A battery cell, a battery, and an electric device

Abstract

A battery cell (20), a battery (100) and an electric device. The battery cell (20) comprises a housing (22) and at least three electrode assemblies (23), the housing (22) defines a cavity therein, the cavity comprises a first region (24) and a second region (25), the first region (24) is closer to the housing (22) than the second region (25). The at least three electrode assemblies (23) are arranged in the cavity, a capacity of a single electrode assembly (23) in the first region (24) is Cap1, a capacity of a single electrode assembly (23) in the second region (25) is Cap2, Cap2>Cap1. By controlling Cap2>Cap1, the electrode assemblies (23) in the second region (25) have more active lithium than the electrode assemblies (23) in the first region (24), so as to match the relative rates of attenuation of the electrode assemblies (23) in the second region (25) and the electrode assemblies (23) in the first region (24), thereby slowing down the overall rate of attenuation and prolonging the service life of the battery cell (20).

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery, and an electrical device. Background Technology

[0002] Due to their significant advantages such as low price, environmental friendliness, long cycle life, and good safety performance, power batteries have been widely used in electric vehicles, mobile phones, tablets, and energy storage. Currently, all sectors are placing higher demands on battery usage, and capacity degradation has become a major limiting factor for power batteries. Summary of the Invention

[0003] In view of the above problems, this application provides a battery cell, a battery, and an electrical device that can alleviate the problem of battery capacity degradation.

[0004] In a first aspect, this application provides a battery cell comprising: a housing and at least three electrode assemblies. A cavity is defined within the housing, the cavity including a first region and a second region, the first region being closer to the housing than the second region. The at least three electrode assemblies are disposed within the cavity, the capacity of a single electrode assembly located in the first region being Cap1, and the capacity of a single electrode assembly located in the second region being Cap2, where Cap2 > Cap1.

[0005] In some known solutions, the electrode assembly in the second region is closer to the center of the casing than the electrode assembly in the first region. This results in a higher operating temperature and a greater degree of side reactions at the electrode interface, leading to greater loss of active lithium and faster capacity decay. The battery cell of this application controls the capacity (Cap2) of the electrode assembly in the second region to be greater than the capacity (Cap1) of the electrode assembly in the first region. The electrode assembly in the second region has more active lithium than the electrode assembly in the first region, thus matching the relative decay rates of the electrode assembly in the second region and the electrode assembly in the first region, thereby slowing down the overall decay rate. Simultaneously, the electrode assembly in the second region has a lower equivalent rate of charge and discharge, i.e., a lower current density, resulting in less heat generation. This further reduces the temperature difference between the electrode assembly in the first and second regions, slowing down the overall capacity decay rate of the battery cell and extending its lifespan.

[0006] In some embodiments, at least three electrode components are stacked in the cavity. Along the stacking direction, the capacity of the electrode components at both ends is Cap1, and the capacity of the electrode component in the middle is Cap2. When at least three electrode components are stacked in the cavity, the electrode components at both ends are closer to the housing than the electrode components in the middle. The temperature rise of the electrode components in the middle during use is higher than that of the electrode components at both ends, meaning that the active lithium loss of the electrode components in the middle is greater. The battery cell of this application controls the capacity Cap2 of the electrode components in the middle to be greater than the capacity Cap1 of the electrode components at both ends. The electrode components in the middle have more active lithium than the electrode components at both ends, thereby matching the relative decay rate of the electrode components in the second region and the electrode components in the first region, thus slowing down the overall decay rate. At the same time, the electrode components in the middle have a lower equivalent rate during charge and discharge, i.e., a lower current density, resulting in less heat generation, further reducing the temperature difference between the electrode components in the middle and the electrode components at both ends, slowing down the capacity decay rate of the entire battery cell, and extending the service life of the battery cell.

[0007] In some embodiments, the thickness of a single electrode assembly in the first region along the stacking direction is H1, and the thickness of a single electrode assembly in the second region along the stacking direction is H2. Cap1, Cap2, H1, and H2 satisfy the following relationship: (Cap1×H2) / (Cap2×H1)<1. Since the capacity and thickness of a battery cell are positively correlated, when (Cap1×H2) / (Cap2×H1)<1, the capacity Cap2 of the electrode assembly in the second region is greater than the capacity Cap1 of the electrode assembly in the first region; when (Cap1×H2) / (Cap2×H1)≥1, the capacity Cap2 of the electrode assembly in the second region is less than or equal to the capacity Cap1 of the electrode assembly in the first region, which will lead to a reduction in the lifespan of the battery cell.

[0008] In some embodiments, the cavity further includes a third region, which is closer to the housing than the second region, and the first region is closer to the housing than the third region. The capacity of a single electrode assembly located in the third region is Cap3, where Cap2 ≥ Cap3 ≥ Cap1. Since the electrode assemblies in the second region are closer to the center of the housing than those in the third region, the operating temperature of the electrode assemblies in the second region is higher. The operating temperature of the electrode assemblies in the third region is also higher than that in the first region. This results in a greater loss of active lithium in the electrode assemblies in the second region compared to those in the third region, and vice versa. The principle of Cap2 ≥ Cap3 ≥ Cap1 helps to ensure that the electrode assemblies in the region with higher temperature rise have more active lithium, making the relative degradation rates of the electrode assemblies in different regions more matched, thereby slowing down the overall degradation rate and extending the lifespan of the battery cell.

