Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises a positive pole piece, a negative pole piece and an electrolyte, the positive pole piece comprises a positive pole current collecting part and a positive pole film layer located on at least one side of the positive pole current collecting part, the positive pole film layer comprises lithium-containing phosphate, and the single-side coating weight of the positive pole film layer is 150 mg / 1540.25 mm < 2 > to 370 mg / 1540.25 mm < 2 >; the negative pole piece comprises a negative pole current collecting part and a negative pole film layer located on at least one side of the negative pole current collecting part, the negative pole film layer comprises a carbon-based material and a silicon-based material, the mass content of a silicon element in the silicon-based material is 0.3%-10%, and the single-side coating weight of the negative pole film layer is 70 mg / 1540.25 mm < 2 >-175 mg / 1540.25 mm < 2 >; the electrolyte comprises a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent is 5%-35%. According to the invention, the fast charging capability and the cycle performance of the battery monomer can be improved.

Description

[0001] This application claims the priority of the 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 thus widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric 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] Thus, the negative electrode sheet of the embodiment of the present application includes a silicon-based material, and 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-shaped 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 amount at high temperature while improving the lithium ion migration rate, thereby comprehensively improving the rapid charging performance and cycling 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 amount per unit area of the positive electrode sheet is not too large, which is conducive to reducing the polarization phenomenon under high-rate charging, and can take into account improving the energy density and rapid 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 conducive to reducing the polarization phenomenon under high-rate charging and is conducive to improving the rapid 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 rapid 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 rapid 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 from 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 from 3% to 6%. When the mass content of the silicon element is within the above range, it can improve the capacity of the negative electrode active material, which is beneficial to increasing 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 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 from 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 from 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 improving 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 increasing 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, it can improve the conductivity of the negative electrode film layer and improve the fast charging ability.

[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, it can improve the conductivity of the negative electrode film layer and improve the fast charging ability.

[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, it can improve the fast charging ability and cycle performance of the battery cell.

[0028] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1including a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 including a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0029] The above-mentioned chain carboxylic ester solvents have a relatively high conductivity, which is beneficial to improving the fast charging ability of battery cells.

[0030] In some embodiments, the chain carboxylic ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8,

[0031] In some embodiments, the organic solvent includes carbonate solvents, and the mass content of the carbonate solvents in the electrolyte is 65% to 75%.

[0032] When the mass contents of the carbonate solvents and the chain carboxylic ester solvents meet the above conditions, the stability of the electrolyte can be improved and its gas generation amount at high temperature can be reduced.

[0033] In some embodiments, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0034] 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 battery cells.

[0035] 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 battery cells.

[0036] In a second aspect, embodiments of the present application also propose a battery device, including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0037] In a third aspect, embodiments of the present application also propose an electrical device, and the electrical device includes the battery device according to any one of the embodiments in the second or third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1It is a schematic structural diagram of an electrical device provided by some embodiments of the present application; Figure 2 It is a schematic structural diagram of a battery pack provided by some embodiments of the present application; Figure 3 It is a schematic structural diagram of a battery module provided by some embodiments of the present application; Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application; Figure 5 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application; Figure 6 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some embodiments of the present application; Figure 7 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 8 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 9 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 10 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 11 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 12 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application; Figure 13 It is a schematic structural diagram of a second electrode tab of a battery cell provided by some embodiments of the present application; Figure 14 It is a schematic structural diagram of a second electrode tab of a battery cell provided by some other embodiments of the present application; Figure 15 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application; Figure 16 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application; Figure 17 It is a schematic structural diagram of a negative electrode tab of a battery cell provided by some embodiments of the present application; Figure 18 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application.

[0040] The drawings are not necessarily drawn to actual scale.

[0041] The description of the reference numerals is as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing part; 5b, second housing part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, first pole piece; 111, first pole tab; 1111, first end; 112, first coating part; 12, second pole piece; 121, second pole tab; 1211, second end; 122, second coating part; 13, separator; 14, negative electrode pole piece; 141, negative electrode film layer; 142, negative electrode current collector part; 1411, first negative electrode film layer; 1412, second negative electrode film layer; 141a, first region; 141b, second region; 141c, third region; 20, outer shell assembly; 21, housing; 22, end cap; 31, first electrode terminal; 32, second electrode terminal. Detailed implementation manners

[0042] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the 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.

[0043] The "range" disclosed in this 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 boundaries of a particular range. The ranges defined in this way can include or exclude 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 understood to be anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all anticipated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this 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" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating 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.

[0044] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0045] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0046] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, 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.

[0047] The "multiple" mentioned in this application refers to two or more (including two).

[0048] In the embodiments of this application, the battery cell can be a secondary battery, and a secondary battery refers to a battery cell that can be activated by charging after discharging so as to be used continuously.

[0049] The battery cell can be a lithium-ion battery, a sodium lithium-ion battery, etc., and the embodiments of this application do not limit this.

[0050] 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 lead to the decomposition of the electrolyte at high temperatures, resulting in an increase in the gas generation 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.

[0051] In view of the above problems, the embodiments of the present application synergistically regulate the positive electrode sheet, the negative electrode sheet, and the electrolyte to improve the fast charging performance and the cycle performance of the battery cell. 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. 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 positive electrode film layer with an appropriate coating weight can improve the rapid migration of active ions in the positive electrode sheet, thereby enhancing the migration rate of active ions in the positive and negative electrode film layers. Further, with an appropriate content of chain carboxylic ester solvents, it can improve the migration rate of lithium ions in the electrolyte, thereby enhancing the liquid-phase transport rate of lithium ions, and thus improving the fast charging ability of the battery cell. However, silicon-based materials containing silicon are more likely to undergo side reactions with the electrolyte, resulting in an increase in gas generation, especially an increase in gas generation at high temperatures. The mass content of the chain carboxylic ester solvent in the embodiments of the present application is less than or equal to 35%, which can, on the basis of the rapid migration of active ions such as lithium ions, alleviate the side reaction between the silicon-based material and the electrolyte, reduce the gas generation amount, 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.

[0052] The battery cell of the present application is applicable to various battery devices and electrical devices that use battery cells.

[0053] Exemplarily, the electrical device can 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. Or, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0054] Figure 1 It 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, or a plug-in hybrid electric vehicle, etc. 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 used.

[0055] The interior of the electrical device 1 is provided with a battery device, which can be arranged at the bottom, head or 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 serve as the operating power source of the electrical device 1 and also 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

[0056] 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 startup, navigation and driving of the electrical device 1.

[0057] 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 hybrid connection through a busbar component.

[0058] In some embodiments, the battery cell assembly (Battery Cell Assembly) is generally formed by arranging a plurality of battery cells.

[0059] As an example, the battery cell assembly can 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.

[0060] As shown in Figure 2 In some embodiments, the battery device can 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.

[0061] As an example, the battery cell assembly can also be accommodated in the box body 5 by directly fixing a plurality of battery cells to the box body 5.

[0062] As an example, the box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a and the second box body part 5b are buckled so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body part 5a can be a top cover or a bottom plate.

