and tilt removal. Select "Plane" mode for length measurement. Use the "3-point circle" measurement tool in the software to select three non-collinear points on the edge of the protrusion. These three points ensure that the defined circle completely encompasses the protrusion; this circle is the minimum circumcircle. The software automatically calculates the center and radius based on these three points. Measure the diameter of the protrusion along the width of the separator sample and calculate the average value. Obviously, the center-to-center distance between two adjacent point protrusions can also be measured in a similar way, which will not be elaborated here.

[0123] When the diameter of the dot-like protrusions is greater than or equal to 210μm, the adhesion of the separator can be improved. At the same time, controlling the diameter of the dot-like protrusions to be less than or equal to 310μm can balance the air permeability of the separator and improve the cycle performance of the battery cells.

[0124] In some embodiments, the area coverage of the adhesive layer on one side of the substrate is 12% to 28%.

[0125] The area coverage of the adhesive layer on one side of the substrate is 12%, 13%, 14%, 15%, 16%, 21%, 22%, 24%, 25%, 26%, 27%, 28%, or any value within the range above.

[0126] In some embodiments, the area coverage of the adhesive layer on one side of the substrate is optionally 16% to 23%.

[0127] The area coverage of the adhesive layer on one side of the substrate is 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, or any value within the range mentioned above.

[0128] The area coverage of the adhesive layer on one side of the substrate can be determined as follows: Disassemble the battery cell, take a sample of the separator with arrayed dot-shaped protrusions, and take a micrograph of the sample containing multiple (no less than 4) dot-shaped protrusions using an optical microscope (such as a Keyence optical microscope). The area of ​​the micrograph is S2. Then, determine the average diameter of the smallest circumcircle of each dot-shaped protrusion and take it as the diameter d (μm) of the dot-shaped protrusion. The area of ​​the dot-shaped protrusion S1 = πd 2 / 4, the area of ​​n point-like protrusions is nS1, and the coverage rate (%) of the adhesive layer is n*S1 / S2. To improve the accuracy of the measurement results, multiple measurements can be taken on the same test sample using different point-like protrusions, and the average value can be calculated. The gaps in the point-like protrusions are small and can be ignored.

[0129] The higher the area coverage of the adhesive layer, the greater the adhesive force it provides. However, if the area coverage is too large, it can easily clog the pores of the substrate and increase the impedance of the separator. Therefore, when the area coverage is within the above range, the adhesive strength and ionic conductivity of the separator can be better balanced.

[0130] In some embodiments, the dotted protrusions include organic particles, which include at least one of non-fluorinated organic particles and fluorinated organic particles.

[0131] In some embodiments, the non-fluorinated organic particles satisfy one or more of the following conditions: the non-fluorinated organic particles have a first glass transition temperature Tg1 and a second glass transition temperature Tg2, and 100°C > Tg1 > Tg2; optionally, Tg1 is 26°C to 54°C, and / or Tg2 is 0°C to 25°C; the non-fluorinated organic particles include at least two types of monomer units selected from acrylate monomer units, acrylic monomer units, vinyl monomer units, unsaturated nitrile monomer units, and amide monomer units; the non-fluorinated organic particles include a first polymer and a second polymer, wherein the first polymer and / or the second polymer includes one or more of copolymers containing acrylate monomer units, copolymers containing acrylic monomer units, and copolymers containing vinyl monomer units; optionally, the first polymer and / or the second polymer includes at least one of carboxyl groups, amide groups, and cyano groups.

[0132] In this application, the glass transition temperature is the temperature at which a polymer transitions from a rubbery state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from a glassy state to a rubbery state, or vice versa. It is the lowest temperature at which the macromolecular chain segments of an amorphous polymer can move freely, and is denoted by Tg. The glass transition temperature can be measured using methods commonly used in the art, such as differential scanning calorimetry as described in GB / T19466.2.

[0133] In this embodiment, the non-fluorinated organic particles have two glass transition temperatures, high and low. During cold pressing, the non-fluorinated organic particles with the relatively lower glass transition temperature soften and undergo rheological changes to a certain extent, which can strengthen the adhesion of the adhesive layer to the positive and negative electrodes. As the battery is charged and discharged and the temperature rises, the non-fluorinated organic particles with the relatively higher glass transition temperature gradually soften. Especially when the battery cell is at risk of thermal runaway, the adhesion of the non-fluorinated organic particles with the high glass transition temperature to the positive and negative electrodes is enhanced, thereby effectively controlling the shrinkage of the separator during thermal runaway, maintaining a stable structure of the separator, and achieving the function of isolating the positive and negative electrodes.

[0134] In one possible implementation, the non-fluorinated organic particles include one or more of the following: copolymers containing acrylate monomer units and styrene monomer units; copolymers containing acrylate monomer units and styrene monomer units; copolymers containing acrylate monomer units, acrylate monomer units, and styrene monomer units; copolymers containing styrene monomer units, aliphatic olefin monomer units, and unsaturated nitrile monomer units; and copolymers containing styrene monomer units, aliphatic olefin monomer units, and unsaturated nitrile monomer units; and modified compounds of the above copolymers.

[0135] In one possible implementation, the non-fluorinated organic particles include at least one of the following: acrylate-styrene-acrylamide copolymers, acrylate-styrene-acrylonitrile copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylic acid-acrylamide copolymers, acrylate-acrylic acid-acrylonitrile copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylonitrile-acrylamide-styrene copolymers, acrylate-styrene-acrylamide copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylonitrile-acrylamide copolymers, acrylate-acrylonitrile-acrylamide-styrene copolymers.

[0136] When non-fluorinated organic particles include the types mentioned above, the carboxyl groups can form bonding forces with the functional groups on the electrode and separator materials, improving the adhesion. Amide and nitrile groups are beneficial for improving the polymer's adhesion, and nitrile groups also help improve ionic conductivity.

[0137] The determination of carboxyl, amide, and nitrile groups in the above polymer structure can be performed using the following method: The battery cell is disassembled to obtain the separator sample. According to the national standard GB / T 6040-2002 General Rules for Infrared Spectroscopy Analysis, the sample is pressed into a KBr pellet using the transmission method. The KBr background blank is subtracted by the transmission method to obtain the sample's test spectrum (resolution: 4 cm⁻¹). -1 Wavenumber range: 400cm -1 ~4000cm - 1 ).

[0138] In some embodiments, the dot-like protrusions include not only non-fluorinated organic particles but also fluorinated organic particles, wherein the fluorinated organic particles satisfy one or more of the following conditions: the melting point temperature of the polymer included in the fluorinated organic particles is 139°C to 154°C; the number average molecular weight of the polymer included in the fluorinated organic particles is 400,000 to 650,000; the fluorinated organic particles include fluorinated polymers, wherein the fluorinated polymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorinated alkenyl monomer units, copolymers of fluorinated alkenyl monomer units and vinyl monomer units, copolymers of fluorinated alkenyl monomer units and acrylic monomer units, copolymers of fluorinated alkenyl monomer units and acrylate monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0139] The polymer's melting point temperature is in the range of 139℃ to 154℃, meaning it can maintain a relatively stable structure under most normal battery operating temperatures. This allows the separator adhesive layer to maintain its integrity for a longer period of time, preventing it from easily melting, deforming, or decomposing due to temperature changes. This effectively maintains the isolation between the positive and negative electrodes inside the battery, preventing short circuits and other safety accidents.

