Electrode assembly, battery cell, battery and electric equipment

Abstract

The invention provides an electrode assembly, a battery monomer, a battery and electric equipment. The electrode assembly comprises a positive pole piece and a negative pole piece which are arranged in a stacked mode. The positive pole piece comprises a positive current collector and a positive active material layer, the positive current collector comprises a positive coating area and a positive pole lug, the positive active material layer is at least partially coated on the positive coating area, the positive pole lug is connected to the end part of the positive coating area along a first direction, and the first direction is perpendicular to the overlapping direction of the positive pole piece and the negative pole piece. The positive pole piece comprises a positive active material layer, the negative pole piece comprises a negative active material layer, the positive active material layer and the negative active material layer are oppositely arranged, and in the first direction, the two ends of the negative active material layer both exceed the positive active material layer. The positive electrode active material layer comprises a positive electrode main body part and a positive electrode edge part, the positive electrode edge part is arranged on one side, deviating from the positive electrode tab in the first direction, of the positive electrode main body part, and the positive electrode edge part is configured as follows: the unit area capacity of the positive electrode edge part is smaller than that of the positive electrode main body part.

Description

[0001] This application is a divisional application based on the application number 202180035399.5, the application date February 4, 2021, the applicant is Contemporary Amperex Technology Co., Ltd., and the application name is "Electrode assembly and its manufacturing method and manufacturing system, battery cell and battery". Technical Field

[0002] The present 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 Art

[0003] Rechargeable batteries, also known as secondary batteries, are batteries that can be recharged to activate the active material after the battery is discharged and continue to be used. Rechargeable batteries are widely used in electronic devices such as mobile phones, laptops, battery cars, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and electric tools, etc.

[0004] In the development of battery technology, in addition to improving battery performance, safety is also an issue that cannot be ignored. If the safety of the battery cannot be guaranteed, the battery cannot be used. Therefore, how to enhance the safety of the battery is a technical problem that needs to be solved urgently in battery technology. Summary of the invention

[0005] The present application provides an electrode assembly, a battery cell, a battery, and an electrical device, which can enhance the safety of the battery.

[0006] In the first aspect, the embodiment of the present application provides an electrode assembly, which includes a positive electrode sheet and a negative electrode sheet arranged in a stacked manner. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode current collector includes a positive electrode coating area and a positive electrode ear, the positive electrode active material layer is at least partially coated on the positive electrode coating area, and the positive electrode ear 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 includes a negative electrode current collector and a negative electrode active material layer coated on the surface of the negative electrode current collector, the positive electrode active material layer and the negative electrode active material layer are arranged opposite to each other, 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 includes a positive electrode main body and a positive electrode edge portion, and a positive electrode edge portion is provided on the side of the positive electrode main body away from the positive electrode ear along the first direction, 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 main body.

[0007] When the capacity per unit area of ​​the positive electrode main body meets the setting requirements, the portion of the negative electrode active material layer overlapping with the positive electrode main body can be made less likely to undergo lithium deposition; since the capacity per unit area of ​​the positive electrode edge portion is less than that of the positive electrode main body, it is equivalent to reducing the capacity per unit area of ​​the positive electrode edge portion, thereby increasing the CB value of the portion of the negative electrode active material layer overlapping with the positive electrode edge portion. During the cycle, even if the portion of the negative electrode active material layer overlapping with the positive electrode edge portion needs to accept lithium ions diffused from the portion of the negative electrode active material layer that exceeds the positive electrode active material layer, the portion of the negative electrode active material layer overlapping with the positive electrode edge portion can be made less likely to undergo lithium deposition.

[0008] In some embodiments, the thickness of at least a portion of the positive electrode edge portion is less than the thickness of the positive electrode main body portion. By reducing the thickness of at least a portion of the positive electrode edge portion, the unit area capacity of the positive electrode edge portion can be reduced.

[0009] In some embodiments, the thickness of the positive electrode edge portion gradually decreases in a direction away from the positive electrode main body portion.

[0010] In some embodiments, the active material of the positive electrode edge portion is the same as the active material of the positive electrode main body portion, and the weight ratio of the active material of the positive electrode edge portion to the positive electrode edge portion is equal to the weight ratio of the active material of the positive electrode main body portion to the positive electrode main body portion. The entire positive electrode active material layer can be coated with a single active slurry.

[0011] In some embodiments, there are at least two positive electrode edge portions, and the two positive electrode edge portions are respectively located on both sides of the positive electrode main body along the first direction. The two positive electrode edge portions further reduce the risk of lithium plating.

[0012] In some embodiments, among the two positive electrode edge portions, at least a portion of the positive electrode edge portion close to the positive electrode tab has a thickness that is smaller than a thickness of the positive electrode main body portion.

[0013] In some embodiments, the weight ratio of the active material in the positive electrode edge portion to the positive electrode edge portion is less than the weight ratio of the active material in the positive electrode main body portion to the positive electrode main body portion, so that the capacity per unit area of ​​the positive electrode edge portion is less than the capacity per unit area of ​​the positive electrode main body portion. By reducing the active material in the positive electrode edge portion, the weight ratio of the active material in the positive electrode edge portion is reduced, and the capacity per unit area of ​​the positive electrode edge portion is reduced, so that the capacity per unit area of ​​the positive electrode edge portion is less than the capacity per unit area of ​​the positive electrode main body portion.

[0014] In some embodiments, the gram capacity of the active material in the positive electrode edge portion is less than the gram capacity of the active material in the positive electrode main body portion, so that the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode main body portion. By reducing the gram capacity of the active material in the positive electrode edge portion, the unit area capacity of the positive electrode edge portion can be reduced, so that the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode main body portion.

[0015] In some embodiments, the positive electrode edge portion includes a first positive electrode coating and a second positive electrode coating stacked in a 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. By reducing the active material in the second positive electrode coating, the weight ratio of the active material in the second positive electrode coating is reduced, and then 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 main body. In other embodiments, the gram capacity of the active material in the second positive electrode coating is less than the gram capacity of the active material in the first positive electrode coating, and by reducing the gram capacity of the 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 main body.

[0016] In some embodiments, the particle size of the active material in the positive electrode edge portion is larger than the particle size of the active material in the positive electrode main body portion. During the charge and discharge process, lithium ions are not easily diffused in the positive electrode edge portion, the rate at which lithium ions in the positive electrode main body diffuse into the positive electrode edge portion is reduced, and the rate at which lithium ions escape from the positive electrode edge portion is also reduced, which can reduce the risk of lithium ions gathering in the portion of the negative electrode active material layer that overlaps with the positive electrode edge portion, making it difficult for the negative electrode active material layer to precipitate lithium.

[0017] In some embodiments, the size of the positive electrode edge portion in the first direction is greater than 0.5 mm, which can reduce the risk of lithium analysis in the portion of the negative electrode active material overlapping with the positive electrode main body portion.

[0018] In some embodiments, the positive electrode edge portion is arranged around the positive electrode main body portion, which can increase the overlap portion of the negative electrode active material layer with the positive electrode edge portion, making it less likely for lithium to be deposited in the negative electrode active material layer.

[0019] In some embodiments, the negative electrode active material layer includes a negative electrode main body and a negative electrode edge portion connected to the negative electrode main body, one end of the negative electrode edge portion facing away from the negative electrode main body exceeds the positive electrode active material layer, and 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, and the negative electrode active material layer is configured as follows: the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode main body.

[0020] The edge of the negative electrode includes a first portion overlapping with the positive electrode active material layer in the superposition direction and a second portion exceeding the positive electrode active material layer. When the capacity per unit area of ​​the negative electrode main body meets the setting requirements, that is, the capacity per unit area of ​​the negative electrode main body reaches the first preset value, the negative electrode main body is not prone to lithium deposition; and because the capacity per unit area of ​​the negative electrode edge is greater than the capacity per unit area of ​​the negative electrode main body, that is, the capacity per unit area of ​​the negative electrode edge is greater than the first preset value, it is equivalent to increasing the capacity per unit area of ​​the negative electrode edge, so that the CB value of the negative electrode edge can be increased. During the cycle, even if the first part needs to accept lithium ions released from the positive electrode active material layer and lithium ions diffused from the second part, the first part is not prone to lithium deposition, thereby reducing the risk of lithium deposition at the edge of the negative electrode.

[0021] 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 the first direction at least partially overlaps with the negative electrode body portion in the stacking direction.