[0063] As an example, the box body 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 box body 5 to accommodate the battery cell assembly.

[0064] In some embodiments, the box body 5 can be part of the chassis structure of a vehicle. For example, part of the box body 5 can form at least part of the floor of the vehicle, or part of the box body 5 can form at least part of the cross beams and longitudinal beams of the vehicle.

[0065] As an example, the battery cell assembly can be a battery module 6, and the battery cell assembly can be accommodated in the box body 5 by fixing the battery module 6 in the box body 5.

[0066] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0067] In some embodiments, during the charging process of the battery device or any battery cell 7 that makes up the battery device from 20% state of charge (SOC) to 80% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25 °C.

[0068] Exemplarily, the charging steps of the battery device or any battery cell 7 that makes up the battery device from 20% SOC to 80% SOC can be carried out in the following manner: Charge at a constant current of 8.00C from 20% SOC to 25% SOC; Charge at a constant current of 8.00C from 25% SOC to 30% SOC; Charge at a constant current of 7.50C from 30% SOC to 35% SOC; Charge at a constant current of 6.87C from 35% SOC to 40% SOC; Charge at a constant current of 6.38C from 40% SOC to 45% SOC; Charge at a constant current of 5.95C from 45% SOC to 50% SOC; Charge at a constant current of 5.53C from 50% SOC to 55% SOC; Charge at a constant current of 5.14C from 55% SOC to 60% SOC; Charge at a constant current of 4.76C from 60% SOC to 65% SOC; Charge at a constant current of 4.36C from 65% SOC to 70% SOC; Charge at a constant current of 3.94C from 70% SOC to 75% SOC; Charge at a constant current of 3.57C from 75% SOC to 80% SOC.

[0069] In some embodiments, the charging time of the battery device or any battery cell 7 that makes up 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 a range composed of any two of the above values.

[0070] As Figure 4 and Figure 5 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20.

[0071] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0072] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0073] 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.

[0074] The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite housing), or an aluminum plastic film, etc. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly 10, and a sealed bag is further included between the housing and the electrode assembly 10. The sealed bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating part or an aluminum plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0075] 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 special limitation in this application.

[0076] In some embodiments, the outer shell includes an end cap 22 and a housing 21. The housing 21 is provided with an opening, and the end cap 22 covers the opening. The housing 21 can be provided with one or more openings. One or more end caps 22 can also be provided.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] As an example, both the first electrode tab 11 and the second electrode tab 12 are folded to form a plurality of folded segments arranged in a stacked manner.

[0084] As an example, a plurality of separators 13 can be provided and are respectively arranged between any adjacent first electrode tab 11 or second electrode tab 12.

[0085] As an example, the separator 13 can be continuously provided and is arranged between any adjacent first electrode tab 11 or second electrode tab 12 by folding or winding.

[0086] In some embodiments, each electrode tab is provided with a tab, and the tab can conduct the current out of the electrode assembly 10. The tab includes a positive tab and a negative tab.

[0087] In some embodiments, both the first electrode tab 11 and the second electrode tab 12 include a coated portion and a tab portion. The coated portion is coated with an active material layer, and the tab portion is disposed on at least one side of the coated 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.

[0088] 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.

[0089] 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 coated portion along the first direction is the length of the coated portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0090] 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 coated portion along the first direction is the width of the coated portion. In this case, the second direction is parallel to the length of the battery cell 7.

[0091] To illustrate the present application more clearly, the tab portion of the first electrode tab 11 is defined as the first tab 111, and the coated portion of the first electrode tab 11 is defined as the first coated portion 112. The tab portion of the second electrode tab 12 is defined as the second tab 121, and the coated portion of the second electrode tab 12 is defined as the second coated portion 122. The electrode terminal that is electrically connected and has the same electrical property as the first tab 111 is the first electrode terminal 31 described above, and the electrode terminal that is electrically connected and has the same electrical property as the second tab 121 is the second electrode terminal 32 described above.

[0092] The polarities of the first electrode tab 11 and the second electrode tab 12 are opposite. When the first electrode tab 11 is a positive electrode tab, the second electrode tab 12 is a negative electrode tab, the first coated portion 112 is a positive electrode coated portion, the first tab 111 is a positive tab, the first electrode terminal 31 is a positive terminal, the second coated portion 122 is a negative electrode coated portion, the second tab 121 is a negative tab, and the second electrode terminal 32 is a negative terminal.

[0093] Or when the first electrode tab 11 is a negative electrode tab, the second electrode tab 12 is a positive electrode tab, the first coated portion 112 is a negative electrode coated portion, the first tab 111 is a negative tab, the first electrode terminal 31 is a negative terminal, the second coated portion 122 is a positive electrode coated portion, the second tab 121 is a positive tab, and the second electrode terminal 32 is a positive terminal.

[0094] The coating part includes a current collector part and a film layer disposed on the current collector part and containing an active material. For example, the positive electrode coating part includes a positive electrode current collector part and a positive electrode film layer disposed on the positive electrode current collector part and containing a positive electrode active material. Another example is that the negative electrode coating part includes a negative electrode current collector part and a negative electrode film layer disposed on the negative electrode current collector part and containing a negative electrode active material.

[0095] As Figures 6 to 8 shown, in some embodiments, in the first electrode tab 11, the tab part is disposed on at least one side of the coating part along the first direction, and the first electrode tab 11 satisfies: n×W1 / W2 is 0.2 to 1.0; n represents the number of all tab parts on the same side of the coating part; W1 represents the average dimension of the tab part along the second direction; W2 represents the dimension of the coating part along the second direction, and the second direction, the first direction, and the thickness direction X are perpendicular to each other in pairs.

[0096] 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.

[0097] When n×W1 / W2 satisfies the above range, the current-carrying area of the tab part is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0098] W1 represents the average dimension of the first tab 111 along the second direction.

[0099] When the first tab 111 has a special-shaped structure, for example, along the first direction, the dimension of the first tab 111 along the second direction gradually increases. In this case, the dimensions of multiple parts of the first tab 111 along the second direction can be measured, and thus the average dimension of the first tab 111 along the second direction can be calculated. Of course, the dimensions of each part of the first tab 111 along the second direction can be the same value. In this case, this value can be used as the average dimension of the first tab 111.

[0100] The first tab 111 can be one or more. For example, n is 1 to 4. When there are multiple first tabs 111, after measuring the average dimensions of each first tab 111 respectively, the average dimension of the first tab 111 can be calculated by adding up the average dimensions and dividing by the number of the first tabs 111.

[0101] The first tab 111 is connected to the first coating portion 112. The first 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 tab 111 itself is relatively large, the contact surface between the first tab 111 and the first coating portion 112 is relatively large, the current-carrying capacity of the first tab 111 is strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0102] Optionally, the current collector portion of the first tab 111 and the first coating portion 112 is an integral structure, so that the internal resistance of the first electrode sheet 11 is low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0103] In some embodiments, the first electrode sheet 11 includes at least one first tab 111, for example, including 1 to 4 first tabs 111. Optionally, the first electrode sheet 11 includes at least two first tabs 111, and optionally four first tabs 111.

