Battery cell, battery, and electrical apparatus

Abstract

The present application is applicable to the technical field of batteries, and provides a battery cell, a battery, and an electrical apparatus. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator; the positive electrode sheet, the negative electrode sheet, and the separator are arranged layer by layer on the basis of a preset sequence and are wound to form a wound body; the positive electrode sheet, the negative electrode sheet, and the separator respectively comprises a plurality of straight portions and a plurality of bent portions that are alternately connected; at least one surface of at least one bent portion is coated with a non-continuously distributed coating. According to the battery cell, the battery, and the electrical apparatus provided by the present application, the risk of phenomena such as electrode sheet breakage and lithium precipitation at a corner can be reduced to a certain extent.

Description

Battery cells, batteries, and electrical devices

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on January 10, 2024, with application number 202410037817.X and invention name “Battery Cell, Battery and Electrical Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of battery technology, and in particular relates to a battery cell, a battery, and an electrical device. Background Art

[0003] During the battery's charge and discharge cycles, the insertion and extraction of ions from the positive and negative active materials, the accumulation of side reactions in the battery cell system, and the peeling of graphite sheets can cause the battery cells to swell, meaning the positive and negative electrodes expand outward. This can easily lead to electrode breakage and lithium deposition at the corners of the battery cells. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a battery cell, a battery, and an electrical device, aiming to improve the technical problem that the corners of the battery cell are prone to electrode breakage, lithium deposition, and the like. Technical Solutions

[0005] The technical solution adopted in the embodiment of this application is:

[0006] In the first aspect, an embodiment of the present application provides a battery cell comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet, the negative electrode sheet and the separator are stacked in a preset order and wound to form a wound body, and the positive electrode sheet, the negative electrode sheet and the separator respectively comprise a plurality of straight portions and a plurality of curved portions alternately connected; at least one side of at least one of the curved portions is coated with a non-continuously distributed coating.

[0007] The battery cell provided in the embodiment of the present application is coated with a discontinuously distributed coating on at least one side of at least one curved portion of at least one component among the positive electrode sheet, the negative electrode sheet and the diaphragm, thereby increasing the spacing between the positive electrode sheet and the negative electrode sheet at at least one corner, reserving the required space for the expansion of the negative electrode sheet and the positive electrode sheet at the corner, and can reduce the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of the battery cell at the corner having adverse conditions such as electrolyte starvation, electrode breakage, deformation, wrinkling, black spots, lithium deposition, etc., thereby improving the service life of the battery cell to a certain extent.

[0008] In addition, the coating used in the battery cell provided in the embodiment of the present application is discontinuously distributed. While playing the above-mentioned role, it can also retain sufficient electrolyte transmission channels, which can improve the cycle performance of the battery cell provided in the embodiment of the present application to a certain extent.

[0009] In some embodiments, the coating has a thickness of 5 μm to 100 μm. The coating has a thickness within the range provided in this embodiment, which can not only ensure that the spacing between the positive and negative electrode sheets at the corresponding corners is sufficiently large, leaving more room for the electrode sheets to expand, but also reduce to a certain extent the risk of problems such as increased lithium ion transmission distance at the corners and lithium plating caused by excessive spacing between the positive and negative electrode sheets.

[0010] In some embodiments, the coating has a thickness of 20 μm to 50 μm. The coating adopts the thickness range provided in this embodiment, which can not only make the spacing between the positive and negative electrode sheets at the corresponding corners sufficiently large, leaving more space for the electrode sheets to expand, but also reduce to a certain extent the risk of problems such as longer lithium ion transmission distance at the corners and lithium plating caused by excessive spacing between the positive and negative electrode sheets. At the same time, the coating thickness difference in different areas can be small, which can reduce to a certain extent the risk of tab misalignment.

[0011] In some embodiments, the coating is provided on both of the two curved portions in the same coil. Generally, the structures at both ends of the coil are roughly symmetrical and subject to similar forces. The structure provided in this embodiment can increase the spacing between the positive and negative electrode sheets at the corners at both ends of the coil, thereby improving the electrochemical performance of the battery cells in that coil.

[0012] In some embodiments, within a same circle, the coefficient of variation of the coating thickness is less than or equal to 15%.

[0013] By adopting the solution provided in this embodiment, the thickness fluctuation of the coating on the same curved portion can be reduced, so that the position of the tab after winding can be close to the designed position, thereby reducing the risk of tab misalignment to a certain extent.

[0014] In some embodiments, in the same circle, the coefficient of variation of the thickness of the coating is less than or equal to 10%. In some embodiments, the thickness of the coating gradually increases from the inner circle to the outer circle, and the thickness variation rate is less than or equal to 10%. Since the expansion force exerted on the outer circle is greater than the expansion force exerted on the inner circle, the coating provided by this embodiment can be used to increase the spacing between the positive electrode sheet and the negative electrode sheet from the inside to the outside along the stacking direction of the battery cell, thereby significantly reducing the expansion stress of the inner, middle and outer circles, so that the risk of fracture of each circle of the electrode is relatively small. The gradual increase in the coating thickness can not only reduce the risk of fracture of each circle of the electrode, but also reduce the energy density of the battery cell due to excessive coating thickness to a certain extent.

[0015] In some embodiments, the thickness of the coating gradually increases from the inner circle to the outer circle, and the thickness change rate is less than or equal to 5%. Using the coating provided in this embodiment, the spacing between the positive and negative electrode sheets can be gradually increased from the inside to the outside along the stacking direction of the battery cell, thereby significantly reducing the expansion stress of the inner, middle and outer layers, thereby reducing the risk of fracture in each layer of the electrode sheet. The gradual increase in coating thickness can not only reduce the risk of fracture in each layer of the electrode sheet, but also reduce the energy density of the battery cell due to excessive coating thickness to a certain extent.

[0016] In some embodiments, on at least one side of at least one of the curved portions, the coating has a coverage of less than or equal to 60%, where the coverage is the percentage of the sum of the coating application areas to the total coating distribution area. By employing the solution provided in this embodiment, the lithium ion conductivity of the surface of the discontinuously distributed coating within the battery cell can be ensured to meet the required performance, thereby ensuring that the dynamic performance of the battery cell meets the required performance.

[0017] In some embodiments, the coating has a coverage rate of less than or equal to 30% on at least one side of at least one of the curved portions, where the coverage rate is the percentage of the sum of the coating application areas to the total area of ​​the coating distribution area. By employing the solution provided in this embodiment, the coating can cover only a small portion of the corresponding curved portion, ensuring that the lithium ion conductivity of the surface of the battery cell where the coating is distributed discontinuously meets the requirements, thereby ensuring that the dynamic performance of the battery cell meets the requirements for use.

[0018] In some embodiments, the coating is arranged in an array or randomly on at least one side of at least one of the curved portions. When the coating is arranged in an array on at least one surface of at least one of the curved portions, design is facilitated. When the coating is arranged randomly on at least one surface of at least one of the curved portions, manufacturing is facilitated.

[0019] In some embodiments, the coating includes spaced-apart segments, each segment having a shape of one or more of regular lines, irregular lines, regular dots, and irregular dots. This embodiment reduces the size of each segment, covers a smaller area, and has minimal adverse effects on battery cell performance.

[0020] In some embodiments, when the split body is in the shape of a regular line or an irregular line, the width of the split body is less than or equal to 2 mm, and the length of the line is not limited. Using the solution provided by this embodiment, the size of a single split body can be made smaller, the coverage area can be smaller, and the adverse effect on the performance of the battery cell can be reduced.

