Battery monomer, battery device, electric equipment and energy storage device

Abstract

The utility model provides a battery monomer, a battery device, electric equipment and an energy storage device, and belongs to the field of batteries. The battery monomer comprises a shell and an electrode assembly arranged in the shell, the electrode assembly comprises a negative plate, and the negative plate comprises a current collector and a negative active material layer arranged on the surface of the current collector; and the compaction density of the negative active material layer is in a decreasing trend from the bottom of the battery cell to the top of the battery cell. The porosity of the active material layer in the battery cell is in a trend of increasing from the bottom of the battery cell to the top of the battery cell, so that the electrolyte climbing difficulty of an electrolyte in a negative plate can be reduced, the infiltration effect of the top of the negative plate is improved, the lithium precipitation degree of the top of the negative plate can be reduced, and the safety risk of lithium precipitation to the battery can be further reduced.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, battery device, electrical equipment, and energy storage device. Background Technology

[0002] Energy conservation and emission reduction are key to sustainable social development. Rechargeable batteries, with their ability to store and release energy as needed, are widely used in various electrical devices and energy storage systems, and are an important component in promoting energy transition and sustainable development. For the new energy industry, battery technology is a crucial factor in its development.

[0003] Heavy-duty trucks, mining trucks, buses, and logistics vehicles typically use large-capacity batteries with a considerable height, usually no less than 300 mm. In actual use, these vehicles' batteries may experience severe lithium plating on the negative electrode during overcurrent charging or low-temperature charging. The deposited metallic lithium accumulates over time, forming lithium dendrites. These sharp lithium dendrites can easily pierce the separator, causing an internal short circuit and leading to safety issues. Utility Model Content

[0004] This application aims to at least address one of the technical problems existing in the background art. Therefore, one objective of this application is to provide a battery cell, battery device, electrical equipment, and energy storage device that can mitigate lithium plating on the negative electrode, thereby reducing the safety risks posed by lithium plating to the battery.

[0005] An embodiment of the first aspect of this application provides a battery cell, including: a housing and an electrode assembly. The housing has a receiving cavity, and the electrode assembly is disposed in the receiving cavity. The electrode assembly includes a negative electrode sheet, which includes a current collector and a negative electrode active material layer disposed on the surface of the current collector. From the bottom to the top of the battery cell, the compaction density of the negative electrode active material layer decreases.

[0006] In the technical solution of this application embodiment, by making the compaction density of the active material layer of the negative electrode decrease from the bottom to the top of the battery cell, the porosity of the active material layer increases from the bottom to the top of the battery cell. This reduces the difficulty of electrolyte migration from the bottom to the top of the negative electrode cell via capillary effect, improving the electrolyte absorption capacity of the top of the negative electrode cell to some extent, and thus promoting the wetting effect of the top of the negative electrode cell. This reduces the degree of lithium plating on the top of the negative electrode cell, thereby helping to reduce the safety risks posed by lithium plating to the battery.

[0007] In some embodiments, the negative electrode active material layer includes a plurality of active regions sequentially arranged along the height direction of the battery cell, and the compaction density of the plurality of active regions decreases sequentially from the bottom to the top of the battery cell. In the manufacturing process of the negative electrode sheet in this embodiment, the plurality of active regions can be processed in steps, thus eliminating the need for continuous adjustment of the negative electrode active material quality and roller pressure during the processing of each active region.

[0008] In some embodiments, the bottom wall of the housing is used to be adjacent to a heat exchange device for heat exchange; the active region closest to the heat exchange device among multiple active regions is the first active region, and the remaining active regions are the second active regions, with the coating area of ​​each second active region being less than or equal to the coating area of ​​the first active region. Compared with technical solutions where the coating area of ​​the first active region is smaller than the coating area of ​​the remaining active regions, the temperature of the first active region closest to the heat exchange device in this embodiment is relatively higher, which can reduce the risk of lithium plating caused by excessively low temperature in the first active region.

[0009] In some embodiments, the second active region has multiple regions, the dimension of the negative electrode active material layer in the height direction of the battery cell is the total dimension, and the proportion of the dimension of the first active region in the height direction of the battery cell in the total dimension is greater than or equal to 20% and less than or equal to 40%. This embodiment makes the proportion of the dimension of the first active region in the height direction of the battery cell in the total dimension moderate, so that the improvement of the wetting effect on the top of the negative electrode sheet and the mitigation of lithium plating due to excessively low temperature can be balanced to a certain extent.

[0010] In some embodiments, the dimensions and coating area of ​​each second active region are the same in the height direction of the battery cell. When manufacturing the negative electrode sheet of this embodiment, the coating process of multiple second active regions can be completed in one step, and then the rolling pressure can be adjusted by dividing the sections, which helps to reduce production interruptions.

[0011] In some embodiments, the proportion of the dimension of each second active region in the height direction of the battery cell to the total dimension is greater than or equal to 20% and less than or equal to 25%. This embodiment reduces the difficulty of coating and rolling by making the proportion of the dimension of the second active region in the height direction of the battery cell moderate.

[0012] In some embodiments, the compaction density of at least a portion of the negative electrode active material layer gradually decreases from the bottom to the top of the battery cell. This embodiment results in a gradual change in the compaction density of at least a portion of the negative electrode active material layer, which reduces the difficulty of electrolyte migration from the bottom to the top of the negative electrode sheet and also improves the uniformity of electrolyte wetting in the negative electrode sheet to some extent.

[0013] In some embodiments, the negative electrode active material layer includes a first coating area and a second coating area arranged sequentially along the height direction of the battery cell. The first coating area is closer to the bottom of the battery cell than the second coating area. The compaction density of the first coating area is equal everywhere, while the compaction density of the second coating area gradually decreases from the bottom to the top of the battery cell.