[0009] In some embodiments, a single battery cell satisfies at least one of the following conditions a and b: a) the coating quality of the positive active material of a single electrode assembly located in the first region is less than the coating quality of the positive active material of a single electrode assembly located in the second region; b) the specific capacity of the positive active material of a single electrode assembly located in the first region is less than the specific capacity of the positive active material of a single electrode assembly located in the second region. Both the coating quality and the specific capacity of the positive active material of a single electrode assembly affect the capacity (Cap) of the electrode assembly.

[0010] In some embodiments, the ratio of the coating mass of the positive active material of a single electrode assembly in the first region to the coating mass of the positive active material of a single electrode assembly in the second region is 0.8 to 0.99:1. The higher the coating mass of the positive active material in a single electrode assembly, the higher the capacity Cap of the electrode assembly. When the ratio of the coating mass of the positive active material of a single electrode assembly in the first region to the coating mass of the positive active material of a single electrode assembly in the second region is 0.8 to 0.99:1, not only can the capacity Cap of a single electrode assembly in the first region be less than the capacity Cap of a single electrode assembly in the second region, but the difference between the capacity Cap1 of a single electrode assembly in the first region and the capacity Cap2 of a single electrode assembly in the second region is also not too large.

[0011] In some embodiments, the ratio of the coating mass of the positive active material of a single electrode assembly in the first region to the coating mass of the positive active material of a single electrode assembly in the second region is 0.92 to 0.95:1. When the ratio of the coating mass of the positive active material of a single electrode assembly in the first region to the coating mass of the positive active material of a single electrode assembly in the second region is 0.8 to 0.99:1, not only can the capacity Cap of a single electrode assembly in the first region be less than the capacity Cap of a single electrode assembly in the second region, but the difference between the capacity Cap1 of a single electrode assembly in the first region and the capacity Cap2 of a single electrode assembly in the second region is also not too large.

[0012] In some embodiments, the specific capacity of the positive active material of a single electrode assembly in the first region and the specific capacity of the positive active material of a single electrode assembly in the second region are 1:1.05 to 1.1. The larger the specific capacity of the positive active material of a single electrode assembly, the higher the capacity (Cap) of the electrode assembly. When the specific capacity of the positive active material of a single electrode assembly in the first region and the specific capacity of the positive active material of a single electrode assembly in the second region are 1:1.05 to 1.1, not only can the capacity (Cap) of a single electrode assembly in the first region be smaller than that of a single electrode assembly in the second region, but it is also necessary to ensure the matching of positive active materials in different regions.

[0013] Secondly, this application provides a battery that includes the battery cell described in the above embodiments.

[0014] Thirdly, this application provides an electrical device that includes the battery described in the above embodiments, the battery being used to provide electrical energy.

[0015] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0017] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0018] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0019] Figure 3 A schematic diagram showing the exploded structure of a first type of battery cell provided in some embodiments of this application;

[0020] Figure 4 A perspective view of a first type of battery cell according to some embodiments of this application from a frontal view;

[0021] Figure 5 This is a schematic diagram showing the arrangement of electrode assemblies in a first type of battery cell according to some embodiments of this application;

[0022] Figure 6 This is a schematic diagram showing the arrangement of electrode components in a second type of battery cell according to some embodiments of this application;

[0023] Figure 7 This is a schematic diagram showing the arrangement of electrode components in a third type of battery cell according to some embodiments of this application;

[0024] Figure 8 This is a schematic diagram showing the arrangement of electrode components in a fourth type of battery cell according to some embodiments of this application.

[0025] The reference numerals in the detailed embodiments are as follows:

[0026] 1000 - Vehicles;

[0027] 100 - Battery; 200 - Controller; 300 - Motor;

[0028] 10-Box body; 11-First part; 12-Second part;

[0029] 20-Battery cell; 21-End cap; 22-Housing casing; 23-Electrode assembly;

[0030] 24 - First area; 25 - Second area; 26 - Third area. Detailed Implementation

[0031] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0033] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0037] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0038] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0039] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of power battery applications, market demand is also constantly increasing.

[0040] The inventors have noticed that for a battery cell with multiple electrode components, the capacity decay rate of different electrode components is different, and during use, due to the "barrel effect", the overall capacity of the battery cell is limited by the electrode component with the fastest capacity decay.

[0041] To alleviate the capacity decay problem of individual battery cells, the inventors discovered that individual battery cells generate and dissipate heat during charging and discharging. For battery cells with multiple electrode components, different battery cells are in different environments. Electrode components far from the casing will accumulate heat because they cannot dissipate heat in time, resulting in higher operating temperatures for electrode components far from the casing. This will lead to greater loss of active lithium in the far-away electrode components, resulting in faster capacity decay.

[0042] Based on the above considerations, in order to improve the technical problem of rapid capacity decay of battery cells due to the loss of active lithium, the inventors, after in-depth research, designed a battery cell. Because the electrode assembly in the second region is closer to the center of the casing than the electrode assembly in the first region, the operating temperature of the electrode assembly in the second region is higher, and the degree of side reactions at the electrode interface is greater, resulting in greater loss of active lithium and faster capacity decay. The battery cell of this application controls the capacity Cap2 of the electrode assembly in the second region to be greater than the capacity Cap1 of the electrode assembly in the first region. The electrode assembly in the second region has more active lithium than the electrode assembly in the first region, thus matching the relative decay rate of the electrode assembly in the second region with that in the first region, thereby slowing down the overall decay rate. Simultaneously, the electrode assembly in the second region has a lower equivalent rate of charge and discharge, i.e., a lower current density, resulting in less heat generation, further reducing the temperature difference between the electrode assembly in the first and second regions, slowing down the overall capacity decay rate of the battery cell, and extending the battery cell's lifespan.

