Battery cell, battery device and electrical device

Abstract

This application relates to a battery cell, a battery device, and an electrical device. The battery cell includes a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive current collector portion and a positive electrode film layer located on at least one side of the positive current collector portion. The positive electrode film layer includes a lithium-containing phosphate, and the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; The negative electrode plate includes a negative current collector portion and a negative electrode film layer located on at least one side of the negative current collector portion. The negative electrode film layer includes a carbon-based material and a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10%. The single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; The electrolyte includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent is 5% to 35%. This application can improve the fast charging ability and cycling performance of the battery cell.

Description

[0001] This application claims priority to PCT International Application PCT / CN2025 / 070963, titled "Battery Cell, Battery Device, and Electrical Device", filed on January 7, 2025, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to a battery cell, a battery device, and an electrical device. Background Art

[0003] Battery cells have characteristics such as high capacity and long life, and are therefore widely used in electronic devices, such as mobile phones, laptop computers, battery-powered vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc. Due to the great progress of batteries, higher requirements are put forward for the performance of batteries. However, the fast charging ability and cycling performance of battery cells need to be further improved. Summary of the Invention

[0004] This application provides a battery cell, a battery device, and an electrical device, and the fast charging ability and cycling performance of the battery cell of this application can be further improved.

[0005] In a first aspect, an embodiment of this application provides a battery cell, which includes a positive electrode tab, a negative electrode tab, and an electrolyte. The positive electrode tab includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a lithium-containing phosphate, and the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; the negative electrode tab includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material and a silicon-based material. The mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.3% to 10%, and the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; the electrolyte includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 35%.

[0006] Accordingly, the negative electrode plate of the embodiment of the present application includes a silicon-based material. The mass content of silicon element and the coating weight of the positive and negative electrode film layers are coordinated so that the battery cell has a relatively high energy density and is conducive to the rapid migration of active ions in the positive and negative electrode film layers. The electrolyte contains a chain carboxylic ester solvent within an appropriate range, which can reduce the side reactions on the negative electrode side, alleviate the interfacial side reactions between the silicon-based material and the electrolyte, and reduce the gas generation at high temperatures while increasing the lithium ion migration rate, thereby comprehensively improving the fast charging performance and cycle performance of the battery cell.

[0007] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 ; when the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode plate will not be too large, which is conducive to reducing the polarization phenomenon under high-rate charging, and can balance the improvement of the energy density and fast charging performance of the battery cell.

[0008] In some embodiments, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 to 142 mg / 1540.25 mm 2 ; when the single-sided coating weight of the negative electrode film layer meets the above range, its combination with an appropriate mass content of silicon element is conducive to improving the energy density of the battery cell, and the migration rate of active ions in the negative electrode film layer is relatively fast, which is also conducive to reducing the polarization phenomenon under high-rate charging and is beneficial to improving the fast charging ability of the battery cell.

[0009] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; when the tap density of the positive electrode film layer is within a reasonable range, the battery cell has both high energy density and fast charging performance.

[0010] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 ; when the tap density of the negative electrode film layer is within a reasonable range, the battery cell has both high energy density and fast charging performance.

[0011] In some embodiments, the charging specific capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g; when the charging specific capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0012] In some embodiments, the charging specific capacity of the negative electrode active material is 350 mAh / g to 540 mAh / g. When the charging specific capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0013] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 3% to 6%. When the mass content of silicon element is within the above range, it can improve the capacity of the negative electrode active material, which is beneficial to improving the energy density of the battery cell; moreover, during the charge and discharge process, the volume expansion of silicon element will not be too large, which is beneficial to maintaining the stability of the solid electrolyte interface film (SEI film) of the negative electrode and improving the cycle performance of the battery cell.

[0014] In some embodiments, the silicon-based material includes one or more of silicon carbide and silicon oxide.

[0015] In some embodiments, the negative electrode film layer includes a first region and a second region. The first region is disposed on the surface of the negative electrode current collector portion, and the thickness of the first region is 1 / 3 of the thickness of the negative electrode film layer; the second region is connected to the side of the first region facing away from the negative electrode current collector portion, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode film layer. Among them, the average particle size of the carbon-based material in the first region is greater than or equal to the average particle size of the carbon-based material in the second region. The difference in particle sizes between the first region and the second region can improve the fast charging performance of the battery cell.

[0016] In some embodiments, the average particle size of the carbon-based material in the first region is 10 μm to 20 μm; when the average particle size of the carbon-based material in the first region is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance, and on the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0017] In some embodiments, the average particle size of the carbon-based material in the second region is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second region is within the above range, it is beneficial to improve the fast charging ability of the battery cell and the stability of the material.

[0018] In some embodiments, the carbon-based material in the first region includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second region includes artificial graphite. The above material settings are beneficial to forming the pore difference between the first region and the second region and improving the fast charging ability of the battery cell.

[0019] In some embodiments, at least one of the first region and the second region includes a silicon-based material. The silicon-based material is beneficial to improving the energy density of the battery cell.

[0020] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector portion; the second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector portion. The double-layer film layer is beneficial to improving the fast charging ability and energy density of the battery cell.

[0021] In some embodiments, the negative electrode film layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of conductive carbon and carbon nanotubes. The negative electrode conductive agent can improve the conductivity of the negative electrode film layer and improve the fast charging ability.

[0022] In some embodiments, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%; when the mass content of the conductive carbon is within the above range, the conductivity of the negative electrode film layer can be improved and the fast charging ability can be improved.

[0023] In some embodiments, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%. When the mass content of the carbon nanotubes is within the above range, the conductivity of the negative electrode film layer can be improved and the fast charging ability can be improved.

[0024] In some embodiments, the conductivity of the electrolyte at room temperature is 10.5 mS / cm to 13.5 mS / cm; when the conductivity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0025] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s; when the viscosity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0026] In some embodiments, the density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0027] In some embodiments, the mass content of the chain carboxylic ester solvent in the electrolyte is 8% to 20%. When the mass content of the chain carboxylic ester solvent is within the above range, the fast charging ability and cycle performance of the battery cell can be improved.

[0028] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I,

[0029] Formula I,

[0030] In Formula I,

[0031] R1 includes a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group,

[0032] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0033] The chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0034] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0035]

[0036] In some embodiments, the organic solvent includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%.

[0037] When the mass contents of the carbonate solvent and the chain carboxylic ester solvent meet the above conditions, the stability of the electrolyte can be improved and its gas generation amount at high temperature can be reduced.

[0038] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0039] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, and the lithium iron phosphate has excellent cycle stability and can improve the cycle performance of the battery cell.

[0040] In some embodiments, the size of the positive electrode film layer in its own length direction is 265 mm to 655 mm. When the size of the positive electrode film layer is within the above range, the electron transmission path will not be too long and the internal resistance is relatively small, which is beneficial to improving the fast charging ability and energy density of the battery cell.

[0041] In a second aspect, an embodiment of the present application further provides a battery device, including the battery cell according to any one of the embodiments of the first aspect of the present application.

[0042] In a third aspect, an embodiment of the present application further provides an electrical device, and the electrical device includes the battery device according to any one of the embodiments of the second or third aspect of the present application. Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0044] Figure 1 is a schematic structural view of an electrical device provided by some embodiments of the present application;

[0045] Figure 2 is a schematic structural view of a battery pack provided by some embodiments of the present application;

[0046] Figure 3 is a schematic structural view of a battery module provided by some embodiments of the present application;

[0047] Figure 4 is a schematic structural view of a battery cell provided by some embodiments of the present application;

[0048] Figure 5 is a schematic structural view of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0049] Figure 6 is a schematic structural view of a first electrode tab of a battery cell provided by some embodiments of the present application;

[0050] Figure 7 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0051] Figure 8 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0052] Figure 9 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0053] Figure 10 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0054] Figure 11 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0055] Figure 12 is a schematic structural view of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0056] Figure 13 is a schematic structural view of a second electrode tab of a battery cell provided by some embodiments of the present application; ]>

[0057] Figure 14 is a schematic structural view of a second electrode tab of a battery cell provided by some other embodiments of the present application;

[0058] [[ID=`58]] Figure 15 is a schematic structural view of a battery cell provided by some other embodiments of the present application;

[0059] Figure 16 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0060] Figure 17 is a schematic structural diagram of a negative electrode sheet of a battery cell provided in some embodiments of the present application;

[0061] Figure 18 It is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

[0062] The drawings are not necessarily drawn to scale.

[0063] The following are the descriptions of the reference numerals:

[0064] X, thickness direction; Y, width direction; Z, length direction;

[0065] 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space; 6. Battery module;

[0066] 7. Battery cells;

[0067] 10. Electrode assembly;

[0068] 11. first pole piece; 111. first pole tab; 1111. first end; 112. first coating portion;

[0069] 12. Second pole piece; 121. Second pole tab; 1211. Second end; 122. Second coating portion;

[0070] 13. Isolation parts;

[0071] 14, negative electrode sheet; 141, negative electrode film layer; 142, negative electrode current collector; 1411, first negative electrode film layer; 1412, second negative electrode film layer; 141a, first region; 141b, second region; 141c, third region;

[0072] 20. Housing assembly;

[0073] 21. Shell; 22. End cover; 31. First electrode terminal; 32. Second electrode terminal. DETAILED DESCRIPTION

[0074] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0075] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0076] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0077] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0078] If there is no special instruction, all steps of the present application can be carried out sequentially or randomly, and preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0079] In this application, "a plurality of" means two or more (including two).

[0080] In the embodiments of this application, the battery cell may be a secondary battery, which refers to a battery cell that can activate the active material through charging and continue to be used after the battery cell discharges.

[0081] The battery cell may be a lithium-ion battery, a sodium lithium-ion battery, etc., and the embodiments of this application do not limit this.

[0082] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, with the improvement of the fast charging performance requirements, in related technologies, it can be achieved by increasing the conductivity of the electrolyte. However, the increase in conductivity may cause the electrolyte to decompose at high temperatures, resulting in an increase in the gas production of the battery cell at high temperatures, which may deteriorate the cycle performance of the battery cell, making it impossible to simultaneously improve the fast charging performance and the cycle performance of the battery cell, especially at high energy densities.

[0083] In view of the above problems, the embodiments of this application improve the fast charging performance and the cycle performance of the battery cell by coordinately regulating the positive electrode sheet, the negative electrode sheet, and the electrolyte. Specifically, the negative electrode sheet of the battery cell includes a silicon-containing negative electrode active material, which, with an appropriate coating weight, enables the battery cell to have a relatively high energy density.

[0084] The negative electrode sheet includes silicon, which is beneficial for thin coating and beneficial for the rapid migration of active ions such as lithium ions in the negative electrode sheet. Its cooperation with a positive electrode film layer with an appropriate coating weight can improve the rapid migration of active ions in the positive electrode sheet, thereby improving the migration rate of active ions in the positive and negative electrode film layers. Further cooperation with an appropriate content of chain-like carboxylic ester solvents can improve the migration rate of lithium ions in the electrolyte, thereby improving the liquid-phase transport rate of lithium ions, and thus improving the fast charging ability of the battery cell.

