Electrode assembly, battery cell, battery, and electric device

Abstract

The application provides an electrode assembly, a battery monomer, a battery and an electric device. The electrode assembly comprises a positive electrode sheet and a negative electrode sheet arranged in a stack. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode current collector comprises a positive electrode coating area and a positive electrode tab, the positive electrode active material layer is at least partially coated on the positive electrode coating area, the positive electrode tab is connected to the end of the positive electrode coating area along a first direction, and the first direction is perpendicular to the stacking direction of the positive electrode sheet and the negative electrode sheet. The negative electrode sheet comprises a negative electrode active material layer, the positive electrode active material layer and the negative electrode active material layer are arranged in a face-to-face mode, and in the first direction, both ends of the negative electrode active material layer exceed the positive electrode active material layer. The positive electrode active material layer comprises a positive electrode main body and a positive electrode edge, the positive electrode main body is provided with the positive electrode edge on the side away from the positive electrode tab along the first direction, and the positive electrode edge is configured such that the unit area capacity of the positive electrode edge is less than the unit area capacity of the positive electrode main body.

Description

[0001] This application is a divisional application based on application number 202180035399.5, filed on February 4, 2021, by CATL (Contemporary Amperex Technology Co., Ltd.), entitled "Electrode Components and Manufacturing Methods and Systems Thereof, Battery Cells and Batteries". Technical Field

[0002] This application relates to the field of battery technology, and more specifically, to an electrode assembly, a battery cell, a battery, and an electrical device. Background Technology

[0003] Rechargeable batteries, also known as secondary batteries, are batteries that can be recharged after being discharged to reactivate the active materials and continue to be used. Rechargeable batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc.

[0004] In the development of battery technology, besides improving battery performance, safety is also a crucial issue that cannot be ignored. If battery safety cannot be guaranteed, then the battery is unusable. Therefore, how to enhance battery safety is a pressing technical problem that needs to be solved in battery technology. Summary of the Invention

[0005] This application provides an electrode assembly, a battery cell, a battery, and an electrical device that can enhance battery safety.

[0006] In a first aspect, embodiments of this application provide an electrode assembly comprising a positive electrode and a negative electrode stacked together. The positive electrode includes a positive current collector and a positive active material layer. The positive current collector includes a positive electrode coating area and a positive electrode tab. The positive active material layer is at least partially coated on the positive electrode coating area. The positive electrode tab is connected to an end of the positive electrode coating area along a first direction, perpendicular to the stacking direction of the positive and negative electrode. The negative electrode includes a negative current collector and a negative active material layer coated on the surface of the negative current collector. The positive and negative active material layers are disposed opposite each other, and both ends of the negative active material layer extend beyond the positive active material layer in the first direction. The positive active material layer includes a positive electrode body portion and a positive electrode edge portion. The positive electrode body portion has a positive electrode edge portion on the side opposite to the positive electrode tab along the first direction. The positive electrode edge portion is configured such that its unit area capacity is smaller than that of the positive electrode body portion.

[0007] When the unit area capacity of the positive electrode body meets the requirements, lithium plating is less likely to occur in the part of the negative electrode active material layer that overlaps with the positive electrode body. Since the unit area capacity of the positive electrode edge is smaller than that of the positive electrode body, it is equivalent to reducing the unit area capacity of the positive electrode edge. This increases the CB value of the part of the negative electrode active material layer that overlaps with the positive electrode edge. During cycling, even if the part of the negative electrode active material layer that overlaps with the positive electrode edge needs to receive lithium ions diffused from the part of the negative electrode active material layer that extends beyond the positive electrode active material layer, lithium plating is less likely to occur in the part of the negative electrode active material layer that overlaps with the positive electrode edge.

[0008] In some embodiments, there are at least two positive electrode edges, each located on one side of the positive electrode body along a first direction. The two positive electrode edges further reduce the risk of lithium plating.

[0009] In some embodiments, in the two positive electrode edge portions, at least a portion of the thickness of the positive electrode edge portion closer to the positive electrode tab is less than the thickness of the positive electrode body portion.

[0010] In some embodiments, the weight ratio of active material at the positive electrode edge to the positive electrode edge is less than the weight ratio of active material at the positive electrode body to the positive electrode body, so that the unit area capacity at the positive electrode edge is less than the unit area capacity at the positive electrode body. By reducing the amount of active material at the positive electrode edge, the weight ratio of active material at the positive electrode edge is reduced, thereby reducing the unit area capacity at the positive electrode edge to be less than the unit area capacity at the positive electrode body.

[0011] In some embodiments, the specific capacity of the active material at the positive electrode edge is less than the specific capacity of the active material in the positive electrode body, so that the unit area capacity of the positive electrode edge is less than the unit area capacity of the positive electrode body. By reducing the specific capacity of the active material in the positive electrode edge, the unit area capacity of the positive electrode edge can be reduced, so that the unit area capacity of the positive electrode edge is less than the unit area capacity of the positive electrode body.

[0012] In some embodiments, the positive electrode edge portion includes a first positive electrode coating and a second positive electrode coating stacked along the stacking direction. The weight ratio of active material in the second positive electrode coating to the second positive electrode coating is less than the weight ratio of active material in the first positive electrode coating to the first positive electrode coating. By reducing the amount of active material in the second positive electrode coating, the weight ratio of active material in the second positive electrode coating is reduced, thereby reducing the unit area capacity of the positive electrode edge portion, so that the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode body portion. In other embodiments, the specific capacity of active material in the second positive electrode coating is less than the specific capacity of active material in the first positive electrode coating. By reducing the specific capacity of active material in the second positive electrode coating, the unit area capacity of the positive electrode edge portion is reduced, so that the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode body portion.

[0013] In some embodiments, the particle size of the active material at the positive electrode edge is larger than that of the active material in the positive electrode body. During charging and discharging, lithium ions do not diffuse easily in the positive electrode edge, and the rate at which lithium ions diffuse from the positive electrode body to the positive electrode edge is reduced. The rate at which lithium ions are extracted from the positive electrode edge is also reduced. This reduces the risk of lithium ions accumulating in the portion of the negative electrode active material layer that overlaps with the positive electrode edge, making it less prone to lithium deposition in the negative electrode active material layer.

[0014] In some embodiments, the dimension of the positive electrode edge portion in the first direction is greater than 0.5 mm, which can reduce the risk of partial lithium analysis in the negative electrode active material overlapping with the positive electrode body portion.

[0015] In some embodiments, the positive electrode edge portion is disposed around the positive electrode body portion, which can increase the overlap between the negative electrode active material layer and the positive electrode edge portion, making it less likely for lithium plating to occur in the negative electrode active material layer.

[0016] In some embodiments, the negative electrode active material layer includes a negative electrode body portion and a negative electrode edge portion connected to the negative electrode body portion. One end of the negative electrode edge portion away from the negative electrode body portion extends beyond the positive electrode active material layer, and at least a portion of the negative electrode edge portion overlaps with the positive electrode active material layer in the stacking direction of the positive electrode sheet and the negative electrode sheet. The negative electrode active material layer is configured such that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

[0017] The negative electrode edge includes a first portion overlapping the positive electrode active material layer in the stacking direction and a second portion extending beyond the positive electrode active material layer. When the unit area capacity of the negative electrode body meets the setting requirements, that is, when the unit area capacity of the negative electrode body reaches a first preset value, lithium plating is less likely to occur in the negative electrode body. Since the unit area capacity of the negative electrode edge is greater than that of the negative electrode body, that is, the unit area capacity of the negative electrode edge is greater than the first preset value, it is equivalent to increasing the unit area capacity of the negative electrode edge. This can increase the CB value of the negative electrode edge. During cycling, even if the first portion needs to accept lithium ions extracted from the positive electrode active material layer and lithium ions diffused from the second portion, lithium plating is less likely to occur in the first portion, thereby reducing the risk of lithium plating at the negative electrode edge.

[0018] In some embodiments, the positive electrode edge portion located on the side of the positive electrode body portion that is away from the positive electrode tab along a first direction at least partially overlaps the negative electrode body portion in the stacking direction.

[0019] In some embodiments, the positive electrode edge portion located on the side of the positive electrode body portion away from the positive electrode tab along a first direction at least partially overlaps the negative electrode edge portion in the stacking direction.

