Battery cell, method of manufacture, battery device and electric device

Abstract

The application provides a battery monomer, a preparation method, a battery device and a power utilization device. The battery monomer comprises an electrode assembly and a composite film covering the electrode assembly. The composite film comprises a first layer, a second layer and a third layer. The first layer is connected to the surface of the electrode assembly. The second layer is stacked with the first layer in the thickness direction of the composite film and is connected to the side of the first layer away from the electrode assembly. The second layer comprises a porous structure. The third layer is stacked with the second layer in the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer. The use reliability of the battery monomer can be improved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a battery cell, a preparation method, a battery device, and an electrical device. Background Technology

[0002] Battery cells have characteristics such as high capacity and long lifespan, and are therefore widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc.

[0003] As battery cells are used more and more widely, the requirements for battery performance are also gradually increasing, such as the increasing requirements for the reliability of battery cells. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a preparation method, a battery device, and an electrical device that can improve the reliability of the battery cell.

[0005] In a first aspect, embodiments of this application propose a battery cell, which includes an electrode assembly and a composite film covering the electrode assembly. The composite film includes a first layer, a second layer, and a third layer. The first layer is connected to the surface of the electrode assembly. The second layer is stacked with the first layer along the thickness direction of the composite film and is connected to the side of the first layer away from the electrode assembly. The second layer includes a porous structure. The third layer is stacked with the second layer along the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

[0006] Therefore, in this embodiment, the second layer of the composite membrane includes a porous structure with a certain porosity and excellent air permeability, which can effectively reduce the risk of air bubbles between the composite membrane and the electrode assembly. If air bubbles exist between the two, the gas in the air bubbles flows through the first layer to the second layer and then flows out through the porous structure of the second layer, which can effectively improve the flatness of the electrode surface. Since the second layer includes a porous structure, it will cause the surface of the composite membrane to be rough. The flatness of the third layer is relatively small, which can make up for the adverse effects of the porous structure of the second layer and reduce the flatness of the composite membrane. As a result, the overall flatness of the electrode assembly covered by the composite membrane is small, which can effectively improve the reliability of the battery cell.

[0007] In some embodiments, the porosity of the composite membrane is 35% to 90%, optionally 35% to 70%. When the porosity of the composite membrane is within the above range, the air permeability is excellent, which can effectively reduce the risk of air bubbles between the composite membrane and the electrode assembly.

[0008] In some embodiments, the shrinkage rate of the composite membrane is 10% to 70%, optionally 10% to 30%. When the shrinkage rate of the composite membrane is within the above range, the composite membrane has a certain shrinkage capacity and can change with the volume change of the electrode assembly, thereby providing a better protective effect for the electrode assembly.

[0009] In some embodiments, the thickness of the composite film is between 50 μm and 200 μm. When the thickness of the composite film is within this range, the composite film can provide excellent protection for the electrode assembly without occupying too much space, which helps to ensure that the battery cell still has a high volumetric energy density.

[0010] In some embodiments, the shrinkage rate of the second layer is 3% to 60%, optionally 10% to 30%. When the shrinkage rate of the second layer is within the above range, the second layer has a certain shrinkage capacity, which can drive the composite membrane as a whole to change with the volume change of the electrode assembly, thereby providing a better protection effect for the electrode assembly. Moreover, through the shrinkage of the second layer, the gas located in the porous structure can be squeezed out of the composite membrane.

[0011] In some embodiments, the material of the second layer includes one or more of polyolefin materials, polyester materials, polyimide materials, and polysaccharide materials.

[0012] In some embodiments, the polyolefin material includes one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene.

[0013] In some embodiments, the polyester material includes one or more of polyethylene terephthalate and polyethylene naphthalate.

[0014] In some embodiments, the polyimide material includes one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone.

[0015] In some embodiments, the polysaccharide material includes one or more of cellulose, hemicellulose, and lignin.

[0016] In some embodiments, the peel strength of the composite membrane is between 0.5 N / m and 60 N / m. When the peel strength of the composite membrane is within this range, the adhesion between the first layer and the electrode assembly is strong, making it difficult to peel off from the surface of the electrode assembly. Furthermore, the strong adhesion between the first and second layers contributes to the structural stability of the composite membrane itself.

[0017] In some embodiments, the first layer includes a sensitive adhesive. External stimulation of the composite membrane increases the viscosity of the first layer, resulting in stronger adhesion between the first layer and the electrode assembly, and a more stable structure.

[0018] In some embodiments, the sensitive adhesive includes one or more of photosensitive adhesives, heat-sensitive adhesives, and pressure-sensitive adhesives.

[0019] In some embodiments, the photosensitive adhesive includes one or more of polyacrylates, azobenzene, acetophenone derivatives, aromatic ketone compounds, and acylphosphine oxides.

[0020] In some embodiments, the heat-sensitive adhesive includes one or more of polyurethane, polystyrene, ethylene-vinyl acetate copolymer, polypropylene glycol, and polyorganosiloxane.

[0021] In some embodiments, the pressure-sensitive adhesive includes one or more of polyacrylate, polyorganosiloxane, styrene-butadiene rubber, cis-1,4-polyisoprene, polyisobutylene, butadiene-styrene copolymer, polyvinyl ether, and vinyl acetate polymer.

[0022] In some embodiments, the flatness of the third layer is 0.001 mm to 0.05 mm. The relatively small flatness of the third layer, after the composite film is used to coat the electrode assembly, results in a smaller flatness of the coated assembly, which is beneficial to improving the overall reliability of the battery cell.

[0023] In some embodiments, the third layer includes one or more of the following: polyolefin materials, polyester materials, polyimide materials, paraffin wax, ceramic materials, carboxymethyl cellulose, and styrene-maleic anhydride polymers.

[0024] In some embodiments, the polyolefin material includes one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene.

[0025] In some embodiments, the polyester material includes one or more of polyethylene terephthalate and polyethylene naphthalate.

[0026] In some embodiments, the polyimide material includes one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone.

[0027] In some embodiments, the ceramic material includes at least one of alumina, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide, and calcium oxide.

[0028] In some embodiments, the thickness of the first layer is 5 μm to 10 μm; when the thickness of the first layer is within the above range, the thickness of the first layer is moderate, which is conducive to the gas entering the second layer through the first layer, thereby allowing the gas to flow out from the second layer.

[0029] In some embodiments, the thickness of the second layer is 25 μm to 150 μm; when the thickness of the second layer is within the above range, the second layer has a relatively large porous structure, which can guide the gas located between the composite membrane and the electrode assembly to flow into the second layer and out of the composite membrane.

[0030] In some embodiments, the thickness of the third layer is between 5 μm and 20 μm. When the thickness of the third layer is within the above range, it is beneficial to provide a smaller flatness, and the thickness of the third layer is not too thick, which is beneficial to improving the volumetric energy density of the battery cell.

[0031] In some embodiments, the electrode assembly includes a main body and a tab. The main body is coated with an active material, and the tab is connected to at least one side of the main body along a first direction. The tab is not coated with an active material, and the first direction is perpendicular to the thickness direction of the electrode assembly. A composite film covers the surface of the main body. The composite film provides excellent protection for the main body.

[0032] In some embodiments, the main body includes two first surfaces and two second surfaces, the two first surfaces being opposite to each other along the thickness direction of the electrode assembly; the two second surfaces being opposite to each other along a second direction, the second direction, the first direction and the thickness direction of the electrode assembly being perpendicular to each other, wherein a composite film is disposed around the two first surfaces and the two second surfaces.

[0033] Therefore, the composite film in the present invention is disposed around the outside of the main body, which fastens and constrains the main body, making it less prone to internal layer peeling and improving the structural stability of the electrode assembly.

[0034] In some embodiments, the composite film includes a first cover and a second cover. The first cover includes a first body portion and a first protrusion. The first body portion covers one of two first surfaces, and the first protrusion is connected to the first body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface. The second cover includes a second body portion and a second protrusion. The second body portion covers the other of the two first surfaces, and the second protrusion is connected to the second body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface. The projection of the second protrusion along a second direction and the projection of the first protrusion along the second direction are continuously arranged.

[0035] Therefore, the embodiments of this application can cover the first surface by covering the first body portion and the second body portion, and can cover the second surface by covering the first protrusion and the second protrusion together, so that the composite film can play an excellent protective role for the electrode assembly.

[0036] In some embodiments, the composite film includes a first cover and a second cover. The first cover includes a first body portion and a first protrusion. The first body portion covers one of two first surfaces, and the first protrusion is connected to the first body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface. The second cover includes a second body portion and a second protrusion. The second body portion covers the other of the two first surfaces, and the second protrusion is connected to the second body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface. The projection of the second protrusion along a second direction and the projection of the first protrusion along the second direction at least partially overlap.

[0037] Therefore, the composite membrane in the embodiments of this application has a more stable structure, is less prone to cracking at the sealing edge, and can play an excellent role in fastening and protecting the electrode assembly.

[0038] In some embodiments, the main body includes two third surfaces facing each other along a first direction, and the composite film further covers at least one of the two third surfaces. The composite film further enhances the protective capability of the electrode assembly, and because the composite film is insulating, it can effectively isolate the electrode assembly from the housing assembly, thereby improving the reliability of the battery cell.

[0039] Secondly, this application also proposes a method for preparing a single battery cell, comprising:

[0040] Provide initial electrode assembly;

[0041] A composite film is provided to coat the initial electrode assembly to obtain the electrode assembly to be pressurized;

[0042] After isostatic pressing, an electrode assembly coated with a composite film is obtained.