[0140] Fluorinated organic particles contain polymers with a weight-average molecular weight (Mw) of 400,000 to 800,000, which is beneficial for obtaining suitable adhesion. The number-average molecular weight can be determined using methods commonly used in the art, such as gel permeation chromatography as described in GB / T 21863-2008.

[0141] Fluorinated and / or non-fluorinated organic particles provide adhesion between the separator and the electrode to meet the requirements of the battery cell winding and shaping process. The two types of organic particles can be used in combination, or either non-fluorinated or fluorinated organic particles can be used alone. Generally, the higher the content of non-fluorinated organic particles, the stronger the adhesion between the separator and the electrode after winding and cold pressing. Those skilled in the art can flexibly adjust the type, amount, or ratio of organic particles according to the adhesion strength required to meet the winding and shaping process requirements.

[0142] In some embodiments, the volume average particle size Dv50 of the organic particles is 5 μm to 25 μm.

[0143] The volume average particle size Dv50 of the organic particles can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 20μm, 21μm, 23μm, 25μm or any value within the above range.

[0144] In some embodiments, the volume average particle size Dv50 of the organic particles is 7 μm to 20 μm.

[0145] The volume average particle size Dv50 of the organic particles can be 7μm, 8μm, 9μm, 10μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 20μm or any value within the above range.

[0146] When the volume average particle size Dv50 of organic particles is greater than or equal to 5 μm, it can effectively increase the height of the dot-like protrusions, increase the expansion space in the corner area, and improve cycle performance. When the volume average particle size Dv50 of organic particles is less than or equal to 25 μm, it can reduce the blockage of the separator, improve the air permeability of the separator, and help to further improve the cycle life of the battery cell.

[0147] When the volume average particle size Dv50 of organic particles is greater than or equal to 7 μm, it helps to form frustum-shaped dot protrusions. Compared with the ring-shaped dot protrusions formed by smaller particles, the number of bonding sites increases, thereby improving the bonding force. When the volume average particle size Dv50 of organic particles is less than or equal to 20 μm, the risk of separator blockage can be further reduced, the air permeability of the separator can be improved, and the cycle performance of battery cells can be improved.

[0148] In some embodiments, the dot-like protrusions include an edge protrusion area and a recessed area surrounded by the edge protrusion area.

[0149] The raised edge area not only stably bonds the separator to the electrode, but also creates a suitable electrode gap, providing sufficient buffer space for electrode expansion and improving the shaping effect of the electrode assembly. The recessed area has less polymer for bonding, making the separator easier to wet with electrolyte, which correspondingly reduces the tortuosity of active ions passing through the separator and is beneficial to improving the dynamic properties of the separator.

[0150] In some embodiments, the dot-like protrusions include a platform region and an edge region surrounding the platform region, wherein the minimum height of the platform region is not less than the maximum height of the edge region. As shown in Figure 8, which is a SEM image of the separator, the organic particles in the dot-like protrusions are distributed in a dispersed manner, forming a frustum shaped morphology.

[0151] In this embodiment, the dot-shaped protrusions have a frustum shape, and the organic particles are medium-sized particles that are randomly distributed within the dot-shaped protrusions, increasing the number of bonding sites and improving the bonding force.

[0152] In some embodiments, the adhesive layer further includes invalid protrusions with a diameter of less than 100 μm; the ratio of invalid protrusions to dot-like protrusions is less than or equal to 5:95.

[0153] In this embodiment, the ratio of invalid protrusions to dot-like protrusions in the adhesive layer is within the above-mentioned range. By using a dot-coating method and simultaneously increasing the dot-coating height, the number of invalid protrusions is reduced, and the adhesive layer is mostly composed of uniformly distributed and height-consistent dot-like protrusions. This reduces the risk of invalid protrusions clogging the micropores of the separator, improves the air permeability of the separator, enhances ion transport efficiency, and improves the cycle performance of the battery cell.

[0154] In some embodiments, the release film includes a first adhesive layer and a second adhesive layer respectively disposed on two surfaces of the substrate. The first adhesive layer includes a plurality of first dot-shaped protrusions disposed at a first predetermined interval, and the second adhesive layer includes a plurality of second dot-shaped protrusions disposed at a second predetermined interval.

[0155] By setting adhesive layers on both sides of the separator, the adhesion of the separator can be improved. At the same time, the gap between the separator and the electrode is further increased, the expansion space in the corner area is increased, and the cycle performance is improved.

[0156] In some embodiments, the first dot-shaped protrusion includes a first organic particle, and the second dot-shaped protrusion includes a second organic particle, wherein the first organic particle and the second organic particle are made of different materials.

[0157] The first dot-shaped protrusion can be configured to include fluorinated organic particles, and the second dot-shaped protrusion can be configured to include non-fluorinated organic particles.

[0158] By setting different materials for the dotted protrusions on both sides, different bonding forces are achieved on both sides, avoiding the risk of self-adhesion and improving processing performance.

[0159] In some embodiments, the first predetermined interval is different from the second predetermined interval.

[0160] The spacing between adjacent dots in the first adhesive layer and the second adhesive layer differs. This difference exists both along the film's width and along the film's belt direction, resulting in fewer dots and higher permeability, thus improving ion transport efficiency. Conversely, the smaller spacing results in more dots and stronger adhesion. Furthermore, the different adhesion on both sides of the film reduces self-adhesion during unpressurized film preparation and winding processes, improving processing performance.

[0161] In some embodiments, in a direction perpendicular to the release membrane, the center of the first dotted protrusion in the first adhesive layer coincides with the center of at least a portion of the second dotted protrusion in the second adhesive layer.

[0162] During the double-sided coating process, since the coating is done on both sides separately, and after one side is dried, the other side of the separator is then coated. There is a risk that the dotted protrusions on both sides may be completely misaligned, resulting in uneven thickness of the separator adhesive layer and misalignment of the tabs. By controlling the dotted protrusions on both sides to at least partially overlap, the expansion space in the corner area can be further increased. At the same time, the air permeability of the separator can be taken into account while satisfying the adhesion, reducing the blockage of the separator and improving the cycle performance of the battery cell.

[0163] In some embodiments, the first adhesive layer includes a plurality of adjacent first repeating units, each first repeating unit including a plurality of first dot-shaped protrusions, the plurality of first dot-shaped protrusions being arranged at a third predetermined interval in a first direction and at a fourth predetermined interval in a second direction, the third predetermined interval being different from the fourth predetermined interval, and the first direction being perpendicular to the second direction; the second adhesive layer includes a plurality of adjacent second repeating units, each second repeating unit including a plurality of second dot-shaped protrusions, the plurality of second dot-shaped protrusions being arranged at a fourth predetermined interval in a first direction and at a third predetermined interval in a second direction.