[0021] In some embodiments, when the split body is in the shape of regular dots or irregular dots, the maximum size of the split body is greater than 0 mm and less than or equal to 2 mm. The solution provided by this embodiment can reduce the size of a single split body, reduce the coverage area, and minimize the adverse effects on battery cell performance.

[0022] In some embodiments, the spacing between the outer contours of adjacent split bodies is 0.01 mm to 5 mm. The spacing between two adjacent split bodies is within the range provided in this embodiment, so that the spacing between two adjacent split bodies is larger than the size of a single split body, thereby reducing the coverage of the coating, ensuring that the lithium ion conductivity of the surface of the discontinuously distributed coating in the battery cell meets the requirements, and ensuring that the dynamic performance of the battery cell meets the use requirements.

[0023] In some embodiments, multiple layers of the coating are provided along the stacking direction of the battery cells, and the thickness of all the coatings gradually increases from the inside to the outside. Because the expansion force on the outer layers is greater than that on the inner layers, the patented coating can be used to increase the spacing between the positive and negative electrode sheets from the inside to the outside along the stacking direction of the battery cells. This can significantly reduce the expansion stress of the inner, middle, and outer layers, thereby reducing the risk of fracture in each layer of the electrode sheet.

[0024] In some embodiments, at least one side of each curved portion of the positive electrode sheet is provided with the coating; and / or at least one side of each curved portion of the negative electrode sheet is provided with the coating; and / or at least one side of each curved portion of the separator is provided with the coating. Because the battery cell is a wound body with multiple turns, each turn has a curved portion, which poses risks of high stress and electrode sheet breakage. The solution provided in this embodiment can increase the spacing between the positive and negative electrode sheets at any corner, thereby reducing the risk of electrode sheet breakage and other problems at these corners.

[0025] In some embodiments, the coating has a thickness compression ratio of less than or equal to 30% under a first compression condition, wherein the first compression condition includes a pressure of 0.15 MPa to 0.25 MPa and a compression time of 100 to 140 seconds. This first compression condition is equivalent to the compression condition experienced by the coating during the winding process. The solution provided in this embodiment prevents the coating from being over-compressed after the battery cell is wound and formed, allowing it to retain a relatively high thickness. This effectively separates the positive and negative electrode sheets in the corresponding regions, meeting usage requirements.

[0026] In some embodiments, the first compression condition includes a pressure value of 0.2MPa and a compression time of 120s. The first compression condition adopts the numerical value provided in this embodiment, which is convenient for design and is closer to the compression condition to which the coating is subjected during the winding process, so that the winding effect after the coating is prepared is better. In some embodiments, the thickness compression rate of the coating under the second compression condition is ≥60%, and the second compression condition includes a pressure value of 2.5Mpa-3.5Mpa and a compression time of 100s-140s. The second compression condition is equivalent to the extrusion condition of the expansion force to which the coating is subjected when the battery cell is in use. After being subjected to the expansion force, the coating can be compressed to a greater extent, thereby releasing a larger space to reduce the stress on the pole piece and reduce the risk of problems such as pole piece breakage.

[0027] In some embodiments, the second compression condition includes a pressure of 3 MPa and a compression duration of 120 seconds. The second compression condition uses the values ​​provided in this embodiment for ease of design and is closer to the compression conditions experienced by the coating during use, which can, to a certain extent, reduce the risk of problems such as electrode breakage. In some embodiments, the coating comprises a polymer. The polymer is the film-forming material of the coating. Using a polymer coating provides a stable structure and facilitates fabrication.

[0028] In some embodiments, the polymer includes at least one of polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, polyvinyl pyrrolidone, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylate, polydimethylsiloxane, polystyrene, polyethylene, polypropylene, polyacrylate, polyacrylic acid, polybutadiene, sodium carboxymethyl cellulose, and derivatives thereof. The coating material has a stable structure and is easy to obtain and prepare.

[0029] In some embodiments, the coating further comprises an auxiliary binder, which plays a role of auxiliary bonding to further improve the bonding performance of the discontinuously distributed coating.

[0030] In some embodiments, the monomer of the auxiliary binder includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, and butadiene. The auxiliary binder is made of the materials provided in this embodiment, has a stable structure, and provides good bonding performance.

[0031] In some embodiments, the coating further comprises a wetting agent, which functions to reduce the surface energy of the slurry and enhance the affinity between the slurry and the substrate.

[0032] In some embodiments, the wetting agent includes at least one of dimethylsiloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer, and dioctyl sodium sulfosuccinate. The wetting agent is made from the materials provided in this embodiment, has a stable structure, and exhibits excellent wetting properties.

[0033] In a second aspect, an embodiment of the present application provides a battery, including a battery cell provided by any of the above embodiments, or including a battery cell provided by any of the above embodiments. The battery provided by an embodiment of the present application, including a battery cell according to any of the above solutions, or including a battery cell according to any of the above solutions, increases the spacing between the positive electrode sheet and the negative electrode sheet at at least one corner, reserves the required space for the expansion of the negative electrode sheet and the positive electrode sheet at the corner, and can reduce the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of the battery cell experiencing adverse conditions such as electrolyte starvation, electrode sheet breakage, deformation, wrinkling, black spots, and lithium deposition at the corner to a certain extent, thereby improving the service life of the battery cell to a certain extent.

[0034] In a third aspect, an embodiment of the present application provides an electrical device, comprising a battery provided by any of the above embodiments. The electrical device provided by an embodiment of the present application, comprising a battery according to any of the above schemes, increases the spacing between the positive and negative electrode sheets at at least one corner, reserving the required space for the expansion of the negative and positive electrode sheets at the corner, thereby reducing the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of adverse conditions such as electrolyte starvation, electrode breakage, deformation, wrinkling, black spots, and lithium deposition in the battery cell at the corner to a certain extent, thereby improving the service life of the battery cell to a certain extent.

[0035] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] FIG1 is a schematic structural diagram of a vehicle according to some embodiments of the present application;

[0038] FIG2 is a schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0039] FIG3 is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0040] FIG4 is a schematic cross-sectional view of an electrode assembly in a battery cell according to some embodiments of the present application;

[0041] FIG5 is a schematic structural diagram of the innermost pole piece in a battery cell according to some embodiments of the present application;

[0042] FIG6 is a schematic diagram of a single-circle cross-sectional structure of a positive electrode sheet in a battery cell according to some embodiments of the present application;

[0043] FIG7 is a schematic diagram of the cross-sectional structure of a coating layer in a battery cell according to some embodiments of the present application;

[0044] FIG8 is a schematic diagram of a single-circle cross-sectional structure of a positive electrode sheet in a battery cell according to some other embodiments of the present application;

[0045] FIG9 is a schematic diagram of a single-circle cross-sectional structure of a positive electrode sheet in a battery cell according to some other embodiments of the present application;

[0046] FIG10 is a schematic cross-sectional view of an electrode assembly in a battery cell according to some other embodiments of the present application;

[0047] FIG11 is a schematic cross-sectional view of a partial structure of a battery cell according to some other embodiments of the present application.

[0048] The figure numbers in the specific implementation manner are as follows: 1000, vehicle; 100, battery, 200, controller, 300, motor; 10, casing, 11, first part, 12, second part; 20, battery cell, 21, end cover, 21a, electrode terminal, 22, shell, 23, electrode assembly, 23a, tab; 24, coating; 231, positive electrode sheet, 232, negative electrode sheet, 233, diaphragm, 234, straight part, 235, curved part, 236, coating, 236a, split, 237, innermost electrode sheet, 238, first sheet; d, thickness of coating, a, size of split in at least one direction, b, spacing between two adjacent splits. DETAILED DESCRIPTION

[0049] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0051] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0052] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0053] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, "and / or B" can represent three situations: the existence of "A" alone, the existence of "B" and "B" at the same time, and the existence of "B" alone. In addition, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0054] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0055] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0056] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0057] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0058] The electrode assembly is an important component of the battery. Based on the method of manufacturing, it can be divided into wound electrode assemblies and laminated electrode assemblies. Of these, wound electrode assemblies are widely used due to their ease of operation and ease of quality control.

