Battery monomer, battery device, electric equipment and pole piece manufacturing method

Abstract

The embodiment of the invention provides a battery monomer, a battery device, electric equipment and a pole piece manufacturing method, and relates to the technical field of batteries. The battery monomer comprises an electrode assembly, the electrode assembly comprises a negative pole piece and a positive pole piece, a positive coating area of the positive pole piece comprises a first part, a second part and a third part which are arranged in sequence, a first active material layer is arranged on the first part, a second active material layer is arranged on the second part, and a third active material layer is arranged on the third part; wherein the compaction density of the second active material layer is greater than the compaction density of the first active material layer and the compaction density of the third active material layer, respectively. According to the application, the temperatures, the reaction rates and the capacity attenuation of the first active material layer, the second active material layer and the third active material layer are closer, so that the performance of the battery monomer on each region is closer, and the overall capacity retention ratio of the battery monomer is favorably improved; therefore, the cycle performance and the service life of the battery monomer are improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, an electrical device, and a pole piece manufacturing method. Background Art

[0002] Battery devices are widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc.

[0003] The battery device includes a battery cell. The middle part of the pole piece of the battery cell has poor heat dissipation, which causes this part to have a high reaction rate and rapid capacity decay when used, thus affecting the service life of the battery cell. Therefore, how to reduce the reaction rate and capacity decay of the middle part of the pole piece is a research direction in battery technology. Summary of the invention

[0004] The present application provides a battery cell, a battery device, an electrical device and a pole piece manufacturing method, which can reduce the reaction rate and capacity attenuation of the middle part of the pole piece.

[0005] In the first aspect, an embodiment of the present application provides a battery cell, including an electrode assembly, the electrode assembly including a negative electrode plate and a positive electrode plate, the positive electrode plate including a positive current collector, the positive current collector including a positive coating area and a positive electrode tab connected to one side of the positive coating area; from the side where the positive coating area is connected to the positive electrode tab to the side away from the positive electrode tab, the positive coating area includes a first part, a second part and a third part arranged in sequence, the first part is provided with a first active material layer, the second part is provided with a second active material layer, and the third part is provided with a third active material layer; wherein the compaction density of the second active material layer is greater than the compaction density of the first active material layer and the compaction density of the third active material layer, respectively.

[0006] By adopting the above technical scheme, the compaction density of the second active material layer is designed to be greater than the compaction density of the first active material layer and the compaction density of the third active material layer, respectively, so that the porosity in the second active material layer is reduced, which can reduce the liquid absorption of the electrolyte and the migration speed of lithium ions to a certain extent. When the battery cell is charged at a small rate and discharged at a high power, the reaction rate of the second active material layer in the middle can be suppressed, so that the temperature, reaction rate and capacity attenuation of the first active material layer, the second active material layer and the third active material layer are closer, so that the performance of the battery cell in each area is close, which helps to improve the overall capacity retention rate of the battery cell, thereby improving the cycle performance and service life of the battery cell.

[0007] In some embodiments of the present application, the ratio of the compaction density of the second active material layer to the compaction density of the first active material layer ranges from 6 / 5 to 2 / 1; and / or, the ratio of the compaction density of the second active material layer to the compaction density of the third active material layer ranges from 6 / 5 to 2 / 1.

[0008] By adopting the above technical scheme, the ratio of the compaction density of the second active material layer and the compaction density of the first active material layer is controlled within the range of 6 / 5 to 2 / 1, which can reduce the reaction rate in the middle part of the electrode while being easy to implement; similarly, the ratio of the compaction density of the second active material layer and the compaction density of the third active material layer is controlled within the range of 6 / 5 to 2 / 1, which can reduce the reaction rate in the middle part of the electrode while being easy to implement.

[0009] In some embodiments of the present application, the ratio of the compaction density of the second active material layer to the compaction density of the first active material layer ranges from 4 / 3 to 5 / 3, and the ratio of the compaction density of the second active material layer to the compaction density of the third active material layer ranges from 4 / 3 to 5 / 3.

[0010] By adopting the above technical scheme, the ratio of the compaction density of the second active material layer to the compaction density of the first active material layer, and the ratio of the compaction density of the second active material layer to the compaction density of the third active material layer are controlled between 4 / 3 and 5 / 3, which not only facilitates the compaction operation, but also makes the reaction rates of the first active material layer, the second active material layer and the third active material layer of the electrode closer.

[0011] In some embodiments of the present application, the compaction density of the second active material layer is in the range of 4 g / cm 3 Up to 5g / cm 3 .

[0012] Using the above technical solution, the compaction density of the second active material layer is designed to be 4g / cm 3 Up to 5g / cm 3 , which makes it easy to achieve compression, reduce the temperature, reaction rate and capacity attenuation in the middle part of the electrode, and make the performance of the electrode in the middle part closer to that on both sides.

[0013] In some embodiments of the present application, the compaction density of the second active material layer is in the range of 4.3 g / cm 3 Up to 4.5g / cm 3 .

[0014] Using the above technical solution, the compaction density of the second active material layer is designed to be 4.3 g / cm 3 Up to 4.5g / cm 3, which makes it easier to achieve compression, reduce the temperature, reaction rate and capacity attenuation in the middle part of the electrode, and make the performance of the electrode in the middle part closer to that on both sides.

[0015] In some embodiments of the present application, the compaction density of the third active material layer is greater than the compaction density of the first active material layer.

[0016] By adopting the above technical solution, the compaction density of the third active material layer is designed to be greater than the compaction density of the first active material layer and less than the compaction density of the second active material layer, which can suppress the reaction rate of the third active material layer and further make the temperature, reaction rate and capacity attenuation of the first active material layer, the second active material layer and the third active material layer closer.

[0017] In some embodiments of the present application, the compaction density of the first active material layer is in the range of 2 g / cm 3 Up to 4g / cm 3 .

[0018] Using the above technical solution, the compaction density of the first active material layer is designed to be 2g / cm 3 Up to 4g / cm 3 , making the reaction rate and capacity decay of the second active material layer closer to those of the first active material layer.

[0019] In some embodiments of the present application, the compaction density range of the first active material layer is 3.2 g / cm 3 Up to 3.5g / cm 3 .