[0085] However, silicon-based materials containing silicon are more likely to undergo side reactions with the electrolyte, resulting in an increase in gas production, especially an increase in gas production at high temperatures. In the embodiments of this application, the mass content of the chain-like carboxylic ester solvent is less than or equal to 35%, which can relieve the side reaction between the silicon-based material and the electrolyte and reduce the gas production on the basis of the rapid migration of active ions such as lithium ions, thereby comprehensively improving the cycle performance and the fast charging ability of the battery cell at high energy densities and being beneficial for improving the cycle performance under fast charging conditions.

[0086] The battery cell of this application is applicable to various battery devices and electrical devices that use battery cells.

[0087] Exemplarily, the electrical device may be a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric toy, an electric tool, a vehicle, a ship, a spacecraft, etc. Alternatively, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0088] Figure 1 is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0089] A battery device is disposed inside the electrical device 1, and the battery device can be disposed at the bottom, the head, or the tail of the electrical device 1. The battery device can be used to supply power to the electrical device 1. For example, the battery device can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in

[0090] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery device to supply power to the motor 4. For example, it is used for the working power requirements during the start, navigation, and driving of the electrical device 1. <{

[0091] The battery device (Battery Apparatus) 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, and the plurality of battery cells are connected in series, parallel, or in a mixed connection through a busbar component.

[0092] In some embodiments, the battery cell assembly (Battery Cell Assembly) is generally formed by arranging a plurality of battery cells.

[0093] As an example, the battery cell assembly may be a battery module (Battery Module), and the battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0094] As shown in Figure 2 In some embodiments, the battery device may be a battery pack 2 (battery Pack), and the battery pack 2 includes a box body 5 and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body 5.

[0095] As an example, the battery cell assembly may also be accommodated in the box body 5 by directly fixing a plurality of battery cells to the box body 5.

[0096] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has a receiving space 5c. The first housing portion 5a and the second housing portion 5b are snapped together so that a closed space is formed inside the housing 5 to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first housing portion 5a can be a top cover or a bottom plate.

[0097] As an example, the housing 5 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 housing 5 to accommodate the battery cell assembly.

[0098] In some embodiments, the housing 5 can be part of the chassis structure of a vehicle. For example, part of the housing 5 can form at least part of the floor of the vehicle, or part of the housing 5 can form at least part of the cross beams and longitudinal beams of the vehicle.

[0099] As an example, the battery cell assembly can be a battery module 6, and the battery cell assembly can be accommodated in the housing 5 by fixing the battery module 6 in the housing 5.

[0100] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0101] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% state of charge SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0102] Exemplarily, the charging steps of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC can be carried out in the following manner:

[0103] Charge at a constant current of 8.00C from 20% SOC to 25% SOC;

[0104] Charge at a constant current of 8.00C from 25% SOC to 30% SOC;

[0105] Charge at a constant current of 7.50C from 30% SOC to 35% SOC;

[0106] Charge at a constant current of 6.87C from 35% SOC to 40% SOC;

[0107] Charge at a constant current of 6.38C from 40% SOC to 45% SOC;

[0108] Charge at a constant current of 5.95C from 45% SOC to 50% SOC;

[0109] Charge from 50% SOC to 55% SOC at a constant current of 5.53C;

[0110] Charge from 55% SOC to 60% SOC at a constant current of 5.14C;

[0111] Charge from 60% SOC to 65% SOC at a constant current of 4.76C;

[0112] Charge from 65% SOC to 70% SOC at a constant current of 4.36C;

[0113] Charge from 70% SOC to 75% SOC at a constant current of 3.94C;

[0114] Charge from 75% SOC to 80% SOC at a constant current of 3.57C.

[0115] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from 20% state of charge to 80% state of charge is 5 min to 30 min, optionally 5 min to 20 min. The temperature of the external environment of the battery device at 20% state of charge is room temperature, such as 25°C. Exemplarily, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min or the range composed of any two of the above values.

[0116] As Figure 4 and Figure 5 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20.

[0117] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0118] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0119] Exemplarily, the terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32. One of the first electrode terminal 31 and the second electrode terminal 32 is the positive terminal, and the other is the negative terminal.

[0120] The outer casing can be a steel casing, an aluminum casing, a plastic casing (such as polypropylene), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the outer casing can be a sealed structure or a non-sealed structure. As an example, when the outer casing is a non-sealed structure, the outer casing serves to protect the electrode assembly 10, and a sealed bag is further included between the outer casing and the electrode assembly 10, and the sealed bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum-plastic film. When the outer casing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0121] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, and a multi-prismatic battery. The multi-prismatic battery is, for example, a hexagonal prism battery, etc., and there is no particular limitation in this application.

[0122] In some embodiments, the outer casing includes an end cap 22 and a housing 21. The housing 21 is provided with an opening, and the end cap 22 is covered on the opening. The housing 21 can be provided with one or more openings. One or more end caps 22 can also be provided.

[0123] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a housing 21 with a cylindrical structure can be selected; if the electrode assembly 10 is a cuboid structure, a housing 21 with a cuboid structure can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0124] The electrode assembly 10 includes a first electrode tab 11, a second electrode tab 12, and a separator 13. One of the first electrode tab 11 and the second electrode tab 12 is a positive electrode tab, and the other is a negative electrode tab.

[0125] The electrode assembly 10 can be a wound structure, a stacked structure, or a hybrid structure of winding and stacking. The electrode assembly 10 can be optionally a stacked structure, which is beneficial to improving the energy density of the battery cell 7.

[0126] In some embodiments, the electrode assembly 10 is a wound structure. The first electrode tab 11 and the second electrode tab 12 are wound into a wound structure.

[0127] In some other embodiments, the electrode assembly 10 is a stacked structure. As an example, a plurality of first electrode tabs 11 and a plurality of second electrode tabs 12 can be respectively provided, and the plurality of first electrode tabs 11 and the plurality of second electrode tabs 12 are stacked.

[0128] As an example, a plurality of first electrode tabs 11 can be provided, and the second electrode tab 12 is folded to form a plurality of folded segments arranged in a stacked manner, and a first electrode tab 11 is clamped between adjacent folded segments.

[0129] As an example, both the first electrode tab 11 and the second electrode tab 12 are folded to form a plurality of stacked folding segments.

[0130] As an example, a plurality of separators 13 may be provided and are respectively disposed between any adjacent first electrode tab 11 or second electrode tab 12.

[0131] As an example, the separators 13 may be continuously provided and are disposed between any adjacent first electrode tab 11 or second electrode tab 12 by folding or winding.

[0132] In some embodiments, each electrode tab is provided with an electrode ear, and the electrode ear can conduct current out of the electrode assembly 10. The electrode ear includes a positive electrode ear and a negative electrode ear.

[0133] In some embodiments, both the first electrode tab 11 and the second electrode tab 12 include a coating portion and an electrode ear portion. The coating portion is coated with an active material layer, and the electrode ear portion is disposed on at least one side of the coating portion along a first direction and is not coated with the active material layer. The first direction is parallel to the length direction Z of the battery cell 7, or the first direction is parallel to the width direction Y of the battery cell 7.

[0134] In the embodiments of the present application, the first direction, the second direction, and the thickness direction X of the battery cell 7 are perpendicular to each other in pairs.

[0135] When the first direction is parallel to the length direction Z of the battery cell 7, the dimension of the component in this direction can be regarded as the length of the component. For example, the dimension of the coating portion along the first direction is the length of the coating portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0136] When the first direction is parallel to the width direction Y of the battery cell 7, the dimension of the component in this direction can be regarded as the width of the component. For example, the dimension of the coating portion along the first direction is the width of the coating portion. In this case, the second direction is parallel to the length of the battery cell 7.

[0137] To illustrate the present application more clearly, the electrode ear portion of the first electrode tab 11 is defined as the first electrode ear 111, and the coating portion of the first electrode tab 11 is defined as the first coating portion 112. The electrode ear portion of the second electrode tab 12 is defined as the second electrode ear 121, and the coating portion of the second electrode tab 12 is defined as the second coating portion 122. The electrode terminal that is of the same electric property as and electrically connected to the first electrode ear 111 is the above-mentioned first electrode terminal 31, and the electrode terminal that is of the same electric property as and electrically connected to the second electrode ear 121 is the above-mentioned second electrode terminal 32.

[0138] The polarities of the first electrode tab 11 and the second electrode tab 12 are opposite. When the first electrode tab 11 is the positive electrode tab, the second electrode tab 12 is the negative electrode tab, the first coating portion 112 is the positive electrode coating portion, the first tab 111 is the positive tab, the first electrode terminal 31 is the positive terminal, the second coating portion 122 is the negative electrode coating portion, the second tab 121 is the negative tab, and the second electrode terminal 32 is the negative terminal.

[0139] Or when the first electrode tab 11 is the negative electrode tab, the second electrode tab 12 is the positive electrode tab, the first coating portion 112 is the negative electrode coating portion, the first tab 111 is the negative tab, the first electrode terminal 31 is the negative terminal, the second coating portion 122 is the positive electrode coating portion, the second tab 121 is the positive tab, and the second electrode terminal 32 is the positive terminal.

[0140] The coating portion includes a current collector portion and a film layer provided on the current collector portion and containing an active material. For example, the positive electrode coating portion includes a positive electrode current collector portion and a positive electrode film layer provided on the positive electrode current collector portion and containing a positive electrode active material. Another example is that the negative electrode coating portion includes a negative electrode current collector portion and a negative electrode film layer provided on the negative electrode current collector portion and containing a negative electrode active material.

[0141] As Figures 6 to 8 shown, in some embodiments, in the first electrode tab 11, the tab portion is provided on at least one side of the coating portion along the first direction, and the first electrode tab 11 satisfies: n×W1 / W2 is 0.2 to 1.0;

[0142] n represents the number of all tab portions on the same side of the coating portion;

[0143] W1 represents the average dimension of the tab portion along the second direction;

[0144] W2 represents the dimension of the coating portion along the second direction, and the second direction, the first direction, and the thickness direction X are perpendicular to each other in pairs.

[0145] Exemplarily, n×W1 / W2 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range composed of any two of the above values. Optionally, n×W1 / W2 is 0.5 to 1.0.

[0146] When n×W1 / W2 satisfies the above range, the current-carrying area of the tab portion is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0147] W1 represents the average dimension of the first tab 111 along the second direction.

[0148] When the first electrode tab 111 has a special-shaped structure, for example, the size of the first electrode tab 111 along the second direction gradually increases along the first direction, in this case, the size of the first electrode tab 111 along the second direction at multiple locations can be measured to calculate the average size of the first electrode tab 111 along the second direction. Of course, the size of each location of the first electrode tab 111 along the second direction can be the same value, in which case this value can be used as the average size of the first electrode tab 111.

[0149] There may be one or more first pole tabs 111 , for example, n is 1 to 4. In the case of multiple first pole tabs 111 , the average size of each first pole tab 111 may be measured separately, and the sum of the average size values may be divided by the number of first pole tabs 111 to calculate the average size of the first pole tabs 111 .