[0022] In some embodiments, the positive electrode edge portion located on the side of the positive electrode main body portion away from the positive electrode tab along the first direction at least partially overlaps with the negative electrode edge portion in the stacking direction.

[0023] 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 main body portion to the negative electrode main body portion, so that the capacity per unit area of ​​the negative electrode edge portion is greater than the capacity per unit area of ​​the negative electrode main body portion. By increasing the active material in the negative electrode edge portion, the weight ratio of the active material in the negative electrode edge portion is increased, and the capacity per unit area of ​​the negative electrode edge portion is increased, so that the capacity per unit area of ​​the negative electrode edge portion is greater than the capacity per unit area of ​​the negative electrode main body portion.

[0024] In some embodiments, the gram capacity of the active material in the edge portion of the negative electrode is greater than the gram capacity of the active material in the main body of the negative electrode, so that the unit area capacity of the edge portion of the negative electrode is greater than the unit area capacity of the main body of the negative electrode. By increasing the gram capacity of the active material in the edge portion of the negative electrode, the unit area capacity of the edge portion of the negative electrode can be increased, so that the unit area capacity of the edge portion of the negative electrode is greater than the unit area capacity of the main body of the negative electrode.

[0025] In some embodiments, the negative electrode edge portion includes a first negative electrode coating and a second negative electrode coating stacked in a 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 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 main body. In other embodiments, the gram capacity of the active material in the second negative electrode coating is greater than the gram capacity of the active material in the first negative electrode coating; by increasing the gram 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 main body.

[0026] In some embodiments, the particle size of the active material in the edge of the negative electrode is smaller than that of the active material in the main body of the negative electrode. During the charge and discharge process, lithium ions are more easily diffused in the edge of the negative electrode, and are more evenly distributed in the edge of the negative electrode, and are less likely to gather locally at the edge of the negative electrode, thereby reducing the risk of lithium precipitation.

[0027] In some embodiments, the thickness of at least a portion of the negative electrode edge portion is less than the thickness of the negative electrode main body portion. By reducing the thickness of at least a portion of the negative electrode edge portion, the unit area capacity of the negative electrode edge portion can be reduced.

[0028] In some embodiments, the thickness of the edge portion of the negative electrode gradually decreases in a direction away from the main portion of the negative electrode.

[0029] In some embodiments, the negative electrode sheet includes a negative electrode current collector, the negative electrode 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, the negative electrode tab is connected to the end of the negative electrode coating area along a first direction, and the first direction is perpendicular to the stacking direction. A negative electrode edge portion is provided on one side of the negative electrode main body portion close to the negative electrode tab along the first direction.

[0030] In some embodiments, 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 main body along the first direction. By providing two negative electrode edge portions, the risk of lithium chromatography of the negative electrode active material can be further reduced.

[0031] In some embodiments, among the two negative electrode edge portions, at least a portion of the thickness of the negative electrode edge portion close to the negative electrode tab is less than the thickness of the negative electrode main body, and the thickness of the negative electrode edge portion away from the negative electrode tab is equal to the thickness of the negative electrode main body.

[0032] In some embodiments, the portion of the negative electrode edge portion that overlaps with the positive electrode active material layer in the stacking direction has a size in the first direction greater than 0.5 mm to reduce the risk of lithium plating of the negative electrode active material.

[0033] In some embodiments, the negative electrode edge portion is arranged around the negative electrode main body portion to increase the range of the negative electrode edge portion, so that lithium deposition is less likely to occur in the negative electrode active material layer.

[0034] In some embodiments, the negative electrode edge portion includes a first portion and a second portion, the first portion overlaps the positive electrode active material layer in a stacking direction, and the second portion exceeds the positive electrode active material layer.

[0035] In a second aspect, an embodiment of the present application provides a battery cell, comprising a housing and an electrode assembly provided by any embodiment of the first aspect, wherein the electrode assembly is accommodated in the housing.

[0036] In a third aspect, an embodiment of the present application provides a battery, comprising: a box body and a battery cell provided by any embodiment of the second aspect, wherein the battery cell is accommodated in the box body.

[0037] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes a battery provided by any embodiment of the third aspect above, and the battery is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0039] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0040] Figure 2 An exploded schematic diagram of a battery provided in some embodiments of the present application;

[0041] Figure 3 for Figure 2 A schematic diagram of the structure of the battery module shown;

[0042] Figure 4 for Figure 3 An exploded schematic diagram of a battery cell is shown;

[0043] Figure 5 This is a schematic structural diagram of an electrode assembly according to an embodiment of the present application;

[0044] Figure 6 for Figure 5 A partial cross-sectional schematic diagram of the electrode assembly shown along line AA;

[0045] Figure 7 for Figure 5A schematic diagram of the positive electrode sheet and the negative electrode sheet in the unfolded state is shown;

[0046] Figure 8 This is a schematic structural diagram of an electrode assembly according to another embodiment of the present application;

[0047] Fig. 9 for Figure 8 A schematic diagram of the structure of the positive electrode sheet and the negative electrode sheet of the electrode assembly shown;

[0048] Figures 10 to 14 A schematic diagram showing the migration of lithium ions between the positive electrode sheet and the negative electrode sheet;

[0049] Fig.15 A partial cross-sectional schematic diagram of an electrode assembly according to an embodiment of the present application;

[0050] Fig.16 A partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of the present application;

[0051] Fig.17 A partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of the present application;

[0052] Fig.18 A partial cross-sectional schematic diagram of an electrode assembly according to yet another embodiment of the present application;

[0053] Fig.19 A partial cross-sectional schematic diagram of an electrode assembly according to another embodiment of the present application;

[0054] Fig. 20 A schematic top view of a negative electrode sheet of an electrode assembly according to an embodiment of the present application;

[0055] Fig.21 A schematic top view of a positive electrode sheet of an electrode assembly according to an embodiment of the present application;

[0056] Fig. 22 A flow chart of a method for manufacturing an electrode assembly provided in some embodiments of the present application;

[0057] Fig.23 A schematic block diagram of a manufacturing system for an electrode assembly provided in some embodiments of the present application.

[0058] In the drawings, the drawings are not drawn to scale. DETAILED DESCRIPTION

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

[0060] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

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

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

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

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

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

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

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

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

[0069] When an external power source is used to charge a battery cell, the electrons e on the positive electrode run to the negative electrode through an external circuit, and the lithium ions Li+ escape from the active material particles in the positive electrode active material layer and enter the electrode liquid, passing through the tiny pores on the isolation membrane and moving to the negative electrode, where they combine with the electrons that have already run over and enter the active material particles in the negative electrode active material layer. If the negative electrode active material layer does not have a position to accept lithium ions, the lithium ions will precipitate on the surface of the negative electrode active material layer, forming lithium dendrites that pierce the isolation membrane, causing a short circuit in the battery cell and triggering thermal runaway. Therefore, when designing an electrode assembly, it is necessary to ensure that the negative electrode active material layer is excessive to reduce the risk of lithium precipitation.

[0070] Taking into account the reasons such as the assembly accuracy of the electrode assembly, the end of the negative active material layer needs to extend beyond the positive active material layer to reduce the risk that the negative active material layer cannot completely cover the positive active material layer due to assembly errors. At this time, the negative active material layer has an overlapping area overlapping with the positive active material layer and an overhang area that extends beyond the positive active material layer. The inventors found that the overhang area will cause lithium ions to diffuse there and remain, especially if it is kept for a long time in the charged state. After discharge, adding a small current constant voltage discharge can make the residual lithium ions in the overhang area diffuse back to the overlapping area to play a role. However, the diffusion of lithium ions between the overlapping area and the overhang area will also cause the risk of lithium precipitation.

[0071] In view of this, an embodiment of the present application provides an electrode assembly, including a positive electrode sheet and a negative electrode sheet that are stacked, the positive electrode active material layer of the positive electrode sheet and the negative electrode active material layer of the negative electrode sheet are arranged opposite to each other, and the end of the negative electrode active material layer exceeds the positive electrode active material layer. The negative electrode active material layer includes a negative electrode main body and a negative electrode edge portion connected to the negative electrode main body, and one end of the negative electrode edge portion away from the negative electrode main body exceeds the positive electrode active material layer, and in the stacking direction of the positive electrode sheet and the negative electrode sheet, at least a part of the negative electrode edge portion overlaps with the positive electrode active material layer, and the negative electrode active material layer is configured as follows: the unit area capacity of the negative electrode edge portion 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 portion connected to the positive electrode main body, and the positive electrode edge portion is configured as follows: the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode main body. This structure can reduce the risk of lithium plating and enhance the safety of the battery.