[0043] The electrode assembly coated with the composite film is assembled into the housing assembly to prepare a single battery cell.

[0044] in,

[0045] Composite membranes include:

[0046] The first layer is connected to the surface of the electrode assembly;

[0047] The second layer is stacked with the first layer along the thickness direction of the composite film and is connected to the side of the first layer away from the electrode assembly. The second layer includes a porous structure; and

[0048] The third layer is stacked with the second layer along the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

[0049] Therefore, in this embodiment, before isostatic pressing, a composite film is pre-coated onto the surface of the initial electrode assembly. The second layer of the composite film has a porous structure. If there are air bubbles between the composite film and the initial electrode assembly, during the isostatic pressing process, the air bubbles can flow into the porous structure of the composite film and flow through the composite film to the gap between the composite film and the isostatic pressing film. After the isostatic pressing process, the isostatic pressing film is removed, and an electrode assembly coated with the composite film is obtained. It is basically free from wrinkles or air bubble defects, which makes the surface of the electrode assembly smoother and improves the reliability of the battery cell.

[0050] Thirdly, embodiments of this application also propose a battery device, including a battery cell of any embodiment of the first aspect of this application or a battery cell prepared by any method of the second aspect of this application.

[0051] Fourthly, embodiments of this application also propose an electrical device, including the battery device of any embodiment of the third aspect of this application.

[0052] Fifthly, this application also proposes a composite membrane, which includes a first layer, a second layer and a third layer. The second layer is stacked with the first layer along the thickness direction of the composite membrane and is connected to the first layer. The second layer includes a porous structure. The third layer is stacked with the second layer along the thickness direction of the composite membrane and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

[0053] Therefore, in the embodiments of this application, the second layer of the composite membrane includes a porous structure with a certain porosity and excellent air permeability, allowing gas to flow through the first layer to the second layer and then out through the porous structure of the second layer; the third layer has relatively low flatness, which can compensate for the adverse effects of the porous structure of the second layer and reduce the flatness of the composite membrane.

[0054] In some embodiments, the porosity of the composite membrane is 35% to 90%, optionally 35% to 80%. When the porosity of the composite membrane is within this range, its air permeability is superior.

[0055] In some embodiments, the shrinkage rate of the composite film is 10% to 70%, optionally 10% to 30%. When the shrinkage rate of the composite film is within the above range, the composite film has excellent shrinkage capacity.

[0056] In some embodiments, the porosity of the second layer is 40% to 90%. When the porosity of the second layer is within the above range, the air permeability is relatively excellent.

[0057] In some embodiments, the shrinkage rate of the second layer is 3% to 60%, optionally 10% to 30%. When the shrinkage rate of the second layer is within the above range, the second layer has excellent shrinkage capacity.

[0058] In some embodiments, the peel strength of the composite membrane ranges from 0.5 N / m to 60 N / m. The strong adhesion between the first and second layers contributes to the structural stability of the composite membrane itself.

[0059] In some embodiments, the first layer includes a sensitive adhesive. External stimulation of the composite film increases the adhesion of the first layer, strengthens the bond between the first and second layers, and results in a more stable structure.

[0060] In some implementations, the flatness of the third layer is 0.001 mm to 0.05 mm. The relatively small flatness of the third layer results in a smoother surface. Attached Figure Description

[0061] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0062] Figure 1 Structural schematic diagrams of the vehicle provided for some embodiments of this application;

[0063] Figure 2 An exploded view of a battery pack provided for some embodiments of this application;

[0064] Figure 3 Schematic diagram of the structure of a battery module provided for some embodiments of this application

[0065] Figure 4 Schematic diagrams of the structure of a battery cell provided for some embodiments of this application;

[0066] Figure 5 A schematic diagram of the structure of the electrode assembly and composite film in a battery cell provided for some embodiments of this application;

[0067] Figure 6 for Figure 5 A schematic cross-sectional view along line BB;

[0068] Figure 7 A schematic diagram of the exploded structure of the composite film in a battery cell provided for other embodiments of this application;

[0069] Figure 8 A cross-sectional schematic diagram of the composite film in a battery cell after being unfolded, provided for other embodiments of this application;

[0070] Figure 9Schematic diagrams of the electrode assembly and composite film in a battery cell provided for other embodiments of this application;

[0071] Figure 10 Schematic diagrams of the structure of electrode assemblies in a battery cell provided for other embodiments of this application;

[0072] Figure 11 A schematic flowchart illustrating the preparation method of a battery cell provided in other embodiments of this application;

[0073] Figure 12 A schematic diagram showing the state of the composite film covering the initial electrode assembly as provided in some embodiments of this application;

[0074] Figure 13 This is a schematic diagram of the structure of the isostatic pressure membrane-coated electrode assembly provided in some embodiments of this application;

[0075] The accompanying drawings may not be drawn to scale.

[0076] The annotations in the attached figures are explained as follows:

[0077] X, thickness direction of the electrode assembly; Z, first direction; Y, second direction; W, thickness direction of the composite film;

[0078] 1. Vehicle; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Storage space; 6. Battery module;

[0079] 7. Battery cells;

[0080] 10. Electrode assembly;

[0081] 11. Main body; 111. First surface; 112. Second surface; 113. Third surface;

[0082] 12. The outermost part of the ear;

[0083] 20. Housing components;

[0084] 30. Composite membrane;

[0085] 31. First floor;

[0086] 32. Second layer;

[0087] 33. The third layer;

[0088] 40. First cover; 41. First body portion; 42. First protrusion;

[0089] 50. Second cover; 51. Second body part; 52. Second protrusion;

[0090] 70. Isostatic membrane; 71. Encapsulation cavity; 72. Encapsulation cover. Detailed Implementation

[0091] The following detailed description discloses embodiments of the electrode assembly, battery cell, preparation method, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0092] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0093] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0094] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0095] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0096] In this application, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations.

[0097] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0098] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0099] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0100] In this application, "multiple" refers to two or more (including two). In the embodiments of this application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used.

[0101] In this application, the battery cell may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium lithium-ion battery cells, sodium-ion battery cells, magnesium-ion battery cells, lithium metal battery cells, sodium metal batteries, etc., and the embodiments of this application are not limited to these. The battery cell may be cylindrical, flat, cuboid, or other shapes, and the embodiments of this application are not limited to these shapes either. Battery cells are generally classified into three types according to their packaging method: cylindrical battery cells, square battery cells, and pouch battery cells, and the embodiments of this application are not limited to these types either.

[0102] The battery device mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery device mentioned in this application may include a battery module or a battery pack. A battery device generally includes a housing for encapsulating one or more battery cells. The housing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0103] Solid-state battery cells include solid electrolytes. Compared to liquid electrolytes, solid-state battery cells have higher thermal and chemical stability and can withstand higher temperatures and mechanical stresses.

[0104] During the manufacturing process of battery cells, a pressing process is required to make the electrode assembly more compact. The pressing process can be flat pressing or isostatic pressing. For example, an isostatic pressing film is applied to the surface of the electrode assembly and then isostatic pressing is performed. However, when the isostatic pressing film is removed, the main materials in the electrode assembly (such as the base coating, active materials, etc.) may also be removed, resulting in damage to the structure of the electrode assembly.

[0105] In related technologies, an adhesive layer can be pre-applied to the surface of the electrode assembly before isostatic pressing (OSP), and then an isostatic pressing film can be applied over the adhesive layer. When removing the isostatic pressing film, it can peel off from the adhesive layer, thus reducing structural damage to the electrode assembly. However, after applying the adhesive layer to the surface of the electrode assembly, its poor permeability may allow ambient gases to remain on both the adhesive layer and the electrode assembly surface. This can lead to problems such as wrinkles or bubbles in the adhesive layer, poor flatness of the electrode assembly, and consequently, uneven stress on the battery cells during subsequent cycle testing, resulting in structural damage and deteriorated reliability.

[0106] In view of this, the present application proposes a battery cell. The preparation method of the battery cell includes isostatic pressing. Before isostatic pressing, the initial electrode assembly of the battery cell is pre-coated with a composite film. The composite film has a porous structure. If there are air bubbles between the composite film and the initial electrode assembly, during the isostatic pressing process, the air bubbles can flow into the porous structure of the composite film and flow through the composite film to the gap between the composite film and the isostatic pressing film. After isostatic pressing, the isostatic pressing film is removed to obtain an electrode assembly coated with the composite film. It is basically free from wrinkles or air bubble defects, which can make the surface of the electrode assembly smoother and improve the reliability of the battery cell.

[0107] The battery cells described in this application are applicable to battery devices and electrical devices that use battery devices.

[0108] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of this application do not impose special limitations on the above-mentioned electrical devices.

[0109] For ease of explanation, the following implementation method uses a vehicle as an example of an electrical device.

[0110] Figure 1 A schematic diagram of the vehicle structure provided for some embodiments of this application.

[0111] like Figure 1 As shown, a battery pack 2 is installed inside the vehicle 1. The battery pack 2 can be located at the bottom, front, or rear of the vehicle 1. The battery pack 2 can be used to power the vehicle 1; for example, the battery pack 2 can serve as the operating power source for the vehicle 1.

[0112] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery pack 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0113] In some embodiments of this application, the battery pack 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0114] Figure 2 This is an exploded view of a battery pack provided for some embodiments of this application. For example... Figure 2 As shown, the battery pack 2 includes a housing 5 and individual battery cells ( Figure 2 (Not shown), the battery cells are housed inside the casing 5.