[0020] By adopting the above technical solution, the reaction rate and capacity decay of the second active material layer can be further made closer to those of the first active material layer.

[0021] In some embodiments of the present application, the compaction density range of the third active material layer is 2 g / cm 3 Up to 4.5g / cm 3 .

[0022] Using the above technical solution, the compaction density of the third active material layer is designed to be 2g / cm 3 Up to 4.5g / cm 3 , making the reaction rate and capacity decay of the second active material layer closer to those of the third active material layer.

[0023] In some embodiments of the present application, the compaction density range of the third active material layer is 3.2 g / cm 3 Up to 4.35g / cm 3 .

[0024] Using the above technical solution, the compaction density of the third active material layer is designed to be 3.2 g / cm 3 Up to 4.35g / cm 3 , which can further make the reaction rate and capacity decay of the second active material layer closer to those of the third active material layer.

[0025] In some embodiments of the present application, the thicknesses of the first active material layer, the second active material layer, and the third active material layer are equal.

[0026] By adopting the above technical solution, the first active material layer, the second active material layer and the third active material layer are designed to have equal thickness, thereby reducing the possibility of defects occurring during winding or hot pressing due to uneven thickness of the electrode sheet.

[0027] In some embodiments of the present application, along the arrangement direction of the positive electrode tab and the positive electrode coating area, the minimum size of the second active material layer is respectively greater than the minimum size of the first active material layer and the minimum size of the third active material layer.

[0028] By adopting the above technical solution, the width of the second active material layer is designed to be larger than the width of the first active material layer and the width of the third active material layer, respectively, so as to reduce the temperature difference between the second part and the first part and the third active part during the reaction.

[0029] In some embodiments of the present application, along the arrangement direction of the positive electrode tab and the positive electrode coating area, the ratio of the size of the first active material layer to the size of the second active material layer ranges from 1 / 8 to 3 / 8; and / or, along the arrangement direction of the positive electrode tab and the positive electrode coating area, the ratio of the size of the third active material layer to the size of the second active material layer ranges from 3 / 8 to 5 / 8.

[0030] By adopting the above technical solution, the temperature difference between the second part and the first part and the third part can be further reduced, thereby improving the capacity retention rate of the battery cell.

[0031] In a second aspect, an embodiment of the present application provides a battery device, comprising a battery case and a battery cell as described in any one of the above technical solutions, wherein the battery cell is installed in the battery case.

[0032] In a third aspect, an embodiment of the present application provides an electrical device, including the battery device described in the above technical solution, and the battery device is used to store or provide electrical energy.

[0033] In a fourth aspect, an embodiment of the present application provides a method for manufacturing a pole piece, including manufacturing a positive pole piece, wherein the manufacturing of the positive pole piece comprises the following steps:

[0034] Providing a positive electrode current collector, the positive electrode current collector comprising a positive electrode coating region and a positive electrode tab connected to one side of the positive electrode coating region;

[0035] Disposing active material layers, disposing a first active material layer, a second active material layer and a third active material layer on the positive electrode coating area, and disposing the first active material layer, the second active material layer and the third active material layer in sequence from the side of the positive electrode coating area connected to the positive electrode tab to the side away from the positive electrode tab;

[0036] The compaction density of the second active material layer is greater than the compaction density of the first active material layer and the compaction density of the third active material layer.

[0037] By adopting the above technical scheme, when manufacturing the electrode sheet, the compaction density of the second active material layer is formed to be greater than the compaction density of the first active material layer and the compaction density of the third active material layer, so that the porosity in the second active material layer is reduced, which can reduce the liquid absorption of the electrolyte and the migration speed of lithium ions to a certain extent. When the battery cell is charged at a small rate and discharged at a high power, the reaction rate of the second active material layer in the middle can be suppressed, and the reaction rate and capacity attenuation of the first active material layer, the second active material layer and the third active material layer are closer, so that the performance of the battery cell in each area is close, which helps to improve the overall capacity retention rate of the battery cell, thereby improving the cycle performance and service life of the battery cell.

[0038] In some embodiments of the present application, providing a first active material layer, a second active material layer and a third active material layer on the positive electrode coating area comprises the following steps:

[0039] coating a first active material layer, a second active material layer and a third active material layer on the positive electrode coating area, and drying the first active material layer, the second active material layer and the third active material layer;

[0040] Compressing the first active material layer, the second active material layer, and the third active material layer;

[0041] Among them, the unit area coating mass of the second active material layer is respectively greater than the unit area coating mass of the first active material layer and the unit area coating mass of the third active material layer, so that the compaction density of the second active material layer after compaction is respectively greater than the compaction density of the first active material layer and the compaction density of the third active material layer.

[0042] By adopting the above technical solution, the coating mass per unit area of ​​the second active material layer is designed to be maximum during coating. After compacting the first active material layer, the second active material layer and the third active material layer after drying, the compaction density of the second active material layer can be made greater than the compaction density of the first active material layer and the compaction density of the third active material layer, respectively, thereby achieving closer reaction rates and capacity attenuation of the first active material layer, the second active material layer and the third active material layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0044] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0045] Figure 2 A schematic diagram of a battery device provided in some embodiments of the present application;

[0046] Figure 3 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0047] Figure 4 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0048] Figure 5 A schematic diagram of the structure of a positive electrode sheet before coating an active material layer provided in some embodiments of the present application;

[0049] Figure 6 A cross-sectional view of a positive electrode sheet provided in some embodiments of the present application after being coated with an active material layer;

[0050] Figure 7 A flow chart of a pole piece manufacturing method provided for some embodiments of the present application.

[0051] The reference numerals of the specific embodiments are as follows:

[0052] 1000. Vehicles;

[0053] 100. Battery device;

[0054] 10. Battery box; 11. First box; 12. Second box;

[0055] 20. Battery cell; 21. Electrode assembly; 22. Negative electrode plate; 221. Negative current collector; 23. Positive electrode plate; 231. Positive current collector; 2311. Positive electrode coating area; 23111. First part; 23112. Second part; 23113. Third part; 23114. First active material layer; 23115. Second active material layer; 23116. Third active material layer; 2312. Positive electrode tab; 24. Separator; 25. Shell; 251. Shell body; 252. End cover;

[0056] 200, controller;

[0057] 300. Motor. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0059] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0060] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0061] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0062] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, H and / or B can represent: H exists alone, H and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0063] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0064] The term "plurality" used in the present application refers to two or more (including two).