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

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

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

[0075] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1 provided in some embodiments of the present application. A battery 2 is disposed inside the vehicle 1. The battery 2 may be disposed at the bottom, head, or tail of the vehicle 1. The battery 2 may be used to power the vehicle 1. For example, the battery 2 may be used as an operating power source for the vehicle 1.

[0076] The vehicle 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery 2 to supply power to the motor 4 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1 .

[0077] In some embodiments of the present application, the battery 2 can not only serve as an operating power source for the vehicle 1, but also serve as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0078] Please refer to Figure 2 , Figure 2 The exploded diagram of the battery 2 provided in some embodiments of the present application, the battery 2 includes a box 5 and a battery cell ( Figure 2 The battery cells are contained in the box body 5.

[0079] The box 5 is used to accommodate the battery cells, and the box 5 can be of various structures. In some embodiments, the box 5 can include a first box portion 51 and a second box portion 52, the first box portion 51 and the second box portion 52 cover each other, and the first box portion 51 and the second box portion 52 jointly define a storage space 53 for accommodating the battery cells. The second box portion 52 can be a hollow structure with one end open, the first box portion 51 is a plate-like structure, and the first box portion 51 covers the open side of the second box portion 52 to form a box 5 with a storage space 53; the first box portion 51 and the second box portion 52 can also be hollow structures with one side open, and the open side of the first box portion 51 covers the open side of the second box portion 52 to form a box 5 with a storage space 53. Of course, the first box portion 51 and the second box portion 52 can be of various shapes, such as a cylinder, a cuboid, etc.

[0080] In order to improve the sealing performance after the first box body 51 and the second box body 52 are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 51 and the second box body 52 .

[0081] Assuming that the first box body portion 51 covers the top of the second box body portion 52 , the first box body portion 51 can also be referred to as an upper box cover, and the second box body portion 52 can also be referred to as a lower box body.

[0082] In the battery 2, there can be one or more battery cells. If there are multiple battery cells, the multiple battery cells can be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells are both connected in series and in parallel. The multiple battery cells can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells is accommodated in the box 5; of course, multiple battery cells can also be connected in series, in parallel, or in mixed connection to form a battery module 6, and the multiple battery modules 6 are then connected in series, in parallel, or in mixed connection to form a whole, and accommodated in the box 5.

[0083] In some embodiments, please refer to Figure 3 , Figure 3 for Figure 2 The schematic diagram of the structure of the battery module 6 is shown. There are multiple battery cells, which are first connected in series, in parallel or in mixed connection to form the battery module 6. The multiple battery modules 6 are then connected in series, in parallel or in mixed connection to form a whole, and are accommodated in the box.

[0084] The multiple battery cells 7 in the battery module 6 can be electrically connected through a busbar component to achieve parallel connection, series connection or mixed connection of the multiple battery cells 7 in the battery module 6 .

[0085] Please refer to Figure 4 , Figure 4 for Figure 3The exploded schematic diagram of the battery cell 7 is shown. The battery cell 7 provided in the embodiment of the present application comprises an electrode assembly 10 and a housing 20 , wherein the electrode assembly 10 is accommodated in the housing 20 .

[0086] In some embodiments, the housing 20 may also be used to contain electrolyte, such as electrolyte. The housing 20 may be in various structural forms.

[0087] In some embodiments, the housing 20 may include a shell 21 and an end cap 22, wherein the shell 21 is a hollow structure with one side open, and the end cap 22 covers the opening of the shell 21 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte.

[0088] When assembling the battery cell 7 , the electrode assembly 10 may be placed into the housing 21 first, and then the end cover 22 may be closed on the opening of the housing 21 , and then the electrolyte may be injected into the housing 21 through the electrolyte injection port on the end cover 22 .

[0089] The shell 21 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the shell 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 shell can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid shell can be selected. Of course, the end cap 22 can also be in various structures, such as a plate-like structure, a hollow structure with one end open, etc. For example, in Figure 4 In the embodiment, the shell 21 is a rectangular parallelepiped structure, the end cover 22 is a plate-shaped structure, and the end cover 22 covers the opening at the top of the shell 21 .

[0090] 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, and the positive electrode terminal 30, the negative electrode terminal 40 and the pressure relief mechanism 50 are all mounted on the end cover 22. The positive electrode terminal 30 and the negative electrode terminal 40 are both used to be electrically connected to the electrode assembly 10 to output the electric energy generated by the electrode assembly 10. The pressure relief mechanism 50 is used to release the pressure inside the battery cell 7 when the internal pressure or temperature of the battery cell 7 reaches a predetermined value.

[0091] Exemplarily, the pressure relief mechanism 50 is located between the positive electrode terminal 30 and the negative electrode terminal 40 , and the pressure relief mechanism 50 may be a component such as an explosion-proof valve, an explosion-proof disk, an air valve, a pressure relief valve, or a safety valve.

[0092] Of course, in some embodiments, the housing 20 may also be other structures, for example, the housing 20 includes a shell 21 and two end caps 22, the shell 21 is a hollow structure with two opposite openings, and one end cap 22 is correspondingly covered at one opening of the shell 21 and forms a sealed connection to form 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 may be installed on the same end cap 22 or on different end caps 22; the pressure relief mechanism 50 may be installed on one end cap 22 or on both end caps 22.

[0093] It should be noted that, in the battery cell 7, the number of electrode assemblies 10 contained in the housing 20 may be one or more. Figure 4 In the embodiment, there are two electrode assemblies 10.

[0094] Next, the specific structure of the electrode assembly 10 is described in detail with reference to the accompanying drawings.

[0095] Figure 5 This is a schematic diagram of the structure of an electrode assembly according to an embodiment of the present application. Figure 6 for Figure 5 The electrode assembly shown is a schematic partial cross-sectional view taken along line AA.

[0096] like Figure 5 and Figure 6 As shown, the electrode assembly 10 includes a positive electrode sheet 11 and a negative electrode sheet 12 which are stacked, the positive electrode active material layer 111 of the positive electrode sheet 11 and the negative electrode active material layer 121 of the negative electrode sheet 12 are arranged facing each other, and the end of the negative electrode active material layer 121 exceeds the positive electrode active material layer 111. The area where the negative electrode active material layer 121 overlaps with the positive electrode active material layer 111 in the stacking direction X is the overlapping area S1, and the area where the negative electrode active material layer 121 exceeds the positive electrode active material layer 111 is the overhang area S2.

[0097] In some embodiments, the positive electrode sheet 11 includes a positive electrode current collector 112 and a positive electrode active material layer 111 coated on both surfaces of the positive electrode current collector 112, and the negative electrode sheet 12 includes a negative electrode current collector 122 and a negative electrode active material layer 121 coated on both surfaces of the negative electrode current collector 122. The positive electrode current collector 112 includes a positive electrode coating area 1121 and a positive electrode tab 1122, the positive electrode 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, and the positive electrode tab 1122 is at least partially not coated with the positive electrode active material layer 111 and is used to be electrically connected to the positive electrode terminal 30 (please refer to Figure 4The negative electrode current collector 122 includes a negative electrode coating region 1221 and a negative electrode tab 1222. The negative electrode active material layer 121 is at least partially coated on the negative electrode coating region 1221. The negative electrode tab 1222 is connected to the end of the negative electrode coating region 1221 and protrudes from the negative electrode coating region 1221. The negative electrode tab 1222 is at least partially not coated with the negative electrode active material layer 121 and is used to be electrically connected to the negative electrode terminal 40 (see Figure 4 ).

[0098] The electrode assembly 10 also includes a separator 13 separating the positive electrode sheet 11 and the negative electrode sheet 12. The separator 13 has a large number of through micropores, which can ensure that electrolyte ions can pass freely and has good permeability to lithium ions. The material of the separator 13 can be PP or PE.

[0099] In some embodiments, the positive electrode sheet 11 and the negative electrode sheet 12 are wound around a winding axis to form a winding structure. In the winding structure, the positive electrode sheet 11 and the negative electrode sheet 12 are stacked in a direction perpendicular to the winding axis. In other words, the positive electrode sheet 11 and the negative electrode sheet 12 are wound into multiple turns along a winding direction Z, and the winding direction Z is the direction in which the positive electrode sheet 11 and the negative electrode sheet 12 are wound from the inside to the outside. Figure 5 , the winding direction Z is counterclockwise.

[0100] 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.

[0101] 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 both sides of the electrode assembly 10 along the first direction Y, respectively.