[0115] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one open end, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one open side, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0116] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0117] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0118] In battery pack 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells are connected in both series and parallel configurations. Multiple battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed in housing 5. Alternatively, multiple battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed in housing 5.

[0119] A single battery cell can be the smallest unit that makes up a battery device.

[0120] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0121] In some implementations, such as Figure 3As shown, there are multiple battery cells 7, which are first connected in series, parallel, or a combination of both to form a battery module 6. These battery modules 6 are then connected in series, parallel, or a combination of both to form a whole, which is housed within the casing.

[0122] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6. There can be one or more busbars, each used to electrically connect at least two battery cells 7.

[0123] Figure 4 This is a schematic diagram of the structure of a battery cell 7 provided in some embodiments of this application. Figure 5 This is a schematic diagram of the structure of the electrode assembly 10 of the battery cell 7 provided in some embodiments of this application.

[0124] like Figures 4 to 6 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20, with the electrode assembly 10 housed within the housing assembly 20.

[0125] The housing assembly 20 can have various shapes, such as a cylinder or a cuboid. The shape of the housing assembly 20 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, the housing assembly 20 can be a cylindrical structure. If the electrode assembly 10 is a cuboid structure, the housing assembly 20 can be a cuboid structure. Optionally, the electrode assembly 10 can be a cuboid structure.

[0126] The housing assembly 20 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and this application embodiment does not impose any special limitations on this. Optionally, the inner wall of the housing assembly 20 may also include an insulating layer, which can separate the housing assembly 20 from the electrode assembly 10. The material of the insulating layer can be selected from materials commonly used in the art, and is not particularly limited here.

[0127] The electrode assembly 10 housed within the housing assembly 20 may be one or more.

[0128] The electrode assembly 10 includes a positive electrode and a negative electrode. During the charging and discharging process of the battery cell 7, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes. Optionally, the electrode assembly 10 also includes a separator disposed between the positive and negative electrodes, which can reduce the risk of short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0129] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0130] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0131] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, titanium, silver-surfaced aluminum, or stainless steel can be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0132] As an example, when the battery cell 31 in this embodiment is a lithium-ion battery or a lithium metal battery, the positive electrode active material may include one or more of the following materials: phosphates, layered transition metal oxides, and their respective modified compounds; optionally, the positive electrode active material may include layered transition metal oxides and their respective modified compounds, which is beneficial to improving the energy density of the battery cell 7. However, this application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material layer of a battery may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0133] Examples of phosphates may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0134] Layered transition metal oxides include those with the general formula Li a Ni b Co c M d O e A f One or more of the compounds and their modified compounds, 0.8≤a≤1.2, 0.3≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

[0135] Examples of layered transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.80 Co 0.15 Al 0.05 One or more of O2 and its modified compounds.

[0136] When the battery cell 7 in the embodiments of this application is a sodium-ion battery or a sodium metal battery, the positive electrode active material may include, but is not limited to, one or more of sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0137] As an example, positive electrode active materials for sodium-ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, with the general formula X p M' q (PO4) r Ox Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, optionally one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, optionally one or more of F, Cl and Br.

[0138] In the embodiments of this application, the modified compounds of the above-mentioned positive electrode active materials can be doped and / or surface coated to modify the positive electrode active materials, such as carbon coating modification, fast ion conductor coating modification, etc.

[0139] During the charging and discharging process, the battery cell 7 undergoes the insertion and extraction of active ions such as Li, resulting in a different molar content of Li in the battery cell 7 at different discharge states. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li may change after charge-discharge cycles.

[0140] In the embodiments of this application, the molar content of oxygen (O) in the positive electrode active materials is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of oxygen (O) to change. In reality, the molar content of oxygen (O) will fluctuate.

[0141] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not have a positive electrode active material layer. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0142] In some embodiments, the positive electrode active material layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent in the positive electrode active material layer is ≤5 wt%.

[0143] In some embodiments, the positive electrode active material layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder in the positive electrode active material layer is ≤5 wt%.

[0144] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0145] In some embodiments, the battery cell is an ion-type battery such as a lithium-ion battery, and the negative electrode can be a negative electrode sheet. The negative electrode sheet can include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material.

[0146] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0147] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0148] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cell 7. As an example, the negative electrode active material may include one or more of the following materials: carbon materials (e.g., carbon materials include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon), silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active material layers in batteries may also be used. These negative electrode active material layers may be used alone or in combination of two or more.

[0149] In some embodiments, the negative electrode active material layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon fibers. In some embodiments, the mass percentage of the negative electrode conductive agent in the negative electrode active material layer is ≤5 wt%.

[0150] In some embodiments, the negative electrode active material layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder in the negative electrode active material layer is ≤5 wt%.

[0151] In some embodiments, the negative electrode active material layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of other additives in the negative electrode active material layer is ≤2 wt%.

[0152] In other embodiments, the battery cell is a metal-type battery, such as a lithium metal battery, and the negative electrode can be a negative electrode sheet, which may include a negative electrode current collector. Optionally, the negative electrode sheet may also include a conductive layer disposed on the surface of the negative electrode current collector. The conductive layer includes a negative electrode binder. During the charging process of the battery cell 7, lithium ions gain electrons on the negative electrode sheet to form a lithium metal layer.

[0153] In some embodiments, the battery cell 7 also includes an electrolyte. During the charging and discharging process of the battery cell, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates. The embodiments of this application do not impose any particular limitation on the type of electrolyte; it can be selected according to actual needs.

[0154] The electrolyte may include a solid electrolyte, for example, a solid electrolyte disposed in the form of a film between the positive electrode and the negative electrode. For example, the positive electrode, the solid electrolyte layer and the negative electrode are stacked, and the solid electrolyte layer may be coated on the surface of the positive electrode active material layer in the positive electrode, or coated on the surface of the negative electrode active material layer in the negative electrode.

[0155] In some embodiments, the solid electrolyte includes one or more of sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, and polymer solid electrolytes.

[0156] Sulfide solid electrolytes include one or more of the following: sulfide crystalline solid electrolytes, sulfide glass, and glass-ceramic solid electrolytes.

[0157] In some embodiments, the sulfide solid electrolyte includes Li 10 GeP2S 12 Li6PS5Cl, Li 10 Sn P2S 12 One or more of Li2S-P2S5, Li2S-SiS2 and Li2S-B2S3.

[0158] Oxide solid electrolytes are classified into two categories according to their material structure: crystalline oxide electrolytes and glassy oxide electrolytes (amorphous oxide electrolytes). Crystalline oxide electrolytes include one or more types such as perovskite, NASICON, LISICON, and garnet, while glassy oxide electrolytes include LiPON type electrolytes.

[0159] In some embodiments, the oxide solid electrolyte includes Li 3.3 La 0.56 TiO3, LiTi2(PO4)3, Li 14 Zn(GeO4)4, Li7La3Zr2O 12 Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 2), Li 7-a La3Zr 2-a M a O 12 (M includes one or more of Ta and Nb; 0 < a < 2), Lib La 2 / 3-b TiO3 (0 < b < 2), LiAlO2, Li2ZrO3 and Li4Ti5O 12 One or more of them.

[0160] In some embodiments, the halide solid electrolyte includes one or more of Li3YCl6, Li3ErCl6, Li3YBr6, Li3InBr6, and Li3InCl6.

[0161] Polymer solid electrolytes (SPEs) are primarily composed of a polymer matrix and an electrolyte salt. The electrolyte salt may include lithium salts, specifically one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluoroborate (LiBF4). The electrolyte salt may also include sodium salts, specifically one or more of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), and sodium tetrafluoroborate (NaBF4).

[0162] In some embodiments, the SPE includes one or more of the following: epoxy compounds, polyester compounds, polyalkoxy compounds, polyolefin compounds, polyacrylonitrile (PAN), and monoionic polymer electrolytes. For example, epoxy compounds include one or more of polyethylene oxide (PEO) and polypropylene oxide (PPO). Polyolefin compounds include one or more of polyvinylidene fluoride (PVDF) and polyvinylidene chloride (PVDC). Polyester compounds include one or more of polycarbonate compounds and polymethyl methacrylate (PMMA). Polycarbonate compounds include one or more of polypropylene carbonate and polytrimethylene carbonate.

[0163] Furthermore, the polymer matrix can be hybridized with inorganic particles, including metal oxide nanoparticles such as MgO, Al2O3, and SiO2, as well as one or more of zeolites and montmorillonite. The addition of inorganic particles can reduce crystallinity, and the interactions between the polymer matrix, lithium salt, and inorganic particles can improve conductivity and ion transference number. Inorganic particles can also adsorb trace impurities such as moisture in the electrolyte and improve mechanical properties.

[0164] In this embodiment, the polymer matrix and electrolyte salt can be added to a solvent such as N,N-dimethylformamide, dispersed evenly to obtain a slurry, and then molded to obtain a polymer solid electrolyte.

[0165] In the embodiments of this application, the electrode assembly 10 is a wound structure or a stacked structure, and can be selected as a stacked structure.

[0166] When the electrode assembly 10 has a wound structure, the positive electrode sheet is a single piece and the negative electrode sheet is a single piece, and the positive and negative electrode sheets are wound in the same direction.

[0167] When the electrode assembly 10 has a stacked structure, there are multiple positive electrode sheets and multiple negative electrode sheets, and the multiple positive electrode sheets and multiple negative electrode sheets are stacked.