[0059] A wound electrode assembly typically consists of a negative electrode sheet, a positive electrode sheet, and a separator arranged in a predetermined sequence. The positive and negative electrode sheets, respectively, typically consist of a current collector and an active material layer coated on the current collector. Wound electrode assemblies can be square or cylindrical in shape. Square wound electrode assemblies are widely used due to their advantages such as good heat dissipation and safety.

[0060] During the battery's charge and discharge cycles, the positive and negative active materials embed or extract ions, the side reaction accumulation thickness of the battery cell system, and the peeling of graphite sheets cause the battery cells to swell, that is, the positive and negative electrodes expand outward. The expansion of the electrode sheets has an adverse effect on the performance and service life of the battery. For example, forced extrusion may cause the electrode porosity to decrease, affecting the infiltration of the electrolyte into the electrode sheet, causing changes in the ion transmission path and bringing about lithium deposition problems; when the electrode sheet is subjected to large extrusion forces for a long time, it may also break, causing the risk of short circuits in the battery, etc. Especially at the corners of the battery cell, the stress generated by the expansion of the electrode sheet is greater, making it more likely to experience electrolyte starvation and lithium deposition at this location, resulting in a decrease in battery performance, and in severe cases, safety issues.

[0061] To address the aforementioned issues, embodiments of the present application provide a battery cell. This battery cell has a discontinuously distributed coating applied to at least one side of at least one curved portion of at least one of the components: the positive electrode sheet, the negative electrode sheet, and the separator. This increases the spacing between the positive and negative electrode sheets at at least one corner, reserving the required space for expansion of the negative and positive electrode sheets at that corner. This can, to a certain extent, reduce the stress on the battery cell at that corner, thereby reducing the risk of adverse conditions such as electrolyte starvation, electrode sheet breakage, deformation, wrinkling, black spots, and lithium deposition at that corner, thereby improving the battery cell's service life to a certain extent.

[0062] The battery cells disclosed in the embodiments of the present application can be used in batteries, electrical devices using batteries as power sources, or various energy storage systems using batteries as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery-powered vehicles, electric vehicles, ships, spacecraft, and the like. Electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, among others.

[0063] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0064] Please refer to Figure 1, which is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0065] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0066] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc. In some cases, the battery cells can also be directly installed in the vehicle without a box or shell, that is, there is no need to form a battery pack, and the structure of the vehicle body itself serves as the fixing structure of the battery cells.

[0067] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0068] Each battery cell 20 may be a secondary battery or a primary battery, and may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0069] Please refer to Figure 3, which is a schematic diagram of the exploded structure of a battery cell 20 provided in some embodiments of the present application. A battery cell 20 is the smallest unit that makes up a battery. As shown in Figure 3, a battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0070] The end cap 21 is a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the end cap 21 can be adapted to the shape of the housing 22 to fit the housing 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as an aluminum alloy). This prevents the end cap 21 from deforming when subjected to compression or collision, thereby providing the battery cell 20 with greater structural strength and improved safety. The end cap 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect to the electrode assembly 23 for inputting or outputting electrical energy from the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for relieving internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cap 21 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any particular limitations on this. In some embodiments, an insulating member may be provided inside the end cap 21 to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be made of plastic, rubber, or the like.

[0071] The housing 22 is a component that cooperates with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and end cap 21 can be separate components. An opening can be provided in the housing 22, and the end cap 21 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and housing 22 can be integrated. Specifically, the end cap 21 and housing 22 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 22 needs to be enclosed, the end cap 21 is placed over the housing 22. The housing 22 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, or a hexagonal prism. Specifically, the shape of the housing 22 can be determined based on the specific shape and size of the electrode assembly 23. The housing 22 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any particular limitations on this.

[0072] The electrode assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more electrode assemblies 23 may be contained in the housing 22. The electrode assembly 23 is mainly formed by winding a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the positive electrode sheet and the negative electrode sheet. The parts of the positive electrode sheet and the negative electrode sheet with active materials constitute the main body of the electrode assembly, and the parts of the positive electrode sheet and the negative electrode sheet without active materials each constitute a tab 23a. The positive electrode tab and the negative electrode tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the tab 23a connects the electrode terminal to form a current loop.

[0073] As shown in Figure 4, an embodiment of the present application provides a battery cell. The battery cell includes a positive electrode sheet 231, a negative electrode sheet 232, and a separator 233. The positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 are stacked in a predetermined order and wound to form a jellyroll. The positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 each include a plurality of alternating straight portions 234 and a plurality of curved portions 235. At least one side of at least one curved portion 235 is coated with a discontinuously distributed coating 236.

[0074] The battery cell in this embodiment includes a square wound electrode assembly. The battery cell may include a positive electrode sheet 231 and a negative electrode sheet 232, or may include multiple positive electrode sheets 231 and multiple negative electrode sheets 232, with a separator 233 disposed between any two electrode sheets. In the embodiment where the battery cell includes a positive electrode sheet 231 and a negative electrode sheet 232, the negative electrode sheet 232, the separator 233, and the positive electrode sheet 231 are generally stacked in a predetermined order of positive electrode sheet 231, separator 233, negative electrode sheet 232, separator 233, or negative electrode sheet 232, separator 233, positive electrode sheet 231, separator 233. In the embodiment where the wound battery cell uses multiple negative electrode sheets 232 and multiple positive electrode sheets 231, the stacking principle of the negative electrode sheet 232, separator 233, and positive electrode sheet 231 is equivalent to that of the above-mentioned embodiment and will not be described in detail here.

[0075] A wound body refers to a flat multi-turn wound body formed by winding the positive electrode sheet 231, the negative electrode sheet 232 and the separator 233 stacked in a preset order. Winding molding refers to winding the separator 233 and at least two electrode sheets stacked in a preset order around a virtual axis, and forming a flat wound body after hot pressing or cold pressing. The flat wound body is a multi-turn winding structure. As shown in Figure 5, the innermost circle electrode sheet 237 is composed of two mutually connected and oppositely arranged sheets, and the longer of the two sheets is recorded as the first sheet 238. As shown in Figure 6, except for the innermost circle electrode sheet, each circle electrode sheet of the flat wound body includes two oppositely arranged straight portions 234 and two curved portions 235 connecting the two adjacent straight portions 234. It should be noted that, in the pole pieces located in the same circle, one of the curved portions 235 is used to connect the two straight portions 234 in the pole piece of the circle, such as the curved portion 235 located on the left side in Figure 6, and the other curved portion 235 is used to connect one of the straight portions 234 in the pole piece of the circle and one of the straight portions 234 in the pole piece of another circle, such as the curved portion 235 located on the right side in Figure 6.

[0076] For ease of definition, the portion of each pole piece circle corresponding to the position of the first plate 238 and having a similar length can be defined as a straight portion 234, and the portion connecting two adjacent straight portions 234 can be defined as a curved portion 235. For ease of understanding, as shown in Figures 4 and 6, the portion between the first reference line L1 and the second reference line L2 is the straight portion 234, the portion to the left of the first reference line L1 is the curved portion 235, and the portion to the right of the second reference line L2 is the curved portion 235.

[0077] Since the positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 are all sheets, their thickness dimensions are much smaller than their length and width dimensions. The at least one side of the at least one curved portion 235 refers to at least one of the two surfaces (i.e., the inner surface and the outer surface) of the curved portion 235 that are opposite to each other in the thickness direction.