[0102] The electrode assembly 10 with a winding structure includes a straight region B and a bending region C located at both ends of the straight region B. The straight region B refers to a region with a parallel structure in the winding structure, that is, the negative electrode sheet 12, the positive electrode sheet 11 and the separator 13 in the straight region B are substantially parallel to each other, that is, the surface of each layer of the negative electrode sheet 12, the positive electrode sheet 11 and the separator 13 of the electrode assembly 10 in the straight region B is a plane. The bending region C refers to a region with a bending structure in the winding structure, that is, the negative electrode sheet 12, the positive electrode sheet 11 and the separator 13 in the bending region C are all bent, that is, the surface of each layer of the negative electrode sheet 12, the positive electrode sheet 11 and the separator 13 of the electrode assembly 10 in the bending region C is a curved surface.

[0103] In some embodiments, the end of the negative electrode active material layer 121 exceeds the positive electrode active material layer 111. Specifically, both ends of the negative electrode active material layer 121 along the first direction Y exceed the positive electrode active material layer 111 respectively, the starting end of the negative electrode active material layer 121 along the winding direction Z exceeds the positive electrode active material layer 111, and the tail end of the negative electrode active material layer 121 along the winding direction Z exceeds the positive electrode active material layer 111. 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 precipitation.

[0104] Figure 7 for Figure 5 The schematic diagram of the positive electrode sheet 11 and the negative electrode sheet 12 in the unfolded state is shown. Figure 7 As shown, after the winding structure is unfolded, the positive electrode sheet 11 and the negative electrode sheet 12 are basically in the shape of long strips. At this time, the positive electrode sheet 11 and the negative electrode sheet 12 are stacked. In the length direction L of the negative electrode sheet 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 both ends of the negative electrode active material layer 121 exceed the positive electrode active material layer 111; in the width direction W of the negative electrode sheet 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 both ends of the negative electrode active material layer 121 exceed the positive electrode active material layer 111.

[0105] Figure 8 This is a schematic structural diagram of an electrode assembly 10 according to another embodiment of the present application. Fig. 9 for Figure 8 The schematic diagram of the structure of the positive electrode sheet 11 and the negative electrode sheet 12 of the electrode assembly 10 is shown. Figure 8 and Fig. 9 As shown, in some embodiments, the electrode assembly 10 includes a plurality of positive electrode sheets 11 and a plurality of negative electrode sheets 12, and the plurality of negative electrode sheets 12 and the plurality of positive electrode sheets 11 are alternately stacked along a stacking direction X. The stacking direction X is parallel to the thickness direction of the positive electrode sheets 11 and the thickness direction of the negative electrode sheets 12. Both the positive electrode sheets 11 and the negative electrode sheets 12 are generally flat.

[0106] In the direction perpendicular to the stacking direction X, the end of the negative electrode active material layer 121 exceeds the positive electrode active material layer 111. In some embodiments, the negative electrode active material layer 121 and the positive electrode active material layer 111 are both substantially rectangular; in the length direction of the negative electrode active material layer 121, both ends of the negative electrode active material layer 121 exceed 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 exceed the positive electrode active material layer 111.

[0107] After research, the inventor found that the overhang area would cause the risk of lithium deposition.

[0108] Specifically, Figures 10 to 14 Schematic diagram showing the migration of lithium ions between the positive electrode sheet 11 and the negative electrode sheet 12. Fig.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. The overhang region S2 is a region of the negative electrode active material layer 121 that exceeds the positive electrode active material layer 111. During charging, lithium ions Li+ are extracted from the positive electrode active material layer 111 and embedded in the overlapping region S1. Fig.10 As shown, in the fully charged state, lithium ions are generally embedded in the overlapping area S1.

[0109] When the battery is left to stand after self-discharge after charging, lithium ions diffuse themselves and are evenly distributed in the negative electrode active material layer 121, including the overhang area S2. Fig.11 As shown, some lithium ions diffuse from the overlap region S1 to the overhang region S2. This is especially evident if the battery is stored for a long time in a charged state.

[0110] After a period of external discharge, Fig.12 As shown, lithium ions are extracted from the overlapping region S1 and inserted into the positive electrode active material layer 111 .

[0111] The diffusion rate of lithium ions in the positive electrode active material layer 111 is greater than the diffusion rate of lithium ions in the negative electrode active material layer 121. After standing for a period of time, Fig.13 As shown, the lithium ions in the positive electrode active material layer 111 are uniformly diffused and distributed in the positive electrode active material layer 111; and since the diffusion rate of lithium ions in the negative electrode active material layer 121 is low, the lithium ions in the overhang area S2 only diffuse to the portion of the overlapping area S1 close to the overhang area S2.

[0112] When charging again, the lithium ions in the positive electrode active material layer 111 escape from the positive electrode active material layer 111 and are embedded in the overlapping region S1; the portion of the overlapping region S1 close to the overhang region S2 not only receives the lithium ions diffused from the overhang region S2, but also receives the lithium ions escaped from the positive electrode active material layer 111. Fig.14 As shown, after multiple charge and discharge cycles, the portion of the overlapping region S1 close to the overhang region S2 may not be able to fully accept lithium ions, causing the risk of lithium deposition.

[0113] In view of this, the inventors further improved the structure of the electrode assembly 10 .

[0114] Fig.15is a partial cross-sectional schematic diagram of an electrode assembly 10 according to an embodiment of the present application. Fig.16 FIG. 1 is a partial cross-sectional schematic diagram of an electrode assembly 10 according to another embodiment of the present application. Fig.17 FIG. 1 is a partial cross-sectional schematic diagram of an electrode assembly 10 according to another embodiment of the present application. Fig.18 FIG. 1 is a partial cross-sectional schematic diagram of an electrode assembly 10 according to another embodiment of the present application. Fig.19 FIG. 1 is a partial cross-sectional schematic diagram of an electrode assembly 10 according to another embodiment of the present application.

[0115] like Figures 15 to 19 As shown, in some embodiments, the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body 1211, and the end of the negative electrode edge portion 1212 facing away from the negative electrode main body 1211 exceeds the positive electrode active material layer 111, and 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, and the negative electrode active material layer 121 is configured as: the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode main body 1211; and / or, the positive electrode active material layer 111 includes a positive electrode main body 1111 and a positive electrode edge portion 1112 connected to the positive electrode main body 1111, and the positive electrode edge portion 1112 is configured as: the unit area capacity of the positive electrode edge portion 1112 is less than the unit area capacity of the positive electrode main body 1111.

[0116] If the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge 1212, then the negative electrode edge 1212 includes a first portion overlapping with the positive electrode active material layer 111 in the stacking direction X and a second portion exceeding the positive electrode active material layer 111 (i.e., the second portion is at least a portion of the overhang area); when the unit area capacity of the negative electrode main body 1211 meets the setting requirements, that is, the unit area capacity of the negative electrode main body 1211 reaches a first preset value, the negative electrode main body 1211 is not prone to lithium deposition; and due to The capacity per unit area of ​​the negative electrode edge portion 1212 is greater than the capacity per unit area of ​​the negative electrode main body portion 1211, that is, the capacity per unit area of ​​the negative electrode edge portion 1212 is greater than the first preset value, which is equivalent to increasing the capacity per unit area of ​​the negative electrode edge portion 1212. This can increase the CB value of the negative electrode edge portion 1212. During the cycle, even if the first portion needs to accept lithium ions released from the positive electrode active material layer 111 and lithium ions diffused from the second portion, the first portion is not prone to lithium deposition, thereby reducing the risk of lithium deposition in the negative electrode edge portion 1212.

[0117] If the positive electrode active material layer 111 includes the positive electrode main body 1111 and the positive electrode edge portion 1112 , the portion of the negative electrode active material layer 121 overlapping the positive electrode edge portion 1112 is connected to the portion of the negative electrode active material layer 121 extending beyond the positive electrode active material layer 111 . When the capacity per unit area of ​​the positive electrode main body 1111 meets the setting requirements, that is, the capacity per unit area of ​​the positive electrode main body 1111 reaches the second set value, the portion of the negative electrode active material layer 121 overlapping with the positive electrode main body 1111 is not prone to lithium deposition; since the capacity per unit area of ​​the positive electrode edge portion 1112 is less than the capacity per unit area of ​​the positive electrode main body 1111, that is, the capacity per unit area of ​​the positive electrode edge portion 1112 is less than the second set value, it is equivalent to reducing the capacity per unit area of ​​the positive electrode edge portion 1112, which can increase the CB value of the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112. During the cycle, even if the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112 needs to accept lithium ions diffused from the portion of the negative electrode active material layer 121 that exceeds the positive electrode active material layer 111, the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112 can be made less prone to lithium deposition.

