Battery cell, battery and electric device

Abstract

The utility model relates to a battery monomer, a battery and a power utilization device. The battery monomer comprises a positive plate, a diaphragm and a negative plate which are sequentially stacked in the thickness direction, the diaphragm comprises an upper region, a middle region and a lower region which are sequentially distributed from top to bottom along the height direction of the battery monomer; the thickness of the middle area is greater than that of the upper area; the thickness of the middle area is larger than that of the lower area. The battery monomer, the battery and the power utilization device provided by the embodiment of the utility model have the advantage of relatively long service life.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Art

[0002] Currently, judging by market developments, batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields.

[0003] As the application fields of batteries continue to expand, the market demand is also constantly increasing, and the energy density and charging rate of batteries are also getting higher and higher. However, lithium plating will occur after multiple cycles of batteries, which seriously affects the battery life and safety of use. Utility Model Content

[0004] Based on this, it is necessary to provide a battery cell, a battery and an electrical device to address the problem of insufficient battery life.

[0005] A first aspect of an embodiment of the present application provides a battery cell, comprising a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence along the thickness direction thereof; the separator comprises an upper region, a middle region and a lower region distributed in sequence from top to bottom along the height direction of the battery cell; the thickness of the middle region is greater than the thickness of the upper region; the thickness of the middle region is greater than the thickness of the lower region.

[0006] By setting the thickness of the middle area of ​​the diaphragm to be greater than the thickness of the upper area of ​​the diaphragm, and the thickness of the middle area of ​​the diaphragm to be greater than the thickness of the lower area of ​​the diaphragm; the diaphragm presents a structural setting with a thick middle and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle area of ​​the battery cell during migration, effectively balancing the impedance levels of different height positions in the battery cell, and preventing the middle part of the battery cell from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle part of the battery cell, and reducing the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell and improving its safety.

[0007] In one embodiment, the diaphragm includes a base film layer and a coating layer arranged on at least one side surface of the base film layer along the thickness direction; the thickness of the first coating area of ​​the coating layer corresponding to the upper area is S1; the thickness of the second coating area of ​​the coating layer corresponding to the middle area is S2; the thickness of the third coating area of ​​the coating layer corresponding to the lower area is S3; satisfying: S2>S1, S2>S3.

[0008] By setting the thickness of the second coating area of ​​the coating layer to be greater than the thickness of the first coating area of ​​the coating layer; and the thickness of the second coating area of ​​the coating layer to be greater than the thickness of the third coating area of ​​the coating layer, the diaphragm can be made to have a structural setting with a thick middle portion and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle area of ​​the battery cell during migration, effectively balancing the impedance levels of different height positions in the battery cell, and preventing the middle part of the battery cell from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle part of the battery cell, and reducing the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell and improving its safety in use.

[0009] In one embodiment, the first coating region has a uniform thickness throughout; the second coating region has a uniform thickness throughout; and the third coating region has a uniform thickness throughout. This allows the second coating region of the diaphragm to be thicker than both the first and third coating regions, resulting in a thicker center and thinner edges of the diaphragm.

[0010] In one embodiment, the portion of the second coating area close to the first coating area and the first coating area constitute the upper part of the coating layer; the thickness of the upper part of the coating layer gradually becomes thinner upward along the height direction; the portion of the second coating area close to the third coating area and the third coating area constitute the lower part of the coating layer; the thickness of the lower part of the coating layer gradually becomes thinner downward along the height direction.

[0011] By setting the thickness of the upper portion of the coating layer to gradually become thinner in the height direction, and the thickness of the lower portion of the coating layer to gradually become thinner in the height direction, the diaphragm presents a structural setting with a thick middle portion and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle area of ​​the battery cell during migration, effectively balancing the impedance levels of different height positions in the battery cell, and preventing the middle portion of the battery cell from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle portion of the battery cell, and reducing the phenomenon of lithium precipitation in the middle portion, ultimately extending the service life of the battery cell and improving its safety in use.

[0012] In one embodiment, the thickness S1 of the first coating area of ​​the coating layer satisfies 0.1um≤S1≤1um; the thickness S2 of the second coating area of ​​the coating layer satisfies 1.5um≤S2≤5.5um; the thickness S3 of the third coating area of ​​the coating layer satisfies 0.1um≤S3≤1um.

