Electrode assembly, battery cell, battery, and apparatus and method for manufacturing electrode assembly

Abstract

The embodiment of the invention provides an electrode assembly, a battery monomer, a battery and manufacturing equipment and method of the electrode assembly, and belongs to the technical field of batteries. The electrode assembly comprises a negative pole piece and a positive pole piece, the negative pole piece and the positive pole piece are wound in the winding direction and form a winding structure, and the winding structure comprises a bending area. Each of the negative pole piece and the positive pole piece comprises a plurality of bending parts positioned in the bending area. At least one bending part in the negative pole piece is a first bending part, and the active material capacity per unit area on the outer side of the first bending part is greater than the active material capacity per unit area on the inner side of the first bending part; and / or at least one bending part in the positive pole piece is a second bending part, and the active material capacity per unit area on the outer side of the second bending part is greater than the active material capacity per unit area on the inner side of the second bending part. According to the electrode assembly with the structure, the arrangement of the active substances in at least part of the bending area of the pole piece is more reasonable, and better economical efficiency is achieved.

Description

Technical Field

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

[0002] At present, the batteries most commonly used in vehicles are generally lithium-ion batteries. As a rechargeable battery, lithium-ion batteries have the advantages of small size, high energy density, high power density, many cycles and long storage time.

[0003] Rechargeable batteries generally include a shell and an electrode assembly. The shell is used to contain the electrode assembly and an electrolyte. The electrode assembly generally includes a positive electrode sheet and a negative electrode sheet. Electric energy is generated by the movement of metal ions (such as lithium ions) between the positive electrode sheet and the negative electrode sheet.

[0004] For general electrode assemblies, the layout of active materials in the electrode sheets is unreasonable and the economic efficiency is poor. Summary of the invention

[0005] The embodiments of the present application provide an electrode assembly, a battery cell, a battery, and an apparatus and method for manufacturing an electrode assembly to improve the problem of unreasonable arrangement of active materials in an electrode sheet.

[0006] In a first aspect, an embodiment of the present application provides an electrode assembly, comprising a negative electrode sheet and a positive electrode sheet, wherein the negative electrode sheet and the positive electrode sheet are wound along a winding direction to form a winding structure, wherein the winding structure comprises a bending zone; the negative electrode sheet and the positive electrode sheet both comprise a plurality of bending portions located in the bending zone; wherein at least one bending portion in the negative electrode sheet is a first bending portion, and the active material capacity per unit area on the outer side of the first bending portion is greater than the active material capacity per unit area on the inner side of the first bending portion; and / or, at least one bending portion in the positive electrode sheet is a second bending portion, and the active material capacity per unit area on the outer side of the second bending portion is greater than the active material capacity per unit area on the inner side of the second bending portion.

[0007] In the above scheme, the capacity of active material per unit area on the outside of the first bend of the negative electrode is greater than the capacity of active material per unit area on the inside of the first bend, and it is not easy to have excess active material on the inside of the first bend and insufficient active material on the outside of the first bend, so that the active material arrangement of at least part of the area of ​​the negative electrode (the area where the first bend is located) is more reasonable; the capacity of active material per unit area on the outside of the second bend of the positive electrode is greater than the capacity of active material per unit area on the inside of the second bend, and it is not easy to have insufficient active material on the outside of the second bend and excess active material on the inside of the second bend, so that the active material arrangement of at least part of the area of ​​the positive electrode (the area where the second bend is located) is more reasonable. The arrangement of active material in at least part of the area of ​​the electrode in the electrode assembly of this structure is more reasonable and has better economy.

[0008] In some embodiments, at least one bend in the negative electrode sheet is the first bend, at least one bend in the positive electrode sheet is the second bend, and the second bend adjacent to the first bend is arranged on the outer side of the first bend.

[0009] In the above scheme, a second bent portion adjacent to the first bent portion is arranged on the outer side of the first bent portion. When the active material capacity per unit area on the inner side of the first bent portion and the active material capacity per unit area on the outer side of the second bent portion meet the design requirements, the active material capacity per unit area on the outer side of the first bent portion is greater than the active material capacity per unit area on the inner side of the first bent portion, and the active material capacity per unit area on the outer side of the second bent portion is greater than the active material capacity per unit area on the inner side of the second bent portion, which can increase the CB value of the outer part of the first bent portion, thereby reducing the occurrence of lithium plating.

[0010] In some embodiments, at least one bend in the negative electrode sheet is the first bend; the bend adjacent to the first bend in the positive electrode sheet is the third bend; the active material capacity per unit area on the outside of the third bend is equal to the active material capacity per unit area on the inside of the third bend.

[0011] In the above scheme, the bending portion adjacent to the first bending portion in the positive electrode sheet is the third bending portion. When the active material capacity per unit area on the outside of the first bending portion is greater than the active material capacity per unit area on the inside of the first bending portion, the active material capacity per unit area on the outside of the third bending portion can be equal to the active material capacity per unit area on the inside of the third bending portion, which can simplify the manufacturing process of the positive electrode sheet.

[0012] In some embodiments, at least one bend in the positive electrode sheet is the second bend; the bend in the negative electrode sheet adjacent to the second bend is the fourth bend; the active material capacity per unit area on the outside of the fourth bend is equal to the active material capacity per unit area on the inside of the fourth bend.

[0013] In the above scheme, the bending portion adjacent to the second bending portion in the negative electrode sheet is the fourth bending portion. When the active material capacity per unit area on the outside of the second bending portion is greater than the active material capacity per unit area on the inside of the second bending portion, the active material capacity per unit area on the outside of the fourth bending portion can be equal to the active material capacity per unit area on the inside of the fourth bending portion, which can simplify the manufacturing process of the negative electrode sheet.

[0014] In some embodiments, the first bending portion includes a first collecting portion, a first active material portion, and a second active material portion; the first collecting portion has a first inner surface and a first outer surface arranged opposite to each other in its thickness direction, the first active material portion is arranged on the first outer surface, and the second active material portion is arranged on the first inner surface.

[0015] In some embodiments, the material of the second active material portion is the same as that of the first active material portion; and the thickness of the first active material portion is greater than the thickness of the second active material portion.

[0016] In the above scheme, when the material of the first active substance portion is the same as that of the second active substance portion, the thickness of the first active substance portion is greater than the thickness of the second active substance portion, which can make the active substance capacity per unit area of ​​the first active substance portion greater than the active substance capacity per unit area of ​​the second active substance portion, thereby achieving that the active substance capacity per unit area on the outside of the first bending portion is greater than the active substance capacity per unit area on the inside of the first bending portion.

[0017] In some embodiments, the first bending portion further includes a first conductive portion, the first conductive portion is connected between the second active material portion and the first inner surface, and the thickness of the first active material portion is equal to or greater than the total thickness of the second active material portion and the first conductive portion.

[0018] In the above scheme, by setting the first conductive part between the second active material part and the first collecting part, the thickness of the first active material part is equal to or greater than the total thickness of the second active material part and the first conductive part, so as to achieve the thickness of the first active material part being greater than the thickness of the second active material part.

[0019] In some embodiments, the thickness of the first active material portion is equal to the thickness of the second active material portion; and the gram capacity of the active material in the first active material portion is greater than the gram capacity of the active material in the second active material portion.

[0020] In the above scheme, when the thickness of the first active material portion is equal to the thickness of the second active material portion, the gram capacity of the active material in the first active material portion is greater than the gram capacity of the active material in the second active material portion, so that the active material capacity per unit area of ​​the first active material portion is greater than the active material capacity per unit area of ​​the second active material portion, thereby achieving that the active material capacity per unit area on the outside of the first bending portion is greater than the active material capacity per unit area on the inside of the first bending portion.

[0021] In some embodiments, the second bending portion includes a second collecting portion, a third active material portion and a fourth active material portion; the second collecting portion has a second inner surface and a second outer surface arranged opposite to each other in its thickness direction, the third active material portion is arranged on the second outer surface, and the fourth active material portion is arranged on the second inner surface.

[0022] In some embodiments, the material of the fourth active material portion is the same as that of the third active material portion; and the thickness of the third active material portion is greater than the thickness of the fourth active material portion.

[0023] In the above scheme, when the material of the third active substance portion is the same as that of the fourth active substance portion, the thickness of the third active substance portion is greater than the thickness of the fourth active substance portion, which can make the active substance capacity per unit area of ​​the third active substance portion greater than the active substance capacity per unit area of ​​the fourth active substance portion, thereby achieving that the active substance capacity per unit area on the outside of the second bending portion is greater than the active substance capacity per unit area on the inside of the second bending portion.

[0024] In some embodiments, the second bending portion further includes a second conductive portion, the second conductive portion is connected between the fourth active material portion and the second inner surface, and the thickness of the third active material portion is equal to or greater than the total thickness of the fourth active material portion and the second conductive portion.

[0025] In the above scheme, by setting the second conductive part between the fourth active material part and the second current collecting part, the thickness of the third active material part is equal to or greater than the total thickness of the fourth active material part and the second conductive part, so as to achieve the thickness of the third active material part being greater than the thickness of the fourth active material part.

[0026] In some embodiments, the thickness of the third active material portion is equal to the thickness of the fourth active material portion; and the gram capacity of the active material in the third active material portion is greater than the gram capacity of the active material in the fourth active material portion.