[0043] The battery mentioned in the embodiments of this application refers to a single physical module comprising multiple battery cells to provide higher voltage and capacity. A battery generally includes a battery housing for encapsulating the multiple battery cells, which prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0044] Each battery cell 20 is a secondary battery; it can be a lithium-ion battery, or a lithium-sulfur battery, sodium-ion battery, or magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes. Battery cells are generally classified into three types according to their packaging method: cylindrical battery cells, prismatic battery cells, and pouch battery cells.

[0045] A single battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, while the uncoated positive current collector protrudes beyond the coated one, serving as the positive electrode tab. Taking a lithium-ion battery as an example, the positive current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector, while the uncoated negative current collector protrudes beyond the coated one, serving as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative electrode active material can be carbon or silicon, etc. To ensure that a large current can pass through without melting, there are multiple positive electrode tabs stacked together, and there are multiple negative electrode tabs stacked together. The separator can be made of polypropylene (PP) or polyethylene (PE), etc. Furthermore, the electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to these.

[0046] The battery cell also includes a current collector, which is used to electrically connect the tabs and electrode terminals of the battery cell to deliver electrical energy from the electrode assembly to the electrode terminals, and then to the outside of the battery cell via the electrode terminals. Multiple battery cells are electrically connected through a current collector to realize series, parallel or mixed connection of multiple battery cells.

[0047] The battery also includes sampling terminals and a battery management system. The sampling terminals are connected to the busbar and are used to collect information from individual battery cells, such as voltage or temperature. The sampling terminals transmit the collected information from individual battery cells to the battery management system. When the battery management system detects that the information from a battery cell exceeds the normal range, it limits the battery's output power to achieve safety protection.

[0048] It is understood that the power devices applicable to the use of batteries described in the embodiments of this application can take many forms, such as mobile phones, portable devices, laptops, electric vehicles, electric cars, ships, spacecraft, electric toys, and power tools, etc. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0049] The battery cells and batteries described in the embodiments of this application are not limited to the electrical devices described above, but can also be applied to all electrical devices that use battery cells and batteries. However, for the sake of brevity, the following embodiments are all illustrated using electric vehicles as an example.

[0050] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0051] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0052] Please refer to Figure 2 , Figure 2This is an exploded view of a battery provided in some embodiments of this application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, jointly defining a space for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 jointly define the space; alternatively, the first portion 11 and the second portion 12 may both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0053] In battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, battery 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0054] Each battery cell 20 is a secondary battery; it can be a lithium-ion battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0055] Please refer to Figure 3 , Figure 3 This is an exploded structural diagram of a first type of battery cell provided in some embodiments of this application. The battery cell 20 refers to the smallest unit that makes up the battery. Figure 3 The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0056] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, giving battery cell 20 higher structural strength and improved safety performance. Functional components such as electrode terminals can be provided on end cap 21. Electrode terminals can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy into battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0057] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0058] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the electrode assembly, while the portions without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0059] According to some embodiments of this application, please refer to Figures 3-8 , Figure 4 This is a perspective view of a first type of battery cell according to some embodiments of this application, taken from a frontal view. Figure 5 This is a schematic diagram showing the arrangement of electrode assemblies in a first type of battery cell according to some embodiments of this application. Figure 6 This is a schematic diagram showing the arrangement of electrode components in a second type of battery cell according to some embodiments of this application. Figure 7 This is a schematic diagram showing the arrangement of electrode components in a third type of battery cell according to some embodiments of this application. Figure 8 This is a schematic diagram showing the arrangement of electrode components in a fourth type of battery cell according to some embodiments of this application.

[0060] This application provides a battery cell 20, including: a housing 22 and at least three electrode assemblies 23. A cavity is defined within the housing 22, comprising a first region 24 and a second region 25. The first region 24 is closer to the housing 22 than the second region 25. At least three electrode assemblies 23 are disposed within the cavity. The capacity of a single electrode assembly 23 located in the first region 24 is Cap1, and the capacity of a single electrode assembly 23 located in the second region 25 is Cap2, where Cap2 > Cap1.

[0061] The first region 24 is a region closer to the housing 22 than the second region 25, and the first region 24 may contain one or more electrode assemblies 23.

[0062] The second region 25 is a region further away from the housing 22 than the first region 24, and one or more electrode assemblies 23 may be located in the second region 25.

[0063] It should be noted that the first region 24 and the second region 25 are relative. The cavity can be divided into a first cavity and a second cavity, or the cavity can include other regions besides the first cavity and the second cavity.

[0064] For example, please see Figures 3-5The battery cell 20 includes four electrode assemblies 23, which are stacked in a row along the stacking direction. The region containing the two electrode assemblies 23 at both ends is the first region 24, and the region containing the two electrode assemblies 23 in the middle is the second region 25. That is, in this structure, the cavity is divided into a first cavity and a second cavity.