[0013] In one embodiment, along the height direction, the height of the coating layer is L, the height of the first coating area is M1, the height of the second coating area is M2, and the height of the third coating area is M3; satisfying: L=M1+M2+M3, 0.15*L≤M1≤0.4*L, 0.15*L≤M3≤0.4*L, 0.2*L≤M2≤0.7*L.

[0014] In one embodiment, the height M1 of the first coating area is equal to the height M3 of the third coating area; the height M2 of the second coating area and the height L of the coating layer satisfy: M1=M3, M2=2 / 3*L.

[0015] In one embodiment, the thickness of the base film layer is 5um~15um.

[0016] In one embodiment, the coating layer includes an inorganic ceramic layer and an adhesive; the inorganic ceramic layer is disposed on the base film layer, and the adhesive is disposed on a surface of the inorganic ceramic layer away from the base film layer.

[0017] In one embodiment, the diaphragm includes two coating layers, and the two coating layers are respectively arranged on both side surfaces of the base film layer.

[0018] A second aspect of the embodiments of the present application provides a battery comprising the above-mentioned battery cell.

[0019] A third aspect of the embodiments of the present application provides an electrical device comprising the above-mentioned battery.

[0020] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic structural diagram of a vehicle provided for some embodiments of the present application.

[0022] Figure 2 Schematic diagram of the exploded structure of the battery provided in some embodiments of the present application.

[0023] Figure 3 A schematic structural diagram of the battery module provided in some embodiments of the present application.

[0024] Figure 4 Schematic diagram of the exploded structure of a battery cell provided in some embodiments of the present application.

[0025] Figure 5Schematic diagram of the stacking state of the positive electrode sheet, separator and negative electrode sheet provided in some embodiments of the present application.

[0026] Figure 6 Schematic diagram of the structure of the diaphragm provided in some embodiments of the present application.

[0027] Figure 7 Schematic diagram of the structure of the diaphragm provided in other embodiments of the present application.

[0028] Figure 8 Schematic diagram of the structure of the diaphragm provided in some further embodiments of the present application.

[0029] Description of reference numerals:

[0030] Vehicles - 1000;

[0031] Battery 100, housing 110, first portion 111, second portion 112, battery module 120, battery cell 121, end cap 122, housing 123, electrode assembly 124, electrode terminal 125, controller 200, motor 300;

[0032] Positive electrode sheet 10, separator 20, base film layer 20a, coating layer 20b, upper region 21, first coating region 21b, middle region 22, second coating region 22b, lower region 23, third coating region 23b, negative electrode sheet 30;

[0033] Thickness direction - X, height direction - Y. DETAILED DESCRIPTION

[0034] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0036] In the description of the embodiments of the present application, if the technical terms "first" and "second" appear, these terms are only used for descriptive purposes to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0037] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0039] In the description of the embodiments of this application, if the term "plurality" appears, "plurality" means at least two (including two), for example, two, three, etc., unless otherwise specifically defined. Similarly, if the term "multiple groups" appears, "multiple groups" means two or more groups (including two), and if the term "multiple sheets" appears, "multiple sheets" means two or more sheets (including two).

[0040] In the description of the embodiments of the present application, if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0041] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, if technical terms such as "installed", "connected", "connected", and "fixed" appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0042] In this application, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is described as being "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is described as being "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0043] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only embodiment.

[0044] Currently, market developments indicate that batteries are increasingly being used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields. As battery applications continue to expand, market demand is also growing.

[0045] In related technologies, as the battery's charge and discharge cycles proceed, ions are embedded into or extracted from the positive and negative active materials in the battery. Especially for batteries with relatively large dimensions, during actual operation, due to the poor heat dissipation in the middle of the battery cell, continuous operation will cause the temperature in the middle of the battery cell to be significantly higher than at the top and bottom, resulting in lower liquid-phase diffusion impedance, solid-phase diffusion impedance, and reaction impedance of lithium ions in the middle. This, in turn, causes the driving force on lithium ions in the middle of the cell to be significantly higher than at the top and bottom. As the battery is used, lithium ions will accumulate in the middle of the cell, leading to lithium deposition in the middle due to insufficient CB (cell balance), seriously affecting the battery's life and safety.