[0104] In some embodiments, one or more first tabs 111 are disposed on at least one side of the coating portion along the width direction Y.

[0105] As Figures 6 to 8 shown, for example, one or more first tabs 111 are disposed on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all the first tabs 111 are disposed on the same side of the first coating portion 112 along the width direction Y. This kind of setting 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, W1 represents the dimension of a single first 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 7 In, n is 4, and the dimensions of each first tab 111 are the same. W1 can represent the dimension of a single first tab 111. Of course, the dimensions of each first tab 111 can also be slightly different. Figure 8 In, n is 1, and n×W1 / W2 is 1.

[0106] As Figure 9 shown, for example, when the first electrode sheet 11 includes a plurality of first tabs 111, the plurality of first tabs 111 are disposed on both sides of the first coating portion 112 along the width direction Y.

[0107] Optionally, when multiple first tabs 111 are disposed on at least one side of the first coating portion 112 in the width direction Y, there are at least two first tabs 111 on the same side of the first coating portion 112 in the width direction Y, such as two, three, four, five, six, etc.; four are optional. This setting is conducive to the uniform distribution of electrons in the first electrode sheet 11 and is conducive to improving the fast charging performance.

[0108] Optionally, the distance between two adjacent first tabs 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 In [the figure], Z1 represents the distance between two adjacent first tabs 111 in the length direction Z.

[0109] When the distance between two adjacent first tabs 111 in the length direction Z satisfies the above range, it is conducive to the uniform distribution of current in the current collecting portion and is conducive to improving the fast charging performance.

[0110] In some other embodiments, the first electrode sheet 11 includes one or more first tabs 111; the one or more first tabs 111 are disposed on at least one side of the first coating portion 112 in the length direction Z.

[0111] As Figure 10 shown, for example, one or more first tabs 111 are disposed 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 tabs 111 are disposed on the same side of the first coating portion 112 in the length direction Z.

[0112] As Figure 11 and Figure 12 shown, for example, when the first electrode sheet 11 includes multiple first tabs 111, the multiple first tabs 111 are respectively disposed on both sides of the first coating portion 112 in the length direction Z.

[0113] Optionally, the multiple first tabs 111 are respectively disposed on both sides of the first coating portion 112 in the length direction Z. This setting can shorten the transmission path of electrons in the first electrode sheet 11 and is conducive to improving the fast charging performance. For example, two first tabs 111 are located on one side of the first coating portion 112 in the length direction Z, and the other two first tabs 111 are located on the other side of the first coating portion 112 in the length direction Z.

[0114] Optionally, when multiple 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, etc. This setting is beneficial to the uniform distribution of electrons in the first pole piece 11 and is beneficial to improving the fast charging performance.

[0115] 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.

[0116] As Figure 13 shown, in some embodiments, in the second pole piece 12, the tab ear portion is disposed on at least one side of the coating portion along the first direction, and the second pole piece 12 satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all tab ear portions on the same side of the coating portion; W3 represents the average size of the tab ear portion along the second direction; W4 represents the size of the coating portion along the second direction.

[0117] 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.

[0118] 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.

[0119] 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 there are multiple second tab ears 121, the average size can be calculated by measuring the sizes of each second tab ear 121 with a micrometer.

[0120] The second tab ear 121 is connected to the second coating portion 122. The second tab ear 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 ear 121 itself is relatively large, the contact surface between the second tab ear 121 and the second coating portion 122 is relatively large, the current-carrying capacity of the second tab ear 121 is strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0121] Optionally, the current collector 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, which can further improve the fast charging performance and cycling performance of the battery cell 7.

[0122] 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.

[0123] In some embodiments, one or more second tabs 121 are disposed on at least one side of the coating portion in the width direction Y. For example, one or more second tabs 121 are disposed on one side of the second coating portion 122 in 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 in 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 in the width direction Y.

[0124] Optionally, one or more second tabs 121 are respectively disposed on one side of the second coating portion 122 in the width direction Y. This kind of arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0125] Optionally, when a plurality of second tabs 121 are disposed on at least one side of the coating portion in the width direction Y, there are at least two second tabs 121 on the same side of the second coating portion 122 in the width direction Y, such as two, three, four, five, six, etc.; optionally four. This kind of arrangement is beneficial to the uniform distribution of electrons in the second electrode sheet 12 and is beneficial to improving the fast charging performance.

[0126] Optionally, the distance between two adjacent second tabs 121 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.

[0127] As Figure 14 shown, in some other embodiments, the second electrode sheet 12 includes one or more second tabs 121; one or more second tabs 121 are disposed on at least one side of the second coating portion 122 in the length direction Z. For example, one or more second tabs 121 are disposed on one side of the second coating portion 122 in the length direction Z. 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 in the length direction Z. Or for example, when the second electrode sheet 12 includes a plurality of second tabs 121, the plurality of second tabs 121 are respectively disposed on both sides of the second coating portion 122 in the length direction Z.

[0128] Optionally, a plurality of second tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z. This arrangement can shorten the transmission path of electrons in the second electrode sheet 12, which is beneficial to improving the fast charging performance.

[0129] Optionally, when a plurality of second tabs 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 tabs 121 on the same side of the second coating portion 122 along the length direction Z, such as two, three, four, five, six, etc. This arrangement is beneficial to the uniform distribution of electrons in the second electrode sheet 12 and is beneficial to improving the fast charging performance.

[0130] Optionally, the distance between two adjacent second tabs 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.

[0131] As Figure 15 shown, in some embodiments, the terminal assembly can be disposed on the housing 21, or the terminal assembly is disposed on the end cap 22.

[0132] 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 111, and the second electrode terminal 32 is connected to the second tab 121.

[0133] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 can 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.

[0134] On the same end cap 22, the first electrode terminal 31 and the second electrode terminal 32 can be disposed simultaneously. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are disposed at intervals on this end cap 22. Another example is that there are two end caps 22, and the two end caps 22 are disposed opposite to each other, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on each end cap 22.

[0135] The first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on different end caps 22. For example, there are two end caps 22, and the two end caps 22 are disposed opposite to each other. The first electrode terminal 31 is disposed on one of the end caps 22, and the second electrode terminal 32 is disposed on the other end cap 22.

[0136] 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.

[0137] In some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0138] As Figure 15 shown, for example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0139] As Figure 16 shown, and for another example, a plurality of first electrode terminals 31 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.

[0140] Exemplarily, 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. Or, exemplarily, there are four first electrode terminals 31, two of the first electrode terminals 31 are disposed on one side of the electrode assembly 10, and the other two first electrode terminals 31 are disposed on one side of the electrode assembly 10.

[0141] 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 may 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.

[0142] In the above embodiments, the first adapter 51 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.

[0143] 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. And for another example, a plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0144] In some embodiments, the second electrode terminal 32 is at least one, and may be selected as at least two, such as two, three, or four, etc.

[0145] 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.