[0014] In some embodiments, the dimension of the negative electrode active material layer in the height direction of the battery cell is the total dimension, which is greater than or equal to 180 mm and less than or equal to 210 mm. Batteries made using this negative electrode have the characteristics of large capacity and large height, making them suitable for use in heavy-duty trucks, mining trucks, buses, logistics vehicles, and other transport vehicles.

[0015] In some embodiments, the difference between the maximum and minimum values ​​of the thickness t at various points on the negative electrode is greater than 0 μm and less than or equal to 10 μm. This embodiment allows the thickness at various points on the negative electrode to fluctuate within a range not exceeding 10 μm, thereby reducing the precision requirements on the manufacturing equipment.

[0016] In some embodiments, the thickness t at various points on the negative electrode sheet ranges from 94.6 μm ≤ t ≤ 104.6 μm, or the thickness t at various points on the negative electrode sheet ranges from 90 μm ≤ t ≤ 100 μm.

[0017] In some embodiments, the height of a single battery cell is greater than or equal to 300 mm and less than or equal to 400 mm.

[0018] An embodiment of the second aspect of this application provides a battery device that includes the battery cell described in the above embodiments.

[0019] In some embodiments, the battery device further includes a heat exchange device located below the battery cells and exchanging heat with them. By introducing the heat exchange device, this embodiment allows the heat generated by the battery cells during operation to be exchanged with the heat exchange device, which helps reduce the possibility of thermal runaway in the battery cells and improves battery safety.

[0020] An embodiment of the third aspect of this application provides an electrical device that includes the battery device described in the above embodiments, the battery device being used to provide electrical energy.

[0021] An embodiment of the fourth aspect of this application provides an energy storage device, which includes a battery cell as described in the above embodiments, the battery cell being capable of storing and providing electrical energy; or, it includes a battery device as described in the above embodiments, the battery device being capable of storing and providing electrical energy.

[0022] 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

[0023] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0024] Figure 1 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0025] Figure 2 This is an exploded view of the battery device according to some embodiments of this application;

[0026] Figure 3 This is a schematic diagram of the structure of the negative electrode sheet of a battery cell in some embodiments of this application;

[0027] Figure 4 This is a schematic diagram of the structure of a battery cell and a heat exchange device in some embodiments of this application;

[0028] Figure 5 This is a schematic diagram of the negative electrode sheet of a battery cell in some other embodiments of this application.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1000 vehicles;

[0031] Battery unit 100, controller 200, motor 300;

[0032] Battery cell assembly 10, battery cell 11, negative electrode sheet 110, current collector 111, negative electrode active material layer 112, first coating area 1121, second coating area 1122, active area 113, first active area 1131, second active area 1132.

[0033] Box 20, first box 21, second box 22;

[0034] Heat exchange device 30. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation", "connection", "linking", 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 connection of two components or the interaction between two components.

[0043] In this application, the term "parallel" includes not only absolute parallelism but also approximate parallelism as commonly understood in engineering; similarly, "perpendicular" also includes not only absolute perpendicularity but also approximate perpendicularity as commonly understood in engineering. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0044] Currently, the application of rechargeable batteries is becoming increasingly widespread, judging from market trends. They are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also extensively in various electronic devices, such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As the application areas of rechargeable batteries continue to expand, the market demand is also constantly increasing.

[0045] The height of a battery is related to its installation position on electrical equipment or energy storage systems and its power load requirements. For transport vehicles such as heavy-duty trucks, mining trucks, buses, and logistics vehicles, the longitudinal space under the chassis is often used to house the battery in order to reduce its footprint in the cabin (e.g., passenger compartment or cargo compartment). Because the chassis of a transport vehicle is higher than that of a regular passenger car, and to maximize battery capacity to meet power load demands, the batteries used in these vehicles are characterized by large capacity and height. However, in actual use, the negative electrode of such batteries may undergo severe lithium plating, jeopardizing battery safety.

[0046] Lithium-ion batteries primarily function by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, lithium ions repeatedly insert and extract between the two electrodes. When charging, lithium ions extract from the positive electrode and migrate to the negative electrode via the electrolyte. Ideally, lithium ions diffuse into the interior of the negative electrode particles, completing a reversible insertion reaction. When lithium ions fail to successfully insert into the negative electrode, they gain electrons on the surface of the electrode, forming silvery-white metallic lithium—a phenomenon known as lithium plating.

[0047] Electrolyte, as the transport medium for lithium ions, affects lithium ion diffusion and plays a crucial role in lithium plating. Batteries in heavy-duty trucks, mining trucks, buses, and logistics vehicles are tall, resulting in a relatively tall negative electrode. This makes it difficult for the electrolyte to migrate to the top of the negative electrode, leading to poor wetting at the top and consequently lithium plating. This is especially true for batteries with sealed casings (e.g., pouch cells), where electrolyte flow is weak, further complicating the migration process. Furthermore, after a certain period of use, batteries undergo multiple charge-discharge cycles. During these cycles, the electrolyte decomposes and evaporates, continuously consuming the electrolyte and exacerbating lithium plating at the top of the negative electrode.

[0048] In view of this, a battery cell, battery device, electrical equipment and energy storage device are designed. By making the compaction density of the active material layer of the negative electrode decrease from the bottom to the top of the battery cell, the porosity of the active material layer near the top of the battery cell is greater than that near the bottom of the battery cell. This reduces the difficulty of electrolyte creeping in the relatively tall negative electrode, thereby reducing the degree of lithium plating at the top of the negative electrode.

[0049] The battery devices described in this application can be used, but are not limited to, in electrical equipment or energy storage devices such as vehicles, ships, or aircraft. A power system comprising the battery cells and battery devices described in this application can be used to construct such electrical equipment or energy storage devices.

[0050] The energy storage device utilizing a battery as a power system in this application embodiment can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems, etc. The energy storage device can store electrical energy as needed and output it at appropriate times. For example, the energy storage device can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours. The energy storage device provided in this application embodiment can be used in any power system that requires energy storage.