[0046] Based on the above considerations, in order to improve the problem of lithium deposition in the middle of the battery cell, a diaphragm is designed with a thick middle and thin sides structure, which can improve the diffusion impedance of lithium ions located in the middle area 22 of the battery cell during migration, effectively balance the impedance levels of different height positions in the battery cell, and prevent the middle of the battery cell from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle of the battery cell and reducing the phenomenon of lithium deposition in the middle, ultimately extending the service life of the battery cell and improving its safety.

[0047] The embodiments of the present application provide a battery cell, a battery, and an electrical device. The electrical device may be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric car, a ship, a spacecraft, an energy storage product, etc. The electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc. The energy storage product may include an energy storage station, etc.

[0048] It should be understood that the technical solutions generally described in the embodiments of the present application are not limited to the batteries and electrical devices described above, but can also be applied to all batteries including boxes and electrical devices using batteries. However, for the sake of simplicity of description, an electrical device in an embodiment of the present application is taken as an example of vehicle 1000.

[0049] Please refer to Figure 1 , Figure 1 A schematic structural diagram of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000. The battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000. For example, the battery 100 may serve as an operating power source for the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements for starting, navigating and driving the vehicle 1000.

[0050] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0051] Figure 2 An exploded view of a battery 100 provided in some embodiments of the present application; Figure 3This is a schematic diagram of the structure of the battery module provided in some embodiments of the present application. Figure 2 and Figure 3 To meet different power requirements, the battery 100 may include multiple battery cells 121 and a housing 110. A battery cell 121 is the smallest unit that makes up a battery module 120 or battery pack. Multiple battery cells 121 can be connected in series and / or in parallel via electrode terminals for various applications.

[0052] The box 110 is used to accommodate the battery cells 121 or the battery modules 120 to prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells 121 .

[0053] The housing 110 can have various structures. In some embodiments, the housing 110 can include a first portion 111 and a second portion 112. The first portion 111 and the second portion 112 overlap each other, and together define a storage space for accommodating the battery cells 121. The second portion 112 can be a hollow structure with one end open, and the first portion 111 can be a plate-like structure. The first portion 111 overlaps the open side of the second portion 112, so that the first portion 111 and the second portion 112 together define the storage space. The first portion 111 and the second portion 112 can also be hollow structures with one end open, with the open side of the first portion 111 overlapping the open side of the second portion 112. Of course, the housing 110 formed by the first portion 111 and the second portion 112 can have various shapes, such as a simple three-dimensional structure such as a single rectangular parallelepiped, cylinder, or sphere, or a complex three-dimensional structure composed of simple three-dimensional structures such as rectangular parallelepipeds, cylinders, or spheres. This is not limited in the present embodiments. The material of the box body 110 can be an alloy material such as aluminum alloy, iron alloy, etc., or a polymer material such as polycarbonate, polyisocyanurate foam plastic, or a composite material such as glass fiber and epoxy resin, and the embodiment of the present application is not limited to this.

[0054] In the embodiments of the present application, multiple battery cells 121 can be directly assembled into a battery pack, or they can be first assembled into a battery module 120, which can then be assembled into a battery pack. Specifically, multiple battery cells 121 can be directly connected in series, parallel, or in a hybrid manner to form a whole, which can then be housed within the housing 110. Alternatively, multiple battery cells 121 can be first connected in series, parallel, or in a hybrid manner to form a battery module 120, which can then be assembled into a whole, which can then be housed within the housing 110.

[0055] The battery 100 may further include other structures. For example, the battery 100 may further include a busbar component for achieving electrical connection between the plurality of battery cells 121 .

[0056] Each battery cell 121 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 121 can be cylindrical, flat, rectangular, or in other shapes. Battery cells 121 are generally divided into three types based on the packaging method: cylindrical battery cells, square battery cells, and soft-pack battery cells. The embodiments of this application do not limit this. However, for the sake of simplicity, the following embodiments are all described using a square lithium-ion battery cell 121 as an example.

[0057] Please refer to Figure 4 , Figure 4 Schematic diagram of the exploded structure of a battery cell 121 provided in some embodiments of the present application. The battery cell 121 includes an end cap 122, a housing 123, an electrode assembly 124, and other functional components.