[0164] The repeating unit comprises 90 to 140 at least partially overlapping dot-like protrusions.

[0165] By setting the dot-shaped protrusions on one side to have the same spacing in the first direction as the dot-shaped protrusions on the other side in the second direction, and the dot-shaped protrusions on the other side to have the same spacing in the second direction as the dot-shaped protrusions on the other side in the first direction, the risk of complete misalignment due to consistent spacing is avoided. Different spacing can correct the dot-shaped protrusions that do not overlap during the coating process, achieving the effect of constructing repeating units. The repeating unit includes multiple dot-shaped protrusions that at least partially overlap. The repeating units are adjacent to each other in the separator adhesive layer, which increases the overlap rate of the dot-shaped protrusions on both sides. This avoids the misalignment problem caused by inconsistent thickness during the winding of multi-layer battery modules. At the same time, the increased overlap rate can increase the expansion space in the corner area and improve the cycle performance of the battery cells.

[0166] [Positive electrode plate]

[0167] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0168] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0169] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0170] In some embodiments, the positive electrode active material in the positive electrode film layer includes a lithium phosphate with an olivine structure. Examples of lithium phosphate with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0171] In some embodiments, the positive electrode active material is a lithium phosphate, and the compaction density of the positive electrode sheet is 2.6 g / cm³. 3 ~2.8g / cm 3 .

[0172] The positive electrode film may optionally include at least one of the positive electrode active materials known in the art for batteries: lithium transition metal oxides and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0173] In some embodiments, the positive electrode active material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 .

[0174] In some embodiments, the secondary battery cell is a sodium-ion battery, and the positive electrode active material can be a positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc., and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. For example, as an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0175] As an optional technical approach in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, and Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2. y )2(PO4)2F 3-2yat least one of (0 ≤ y ≤ 1).

[0176] As an optional technical solution of the present application, the polyanionic compound may be Na x-a A a V y- b M b (PO4) 2-2c (DO4) 2c F z-d Q d , wherein the A element represents an alkali metal element that dopes and replaces the Na element, the M element represents a metal element that replaces the V element, the D element represents a doping element that replaces the P element, the Q element represents a doping element that replaces the F element, the D element includes at least one of Si and S, the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0177] As an optional technical solution of the present application, the polyanionic compound may be Na x R y (PO4)2P2O7, wherein, x = 3.5 - 4.5, y = 2.75 - 3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0178] As an optional technical solution of the present application, the polyanionic compound may be Na 4+x R 3-y P 4- m O 15 / C; wherein, 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0179] The Prussian blue compound may be a type of compound having sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound is, for example, Na aMe b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0180] In some embodiments, the positive electrode active material includes at least one of sodium-containing layered oxides, polyanionic sodium compounds, and Prussian blue sodium compounds.

[0181] In some embodiments, the sodium-containing layered oxide is an iron-manganese layered oxide, specifically including at least one of nickel-iron-manganese layered oxide and copper-iron-manganese layered oxide.

[0182] During the charging and discharging process, the battery will produce active ions (Na+). + The molar content of sodium varies depending on the insertion / extraction and consumption of sodium (Na) as it is discharged to different states. In the examples of positive electrode active materials in this application, the molar content of Na refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Na changes after charge-discharge cycles.

[0183] In the examples of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0184] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0185] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0186] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, a positive electrode active material is filled and / or deposited within the foamed metal.

[0187] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0188] [Negative electrode plate]

[0189] As described above, the negative electrode current collector has two opposing surfaces along its thickness direction. The negative electrode film layer can be disposed on one surface of the negative electrode current collector or on both surfaces.

[0190] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0191] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0192] In some embodiments, the negative electrode active material includes a silicon-based material.

[0193] In some embodiments, the negative electrode can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0194] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0195] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0196] As described above, in some embodiments, the negative electrode film may optionally include conductive carbon. The conductive carbon may be selected from at least one of superconducting carbon, acetylene black, conductive carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0197] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0198] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive carbon, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0199] In other embodiments, the current collector of the negative electrode sheet typically includes a current collector body and a base coating. The base coating can be disposed on at least one side of the current collector body. The base coating basically does not contain negative electrode active material, but may contain a small amount of carbon material. However, the carbon material forms a thin coating and cannot function as a negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For a negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not contain a base coating, the aforementioned film layer can be disposed on the surface of at least one side of the current collector; when the current collector of the negative electrode sheet includes a base coating, the aforementioned film layer can be disposed on the surface of the base coating away from the current collector.

[0200] [Electrolytes]

[0201] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0202] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0203] For lithium-ion battery cells, the electrolyte salt may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0204] For lithium-ion battery cells, the solvent may include one or more of the following: ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0205] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0206] [Isolation membrane]

[0207] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0208] In some embodiments, the separator includes a substrate and an adhesive layer.

[0209] In some embodiments, the substrate material may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0210] Figure 9 is a SEM image of the release liner. In some embodiments, an adhesive layer is disposed on at least one surface of the substrate; the adhesive layer includes a plurality of dot-shaped protrusions arranged at predetermined intervals; as shown in Figure 9, a plurality of dot-shaped protrusions with uniform spacing are obtained by dot coating. The height of the dot-shaped protrusions is 8 μm to 40 μm, optionally, the height of the dot-shaped protrusions is 15 μm to 35 μm; the center-to-center distance between two adjacent dot-shaped protrusions is 360 μm to 650 μm.

[0211] The height of the dot-like protrusions can be 8μm, 9μm, 10μm, 11μm, 15μm, 17μm, 20μm, 22μm, 26μm, 30μm, 35μm, 37μm, 39μm, 40μm or any value within the above range.

[0212] The height of the dot-like protrusions can also be 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm or any value within the above range.

[0213] The center-to-center distance between two adjacent point protrusions can be 360μm, 370μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm or any value within the above range.

[0214] The height of the dot-like protrusions can be measured using a three-dimensional height imaging test method: Prepare a fresh 10cm × 10cm release liner sample, ensuring the surface of the release liner is free of foreign objects, damage, or other aesthetic defects. Hold the sample securely, ensuring the area to be tested is within the observation range. Use an Olympus OLS5100-SAF laser scanning microscope (measurement accuracy 120nm), adjust the focus and field of view, and magnify until the field of view is close to the size of the dot-like protrusions. Perform 3D data acquisition, moving the contour line to an area without dot-like protrusions, moving the baseline above the substrate surface, selecting the "area / volume" analysis mode, and setting the test area to 50μm. 2 Move the outline back to the position corresponding to the highest height of a point protrusion in the field of view, and output the test data to directly obtain the height of the point protrusion; test the height of multiple (e.g., 15) point protrusions according to the above process, and take the average value as the height of the point protrusions in the separator sample.