[0168] like Figures 4 to 8 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a composite film 30 covering the electrode assembly 10. The composite film 30 includes a first layer 31, a second layer 32, and a third layer 33. The first layer 31 is connected to the surface of the electrode assembly 10. The second layer 32 is stacked with the first layer 31 along the thickness direction W of the composite film 30 and is connected to the side of the first layer 31 away from the electrode assembly 10. The second layer 32 includes a porous structure. The third layer 33 is stacked with the second layer 32 along the thickness direction W of the composite film 30 and is connected to the side of the second layer 32 away from the first layer 31. The flatness of the third layer 33 is less than that of the second layer 32.

[0169] The composite film 30 is connected to the surface of the electrode assembly 10 through the first layer 31, which can effectively protect the electrode assembly 10 and reduce the entry of external impurities into the electrode assembly 10, thus reducing their adverse effects on the electrode assembly 10.

[0170] The second layer 32 of the composite membrane 30 includes a porous structure with a certain porosity and excellent air permeability, which can effectively reduce the risk of bubbles between the composite membrane 30 and the electrode assembly 10. If bubbles exist between the two, the gas in the bubbles flows through the first layer 31 to the second layer 32 and then flows out through the porous structure of the second layer 32, which can effectively improve the flatness of the electrode surface.

[0171] Since the second layer 32 includes a porous structure, it causes the surface of the composite film 30 to be rough. The third layer 33 has relatively small flatness, which can compensate for the adverse effects of the porous structure of the second layer 32 and reduce the flatness of the composite film 30. As a result, the overall flatness of the electrode assembly 10 covered by the composite film 30 is small, which can effectively improve the reliability of the battery cell 7.

[0172] In some embodiments, the porosity of the composite membrane 30 is 35% to 90%, for example, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any combination of two of the above values. Optionally, the porosity of the composite membrane 30 is 35% to 70%.

[0173] When the porosity of the composite membrane 30 is within the above range, its air permeability is excellent, which can effectively reduce the risk of air bubbles between the composite membrane 30 and the electrode assembly 10.

[0174] In the embodiments of this application, the porosity of the composite membrane 30 has a meaning known in the art and can be tested using known methods and equipment, such as measuring it using the gas displacement method according to GB / T24586. Porosity P = (V1-V2) / V1*100%, where V1 is the apparent volume of the sample and V2 is the actual volume of the sample.

[0175] In some embodiments, the shrinkage rate of the composite membrane 30 is from 10% to 70%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range of two of the above values. Optionally, the shrinkage rate of the composite membrane 30 is from 10% to 30%.

[0176] When the shrinkage rate of the composite membrane 30 is within the above range, the composite membrane 30 has a certain shrinkage capacity and can change with the volume change of the electrode assembly 10, thereby providing a good protective effect for the electrode assembly 10.

[0177] In the embodiments of this application, the shrinkage rate of the composite membrane 30 has a meaning known in the art and can be tested using equipment and methods known in the art, such as in accordance with GB / T 36363-2018 Test Methods for Polyolefin Separators for Lithium-ion Batteries.

[0178] In some embodiments, the thickness of the composite film 30 is from 50 μm to 200 μm, for example, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm or any range of two of the above values.

[0179] When the thickness of the composite film 30 is within the above range, the composite film 30 can provide excellent protection for the electrode assembly 10 without taking up too much space, which is beneficial for the battery cell 7 to still have a high volumetric energy density.

[0180] In the embodiments of this application, the thickness of the composite membrane 30 has a meaning known in the art, and can be tested using equipment and methods known in the art. The thickness can be directly measured by performing a tomographic scan on the sample.

[0181] In some embodiments, the shrinkage rate of the second layer 32 is 3% to 60%, for example, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any range of two of the above values. Optionally, the shrinkage rate of the second layer 32 is 10% to 30%.

[0182] When the shrinkage rate of the second layer 32 is within the aforementioned range, the second layer 32 has a certain shrinkage capacity, which can cause the composite membrane 30 to change in accordance with the volume change of the electrode assembly 10, thereby providing a better protective effect for the electrode assembly 10. Moreover, through the shrinkage of the second layer 32, the gas located in the porous structure can be squeezed out of the composite membrane 30. For example, during the charging process of the battery cell 7, the electrode assembly 10 may expand in volume, and the composite membrane 30 can stretch synchronously; during the discharging process of the battery cell 7, the electrode assembly 10 may shrink in volume, and the composite membrane 30 can shrink synchronously.

[0183] In some embodiments, the material of the second layer 32 includes one or more of polyolefin materials, polyester materials, polyimide materials, and polysaccharide materials. Polysaccharide materials may be selected.

[0184] For example, polyolefin materials include one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene.

[0185] For example, polyester materials include one or more of polyethylene terephthalate and polyethylene naphthalate.

[0186] For example, polyimide materials include one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone.

[0187] For example, polysaccharide materials include one or more of cellulose, hemicellulose, and lignin. Polysaccharide materials have relatively higher porosity, which is more conducive to gas expulsion.

[0188] In some embodiments, the thickness of the second layer 32 is from 25 μm to 150 μm, for example, 25 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 100 μm, 120 μm, 150 μm or any combination of two of the above values.

[0189] When the thickness of the second layer 32 is within the above range, the porous structure of the second layer 32 is relatively abundant, which can guide the gas located between the composite membrane 30 and the electrode assembly 10 to flow into the second layer 32 and out of the composite membrane 30.

[0190] In the embodiments of this application, the parameter testing of each membrane layer in the composite membrane 30 can be carried out during the preparation of the composite membrane 30, or after each membrane layer of the composite membrane 30 is peeled off and tested. The specific testing methods for the parameters are as described above and will not be repeated here.

[0191] In some embodiments, the first layer 31 is adhesive, and the peel strength of the composite film 30 is from 0.5 N / m to 90 N / m, for example, 0.5 N / m, 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, 40 N / m, 45 N / m, 50 N / m, 55 N / m, 60 N / m, 70 N / m, 80 N / m, 90 N / m, or any range of two of the above values.

[0192] When the peel strength of the composite membrane 30 is within the above-mentioned range, the bonding force between the first layer 31 and the electrode assembly 10 is strong, and it is not easy to peel off from the surface of the electrode assembly 10. Moreover, the strong bonding force between the first layer 31 and the second layer 32 makes the structure of the composite membrane 30 itself more stable.

[0193] In the embodiments of this application, the peel strength of the composite film 30 characterizes the degree of adhesion of the composite film 30 to the side facing the electrode assembly 10. Peel strength is a well-known concept in the art and can be tested using equipment and methods known in the art, such as the test method for peel strength of adhesive tape in GB / T 2792-2014.

[0194] In some embodiments, the first layer 31 includes an adhesive, which may include one or more of a sensitive adhesive and a non-sensitive adhesive. The adhesive may be a sensitive adhesive, which means that the adhesive changes viscosity after receiving an external stimulus, such as pressure, temperature, or change in light wavelength.

[0195] When the composite membrane 30 is coated onto the electrode assembly 10, the first layer 31 has relatively low viscosity, which is conducive to squeezing the gas between the first layer 31 and the electrode assembly 10 to the external environment; then the composite membrane 30 is externally stimulated, which increases the viscosity of the first layer 31, strengthens the bonding force between the first layer 31 and the electrode assembly 10, and makes the structure more stable.

[0196] Optionally, the initial peel strength of the composite film 30 may be less than or equal to the final peel strength of the composite film 30.

[0197] The initial peel strength of the composite membrane 30 ranges from 0.5 N / m to 90 N / m. Initial peel strength refers to the peel strength of the composite membrane 30 under conditions where it is not subjected to external stimuli.

[0198] The final peel strength of the composite membrane 30 ranges from 0.5 N / m to 90 N / m. Final peel strength refers to the peel strength of the composite membrane after external stimulation.

[0199] Optionally, the sensitive adhesive includes one or more of photosensitive adhesive, thermosensitive adhesive and pressure-sensitive adhesive, and can be selected as pressure-sensitive adhesive, which is more conducive to controlling the bonding of the first layer 31 to the electrode assembly 10.

[0200] For example, the photosensitive adhesive includes one or more of polyacrylates, azobenzene, acetophenone derivatives, aromatic ketone compounds, and acylphosphine oxides.

[0201] For example, the polyacrylate in photosensitive adhesives includes acrylate-olefin copolymers, where the acrylates include one or more of methyl acrylate, ethyl acrylate, and butyl acrylate. The olefins include one or more of ethylene and butadiene.

[0202] For example, acetophenone derivatives include one or more of hydroxyacetophenone, alkylaminoacetophenone, and aryl azoisoxazole.

[0203] For example, aromatic ketones include one or more of benzophenone and dialkoxyacetophenone.

[0204] For example, the heat-sensitive adhesive includes one or more of polyurethane, polystyrene, ethylene-vinyl acetate copolymer, polypropylene glycol, and polyorganosiloxane.

[0205] For example, pressure-sensitive adhesives include one or more of polyacrylates, polyorganosiloxanes, styrene-butadiene rubber, cis-1,4-polyisoprene, polyisobutylene, butadiene-styrene copolymers, polyvinyl ethers, and vinyl acetate polymers.

[0206] For example, the polyacrylate in pressure-sensitive adhesives includes acrylate-olefin copolymers, where the acrylates include one or more of methyl acrylate, ethyl acrylate, and butyl acrylate. The olefins include one or more of ethylene and butadiene.