[0058] The end cap 122 is a component that covers the opening of the housing 123 to isolate the internal environment of the electrode assembly 124 from the external environment. The shape of the end cap 122 can be adapted to the shape of the housing 123 to fit the housing 123. Optionally, the end cap 122 can be made of a material with a certain degree of hardness and strength (such as an aluminum alloy). This prevents the end cap 122 from deforming under pressure or collision, thereby enhancing the structural strength and safety of the battery cell 121. Functional components such as the electrode terminal 125 can be provided on the end cap 122. The electrode terminal 125 can be used to electrically connect to the electrode assembly 124 to transmit or receive electrical energy from the battery cell 121. In some embodiments, the end cap 122 can also be provided with a pressure relief mechanism to release internal pressure when the internal pressure or temperature of the battery cell 121 reaches a threshold. The end cap 122 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, and plastic, and this is not particularly limited in this embodiment of the present application. In some embodiments, an insulating member may be provided inside the end cap 122 to isolate the electrical connection components in the housing 123 from the end cap 122 to reduce the risk of short circuit.

[0059] The shell 123 is a component used to cooperate with the end cap 122 to form the internal environment of the battery cell 121, wherein the formed internal environment can be used to accommodate the electrode assembly 124, electrolyte and other components. The shell 123 and the end cap 122 can be independent components. An opening can be set on the shell 123, and the internal environment of the battery cell 121 is formed by covering the opening with the end cap 122. Without limitation, the end cap 122 and the shell 123 can also be integrated. Specifically, the end cap 122 and the shell 123 can form a common connection surface before other components are inserted into the shell. When the interior of the shell 123 needs to be encapsulated, the end cap 122 is then covered with the shell 123. The shell 123 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 123 can be determined according to the specific shape and size of the electrode assembly 124. The shell 123 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0060] The electrode assembly 124 is a component in the battery cell 121 where electrochemical reactions occur. One or more electrode assemblies 124 may be contained in the housing 123. The electrode assembly 124 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly 124, and the parts of the positive and negative electrode sheets without active materials each constitute a tab (not shown). The positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs are connected to the electrode terminals 125 to form a current loop.

[0061] Figure 5 Schematic diagram of the stacking state of the positive electrode sheet, separator and negative electrode sheet provided in some embodiments of the present application. Figure 6 Schematic diagram of the structure of the diaphragm provided in some embodiments of the present application. Figure 7 Schematic diagram of the structure of the diaphragm provided in other embodiments of the present application. Figure 8 Schematic diagram of the structure of the diaphragm provided in some further embodiments of the present application.

[0062] A first aspect of the present application provides a battery cell 121 .

[0063] See Figures 1 to 8As shown, the battery cell 121 includes a positive electrode sheet 10, a separator 20, and a negative electrode sheet 30 stacked in sequence along its thickness direction X. The separator 20 includes an upper region 21, a middle region 22, and a lower region 23, which are arranged in sequence from top to bottom along the height direction Y of the battery cell 121. The thickness of the middle region 22 is greater than that of the upper region 21. The thickness of the middle region 22 is greater than that of the lower region 23.

[0064] The separator 20 is used to isolate the positive electrode sheet 10 and the negative electrode sheet 30 to prevent the two from directly contacting each other and causing a short circuit.

[0065] Those skilled in the art will appreciate that the battery cell 121 of the present application includes an electrolyte. The positive electrode sheet 10, the separator 20, and the negative electrode sheet 30 are stacked sequentially to form an electrode assembly 124. The electrode assembly 124 is immersed in the electrolyte and is the component within the battery cell 121 where the electrochemical reaction occurs.

[0066] In the embodiment of the present application, the thickness of the middle region 22 of the diaphragm 20 is set to be greater than the thickness of the upper region 21 of the diaphragm 20, and the thickness of the middle region 22 of the diaphragm 20 is greater than the thickness of the lower region 23 of the diaphragm 20; the diaphragm 20 is made to have a structural setting with a thick middle and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle region 22 of the battery cell 121 during migration, effectively balancing the impedance levels of different height positions in the battery cell 121, preventing the middle part of the battery cell 121 from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle part of the battery cell 121, and reducing the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell 121 and improving its safety in use.

[0067] In the present application, the thickness direction X refers to the normal direction perpendicular to the large surface of the battery cell 121, and the height direction Y refers to the direction parallel to the large surface of the battery cell 121, and the two are arranged perpendicularly.