[0146] As Figure 16As shown, for example, at least two second electrode terminals 32 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0147] 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 arranged on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is arranged 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 arranged on one side of the electrode assembly 10, and the other first electrode terminal 31 is arranged on the other side of the electrode assembly 10.

[0148] For another example, all the second electrode terminals 32 are arranged 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 arranged on both sides of the electrode assembly 10 along the length direction Z, and there will be no mutual interference when they are respectively electrically connected to the pole ear parts.

[0149] Exemplarily, there is one first electrode terminal 31 and one second electrode terminal 32. The first electrode terminal 31 is arranged on one side of the electrode assembly 10 along the length direction Z, and the second electrode terminal 32 is arranged 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 arranged in a staggered manner along the width direction Y. Of course, the first electrode terminal 31 and the second electrode terminal 32 can also be arranged 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 arranged on both sides of the electrode assembly 10.

[0150] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32. The two first electrode terminals 31 are arranged on one side of the electrode assembly 10 along the length direction Z, and the two second electrode terminals 32 are arranged on the other side of the electrode assembly 10 along the length direction Z.

[0151] In the embodiment of the present application, the second pole ear 121 and the second electrode terminal 32 can be directly connected or indirectly connected; when the second pole ear 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter, and the second adapter is located between the second electrode terminal 32 and the second pole ear 121 and connects the second electrode terminal 32 and the second pole ear 121.

[0152] 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, the connection between the second tab 121 and the second electrode terminal 32 is more facilitated by the second adapter.

[0153] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0154] 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.

[0155] 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 portion and a positive electrode film layer disposed on at least one side of the positive current collector portion. The positive electrode film layer includes a positive electrode active material. 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 portion and a negative electrode film layer disposed on at least one side of the negative current collector portion. The negative electrode film layer includes a negative electrode active material. 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%. 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. The organic solvent includes a chain carboxylic ester solvent. The mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 35%.

[0156] The negative electrode plate 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%. The coating weight of the negative electrode film layer is greater than or equal to 80 mg / 1540.25 mm 2 and 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; During the charging process of the battery cell 7, active ions such as lithium ions migrate from the positive electrode plate to the negative electrode plate 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, and 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 battery cell 7; 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 chain carboxylic ester solvents 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 carboxylic ester solvents, the interfacial reaction between the silicon-based material and the electrolyte intensifies and the gas generation increases. Therefore, 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 chain carboxylic ester solvents in the electrolyte is less than or equal to 35%, which can alleviate the interfacial side reaction between the negative active material and the electrolyte, reduce the gas generation amount, and improve the cycle performance of battery cell 7; The positive electrode plate of the present application further includes lithium-containing phosphate, and the negative electrode plate further includes a carbon-based material, and the cycle stability is relatively excellent, which can further improve the cycle performance of battery cell 7; Therefore, the embodiments of the present application can improve the fast charging performance and cycle performance of battery cell 7 at high energy density, and are conducive to improving the cycle performance of battery cell 7 under fast charging conditions.

[0157] Negative electrode plate The negative electrode plate 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 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.

[0158] The charging upper limit voltage and the discharge cut-off voltage of the battery cell vary according to the different positive active materials. For example, when the phosphate material includes lithium iron phosphate, the charging upper limit voltage can be 3.65 V and the discharge cut-off voltage can be 2.0 V, or the charging upper limit voltage can be 3.8 V and the discharge cut-off voltage can be 2.0 V; Another example is that when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3 V and the discharge cut-off voltage can be 2.0 V. Next, taking the charging upper limit voltage of 3.8 V and the discharge cut-off voltage of 2.0 V 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% state of charge SOC of the battery cell are defined as follows, The battery cell is charged at a constant current charging rate of 0.05C to the charging upper limit voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged at a constant current discharge rate of 0.05C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0159] In some embodiments, when the battery cell is in the 100% state of charge (SOC), the compaction density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 . Exemplarily, when the battery cell is in the 100% state of charge, the compaction density of the negative electrode film layer 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.

[0160] 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 material in the negative electrode film layer is 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 negative electrode film layer to a reasonable range, the battery cell can improve its fast charging ability and cycle performance at high energy density.

[0161] 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 .

[0162] 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.

[0163] 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 plate is disassembled from the battery cell in the 100% state of charge (SOC), and the compaction density of the negative electrode film layer is measured. For example, take the single-sided coated negative electrode plate (if it is a double-sided coated plate, one side of the negative electrode film layer 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 plate, weigh the weight of the negative electrode current collector, 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 plate - the weight M0 of the negative electrode current collector) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode plate - the thickness H0 of the negative electrode current collector, 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.

[0164] In some embodiments, the charging specific capacity of the negative electrode active material is 350 mAh / g to 540 mAh / g. Exemplarily, the charging 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.

[0165] 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.

[0166] In the embodiments of the present application, the specific capacity per gram 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 first Coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted to test the charging specific capacity per gram of the negative active material at a rate of 0.1C in a half-button cell. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-button cell is assembled. Under the condition of 23°C ± 2°C, the half-button cell is placed on a battery tester or other test equipment with equivalent performance, and the charging and discharging capacity is obtained through charging and discharging 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 charging specific capacity parameter.

[0167] In some embodiments, the negative 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 (where 0 < x ≤ 2). For example, the silicon-carbon composite can be silicon carbide.

[0168] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 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 the 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 3% to 6%.

[0169] When the mass content of silicon element is within the above range, the capacity of the negative active material can be improved, which is beneficial to increasing 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 negative SEI film and improving the cycle performance of the battery cell at high energy density.

[0170] In some embodiments, the negative active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the cycle performance of the battery cell.

[0171] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0172] In some embodiments, in addition to the above-mentioned carbon-based material and optionally silicon-based material, the negative 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.

[0173] The qualitative and quantitative properties of each substance or element in this application can be detected by appropriate 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 certain 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.

[0174] For example, the present application may combine JIS / K0131-1996 X-ray diffraction analysis method general rules to perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0175] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flaky structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0176] like Figure 17 As shown, the negative electrode film layer 141 of the negative electrode plate 14 in the embodiment of the present application includes at least one film layer, which may be a single film layer or at least two film layers. Optionally, the negative electrode film layer 141 includes at least two film layers.

[0177] In the case where the negative electrode film layer 141 is 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.

[0178] When the negative electrode film layer 141 has at least two layers, the negative electrode active material in the negative electrode film layer 141 includes carbon-based materials and optional silicon-based materials. The negative electrode film layer 141 may include two layers, three layers, four layers, or even more layers.

[0179] 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, 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 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 is regular or irregular, optionally irregular; or there is no obvious interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0180] The negative electrode film layer 141 includes at least two film layers, and the layered 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 improve the fast charging performance of the battery cell.

[0181] 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.

[0182] Optionally, the first negative electrode film layer 1411 further includes a silicon-based material.

[0183] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0184] 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 improve 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 cycling performance under high energy density; and because each layer includes a silicon-based material, the coating thickness is relatively thin, which is beneficial to shortening the lithium ion transmission path and improving the fast charging performance under high energy density.