[0065] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, which are connected in series, in parallel or in mixed connection through a busbar component.

[0066] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells; as an example, a battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, a battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0067] In some embodiments, the battery device may be a battery pack, which includes a battery case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the battery case.

[0068] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the battery case by fixing the battery module in the battery case.

[0069] As an example, the battery cell assembly may also be housed in the battery case by directly fixing a plurality of battery cells to the battery case.

[0070] As an example, the battery case may include a first case and a second case. The first case and the second case are buckled together to form a closed space inside the battery case to accommodate the battery cell assembly. The closed space here means to cover or close, which may be sealed or unsealed. The first case may be a top cover or a bottom plate.

[0071] As an example, the battery case 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 a closed space is formed inside the battery case to accommodate the battery cell assembly.

[0072] As an example, the battery box can be used as part of the chassis structure of the vehicle. For example, the top cover of the battery box can become at least a part of the floor of the vehicle, or the frame of the battery box can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0073] In some embodiments, the battery device refers to an energy storage device, which includes a battery box, at least one side of which is provided with a door. The energy storage device includes an energy storage container, an energy storage cabinet, and the like.

[0074] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells and battery devices, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, for example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

[0075] The battery cell mentioned in the embodiments of the present application may include an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive current collector and a positive active material layer, and the positive active material layer is coated on the surface of the positive current collector; the positive current collector includes a positive electrode coating area and a positive electrode ear connected to the positive electrode coating area, the positive electrode coating area is coated with a positive electrode active material layer, and the positive electrode ear is not coated with a positive electrode active material layer. Taking a lithium-ion battery cell as an example, the material of the positive current collector can be aluminum, and the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is coated on the surface of the negative electrode current collector; the negative electrode current collector includes a negative electrode coating area and a negative electrode tab connected to the negative electrode coating area, and the negative electrode coating area is coated with a negative electrode active material layer, and the negative electrode tab is not coated with a negative electrode active material layer. The material of the negative electrode current collector can be copper, and the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene), etc.

[0076] Battery devices are constantly developing towards high power and high energy density. The battery cells include the upper part closest to the pole ear, the lower part farthest from the pole ear, and the middle part between the upper and lower parts. Since the heat in the middle part cannot be effectively dissipated, the temperature is higher, resulting in the highest reaction rate and the fastest capacity decay in the middle of the battery cell.

[0077] Therefore, how to effectively reduce the reaction rate and capacity decay among battery cells is an important topic in the research and development of battery devices.

[0078] In view of this, the present application provides a technical solution to solve the above technical problems by designing the compaction density of the middle area of ​​the battery cell pole piece to be greater than the compaction density of the upper area and the lower area.

[0079] The battery cells described in the embodiments of the present application are suitable for batteries and electrical equipment using the batteries.

[0080] Electrical equipment may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, electric tools, and the like. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, and the like; spacecraft include airplanes, rockets, space shuttles, and spacecraft, and the like; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0081] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0082] Combined with Figure 1 As shown, the vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery device 100 is arranged inside the vehicle 1000, and the battery device 100 can be arranged at the bottom, head or tail of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000, for example, the battery device 100 can be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to power the motor 300, for example, for the starting, navigation and driving power requirements of the vehicle 1000.

[0083] In some embodiments of the present application, the battery device 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0084] Combined with Figure 2 As shown, the embodiment of the present application provides a battery device 100, which can be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 and the battery device 100 can be cylindrical, flat, rectangular, or other shapes.

[0085] The battery device 100 (Battery Apparatus) mentioned in the embodiment of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly (Battery Cell Assembly) may include a plurality of battery cells 20, and the plurality of battery cells 20 are connected in series, in parallel or in mixed connection through a busbar component.

[0086] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells 20; as an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells 20 to form an independent module. As an example, a battery module may be formed by bundling a plurality of battery cells 20 by a cable tie.

[0087] In some embodiments, the battery device 100 may be a battery pack, which includes a battery case 10 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the battery case 10 .

[0088] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the battery case 10 by fixing the battery module in the battery case 10 .

[0089] As an example, the battery cell assembly may also be accommodated in the battery case 10 by directly fixing the plurality of battery cells 20 to the battery case 10 .

[0090] The battery case 10 is used to provide a storage space for the battery cells 20, and the battery case 10 can adopt a variety of structures. In some embodiments, the battery case 10 may include a first case 11 and a second case 12, the first case 11 and the second case 12 cover each other, and the first case 11 and the second case 12 together define a storage space for accommodating the battery cells 20.

[0091] As an example, the battery box 10 can be used as a part of the chassis structure of the vehicle 1000. For example, the battery box 10 can become at least a part of the floor of the vehicle 1000, or the frame of the battery box 10 can become at least a part of the cross beam and longitudinal beam of the vehicle 1000.

[0092] Combined with Figure 3 and 4 As shown, the embodiment of the present application provides a battery cell 20, including an electrode assembly 21, the electrode assembly 21 includes a negative electrode sheet 22 and a positive electrode sheet 23, the positive electrode sheet 23 includes a positive electrode collector 231, the positive electrode collector 231 includes a positive electrode coating area 2311 and a positive electrode ear 2312 connected to one side of the positive electrode coating area 2311; from the side where the positive electrode coating area 2311 is connected to the positive electrode ear 2312 to the side away from the positive electrode ear 2312, the positive electrode coating area 2311 includes a positive electrode sheet 2311 and a positive electrode ear 2312 connected to one side of the positive electrode coating area 2311. The first part 23111, the second part 23112 and the third part 23113, the first part 23111 is provided with a first active material layer 23114, the second part 23112 is provided with a second active material layer 23115, and the third part 23113 is provided with a third active material layer 23116; wherein the compaction density of the second active material layer 23115 is greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116, respectively.