[0068] In some possible embodiments, see Figures 5 to 8 As shown, the diaphragm 20 includes a base membrane layer 20a and a coating layer 20b disposed on at least one surface of the base membrane layer 20a along the thickness direction X. The thickness of the first coating region 21b of the coating layer 20b corresponding to the upper region 21 is S1. The thickness of the second coating region 22b of the coating layer 20b corresponding to the middle region 22 is S2. The thickness of the third coating region 23b of the coating layer 20b corresponding to the lower region 23 is S3. The following conditions are satisfied: S2>S1, S2>S3.

[0069] The base film layer 20a has the same thickness at all locations.

[0070] By setting the thickness S2 of the second coating area 22b of the coating layer 20b to be greater than the thickness S1 of the first coating area 21b of the coating layer 20b; the thickness S2 of the second coating area 22b of the coating layer 20b is greater than the thickness S3 of the third coating area 23b of the coating layer 20b, the diaphragm 20 can be made to have a structural setting with a thick middle portion and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle area 22 of the battery cell 121 during migration, effectively balancing the impedance levels of different height positions in the battery cell 121, and preventing the middle portion of the battery cell 121 from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle portion of the battery cell 121, and reducing the phenomenon of lithium precipitation in the middle portion, ultimately extending the service life of the battery cell 121 and improving its safety in use.

[0071] The present application does not specifically limit the material or thickness of the base film layer, as long as it meets the objectives of the present application. For example, the thickness of the base film layer 20a can be 5 μm (micrometers) to 15 μm (micrometers); the material of the base film layer 20a can be at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, the base film layer 20a can be a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film.

[0072] In some possible embodiments, the coating layer 20b includes an inorganic ceramic layer and an adhesive; the inorganic ceramic layer is disposed on the base film layer 20a, and the adhesive is disposed on a surface of the inorganic ceramic layer away from the base film layer 20a.

[0073] The present application has no particular restrictions on the material and thickness of the inorganic ceramic layer, as long as it can meet the purpose of this application. Specifically, the inorganic ceramic layer may include 85% to 95% inorganic particles and 5% to 15% inorganic layer binder, wherein the inorganic particles include at least one of aluminum oxide, aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.

[0074] The adhesive may include polyacrylate and may be adhered to the inorganic ceramic layer in the form of dots or strips.

[0075] In some possible embodiments, see Figure 6 As shown, the thickness of the first coating area 21b is equal at all locations; the thickness of the second coating area 22b is equal at all locations; and the thickness of the third coating area 23b is equal at all locations.

[0076] Specifically, the first coating area 21b, the second coating area 22b and the third coating area 23b of the coating layer 20b are distributed in a stepped manner, wherein the first coating area 21b of the coating layer 20b is a plane as a whole, and the thickness is equal at all places; the second coating area 22b of the coating layer 20b is a plane as a whole, and the thickness is equal at all places; the third coating area 23b of the coating layer 20b is a plane as a whole, and the thickness is equal at all places; in this way, the second coating area 22b of the diaphragm 20 is thicker than the first coating area 21b and the third coating area 23b as a whole, so that the diaphragm 20 presents a structure with a thick middle and thin sides, thereby improving the lithium ion in the middle area 22 of the battery cell 121. The diffusion impedance during migration makes the transmission impedance of lithium ions in the middle position of the second coating area 22b of the battery cell 121 significantly greater than the transmission impedance of lithium ions in the upper position of the first coating area 21b and the bottom position of the third coating area 23b during continuous use; effectively balances the impedance levels of different height positions in the battery cell 121, prevents the middle part of the battery cell 121 from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, and thus effectively improves the enrichment of lithium ions in the middle part of the battery cell 121, and reduces the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell 121 and improving its safety.

[0077] In some possible embodiments, see Figure 7 and Figure 8 As shown, the portion of the second coating region 22b adjacent to the first coating region 21b and the first coating region 21b constitute the upper portion of the coating layer 20b; the thickness of the upper portion of the coating layer 20b gradually decreases upward along the height direction Y. The portion of the second coating region 22b adjacent to the third coating region 23b and the third coating region 23b constitute the lower portion of the coating layer 20b; the thickness of the lower portion of the coating layer 20b gradually decreases downward along the height direction Y.