[0020] In some embodiments, the weight ratio of the active material in the negative electrode edge portion to the negative electrode edge portion is greater than the weight ratio of the active material in the negative electrode body portion to the negative electrode body portion, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion. By increasing the amount of active material in the negative electrode edge portion, the weight ratio of the active material in the negative electrode edge portion is increased, thereby increasing the unit area capacity of the negative electrode edge portion, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

[0021] In some embodiments, the specific capacity of the active material in the negative electrode edge portion is greater than the specific capacity of the active material in the negative electrode body portion, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion. By increasing the specific capacity of the active material in the negative electrode edge portion, the unit area capacity of the negative electrode edge portion can be increased, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

[0022] In some embodiments, the negative electrode edge portion includes a first negative electrode coating and a second negative electrode coating stacked along the stacking direction. The weight ratio of the active material in the second negative electrode coating to the second negative electrode coating is greater than the weight ratio of the active material in the first negative electrode coating to the first negative electrode coating. By increasing the amount of active material in the second negative electrode coating, the weight ratio of the active material in the second negative electrode coating is increased, thereby increasing the unit area capacity of the negative electrode edge portion, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion. In other embodiments, the specific capacity of the active material in the second negative electrode coating is greater than the specific capacity of the active material in the first negative electrode coating; by increasing the specific capacity of the active material in the second negative electrode coating, the unit area capacity of the negative electrode edge portion is increased, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

[0023] In some embodiments, the particle size of the active material in the negative electrode edge is smaller than that in the negative electrode body. During charging and discharging, lithium ions diffuse more easily in the negative electrode edge, are more evenly distributed, and are less likely to accumulate locally, thereby reducing the risk of lithium plating.

[0024] In some embodiments, the negative electrode sheet includes a negative electrode current collector, which includes a negative electrode coating area and a negative electrode tab. The negative electrode active material layer is at least partially coated on the negative electrode coating area, and the negative electrode tab is connected to the end of the negative electrode coating area along a first direction, which is perpendicular to the stacking direction. The negative electrode body portion has a negative electrode edge portion on the side near the negative electrode tab along the first direction.

[0025] In some embodiments, there are at least two negative electrode edges, each located on one side of the negative electrode body along a first direction. By providing two negative electrode edges, the risk of lithium deposition from the negative electrode active material can be further reduced.

[0026] In some embodiments, in the two negative electrode edge portions, at least a portion of the thickness of the negative electrode edge portion closer to the negative electrode tab is less than the thickness of the negative electrode body portion, and the thickness of the negative electrode edge portion farther from the negative electrode tab is equal to the thickness of the negative electrode body portion.

[0027] In some embodiments, the portion of the negative electrode edge that overlaps with the positive electrode active material layer in the stacking direction has a dimension greater than 0.5 mm in the first direction to reduce the risk of lithium deposition in the negative electrode active material.

[0028] In some embodiments, the negative electrode edge portion is disposed around the negative electrode body portion to increase the range of the negative electrode edge portion, making it less likely for lithium plating to occur in the negative electrode active material layer.

[0029] In some embodiments, the negative electrode edge portion includes a first portion and a second portion, the first portion overlapping the positive electrode active material layer in the stacking direction, and the second portion extending beyond the positive electrode active material layer.

[0030] 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, wherein the electrode assembly is housed in the housing.

[0031] 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, wherein the battery cell is housed within the housing.

[0032] Fourthly, embodiments of this application provide an electrical device that includes a battery provided in any of the embodiments of the third aspect above, the battery being used to provide electrical energy. Attached Figure Description

[0033] 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.

[0034] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0035] Figure 2 Explosion diagrams of batteries provided for some embodiments of this application;

[0036] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0037] Figure 4 for Figure 3 The diagram shows an exploded battery cell;

[0038] Figure 5 This is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application;

[0039] Figure 6 for Figure 5 A partial cross-sectional view of the electrode assembly shown along line AA;

[0040] Figure 7 for Figure 5 A schematic diagram showing the positive and negative electrode plates in their unfolded state;

[0041] Figure 8 This is a schematic diagram of the structure of an electrode assembly according to another embodiment of this application;

[0042] Figure 9 for Figure 8 The diagram shows the structure of the positive and negative electrode plates of the electrode assembly.

[0043] Figures 10 to 14 A schematic diagram showing the migration of lithium ions between the positive and negative electrode plates is shown.

[0044] Figure 15 This is a partial cross-sectional schematic diagram of an electrode assembly according to an embodiment of this application;

[0045] Figure 16 This is a partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of this application;

[0046] Figure 17 This is a partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of this application;

[0047] Figure 18 This is a partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of this application;

[0048] Figure 19 This is a partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of this application;

[0049] Figure 20 This is a top view schematic diagram of the negative electrode sheet of an electrode assembly according to an embodiment of this application;

[0050] Figure 21 This is a top view schematic diagram of the positive electrode sheet of an electrode assembly according to an embodiment of this application;

[0051] Figure 22 A flowchart illustrating a method for manufacturing an electrode assembly provided in some embodiments of this application;

[0052] Figure 23 A schematic block diagram of a manufacturing system for an electrode assembly provided in some embodiments of this application.

[0053] The accompanying drawings are not drawn to scale. Detailed Implementation

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] In this application, "multiple" means two or more (including two).

[0061] In this application, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc., and the embodiments of this application are not limited thereto. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited thereto. Battery cells are generally classified into three types according to their packaging method: cylindrical battery cells, square battery cells, and pouch battery cells, and the embodiments of this application are not limited thereto.

[0062] 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.

[0063] 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.

[0064] When an external power source charges a battery cell, electrons (e) from the positive electrode travel through the external circuit to the negative electrode. Lithium ions (Li+) escape from the active material particles in the positive electrode active material layer and enter the electrode solution. They then pass through the tiny pores in the separator and move to the negative electrode, where they combine with the electrons that have already arrived and enter the active material particles in the negative electrode active material layer. If there are no sites in the negative electrode active material layer to accept lithium ions, the lithium ions will deposit on the surface of the negative electrode active material layer, forming lithium dendrites. These dendrites can pierce the separator, causing a short circuit within the battery cell and triggering thermal runaway. Therefore, when designing electrode assemblies, it is essential to ensure an excess of negative electrode active material to reduce the risk of lithium plating.

[0065] Considering factors such as the assembly precision of the electrode components, the end of the negative electrode active material layer needs to extend beyond the positive electrode active material layer to reduce the risk that the negative electrode active material layer may not completely cover the positive electrode active material layer due to assembly errors. In this case, the negative electrode active material layer has an overlapping region that overlaps with the positive electrode active material layer and an overhang region extending beyond the positive electrode active material layer. The inventors discovered that the overhang region allows lithium ions to diffuse to and remain there, especially if stored for a long time while charged. Applying a small current constant voltage discharge after discharge can allow the residual lithium ions in the overhang region to diffuse back to the overlapping region and play a role. However, the diffusion of lithium ions between the overlapping region and the overhang region also poses a risk of lithium plating.

[0066] In view of this, embodiments of this application provide an electrode assembly including a positive electrode and a negative electrode stacked together. The positive active material layer of the positive electrode and the negative active material layer of the negative electrode are disposed opposite each other, and the end of the negative active material layer extends beyond the positive active material layer. The negative active material layer includes a negative electrode body portion and a negative electrode edge portion connected to the negative electrode body portion. One end of the negative electrode edge portion away from the negative electrode body portion extends beyond the positive active material layer, and in the stacking direction of the positive and negative electrode electrodes, at least a portion of the negative electrode edge portion overlaps with the positive active material layer. The negative active material layer is configured such that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion; and / or, the positive active material layer includes a positive electrode body portion and a positive electrode edge portion connected to the positive electrode body portion, and the positive electrode edge portion is configured such that the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode body portion. This structure can reduce the risk of lithium plating and enhance battery safety.

[0067] The technical solutions described in the embodiments of this application are applicable to batteries and electrical devices that use batteries.

[0068] 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.

[0069] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0070] Please refer to Figure 1 , Figure 1 The diagram below illustrates the structure of a vehicle 1 according to some embodiments of this application. A battery 2 is disposed inside the vehicle 1, and the battery 2 may be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0071] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0072] In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0073] Please refer to Figure 2 , Figure 2 This is an exploded view of battery 2 provided in some embodiments of this application. Battery 2 includes a housing 5 and battery cells ( Figure 2 (Not shown), the battery cells are housed inside the casing 5.

[0074] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 51 and a second housing portion 52, which overlap each other, and together define a housing space 53 for housing the individual battery cells. The second housing portion 52 may be a hollow structure with one end open, and the first housing portion 51 may be a plate-like structure, with the first housing portion 51 covering the open side of the second housing portion 52 to form a housing 5 with the housing space 53; alternatively, both the first housing portion 51 and the second housing portion 52 may be hollow structures with one side open, with the open side of the first housing portion 51 covering the open side of the second housing portion 52 to form a housing 5 with the housing space 53. Of course, the first housing portion 51 and the second housing portion 52 can have various shapes, such as cylinders, cuboids, etc.

[0075] To improve the sealing performance after the first housing part 51 and the second housing part 52 are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 51 and the second housing part 52.

[0076] Assuming that the first box part 51 covers the top of the second box part 52, the first box part 51 can also be called the upper box cover, and the second box part 52 can also be called the lower box.