[0185] 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 relieve 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 under high energy density.

[0186] 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 transmission ability of lithium ions, enhance the kinetic performance of the battery cell, and improve the cycling performance under high energy density.

[0187] When the negative electrode film layer 141 adopts at least two film layers, along 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 place, and 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.

[0188] 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 141.

[0189] The cross-sectional morphologies of the first region 141a and the second region 141b can be the same or similar, and of course, they can also be different. The cross-sectional morphologies of the first region 141a and the third region 141c can be the same or similar, and of course, they can also be different. The cross-sectional morphologies of the second region 141b and the third region 141c can be the same or similar, and of course, they can also be different.

[0190] There may be an obvious layer interface between the first region 141a, the second region 141b, and the third region 141c, or there may be no obvious layer interface. 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 can be a part of the first negative electrode film layer 1411, or the third region 141c can be a part of the second negative electrode film layer 1412, or the third region 141c can be a part of the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0191] Optionally, the average particle size of the carbon-based material in the first region 141a can 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 can be greater than the average particle size of the carbon-based material in the second region 141b, which is beneficial to the rapid migration of lithium ions from the second region 141b to the first region 141a and improves the rapid charging ability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a can be less than the average particle size of the carbon-based material in the second region 141b.

[0192] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 can 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 can be greater than the average particle size of the carbon-based material in the second negative electrode film layer 1412.

[0193] There are differences in the particle sizes of 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 fast charging, the overpotential of the second negative electrode film layer 1412 is usually relatively 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 also improve the problem of lithium deposition on the surface of the negative electrode sheet 14 and improve the cycle performance under high energy density.

[0194] 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.

[0195] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material in 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.

[0196] 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 in 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 under high energy density.

[0197] Optionally, the average particle size of the carbon-based material in the second negative electrode film layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material in 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 other hand, the cooperation of the negative electrode active material in the second negative electrode film layer 1412 with the negative electrode active material in the first negative electrode film layer 1411 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 under high energy density.

[0198] Exemplarily, the carbon-based material of the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region 141b includes artificial graphite. For example, the negative electrode active material of the first region 141a includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material of the second region 141b includes a silicon-based material and artificial graphite.

[0199] 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.

[0200] In the embodiments of the present application, the average particle size of the carbon-based materials 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, cross-section polishing is performed by using an argon ion beam, a cross-section is photographed by using a scanning electron microscope SEM to obtain an SEM cross-sectional view, the particle sizes of the carbon-based materials in the SEM cross-section are counted, and the average particle size of the carbon-based materials is calculated according to the counted quantity. In the case where the proportion of the carbon-based materials in the negative electrode film layer is relatively high, the average particle size of the negative electrode active materials can be roughly evaluated by using the average particle size of the carbon-based materials.

[0201] 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%.

[0202] The negative electrode conductive agent can make up for the disadvantage of the 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 improving the fast charging ability of the battery cell at a high energy density.

[0203] 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 a high energy density can be improved.

[0204] Optionally, the mass content of 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 a range composed of any two of the above values. Optionally, the mass content of carbon nanotubes in the negative electrode film layer is 0.1% to 0.5%. When the mass content of carbon nanotubes is within the above mass content, the rapid charging ability of the battery cell at high energy density can be improved.

[0205] 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%.

[0206] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., for example, 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%.

[0207] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. 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 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).

[0208] In some embodiments, the thickness of the negative electrode current collector is 4μm to 8.5μm, such as 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm or a range composed of any two of the above values.

[0209] In some embodiments, the negative electrode plate further includes a negative electrode tab connected to the negative electrode current collector. The thickness of the negative electrode tab is 4μm to 8.5μm, such as 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm 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 the rapid charging ability of the battery cell.

[0210] The negative electrode film layer is usually formed by coating a negative electrode paste on a negative electrode current collector part and then drying and cold pressing. The negative electrode paste 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 can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0211] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiment of the present application further includes a negative electrode conductive layer disposed on the surface of the negative electrode current collector part and sandwiched between the negative electrode current collector part and the negative electrode film layer. In other embodiments, the negative electrode plate of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0212] Positive electrode plate The positive electrode plate includes a positive electrode current collector part and a positive electrode film layer disposed on at least one side of the positive electrode current collector part and including a positive electrode active material. For example, the positive electrode current collector part has two opposite surfaces in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector part.

[0213] In the case where 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.

[0214] 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.

[0215] 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.

[0216] For example, the size 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 size of the positive electrode film layer in the length direction of the positive electrode plate to the size 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 in the positive electrode film layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the size of the positive electrode film layer should not be too long. When the size of the positive electrode film layer is within the above range, the electron transport path will not be too long, and the internal resistance is relatively small, which is beneficial to improving the fast charging ability of the battery cell at high energy density.

[0217] Optionally, the size of the positive electrode film layer in the length direction of the positive electrode plate 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 plate to the size of the positive electrode film layer in the width direction of the positive electrode plate is 4 to 8.

[0218] For example, the size of the positive electrode film layer in the length direction of the positive electrode plate 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 plate to the size of the positive electrode film layer in the width direction of the positive electrode plate is 2 to 12.5.

[0219] 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, so that the lithium ions released from the positive electrode film layer can basically be embedded in the negative electrode film layer, reducing the risk of lithium precipitation on the negative electrode side and improving the use reliability 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.

[0220] 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 composed of any two of the above values.

[0221] 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, so that the lithium ions released from the positive electrode film layer can basically be embedded in the negative electrode film layer, reducing the risk of lithium precipitation 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.

[0222] 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 a range composed of any two of the above values.

[0223] 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.

[0224] 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 tab and the negative electrode tab, 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.

[0225] 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.

[0226] 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 tab and the negative electrode tab, 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.

[0227] 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.

[0228] As Figure 18 shown, taking the first direction being parallel to the length direction Z, the second direction being parallel to the width direction Y, the first electrode tab 11 being the positive electrode tab, and the second electrode tab 12 being the negative electrode tab as an example for illustration. The dimension of the positive electrode film layer of the first electrode tab 11 along the length direction Z is the length of the positive electrode film layer of the first electrode tab 11, the dimension of the negative electrode film layer of the second electrode tab 12 along the length direction Z is the length of the negative electrode film layer of the second electrode tab 12, and the dimension of the separator 13 along the length direction Z is the length of the separator 13.

[0229] The difference between the length of the negative electrode film layer of the second electrode tab 12 and the length of the positive electrode film layer of the first electrode tab 11 is OH 11 , Figure 18 As shown in, both sides of the negative electrode film layer along the length direction Z exceed the positive electrode film layer, and each side exceeds OH 11 / 2. Of course, the negative electrode film layer may also exceed the positive electrode film layer on one side along the length direction Z.

[0230] The difference between the length of the separator 13 and the length of the negative electrode film layer of the second electrode tab 12 is OH 21 , Figure 18 As shown in, both sides of the separator 13 along the length direction Z exceed the negative electrode film layer, and each side exceeds OH 21 / 2. Of course, the separator 13 may exceed the negative electrode film layer on one side along the length direction Z.