[0215] In this embodiment, the adhesive layer is obtained by dot coating. The height of the multiple dot-shaped protrusions on the surface of the isolation membrane is within the above-mentioned range. While providing support and constructing a moderate gap, the height consistency is good, which is conducive to obtaining a more uniform bonding effect.

[0216] In one possible implementation, the separator membrane satisfies one or more of the following conditions: the diameter of the dot-shaped protrusions is 210 μm to 310 μm, optionally, the diameter of the dot-shaped protrusions is 240 μm to 280 μm; the center-to-center distance between two adjacent dot-shaped protrusions is 480 μm to 580 μm; the dot-shaped protrusions include at least one of non-fluorinated organic particles and fluorinated organic particles; and the adhesive forces of the adhesive layers on both sides of the substrate are different.

[0217] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0218] [Preparation method of the separating membrane]

[0219] In some embodiments, a slurry is applied to the surface of a substrate by a dotting roller and dried to form an adhesive layer comprising a plurality of dot-shaped protrusions to obtain a release film, wherein the solid content of the slurry is 15% to 22%.

[0220] The solid content of the slurry can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22% or any value within the above range.

[0221] In some embodiments, the solid content of the slurry is optionally 16% to 20%.

[0222] The solid content of the slurry can be 16%, 17%, 18%, 19%, 20%, or any value within the above range.

[0223] In this embodiment, the adhesive layer slurry is applied to the separator by a dotting roller. When the solid content of the slurry is greater than or equal to 15%, the transferability of a single slurry dot can be increased, and dot-shaped protrusions with a height significantly greater than those obtained by conventional processes can be prepared simply and efficiently. This is beneficial for the effective bonding between the separator and the electrode sheet, and at the same time, a suitable gap between the positive and negative electrode sheets is constructed. This gap can buffer the cyclic expansion force of the electrode assembly and help the electrolyte to wet the electrode assembly, thereby improving the cycle life of the battery cell. When the solid content of the slurry is less than or equal to 22%, the fluidity of the slurry can be maintained, allowing the slurry to adhere evenly to the surface of the separator, forming uniformly arranged dot-shaped protrusions.

[0224] In some embodiments, the solid content of the adhesive slurry is 16% to 20%. This allows for better adjustment of the slurry's surface tension and enables the organic binder particles to form an effective buildup after drying, resulting in higher dot-like protrusions.

[0225] In some embodiments, the dispensing roller includes a dispensing roller with a plurality of raised structures arranged at predetermined intervals along the axial and circumferential directions of the dispensing roller.

[0226] The dispensing roller includes a dispensing roller base and multiple raised structures disposed on the dispensing roller base. The raised structures are arranged at predetermined intervals along the axial and circumferential directions of the dispensing roller. The bottom diameter of the raised structure is 300μm to 340μm, the top diameter is 200μm to 240μm, the center-to-center distance between two adjacent raised structures is 480μm to 580μm, and the height of the raised structure is 150μm to 250μm. The spacing of 480μm to 580μm between two adjacent raised structures results in an adhesive layer with a larger area coverage, which is beneficial for optimizing the adhesion between the separator and the electrode, and also makes the thickness and permeability of the separator more uniform, thus improving the transport of active ions. It should be noted that the distance between two adjacent protrusions refers to the shortest distance formed by the outer surfaces of the two adjacent protrusions. For example, when the protrusion is a hemisphere, the distance between two adjacent protrusions is the shortest distance formed by the spherical surfaces of the two hemispheres on their adjacent sides. It can be measured directly or determined based on the difference between the distance between the centers of the two hemispheres and the diameter of the hemisphere.

[0227] The base material of the dispensing roller is the same as that of the raised structure, and the raised structure can be engraved from the base material of the dispensing roller by laser engraving.

[0228] The contact angle between the raised structure material of the dot coating roller and the slurry is 65° to 75°, and the Shore hardness is 70 to 75.

[0229] If the contact angle of the dispensing roller is too large, it is difficult for the adhesive layer paste to be transferred to the raised structure of the dispensing roller; if the contact angle is too small, less adhesive layer paste will be transferred to the release film. When the contact angle between the raised structure of the dispensing roller and the paste is between 65° and 75°, sufficient paste can be adhered to the surface of the raised structure of the dispensing roller and is easily transferred to the release film.

[0230] If the Shore hardness of the dispensing roller is too low, the roller is prone to deformation. During the extrusion process between the gravure roller and the dispensing roller, the raised structure of the roller is easily deformed, leading to deformation of the dot-like protrusions transferred to the release film. Conversely, if the Shore hardness of the dispensing roller is too high, processing becomes difficult, hardness consistency is poor, and the amount of paste transferred from the gravure roller to the dispensing roller is less, affecting the height of the dot-like protrusions. A Shore hardness of 70-75 for the raised structure of the dispensing roller facilitates processing, ensures hardness consistency, increases paste transfer volume, and thus guarantees the height of the dot-like protrusions during dotting, while also ensuring the integrity and consistency of the morphology of multiple dot-like protrusions.

[0231] In some embodiments, the protrusion structure is shaped like a frustum.

[0232] In some embodiments, the dotting roller further includes a gravure roller, the surface of which includes a plurality of protrusions arranged in a honeycomb hexagonal structure along the axial and circumferential directions of the gravure roller.

[0233] The raised dots on the surface of the gravure roller are arranged in a honeycomb hexagonal pattern, which helps to adhere more paste, thereby transferring enough paste to the dispensing roller and increasing the height of the raised dots.

[0234] The line count of a gravure roller can range from 40 lines / inch to 100 lines / inch.

[0235] In some embodiments, the pressing depth of the gravure roller toward the dispensing roller is 10 μm to 30 μm.

[0236] The zero displacement is defined as the state where the gravure roller and the dispensing roller are just in contact but not under any force. The extrusion depth of the gravure roller and the dispensing roller is controlled by a displacement sensor. When the extrusion depth from the gravure roller to the dispensing roller is greater than or equal to 10μm, the amount of paste transfer meets the requirements and a high dot height can be maintained. When the extrusion depth is less than or equal to 30μm, the amount of paste adhesion can be controlled more precisely, improving the uniformity of the dotting.

[0237] In some embodiments, during the preparation of the adhesive layer, the substrate moving speed is 60 m / min to 150 m / min, optionally 80 m / min to 120 m / min. This can improve the integrity of the slurry points and reduce tailing and sticking phenomena while meeting production efficiency requirements.

[0238] In some embodiments, the drying temperature used during drying is 55°C to 75°C, and optionally 60°C to 70°C. Adjusting the drying temperature helps to control the area coverage within an optimal range.

[0239] [Battery Device]

[0240] In some embodiments, the secondary battery is a single battery cell, which can be the smallest structural unit of the battery.

[0241] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0242] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0243] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 5 shows a square battery cell 3 as an example.