[0118] The CB (Cell Balance) value 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 1211 and a negative electrode edge 1212, then the CB value of the negative electrode main body 1211 = Q1 / Q2, and the CB value of the negative electrode edge 1212 = Q3 / Q4, the unit area capacity of the negative electrode main body 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 1211 is Q2, the unit area capacity of the negative electrode edge 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 1212 is Q4. For another example, if the positive electrode active material layer 111 includes a positive electrode main body 1111 and a positive electrode edge portion 1112, the CB value of the portion of the negative electrode active material layer 121 overlapping with the positive electrode main body 1111 is Q5 / Q6, and the CB value of the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112 is Q7 / Q8, wherein the capacity per unit area of ​​the portion of the negative electrode active material layer 121 overlapping with the positive electrode main body 1111 is Q5, the capacity per unit area of ​​the positive electrode main body 1111 is Q6, the capacity per unit area of ​​the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112 is Q7, and the capacity per unit area of ​​the positive electrode edge portion 1112 is Q8.

[0119] If the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge 1212, the negative electrode edge 1212 is arranged along the edge of the negative electrode active material layer 121, and the end of the negative electrode edge 1212 away from the negative electrode main body 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 1111 and a positive electrode edge 1112, the positive electrode edge 1112 is arranged along the edge of the positive electrode active material layer 111, and the end of the positive electrode edge 1112 away from the positive electrode main body 1111 is the free end of the positive electrode active material layer 111.

[0120] In the embodiment of the present application, negative electrode active material layers 121 are provided on both sides of the negative electrode current collector 122. The negative electrode active material layers 121 described in the present application refer to the negative electrode active material layers 121 on one side. The unit area capacity of the negative electrode active material layers 121 refers to the unit area capacity of the negative electrode active material layers 121 on one side of the negative electrode sheet 12. Similarly, positive electrode active material layers 111 are provided on both sides of the positive electrode current collector 112. The positive electrode active material layers 111 described in the present application refer to the positive electrode active material layers 111 on one side. The unit area capacity of the positive electrode active material layers 111 refers to the unit area capacity of the positive electrode active material layers 111 on one side of the positive electrode sheet 11.

[0121] In the embodiment of the present application, the capacity per unit area 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 capacity per unit area of ​​the negative electrode edge 1212 is the ratio of the active material capacity of the negative electrode edge 1212 to the area of ​​the portion of the negative electrode current collector 122 covered by the negative electrode edge 1212. Similarly, the capacity per unit area 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 capacity per unit area of ​​the positive electrode edge 1112 is the ratio of the active material capacity of the positive electrode edge 1112 to the area of ​​the portion of the positive electrode current collector 112 covered by the positive electrode edge 1112.

[0122] In some embodiments, Fig.15 As shown, the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body 1211, and the end of the negative electrode edge portion 1212 facing away from the negative electrode main body 1211 exceeds the positive electrode active material layer 111, and in the stacking direction X of the positive electrode sheet 11 and the negative electrode sheet 12, at least a part of the negative electrode edge portion 1212 overlaps with the positive electrode active material layer 111, and the negative electrode active material layer 121 is configured as follows: the unit area capacity of the negative electrode edge portion 1212 is greater than the unit area capacity of the negative electrode main body 1211.

[0123] At the same thickness, each portion of the positive electrode active material layer 111 has the same capacity per unit area. Specifically, the entire positive electrode active material layer 111 is coated with a single active slurry.

[0124] When the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge 1212 having different capacities per unit area, the positive electrode active material layer 111 can be formed by coating a single active slurry to simplify the manufacturing process of the positive electrode sheet 11 .

[0125] In the present application, the position and number of the negative electrode edge portions 1212 can be set according to requirements.

[0126] 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 main body 1211 along the first direction Y, that is, the negative electrode edge portion 1212 and the negative electrode main body 1211 are arranged along the first direction Y, and the size of the negative electrode edge portion 1212 along the first direction Y is smaller than the size of the negative electrode main body 1211 along the first direction Y. In some embodiments, the negative electrode edge portion 1212 is located on the side of the negative electrode main body 1211 away from the negative electrode tab 1222 along the first direction Y. In some embodiments, the negative electrode edge portion 1212 and the negative electrode main body 1211 have the same thickness.

[0127] In other embodiments, there are at least two negative electrode edge portions 1212 , and the two negative electrode edge portions 1212 are respectively located on both sides of the negative electrode main body 1211 along the first direction Y. The two negative electrode edge portions 1212 can prevent lithium deposition from occurring in the negative electrode active material layer 121 .

[0128] During the forming process of the negative electrode sheet 12, the negative electrode active slurry is first coated on 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 negative electrode active material layer 121 is formed, a thin layer region with a smaller thickness will be formed at the end of the negative electrode active material layer 121 close to the negative electrode tab 1222. In an embodiment of the present application, a negative electrode edge portion 1212 is provided at one end of the negative electrode active material layer 121 close to 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 be met, thereby reducing the risk of lithium deposition. In this way, among the two negative electrode edge portions 1212, the thickness of at least a portion of the negative electrode edge portion 1212 close to the negative electrode tab 1222 is less than the thickness of the negative electrode main body 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 .

[0129] During the forming process of the positive electrode sheet 11, the positive electrode active slurry is first coated on the positive electrode current collector 112, and then rolled to form the positive electrode active material layer 111. Due to the fluidity and surface tension of the positive electrode active slurry, after the positive electrode active material layer 111 is formed, a thin layer region with a smaller thickness is formed at the end of the positive electrode active material layer 111 close to the positive electrode tab 1122.

[0130] In some embodiments, the positive electrode sheet 11 further includes an insulating layer 113, a portion of the insulating layer 113 is coated on the positive electrode coating area 1121, and another portion of the insulating layer 113 is coated on the root of the positive electrode tab 1122 close to the positive electrode coating area 1121. The insulating layer 113 can reduce burrs during the cutting process of the positive electrode tab 1122, and at the same time improve the insulation performance of the positive electrode tab 1122, and reduce the risk of conduction between the root of the positive electrode tab 1122 and the negative electrode sheet 12.

[0131] The lithium ions in the second part will diffuse to the first part. If the size of the first part along the first direction Y is too small, the lithium ions in the second part may diffuse to the negative electrode main body 1211. The unit area capacity of the negative electrode main body 1211 is smaller than the unit area capacity of the first part, so it is easy to cause the risk of the negative electrode main 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 size of the portion of the negative electrode edge 1212 that overlaps with the positive electrode active material layer 111 in the stacking direction X in the first direction Y is greater than 0.5 mm.

[0132] In the embodiment of the present application, a plurality of methods can be used to achieve 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 main body portion 1211 .

[0133] 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 main body 1211 to the negative electrode main body 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 main body 1211. Both the negative electrode edge portion 1212 and the negative electrode main body 1211 include active materials, binders, and conductive agents. By increasing the active material in the negative electrode edge portion 1212 and improving the weight ratio of the active material in the negative electrode edge portion 1212, 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 the unit area capacity of the negative electrode main body 1211.

[0134] 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.

[0135] Optionally, the active material in the negative electrode edge portion 1212 is the same as the active material in the negative electrode main body portion 1211. The active material in the negative electrode edge portion 1212 is the same as the active material in the negative electrode main body portion 1211, and can be graphite or silicon compounds.

[0136] In this embodiment, the thickness of the negative electrode edge portion 1212 can be set according to the position. For example, the thickness of the negative electrode edge portion 1212 close to the negative electrode tab 1222 is less than the thickness of the negative electrode main body 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 1211.

[0137] In other embodiments, the gram capacity of the active material in the negative electrode edge portion 1212 is greater than the gram capacity of the active material in the negative electrode main body 1211. By increasing the gram capacity of the active material in the negative electrode edge portion 1212, the unit area capacity of the negative electrode edge portion 1212 can be increased, so 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 1211.

[0138] Gram capacity refers to the ratio of the capacitance released by the active material to the mass of the active material.

[0139] In this embodiment, the active material in the negative electrode edge portion 1212 is different from the active material in the negative electrode main body portion 1211 . For example, the active material in the negative electrode edge portion 1212 is a silicon compound, and the active material in the negative electrode main body portion 1211 is graphite.