[0051] In some embodiments, the energy storage device is an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0052] In some embodiments, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet. Each battery cluster may include multiple battery units connected in series via a busbar to increase the voltage of the energy storage device. When the energy storage device includes multiple battery clusters, these clusters are connected in parallel to increase the capacity of the energy storage device.

[0053] In this application embodiment, the electrical devices using battery devices as power sources can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0054] It should be understood that the technical solutions described in the embodiments of this application are not limited to the battery devices and electrical equipment described above, but can also be applied to all battery devices including housings and electrical equipment using battery devices. However, for the sake of brevity, the following embodiments are all illustrated using electric vehicles as examples.

[0055] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 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. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is provided inside the vehicle 1000, and the battery device 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 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 device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0056] In some embodiments of this application, the battery device 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.

[0057] Figure 2 A schematic diagram of the structure of a battery device 100 according to an embodiment of this application is shown. Figure 2 As shown, the battery device 100 mentioned in the embodiments of this application may include one or more battery cell assemblies 10 for providing voltage and capacity. The battery cell assembly 10 may include multiple battery cells 11, which are connected in series, parallel, or mixed connection via a busbar.

[0058] In some embodiments, the battery cell assembly 10 is typically formed by arranging a plurality of battery cells 11.

[0059] As an example, the battery cell assembly 10 can be a battery module, which is formed by arranging and fixing multiple battery cells 11 in a horizontal direction to form an independent module. Alternatively, the battery module can be formed by stacking and fixing multiple battery cells 11 to form an independent module.

[0060] In some embodiments, such as Figure 2 As shown, the battery device 100 can be a battery pack, which includes a housing 20 and one or more individual battery cells 10, with the individual battery cells 10 housed within the housing 20. The housing 20 can be a simple three-dimensional structure such as a single cuboid, cylinder, or sphere, or a complex three-dimensional structure composed of combinations of simple cuboids, cylinders, or spheres. The material of the housing 20 can be an alloy such as aluminum alloy or iron alloy, a polymer such as polycarbonate or polyisocyanurate foam, or a composite material such as glass fiber and epoxy resin.

[0061] As an example, the battery cell assembly 10 can be a battery module, and the battery cell assembly 10 can be housed in the housing 20 by fixing the battery module in the housing 20.

[0062] As an example, the battery cell assembly 10 can also be housed in the housing 20 by directly fixing multiple battery cells 11 to the housing 20.

[0063] As an example, the housing 20 may include a first housing 21 and a second housing 22. The first housing 21 and the second housing 22 are fastened together to form a closed space inside the housing 20 to house the battery cell assembly 10. Here, "closed" refers to covering or closing, and can be either non-sealed or sealed to prevent liquids or other foreign objects from affecting the charging or discharging of the battery cell 11. The first housing 21 may be a top cover or a bottom plate.

[0064] As an example, the housing 20 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that the interior of the housing 20 forms an enclosed space to house the battery cell assembly 10.

[0065] In some embodiments, the housing 20 may be part of the vehicle's chassis structure. For example, a portion of the housing 20 may be at least a portion of the vehicle's floor, or a portion of the housing 20 may be at least a portion of the vehicle's crossbeams and longitudinal beams.

[0066] The battery cell 11 provided in the embodiments of this application can be a secondary battery. A secondary battery refers to a battery cell 11 that can be used again after being discharged by recharging to activate the active material.

[0067] The battery cell 11 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application embodiment is not limited to this. As an example, the battery cell 11 can be a cylindrical battery cell, a prismatic battery cell, or a battery cell 11 of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic battery cells, such as hexagonal prismatic battery cells, etc., and this application has no particular limitation.

[0068] The battery cell 11 provided in the embodiments of this application includes a casing, an electrode assembly, and an electrolyte. The casing has a receiving cavity, and the electrode assembly is the component in the battery cell 11 where the electrochemical reaction occurs. The electrode assembly and the electrolyte are contained within the receiving cavity. As an example, the casing can be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing can be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag may be included between the casing and the electrode assembly. The sealing bag is used to encapsulate the electrode assembly and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate the electrode assembly and the electrolyte, etc.

[0069] The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell 11, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrode. The separator, located between the positive and negative electrode, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0070] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked. In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0071] Figure 3 This is a schematic diagram of the negative electrode 110 of a battery cell 11 according to some embodiments of this application. In the battery cell 11 provided in the embodiments of this application, such as... Figure 3 As shown, the negative electrode 110 includes a current collector 111 and a negative electrode active material layer 112 disposed on the surface of the current collector 111; from the bottom of the battery cell 11 to the top of the battery cell 11, the compaction density of the negative electrode active material layer 112 tends to decrease.

[0072] The current collector 111 can be made of metal foil, conductive polymer material, carbon material, or composite current collector. For example, as a metal foil, it can be made of pure metal, alloy, or surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). As an example, the material of current collector 111 can be copper.

[0073] The current collector 111 has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer 112 is disposed on either or both of the two surfaces opposite to each other of the current collector 111.

[0074] The negative electrode active material layer 112 can be formed by coating the negative electrode active material onto the surface of the current collector 111. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Because the compaction density of the portion of the negative electrode active material layer 112 near the top of the battery cell 11 is lower than the compaction density of the portion of the negative electrode active material layer 112 near the bottom of the battery cell 11, the porosity of the portion of the negative electrode active material layer 112 near the top of the battery cell 11 is higher than the porosity of the portion of the negative electrode active material layer 112 near the bottom of the battery cell 11.