[0150] The first pole tab 111 is connected to the first coating portion 112, and the first pole tab 111 includes a first end 1111 connected to the first coating portion 112. When n×W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first pole tab 111 itself is relatively large, and the contact area between the first pole tab 111 and the first coating portion 112 is relatively large. The first pole tab 111 has a strong current-carrying capacity, which can improve the fast charging performance and cycle performance of the battery cell 7.

[0151] Optionally, the first electrode tab 111 and the current collecting portion of the first coating portion 112 are of an integrated structure, so that the internal resistance of the first electrode sheet 11 is low, which can further improve the fast charging performance and cycle performance of the battery cell 7 .

[0152] In some embodiments, the first pole piece 11 includes at least one first pole tab 111 , for example, 1 to 4 first pole tabs 111 . Optionally, the first pole piece 11 includes at least two first pole tabs 111 , and optionally four first pole tabs 111 .

[0153] In some embodiments, one or more first electrode tabs 111 are disposed on at least one side of the coating portion along the width direction Y.

[0154] like Figures 6 to 8 As shown, for example, one or more first pole ears 111 are arranged on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all first pole ears 111 are arranged on the same side of the first coating portion 112 along the width direction Y. This arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7. Figure 6 In FIG. 1 , W1 represents the dimension of a single first electrode tab 111 along the length direction Z, and n is 1; W2 represents the dimension of the first coating portion 112 along the length direction Z. Figure 7Among them, n is 4, and the sizes of all the first tab ears 111 are the same. W1 can represent the size of a single first tab ear 111. Of course, the sizes of the first tab ears 111 can also have slight differences. Figure 8 Among them, n is 1, and n×W1 / W2 is 1.

[0155] Such as Figure 9 As shown, for example, when the first electrode sheet 11 includes a plurality of first tab ears 111, the plurality of first tab ears 111 are arranged on both sides of the first coating portion 112 in the width direction Y.

[0156] Optionally, when the plurality of first tab ears 111 are arranged on at least one side of the first coating portion 112 in the width direction Y, there are at least two first tab ears 111 on the same side of the first coating portion 112 in the width direction Y, such as two, three, four, five, six, etc.; it can be selected as four. This setting is beneficial to the uniform distribution of electrons in the first electrode sheet 11 and is beneficial to improving the fast charging performance.

[0157] Optionally, the distance between two adjacent first tab ears 111 in the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or the range composed of any two of the above values. Figure 9 Among them, Z1 represents the distance between two adjacent first tab ears 111 in the length direction Z.

[0158] When the distance between two adjacent first tab ears 111 in the length direction Z satisfies the above range, it is beneficial to the uniform distribution of current in the current collecting portion and is beneficial to improving the fast charging performance.

[0159] In some other embodiments, the first electrode sheet 11 includes one or more first tab ears 111; the one or more first tab ears 111 are arranged on at least one side of the first coating portion 112 in the length direction Z.

[0160] Such as Figure 10 As shown, for example, one or more first tab ears 111 are arranged on one side of the first coating portion 112 in the length direction Z. In this case, it can be understood that all the first tab ears 111 are arranged on the same side of the first coating portion 112 in the length direction Z.

[0161] Such as Figure 11 And Figure 12 As shown, for example, when the first electrode sheet 11 includes a plurality of first tab ears 111, the plurality of first tab ears 111 are respectively arranged on both sides of the first coating portion 112 in the length direction Z.

[0162] Optionally, a plurality of first tab ears 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z. This kind of arrangement can shorten the transmission path of electrons in the first electrode tab 11, which is beneficial to improving the fast charging performance. For example, two first tab ears 111 are located on one side of the first coating portion 112 along the length direction Z, and the other two first tab ears 111 are located on the other side of the first coating portion 112 along the length direction Z.

[0163] Optionally, when a plurality of first tab ears 111 are respectively disposed on at least one side of the first coating portion 112 along the length direction Z, there are at least two first tab ears 111 on the same side of the first coating portion 112 along the length direction Z, such as two, three, four, five, six, and so on. This kind of arrangement is beneficial to the uniform distribution of electrons in the first electrode tab 11, which is beneficial to improving the fast charging performance.

[0164] Optionally, the distance between two adjacent first tab ears 111 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or the range composed of any two of the above values.

[0165] As Figure 13 shown, in some embodiments, in the second electrode tab 12, the tab ear portion is disposed on at least one side of the coating portion along the first direction, and the second electrode tab 12 satisfies: m×W3 / W4 is 0.2 to 1.0;

[0166] m represents the number of all tab ear portions on the same side of the coating portion;

[0167] W3 represents the average size of the tab ear portion along the second direction;

[0168] W4 represents the size of the coating portion along the second direction.

[0169] Exemplarily, m×W3 / W4 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or the range composed of any two of the above values. Optionally, m×W3 / W4 is 0.5 to 1.0.

[0170] When m×W3 / W4 satisfies the above range, the current-carrying area of the second tab ear 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0171] W3 represents the average size of the second tab ear 121 along the second direction. The second tab ear 121 can be one or more. For example, m is 1 to 4. When the second tab ear 121 is multiple, the average size can be calculated by measuring the sizes of each second tab ear 121 with a micrometer.

[0172] The second tab 121 is connected to the second coating portion 122. The second tab 121 includes a second end 1211 connected to the second coating portion 122. When n×W3 / W4 satisfies the above range, it means that the cross-section of the second end 1211 along the thickness direction of the second tab 121 itself is relatively large, the contact surface between the second tab 121 and the second coating portion 122 is relatively large, the current-carrying capacity of the second tab 121 is relatively strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0173] Optionally, the current collector portion of the second tab 121 and the second coating portion 122 is an integral structure, so that the internal resistance of the second electrode sheet 12 is relatively low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0174] In some embodiments, the second electrode sheet 12 includes at least one second tab 121, optionally at least two second tabs 121, and optionally four second tabs 121.

[0175] In some embodiments, one or more second tabs 121 are disposed on at least one side of the coating portion along the width direction Y. For example, one or more second tabs 121 are disposed on one side of the second coating portion 122 along the width direction Y. In this case, it can be understood that all the second tabs 121 are disposed on the same side of the second coating portion 122 along the width direction Y. Or for example, when the second electrode sheet 12 includes a plurality of second tabs 121, the plurality of second tabs 121 are disposed on both sides of the second coating portion 122 along the width direction Y.

[0176] Optionally, one or more second tabs 121 are respectively disposed on one side of the second coating portion 122 along the width direction Y. This kind of setting is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0177] Optionally, when a plurality of second tabs 121 are disposed on at least one side of the coating portion along the width direction Y, the number of second tabs 121 located on the same side of the second coating portion 122 along the width direction Y is at least two, such as two, three, four, five, six, etc.; optionally four. This kind of setting is beneficial to the uniform distribution of electrons in the second electrode sheet 12 and is beneficial to improving the fast charging performance.

[0178] Optionally, the distance between two adjacent second tabs 121 along the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or the range composed of any two of the above values.

[0179] As Figure 14As shown, in some other embodiments, the second pole piece 12 includes one or more second tab ears 121; one or more second tab ears 121 are disposed on at least one side of the second coating portion 122 along the length direction Z. For example, one or more second tab ears 121 are disposed on one side of the second coating portion 122 along the length direction Z. In this case, it can be understood that all the second tab ears 121 are disposed on the same side of the second coating portion 122 along the length direction Z. Or for example, in the case where the second pole piece 12 includes a plurality of second tab ears 121, the plurality of second tab ears 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z.

[0180] Optionally, the plurality of second tab ears 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z. This setting can shorten the transmission path of electrons in the second pole piece 12, which is beneficial to improving the fast charging performance.

[0181] Optionally, in the case where the plurality of second tab ears 121 are disposed on at least one side of the second coating portion 122 along the length direction Z, there are at least two second tab ears 121 on the same side of the second coating portion 122 along the length direction Z, such as two, three, four, five, six, and so on. This setting is beneficial to the uniform distribution of electrons in the second pole piece 12, which is beneficial to improving the fast charging performance.

[0182] Optionally, the distance between two adjacent second tab ears 121 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or the range composed of any two of the above values.

[0183] As Figure 15 shown, in some embodiments, the terminal assembly may be disposed on the housing 21, or the terminal assembly is disposed on the end cap 22.

[0184] The terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32. The first electrode terminal 31 is connected to the first tab ear 111, and the second electrode terminal 32 is connected to the second tab ear 121.

[0185] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 may be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22.

[0186] On the same end cap 22, the first electrode terminal 31 and the second electrode terminal 32 can be provided simultaneously. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are arranged at intervals on the end cap 22. Another example is that there are two end caps 22, the two end caps 22 are arranged oppositely, and the first electrode terminal 31 and the second electrode terminal 32 are provided on each end cap 22.

[0187] The first electrode terminal 31 and the second electrode terminal 32 are respectively provided on different end caps 22. For example, there are two end caps 22, the two end caps 22 are arranged oppositely, the first electrode terminal 31 is provided on one of the end caps 22, and the second electrode terminal 32 is provided on the other end cap 22.

[0188] In some embodiments, the first electrode terminal 31 is at least one, and can be optionally at least two, such as two, three, or four, etc.

[0189] In some embodiments, at least one first electrode terminal 31 is provided on at least one side of the electrode assembly 10 along the length direction Z.

[0190] As Figure 15 shown, for example, all the first electrode terminals 31 are provided on one side of the electrode assembly 10 along the length direction Z.

[0191] As Figure 16 shown, another example is that multiple first electrode terminals 31 are respectively provided on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0192] Exemplarily, there are two first electrode terminals 31, one of the first electrode terminals 31 is provided on one side of the electrode assembly 10, and the other first electrode terminal 31 is provided on the other side of the electrode assembly 10. Or, exemplarily, there are four first electrode terminals 31, two of the first electrode terminals 31 are provided on one side of the electrode assembly 10, and the other two first electrode terminals 31 are provided on one side of the electrode assembly 10.

[0193] In the embodiments of the present application, the first tab 111 and the first electrode terminal 31 can be directly connected or indirectly connected; when the first tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 can include a first adapter 51, and the first adapter 51 is located between the first electrode terminal 31 and the first tab 111 and connects the first electrode terminal 31 and the first tab 111.

[0194] In the above embodiments, the first adapter 51 can include a conductive polymer or a conductive metal material, and the conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0195] In some other embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. As another example, a plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0196] In some embodiments, the second electrode terminal 32 is at least one, and may be alternatively at least two, such as two, three, or four, etc.

[0197] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0198] As Figure 16 shown, for example, at least two second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0199] Figure 16 It shows that the battery cell 7 includes four electrode terminals. Specifically, there are two second electrode terminals 32, one of the second electrode terminals 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0200] As another example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 along the length direction Z, and when being electrically connected to the tab portions respectively, they will not interfere with each other.

[0201] Exemplarily, there is one first electrode terminal 31 and one second electrode terminal 32. The first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, and the second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. Optionally, the first electrode terminal 31 and the second electrode terminal 32 can be disposed offset along the width direction Y. Of course, the first electrode terminal 31 and the second electrode terminal 32 can also be disposed opposite to each other along the length direction Z. Figure 15 It shows a schematic diagram in which the first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on both sides of the electrode assembly 10.