[0140] Optionally, the gram capacity of the active material in the negative electrode edge portion 1212 is 0.5%-20% greater than the gram capacity of the active material in the negative electrode main body 1211. Exemplarily, the gram capacity of the active material in the negative electrode edge portion 1212 is 1.5%-12% greater than the gram capacity of the active material in the negative electrode main body 1211.

[0141] 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 main body portion 1211 to the negative electrode main body portion 1211 .

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

[0143] Reference Fig.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.

[0144] In some embodiments, the active material in the first negative electrode coating 1212a is the same as the active material in the negative electrode main body 1211; the weight ratio of the active material in the first negative electrode coating 1212a to the first negative electrode coating 1212a is equal to the weight ratio of the active material in the negative electrode main body 1211 to the negative electrode main body 1211. Optionally, the first negative electrode coating 1212a and the negative electrode main body 1211 have the same composition, that is, the first negative electrode coating 1212a and the negative electrode main body 1211 can be formed of the same negative electrode active slurry, which can simplify the manufacturing process of the negative electrode plate 12.

[0145] In some embodiments, the weight ratio of the active material in the second negative electrode coating 1212b to the second negative electrode coating 1212b is greater than the weight ratio of the active material in the first negative electrode coating 1212a to 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 main body 1211.

[0146] 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. The active material in the second negative electrode coating 1212b is the same as the active material in the first negative electrode coating 1212a, and can be graphite or a silicon compound.

[0147] In this embodiment, the thickness of the negative electrode edge portion 1212 can be set according to the position. For example, the thickness of the negative electrode edge portion 1212 close to the negative electrode tab 1222 is less than the thickness of the negative electrode main body 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 1211.

[0148] In other embodiments, the gram capacity of the active material in the second negative electrode coating 1212b is greater than the gram capacity of the active material in the first negative electrode coating 1212a. By increasing the gram 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 the unit area capacity of the negative electrode main body 1211.

[0149] In the present application, in addition to increasing the capacity per unit area of ​​the negative electrode edge portion 1212, the risk of lithium deposition in the negative electrode edge portion 1212 can also be reduced by improving the kinetic performance of the negative electrode edge portion 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 aggregate locally. In some embodiments, the particle size of the active material in the negative electrode edge portion 1212 is smaller than the particle size of the active material in the negative electrode main body 1211. In this way, during the charge and discharge process, lithium ions are more easily diffused in the negative electrode edge portion 1212, and are more evenly distributed in the negative electrode edge portion 1212, and are not easily aggregated locally in the negative electrode edge portion 1212, thereby reducing the risk of lithium deposition.

[0150] Reference Fig.17 In some embodiments, the positive electrode active material layer 111 includes a positive electrode main body 1111 and a positive electrode edge portion 1112 connected to the positive electrode main body 1111, and the positive electrode edge portion 1112 is configured such that the capacity per unit area of ​​the positive electrode edge portion 1112 is smaller than the capacity per unit area of ​​the positive electrode main body 1111. At the same thickness, the capacity per unit area of ​​each part of the negative electrode active material layer 121 is the same. Specifically, the entire negative electrode active material layer 121 is coated with a single active slurry.

[0151] 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 .

[0152] In the present application, the position and number of the positive electrode edge portions 1112 can be set according to requirements.

[0153] 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 main body portion 1111 along the first direction Y, that is, the positive electrode edge portion 1112 and the positive electrode main body portion 1111 are arranged along the first direction Y, and the size of the positive electrode edge portion 1112 along the first direction Y is smaller than the size of the positive electrode main 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 main body portion 1111 away from the positive electrode tab 1122 along the first direction Y. In some embodiments, the positive electrode edge portion 1112 and the positive electrode main body portion 1111 have the same thickness.

[0154] In other embodiments, there are at least two positive electrode edge portions 1112 , and the two positive electrode edge portions 1112 are respectively located on both sides of the positive electrode main body 1111 along the first direction Y. The two positive electrode edge portions 1112 can prevent lithium deposition from occurring in the positive electrode active material layer 111 .

[0155] In the two positive electrode edge portions 1112, at least a portion of the positive electrode edge portion 1112 close to the positive electrode tab 1122 has a thickness less than the thickness of the positive electrode main body 1111. The portion of the positive electrode edge portion 1112 that is thinner than the positive electrode main body 1111 is the 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 main body 1111.

[0156] The lithium ions in the portion of the negative electrode active material layer 121 that exceeds the positive electrode active material layer 111 will diffuse into the portion of the negative electrode active material that overlaps with the positive electrode edge portion 1112. If the size of the positive electrode edge portion 1112 in the first direction Y is too small, the size of the portion of the negative electrode active material that overlaps with the positive electrode edge portion 1112 in the first direction Y will also be too small, and the lithium ions may diffuse into the portion of the negative electrode active material that overlaps with the positive electrode main body 1111. Since the unit area capacity of the positive electrode main body 1111 is greater than the unit area capacity of the positive electrode edge portion 1112, the portion of the negative electrode active material that overlaps with the positive electrode main body 1111 may precipitate lithium. Therefore, in order to reduce the risk of lithium precipitation, the size of the portion of the negative electrode active material that overlaps with the positive electrode edge portion 1112 in the first direction Y is greater than 0.5 mm, that is, the size of the positive electrode edge portion 1112 in the first direction Y is greater than 0.5 mm.

[0157] In the embodiment of the present application, a plurality of methods can be used to achieve that the capacity per unit area of ​​the positive electrode edge portion 1112 is greater than the capacity per unit area of ​​the positive electrode main body portion 1111 .

[0158] 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 main body portion 1111 to the positive electrode main 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 main body portion 1111. Both the positive electrode edge portion 1112 and the positive electrode main body portion 1111 include active materials, binders, and conductive agents. By reducing the active materials in the positive electrode edge portion 1112, the weight ratio of the active materials in the positive electrode edge portion 1112 is reduced, and 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 main body portion 1111.

[0159] 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% less than the weight ratio of the active material in the positive electrode body portion 1111 , and optionally, 1.5%-12% less.

[0160] Optionally, the active material in the positive electrode edge portion 1112 is the same as the active material in the positive electrode main body portion 1111. The active material in the positive electrode edge portion 1112 and the active material in the positive electrode main body portion 1111 can be lithium iron phosphate, lithium manganese oxide, ternary lithium, lithium cobalt oxide, etc.

[0161] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to the position. For example, the thickness of the positive electrode edge portion 1112 close to the positive electrode tab 1122 is less than the thickness of the positive electrode main body 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 main body 1111.

[0162] In other embodiments, the gram capacity of the active material in the positive electrode edge portion 1112 is less than the gram capacity of the active material in the positive electrode main body portion 1111. By reducing the gram 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 main body portion 1111.

[0163] In this embodiment, the active material in the positive electrode edge portion 1112 is different from the active material in the positive electrode main body portion 1111. For example, the active material in the positive electrode edge portion 1112 is lithium iron phosphate, and the active material in the positive electrode main body portion 1111 is ternary lithium.

[0164] Optionally, the gram capacity of the active material in the positive electrode edge portion 1112 is 0.5%-20% less than that in the positive electrode main body 1111. Exemplarily, the gram capacity of the active material in the positive electrode edge portion 1112 is 1.5%-12% less than that in the positive electrode main body 1111.

[0165] 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 main body portion 1111 to the positive electrode main body portion 1111 .

[0166] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to the position. For example, the thickness of the positive electrode edge portion 1112 close to the positive electrode tab 1122 is less than the thickness of the positive electrode main body 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 main body 1111.

[0167] Reference Fig.18 The positive electrode edge portion 1112 includes a first positive electrode coating 1112 a and a second positive electrode coating 1112 b stacked along a stacking direction X. Optionally, the second positive electrode coating 1112 b is connected between the first positive electrode coating 1112 a and the positive electrode current collector 112 .

[0168] In some embodiments, the active material in the first positive electrode coating 1112a is the same as the active material in the positive electrode main body 1111; the weight ratio of the active material in the first positive electrode coating 1112a to the first positive electrode coating 1112a is equal to the weight ratio of the active material in the positive electrode main body 1111 to the positive electrode main body 1111. Optionally, the first positive electrode coating 1112a and the positive electrode main body 1111 have the same composition, that is, the first positive electrode coating 1112a and the positive electrode main body 1111 can be formed of the same positive active slurry, which can simplify the manufacturing process of the positive electrode plate 11.