[0075] In this embodiment, by making the compaction density of the active material layer of the negative electrode 110 decrease from the bottom to the top of the battery cell 11, the porosity of the active material layer increases from the bottom to the top of the battery cell 11. This reduces the difficulty of electrolyte migration from the bottom to the top of the negative electrode 110 via capillary effect, improving the electrolyte absorption capacity of the top of the negative electrode 110 to some extent, and thus promoting the wetting effect of the top of the negative electrode 110. This reduces the degree of lithium plating on the top of the negative electrode 110, thereby reducing the safety risks posed by lithium plating to the battery.

[0076] According to some embodiments of this application, the height of the battery cell 11 can be configured to be greater than or equal to 300 mm and less than or equal to 400 mm. Specifically, the height of the battery cell 11 can be selected from any value among 300 mm, 330 mm, 350 mm, and 400 mm. This embodiment, by making the height of the battery cell 11 range between 300 mm and 400 mm, allows the battery cell 11 to be matched with the longitudinal space under the chassis of heavy-duty trucks / mining trucks / buses / logistics vehicles, etc., so that it can be used to form the power system of such vehicles.

[0077] It is understandable that the decreasing trend in the compaction density of the negative electrode active material layer 112 should be interpreted broadly. For example, it can be understood that the compaction density of the negative electrode active material layer 112 gradually decreases from the bottom to the top of the battery cell 11. Alternatively, it can be understood that the compaction density of the negative electrode active material layer 112 remains constant and then gradually decreases from the bottom to the top of the battery cell 11. Yet another example is that the compaction density of the negative electrode active material layer 112 decreases in stages from the bottom to the top of the battery cell 11. These different interpretations will be described in detail below.

[0078] According to some embodiments of this application, the negative electrode active material layer 112 may specifically include a plurality of active regions 113 arranged sequentially along the height direction of the battery cell 11, and the compaction density of the plurality of active regions 113 decreases sequentially from the bottom of the battery cell 11 to the top of the battery cell 11.

[0079] This embodiment does not specify the number of active regions 113; the number of active regions 113 can be any number such as 2, 3, 4, or 5. For a specific example, please refer to [reference needed]. Figure 3 There are 5 active zones 113. The compaction density of each active zone 113 can be flexibly designed according to actual needs.

[0080] In this application, the compaction density at various points within the same active region 113 is substantially equal, meaning the compaction density of the same active region 113 is uniform. The term "substantially equal" includes not only the case where the compaction density at various points within the same active region 113 is absolutely equal, but also the case where it is generally considered equal in engineering practice, meaning that the compaction density at each point performs within the permissible dimensional tolerances intended for the purposes described herein.

[0081] In this embodiment, the compaction density of the negative electrode active material layer 112 decreases gradually from the bottom to the top of the battery cell 11, while the compaction density of the same active region 113 remains essentially equal. During manufacturing, multiple active regions 113 can be processed in steps. For each active region 113, the negative electrode active material can be coated onto the surface of the current collector 111 before rolling. Therefore, when processing each active region 113, the mass of the negative electrode active material in the coating process can be a fixed value, and the rolling pressure in the rolling process can be constant; that is, the mass of the negative electrode active material and the rolling pressure do not need to be continuously adjusted.

[0082] Figure 4 This is a schematic diagram illustrating the structure of the battery cell 11 and the heat exchange device 30 in some embodiments of this application. Please refer to [reference needed] for some embodiments of this application. Figure 4 The bottom wall of the outer casing is used to be adjacent to the heat exchange device 30 for heat exchange. The active area 113 closest to the heat exchange device 30 among the multiple active areas 113 is the first active area 1131, and the remaining active areas 113 are the second active areas 1132. The coating area of ​​each second active area 1132 can be less than or equal to the coating area of ​​the first active area 1131.

[0083] In other words, the coating area of ​​the first active region 1131 is greater than or equal to the coating area of ​​the remaining active regions 113. For example, the first active region 1131 is the active region 113 with the largest coating area among the plurality of active regions 113, and the coating area of ​​the first active region 1131 is greater than the coating area of ​​the remaining active regions 113. For example, the coating area of ​​the first active region 1131 is equal to that of at least a portion of the second active region 1132.

[0084] Taking the electrode assembly as a stacked structure as an example, the coating area of ​​the active region 113 = the dimension of the active region 113 in the height direction of the battery cell 11 × the dimension of the active region 113 in the width direction of the negative electrode sheet 110. Taking the electrode assembly as a wound structure as an example, the coating area of ​​the active region 113 = the dimension of the active region 113 in the height direction of the battery cell 11 × the width of the active region 113 in the flattened state of the negative electrode sheet 110.

[0085] When the battery cell 11 and the heat exchange device 30 of this embodiment are used to form the battery device 100, the heat exchange device 30 is arranged below the battery cell 11. During charging, lithium ions are deintercalated from the positive electrode and migrate through the electrolyte to the negative electrode 110 and intercalate into the negative electrode active material layer 112. It is understood that the process of lithium ions intercalating into the negative electrode active material layer 112 generates heat.

[0086] In the technical solution where the coating area of ​​the first active region 1131 is smaller than the coating area of ​​the other active regions 113, the heat generation and temperature of the first active region 1131 are relatively small during the charging process. In addition, the first active region 1131 is the one closest to the heat exchange device 30 among the multiple active regions 113. The heat transfer path between the first active region 1131 and the heat exchange device 30 is short, so the first active region 1131 dissipates heat quickly, which makes the temperature of the first active region 1131 easy to be too low, thereby causing lithium plating.

[0087] The technical solution of this embodiment benefits from the fact that the coating area of ​​the first active region 1131 is greater than or equal to the coating area of ​​the other active regions 113, and the temperature of the first active region 1131 is greater than or equal to the temperature of the other active regions 113, making the first active region 1131 the active region 113 that generates the most heat and has the highest temperature among the multiple active regions 113. Compared with the technical solution where the coating area of ​​the first active region 1131 is smaller than the coating area of ​​the other active regions 113, the temperature of the first active region 1131 closest to the heat exchange device 30 in this embodiment is relatively higher, which can reduce the risk of lithium plating caused by the first active region 1131 being too low in temperature.