[0093] In addition to the negative electrode sheet 22 and the positive electrode sheet 23 , the electrode assembly 21 of this embodiment may further include a separator 24 located between the negative electrode sheet 22 and the positive electrode sheet 23 .

[0094] The negative electrode plate 22 of the present embodiment includes a negative electrode current collector 221 and a negative electrode active material (not shown in the figure) disposed on at least one surface of the negative electrode current collector 221 .

[0095] As an example, the negative electrode current collector 221 has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector 221 .

[0096] As an example, the negative electrode current collector 221 may be a metal foil, a conductive polymer material, a carbon material or a composite current collector. For example, as a metal foil, a pure metal, an alloy, a surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, nickel, titanium or silver, etc., may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum 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.).

[0097] As an example, the negative electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, also referred to as LFP), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co At least one of LiNi0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.8Co0.15Al0.05O2) and modified compounds thereof. The modified compound refers to a substance obtained by modification means such as doping or coating on the basis of the above substances.

[0098] Combined with Figure 5 and 6 As shown ( Figure 5 The dotted lines are mainly used to show the positions of the first part 23111, the second part 23112 and the third part 23113. Figure 6 Only the active material layer on one surface of the positive electrode current collector 231 is shown, and the active material layer may also be coated on the other surface). The positive electrode current collector 231 may be made of metal foil, conductive polymer material, carbon material or composite current collector.

[0099] For example, the positive electrode current collector 231 can be made of pure metal, alloy, or surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, nickel, titanium, or silver.

[0100] The positive electrode current collector 231 includes a positive electrode coating region 2311 and a positive electrode tab 2312 connected to one side of the positive electrode coating region 2311 . The positive electrode coating region 2311 can be understood as a surface of the positive electrode current collector 231 .

[0101] In some embodiments, two opposite surfaces of the positive electrode collector 231 may be positive electrode coating regions 2311 , so that both surfaces of the positive electrode collector 231 are coated with a positive electrode active material layer.

[0102] From the side where the positive electrode coating area 2311 is connected to the positive electrode ear 2312 to the side away from the positive electrode ear 2312, the positive electrode coating area 2311 includes a first part 23111, a second part 23112 and a third part 23113 arranged in sequence, the first part 23111 can be understood as a part of the positive electrode coating area 2311 close to the positive electrode ear 2312, the third part 23113 can be understood as a part of the positive electrode coating area 2311 away from the positive electrode ear 2312, and the second part 23112 is the middle part between the first part 23111 and the third part 23113. The sizes of the first part 23111, the second part 23112 and the third part 23113 are given below.

[0103] The positive electrode active material layer includes a first active material layer 23114 coated on the first portion 23111 , a second active material layer 23115 coated on the second portion 23112 , and a third active material layer 23116 coated on the third portion 23113 .

[0104] The materials of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 can be the same or different. For example, all three can select at least one of nickel manganese cobalt lithium oxide (NMC), nickel cobalt aluminum lithium oxide (NCA), lithium iron phosphate (LFP), and lithium manganese oxide (LMO) as the material.

[0105] For example, in some embodiments, the first active material layer 23114 is made of LMO, the second active material layer 23115 is made of NCM, and the third active material layer 23116 is made of NCA or LFP.

[0106] In some embodiments, the first active substance layer 23114, the second active substance layer 23115 and the third active substance layer 23116 are made of the same material, and / or, when the first active substance layer 23114, the second active substance layer 23115 and the third active substance layer 23116 are a mixture of two or more materials, the mixing ratio of the three is also set in equal proportion. The above design can reduce the influence of other factors (such as material ratio or material type) and only adjust the consistency through different compaction density / coating weight.

[0107] The compaction density of the second active material layer 23115 is greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116 .

[0108] The compaction density refers to the density of the active material layer after it is coated and compacted by a roller or other equipment. The unit can be g / cm 3 In some embodiments, the compaction density of the active material layer may be in the range of 2.5 g / cm 3 Up to 5g / cm 3 Of course, the compaction density of battery cells 20 made of different materials may be different, which will not be listed one by one in this embodiment.

[0109] The reason why the reaction rate and capacity decay quickly in the middle part of the electrode assembly 21 is that its heat dissipation is poor, but it is difficult to optimize its heat dissipation from a structural point of view. Experimental analysis shows that the greater the compaction density within a certain range, the slower the reaction rate and capacity decay of the active material layer. This embodiment uses this property to improve and optimize the battery cell 20, and designs the compaction density of the second active material layer 23115 to be greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116, respectively.

[0110] In this way, the porosity in the second active material layer 23115 is reduced, which can reduce the amount of electrolyte absorbed and the migration speed of lithium ions to a certain extent. When the battery cell 20 is charged at a small rate and discharged at a high power, the reaction rate of the second active material layer 23115 in the middle can be suppressed, so that the temperature, reaction rate and capacity attenuation of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are closer, thereby making the performance of the battery cell 20 in various regions close, which helps to improve the overall capacity retention rate of the battery cell 20, thereby improving the cycle performance and service life of the battery cell 20.

[0111] It should be noted that the temperature, reaction rate and capacity decay of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 can directly reflect the temperature, reaction rate and capacity decay of the corresponding area of ​​the battery cell 20. Therefore, the temperature, reaction rate and capacity decay described in this embodiment can also be understood as the temperature, reaction rate and capacity decay of the battery cell 20.

[0112] In some embodiments, the battery cell 20 also includes a shell 25 and an adapter (not shown in the figure), the shell 25 includes a shell body 251 and an end cover 252, the shell body 251 is an open structure at the upper end, the electrode assembly 21 is installed in the shell 25, the end cover 252 is covered on the shell body 251, and is connected to the pole ear of the electrode assembly 21 through the adapter.

[0113] In some examples, optionally, the ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 ranges from 6 / 5 to 2 / 1; and / or, the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 ranges from 6 / 5 to 2 / 1.

[0114] The above technical solution includes three implementation methods. One is that the ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is in the range of 6 / 5 to 2 / 1, and the compaction density of the second active material layer 23115 only needs to be greater than the compaction density of the third active material layer 23116.