[0078] The non-continuously distributed coating layer 236 means that there are multiple coating layers 236 on the same surface, and the multiple coating layers 236 are arranged at intervals on the corresponding surface.

[0079] At least one side of at least one curved portion 235 is coated with a discontinuously distributed coating 236, which means that at least one side of at least one curved portion 235 of at least one component of the positive electrode sheet 231, the negative electrode sheet 232 and the separator 233 is coated with a discontinuously distributed coating 236, including but not limited to the following situations: First, at least one side of at least one curved portion 235 of the positive electrode sheet 231 is coated with a discontinuously distributed coating 236; Second, at least one side of at least one curved portion 235 of the negative electrode sheet 232 is coated with a discontinuously distributed coating 236; Third, at least one side of at least one curved portion 235 of the separator 233 is coated with a discontinuously distributed coating 236; Fourth, at least one side of at least one curved portion 235 of the positive electrode sheet 231 is coated with a discontinuously distributed coating 236, and at least one side of at least one curved portion 235 of the negative electrode sheet 232 is coated with a discontinuously distributed coating 236. The positive electrode sheet 231 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235, and the separator 233 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235. The negative electrode sheet 232 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235, and the separator 233 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235. The positive electrode sheet 231 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235, and the separator 233 is coated with a discontinuously distributed coating 236 on at least one side of at least one curved portion 235.

[0080] Using the battery cell provided in the embodiment of the present application, a discontinuously distributed coating 236 is coated on at least one side of at least one bent portion 235 of at least one component among the positive electrode sheet 231, the negative electrode sheet 232 and the diaphragm 233, thereby increasing the distance between the positive electrode sheet 231 and the negative electrode sheet 232 at at least one corner, and reserving the required space for the expansion of the negative electrode sheet 232 and the positive electrode sheet 231 at the corner, which can reduce the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of the battery cell at the corner having adverse conditions such as electrolyte starvation, electrode breakage, deformation, wrinkling, black spots, lithium deposition, etc., thereby improving the service life of the battery cell to a certain extent.

[0081] In addition, the coating 236 used in the battery cell provided in the embodiment of the present application is discontinuously distributed. While playing the above-mentioned role, it can also ensure sufficient electrolyte channels, which can improve the cycle performance of the battery cell provided in the embodiment of the present application to a certain extent.

[0082] As shown in FIG. 7 , in some embodiments, the coating layer 236 has a thickness d of 5 μm-100 μm.

[0083] In an exemplary embodiment, the thickness d of the coating 236 may be 5 μm, 6 μm, 10 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 75 μm, 90 μm, and other typical but non-limiting values.

[0084] The coating 236 adopts the thickness range provided in this embodiment, which can not only make the distance between the positive electrode sheet 231 and the negative electrode sheet 232 at the corresponding corner sufficiently large, reserving a larger space for the expansion of the electrode sheet, but also reduce to a certain extent the risk of problems such as longer lithium ion transmission distance at the corner and lithium plating occurring due to the excessive distance between the positive electrode sheet 231 and the negative electrode sheet 232.

[0085] In some embodiments, the coating 236 has a thickness d of 20 μm to 50 μm.

[0086] In an exemplary embodiment, the thickness d of the coating 236 may be 20 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, etc., which are typical but non-limiting values.

[0087] The coating 236 adopts the thickness range provided in this embodiment, which can not only make the distance between the positive electrode sheet 231 and the negative electrode sheet 232 at the corresponding corner sufficiently large, reserving a larger space for the expansion of the electrode sheet, but also reduce to a certain extent the risk of problems such as longer lithium ion transmission distance at the corner and lithium plating occurring due to the excessive distance between the positive electrode sheet 231 and the negative electrode sheet 232; at the same time, the thickness difference of the coating 236 in different areas can be made smaller, which can reduce to a certain extent the risk of misalignment of the tab 23a.

[0088] As shown in FIG. 8 and FIG. 9 , in some embodiments, a coating 236 is provided on both of the two curved portions 235 in the same circle.

[0089] As mentioned above, the wound body generally has a multi-turn structure, wherein two straight portions 234 and two curved portions 235 connected end to end form a single turn structure. It is understood that the single turn structure can be a single turn structure of the separator 233 formed by two straight portions 234 and two curved portions 235 connected end to end, or a single turn structure of the positive electrode sheet 231 formed by two straight portions 234 and two curved portions 235 connected end to end, or a single turn structure of the negative electrode sheet 232 formed by two straight portions 234 and two curved portions 235 connected end to end.

[0090] The two curved portions 235 located in the same circle refer to two curved portions 235 in at least one circle.

[0091] Generally speaking, the structures at both ends of the winding body are roughly symmetrical and the stress conditions are similar. By adopting the structure provided in this embodiment, the distance between the positive electrode sheet 231 and the negative electrode sheet 232 at the corners at both ends of the same circle can be expanded, thereby improving the electrochemical performance of the battery cell in the circle.

[0092] In some embodiments, the coefficient of variation of the thickness of the coating 236 within a circle is less than or equal to 15%.

[0093] The coefficient of variation (CV) is the ratio of the variation index of a set of data to its mean index (the ratio of the standard deviation to the mean is called the coefficient of variation). It is a relative variation index. The mean is the average of a set of thickness data, which is also the sum of all data points in a set divided by the number of data points.

[0094] The standard deviation is the average of how far a set of data deviates from the mean. It is the square root of the average of the squared deviations from the mean and is represented by σ. The standard deviation is the square root of the thickness variance. The standard deviation reflects the degree of dispersion of the thickness data set.

[0095] That is, the coefficient of variation of the coating thickness CV = sample thickness standard deviation σ / sample thickness mean.

[0096] It should be noted that the data used to calculate the coefficient of variation is the thickness of the coating 236 on either side of the same coil of substrate. The substrate may be a positive electrode sheet, a negative electrode sheet, or a separator. It is understood that when both surfaces of the same coil of substrate have a coating, the coefficient of variation of the coating thickness on each surface is calculated separately.

[0097] By adopting the solution provided in this embodiment, the thickness fluctuation of the coating 236 on the same circle can be reduced, so that the position of the tab 23a after winding can be close to the designed position, thereby reducing the risk of misalignment of the tab 23a to a certain extent.

[0098] In some embodiments, the coefficient of variation of the thickness of the coating 236 within a circle is less than or equal to 10%.

[0099] By adopting the solution provided in this embodiment, the thickness fluctuation of the coating 236 on the same circle can be reduced, so that the position of the tab 23a after winding can be close to the designed position, thereby reducing the risk of misalignment of the tab 23a to a certain extent.

[0100] In some embodiments, the thickness of the coating gradually increases from the inner ring to the outer ring, and the thickness variation rate is less than or equal to 10%.

[0101] The thickness variation rate reflects the thickness variation of the coating in different layers.

[0102] Thickness change rate = thickness change / thickness original value * 100%.

[0103] Assume that, from the inside out of the battery cell stacking direction, the thickness of the first coating layer 236 is d1, the thickness of the second coating layer 236 is d2, the thickness of the third coating layer 236 is d3, and the thickness of the fourth coating layer 236 is d4, and d4>d3>d2>d1. Then, the thickness variation rate of the second coating layer 236 is (d2-d1) / d1, the thickness variation rate of the third coating layer 236 is (d3-d2) / d2, and the thickness variation rate of the fourth coating layer 236 is (d4-d3) / d3.