[0027] In the above scheme, when the thickness of the third active material portion is equal to the thickness of the fourth active material portion, the gram capacity of the active material in the third active material portion is greater than the gram capacity of the active material in the fourth active material portion, which can make the active material capacity per unit area of ​​the third active material portion greater than the active material capacity per unit area of ​​the fourth active material portion, thereby achieving that the active material capacity per unit area on the outside of the second bending portion is greater than the active material capacity per unit area on the inside of the second bending portion.

[0028] In some embodiments, the negative electrode sheet includes a negative electrode current collector and negative electrode active material layers disposed on both sides of the negative electrode current collector in a thickness direction; each negative electrode active material layer is distributed on the negative electrode current collector with equal thickness along the winding direction.

[0029] In the above solution, each negative electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction, which can simplify the manufacturing process of the negative electrode sheet and is conducive to reducing production costs.

[0030] In some embodiments, the positive electrode sheet includes a positive electrode current collector and positive electrode active material layers disposed on both sides of the positive electrode current collector in a thickness direction; each positive electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction.

[0031] In the above solution, each positive electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction, which can simplify the manufacturing process of the positive electrode sheet and is conducive to reducing production costs.

[0032] In some embodiments, all the bent portions in the negative electrode plate are the first bent portions.

[0033] In the above scheme, all the bends in the negative electrode sheet are the first bends, that is, all the bends in the negative electrode sheet have a unit active material capacity on the outside that is greater than the unit active material capacity on the inside, so that the active material arrangement of the part of the negative electrode sheet located in the bend area is more reasonable. When the active material capacity per unit area inside the first bend meets the design requirements, since the active material capacity per unit area outside the first bend is greater than the active material capacity per unit area inside the first bend, it is equivalent to increasing the active material capacity per unit area outside the first bend, so that the CB value of the outer part of all the bends in the negative electrode sheet increases, and the part of the negative electrode sheet located in the bend area is not prone to lithium precipitation.

[0034] In some embodiments, all the bent portions in the positive electrode sheet are the second bent portions.

[0035] In the above scheme, all the bends in the positive electrode sheet are second bends, that is, all the bends in the positive electrode sheet are outer unit active material capacity greater than inner unit active material capacity, so that the active material arrangement of the part of the positive electrode sheet located in the bend area is more reasonable. When the active material capacity per unit area outside the second bend meets the design requirements, since the active material capacity per unit area outside the second bend is greater than the active material capacity per unit area inside the second bend, it is equivalent to reducing the active material capacity per unit area inside the second bend, so that the CB values ​​of the outer parts of the multiple bends in the negative electrode sheet are all increased, and the part of the negative electrode sheet located in the bend area is not prone to lithium precipitation.

[0036] In a second aspect, an embodiment of the present application provides a battery cell, comprising a housing and an electrode assembly provided by any one of the embodiments of the first aspect; the electrode assembly is accommodated in the housing.

[0037] In a third aspect, an embodiment of the present application provides a battery, comprising a housing and a battery cell provided by any one of the embodiments of the second aspect; the battery cell is accommodated in the housing.

[0038] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising a battery provided by any embodiment of the second aspect.

[0039] In a fifth aspect, an embodiment of the present application provides a method for manufacturing an electrode assembly, comprising:

[0040] A positive electrode sheet and a negative electrode sheet are provided; the negative electrode sheet and the positive electrode sheet are wound along a winding direction to form a winding structure; wherein the winding structure includes a bending area, and the negative electrode sheet and the positive electrode sheet both include a plurality of bending portions located in the bending area; at least one bending portion in the negative electrode sheet is a first bending portion, and the active material capacity per unit area on the outer side of the first bending portion is greater than the active material capacity per unit area on the inner side of the first bending portion; and / or, at least one bending portion in the positive electrode sheet is a second bending portion, and the active material capacity per unit area on the outer side of the second bending portion is greater than the active material capacity per unit area on the inner side of the second bending portion.

[0041] In the sixth aspect, an embodiment of the present application also provides an electrode assembly manufacturing device, comprising: a providing device for providing a positive electrode sheet and a negative electrode sheet; an assembling device for winding the negative electrode sheet and the positive electrode sheet along a winding direction to form a winding structure; wherein the winding structure includes a bending area, and the negative electrode sheet and the positive electrode sheet both include a plurality of bending portions located in the bending area; at least one bending portion in the negative electrode sheet is a first bending portion, and the active material capacity per unit area on the outer side of the first bending portion is greater than the active material capacity per unit area on the inner side of the first bending portion; and / or, at least one bending portion in the positive electrode sheet is a second bending portion, and the active material capacity per unit area on the outer side of the second bending portion is greater than the active material capacity per unit area on the inner side of the second bending portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0043] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0044] Figure 2 An exploded view of a battery provided for some embodiments of the present application;

[0045] Figure 3 for Figure 2 A schematic diagram of the structure of the battery module shown;

[0046] Figure 4 for Figure 3 An exploded view of a battery cell is shown;

[0047] Figure 5 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0048] Figure 6 A schematic diagram of the structure of an electrode assembly provided in some other embodiments of the present application;

[0049] Figure 7 for Figure 5 A partial enlarged view of the electrode assembly shown;

[0050] Figure 8 A partial enlarged view of a portion of an electrode assembly located in a bending area provided in some embodiments of the present application;

[0051] Fig. 9A partial enlarged view of a portion of an electrode assembly located in a bending area provided in some other embodiments of the present application;

[0052] Fig.10 A partial enlarged view of a portion of an electrode assembly located in a bending area provided in some other embodiments of the present application;

[0053] Fig.11 A partial enlarged view of a portion of an electrode assembly located in a bending area provided in some other embodiments of the present application;

[0054] Fig.12 A partial enlarged view of a portion of an electrode assembly located in a bending area provided in some other embodiments of the present application;

[0055] Fig.13 A flow chart of a method for manufacturing an electrode assembly provided in some embodiments of the present application;

[0056] Fig.14 A schematic block diagram of a manufacturing device for an electrode assembly provided in some embodiments of the present application.

[0057] In the drawings, the drawings are not drawn to scale.

[0058] Marking description: 10-box; 11-first part; 12-second part; 13-accommodation space; 20-battery cell; 21-housing; 211-housing; 212-cover; 213-sealed space; 214-positive electrode terminal; 215-negative electrode terminal; 216-pressure relief mechanism; 22-electrode assembly; 220-negative electrode sheet; 2201-negative current collector; 2202-first negative active material layer; 2203-second negative active material layer material layer; 221-positive electrode sheet; 2211-positive current collector; 2212-first positive active material layer; 2213-second positive active material layer; 222-separator; 223-bending portion; 224-first bending portion; 2241-first current collector; 2241a-first inner surface; 2241b-first outer surface; 2242-first active material portion; 2243-second active material portion; 225-second bending portion; 2251- Second collector; 2251a-second inner surface; 2251b-second outer surface; 2252-third active material portion; 2253-fourth active material portion; 226-third bending portion; 2261-third collector; 2261a-third inner surface; 2261b-third outer surface; 2262-fifth active material portion; 2263-sixth active material portion; 227-fourth bending portion; 2271-fourth collector; 2271a-fourth Inner surface; 2271b-fourth outer surface; 2272-seventh active material portion; 2273-eighth active material portion; 228-first conductive portion; 229-second conductive portion; 30-battery module; 31-bus component; 100-battery; 200-controller; 300-motor; 1000-vehicle; 2000-manufacturing equipment; 2100-providing device; 2200-assembling device; A-winding direction; B-bending area; C-straight area. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0060] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; 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" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. 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 and secondary relationship.

[0061] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0062] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0063] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0064] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0065] The term "plurality" used in the present application refers to two or more (including two).

[0066] In the present application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries or magnesium-ion batteries, etc., and the embodiments of the present application do not limit this. Battery cells may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this. Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of the present application do not limit this.

[0067] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module or a battery pack. The battery generally includes a box for encapsulating one or more battery cells. The box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells.

[0068] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer. The positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode collector. The negative electrode collector not coated with the negative electrode active material layer protrudes from the negative electrode collector coated with the negative electrode active material layer. The negative electrode collector not coated with the negative electrode active material layer serves as the negative electrode tab. The material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon or silicon, etc. In order to ensure that a large current can pass without melting, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together. The material of the isolation film may be PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto.

[0069] For general electrode assemblies, the layout of active materials in the electrode sheets is unreasonable and the economic efficiency is poor.

[0070] The inventor found that the thickness of the inner active material layer of the negative electrode sheet in the electrode assembly is equal to the thickness of the outer active material layer of the negative electrode sheet, and the material of the inner active material layer of the negative electrode sheet is the same as the material of the outer active material layer; the thickness of the inner active material layer of the positive electrode sheet is equal to the thickness of the outer active material layer of the positive electrode sheet, and the material of the inner active material layer of the positive electrode sheet is the same as the active material of the outer active material layer; in the bending area of ​​the electrode assembly, the radius of the inner active material layer of the negative electrode sheet is greater than the radius of the outer active material layer of the positive electrode sheet located inside the negative electrode sheet, while the radius of the outer active material layer of the negative electrode sheet is smaller than the radius of the inner active material layer of the positive electrode sheet outside the negative electrode sheet, so that the inner active material of the bending part of the negative electrode sheet in the bending area is excessive and the outer active material is insufficient. Similarly, the outer active material of the bending part of the positive electrode sheet in the bending area is insufficient, while the inner active material is excessive. In the electrode assembly with this structure, the active material arrangement in the electrode sheet is unreasonable and the economic efficiency is poor.