[0244] In some embodiments, referring to FIG5, the battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31. The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 has an opening communicating with the receiving cavity, and the end cap assembly 32 can be closed by covering the opening. The end cap assembly 32 includes electrode terminals 322, as shown in FIG5, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal. The electrode assembly 33 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 33. The positive electrode sheet, negative electrode sheet, and separator can be formed into the electrode assembly 33 by a winding process or a stacking process. The electrode assembly 33 includes an electrode assembly body 330 and tabs 331 extending from the electrode assembly body 330. The battery cell 3 also includes a connecting member 34, which is used to connect the tabs 331 and the electrode terminals 322 of the electrode assembly 33. The battery cell 3 may contain one or more electrode assemblies 33, which can be selected by those skilled in the art according to specific practical needs.

[0245] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0246] In some embodiments, the battery device includes at least one of a battery module and a battery pack.

[0247] Figure 6 is a schematic diagram of the structure of a battery device according to an embodiment of this application. For example, as shown in Figure 6, the battery device 4 is a battery pack. The battery pack may include a housing and multiple battery cells 3 housed in the housing. The multiple battery cells 3 are connected in series, parallel, or mixed connections. The battery cells 3 can directly form a battery pack, or they can first form battery modules, and then multiple battery modules form a battery pack. Referring to Figure 6, in the battery device 4, the multiple battery cells 3 can be arranged sequentially along the length of the battery device 4. Of course, they can also be arranged in any other arbitrary manner. Furthermore, the multiple battery cells 3 can be fixed using fasteners.

[0248] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 3 are received.

[0249] [Electrical appliances]

[0250] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0251] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0252] Figure 7 shows an example of an electrical device 5. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0253] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0254] [Example]

[0255] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0256] Example 1

[0257] Preparation of positive electrode sheet

[0258] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 and mixed thoroughly to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil. After drying, rolling, and slitting, a coating weight of 391 mg / cm³ was obtained. 2 The compacted density is 2.63 g / cm³. 3 The positive electrode sheet.

[0259] Preparation of negative electrode sheet

[0260] Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) were mixed in a weight ratio of 96.4:0.7:1:8:1.1. Deionized water was added, and the mixture was stirred in a vacuum mixer to form a negative electrode slurry. After drying, the slurry was cold-pressed, trimmed, cut, and slit to obtain the negative electrode sheet. The coating weight was 178 mg / cm³. 2 The compacted density is 1.65 g / cm³. 3 The negative electrode sheet.

[0261] Separating membrane

[0262] A ceramic coating with a total thickness of 2 μm was applied to both sides of a 7 μm thick polyethylene porous film with a porosity of 40%. (The slurry for the ceramic coating can be prepared by mixing inorganic ceramic particles of alumina (Al2O3), polymethyl methacrylate binder, dispersant sodium carboxymethyl cellulose (CMC-Na), and wetting agent organosilicon modified polyether in a mass ratio of 93:6:0.5:0.5 in an appropriate amount of deionized water.)

[0263] Organic particles and binder are mixed evenly in an appropriate amount of deionized water at a solid content mass ratio of 9:1 to obtain a binder slurry; wherein the binder includes a linear copolymer having hydroxyl, carboxyl, amide and epoxy groups.

[0264] The organic particles have a volume average particle size Dv50 of 12 μm and are composed of a first organic particle and a second organic particle with a mass ratio of 1:1. The first organic particle is a fluorinated organic particle and the second organic particle is a non-fluorinated organic particle. Specifically, the first organic particle is a fluorinated organic particle of polyvinylidene fluoride (PVDF) and the second organic particle is a polyacrylate.

[0265] The solid content of the adhesive layer slurry was determined to be 20%.

[0266] The adhesive layer slurry is transferred to the gravure roller through the material box. The gravure roller and the dispensing roller are transferred to the dispensing roller through extrusion (the degree of extrusion is controlled by displacement sensors of the gravure roller and the dispensing roller). The slurry on the dispensing roller is transferred to the release film substrate through contact. The raised structure on the surface of the dispensing roller is a frustum-shaped structure with a top diameter of 220μm and a bottom diameter of 320μm. The center distance between two adjacent raised structures in the axial direction is 500μm, the center distance between two adjacent raised structures in the circumferential direction is 550μm, and the height of the raised structure is 200μm. The coating speed of the dot coating process is 100m / min, and the speed ratio of the gravure roller and the dispensing roller is 1:1, forming multiple dot-shaped raised structures. After the first adhesive layer is coated, the release film enters the oven to dry the first adhesive layer slurry. The oven temperature is 55-60℃. The release film conveyor belt passes through a flipping mechanism for the second adhesive layer to be applied, following the same process as the first adhesive layer application. However, in the dispensing roller for the second adhesive layer, the center-to-center distance between two adjacent protrusions along the circumferential direction of the roller is 500 μm, and the center-to-center distance between two adjacent protrusions along the axial direction is 550 μm. The film then re-enters the drying oven to dry the slurry, resulting in the final dotted release film. The basis weight of the adhesive layer is 1.2 g / m³. 2 The center-to-center distance between adjacent point protrusions in the first adhesive layer of the separator along the width direction of the separator (i.e., the first direction) is 501 μm, the center-to-center distance between adjacent point protrusions in the adhesive layer along the second direction (i.e., the length direction of the separator) is 550 μm, the center-to-center distance between adjacent point protrusions in the second adhesive layer of the separator along the first direction is 552 μm, and the center-to-center distance between adjacent point protrusions in the adhesive layer along the second direction is 500 μm.

[0267] Preparation of electrolyte

[0268] The organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 30:70 to obtain a mixed solvent. Then, a fully dried lithium salt (LiPF6) is dissolved in the above mixed solvent at a ratio of 1 mol / L to obtain an electrolyte.

[0269] Preparation of secondary batteries

[0270] The positive electrode, separator, and negative electrode are prepared in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound, hot-pressed, shaped, and welded to obtain the electrode assembly. The electrode assembly is placed in a square aluminum shell, vacuum-dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0271] Example 2

[0272] Compared with Example 1, the solid content of the adhesive layer slurry in Example 2 is 15.7%, the height of the dot-shaped protrusions in the corner area is 25.6 μm, the height of the dot-shaped protrusions in the first area of ​​the planar area is 1.09 μm, and the height of the dot-shaped protrusions in the second area is 27.6 μm.

[0273] Example 3

[0274] Compared with Example 1, the solid content of the adhesive layer slurry in Example 3 is 18.5%, the height of the dot-shaped protrusions in the corner area is 26.8 μm, the height of the dot-shaped protrusions in the first area of ​​the planar area is 1.15 μm, and the height of the dot-shaped protrusions in the second area is 29 μm.

[0275] Example 4

[0276] Compared with Example 1, the solid content of the adhesive layer slurry in Example 4 is 22.0%, the height of the dot-shaped protrusions in the corner area is 30.4 μm, the height of the dot-shaped protrusions in the first area of ​​the planar area is 1.29 μm, and the height of the dot-shaped protrusions in the second area is 32.5 μm.

[0277] Example 5

[0278] Compared with Example 1, in Example 5, the dot-shaped protrusion material Dv50 is 5μm, the solid content of the adhesive layer slurry is 19.8%, the height of the dot-shaped protrusion in the corner area is 6.8μm, the height of the dot-shaped protrusion in the first area of ​​the planar area is 0.78μm, and the height of the dot-shaped protrusion in the second area is 8.1μm.