[0231] The dimension of the positive electrode film layer of the first electrode tab 11 along the width direction Y is the width of the positive electrode film layer of the first electrode tab 11, the dimension of the negative electrode film layer of the second electrode tab 12 along the width direction Y is the width of the negative electrode film layer of the second electrode tab 12, and the dimension of the separator 13 along the width direction Y is the width of the separator 13.

[0232] 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 in, both sides of the negative electrode film layer along the width direction Y exceed the positive electrode film layer, and each side exceeds OH 12 / 2. Of course, the negative electrode film layer may also exceed the positive electrode film layer on one side along the width direction Y.

[0233] 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 in, both sides of the separator 13 along the width direction Y exceed the negative electrode film layer, and each side exceeds OH 22 / 2. Of course, the separator 13 may exceed the negative electrode film layer on one side along the width direction Y.

[0234] In some embodiments, when the battery cell is in the 100% state of charge SOC, the compaction density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3Exemplarily, 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 3 、2.80 g / cm 3 or a range composed of any two of the above values.

[0235] When the tap 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 material of the positive electrode film layer is 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 tap 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.

[0236] 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 .

[0237] 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, reducing the risk of accelerated 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.

[0238] In the embodiments of the present application, the tap 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 from the battery cell in the 100% state of charge (SOC) and measuring the tap 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, the positive electrode film layer on one side 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-mentioned weighed positive electrode sheet, weigh the weight of the positive electrode 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 electrode 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 electrode current collector, and the tap 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.

[0239] In some embodiments, the charging specific capacity of the positive electrode active material is 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 the range composed of any two of the above values.

[0240] 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.

[0241] 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 the testing method for the specific capacity of the negative electrode active material can be used for detection.

[0242] 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.

[0243] Optionally, the positive electrode active material can further include lithium-containing transition metal oxides. Examples of the lithium-containing transition metal oxides can 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.

[0244] 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 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.

[0245] In some embodiments, the lithium-containing phosphate includes a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1 ≤ 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.

[0246] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO 4 , LiMnPO 4 , LiNiPO 4 , and LiCoPO 4 . During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li in the battery cell is different when the battery cell is discharged to different states. Regarding the listing of the cathode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , etc., 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, regarding the listing of the cathode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , etc., the molar content of oxygen O is only the theoretical state value, and 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.

[0247] In the embodiments of the present application, the content of elements in the positive electrode 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 positive electrode plate, it is cleaned with dimethyl carbonate (DMC) and dried, then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode 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.

[0248] In some embodiments, the lithium-containing phosphate is granular, and the volume average particle size Dv50 of the lithium-containing phosphate is 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.

[0249] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium deintercalation / insertion 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, so that the performance of the lithium-containing phosphate is stable.

[0250] In some embodiments, the positive electrode film layer further includes a positive electrode additive, and the positive electrode additive includes one or more of lithium-containing ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate and lithium ferrate. The above materials can be used as lithium supplement agents, which can supplement lithium ions for 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.

[0251] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode additive is 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 for 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.

[0252] 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.

[0253] In some embodiments, the volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or the range composed of any two of the above.

[0254] 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 size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution, and can be detected by the equipment and methods well-known in the art. After fully discharging the fresh battery monomer to 0% state of charge (SOC), disassemble the positive electrode plate, remove the positive electrode current collector part and retain the positive electrode film layer. Immerse the positive electrode film layer in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, and retain the positive electrode active material or lithium supplement agent as a sample. After drying the sample, according to the test standard GB / T 19077-2016, test the volume average particle size Dv50 of the particles by a Mastersizer 2000E laser particle size analyzer.

[0255] 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%.

[0256] 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%.

[0257] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils may be used. The composite current collector 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).

[0258] In some embodiments, the thickness of the positive current collector is 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.

[0259] In some embodiments, the positive electrode tab further includes a positive electrode ear connected to the positive current collector. The thickness of the positive electrode ear is 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 ear is within the above range, it is beneficial to improve the overcurrent capacity and the fast charging capacity of the battery cell.

[0260] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive current collector 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 may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0261] 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 present application further includes a positive electrode conductive layer sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector. In some other embodiments, the positive electrode tab of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0262] [Electrolyte] During the charge and discharge process of the battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The electrolyte includes an organic solvent and an electrolyte salt.

[0263] 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 the range composed of any two of the above values.

[0264] 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.

[0265] 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.

[0266] 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.

[0267] 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.

[0268] In the embodiments of the present application, the viscosity of the electrolyte 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, it can be detected according to GB / T10247-2008.

[0269] 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.

[0270] 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.

[0271] In the embodiments of the present application, the density of the electrolyte 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, the test can be carried out with reference to GB / T 2013-2010.

[0272] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0273] Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylic ester solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35% or the range composed of any two of the above values. Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is 8% to 20%.

[0274] When the mass content of the chain carboxylic 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 interface film on the negative electrode side, and improve the fast charging ability and cycle performance of the battery cell.

[0275] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0276] The conductivity of the above chain carboxylic ester solvent is relatively high, which is beneficial to improving the fast charging ability of the battery cell.

[0277] Optionally, R 1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0278] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2It includes C1 to C2 alkyl or C1 to C2 haloalkyl.

[0279] In each of the above embodiments, the haloalkyl includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl, and iodoalkyl. Optionally, the haloalkyl includes fluoroalkyl.

[0280] Exemplarily, the chain carboxylic acid ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8.

[0281] In some embodiments, the organic solvent includes carbonate solvents.

[0282] When the carbonate solvents and the chain carboxylic acid ester solvents are used in combination, the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions and improves the rapid charging ability of the battery monomer.

[0283] Optionally, the mass content of the carbonate solvents in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvents is 65%, 70%, 75% or the range composed of any two of the above values.

[0284] When the mass contents of the carbonate solvents and the chain carboxylic acid ester solvents meet the above conditions, the stability of the electrolyte can be improved, the gas generation amount thereof can be reduced, and the cycle performance can be improved.

[0285] Exemplarily, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0286] In some embodiments, the electrolyte salt includes lithium salts, and the lithium salts include one or more of lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salts include lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0287] 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 cause an increase in gas generation during high-temperature storage. When lithium hexafluorophosphate and lithium fluorosulfonylimide are used in combination, the content of hydrofluoric acid can be reduced, the side reaction at the negative electrode interface can be slowed down, the gas generation amount during high-temperature storage can be reduced, and the cycle performance of the battery monomer can be improved. Moreover, the transference number of lithium ions increases, the lithium ion conduction ability increases, and the rapid charging ability of the battery monomer can be improved.

[0288] Exemplarily, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide, and may be lithium bis(fluorosulfonyl)imide.

[0289] 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%.

[0290] 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 can be optionally 4% to 16%.

[0291] 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 a 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.

[0292] When the ratio of the mass content of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide satisfies the above range, on the one hand, it can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, and reduce the gas generation amount during high-temperature storage; 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 cycle performance.

[0293] 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 interface film performance 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 cycle performance.

