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

Abstract

The embodiment of the application provides an electrode assembly, a battery monomer, a battery, and a manufacturing device and method of the electrode assembly, and belongs to the technical field of batteries. The electrode assembly comprises a negative electrode sheet and a positive electrode sheet. The negative electrode sheet and the positive electrode sheet are wound along a winding direction and form a winding structure. The winding structure comprises a bending area. The negative electrode sheet and the positive electrode sheet each comprise a plurality of bending parts in the bending area. At least one bending part in the negative electrode sheet is a first bending part. The unit area active material capacity outside the first bending part is greater than the unit area active material capacity inside the first bending part. And / or, at least one bending part in the positive electrode sheet is a second bending part. The unit area active material capacity outside the second bending part is greater than the unit area active material capacity inside the second bending part. In the electrode assembly with the structure, the active material arrangement of the electrode sheet in at least part of the area of the bending area is more reasonable, and the economy is better.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to an apparatus and method for manufacturing an electrode assembly, a battery cell, a battery, and an electrode assembly. Background Technology

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

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

[0004] For typical electrode assemblies, the arrangement of active materials in the electrode sheets is unreasonable, resulting in poor economic efficiency. Summary of the Invention

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

[0006] In a first aspect, embodiments of this application provide an electrode assembly, including a negative electrode and a positive electrode, wherein the negative electrode and the positive electrode are wound along a winding direction to form a winding structure, the winding structure including a bending region; both the negative electrode and the positive electrode include a plurality of bending portions located in the bending region; wherein at least one bending portion of the negative electrode is a first bending portion, 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, at least one bending portion of the positive electrode is a second bending portion, 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.

[0007] In the above scheme, the active material capacity per unit area on the outer side of the first bend of the negative electrode is greater than that on the inner side of the first bend, reducing the likelihood of an excess of active material on the inner side of the first bend and an insufficient amount on the outer side. This results in a more rational arrangement of active material in at least a portion of the negative electrode (the area where the first bend is located). Similarly, the active material capacity per unit area on the outer side of the second bend of the positive electrode is greater than that on the inner side of the second bend, reducing the likelihood of an insufficient amount of active material on the outer side of the second bend and an excess on the inner side. This again results in a more rational arrangement of active material in at least a portion of the positive electrode (the area where the second bend is located). This electrode assembly structure exhibits a more rational arrangement of active material in at least a portion of the electrode, leading to better economic efficiency.

[0008] In some embodiments, at least one bent portion in the negative electrode sheet is the first bent portion, at least one bent portion in the positive electrode sheet is the second bent portion, and a second bent portion adjacent to the first bent portion is arranged on the outside of the first bent portion.

[0009] In the above scheme, a second bend is arranged on the outer side of the first bend. When the active material capacity per unit area inside the first bend and the active material capacity per unit area outside the second bend meet the design requirements, the active material capacity per unit area outside the first bend is greater than that inside the first bend, and the active material capacity per unit area outside the second bend is greater than that inside the second bend. This can increase the CB value of the outer part of the first bend, 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 outside the third bend is equal to the active material capacity per unit area inside 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 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, the active material capacity per unit area on the outer side of the third bending portion can be equal to the active material capacity per unit area on the inner side 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 outside the fourth bend is equal to the active material capacity per unit area inside 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 current collection portion, a first active material portion, and a second active material portion; the first current collection 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 disposed on the first outer surface, and the second active material portion is disposed on the first inner surface.

[0015] In some embodiments, the material of the second active material portion is the same as the material of the first active material portion; 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 materials of the first active material part and the second active material part are the same, the thickness of the first active material part is greater than the thickness of the second active material part, which makes the active material capacity per unit area of ​​the first active material part greater than the active material capacity per unit area of ​​the second active material part, thereby realizing that 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.

[0017] In some embodiments, the first bending portion further includes a first conductive portion, which 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 providing a first conductive part between the second active material part and the first current collector 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 that the thickness of the first active material part is 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; the specific capacity of the active material in the first active material portion is greater than the specific capacity of the active material in the second active material portion.

[0020] In the above scheme, when the thickness of the first active material part is equal to the thickness of the second active material part, the specific capacity of the active material in the first active material part is greater than that in the second active material part. This makes the specific capacity of the active material per unit area of ​​the first active material part greater than that of the second active material part, thereby achieving a specific capacity of the active material per unit area on the outer side of the first bending part greater than that on the inner side of the first bending part.

[0021] In some embodiments, the second bending portion includes a second current collection portion, a third active material portion, and a fourth active material portion; the second current collection 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 disposed on the second outer surface, and the fourth active material portion is disposed on the second inner surface.

[0022] In some embodiments, 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.

[0023] In the above scheme, when the materials of the third active material part and the fourth active material part are the same, the thickness of the third active material part is greater than the thickness of the fourth active material part, which makes the active material capacity per unit area of ​​the third active material part greater than the active material capacity per unit area of ​​the fourth active material part, thereby realizing that the active material capacity per unit area on the outer side of the second bend is greater than the active material capacity per unit area on the inner side of the second bend.

[0024] In some embodiments, the second bending portion further includes a second conductive portion, which 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 providing a second conductive part between the fourth active material part and the second current collector 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 that the thickness of the third active material part is 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; the specific capacity of the active material in the third active material portion is greater than the specific capacity of the active material in the fourth active material portion.

[0027] In the above scheme, when the thickness of the third active material part is equal to the thickness of the fourth active material part, the specific capacity of the active material in the third active material part is greater than that in the fourth active material part. This makes the specific capacity of the active material per unit area of ​​the third active material part greater than that of the fourth active material part, thereby achieving a specific capacity of the active material per unit area on the outer side of the second bend greater than that on the inner side of the second bend.

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

[0029] In the above scheme, each negative electrode active material layer is distributed with equal thickness along the winding direction in the positive electrode current collector, which can simplify the manufacturing process of the negative electrode sheet and help reduce production costs.

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

[0031] In the above scheme, each positive electrode active material layer is distributed with equal thickness along the winding direction in the positive electrode current collector, which can simplify the manufacturing process of the positive electrode sheet and help reduce production costs.