[0115] Another example is that the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is in the range of 6 / 5 to 2 / 1, and the compaction density of the second active material layer 23115 only needs to be greater than the compaction density of the first active material layer 23114 .

[0116] Another example is that the ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is in the range of 6 / 5 to 2 / 1. At the same time, the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is also in the range of 6 / 5 to 2 / 1.

[0117] The ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is controlled within a range of 6 / 5 to 2 / 1. This can reduce the reaction rate in the middle portion of the electrode while also making it easy to compact the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 to the above ratio by means of equipment such as a pressing roller.

[0118] Similarly, the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is controlled to be between 6 / 5 and 2 / 1. While reducing the reaction rate in the middle part of the electrode, it is also easy to compact the compaction density of the second active material layer 23115 and the compaction density of the third active material layer 23116 to the above ratio by means of equipment such as pressing rollers.

[0119] The above design reduces the reaction rate by reducing the porosity of the second active material layer 23115, reducing the degree of wetting in the middle of the electrode, and reducing the contact area between the second active material layer 23115 and the electrolyte, so as to achieve a consistent reaction rate of the electrode.

[0120] In some examples, optionally, the ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 ranges from 4 / 3 to 5 / 3, and the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 ranges from 4 / 3 to 5 / 3.

[0121] This technical solution is a further limitation of the last solution among the above three implementation modes. The ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is in the range of 4 / 3 to 5 / 3, and the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is in the range of 4 / 3 to 5 / 3. This reduces the gap between the compaction density of the second active material layer 23115 and the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116, respectively, and makes it more convenient to achieve through the compaction process.

[0122] At the same time, when the above ratio range is adopted, the reaction rates of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 of the electrode can be made closer, thereby making the performance of the battery cell 20 in various regions close, which helps to improve the overall capacity retention rate of the battery cell 20, thereby improving the cycle performance and service life of the battery cell 20.

[0123] In some examples, optionally, the compaction density of the second active material layer 23115 is in the range of 4 g / cm 3 Up to 5g / cm 3 .

[0124] For example, the compaction density of the second active material layer 23115 may be 4 g / cm 3 , 4.1g / cm 3 , 4.2g / cm 3 , 4.3g / cm 3 4.4g / cm 3 , 4.5g / cm 3 4.6g / cm 3 , 4.7g / cm 3 , 4.8g / cm 3 , 4.9g / cm 3 and 5g / cm 3 Etc., which will not be listed one by one in this embodiment.

[0125] When the compaction density of the second active material layer 23115 is 4 g / cm 3 Up to 5g / cm 3It is not only easy to achieve compression, but also can reduce the temperature, reaction rate and capacity attenuation of the middle part of the electrode, making the performance of the middle part of the electrode closer to that of the two side parts.

[0126] In some embodiments of the present application, the compaction density of the second active material layer 23115 is in the range of 4.3 g / cm 3 Up to 4.5g / cm 3 .

[0127] For example, the compaction density of the second active material layer 23115 may be 4.3 g / cm 3 , 4.31g / cm 3 4.33g / cm 3 4.37g / cm 3 4.4g / cm 3 4.42g / cm 3 4.45g / cm 3 and 4.5g / cm 3 Etc., which will not be listed one by one in this embodiment.

[0128] By adopting the above technical solution, the compaction density of the second active material layer 23115 is further optimized to achieve easier compaction, and better effects of reducing the temperature, reaction rate and capacity attenuation in the middle part of the electrode.

[0129] In some examples, optionally, the compaction density of the third active material layer 23116 is greater than the compaction density of the first active material layer 23114 .

[0130] The reason for adopting this design is that although the first part 23111 is closest to the positive electrode ear 2312 and will receive a larger current and heat up faster, the first part 23111 has a certain amount of spare structure and is at the edge, so the heat dissipation is better, so the temperature and performance attenuation are minimal.

[0131] Although the third portion 23113 is located at the edge, there is usually no spare structure nearby, so the temperature and performance attenuation of the third portion 23113 are between the upper and middle ones.

[0132] Therefore, in this embodiment, the compaction density of the third active material layer 23116 is designed to be greater than the compaction density of the first active material layer 23114 and less than the compaction density of the second active material layer 23115, which can suppress the reaction rate of the third active material layer 23116 and further make the temperature, reaction rate and capacity attenuation of the first part 23111, the second part 23112 and the third part 23113 closer.

[0133] In some examples, optionally, the compaction density of the first active material layer 23114 is in the range of 2 g / cm 3 Up to 4g / cm 3 .

[0134] For example, the compaction density of the first active material layer 23114 may be 2 g / cm 3 , 2.3g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 、3.3g / cm 3 , 3.5g / cm 3 and 4g / cm 3 Etc., which are not listed one by one in this embodiment.

[0135] The compaction density of the first active material layer 23114 is designed to be 2 g / cm 3 Up to 4g / cm 3 The compaction density of the second active material layer 23115 is designed to be 4.3 g / cm 3 Up to 4.5g / cm 3 , the temperature, rate and capacity attenuation of the second active material layer 23115 during the reaction can be made closer to those of the first active material layer 23114.

[0136] In some examples, optionally, the compaction density of the first active material layer 23114 is in the range of 3.2 g / cm 3 Up to 3.5g / cm 3 .

[0137] For example, the compaction density of the first active material layer 23114 may be 3.2 g / cm 3 , 3.25g / cm 3 、3.3g / cm 3 、3.35g / cm 3 、3.4g / cm 3 、3.45g / cm 3 and 3.5g / cm 3 wait.

[0138] The compaction density of the first active material layer 23114 is designed to be within the range of 3.2 g / cm 3 Up to 3.5g / cm 3 The compaction density of the second active material layer 23115 is designed to be 4.3 g / cm 3 Up to 4.5g / cm 3 , which can further make the reaction rate and capacity decay of the second active material layer 23115 closer to those of the first active material layer 23114.

[0139] In some examples, optionally, the compaction density of the third active material layer 23116 is in the range of 2 g / cm 3 Up to 4.5g / cm 3 .

[0140] For example, the compaction density of the third active material layer 23116 may be 2 g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 , 3.3g / cm 3 , 3.5g / cm 3 , 4g / cm 3 and 4.5g / cm 3 Etc., which are not listed one by one in this embodiment.