[0088] There are N active regions 113, and correspondingly, there are N-1 second active regions 1132, where N is a positive integer greater than or equal to 2. For example, when N = 2, there is one second active region 1132. For example, when N > 2, there are multiple second active regions 1132.

[0089] It should be noted that the relationship between areal density and the mass of active material and coating area is: areal density = mass of active material / coating area. The relationship between the thickness of the negative electrode active material layer 112 and areal density and compaction density is: compaction density = areal density / thickness of negative electrode active material layer 112. Therefore, in the specific example where N=2 and there is one first active region 1131 and one second active region 1132, when the coating area of ​​the first active region 1131 and the second active region 1132 and their dimensions in the height direction of the battery cell 11 are equal, in order to make the compaction density of the first active region 1131 greater than that of the second active region 1132, the areal density of the negative electrode active material layer 112 of the first active region 1131 and the second active region 1132 can be the same but the thickness is different, or the areal density of the negative electrode active material layer 112 of the first active region 1131 and the second active region 1132 can be different but the thickness is the same.

[0090] In some exemplary embodiments, by making the areal density of the negative electrode active material layer 112 of the first active region 1131 and the second active region 1132 the same but the thickness different, the compaction density of the first active region 1131 is greater than that of the second active region 1132. The manufacturing process of the negative electrode sheet 110 in this embodiment can be as follows: Two regions with the same area on the surface of the current collector 111 are coated with negative electrode active material, and the mass of the negative electrode active material coated on the two regions is the same. Then, a drying process is performed to ensure that the areal density of the negative electrode active material coated on the two regions is consistent. The dried current collector 111 with negative electrode active material is then subjected to segmented rolling pressing using a roller press. The rolling pressures applied to the two regions are controlled as F1 and F2, respectively, where F1 < F2. Thus, the active region 113 obtained after rolling under pressure F1 is the second active region 1132, and the active region 113 obtained after rolling under pressure F2 is the first active region 1131. The thickness of the second active region 1132 is greater than the thickness of the first active region 1131, resulting in a lower compaction density of the second active region 1132 than the first active region 1131. When the electrode assembly composed of this negative electrode sheet 110 is installed into the housing, the first active region 1131 is positioned below the second active region 1132, close to the bottom of the housing.

[0091] In some other exemplary embodiments, the compaction density of the first active region 1131 is greater than that of the second active region 1132 by making the areal density of the negative electrode active material layer 112 of the first active region 1131 and the second active region 1132 different but the thickness the same. The manufacturing process of the negative electrode sheet 110 in this embodiment can be as follows: two regions with the same area on the surface of the current collector 111 are coated with negative electrode active material, the negative electrode active material coated in the two regions has different masses, and then dried to make the areal density of the negative electrode active material coated in the two regions different; the dried current collector 111 with negative electrode active material is rolled using a roller press, the rolling is continuously rolled and the rolling pressure applied to the two regions is controlled to be the same, or the rolling pressure is increased in the region with greater negative electrode active material mass by partitioned rolling, so that the region with greater negative electrode active material mass is formed as the first active region 1131 and the region with less negative electrode active material mass is formed as the second active region 1132, and the thickness of the first active region 1131 and the thickness of the second active region 1132 obtained after rolling are equal.

[0092] According to some embodiments of this application, the second active region 1132 has multiple regions, and the dimension of the negative electrode active material layer 112 in the height direction of the battery cell 11 is the total dimension L. 总 The first active region 1131 has a dimension L1 in the height direction of the battery cell 11, and its total dimension L is L1. 总The proportion in L1 / L can be designed to be greater than or equal to 20% and less than or equal to 40%. It can be understood that, based on the fact that the coating area of ​​the first active region 1131 is greater than or equal to the coating area of ​​the remaining active regions 113, L1 / L 总 The smaller the value, the more 1132 cells are in the second active region, and the higher the L1 / L ratio. 总 The larger the value, the smaller the number of second active regions 1132.

[0093] If L1 / L 总 If the density is too large, the second active region 1132 will be less. In order to prevent a significant abrupt change in the compaction density of the negative electrode active material layer 112 from the bottom to the top of the battery cell 11, the compaction density of the negative electrode active material layer 112 near the bottom of the battery cell 11 will be difficult to reduce to a smaller value, resulting in a lower degree of improvement in the wetting effect at the top of the negative electrode sheet 110. If L1 / L 总 If the size is too small, the heat generation and temperature of the first active region 1131 are prone to being too low, leading to lithium plating. This embodiment makes L1 / L... 总 The appropriate temperature range allows for a balance between improving the wetting effect on the top of the negative electrode 110 and mitigating lithium plating caused by excessively low temperatures.

[0094] According to some embodiments of this application, the dimensions and coating area of ​​each second active region 1132 in the height direction of the battery cell 11 can also be configured to be the same.

[0095] like Figure 3 As shown, the negative electrode active material layer 112 has five active regions 113. The five active regions 113 are divided into one first active region 1131 and four second active regions (1132a, 1132b, 1132c, 1132d, which can be referred to individually or collectively as "second active regions 1132"). The four second active regions 1132 have the same size and coating area in the height direction of the battery cell 11. Therefore, the size ratio of the four second active regions 1132a, 1132b, 1132c, 1132d in the height direction of the battery cell 11 is 1:1:1:1.