[0279] Example 6

[0280] Compared with Example 1, in Example 6, the dot-shaped protrusion material Dv50 is 7μm, the solid content of the adhesive layer slurry is 20.0%, the height of the dot-shaped protrusions in the corner area is 16.5μm, the height of the dot-shaped protrusions in the first area of ​​the planar area is 0.83μm, and the height of the dot-shaped protrusions in the second area is 18.6μm.

[0281] Example 7

[0282] Compared with Example 1, in Example 7, the dot-shaped protrusion material Dv50 is 20 μm, the solid content of the adhesive layer slurry is 20.2%, the height of the dot-shaped protrusions in the corner area is 33.4 μm, the height of the dot-shaped protrusions in the first area of ​​the planar area is 1.52 μm, and the height of the dot-shaped protrusions in the second area is 35.3 μm.

[0283] Example 8

[0284] Compared with Example 1, in Example 8, the center-to-center distance between two adjacent dot-shaped protrusions of the first adhesive layer along the first direction is 402 μm.

[0285] Example 9

[0286] Compared with Example 1, in Example 9, the center-to-center distance between two adjacent dot-shaped protrusions of the first adhesive layer along the first direction is 602 μm.

[0287] Example 10

[0288] Compared with Example 1, in Example 10, the diameter of the dot-shaped protrusions in the first adhesive layer is 220 μm, the diameter of the dot-shaped protrusions in the second adhesive layer is 222 μm, the coverage of the first adhesive layer is 14.1%, and the coverage of the second adhesive layer is 13.8%.

[0289] Example 11

[0290] Compared with Example 1, in Example 11, the diameter of the dot-shaped protrusions in the first adhesive layer is 305 μm, the diameter of the dot-shaped protrusions in the second adhesive layer is 310 μm, the coverage of the first adhesive layer is 26.9%, and the coverage of the second adhesive layer is 27.3%.

[0291] Example 12

[0292] Compared with Example 1, in Example 12, the diameter of the dot-shaped protrusions in the first adhesive layer is 280 μm, the diameter of the dot-shaped protrusions in the second adhesive layer is 283 μm, the coverage of the first adhesive layer is 22.6%, and the coverage of the second adhesive layer is 22.7%.

[0293] Example 13

[0294] Compared with Example 1, in Example 13, the diameter of the dot-shaped protrusions in the first adhesive layer is 310 μm, the diameter of the dot-shaped protrusions in the second adhesive layer is 220 μm, the coverage of the first adhesive layer is 27.3%, and the coverage of the second adhesive layer is 14.1%.

[0295] Example 14

[0296] Compared with Example 1, in Example 14, the center-to-center distance between two adjacent dot-shaped protrusions in the first direction of the first adhesive layer is 480 μm, and the center-to-center distance between adjacent dot-shaped protrusions in the second direction is 530 μm; in the second adhesive layer, the center-to-center distance between adjacent dot-shaped protrusions in the first direction is 531 μm, and the center-to-center distance between adjacent dot-shaped protrusions in the second direction is 482 μm. The coverage of the first adhesive layer is 21.6%, and the coverage of the second adhesive layer is 20.7%.

[0297] Example 15

[0298] Compared with Example 1, in Example 15, the center-to-center distance between adjacent point protrusions in the first direction of the first adhesive layer is 530 μm, and the center-to-center distance between adjacent point protrusions in the second direction is 580 μm; in the second adhesive layer, the center-to-center distance between adjacent point protrusions in the first direction is 580 μm, and the center-to-center distance between adjacent point protrusions in the second direction is 528 μm. The coverage of the first adhesive layer is 17.6%, and the coverage of the second adhesive layer is 17.2%.

[0299] Comparative Example 1

[0300] Compared with Example 1, the solid content of the adhesive layer slurry in Comparative Example 1 is %, the dot protrusion material Dv50 is 3μm, the dot protrusion height in the corner area is 1.5μm, the dot protrusion height in the first area of ​​the planar area is 0.32μm, and the dot protrusion height in the second area is 5.7μm.

[0301] Comparative Example 2

[0302] Compared to Example 1, Comparative Example 2 uses a spray coating method: A slurry for the release membrane adhesive layer is applied to both sides of a 7 μm thick polyethylene porous film with a porosity of 40% to form a ceramic coating with a total thickness of 2 μm. (The ceramic coating slurry can be prepared as follows: inorganic ceramic particles (Al2O3), polymethyl methacrylate binder, dispersant sodium carboxymethyl cellulose (CMC-Na), and wetting agent organosilicon-modified polyether are mixed evenly in a suitable amount of deionized water at a mass ratio of 93:6:0.5:0.5). Organic particles and binder are stirred evenly in a suitable amount of deionized water at a solid content mass ratio of 9:1 to obtain the adhesive layer slurry. The organic particles have a volume average particle size (Dv50) of 12 μm and consist of a first organic particle and a second organic particle in a mass ratio of 1:1. The first organic particle is a fluorinated organic particle, and the second organic particle is a non-fluorinated organic particle. Specifically, the first organic particle is a fluorinated organic particle (polyvinylidene fluoride, PVDF); the second organic particle is a polyacrylate. The binder includes linear copolymers having hydroxyl, carboxyl, amide, and epoxy groups.

[0303] The solid content of the adhesive layer slurry was determined to be 20.0%.

[0304] The adhesive slurry is atomized into small droplets by a spraying mechanism. The release membrane conveyor enters the atomization chamber of the spraying mechanism, where the droplets are transferred to the release membrane by gravity and centrifugal force. The spraying speed is 100 m / min. The release membrane is then dried in an oven at 55℃~60℃ to obtain the final sprayed release membrane. The height of the dot-shaped protrusions in the corner area is 28.1 μm, the height of the dot-shaped protrusions in the first region of the planar area is 1.19 μm, and the height of the dot-shaped protrusions in the second region is 32.2 μm.

[0305] Comparative Example 3

[0306] Compared with Example 1, in Comparative Example 3, the center-to-center distance between two adjacent dot-shaped protrusions of the first adhesive layer along the first direction is 700 μm.

[0307] Comparative Example 4

[0308] Compared with Example 1, in Comparative Example 4, the center-to-center distance between two adjacent dot-shaped protrusions of the first adhesive layer along the first direction is 350 μm.

[0309] The secondary batteries obtained in Examples 1-15 and Comparative Examples 1-4 were subjected to parameter and performance tests.

[0310] Cyclic life test

[0311] At 25℃, the battery cell was charged at a constant current rate of 1C to the charging cutoff voltage of 4.2V, then charged at a constant voltage until the current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to the discharge cutoff voltage of 2.8V, allowed to stand for 5 minutes. The battery capacity C0 at this point was recorded. The battery cell was subjected to 1000 charge-discharge cycles using this method, and the battery cell capacity after 1000 cycles was recorded as C1.