[0104] The solution provided in this embodiment allows the spacing between the positive electrode sheet 231 and the negative electrode sheet 232 to increase from the inside to the outside along the stacking direction of the battery cells. This allows the outer layers to withstand greater expansion forces, thereby reducing the risk of fracture in each layer of the electrode sheet. Using the thickness variation rate within the range provided in this embodiment can not only reduce the risk of fracture in each layer of the electrode sheet, but also reduce, to a certain extent, the impact of excessive coating 236 thickness on the energy density of the battery 100.

[0105] In some embodiments, the thickness of the coating gradually increases from the inner ring to the outer ring, and the thickness variation rate is less than or equal to 5%.

[0106] The thickness variation rate adopts the range provided in this embodiment, which can not only reduce the risk of fracture of each layer of the electrode, but also reduce the impact of excessive thickness of the coating 236 on the energy density of the battery 100 to a certain extent.

[0107] In some embodiments, on at least one side of at least one curved portion 235 , the coverage of the coating 236 is less than or equal to 60%, where the coverage is the percentage of the sum of the areas of the coating points of the coating 236 on the same side to the total area of ​​the distribution area of ​​the coating 236 .

[0108] Because coating 236 is a discontinuous structure, meaning it has many coating points with gaps between adjacent coating points, a coating point refers to the continuous structure formed when the coating material falls onto curved portion 235. This continuous structure can be a dot-like structure, a strip-like structure, or other structures. The sum of the areas of these coating points is the total coverage area of ​​all coating points in coating 236. The coverage area is the area covering the surface of curved portion 235. The total distribution area refers to the area of ​​the closed shape enclosed by the outer contour of coating 236.

[0109] By adopting the solution provided in this embodiment, the lithium ion conductivity of the surface of the discontinuously distributed coating 236 in the battery cell can meet the requirements, so that the dynamic performance of the battery cell can meet the use requirements.

[0110] In some embodiments, the coverage of the coating 236 on at least one side of at least one curved portion 235 is less than or equal to 30%. The coverage is the percentage of the sum of the coating application areas to the total distribution area of ​​the coating.

[0111] By adopting the solution provided in this embodiment, the coating 236 can cover only a small area of ​​the corresponding curved portion 235, so that the lithium ion conductivity of the surface of the discontinuously distributed coating 236 in the battery cell meets the requirements, so that the dynamic performance of the battery cell meets the use requirements.

[0112] In some embodiments, on at least one surface of at least one curved portion 235 , the coating 236 is arranged in an array or randomly arranged.

[0113] The array arrangement can be a one-dimensional array arrangement or a two-dimensional array arrangement, which can be determined according to the specific use requirements.

[0114] The random arrangement means that the arrangement of the parts in the coating 236 is irregular.

[0115] When the coating 236 is arranged in an array on at least one surface of at least one curved portion 235 , it is convenient for design. When the coating 236 is arranged in a random pattern on at least one surface of at least one curved portion 235 , it is convenient for manufacturing.

[0116] In some embodiments, the coating 236 includes spaced-apart segments 236 a , and the segments 236 a are shaped like one or more of regular lines, irregular lines, regular dots, and irregular dots.

[0117] By adopting the solution provided in this embodiment, the size of a single split body 236a can be made smaller, the coverage area can be made smaller, and the adverse effect on the performance of the battery cell can be made smaller.

[0118] In some embodiments, when the split body 236a is in the shape of a regular line or an irregular line, the width of the split body 236a is less than or equal to 2 mm, and the length of the line is not limited.

[0119] By adopting the solution provided in this embodiment, the size of a single split body 236a can be made smaller, the coverage area can be made smaller, and the adverse effect on the performance of the battery cell can be made smaller.

[0120] In other embodiments, when the split body 236a is in the shape of regular dots or irregular dots, the maximum size of the split body 236a is greater than 0 mm and less than or equal to 2 mm.

[0121] By adopting the solution provided in this embodiment, the size of a single split body 236a can be made smaller, the coverage area can be made smaller, and the adverse effect on the performance of the battery cell can be made smaller.

[0122] In some embodiments, the distance between the outer contours of adjacent segments 236 a is 0.01 mm-5 mm.

[0123] The spacing between the outer contours of two adjacent segments 236a can be the same or different at different locations. The spacing between the outer contours of adjacent segments 236a is within the range provided in this embodiment, so that the spacing between two adjacent segments 236a is greater than the size of a single segment 236a. This reduces the coverage of the coating 236, ensures that the lithium ion conductivity of the surface of the non-continuously distributed coating 236 in the battery cell meets the requirements, and ensures that the dynamic performance of the battery cell meets the usage requirements.

[0124] As shown in FIG10 , in some embodiments, multiple coatings 236 are provided along the stacking direction of the battery cells, and the thickness of all coatings 236 gradually increases from the inside to the outside. That is, along the X direction in FIG11 , the thickness of all coatings 236 gradually increases from the inside to the outside.

[0125] The thickness of all coatings 236 gradually increases from the inside to the outside, meaning that the thickness of the coating 236 on the outside is greater than the thickness of the coating 236 on the inside. It is understood that the above-mentioned inside and outside are relative. For example, the innermost circle in the battery cell is the first circle. From the inside to the outside of the battery cell stacking direction, each circle is sequentially recorded as the first circle, the second circle, the third circle, ..., and the nth circle. The fourth circle is located on the outside relative to the third circle, the second circle, and the first circle, and the circle layers are located on the inside relative to the fifth circle and the circles beyond the fifth circle.

[0126] Since the expansion force exerted on the outer layer is greater than that exerted on the inner layer, the solution provided in this embodiment can be used to increase the spacing between the positive electrode sheet 231 and the negative electrode sheet 232 from the inside to the outside along the stacking direction of the battery cell, so that the outer layer can withstand a larger expansion force, so that the risk of breakage of each layer of the electrode sheet is relatively small.

[0127] In some embodiments, at least one side of each bent portion 235 of the positive electrode sheet 231 is provided with a coating 236 ;

[0128] and / or, at least one side of each bent portion 235 of the negative electrode sheet 232 is provided with a coating 236;

[0129] And / or, as shown in FIG11 , at least one surface of each curved portion 235 in the diaphragm 233 is provided with a coating 236 .

[0130] The solutions provided in this embodiment include the following situations: First, at least one side of each curved portion 235 of the positive electrode sheet 231 is provided with a coating 236; Second, at least one side of each curved portion 235 of the negative electrode sheet 232 is provided with a coating 236; Third, at least one side of each curved portion 235 of the separator 233 is provided with a coating 236; Fourth, at least one side of each curved portion 235 of the positive electrode sheet 231 is provided with a coating 236, and at least one side of each curved portion 235 of the negative electrode sheet 232 is provided with a coating 236; Fifth, each curved portion 235 of the positive electrode sheet 231 is provided with a coating 236. 5 is provided with a coating 236 on at least one side, and each bent portion 235 of the separator 233 is provided with a coating 236; the sixth type, at least one side of each bent portion 235 of the negative electrode sheet 232 is provided with a coating 236, and at least one side of each bent portion 235 of the separator 233 is provided with a coating 236; the seventh type, at least one side of each bent portion 235 of the positive electrode sheet 231 is provided with a coating 236, and at least one side of each bent portion 235 of the negative electrode sheet 232 is provided with a coating 236, and at least one side of each bent portion 235 of the separator 233 is provided with a coating 236.

[0131] Since the battery cell is a wound body with a multi-turn structure, each turn has a bent portion 235, which is subject to risks such as high stress and electrode breakage. By adopting the solution provided in this embodiment, the distance between the positive electrode sheet 231 and the negative electrode sheet 232 at any corner can be increased, thereby reducing the risk of problems such as electrode breakage at each corner.