[0065] Please see Figure 6 The battery cell 20 includes five electrode components 23, which are stacked in a row along the stacking direction. The region containing the two electrode components 23 at both ends is the first region 24, and the region containing the middle electrode component 23 is the second region 25. In this structure, the cavity also includes other regions besides the first and second cavities.

[0066] Furthermore, the fact that the second region 25 is farther away from the housing 22 than the first region 24 does not necessarily mean that the second region 25 does not directly contact the housing 22.

[0067] For example, please see Figures 3-5 Each electrode assembly 23 located in the second region 25 has two sides that abut or approach the housing 22, and each electrode assembly 23 located in the first region 24 has three sides that abut or approach the housing 22. Therefore, it can be understood that the area of ​​the surface of a single electrode assembly 23 located in the first region 24 that abuts or approaches the housing 22 is greater than the area of ​​the surface of a single electrode assembly 23 located in the second region 25 that abuts or approaches the housing 22. Alternatively, it can be considered that the second region 25 is farther away from the housing 22 than the first region 24.

[0068] Please see Figure 7 The battery cell 20 includes six electrode components 23, which are stacked in two rows along the stacking direction. The region containing the four electrode components 23 at both ends is designated as the first region 24, and the region containing the two middle electrode components 23 is designated as the second region 25. Each electrode component 23 in the second region 25 has one side abutting or approaching the housing 22, while each electrode component 23 in the first region 24 has three sides abutting or approaching the housing 22. Therefore, it can be understood that the area of ​​the surface of a single electrode component 23 in the first region 24 that abuts or approaches the housing 22 is larger than the area of ​​the surface of a single electrode component 23 in the second region 25 that abuts or approaches the housing 22. Alternatively, the second region 25 can be considered to be further away from the housing 22 than the first region 24.

[0069] Please see Figure 8The battery cell 20 includes nine electrode components 23, which are stacked in three rows along the stacking direction. The region containing the central electrode component 23 is designated as the second region 25, and the region containing the remaining eight electrode components 23 surrounding the central electrode component 23 is designated as the first region 24. Each electrode component 23 in the second region 25 is located away from the housing 22, while each electrode component 23 in the first region 24 has a side contact with or proximity to the housing 22. Therefore, the second region 25 can be considered to be further away from the housing 22 than the first region 24.

[0070] At least one of the positive or negative electrode plates in the electrode assembly 23 is a single piece, that is, the electrode assembly 23 may include a single positive electrode plate and a single negative electrode plate, or may include a single positive electrode plate and multiple negative electrode plates, or may include a single negative electrode plate and multiple positive electrode plates.

[0071] Optionally, the cavity is divided into multiple temperature rise zones, with different temperature rises in different zones. The first zone 24 has the lowest temperature rise, and the second zone 25 has the highest temperature rise.

[0072] The capacity test of electrode assembly 23 is performed using test methods known in the art. As an example, the following method can be used for testing: The test instrument can be a Blue Electric Tester, and the specific steps are as follows: After fully disassembling the positive electrode sheet, soak it in DMC for 30 minutes and then perform single-sided treatment (use NMP or other solvents to wipe off the active material on one side of the electrode sheet and then dry it). Use a Yuan Neng punching machine to punch the treated single-sided electrode sheet (diameter D = 14 mm). Assemble the punched electrode sheet in a glove box. The assembly can be performed in the following order: negative electrode shell, lithium sheet, one drop of electrolyte, separator, one drop of electrolyte, punched positive electrode sheet, gasket, and spring. Perform constant current charge and discharge at 0.1 mA / 0.1 mA to confirm the capacity per unit area (CAP_s). Then, the total capacity of electrode assembly 23 CAP = (8H*L / ΠD^2)*CPA_s.

[0073] Because the electrode assembly 23 in the second region 25 is closer to the center of the casing 22 than the electrode assembly 23 in the first region 24, the operating temperature of the electrode assembly 23 in the second region 25 is higher, and the degree of side reaction at the electrode interface is higher, resulting in greater loss of active lithium and faster capacity decay. The battery cell 20 of this application controls the capacity Cap2 of the electrode assembly 23 in the second region 25 to be greater than the capacity Cap1 of the electrode assembly 23 in the first region 24. The electrode assembly 23 in the second region 25 has more active lithium than the electrode assembly 23 in the first region 24, thereby matching the relative decay rates of the electrode assembly 23 in the second region 25 and the electrode assembly 23 in the first region 24, and thus slowing down the overall decay rate. Meanwhile, the electrode assembly 23 in the second region 25 has a lower equivalent rate during charging and discharging, i.e., a lower current density, which results in less heat generation. This further reduces the temperature difference between the electrode assembly 23 in the first region 24 and the electrode assembly 23 in the second region 25, slows down the capacity decay rate of the entire battery cell 20, and extends the service life of the battery cell 20.

[0074] According to some embodiments of this application, optionally, please continue to refer to Figures 3-6 At least three electrode assemblies 23 are stacked in the cavity. Along the stacking direction, the capacity of the electrode assemblies 23 located at both ends is Cap1, and the capacity of the electrode assemblies 23 located in the middle is Cap2.