[0096] Since the dimensions and coating areas of each second active region 1132 are the same in the height direction of the battery cell 11, in order to make the compaction density of each second active region 1132 decrease sequentially from the bottom to the top of the battery cell 11, the areal density of the negative electrode active material layer 112 of each second active region 1132 can be made the same, and the thickness of each second active region 1132 can be made to increase sequentially from the bottom to the top of the battery cell 11. In this embodiment, when processing the negative electrode sheet 110, only the rolling pressure in the rolling process and the coating amount of the negative electrode active material in the coating process can be adjusted to be constant. Alternatively, the thickness of the negative electrode active material layer 112 of each second active region 1132 can be made the same, and the areal density of each second active region 1132 can decrease sequentially from the bottom to the top of the battery cell 11. In this embodiment, when processing the negative electrode sheet 110, only the mass of the negative electrode active material layer 112 in the coating process can be adjusted, and the rolling pressure in the rolling process can be kept constant.

[0097] When manufacturing the negative electrode 110 of this embodiment, the coating process of multiple second active regions 1132 can be completed in one go and then rolled in sections to adjust the rolling pressure. This makes the size and coating area of ​​each second active region 1132 the same in the height direction of the battery cell 11. This helps to reduce production interruptions and improve the production cycle of the negative electrode 110.

[0098] According to some embodiments of this application, the dimension L2 of each second active region 1132 in the height direction of the battery cell 11 is less than the total dimension L. 总 The proportion in the active area can be designed to be greater than or equal to 20% and less than or equal to 25%. As an example, the second active area 1132 has four regions, L2 / L... 总 It is 20%, and L1 / L 总 Also 20%. As an example, the second active region 1132 has 3, L2 / L 总 It is 25%, and L1 / L 总 Also 25%. In L1 / L 总 Under the premise of being greater than or equal to 20% and less than or equal to 40%, this embodiment ensures that the proportion of the second active region 1132 in the height direction of the battery cell 11 in the total size is greater than or equal to 20% and less than or equal to 25%, so that the number of the second active region 1132 is not too large, which can reduce the difficulty of coating and rolling.

[0099] Figure 5 This is a schematic diagram of the negative electrode 110 of a battery cell 11 according to some embodiments of this application. According to some embodiments of this application, such as... Figure 5 As shown, the negative electrode 110 can be configured such that the compaction density of at least a portion of the negative electrode active material layer 112 gradually decreases from the bottom of the battery cell 11 to the top of the battery cell 11.

[0100] Here, it can be understood that the compaction density of the entire negative electrode active material layer 112 gradually decreases from the bottom to the top of the battery cell 11. Alternatively, it can be understood that the compaction density of a portion of the negative electrode active material layer 112 gradually decreases from the bottom to the top of the battery cell 11, that is, from the bottom to the top of the battery cell 11, the compaction density of the negative electrode active material layer 112 first remains constant and then gradually decreases, or first gradually decreases and then remains constant.

[0101] This embodiment makes the compaction density of at least part of the negative electrode active material layer 112 change gradually. This reduces the difficulty of electrolyte migration from the bottom to the top of the negative electrode 110, and also improves the uniformity of electrolyte wetting in the negative electrode 110 to a certain extent.

[0102] According to some embodiments of this application, such as Figure 5 As shown in (a), the compaction density of the entire negative electrode active material layer 112 gradually decreases from the bottom to the top of the battery cell 11. In this embodiment, during the manufacturing of the negative electrode sheet 110, the coating machine performing the coating process is equipped with a scraper. The scraper thins the negative electrode active material coated on the surface of the current collector 111, and the shape of the scraper is configured such that the amount of thinning of the negative electrode active material gradually increases along the conveying direction of the current collector 111. Therefore, using this coating machine allows for continuous production of the aforementioned negative electrode sheet 110 with high production efficiency.

[0103] According to some embodiments of this application, such as Figure 5 As shown in (b), the negative electrode active material layer 112 includes a first coating area 1121 and a second coating area 1122 arranged sequentially along the height direction of the battery cell 11. The first coating area 1121 is closer to the bottom of the battery cell 11 than the second coating area 1122. The compaction density of the first coating area 1121 is equal everywhere, while the compaction density of the second coating area 1122 gradually decreases from the bottom to the top of the battery cell 11.

[0104] The compaction density of the first coating area 1121 is constant throughout, including not only absolute equality but also generally consistent equality as commonly understood in engineering. That is, the compaction density of the first coating area 1121 adheres to the allowable dimensional tolerances as described herein for the intended purpose. The dimension of the first coating area 1121 in the height direction of the battery cell 11 can be greater than or equal to 2 mm and less than or equal to 50 mm, specifically any value selected from 2 mm, 5 mm, 10 mm, 20 mm, and 50 mm.

[0105] The negative electrode 110 in this embodiment can be processed in stages. For example, the first coating area 1121 can be formed first, and then a coating machine equipped with a scraper can be used to coat it. After drying and rolling, the second coating area 1122 can be formed.

[0106] In this embodiment, when manufacturing the negative electrode 110, a first coating area 1121 can be formed first. The compaction density of the first coating area 1121 is uniform, so the first coating area 1121 can serve as the basis for the subsequent stable processing of the second coating area 1122, which has a positive effect on reducing the processing difficulty.

[0107] According to some embodiments of this application, the dimension of the negative electrode active material layer 112 in the height direction of the battery cell 11 is the total dimension L. 总 Overall dimensions L 总 The value range can be greater than or equal to 180mm and less than or equal to 210mm. The total size can be selected from any value of 180mm, 190mm, 200mm, and 210mm. In this embodiment, by making the dimension of the negative electrode active material layer 112 in the height direction of the battery cell 11 between 180mm and 210mm, the height of the resulting negative electrode sheet 110 is relatively large. This is beneficial for the battery made using the negative electrode sheet 110 to have the characteristics of large capacity and large height, so that it can be used in transportation vehicles such as heavy trucks, mining trucks, buses, and logistics vehicles.