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

[0033] In the above scheme, all bends in the negative electrode sheet are first bends, meaning that the unit active material capacity on the outer side of all bends in the negative electrode sheet is greater than that on the inner side. This makes the arrangement of active material in the bend areas of the negative electrode sheet more reasonable. When the unit active material capacity on the inner side of the first bend meets the design requirements, since the unit active material capacity on the outer side of the first bend is greater than that on the inner side, it is equivalent to increasing the unit active material capacity on the outer side of the first bend. This increases the CB value of the outer portion of all bends in the negative electrode sheet, making lithium plating less likely to occur in the bend areas of the negative electrode sheet.

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

[0035] In the above scheme, all bends in the positive electrode are second bends, meaning that the unit active material capacity on the outer side of all bends in the positive electrode is greater than that on the inner side. This makes the arrangement of active material in the bend areas of the positive electrode more reasonable. When the unit active material capacity on the outer side of the second bend meets the design requirements, because the unit active material capacity on the outer side of the second bend is greater than that on the inner side, it is equivalent to reducing the unit active material capacity on the inner side of the second bend. This increases the CB value of the outer parts of multiple bends in the negative electrode, making lithium plating less likely to occur in the bend areas of the negative electrode.

[0036] Secondly, embodiments of this application provide a battery cell, including a housing and an electrode assembly provided in any of the embodiments of the first aspect above; the electrode assembly is housed within the housing.

[0037] Thirdly, embodiments of this application provide a battery, including a housing and a battery cell provided in any of the embodiments of the second aspect above; the battery cell is housed within the housing.

[0038] Fourthly, embodiments of this application provide an electrical device, including the battery provided in any one of the embodiments of the second aspect.

[0039] Fifthly, embodiments of this application provide a method for manufacturing an electrode assembly, comprising:

[0040] A positive electrode and a negative electrode are provided; the negative electrode and the positive electrode are wound along a winding direction to form a winding structure; wherein the winding structure includes a bending region, and both the negative electrode and the positive electrode include a plurality of bending portions located in the bending region; at least one bending portion of the negative electrode is a first bending portion, 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, at least one bending portion of the positive electrode is a second bending portion, 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.

[0041] In a sixth aspect, embodiments of this application also provide an electrode assembly manufacturing apparatus, comprising: a providing device for providing a positive electrode sheet and a negative electrode sheet; an assembly 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 region, and both the negative electrode sheet and the positive electrode sheet include a plurality of bending portions located in the bending region; at least one bending portion of the negative electrode sheet is a first bending portion, wherein 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, at least one bending portion of the positive electrode sheet is a second bending portion, wherein 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. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0043] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0044] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0045] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0046] Figure 4 for Figure 3 The exploded view of the battery cell shown;

[0047] Figure 5 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0048] Figure 6 This application provides schematic diagrams of the structure of electrode assemblies in some of its embodiments.

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

[0050] Figure 8 A partial enlarged view of the portion of the electrode assembly located in the bending region provided in some embodiments of this application;

[0051] Figure 9A partial enlarged view of the portion of the electrode assembly located in the bending region provided in some embodiments of this application;

[0052] Figure 10 A partial enlarged view of the portion of the electrode assembly located in the bending region provided in some embodiments of this application;

[0053] Figure 11 A partially enlarged view of the portion of the electrode assembly located in the bending region provided for other embodiments of this application;

[0054] Figure 12 A partial enlarged view of the portion of the electrode assembly located in the bending region provided in some embodiments of this application;

[0055] Figure 13 A flowchart illustrating a method for manufacturing an electrode assembly provided in some embodiments of this application;

[0056] Figure 14 A schematic block diagram of an apparatus for manufacturing electrode assemblies provided in some embodiments of this application.

[0057] The accompanying drawings are not drawn to scale.

[0058] Marking Explanation: 10-Box; 11-First Part; 12-Second Part; 13-Accommodation Space; 20-Battery Cell; 21-Outer Shell; 211-Shell; 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 Electrode Active Material Layer; 2203-Second Negative Electrode Active Material Layer 221-Positive electrode layer; 2211-Positive current collector; 2212-First positive electrode active material layer; 2213-Second positive electrode active material layer; 222-Separating membrane; 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 current collection section; 2251a-Second inner surface; 2251b-Second outer surface; 2252-Third active material section; 2253-Fourth active material section; 226-Third bending section; 2261-Third current collection section; 2261a-Third inner surface; 2261b-Third outer surface; 2262-Fifth active material section; 2263-Sixth active material section; 227-Fourth bending section; 2271-Fourth current collection section; 2271a-Fourth Inner surface; 2271b - Fourth outer surface; 2272 - Seventh active material section; 2273 - Eighth active material section; 228 - First conductive section; 229 - Second conductive section; 30 - Battery module; 31 - Busbar component; 100 - Battery; 200 - Controller; 300 - Motor; 1000 - Vehicle; 2000 - Manufacturing equipment; 2100 - Supply device; 2200 - Assembly device; A - Winding direction; B - Bending area; C - Straight area. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort 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 meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

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

[0062] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0063] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

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

[0065] In this application, "multiple" means two or more (including two).

[0066] In this application, the battery cell 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 this application are not limited to these. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited to these. Battery cells are generally divided into three types according to their packaging method: cylindrical battery cells, square battery cells, and pouch battery cells, and the embodiments of this application are not limited to these.

[0067] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0068] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, and the uncoated positive current collector protrudes beyond the coated one, serving as the positive electrode tab. Taking a lithium-ion battery as an example, the positive current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector, and the uncoated negative current collector protrudes beyond the coated one, serving as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative electrode active material can be carbon or silicon, etc. To ensure that a large current can pass through without melting, there are multiple positive electrode tabs stacked together, and there are multiple negative electrode tabs stacked together. The separator can be made of PP (polypropylene) or PE (polyethylene), etc. In addition, the electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to these.

[0069] For typical electrode assemblies, the arrangement of active materials in the electrode sheets is unreasonable, resulting in poor economic efficiency.

[0070] The inventors discovered that in an electrode assembly, the thickness of the inner active material layer of the negative electrode is the same as the thickness of the outer active material layer, and the material of the inner active material layer is the same as that of the outer active material layer; similarly, the thickness of the inner active material layer of the positive electrode is the same as that of the outer active material layer, and the material of the inner active material layer is the same as that of the outer active material layer. Within the bending region of the electrode assembly, the radius of the inner active material layer of the negative electrode is larger than the radius of the outer active material layer of the positive electrode located inside the negative electrode, while the radius of the outer active material layer of the negative electrode is smaller than the radius of the inner active material layer of the positive electrode located outside the negative electrode. This results in an excess of inner active material and a deficiency of outer active material in the bending portion of the negative electrode within the bending region. Similarly, it may also result in a deficiency of outer active material and an excess of inner active material in the bending portion of the positive electrode within the bending region. This electrode assembly structure suffers from an unreasonable arrangement of active materials within the electrodes, leading to poor economic efficiency.