[0077] In battery 2, there can be one or more individual battery cells. If there are multiple individual battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple individual battery cells are connected in both series and parallel configurations. Multiple individual battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed within housing 5. Alternatively, multiple individual battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed within housing 5.

[0078] In some embodiments, please refer to Figure 3 , Figure 3 for Figure 2 The diagram shows the structure of battery module 6. Multiple battery cells are connected in series, parallel, or a combination thereof to form battery module 6. These battery modules 6 are then connected in series, parallel, or a combination thereof to form a single unit, which is housed within a casing.

[0079] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0080] Please refer to Figure 4 , Figure 4 for Figure 3The diagram shows an exploded view of the battery cell 7. The battery cell 7 provided in this embodiment includes an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20.

[0081] In some embodiments, the housing 20 may also be used to contain an electrolyte, such as an electrolyte solution. The housing 20 may have various structural forms.

[0082] In some embodiments, the housing 20 may include a housing 21 and an end cap 22. The housing 21 is a hollow structure with an opening on one side, and the end cap 22 covers the opening of the housing 21 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte.

[0083] When assembling the battery cell 7, the electrode assembly 10 can be placed into the housing 21 first, and then the end cap 22 can be closed on the opening of the housing 21. Then, the electrolyte can be injected into the housing 21 through the electrolyte injection port on the end cap 22.

[0084] The housing 21 can be of various shapes, such as a cylinder or a cuboid. The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing can be used; if the electrode assembly 10 is a cuboid structure, a cuboid housing can be used. Of course, the end cap 22 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 21 has a cuboid structure, and the end cap 22 has a plate-like structure, which is closed on the opening at the top of the shell 21.

[0085] In some embodiments, the battery cell 7 may further include a positive electrode terminal 30, a negative electrode terminal 40, and a pressure relief mechanism 50, all of which are mounted on the end cap 22. The positive electrode terminal 30 and the negative electrode terminal 40 are both used for electrical connection with the electrode assembly 10 to output the electrical energy generated by the electrode assembly 10. The pressure relief mechanism 50 is used to release the internal pressure of the battery cell 7 when the internal pressure or temperature reaches a predetermined value.

[0086] For example, the pressure relief mechanism 50 is located between the positive electrode terminal 30 and the negative electrode terminal 40. The pressure relief mechanism 50 can be a component such as an explosion-proof valve, explosion-proof disc, gas valve, pressure relief valve or safety valve.

[0087] Of course, in some embodiments, the outer casing 20 can also be other structures. For example, the outer casing 20 includes a housing 21 and two end caps 22. The housing 21 is a hollow structure with openings on opposite sides. One end cap 22 is fitted onto one opening of the housing 21 to form a sealed connection, thereby forming a sealed space for accommodating the electrode assembly 10 and the electrolyte. In this structure, the positive electrode terminal 30 and the negative electrode terminal 40 can be mounted on the same end cap 22 or on different end caps 22; a pressure relief mechanism 50 can be mounted on one end cap 22 or both end caps 22 can be equipped with a pressure relief mechanism 50.

[0088] It should be noted that in the battery cell 7, the electrode assembly 10 housed within the casing 20 can be one or more. For example, in... Figure 4 In the middle, there are two electrode components 10.

[0089] The specific structure of the electrode assembly 10 will now be described in detail with reference to the accompanying drawings.

[0090] Figure 5 This is a schematic diagram of the structure of an electrode assembly according to one embodiment of this application. Figure 6 for Figure 5 The diagram shows a partial cross-sectional view of the electrode assembly along line AA.

[0091] like Figure 5 and Figure 6 As shown, the electrode assembly 10 includes a positive electrode 11 and a negative electrode 12 stacked together. The positive active material layer 111 of the positive electrode 11 and the negative active material layer 121 of the negative electrode 12 face each other, and the end of the negative active material layer 121 extends beyond the positive active material layer 111. The region where the negative active material layer 121 overlaps with the positive active material layer 111 in the stacking direction X is called the overlap region S1, and the region where the negative active material layer 121 extends beyond the positive active material layer 111 is called the overhang region S2.

[0092] In some embodiments, the positive electrode 11 includes a positive current collector 112 and a positive active material layer 111 coated on both surfaces of the positive current collector 112, and the negative electrode 12 includes a negative current collector 122 and a negative active material layer 121 coated on both surfaces of the negative current collector 122. The positive current collector 112 includes a positive electrode coating area 1121 and a positive electrode tab 1122. The positive active material layer 111 is at least partially coated on the positive electrode coating area 1121. The positive electrode tab 1122 is connected to the end of the positive electrode coating area 1121 and protrudes from the positive electrode coating area 1121. The positive electrode tab 1122 is at least partially uncoated with the positive active material layer 111 and is used for electrical connection to the positive electrode terminal 30 (see reference). Figure 4The negative electrode current collector 122 includes a negative electrode coating area 1221 and a negative electrode tab 1222. The negative electrode active material layer 121 is at least partially coated on the negative electrode coating area 1221. The negative electrode tab 1222 is connected to the end of the negative electrode coating area 1221 and protrudes from the negative electrode coating area 1221. The negative electrode tab 1222 is at least partially uncoated with the negative electrode active material layer 121 and is used for electrical connection to the negative electrode terminal 40 (see reference). Figure 4 ).

[0093] The electrode assembly 10 also includes a separator 13 that separates the positive electrode 11 and the negative electrode 12. The separator 13 has a large number of interconnected micropores, which can ensure the free passage of electrolyte ions and has good permeability to lithium ions. The separator 13 can be made of PP or PE, etc.

[0094] In some embodiments, the positive electrode 11 and the negative electrode 12 are wound around a winding axis to form a winding structure. In the winding structure, the positive electrode 11 and the negative electrode 12 are stacked in a direction perpendicular to the winding axis. In other words, the positive electrode 11 and the negative electrode 12 are wound multiple turns along the winding direction Z, where Z is the direction in which the positive electrode 11 and the negative electrode 12 are wound circumferentially from the inside out. Figure 5 In the middle, the winding direction Z is counterclockwise.

[0095] In some embodiments, the positive electrode tab 1122 is connected to the end of the positive electrode coating region 1121 along the first direction Y, and the negative electrode tab 1222 is connected to the end of the negative electrode coating region 1221 along the first direction Y. The first direction Y is perpendicular to the winding direction Z and parallel to the winding axis of the electrode assembly 10.

[0096] In some embodiments, the positive electrode tab 1122 and the negative electrode tab 1222 are located on the same side of the electrode assembly 10 along the first direction Y; in other embodiments, the positive electrode tab 1122 and the negative electrode tab 1222 may also be located on opposite sides of the electrode assembly 10 along the first direction Y.

[0097] The electrode assembly 10 with a wound structure includes a flat region B and bent regions C located at both ends of the flat region B. The flat region B refers to the area in the wound structure with a parallel structure, meaning that the negative electrode 12, positive electrode 11, and separator 13 within the flat region B are substantially parallel to each other; that is, the surfaces of each layer of negative electrode 12, positive electrode 11, and separator 13 in the flat region B of the electrode assembly 10 are planar. The bent region C refers to the area in the wound structure with a bent structure, meaning that the negative electrode 12, positive electrode 11, and separator 13 within the bent region C are all bent; that is, the surfaces of each layer of negative electrode 12, positive electrode 11, and separator 13 in the bent region C of the electrode assembly 10 are curved surfaces.

[0098] In some embodiments, the ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111. Specifically, both ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111 along the first direction Y, the starting end of the negative electrode active material layer 121 extends beyond the positive electrode active material layer 111 along the winding direction Z, and the tail end of the negative electrode active material layer 121 extends beyond the positive electrode active material layer 111 along the winding direction Z. In this way, in the stacking direction X, the negative electrode active material layer 121 can completely cover the positive electrode active material layer 111 to reduce the risk of lithium plating.

[0099] Figure 7 for Figure 5 This is a schematic diagram of the positive electrode 11 and the negative electrode 12 in their unfolded state. Figure 7 As shown, after the wound structure is unwound, the positive electrode 11 and the negative electrode 12 are essentially long strips. At this time, the positive electrode 11 and the negative electrode 12 are stacked. In the length direction L of the negative electrode 12, the length of the negative electrode active material layer 121 is greater than the length of the positive electrode active material layer 111, and the two ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111; in the width direction W of the negative electrode 12, the width of the negative electrode active material layer 121 is greater than the width of the positive electrode active material layer 111, and the two ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111.

[0100] Figure 8 This is a schematic diagram of the structure of an electrode assembly 10 according to another embodiment of this application. Figure 9 for Figure 8 The diagram shows the structure of the positive electrode 11 and the negative electrode 12 of the electrode assembly 10. Figure 8 and Figure 9 As shown, in some embodiments, the electrode assembly 10 includes a plurality of positive electrode plates 11 and a plurality of negative electrode plates 12, with the plurality of negative electrode plates 12 and the plurality of positive electrode plates 11 alternately stacked along a stacking direction X. The stacking direction X is parallel to the thickness direction of the positive electrode plates 11 and the thickness direction of the negative electrode plates 12. Both the positive electrode plates 11 and the negative electrode plates 12 are generally flat.