[0108] According to some embodiments of this application, the difference between the maximum and minimum values ​​of the thickness t at various points on the negative electrode 110 can be designed to be greater than 0 μm (micrometers) and less than or equal to 10 μm. That is, the thickness at various points on the negative electrode 110 can be equal, or the thickness at various points on the negative electrode 110 can be unequal, and the maximum thickness difference does not exceed 10 μm. In this embodiment, regardless of whether the compaction density of the negative electrode 110 decreases in stages or gradually from the bottom to the top of the battery cell 11, the thickness of the negative electrode 110 can be kept constant and the coating amount of the negative electrode active material can be adjusted during processing.

[0109] This embodiment allows the thickness of the negative electrode 110 to fluctuate within a range of no more than 10 μm, rather than requiring a completely uniform thickness. This reduces the precision requirements of the manufacturing equipment (e.g., coating amount control precision, roller pressure control precision) while ensuring that the thickness of the negative electrode 110 has high uniformity, thereby improving the production yield.

[0110] According to some embodiments of this application, the thickness t at various points on the negative electrode 110 can be in the range of 94.6 μm ≤ t ≤ 104.6 μm. Specifically, the thickness t at various points on the negative electrode 110 can be any value among 94.6 μm, 95 μm, 96 μm, 97 μm, 100 μm, and 104.6 μm. According to some embodiments of this application, the thickness t at various points on the negative electrode 110 can also be in the range of 90 μm ≤ t ≤ 100 μm. Specifically, the thickness t at various points on the negative electrode 110 can be any value among 90 μm, 92 μm, 95 μm, 96 μm, 98 μm, and 100 μm.

[0111] In some embodiments, the battery cell 11 may specifically be a square pouch battery cell, i.e., the outer casing is an aluminum-plastic film, and the electrode assembly may specifically be a wound structure. An exemplary manufacturing process of the battery cell 11 in this embodiment may include the following steps.

[0112] Preparation of the positive electrode sheet: The positive electrode active material LiCoO2, binder PVDF, and conductive agent Super P were mixed at a mass ratio of 97%:1.5%:1.5% and dispersed in N-methylpyrrolidone (NMP). The mixture was stirred until homogeneous to form a slurry. The slurry was coated onto both sides of a metal foil and baked for 4 to 8 hours at a controlled temperature of 100℃-150℃. After cold pressing and slitting, the positive electrode sheet was formed. Both sides of the metal foil of the positive electrode sheet have a layer of positive electrode active material, with a compaction density of 3.0 g / cm³. 3 The thickness is 60μm.

[0113] A negative electrode sheet 110 is prepared. First, a negative electrode active material is uniformly coated onto a region of the surface of the current collector 111, and then dried. Next, the negative electrode active material is coated onto another region of the surface of the current collector 111, with the amount of coating material gradually decreasing from one end of the first region to the other along the extension direction of the current collector 111, and then dried again. The current collector 111 with the negative electrode active material is rolled using a roller press to obtain the negative electrode sheet 110. The surface of the current collector 111 of the negative electrode sheet 110 has a negative electrode active material layer 112, and the thickness of the negative electrode sheet 110 at various points is between 94.6 μm and 104.6 μm. The drying process specifically involves five baking cycles at temperatures of 60℃, 80℃, 110℃, 110℃, and 100℃, respectively.

[0114] Battery cell 11 preparation. The prepared negative electrode sheet 110, separator and prepared positive electrode sheet are stacked together, and then the electrode assembly is prepared by winding with a winding machine. The electrode assembly is encapsulated in aluminum-plastic film, baked in vacuum for 48 hours to remove moisture, and then injected with electrolyte. After formation and sorting, square soft-pack battery cells are obtained.

[0115] This application provides a battery device 100, such as... Figure 2 As shown, it includes the battery cell 11 in the above embodiments. It is understood that the battery device 100 provided in this application, by using any of the above-described battery cells 11, has all the beneficial effects of the battery cells 11, which will not be repeated here.

[0116] Based on some embodiments of this application, please continue to refer to Figure 2 The battery device 100 may further include a heat exchange device 30, which is located below the battery cell 11 and exchanges heat with the battery cell 11. The heat exchange device 30 may be a heat exchange plate prepared by any of the following processes: embedded tube process, welded tube process, double-sided clamped tube process, etc.

[0117] The structure of the negative electrode 110 in the battery cell 11 is as follows: Figure 3 As shown, the negative electrode active material layer 112 includes multiple active regions 113 sequentially arranged along the height direction of the battery cell 11. The compaction density of the multiple active regions 113 decreases sequentially from the bottom to the top of the battery cell 11. The active region 113 closest to the bottom of the battery cell 11 is the first active region 1131, and the remaining active regions 113 are the second active regions 1132. The coating area of ​​all second active regions 1132 can be less than or equal to the coating area of ​​the first active region 1131. It is understood that the insertion of lithium ions into the negative electrode active material layer 112 generates heat. Since the coating area of ​​the first active region 1131 is greater than or equal to the coating area of ​​the remaining active regions 113, the temperature of the first active region 1131 is greater than or equal to the temperature of the remaining active regions 113.

[0118] In this embodiment, by introducing a heat exchange device 30, the heat generated by the battery cell 11 during operation can be exchanged with the heat exchange device 30, which helps to reduce the possibility of thermal runaway of the battery cell 11 and improves battery safety. Furthermore, in the technical solution where the coating area of ​​the first active region 1131 is greater than or equal to the coating area of ​​the other active regions 113, since the first active region 1131 generates the most heat and has the highest temperature, this can reduce the risk of lithium plating caused by excessively low temperatures in the first active region 1131.

[0119] An embodiment of the third aspect of this application provides an electrical device including the battery device 100 described in the above embodiments, the battery device 100 being used to provide electrical energy. It is understood that the electrical device provided in this application, by employing any of the aforementioned battery cells 11, possesses all the beneficial effects of the aforementioned battery cells 11, which will not be elaborated further here.