[0071] In view of this, embodiments of this application provide a technical solution whereby the negative electrode includes a first bent portion located within a bending region, wherein 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 / or, the positive electrode includes a second bent portion located within a bending region, wherein 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. This structure makes the active material arrangement in at least a portion of the bending region of the electrode more rational and has better economic efficiency.

[0072] The technical solutions described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0073] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0074] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0075] Please refer to Figure 1 , Figure 1 The diagram below illustrates the structure of a vehicle 1000 according to some embodiments of this application. A battery 100 is disposed inside the vehicle 1000, and the battery 100 may be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000.

[0076] The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for the power needs of the vehicle 1000 during startup, navigation and driving.

[0077] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the 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 This is an exploded view of a battery 100 provided in some embodiments of this application. The battery 100 includes a housing 10 and battery cells 20. Figure 2 (Not shown), the battery cell 20 is housed inside the casing 10.

[0079] The housing 10 is used to accommodate the battery cell 20, and the housing 10 can have various structures. In some embodiments, the housing 10 may include a first part 11 and a second part 12, which overlap each other, and the first part 11 and the second part 12 together define a receiving space 13 for accommodating the battery cell 20. The second part 12 may be a hollow structure with one open end, and the first part 11 may be a plate-like structure, with the first part 11 covering the open side of the second part 12 to form a housing 10 with the receiving space 13; alternatively, the first part 11 and the second part 12 may both be hollow structures with one open side, with the open side of the first part 11 covering the open side of the second part 12 to form a housing 10 with the receiving space 13. Of course, the first part 11 and the second part 12 can have various shapes, such as cylinders, cuboids, etc.

[0080] To improve the sealing performance after the first part 11 and the second part 12 are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first part 11 and the second part 12.

[0081] Assuming that the first part 11 covers the top of the second part 12, the first part 11 can also be called the upper cover, and the second part 12 can also be called the lower box.

[0082] In battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, in parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 20 is housed in the housing 10. Alternatively, multiple battery cells 20 can first be connected in series, in parallel, or in a mixed manner to form a battery module 30, and then multiple battery modules 30 can be connected in series, in parallel, or in a mixed manner to form a whole assembly, which is then housed in the housing 10.

[0083] In some embodiments, please refer to Figure 3 , Figure 3 for Figure 2 The diagram shows the structure of the battery module 30. Multiple battery cells 20 are connected in series, parallel, or a combination thereof to form the battery module 30. These battery modules 30 are then connected in series, parallel, or a combination thereof to form a single unit, which is housed within the casing 10.

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

[0085] Please refer to Figure 4 , Figure 4 for Figure 3 The image shows an exploded view of the battery cell 20. The battery cell 20 provided in this embodiment includes a housing 21 and an electrode assembly 22, with the electrode assembly 22 housed within the housing 21.

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

[0087] In some embodiments, the housing 21 may include a housing 211 and a cover 212. The housing 211 is a hollow structure with an opening on one side, and the cover 212 covers the opening of the housing 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 can be placed into the housing 211 first, and the electrolyte can be filled into the housing 211. Then, the cover 212 can be placed over the opening of the housing 211.

[0089] The housing 211 can have various shapes, such as a cylinder or a cuboid. The shape of the housing 211 can be determined based on the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, a cylindrical housing 211 can be used; if the electrode assembly 22 is a cuboid structure, a cuboid housing 211 can be used. Of course, the cover 212 can also have various structures, such as a plate-like structure or a hollow structure with one open end. For example, in… Figure 4 In the case, the shell 211 has a cuboid structure, and the cover 212 has a plate-like structure, with the cover 212 covering 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, all of which are mounted on the cover 212. The positive electrode terminal 214 and the negative electrode terminal 215 are both used for electrical connection with 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 internal pressure of the battery cell 20 when the internal pressure or temperature reaches a predetermined value.

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

[0092] Of course, in some embodiments, the outer casing 21 can also be other structures. For example, the outer casing 21 includes a shell 211 and two covers 212. The shell 211 is a hollow structure with openings on opposite sides. One cover 212 is fitted onto one opening of the shell 211 to form a sealed connection, thereby forming 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 can be mounted on the same cover 212 or on different covers 212. A pressure relief mechanism 216 can be mounted on one cover 212 or on both covers 212.

[0093] It should be noted that in the battery cell 20, the electrode assembly 22 housed within the casing 21 can be one or more. For example, in... Figure 4 In the middle, there are two electrode components 22.

[0094] The specific structure of electrode assembly 22 will now be described in detail with reference to the accompanying drawings.

[0095] Please refer to Figure 5 , Figure 5The diagram below shows the structure of an electrode assembly 22 provided in some embodiments of this application. The electrode assembly 22 includes a negative electrode 220 and a positive electrode 221. The negative electrode 220 and the positive electrode 221 are wound along the winding direction A to form a winding structure. The winding structure includes a bending region B. Both the negative electrode 220 and the positive electrode 221 include multiple bending portions 223 located in the bending region B.

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

[0097] If the active material capacity per unit area on the outer side of the first bend 224 of the negative electrode 220 is greater than that on the inner side, the situation of excess active material on the inner side of the first bend 224 and insufficient active material on the outer side is less likely to occur, resulting in a more rational arrangement of active material in at least a portion of the negative electrode 220 (the area where the first bend 224 is located). Similarly, if the active material capacity per unit area on the outer side of the second bend 225 of the positive electrode 221 is greater than that on the inner side, the situation of insufficient active material on the outer side of the second bend 225 and excess active material on the inner side is less likely to occur, resulting in a more rational arrangement of active material in at least a portion of the positive electrode 221 (the area where the second bend 225 is located). This structure of the electrode assembly 22 results in a more rational arrangement of active material in at least a portion of the electrode, leading to better economic efficiency.