[0101] In a direction perpendicular to the stacking direction X, the ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111. In some embodiments, both the negative electrode active material layer 121 and the positive electrode active material layer 111 are generally rectangular; in the length direction of the negative electrode active material layer 121, both ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111; in the width direction of the negative electrode active material layer 121, both ends of the negative electrode active material layer 121 extend beyond the positive electrode active material layer 111.

[0102] The inventors discovered through research that the overhang region poses a risk of lithium plating.

[0103] Specifically, Figures 10 to 14 A schematic diagram showing the migration of lithium ions between the positive electrode 11 and the negative electrode 12 is shown. Figure 10 As shown, the negative electrode active material layer 121 includes an overlapping region S1 and an overhang region S2. The overlapping region S1 overlaps with the positive electrode active material layer 111 in the stacking direction X, and the overhang region S2 is the region of the negative electrode active material layer 121 that extends beyond the positive electrode active material layer 111. During charging, lithium ions Li+ are extracted from the positive electrode active material layer 111 and inserted into the overlapping region S1, as shown... Figure 10 As shown, in the fully charged state, lithium ions are largely embedded in the overlapping region S1.

[0104] After charging and self-discharging, lithium ions undergo self-diffusion and are relatively evenly distributed within the negative electrode active material layer 121, including the overhang region S2; that is, as... Figure 11 As shown, some lithium ions diffuse from the overlapping region S1 to the overhang region S2. This is especially noticeable if stored for a long time while charged.

[0105] After discharging externally for a period of time, such as Figure 12 As shown, lithium ions are extracted from the overlapping region S1 and embedded into the positive electrode active material layer 111.

[0106] The diffusion rate of lithium ions in the positive electrode active material layer 111 is greater than that in the negative electrode active material layer 121. After standing for a period of time, as... Figure 13 As shown, lithium ions in the positive electrode active material layer 111 diffuse and distribute uniformly in the positive electrode active material layer 111; while due to the low diffusion rate of lithium ions in the negative electrode active material layer 121, lithium ions in the overhang region S2 only diffuse to the part of the overlapping region S1 near the overhang region S2.

[0107] During recharging, lithium ions in the positive electrode active material layer 111 are extracted from the positive electrode active material layer 111 and embedded into the overlapping region S1; the portion of the overlapping region S1 near the overhang region S2 must accept both lithium ions diffused from the overhang region S2 and lithium ions extracted from the positive electrode active material layer 111. Figure 14 As shown, after multiple charge-discharge cycles, the portion of the overlapping region S1 near the overhang region S2 may not be able to fully accept lithium ions, leading to the risk of lithium plating.

[0108] In view of this, the inventors made further improvements to the structure of the electrode assembly 10.

[0109] Figure 15This is a partial cross-sectional schematic diagram of an electrode assembly 10 according to an embodiment of this application. Figure 16 This is a partial cross-sectional schematic diagram of the electrode assembly 10 according to another embodiment of this application. Figure 17 This is a partial cross-sectional schematic diagram of the electrode assembly 10 according to another embodiment of this application. Figure 18 This is a partial cross-sectional schematic diagram of the electrode assembly 10 according to another embodiment of this application. Figure 19 This is a partial cross-sectional schematic diagram of an electrode assembly 10 according to another embodiment of this application.

[0110] like Figures 15 to 19 As shown, in some embodiments, the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body portion 1211. One end of the negative electrode edge portion 1212 facing away from the negative electrode main body portion 1211 extends beyond the positive electrode active material layer 111. In the stacking direction X of the positive electrode sheet 11 and the negative electrode sheet 12, at least a portion of the negative electrode edge portion 1212 overlaps with the positive electrode active material layer 111. The negative electrode active material layer 121 is configured such that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode main body portion 1211. And / or, the positive electrode active material layer 111 includes a positive electrode main body portion 1111 and a positive electrode edge portion 1112 connected to the positive electrode main body portion 1111. The positive electrode edge portion 1112 is configured such that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode main body portion 1111.

[0111] If the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212, then the negative electrode edge portion 1212 includes a first portion overlapping with the positive electrode active material layer 111 in the stacking direction X and a second portion extending beyond the positive electrode active material layer 111 (i.e., the second portion is at least a portion of the overhang region); when the unit area capacity of the negative electrode main body portion 1211 meets the setting requirements, that is, the unit area capacity of the negative electrode main body portion 1211 reaches a first preset value, making lithium plating less likely to occur in the negative electrode main body portion 1211; and because The unit area capacity of the negative electrode edge portion 1212 is greater than that of the negative electrode body portion 1211, that is, the unit area capacity of the negative electrode edge portion 1212 is greater than the first preset value, which is equivalent to increasing the unit area capacity of the negative electrode edge portion 1212. This can increase the CB value of the negative electrode edge portion 1212. During cycling, even if the first part needs to receive lithium ions extracted from the positive electrode active material layer 111 and lithium ions diffused from the second part, lithium plating is less likely to occur in the first part, thereby reducing the risk of lithium plating in the negative electrode edge portion 1212.

[0112] If the positive electrode active material layer 111 includes a positive electrode body portion 1111 and a positive electrode edge portion 1112, then the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112 is connected to the portion of the negative electrode active material layer 121 that extends beyond the positive electrode active material layer 111. When the unit area capacity of the positive electrode body 1111 meets the setting requirements, that is, when the unit area capacity of the positive electrode body 1111 reaches the second set value, lithium plating is less likely to occur in the portion of the negative electrode active material layer 121 that overlaps with the positive electrode body 1111. Since the unit area capacity of the positive electrode edge 1112 is less than the unit area capacity of the positive electrode body 1111, that is, the unit area capacity of the positive electrode edge 1112 is less than the second set value, it is equivalent to reducing the unit area capacity of the positive electrode edge 1112. This can increase the CB value of the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge 1112. During cycling, even if the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge 1112 needs to receive lithium ions diffused from the portion of the negative electrode active material layer 121 that extends beyond the positive electrode active material layer 111, lithium plating is less likely to occur in the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge 1112.

[0113] Wherein, CB (Cell Balance) is the ratio of the unit area capacity of the negative electrode active material layer 121 to the unit area capacity of the positive electrode active material layer 111. For example, if the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212, then the CB value of the negative electrode main body portion 1211 = Q1 / Q2, the CB value of the negative electrode edge portion 1212 = Q3 / Q4, the unit area capacity of the negative electrode main body portion 1211 is Q1, the unit area capacity of the portion of the positive electrode active material layer 111 overlapping with the negative electrode main body portion 1211 is Q2, the unit area capacity of the negative electrode edge portion 1212 is Q3, and the unit area capacity of the portion of the positive electrode active material layer 111 overlapping with the negative electrode edge portion 1212 is Q4. For example, if the positive electrode active material layer 111 includes a positive electrode main body portion 1111 and a positive electrode edge portion 1112, then the CB value of the portion of the negative electrode active material layer 121 that overlaps with the positive electrode main body portion 1111 is Q5 / Q6, and the CB value of the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112 is Q7 / Q8. In this case, the unit area capacity of the portion of the negative electrode active material layer 121 that overlaps with the positive electrode main body portion 1111 is Q5, the unit area capacity of the positive electrode main body portion 1111 is Q6, the unit area capacity of the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112 is Q7, and the unit area capacity of the positive electrode edge portion 1112 is Q8.

[0114] If the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212, the negative electrode edge portion 1212 is disposed along the edge of the negative electrode active material layer 121, and the end of the negative electrode edge portion 1212 facing away from the negative electrode main body portion 1211 is the free end of the negative electrode active material layer 121. If the positive electrode active material layer 111 includes a positive electrode main body portion 1111 and a positive electrode edge portion 1112, the positive electrode edge portion 1112 is disposed along the edge of the positive electrode active material layer 111, and the end of the positive electrode edge portion 1112 facing away from the positive electrode main body portion 1111 is the free end of the positive electrode active material layer 111.

[0115] In this embodiment, negative electrode current collector 122 has negative electrode active material layers 121 on both sides. The negative electrode active material layer 121 described in this application refers to a single-sided negative electrode active material layer 121, and the unit area capacity of the negative electrode active material layer 121 refers to the unit area capacity of the negative electrode active material layer 121 on one side of the negative electrode plate 12. Similarly, positive electrode current collector 112 has positive electrode active material layers 111 on both sides. The positive electrode active material layer 111 described in this application refers to a single-sided positive electrode active material layer 111, and the unit area capacity of the positive electrode active material layer 111 refers to the unit area capacity of the positive electrode active material layer 111 on one side of the positive electrode plate 11.