[0312] The cycle capacity retention rate of a single battery cell at 25°C = C1 / C0 × 100%.

[0313] Among them, the higher the capacity retention rate, the longer the cycle life of the battery cell.

[0314] Breathability test

[0315] Air permeability refers to the time it takes for a certain volume of air to pass through a unit area of ​​paper or cardboard under specified conditions and pressure. The air permeability test for release films is conducted according to GB / T 458-2008, with an air column volume of 100cc and a test area of ​​1 square inch.

[0316] Adhesion test

[0317] Select a separator membrane with a length of 300 mm and a width of 100 mm, as well as the positive and negative electrode sheets prepared above. Wrap the separator membrane with paper on both sides and cut it into 54.2 mm × 72.5 mm samples using a die and a punch. Neatly stack the cut separator membrane samples with the positive electrode sheet, placing 130 mm × 130 mm Teflon sheets on both sides. Place the stacked samples in the middle of a 200 mm × 200 mm cardboard sheet, and cover them with another 150 mm × 160 mm cardboard sheet. Place the stacked samples into a flatbed press and adjust the pressure. The flatbed press pressure is set to 1964 kg ± 10 kg (the contact area is approximately 54.2 mm × 72.5 mm, which translates to an actual pressure of approximately 5 MPa). Set T = 25 °C and the time to 10 s for pressing. Use a die and a punch to cut the hot-pressed samples into 72.5 mm × 15 mm strips. One side of the positive electrode sheet is fixed to the steel plate using double-sided tape, and the other side is bonded to the first adhesive layer of the separator. A 15mm wide strip of A4 paper is then attached to the separator using double-sided tape to complete the test sample preparation. The high-speed rail tensile testing machine is turned on, and the parameters are set sequentially as follows: adhesive force test, speed 50mm / min, and initial clamp spacing 40mm. The test sample is placed between the clamps, with the end of the steel plate fixed to the lower clamp and the A4 paper to the upper clamp. The upper and lower clamps are then clamped. The tensile testing interface on the computer desktop is clicked, and the force and displacement parameters are zeroed. Then, "Start" is clicked to perform a pre-stretch of approximately 5mm. After the pre-stretch, the force and displacement parameters are zeroed again, and the test begins. During the test, the steel plate holding the electrode sheet is fixed, while the tensile testing machine pulls the A4 paper strip upwards, separating the separator from the positive electrode sheet. After the test is completed, the complete data is exported and saved. For each group, at least 5 test samples must be measured, and the repeatability of the adhesion test curves for the 5 test samples must be good before proceeding to the next group. Otherwise, the test needs to be repeated until the repeatability of the 5 test samples is good. After the test is completed, a adhesion strength (N / m)-displacement curve is plotted, and the average value of the 100th to 300th data points is taken as the adhesion force, which is recorded as F1. One side of the negative electrode sheet is fixed to the steel plate with double-sided adhesive, and the other side is bonded to the second adhesive layer of the separator. Using the above method, the adhesion force is measured and recorded as F2.

[0318] The test results for the above parameters are shown in Table 1-3.

[0319] Table 1: Specific parameters and test results of Examples 1-9 and Comparative Examples 1-4

[0320] As shown in Examples 1-9 and Comparative Example 1, the increased height of the dotted protrusions increases the adhesion of the adhesive layer, improves the cycle capacity retention rate, and enhances cycle performance.

[0321] As shown in Examples 1-9 and Comparative Example 2, the dot-coating method can improve the air permeability and adhesion of the separator, thereby improving the cycle performance of the battery cell.

[0322] As shown in Examples 1-7, a slurry solid content in the range of 15% to 22% can result in a higher dot-like protrusion height, providing sufficient expansion space for the corner area and improving circulation performance.

[0323] As shown in Examples 1 and 5-7, as the Dv50 of the organic particles in the dotted protrusions increases, the height of the dotted protrusions also increases. When the Dv50 of the organic particles is between 7μm and 20μm, it is beneficial to form dotted protrusions with a frustum shape, increasing the bonding sites and improving the adhesion of the separator. However, a smaller Dv50 can improve the air permeability of the separator. Therefore, when the Dv50 of the organic particles is between 5μm and 25μm, both the adhesion and air permeability of the separator can be balanced.

[0324] As shown in Examples 1, 8-9, and Comparative Examples 3-4, when the center-to-center distance between adjacent dot-shaped protrusions is between 360 μm and 650 μm, both the air permeability of the separator and the expansion space of the battery cell can be balanced, thus improving the cycle performance of the battery cell. As the center-to-center distance between adjacent dot-shaped protrusions in the separator's adhesive layer increases, the air permeability of the separator improves, which is beneficial for increasing the ion transport efficiency of the separator.

[0325] Table 2: Specific parameters and test results of Examples 1 and 10-13

[0326] As shown in Examples 1 and 10-13, as the diameter of the dotted protrusions increases, the coverage of the adhesive layer increases accordingly, the air permeability of the separator decreases, but the adhesion increases. When the diameter of the dotted protrusions is between 210μm and 310μm, it is beneficial to balance the air permeability and adhesion of the separator, thereby improving the cycle performance of the battery cell.

[0327] Table 3: Specific parameters and test results of Examples 1 and 14-15

[0328] As shown in Examples 1 and 14-15, with the diameter of the dotted protrusions remaining constant, the coverage of the adhesive layer decreases as the spacing between the dotted protrusions increases, the air permeability of the separator is improved, and the adhesion force can be kept within a suitable range, which is beneficial to improving the cycle performance of the battery cells.

[0329] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, include: Positive electrode, negative electrode, and separator; The positive electrode, negative electrode, and separator are wound together to form a wound structure, which includes corner areas at both ends and a planar area connecting the corner areas. The isolation membrane includes a substrate and an adhesive layer. The adhesive layer is disposed on at least one surface of the substrate and includes a plurality of dot-shaped protrusions arranged at predetermined intervals. The height of the dot-shaped protrusions in the corner area is 5 μm to 35 μm. The center-to-center distance between two adjacent dot-shaped protrusions is 360μm to 650μm.

2. The battery cell according to claim 1, characterized in that, The height of the dot-shaped protrusions in the corner area is 8μm to 30μm.

3. The battery cell according to claim 1 or 2, characterized in that, The planar region includes a first region and a second region that are adjacent to each other along the width direction of the separator. The first region is the projection area of ​​the positive electrode sheet in the separator along a direction perpendicular to the separator. The height of the dot-shaped protrusions in the first region is 0.5μm to 2μm. The height of the dot-shaped protrusions in the second region is 8μm to 40μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The center-to-center distance between two adjacent dot-shaped protrusions is 480μm to 580μm.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The diameter of the dot-shaped protrusion is 210μm to 310μm, and optionally, the diameter of the dot-shaped protrusion is 240μm to 280μm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The adhesive layer has an area coverage of 12% to 28% on one side of the substrate, and optionally, the area coverage is 16% to 23%.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The dotted protrusions include organic particles, which include at least one of non-fluorinated organic particles and fluorinated organic particles.