[0141] The compaction density of the third active material layer 23116 is designed to be 2 g / cm 3 Up to 4.5g / cm 3 , making the reaction rate and capacity decay of the second active material layer 23115 closer to those of the third active material layer 23116.

[0142] In some examples, optionally, the compaction density range of the third active material layer 23116 is 3.2 g / cm 3 Up to 4.35g / cm 3 .

[0143] For example, the compaction density of the third active material layer 23116 may be 3.2 g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.7g / cm 3 、3.8g / cm 3 and 4.35g / cm 3 Etc., which are not listed one by one in this embodiment.

[0144] The compaction density of the third active material layer 23116 is designed to be 3.2 g / cm 3 Up to 4.35g / cm 3 , which can further make the reaction rate and capacity decay of the second active material layer 23115 closer to those of the third active material layer 23116.

[0145] In order to better understand the invention purpose, technical scheme and beneficial technical effect of the compacted density of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116, the present application is further described in detail below in combination with Examples 1-6 and Comparative Example 1. However, it should be understood that the embodiments of the present application are only for explaining the present application, not for limiting the present application, and the embodiments of the present application are not limited to the embodiments given in the specification. The specific experimental conditions or operating conditions not specified in the embodiments are made under conventional conditions, or are made under the conditions recommended by the material supplier.

[0146] Example 1 can be operated according to the following steps: an aluminum foil with a thickness of 13 μm is used as the positive electrode current collector 231, and a first active material layer 23114, a second active material layer 23115 and a third active material layer 23116 are coated on the aluminum foil, wherein the mass ratio of the three is 3.3:4.35:3.3, and after coating, the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 with equal thickness are obtained, and the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.35 g / cm 3 The compaction density of the third active material layer 23116 is 3.3 g / cm 3 , the operating condition of the battery cell 20 is simulated, and two hundred charge and discharge cycles are performed to test the temperature distribution of the area corresponding to the first part 23111 of the battery cell 20, the area corresponding to the second part 23112, and the area corresponding to the third part 23113, as well as the retention ratio of the capacity of the battery cell 20 relative to the initial capacity, that is, the 200cls capacity retention rate in Table 1 below.

[0147] Example 2, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.37 g / cm 3 The third active material layer 23116 has a compaction density of 3.75 g / cm 3 .

[0148] Example 3, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.4 g / cm 3 The compaction density of the third active material layer 23116 is 3.88 g / cm 3 .

[0149] Example 4, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.42 g / cm 3 The compaction density of the third active material layer 23116 is 4.32 g / cm 3 .

[0150] Example 5, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.45 g / cm 3 The compaction density of the third active material layer 23116 is 4.35 g / cm 3 .

[0151] Example 6, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 4.5 g / cm 3 The compaction density of the third active material layer 23116 is 4.38 g / cm 3 .

[0152] Comparative Example 1, the operation steps are the same as those of Example 1, except that the compaction density of the first active material layer 23114 is 3.3 g / cm 3 The compaction density of the second active material layer 23115 is 3.3 g / cm 3 The compaction density of the third active material layer 23116 is 3.3 g / cm 3 .

[0153] The evaluation structures of Examples 1 to 6 and Comparative Example 1 are shown in Table 1 below.

[0154]

[0155] Referring to Examples 1-6 and Comparative Example 1, it can be seen that when the compaction density range of the first active material layer 23114 of this embodiment is designed to be 3.2 g / cm 3 Up to 3.5g / cm 3 The compaction density range of the second active material layer 23115 is designed to be 4.3 g / cm 3 Up to 4.5g / cm 3 The compaction density range of the third active material layer 23116 is designed to be 3.2 g / cm 3 Up to 4.35g / cm 3When the compaction density of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are equal, the temperature difference among the first part 23111, the second part 23112 and the third part 23113 of the electrode can be effectively reduced, the temperature of the second part 23112 can be suppressed, and the reaction rate of the second active material layer 23115 on the second part 23112 can be reduced. At the same time, the capacity retention rate of the battery cell 20 can be improved and the capacity attenuation can be reduced.

[0156] Moreover, when the compaction density of the second active material layer 23115 is close to or equal to 4.5 g / cm 3 When , the capacity retention rate decreases, and the temperature of the second portion 23112 increases accordingly, and the inhibitory effect on the reaction rate of the second active material layer 23115 decreases.

[0157] In some examples, optionally, the thicknesses of the first active material layer 23114 , the second active material layer 23115 , and the third active material layer 23116 are equal.

[0158] The thickness of the first active material layer 23114 may refer to the thickness of the first active material layer 23114 on the positive electrode coating area 2311 after being dried and pressed. Similarly, the thicknesses of the second active material layer 23115 and the third active material layer 23116 are also understood in the same way.

[0159] However, the equal thickness should be understood in a broad sense, that is, the thicknesses of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are substantially equal after being pressed, and the existence of errors is not excluded.

[0160] The reason for designing the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 to have equal thickness is that when the thickness of the electrode is uneven, the electrode gap cannot be controlled during the winding process into a bare battery cell, the alignment fluctuates significantly, and defects such as crushing are prone to occur during hot pressing, resulting in an increase in the overall scrap rate of the battery cell 20 and an increase in production costs.

[0161] In some examples, optionally, along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311 , the minimum size of the second active material layer 23115 is larger than the minimum size of the first active material layer 23114 and the minimum size of the third active material layer 23116 .

[0162] Along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311 , the minimum size of the second active material layer 23115 can be understood as the width of the second active material layer 23115 , and the above-mentioned minimum sizes of the first active material layer 23114 and the third active material layer 23116 can also be understood as width.

[0163] The reason for adopting this design is that when the width of the second active material layer 23115 is large, the heat of the second part 23112 having the second active material layer 23115 during the reaction can be quickly transferred to the first part 23111 and the second part 23112, which can reduce the temperature difference between the second part 23112 and the first part 23111 and the third part during the reaction, so that the temperature difference between the first part 23111, the second part 23112 and the third part 23113 is within a controllable range.