[0116] In this embodiment, the unit area capacity of the negative electrode main body 1211 is the ratio of the active material capacity of the negative electrode main body 1211 to the area of ​​the portion of the negative electrode current collector 122 covered by the negative electrode main body 1211, and the unit area capacity of the negative electrode edge portion 1212 is the ratio of the active material capacity of the negative electrode edge portion 1212 to the area of ​​the portion of the negative electrode current collector 122 covered by the negative electrode edge portion 1212. Similarly, the unit area capacity of the positive electrode main body 1111 is the ratio of the active material capacity of the positive electrode main body 1111 to the area of ​​the portion of the positive electrode current collector 112 covered by the positive electrode main body 1111, and the unit area capacity of the positive electrode edge portion 1112 is the ratio of the active material capacity of the positive electrode edge portion 1112 to the area of ​​the portion of the positive electrode current collector 112 covered by the positive electrode edge portion 1112.

[0117] In some embodiments, such as Figure 15 As shown, the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body portion 1211. One end of the negative electrode edge portion 1212 that is away from the negative electrode main body portion 1211 extends beyond the positive electrode active material layer 111. In the stacking direction X of the positive electrode plate 11 and the negative electrode plate 12, at least a portion of the negative electrode edge portion 1212 overlaps with the positive electrode active material layer 111. The negative electrode active material layer 121 is configured such that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode main body portion 1211.

[0118] At the same thickness, the capacity per unit area of ​​each part of the positive electrode active material layer 111 is the same. Specifically, the positive electrode active material layer 111 is entirely coated with a single active slurry.

[0119] When the negative electrode active material layer 121 is provided with a negative electrode main body portion 1211 and a negative electrode edge portion 1212 having different unit area capacities, the positive electrode active material layer 111 can be formed by coating a single active slurry, thereby simplifying the manufacturing process of the positive electrode sheet 11.

[0120] In this application, the position and number of the negative electrode edge portion 1212 can be set according to requirements.

[0121] In some embodiments, there is one negative electrode edge portion 1212, and the negative electrode edge portion 1212 is located on one side of the negative electrode body portion 1211 along the first direction Y. That is, the negative electrode edge portion 1212 and the negative electrode body portion 1211 are arranged along the first direction Y, and the dimension of the negative electrode edge portion 1212 along the first direction Y is smaller than the dimension of the negative electrode body portion 1211 along the first direction Y. In some embodiments, the negative electrode edge portion 1212 is located on the side of the negative electrode body portion 1211 opposite to the negative electrode tab 1222 along the first direction Y. In some embodiments, the negative electrode edge portion 1212 and the negative electrode body portion 1211 have the same thickness.

[0122] In other embodiments, there are at least two negative electrode edge portions 1212, which are located on opposite sides of the negative electrode body portion 1211 along the first direction Y. The two negative electrode edge portions 1212 can make it less likely for lithium plating to occur in the negative electrode active material layer 121.

[0123] During the forming process of the negative electrode sheet 12, the negative electrode active slurry is first coated onto the negative electrode current collector 122, and then rolled to form the negative electrode active material layer 121. Due to the fluidity and surface tension of the negative electrode active slurry, after the formation of the negative electrode active material layer 121, a thin layer region with a small thickness will be formed at the end of the negative electrode active material layer 121 near the negative electrode tab 1222. In the embodiments of this application, a negative electrode edge portion 1212 is provided at one end of the negative electrode active material layer 121 near the negative electrode tab 1222. Even if the negative electrode edge portion 1212 is thinned during the forming process, the CB value requirement of the negative electrode edge portion 1212 can still be met, reducing the risk of lithium plating. Thus, in the two negative electrode edge portions 1212, at least a portion of the thickness of the negative electrode edge portion 1212 near the negative electrode tab 1222 is less than the thickness of the negative electrode body portion 1211. In some embodiments, the thickness of the negative electrode edge portion 1212 away from the negative electrode tab 1222 is equal to the thickness of the negative electrode body portion 1211.

[0124] During the forming process of the positive electrode sheet 11, the positive active slurry is first coated onto the positive current collector 112, and then rolled to form the positive active material layer 111. Due to the fluidity and surface tension of the positive active slurry, after the positive active material layer 111 is formed, a thin layer region with a small thickness will be formed at the end of the positive active material layer 111 near the positive electrode tab 1122.

[0125] In some embodiments, the positive electrode 11 further includes an insulating layer 113, a portion of which is coated on the positive electrode coating area 1121, and another portion of which is coated on the root of the positive electrode tab 1122 near the positive electrode coating area 1121. The insulating layer 113 can reduce burrs during the cutting of the positive electrode tab 1122, and also improve the insulation performance of the positive electrode tab 1122, reducing the risk of conduction between the root of the positive electrode tab 1122 and the negative electrode 12.

[0126] Lithium ions in the second part can diffuse into the first part. If the size of the first part along the first direction Y is too small, lithium ions in the second part may diffuse into the negative electrode body 1211. Since the capacity per unit area of ​​the negative electrode body 1211 is smaller than that of the first part, it is easy to cause a risk to the negative electrode body 1211. Therefore, in order to reduce the risk of lithium plating, in some embodiments, the size of the first part in the first direction Y is greater than 0.5 mm, that is, the portion of the negative electrode edge 1212 that overlaps with the positive electrode active material layer 111 in the stacking direction X has a size greater than 0.5 mm in the first direction Y.

[0127] In the embodiments of this application, the unit area capacity of the negative electrode edge portion 1212 can be made greater than the unit area capacity of the negative electrode body portion 1211 in a variety of ways.

[0128] In some embodiments, the weight ratio of the active material in the negative electrode edge portion 1212 to the negative electrode edge portion 1212 is greater than the weight ratio of the active material in the negative electrode body portion 1211 to the negative electrode body portion 1211, so that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode body portion 1211. Both the negative electrode edge portion 1212 and the negative electrode body portion 1211 include active material, binder, and conductive agent. By increasing the active material in the negative electrode edge portion 1212, the weight ratio of the active material in the negative electrode edge portion 1212 is increased, thereby increasing the unit area capacity of the negative electrode edge portion 1212, so that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode body portion 1211.

[0129] In some examples, the weight ratio of the active material in the negative electrode edge portion 1212 to the negative electrode edge portion 1212 is 0.5%-20% greater than the weight ratio of the active material in the negative electrode body portion 1211 to the negative electrode body portion 1211, and optionally, 1.5%-12% greater.

[0130] Optionally, the active material in the negative electrode edge portion 1212 is the same as the active material in the negative electrode body portion 1211. Both the active material in the negative electrode edge portion 1212 and the active material in the negative electrode body portion 1211 can be graphite or silicon compounds, etc.

[0131] In this embodiment, the thickness of the negative electrode edge portion 1212 can be set according to its position. For example, the thickness of the negative electrode edge portion 1212 near the negative electrode tab 1222 is less than the thickness of the negative electrode main body portion 1211, and the thickness of the negative electrode edge portion 1212 away from the negative electrode tab 1222 is equal to the thickness of the negative electrode main body portion 1211.

[0132] In other embodiments, the specific capacity of the active material in the negative electrode edge portion 1212 is greater than the specific capacity of the active material in the negative electrode body portion 1211. By increasing the specific capacity of the active material in the negative electrode edge portion 1212, the capacity per unit area of ​​the negative electrode edge portion 1212 can be increased, so that the capacity per unit area of ​​the negative electrode edge portion 1212 is greater than the capacity per unit area of ​​the negative electrode body portion 1211.

[0133] Specific capacity refers to the ratio of the electrical capacity released by an active material to the mass of the active material.

[0134] In this embodiment, the active material in the negative electrode edge portion 1212 is different from the active material in the negative electrode body portion 1211. For example, the active material in the negative electrode edge portion 1212 is a silicon compound, while the active material in the negative electrode body portion 1211 is graphite.

[0135] Optionally, the specific capacity of the active material in the negative electrode edge portion 1212 is 0.5%-20% greater than the specific capacity of the active material in the negative electrode body portion 1211. For example, the specific capacity of the active material in the negative electrode edge portion 1212 is 1.5%-12% greater than the specific capacity of the active material in the negative electrode body portion 1211.

[0136] Optionally, the weight ratio of the active material in the negative electrode edge portion 1212 to the negative electrode edge portion 1212 is equal to the weight ratio of the active material in the negative electrode body portion 1211 to the negative electrode body portion 1211.

[0137] In this embodiment, the thickness of the negative electrode edge portion 1212 can be set according to its position. For example, the thickness of the negative electrode edge portion 1212 near the negative electrode tab 1222 is less than the thickness of the negative electrode main body portion 1211, and the thickness of the negative electrode edge portion 1212 away from the negative electrode tab 1222 is equal to the thickness of the negative electrode main body portion 1211.