[0120] An embodiment of the fourth aspect of this application provides an energy storage device, which includes the battery device 100 described in the above embodiments, the battery device 100 being used to store electrical energy. It is understood that the energy storage device provided in this application, by utilizing any of the aforementioned battery cells 11, possesses all the beneficial effects of the aforementioned battery cells 11, which will not be elaborated further here.

[0121] 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.

[0122] A specific embodiment of this application is described below. It should be understood that this specific embodiment is described for illustrative purposes only and should not be construed as limiting the scope of this application.

[0123] <Example 1>

[0124] like Figure 2 As shown, a battery device 100 includes a battery cell 11 and a heat exchange device 30. The heat exchange device 30 is located below the battery cell 11 and exchanges heat with the battery cell 11. This battery device is used to form the battery system of transportation vehicles such as heavy trucks, mining trucks, buses, and logistics vehicles.

[0125] The battery cell 11 is a square pouch cell 11, with a height greater than or equal to 300 mm and less than or equal to 400 mm. The battery cell 11 includes an electrode assembly, which is a wound structure. For example... Figure 3As shown, the negative electrode 110 of the electrode assembly includes a current collector 111 and a negative electrode active material layer 112 disposed on the surface of the current collector 111. The negative electrode active material layer 112 includes five active regions 113, which are a first active region 1131 and four second active regions 1132a, 1132b, 1132c, and 1132d. The first active region 1131 is located above the second active regions 1132, and the compaction density of the first active region 1131 is higher than that of the second active regions 1132. The four second active regions 1132a, 1132b, 1132c, and 1132d are arranged sequentially along the height direction of the battery cell 11, and the compaction density of the four second active regions 1132a, 1132b, 1132c, and 1132d decreases sequentially from the bottom to the top of the battery cell 11. The five active regions 113 have the same size and coating area along the height direction of the battery cell 11.

[0126] During the coating process, the mass of the negative electrode active material coated in the five active regions 113 gradually decreases from the bottom to the top of the battery cell 11. The thickness t at various points on the negative electrode sheet 110 ranges from 94.6 μm ≤ t ≤ 104.6 μm.

[0127] <Example 2>

[0128] Similar to Embodiment 1, the difference is that: in Embodiment 2, the negative electrode active material layer 112 includes a first coating area 1121 and a second coating area 1122 arranged sequentially along the height direction of the battery cell 11. The first coating area 1121 is closer to the bottom of the battery cell 11 than the second coating area 1122. The compaction density of the first coating area 1121 is equal everywhere, while the compaction density of the second coating area 1122 gradually decreases from the bottom to the top of the battery cell 11.

[0129] 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 in that, include: The outer shell has a receiving cavity; An electrode assembly is disposed within the receiving cavity, the electrode assembly including a negative electrode sheet; wherein the negative electrode sheet includes a current collector and a negative electrode active material layer disposed on the surface of the current collector; from the bottom of the battery cell to the top of the battery cell, the compaction density of the negative electrode active material layer tends to decrease.

2. The battery cell according to claim 1, characterized in that, The negative electrode active material layer includes a plurality of active regions arranged sequentially along the height direction of the battery cell, and the compaction density of the plurality of active regions decreases sequentially from the bottom to the top of the battery cell.

3. The battery cell according to claim 2, characterized in that, The bottom wall of the housing is used to be adjacent to the heat exchange device for heat exchange; the active area closest to the heat exchange device among the plurality of active areas is the first active area, and the remaining active areas are the second active areas, and the coating area of ​​each second active area is less than or equal to the coating area of ​​the first active area.

4. The battery cell according to claim 3, characterized in that, The second active region has multiple regions, and the dimension of the negative electrode active material layer in the height direction of the battery cell is the total dimension. The proportion of the dimension of the first active region in the height direction of the battery cell in the total dimension is greater than or equal to 20% and less than or equal to 40%.

5. The battery cell according to claim 4, characterized in that, Each of the second active regions has the same size and coating area in the height direction of the battery cell.

6. The battery cell according to claim 5, characterized in that, The proportion of the dimension of each second active region in the height direction of the battery cell to the total dimension is greater than or equal to 20% and less than or equal to 25%.

7. The battery cell according to claim 1, characterized in that, The compaction density of at least a portion of the negative electrode active material layer gradually decreases from the bottom to the top of the battery cell.

8. The battery cell according to claim 7, characterized in that, The negative electrode active material layer includes a first coating area and a second coating area arranged sequentially along the height direction of the battery cell. The first coating area is closer to the bottom of the battery cell than the second coating area. The compaction density of the first coating area is equal everywhere, while the compaction density of the second coating area gradually decreases from the bottom to the top of the battery cell.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The dimension of the negative electrode active material layer in the height direction of the battery cell is the total dimension, which is greater than or equal to 180 mm and less than or equal to 210 mm.

10. The battery cell according to any one of claims 1 to 8, characterized in that, The difference between the maximum and minimum values ​​of the thickness t at various points on the negative electrode sheet is greater than 0 μm and less than or equal to 10 μm.

11. The battery cell according to claim 10, characterized in that, The thickness t at various points on the negative electrode sheet ranges from 94.6 μm ≤ t ≤ 104.6 μm, or the thickness t at various points on the negative electrode sheet ranges from 90 μm ≤ t ≤ 100 μm.

12. The battery cell according to any one of claims 1 to 8, characterized in that, The height of the battery cell is greater than or equal to 300 mm and less than or equal to 400 mm.

13. A battery device, characterized in that, include: The battery cell as described in any one of claims 1 to 12.

14. The battery device according to claim 13, characterized in that, Also includes: A heat exchange device is located below the battery cell and exchanges heat with the battery cell.

15. An electrical appliance, characterized in that, The electrical equipment includes a battery device as described in claim 13 or 14, the battery device being used to provide electrical energy.

16. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 13 or 14, the battery device being used to store electrical energy.

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