[0202] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32. The two first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the length direction Z.

[0203] In the embodiment of the present application, the second tab 121 and the second electrode terminal 32 can be directly connected or indirectly connected; when the second tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, and the second adapter is located between the second electrode terminal 32 and the second tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0204] For example, when the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z and the second tab 121 is disposed on one side of the second coating portion 122 along the width direction Y, it is more beneficial to connect the second tab 121 and the second electrode terminal 32 through the second adapter.

[0205] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0206] In some other embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y, or a plurality of second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the width direction Y.

[0207] In some embodiments, the battery cell 7 includes a positive electrode plate, a negative electrode plate, and an electrolyte. The positive electrode plate includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate. The single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; the negative electrode plate includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material and a silicon-based material. The mass content of silicon element in the negative electrode film layer is 0.3% to 10%, and the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; the electrolyte includes an organic solvent, and the organic solvent includes a chain carboxylic acid ester solvent. The mass content of the chain carboxylic acid ester solvent in the electrolyte is 5% to 35%.

[0208] The negative electrode tab includes a silicon-based material, the mass content of silicon element in the negative electrode active material is greater than or equal to 0.3%, and the coating weight of the negative electrode film layer is greater than or equal to 80 mg / 1540.25 mm 2 The coating weight of the positive electrode film layer is greater than or equal to 150 mg / 1540.25 mm 2 so that the energy density of the battery cell 7 is relatively high;

[0209] During the charging process of the battery cell 7, active ions such as lithium ions migrate from the positive electrode tab to the negative electrode tab through the electrolyte. The mass content of the chain carboxylic ester solvent in the electrolyte is greater than or equal to 5%, so that the migration rate of the active ions in the electrolyte is relatively fast; and the coating weight of the negative electrode film layer is less than or equal to 150 mg / 1540.25 mm 2 which is conducive to the rapid migration of active ions in the negative electrode film layer. The coating weight of the positive electrode film layer is less than or equal to 370 mg / 1540.25 mm 2 which is conducive to the rapid migration of active ions in the positive electrode film layer. Through the cooperation of the coating weights of the positive and negative electrode film layers and the components in the electrolyte, it is conducive to improving the liquid-phase migration rate of lithium ions and enhancing the fast charging ability of the battery cell 7;

[0210] The increase in the mass content of silicon element is conducive to the improvement of energy density, and the increase in the addition amount of the chain carboxylic ester solvent is conducive to the improvement of the migration rate of lithium ions. However, with the increase in the mass content of silicon element and the mass content of the carboxylic ester solvent, the interfacial reaction between the silicon-based material and the electrolyte intensifies and the gas generation increases; thus, in the embodiments of the present application, the mass content of silicon element is further regulated to be less than or equal to 10%, and the mass content of the chain carboxylic ester solvent in the electrolyte is less than or equal to 35%, which can alleviate the interfacial side reaction between the negative electrode active material and the electrolyte, reduce the gas generation amount, and improve the cycle performance of the battery cell 7; the positive electrode tab of the present application further includes lithium-containing phosphate, and the negative electrode tab further includes a carbon-based material, and the cycle stability is relatively excellent, which can further improve the cycle performance of the battery cell 7;

[0211] Thus, the embodiments of the present application can improve the fast charging performance and cycle performance of the battery cell 7 at high energy density, and are conducive to improving the cycle performance of the battery cell 7 under fast charging conditions.

[0212] Negative electrode sheet

[0213] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0214] The upper charging limit voltage and the lower discharging cut-off voltage of the battery cell vary according to the different cathode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charging limit voltage can be 3.65V and the lower discharging cut-off voltage can be 2.0V, or the upper charging limit voltage can be 3.8V and the lower discharging cut-off voltage can be 2.0V; Another example is when the phosphate material includes lithium manganese iron phosphate, the upper charging limit voltage can be 4.3V and the lower discharging cut-off voltage can be 2.0V. Next, taking the upper charging limit voltage of 3.8V and the lower discharging cut-off voltage of 2.0V as an example, the state of the battery cell will be described: In the embodiments of the present application, the 100% state of charge (SOC) and the 0% SOC of the battery cell are defined as follows,

[0215] The battery cell is charged at a constant current charging rate of 0.05C to the upper charging limit voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged at a constant current discharging rate of 0.05C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0216] In some embodiments, when the battery cell is at 100% SOC, the compaction density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 . Exemplarily, the compaction density of the negative electrode film layer of the battery cell at 100% SOC is 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 , 1.66 g / cm³, 1.68 g / cm³, 1.70 g / cm³ or the range composed of any two of the above values.

[0217] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the negative electrode active materials in the negative electrode film layer are stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle performance. Therefore, by adjusting the compaction density of the negative electrode film layer to a reasonable range, the battery cell can improve its fast charging ability and cycle performance at high energy density.

[0218] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2, 80 mg / 1540.25 mm², 85 mg / 1540.25 mm², 90 mg / 1540.25 mm², 95 mg / 1540.25 mm², 100 mg / 1540.25 mm², 105 mg / 1540.25 mm², 110 mg / 1540.25 mm², 115 mg / 1540.25 mm², 120 mg / 1540.25 mm², 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 , 175 mg / 1540.25 mm 2 or a range composed of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 to 142 mg / 1540.25 mm 2 .

[0219] When the single-sided coating weight of the negative electrode film layer meets the above range, in combination with an appropriate mass content of silicon element, it is beneficial to improve the energy density of the battery cell, and the migration rate of active ions in the negative electrode film layer is relatively fast, and it is beneficial to reduce the polarization phenomenon under high-rate charging, which is beneficial to improving the fast charging ability of the battery cell at high energy density.

[0220] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, the negative electrode pole piece of the battery cell in the 100% state of charge (SOC) is disassembled, and the compaction density of the negative electrode film layer is measured. For example, take a single-sided coated negative electrode pole piece (if it is a double-sided coated pole piece, the negative electrode film layer on one side can be wiped off first), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the negative electrode film layer of the above weighed negative electrode pole piece, weigh the weight of the negative electrode current collector part, record it as M0, and measure its thickness H0. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode pole piece - the weight M0 of the negative electrode current collector part) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode pole piece - the thickness H0 of the negative electrode current collector part, and the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0221] In some embodiments, the charge specific capacity of the negative electrode active material is from 350 mAh / g to 540 mAh / g. Exemplarily, the charge specific capacity of the negative electrode active material is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g, 530 mAh / g, 540 mAh / g, or a range composed of any two of the above values.

[0222] When the charge specific capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0223] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art, and can be tested by the equipment and methods well-known in the art. The test method for the initial Coulomb efficiency and the initial discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used to test the charge specific capacity of the negative electrode active material at a rate of 0.1C in a half-cell. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-cell is assembled. Under the condition of 23°C ± 2°C, the half-cell is placed on a battery tester or other test equipment with the same performance, and the charge-discharge capacity is obtained through charge and discharge at a rate of 0.1C. Then, the capacity is divided by the mass of the active material of the electrode sheet to obtain the charge specific capacity parameter.

[0224] In some embodiments, the negative electrode active material includes a silicon-based material. Optionally, the silicon-based material may include at least one of elemental silicon, silicon-carbon composite, and silicon oxide SiO x (0 < x ≤ 2). For example, the silicon-carbon composite may be silicon carbide.

[0225] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is from 0.3% to 10%, such as 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range composed of any two of the above values. Optionally, the mass content of silicon element in the silicon-based material in the negative electrode film layer is from 3% to 6%.

[0226] When the mass content of silicon element is within the above range, it can improve the capacity of the negative electrode active material, which is beneficial to improving the energy density of the battery cell; moreover, during the charge and discharge process, the volume expansion of the silicon element will not be too large, which is beneficial to maintaining the stability of the negative electrode SEI film and improving the cycle performance of the battery cell at high energy density.

[0227] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has high cycle stability and can improve the cycle performance of the battery cell.

[0228] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0229] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0230] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0231] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to perform X-ray powder diffraction test and qualitative analysis on the negative electrode plate or the negative electrode active material.

[0232] Artificial graphite and natural graphite can be distinguished by the SEM cross-section diagram taken by scanning electron microscope SEM. There are gaps between the flaky structures in the SEM cross-section diagram of natural graphite, and the SEM cross-section diagram of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0233] As Figure 17 shown, in the embodiment of this application, the negative electrode film layer 141 of the negative electrode plate 14 includes at least one film layer, which can be a single-layer film layer or at least two film layers. Optionally, the negative electrode film layer 141 includes at least two film layers.

[0234] When the negative electrode film layer 141 adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material.

[0235] When the negative electrode film layer 141 adopts at least two film layers, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material. The negative electrode film layer 141 can include two film layers, three film layers, four film layers, or even more film layers.

[0236] In some embodiments, the negative electrode film layer 141 includes a first negative electrode film layer 1411 and a second negative electrode film layer 1412. The first negative electrode film layer 1411 is disposed on the surface of the negative electrode current collector 142, and the negative electrode active material of the first negative electrode film layer 1411 includes a carbon-based material. The second negative electrode film layer 1412 is connected to the side of the first negative electrode film layer 1411 facing away from the negative electrode current collector 142, and the negative electrode active material of the second negative electrode film layer 1412 includes a carbon-based material. The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 can be regular or irregular, and is optionally irregular; or there is no obvious interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0237] The negative electrode film layer 141 includes at least two film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there is a difference in the porosity between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, it is beneficial to improving the fast charging performance of the battery cell.

[0238] In some embodiments, at least one of the first negative electrode film layer 1411 and the second negative electrode film layer 1412 includes a silicon-based material.

[0239] Optionally, the first negative electrode film layer 1411 further includes a silicon-based material.

[0240] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0241] Exemplarily, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 include a silicon-based material, it is more beneficial to improving the energy density of the battery cell; and it can enable each layer to relieve the volume expansion of the silicon-based material through the carbon-based material, enable the negative electrode SEI film to be more stable, and improve the cycle performance under high energy density; and since each layer includes a silicon-based material, the coating thickness is relatively thin, which is beneficial to shortening the transmission path of lithium ions and improving the fast charging performance under high energy density.

[0242] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material. When the first negative electrode film layer 1411 includes a silicon-based material and the second negative electrode film layer 1412 does not include a silicon-based material, the second negative electrode film layer 1412 can alleviate the volume expansion of the first negative electrode film layer 1411, reduce the side reaction between the negative electrode film layer 141 and the electrolyte, and improve the cycling performance at high energy density.

[0243] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode film layer 1412 includes a silicon-based material, it is beneficial to form more film layer pores through the volume change of the silicon-based material, improve the liquid-phase transport ability of lithium ions, enhance the kinetic performance of the battery cell, and improve the cycling performance at high energy density.