[0138] Reference Figure 16 In some embodiments, the negative electrode edge portion 1212 includes a first negative electrode coating 1212a and a second negative electrode coating 1212b stacked along the stacking direction X. Optionally, the second negative electrode coating 1212b is connected between the first negative electrode coating 1212a and the negative electrode current collector 122. Both the first negative electrode coating 1212a and the second negative electrode coating 1212b are active coatings containing active materials.

[0139] In some embodiments, the active material in the first negative electrode coating 1212a is the same as the active material in the negative electrode body 1211; the weight ratio of the active material in the first negative electrode coating 1212a to the active material in the negative electrode body 1211 is equal to the weight ratio of the active material in the negative electrode body 1211 to the negative electrode body 1211. Optionally, the first negative electrode coating 1212a and the negative electrode body 1211 have the same composition, that is, the first negative electrode coating 1212a and the negative electrode body 1211 can be formed from the same negative electrode active slurry, which simplifies the manufacturing process of the negative electrode sheet 12.

[0140] In some embodiments, the weight ratio of the active material in the second negative electrode coating 1212b to the active material in the first negative electrode coating 1212a is greater than the weight ratio of the active material in the first negative electrode coating 1212a. By increasing the active material in the second negative electrode coating 1212b, the weight ratio of the active material in the second negative electrode coating 1212b is increased, thereby increasing the unit area capacity of the negative electrode edge portion 1212, so that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode body portion 1211.

[0141] Optionally, the active material in the second negative electrode coating 1212b is the same as the active material in the first negative electrode coating 1212a. Both the active material in the second negative electrode coating 1212b and the active material in the first negative electrode coating 1212a can be graphite or silicon compounds, etc.

[0142] In this embodiment, the thickness of the negative electrode edge portion 1212 can be set according to its position. For example, the thickness of the negative electrode edge portion 1212 near the negative electrode tab 1222 is less than the thickness of the negative electrode main body portion 1211, and the thickness of the negative electrode edge portion 1212 away from the negative electrode tab 1222 is equal to the thickness of the negative electrode main body portion 1211.

[0143] In other embodiments, the specific capacity of the active material in the second negative electrode coating 1212b is greater than that of the active material in the first negative electrode coating 1212a. By increasing the specific capacity of the active material in the second negative electrode coating 1212b, the unit area capacity of the negative electrode edge portion 1212 is increased, so that the unit area capacity of the negative electrode edge portion 1212 is greater than that of the negative electrode body portion 1211.

[0144] In this application, besides increasing the capacity per unit area of ​​the negative electrode edge 1212, the risk of lithium plating at the negative electrode edge 1212 can also be reduced by improving the kinetic performance of the negative electrode edge 1212. For example, the smaller the particle size of the active material, the easier it is for lithium ions to diffuse, and the less likely they are to accumulate locally. In some embodiments, the particle size of the active material in the negative electrode edge 1212 is smaller than the particle size of the active material in the negative electrode body 1211. Thus, during charging and discharging, lithium ions diffuse more easily in the negative electrode edge 1212, are more evenly distributed in the negative electrode edge 1212, and are less likely to accumulate locally, thereby reducing the risk of lithium plating.

[0145] Reference Figure 17 In some embodiments, the positive electrode active material layer 111 includes a positive electrode body portion 1111 and a positive electrode edge portion 1112 connected to the positive electrode body portion 1111. The positive electrode edge portion 1112 is configured such that its unit area capacity is smaller than that of the positive electrode body portion 1111. At the same thickness, the unit area capacity of each portion of the negative electrode active material layer 121 is the same. Specifically, the negative electrode active material layer 121 is entirely coated with a single active slurry.

[0146] When the positive electrode active material layer 111 is provided with a positive electrode main body portion 1111 and a positive electrode edge portion 1112 having different unit area capacities, the negative electrode active material layer 121 can be formed by coating a single active slurry to simplify the manufacturing process of the negative electrode sheet 12.

[0147] In this application, the position and number of the positive electrode edge portion 1112 can be set according to requirements.

[0148] In some embodiments, there is one positive electrode edge portion 1112, and the positive electrode edge portion 1112 is located on one side of the positive electrode body portion 1111 along the first direction Y. That is, the positive electrode edge portion 1112 and the positive electrode body portion 1111 are arranged along the first direction Y, and the dimension of the positive electrode edge portion 1112 along the first direction Y is smaller than the dimension of the positive electrode body portion 1111 along the first direction Y. In some embodiments, the positive electrode edge portion 1112 is located on the side of the positive electrode body portion 1111 opposite to the positive electrode tab 1122 along the first direction Y. In some embodiments, the positive electrode edge portion 1112 and the positive electrode body portion 1111 have the same thickness.

[0149] In other embodiments, there are at least two positive electrode edge portions 1112, which are located on opposite sides of the positive electrode body portion 1111 along the first direction Y. The two positive electrode edge portions 1112 can make it less likely for lithium plating to occur in the positive electrode active material layer 111.

[0150] In the two positive electrode edge portions 1112, at least a portion of the thickness of the positive electrode edge portion 1112 near the positive electrode tab 1122 is less than the thickness of the positive electrode body portion 1111. The portion of the positive electrode edge portion 1112 that is thinner than the thickness of the positive electrode body portion 1111 constitutes a thin layer region of the positive electrode active material layer 111. In some embodiments, the thickness of the positive electrode edge portion 1112 away from the positive electrode tab 1122 is equal to the thickness of the positive electrode body portion 1111.

[0151] Lithium ions in the portion of the negative electrode active material layer 121 that extends beyond the positive electrode active material layer 111 can diffuse into the portion of the negative electrode active material that overlaps with the positive electrode edge 1112. If the size of the positive electrode edge 1112 in the first direction Y is too small, the size of the portion of the negative electrode active material overlapping with the positive electrode edge 1112 in the first direction Y will also be too small. Lithium ions may diffuse into the portion of the negative electrode active material that overlaps with the positive electrode body 1111. Since the unit area capacity of the positive electrode body 1111 is greater than that of the positive electrode edge 1112, lithium plating may occur in the portion of the negative electrode active material that overlaps with the positive electrode body 1111. Therefore, to reduce the risk of lithium plating, the size of the portion of the negative electrode active material that overlaps with the positive electrode edge 1112 in the first direction Y is greater than 0.5 mm, that is, the size of the positive electrode edge 1112 in the first direction Y is greater than 0.5 mm.

[0152] In the embodiments of this application, the unit area capacity of the positive electrode edge portion 1112 can be made greater than the unit area capacity of the positive electrode body portion 1111 in a variety of ways.

[0153] In some embodiments, the weight ratio of the active material in the positive electrode edge portion 1112 to the positive electrode edge portion 1112 is less than the weight ratio of the active material in the positive electrode body portion 1111 to the positive electrode body portion 1111, so that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode body portion 1111. Both the positive electrode edge portion 1112 and the positive electrode body portion 1111 include active material, binder, and conductive agent. By reducing the amount of active material in the positive electrode edge portion 1112, the weight ratio of the active material in the positive electrode edge portion 1112 is reduced, thereby reducing the unit area capacity of the positive electrode edge portion 1112, so that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode body portion 1111.

[0154] In some examples, the weight ratio of the active material in the positive electrode edge portion 1112 to the positive electrode edge portion 1112 is 0.5%-20% smaller than the weight ratio of the active material in the positive electrode body portion 1111 to the positive electrode body portion 1111, and optionally, 1.5%-12% smaller.

[0155] Optionally, the active material in the positive electrode edge portion 1112 is the same as the active material in the positive electrode body portion 1111. The active material in the positive electrode edge portion 1112 and the active material in the positive electrode body portion 1111 can be lithium iron phosphate, lithium manganese oxide, ternary lithium, lithium cobalt oxide, etc.

[0156] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to its position. For example, the thickness of the positive electrode edge portion 1112 near the positive electrode tab 1122 is less than the thickness of the positive electrode body portion 1111, and the thickness of the positive electrode edge portion 1112 away from the positive electrode tab 1122 is equal to the thickness of the positive electrode body portion 1111.

[0157] In other embodiments, the specific capacity of the active material in the positive electrode edge portion 1112 is less than the specific capacity of the active material in the positive electrode body portion 1111. By reducing the specific capacity of the active material in the positive electrode edge portion 1112, the unit area capacity of the positive electrode edge portion 1112 can be reduced, so that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode body portion 1111.

[0158] In this embodiment, the active material in the positive electrode edge portion 1112 is different from the active material in the positive electrode body portion 1111. For example, the active material in the positive electrode edge portion 1112 is lithium iron phosphate, while the active material in the positive electrode body portion 1111 is ternary lithium.

[0159] Optionally, the specific capacity of the active material in the positive electrode edge portion 1112 is 0.5%-20% smaller than the specific capacity of the active material in the positive electrode body portion 1111. For example, the specific capacity of the active material in the positive electrode edge portion 1112 is 1.5%-12% smaller than the specific capacity of the active material in the positive electrode body portion 1111.