[0078] In this way, by setting the thickness of the upper part of the coating layer 20b to gradually become thinner along the height direction Y, and the thickness of the lower part of the coating layer 20b to gradually become thinner along the height direction Y, the diaphragm 20 presents a structural setting with a thick middle part and thin sides, thereby improving the diffusion impedance of lithium ions located in the middle area 22 of the battery cell 121 during migration, effectively balancing the impedance levels of different height positions in the battery cell 121, and preventing the middle part of the battery cell 121 from dissipating heat slowly and the middle temperature from being too high during the charge and discharge cycle, resulting in low diffusion impedance and reaction impedance, thereby effectively improving the enrichment of lithium ions in the middle part of the battery cell 121, and reducing the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell 121 and improving its safety in use.

[0079] In some possible embodiments, see Figures 5 to 8As shown, the thickness S1 of the first coating region 21b of the coating layer 20b satisfies 0.1um≤S1≤1um.

[0080] The thickness S2 of the second coating region 22b of the coating layer 20b satisfies 1.5 μm ≤ S2 ≤ 5.5 μm.

[0081] The thickness of the third coating region 23b of the coating layer 20b is S3, which satisfies 0.1um≤S3≤1um.

[0082] In this way, by limiting the thickness S1 of the first coating area 21b to 0.1um (micrometer) ~ 1um (micrometer), the thickness S3 of the third coating area 23b to 0.1um (micrometer) ~ 1um (micrometer), and the thickness S2 of the second coating area 22b to 1.5um (micrometer) ~ 5.5um (micrometer); ensuring that the thickness S2 of the second coating area 22b of the coating layer 20b is greater than the thickness S1 of the first coating area 21b of the coating layer 20b; the thickness S2 of the second coating area 22b of the coating layer 20b is greater than the thickness S3 of the third coating area 23b of the coating layer 20b, the diaphragm 20 can be made to have a structure that is thick in the middle and thin on both sides.

[0083] Specifically, in the embodiment of the present application, for the first coating region 21b, the thickness of the inorganic ceramic layer can be 0.5 μm, and the mass of the adhesive can be 1 mg. For the third coating region 23b, the thickness of the inorganic ceramic layer can be 0.5 μm, and the mass of the adhesive can be 1 mg. For the second coating region 22b, the thickness of the inorganic ceramic layer can be 2.5 μm, and the mass of the adhesive can be 2 mg.

[0084] In some possible embodiments, see Figures 5 to 8 As shown, along the height direction Y, the height of the coating layer 20b is L, the height of the first coating area 21b is M1, the height of the second coating area 22b is M2, and the height of the third coating area 23b is M3; satisfying: L=M1+M2+M3, 0.15*L≤M1≤0.4*L, 0.15*L≤M3≤0.4*L, 0.2*L≤M2≤0.7*L.

[0085] In this way, by limiting the ratio of the height M1 of the first coating area 21b, the height M3 of the third coating area 23b, the height M2 of the second coating area 22b and the height L of the coating layer 20b, the gradient thinning of the isolation membrane is ensured, the transmission impedance of lithium ions corresponding to the upper position of the first coating area 21b and the bottom position of the third coating area 23b is small, and the transmission impedance of lithium ions corresponding to the middle position of the second coating area 22b is large, thereby effectively improving the enrichment of lithium ions in the middle part of the battery cell 121 and reducing the phenomenon of lithium precipitation in the middle part, ultimately extending the service life of the battery cell 121 and improving its safety in use.

[0086] Specifically, in this embodiment, the height M1 of the first coating region 21b and the height M3 of the third coating region 23b are equal. The thickness of the inorganic ceramic layer can be 0.5 μm, and the mass of the adhesive can be 1 mg. The height M2 of the second coating region 22b and the height L of the coating layer 20b satisfy the following conditions: M1 = M3, and M2 = 2 / 3 * L. Along the height direction Y, the second coating region 22b occupies the middle two-thirds of the width of the diaphragm 20. The thickness of the inorganic ceramic layer can be 2.5 μm, and the mass of the adhesive can be 2 mg.

[0087] In some possible embodiments, see Figures 5 to 8 As shown, the diaphragm 20 includes two coating layers 20b, which are respectively arranged on both side surfaces of the base film layer 20a.