[0075] When at least three electrode components 23 are stacked in the cavity, the electrode components 23 at both ends are closer to the housing 22 than the electrode components 23 in the middle. The temperature rise of the electrode components 23 in the middle during use is higher than that of the electrode components at both ends, meaning that the active lithium loss of the electrode components 23 in the middle is greater. The battery cell 20 of this application controls the capacity Cap2 of the electrode components 23 in the middle to be greater than the capacity Cap1 of the electrode components 23 at both ends. The electrode components 23 in the middle have more active lithium than those at both ends, thus matching the relative decay rates of the electrode components 23 in the second region 25 and the electrode components 23 in the first region 24, thereby slowing down the overall decay rate. Simultaneously, the electrode components 23 in the middle have a lower equivalent rate of charge and discharge, i.e., a lower current density, resulting in less heat generation. This further reduces the temperature difference between the electrode components 23 in the middle and those at both ends, slowing down the capacity decay rate of the entire battery cell 20 and extending its service life.

[0076] According to some embodiments of this application, optionally, please refer to... Figure 4The thickness of a single electrode assembly 23 located in the first region 24 along the stacking direction is H1, and the thickness of a single electrode assembly 23 located in the second region 25 along the stacking direction is H2. Cap1, Cap2, H1 and H2 satisfy the following relationship: (Cap1×H2) / (Cap2×H1)<1.

[0077] The stacking direction is the arrangement direction of the electrode assembly 23.

[0078] Optionally, 0.8 ≤ (Cap1×H2) / (Cap2×H1) < 1.

[0079] Since the capacity and thickness of the battery cell 20 are positively correlated, when (Cap1×H2) / (Cap2×H1)<1, the capacity Cap2 of the electrode assembly 23 in the second region 25 is greater than the capacity Cap1 of the electrode assembly 23 in the first region 24. When (Cap1×H2) / (Cap2×H1)≥1, the capacity Cap2 of the electrode assembly 23 in the second region 25 is less than the capacity Cap1 of the electrode assembly 23 in the first region 24, which will lead to a reduction in the service life of the battery cell 20. When (Cap1×H2) / (Cap2×H1)<0.8, it will also lead to a reduction in the service life of the battery cell 20.

[0080] According to some embodiments of this application, optionally, please refer to... Figure 6 The cavity also includes a third region 26, which is closer to the housing 22 than the second region 25. The first region 24 is closer to the housing 22 than the third region 26. The capacity of a single electrode assembly 23 located in the third region 26 is Cap3, where Cap2≥Cap3≥Cap1.

[0081] The third region 26 is a region that is farther away from the housing 22 than the first region 24 and closer to the housing 22 than the second region 25. The third region 26 may contain one or more electrode assemblies 23.

[0082] It should be noted that when Cap2 ≥ Cap3, Cap2 = Cap3 satisfies the condition, then Cap3 > Cap1; when Cap3 ≥ Cap1, Cap3 = Cap1 satisfies the condition, then Cap2 > Cap3. That is, the two equality signs in Cap2 ≥ Cap3 ≥ Cap1 cannot be satisfied at the same time.

[0083] Optionally, Cap2 > Cap3 > Cap1.

[0084] Because the electrode assembly 23 in the second region 25 is closer to the center of the casing 22 than the electrode assembly 23 in the third region 26, the operating temperature of the electrode assembly 23 in the second region 25 is higher. The operating temperature of the electrode assembly 23 in the third region 26 is higher than that of the electrode assembly 23 in the first region 24. This results in a greater loss of active lithium in the electrode assembly 23 in the second region 25 compared to the third region 26, and a greater loss of active lithium in the electrode assembly 23 in the third region 26 compared to the first region 24. The principle of Cap2≥Cap3≥Cap1 helps to ensure that the electrode assembly 23 in the region with higher temperature rise has more active lithium, making the relative decay rate of the electrode assembly 23 in different regions more matched, thereby slowing down the overall decay rate and extending the service life of the battery cell 20.

[0085] According to some embodiments of this application, optionally, the battery cell 20 satisfies at least one of the following conditions a and b: a) the coating mass of the positive electrode active material of the single electrode assembly 23 located in the first region 24 is less than the coating mass of the positive electrode active material of the single electrode assembly 23 located in the second region 25; b) the specific capacity of the positive electrode active material of the single electrode assembly 23 located in the first region 24 is less than the specific capacity of the positive electrode active material of the single electrode assembly 23 located in the second region 25.

[0086] The coating quality of the positive active material of a single electrode assembly 23 and the specific capacity of the positive active material of a single electrode assembly 23 both affect the capacity Cap of the electrode assembly 23.

[0087] According to some embodiments of this application, optionally, the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 located in the second region 25 is 0.8 to 0.99:1.

[0088] As an example, the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 located in the second region 25 can be 0.8∶1, 0.82∶1, 0.85∶1, 0.88∶1, 0.9∶1, 0.92∶1, 0.95∶1 or 0.99∶1.

[0089] The higher the coating quality of the positive electrode active material of a single electrode assembly 23, the higher the capacity Cap of the electrode assembly 23. When the ratio of the coating quality of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the coating quality of the positive electrode active material of a single electrode assembly 23 located in the second region 25 is 0.8 to 0.99:1, not only can the capacity Cap of a single electrode assembly 23 located in the first region 24 be less than the capacity Cap of a single electrode assembly 23 located in the second region 25, but the difference between the capacity Cap1 of a single electrode assembly 23 located in the first region 24 and the capacity Cap2 of a single electrode assembly 23 located in the second region 25 of the battery cell 20 will not be too large.