[0244] When the negative electrode film layer 141 adopts at least two film layers, in the thickness direction X of the negative electrode film layer 141, the cross-sectional morphology of the negative electrode film layer 141 can be the same or similar at each location, or of course, it can also be different. When the electrode assembly is a stacked structure, the thickness direction of the battery cell can be parallel to the thickness direction of the electrode assembly and the thickness direction X of the negative electrode film layer 141.

[0245] Along the thickness direction X of the negative electrode film layer 141, the negative electrode film layer 141 is divided into three regions, namely the first region 141a, the third region 141c, and the second region 141b in sequence. The first region 141a is the region of the negative electrode film layer 141 close to the negative electrode current collector 142 along the thickness direction X, and the thickness of the first region 141a is 1 / 3 of the thickness of the negative electrode film layer 141; the second region 141b is the region of the negative electrode film layer 141 away from the negative electrode current collector 142 along the thickness direction X, and the thickness of the second region 141b is 1 / 3 of the thickness of the negative electrode film layer 14*.

[0246] The cross-sectional morphology of the first region 141a and the second region 141b can be the same or similar, or of course, it can also be different. The cross-sectional morphology of the first region 141a and the third region 141c can be the same or similar, or of course, it can also be different. The cross-sectional morphology of the second region 141b and the third region 141c can be the same or similar, or of course, it can also be different.

[0247] There may or may not be an obvious layer interface between the first region 141a, the second region 141b, and the third region 141c. For example, the first negative electrode film layer 1411 includes the first region 141a, the second negative electrode film layer 1412 includes the second region 141b, the third region 141c may be a part of the first negative electrode film layer 1411, or the third region 141c may be a part of the second negative electrode film layer 1412, or the third region 141c may be a part of both the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0248] Optionally, the average particle size of the carbon-based material in the first region 141a may be greater than or equal to the average particle size of the carbon-based material in the second region 141b. Further optionally, the average particle size of the carbon-based material in the first region 141a may be greater than the average particle size of the carbon-based material in the second region 141b, which is beneficial for lithium ions to quickly migrate from the second region 141b to the first region 141a and improve the fast charging ability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a may be less than the average particle size of the carbon-based material in the second region 141b.

[0249] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 may be greater than or equal to the average particle size of the carbon-based material in the second negative electrode film layer 1412. Further optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 may be greater than the average particle size of the carbon-based material in the second negative electrode film layer 1412.

[0250] There is a difference in the particle size between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer 1412 is usually high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer 1412. In the embodiments of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface of the negative electrode sheet 14 and improve the cycle performance under high energy density.

[0251] Optionally, the average particle size of the carbon-based material in the first region 141a is 10 μm to 20 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or the range composed of any two of the above values. When the average particle size of the carbon-based material in the first region 141a is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material and improve the cycle performance under high energy density.

[0252] Optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material of the first negative electrode film layer 1411 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0253] Optionally, the average particle size of the carbon-based material in the second region 141b is 5 μm to 12 μm, such as 5 μm, 8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm or the range composed of any two of the above values. When the average particle size of the carbon-based material of the second negative electrode film layer 1412 is within the above range, it can improve the stability of the material, which is beneficial to improving the fast charging ability and cycle performance of the battery cell at high energy density.

[0254] Optionally, the average particle size of the carbon-based material of the second negative electrode film layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material of the second negative electrode film layer 1412 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the third hand, the negative electrode active material in the second negative electrode film layer 1412 with the above average particle size range cooperates with the negative electrode active material in the first negative electrode film layer 1411, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer 1412 and the first negative electrode film layer 1411, reducing the tortuosity of lithium ion transmission, and improving the fast charging ability of the battery cell at high energy density.

[0255] Exemplarily, the carbon-based material in the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second region 141b includes artificial graphite. For example, the negative electrode active material in the first region 141a includes a silicon-based material, artificial graphite and natural graphite, and the negative electrode active material in the second region 141b includes a silicon-based material and artificial graphite.

[0256] Exemplarily, the carbon-based material of the first negative electrode film layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer 1412 includes artificial graphite. For example, the negative electrode active material of the first negative electrode film layer 1411 includes a silicon-based material, artificial graphite and natural graphite, and the negative electrode active material of the second negative electrode film layer 1412 includes a silicon-based material and artificial graphite.

[0257] In the embodiments of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the negative electrode sheet 14 as a sample, cross-section polishing is performed along the thickness direction X of the negative electrode film layer 141. For example, argon ion beam is used for cross-section polishing, and a scanning electron microscope (SEM) is used to take a cross-section photograph to obtain an SEM cross-sectional view. The particle size of the carbon-based material in the SEM cross-section is counted, and the average particle size of the carbon-based material is calculated according to the counted quantity. In the case where the proportion of the carbon-based material in the negative electrode film layer is relatively high, the average particle size of the carbon-based material can be used to roughly evaluate the average particle size of the negative electrode active material.

[0258] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The embodiments of the present application do not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0259] The negative electrode conductive agent can compensate for the disadvantage of insufficient conductivity of the silicon-based material, improve the conductivity of the negative electrode film layer, and is beneficial to improving the kinetic performance of the battery cell and the fast charging ability of the battery cell at high energy density.

[0260] Optionally, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%, such as 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7% or the range composed of any two of the above values. When the mass content of the conductive carbon is within the above mass content, the fast charging ability of the battery cell at high energy density can be improved.

[0261] Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 0.5%. When the mass content of the carbon nanotubes is within the above mass content, the fast charging ability of the battery cell at high energy density can be improved.

[0262] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0263] In some embodiments, the negative electrode film layer may also optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0264] In some embodiments, the negative electrode current collector portion may employ a metal foil or a composite current collector portion. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector portion may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0265] In some embodiments, the thickness of the negative electrode current collector portion is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values.

[0266] In some embodiments, the negative electrode plate further includes a negative electrode tab connected to the negative electrode current collector portion, and the thickness of the negative electrode tab is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values. When the thickness of the negative electrode tab is within the above range, it is beneficial to improve the overcurrent capacity and improve the fast charging capacity of the battery cell.

[0267] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector portion and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0268] The negative electrode plate does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application embodiment further includes a negative electrode conductive layer sandwiched between the negative electrode current collector portion and the negative electrode film layer and disposed on the surface of the negative electrode current collector portion. In some other embodiments, the negative electrode plate of the present application embodiment further includes a protective layer covering the surface of the negative electrode film layer.

[0269] Positive electrode sheet

[0270] The positive electrode plate includes a positive current collector portion and a positive electrode film layer provided on at least one side of the positive current collector portion and including a positive electrode active material. For example, the positive current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive current collector portion.

[0271] When the battery cell includes a stacked electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode plate. The dimension of the battery cell in the length direction can be understood as the length of the battery cell, and the dimension of the positive electrode film layer in the length direction can be understood as the length of the positive electrode film layer; the width direction of the battery cell is parallel to the width direction of the positive electrode plate. The dimension of the battery cell in the width direction can be understood as the width of the battery cell, and the dimension of the positive electrode film layer in the width direction can be understood as the width of the positive electrode film layer.

[0272] In some embodiments, the dimension of the positive electrode film layer in the length direction of the positive electrode plate is 265 mm to 1200 mm, such as 265 mm, 350 mm, 450 mm, 550 mm, 650 mm, 750 mm, 850 mm, 950 mm, 1050 mm, 1150 mm, 1200 mm or the range composed of any two of the above values.

[0273] In some embodiments, the ratio of the dimension of the positive electrode film layer in the length direction of the positive electrode plate to the dimension of the positive electrode film layer in the width direction of the positive electrode plate is greater than 1 and less than or equal to 18.5, and can be selected as 1.25 to 18.5, such as 1.25, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5 or the range composed of any two of the above values.

[0274] For example, the dimension of the positive electrode film layer in the length direction of the positive electrode plate is 265 mm to 655 mm, and the ratio of the dimension of the positive electrode film layer in the length direction of the positive electrode plate to the dimension of the positive electrode film layer in the width direction of the positive electrode plate is greater than 1 and less than or equal to 12.5, and can be selected as 2 to 12.5. When the positive electrode active material of the positive electrode film layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the dimension of the positive electrode film layer should not be too long. When the dimension of the positive electrode film layer is within the above range, the electron transmission path will not be too long, the internal resistance is relatively small, which is beneficial to improving the fast charging ability of the battery cell at high energy density.

[0275] Optionally, the size of the positive electrode film layer in the length direction of the positive electrode tab is 400 mm to 600 mm, and the ratio of the size of the positive electrode film layer in the length direction of the positive electrode tab to the size of the positive electrode film layer in the width direction of the positive electrode tab is 4 to 8.

[0276] For example, the size of the positive electrode film layer in the length direction of the positive electrode tab is greater than 655 mm and less than or equal to 1155 mm, and the ratio of the size of the positive electrode film layer in the length direction of the positive electrode tab to the size of the positive electrode film layer in the width direction of the positive electrode tab is 2 to 12.5.

[0277] In some embodiments, the size of the negative electrode film layer in the first direction is greater than the size of the positive electrode film layer in the first direction, such that substantially all of the lithium ions released from the positive electrode film layer can be embedded in the negative electrode film layer, reducing the risk of lithium plating on the negative electrode side and improving the reliability of use of the battery cell. Of course, the size of the negative electrode film layer in the first direction can also be less than or equal to the size of the positive electrode film layer in the first direction.

[0278] Optionally, the difference between the size of the negative electrode film layer in the first direction and the size of the positive electrode film layer in the first direction is 5 mm to 11 mm, such as 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or the range formed by any two of the above values.

[0279] In some embodiments, the size of the negative electrode film layer in the second direction is greater than the size of the positive electrode film layer in the second direction, such that substantially all of the lithium ions released from the positive electrode film layer can be embedded in the negative electrode film layer, reducing the risk of lithium plating on the negative electrode side and improving the cycle life of the battery cell. Of course, the size of the negative electrode film layer in the second direction can also be less than or equal to the size of the positive electrode film layer in the second direction.

[0280] Optionally, the difference between the size of the negative electrode film layer in the second direction and the size of the positive electrode film layer in the second direction is 5 mm to 11 mm, such as 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or the range formed by any two of the above values.

[0281] The first direction is perpendicular to the second direction. The first direction can be parallel to the length direction of the battery cell, or the first direction can be parallel to the width direction of the battery cell. When the first direction is parallel to the length direction of the battery cell, the second direction is parallel to the width direction of the battery cell. When the first direction is parallel to the width direction of the battery cell, the second direction is parallel to the length direction of the battery cell.

[0282] In some embodiments, the size of the separator in the first direction is greater than the size of the negative electrode film layer in the first direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reduce the risk of short circuit, and improve the reliability of use of the battery cell. Of course, the size of the separator in the first direction can also be less than or equal to the size of the negative electrode film layer in the first direction.

[0283] Optionally, the difference between the size of the separator in the first direction and the size of the negative electrode film layer in the first direction is 6 mm to 10 mm, such as 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range composed of any two of the above values.

[0284] In some embodiments, the size of the separator in the second direction is greater than the size of the negative electrode film layer in the second direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reduce the risk of short circuit, and improve the reliability of use of the battery cell. Of course, the size of the separator in the second direction can also be less than or equal to the size of the negative electrode film layer in the second direction.