[0169] The second positive electrode coating 1112b can be a pure conductive coating, for example, the second positive electrode coating 1112b is a pure conductive coating composed of an adhesive 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, an adhesive 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 an adhesive, a conductive agent and lithium powder coated with lithium carbonate.

[0170] 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 main body 1111. Optionally, the second positive electrode coating 1112b does not contain active materials, 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.

[0171] In this embodiment, the thickness of the positive electrode edge portion 1112 can be set according to the position. For example, the thickness of the positive electrode edge portion 1112 close to the positive electrode tab 1122 is less than the thickness of the positive electrode main body 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 main body 1111.

[0172] In other embodiments, the gram capacity of the active material in the second positive electrode coating 1112b is less than the gram capacity of the active material in the first positive electrode coating 1112a. By reducing the gram 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 main body 1111.

[0173] In the present application, in addition to reducing the unit area capacity of the positive electrode edge portion 1112, the risk of lithium precipitation in the negative electrode active material layer 121 can also be reduced by adjusting the kinetic performance of the positive electrode edge portion 1112. In some embodiments, the particle size of the active material of the positive electrode edge portion 1112 is larger than the particle size of the active material of the positive electrode main body 1111. In this way, during the charge and discharge process, lithium ions are not easy to diffuse in the positive electrode edge portion 1112, the rate at which lithium ions in the positive electrode main body 1111 diffuse into the positive electrode edge portion 1112 is reduced, and the rate at which lithium ions escape from the positive electrode edge portion 1112 is also reduced, which can reduce the risk of lithium ions gathering in the portion of the negative electrode active material layer 121 that overlaps with the positive electrode edge portion 1112, making it difficult for the negative electrode active material layer 121 to precipitate lithium.

[0174] In some embodiments, Fig.19 As shown, the negative electrode active material layer 121 includes a negative electrode main body 1211 and a negative electrode edge portion 1212 connected to the negative electrode main body 1211. The end of the negative electrode edge portion 1212 away from the negative electrode main body 1211 exceeds the positive electrode active material layer 111, and in the stacking direction X of the positive electrode sheet 11 and the negative electrode sheet 12, at least a part 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 1211. The positive electrode active material layer 111 includes a positive electrode main body 1111 and a positive electrode edge portion 1112 connected to the positive electrode main body 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 1111.

[0175] In the embodiment of the present application, the capacity per unit area of ​​the negative electrode edge portion 1212 can be made greater than the capacity per unit area of ​​the negative electrode main body 1211 by increasing the weight ratio of the active material of the negative electrode edge portion 1212, or increasing the gram capacity of the active material of the negative electrode edge portion 1212, or other methods. Similarly, the capacity per unit area of ​​the positive electrode edge portion 1112 can be made smaller than the capacity per unit area of ​​the positive electrode main body 1111 by reducing the weight ratio of the active material of the positive electrode edge portion 1112, or reducing the gram capacity of the active material of the positive electrode edge portion 1112, or other methods.

[0176] In some embodiments, the positive electrode edge portion 1112 and the negative electrode edge portion 1212 at least partially overlap in the stacking direction X. In some embodiments, a portion of the positive electrode edge portion 1112 overlaps with the negative electrode main body portion 1211 in the stacking direction X.

[0177] When the capacity per unit area of ​​the negative electrode main body 1211 and the capacity per unit area of ​​the positive electrode main body 1111 meet the requirements, the capacity per unit area of ​​the negative electrode edge portion 1212 is greater than the capacity per unit area of ​​the negative electrode main body 1211, and the capacity per unit area of ​​the positive electrode edge portion 1112 is less than the capacity per unit area 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 deposition to occur in the negative electrode active material layer 121.

[0178] Fig. 20 FIG. 1 is a schematic top view of a negative electrode sheet 12 of an electrode assembly 10 according to an embodiment of the present application. Fig. 20 As shown, in some embodiments, the negative electrode edge portion 1212 is arranged around the negative electrode main body portion 1211, so that the range of the negative electrode edge portion 1212 can be increased, making it difficult for lithium deposition to occur in the negative electrode active material layer 121.

[0179] Fig.21 FIG. 1 is a schematic top view of a positive electrode sheet 11 of an electrode assembly 10 according to an embodiment of the present application. Fig.21 As shown, in some embodiments, the positive electrode edge portion 1112 is arranged around the positive electrode main body 1111, so that the portion of the negative electrode active material layer 121 overlapping with the positive electrode edge portion 1112 can be increased, making it difficult for lithium deposition to occur in the negative electrode active material layer 121.

[0180] The test steps for capacity per unit area and CB value are as follows:

[0181] Step 1): Test of the average discharge capacity of the single-sided active material layer of the positive electrode. Take the positive electrode sheets of the above-mentioned embodiments, and use a punching die to obtain a small disc containing a single-sided active material layer of the positive electrode. Use a metal lithium sheet as the counter electrode, a Celgard membrane as the isolation membrane, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved with LiPF6 (1 mol / L) as the electrolyte, and assemble 6 identical CR2430 button batteries in an argon-protected glove box. ① After the battery is assembled, let it stand for 12 hours, ② perform constant current charging at a charging current of 0.1C until the voltage reaches the upper limit cut-off voltage x1V, and then maintain the voltage x1V for constant voltage charging until the current is 50uA, ③ let it stand for 5min, ④ finally, perform constant current discharge at a discharge current of 0.1C until the voltage reaches the lower limit cut-off voltage y1V, ⑤ let it stand for 5min, repeat steps 2-5, and record the discharge capacity of the second cycle. The average discharge capacity of the six button 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 cut-off voltage x1V = 3.75V, and the lower cut-off voltage y1V = 2V. When the positive electrode active material is lithium nickel cobalt manganese oxide (NCM), the upper cut-off voltage x1V = 4.25V, and the lower cut-off voltage y1V = 2.8V. 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.

[0182] Step 2): Test the average charging capacity of the single-sided active material layer of the negative electrode. Take the negative electrode sheets of the above-mentioned embodiments, and use a punching die to obtain a small disc with the same area as the small positive disc in the above step 1) and containing a single-sided active material layer of the negative electrode. Use a metal lithium sheet as the counter electrode, a Celgard membrane as the isolation membrane, and a solution of EC+DMC+DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved with LiPF6 (1 mol / L) as the electrolyte, and assemble 6 CR2430 button batteries in an argon-protected glove box. ① After the battery is assembled, let it stand for 12 hours, ② discharge it at a constant current of 0.05C until the voltage reaches the lower cut-off voltage y2mV, ③ then discharge it at a constant current of 50uA until the voltage reaches the lower cut-off voltage y2mV, ④ let it stand for 5min, ⑤ then discharge it at a constant current of 10uA until the lower cut-off voltage y2mV is reached, ⑥ let it stand for 5 minutes, ⑦ finally charge it at a constant current of 0.1C until the final voltage reaches the upper cut-off voltage x2V, ⑧ let it stand for 5 minutes, repeat steps 2-8, and record the charging capacity of the second cycle. The average value of the charging capacity of the 6 button batteries is the average charging capacity of the single-sided active material layer of the negative electrode. For example, when the negative electrode active material is graphite, the upper cut-off voltage x2V = 2V, and the lower cut-off voltage y2V = 5mV. When the negative electrode active material is silicon, the upper cut-off voltage x2V = 2V, and the lower cut-off voltage y2V = 5mV. Taking the area of ​​the small disc including the single-sided negative electrode active material layer as the unit area, the average charge capacity of the single-sided negative electrode active material layer is the unit area capacity of the single-sided negative electrode active material layer.

[0183] Step 3): Calculate the CB value according to CB value = average charge capacity (mAh) of the above-mentioned single-sided active material layer of the negative electrode / average discharge capacity (mAh) of the above-mentioned single-sided active material layer of the positive electrode.

[0184] Fig. 22 Flow chart of a method for manufacturing an electrode assembly provided in some embodiments of the present application. Fig. 22 As shown, in some embodiments, the method for manufacturing an electrode assembly includes:

[0185] S100: Provides positive electrode;

[0186] S200: providing negative electrode sheet;

[0187] S300: stacking the positive electrode sheet and the negative electrode sheet so that the positive electrode active material layer of the positive electrode sheet faces the negative electrode active material layer of the negative electrode sheet, and the end of the negative electrode active material layer exceeds the positive electrode active material layer.