[0207] Optionally, the non-sensitive adhesive includes one or more of cis-1,4-polyisoprene, acrylate, polymethylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, polyurethane, polystyrene, polyacrylate, ethylene-vinyl acetate copolymer, and styrene-butadiene copolymer.

[0208] In some embodiments, the thickness of the first layer 31 is 5 μm to 10 μm, for example 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or any range of two of the above values.

[0209] When the thickness of the first layer 31 is within the above range, the thickness of the first layer 31 is moderate, which is conducive to the gas entering the second layer 32 through the first layer 31, thereby allowing the gas to flow out from the second layer 32.

[0210] In some embodiments, the flatness of the third layer 33 is from 0.001 mm to 0.05 mm, for example, 0.001 mm, 0.005 mm, 0.01 mm, 0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm, 0.05 mm, or a range of any two of the above values. Optionally, the flatness of the third layer 33 is from 0.001 mm to 0.005 mm.

[0211] The third layer 33 has relatively small flatness. After the composite film 30 covers the electrode assembly 10, the flatness of the covered assembly is small, which is beneficial to improving the overall reliability of the battery cell 7.

[0212] Optionally, the third layer 33 includes one or more of the following materials: polyolefin, polyester, polyimide, paraffin, ceramic, carboxymethyl cellulose, and styrene-maleic anhydride polymer. This material has shrinkage properties and can shrink along with the electrode assembly 10.

[0213] For example, polyolefin materials include one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene.

[0214] For example, polyester materials include one or more of polyethylene terephthalate and polyethylene naphthalate.

[0215] For example, polyimide materials include one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone.

[0216] For example, the ceramic material includes at least one of alumina, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide, and calcium oxide.

[0217] In the case where the third layer 33 includes paraffin wax, the paraffin wax can be applied to the second layer 32 by spraying, solvent dissolution coating, or other methods.

[0218] When the third layer 33 includes ceramic material, the ceramic material can be deposited on the second layer 32 by physical vapor deposition, chemical vapor deposition, or other methods.

[0219] When the third layer 33 comprises one or more of the following materials: polyolefin, polyester, polyimide, carboxymethyl cellulose, and styrene-maleic anhydride polymer, the third layer 33 and the second layer 32 can be bonded together using an adhesive. Alternatively, the third layer 33 and the second layer 32 can be bonded together using methods such as heat fusion without adhesive bonding.

[0220] The adhesive may include one or more of the following: cis-1,4-polyisoprene, acrylate, polymethylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, polyurethane, polystyrene, polyacrylate, ethylene-vinyl acetate copolymer, and styrene-butadiene copolymer.

[0221] In some embodiments, the thickness of the third layer 33 is from 5 μm to 20 μm, for example 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 15 μm, 20 μm, or any combination of two of the above values.

[0222] When the thickness of the third layer 33 is within the above range, it is beneficial to provide a smaller flatness, and the thickness of the third layer 33 will not be too thick, which is beneficial to improving the volumetric energy density of the battery cell 7.

[0223] The method of coating the electrode assembly 10 with the composite film 30 will be described next.

[0224] like Figure 9 and Figure 10 As shown, from the external shape of the electrode assembly 10, the electrode assembly 10 includes a tab portion 12 and a main body portion 11. The tab portion 12 includes a first tab and a second tab, which have opposite polarities. One of the first tab and the second tab is a positive tab, and the other is a negative tab. The first tab and the second tab extend beyond the main body portion 11. The first tab is the portion of the first electrode sheet that is not coated with active material, and the second tab is the portion of the second electrode sheet that is not coated with active material. The first tab and the second tab are used to draw current out from the main body portion 11. The first electrode sheet and the second electrode sheet have opposite polarities; in other words, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet.

[0225] The positive electrode tab and the negative electrode tab can be drawn from the same end of the main body 11, or the positive electrode tab and the negative electrode tab can be drawn from opposite ends of the main body 11 respectively.

[0226] In some embodiments, the tab 12 is connected to at least one side of the main body 11 along a first direction Z, which is perpendicular to the thickness direction X of the electrode assembly 10; the first direction Z may be parallel to the length direction or the width direction of the electrode assembly 10.

[0227] In some embodiments, the composite film 30 covers the surface of the main body 11. The composite film 30 can provide excellent protection for the main body 11.

[0228] The composite film 30 covers the surface of the main body 11, and can cover at least a portion of the surface of the main body 11. In other words, the composite film 30 can cover a portion of the surface of the main body 11, or cover the entire surface of the main body 11.

[0229] In some embodiments, the main body 11 includes two first surfaces 111 and two second surfaces 112, the two first surfaces 111 being opposite to each other along the thickness direction X of the electrode assembly 10, and the two second surfaces 112 being opposite to each other along the second direction Y, wherein the composite film 30 is disposed around the two first surfaces 111 and the two second surfaces 112.

[0230] The composite film 30 can be understood as a ring structure, surrounding the main body 11, and serves to fasten and constrain the main body 11, making it less prone to internal layer peeling and improving the structural stability of the electrode assembly 10. Of course, the composite film 30 may also only cover the two first surfaces 111.

[0231] The first surface 111 and the second surface 112 are covered by a composite film 30. The composite film 30 can completely cover the first surface 111 and the second surface 112, or it can partially cover the first surface 111 and the second surface 112.

[0232] The first surface 111 is covered with a composite film 30. Optionally, the projection of the first surface 111 along the thickness direction X of the electrode assembly 10 lies within the projection of the composite film 30 along the thickness direction X of the electrode assembly 10. In this case, the composite film 30 completely covers the first surface 111, which can reduce the flatness of the coated electrode assembly 10 and improve its density. Of course, the composite film 30 can also partially cover the first surface 111. The thickness direction X of the electrode assembly 10 is the projection normal, that is, the thickness direction X of the electrode assembly 10 is perpendicular to the projection plane. The dimension of the composite film 30 along the first direction Z can be greater than or equal to the dimension of the first surface 111 along the first direction Z. The dimension of the composite film 30 along the second direction Y can be greater than or equal to the dimension of the first surface 111 along the second direction Y.

[0233] The second surface 112 is covered by a composite film 30. Optionally, the projection of the second surface 112 along the second direction Y of the electrode assembly 10 lies within the projection of the composite film 30 along the second direction Y of the electrode assembly 10. In this case, the composite film 30 completely covers the second surface 112; of course, the composite film 30 may also partially cover the second surface 112. The dimension of the composite film 30 along the thickness direction X of the electrode assembly 10 may be greater than or equal to the dimension of the second surface 112 along the thickness direction X of the electrode assembly 10.

[0234] The second direction Y, the first direction Z, and the thickness direction X of the electrode assembly 10 are all perpendicular to each other. When the first direction Z is parallel to the length direction of the electrode assembly 10, the second direction Y is parallel to the width direction of the electrode assembly 10. When the first direction Z is parallel to the width direction of the electrode assembly 10, the second direction Y is parallel to the length direction of the electrode assembly 10.

[0235] The composite membrane 30 can be a single layer of membrane, with edge sealing treatment performed on one of the two second surfaces 112, so that the composite membrane 30 forms a ring structure surrounding the main body 11.

[0236] The composite membrane 30 can also be made of two parts, which can be arranged opposite each other and sealed at two different surfaces, so that the composite membrane 30 forms a ring structure around the main body 11.

[0237] When the composite membrane 30 uses a two-part membrane, the two parts of the membrane can be defined as a first cover 40 and a second cover 50, respectively.

[0238] The first cover 40 includes a first body portion 41 and a first protrusion 42. The first body portion 41 covers one of the two first surfaces 111. The first protrusion 42 is connected to the first body portion 41 and protrudes along the thickness direction X of the electrode assembly 10, and covers at least a portion of the second surface 112.

[0239] The second cover 50 includes a second body portion 51 and a second protrusion 52. The second body portion 51 covers the other of the two first surfaces 111. The second protrusion 52 is connected to the second body portion 51 and protrudes along the thickness direction X of the electrode assembly 10, covering at least a portion of the second surface 112.

[0240] The projection of the second surface 112 along the second direction Y is located within the projections of the first protrusion 42 and the second protrusion 52 along the second direction Y.

[0241] The projection of the first protrusion 42 and the second protrusion 52 along the second direction Y refers to the projection area obtained by projecting the first protrusion 42 and the second protrusion 52 as a whole along the second direction Y. The second direction Y is the projection normal, that is, the second direction Y is perpendicular to the projection plane.

[0242] In this embodiment, the first surface 111 can be covered by the first body portion 41 and the second body portion 51, and the second surface 112 can be covered by the first protrusion 42 and the second protrusion 52, so that the composite film 30 can provide excellent protection for the electrode assembly 10.

[0243] For example, the projection of the second protrusion 52 along the second direction Y and the projection of the first protrusion 42 along the second direction Y are continuously arranged. It can be understood that the second protrusion 52 and the first protrusion are connected along the thickness direction of the electrode assembly 10.

[0244] For example, the projection of the second protrusion 52 along the second direction Y and the projection of the first protrusion 42 along the second direction Y at least partially overlap. For instance, the projection of the second protrusion 52 along the second direction Y and the projection of the first protrusion 42 along the second direction Y partially overlap; or the projection of the second protrusion 52 along the second direction Y and the projection of the first protrusion 42 along the second direction Y completely overlap. This arrangement makes the sealing edge of the composite film 30 more stable, the structure more stable, and less prone to cracking at the sealing edge, thus providing excellent fastening and protection for the electrode assembly 10.

