Electrode assembly, battery cell, battery, electric equipment and manufacturing method of diaphragm

Abstract

The embodiment of the invention provides an electrode assembly, a battery monomer, a battery, electric equipment and a manufacturing method of a diaphragm, and belongs to the technical field of batteries. The electrode assembly comprises a positive pole piece, a negative pole piece and a diaphragm, and the diaphragm is arranged between the positive pole piece and the negative pole piece; the diaphragm comprises a first area, a second area and a third area which are sequentially distributed in the width direction of the diaphragm, and the porosity of the second area is smaller than that of the first area and that of the third area. The electrode assembly provided by the embodiment of the invention is provided with the diaphragms with different porosities, and the porosities of different parts of the diaphragms are different, so that the condition of separating out metal ions of the electrode assembly can be improved.

Description

Method for manufacturing electrode assembly, battery cell, battery, electrical equipment and diaphragm Technical Field

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

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. Electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. For electric vehicles, battery technology is a key factor in their development.

[0003] During the manufacturing process of batteries, battery safety is an issue that cannot be ignored. Therefore, how to improve battery safety is a technical problem that needs to be solved urgently in battery technology.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a method for manufacturing an electrode assembly, a battery cell, a battery, an electrical device, and a diaphragm. The battery cell composed of the electrode assembly provided in the embodiments of this application has high safety.

[0006] This application is achieved through the following technical solutions:

[0007] In a first aspect, the present application provides an electrode assembly, which includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; the separator includes a first zone, a second zone and a third zone distributed in sequence along its width direction, and the porosity of the second zone is smaller than the porosity of the first zone and smaller than the porosity of the third zone.

[0008] According to the electrode assembly of the embodiment of the present application, by setting the porosity of the second zone to be different from the porosity of the first zone and the porosity of the third zone, the porosity of different parts of the diaphragm is different, and different parts are adapted to different metal ion penetration capabilities, which can improve the situation of metal ion precipitation on the surface of the negative electrode plate, so that the battery cell composed of the electrode assembly has higher safety.

[0009] According to some embodiments of the present application, the negative electrode sheet has a first edge and a second edge opposite to each other in the width direction thereof, the first edge falls into the first region, and the second edge falls into the third region.

[0010] In the above scheme, when observed along the thickness direction of the negative electrode sheet, the projection of the first edge falls into the projection of the first zone, and the projection of the second edge falls into the projection of the third zone. The projection of the second zone and the projection of the negative electrode sheet have a large overlapping area in the width direction, which can effectively reduce the ability of metal ions to penetrate the second zone, thereby improving the situation of metal ion precipitation on the surface of the negative electrode sheet.

[0011] According to some embodiments of the present application, the positive electrode sheet has a third edge and a fourth edge opposite to each other in the width direction thereof, the third edge falls into the first region, and the fourth edge falls into the third region.

[0012] In the above scheme, when observed along the thickness direction of the positive electrode sheet, the projection of the third edge falls into the projection of the first zone, and the projection of the fourth edge falls into the projection of the third zone. The projection of the second zone and the projection of the positive electrode sheet have a large overlapping area in the width direction, which can effectively reduce the ability of metal ions to penetrate the second zone, thereby improving the amount of metal ions moving from the positive electrode sheet to the negative electrode sheet, and further improving the situation of metal ion precipitation on the surface of the negative electrode sheet.

[0013] According to some embodiments of the present application, along the width direction of the diaphragm, the dimensions of the two ends of the positive electrode sheet exceeding the two ends of the second zone are b1 and b2 respectively, and the dimension of the second zone along the width direction of the diaphragm is bx, satisfying 0<b1≤bx / 2, and / or 0<b2≤bx / 2.

[0014] In the above scheme, the dimensions of the two ends of the positive electrode sheet exceeding the two ends of the second zone meet the above range, so that the part of the diaphragm corresponding to the overlapping area of ​​the positive electrode sheet and the negative electrode sheet has two different porosities, so that the penetration ability of the metal ions in the overlapping area is different, which can reduce the penetration ability of the metal ions in some areas, thereby improving the situation of metal ion precipitation on the surface of the negative electrode sheet.

[0015] According to some embodiments of the present application, bx / 5≤b1≤bx / 3, and / or, bx / 5≤b2≤bx / 3.

[0016] In the above scheme, compared with 0<b1≤bx / 2, and / or, 0<b2≤bx / 2, when bx / 5≤b1≤bx / 3, and / or, bx / 5≤b2≤bx / 3, on the one hand, it can effectively reduce the precipitation of metal ions on the surface of the negative electrode plate, and on the other hand, it allows more metal ions to penetrate the overlapping area, so that more current passes through the electrode assembly.

[0017] According to some embodiments of the present application, along the width direction of the separator, the opposite ends of the negative electrode sheet respectively exceed the opposite ends of the positive electrode sheet, and the opposite ends of the separator respectively exceed the opposite ends of the negative electrode sheet.

[0018] In the above scheme, the opposite ends of the negative electrode sheet respectively extend beyond the opposite ends of the positive electrode sheet, which can effectively reduce the precipitation of metal ions on the surface of the negative electrode sheet; the opposite ends of the diaphragm respectively extend beyond the opposite ends of the negative electrode sheet, so that the electrode assembly has higher safety and reduces the risk of short circuit between the positive electrode sheet and the negative electrode sheet.

[0019] According to some embodiments of the present application, the porosity of the second zone is K2, which satisfies 25%≤K2≤35%.

[0020] In the above scheme, the porosity of the second zone meets the above range. When applied to a battery cell, it can both meet the metal ion penetration requirements and limit the metal ion penetration efficiency. When the separator is applied to a battery cell, if the porosity of the second zone is small (e.g., less than 25%), the ability of metal ions to pass through the separator is hindered, and the metal ion penetration rate is low. If the porosity of the second zone is large (e.g., greater than 35%), the metal ion penetration efficiency is high, which can easily cause metal ions to precipitate on the surface of the negative electrode, thereby posing a safety risk.

[0021] According to some embodiments of the present application, 28%≤K2≤32%.

[0022] In the above scheme, compared with 25%≤K2≤35%, when 28%≤K2≤32%, it has both better metal ion penetration ability and can limit the penetration efficiency of metal ions.

[0023] According to some embodiments of the present application, the porosity of the first region is equal to the porosity of the third region.

[0024] In the above solution, the porosity of the first zone is the same as the porosity of the third zone, which facilitates processing and manufacturing.

[0025] According to some embodiments of the present application, the porosity of the first zone is K1, and the porosity of the third zone is K3, satisfying 35%≤K1=K3≤45%.

[0026] In the above scheme, the porosity of the first zone and the porosity of the third zone meet the above ranges. When applied to battery cells, they have both high metal ion penetration ability and good liquid retention ability; if K1 (K3) is small (such as less than 35%), the metal ion penetration ability is weak; if K1 (K3) is large (such as greater than 45%), the battery cell composed of the diaphragm is prone to self-discharge, thereby reducing the capacity of the battery cell.

[0027] According to some embodiments of the present application, 38%≤K1=K3≤42%.

[0028] In the above scheme, compared with 35%≤K1=K3≤45%, when 38%≤K1=K3≤42%, when applied to battery cells, the diaphragm has both good metal ion penetration ability, reducing the risk of metal ion precipitation from the negative electrode plate, and reducing the risk of self-discharge of the battery cell.

[0029] According to some embodiments of the present application, the porosity of the first region is greater than the porosity of the third region.

[0030] In the above solution, the porosity of the first region is greater than that of the third region, so that the diaphragm has multiple regions with different porosities, which can meet the requirements of having different metal ion penetration capabilities at different locations.