[0098] Furthermore, when the active material capacity per unit area inside the first bend 224 meets the design requirements, that is, when the active material capacity per unit area inside the first bend 224 reaches the first preset value, lithium plating is less likely to occur in the inner part of the first bend 224. Since the active material capacity per unit area outside the first bend 224 is greater than that inside the first bend 224, it is equivalent to increasing the active material capacity per unit area outside the first bend 224 relative to the first preset value, which can increase the CB value of the outer part of the first bend 224, thereby making lithium plating less likely to occur in the outer part of the first bend 224. Similarly, when the active material capacity per unit area on the outer side of the second bend 225 meets the design requirements, that is, when the active material capacity per unit area on the outer side of the second bend 225 reaches the second preset value, lithium plating is less likely to occur on the inner side of the bend 223 of the negative electrode 220 located on the outer side of the second bend 225. Since the active material capacity per unit area on the outer side of the second bend 225 is greater than the active material capacity per unit area on the inner side of the second bend 225, it is equivalent to reducing the active material capacity per unit area on the inner side of the second bend 225 relative to the second preset value, making lithium plating less likely to occur on the outer side of the bend 223 of the negative electrode 220 located on the inner side of the second bend 225.

[0099] The Cell Balance (CB) 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 value of the outer portion of the bend 223 in the negative electrode 220 is Q1 / Q2, where Q1 is the capacity of the active material per unit area on the outer side of the bend 223 in the negative electrode 220, and Q2 is the capacity of the active material per unit area on the inner side of the bend 223 in the positive electrode 221 that is located outside and adjacent to the bend 223.

[0100] In this embodiment, the winding direction A is the direction in which the positive electrode 221 and the negative electrode 220 are wound circumferentially from the inside out. Figure 5 In the middle, the winding direction A is clockwise.

[0101] In some embodiments, the electrode assembly 22 may further include a separator 222 for isolating the positive electrode 221 and the negative electrode 220 to reduce the risk of a short circuit between the positive electrode 221 and the negative electrode 220.

[0102] The material of the separator 222 can be PP (polypropylene) or PE (polyethylene), etc.

[0103] In some embodiments, such as Figure 5 As shown, the winding structure also includes a straight region C, which is connected to a bending region B. The straight region C may have bending regions B at both opposite ends. The straight region C is the area of ​​the winding structure with a straight structure, where both the positive electrode 221 and the negative electrode 220 are arranged in a basically straight manner. The bending region B is the area of ​​the winding structure with a bent structure, where both the positive electrode 221 (bent portion 223) and the negative electrode 220 are bent. For example, the bent portions 223 of both the positive electrode 221 and the negative electrode 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 is a flat body as a whole.

[0105] It should be noted that when the first bending part 224 is arranged in the bending area B, it can be arranged in only one bending area B or in both bending areas B; when the second bending part 225 is arranged in the bending area B, it can be arranged in only one bending area B or in both bending areas B.

[0106] For example, such as Figure 5 As shown, in the bending region B, the multiple bends 223 in the positive electrode 221 and the multiple bends 223 in the negative electrode 220 are arranged alternately, that is, in the bending region B, they are arranged in the order of one bend 223 of the negative electrode 220, one bend 223 of the positive electrode 221, one bend 223 of the negative electrode 220, and so on.

[0107] In other embodiments, please refer to Figure 6 , Figure 6 The diagram below shows the structure of an electrode assembly 22 provided in some embodiments of this application. The wound structure may only have a bending region B, without a straight region C. The electrode assembly 22 with this structure can be a cylinder overall. In the positive electrode 221, one ring of the positive electrode 221 constitutes a bending portion 223; in the negative electrode 220, one ring of the negative electrode 220 constitutes 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 shows that the negative electrode sheet 220 includes a negative electrode current collector 2201 and negative electrode active material layers disposed on both sides of the negative electrode current collector 2201 in the thickness direction. The negative electrode active material layers on both sides of the negative electrode current collector 2201 in the thickness direction are a first negative electrode active material layer 2202 and a second negative electrode active material layer 2203, respectively. The first negative electrode active material layer 2202 is disposed on the outer surface of the negative electrode current collector 2201, and the second negative electrode active material layer 2203 is disposed on the inner surface of the negative electrode current collector 2201. The positive electrode 221 includes a positive current collector 2211 and positive active material layers disposed on both sides of the positive current collector 2211 in the thickness direction. The positive active material layers on both sides of the positive current collector 2211 in the thickness direction are a first positive active material layer 2212 and a second positive active material layer 2213, respectively. The first positive active material layer 2212 is disposed on the outer surface of the positive current collector 2211, and the second positive active material layer 2213 is disposed on the inner surface of the positive current collector 2211.

[0109] The negative electrode current collector 2201 may have a portion uncoated with a negative electrode active material layer; this portion is the negative electrode tab (not shown in the figure). The positive electrode current collector 2211 may have a portion uncoated with a negative electrode active material layer; this portion is the positive electrode tab (not shown in the figure). The positive electrode tab is used to connect with the positive electrode terminal 214 (see Figure 2201). Figure 4 Electrical connection, the negative electrode tab is used to connect with 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 with equal thickness along the winding direction A in the negative electrode current collector 2201, that is, the first negative electrode active material layer 2202 is distributed with equal thickness along the winding direction A in the negative electrode current collector 2201, and the second negative electrode active material layer 2203 is distributed with equal thickness along the winding direction A in the negative electrode current collector 2201. This structure simplifies the manufacturing process of the negative electrode sheet 220 and helps to reduce production costs.

[0111] Understandably, the thickness of each layer of the first negative electrode active material layer 2202 in the bending region B is equal to the thickness of each layer of the first negative electrode active material layer 2202 in the straight region C; the thickness of each layer of the second negative electrode active material layer 2203 in the bending region B is equal to the thickness of each layer of the second negative electrode active material layer 2203 in the straight region C.

[0112] In some embodiments, in the positive electrode 221, each positive active material layer is distributed of equal thickness along the winding direction A in the positive current collector 2211, that is, the first positive active material layer 2212 is distributed of equal thickness along the winding direction A in the positive current collector 2211, and the second positive active material layer 2213 is distributed of equal thickness along the winding direction A in the positive current collector 2211. This structure simplifies the manufacturing process of the positive electrode 221 and helps to reduce production costs.