[0294] 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 a 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%.

[0295] The additives with the above mass content can effectively improve the interface film performance 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 cycle performance.

[0296] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive comprises fluoroethylene carbonate and vinylene carbonate.

[0297] Fluoroethylene carbonate can form an interfacial film rich in lithium fluoride (LiF) on the surface of the negative electrode, which can alleviate the volume expansion of silicon, improve the lifespan of the silicon-containing system, and reduce the gas generation at high temperatures. When fluoroethylene carbonate and vinylene carbonate are used in combination, the interfacial film on the surface of the negative electrode has better compactness, can more effectively protect the silicon-containing negative electrode, reduce the degree of side reactions at the negative electrode interface, and reduce the gas generation at high temperatures.

[0298] Exemplarily, the sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate.

[0299] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0300] 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 method. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a discharged battery (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography analysis method.

[0301] 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.

[0302] 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. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0303] Taking carbonate additives (such as fluorinated cyclic carbonates, vinylene carbonate) as additives to the electrolyte, and calculating the mass content of each component based on the mass of the electrolyte being 100%.

[0304] Separator In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0305] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any publicly known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0306] As an example, the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane 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 membrane.

[0307] 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.

[0308] 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 equipment and methods well-known in the art. For example, taking the upper charging limit voltage of the battery as 3.8 V and the discharge cut-off voltage of the battery as 2.0 V as an example for illustration, The battery cell is placed at 25 °C and charged at a constant current of 0.05 C to 3.8 V, and discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A0 at this time is recorded, unit: Ah. The length, width, and height of the battery cell are measured using a caliper (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), and the volume V0 of the single battery cell is calculated, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0309] Embodiment 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.

[0310] Example 1 1. Preparation of the positive electrode sheet The positive electrode sheet includes a positive current collector and positive electrode layers provided on both sides of the positive current collector. The positive current collector is aluminum foil.

[0311] The positive electrode 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 layer is a film layer formed by uniformly coating the positive electrode slurry (solvent: N-methylpyrrolidone NMP) on both sides of the positive current collector and then drying and cold pressing.

[0312] The volume average particle size Dv50 of the lithium-containing phosphate is 1.5 μm. The charging specific 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.

[0313] The single-sided coating weight of the positive electrode layer is 284 mg / 1540.25 mm 2 . The length of the positive electrode layer is 592 mm.

[0314] 2. Preparation of the negative electrode sheet The negative electrode sheet includes a negative current collector and negative electrode layers provided on both sides of the negative current collector. The negative current collector is copper foil.

[0315] The negative electrode layer is a film layer formed by uniformly coating the negative electrode slurry (solvent: deionized water) on the surface of the negative current collector and then drying and cold pressing.

[0316] The single-sided coating weight of the negative electrode layer is 135 mg / 1540.25 mm 2 .

[0317] The negative electrode layer includes a first negative electrode layer and a second negative electrode layer. The first negative electrode layer is located on the surface of the negative current collector, and the second negative electrode layer is located on the surface of the first negative electrode layer.

[0318] The first negative electrode film layer comprises 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 comprises artificial graphite and silicon carbide; The second negative electrode film layer comprises 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 comprises artificial graphite and silicon carbide, and the average particle size of the artificial graphite is 10 μm; 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 measured to be 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 required average particle size can be obtained by adjusting the volume average particle size of the artificial graphite multiple times.

[0319] 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 comprise 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 5:1.

[0320] 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.

[0321] 3. Separator The separator comprises a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0322] 4. Preparation of electrolyte The electrolyte comprises 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.

[0323] The organic solvent comprises 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.

[0324] Based on the mass of the electrolyte, the mass content of the additive is 2.5% vinylene carbonate VC.

[0325] The lithium salt comprises 10% lithium hexafluorophosphate LiPF 6 and 4% lithium bis(fluorosulfonyl)imide.

[0326] 5. Preparation of battery cell Stack the above positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an insulating role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging case, inject electrolyte after drying, and go through processes such as vacuum packaging, standing, forming, and shaping to obtain a battery cell. 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 .

[0327] Comparative Examples 1-1 and 1-2 Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the positive electrode film layer and the negative electrode film layer is adjusted.

[0328] Examples 2-1 to 2-4 Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the positive electrode film layer and the negative electrode film layer is adjusted.

[0329] Examples 2-5 and 2-6 Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the compaction density of the positive electrode film layer and the negative electrode film layer is adjusted.

[0330] Performance test 1. DC Resistance DCR Test of Battery Cell The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0331] For example, at 25 °C, charge the battery cell at a constant current of 0.33 C to 3.65 V, let it stand for 1 min, then charge it at a constant current of 0.1 C to 3.65 V, let it stand for 30 min, discharge it at a constant current of 0.33 C to 2.0 V, and record the discharge capacity A at this time 0 , with the unit Ah, and then charge it at a constant current of 0.33 C for 0.5 A 0 Ah, and adjust the SOC to 50%.

[0332] After leaving the battery cell at 25 °C for 2 h, discharge it at a current of 4 C for 10 s, and record ∆U 放电 , ∆I 放电 , and calculate the discharge DCR data of the battery cell through the following formula, R 放电 = ∆U 放电 / ∆I 放电 , where, ∆U 放电Indicates the voltage change within 10 s after the start of discharge, ∆I 放电 Indicates the current value within 10 s after the start of discharge.

[0333] 2. High-temperature cycle performance test of battery cells Under the environment of 60±5°C, charge the battery cell at a constant current of 1C to 3.65V, then charge it at a constant voltage until the cut-off current of 0.05C, and then discharge it at a constant current of 1C to 2.0V. This is one charge-discharge cycle.

[0334] The discharge capacity of this time is recorded as the discharge capacity C1 of the first cycle of the lithium-ion 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 this 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.

[0335] 3. Normal-temperature cycle performance test of battery cells Under the environment of 25±5°C, charge the battery cell with Stercharge constant current: Charge from 0% SOC to 20% SOC at a constant current of 0.33C; Charge from 20% SOC to 25% SOC at a constant current of 8C; Charge from 25% SOC to 30% SOC at a constant current of 8C; Charge from 30% SOC to 35% SOC at a constant current of 7.5C; Charge from 35% SOC to 40% SOC at a constant current of 6.87C; Charge from 40% SOC to 45% SOC at a constant current of 6.38C; Charge from 45% SOC to 50% SOC at a constant current of 5.95C; Charge from 50% SOC to 55% SOC at a constant current of 5.53C; Charge from 55% SOC to 60% SOC at a constant current of 5.14C; Charge from 60% SOC to 65% SOC at a constant current of 4.76C; Charge from 65% SOC to 70% SOC at a constant current of 4.36C; Charge from 70% SOC to 75% SOC at a constant current of 3.94C; Charge from 75% SOC to 80% SOC at a constant current of 3.57C; Charge from 80% SOC to 85% SOC at a constant current of 2C; Charge from 90% SOC to 95% SOC at a constant current of 1C; Charge from 95% SOC to 98% SOC at a constant current of 0.5C; Charge from 98% SOC to 100% SOC at a constant current of 0.25C.