[0090] Optionally, the coating mass of the positive electrode active material layer of the electrode assembly 23 is 0.1 g / 1540.25 mm. 2 ~0.6g / 1540.25mm 2 .

[0091] As an example, the coating quality of the positive electrode active material layer of electrode assembly 23 can be 0.1 g / 1540.25 mm. 2 0.2g / 1540.25mm 2 0.3g / 1540.25mm 2 0.4g / 1540.25mm 2 0.5g / 1540.25mm 2 Or 0.6g / 1540.25mm 2 .

[0092] Optionally, the coating mass of the positive electrode active material layer of the electrode assembly 23 is 0.2 g / 1540.25 mm. 2 ~0.45g / 1540.25mm 2 .

[0093] Optionally, the compaction density of the positive electrode sheet is 1.8 g / cc to 3.9 g / cc.

[0094] As an example, the compaction density of the positive electrode sheet can be 1.8 g / cc, 1.9 g / cc, 2 g / cc, 2.1 g / cc, 2.2 g / cc, 2.3 g / cc, 2.4 g / cc, 2.5 g / cc, 2.6 g / cc, 2.7 g / cc, 2.8 g / cc, 2.9 g / cc, 3 g / cc, 3.1 g / cc, 3.2 g / cc, 3.3 g / cc, 3.4 g / cc, 3.5 g / cc, 3.6 g / cc, 3.7 g / cc, 3.8 g / cc, or 3.9 g / cc.

[0095] Optionally, the compaction density of the positive electrode sheet is 2.1 g / cc to 3.6 g / cc.

[0096] Optionally, the positive electrode active material includes any one or more of nickel cobalt manganese (NCM), nickel cobalt aluminum (NCA), lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, and sodium ion compounds.

[0097] Optionally, the coating mass of the negative electrode active material layer of the electrode assembly 23 is 0.05 g / 1540.25 mm. 2 ~0.4g / 1540.25mm 2 .

[0098] As an example, the coating quality of the negative electrode active material layer of electrode assembly 23 can be 0.05 g / 1540.25 mm. 2 0.1g / 1540.25mm 2 0.2g / 1540.25mm 2 0.3g / 1540.25mm 2 Or 0.4g / 1540.25mm 2 .

[0099] Optionally, the coating mass of the negative electrode active material layer of the electrode assembly 23 is 0.12 g / 1540.25 mm. 2 ~0.2g / 1540.25mm 2 .

[0100] Optionally, the compaction density of the negative electrode sheet is 0.5 g / cc to 2.2 g / cc.

[0101] As an example, the compaction density of the negative electrode sheet can be 0.5 g / cc, 0.6 g / cc, 0.7 g / cc, 0.8 g / cc, 0.9 g / cc, 1 g / cc, 1.1 g / cc, 1.2 g / cc, 1.3 g / cc, 1.4 g / cc, 1.5 g / cc, 1.6 g / cc, 1.7 g / cc, 1.8 g / cc, 1.9 g / cc, 2 g / cc, 2.1 g / cc, or 2.2 g / cc.

[0102] Optionally, the compaction density of the negative electrode sheet is 2.1 g / cc to 3.6 g / cc.

[0103] Optionally, the negative electrode active material includes any one or more of artificial graphite, natural graphite, soft carbon, hard carbon, graphene, carbon nanotubes, and lithium titanate.

[0104] According to some embodiments of this application, optionally, the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 located in the second region 25 is 0.92 to 0.95:1.

[0105] When the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 located in the second region 25 is 0.8 to 0.99:1, not only can the capacity Cap of a single electrode assembly 23 located in the first region 24 be less than the capacity Cap of a single electrode assembly 23 located in the second region 25, but the difference between the capacity Cap1 of a single electrode assembly 23 located in the first region 24 and the capacity Cap2 of a single electrode assembly 23 located in the second region 25 of the battery cell 20 will not be too large.

[0106] According to some embodiments of this application, optionally, the ratio of the specific capacity of the positive electrode active material of a single electrode assembly 23 located in the first region 24 to the specific capacity of the positive electrode active material of a single electrode assembly 23 located in the second region 25 is 1:1.05 to 1.1.

[0107] As an example, the ratio of the specific capacity of the positive active material of a single electrode assembly 23 located in the first region 24 to the specific capacity of the positive active material of a single electrode assembly 23 located in the second region 25 can be 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09 or 1:1.1.

[0108] The larger the specific capacity of the positive active material of a single electrode assembly 23, the higher the capacity Cap of the electrode assembly 23. When the ratio of the specific capacity of the positive active material of a single electrode assembly 23 located in the first region 24 to the specific capacity of the positive active material of a single electrode assembly 23 located in the second region 25 is 1:1.05 to 1.1, it is possible not only to make the capacity Cap of a single electrode assembly 23 located in the first region 24 smaller than the capacity Cap of a single electrode assembly 23 located in the second region 25, but also to ensure that the positive active materials in different regions are matched.

[0109] The following describes the battery cell 20 of this application in further detail with reference to the embodiments.

[0110] The battery cell 20 of Examples 1-10 and Comparative Example 1 are as follows: Figures 3-5 As shown, the battery cell 20 includes four electrode components 23, which are stacked in a row along the stacking direction. The area containing the two electrode components 23 at both ends is the first region 24, and the area containing the two electrode components 23 in the middle is the second region 25.