[0071] In view of this, the embodiment of the present application provides a technical solution, wherein the negative electrode plate includes a first bending portion located in the bending area, and the active material capacity per unit area outside the first bending portion is greater than the active material capacity per unit area inside the first bending portion, and / or the positive electrode plate includes a second bending portion located in the bending area, and the active material capacity per unit area outside the second bending portion is greater than the active material capacity per unit area inside the second bending portion. This structure makes the active material arrangement of the electrode plate in at least part of the bending area more reasonable and has better economy.

[0072] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical equipment using batteries.

[0073] Electrical equipment may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, electric tools, and the like. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, and the like; spacecraft include airplanes, rockets, space shuttles, and spacecraft, and the like; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0074] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0075] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery 100 is disposed inside the vehicle 1000. The battery 100 may be disposed 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 be used as an operating power source for the vehicle 1000.

[0076] The vehicle 1000 may further include a controller 200 and a motor 300 , wherein 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 starting, navigating, and driving the vehicle 1000 .

[0077] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve 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.

[0078] Please refer to Figure 2 , Figure 2 The exploded view of the battery 100 provided in some embodiments of the present application, the battery 100 includes a box 10 and a battery cell 20 ( Figure 2 The battery cell 20 is accommodated in the box body 10 .

[0079] The box 10 is used to accommodate the battery cell 20, and the box 10 can be a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 together define a storage space 13 for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, the first part 11 is a plate-like structure, and the first part 11 covers the open side of the second part 12 to form a box 10 with a storage space 13; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12 to form a box 10 with a storage space 13. Of course, the first part 11 and the second part 12 can be a variety of shapes, such as a cylinder, a cuboid, etc.

[0080] In order to improve the sealing performance after the first part 11 and the second part 12 are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first part 11 and the second part 12 .

[0081] Assuming that the first portion 11 covers the top of the second portion 12 , the first portion 11 can also be referred to as an upper cover, and the second portion 12 can also be referred to as a lower box body.

[0082] In the battery 100, there can be one or more battery cells 20. If there are more than one battery cell 20, the battery cells 20 can be connected in series, in parallel, or in a mixed connection. A mixed connection means that the battery cells 20 are both connected in series and in parallel. The battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the battery cells 20 can be accommodated in the box 10; of course, the battery modules 30 can also be formed by connecting the battery cells 20 in series, in parallel, or in a mixed connection, and then the battery modules 30 can be formed into a whole by connecting the battery cells 20 in series, in parallel, or in a mixed connection, and then accommodated in the box 10.

[0083] In some embodiments, please refer to Figure 3 , Figure 3 for Figure 2 The schematic diagram of the structure of the battery module 30 is shown. There are multiple battery cells 20, and the multiple battery cells 20 are first connected in series, in parallel, or in mixed series to form a battery module 30. The multiple battery modules 30 are then connected in series, in parallel, or in mixed series to form a whole, and are accommodated in the box 10.

[0084] The multiple battery cells 20 in the battery module 30 can be electrically connected through the busbar component 31 to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 20 in the battery module 30 .

[0085] Please refer to Figure 4 , Figure 4 for Figure 3 The exploded view of the battery cell 20 is shown. The battery cell 20 provided in the embodiment of the present application comprises a housing 21 and an electrode assembly 22 , wherein the electrode assembly 22 is accommodated in the housing 21 .

[0086] In some embodiments, the housing 21 may also be used to contain electrolyte, such as electrolyte. The housing 21 may be in various structural forms.

[0087] In some embodiments, the housing 21 may include a shell 211 and a cover 212, wherein the shell 211 is a hollow structure with one side open, and the cover 212 covers the opening of the shell 211 and forms a sealed connection to form a sealed space 213 for accommodating the electrode assembly 22 and the electrolyte.

[0088] When assembling the battery cell 20 , the electrode assembly 22 may be placed in the housing 211 first, and the housing 211 may be filled with electrolyte, and then the cover 212 may be closed on the opening of the housing 211 .

[0089] The shell 211 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the shell 211 can be determined according to the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, a cylindrical shell 211 can be selected; if the electrode assembly 22 is a cuboid structure, a cuboid shell 211 can be selected. Of course, the cover 212 can also be in various structures, such as a plate-like structure, a hollow structure with one end open, etc. For example, in Figure 4 In the embodiment, the shell 211 is a rectangular parallelepiped structure, the cover 212 is a plate-shaped structure, and the cover 212 covers the opening at the top of the shell 211 .

[0090] In some embodiments, the battery cell 20 may further include a positive electrode terminal 214, a negative electrode terminal 215, and a pressure relief mechanism 216, which are all mounted on the cover 212. The positive electrode terminal 214 and the negative electrode terminal 215 are both used to electrically connect to the electrode assembly 22 to output the electrical energy generated by the electrode assembly 22. The pressure relief mechanism 216 is used to release the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0091] Exemplarily, the pressure relief mechanism 216 is located between the positive electrode terminal 214 and the negative electrode terminal 215 , and the pressure relief mechanism 216 may be a component such as an explosion-proof valve, an explosion-proof disk, an air valve, a pressure relief valve, or a safety valve.

[0092] Of course, in some embodiments, the housing 21 may also be other structures, for example, the housing 21 includes a shell 211 and two covers 212, the shell 211 is a hollow structure with two opposite openings, and one cover 212 is correspondingly covered at one opening of the shell 211 and forms a sealed connection to form a sealed space 213 for accommodating the electrode assembly 22 and the electrolyte. In this structure, the positive electrode terminal 214 and the negative electrode terminal 215 may be installed on the same cover 212 or on different covers 212; the pressure relief mechanism 216 may be installed on one cover 212 or on both covers 212.

[0093] It should be noted that, in the battery cell 20, the number of electrode assemblies 22 contained in the housing 21 may be one or more. Figure 4 In the embodiment, there are two electrode assemblies 22 .

[0094] Next, the specific structure of the electrode assembly 22 is described in detail with reference to the accompanying drawings.

[0095] Please refer to Figure 5 , Figure 5A structural schematic diagram of an electrode assembly 22 provided in some embodiments of the present application, wherein the electrode assembly 22 includes a negative electrode sheet 220 and a positive electrode sheet 221, wherein the negative electrode sheet 220 and the positive electrode sheet 221 are wound along a winding direction A to form a winding structure, wherein the winding structure includes a bending area B, and the negative electrode sheet 220 and the positive electrode sheet 221 both include a plurality of bending portions 223 located in the bending area B.

[0096] Among them, at least one bending portion 223 in the negative electrode sheet 220 is a first bending portion 224 ( Figure 5 (not shown), the active material capacity per unit area outside the first bent portion 224 is greater than the active material capacity per unit area inside the first bent portion 224; and / or at least one bent portion 223 in the positive electrode sheet 221 is a second bent portion 225 ( Figure 5 (not shown), the active material capacity per unit area on the outer side of the second bent portion 225 is greater than the active material capacity per unit area on the inner side of the second bent portion 225.

[0097] If the capacity of active material per unit area on the outside of the first bend 224 of the negative electrode plate 220 is greater than the capacity of active material per unit area on the inside of the first bend 224, it is not easy for the active material inside the first bend 224 to be excessive, while the active material outside the first bend 224 is insufficient, so that the active material arrangement of at least part of the area of ​​the negative electrode plate 220 (the area where the first bend 224 is located) is more reasonable. If the capacity of active material per unit area on the outside of the second bend 225 of the positive electrode plate 221 is greater than the capacity of active material per unit area on the inside of the second bend 225, it is not easy for the active material outside the second bend 225 to be insufficient, while the active material inside the second bend 225 is excessive, so that the active material arrangement of at least part of the area of ​​the positive electrode plate 221 (the area where the second bend 225 is located) is more reasonable. The arrangement of active materials in at least part of the area of ​​the plate in the electrode assembly 22 of this structure is more reasonable and has better economy.

[0098] In addition, when the active material capacity per unit area on the inner side of the first bend portion 224 meets the design requirements, that is, the active material capacity per unit area on the inner side of the first bend portion 224 reaches the first preset value, the inner part of the first bend portion 224 is not prone to lithium deposition. Since the active material capacity per unit area on the outer side of the first bend portion 224 is greater than the active material capacity per unit area on the inner side of the first bend portion 224, relative to the first preset value, it is equivalent to increasing the active material capacity per unit area on the outer side of the first bend portion 224, which can increase the CB value of the outer part of the first bend portion 224, thereby making it less likely for lithium deposition to occur on the outer part of the first bend portion 224. Similarly, when the active material capacity per unit area on the outside of the second bend portion 225 meets the design requirements, that is, the active material capacity per unit area on the outside of the second bend portion 225 reaches the second preset value, the negative electrode sheet 220 is located on the inner side of the bend portion 223 on the outside of the second bend portion 225. It is not easy for lithium deposition to occur. Since the active material capacity per unit area on the outside of the second bend portion 225 is greater than the active material capacity per unit area on the inside of the second bend portion 225, relative to the second preset value, it is equivalent to reducing the active material capacity per unit area on the inside of the second bend portion 225, so that the negative electrode sheet 220 is located on the outer side of the bend portion 223 on the inside of the second bend portion 225. Lithium deposition is also not easy to occur.