[0245] The first protrusion 42 and the second protrusion 52 can be connected by means of heat fusion, bonding, etc.

[0246] In some embodiments, the main body 11 further includes two third surfaces 113 facing each other along the first direction Z, and the composite film 30 also covers at least one of the two third surfaces 113.

[0247] The tab 12 can be connected to one of the third surfaces 113 or to both of the third surfaces 113. The composite film 30 can cover the third surface 113 that is not connected to the tab 12 or the third surface 113 that is connected to the tab 12.

[0248] Optionally, the projection of the third surface 113 along the first direction Z can be located within the projection of the composite film 30 along the first direction Z, where the first direction Z is the projection normal and is perpendicular to the projection surface.

[0249] The fact that at least one third surface 113 is covered can further enhance the protective capability of the composite film 30 for the electrode assembly 10. Furthermore, since the composite film 30 is insulating, it can effectively isolate the electrode assembly 10 from the housing assembly 20 and the like, thereby improving the reliability of the battery cell 7.

[0250] In some embodiments, the density of the electrode assembly 10 is greater than or equal to 94% and less than 100%, for example, 94%, 95%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, or any combination of two of the above values. A density of the electrode assembly 10 within the above range can improve the energy density of the battery cell 77. Optionally, the density of the electrode assembly 10 is greater than or equal to 96% and less than 100%.

[0251] The degree of densification of the electrode assembly 10 can be characterized by density, for example, the calculation method is as follows:

[0252]

[0253] In the formula, τ is the packing density; m is the mass; V is the volume; and ρ is the theoretical true density.

[0254] This application also provides a method for preparing a single battery cell.

[0255] Figure 11 This application provides a schematic flowchart of a method for preparing a single battery cell for some embodiments.

[0256] like Figure 10 As shown, the preparation method includes:

[0257] Step S110: Provide the initial electrode assembly;

[0258] Step S120: A composite membrane is provided to coat the initial electrode assembly to obtain the electrode assembly to be pressed. The composite membrane can be any of the composite membranes described above.

[0259] Step S130: After isostatic pressing the electrode assembly to be pressed, an electrode assembly coated with a composite film is obtained.

[0260] Step S140: Assemble the electrode assembly covered with the composite film into the housing assembly to prepare the battery cell.

[0261] After a composite membrane undergoes a pressing process, such as isostatic pressing, its porosity may decrease. The composite membrane includes both a pre-pressed and post-pressed state. The porosity of the composite membrane in the pre-pressed state is greater than or equal to the porosity in the post-pressed state. The composite membrane in a single battery cell is in the post-pressed state. The state of the composite membrane before isostatic pressing is the pre-pressed state.

[0262] Optionally, the porosity of the composite membrane before pressing can be greater than or equal to the porosity of the composite membrane after pressing.

[0263] For example, in the pre-pressed state, the porosity of the composite membrane is 35% to 90%, optionally 35% to 80%.

[0264] For example, in the pressed state, the porosity of the composite membrane is 35% to 90%, optionally 35% to 70%.

[0265] For example, in the pre-pressed state, the shrinkage rate of the composite film is 10% to 70%, optionally 10% to 30%.

[0266] For example, in the pressed state, the shrinkage rate of the composite film is 10% to 70%, optionally 10% to 30%.

[0267] Optionally, the peel strength of the composite film in the pre-pressing state can be less than or equal to the peel strength of the composite film in the post-pressing state. For example, the adhesiveness of the composite film increases after external stimulation.

[0268] For example, in the pre-pressed state, the peel strength of the composite film is 0.5 N / m to 60 N / m.

[0269] For example, in the pressed state, the peel strength of the composite film is 0.5 N / m to 60 N / m.

[0270] Optionally, the thickness of the composite film before pressing can be greater than or equal to the thickness of the composite film after pressing.

[0271] For example, the thickness of the composite film is 50 μm to 200 μm before pressing.

[0272] For example, in the pressed state, the thickness of the composite film is 50 μm to 200 μm.

[0273] Optionally, the porosity of the second layer before pressing can be greater than or equal to the porosity of the second layer after pressing.

[0274] For example, before pressing, the porosity of the second layer is 40% to 90%; after pressing, the porosity of the second layer decreases.

[0275] For example, in the pre-pressed state, the shrinkage rate of the second layer is 3% to 60%, optionally 10% to 30%.

[0276] For example, in the compressed state, the shrinkage rate of the second layer is 3% to 60%, optionally 10% to 30%.

[0277] Optionally, the thickness of the second layer before pressing can be greater than or equal to the thickness of the second layer after pressing.

[0278] For example, in the pre-pressed state, the thickness of the second layer is 25 μm to 150 μm.

[0279] For example, in the pressed state, the thickness of the second layer is 25 μm to 150 μm.

[0280] Before isostatic pressing, a composite film is pre-coated onto the surface of the initial electrode assembly. The second layer of the composite film has a porous structure. If there are air bubbles between the composite film and the initial electrode assembly, during the isostatic pressing process, the air bubbles can flow into the porous structure of the composite film and then flow through the composite film to the gap between the composite film and the isostatic pressing film. After the isostatic pressing process, the isostatic pressing film is removed, and an electrode assembly coated with the composite film is obtained. It is basically free from wrinkles or air bubble defects, which makes the surface of the electrode assembly smoother and improves the reliability of the battery cell.

[0281] Step S110: Provide the initial electrode assembly.

[0282] In some implementations, step S110 may include:

[0283] Step S111: Provide multiple positive electrode plates, multiple negative electrode plates, and multiple solid electrolyte layers;

[0284] Step S112: The positive electrode, solid electrolyte layer and negative electrode are alternately stacked along the thickness direction to obtain the initial electrode assembly.

[0285] The initial electrode assembly includes a positive electrode, a solid electrolyte layer, and a negative electrode stacked together. The outermost part of the initial electrode assembly along the thickness direction can be a positive electrode, a solid electrolyte layer, or a negative electrode.

[0286] It should be noted that the difference between the initial electrode assembly and the electrode assembly to be pressed is that the electrode assembly to be pressed is coated with a composite film; both the initial electrode assembly and the electrode assembly include a positive electrode, a negative electrode, and a solid electrolyte layer, but their densities differ. The initial electrode assembly has more gaps between the positive electrode, the solid electrolyte layer, and the negative electrode, resulting in a relatively lower density. The initial electrode assembly coated with the composite film is press-fitted to form the electrode assembly. The density of the electrode assembly meets a preset density, for example, a preset density greater than or equal to 94% and less than 100%, which can be selected as 96% and less than 100%.

[0287] Step S120: The initial electrode assembly is coated with a composite film.

[0288] When the composite membrane is initially coated onto the initial electrode assembly, the first layer of the composite membrane has low viscosity, which is beneficial for removing gas between the composite membrane and the initial electrode assembly, thereby reducing the adverse effects of gas on subsequent processes.

[0289] Then, external stimuli are applied to the composite membrane. For example, the first layer includes a pressure-sensitive adhesive. By increasing the external pressure, the adhesion of the first layer increases, the peel strength increases, and the bonding force between the first layer and the initial electrode assembly becomes stronger. The two are less likely to peel off, and gas cannot easily pass between them, which can further reduce the adverse effects of air bubbles. The adhesion of the first layer can be irreversible to make the bonding force between the first layer and the electrode assembly more stable.

[0290] like Figure 12 As shown, when the composite membrane 30 uses two parts, the first cover 40 and the second cover 50 are respectively arranged opposite each other, and the ends of the first cover 40 and the second cover 50 are sealed by means such as heat sealing or bonding, so that the composite membrane 30 is arranged around the electrode assembly 10. The structure after sealing is as follows. Figure 9 As shown.

[0291] Specifically, the first body portion covers one of the two first surfaces, the first protrusion is connected to the first body portion and protrudes along the thickness direction of the electrode assembly, and covers at least a portion of the second surface;

[0292] The second body portion covers the other of the two first surfaces, and the second protrusion is connected to the second body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface.

[0293] The first protrusion and the second protrusion are connected together by means of heat fusion, bonding or other methods.

[0294] Step 130: Isostatically press the electrode assembly to be pressed.

[0295] In some implementations, step 130 may include:

[0296] Step S131: Provide an isostatic membrane to the electrode assembly to be pressed to wrap the electrode assembly to be pressed;

[0297] Step S132: Extract the gas from the electrode assembly to be pressurized until the vacuum level in the electrode assembly to be pressurized meets the preset vacuum level.

[0298] Step S133: After sealing the electrode assembly to be pressed, perform isostatic pressing on the electrode assembly to be pressed.

[0299] Step S134: Remove the isostatic film on the electrode assembly to be pressed after isostatic pressing treatment to obtain an electrode assembly coated with a composite film.

[0300] An isostatic membrane can effectively isolate the electrode assembly to be pressurized from the isostatic medium, reducing the risk of contamination of the active material in the electrode assembly. Optionally, the isostatic medium may include one or more of a gaseous medium and a liquid medium. For example, the gaseous medium includes one or more inert gases, such as helium, neon, or argon. Another example is the liquid medium, which includes one or more of hydraulic oil, water, silicone oil, or dioctyl sebacate.

[0301] Optionally, the isostatic membrane can adopt the same external shape as the electrode assembly to be pressed. For example, if the electrode assembly to be pressed is a cuboid, the isostatic membrane can adopt a similar cuboid structure. Or, if the electrode assembly to be pressed is a cylinder, the isostatic membrane can adopt a similar cylindrical structure.