[0031] According to some embodiments of the present application, the porosity of the first zone is K1, and the porosity of the third zone is K3, satisfying 45%≤K1≤55%, and 35%≤K3≤45%.

[0032] In the above solution, when the separator is applied to a battery cell, the porosity of the first region and the porosity of the third region meet the above ranges, and the separator has different metal ion penetration capabilities to adapt to different scenarios.

[0033] According to some embodiments of the present application, 48%≤K1≤52%, and 38%≤K3≤42%.

[0034] In the above scheme, compared with 45%≤K1≤55% and 35%≤K3≤45%, when 48%≤K1≤52% and 38%≤K3≤42%, when applied to battery cells, the diaphragm has better metal ion penetration ability, reducing the risk of metal ion precipitation from the negative electrode plate, and reducing the risk of self-discharge of the battery cell.

[0035] According to some embodiments of the present application, a size of the first region along the width direction of the diaphragm is equal to a size of the third region along the width direction of the diaphragm.

[0036] In the above solution, the first area and the third area have the same size in the width direction of the diaphragm, which facilitates processing and manufacturing.

[0037] In a second aspect, an embodiment of the present application provides a battery cell, comprising a housing and an electrode assembly provided by any of the above embodiments, wherein the electrode assembly is disposed in the housing.

[0038] According to some embodiments of the present application, along a height direction of the battery cell, the first region is located above the third region.

[0039] In the above scheme, the first zone is located above the third zone, the porosity of the first zone is greater than that of the second zone, the first zone has better liquid retention ability, and the metal ion penetration ability of the second zone is weak, which can improve the problem of metal ion precipitation on the surface of the negative electrode plate at the position corresponding to the first zone and the second zone in the height direction of the battery cell.

[0040] According to some embodiments of the present application, along the width direction of the diaphragm, the size of the housing is a, the size of the second region is bx, and bx=a / 2 is satisfied.

[0041] In the above scheme, the size of the second area in the width direction of the diaphragm and the size of the outer shell in the width direction of the diaphragm satisfy the above relationship. Along the width direction of the diaphragm, the projection of the second area on the negative electrode sheet has a larger corresponding area with the negative electrode sheet, which can improve the problem of metal ion precipitation on the surface of the negative electrode sheet at the corresponding position of the second area, so that the battery cell has higher safety.

[0042] According to some embodiments of the present application, 25 mm ≤ bx ≤ 300 mm.

[0043] In the above solution, the size of the second region in the width direction of the separator meets the above range, so that the separator can adapt to battery cells of different specifications and has a wider range of applications.

[0044] According to some embodiments of the present application, 50 mm ≤ a ≤ 600 mm.

[0045] In the above solution, the size of the battery cell in the width direction of the separator meets the above range, and the use of separators with different porosities at different positions can reduce the risk of metal ion precipitation.

[0046] According to some embodiments of the present application, the battery cell is a lithium-ion battery.

[0047] In the above solution, the battery cell is a lithium-ion battery, and the use of the diaphragm of the above embodiment effectively reduces the risk of lithium plating and has higher safety.

[0048] In a third aspect, an embodiment of the present application provides a battery, comprising a battery cell provided by any of the above embodiments.

[0049] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising a battery provided by any of the above embodiments, and the battery is used to provide electrical energy.

[0050] In a fifth aspect, an embodiment of the present application provides a method for manufacturing a diaphragm, comprising: preparing a diaphragm; heating the diaphragm so that the temperature of the second zone of the diaphragm is lower than the temperatures of the first zone and the third zone, and the first zone, the second zone and the third zone are distributed in sequence along the width direction of the diaphragm; stretching the diaphragm to obtain a thin film, so that the porosity of the second zone after stretching is less than the porosity of the first zone after stretching and less than the porosity of the third zone after stretching.

[0051] According to the method for manufacturing the diaphragm of the embodiment of the present application, by heating different positions of the diaphragm to different temperatures and stretching the diaphragm, diaphragms with different porosities at different positions are obtained, which is easy to process and manufacture.

[0052] According to some embodiments of the present application, stretching the membrane to obtain a thin film includes: simultaneously stretching the membrane in the width direction and the length direction.

[0053] In the above solution, the membrane is stretched simultaneously in the width direction and the length direction to ensure that the porosity of each area of ​​the membrane is uniform.

[0054] According to some embodiments of the present application, preparing a membrane includes: mixing polyolefin and a pore-forming agent to obtain a mixture; heating the mixture and then extruding it into a substrate; and cooling and phase separation to obtain a membrane with micropores.

[0055] In the above solution, through the above process, a membrane with micropores can be obtained, so that the diaphragm has a certain porosity.

[0056] According to some embodiments of the present application, after the membrane is stretched to obtain a thin film, the method for manufacturing the diaphragm further includes: extracting and heat-setting the thin film to extract the pore-forming agent to obtain the diaphragm.

[0057] In the above scheme, the film is extracted and heat-set to facilitate the formation of the diaphragm.

[0058] According to some embodiments of the present application, heating the membrane includes: heating the first zone to 120°C to 130°C, heating the second zone to 100°C to 110°C, and heating the third zone to 110°C to 120°C.

[0059] In the above solution, the first zone, the second zone and the third zone are respectively heated to the above temperature ranges, so as to facilitate the control of the porosity at different positions.

[0060] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0062] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0063] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0064] FIG3 is an exploded view of a battery cell provided in some embodiments of the present application;

[0065] FIG4 is a schematic structural diagram of an electrode assembly provided in some embodiments of the present application;

[0066] FIG5 is a schematic structural diagram of a diaphragm provided in some embodiments of the present application;

[0067] FIG6 is a cross-sectional view of an electrode assembly provided in some embodiments of the present application;

[0068] FIG7 is a schematic diagram of the assembly of the diaphragm and the housing provided in some embodiments of the present application;

[0069] FIG8 is a schematic flow chart of a method for manufacturing a diaphragm provided in some embodiments of the present application;

[0070] FIG9 is a schematic flow chart of preparing a membrane in a method for manufacturing a diaphragm according to some embodiments of the present application;

[0071] FIG10 is a schematic flow chart of a method for manufacturing a diaphragm provided in some other embodiments of the present application;

[0072] In the drawings, the drawings are not drawn to scale.

[0073] Marking instructions: 100-battery; 10-case; 11-first subcase; 12-second subcase; 20-battery cell; 21-outer casing; 211-shell; 212-cover; 21a-electrode terminal; 22-electrode assembly; 221-positive electrode plate; 221a-third edge; 221b-fourth edge; 222-negative electrode plate; 222a-first edge; 222b-second edge; 223-main body; 224-ear; 30-diaphragm; 30a-seventh edge; 30b-eighth edge; 31-first zone; 32-second zone; 32a-fifth edge; 32b-sixth edge; 33-third zone; 200-controller; 300-motor; 1000-vehicle. DETAILED DESCRIPTION

[0074] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0075] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application 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 drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0076] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the 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 in this application may be combined with other embodiments.

[0077] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0078] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0079] The term "multiple" in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0080] In this application, reference to a battery refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity.

[0081] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive electrode current collector, and the current collector uncoated with the positive active material layer serves as the positive electrode tab. For lithium-ion batteries, for example, the positive electrode current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative electrode current collector, and the current collector uncoated with the negative active material layer serves as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative active material can be carbon or silicon, among others. To ensure that high currents can be passed without melting, multiple positive electrode tabs are stacked, and multiple negative electrode tabs are stacked. The material of the diaphragm can be PP (polypropylene) or PE (polyethylene).