[0099] The CB (Cell Balance) value is the ratio of the capacity of the negative electrode active material per unit area to the capacity of the positive electrode active material per unit area. The CB (Cell Balance) value of the outer portion of the bent portion 223 of the negative electrode sheet 220 = Q1 / Q2, wherein the active material capacity per unit area of ​​the outer active material of one bent portion 223 in the negative electrode sheet 220 is Q1, and the active material capacity per unit area of ​​the inner active material of the bent portion 223 located outside and adjacent to the bent portion 223 in the positive electrode sheet 221 is Q2.

[0100] In the embodiment of the present application, the winding direction A is the direction in which the positive electrode sheet 221 and the negative electrode sheet 220 are wound from the inside to the outside. Figure 5 , the winding direction A is clockwise.

[0101] In some embodiments, the electrode assembly 22 may further include an isolation film 222 , which is used to isolate the positive electrode plate 221 from the negative electrode plate 220 to reduce the risk of short circuit between the positive electrode plate 221 and the negative electrode plate 220 .

[0102] The material of the isolation film 222 can be PP (polypropylene) or PE (polyethylene).

[0103] In some embodiments, Figure 5 As shown, the winding structure also includes a straight area C, which is connected to the bending area B, and the two opposite ends of the straight area C may be provided with bending areas B. The straight area C is the area where the winding structure has a straight structure, and the part of the positive electrode sheet 221 located in the straight area C and the part of the negative electrode sheet 220 located in the straight area C are both basically arranged straight. The bending area B is the area where the winding structure has a bending structure, and the part of the positive electrode sheet 221 located in the bending area B (bending portion 223) and the part of the negative electrode sheet 220 located in the bending area B (bending portion 223) are both bent and distributed. Exemplarily, the bending portion 223 of the positive electrode sheet 221 and the bending portion 223 of the negative electrode sheet 220 are at least partially arc-shaped.

[0104] In this embodiment, the winding structure includes a straight area C and a bent area B, and the electrode assembly as a whole is a flat body.

[0105] It should be noted that, when a first bending portion 224 is arranged in the bending zone B, only one bending zone B may have the first bending portion 224 arranged therein, or both bending zones B may have the first bending portion 224 arranged therein; when a second bending portion 225 is arranged in the bending zone B, only one bending zone B may have the second bending portion 225 arranged therein, or both bending zones B may have the second bending portion 225 arranged therein.

[0106] For example, Figure 5 As shown, in the bending zone B, the multiple bending portions 223 in the positive electrode sheet 221 and the multiple bending portions 223 in the negative electrode sheet 220 are arranged alternately, that is, in the bending zone B, they are arranged in the order of a bending portion 223 of the negative electrode sheet 220, a bending portion 223 of the positive electrode sheet 221, a bending portion 223 of the negative electrode sheet 220, and so on.

[0107] In other embodiments, please refer to Figure 6 , Figure 6 The schematic diagram of the structure of the electrode assembly 22 provided in some embodiments of the present application, the winding structure may only have a bending area B, but no straight area C, and the electrode assembly 22 of this structure may be a cylinder as a whole. In the positive electrode sheet 221, a circle of the positive electrode sheet 221 is a bending portion 223; in the negative electrode sheet 220, a circle of the negative electrode sheet 220 is a bending portion 223.

[0108] In some embodiments, please refer to Figure 7 , Figure 7 for Figure 5The partial enlarged view of the electrode assembly 22 shown in the figure shows that the negative electrode plate 220 includes a negative electrode collector 2201 and negative electrode active material layers arranged on both sides of the negative electrode collector 2201 in the thickness direction, and the negative electrode active material layers on both sides of the negative electrode collector 2201 in the thickness direction are respectively a first negative electrode active material layer 2202 and a second negative electrode active material layer 2203, the first negative electrode active material layer 2202 is arranged on the outer surface of the negative electrode collector 2201, and the second negative electrode active material layer 2203 is arranged on the inner surface of the negative electrode collector 2201. The positive electrode sheet 221 includes a positive electrode collector 2211 and positive electrode active material layers arranged on both sides of the positive electrode collector 2211 in the thickness direction. The positive electrode active material layers on both sides of the positive electrode collector 2211 in the thickness direction are respectively a first positive electrode active material layer 2212 and a second positive electrode active material layer 2213. The first positive electrode active material layer 2212 is arranged on the outer surface of the positive electrode collector 2211, and the second positive electrode active material layer 2213 is arranged on the inner surface of the positive electrode collector 2211.

[0109] The negative electrode current collector 2201 may have a portion not coated with the negative electrode active material layer, which is the negative electrode tab (not shown); the positive electrode current collector 2211 may have a portion not coated with the negative electrode active material layer, which is the positive electrode tab (not shown). The positive electrode tab is used to connect to the positive electrode terminal 214 (see Figure 4 ) is electrically connected, and the negative electrode tab is used to connect to the negative electrode terminal 215 (see Figure 4 )Electrical connection.

[0110] In some embodiments, in the negative electrode sheet 220, each negative electrode active material layer is distributed on the negative electrode current collector 2201 with equal thickness along the winding direction A, that is, the first negative electrode active material layer 2202 is distributed on the negative electrode current collector 2201 with equal thickness along the winding direction A, and the second negative electrode active material layer 2203 is distributed on the negative electrode current collector 2201 with equal thickness along the winding direction A. This structure can simplify the manufacturing process of the negative electrode sheet 220, which is conducive to reducing production costs.

[0111] It can be understood that the thickness of each layer of the first negative electrode active material layer 2202 located in the bending area B is equal to the thickness of each layer of the first negative electrode active material layer 2202 located in the straight area C; the thickness of each layer of the second negative electrode active material layer 2203 located in the bending area B is equal to the thickness of each layer of the second negative electrode active material layer 2203 located in the straight area C.

[0112] In some embodiments, in the positive electrode sheet 221, each positive electrode active material layer is distributed in equal thickness on the positive electrode collector 2211 along the winding direction A, that is, the first positive electrode active material layer 2212 is distributed in equal thickness on the positive electrode collector 2211 along the winding direction A, and the second positive electrode active material layer 2213 is distributed in equal thickness on the positive electrode collector 2211 along the winding direction A. This structure can simplify the manufacturing process of the positive electrode sheet 221, which is conducive to reducing production costs.

[0113] It can be understood that the thickness of each layer of the first positive electrode active material layer 2212 located in the bending area B is equal to the thickness of each layer of the first positive electrode active material layer 2212 located in the straight area C; the thickness of each layer of the second positive electrode active material layer 2213 located in the bending area B is equal to the thickness of each layer of the second positive electrode active material layer 2213 located in the straight area C.

[0114] In some embodiments, please refer to Figure 8 , Figure 8 This is a partial enlarged view of the portion of the electrode assembly 22 provided in some embodiments of the present application located in the bending area B, wherein at least one bending portion 223 in the negative electrode plate 220 is a first bending portion 224, and the active material capacity per unit area outside the first bending portion 224 of the negative electrode plate 220 is greater than the active material capacity per unit area inside the first bending portion 224. The bending portion 223 in the positive electrode plate 221 adjacent to the first bending portion 224 is a third bending portion 226, and the active material capacity per unit area outside the third bending portion 226 is equal to the active material capacity per unit area inside the third bending portion 226.

[0115] When the active material capacity per unit area on the outside of the first bend 224 is greater than the active material capacity per unit area on the inside of the first bend 224 , the active material capacity per unit area on the outside of the third bend 226 can be equal to the active material capacity per unit area on the inside of the third bend 226 to simplify the manufacturing process of the positive electrode sheet 221 .

[0116] The first bending portion 224 includes a first current collecting portion 2241, a first active material portion 2242, and a second active material portion 2243. The first current collecting portion 2241 has a first inner surface 2241a and a first outer surface 2241b arranged oppositely in the thickness direction thereof, the first active material portion 2242 is arranged on the first outer surface 2241b, and the second active material portion 2243 is arranged on the first inner surface 2241a. The third bending portion 226 includes a third current collecting portion 2261, a fifth active material portion 2262, and a sixth active material portion 2263. The third current collecting portion 2261 has a third inner surface 2261a and a third outer surface 2261b arranged oppositely in the thickness direction thereof, the fifth active material portion 2262 is arranged on the third outer surface 2261b, and the sixth active material portion 2263 is arranged on the third inner surface 2261a.

[0117] It can be understood that the first current collecting portion 2241 is the negative electrode current collector 2201 (see Figure 7 ) in the bending region B, the first active material portion 2242 is the first negative electrode active material layer 2202 (see Figure 7 ) in the bending region B, the second active material portion 2243 is the second negative electrode active material layer 2203 (see Figure 7 ) is a layer in the bending area B. The third current collector 2261 is a positive electrode current collector 2211 (see Figure 7 ) is a layer in the bending region B, the fifth active material portion 2262 is the first positive electrode active material layer 2212 (see Figure 7 ) In the bending region B, the sixth active material portion 2263 is the second positive electrode active material layer 2213 (see Figure 7 ) in a layer of the bending zone B.