8. The battery cell according to claim 7, characterized in that, The non-fluorinated organic particles satisfy one or more of the following conditions: The non-fluorinated organic particles have a first glass transition temperature Tg1 and a second glass transition temperature Tg2, and 100℃>Tg1>Tg2. Optionally, Tg1 is 26℃~54℃, and / or Tg2 is 0℃~25℃. The non-fluorinated organic particles include at least two types of monomer units selected from acrylate monomer units, acrylic monomer units, vinyl monomer units, unsaturated nitrile monomer units, and amide monomer units. The non-fluorinated organic particles comprise a first polymer and a second polymer, wherein the first polymer and / or the second polymer comprises one or more copolymers containing acrylate monomer units, copolymers containing acrylic monomer units, and copolymers containing vinyl monomer units. Optionally, the first polymer and / or the second polymer comprises at least one of carboxyl, amide, and cyano groups.

9. The battery cell according to claim 7 or 8, characterized in that, The fluorinated organic particles satisfy one or more of the following conditions: The fluorinated organic particles include polymers with melting points of 139°C to 154°C. The fluorinated organic particles comprise polymers with a number average molecular weight of 400,000 to 650,000. The fluorinated organic particles comprise fluorinated polymers, wherein the fluorinated polymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorinated alkenyl monomer units, copolymers of fluorinated alkenyl monomer units and vinyl monomer units, copolymers of fluorinated alkenyl monomer units and acrylic monomer units, copolymers of fluorinated alkenyl monomer units and acrylate monomer units, and one or more modified compounds of the above homopolymers or copolymers.

10. The battery cell according to any one of claims 7 to 9, characterized in that, The volume average particle size Dv50 of the organic particles is 5 μm to 25 μm.

11. The battery cell according to claim 10, characterized in that, The volume average particle size Dv50 of the organic particles is 7 μm to 20 μm.

12. The battery cell according to claim 11, characterized in that, The dot-shaped protrusions include a platform area and an edge area surrounding the platform area, wherein the minimum height of the platform area is not less than the maximum height of the edge area.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The adhesive layer also includes invalid protrusions, the diameter of which is less than 100 μm; The ratio of the number of invalid protrusions to the number of dot-shaped protrusions is less than or equal to 5:

95.

14. The battery cell according to any one of claims 1 to 13, characterized in that, The positive electrode sheet includes a positive active material, and the negative electrode sheet includes a negative active material; The positive electrode active material is a lithium phosphate, and the compaction density of the positive electrode sheet is 2.6 g / cm³. 3 ~2.8g / cm 3 Alternatively, the positive electrode active material is lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, and the compaction density of the positive electrode sheet is 3.4 g / cm³. 3 ~3.7g / cm 3 ; and / or, The negative electrode active material includes silicon-based materials.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The release membrane includes a first adhesive layer and a second adhesive layer respectively disposed on two surfaces of the substrate. The first adhesive layer includes a plurality of first dot-shaped protrusions disposed at a first predetermined interval, and the second adhesive layer includes a plurality of second dot-shaped protrusions disposed at a second predetermined interval.

16. The battery cell according to claim 15, characterized in that, The first dot-shaped protrusion includes a first organic particle, and the second dot-shaped protrusion includes a second organic particle, wherein the first organic particle and the second organic particle are made of different materials.

17. The battery cell according to claim 15 or 16, characterized in that, The first predetermined interval is different from the second predetermined interval.

18. The battery cell according to any one of claims 15 to 17, characterized in that, In a direction perpendicular to the separating membrane, the center of the first dotted protrusion in the first adhesive layer coincides with the center of at least a portion of the second dotted protrusion in the second adhesive layer.

19. The battery cell according to any one of claims 15 to 18, characterized in that, The first adhesive layer includes a plurality of adjacent first repeating units, each of which includes a plurality of first dot-shaped protrusions. The plurality of first dot-shaped protrusions are arranged at a third predetermined interval in a first direction and at a fourth predetermined interval in a second direction. The third predetermined interval is different from the fourth predetermined interval, and the first direction is perpendicular to the second direction. The second adhesive layer includes a plurality of adjacent second repeating units, each second repeating unit including a plurality of second dot-shaped protrusions, the plurality of second dot-shaped protrusions being arranged at the fourth predetermined interval in the first direction and at the third predetermined interval in the second direction.

20. A separating membrane, characterized in that, include: A substrate and an adhesive layer, the adhesive layer being disposed on at least one surface of the substrate; The adhesive layer includes a plurality of dot-shaped protrusions arranged at predetermined intervals; The height of the dot-shaped protrusions is 8μm to 40μm, and optionally, the height of the dot-shaped protrusions is 15μm to 35μm. The center-to-center distance between two adjacent dot-shaped protrusions is 360μm to 650μm.

21. The separator according to claim 20, characterized in that, The isolation membrane satisfies one or more of the following conditions: The diameter of the dot-shaped protrusion is 210μm to 310μm, and optionally, the diameter of the dot-shaped protrusion is 240μm to 280μm; The center-to-center distance between two adjacent dot-shaped protrusions is 480μm to 580μm; The dot-like protrusions include at least one of non-fluorinated organic particles and fluorinated organic particles. The adhesive forces of the adhesive layers on both sides of the substrate are different.

22. A method for preparing a separating membrane, characterized in that, include: The slurry is applied to the surface of the substrate by a dotting roller and dried to form an adhesive layer including multiple dot-shaped protrusions to obtain a release film. The solid content of the slurry is 15% to 22%, and optionally, the solid content of the slurry is 16% to 20%.

23. The method according to claim 22, characterized in that, The dispensing roller includes a dispensing roller with a plurality of raised structures arranged at predetermined intervals along the axial and circumferential directions of the dispensing roller.

24. The method according to claim 23, characterized in that, The contact angle between the protruding structure material and the slurry is 65° to 75°. The Shore hardness of the material used for the raised structure is 70 to 75.

25. The method according to claim 23 or 24, characterized in that, The protruding structure is shaped like a frustum.

26. The method according to any one of claims 22 to 25, characterized in that, The dotting roller also includes a gravure roller, the surface of which includes a plurality of protrusions arranged in a honeycomb hexagonal structure along the axial and circumferential directions of the gravure roller.

27. The method according to claim 26, characterized in that, The gravure roller has a line count of 40 lines / inch to 100 lines / inch.

28. The method according to claim 26 or 27, characterized in that, The pressing depth of the gravure roller onto the dispensing roller is 10μm to 30μm.

29. The method according to any one of claims 22 to 28, characterized in that, During the preparation of the adhesive layer, the moving speed of the substrate is 60m / min to 150m / min, and can be selected as 80m / min to 120m / min.

30. A battery, characterized in that, Includes a battery cell as described in any one of claims 1-19, and / or a separator as described in claim 20 or 21, and / or a separator prepared by the method as described in any one of claims 22-29.

31. An electrical device, characterized in that, Includes the battery as described in claim 30.

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