[0082] The electrode assembly of a battery cell includes a positive electrode sheet, a negative electrode sheet and a separator. The separator has two functions: one is to act as an insulating layer to prevent the positive electrode sheet and the negative electrode sheet from contacting each other and causing a short circuit inside the battery cell; the other is to act as a semi-permeable layer to prevent larger molecules from passing through and allow small charged ions to pass through.

[0083] In the related art, the porosity distribution at any position of the diaphragm is uniform, and the ability to penetrate metal ions at any position is the same. However, the applicable scenarios are limited, and it is difficult to adjust the efficiency of different metal ion precipitation at different positions of the diaphragm. For example, along the width of the diaphragm, the current density in the overlapping area of ​​the negative and positive electrode sheets is relatively high. When a diaphragm with a uniform porosity distribution at any position is used, the negative electrode sheet is prone to metal ion precipitation in this overlapping area. The precipitated metal ions can easily scratch the diaphragm, which can easily cause the positive and negative electrode sheets to short-circuit, thereby reducing the safety of the battery cell.

[0084] In view of this, in order to solve the problem of uniform porosity distribution at various positions of the diaphragm, which leads to lower safety of the battery cell composed of the diaphragm, the inventors conducted in-depth research and designed a technical solution to set different porosities at different positions of the diaphragm of the electrode assembly to improve the situation of metal ion precipitation in the electrode assembly.

[0085] When such a diaphragm is used in a battery cell, the porosity of the second zone of the diaphragm in its width direction is smaller than the porosity of its adjacent zone, and the metal ion penetration ability of the second zone is smaller than the metal ion penetration ability of other zones, thereby effectively controlling the penetration efficiency of metal ions. For example, when the second zone overlaps with the zone with higher current density of the negative electrode plate, the risk of metal ions precipitating on the surface of the negative electrode plate can be reduced, thereby making the battery cell safer.

[0086] The battery cells disclosed in the embodiments of the present application can be used, but are not limited to, in electrical equipment such as vehicles, ships, or aircraft. A power supply system comprising the battery cells and batteries disclosed in the present application can be used to form the electrical equipment.

[0087] The present invention provides an electric device that uses a battery as a power source. The electric device may include, but is not limited to, a mobile phone, a tablet computer, a laptop computer, an electric toy, an electric tool, an electric bicycle, an electric motorcycle, an electric car, a ship, a spacecraft, and the like. 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. The spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft.

[0088] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0089] Please refer to Figure 1, which is a schematic diagram of the structure of the vehicle provided in some embodiments of the present application. Vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can be used as an operating power source for the vehicle 1000, for the circuit system of the vehicle 1000, such as for the working power requirements during the startup, navigation and operation of the vehicle 1000.

[0090] The vehicle 1000 may further include a controller 200 and a motor 300 . The controller 200 is used to control the battery 100 to supply power to the motor 300 , for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0091] 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.

[0092] Please refer to Figure 2, which is an exploded view of a battery provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 being housed within the housing 10. The housing 10 is used to provide a storage space for the battery cell 20, and the housing 10 can adopt a variety of structures. In some embodiments, the housing 10 can include a first sub-housing 11 and a second sub-housing 12, which cover each other and together define a storage space for accommodating the battery cell 20. The second sub-housing 12 can be a hollow structure with one end open, and the first sub-housing 11 can be a plate-like structure, with the first sub-housing 11 covering the open side of the second sub-housing 12, so that the first sub-housing 11 and the second sub-housing 12 jointly define a storage space; the first sub-housing 11 and the second sub-housing 12 can also be hollow structures with one end open, with the open side of the first sub-housing 11 covering the open side of the second sub-housing 12.

[0093] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0094] The battery cell 20 may be a secondary battery or a primary battery; the battery cell 20 may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto.

[0095] Please refer to Figure 3 , which is an exploded view of a battery cell provided in some embodiments of the present application. As shown in Figure 3 , a battery cell 20 includes a housing 21 and an electrode assembly 22 , wherein the electrode assembly 22 is disposed within the housing 21 .

[0096] The housing 21 includes a shell 211 and a cover 212 . The shell 211 has an opening, and the cover 212 closes the opening to isolate the internal environment of the battery cell 20 from the external environment.

[0097] The shell 211 is a component used to cooperate with the cover 212 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 22, electrolyte and other components. The shell 211 and the cover 212 can be independent components. The shell 211 can be of various shapes and sizes. Specifically, the shape of the shell 211 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell 211 can be various, 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. The embodiment of the present application takes the shell 211 as a rectangular parallelepiped as an example.

[0098] The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the cover 212 can be adapted to the shape of the shell 211 to match the shell 211. Optionally, the cover 212 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the cover 212 is not easily deformed when squeezed or collided, so that the battery cell 20 can have a higher structural strength and improved safety performance. Functional components such as electrode terminals 21a can be provided on the cover 212. The electrode terminal 21a can be used to electrically connect to the electrode assembly 22 for outputting or inputting electrical energy of the battery cell 20. The material of the cover 212 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this. In some embodiments, an insulating structure may be provided inside the cover 212 to isolate the electrical connection components in the housing 211 from the cover 212 to reduce the risk of short circuits. For example, the insulating structure may be made of plastic, rubber, or the like.

[0099] The electrode assembly 22 is a component where electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 22 may be contained in the housing 211.

[0100] Please refer to Figures 4 to 6. Figure 4 is a schematic diagram of the structure of the electrode assembly provided in some embodiments of the present application. In Figure 4, the electrode assembly 22 is a wound electrode assembly. Figure 5 is a schematic diagram of the structure of the diaphragm provided in some embodiments of the present application. Figure 6 is a cross-sectional view of the electrode assembly provided in some embodiments of the present application. Figure 6 shows the distribution of the diaphragm, the negative electrode sheet, and the positive electrode sheet in the width direction of the diaphragm. According to some embodiments of the present application, the electrode assembly 22 includes a positive electrode sheet 221, a negative electrode sheet 222, and a diaphragm 30. The diaphragm 30 is arranged between the positive electrode sheet 221 and the negative electrode sheet 222. The diaphragm 30 includes a first region 31, a second region 32, and a third region 33 distributed in sequence along its width direction. The porosity of the second region 32 is less than the porosity of the first region 31 and less than the porosity of the third region 33.

[0101] The positive electrode sheet 221, the separator 30 and the negative electrode sheet 222 are stacked or wound to form the electrode assembly 22. That is, the electrode assembly 22 can be a wound electrode assembly or a laminated electrode assembly.

[0102] The separator 30 is used to separate the positive electrode sheet 221 and the negative electrode sheet 222 to avoid internal short circuit between the positive electrode sheet 221 and the negative electrode sheet 222 . At the same time, metal ions can penetrate the separator 30 and move between the positive electrode sheet 221 and the negative electrode sheet 222 .

[0103] The portions of the positive electrode sheet 221 and the negative electrode sheet 222 containing active material constitute the main body 223 of the electrode assembly 22, while the portions of the positive electrode sheet 221 and the negative electrode sheet 222 not containing active material each constitute a tab 224. The positive and negative tabs can be located together at one end of the main body 223 or separately at both ends of the main body 223.

[0104] The separator 30 is in the form of a coil during the manufacturing process, with the width of the separator 30 being perpendicular to the length of the separator 30. In a wound electrode assembly, the width of the separator 30 is parallel to the winding axis of the electrode assembly 22. In a laminated electrode assembly 22, the width of the separator 30 can be parallel to the width of the positive electrode sheet 221 or the negative electrode sheet 222.