[0118] The active material capacity per unit area outside the first bend 224 is greater than the active material capacity per unit area inside the first bend 224, that is, the active material capacity per unit area of ​​the first active material portion 2242 (the outer portion of the first bend 224) is greater than the active material capacity per unit area of ​​the second active material portion 2243 (the inner portion of the first bend 224). The active material capacity per unit area outside the first bend 224 may be the ratio of the active material capacity of the first active material portion 2242 to the area of ​​the first outer surface 2241b, and the active material capacity per unit area inside the first bend 224 may be the ratio of the active material capacity of the second active material portion 2243 to the area of ​​the first inner surface 2241a.

[0119] The active material capacity per unit area outside the third bend 226 is equal to the active material capacity per unit area inside the third bend 226, that is, the active material capacity per unit area of ​​the fifth active material portion 2262 (the outer portion of the third bend 226) is equal to the active material capacity per unit area of ​​the sixth active material portion 2263 (the inner portion of the third bend 226). The active material capacity per unit area outside the third bend 226 may be the ratio of the active material capacity of the fifth active material portion 2262 to the area of ​​the third outer surface 2261b, and the active material capacity per unit area inside the third bend 226 may be the ratio of the active material capacity of the sixth active material portion 2263 to the third inner surface 2261a.

[0120] In the negative electrode sheet 220, all the bent portions 223 may be the first bent portion 224, or part of the bent portions 223 may be the first bent portion 224. If all the bent portions 223 in the negative electrode sheet 220 are the first bent portion 224, the unit surface active material capacity of the outer side of all the bent portions 223 in the negative electrode sheet 220 is greater than the unit surface active material capacity of the inner side. If only part of the bent portions 223 of the negative electrode sheet 220 are the first bent portion 224, all the bent portions 223 in the negative electrode sheet 220 except the first bent portion 224 may adopt a structure in which the unit surface active material capacity of the outer side is equal to the unit surface active material capacity of the inner side. In the positive electrode sheet 221, all the bent portions 223 may be the third bent portion 226, or only part of the bent portions 223 may be the third bent portion 226.

[0121] In some embodiments, part of the bent portion 223 in the negative electrode sheet 220 is the first bent portion 224 , and all of the bent portion 223 in the positive electrode sheet 221 is the third bent portion 226 .

[0122] In the negative electrode sheet 220 , one or more innermost bending portions 223 of the bending zone B may be the first bending portion 224 . Exemplarily, the innermost two bending portions 223 of the negative electrode sheet 220 are the first bending portions 224 .

[0123] In some embodiments, all the bent portions 223 in the negative electrode sheet 220 are first bent portions 224 , and all the bent portions 223 in the positive electrode sheet 221 are third bent portions 226 .

[0124] In this embodiment, in the negative electrode sheet 220 , each negative electrode active material layer may be distributed in the negative electrode collector 2201 with equal thickness along the winding direction A; in the positive electrode sheet 221 , each positive electrode active material layer may be distributed in the positive electrode collector 2211 with equal thickness along the winding direction A.

[0125] In the embodiment of the present application, a plurality of methods can be used to achieve that the active material capacity per unit area on the outer side of the first bending portion 224 is greater than the active material capacity per unit area on the inner side of the first bending portion 224 .

[0126] In some embodiments, please refer to Figure 8 The material of the first active material portion 2242 in the first bending portion 224 is the same as that of the second active material portion 2243 , and the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243 .

[0127] When the material of the first active substance portion 2242 is the same as that of the second active substance portion 2243, the thickness of the first active substance portion 2242 is greater than that of the second active substance portion 2243, so that the active substance capacity per unit area of ​​the first active substance portion 2242 is greater than that of the second active substance portion 2243, thereby achieving that the active substance capacity per unit area on the outer side of the first bend portion 224 is greater than the active substance capacity per unit area on the inner side of the first bend portion 224.

[0128] It should be noted that the material of the first active material portion 2242 is the same as that of the second active material portion 2243, that is, the same active material portion is coated on the first inner surface 2241a and the first outer surface 2241b of the first current collecting portion 2241. It is understandable that the components of the first active material portion 2242 are the same as those of the second active material portion 2243, and the proportion of each component of the first active material portion 2242 is the same as that of each component of the second active material portion 2243. For example, the first active material portion 2242 and the second active material portion 2243 both include active materials, conductive agents, and adhesives, the proportion of active materials in the first active material portion 2242 is the same as that of active materials in the second active material portion 2243, the proportion of conductive agents in the first active material portion 2242 is the same as that of conductive agents in the second active material portion 2243, and the proportion of adhesives in the first active material portion 2242 is the same as that of adhesives in the second active material portion 2243.

[0129] Optionally, the thickness of the first active material portion 2242 is 0.5%-20% greater than the thickness of the second active material portion 2243 .

[0130] Exemplarily, the thickness of the first active material portion 2242 is 1.5%-12% greater than the thickness of the second active material portion 2243 .

[0131] If one or more innermost bent portions 223 of the negative electrode sheet 220 in the bending area B are the first bent portions 224, the thickness of the first negative electrode active material layer 2202 in the innermost one or more circles of the negative electrode sheet 220 may be greater than the thickness of the second negative electrode active material layer 2203. Taking the two innermost bent portions 223 of the negative electrode sheet 220 in the bending area B as the first bent portions 224 as an example, the thickness of the first negative electrode active material layer 2202 in the innermost two circles of the negative electrode sheet 220 may be greater than the thickness of the second negative electrode active material layer 2203, so that the thickness of the first active material part 2242 of the first bent portion 224 is greater than the thickness of the second active material part 2243, so that the first bent portions 224 in the innermost two circles of the negative electrode sheet 220 are not prone to lithium deposition, which can improve the safety of the battery cell 20 and reduce the production cost.

[0132] In some embodiments, please refer to Fig. 9 , Fig. 9 The partial enlarged view of the portion of the electrode assembly 22 provided in some other embodiments of the present application located in the bending area B, the first bending portion 224 also includes a first conductive portion 228, the first conductive portion 228 is connected between the second active material portion 2243 and the first inner surface 2241a of the first current collecting portion 2241, and the thickness of the first active material portion 2242 is equal to or greater than the total thickness of the second active material portion 2243 and the first conductive portion 228. That is, by providing the first conductive portion 228 between the second active material portion 2243 and the first current collecting portion 2241, the thickness of the first active material portion 2242 is equal to or greater than the total thickness of the second active material portion 2243 and the first conductive portion 228, so that the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243.

[0133] When producing the negative electrode sheet 220 , the thickness of the first active material portion 2242 only needs to be equal to or greater than the total thickness of the second active material portion 2243 and the first conductive portion 228 , so that the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243 .

[0134] Among them, the first conductive part 228 can be a pure conductive coating, for example, the first conductive part 228 is a pure conductive coating composed of an adhesive and a conductive agent; the first conductive part 228 can also be an active coating containing lithium ions, for example, the first conductive part 228 is an active coating containing lithium ions composed of a lithium-rich material, an adhesive and a conductive agent; the first conductive part 228 can also be an inactive coating containing lithium ions, for example, the first conductive part 228 is an inactive coating containing lithium ions composed of an adhesive, a conductive agent and lithium powder coated with lithium carbonate.

[0135] It should be noted that, in other embodiments, the second active material portion 2243 may be connected between the first conductive portion 228 and the first inner surface 2241a of the first current collecting portion 2241, and the thickness of the first active material portion 2242 may be equal to or greater than the total thickness of the second active material portion 2243 and the first conductive portion 228.

[0136] In some embodiments, other methods can also be used to achieve that the active material capacity per unit area on the outside of the first bend portion 224 is greater than the active material capacity per unit area on the inside of the first bend portion 224. For example, the thickness of the first active material portion 2242 is equal to the thickness of the second active material portion 2243, and the gram capacity of the active material in the first active material portion 2242 is greater than the gram capacity of the active material in the second active material portion 2243, thereby achieving that the active material capacity per unit area on the outside of the first bend portion 224 is greater than the active material capacity per unit area on the inside of the first bend portion 224.

[0137] Gram capacity refers to the ratio of the capacitance released by the active material to the mass of the active material.

[0138] In this embodiment, the active material of the first active material unit 2242 is different from the active material of the second active material unit 2243 . For example, the active material of the first active material unit 2242 is silicon, and the active material of the second active material unit 2243 is graphite.

[0139] Optionally, the gram capacity of the active material in the first active material portion 2242 is 0.5%-20% greater than the gram capacity of the active material in the second active material portion 2243 .

[0140] Illustratively, the gram capacity of the active material in the first active material portion 2242 is 1.5%-12% greater than the gram capacity of the active material in the second active material portion 2243 .

[0141] In other embodiments, other methods can also be used to achieve that the active material capacity per unit area on the outer side of the first bend portion 224 is greater than the active material capacity per unit area on the inner side of the first bend portion 224. For example, the thickness of the first active material portion 2242 is equal to the thickness of the second active material portion 2243, the active material in the first active material portion 2242 is the same as the active material in the second active material portion 2243, and the proportion of the active material in the first active material portion 2242 is greater than the proportion of the active material in the second active material portion 2243.

[0142] It should be noted that in the embodiment of the present application, various methods can be used to achieve that the active material capacity per unit area outside the third bent portion 226 is equal to the active material capacity per unit area inside the third bent portion 226. For example, the material of the fifth active material portion 2262 in the third bent portion 226 is the same as the material of the sixth active material portion 2263, and the thickness of the fifth active material portion 2262 is equal to the thickness of the fifth active material portion 2262.