[0132] In some embodiments, the thickness compression rate of the coating 236 under the first compression condition is less than or equal to 30%. The first compression condition includes a pressure value of 0.15 MPa-0.25 MPa and a compression time of 100 s-140 s.

[0133] The thickness compression ratio refers to the ratio of the thickness reduction of the coating 236 after compression to the thickness before compression. For example, the thickness of the coating 236 before compression is d0, and the thickness after compression is d 缩 , then the thickness compression rate is (d0-d 缩 ) / d0.

[0134] The first compression condition is equivalent to the compression condition to which the coating 236 is subjected during the winding process. The solution provided in this embodiment can prevent the coating 236 from being over-compressed after the battery cell is wound and formed, and can retain a relatively large thickness, thereby playing a good spacing role for the positive electrode sheet 231 and the negative electrode sheet 232 in the corresponding area, meeting the use requirements.

[0135] In some embodiments, the first compression condition includes a pressure value of 0.2 MPa and a compression time of 120 seconds.

[0136] The first compression condition adopts the value provided in this embodiment, which is easy to design and is closer to the compression condition to which the coating 236 is subjected during the winding process, so that the winding effect of the coating 236 after preparation is better.

[0137] In some embodiments, the thickness compression rate of the coating 236 under the second compression condition is ≥60%, and the second compression condition includes a pressure value of 2.5 MPa-3.5 MPa and a compression time of 100 s-140 s.

[0138] The second compression condition is equivalent to the extrusion condition of the expansion force to which the coating 236 is subjected when the battery cell is in use. The solution provided in this embodiment can enable the coating 236 to be compressed to a greater extent after being subjected to the expansion force, thereby releasing a larger space to reduce the stress on the electrode and reduce the risk of problems such as electrode breakage.

[0139] In some embodiments, the second compression condition includes a pressure value of 3 MPa and a compression time of 120 seconds.

[0140] The second compression condition adopts the value provided in this embodiment, which is easy to design and is closer to the compression condition to which the coating 236 is subjected during use, and can reduce the risk of problems such as pole piece breakage to a certain extent.

[0141] In some embodiments, coating 236 includes a polymer.

[0142] The polymer is the molding material of the coating 236. The coating 236 is made of polymer, has a stable structure, and is easy to prepare.

[0143] In some embodiments, coating 236 includes at least one of polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, polyvinyl pyrrolidone, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylate, polydimethylsiloxane, polystyrene, polyethylene, polypropylene, polyacrylate, polyacrylic acid, polybutadiene, sodium carboxymethyl cellulose, and derivatives thereof.

[0144] Specifically, the coating 236 includes polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, polyvinyl pyrrolidone, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylate, polydimethylsiloxane, polystyrene, polyethylene, polypropylene, polyacrylate, polyacrylic acid, polybutadiene, sodium carboxymethyl cellulose (CMC), etc., and at least one of the blended, copolymerized, and surface-modified polymers derived from the aforementioned polymer modifications.

[0145] The material structure of the coating 236 is stable and easy to obtain and prepare.

[0146] In some embodiments, coating 236 also includes a thickener.

[0147] There is no particular limitation on the thickener in this embodiment, as long as the purpose of the invention can be achieved. For example, it can be sodium carboxymethyl cellulose.

[0148] The thickener serves to increase the stability of the slurry used to prepare the coating 236 and to prevent the slurry from settling.

[0149] In some embodiments, the thickening agent includes sodium carboxymethylcellulose.

[0150] Sodium carboxymethyl cellulose (also known as sodium salt of caboxy methyl cellulose, CMC, carboxymethyl, cellulose sodium, sodium salt of caboxy methyl cellulose) is the most widely used and consumed type of cellulose in the world today, with excellent thickening properties. The solution provided in this embodiment can impart excellent viscosity and rheological properties to the slurry of coating 236.

[0151] In some embodiments, coating 236 also includes an auxiliary binder.

[0152] The auxiliary adhesive plays the role of auxiliary bonding to further improve the bonding performance of the discontinuously distributed coating 236. The present application has no special restrictions on the auxiliary adhesive, as long as it can achieve the purpose of the present application.

[0153] In some embodiments, the auxiliary binder includes at least one homopolymer or copolymer of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, or butadiene.

[0154] The auxiliary adhesive is made of the material provided in this embodiment, has a stable structure and good bonding effect.

[0155] In some embodiments, coating 236 also includes a wetting agent.

[0156] The function of the wetting agent is to reduce the surface energy of the slurry and enhance the affinity between the slurry and the substrate. This application has no special restrictions on the wetting agent, as long as it can achieve the purpose of this application.

[0157] In some embodiments, the wetting agent includes at least one of dimethylsiloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer, or dioctyl sodium sulfosuccinate.

[0158] The wetting agent is made of the material provided in this embodiment, has a stable structure and good wetting effect.

[0159] In the above embodiments, there are no special requirements for the preparation method of the coating 236. For example, at least one of micro-gravure coating, gravure coating, spraying, extrusion coating, dispensing coating, 3D printing, etc. can be selected.

[0160] According to some embodiments of the present application, the present application also provides a battery comprising a battery cell according to any of the above solutions.

[0161] The battery provided in the embodiments of the present application, including the battery cell of any of the above schemes, increases the distance between the positive electrode sheet and the negative electrode sheet at at least one corner, reserves the required space for the expansion of the negative electrode sheet and the positive electrode sheet at the corner, and can reduce the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of the battery cell experiencing adverse conditions such as electrolyte starvation, electrode breakage, deformation, wrinkling, black spots, lithium deposition, etc. at the corner, thereby improving the service life of the battery cell to a certain extent.

[0162] According to some embodiments of the present application, the present application further provides an electrical device, comprising a battery according to any of the above solutions, and the battery is used to provide electrical energy to the electrical device.

[0163] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0164] The electrical device provided in the embodiment of the present application includes a battery of any of the above schemes, which increases the distance between the positive electrode sheet and the negative electrode sheet at at least one corner, reserves the required space for the expansion of the negative electrode sheet and the positive electrode sheet at the corner, and can reduce the stress of the battery cell at the corner to a certain extent, thereby reducing the risk of the battery cell at the corner having adverse conditions such as electrolyte deficiency, electrode breakage, deformation, wrinkling, black spots, lithium deposition, etc., thereby improving the service life of the battery cell to a certain extent.

[0165] According to some embodiments of the present application, a battery cell is provided. As shown in Figures 4 to 11, the battery cell includes a positive electrode sheet 231, a negative electrode sheet 232, and a separator 233. The positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 are stacked in a predetermined order and wound to form a jellyroll. The positive electrode sheet 231, the negative electrode sheet 232, and the separator 233 each include a plurality of alternating straight portions 234 and a plurality of curved portions 235.

[0166] At least one side of all the curved portions 235 of at least one of the positive electrode sheet 231 , the negative electrode sheet 232 and the separator 233 is coated with a discontinuously distributed coating 236 .

[0167] The thickness of the coating layer 236 is 5 μm to 100 μm. Preferably, the thickness of the coating layer 236 is 20 μm to 50 μm.

[0168] The thickness of the coating 236 gradually increases from the inner ring to the outer ring, and the thickness variation rate is less than or equal to 10%.

[0169] On at least one side of at least one curved portion, the coverage of coating 236 is less than or equal to 60%, where the coverage is the percentage of the sum of the areas of the coating points of coating 236 to the total area of ​​the distribution region of coating 236. Coating 236 includes spaced-apart segments 236a, each of which has a shape of one or more of regular lines, irregular lines, regular dots, and irregular dots.

[0170] When the split body 236a is in the shape of a regular line or an irregular line, the width of the split body 236a is less than or equal to 2 mm.