[0160] Optionally, the weight ratio of the active material in the positive electrode edge portion 1112 to the positive electrode edge portion 1112 is equal to the weight ratio of the active material in the positive electrode body portion 1111 to the positive electrode body portion 1111.

[0161] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to its position. For example, the thickness of the positive electrode edge portion 1112 near the positive electrode tab 1122 is less than the thickness of the positive electrode body portion 1111, and the thickness of the positive electrode edge portion 1112 away from the positive electrode tab 1122 is equal to the thickness of the positive electrode body portion 1111.

[0162] Reference Figure 18 The positive electrode edge portion 1112 includes a first positive electrode coating 1112a and a second positive electrode coating 1112b stacked along the stacking direction X. Optionally, the second positive electrode coating 1112b is connected between the first positive electrode coating 1112a and the positive electrode current collector 112.

[0163] In some embodiments, the active material in the first positive electrode coating 1112a is the same as the active material in the positive electrode body 1111; the weight ratio of the active material in the first positive electrode coating 1112a to the active material in the positive electrode body 1111 is equal to the weight ratio of the active material in the positive electrode body 1111 to the positive electrode body 1111. Optionally, the first positive electrode coating 1112a and the positive electrode body 1111 have the same composition, that is, the first positive electrode coating 1112a and the positive electrode body 1111 can be formed from the same positive electrode active slurry, which simplifies the manufacturing process of the positive electrode sheet 11.

[0164] The second positive electrode coating 1112b can be a purely conductive coating, for example, the second positive electrode coating 1112b is a purely conductive coating composed of a binder and a conductive agent; the second positive electrode coating 1112b can also be an active coating containing lithium ions, for example, the second positive electrode coating 1112b is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the second positive electrode coating 1112b can also be an inactive coating containing lithium ions, for example, the second positive electrode coating 1112b is an inactive coating containing lithium ions composed of a binder, a conductive agent and lithium powder coated with lithium carbonate.

[0165] In some embodiments, the weight ratio of the active material in the second positive electrode coating 1112b to the second positive electrode coating 1112b is less than the weight ratio of the active material in the first positive electrode coating 1112a to the first positive electrode coating 1112a. By reducing the active material in the second positive electrode coating 1112b, the weight ratio of the active material in the second positive electrode coating 1112b is reduced, thereby reducing the unit area capacity of the positive electrode edge portion 1112, so that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode body portion 1111. Optionally, the second positive electrode coating 1112b does not contain any active material, that is, the weight ratio of the active material in the second positive electrode coating 1112b to the second positive electrode coating 1112b is 0.

[0166] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to its position. For example, the thickness of the positive electrode edge portion 1112 near the positive electrode tab 1122 is less than the thickness of the positive electrode body portion 1111, and the thickness of the positive electrode edge portion 1112 away from the positive electrode tab 1122 is equal to the thickness of the positive electrode body portion 1111.

[0167] In other embodiments, the specific capacity of the active material in the second positive electrode coating 1112b is less than the specific capacity of the active material in the first positive electrode coating 1112a. By reducing the specific capacity of the active material in the second positive electrode coating 1112b, the unit area capacity of the positive electrode edge portion 1112 is reduced, so that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode body portion 1111.

[0168] In this application, besides reducing the unit area capacity of the positive electrode edge portion 1112, the risk of lithium deposition in the negative electrode active material layer 121 can also be reduced by adjusting the kinetic properties of the positive electrode edge portion 1112. In some embodiments, the particle size of the active material in the positive electrode edge portion 1112 is larger than the particle size of the active material in the positive electrode body portion 1111. Thus, during charging and discharging, lithium ions are less likely to diffuse in the positive electrode edge portion 1112, the rate at which lithium ions diffuse from the positive electrode body portion 1111 to the positive electrode edge portion 1112 is reduced, and the rate at which lithium ions are extracted from the positive electrode edge portion 1112 is also reduced. This reduces the risk of lithium ions accumulating in the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112, making lithium deposition in the negative electrode active material layer 121 less likely.

[0169] In some embodiments, such as Figure 19 As shown, the negative electrode active material layer 121 includes a negative electrode main body portion 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body portion 1211. One end of the negative electrode edge portion 1212 facing away from the negative electrode main body portion 1211 extends beyond the positive electrode active material layer 111. In the stacking direction X of the positive electrode sheet 11 and the negative electrode sheet 12, at least a portion of the negative electrode edge portion 1212 overlaps with the positive electrode active material layer 111. The negative electrode active material layer 121 is configured such that the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode main body portion 1211. The positive electrode active material layer 111 includes a positive electrode main body portion 1111 and a positive electrode edge portion 1112 connected to the positive electrode main body portion 1111. The positive electrode edge portion 1112 is configured such that the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode main body portion 1111.

[0170] In the embodiments of this application, the unit area capacity of the negative electrode edge portion 1212 can be made greater than that of the negative electrode body portion 1211 by increasing the weight ratio of the active material in the negative electrode edge portion 1212, increasing the specific capacity of the active material in the negative electrode edge portion 1212, or by other means. Similarly, the unit area capacity of the positive electrode edge portion 1112 can be made smaller than that of the positive electrode body portion 1111 by decreasing the weight ratio of the active material in the positive electrode edge portion 1112, decreasing the specific capacity of the active material in the positive electrode edge portion 1112, or by other means.

[0171] In some embodiments, the positive electrode edge portion 1112 and the negative electrode edge portion 1212 at least partially overlap in the superposition direction X. In some embodiments, a portion of the positive electrode edge portion 1112 overlaps with the negative electrode body portion 1211 in the superposition direction X.

[0172] When the unit area capacity of the negative electrode main body 1211 and the unit area capacity of the positive electrode main body 1111 meet the requirements, the unit area capacity of the negative electrode edge portion 1212 is greater than that of the negative electrode main body 1211, and the unit area capacity of the positive electrode edge portion 1112 is less than that of the positive electrode main body 1111. This can increase the CB value of the negative electrode edge portion 1212 and the CB value of the portion of the negative electrode main body 1211 that overlaps with the positive electrode edge portion 1112, thereby making it less likely for lithium to be deposited in the negative electrode active material layer 121.

[0173] Figure 20 This is a top view schematic diagram of the negative electrode plate 12 of the electrode assembly 10 according to an embodiment of this application. Figure 20 As shown, in some embodiments, the negative electrode edge portion 1212 is disposed around the negative electrode body portion 1211, which can increase the range of the negative electrode edge portion 1212 and make it less likely for lithium to be deposited on the negative electrode active material layer 121.

[0174] Figure 21 This is a top view schematic diagram of the positive electrode plate 11 of the electrode assembly 10 according to an embodiment of this application. Figure 21 As shown, in some embodiments, the positive electrode edge portion 1112 is disposed around the positive electrode body portion 1111, which can increase the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112, making it less likely for lithium to be deposited on the negative electrode active material layer 121.

[0175] The testing steps for unit area capacity and CB value are as follows:

[0176] Step 1): Average discharge capacity test of the positive electrode single-sided active material layer. Take the positive electrode sheets from the above embodiments and obtain small discs 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 the 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 six 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. Taking the area of ​​the small disc containing the single-sided active material layer of the positive electrode as the unit area, the average discharge capacity of the single-sided active material layer of the positive electrode is the unit area capacity of the single-sided active material layer of the positive electrode.

[0177] Step 2): Average charging capacity test of the single-sided active material layer of the negative electrode. Take the negative electrode sheet from 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 active material 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 single-sided active material layer of the negative electrode. 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. Using the area of ​​the small disc containing the single-sided active material layer of the negative electrode as the unit area, the average charging capacity of the single-sided active material layer of the negative electrode is the unit area capacity of the single-sided active material layer of the negative electrode.

[0178] Step 3): Calculate the CB value based on the formula: CB value = average charging capacity (mAh) of the above negative electrode single-sided active material layer / average discharging capacity (mAh) of the above positive electrode single-sided active material layer.

[0179] Figure 22 A flowchart illustrating a method for manufacturing an electrode assembly provided in some embodiments of this application. For example... Figure 22 As shown, in some embodiments, the method of manufacturing the electrode assembly includes:

[0180] S100: Provides positive electrode plates;

[0181] S200: Provides negative electrode plates;

[0182] S300: The positive electrode and the negative electrode are stacked so that the positive active material layer of the positive electrode is facing the negative active material layer of the negative electrode, and the end of the negative active material layer extends beyond the positive active material layer.