[0285] Optionally, the difference between the size of the separator in the second direction and the size of the negative electrode film layer in the second direction is 6 mm to 10 mm, such as 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range composed of any two of the above values.

[0286] As Figure 18 shown, taking the first direction parallel to the length direction Z, the second direction parallel to the width direction Y, the first electrode plate 11 as the positive electrode plate, and the second electrode plate 12 as the negative electrode plate as an example for illustration,

[0287] The size of the positive electrode film layer of the first electrode plate 11 in the length direction Z is the length of the positive electrode film layer of the first electrode plate 11, the size of the negative electrode film layer of the second electrode plate 12 in the length direction Z is the length of the negative electrode film layer of the second electrode plate 12, and the size of the separator 13 in the length direction Z is the length of the separator 13.

[0288] The difference between the length of the negative electrode film layer of the second electrode plate 12 and the length of the positive electrode film layer of the first electrode plate 11 is OH 11 , Figure 18 as shown in 11 , on both sides of the negative electrode film layer in the length direction Z, it exceeds the positive electrode film layer, and each side exceeds OH

[0289] / 2. Of course, the negative electrode film layer can also exceed the positive electrode film layer on one side in the length direction Z. 21 , Figure 18As shown, both sides of the separator 13 in the length direction Z extend beyond the negative electrode film layer, and each side extends beyond OH 21 / 2. Of course, the separator 13 may extend beyond the negative electrode film layer on one side in the length direction Z.

[0290] The size of the positive electrode film layer of the first electrode tab 11 in the width direction Y is the width of the positive electrode film layer of the first electrode tab 11, the size of the negative electrode film layer of the second electrode tab 12 in the width direction Y is the width of the negative electrode film layer of the second electrode tab 12, and the size of the separator 13 in the width direction Y is the width of the separator 13.

[0291] The difference between the width of the negative electrode film layer of the second electrode tab 12 and the width of the positive electrode film layer of the first electrode tab 11 is OH 12 , Figure 8 As shown, both sides of the negative electrode film layer in the width direction Y extend beyond the positive electrode film layer, and each side extends beyond OH 12 / 2. Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side in the width direction Y.

[0292] The difference between the width of the separator 13 and the width of the negative electrode film layer of the second electrode tab 12 is OH 22 , Figure 18 As shown, both sides of the separator 13 in the width direction Y extend beyond the negative electrode film layer, and each side extends beyond OH 22 / 2. Of course, the separator 13 may extend beyond the negative electrode film layer on one side in the width direction Y.

[0293] In some embodiments, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm[[ID=�3]] 3 , 2.80 g / cm 3 or a range composed of any two of the above values.

[0294] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle performance. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell can improve its fast charging ability and cycle performance at high energy density.

[0295] In some embodiments, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm², 200 mg / 1540.25 mm², 250 mg / 1540.25 mm², 300 mg / 1540.25 mm², 350 mg / 1540.25 mm², 370 mg / 1540.25 mm² or a range composed of any two of the above values. Optionally, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 .

[0296] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet will not be too large, slowing down the risk of exacerbating side reactions due to heat accumulation, which is beneficial to improving the fast charging ability and cycle performance of the battery cell at high energy density.

[0297] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, disassembling the positive electrode sheet of the battery cell in the 100% state of charge (SOC) and measuring the compaction density of the positive electrode film layer. For example, taking a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, one side of the positive electrode film layer can be wiped off first), punching it into small round pieces with an area of S1, weighing it, recording it as M1, and measuring its thickness H1. Then wipe off the positive electrode film layer of the above weighed positive electrode sheet, weigh the weight of the positive current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0298] In some embodiments, the charging specific capacity of the positive electrode active material is from 150 mAh / g to 170 mAh / g. Exemplarily, the charging specific capacity of the positive electrode active material is 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range composed of any two of the above values.

[0299] When the charging specific capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0300] In the embodiments of the present application, the specific capacity of the positive electrode active material has the meaning well known in the art and can be detected by the testing method of the specific capacity of the negative electrode active material.

[0301] In some embodiments, the positive electrode active material includes lithium-containing phosphate. The lithium-containing phosphate can have an olivine structure, which is stable in structure during charge and discharge, and can improve the cycle life of the battery cell.

[0302] Optionally, the positive electrode active material may further include lithium-containing transition metal oxide. Examples of the lithium-containing transition metal oxide may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0303] The lithium-containing phosphate with an olivine structure can be an unmodified lithium-containing phosphate or a material obtained by coating modification thereof. For example, a carbon-containing material is provided on the surface of the lithium-containing phosphate, and the carbon-containing material can be used as a coating layer to coat on the surface of the lithium-containing phosphate, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, being beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery cell, and reducing the heat generation of the battery cell.

[0304] In some embodiments, the lithium-containing phosphate includes a general formula of Li x1 A y1 Me a M b P 1-c X c Y zA compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of Cl, C, and N, and Y includes one or more of O and F. The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0305] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur. The molar content of Li in the battery cell is different when the battery cell is discharged to different states. In the listing of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the listing of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0306] In the embodiments of the present application, the content of elements in the cathode active material has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the cathode electrode sheet, it is cleaned with dimethyl carbonate (DMC) and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the cathode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0307] In some embodiments, the lithium-containing phosphate is granular, and the volume-average particle size Dv50 of the lithium-containing phosphate is from 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or a range composed of any two of the above values.

[0308] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium intercalation / deintercalation path of lithium ions in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the lithium-containing phosphate stable.

[0309] In some embodiments, the positive electrode film layer further includes a positive electrode additive, and the positive electrode additive includes one or more of a lithium-containing ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as a lithium supplement agent, which can supplement lithium ions to the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and improve the energy density of the battery cell.

[0310] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode additive is from 0.1% to 5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above. When using a positive electrode additive within the mass range, it can supplement lithium ions to the positive electrode film layer and make up for the irreversible loss of lithium ions in the system, and the mass content of the positive electrode additive is not too high, so that the discharge specific capacity of the positive electrode is still relatively high, and the energy density is basically not reduced.

[0311] In some embodiments, the volume-average particle size Dv50 of the positive electrode additive is greater than the volume-average particle size Dv50 of the lithium-containing phosphate. The combination of particles of different sizes is beneficial to uniform dispersion and improves the uniformity of the distribution of the lithium supplement agent.

[0312] In some embodiments, the volume-average particle size Dv50 of the positive electrode additive is from 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range composed of any two of the above.

[0313] In the embodiments of the present application, the volume average particle size Dv50 of the particles has the meaning well-known in the art. The volume average particle diameter Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution, and can be detected by using the equipment and methods well-known in the art. After fully discharging a fresh battery cell to a 0% state of charge (SOC), the positive electrode plate is disassembled, the positive electrode current collector part is removed, and the positive electrode film layer is retained. The positive electrode film layer is immersed in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, and the positive electrode active material or lithium supplement agent is retained as a sample. After drying the sample, according to the test standard GB / T 19077-2016, the volume average particle diameter Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer.

[0314] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0315] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0316] In some embodiments, the positive electrode current collector part may be made of a metal foil or a composite current collector part. As an example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector part may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0317] In some embodiments, the thickness of the positive current collector portion is from 10 μm to 16 μm, such as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or a range composed of any two of the above values.

[0318] In some embodiments, the positive electrode tab further includes a positive electrode tab connected to the positive current collector portion. The thickness of the positive electrode tab is from 10 μm to 16 μm, such as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or a range composed of any two of the above values. When the thickness of the positive electrode tab is within the above range, it is beneficial to improve the overcurrent capacity and the fast charging capacity of the battery cell.

[0319] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive current collector portion and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0320] The positive electrode tab does not exclude other additional functional layers other than the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiment of the present application further includes a positive electrode conductive layer sandwiched between the positive current collector portion and the positive electrode film layer and disposed on the surface of the positive current collector portion. In some other embodiments, the positive electrode tab of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0321] [Electrolyte]

[0322] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting the active ions between the positive electrode tab and the negative electrode tab. The electrolyte includes an organic solvent and an electrolyte salt.

[0323] In some embodiments, the conductivity of the electrolyte at room temperature is from 10.5 mS / cm to 13.5 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm or a range composed of any two of the above values.

[0324] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0325] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using the equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0326] In some embodiments, the viscosity of the electrolyte at room temperature is from 1.5 mPa·s to 5.5 mPa·s. Exemplarily, the viscosity of the electrolyte is 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s or the range composed of any two of the above values.

[0327] When the viscosity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0328] In the embodiments of the present application, the viscosity of the electrolyte has the meaning well-known in the art, and it can be detected by using the equipment and methods well-known in the art. For example, it can be detected according to GB / T10247-2008.

[0329] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 1.05 g / mL to 1.35 g / mL. Exemplarily, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL or the range composed of any two of the above values.

[0330] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0331] In the embodiments of the present application, the density of the electrolyte has the meaning well-known in the art, and it can be detected by using the equipment and methods well-known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0332] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0333] Optionally, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35% or a range composed of any two of the above values. Optionally, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 8% to 20%.

[0334] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte is small, which can improve the conductivity of the electrolyte, reduce the internal resistance of the battery cell, and is beneficial to the rapid migration of lithium ions; and the electrolyte is compatible with the silicon-containing negative electrode, which can effectively reduce the gas generation amount of the battery cell, reduce the influence on the negative electrode side interface film, and improve the rapid charging ability and cycle performance of the battery cell.

[0335] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I,

[0336] Formula I,

[0337] In Formula I,

[0338] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0339] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0340] The above chain carboxylic acid ester solvent has a relatively high conductivity, which is beneficial to improving the rapid charging ability of the battery cell.

[0341] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0342] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0343] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0344] Exemplarily, the chain carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0345]

[0346] In some embodiments, the organic solvent includes a carbonate solvent.

[0347] The use of carbonate solvents and chain carboxylic ester solvents in combination improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions and improves the rapid charging ability of the battery cell.

[0348] Optionally, the mass content of the carbonate solvent in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvent is 65%, 70%, 75% or a range composed of any two of the above values.

[0349] When the mass contents of the carbonate solvent and the chain carboxylic ester solvent meet the above conditions, the stability of the electrolyte can be improved, its gas generation amount can be reduced, and the cycle performance can be improved.

[0350] Exemplarily, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0351] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0352] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF. The side reaction between hydrofluoric acid and the negative electrode, especially the silicon-containing negative electrode, may lead to an increase in gas generation during high-temperature storage. The compound use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, reduce the gas generation amount during high-temperature storage, and can improve the cycle performance of the battery cell. Moreover, the transference number of lithium ions increases, the lithium ion conduction ability increases, and the rapid charging ability of the battery cell can be improved.

[0353] Exemplarily, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide, and may be lithium bis(fluorosulfonyl)imide.

[0354] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is greater than 0 and less than or equal to 18%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or a range composed of any two of the above values. Optionally, the mass content of the lithium salt is 4% to 16%.

[0355] Exemplarily, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and may be 4% to 16%.