[0113] Understandably, the thickness of each layer of the first positive electrode active material layer 2212 in the bending region B is equal to the thickness of each layer of the first positive electrode active material layer 2212 in the straight region C; the thickness of each layer of the second positive electrode active material layer 2213 in the bending region B is equal to the thickness of each layer of the second positive electrode active material layer 2213 in the straight region 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 located in the bending region B according to some embodiments of this application. At least one bending portion 223 in the negative electrode 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 of the negative electrode 220 is greater than the active material capacity per unit area on the inner side of the first bending portion 224. The bending portion 223 adjacent to the first bending portion 224 in the positive electrode 221 is a third bending portion 226, and the active material capacity per unit area on the outer side of the third bending portion 226 is equal to the active material capacity per unit area on the inner side of the third bending portion 226.

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

[0116] The first bending portion 224 includes a first current collector 2241, a first active material portion 2242, and a second active material portion 2243. The first current collector 2241 has a first inner surface 2241a and a first outer surface 2241b arranged opposite to each other in its thickness direction. The first active material portion 2242 is disposed on the first outer surface 2241b, and the second active material portion 2243 is disposed on the first inner surface 2241a. The third bending portion 226 includes a third current collector 2261, a fifth active material portion 2262, and a sixth active material portion 2263. The third current collector 2261 has a third inner surface 2261a and a third outer surface 2261b arranged opposite to each other in its thickness direction. The fifth active material portion 2262 is disposed on the third outer surface 2261b, and the sixth active material portion 2263 is disposed on the third inner surface 2261a.

[0117] Understandably, the first current collector 2241 is the negative current collector 2201 (see...). Figure 7 In the layer of the bending region B, the first active material part 2242 is the first negative electrode active material layer 2202 (see...). Figure 7 In the layer of the bending region B, the second active material part 2243 is the second negative electrode active material layer 2203 (see...). Figure 7 In the layer of the bending region B. The third current collector 2261 is the positive current collector 2211 (see Figure 7 Within the bending region B, the fifth active material layer 2262 is the first positive electrode active material layer 2212 (see...). Figure 7 In the layer of the bending region B, the sixth active material part 2263 is the second positive electrode active material layer 2213 (see...). Figure 7 ) In the layer of the bending area B.

[0118] The active material capacity per unit area on the outer side of the first bend 224 is greater than that on the inner side of 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 that of the second active material portion 2243 (the inner portion of the first bend 224). The active material capacity per unit area on the outer side of the first bend 224 can 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 on the inner side of the first bend 224 can 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 on the outer side of the third bend 226 is equal to the active material capacity per unit area on the inner side of 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 on the outer side of the third bend 226 can 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 on the inner side of the third bend 226 can be the ratio of the active material capacity of the sixth active material portion 2263 to the area of ​​the third inner surface 2261a.

[0120] In the negative electrode 220, all the bent portions 223 can be the first bent portions 224, or only some of the bent portions 223 can be the first bent portions 224. If all the bent portions 223 in the negative electrode 220 are the first bent portions 224, the active material capacity per unit area on the outer side of all the bent portions 223 in the negative electrode 220 is greater than the active material capacity per unit area on the inner side. If only some of the bent portions 223 in the negative electrode 220 are the first bent portions 224, all the bent portions 223 in the negative electrode 220 except for the first bent portions 224 can have a structure in which the active material capacity per unit area on the outer side is equal to the active material capacity per unit area on the inner side. In the positive electrode 221, all the bent portions 223 can be the third bent portions 226, or only some of the bent portions 223 can be the third bent portions 226.

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

[0122] In the negative electrode 220, one or more bends 223 on the innermost side of the bending region B may be the first bends 224. For example, the two innermost bends 223 in the negative electrode 220 are the first bends 224.

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

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

[0125] In the embodiments of this application, the active material capacity per unit area on the outer side of the first bend 224 can be greater than the active material capacity per unit area on the inner side of the first bend 224 in a variety of ways.

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

[0127] When the materials of the first active material portion 2242 and the second active material portion 2243 are the same, the thickness of the first active material portion 2242 is greater than the thickness of the second active material portion 2243. This allows the active material capacity per unit area of ​​the first active material portion 2242 to be greater than the active material capacity per unit area of ​​the second active material portion 2243. As a result, 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.

[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 collector 2241. Understandably, the composition of the first active material portion 2242 is the same as that of the second active material portion 2243, and the proportions of each component in the first active material portion 2242 are the same as those in the second active material portion 2243. For example, both the first active material portion 2242 and the second active material portion 2243 include an active material, a conductive agent, and a binder. The proportion of active material in the first active material portion 2242 is the same as that in the second active material portion 2243; the proportion of conductive agent in the first active material portion 2242 is the same as that in the second active material portion 2243; and the proportion of binder in the first active material portion 2242 is the same as that 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] For example, 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 bends 223 on the innermost side of the bending region B of the negative electrode sheet 220 are the first bends 224, the thickness of the first negative electrode active material layer 2202 in the innermost one or more rings of the negative electrode sheet 220 can be greater than the thickness of the second negative electrode active material layer 2203. Taking the two bends 223 on the innermost side of the bending region B of the negative electrode sheet 220 as the first bends 224 as an example, the thickness of the first negative electrode active material layer 2202 in the innermost two rings of the negative electrode sheet 220 can be greater than the thickness of the second negative electrode active material layer 2203, so that the thickness of the first active material portion 2242 of the first bend 224 is greater than the thickness of the second active material portion 2243, making it less likely for lithium plating to occur in the innermost two rings of the first bend 224 of the negative electrode sheet 220, which can improve the safety of the battery cell 20 and reduce production costs.

[0132] In some embodiments, please refer to Figure 9 , Figure 9 This is a partial enlarged view of the portion of the electrode assembly 22 located in the bending region B according to some embodiments of this application. The first bending portion 224 further includes a first conductive portion 228, which connects the second active material portion 2243 and the first inner surface 2241a of the first current collector 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. In other words, by providing the first conductive portion 228 between the second active material portion 2243 and the first current collector 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, thereby achieving a thickness of the first active material portion 2242 greater than the thickness of the second active material portion 2243.

[0133] When producing the negative electrode 220, it is only necessary to make the thickness of the first active material portion 2242 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] The first conductive part 228 can be a purely conductive coating, for example, the first conductive part 228 is a purely 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 collector 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, the active material capacity per unit area on the outer side of the first bending portion 224 can also be made greater than that on the inner side of the first bending portion 224 by other means. 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 specific capacity of the active material in the first active material portion 2242 is greater than that in the second active material portion 2243, thereby making the active material capacity per unit area on the outer side of the first bending portion 224 greater than that on the inner side of the first bending portion 224.