[0111] The battery cell 20 of Examples 11-13 and Comparative Example 2 are as follows: Figure 6As shown, the battery cell 20 includes five electrode components 23, which are stacked in a row along the stacking direction. The area containing the two electrode components 23 at both ends is the first region 24, the area containing the middle electrode component 23 is the second region 25, and the area containing the second and fourth electrode components 23 along the stacking direction is the third region 26.

[0112] The material selection and parameters of the electrode assembly 23 located in the first region 24 of Examples 1-13 and Comparative Examples 1-2 are shown in Table 1. The material selection and parameters of the electrode assembly 23 located in the second region 25 of Examples 1-13 and Comparative Examples 1-2 are shown in Table 2. The material selection and parameters of the electrode assembly 23 located in the third region 26 of Examples 10-13 and Comparative Example 2 are shown in Table 3.

[0113] Table 1. Electrode assemblies 23 located in the first region 24 of Examples 1-13 and Comparative Examples 1-2.

[0114]

[0115]

[0116]

[0117] Table 2 shows the electrode assembly 23 located in the second region 25 of Examples 1-13 and Comparative Examples 1-2.

[0118]

[0119]

[0120] Table 3 Electrode assembly 23 located in the third region 26 of Examples 10-13 and Comparative Example 2

[0121]

[0122]

[0123] Preparation method of battery cell 20:

[0124] S1. Dissolve the positive electrode material in N-methylpyrrolidone at a suitable weight ratio, stir under vacuum to obtain a positive electrode slurry, coat the slurry evenly on the surface of an aluminum foil, ensuring that the coating weight on both sides of the aluminum foil is the same, and then cold press the electrode sheet to obtain a positive electrode sheet.

[0125] S2. Dissolve the negative electrode material in deionized water in a certain order according to a suitable weight ratio and stir thoroughly to obtain a negative electrode slurry. Coat the slurry evenly on the surface of the copper foil, ensuring that the coating weight on both sides is the same. Then, cold press the electrode sheet to obtain the negative electrode sheet.

[0126] S3. The positive and negative electrode sheets prepared under the above different conditions are die-cut, wound, hot-pressed, welded and injected with liquid to obtain a hard-shell lithium-ion battery 100.

[0127] S4. Form the lithium-ion battery 100, charge it to 3.0V with a constant current of 0.1C, and charge it to 3.75V with a constant current of 0.2C.

[0128] S5. Perform capacity testing on lithium-ion battery 100. The charging method is to charge at a constant current of 0.33C to the rated upper limit voltage and then charge at a constant voltage to the current of 0.05C. Discharge the charged lithium-ion battery 100 by discharging at a DC current of 0.33C to the rated lower limit voltage to obtain the discharge capacity of lithium-ion battery 100.

[0129] Test case

[0130] Battery cells 20 from Examples 1 to 13 and Comparative Examples 1 to 2 of this application were used to measure their cycle number and energy density, and the (Cap1×H2) / (Cap2×H1) value was calculated. The results are shown in Table 4.

[0131] The number of cycles was measured using the following method:

[0132] The battery cell 20 was subjected to a 0.5C / 0.5C cycle test at 25°C until the capacity decayed to 80% of the initial capacity, and the number of cycles was measured.

[0133] Energy density = energy / volume, unit: wh / L.

[0134] Energy testing method: Constant current at 0.33C to the upper limit voltage, constant voltage at 0.05C, discharge at 0.33C to the lower limit voltage, and measure the discharge energy (Wh).

[0135] The volume is calculated based on the external dimensions (length, width, and height) of the battery cell (20) and the casing (22).

[0136] Table 4 shows the cycle number, energy density, and (Cap1×H2) / (Cap2×H1) value of cell 20 in Examples 1-13 and Comparative Examples 1-2.

[0137]

[0138]

[0139] As can be seen from Examples 1 to 4, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.8 to 0.99:1, and the thickness of the electrode assembly 23 in the first region 24 is the same as the thickness of the electrode assembly 23 in the second region 25, Cap1 < Cap2, and 0.8 ≤ (Cap1 × H2) / (Cap2 × H1) < 1, the number of cycles of the battery cell 20 is 2100 to 2500, and the energy density is 603 Wh / L to 630 Wh / L.

[0140] As can be seen from the comparison between Example 5 and Example 1, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.92:1, the thickness of the electrode assembly 23 in the first region 24 < the thickness of the electrode assembly 23 in the second region 25, the value of (Cap1 × H2) / (Cap2 × H1) is 0.98. Compared with Example 1, the number of cycles of the battery cell 20 in Example 5 slightly decreases to 2300, and the energy density slightly decreases to 615 Wh / L.

[0141] As can be seen from the comparison between Example 6 and Example 3, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.95:1, the thickness of the electrode assembly 23 in the first region 24 < the thickness of the electrode assembly 23 in the second region 25, the value of (Cap1 × H2) / (Cap2 × H1) is 0.99. Compared with Example 3, the number of cycles of the battery cell 20 in Example 6 slightly decreases to 2300, and the energy density slightly decreases to 610 Wh / L.