[0356] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.2 to 1.5, such as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or the range composed of any two of the above values. Optionally, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.4 to 0.8.

[0357] When the ratio of the mass content of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide satisfies the above range, on the one hand, the content of hydrofluoric acid can be reduced, the side reaction at the negative electrode interface can be slowed down, and the gas generation amount during high-temperature storage can be reduced; on the other hand, the content of the organic component of the interface film formed at the negative electrode interface is appropriate, which can also reduce the gas generation amount during high-temperature storage and improve the cycling performance.

[0358] In some embodiments, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. The above additives can improve the performance of the interface film on the negative electrode side, the formed interface film has higher stability, and the impedance of the interface film is relatively low, which is beneficial to improving the fast charging performance of the battery cell and improving the cycling performance.

[0359] In some embodiments, the mass content of the additives in the electrolyte is 0.5% to 10%. Exemplarily, the mass content of the additives in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. Optionally, the mass content of the additives in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0360] The additives with the above mass content can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycling performance.

[0361] In some embodiments, the carbonate additives include one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additives include fluoroethylene carbonate and vinylene carbonate.

[0362] Fluoroethylene carbonate can form an interface film rich in lithium fluoride (LiF) on the surface of the negative electrode, which can relieve the volume expansion of silicon, improve the life of the silicon-containing system, and reduce the gas generation amount at high temperature.

[0363] When fluoroethylene carbonate and vinylene carbonate are used in combination, the compactness of the interface film on the surface of the negative electrode is better, which can more effectively protect the silicon-containing negative electrode, reduce the degree of side reaction at the negative electrode interface, and reduce the gas generation amount at high temperature.

[0364] Exemplarily, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butylene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate.

[0365] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0366] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have meanings well known in the art, and can be detected by equipment and methods well known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography analysis methods. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be reverse disassembled, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography analysis methods.

[0367] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well known in the art, and can be detected by equipment and methods well known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0368] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified, and chain carboxylic ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0369] Carbonate additives (such as fluorinated cyclic carbonates and vinylene carbonate) are used as additives to the electrolyte, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0370] Separator

[0371] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode plate and the negative electrode plate.

[0372] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0373] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0374] In some embodiments, the volumetric energy density of the battery cell is from 350 Wh / L to 430 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 350 Wh / L, 370 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L or a range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0375] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.8 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration,

[0376] Place the battery cell at 25 °C, charge it at a constant current of 0.05 C to 3.8 V, discharge it at a constant current of 0.33 C to 2.0 V, and record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and excluding the insulating film outside the outer shell), calculate the volume V0 of the single battery cell, unit: L, and the volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0377] Embodiment

[0378] The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are all commercially available.

[0379] Example 1

[0380] 1. Preparation of the positive electrode sheet

[0381] The positive electrode plate includes a positive current collector part and positive electrode film layers disposed on both sides of the positive current collector part. The positive current collector part is an aluminum foil.

[0382] The positive electrode film layer includes lithium-containing phosphate lithium iron phosphate, positive electrode additive lithium ferrite, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black with a mass ratio of 95:1.85:2:1.15. The positive electrode film layer is a film layer formed by uniformly coating a positive electrode slurry (solvent is N-methylpyrrolidone NMP) on both sides of the positive current collector part and then drying and cold pressing.

[0383] The volume average particle size Dv50 of the lithium-containing phosphate is 1.5 μm. The charging gram capacity of the positive electrode active material is 161 mAh / g. The volume average particle size Dv50 of the positive electrode additive is 9.5 μm.

[0384] The single-sided coating weight of the positive electrode film layer is 284 mg / 1540.25 mm 2 . The length of the positive electrode film layer is 592 mm.

[0385] 2. Preparation of the negative electrode plate

[0386] The negative electrode plate includes a negative current collector part and negative electrode film layers disposed on both sides of the negative current collector part. The negative current collector part is a copper foil.

[0387] The negative electrode film layer is a film layer formed by uniformly coating a negative electrode slurry (solvent is deionized water) on the surface of the negative current collector part and then drying and cold pressing.

[0388] The single-sided coating weight of the negative electrode film layer is 135 mg / 1540.25 mm 2 .

[0389] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative current collector part, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0390] The first negative electrode film layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.3:0.5:2.5:0.7. The negative electrode active material of the first negative electrode film layer includes artificial graphite and silicon carbide;

[0391] The second negative electrode film layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickening agent sodium carboxymethyl cellulose with a mass ratio of 97.8:0.7:0.8:0.7. The negative electrode active material of the second negative electrode film layer includes artificial graphite and silicon carbide, and the average particle size of the artificial graphite is 10 μm;

[0392] In the cross-section along the thickness direction of the negative electrode film layer, the average particle size of the artificial graphite in the first negative electrode film layer is 13 μm; the average particle size of the artificial graphite in the second negative electrode film layer is 10 μm. During the preparation of the negative electrode film layer, the film layer with the desired average particle size can be obtained by adjusting the volume average particle size of the artificial graphite multiple times.

[0393] The ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 1; the conductive agents of the first negative electrode film layer and the second negative electrode film layer both include conductive carbon and carbon nanotubes, and the mass ratio of conductive carbon to carbon nanotubes in the first negative electrode film layer and the second negative electrode film layer is both 5:1.

[0394] The mass content of silicon element in the negative electrode film layer is 3.0%. The charging specific capacity of the negative electrode active material is 420 mAh / g.

[0395] 3. Separator

[0396] The separator includes a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0397] 4. Preparation of electrolyte

[0398] The electrolyte includes an organic solvent, a lithium salt, and an additive. The components of the organic solvent are mixed, and the lithium salt and the additive are added to prepare the electrolyte.

[0399] The organic solvent includes 15% chain carboxylic ester solvent (ethyl acetate) and 68.5% carbonate solvent (ethylene carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0400] Based on the mass of the electrolyte, the mass content of the additive is 2.5% of vinylene carbonate VC.

[0401] The lithium salt includes 10% lithium hexafluorophosphate LiPF6 and 4% lithium bis(fluorosulfonyl)imide.

[0402] 5. Preparation of battery cell

[0403] The above-mentioned positive electrode plate, separator, and negative electrode plate are stacked in sequence, and the separator is placed between the positive electrode plate and the negative electrode plate to play a separation role, obtaining a stacked electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After processes such as vacuum packaging, standing, formation, and shaping, a battery cell is obtained. The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.62 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.30 g / cm 3 .

[0404] Comparative Example 1-1 and Comparative Example 1-2

[0405] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the single-sided coating weights of the positive electrode film layer and the negative electrode film layer were adjusted.

[0406] Examples 2-1 to 2-4

[0407] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the single-sided coating weights of the positive electrode film layer and the negative electrode film layer were adjusted.

[0408] Examples 2-5 and 2-6

[0409] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the compaction densities of the positive electrode film layer and the negative electrode film layer were adjusted.

[0410] Performance test

[0411] 1. DC resistance DCR test of battery single cells

[0412] The method in GB / T 31467 "Performance Test Specification for High-power Lithium-ion Power Batteries for HEV" can be referred to.

[0413] For example, at 25 °C, the battery single cell was charged to 3.65 V at a constant current of 0.33 C, left standing for 1 min, then charged to 3.65 V at a constant current of 0.1 C, left standing for 30 min, discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A0 at this time was recorded, with the unit of Ah. Then it was charged at a constant current of 0.33 C for 0.5A0 Ah to adjust the SOC to 50%.

[0414] After the battery single cell was placed at 25 °C for 2 h, it was discharged at a current of 4C for 10 s, and ∆U was recorded 放电 、∆I 放电 , and the discharge DCR data of the battery single cell, R 放电 =∆U 放电 / ∆I 放电 ,

[0415] where ∆U 放电 represents the voltage change within 10 s at the start of discharge, and ∆I 放电 represents the current value within 10 s at the start of discharge.

[0416] 2. High-temperature cycle performance test of battery single cells

[0417] In an environment of 60 ± 5 °C, the battery single cell was charged at a constant current of 1C to 3.65 V, then charged at a constant voltage to the cut-off current of 0.05C, and then discharged at a constant current of 1C to 2.0 V. This was one charge-discharge cycle.

[0418] The discharge capacity of this battery cell is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycling process for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery cell = Cn / C1 × 100%. Record the number of cycles at which the cycle capacity retention rate reaches 80%. For accuracy, take the average of five replicate samples as the test result.

[0419] 3. Room temperature cycle performance test of battery cells

[0420] At 25±5℃, charge the battery cells with Stercharge constant current:

[0421] Charge from 0% SOC to 20% SOC at 0.33C constant current;

[0422] Charge from 20% SOC to 25% SOC at 8C constant current;

[0423] Charge from 25% SOC to 30% SOC at 8C constant current;

[0424] Charge from 30% SOC to 35% SOC at 7.5C constant current;

[0425] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0426] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0427] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0428] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0429] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0430] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0431] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0432] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0433] Charge from 75% SOC to 80% SOC at 3.57C constant current;

[0434] Charge from 80% SOC to 85% SOC at 2C constant current;

[0435] Charge from 90% SOC to 95% SOC at 1C constant current;

[0436] Charge from 95% SOC to 98% SOC at a constant current of 0.5C;

[0437] Charge from 98% SOC to 100% SOC at a constant current of 0.25C.

[0438] Charge at a constant current of 0.1C until the charge cut-off voltage;

[0439] Then discharge at a constant current of 1C until the discharge cut-off voltage. This is one charge-discharge cycle.

[0440] The discharge capacity of this time is recorded as the discharge capacity C1 of the first cycle of the battery cell. Repeat this cycle step for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of the battery cell = Cn / C1×100%. Record the number of cycles when the cycle capacity retention rate is 80%. For accuracy, take the average value of 5 parallel samples as the test result.

[0441] 4. Fast charge time test for the battery cell from 20% to 80% SOC

[0442] Under the environment of 25±5℃, charge the battery cell at a constant current of Stercharge:

[0443] Charge from 0% SOC to 20% SOC at a constant current of 0.33C;

[0444] Charge from 20% SOC to 25% SOC at a constant current of 8C;

[0445] Charge from 25% SOC to 30% SOC at a constant current of 8C;

[0446] Charge from 30% SOC to 35% SOC at a constant current of 7.5C;

[0447] Charge from 35% SOC to 40% SOC at a constant current of 6.87C;

[0448] Charge from 40% SOC to 45% SOC at a constant current of 6.38C;

[0449] Charge from 45% SOC to 50% SOC at a constant current of 5.95C;

[0450] Charge from 50% SOC to 55% SOC at a constant current of 5.53C;

[0451] Charge from 55% SOC to 60% SOC at a constant current of 5.14C;

[0452] Charge from 60% SOC to 65% SOC at a constant current of 4.76C;

[0453] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0454] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0455] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0456] The test results are shown in Table 1.

[0457] Table 1

[0458]

[0459] The coating weight of the positive and negative electrode film layers of Comparative Example 1-1 is relatively small, and the volume energy density of the battery cell is low; the coating weight of the positive and negative electrode film layers of Comparative Example 1-2 is relatively high. Although the volume energy density of the battery cell is high, the migration resistance of lithium ions in the positive and negative electrode film layers is large, which is not conducive to the rapid charging of the battery cell under high energy density; and the side reactions on the negative electrode side are aggravated, and the cycle is deteriorated, especially the cycle under fast charging is deteriorated.