[0137] Specific capacity refers to the ratio of the electrical capacity released by an active material to the mass of the active material.

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

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

[0140] For example, the specific capacity of the active material in the first active material portion 2242 is 1.5%-12% greater than that of the active material in the second active material portion 2243.

[0141] In other embodiments, the active material capacity per unit area on the outer side of the first bending portion 224 can be greater than that on the inner side of the first bending portion 224 by other means. 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 active material in the first active material portion 2242 is greater than that in the second active material portion 2243.

[0142] It should be noted that, in the embodiments of this application, the active material capacity per unit area on the outer side of the third bend 226 can also be equal to the active material capacity per unit area on the inner side of the third bend 226 in various ways. For example, the material of the fifth active material portion 2262 in the third bend 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 Figure 10 , Figure 10 This is a partial enlarged view of the portion of the electrode assembly 22 located in the bending region B according to some embodiments of this application. At least one bending portion 223 in the positive electrode 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. In the negative electrode 220, the bending portion 223 adjacent to the second bending portion 225 is a fourth bending portion 227, and the active material capacity per unit area on the outer side of the fourth bending portion 227 is equal to the active material capacity per unit area on the inner side of the fourth bending portion 227.

[0144] When the active material capacity per unit area on the outer side of the second bend 225 is greater than the active material capacity per unit area on the inner side of the second bend 225, the active material capacity per unit area on the outer side of the fourth bend 227 can be equal to the active material capacity per unit area on the inner side of the fourth bend 227, thereby simplifying the manufacturing process of the negative electrode 220.

[0145] The second bending portion 225 includes a second current collection portion 2251, a third active material portion 2252, and a fourth active material portion 2253. The second current collection portion 2251 has a second inner surface 2251a and a second outer surface 2251b arranged opposite each other in its thickness direction. The third active material portion 2252 is disposed on the second outer surface 2251b, and the fourth active material portion 2253 is disposed on the second inner surface 2251a. The fourth bending portion 227 includes a fourth current collection portion 2271, a seventh active material portion 2272, and an eighth active material portion 2273. The fourth current collection portion 2271 has a fourth inner surface 2271a and a fourth outer surface 2271b arranged opposite each other in its thickness direction. The seventh active material portion 2272 is disposed on the fourth outer surface 2271b, and the eighth active material portion 2273 is disposed on the fourth inner surface 2271a.

[0146] Understandably, the second current collector 2251 is the positive current collector 2211 (see...). Figure 7 In the layer of the bending region B, the third active material part 2252 is the first positive electrode active material layer 2212 (see...). Figure 7 In the layer of the bending region B, the fourth active material part 2253 is the second positive electrode active material layer 2213 (see...). Figure 7 In the layer of the bending zone B. The fourth current collector 2271 is the negative current collector 2201 (see Figure 7 Within the bending region B, the seventh active material layer 2272 is the first negative electrode active material layer 2202 (see...). Figure 7 In the layer of the bending region B, the eighth active material part 2273 is the second negative electrode active material layer 2203 (see...). Figure 7 ) In the layer of the bending area B.

[0147] The active material capacity per unit area on the outer side of the second bend 225 is greater than that on the inner side of 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 that of the fourth active material portion 2253 (the inner portion of the second bend 225). The active material capacity per unit area on the outer side of the second bend 225 can 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 on the inner side of the second bend 225 can 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 on the outer side of the fourth bend 227 is equal to the active material capacity per unit area on the inner side of 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 on the outer side of the fourth bend 227 can 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 on the inner side of the fourth bend 227 can 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 221, all the bent portions 223 can be second bent portions 225, or only some of the bent portions 223 can be second bent portions 225. If all the bent portions 223 in the positive electrode 221 are second bent portions 225, the active material capacity per unit area on the outer side of all the bent portions 223 in the positive electrode 221 is greater than the active material capacity per unit area on the inner side. If only some of the bent portions 223 in the positive electrode 221 are second bent portions 225, all the bent portions 223 in the positive electrode 221 except for the second bent portions 225 can have a structure in which the active material capacity per unit area on the outer side is equal to the active material capacity per unit area on the inner side. In the negative electrode 220, all the bent portions 223 can be fourth bent portions 227, or only some of the bent portions 223 can be fourth bent portions 227.

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

[0151] In this embodiment, the positive electrode 221 may have one or more bends 223 on the innermost side of the bending region B, which are second bends 225. For example, the two innermost bends 223 in the positive electrode 221 are second bends 225.

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

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

[0154] In the embodiments of this application, the active material capacity per unit area on the outer side of the second bend 225 can be made greater than the active material capacity per unit area on the inner side of the second bend 225 in a variety of ways.

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

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

[0157] It should be noted that the material of the third active material portion 2252 is the same as that of the fourth active material portion 2253, that is, the same active material portion is coated on the second inner surface 2251a and the second outer surface 2251b of the second current collector 2251. Understandably, the composition of the third active material portion 2252 is the same as that of the fourth active material portion 2253, and the proportions of each component in the third active material portion 2252 are the same as those in the fourth active material portion 2253. For example, both the third active material portion 2252 and the fourth active material portion 2253 include an active material, a conductive agent, and a binder. The proportion of active material in the third active material portion 2252 is the same as that in the fourth active material portion 2253; the proportion of conductive agent in the third active material portion 2252 is the same as that in the fourth active material portion 2253; and the proportion of binder in the third active material portion 2252 is the same as that in the fourth active material portion 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] For example, 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 bends 223 on the innermost side of the bending region B of the positive electrode 221 are the second bends 225, the thickness of the first positive active material layer 2212 in the innermost one or more rings of the positive electrode 221 can be greater than the thickness of the second positive active material layer 2213. Taking the two bends 223 on the innermost side of the bending region B of the positive electrode 221 as the second bends 225 as an example, the thickness of the first positive active material layer 2212 in the innermost two rings of the positive electrode 221 can be greater than the thickness of the second positive active material layer 2213, so that the thickness of the third active material portion 2252 of the second bend 225 is greater than the thickness of the fourth active material portion 2253, making it less likely for lithium plating to occur in the second bends 225 in the innermost two rings of the positive electrode 221, which improves both the safety and energy density of the battery cell 20.