[0142] As can be seen from the comparison between Example 7 and Example 2, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.8:1, the thickness of the electrode assembly 23 in the first region 24 > the thickness of the electrode assembly 23 in the second region 25, the value of (Cap1 × H2) / (Cap2 × H1) is 0.75. Compared with Example 2, the number of cycles of the battery cell 20 in Example 6 decreases to 1800, and the energy density remains unchanged at 630 Wh / L.

[0143] As can be seen from Examples 8 to 9, when the ratio of the gram capacity of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the gram capacity of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 1:1.05 to 1.1, and the thickness of the electrode assembly 23 in the first region 24 is the same as the thickness of the electrode assembly 23 in the second region 25, Cap1 < Cap2, and 0.91 ≤ (Cap1 × H2) / (Cap2 × H1) ≤ 0.95, the number of cycles of the battery cell 20 is 2200 to 2300, and the energy density is 610 Wh / L to 618 Wh / L.

[0144] As can be seen from Example 10, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.92:1, and the ratio of the gram capacity of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the gram capacity of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 1:1.05 to 1.1, and the thickness of the electrode assembly 23 in the first region 24 is the same as the thickness of the electrode assembly 23 in the second region 25, Cap1 < Cap2, and the value of (Cap1 × H2) / (Cap2 × H1) is 0.876, the number of cycles of the battery cell 20 is 2400, and the energy density is 625 Wh / L.

[0145] As can be seen from Examples 11 to 13, when the ratio of the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24 to the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25 is 0.92:1, the coating mass of the positive electrode active material of a single electrode assembly 23 in the third region 26 is the same as the coating mass of the positive electrode active material of a single electrode assembly 23 in the second region 25, or the coating mass of the positive electrode active material of a single electrode assembly 23 in the third region 26 is the same as the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24, or the coating mass of the positive electrode active material of a single electrode assembly 23 in the third region 26 > the coating mass of the positive electrode active material of a single electrode assembly 23 in the first region 24, and the thickness of the electrode assembly 23 in the first region 24, the thickness of the electrode assembly 23 in the second region 25, and the thickness of the electrode assembly 23 in the third region 26 are all the same, Cap1 < Cap2, and the value of (Cap1 × H2) / (Cap2 × H1) is 0.92, the number of cycles of the battery cell 20 is 2200 to 2400, and the energy density is 618 Wh / L to 623 Wh / L.

[0146] As can be seen from the comparison between Comparative Example 1 and Example 1, when the capacity Cap1 of a single electrode assembly 23 located in the first region 24 and the capacity Cap2 of a single electrode assembly 23 located in the second region 25 are the same, the number of cycles of Comparative Example 1 is only 2400 and the energy density is 600Wh / L. That is, the battery cell 20 of Comparative Example 1 has a shorter service life than the battery cell 20 of Example 1.

[0147] As can be seen from the comparison between Comparative Example 2 and Example 11, when the capacity Cap1 of a single electrode assembly 23 located in the first region 24 and the capacity Cap2 of a single electrode assembly 23 located in the second region 25 are the same, the number of cycles of Comparative Example 1 is only 1800 and the energy density is 600Wh / L. That is, the battery cell 20 of Comparative Example 2 has a shorter service life than the battery cell 20 of Example 11.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The battery cell comprises: a housing, the housing defining a cavity therein, the cavity comprising a first region and a second region, the first region being closer to the housing than the second region; at least three electrode assemblies arranged in the cavity, a capacity of a single electrode assembly in the first region being Cap1, a capacity of a single electrode assembly in the second region being Cap2, Cap2>Cap1; the at least three electrode assemblies are arranged in a stack in the cavity, along a stacking direction, a capacity of the electrode assemblies at both ends being Cap1, a capacity of the electrode assemblies in the middle being Cap2; a thickness of a single electrode assembly in the first region along the stacking direction being H1, a thickness of a single electrode assembly in the second region along the stacking direction being H2, Cap1, Cap2, H1 and H2 satisfying the following relationship: 0.8≤(Cap1×H2) / (Cap2×H1)<1.

2. The battery cell of claim 1, wherein, the cavity further comprises a third region, the third region being closer to the housing than the second region, the first region being closer to the housing than the third region, a capacity of a single electrode assembly in the third region being Cap3, Cap2≥Cap3≥Cap1.

3. The battery cell according to claim 1 or 2, characterized in that, at least one of the following conditions a and b is satisfied: a, a coating mass of positive active material of a single electrode assembly in the first region is < a coating mass of positive active material of a single electrode assembly in the second region; b, a gram capacity of positive active material of a single electrode assembly in the first region is < a gram capacity of positive active material of a single electrode assembly in the second region.

4. The battery cell of claim 3, wherein, a ratio of a coating mass of positive active material of a single electrode assembly in the first region to a coating mass of positive active material of a single electrode assembly in the second region is 0.8-0.99:

1.

5. The battery cell of claim 3, wherein, a ratio of a coating mass of positive active material of a single electrode assembly in the first region to a coating mass of positive active material of a single electrode assembly in the second region is 0.92-0.95:

1.

6. The battery cell of claim 3, wherein, a ratio of a gram capacity of positive active material of a single electrode assembly in the first region to a gram capacity of positive active material of a single electrode assembly in the second region is 1:1.05-1.

1.

7. A battery, characterized by The battery comprises the battery cell according to any one of claims 1-6.

8. An electrical device, characterized by The electric device comprises the battery according to claim 7, the battery being used to provide electric energy.

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