[0105] In the figure, the direction indicated by the letter Z can be the width direction, the direction indicated by the letter C can be the length direction, and the direction indicated by the letter D can be the thickness direction. The width direction of the separator 30, the width direction of the positive electrode sheet 221, and the width direction of the negative electrode sheet 222 can be parallel to the Z direction, the length direction of the separator 30, the length direction of the positive electrode sheet 221, and the length direction of the negative electrode sheet 222 can be parallel to the D direction, and the thickness direction of the separator 30, the thickness direction of the positive electrode sheet 221, and the thickness direction of the negative electrode sheet 222 can be parallel to the D direction.

[0106] The first area 31 , the second area 32 and the third area 33 are sequentially distributed along the width direction (Z direction) of the diaphragm 30 , and the second area 32 is located between the first area 31 and the third area 33 in the width direction of the diaphragm 30 .

[0107] The porosity of the second zone 32 is smaller than the porosity of the first zone 31 and smaller than the porosity of the third zone 33, so that the porosity of the diaphragm 30 is different in different parts, and different parts of the diaphragm 30 have different metal ion penetration capabilities, thereby controlling the metal ion penetration efficiency of different parts. It can be suitable for scenarios with different requirements for metal ion penetration capabilities and is suitable for a wider range of scenarios.

[0108] In a battery cell 20, metal ions may precipitate at different locations on the negative electrode sheet 222. By using the separator 30 of the present embodiment, where regions of different porosities correspond to different regions of the negative electrode sheet 222, this can effectively mitigate the occurrence of metal ion precipitation on the surface of the negative electrode sheet 222. For example, in a battery cell 20, the second region 32 has a lower porosity. When the second region 32 is positioned to correspond to a region of concentrated current in the electrode assembly 22, the penetration efficiency of metal ions can be effectively controlled, thereby reducing the risk of metal ion precipitation on the surface of the negative electrode sheet 222 at the corresponding location in the second region 32, thereby enhancing the safety of the battery cell 20.

[0109] The porosity test method can be:

[0110] The diaphragm 30 (sample) is rolled into a ball and stuffed into the sample cup. The sample cup containing the sample is placed in the true density tester. The test system is sealed and the gas displacement method is used to introduce helium. The pressure of the gas in the sample chamber and the expansion chamber is detected. Then, the true density of the sample is calculated according to the ideal gas state equation (PV=nRT), thereby obtaining the porosity of the sample to be tested. Where: P is pressure (Pa), V is gas volume (m 3 ), T is the temperature (K), n is the amount of substance in the gas (mol), and R is the molar gas constant (also called the universal gas constant) (J / (mol.K)).

[0111] The sample cup volume can be 3.5 cm3 and the analysis gas is helium.

[0112] Porosity is the percentage of the pore volume of the sample to the total volume, porosity = (V1-V2) / V1*100%, V1 is the apparent volume of the sample, and V2 is the actual volume of the sample.

[0113] According to the electrode assembly of the embodiment of the present application, by setting the porosity of the second zone 32 to be different from the porosity of the first zone 31 and the porosity of the third zone 33, the porosity of different parts of the diaphragm 30 is different, and different parts are adapted to different metal ion penetration capabilities, which can improve the situation of metal ion precipitation on the surface of the negative electrode plate 222, so that the battery cell 20 composed of the electrode assembly 22 has higher safety.

[0114] 6 , according to some embodiments of the present application, the negative electrode tab 222 has a first edge 222 a and a second edge 222 b opposite to each other in the width direction. The first edge 222 a falls into the first region 31 , and the second edge 222 b falls into the third region 33 .

[0115] The first edge 222a and the second edge 222b are edges of the negative electrode sheet 222 that are disposed opposite each other in the width direction (Z direction) of the negative electrode sheet. The first edge 222a and the second edge 222b may extend in a direction perpendicular to the width direction of the negative electrode sheet 222. It should be noted that the tab 224 of the negative electrode sheet 222 may extend from the first edge 222a and / or the second edge 222b.

[0116] The first edge 222a falls into the first area 31 and the second edge 222b falls into the third area 33, which means that when observed along the thickness direction (D direction) of the negative electrode sheet 222, the projection of the first edge 222a falls into the projection of the first area 31, and the projection of the second edge 222b falls into the projection of the third area 33.

[0117] In the above scheme, when observed along the thickness direction (D direction) of the negative electrode sheet 222, the projection of the first edge 222a falls into the projection of the first area 31, and the projection of the second edge 222b falls into the projection of the third area 33. The projection of the second area 32 and the projection of the negative electrode sheet 222 have a large overlapping area in their width direction, which can effectively reduce the ability of metal ions to penetrate the second area 32, thereby improving the situation of metal ion precipitation on the surface of the negative electrode sheet 222.

[0118] 6 , according to some embodiments of the present application, the positive electrode sheet 221 has a third edge 221 a and a fourth edge 221 b opposite to each other in its width direction. The third edge 221 a falls into the first region 31 , and the fourth edge 221 b falls into the third region 33 .

[0119] The third edge 221a and the fourth edge b are edges of the positive electrode sheet 221 that are arranged opposite each other in the width direction (Z direction) thereof. The extension direction of the third edge 221a and the fourth edge b may be perpendicular to the width direction of the positive electrode sheet 221. The third edge 221a is closer to the first edge 222a than the fourth edge 221b, and the fourth edge 221b is closer to the second edge 222b than the third edge 221a.

[0120] The third edge 221a falls into the first area 31 and the fourth edge 221b falls into the third area 33, which means that when observed along the thickness direction (D direction) of the positive electrode sheet 221, the projection of the third edge 221a falls into the projection of the first area 31, and the projection of the fourth edge 221b falls into the projection of the third area 33.

[0121] In the above scheme, when observed along the thickness direction (D direction) of the positive electrode sheet 221, the projection of the third edge 221a falls into the projection of the first area 31, and the projection of the fourth edge 221b falls into the projection of the third area 33. The projection of the second area 32 and the projection of the positive electrode sheet 221 have a large overlapping area in their width direction, which can effectively reduce the ability of metal ions to penetrate the second area 32, thereby improving the amount of metal ions moving from the positive electrode sheet 221 to the negative electrode sheet 222, and further improving the situation of metal ions precipitating on the surface of the negative electrode sheet 222.

[0122] It should be noted that the projection of the third edge 221a of the positive electrode sheet 221 can be flush with the boundary edge of the projection of the first area 31 and the projection of the second area 32, or the projection of the fourth edge 221b of the positive electrode sheet 221 can be flush with the boundary edge of the projection of the third area 33 and the projection of the second area 32, so that the area corresponding to the positive electrode sheet 221 and the diaphragm 30 has at least two areas with different porosities.

[0123] Please refer to Figure 6. According to some embodiments of the present application, along the width direction (Z direction) of the diaphragm 30, the dimensions of the two ends of the positive electrode sheet 221 exceeding the two ends of the second area 32 are b1 and b2 respectively, and the dimension of the second area 32 along the width direction of the diaphragm 30 is bx, satisfying 0<b1≤bx / 2, and / or 0<b2≤bx / 2.

[0124] Along the width direction (Z direction) of the diaphragm 30, the opposite ends of the positive electrode sheet 221 respectively extend beyond the opposite ends of the second region 32. For example, the second region 32 has a fifth edge 32a and a sixth edge 32b opposite to each other along the width direction of the diaphragm 30. The fifth edge 32a is closer to the third edge 221a of the positive electrode sheet 221 than the sixth edge 32b, and the sixth edge 32b is closer to the fourth edge 221b of the positive electrode sheet 221 than the fifth edge 32a.