[0143] In some embodiments, please refer to Fig.10 , Fig.10 This is a partial enlarged view of the portion of the electrode assembly 22 provided in some other embodiments of the present application located in the bending area B, wherein at least one bending portion 223 in the positive electrode sheet 221 is a second bending portion 225, and the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225. The bending portion 223 in the negative electrode sheet 220 adjacent to the second bending portion 225 is a fourth bending portion 227, and the active material capacity per unit area outside the fourth bending portion 227 is equal to the active material capacity per unit area inside the fourth bending portion 227.

[0144] When the active material capacity per unit area on the outside of the second bend 225 is greater than the active material capacity per unit area on the inside of the second bend 225, the active material capacity per unit area on the outside of the fourth bend 227 can be equal to the active material capacity per unit area on the inside of the fourth bend 227 to simplify the manufacturing process of the negative electrode sheet 220.

[0145] The second bend portion 225 includes a second current collecting portion 2251, a third active material portion 2252, and a fourth active material portion 2253. The second current collecting portion 2251 has a second inner surface 2251a and a second outer surface 2251b arranged oppositely in the thickness direction thereof, the third active material portion 2252 is arranged on the second outer surface 2251b, and the fourth active material portion 2253 is arranged on the second inner surface 2251a. The fourth bend portion 227 includes a fourth current collecting portion 2271, a seventh active material portion 2272, and an eighth active material portion 2273. The fourth current collecting portion 2271 has a fourth inner surface 2271a and a fourth outer surface 2271b arranged oppositely in the thickness direction thereof, the seventh active material portion 2272 is arranged on the fourth outer surface 2271b, and the eighth active material portion 2273 is arranged on the fourth inner surface 2271a.

[0146] It can be understood that the second current collecting portion 2251 is the positive electrode current collector 2211 (see Figure 7 ) in the bending region B, the third active material portion 2252 is the first positive electrode active material layer 2212 (see Figure 7 ) In the bending region B, the fourth active material portion 2253 is the second positive electrode active material layer 2213 (see Figure 7 ) is a layer in the bending region B. The fourth current collector 2271 is the negative electrode current collector 2201 (see Figure 7 ) is a layer in the bending region B, the seventh active material portion 2272 is the first negative electrode active material layer 2202 (see Figure 7 ) In the bending region B, the eighth active material portion 2273 is the second negative electrode active material layer 2203 (see Figure 7 ) in a layer of the bending zone B.

[0147] The active material capacity per unit area outside the second bend 225 is greater than the active material capacity per unit area inside the second bend 225, that is, the active material capacity per unit area of ​​the third active material portion 2252 (the outer portion of the second bend 225) is greater than the active material capacity per unit area of ​​the fourth active material portion 2253 (the inner portion of the second bend 225). The active material capacity per unit area outside the second bend 225 may be the ratio of the active material capacity of the third active material portion 2252 to the area of ​​the second outer surface 2251b, and the active material capacity per unit area inside the second bend 225 may be the ratio of the active material capacity of the fourth active material portion 2253 to the area of ​​the second inner surface 2251a.

[0148] The active material capacity per unit area outside the fourth bend 227 is equal to the active material capacity per unit area inside the fourth bend 227, that is, the active material capacity per unit area of ​​the seventh active material portion 2272 (the outer portion of the fourth bend 227) is equal to the active material capacity per unit area of ​​the eighth active material portion 2273 (the inner portion of the fourth bend 227). The active material capacity per unit area outside the fourth bend 227 may be the ratio of the active material capacity of the seventh active material portion 2272 to the area of ​​the fourth outer surface 2271b, and the active material capacity per unit area inside the fourth bend 227 may be the ratio of the active material capacity of the eighth active material portion 2273 to the area of ​​the fourth inner surface 2271a.

[0149] In the positive electrode sheet 221, all the bent portions 223 may be the second bent portion 225, or part of the bent portions 223 may be the second bent portion 225. If all the bent portions 223 in the positive electrode sheet 221 are the second bent portion 225, the active material capacity per unit area on the outside of all the bent portions 223 in the positive electrode sheet 221 is greater than the active material capacity per unit area on the inside. If only part of the bent portions 223 in the positive electrode sheet 221 are the second bent portion 225, all the bent portions 223 in the positive electrode sheet 221 except the second bent portion 225 may adopt a structure in which the active material capacity per unit area on the outside is equal to the active material capacity per unit area on the inside. In the negative electrode sheet 220, all the bent portions 223 may be the fourth bent portion 227, or only part of the bent portions 223 may be the fourth bent portion 227.

[0150] In some embodiments, part of the bent portion 223 in the positive electrode sheet 221 is the second bent portion 225 , and all of the bent portion 223 in the negative electrode sheet 220 is the fourth bent portion 227 .

[0151] The positive electrode sheet 221 may have one or more innermost bent portions 223 in the bending zone B as the second bent portion 225 . Exemplarily, the innermost two bent portions 223 in the positive electrode sheet 221 are the second bent portions 225 .

[0152] In some embodiments, all the bent portions 223 in the positive electrode sheet 221 are the second bent portions 225 , and all the bent portions 223 in the negative electrode sheet 220 are the fourth bent portions 227 .

[0153] In this embodiment, in the negative electrode sheet 220 , each negative electrode active material layer may be distributed in the negative electrode collector 2201 with equal thickness along the winding direction A; in the positive electrode sheet 221 , each positive electrode active material layer may be distributed in the positive electrode collector 2211 with equal thickness along the winding direction A.

[0154] In the embodiment of the present application, a plurality of methods can be used to achieve that the active material capacity per unit area on the outer side of the second bent portion 225 is greater than the active material capacity per unit area on the inner side of the second bent portion 225 .

[0155] In some embodiments, please refer to Fig.10 The material of the third active material portion 2252 in the second bent portion 225 is the same as that of the fourth active material portion 2253 , and the thickness of the third active material portion 2252 is greater than the thickness of the fourth active material portion 2253 .

[0156] When the material of the third active substance portion 2252 is the same as that of the fourth active substance portion 2253, the thickness of the third active substance portion 2252 is greater than that of the fourth active substance portion 2253, so that the active substance capacity per unit area of ​​the third active substance portion 2252 is greater than that of the fourth active substance portion 2253, thereby achieving that the active substance capacity per unit area on the outer side of the second bend portion 225 is greater than the active substance capacity per unit area on the inner side of the second bend portion 225.

[0157] It should be noted that the material of the third active material unit 2252 is the same as that of the fourth active material unit 2253, that is, the same active material unit is coated on the second inner surface 2251a and the second outer surface 2251b of the second current collecting unit 2251. It can be understood that the components of the third active material unit 2252 are the same as those of the fourth active material unit 2253, and the proportion of each component of the third active material unit 2252 is the same as that of each component of the fourth active material unit 2253. For example, the third active material unit 2252 and the fourth active material unit 2253 both include active materials, conductive agents, and adhesives. The proportion of active materials in the third active material unit 2252 is the same as that of active materials in the fourth active material unit 2253, the proportion of conductive agents in the third active material unit 2252 is the same as that of conductive agents in the fourth active material unit 2253, and the proportion of adhesives in the third active material unit 2252 is the same as that of adhesives in the fourth active material unit 2253.

[0158] Optionally, the thickness of the third active material portion 2252 is 0.5%-20% greater than the thickness of the fourth active material portion 2253 .

[0159] Illustratively, the thickness of the third active material portion 2252 is 1.5%-12% greater than the thickness of the fourth active material portion 2253 .

[0160] If one or more innermost bent portions 223 of the positive electrode sheet 221 in the bending area B are the second bent portions 225, the thickness of the first positive electrode active material layer 2212 in the innermost one or more circles of the positive electrode sheet 221 may be greater than the thickness of the second positive electrode active material layer 2213. Taking the two innermost bent portions 223 of the positive electrode sheet 221 in the bending area B as the second bent portions 225 as an example, the thickness of the first positive electrode active material layer 2212 in the innermost two circles of the positive electrode sheet 221 may be greater than the thickness of the second positive electrode active material layer 2213, so that the thickness of the third active material part 2252 of the second bent portion 225 is greater than the thickness of the fourth active material part 2253, so that the second bent portions 225 in the innermost two circles of the positive electrode sheet 221 are not prone to lithium deposition, which not only improves the safety of the battery cell 20, but also improves the energy density of the battery cell 20.

[0161] In some embodiments, please refer to Fig.11 , Fig.11The partial enlarged view of the portion of the electrode assembly 22 provided in some other embodiments of the present application located in the bending area B, the second bending portion 225 further includes a second conductive portion 229, the second conductive portion 229 is connected between the fourth active material portion 2253 and the second inner surface 2251a of the second current collecting portion 2251, and the thickness of the third active material portion 2252 is equal to or greater than the total thickness of the fourth active material portion 2253 and the second conductive portion 229. That is, by providing the second conductive portion 229 between the fourth active material portion 2253 and the second current collecting portion 2251, the thickness of the third active material portion 2252 is equal to or greater than the total thickness of the fourth active material portion 2253 and the second conductive portion 229, so as to achieve that the thickness of the third active material portion 2252 is greater than the thickness of the fourth active material portion 2253.

[0162] When producing the positive electrode sheet 221 , the thickness of the third active material portion 2252 only needs to be equal to or greater than the total thickness of the fourth active material portion 2253 and the second conductive portion 229 , so that the thickness of the third active material portion 2252 is greater than the thickness of the fourth active material portion 2253 .