[0302] like Figure 13 As shown, the isostatic pressure membrane 70 may include an encapsulation cavity 71 and an encapsulation cover 72. The encapsulation cavity 71 contains the electrode assembly to be pressured, and the encapsulation cover 72 covers the encapsulation cavity 71. The encapsulation cover 72 may extend beyond the encapsulation cavity 71, which facilitates sealing of the isostatic pressure membrane 70. The encapsulation cavity 71 and the encapsulation cover 72 can be encapsulated by one of the following methods: heat sealing, ultrasonic roll welding, laser welding, etc.

[0303] Optionally, the isostatic membrane may be made of one or more of the following materials: polyolefin, polyimide, polyphenylene sulfide, and metal.

[0304] For example, polyolefin materials include one or more of polyethylene, polypropylene, and polytetrafluoroethylene.

[0305] For example, polyimide materials include one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone.

[0306] For example, the metal material includes one or more of aluminum, copper, and steel.

[0307] In step S132, the preset vacuum level can be from -101KPa to -50KPa, such as -101KPa, -100KPa, -90KPa, -80KPa, -70KPa, -60KPa, -50KPa, or any range of two of the above values.

[0308] In step S133,

[0309] For example, the isostatic pressing temperature is from 25°C to 300°C, such as 25°C, 30°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 270°C, 300°C, or any range of two of the above values.

[0310] For example, the isostatic pressure treatment pressure is from 100 MPa to 2000 MPa, such as 100 MPa, 200 MPa, 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa, 1000 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa, 2000 MPa, or any range of two of the above values.

[0311] For example, the isostatic pressing time is from 5 min to 60 min, such as 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any range of two of the above values.

[0312] In this embodiment of the application, the electrode assembly to be pressed is subjected to a pressing process, which may include one or more pressing steps. After the pressing process, the density of the electrode assembly meets a preset density requirement, such as a density greater than or equal to 94% and less than 100%, or optionally 96% and less than 100%.

[0313] When the lamination process includes one lamination step, it may include isostatic pressing. When the lamination process includes multiple lamination steps, it may include multiple isostatic pressing processes, or it may include flat pressing and isostatic pressing processes. Through multiple lamination processes, the density can be improved, thereby further increasing the energy density of the battery cell.

[0314] The pressing process makes the electrode assembly more compact inside, reduces the gap between the electrode and the solid electrolyte layer, and allows the electrode and the solid electrolyte layer to make face-to-face contact, which helps to reduce the transport resistance of active ions at the solid-solid interface. In addition, the pressing process also makes the particles in the active material layer more compact, increases the compaction density of the active material layer, and thus increases the energy density of the battery cell.

[0315] For example, the preparation method may also include a flat pressing treatment prior to the isostatic pressing treatment.

[0316] For example, after isostatic pressing, the preparation method may also include flat pressing.

[0317] Flattening is a process in which a force is applied to the electrode assembly to be pressed along the thickness direction of the electrode assembly, making the interior of the electrode assembly to be pressed more compact and forming an integral structure, which can reduce the misalignment between electrodes in subsequent processes.

[0318] For example, the flat pressing temperature is from 25°C to 200°C, such as 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or any range of two of the above values.

[0319] For example, the pressure for the flattening process is from 3 MPa to 20 MPa, such as 3 MPa, 5 MPa, 8 MPa, 10 MPa, 12 MPa, 15 MPa, 18 MPa, 20 MPa, or any range of two of the above values.

[0320] For example, the flattening process time is from 10s to 180s, such as 10s, 20s, 50s, 80s, 100s, 120s, 150s, 180s or any range of two of the above values.

[0321] For example, the flat pressing process uses a flat pressing plate, and the parallelism of the flat pressing plate is controlled to be 0.05mm to 0.50mm, such as 0.05mm, 0.10mm, 0.20mm, 0.30mm, 0.40mm, 0.50mm or any two of the above values.

[0322] Example

[0323] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0324] Example 1

[0325] 1. Fabrication of stacked electrode assemblies

[0326] The initial electrode assembly is obtained by stacking the negative electrode, the solid electrolyte layer and the positive electrode.

[0327] The initial electrode assembly is integrated for flattening treatment. The flattening temperature is 85℃, the pressure is 10MPa, the time is 60s, and the parallelism of the pressure plate is 0.1mm.

[0328] The initial electrode assembly after flattening is coated with a composite film to obtain the electrode assembly to be pressed.

[0329] An isostatic membrane is used to encapsulate the electrode assembly to be pressurized; the gas inside the electrode assembly is extracted until the vacuum level inside the electrode assembly is -95 kPa; the electrode assembly to be pressurized is then sealed; the electrode assembly to be pressurized is then subjected to isostatic pressing, with hydraulic oil as the isostatic medium, a temperature of 25°C, a pressure of 2000 MPa, and a time of 20 min; the isostatic membrane is then removed to obtain the electrode assembly coated with the composite membrane.

[0330] Comparative Example 1

[0331] 1. Fabrication of stacked electrode assemblies

[0332] The initial electrode assembly is obtained by stacking the negative electrode, the solid electrolyte layer and the positive electrode.

[0333] The initial electrode assembly is integrated for flattening treatment. The flattening temperature is 85℃, the pressure is 10MPa, the time is 60s, and the parallelism of the pressure plate is 0.1mm.

[0334] After flattening, the initial electrode assembly is wrapped with adhesive paper (polyethylene terephthalate, PET) to obtain the electrode assembly to be pressed.

[0335] The electrode assembly to be pressurized is encapsulated using an isostatic membrane; the gas inside the electrode assembly is extracted until the vacuum level inside the electrode assembly is -95 kPa; the electrode assembly to be pressurized is then sealed; the electrode assembly to be pressurized is then subjected to isostatic pressing, with silicone oil as the isostatic medium, a temperature of 150°C, a pressure of 800 MPa, and a time of 5 min; the isostatic membrane is then removed to obtain the electrode assembly covered with adhesive paper.

[0336] Examples 2-1 to 2-4

[0337] The stacked electrode assembly was prepared using a method similar to that of Example 1, except that the material of the first layer was adjusted.

[0338] Examples 3-1 and 3-2

[0339] The stacked electrode assembly was prepared using a method similar to that in Example 1, except that the thickness of the first layer was adjusted.

[0340] Examples 4-1 to 4-3

[0341] The stacked electrode assembly was prepared using a method similar to that of Example 1, except that the material of the second layer was adjusted.

[0342] Examples 5-1 to 5-2

[0343] A stacked electrode assembly was prepared using a method similar to that in Example 1, except that the porosity of the second layer was adjusted.

[0344] Examples 6-1 to 6-2

[0345] The stacked electrode assembly was prepared using a method similar to that of Example 1, except that the thickness of the second layer was adjusted.

[0346] Examples 7-1 to 7-2

[0347] The stacked electrode assembly was prepared using a method similar to that in Example 1, except that the flatness of the third layer was adjusted.

[0348] Examples 8-1 to 8-2

[0349] The stacked electrode assembly was prepared using a method similar to that of Example 1, except that the thickness of the third layer was adjusted.

[0350] Example 9

[0351] The stacked electrode assembly was prepared using a method similar to that of Example 1, except that the material of the third layer was adjusted.

[0352] Performance testing:

[0353] 1. Flatness test of stacked electrode assembly

[0354] (1) The sample to be tested was placed on a marble platform and compacted using 2 kg·f.

[0355] (2) The flatness value of the sample is output by laser surface scanning.

[0356] Flatness can characterize the deviation of the macroscopic unevenness of a sample surface from an ideal plane. The smaller the flatness, the smoother the surface.

[0357] 2. Density testing of stacked electrode assemblies

[0358] (1) The sample was weighed using an analytical balance, and the mass m of the electrode assembly was used.

[0359] (2) Three Dimensions (3D) scan the geometric volume of the test sample, which is the volume V of the electrode assembly. The ratio of the mass m of the electrode assembly to the volume V is the apparent density m / V.

[0360] (3) The theoretical true density of the sample was determined by the helium displacement method as ρ, and the ratio of the apparent density m / V to the theoretical true density ρ was the density.

[0361] Using the method described in Example 1, multiple sets of stacked electrode assemblies were prepared. The electrode assemblies were placed in the outer shell assembly and then processed through vacuum sealing, settling, formation, and shaping to obtain stacked battery cells. Statistical analysis was then performed.

[0362] 3. Cyclic failure rate of individual battery cells

[0363] Assemble the battery cells with the fixture, with the fixture surface pressure being 10 MPa;

[0364] At 60℃, the battery cells were subjected to 0.33C low-rate charging and discharging cycles according to the set test procedure to test the cycle failure rate.

[0365] The test results are shown in Table 1.

[0366] Table 1

[0367]

[0368] In Table 1,

[0369] In Example 1, the first layer of polyacrylate is a pressure-sensitive adhesive polyacrylate.

[0370] The initial peel strength of the first layer refers to the peel strength of the composite film when it is not subjected to external stimuli, and it can be used to characterize the initial peel strength of the composite film.

[0371] The final peel strength of the first layer refers to the peel strength of the composite film after external stimulation, which can be used to characterize the final peel strength of the composite film.

[0372] The initial porosity of the second layer refers to the porosity of the second layer of the composite membrane before it is subjected to isostatic pressure.

[0373] The initial porosity of a composite membrane refers to the porosity of the composite membrane before it is subjected to isostatic pressure.