[0125] The third edge 221a extends beyond the fifth edge 32a by a dimension b1; the fourth edge 221b extends beyond the sixth edge 32b by a dimension b2. In other embodiments, the third edge 221a extends beyond the fifth edge 32a by a dimension b2, and the fourth edge 221b extends beyond the sixth edge 32b by a dimension b1.

[0126] A dimension bx of the second region 32 along the width direction of the diaphragm 30 may be a distance between the fifth edge 32 a and the sixth edge 32 b .

[0127] In the above solution, the dimensions of the ends of the positive electrode tab 221 that extend beyond the ends of the second region 32 fall within the aforementioned ranges. This allows the portion of the separator 30 corresponding to the overlapping region of the positive electrode tab 221 and the negative electrode tab 222 to have two different porosities. This results in different metal ion penetration capabilities within the overlapping region, reducing the penetration capability of metal ions in certain regions and thereby improving the precipitation of metal ions on the surface of the negative electrode tab 222. If b1 or b2 is greater than bx / 2, the overlapping region of the second region 32 and the positive electrode tab 221 is smaller, while the larger overlapping region of the separator 30 with the positive electrode tab 221 has a higher porosity, making it easier for metal ions to precipitate on the surface of the negative electrode tab.

[0128] Alternatively, b1 may be bx / 7, bx / 6, bx / 5, bx / 4, bx / 3, or bx / 2. B2 may be bx / 7, bx / 6, bx / 5, bx / 4, bx / 3, or bx / 2.

[0129] According to some embodiments of the present application, bx / 5≤b1≤bx / 3, and / or, bx / 5≤b2≤bx / 3.

[0130] In the above scheme, compared with 0<b1≤bx / 2, and / or, 0<b2≤bx / 2, when bx / 5≤b1≤bx / 3, and / or, bx / 5≤b2≤bx / 3, on the one hand, it can effectively reduce the situation of metal ion precipitation on the surface of the negative electrode plate 222, and on the other hand, it allows more metal ions to penetrate the overlapping area, so that more current passes through the electrode assembly 22.

[0131] Please refer to Figure 6. According to some embodiments of the present application, along the width direction (Z direction) of the diaphragm 30, the opposite ends of the negative electrode sheet 222 respectively extend beyond the opposite ends of the positive electrode sheet 221, and the opposite ends of the diaphragm 30 respectively extend beyond the opposite ends of the negative electrode sheet 222.

[0132] As shown in FIG6 , the negative electrode tab 222 has a first edge 222a and a second edge 222b that are opposite to each other in the width direction thereof, the positive electrode tab 221 has a third edge 221a and a fourth edge 221b that are opposite to each other in the width direction thereof, and the separator 30 has a seventh edge 30a and an eighth edge 30b that are opposite to each other in the width direction of the separator 30. In the width direction of the separator 30, the first edge 222a extends beyond the third edge 221a, the seventh edge 30a extends beyond the first edge 222a, the second edge 222b extends beyond the fourth edge 221b, and the eighth edge 30b extends beyond the second edge 222b.

[0133] In the above scheme, the opposite ends of the negative electrode sheet 222 respectively extend beyond the opposite ends of the positive electrode sheet 221, which can effectively reduce the precipitation of metal ions on the surface of the negative electrode sheet 222; the opposite ends of the diaphragm 30 respectively extend beyond the opposite ends of the negative electrode sheet 222, which can reduce the risk of short circuit between the positive electrode sheet 221 and the negative electrode sheet 222, so that the battery cell 20 composed of the electrode assembly 22 has higher safety.

[0134] According to some embodiments of the present application, the porosity of the second region 32 is K2, which satisfies 25%≤K2≤35%.

[0135] Alternatively, K2 may be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%.

[0136] In the above solution, the porosity K2 of the second region 32 falls within the above range. When applied to a battery cell 20, this allows both the required metal ion permeation and the limited metal ion permeation efficiency. When the separator 30 is applied to a battery cell 20, if the porosity of the second region 32 is low (e.g., less than 25%), the ability of metal ions to pass through the separator 30 is hindered, resulting in a low metal ion permeation rate and weak battery cell 20 performance. If the porosity of the second region 32 is high (e.g., greater than 35%), the metal ion permeation efficiency is high, which can easily cause metal ions to precipitate on the surface of the negative electrode 222, thereby posing a safety risk.

[0137] According to some embodiments of the present application, 28%≤K2≤32%.

[0138] Alternatively, K2 may be 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5% or 32%.

[0139] In the above scheme, compared with 25%≤K2≤35%, when 28%≤K2≤32%, it has both better metal ion penetration ability and can limit the penetration efficiency of metal ions.

[0140] According to some embodiments of the present application, the porosity of the first region 31 is equal to the porosity of the third region 33 .

[0141] In the above solution, the porosity of the first region 31 is the same as the porosity of the third region 33 , which facilitates processing and manufacturing.

[0142] According to some embodiments of the present application, the porosity of the first region 31 is K1, and the porosity of the third region 33 is K3, satisfying 35%≤K1=K3≤45%.

[0143] Alternatively, K1 (K3) may be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%.

[0144] In the above scheme, the porosity of the first region 31 and the porosity of the third region 33 meet the above ranges. When applied to the battery cell 20, it has both high metal ion penetration ability and good liquid retention ability; if K1 (K3) is small (such as less than 35%), the metal ion penetration ability is weak, and metal ions are easily precipitated on the surface of the negative electrode plate 222; if K1 (K3) is large (such as greater than 45%), the battery cell 20 composed of the diaphragm 30 is prone to self-discharge, thereby reducing the capacity of the battery cell 20.

[0145] According to some embodiments of the present application, 38%≤K1=K3≤42%.

[0146] Alternatively, K1 (K3) may be 38%, 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5% or 42%.

[0147] In the above solution, compared with 35%≤K1=K3≤45%, when 38%≤K1=K3≤42%, when applied to the battery cell 20, the diaphragm 30 has better metal ion penetration ability, reducing the risk of metal ion precipitation from the negative electrode plate 222, and reducing the risk of self-discharge of the battery cell 20.

[0148] According to some embodiments of the present application, the porosity of the first region 31 is greater than the porosity of the third region 33 .

[0149] In the battery cell 20, due to the charge and discharge cycle, the electrolyte is consumed, and the electrolyte in the upper part of the diaphragm 30 in the height direction of the battery cell 20 is replenished slowly, and it is difficult to absorb back, which makes it easy for metal ions to be short-circuited, causing the negative electrode plate 222 to precipitate metal ions at the position corresponding to this part. When the width direction of the diaphragm 30 is parallel to the height direction of the battery cell 20 and the first area 31 is located above the third area 33, the porosity of the first area 31 is greater than the porosity of the third area 33. The first area 31 has a higher metal ion penetration ability, which can reduce the risk of metal ions precipitating on the surface of the negative electrode plate 222, so that the battery cell 20 has higher safety.

[0150] In the above solution, the porosity of the first region 31 is greater than the porosity of the third region 33 , so that the diaphragm 30 has multiple regions with different porosities, which can meet the requirements of having different metal ion penetration capabilities at different locations.

[0151] According to some embodiments of the present application, the porosity of the first region 31 is K1, and the porosity of the third region 33 is K3, satisfying 45%≤K1≤55% and 35%≤K3≤45%.

[0152] Alternatively, the porosity K1 of the first region 31 may be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%.

[0153] Alternatively, the porosity K3 of the third region 33 may be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%.