[0188] Among them, the negative electrode active material layer includes a negative electrode main body and a negative electrode edge portion connected to the negative electrode main body, one end of the negative electrode edge portion facing away from the negative electrode main body exceeds the positive electrode active material layer, and in the superimposing direction of the positive electrode sheet and the negative electrode sheet, at least a part of the negative electrode edge portion overlaps with the positive electrode active material layer, and the negative electrode active material layer is configured as: the unit area capacity of the negative electrode edge portion 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 portion connected to the positive electrode main body, and the positive electrode edge portion is configured as: the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode main body.

[0189] It should be noted that the relevant structure of the electrode assembly manufactured by the above-mentioned electrode assembly manufacturing method can refer to the electrode assembly provided in the above-mentioned embodiments.

[0190] When assembling an electrode assembly based on the manufacturing method of the electrode assembly, it is not necessary to perform the steps in sequence. That is, the steps may be performed in the order mentioned in the embodiment, or in a different order from the order mentioned in the embodiment, or several steps may be performed simultaneously. For example, the execution of step S100 and step S200 is not in order, and may be performed simultaneously.

[0191] Please refer to Fig.23 , Fig.23 A schematic block diagram of a manufacturing system for an electrode assembly provided for some embodiments of the present application, the manufacturing system for the electrode assembly comprising: a first providing device 91 for providing a positive electrode sheet; a second providing device 92 for providing a negative electrode sheet; an assembling 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 exceeds the positive active material layer.

[0192] Among them, the negative electrode active material layer includes a negative electrode main body and a negative electrode edge portion connected to the negative electrode main body, one end of the negative electrode edge portion facing away from the negative electrode main body exceeds the positive electrode active material layer, and in the superimposing direction of the positive electrode sheet and the negative electrode sheet, at least a part of the negative electrode edge portion overlaps with the positive electrode active material layer, and the negative electrode active material layer is configured as: the unit area capacity of the negative electrode edge portion 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 portion connected to the positive electrode main body, and the positive electrode edge portion is configured as: the unit area capacity of the positive electrode edge portion is less than the unit area capacity of the positive electrode main body.

[0193] In some embodiments, the manufacturing system further includes a third providing device (not shown), which is used to provide a separator for isolating the positive electrode sheet from the negative electrode sheet. The assembling device is used to stack the positive electrode sheet, the separator and the negative electrode sheet.

[0194] The relevant structure of the electrode assembly manufactured by the above-mentioned manufacturing system can refer to the electrode assembly provided in the above-mentioned embodiments.

[0195] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0196] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, but these modifications or replacements 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 the present application.

Claims

1. An electrode assembly, characterized in that: It includes a positive electrode sheet and a negative electrode sheet which are stacked and arranged; 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, and the positive electrode tab is connected to an 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 current collector and a negative electrode active material layer coated on the surface of the negative electrode current collector, the positive electrode active material layer is arranged opposite to the negative electrode active material layer, and in the first direction, both ends of the negative electrode active material layer are beyond the positive electrode active material layer; The positive electrode active material layer includes a positive electrode main body and a positive electrode edge portion. The positive electrode edge portion is provided on the side of the positive electrode main body away from the positive electrode ear along the first direction. The positive electrode edge portion is configured as follows: the unit area capacity of the positive electrode edge portion is smaller than the unit area capacity of the positive electrode main body.

2. The electrode assembly according to claim 1, characterized in that: The thickness of at least a portion of the positive electrode edge portion is smaller than the thickness of the positive electrode main body portion.

3. The electrode assembly according to claim 2, characterized in that: The thickness of the positive electrode edge portion gradually decreases in a direction away from the positive electrode main body portion.

4. The electrode assembly according to claim 2, characterized in that: The active material of the positive electrode edge portion is the same as the active material of the positive electrode main body portion, and the weight ratio of the active material of the positive electrode edge portion to the positive electrode edge portion is equal to the weight ratio of the active material of the positive electrode main body portion to the positive electrode main body portion.

5. The electrode assembly according to any one of claims 1 to 4, characterized in that: There are at least two positive electrode edge portions, and the two positive electrode edge portions are respectively located on two sides of the positive electrode main body portion along the first direction.

6. The electrode assembly according to claim 5, characterized in that: Among the two positive electrode edge portions, at least a portion of the positive electrode edge portion close to the positive electrode tab has a thickness smaller than a thickness of the positive electrode main body portion.

7. The electrode assembly according to claim 1, characterized in that: The weight ratio of the active material in the positive electrode edge portion to the positive electrode edge portion is smaller than the weight ratio of the active material in the positive electrode main body portion to the positive electrode main body portion, so that the unit area capacity of the positive electrode edge portion is smaller than the unit area capacity of the positive electrode main body portion.

8. The electrode assembly according to claim 1, characterized in that: The gram capacity of the active material in the positive electrode edge portion is smaller than the gram capacity of the active material in the positive electrode main portion, so that the unit area capacity of the positive electrode edge portion is smaller than the unit area capacity of the positive electrode main portion.

9. 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 gram capacity of the active material in the second positive electrode coating is less than the gram capacity of the active material in the first positive electrode coating.

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

11. 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.

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

13. The electrode assembly according to claim 1, characterized in that: The negative electrode active material layer includes a negative electrode main body and a negative electrode edge portion connected to the negative electrode main body, one end of the negative electrode edge portion facing away from the negative electrode main body exceeds the positive electrode active material layer, and 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, and the negative electrode active material layer is configured as follows: the unit area capacity of the negative electrode edge portion is greater than the unit area capacity of the negative electrode main body.

14. The electrode assembly according to claim 13, characterized in that: The positive electrode edge portion located on a side of the positive electrode main portion away from the positive electrode tab along the first direction at least partially overlaps with the negative electrode main portion in the stacking direction.

15. The electrode assembly according to claim 13, characterized in that: The positive electrode edge portion located on the side of the positive electrode main body portion away from the positive electrode tab along the first direction at least partially overlaps with the negative electrode edge portion in the stacking direction.

16. The electrode assembly according to claim 13, 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 main body portion to the negative electrode main 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 main body portion.

17. The electrode assembly according to claim 13, characterized in that: The gram capacity of the active material in the negative electrode edge portion is greater than the gram capacity of the active material in the negative electrode main 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 main body portion.

18. The electrode assembly according to claim 13, 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 gram capacity of the active material in the second negative electrode coating is greater than the gram capacity of the active material in the first negative electrode coating.

19. The electrode assembly according to claim 13, characterized in that: The particle size of the active material in the negative electrode edge portion is smaller than the particle size of the active material in the negative electrode main body portion.

20. The electrode assembly according to claim 13, characterized in that The thickness of at least a portion of the negative electrode edge portion is smaller than the thickness of the negative electrode main body portion.

21. The electrode assembly according to claim 20, characterized in that The thickness of the negative electrode edge portion gradually decreases in a direction away from the negative electrode main body portion.

22. The electrode assembly according to claim 13, characterized in that The negative electrode sheet includes a negative electrode current collector, the negative electrode 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 an end of the negative electrode coating area along a first direction, and the first direction is perpendicular to the stacking direction; The negative electrode edge portion is provided on one side of the negative electrode main body portion close to the negative electrode tab along the first direction.

23. The electrode assembly according to claim 22, characterized in that There are at least two negative electrode edge portions, and the two negative electrode edge portions are respectively located on two sides of the negative electrode main body portion along the first direction.

24. The electrode assembly according to claim 23, characterized in that Among the two negative electrode edge portions, at least a portion of the negative electrode edge portion close to the negative electrode tab has a thickness less than that of the negative electrode main body portion, and the thickness of the negative electrode edge portion away from the negative electrode tab is equal to the thickness of the negative electrode main body portion.

25. The electrode assembly according to claim 13, characterized in that A portion of the negative electrode edge portion that overlaps with the positive electrode active material layer in the stacking direction has a size in the first direction that is greater than 0.5 mm.

26. The electrode assembly according to claim 13, characterized in that The negative electrode edge portion is arranged around the negative electrode main body portion.

27. The electrode assembly according to any one of claims 13 to 26, characterized in that: The negative electrode edge portion includes a first portion and a second portion, the first portion overlaps the positive electrode active material layer in the stacking direction, and the second portion extends beyond the positive electrode active material layer.

28. A battery cell, characterized in that: include: shell; At least one electrode assembly according to any one of claims 1 to 27 is housed in the housing.

29. A battery, characterized in that: include: Box; At least one battery cell as claimed in claim 28, wherein the battery cell is accommodated in the box.

30. An electrical equipment, characterized in that: The battery of claim 29 is used to provide electrical energy.

Images