[0171] When the split bodies 236a are in the shape of regular dots or irregular dots, the maximum size of the split bodies 236a is greater than 0 mm and less than or equal to 2 mm. The spacing between the outer contours of adjacent split bodies 236a is 0.01 mm to 5 mm.

[0172] Along the stacking direction of the battery cells, the thickness of all coatings 236 gradually increases from the inside to the outside.

[0173] Except for the coating layer 236 located in the innermost circle, the thickness variation rate of each coating layer 236 is greater than or equal to 0. Preferably, the thickness variation rate is 0%-10%.

[0174] The thickness compression ratio of the coating 236 under the first compression condition is less than or equal to 30%, wherein the first compression condition includes a pressure value of 0.2 MPa and a compression time of 120 seconds. The thickness compression ratio of the coating 236 under the second compression condition is greater than or equal to 60%, wherein the second compression condition includes a pressure value of 3 MPa and a compression time of 120 seconds.

[0175] The coating 236 includes a polymer, a thickener, an auxiliary binder, and a wetting agent.

[0176] The polymer includes at least one of polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, polyvinyl pyrrolidone, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylate, polydimethylsiloxane, polystyrene, polyethylene, polypropylene, polyacrylate, polyacrylic acid, polybutadiene, sodium carboxymethyl cellulose and its derivatives. The thickener is sodium carboxymethyl cellulose.

[0177] The monomer of the auxiliary binder includes at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile and butadiene.

[0178] The wetting agent includes at least one of dimethylsiloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer and dioctyl sodium sulfosuccinate.

[0179] Example

[0180] The following takes the preparation of a battery cell by coating the electrode pieces in the corner area of ​​the battery cell with a regularly lattice-distributed PVDF (Poly (vinylidene fluoride)) coating as an example to further illustrate the embodiments of the present application.

[0181] It is understood that the examples described below are illustrative and are only used to explain this application, and should not be construed as limiting this application. The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, instruments, etc. used in the following examples, if the manufacturer is not indicated, are all commercially available conventional products unless otherwise specified. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in this field or the product instructions are followed.

[0182] This embodiment provides a battery cell and a battery cell. The battery cell includes a positive electrode, a negative electrode, a separator, and an electrolyte. The regularly dotted PVDF coating on the electrode surface in the corner area of ​​the battery cell is the discontinuously distributed coating described in this application. The PVDF coating dots have a diameter of 0.5 μm, and the distance between the center of the dots is 1 μm. The layer-by-layer thickness variation of the coating is 0%. The battery cells of Comparative Examples 1-4 and Examples 1-10 were all prepared according to the following preparation method, differing only in the specifications of the discontinuously distributed coating, as shown in Table 1.

[0183] Preparation of isolation membrane:

[0184] In the embodiments of the present application, there is no special limitation on the material of the base of the isolation membrane. The substrate of the present application includes but is not limited to at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide or aramid. For example, polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene and ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene, they have a good effect on preventing short circuits and can improve the stability of battery cells through the shutdown effect. The surface of the substrate can be coated with a heat-resistant coating to increase the heat resistance of the diaphragm. There are no special requirements for the heat-resistant coating. For example, a common ceramic coating can be used. The surface of the substrate can be coated with an adhesive coating to improve the interface adhesion of the diaphragm pole piece. There are no special requirements for the adhesive coating. For example, a common PVDF coating can be used.

[0185] Preparation of positive electrode:

[0186] The positive electrode active material, conductive carbon black SP, and binder PVDF (polyvinylidene fluoride) are dispersed in the solvent NMP (N-methylpyrrolidone) and mixed uniformly to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, then dried at 85°C, cold pressed, trimmed, cut, and slit. Finally, it is dried under vacuum at 85°C for 4 hours to obtain a positive electrode sheet. The mass ratio of the positive electrode active material, conductive carbon black, and binder PVDF is 96:2:2, and the resulting positive electrode slurry has a solids content of 75%. In this example, lithium nickel cobalt manganese oxide 811 is used as the positive electrode active material.

[0187] Preparation of discontinuously distributed coatings:

[0188] PVDF powder, auxiliary binder polyacrylate, and thickener CMC were added to a blender in a mass ratio of 95 / 3 / 2, and stirred evenly in deionized water to obtain a slurry with a solid content of 25%. A wetting agent, polyoxyethylene fatty alcohol ether, was then added at a content of 0.1% of the total mass of the slurry to obtain a slurry. A discontinuously distributed coating was prepared on both sides of the positive electrode sheet in the corner area of ​​the battery cell using a dispensing device.

[0189] Preparation of negative electrode sheet:

[0190] The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the binder, styrene, 1,3-butadiene polymer (SBR), and the thickener, carboxymethylcellulose sodium (CMC), were mixed in a weight ratio of 96:1:2:1. Deionized water was added as a solvent and stirred until uniformly mixed to produce a negative electrode slurry with a solid content of 70%. The negative electrode slurry was evenly coated on the negative electrode current collector copper foil. After coating, the negative electrode was dried at 80-90°C, cold pressed, trimmed, cut into pieces, and slit. Finally, it was dried at 110°C under vacuum for 4 hours to obtain the negative electrode sheet.

[0191] Preparation of electrolyte:

[0192] An electrolyte solution is prepared, consisting of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in a mass ratio of 5:2:3. Electrolyte salt is then added to bring the lithium hexafluorophosphate concentration in the electrolyte to 1 mol / L.

[0193] Preparation of battery cells:

[0194] The negative electrode sheet, separator, and positive electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrodes. The cells are then wound into a square bare cell. The cell is then welded to the adapter and top cover, covered with an insulating film, and encapsulated in an aluminum shell. The cells are vacuum-baked at 105°C for 12 hours, injected with electrolyte, left to stand, formed, and then refilled with electrolyte. The sealing pins are then welded, helium-sealed, and aged. This completes the cell fabrication process.

[0195] The test method and equipment are as follows:

[0196] Thickness and coefficient of variation test of non-continuously distributed coatings:

[0197] Coated substrate thickness test: At room temperature, cut the coated substrate into 50 μm wide strips along the transverse direction (TD). Six parallel samples were tested using a micrometer thickness gauge (Mitutoyo Litematic VL-50B, test head diameter 5 μm, test pressure 0.01 N). Ten data points were uniformly measured along the center of the TD direction. After testing the six parallel samples, the average value h1 of the 60 test data points was taken as the substrate thickness.

[0198] Total thickness test of coating coated diaphragm:

[0199] According to the substrate thickness test method, the thickness of the substrate is first measured, recorded as h1, and then the coating is applied on the surface of the substrate. The total thickness of the diaphragm after coating is measured, recorded as h2;

[0200] The thickness h of a discontinuously distributed coating is calculated as: h = h2 - h1. There are 60 thickness values ​​in total, and the mean H and standard deviation σ of the coating can be calculated.

[0201] Second coefficient of variation CV calculation:

[0202] CV = σ / H;

[0203] Wherein, H is the average value of the above 60 thickness values, σ is the standard deviation of the above 60 thickness values, and CV is the coefficient of variation of the above 60 thickness values.

[0204] Coating coverage test:

[0205] Use the Keyence VHX5000 tester in the coverage test mode to test the coating coverage on the substrate. When determining the coating coverage, the minimum area of ​​the substrate determination area must be ≥5μm*6μm.

[0206] Battery cell capacity test:

[0207] In a constant temperature box at 25°C, charge at a constant current rate of 1C to a voltage of 4.2V, then charge at a constant voltage of 4.2V to a current of 0.05C, and then discharge at a constant current rate of 1C to a voltage of 2.8V. The discharge capacity obtained is the battery capacity.