[0154] In the above embodiment, when the separator 30 is applied to the battery cell 20, the porosity K1 of the first region 31 and the porosity K3 of the third region 33 meet the above ranges. The separator 30 has different metal ion penetration capabilities to adapt to different scenarios. For example, when the width direction of the separator 30 is parallel to the height direction of the battery cell 20 and the first region 31 is located above the third region 33, 45% ≤ K1 ≤ 55% and 35% ≤ K3 ≤ 45% can reduce the risk of metal ion precipitation from the negative electrode plate 222, thereby improving the safety of the battery cell 20. If K1 is small (e.g., less than 45%) and K3 is small (e.g., less than 35%), metal ions are easily precipitated on the surface of the negative electrode plate 222. If K1 is large (e.g., greater than 55%) and K3 is large (e.g., greater than 45%), the battery cell 20 is prone to self-discharge, reducing the capacity of the battery cell 20.

[0155] According to some embodiments of the present application, 48%≤K1≤52%, and 38%≤K3≤42%.

[0156] Alternatively, the porosity K1 of the first region 31 may be 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5% or 52%.

[0157] Alternatively, the porosity K3 of the third region 33 may be 38%, 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5% or 42%.

[0158] In the above solution, compared with 45%≤K1≤55% and 35%≤K3≤45%, when 48%≤K1≤52% and 38%≤K3≤42%, when applied to the battery cell 20, the diaphragm 30 has better metal ion penetration ability, reducing the risk of metal ion precipitation from the negative electrode plate 222, and reducing the risk of self-discharge of the battery cell 20.

[0159] 5 , according to some embodiments of the present application, the size of the first region 31 along the width direction of the diaphragm 30 is equal to the size of the third region 33 along the width direction of the diaphragm 30 .

[0160] In the above solution, the first region 31 and the third region 33 have the same size in the width direction of the diaphragm 30 , which facilitates processing and manufacturing.

[0161] 3 , 5 and 6 , according to some embodiments of the present application, along the height direction of the battery cell 20 , the first region 31 is located above the third region 33 .

[0162] The height direction of the battery cell 20 refers to the direction parallel to the gravity direction of the battery cell 20 when the battery cell 20 is placed upright. Optionally, the height direction of the battery cell 20 is parallel to the width direction (Z direction) of the separator 30 when the battery cell 20 is placed upright.

[0163] 3 , the tabs 224 may extend from the main body 223 along the height direction of the battery cell 20 . In other embodiments, the tabs 224 may also extend from the main body 223 along the length direction of the battery cell 20 .

[0164] In the height direction of the battery cell 20, the first zone 31, the second zone 32 and the third zone 33 are distributed from top to bottom. The first zone 31 can correspond to the upper position of the negative electrode plate 222 in the height direction of the electrode assembly 22, and the second zone 32 can correspond to the middle position of the negative electrode plate 222 in the height direction of the electrode assembly 22. Even if the electrolyte in the first zone 31 is slowly resorbed and the current density of the battery cell 20 at the corresponding position of the second zone 32 is high, the porosity of the first zone 31 is greater than the porosity of the second zone 32. The first zone 31 has a better liquid retention ability, and the metal ion penetration ability of the second zone 32 is weak, which can improve the problem of metal ion precipitation on the surface of the negative electrode plate 222 at the position corresponding to the first zone 31 and the second zone 32 in the height direction of the battery cell 20.

[0165] Please refer to Figure 7, which is a schematic diagram of the assembly of the diaphragm and the housing provided in some embodiments of the present application. Figure 7 shows a schematic diagram of the cooperation between the diaphragm and the housing, hiding the positive electrode sheet, the negative electrode sheet, and other functional components. According to some embodiments of the present application, along the width direction (Z direction) of the diaphragm 30, the size of the housing is a, and the size of the second area 32 is bx, satisfying bx = a / 2.

[0166] In the above scheme, the size of the second area 32 in the width direction of the diaphragm 30 and the size of the outer shell in the width direction of the diaphragm 30 satisfy the above relationship. Along the width direction of the diaphragm 30, the projection of the second area 32 on the negative electrode plate 222 has a larger corresponding area with the negative electrode plate 222, which can improve the problem of metal ion precipitation on the surface of the negative electrode plate 222 at the corresponding position of the second area 32, so that the battery cell 20 has higher safety.

[0167] In an embodiment where the dimension of the first zone 31 along the width direction of the diaphragm 30 is equal to the dimension of the third zone 33 along the width direction of the diaphragm 30, the width of the diaphragm 30 is b, and the dimension of the first zone 31 along the width direction of the diaphragm 30 and the dimension of the third zone 33 along the width direction of the diaphragm 30 are both by, satisfying: by = (b-bx) / 2.

[0168] According to some embodiments of the present application, 25 mm ≤ bx ≤ 300 mm.

[0169] Alternatively, bx may be 25 mm, 30 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 200 mm, 225 mm, 250 mm, 275 mm, or 300 mm.

[0170] In the above solution, the size of the second region 32 in the width direction of the separator 30 satisfies the above range, so that the separator 30 can adapt to battery cells 20 of different specifications and has a wider range of applications.

[0171] According to some embodiments of the present application, 50 mm ≤ a ≤ 600 mm.

[0172] Alternatively, a may be 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm or 600 mm.

[0173] In the above solution, the size of the battery cell 20 in the width direction of the separator 30 satisfies the above range. Using separators 30 with different porosities at different positions can reduce the risk of metal ion precipitation.

[0174] According to some embodiments of the present application, the battery cell 20 is a lithium-ion battery.

[0175] In the above solution, the battery cell 20 is a lithium-ion battery, and the separator 30 of the above embodiment is used to effectively reduce the risk of lithium plating and has higher safety.

[0176] According to some embodiments of the present application, an embodiment of the present application provides a battery 100, including the battery cell 20 provided by any of the above embodiments.

[0177] According to some embodiments of the present application, an electric device is provided, including the battery 100 provided in any of the above embodiments, and the battery 100 is used to provide electric energy.

[0178] The power-consuming device may be any of the above-mentioned devices or systems using the battery 100 .

[0179] The above describes the diaphragm 30, electrode assembly 22, battery cell 20, battery and electrical equipment of the embodiment of the present application. The manufacturing method of the diaphragm provided by the embodiment of the present application will be described below. For the parts not described in detail, please refer to the aforementioned embodiments.

[0180] FIG8 is a schematic flow chart of a method for manufacturing a diaphragm according to some embodiments of the present application. As shown in FIG8 , the method 400 for manufacturing a diaphragm may include:

[0181] S410, preparing a membrane;

[0182] S420, heating the diaphragm so that the temperature of the second area 32 of the diaphragm is lower than the temperatures of the first area 31 and the third area 33, wherein the first area 31, the second area 32 and the third area 33 are sequentially distributed along the width direction of the diaphragm;

[0183] S430 , stretching the membrane to obtain a thin film, so that the porosity of the second region 32 after stretching is smaller than the porosity of the first region 31 after stretching and smaller than the porosity of the third region 33 after stretching.

[0184] According to the manufacturing method 400 of the diaphragm of the embodiment of the present application, by heating different positions of the diaphragm to different temperatures and stretching the diaphragm, the diaphragm 30 with different porosities at different positions is obtained, which is easy to process and manufacture.

[0185] According to some embodiments of the present application, the step of "stretching the membrane to obtain a film" includes: synchronously stretching the membrane in the width direction and the length direction.

[0186] The width direction and the length direction correspond to the width direction and the length direction of the diaphragm 30 after molding.

[0187] In the above scheme, the diaphragm is stretched synchronously in the width direction and the length direction to ensure that the porosity of each area of ​​the diaphragm is uniform. For example, the porosity of each part of the first zone 31 is uniform, the porosity of each part of the second zone 32 is uniform, and the porosity of each part of the third zone 33 is uniform.