[0164] In some examples, optionally, along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311, the ratio of the size of the first active material layer 23114 to the size of the second active material layer 23115 ranges from 1 / 8 to 3 / 8; and / or, along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311, the ratio of the size of the third active material layer 23116 to the size of the second active material layer 23115 ranges from 3 / 8 to 5 / 8.

[0165] The above technical solution also includes three implementations. One is that the ratio of the width of the first active material layer 23114 to the width of the second active material layer 23115 is in the range of 1 / 8 to 3 / 8, and the width of the third active material layer 23116 only needs to be smaller than the width of the second active material layer 23115.

[0166] Another example is that the ratio of the width of the third active material layer 23116 to the width of the second active material layer 23115 is in a range of 3 / 8 to 5 / 8, and the width of the first active material layer 23114 only needs to be smaller than the width of the second active material layer 23115 .

[0167] The third type is that the ratio of the width of the first active material layer 23114 to the width of the second active material layer 23115 is in the range of 1 / 8 to 3 / 8, and at the same time, the ratio of the width of the third active material layer 23116 to the width of the second active material layer 23115 is in the range of 3 / 8 to 5 / 8.

[0168] In some embodiments, the ratio of the widths of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 may be 1:3:2, or 1:5:3, or 2:5:3, or 1:8:3, or 3:8:5, etc., which are not listed one by one in this embodiment.

[0169] Finally, please see the attached Figure 3-6 As shown, the embodiment of the present application provides a battery cell 20, including an electrode assembly 21, the electrode assembly 21 includes a negative electrode sheet 22 and a positive electrode sheet 23, the positive electrode sheet 23 includes a positive electrode collector 231, the positive electrode collector 231 includes a positive electrode coating area 2311 and a positive electrode ear 2312 connected to one side of the positive electrode coating area 2311; from the side where the positive electrode coating area 2311 is connected to the positive electrode ear 2312 to the side away from the positive electrode ear 2312, the positive electrode coating area 2311 includes a positive electrode sheet 2311 and a positive electrode ear 2312 connected to one side of the positive electrode coating area 2311. The first part 23111, the second part 23112 and the third part 23113 are provided with a first active material layer 23114 on the first part 23111, a second active material layer 23115 on the second part 23112, and a third active material layer 23116 on the third part 23113; wherein the compaction density of the second active material layer 23115 is greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116. The ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is in the range of 6 / 5 to 2 / 1; and / or the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is in the range of 6 / 5 to 2 / 1. The ratio of the compaction density of the second active material layer 23115 to the compaction density of the first active material layer 23114 is in the range of 4 / 3 to 5 / 3, and the ratio of the compaction density of the second active material layer 23115 to the compaction density of the third active material layer 23116 is in the range of 4 / 3 to 5 / 3. The compaction density of the second active material layer 23115 is in the range of 4 g / cm 3 Up to 5g / cm 3 The compaction density of the second active material layer 23115 is in the range of 4.3 g / cm 3 Up to 4.5g / cm 3 The compaction density of the third active material layer 23116 is greater than the compaction density of the first active material layer 23114. The compaction density of the first active material layer 23114 is in the range of 2 g / cm 3 Up to 4g / cm 3 The compaction density of the first active material layer 23114 is in the range of 3.2 g / cm 3 Up to 3.5g / cm 3 The compaction density of the third active material layer 23116 is in the range of 2 g / cm 3 Up to 4.5g / cm 3 The compaction density of the third active material layer 23116 is in the range of 3.2 g / cm 3 Up to 4.35g / cm 3. The thicknesses of the first active material layer 23114, the second active material layer 23115, and the third active material layer 23116 are equal. Along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311, the minimum size of the second active material layer 23115 is greater than the minimum size of the first active material layer 23114 and the minimum size of the third active material layer 23116, respectively. Along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311, the ratio of the size of the first active material layer 23114 to the size of the second active material layer 23115 ranges from 1 / 8 to 3 / 8; and / or, along the arrangement direction of the positive electrode tab 2312 and the positive electrode coating area 2311, the ratio of the size of the third active material layer 23116 to the size of the second active material layer 23115 ranges from 3 / 8 to 5 / 8.

[0170] Based on the above-mentioned battery cell 20 , an embodiment of the present application provides a battery device 100 , including a battery case 10 and the above-mentioned battery cell 20 , wherein the battery cell 20 is installed in the battery case 10 .

[0171] Based on the above-mentioned battery device 100 , an embodiment of the present application provides an electric device, including the above-mentioned battery device 100 , the battery device 100 is used to store or provide electric energy, and the electric device may be a vehicle 1000 .

[0172] Combined with Figure 7 As shown, based on the above-mentioned battery cell 20, the embodiment of the present application provides a method for manufacturing a pole piece, including manufacturing a positive pole piece, and manufacturing a positive pole piece includes the following steps:

[0173] Providing a positive electrode current collector 231, the positive electrode current collector 231 includes a positive electrode coating region 2311 and a positive electrode tab 2312 connected to one side of the positive electrode coating region 2311;

[0174] Active material layers are provided, and a first active material layer 23114, a second active material layer 23115 and a third active material layer 23116 are provided on the positive electrode coating area 2311, and the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are provided in sequence from the side where the positive electrode coating area 2311 is connected to the positive electrode tab 2312 to the side away from the positive electrode tab 2312;

[0175] The compaction density of the second active material layer 23115 is greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116 .

[0176] When the electrode is manufactured, the compaction density of the second active material layer 23115 is formed to be greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116, respectively, so that the porosity in the second active material layer 23115 is reduced, which can reduce the liquid absorption of the electrolyte and the migration speed of lithium ions to a certain extent. When the battery cell 20 is charged at a small rate and discharged at a high power, the reaction rate of the second active material layer 23115 in the middle can be suppressed, and the reaction rates and capacity attenuation of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are closer, so that the performance of the battery cell 20 in each area is close, which helps to improve the overall capacity retention rate of the battery cell 20, thereby improving the cycle performance and service life of the battery cell 20.