[0161] In some embodiments, please refer to Figure 11 , Figure 11This is a partial enlarged view of the portion of the electrode assembly 22 located in the bending region B according to other embodiments of this application. The second bending portion 225 further includes a second conductive portion 229, which connects the fourth active material portion 2253 and the second inner surface 2251a of the second current collector 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. In other words, by providing the second conductive portion 229 between the fourth active material portion 2253 and the second current collector 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, thereby achieving a thickness greater than the thickness of the fourth active material portion 2253.

[0162] When producing the positive electrode 221, it is only necessary to make the thickness of the third active material portion 2252 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] The second conductive part 229 can be a purely conductive coating, for example, the second conductive part 229 is a purely 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 collector 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, the active material capacity per unit area on the outer side of the second bend 225 can also be made greater than that on the inner side of the second bend 225 by other means. 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 specific capacity of the active material in the third active material portion 2252 is greater than that in the fourth active material portion 2253, thereby making the active material capacity per unit area on the outer side of the second bend 225 greater than that on the inner side of the second bend 225.

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

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

[0168] For example, the specific capacity of the active material in the third active material section 2252 is 1.5%-12% greater than that of the active material in the fourth active material section 2253.

[0169] In other embodiments, the active material capacity per unit area on the outer side of the second bend 225 can be made greater than that on the inner side of the second bend 225 by other means. 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 active material in the third active material portion 2252 is greater than that in the fourth active material portion 2253.

[0170] It should be noted that, in the embodiments of this application, the active material capacity per unit area on the outer side of the fourth bend 227 can also be equal to the active material capacity per unit area on the inner side of the fourth bend 227 in various ways. For example, the material of the seventh active material portion 2272 in the fourth bend 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 Figure 12 , Figure 12 This is a partial enlarged view of the portion of the electrode assembly 22 located in the bending region B according to some embodiments of this application. At least one bending portion 223 in the negative electrode 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 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 outer side of the first bent portion 224 can be greater than that on the inner side of the first bent portion 224 by making the thickness of the first active material portion 2242 of the first bent portion 224 greater than the thickness of the second active material portion 2243, or by making the specific capacity of the active material in the first active material portion 2242 of the first bent portion 224 greater than the specific capacity of the active material in the second active material portion 2243. Similarly, the active material capacity per unit area on the outer side of the second bent portion 225 can be greater than that on the inner side of the second bent portion 225 by making the thickness of the third active material portion 2252 of the second bent portion 225 greater than the thickness of the fourth active material portion 2253, or by making the specific capacity of the active material in the third active material portion 2252 of the second bent portion 225 greater than the specific capacity of the active material in the fourth active material portion 2253.

[0173] For example, in Figure 12 In the first bending portion 224, the material of the first active material portion 2242 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 bend 225 adjacent to the first bend 224 is arranged on the outer side of the first bend 224.

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

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

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

[0178] In this design, the negative electrode 220 may have one or more bends 223 on the innermost side of the bending region B, which can be considered as first bends 224. For example, the two innermost bends 223 in the negative electrode 220 can be considered as first bends 224. Similarly, the positive electrode 221 may have one or more bends 223 on the innermost side of the bending region B, which can be considered as second bends 225. For example, the two innermost bends 223 in the positive electrode 221 can be considered as second bends 225.

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

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

[0181] All the bends 223 in the negative electrode 220 are the first bends 224. When the active material capacity per unit area inside the first bend 224 meets the design requirements, since 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, it is equivalent to increasing the active material capacity per unit area outside the first bend 224. This increases the CB value of the outer part of all the bends 223 in the negative electrode 220, and the portion of the negative electrode 220 located in the bend region B is less prone to lithium plating. All the bends 223 in the positive electrode 221 are the second bends 225. When the active material capacity per unit area on the outer side of the second bend 225 meets the design requirements, since the active material capacity per unit area on the outer side of the second bend 225 is greater than the active material capacity per unit area on the inner side of the second bend 225, it is equivalent to reducing the active material capacity per unit area on the inner side of the second bend 225. This makes the CB value of the outer part of the multiple bends 223 in the negative electrode 220 increase, and the part of the negative electrode 220 located in the bending region B is less prone to lithium plating.

[0182] Please refer to Figure 13 , Figure 13 The flowchart illustrates a method for manufacturing an electrode assembly 22 according to some embodiments of this application. The method for manufacturing the electrode assembly 22 includes:

[0183] S100: Provides negative electrode plate 220 and positive electrode plate 221;

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

[0185] The winding structure includes a bending region B, and both the negative electrode 220 and the positive electrode 221 include multiple bending portions 223 located in the bending region B. At least one bending portion 223 in the negative electrode 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; and / or, at least one bending portion 223 in the positive electrode 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.

[0186] In some embodiments, a separator 222 is also provided for separating the positive electrode 221 and the negative electrode 220, wherein the first electrode, the separator 222 and the second electrode are wound along the winding direction A to form a wound structure.

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

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

[0189] The winding structure includes a bending region B, and both the negative electrode 220 and the positive electrode 221 include multiple bending portions 223 located in the bending region B. At least one bending portion 223 in the negative electrode 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; and / or, at least one bending portion 223 in the positive electrode 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.

[0190] In some embodiments, the providing device 2100 is further configured to provide a separator 222 that isolates the positive electrode 221 and the negative electrode 220. The assembly device 2200 is configured to wind the first electrode, the separator 222, and the second electrode along the winding direction A to form a wound structure.

[0191] The structure of the electrode assembly 22 manufactured by the above-described manufacturing equipment 2000 can be found in the electrode assembly 22 provided in the above embodiments.

[0192] Furthermore, this application embodiment also provides a method for testing the CB value of the electrode assembly 22.

[0193] The steps for testing the CB value are as follows:

[0194] Step 1): Average discharge capacity test of the positive electrode single-sided active material layer. Take the positive electrode sheet 221 of the above embodiments and obtain a small disc containing the positive electrode single-sided active material layer using a stamping die. Using a lithium metal sheet as the counter electrode, a Celgard film as the separator, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) containing LiPF6 (1 mol / L) as the electrolyte, assemble 6 identical CR2430 coin cells in an argon-protected glove box. ① After battery assembly, let it stand for 12 hours. ② Perform constant current charging at a charging current of 0.1C until the voltage reaches the upper limit cutoff voltage x1V. Then maintain the voltage x1V and perform 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 limit cutoff voltage y1V. ⑤ Let it stand for 5 minutes. Repeat steps 2-5 and record the discharge capacity of the second cycle. The average discharge capacity of the 6 coin cells is the average discharge capacity of the single-sided active material layer of the positive electrode. For example, when the positive electrode active material is lithium iron phosphate (LFP), the upper limit cutoff voltage x1V = 3.75V and the lower limit cutoff voltage y1V = 2V. When the positive electrode active material is lithium nickel cobalt manganese oxide (NCM), the upper limit cutoff voltage x1V = 4.25V and the lower limit cutoff voltage y1V = 2.8V.