[0460] As the single-sided coating weight of the positive electrode film layer increases, the energy density of the battery cell increases, but the DCR of the battery cell also increases, which is not conducive to fast charging of the battery cell.

[0461] The single-sided coating weight of the positive electrode film layer in Examples 2-1 to 2-4 of the present application is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 The single-sided coating weight of the negative electrode film is 70mg / 1540.25mm 2 Up to 175mg / 1540.25mm 2 ; This makes the energy density of the battery cell relatively high, and the migration resistance of lithium ions will not be too large, which can effectively improve the cycle performance under fast charging conditions and high-temperature cycle performance.

[0462] Furthermore, the charging time of the battery cells of the embodiments from 20% SOC to 80% SOC is relatively short, for example, 7 minutes for embodiment 1 and 14 minutes for embodiments 2-4. The charging time is relatively short, and a fast charging effect can be achieved.

[0463] By setting the compaction density of the positive and negative electrode film layers within an appropriate range, Examples 2-5 and 2-6 can effectively improve the volume energy density of the battery cell, and can effectively improve the cycle performance of the battery cell under high energy density and fast charging, and are conducive to improving the cycle performance under fast charging conditions.

[0464] Comparative Example 2-1

[0465] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the negative electrode film layer does not contain silicon element, and the single-sided coating weight of the negative electrode film layer was adjusted.

[0466] Comparative Example 2-2

[0467] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of silicon element was adjusted.

[0468] Examples 3-1 to 3-3

[0469] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of silicon element was adjusted.

[0470] Example 3-4

[0471] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the mass content of silicon element and the single-sided coating weight of the negative electrode film layer were adjusted.

[0472] Example 4

[0473] The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the material of the silicon-based material was adjusted.

[0474] The test results are shown in Table 2.

[0475] Table 2

[0476]

[0477] In Comparative Example 2-1, no silicon-based material was added. At a relatively high energy density, the coating weight of the negative electrode film layer was relatively high, and the migration resistance of the active ions on the negative electrode side was relatively large, which was not conducive to fast charging.

[0478] In Comparative Example 2-2, the addition amount of the silicon-based material was relatively high, resulting in relatively serious side reactions on the negative electrode side, increased gas production, especially increased gas production at high temperatures, deteriorating the cycle.

[0479] In Examples 3-1 to 3-4 of the present application, by controlling the mass content of silicon element, the mass content of silicon element was within an appropriate range and the coating weight was appropriate, which could effectively improve the cycle performance and fast charging performance of the battery monomer at a high energy density.

[0480] For example, in Example 3-4, when the mass content of silicon element was 10%, combined with the single-sided coating weight of the negative electrode film layer being 80 mg / 1540.25 mm 2, so that the volumetric energy density of the battery cell will not be too low, and since the coating thickness of the negative electrode film layer is relatively thin, the lithium ion migration path is short, which is beneficial to improving the fast charging ability of the battery cell; moreover, since the overall coating amount of the negative electrode film layer is low, the total amount of negative electrode active material participating in side reactions can be reduced, improving the cycle performance.

[0481] As the mass content of silicon element increases, the charging specific capacity of the negative electrode active material increases. For example, in Example 3-3, the charging specific capacity of the negative electrode active material can reach 534 mAh / g.

[0482] This application is applicable to silicon-based materials of different materials. For example, silicon-carbon materials and silicon-oxygen materials can effectively improve the cycle performance of the battery cell and are beneficial to improving the fast charging performance of the battery cell; compared with the silicon-oxygen material in Example 4, the volume expansion of the silicon-carbon material during charge and discharge is relatively small, and the cycle performance is relatively excellent.

[0483] Examples 5-1 to 5-2

[0484] A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the average particle size of the carbon-based material in the negative electrode film layer was adjusted.

[0485] Examples 6-1 and 6-2

[0486] A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the composition and mass content of the negative electrode conductive agent in the negative electrode film layer were adjusted.

[0487] The test results are shown in Table 3.

[0488] Table 3

[0489]

[0490] A part of the first negative electrode film layer is the first region, and a part of the second negative electrode film layer is the second region. On the cross-section along the thickness direction of the negative electrode film layer, the average particle size of the carbon-based material is observed, and the average particle sizes of the first region and the second region are respectively recorded and statistically analyzed.

[0491] The negative electrode film layer can be coated in a single layer or a double layer. By differentially setting the average particle sizes of the carbon-based materials in the first region and the second region in Examples 5-1 and 5-2, the porosity of the negative electrode film layer can be effectively regulated, the fast charging ability of the battery cell at high energy density can be improved, the risk of lithium plating can be reduced, and the cycle life can be extended.

[0492] In Example 6-1 and Example 6-2, by regulating the mass content of the negative electrode conductive agent in the negative electrode film layer, as the mass content of the negative electrode conductive agent increases, the conductivity of the negative electrode plate increases, which can reduce the DCR of the battery cell and effectively improve the fast charging ability of the battery cell at high energy density. However, if the mass content of the negative electrode conductive agent is too high, the proportion of the negative electrode active material will decrease, which is not conducive to the improvement of the energy density.

[0493] Comparative Example 3-1 and Comparative Example 3-2

[0494] The battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted.

[0495] Example 7-1 and Example 7-2

[0496] The battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted.

[0497] The test results are shown in Table 4.

[0498] Table 4

[0499]

[0500] In Table 4,

[0501] In Comparative Example 3-1, the mass content of the chain carboxylic ester solvent is relatively small, resulting in a lower conductivity of the electrolyte, a higher DCR of the battery cell, and relatively large lithium ion transmission resistance, which is not conducive to fast charging;

[0502] In Comparative Example 3-2, the mass content of the chain carboxylic ester solvent is relatively high, and the conductivity of the electrolyte is high, which is beneficial to reducing the DCR of the battery cell; however, the side reaction between the above solvent and the negative electrode active material is relatively serious, the gas generation is intensified, especially the gas generation at high temperature is intensified, deteriorating the cycle.

[0503] While the mass content of the chain carboxylic ester solvent in the examples of the present application is within an appropriate range, it can effectively improve the conductivity of the electrolyte, improve the lithium ion transmission ability, and improve the fast charging performance of the battery cell; moreover, the electrolyte components are relatively stable, which can improve the cycle performance; it should be noted that the change of the electrolyte components has a relatively small impact on the energy density, and the energy density is not reflected in the table.

[0504] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as limiting the embodiments of the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principle, and scope of the embodiments of the present application.

Claims

1. A battery cell, characterized in that, Comprising: Positive electrode tab, comprising a positive current collector portion and a positive electrode film layer disposed on at least one side of the positive current collector portion, the positive electrode film layer comprising a lithium-containing phosphate, and the single-sided coating weight of the positive electrode film layer being 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; The negative electrode plate includes a negative current collector portion and a negative electrode film layer provided on at least one side of the negative current collector portion. The negative electrode film layer includes a carbon-based material and a silicon-based material. The mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.3% to 10%. The single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; and An electrolyte solution comprising a chain carboxylic ester solvent, wherein the mass content of the chain carboxylic ester solvent in the electrolyte solution is 5% to 35%.

2. The battery cell according to claim 1, wherein The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 ; and / or The single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 to 142 mg / 1540.25 mm 2 .

3. The battery cell according to claim 1, characterized in that, When the battery cell is in a 100% state of charge, the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; and / or When the battery cell is in a 100% state of charge, the tap density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 .

4. The battery cell according to any one of claims 1 to 3, characterized in that, The positive electrode film layer comprises a positive electrode active material, and the charging gram capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g; and / or The negative electrode film layer comprises a negative electrode active material, and the charging gram capacity of the negative electrode active material is 350 mAh / g to 540 mAh / g.

5. The battery cell according to claim 1, characterized in that, The mass content of silicon element of the silicon-based material in the negative electrode film layer is 3% to 6%.

6. The battery cell according to claim 1, characterized in that, The silicon-based material comprises one or more of silicon carbide and silicon oxide.

7. The battery cell according to claim 1, characterized in that, The negative electrode film layer comprises: A first region disposed on the surface of the negative electrode current collector, and the thickness of the first region is 1 / 3 of the thickness of the negative electrode film layer; and A second region connected to a side of the first region facing away from the negative electrode current collector, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode film layer. Wherein, The average particle size of the carbon-based material in the first region is greater than or equal to the average particle size of the carbon-based material in the second region.

8. The battery cell according to claim 7, wherein The average particle size of the carbon-based material in the first region is 10 μm to 20 μm; and / or The average particle size of the carbon-based material in the second region is 5 μm to 12 μm.

9. The battery cell according to claim 7, wherein, The carbon-based material in the first region comprises at least one of artificial graphite and natural graphite, and the carbon-based material in the second region comprises artificial graphite.

10. The battery cell according to claim 7, wherein, At least one of the first region and the second region comprises a silicon-based material.

11. The battery cell according to claim 1, characterized in that, The negative electrode film layer comprises: A first negative electrode film layer disposed on the surface of the negative electrode current collector; and A second negative electrode film layer connected to a side of the first negative electrode film layer facing away from the negative electrode current collector.

12. The battery cell according to claim 1, characterized in that, The negative electrode film layer comprises a negative electrode conductive agent, and the negative electrode conductive agent comprises one or more of conductive carbon and carbon nanotubes.

13. The battery cell according to claim 12, wherein, The mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%; and / or The mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%.

14. The battery cell according to claim 1, wherein The conductivity of the electrolyte solution at room temperature is 10.5 mS / cm to 13.5 mS / cm; and / or The viscosity of the electrolyte solution at room temperature is 1.5 mPa·s to 5.5 mPa·s; and / or The density of the electrolyte solution at room temperature is 1.05 g / mL to 1.35 g / mL.

15. The battery cell according to claim 1, characterized in that, The mass content of the chain carboxylic ester solvent in the electrolyte solution is 8% to 20%.

16. The battery cell according to claim 1, wherein, The chain carboxylic ester solvent comprises a compound represented by Formula I. Formula I, In Formula I, R1 comprises a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group. R2 comprises a C1-C5 alkyl group or a C1-C5 haloalkyl group.

17. The battery cell according to claim 16, wherein, The chain carboxylic ester solvent comprises one or more of the compounds represented by Formula I-1 to Formula I-8. 。 18. The battery cell according to claim 1, characterized in that, The electrolyte solution comprises a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte solution is 65% to 75%.

19. The battery cell according to claim 18, wherein The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

20. The battery cell according to claim 1, wherein The lithium-containing phosphate includes lithium iron phosphate.

21. The battery cell according to claim 1, characterized in that, The size of the positive electrode film layer in the direction of its own length is 265 mm to 655 mm.

22. A battery device, characterized in that, It includes a battery cell as described in any one of claims 1 to 21.

23. An electrical device, characterized in that, It includes a battery device as described in claim 22.

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