[0177] In some examples, optionally, disposing the first active material layer 23114, the second active material layer 23115, and the third active material layer 23116 on the positive electrode coating region 2311 includes the following steps:

[0178] Coating a first active material layer 23114, a second active material layer 23115, and a third active material layer 23116 on the positive electrode coating region 2311, and drying the first active material layer 23114, the second active material layer 23115, and the third active material layer 23116;

[0179] Compressing the first active material layer 23114 , the second active material layer 23115 , and the third active material layer 23116 ;

[0180] Among them, the coating mass per unit area of ​​the second active material layer 23115 is respectively greater than the coating mass per unit area of ​​the first active material layer 23114 and the coating mass per unit area of ​​the third active material layer 23116, so that the compaction density of the second active material layer 23115 after compaction is respectively greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116.

[0181] During coating, the coating mass per unit area of ​​the second active material layer 23115 is designed to be maximum. After the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are compacted after drying, the compaction density of the second active material layer 23115 can be made greater than the compaction density of the first active material layer 23114 and the compaction density of the third active material layer 23116, respectively, so that the reaction rates and capacity attenuation of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 are closer.

[0182] The coating of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 can be achieved by a coating structure such as an extrusion coating device, the drying of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 can be achieved by a conveyor oven, and the pressing of the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116 can be achieved by a pressing roller device.

[0183] In addition, in addition to sequentially coating the first active material layer 23114, the second active material layer 23115 and the third active material layer 23116, other coating orders may also be selected, such as first coating the second active material layer 23115 and then coating the first active material layer 23114 and the third active material layer 23116, which will not be listed in detail in this embodiment.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for the intermediate technical features, but these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell, comprising an electrode assembly, wherein the electrode assembly comprises a negative electrode sheet and a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector, wherein the positive electrode current collector comprises a positive electrode coating region and a positive electrode tab connected to one side of the positive electrode coating region; It is characterized in that From the side where the positive electrode coating area is connected to the positive electrode tab to the side away from the positive electrode tab, the positive electrode coating area includes a first part, a second part and a third part which are arranged in sequence, the first part is provided with a first active material layer, the second part is provided with a second active material layer, and the third part is provided with a third active material layer; The compaction density of the second active material layer is greater than the compaction density of the first active material layer and the compaction density of the third active material layer.

2. The battery cell according to claim 1, characterized in that: The ratio of the compaction density of the second active material layer to the compaction density of the first active material layer is in the range of 6 / 5 to 2 / 1; And / or, a ratio of a compaction density of the second active material layer to a compaction density of the third active material layer is in a range of 6 / 5 to 2 / 1.

3. The battery cell according to claim 2, characterized in that: The ratio of the compaction density of the second active material layer to the compaction density of the first active material layer is in the range of 4 / 3 to 5 / 3, and the ratio of the compaction density of the second active material layer to the compaction density of the third active material layer is in the range of 4 / 3 to 5 / 3.

4. The battery cell according to claim 3, characterized in that: The compaction density of the second active material layer is in the range of 4 g / cm 3 to 5 g / cm 3 .

5. The battery cell according to claim 4, characterized in that: The compaction density of the second active material layer is in the range of 4.3 g / cm 3 to 4.5 g / cm 3 .

6. The battery cell according to any one of claims 1 to 5, characterized in that: The compaction density of the third active material layer is greater than the compaction density of the first active material layer.

7. The battery cell according to claim 6, characterized in that: The compaction density of the first active material layer is in the range of 2 g / cm 3 to 4 g / cm 3 .

8. The battery cell according to claim 7, characterized in that: The compaction density of the first active material layer is in the range of 3.2 g / cm 3 to 3.5 g / cm 3 .

9. The battery cell according to claim 6, characterized in that: The compaction density of the third active material layer is in the range of 2.5 g / cm 3 to 4.5 g / cm 3 .

10. The battery cell according to claim 9, characterized in that: The compaction density of the third active material layer is in the range of 3.3 g / cm 3 to 4.35 g / cm 3 .

11. The battery cell according to any one of claims 1 to 5, characterized in that: The first active material layer, the second active material layer, and the third active material layer have the same thickness.

12. The battery cell according to any one of claims 1 to 5, characterized in that: Along the arrangement direction of the positive electrode tab and the positive electrode coating area, the minimum size of the second active material layer is respectively greater than the minimum size of the first active material layer and the minimum size of the third active material layer.

13. The battery cell according to claim 12, characterized in that: Along the arrangement direction of the positive electrode tab and the positive electrode coating area, the ratio of the size of the first active material layer to the size of the second active material layer is in a range of 1 / 8 to 3 / 8; And / or, along the arrangement direction of the positive electrode tab and the positive electrode coating area, the ratio of the size of the third active material layer to the size of the second active material layer is in a range of 3 / 8 to 5 / 8.

14. A battery device, characterized in that: It comprises a battery box and a battery cell as claimed in any one of claims 1 to 13, wherein the battery cell is installed in the battery box.

15. An electrical equipment, characterized in that: The battery device as claimed in claim 14 is used to store or provide electrical energy.

16. A method for manufacturing a positive electrode sheet, comprising manufacturing a positive electrode sheet, wherein the manufacturing of the positive electrode sheet comprises the following steps: Providing a positive electrode current collector, the positive electrode current collector comprising a positive electrode coating region and a positive electrode tab connected to one side of the positive electrode coating region; Disposing active material layers, disposing a first active material layer, a second active material layer and a third active material layer on the positive electrode coating area, and disposing the first active material layer, the second active material layer and the third active material layer in sequence from the side of the positive electrode coating area connected to the positive electrode tab to the side away from the positive electrode tab; in, The compaction density of the second active material layer is greater than the compaction density of the first active material layer and the compaction density of the third active material layer.

17. The method for manufacturing a pole piece according to claim 16, characterized in that: The step of providing a first active material layer, a second active material layer and a third active material layer on the positive electrode coating region comprises the following steps: coating a first active material layer, a second active material layer and a third active material layer on the positive electrode coating area, and drying the first active material layer, the second active material layer and the third active material layer; Compressing the first active material layer, the second active material layer, and the third active material layer; Among them, the unit area coating mass of the second active material layer is respectively greater than the unit area coating mass of the first active material layer and the unit area coating mass of the third active material layer, so that the compaction density of the second active material layer after compaction is respectively greater than the compaction density of the first active material layer and the compaction density of the third active material layer.

Images