[0195] Step 2): Average charging capacity test of the single-sided active material layer of the negative electrode. Take the negative electrode sheet 220 of each of the above embodiments, and use a stamping die to obtain a small disc with the same area as the small disc of the positive electrode in Step 1) and containing a single-sided film layer of the negative electrode. Using a lithium metal sheet as the counter electrode, a Celgard film as the separator, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) containing LiPF6 (1 mol / L) as the electrolyte, assemble 6 CR2430 coin cells in an argon-protected glove box. ① After battery assembly, let it stand for 12 hours. ② Perform constant current discharge at a discharge current of 0.05C until the voltage reaches the lower cutoff voltage y2mV. ③ Then perform constant current discharge at a discharge current of 50uA until the voltage reaches the lower cutoff voltage y2mV. ④ Let it stand for 5 minutes. ⑤ Then perform constant current discharge at a discharge current of 10uA until the lower cutoff voltage y2mV is reached. ⑥ Let it stand for 5 minutes. ⑦ Finally, perform constant current charging at a charging current of 0.1C until the final voltage reaches the upper cutoff voltage x2V. ⑧ Let it stand for 5 minutes. Repeat steps 2-8 and record the charging capacity of the second cycle. The average charging capacity of the 6 coin cells is the average charging capacity of the negative electrode single-sided film layer. For example, when the negative electrode active material is graphite, the upper cutoff voltage x2V = 2V and the lower cutoff voltage y2V = 5mV. When the negative electrode active material is silicon, the upper cutoff voltage x2V = 2V and the lower cutoff voltage y2V = 5mV.

[0196] Step 3): Calculate the CB value based on the formula: CB = Average charging capacity (mAh) of the above negative electrode single-sided active material layer / Average discharge capacity (mAh) of the above positive electrode single-sided active material layer.

[0197] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0198] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit this application. For those skilled in the art, this application can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrode assembly comprising a negative electrode and a positive electrode, wherein the negative electrode and the positive electrode are wound along a winding direction to form a winding structure, the winding structure including a bending region; Both the negative electrode and the positive electrode include multiple bent portions located in the bending region; in, At least one bent portion in the negative electrode sheet is a first bent portion, and 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. The bending portion adjacent to the first bending portion in the positive electrode sheet is the third bending portion; The active material capacity per unit area on the outer side of the third bend is equal to the active material capacity per unit area on the inner side of the third bend. The first bending portion includes a first current collection portion, a first active material portion, and a second active material portion; The first current collection section has a first inner surface and a first outer surface arranged opposite to each other in its thickness direction, the first active material part is disposed on the first outer surface, and the second active material part is disposed on the first inner surface; The material of the second active material portion is the same as the material of the first active material portion; The thickness of the first active material portion is greater than the thickness of the second active material portion.

2. The electrode assembly according to claim 1, wherein, The first bending portion further includes a first conductive portion, which is connected between the second active material portion and the first inner surface. 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.

3. The electrode assembly according to claim 1, wherein, The negative electrode sheet includes a negative current collector and negative active material layers disposed on both sides of the negative current collector in the thickness direction. Each negative electrode active material layer is distributed of equal thickness along the winding direction in the negative electrode current collector.

4. The electrode assembly according to claim 1, wherein, The positive electrode sheet includes a positive current collector and positive active material layers disposed on both sides of the positive current collector in the thickness direction; Each positive electrode active material layer is distributed of equal thickness along the winding direction in the positive electrode current collector.

5. The electrode assembly according to any one of claims 1-4, wherein, All the bent portions in the negative electrode sheet are the first bent portions.

6. A battery cell, comprising a housing and an electrode assembly according to any one of claims 1-5; The electrode assembly is housed within the housing.

7. A battery, comprising a housing and a battery cell according to claim 6; The individual battery cells are housed within the casing.

8. An electrical device comprising the battery of claim 7.

9. A method for manufacturing an electrode assembly, comprising: We provide positive and negative electrode plates; The negative electrode and the positive electrode are wound along the winding direction to form a winding structure; The winding structure includes a bending region, and both the negative electrode sheet and the positive electrode sheet include multiple bending portions located in the bending region. At least one bent portion in the negative electrode sheet is a first bent portion, and 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. The bending portion adjacent to the first bending portion in the positive electrode sheet is the third bending portion; The active material capacity per unit area on the outer side of the third bend is equal to the active material capacity per unit area on the inner side of the third bend. The first bending portion includes a first current collection portion, a first active material portion, and a second active material portion; The first current collection section has a first inner surface and a first outer surface arranged opposite to each other in its thickness direction, the first active material part is disposed on the first outer surface, and the second active material part is disposed on the first inner surface; The material of the second active material portion is the same as the material of the first active material portion; The thickness of the first active material portion is greater than the thickness of the second active material portion.

10. An apparatus for manufacturing an electrode assembly, comprising: A device is provided for providing positive and negative electrode plates; as well as An assembly device for winding the negative electrode sheet and the positive electrode sheet along a winding direction to form a winding structure; The winding structure includes a bending region, and both the negative electrode sheet and the positive electrode sheet include multiple bending portions located in the bending region. At least one bent portion in the negative electrode sheet is a first bent portion, and 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. The bending portion adjacent to the first bending portion in the positive electrode sheet is the third bending portion; The active material capacity per unit area on the outer side of the third bend is equal to the active material capacity per unit area on the inner side of the third bend. The first bending portion includes a first current collection portion, a first active material portion, and a second active material portion; The first current collection section has a first inner surface and a first outer surface arranged opposite to each other in its thickness direction, the first active material part is disposed on the first outer surface, and the second active material part is disposed on the first inner surface; The material of the second active material portion is the same as the material of the first active material portion; The thickness of the first active material portion is greater than the thickness of the second active material portion.

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