[0183] The negative electrode active material layer includes a negative electrode main body and a negative electrode edge connected to the negative electrode main body. One end of the negative electrode edge, which is away from the negative electrode main body, extends beyond the positive electrode active material layer. In the stacking direction of the positive electrode sheet and the negative electrode sheet, at least a portion of the negative electrode edge overlaps with the positive electrode active material layer. The negative electrode active material layer is configured such that the unit area capacity of the negative electrode edge is greater than the unit area capacity of the negative electrode main body. And / or, the positive electrode active material layer includes a positive electrode main body and a positive electrode edge connected to the positive electrode main body. The positive electrode edge is configured such that the unit area capacity of the positive electrode edge is less than the unit area capacity of the positive electrode main body.

[0184] It should be noted that the relevant structure of the electrode assembly manufactured by the above-described electrode assembly manufacturing method can be found in the electrode assemblies provided in the above embodiments.

[0185] When assembling the electrode assembly based on the above-described manufacturing method, the steps do not necessarily need to be performed sequentially. That is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously. For example, steps S100 and S200 can be performed concurrently without any order.

[0186] Please refer to Figure 23 , Figure 23 This is a schematic block diagram of an electrode assembly manufacturing system provided in some embodiments of this application. The electrode assembly manufacturing system includes: a first providing device 91 for providing a positive electrode sheet; a second providing device 92 for providing a negative electrode sheet; and an assembly device 93 for stacking the positive electrode sheet and the negative electrode sheet so that the positive active material layer of the positive electrode sheet and the negative active material layer of the negative electrode sheet are arranged facing each other, and the end of the negative active material layer extends beyond the positive active material layer.

[0187] The negative electrode active material layer includes a negative electrode main body and a negative electrode edge connected to the negative electrode main body. One end of the negative electrode edge, which is away from the negative electrode main body, extends beyond the positive electrode active material layer. In the stacking direction of the positive electrode sheet and the negative electrode sheet, at least a portion of the negative electrode edge overlaps with the positive electrode active material layer. The negative electrode active material layer is configured such that the unit area capacity of the negative electrode edge is greater than the unit area capacity of the negative electrode main body. And / or, the positive electrode active material layer includes a positive electrode main body and a positive electrode edge connected to the positive electrode main body. The positive electrode edge is configured such that the unit area capacity of the positive electrode edge is less than the unit area capacity of the positive electrode main body.

[0188] In some embodiments, the manufacturing system further includes a third providing device (not shown) for providing a separator that isolates the positive electrode and the negative electrode. An assembly device is used to stack the positive electrode, the separator, and the negative electrode.

[0189] The structure of the electrode assembly manufactured by the above manufacturing system can be found in the electrode assemblies provided in the above embodiments.

[0190] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0191] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode assembly, characterized in that, This includes positive and negative electrode plates that are stacked together; The positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector includes a positive coating area and a positive electrode tab. The positive active material layer is at least partially coated on the positive coating area. The positive electrode tab is connected to the end of the positive coating area along a first direction, which is perpendicular to the stacking direction of the positive electrode sheet and the negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative active material layer coated on the surface of the negative current collector. The positive active material layer and the negative active material layer are disposed opposite each other. In the first direction, both ends of the negative active material layer extend beyond the positive active material layer. The positive electrode active material layer includes a positive electrode body portion and a positive electrode edge portion. The positive electrode body portion is provided on the side away from the positive electrode tab along the first direction. The positive electrode edge portion is configured such that the unit area capacity of the positive electrode edge portion is smaller than the unit area capacity of the positive electrode body portion.

2. The electrode assembly according to claim 1, characterized in that, The positive electrode edge portion is at least two, and the two positive electrode edge portions are respectively located on both sides of the positive electrode body portion along the first direction.

3. The electrode assembly according to claim 2, characterized in that, In the two positive electrode edge portions, at least a portion of the thickness of the positive electrode edge portion closer to the positive electrode tab is less than the thickness of the positive electrode body portion.

4. The electrode assembly according to claim 1, characterized in that, The weight ratio of the active material at the edge of the positive electrode to the weight ratio of the active material at the edge of the positive electrode to the weight ratio of the active material at the body of the positive electrode is less than that at the body of the positive electrode, so that the unit area capacity of the edge of the positive electrode is less than that of the body of the positive electrode.

5. The electrode assembly according to claim 1, characterized in that, The specific capacity of the active material at the edge of the positive electrode is less than that of the active material in the main body of the positive electrode, so that the unit area capacity of the positive electrode edge is less than that of the main body of the positive electrode.

6. The electrode assembly according to claim 1, characterized in that, The positive electrode edge portion includes a first positive electrode coating and a second positive electrode coating stacked along the stacking direction; The weight ratio of the active material in the second positive electrode coating to the second positive electrode coating is less than the weight ratio of the active material in the first positive electrode coating to the first positive electrode coating; or, the specific capacity of the active material in the second positive electrode coating is less than the specific capacity of the active material in the first positive electrode coating.

7. The electrode assembly according to claim 1, characterized in that, The particle size of the active material at the edge of the positive electrode is larger than that of the active material in the main body of the positive electrode.

8. The electrode assembly according to claim 1, characterized in that, The dimension of the positive electrode edge portion in the first direction is greater than 0.5 mm.

9. The electrode assembly according to claim 1, characterized in that, The positive electrode edge portion is arranged around the positive electrode body portion.

10. The electrode assembly according to claim 1, characterized in that, The negative electrode active material layer includes a negative electrode body portion and a negative electrode edge portion connected to the negative electrode body portion. One end of the negative electrode edge portion, facing away from the negative electrode body portion, extends beyond the positive electrode active material layer. In the stacking direction of the positive electrode sheet and the negative electrode sheet, at least a portion of the negative electrode edge portion overlaps with the positive electrode active material layer. The negative electrode active material layer is configured such that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

11. The electrode assembly according to claim 10, characterized in that, The positive electrode edge portion located on the side of the positive electrode body portion away from the positive electrode tab along the first direction at least partially overlaps with the negative electrode body portion in the superposition direction.

12. The electrode assembly according to claim 10, characterized in that, The positive electrode edge portion located on the side of the positive electrode body portion facing away from the positive electrode tab along the first direction at least partially overlaps with the negative electrode edge portion in the superposition direction.

13. The electrode assembly according to claim 10, characterized in that, The weight ratio of the active material in the negative electrode edge portion to the negative electrode edge portion is greater than the weight ratio of the active material in the negative electrode body portion to the negative electrode body portion, so that the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode body portion.

14. The electrode assembly according to claim 10, characterized in that, The specific capacity of the active material in the negative electrode edge portion is greater than that in the negative electrode body portion, so that the unit area capacity of the negative electrode edge portion is greater than that of the negative electrode body portion.

15. The electrode assembly according to claim 10, characterized in that, The negative electrode edge portion includes a first negative electrode coating and a second negative electrode coating stacked along the stacking direction; The weight ratio of the active material in the second negative electrode coating to the second negative electrode coating is greater than the weight ratio of the active material in the first negative electrode coating to the first negative electrode coating; or, the specific capacity of the active material in the second negative electrode coating is greater than the specific capacity of the active material in the first negative electrode coating.

16. The electrode assembly according to claim 10, characterized in that, The particle size of the active material in the edge portion of the negative electrode is smaller than that of the active material in the main body portion of the negative electrode.

17. The electrode assembly according to claim 10, characterized in that, The negative electrode sheet includes a negative current collector, the negative current collector includes a negative electrode coating area and a negative electrode tab, the negative electrode active material layer is at least partially coated on the negative electrode coating area, and the negative electrode tab is connected to the end of the negative electrode coating area along a first direction, the first direction being perpendicular to the stacking direction; The negative electrode body portion has the negative electrode edge portion on the side close to the negative electrode tab along the first direction.

18. The electrode assembly according to claim 17, characterized in that, There are at least two negative electrode edge portions, and the two negative electrode edge portions are respectively located on both sides of the negative electrode body portion along the first direction.

19. The electrode assembly according to claim 18, characterized in that, In the two negative electrode edges, at least a portion of the thickness of the negative electrode edge closer to the negative electrode tab is less than the thickness of the negative electrode body, and the thickness of the negative electrode edge farther from the negative electrode tab is equal to the thickness of the negative electrode body.

20. The electrode assembly according to claim 10, characterized in that, The portion of the negative electrode edge that overlaps with the positive electrode active material layer in the stacking direction has a dimension greater than 0.5 mm in the first direction.

21. The electrode assembly according to claim 10, characterized in that, The negative electrode edge portion is arranged around the negative electrode body portion.

22. The electrode assembly according to any one of claims 10-21, characterized in that, The negative electrode edge portion includes a first portion and a second portion, the first portion overlapping the positive electrode active material layer in the stacking direction, and the second portion extending beyond the positive electrode active material layer.

23. A single battery cell, characterized in that, include: shell; At least one electrode assembly as described in any one of claims 1-22 is housed in the housing.

24. A battery, characterized in that, include: Box; At least one battery cell as described in claim 23, wherein the battery cell is housed within the casing.

25. An electrical appliance, characterized in that, Includes the battery of claim 24, the battery being used to provide electrical energy.

Images