[0374] The final porosity of a composite membrane refers to the porosity of the composite membrane after isostatic pressing.

[0375] The final thickness of the composite membrane refers to the thickness of the composite membrane after isostatic pressing.

[0376] The initial thickness of the second layer refers to the thickness of the second layer of the composite membrane before it is subjected to isostatic pressure.

[0377] The final thickness of the second layer refers to the thickness of the second layer of the composite membrane after isostatic pressing. Since the second layer has a porous structure, it may show a decreasing thickness trend after isostatic pressing. Of course, the thickness of the second layer may also remain unchanged.

[0378] The flatness of the third layer can be used to characterize the flatness of the electrode assembly coated with the composite film.

[0379] As can be seen from Table 1,

[0380] Comparative document 1 uses adhesive tape, which has relatively high flatness, but has problems such as wrinkles or bubbles. When conducting cyclic hanging test failure rate test, the cyclic hanging test failure rate reaches 5%.

[0381] The embodiments of this application employ a composite membrane with a porous structure. During the isostatic pressing process, air bubbles can flow into the porous structure of the composite membrane and then through the composite membrane to the gap between the composite membrane and the isostatic pressing membrane. After the isostatic pressing process, the isostatic pressing membrane is removed, resulting in an electrode assembly coated with the composite membrane. This assembly is essentially free of wrinkles or air bubbles, making the surface of the electrode assembly smoother and reducing the cycle failure rate to approximately 0%, thus improving the reliability of the battery cell. Furthermore, its high density further enhances the reliability of the battery cell.

[0382] Based on the porous structure of the second layer, Examples 4-1 to 4-3 adjust the material of the second layer to obtain an electrode assembly with good flatness.

[0383] The porosity of the composite membrane is within an appropriate range, for example, from 35% to 90%. In Examples 4-1 to 5-2, by adjusting the porosity, air bubbles can be effectively eliminated, resulting in electrode assemblies with good flatness. Furthermore, in Examples 6-1 and 6-2, by adjusting the thickness of the second layer, electrode assemblies with good flatness can also be obtained.

[0384] Examples 2-1 to 2-4 all obtained a first layer with strong bonding force by adjusting the material of the first layer, thereby improving the bonding force between the first layer and the electrode assembly; Examples 3-1 and 3-2 adjusted the thickness of the first layer to make the bonding force between the first layer and the electrode assembly stronger.

[0385] Examples 7-1 to 9 respectively adjust the material, flatness, and thickness of the third layer, so that the final electrode assembly has a small flatness, a smooth surface, and a relatively high density, resulting in high reliability of the battery cell.

[0386] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising an electrode assembly and a composite film covering the electrode assembly, the composite film comprising: The first layer is connected to the surface of the electrode assembly; The second layer is stacked with the first layer along the thickness direction of the composite film and is connected to the side of the first layer opposite to the electrode assembly. The second layer includes a porous structure. The third layer is stacked with the second layer along the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

2. The battery cell according to claim 1, wherein, The porosity of the composite membrane is 35% to 90%.

3. The battery cell according to claim 2, wherein, The porosity of the composite membrane is 35% to 70%.

4. The battery cell according to any one of claims 1 to 3, wherein, The shrinkage rate of the composite membrane is 10% to 70%.

5. The battery cell according to any one of claims 1 to 4, wherein, The thickness of the composite membrane is 50 μm to 200 μm.

6. The battery cell according to any one of claims 1 to 5, wherein, The shrinkage rate of the second layer is 3% to 60%.

7. The battery cell according to any one of claims 1 to 6, wherein, The material of the second layer includes one or more of the following: polyolefin materials, polyester materials, polyimide materials, and polysaccharide materials.

8. The battery cell according to claim 7, wherein, The polyolefin material includes one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene; and / or The polyester material includes one or more of polyethylene terephthalate and polyethylene naphthalate; and / or The polyimide material includes one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone; and / or The polysaccharide material includes one or more of cellulose, hemicellulose, and lignin.

9. The battery cell according to any one of claims 1 to 8, wherein, The peel strength of the composite film is from 0.5 N / m to 90 N / m.

10. The battery cell according to any one of claims 1 to 9, wherein, The first layer includes a sensitive adhesive.

11. The battery cell according to claim 10, wherein, The sensitive adhesive includes one or more of photosensitive adhesives, heat-sensitive adhesives, and pressure-sensitive adhesives.

12. The battery cell according to claim 11, wherein, The photosensitive adhesive comprises one or more of polyacrylate, azobenzene, acetophenone derivatives, aromatic ketone compounds, and acylphosphine oxides; and / or The heat-sensitive adhesive comprises one or more of polyurethane, polystyrene, ethylene-vinyl acetate copolymer, polypropylene glycol, and polyorganosiloxane; and / or The pressure-sensitive adhesive includes one or more of the following: polyacrylate, polyorganosiloxane, styrene-butadiene rubber, cis-1,4-polyisoprene, polyisobutylene, butadiene-styrene copolymer, polyvinyl ether, and vinyl acetate polymer.

13. The battery cell according to any one of claims 1 to 12, wherein, The flatness of the third layer is 0.001 mm to 0.05 mm.

14. The battery cell according to any one of claims 1 to 13, wherein, The third layer includes one or more of the following materials: polyolefin, polyester, polyimide, paraffin, ceramic, carboxymethyl cellulose, and styrene-maleic anhydride polymer.

15. The battery cell according to claim 14, wherein, The polyolefin material includes one or more of polyethylene, polypropylene, cis-1,4-polyisoprene, polyvinyl chloride, and polytetrafluoroethylene; and / or The polyester material includes one or more of polyethylene terephthalate and polyethylene naphthalate; and / or The polyimide material includes one or more of polyimide, polyimide ether ketone, polyetherimide, and polyimide ether sulfone; and / or The ceramic material includes at least one of aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide, and calcium oxide.

16. The battery cell according to any one of claims 1 to 15, wherein, The thickness of the first layer is 5 μm to 10 μm; and / or The thickness of the second layer is 25 μm to 150 μm; and / or The thickness of the third layer is 5 μm to 20 μm.

17. The battery cell according to any one of claims 1 to 16, wherein, The electrode assembly includes a main body and a tab. The main body is coated with an active material, and the tab is connected to at least one side of the main body along a first direction. The tab is not coated with an active material, and the first direction is perpendicular to the thickness direction of the electrode assembly. The composite film is applied to the surface of the main body.

18. The battery cell according to claim 17, wherein, The main body includes: The two first surfaces are opposite each other along the thickness direction of the electrode assembly; The two second surfaces are opposite each other along a second direction, and the second direction, the first direction, and the thickness direction of the electrode assembly are all perpendicular to each other. in, The composite membrane is disposed around the two first surfaces and the two second surfaces.

19. The battery cell according to claim 18, wherein, The composite film includes a first cover and a second cover. The first cover includes a first body portion and a first protrusion portion. The first body portion covers one of the two first surfaces, and the first protrusion portion is connected to the first body portion and protrudes along the thickness direction of the electrode assembly, covering at least a portion of the second surface. The second cover includes a second body portion and a second protrusion. The second body portion covers the other of the two first surfaces, and the second protrusion is connected to the second body portion, protrudes along the thickness direction of the electrode assembly, and covers at least a portion of the second surface. Wherein, the projection of the second protrusion along the second direction and the projection of the first protrusion along the second direction are continuously arranged; or The projection of the second protrusion along the second direction and the projection of the first protrusion along the second direction at least partially overlap.

20. The battery cell according to any one of claims 17 to 19, wherein, The main body includes two third surfaces that are opposite to each other along the first direction. The composite film also covers at least one of the two third surfaces.

21. A method for preparing a single battery cell, comprising: Provide initial electrode assembly; A composite film is provided to coat the initial electrode assembly to obtain the electrode assembly to be pressurized; After isostatic pressing the electrode assembly to be pressed, an electrode assembly coated with a composite film is obtained. The electrode assembly coated with the composite film is assembled into the housing assembly to prepare a battery cell. in, The composite membrane comprises: The first layer is connected to the surface of the electrode assembly; The second layer is stacked with the first layer along the thickness direction of the composite film and is connected to the side of the first layer opposite to the electrode assembly. The second layer includes a porous structure. The third layer is stacked with the second layer along the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

22. A battery device comprising a battery cell as described in any one of claims 1 to 20 or a battery cell prepared by the preparation method described in claim 21.

23. An electrical device comprising the battery device according to claim 22.

24. A composite membrane, comprising: First layer; The second layer is stacked with the first layer along the thickness direction of the composite film and is connected to the first layer. The second layer includes a porous structure. The third layer is stacked with the second layer along the thickness direction of the composite film and is connected to the side of the second layer away from the first layer. The flatness of the third layer is less than that of the second layer.

25. The composite membrane according to claim 24, wherein, The porosity of the composite membrane is 35% to 90%; and / or The shrinkage rate of the composite membrane is 10% to 70%.

26. The composite membrane according to claim 24 or 25, wherein, The porosity of the second layer is 40% to 90%; and / or The shrinkage rate of the second layer is 3% to 60%.

27. The composite membrane according to any one of claims 24 to 26, wherein, The peel strength of the composite film is from 0.5 N / m to 60 N / m.

28. The composite membrane according to any one of claims 24 to 27, wherein, The first layer includes a sensitive adhesive.

29. The composite membrane according to any one of claims 24 to 28, wherein, The flatness of the third layer is 0.001 mm to 0.05 mm.

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