[0163] Among them, the second conductive part 229 can be a pure conductive coating, for example, the second conductive part 229 is a pure conductive coating composed of an adhesive and a conductive agent; the second conductive part 229 can also be an active coating containing lithium ions, for example, the second conductive part 229 is an active coating containing lithium ions composed of a lithium-rich material, an adhesive and a conductive agent; the second conductive part 229 can also be an inactive coating containing lithium ions, for example, the second conductive part 229 is an inactive coating containing lithium ions composed of an adhesive, a conductive agent and lithium powder coated with lithium carbonate.

[0164] It should be noted that, in other embodiments, the fourth active material portion 2253 may be connected between the second conductive portion 229 and the second inner surface 2251a of the second current collecting portion 2251, and the thickness of the third active material portion 2252 may be equal to or greater than the total thickness of the fourth active material portion 2253 and the second conductive portion 229.

[0165] In some embodiments, other methods can also be used to achieve that the active material capacity per unit area on the outside of the second bend portion 225 is greater than the active material capacity per unit area on the inside of the second bend portion 225. For example, the thickness of the third active material portion 2252 is equal to the thickness of the fourth active material portion 2253, and the gram capacity of the active material in the third active material portion 2252 is greater than the gram capacity of the active material in the fourth active material portion 2253, thereby achieving that the active material capacity per unit area on the outside of the second bend portion 225 is greater than the active material capacity per unit area on the inside of the second bend portion 225.

[0166] In this embodiment, the active material of the third active material unit 2252 may be different from the active material of the fourth active material unit 2253 . For example, the active material in the third active material unit 2252 is ternary lithium, and the active material in the fourth active material unit 2253 is lithium iron phosphate.

[0167] Optionally, the gram capacity of the active material in the third active material portion 2252 is 0.5%-20% greater than the gram capacity of the active material in the fourth active material portion 2253 .

[0168] Illustratively, the gram capacity of the active material in the third active material portion 2252 is 1.5%-12% greater than the gram capacity of the active material in the fourth active material portion 2253 .

[0169] In other embodiments, other methods can be used to achieve that the active material capacity per unit area on the outer side of the second bend portion 225 is greater than the active material capacity per unit area on the inner side of the second bend portion 225. For example, the thickness of the third active material portion 2252 is equal to the thickness of the fourth active material portion 2253, the active material in the third active material portion 2252 is the same as the active material in the fourth active material portion 2253, and the proportion of the active material in the third active material portion 2252 is greater than the proportion of the active material in the fourth active material portion 2253.

[0170] It should be noted that in the embodiment of the present application, various methods can be used to achieve that the active material capacity per unit area on the outside of the fourth bent portion 227 is equal to the active material capacity per unit area on the inside of the fourth bent portion 227. For example, the material of the seventh active material portion 2272 in the fourth bent portion 227 is the same as the material of the eighth active material portion 2273, and the thickness of the seventh active material portion 2272 is equal to the thickness of the eighth active material portion 2273.

[0171] In some embodiments, please refer to Fig.12 , Fig.12 A partial enlarged view of the portion of the electrode assembly 22 located in the bending zone B provided in some other embodiments of the present application, at least one bending portion 223 in the negative electrode plate 220 is a first bending portion 224, and the active material capacity per unit area on the outer side of the first bending portion 224 is greater than the active material capacity per unit area on the inner side of the first bending portion 224; at least one bending portion 223 in the positive electrode plate 221 is a second bending portion 225, and the active material capacity per unit area on the outer side of the second bending portion 225 is greater than the active material capacity per unit area on the inner side of the second bending portion 225.

[0172] In this embodiment, the active material capacity per unit area on the outside of the first bend portion 224 can be greater than the active material capacity per unit area on the inside of the first bend portion 224 by making the thickness of the first active material portion 2242 of the first bend portion 224 greater than the thickness of the second active material portion 2243, or by making the gram capacity of the active material of the first active material portion 2242 of the first bend portion 224 greater than the gram capacity of the active material of the second active material portion 2243. Similarly, the active material capacity per unit area on the outside of the second bend portion 225 can be greater than the active material capacity per unit area on the inside of the second bend portion 225 by making the thickness of the third active material portion 2252 of the second bend portion 225 greater than the thickness of the fourth active material portion 2253, or by making the gram capacity of the active material of the third active material portion 2252 of the second bend portion 225 greater than the gram capacity of the active material of the fourth active material portion 2253.

[0173] For example, in Fig.12 In the figure, the material of the first active material portion 2242 of the first bending portion 224 is the same as the material of the second active material portion 2243, and the thickness of the first active material portion 2242 of the first bending portion 224 is greater than the thickness of the second active material portion 2243; the material of the third active material portion 2252 of the second bending portion 225 is the same as the material of the fourth active material portion 2253, and the thickness of the third active material portion 2252 of the second bending portion 225 is greater than the thickness of the fourth active material portion 2253.

[0174] In some embodiments, a second bending portion 225 adjacent to the first bending portion 224 is arranged on the outer side of the first bending portion 224 .

[0175] When the active material capacity per unit area on the inner side of the first bend portion 224 and the active material capacity per unit area on the outer side of the second bend portion 225 meet the design requirements, the active material capacity per unit area on the outer side of the first bend portion 224 is greater than the active material capacity per unit area on the inner side of the first bend portion 224, and the active material capacity per unit area on the outer side of the second bend portion 225 is greater than the active material capacity per unit area on the inner side of the second bend portion 225, which can increase the CB value of the outer part of the first bend portion 224, thereby reducing the occurrence of lithium plating.

[0176] In this embodiment, in the negative electrode sheet 220, all or part of the bent portions 223 may be the first bent portion 224. In the positive electrode sheet 221, all or part of the bent portions 223 may be the second bent portion 225.

[0177] In some embodiments, a portion of the bent portion 223 in the negative electrode sheet 220 is a first bent portion 224 , and a portion of the bent portion 223 in the positive electrode sheet 221 is a second bent portion 225 .

[0178] Among them, the negative electrode sheet 220 may have one or more innermost bent portions 223 of the bending zone B as the first bent portion 224. Exemplarily, the two innermost bent portions 223 of the negative electrode sheet 220 are the first bent portions 224. The positive electrode sheet 221 may have one or more innermost bent portions 223 of the bending zone B as the second bent portion 225. Exemplarily, the two innermost bent portions 223 of the positive electrode sheet 221 are the second bent portions 225.

[0179] In some embodiments, all the bent portions 223 in the negative electrode sheet 220 are first bent portions 224 , and all the bent portions 223 in the positive electrode sheet 221 are second bent portions 225 .

[0180] In this embodiment, in the negative electrode sheet 220, each negative electrode active material layer may be distributed in the negative electrode current collector 2201 with equal thickness along the winding direction A (see Figure 7 ); In the positive electrode sheet 221, each positive electrode active material layer may be distributed in equal thickness on the positive electrode current collector 2211 along the winding direction A (see Figure 7 ).

[0181] All the bent portions 223 in the negative electrode sheet 220 are the first bent portions 224. When the active material capacity per unit area on the inner side of the first bent portion 224 meets the design requirements, since the active material capacity per unit area on the outer side of the first bent portion 224 is greater than the active material capacity per unit area on the inner side of the first bent portion 224, it is equivalent to increasing the active material capacity per unit area on the outer side of the first bent portion 224, so that the CB values ​​of the outer parts of all the bent portions 223 in the negative electrode sheet 220 are increased, and the part of the negative electrode sheet 220 located in the bending zone B is not prone to lithium deposition. All the bent portions 223 in the positive electrode sheet 221 are second bent portions 225. When the active material capacity per unit area outside the second bent portion 225 meets the design requirements, since the active material capacity per unit area outside the second bent portion 225 is greater than the active material capacity per unit area inside the second bent portion 225, it is equivalent to reducing the active material capacity per unit area inside the second bent portion 225, so that the CB values ​​of the outer parts of multiple bent portions 223 in the negative electrode sheet 220 are all increased, and the part of the negative electrode sheet 220 located in the bending area B is not prone to lithium deposition.

[0182] Please refer to Fig.13 , Fig.13 A flowchart of a method for manufacturing an electrode assembly 22 provided in some embodiments of the present application, the method for manufacturing the electrode assembly 22 includes:

[0183] S100: providing a negative electrode sheet 220 and a positive electrode sheet 221;

[0184] S200: Winding the negative electrode sheet 220 and the positive electrode sheet 221 along a winding direction A to form a winding structure;

[0185] The winding structure includes a bending area B, and the negative electrode sheet 220 and the positive electrode sheet 221 both include a plurality of bending portions 223 located in the bending area B. At least one bending portion 223 in the negative electrode sheet 220 is a first bending portion 224, and the active material capacity per unit area outside the first bending portion 224 is greater than the active material capacity per unit area inside the first bending portion 224; and / or, at least one bending portion 223 in the positive electrode sheet 221 is a second bending portion 225, and the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225.

[0186] In some embodiments, a separation film 222 is further provided for isolating the positive electrode sheet 221 and the negative electrode sheet 220 , and the first electrode sheet, the separation film 222 and the second electrode sheet are wound along a winding direction A to form a winding structure.

[0187] It should be noted that the relevant structure of the electrode assembly 22 manufactured by the manufacturing method of the electrode assembly 22 can refer to the electrode assembly 22 provided in the above embodiments.