[0188] Please refer to FIG9 , which is a schematic flow chart of a method for manufacturing a diaphragm according to some embodiments of the present application. According to some embodiments of the present application, preparing the diaphragm includes:

[0189] S411, mixing a polyolefin and a pore-forming agent to obtain a mixture;

[0190] S412, heating the mixture and then extruding it into a substrate;

[0191] S413, obtaining a membrane with micropores by cooling and phase separation.

[0192] The polyolefin is selected from any one or a combination of homopolymers, copolymers, and multi-stage polymers of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. For example, the polyolefin may be polyethylene or polypropylene.

[0193] The pore-forming agent is a non-volatile substance that is liquid above the melting point of the polyolefin. The pore-forming agent is preferably liquid at room temperature, for example, any one or a combination of paraffin oil, dioctyl phthalate, dibutyl phthalate, oleyl alcohol, and stearyl alcohol. Optionally, the pore-forming agent is paraffin oil.

[0194] In step “S411, mixing the polyolefin and the pore-forming agent to obtain a mixture”, the polyolefin and the pore-forming agent are mixed in a certain proportion and stirred sufficiently to ensure that the polyolefin and the pore-forming agent are uniformly mixed.

[0195] In step "S413, obtaining a membrane with micropores by cooling and phase separation", the mixture is phase separated by cooling to obtain a membrane with micropores.

[0196] In the above solution, through the above process, a membrane with micropores can be obtained, so that the diaphragm 30 has a certain porosity.

[0197] Please refer to FIG10 , which is a schematic flow chart of a method for manufacturing a diaphragm provided in some other embodiments of the present application. According to some embodiments of the present application, after the diaphragm is stretched to obtain a thin film, the diaphragm manufacturing method 400 further includes:

[0198] S440 , extracting and heat-setting the film to extract the pore-forming agent, thereby obtaining the separator 30 .

[0199] In the above steps, the pore-forming agent in the micropores of the film is extracted by adding an extractant. The process for extracting the pore-forming agent can refer to the extraction process of the pore-forming agent in the prior art.

[0200] In the above scheme, the film is extracted and heat-set to facilitate the formation of the diaphragm 30.

[0201] According to some embodiments of the present application, the step of “heating the membrane” includes:

[0202] The first zone 31 is heated to 120°C to 130°C, the second zone 32 is heated to 100°C to 110°C, and the third zone 33 is heated to 110°C to 120°C.

[0203] By changing the heating temperature, the porosity of the areas corresponding to different temperatures is different after stretching.

[0204] In the above solution, the first zone 31 , the second zone 32 and the third zone 33 are respectively heated to the above temperature ranges, so as to facilitate the control of the porosity at different positions.

[0205] According to some embodiments of the present application, the present application provides a battery cell 20, which includes a housing and an electrode assembly 22, wherein the electrode assembly 22 is disposed within the housing. The electrode assembly 22 includes a positive electrode sheet 221, a negative electrode sheet 222, and a separator 30, and the electrode assembly 22 is a wound electrode assembly. The separator 30 includes a first region 31, a second region 32, and a third region 33 sequentially distributed along its width direction. The width direction of the separator 30 is parallel to the height direction of the battery cell 20. The first region 31 is located above the third region 33. The porosity of the second region 32 is less than the porosity of the first region 31 and less than the porosity of the third region 33. The porosity of the first region 31 is greater than the porosity of the third region 33. The second region 32 has a dimension in the width direction of the separator 30 that is half the dimension of the outer shell in the width direction of the separator 30. The second region 32 corresponds to the area of ​​the battery cell 20 with higher current density. Due to the lower porosity of the second region 32, the risk of metal ion precipitation on the surface of the negative electrode tab 222 is reduced, resulting in a higher safety of the battery cell 20. Because the first region 31 is located above the third region 33 and has a higher porosity than the third region 33, the first region 31 has a higher metal ion penetration ability, reducing the risk of metal ion precipitation on the surface of the negative electrode tab 222 corresponding to the first region 31.

[0206] According to some embodiments of the present application, a battery cell 20 is provided. The battery cell 20 includes a housing and an electrode assembly 22. The electrode assembly 22 is disposed within the housing. The electrode assembly 22 includes a positive electrode sheet 221, a negative electrode sheet 222, and a separator 30. The electrode assembly 22 is a wound electrode assembly. The separator 30 includes a first region 31, a second region 32, and a third region 33 sequentially distributed along its width. The width direction of the separator 30 is parallel to the height direction of the battery cell 20. The first region 31 is located above the third region 33. The porosity of the second region 32 is less than the porosity of the first region 31 and less than the porosity of the third region 33. The porosity of the first region 31 is equal to the porosity of the third region 33. The second region 32 has a width dimension in the separator 30 that is half the width dimension of the outer shell in the separator 30. The second region 32 corresponds to the region of higher current density in the battery cell 20. The lower porosity in the second region 32 reduces the risk of metal ion precipitation on the surface of the negative electrode tab 222, resulting in a higher safety profile for the battery cell 20. The porosity of the first region 31 is equal to that of the third region 33, facilitating the processing and manufacturing of the separator 30.

[0207] Taking the battery cell 20 as a lithium-ion battery cell as an example, the following describes the effect of porosity on the precipitation of metal ions from the battery cell 20 in combination with embodiments and comparative examples.

[0208] In the following embodiments and comparative examples, the height of the housing 21 of the battery cell 20 is 203.7 mm, the width of the separator 30 is 197 mm, the dimension of the second region 32 along the width direction of the separator 30 is 101.85 mm, the dimension of the first region 31 along the width direction of the separator 30 is equal to the dimension of the third region 33 along the width direction of the separator 30, the width direction of the separator 30 is parallel to the height direction of the battery cell 20, and the first region 31 is located above the third region 33. Along the width direction of the separator 30, the middle portion of the battery cell 20 corresponds to the second region 32 of the separator 30, the top portion of the battery cell 20 corresponds to the first region 31 of the separator 30, and the bottom portion of the battery cell 20 corresponds to the third region 33 of the separator 30.

[0209] 1. Battery Cell 20 Upright Placement Test

[0210] Table 1 shows the effect of separators 30 with different porosities on lithium deposition in the battery cells 20 during charge and discharge cycles when the battery cells 20 are placed upright. Upright placement means that the height direction of the battery cells 20 is perpendicular to the surface on which the battery cells 20 are placed. In Table 1, in Examples 1 to 7, the porosity of the second zone 32 is 28%-32%, the porosity of the third zone 33 is 38%-42%, and the porosity of the first zone 31 is 48%-52%; in Comparative Example 1, the porosity of the second zone 32 is 20%, the porosity of the third zone 33 is 40%, and the porosity of the first zone 31 is 50%; in Comparative Example 2, the porosity of the second zone 32 is 40%, the porosity of the third zone 33 is 40%, and the porosity of the first zone 31 is 50%; in Comparative Example 3, the porosity of the second zone 32 is 30%, the porosity of the third zone 33 is 40%, and the porosity of the first zone 31 is 32%; in Comparative Example 4, the porosity of the second zone 32 is 30%, the porosity of the third zone 33 is 40%, and the porosity of the first zone 31 is 60%.

[0211] Table 1

[0212]

[0213]

[0214] According to the above test data, for the porosity of the second region 32, when the porosity of the second region 32 is small (e.g., less than 25%) or large (e.g., greater than 35%), lithium deposition occurs in the middle of the height direction of the battery cell 20. For the porosity of the first region 31, when the porosity of the first region 31 is small (e.g., less than 35%), lithium deposition occurs at the top of the battery cell 20 in the height direction; when the porosity of the first region 31 is large (e.g., greater than 55%), the self-discharge of the battery cell 20 is excessive, and the performance of the battery cell 20 is degraded.