[0208] Room temperature cycle performance test of battery cells:

[0209] At 25°C, charge at a constant current rate of 0.7C to a voltage of 4.2V, then charge at a constant voltage of 4.2V to a current of 0.05C, and then discharge at a constant current rate of 1C to a voltage of 2.8V. This is a charge and discharge cycle process, and this charge and discharge cycle process is repeated according to the required number of cycles.

[0210] Capacity retention after 1000 cycles=discharge capacity after 1000th cycle / discharge capacity after first cycle×100%.

[0211] Battery cell disassembly test:

[0212] After fully charging the battery cells that have completed the required number of cycle tests, remove them and disassemble them in a battery cell disassembly and drying room. Open the diaphragm and electrode interface to confirm the cracks in the corners of the battery cells and the lithium precipitation of black spots on the interface.

[0213] Battery cell winding tab misalignment test:

[0214] After the winding of the multi-tab battery cell is completed, the distance from the right root of the first positive tab to the right root of the last positive tab is measured, which is the tab misalignment distance.

[0215] According to Table 1, it can be seen from Examples 1 to 5 and Comparative Examples 1 to 2 that the coating thickness must be controlled within an appropriate range. If the thickness is too large, the corner spacing between the battery cells will be too large, resulting in lithium deposition at the interface. If the thickness is too small, the corner spacing between the battery cells will be insufficient, and the expansion stress of the electrode will accumulate during cycling, causing cracks.

[0216] It can be seen from Examples 3, 6, 7 and Comparative Example 3 that the coating variation coefficient cannot be too large. If the variation coefficient is too large, the battery cell tab misalignment will exceed the standard, and the battery cell cannot be processed normally in the subsequent process.

[0217] It can be seen from Examples 3, 8, 9, 10 and Comparative Example 4 that the coating coverage cannot be too high. If the coating coverage is too high, the ion channels at the battery cell interface will decrease, the interface dynamics will deteriorate, and the problem of black spots and lithium precipitation at the interface will occur.

[0218] Table 1

[0219] In summary, at least part of the surface of the positive electrode and / or the negative electrode and / or the separator at the corner of the wound battery cell described in the present application is distributed with a discontinuously distributed coating. The average number of the discontinuously distributed coating in the entire battery cell ranges from 5μm to 100μm, and the coefficient of variation of the coating in the same layer of the battery cell is ≤15%. The discontinuously distributed coating can meet the requirement of reserved space at the corner of the battery cell and provide the space required for the expansion of the pole piece, thereby avoiding the battery cell pole piece fracture, deformation, wrinkling, black spots, lithium deposition and other adverse conditions; the coating thickness fluctuation in the same layer is small, which can avoid the problem of misalignment of the battery cell tabs. The coating has good ion conductivity and can prevent the problem of black spots and lithium deposition at the battery cell interface.

[0220] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that, It includes a positive electrode sheet, a negative electrode sheet and a separator. The positive electrode sheet, the negative electrode sheet and the separator are stacked in a preset order and wound into a wound body. The positive electrode sheet, the negative electrode sheet and the separator respectively include a plurality of straight portions and a plurality of bent portions that are alternately connected; At least one side of at least one of the bent portions is coated with a discontinuously distributed coating.

2. The battery cell according to claim 1, wherein, The thickness of the coating is 5μm - 100μm.

3. The battery cell according to claim 2, wherein, The thickness of the coating is 20μm - 50μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that The coating is provided on both of the bent portions in the same circle.

5. The battery cell according to any one of claims 1-4, characterized in that In the same circle, the coefficient of variation of the thickness of the coating is less than or equal to 15%.

6. The battery cell according to any one of claims 1-5, characterized in that, In the same circle, the coefficient of variation of the thickness of the coating is less than or equal to 10%.

7. The battery cell according to any one of claims 1-6, characterized in that, From the inner circle to the outer circle, the thickness of the coating gradually increases, and the thickness change rate is less than or equal to 10%.

8. The battery cell according to any one of claims 1-7, characterized in that From the inner circle to the outer circle, the thickness of the coating gradually increases, and the thickness change rate is less than or equal to 5%.

9. The battery cell according to any one of claims 1-8, characterized in that, On at least one side of at least one of the bent portions, the coverage rate of the coating is less than or equal to 60%. The coverage rate is the percentage of the total area of the coating application points of the coating in the total area of the distribution area of the coating.

10. The battery cell according to any one of claims 1-9, characterized in that, On at least one side of at least one of the bent portions, the coverage rate of the coating is less than or equal to 30%. The coverage rate is the percentage of the total area of the coating application points of the coating in the total area of the distribution area of the coating.

11. The battery cell according to any one of claims 1-10, characterized in that, On at least one side of at least one of the bent portions, the coating is arranged in an array or irregularly.

12. The battery cell according to any one of claims 1-11, characterized in that, The coating includes spaced-apart segments, and the shape of the segments is one or more of regular linear, irregular linear, regular dot-like, and irregular dot-like.

13. The battery cell according to claim 12, characterized in that, When the segment is regular linear or irregular linear, the width of the segment is less than or equal to 2mm.

14. The battery cell according to claim 12, characterized in that, When the segment is regular dot-like or irregular dot-like, the maximum size of the segment is greater than 0mm and less than or equal to 2mm.

15. The battery cell according to any one of claims 12-14, characterized in that, The distance between the outer contours of adjacent segments is 0.01mm - 5mm.

16. The battery cell according to any one of claims 1-15, characterized in that, At least one side of each of the bent portions in the positive electrode sheet is provided with the coating; And / or, at least one side of each of the bent portions in the negative electrode sheet is provided with the coating; And / or, at least one side of each of the bent portions in the separator is provided with the coating.

17. The battery cell according to any one of claims 1-16, characterized in that, The thickness compression rate of the coating under the first compression condition is less than or equal to 30%. The first compression condition includes a pressure value of 0.15Mpa - 0.25MPa and a compression duration of 100s - 140s.

18. The battery cell according to claim 17, wherein, The first compression condition includes a pressure value of 0.2MPa and a compression duration of 120s.

19. The battery cell according to any one of claims 1-18, characterized in that, The thickness compression rate of the coating under the second compression condition is ≥60%. The second compression condition includes a pressure value of 2.5Mpa - 3.5Mpa and a compression duration of 100s - 140s.

20. The battery cell according to claim 19, wherein The second compression condition includes a pressure value of 3Mpa and a compression duration of 120s.

21. The battery cell according to any one of claims 1-20, characterized in that, The coating includes a polymer.

22. The battery cell according to claim 21, wherein, The polymer includes at least one of polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, polyurethane, polyvinylpyrrolidone, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyacrylate, polydimethylsiloxane, polystyrene, polyethylene, polypropylene, polyacrylate salt, polyacrylic acid, polybutadiene, sodium carboxymethyl cellulose and its derivatives.

23. The battery cell according to claim 21 or 22, characterized in that, The coating further includes an auxiliary binder.

24. The battery cell according to claim 23, wherein, The monomers of the auxiliary binder include at least one of ethyl acrylate, butyl acrylate, ethyl methacrylate, styrene, chlorostyrene, fluorostyrene, methylstyrene, acrylic acid, methacrylic acid, maleic acid, acrylonitrile and butadiene.

25. The battery cell according to any one of claims 21-24, characterized in that, The coating further includes a wetting agent.

26. The battery cell according to claim 25, wherein The wetting agent includes at least one of dimethylsiloxane, polyethylene oxide, oxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer and dioctyl sodium sulfosuccinate.

27. A battery, characterized in that, Comprising the battery monomer according to any one of claims 1-26.

28. An electrical device, characterized in that, Comprising the battery according to claim 27.

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