[0188] Please refer to Fig.14 , Fig.14 A schematic block diagram of a manufacturing device 2000 for an electrode assembly 22 provided in some embodiments of the present application, wherein the manufacturing device 2000 includes a providing device 2100 and an assembling device 2200, wherein the providing device 2100 is used to provide a negative electrode sheet 220 and a positive electrode sheet 221, and the assembling device 2200 is used to wind the negative electrode sheet 220 and the positive electrode sheet 221 along a winding direction A to form a winding structure.

[0189] The winding structure includes a bending area B, and the negative electrode sheet 220 and the positive electrode sheet 221 both include a plurality of bending portions 223 located in the bending area B. At least one bending portion 223 in the negative electrode sheet 220 is a first bending portion 224, and the active material capacity per unit area outside the first bending portion 224 is greater than the active material capacity per unit area inside the first bending portion 224; and / or, at least one bending portion 223 in the positive electrode sheet 221 is a second bending portion 225, and the active material capacity per unit area outside the second bending portion 225 is greater than the active material capacity per unit area inside the second bending portion 225.

[0190] In some embodiments, the providing device 2100 is further used to provide a separator 222 for isolating the positive electrode sheet 221 from the negative electrode sheet 220. The assembling device 2200 is used to wind the first electrode sheet, the separator 222 and the second electrode sheet along a winding direction A to form a winding structure.

[0191] The relevant structure of the electrode assembly 22 manufactured by the above-mentioned manufacturing equipment 2000 can refer to the electrode assembly 22 provided in the above-mentioned embodiments.

[0192] In addition, the present embodiment also provides a method for testing the CB value of the electrode assembly 22. The CB value test steps are as follows:

[0193] Step 1): Test the average discharge capacity of the single-sided active material layer of the positive electrode. Take the positive electrode sheet 221 of each of the above embodiments, and use a punching die to obtain a small disc containing a single-sided active material layer of the positive electrode. Use a metal lithium sheet as the counter electrode, a Celgard membrane as the isolation membrane, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved with LiPF6 (1 mol / L) as the electrolyte, and assemble 6 identical CR2430 button batteries in an argon-protected glove box. ① After the battery is assembled, let it stand for 12 hours, ② perform constant current charging at a charging current of 0.1C until the voltage reaches the upper cut-off voltage x1V, then maintain the voltage x1V for constant voltage charging until the current is 50uA, ③ let it stand for 5 minutes, ④ finally perform constant current discharge at a discharge current of 0.1C until the voltage reaches the lower cut-off voltage y1V, ⑤ let it stand for 5 minutes, repeat steps 2-5, and record the discharge capacity of the second cycle. The average value of the discharge capacity of the 6 button batteries is the average discharge capacity of the single-sided active material layer of the positive electrode. For example, when the positive active material is lithium iron phosphate (LFP), the upper cut-off voltage x1V = 3.75V, and the lower cut-off voltage y1V = 2V. When the positive active material is lithium nickel cobalt manganese oxide (NCM), the upper cut-off voltage x1V = 4.25V, and the lower cut-off voltage y1V = 2.8V.

[0194] Step 2): Test the average charging capacity of the single-sided active material layer of the negative electrode. Take the negative electrode plate 220 of each of the above embodiments, and use a punching mold to obtain a small disc with the same area as the small positive electrode disc in the above step 1) and containing a single-sided negative electrode film layer. Use a metal lithium sheet as the counter electrode, a Celgard membrane as the isolation membrane, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved with LiPF6 (1 mol / L) as the electrolyte, and assemble 6 CR2430 button batteries in an argon-protected glove box. ① After the battery is assembled, let it stand for 12 hours, ② discharge it at a constant current of 0.05C until the voltage reaches the lower cut-off voltage y2mV, ③ then discharge it at a constant current of 50uA until the voltage reaches the lower cut-off voltage y2mV, ④ let it stand for 5min, ⑤ then discharge it at a constant current of 10uA until the lower cut-off voltage y2mV is reached, ⑥ let it stand for 5 minutes, ⑦ finally charge it at a constant current of 0.1C until the final voltage reaches the upper cut-off voltage x2V, ⑧ let it stand for 5 minutes, repeat steps 2-8, and record the charging capacity of the second cycle. The average value of the charging capacity of the 6 button batteries is the average charging capacity of the single-sided film layer of the negative electrode. For example, when the negative electrode active material is graphite, the upper cut-off voltage x2V = 2V, and the lower cut-off voltage y2V = 5mV. When the negative electrode active material is silicon, the upper cut-off voltage x2V = 2V, and the lower cut-off voltage y2V = 5mV.

[0195] Step 3): Calculate the CB value according to CB value = average charge capacity (mAh) of the above-mentioned single-sided active material layer of the negative electrode / average discharge capacity (mAh) of the above-mentioned single-sided active material layer of the positive electrode.

[0196] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0197] The above embodiments are only used to illustrate the technical solution of the present application and are not used to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An electrode assembly, characterized in that: Applicable to a cylindrical battery cell, comprising a negative electrode sheet and a positive electrode sheet, wherein the negative electrode sheet and the positive electrode sheet are wound along a winding direction to form a winding structure, wherein the winding structure comprises a bending area; The negative electrode sheet and the positive electrode sheet both include a plurality of bending portions located in the bending area; Wherein, at least one bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion; The bent portion of the negative electrode sheet adjacent to the second bent portion is a fourth bent portion; The active material capacity per unit area outside the fourth bent portion is equal to the active material capacity per unit area inside the fourth bent portion; The second bending portion includes a second current collecting portion, a third active material portion and a fourth active material portion; The second current collecting portion has a second inner surface and a second outer surface arranged opposite to each other in the thickness direction thereof, the third active material portion is arranged on the second outer surface, and the fourth active material portion is arranged on the second inner surface; The material of the fourth active material portion is the same as the material of the third active material portion; The thickness of the third active material portion is greater than the thickness of the fourth active material portion.

2. The electrode assembly according to claim 1, characterized in that: The second bending portion further includes a second conductive portion, the second conductive portion is connected between the fourth active material portion and the second inner surface, and the thickness of the third active material portion is equal to or greater than the total thickness of the fourth active material portion and the second conductive portion.

3. The electrode assembly according to claim 1, characterized in that: The thickness of the third active material portion is equal to the thickness of the fourth active material portion; The gram capacity of the active material in the third active material portion is greater than the gram capacity of the active material in the fourth active material portion.

4. The electrode assembly according to any one of claims 1 to 3, characterized in that: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on both sides of the negative electrode current collector in the thickness direction; Each negative electrode active material layer is distributed on the negative electrode current collector with equal thickness along the winding direction.

5. The electrode assembly according to any one of claims 1 to 3, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on both sides of the positive electrode current collector in the thickness direction; Each positive electrode active material layer is distributed on the positive electrode current collector with equal thickness along the winding direction.

6. The electrode assembly according to any one of claims 1 to 3, characterized in that: All the bent portions in the positive electrode sheet are the second bent portions.

7. A battery cell, characterized in that: comprising a housing and an electrode assembly according to any one of claims 1 to 6; The electrode assembly is accommodated in the housing, and the battery cell is a cylindrical battery cell.

8. A battery, characterized in that: comprising a box body and a battery cell according to claim 7; The battery cells are accommodated in the box.

9. An electrical device, characterized in that: Comprising the battery as claimed in claim 8.

10. A method for manufacturing an electrode assembly, characterized in that: Applicable to cylindrical battery cells, including: Providing positive electrode sheets and negative electrode sheets; Winding the negative electrode sheet and the positive electrode sheet along a winding direction to form a winding structure; Wherein, the winding structure includes a bending area, and the negative electrode sheet and the positive electrode sheet both include a plurality of bending portions located in the bending area; At least one bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion; The bent portion of the negative electrode sheet adjacent to the second bent portion is a fourth bent portion; The active material capacity per unit area outside the fourth bent portion is equal to the active material capacity per unit area inside the fourth bent portion; The second bending portion includes a second current collecting portion, a third active material portion and a fourth active material portion; The second current collecting portion has a second inner surface and a second outer surface arranged opposite to each other in the thickness direction thereof, the third active material portion is arranged on the second outer surface, and the fourth active material portion is arranged on the second inner surface; The material of the fourth active material portion is the same as the material of the third active material portion; The thickness of the third active material portion is greater than the thickness of the fourth active material portion.

11. A manufacturing device for an electrode assembly, characterized in that: Applicable to cylindrical battery cells, including: Providing a device for providing a positive electrode sheet and a negative electrode sheet; and An assembling device, used for winding the negative electrode sheet and the positive electrode sheet along a winding direction to form a winding structure; Wherein, the winding structure includes a bending area, and the negative electrode sheet and the positive electrode sheet both include a plurality of bending portions located in the bending area; At least one bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion; The bent portion of the negative electrode sheet adjacent to the second bent portion is a fourth bent portion; The active material capacity per unit area outside the fourth bent portion is equal to the active material capacity per unit area inside the fourth bent portion; The second bending portion includes a second current collecting portion, a third active material portion and a fourth active material portion; The second current collecting portion has a second inner surface and a second outer surface arranged opposite to each other in the thickness direction thereof, the third active material portion is arranged on the second outer surface, and the fourth active material portion is arranged on the second inner surface; The material of the fourth active material portion is the same as the material of the third active material portion; The thickness of the third active material portion is greater than the thickness of the fourth active material portion.

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