[0215] 2. Battery Cell 20 Non-upright Placement (Lying Flat) Test

[0216] Table 2 shows the effects of separators 30 with different porosities on lithium deposition in battery cells 20 during charge-discharge cycles when the battery cells 20 are positioned non-upright (lying flat). Lying flat means that the height of the battery cells 20 is parallel to the surface on which they are placed. In Table 2, for Examples 1-7, the porosity of the second region 32 is 28%-32%, the porosity of the third region 33 is 38%-42%, and the porosity of the first region 31 is 38%-42%. For Comparative Example 1, the porosity of the second region 32 is 20%, the porosity of the third region 33 is 40%, and the porosity of the first region 31 is 40%. For Comparative Example 2, the porosity of the second region 32 is 40%, the porosity of the third region 33 is 40%, and the porosity of the first region 31 is 40%.

[0217] Table 2

[0218]

[0219] According to the above test data, when the battery cell 20 is set flat, for the porosity of the second zone 32, when the porosity of the second zone 32 is small (such as less than 25%) or the porosity of the second zone 32 is large (such as greater than 35%), lithium deposition occurs in the middle of the battery cell 20 in the height direction of the battery cell 20.

[0220] Lithium plating test process:

[0221] 1. Battery Cell Activation

[0222] 0.33C / 1C

[0223] 1. Keep the temperature constant at 25℃ and rest for 5 minutes;

[0224] 2, 0.5C DC to 2.5V;

[0225] 3. Rest 60 minutes;

[0226] 4, 0.33C CC to 3.65V, CV to 0.05C;

[0227] 5, Rest 5min;

[0228] 6, 1C DC to 2.5V (extract C0);

[0229] Repeat steps 3-6 for 3 cycles.

[0230] 2. Cyclic lithium deposition test

[0231] Temperature: 25℃

[0232] 1. After the battery cell is activated, rest for 120 minutes;

[0233] 2, xx C0 CC to 3.65V (xx = product verification test rate);

[0234] 3. Rest 5 minutes;

[0235] 4, 0.5C0 DC to 2.5V;

[0236] 5, Rest 5min;

[0237] 6. Cycle steps 2 to 5 until the capacity reaches 0.8C0 Ah;

[0238] 7, 25℃ Rest>2.0h;

[0239] 8, 25℃ 0.33C0 CC to 3.65V, CV to 0.05 C0.

[0240] After the test is completed, the battery cell 20 is disassembled, and the fully charged interface of the battery cell 20 is observed to confirm the lithium deposition position and lithium deposition situation.

[0241] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. An electrode assembly, comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet; The diaphragm includes a first region, a second region and a third region sequentially arranged along a width direction thereof, and the porosity of the second region is smaller than the porosity of the first region and smaller than the porosity of the third region.

2. The electrode assembly according to claim 1, wherein: The negative electrode sheet has a first edge and a second edge opposite to each other in the width direction thereof, the first edge falls into the first region, and the second edge falls into the third region.

3. The electrode assembly according to claim 1 or 2, wherein: The positive electrode sheet has a third edge and a fourth edge opposite to each other in the width direction thereof, the third edge falls into the first region, and the fourth edge falls into the third region.

4. The electrode assembly according to any one of claims 1 to 3, wherein: Along the width direction of the diaphragm, the dimensions of the two ends of the positive electrode sheet exceeding the two ends of the second zone are b1 and b2 respectively, and the dimension of the second zone along the width direction of the diaphragm is bx, satisfying 0<b1≤bx / 2, and / or 0<b2≤bx / 2.

5. The electrode assembly according to claim 4, wherein: bx / 5≤b1≤bx / 3, and / or, bx / 5≤b2≤bx / 3.

6. The electrode assembly according to any one of claims 1 to 5, wherein: Along the width direction of the separator, two opposite ends of the negative electrode sheet respectively exceed two opposite ends of the positive electrode sheet, and two opposite ends of the separator respectively exceed two opposite ends of the negative electrode sheet.

7. The electrode assembly according to any one of claims 1 to 6, wherein: The porosity of the second zone is K2, which satisfies 25%≤K2≤35%.

8. The electrode assembly according to claim 7, wherein: 28％≤K2≤32％。 9. The electrode assembly according to any one of claims 1 to 8, wherein: The porosity of the first zone is equal to the porosity of the third zone.

10. The electrode assembly according to claim 9, wherein: The porosity of the first zone is K1, and the porosity of the third zone is K3, which satisfies 35%≤K1=K3≤45%.

11. The electrode assembly according to claim 10, wherein: 38%≤K1=K3≤42%.

12. The electrode assembly according to any one of claims 1 to 8, wherein: The porosity of the first region is greater than the porosity of the third region.

13. The electrode assembly according to claim 12, wherein: The porosity of the first zone is K1, and the porosity of the third zone is K3, which satisfies 45%≤K1≤55% and 35%≤K3≤45%.

14. The electrode assembly according to claim 13, wherein: 48%≤K1≤52%, 38%≤K3≤42%.

15. The electrode assembly according to any one of claims 1 to 14, wherein: A size of the first region along the width direction of the diaphragm is equal to a size of the third region along the width direction of the diaphragm. 16 . A battery cell comprising a housing and the electrode assembly according to claim 15 , wherein the electrode assembly is disposed in the housing.

17. The battery cell according to claim 16, wherein: Along a height direction of the battery cell, the first region is located above the third region.

18. The battery cell according to claim 16 or 17, wherein: Along the width direction of the diaphragm, the size of the housing is a, and the size of the second region is bx, satisfying that bx=a / 2.

19. The battery cell according to claim 18, wherein: 25mm≤bx≤300mm.

20. The battery cell according to claim 18 or 19, wherein: 50mm≤a≤600mm.

21. The battery cell according to any one of claims 16 to 20, wherein: The battery cell is a lithium-ion battery.

22. A battery comprising the battery cell according to any one of claims 16 to 21.

23. An electrical device comprising the battery as claimed in claim 22, wherein the battery is used to provide electrical energy.

24. A method for manufacturing a diaphragm, comprising: preparing a membrane; Heating the diaphragm so that the temperature of the second zone of the diaphragm is lower than the temperatures of the first zone and the third zone, wherein the first zone, the second zone and the third zone are sequentially distributed along the width direction of the diaphragm; The membrane is stretched to obtain a thin film, so that the porosity of the second zone after stretching is smaller than the porosity of the first zone after stretching and smaller than the porosity of the third zone after stretching.

25. The method for manufacturing a diaphragm according to claim 24, wherein: The stretching of the membrane to obtain a film comprises: The film is stretched synchronously in the width direction and the length direction.

26. The method for manufacturing a diaphragm according to claim 24 or 25, wherein: The preparation of the membrane comprises: mixing a polyolefin and a pore former to obtain a mixture; Heating the mixture and then extruding it into a substrate; The membrane with micropores is obtained by phase separation through cooling.

27. The method for manufacturing a diaphragm according to claim 26, wherein: After the diaphragm is stretched to obtain a thin film, the method for manufacturing the diaphragm further comprises: The film is subjected to extraction and heat setting to extract the pore-forming agent and obtain a separator.

28. The method for manufacturing a diaphragm according to claim 27, wherein: The step of heating the diaphragm comprises: The first zone is heated to 120°C to 130°C, the second zone is heated to 100°C to 110°C, and the third zone is heated to 110°C to 120°C.

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