[0088] In this way, the two coating layers 20b are respectively arranged on the two side surfaces of the base film layer 20a, and are in contact with the positive electrode sheet 10 and the negative electrode sheet 30 respectively, so that the electrode assembly 124 formed by the stacked positive electrode sheet 10, the diaphragm 20 and the negative electrode sheet 30 can be better infiltrated by the electrolyte, thereby effectively improving the electrolyte replenishment capacity. The electrolyte can better infiltrate the diaphragm 20, improve the circulation interface on both sides of the diaphragm 20, and thereby improve the high-temperature cycle performance of the battery cell 121.

[0089] In some other possible embodiments, the separator 20 includes a coating layer 20 b , which is disposed on a surface of the base film layer 20 a facing the positive electrode sheet 10 .

[0090] A second aspect of the present application provides a battery 100 including at least one battery cell 121 described in the above embodiment.

[0091] A third aspect of the present application provides an electrical device, comprising the battery 100 in the above embodiment, and the battery 100 is used to provide electrical energy.

[0092] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A battery cell, characterized in that: The battery cell comprises a positive electrode sheet (10), a separator (20), and a negative electrode sheet (30) stacked in sequence along a thickness direction (X) thereof; The diaphragm (20) comprises an upper region (21), a middle region (22), and a lower region (23) distributed sequentially from top to bottom along a height direction (Y) of the battery cell; The thickness of the middle region is greater than the thickness of the upper region (21); The thickness of the middle region is greater than the thickness of the lower region (23).

2. The battery cell according to claim 1, wherein: The diaphragm (20) comprises a base film layer (20a) and a coating layer (20b) provided on at least one surface of the base film layer (20a) along the thickness direction (X); The thickness of the first coating area (21b) of the coating layer (20b) corresponding to the upper area (21) is S1; The thickness of the second coating region (22b) of the coating layer (20b) corresponding to the middle region (22) is S2; The thickness of the third coating region (23b) of the coating layer (20b) corresponding to the lower region (23) is S3; Satisfies: S2>S1, S2>S3.

3. The battery cell according to claim 2, characterized in that: The first coating area (21b) has the same thickness at all locations; The second coating area (22b) has the same thickness at all locations; The third coating area (23b) has the same thickness at all locations.

4. The battery cell according to claim 2, characterized in that: The portion of the second coating region (22b) close to the first coating region (21b) and the first coating region (21b) constitute the upper portion of the coating layer (20b); the thickness of the upper portion of the coating layer (20b) gradually becomes thinner upward along the height direction (Y); The portion of the second coating region (22b) close to the third coating region (23b) and the third coating region (23b) constitute the lower portion of the coating layer (20b); the thickness of the lower portion of the coating layer (20b) gradually becomes thinner downward along the height direction (Y).

5. The battery cell according to claim 2, characterized in that: The thickness S1 of the first coating area (21b) of the coating layer (20b) satisfies 0.1um≤S1≤1um; The thickness S2 of the second coating area (22b) of the coating layer (20b) satisfies 1.5um≤S2≤5.5um; The thickness of the third coating area (23b) of the coating layer (20b) is S3, satisfying 0.1um≤S3≤1um.

6. The battery cell according to any one of claims 2 to 5, characterized in that: Along the height direction (Y), the height of the coating layer (20b) is L, the height of the first coating area (21b) is M1, the height of the second coating area (22b) is M2, and the height of the third coating area (23b) is M3; Satisfies: L=M1+M2+M3, 0.15*L≤M1≤0.4*L, 0.15*L≤M3≤0.4*L, 0.2*L≤M2≤0.7*L.

7. The battery cell according to claim 6, characterized in that The height M1 of the first coating area (21b) is equal to the height M3 of the third coating area (23b); The height M2 of the second coating area (22b) and the height L of the coating layer (20b) satisfy: M1=M3, M2=2 / 3*L.

8. The battery cell according to any one of claims 2 to 5, characterized in that: The base film layer (20a) has a thickness of 5um to 15um.

9. The battery cell according to any one of claims 2 to 5, characterized in that: The coating layer (20b) comprises an inorganic ceramic layer and an adhesive; the inorganic ceramic layer is arranged on the base film layer (20a), and the adhesive is arranged on a surface of the inorganic ceramic layer that is away from the base film layer (20a).

10. The battery cell according to any one of claims 2 to 5, characterized in that: The diaphragm (20) comprises two coating layers (20b), and the two coating layers (20b) are respectively arranged on both side surfaces of the base film layer (20a).

11. A battery, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 10.

12. An electrical device, characterized in that: Comprising the battery of claim 11.

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