[0336] Charge at a constant current of 0.1C until the charge cut-off voltage; Then discharge at a constant current of 1C until the discharge cut-off voltage. This is one charge-discharge cycle.

[0337] 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.

[0338] 4. Fast charging time test of the battery cell from 20% to 80% SOC In an environment of 25±5°C, charge the battery cell with Stercharge at a constant current: Charge from 0% SOC to 20% SOC at a constant current of 0.33C; Charge from 20% SOC to 25% SOC at a constant current of 8C; Charge from 25% SOC to 30% SOC at a constant current of 8C; Charge from 30% SOC to 35% SOC at a constant current of 7.5C; Charge from 35% SOC to 40% SOC at a constant current of 6.87C; Charge from 40% SOC to 45% SOC at a constant current of 6.38C; Charge from 45% SOC to 50% SOC at a constant current of 5.95C; Charge from 50% SOC to 55% SOC at a constant current of 5.53C; Charge from 55% SOC to 60% SOC at a constant current of 5.14C; Charge from 60% SOC to 65% SOC at a constant current of 4.76C; Charge from 65% SOC to 70% SOC at a constant current of 4.36C; Charge from 70% SOC to 75% SOC at a constant current of 3.94C; Charge from 75% SOC to 80% SOC at a constant current of 3.57C.

[0339] The test results are shown in Table 1.

[0340] Table 1

[0341] 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 intensified, and the cycle is deteriorated, especially the cycle under fast charging is deteriorated.

[0342] 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 increases accordingly, which is not conducive to fast charging of the battery cell.

[0343] 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 layer is 70mg / 1540.25mm 2 Up to 175mg / 1540.25mm 2 ; The energy density of the battery cell is 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.

[0344] 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 can achieve a fast charging effect.

[0345] Embodiment 2-5 and Embodiment 2-6 can effectively improve the volume energy density of the battery cell by setting the compaction density of the positive and negative electrode film layers within an appropriate range, and can effectively improve the cycle performance of the battery cell under high energy density and fast charging, and are beneficial to improving the cycle performance under fast charging conditions.

[0346] Comparative Example 2-1 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the negative electrode film layer did not contain silicon element and the single-side coating weight of the negative electrode film layer was adjusted.

[0347] Comparative Example 2-2 A battery cell was prepared by a method similar to that of Example 1, except that the mass content of silicon was adjusted.

[0348] Example 3-1 to Example 3-3 A battery cell was prepared by a method similar to that of Example 1, except that the mass content of silicon was adjusted.

[0349] Example 3-4 The battery single cells were 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.

[0350] Example 4 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the material of the silicon-based material was adjusted.

[0351] The test results are shown in Table 2.

[0352] Table 2

[0353] 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.

[0354] 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 generation, especially increased gas generation at high temperatures, deteriorating the cycle performance.

[0355] In Examples 3-1 to 3-4 of the present application, by regulating 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 single cells at a high energy density.

[0356] 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 , the volume energy density of the battery single cell was not too low, and since the coating thickness of the negative electrode film layer was relatively thin, the lithium ion migration path was relatively short, which was beneficial to improving the fast charging ability of the battery single cell; moreover, since the overall coating amount of the negative electrode film layer was relatively low, the total amount of the negative electrode active material participating in the side reaction could be reduced, improving the cycle performance.

[0357] As the mass content of silicon element increased, the charging specific capacity of the negative electrode active material increased. For example, in Example 3-3, the charging specific capacity of the negative electrode active material could reach 534 mAh / g.

[0358] The present 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 single cell and are beneficial to improving the fast charging performance of the battery single cell; compared with the silicon-oxygen material of Example 4, the silicon-carbon material has relatively less volume expansion during charge and discharge, and the cycle performance is relatively excellent.

[0359] Examples 5-1 to 5-2 The battery monomer 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.

[0360] Examples 6-1 and 6-2 The battery monomer 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.

[0361] The test results are shown in Table 3.

[0362] Table 3

[0363] 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 was observed, and the average particle sizes of the first region and the second region were respectively recorded and statistically analyzed.

[0364] 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 monomer at high energy density can be improved, the risk of lithium deposition can be reduced, and the cycle life can be enhanced.

[0365] In Examples 6-1 and 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, the DCR of the battery monomer can be reduced, and the fast charging ability of the battery monomer at high energy density can be effectively improved. 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.

[0366] Comparative Examples 3-1 and 3-2 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the composition of the electrolyte was adjusted.

[0367] Examples 7-1 and 7-2 The battery monomer was prepared by a method similar to that of Example 1. Different from Example 1, the composition of the electrolyte was adjusted.

[0368] The test results are shown in Table 4.

[0369] Table 4

[0370] In Table 4, In Comparative Example 3-1, the mass content of the chain carboxylic ester solvent is relatively small, resulting in a low conductivity of the electrolyte, a high DCR of the battery cell, and a relatively large resistance to lithium ion transport, which is not conducive to fast charging; 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, and the gas generation is aggravated, especially the gas generation at high temperature is aggravated, deteriorating the cycle.

[0371] In the embodiment of the present application, the mass content of the chain carboxylic ester solvent is within an appropriate range, which can effectively improve the conductivity of the electrolyte, improve the lithium ion transport 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 small impact on the energy density, and the energy density is not reflected in the table.

[0372] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the embodiments of the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: include: A positive electrode sheet, comprising a positive current collecting portion and a positive electrode film layer disposed on at least one side of the positive current collecting portion, wherein the positive electrode film layer comprises a lithium-containing phosphate, and the single-side coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 ; A negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises a carbon-based material and a silicon-based material, wherein the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.3% to 10%, and the single-side coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 ;as well as The electrolyte comprises a chain carboxylate solvent, wherein the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%.

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

3. The battery cell according to claim 1, characterized in that: The battery cell is at 100% charge state, and the compaction density of the positive electrode film layer is 2.50 g / cm 3 Up to 2.80g / cm 3 ; and / or The battery cell is at 100% charge state, and the compaction density of the negative electrode film layer is 1.5 g / cm 3 Up to 1.7g / 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 charge gram capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g; and / or The negative electrode film layer includes a negative electrode active material, and the charge 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 includes 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 is provided on the surface of the negative electrode current collecting portion, and a thickness of the first region is 1 / 3 of a thickness of the negative electrode film layer; and The second region is connected to the side of the first region 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. in, An average particle size of the carbon-based material in the first region is greater than or equal to an average particle size of the carbon-based material in the second region.

8. The battery cell according to claim 7, characterized in that: 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, characterized in that: The carbon-based material of the first region includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region includes artificial graphite.

10. The battery cell according to claim 7, characterized in that: At least one of the first region and the second region includes 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 is disposed on the surface of the negative electrode current collecting portion; and The second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion.

12. The battery cell according to claim 1, characterized in that: 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.

13. The battery cell according to claim 12, characterized in that: 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, characterized in that: The conductivity of the electrolyte at room temperature is 10.5 mS / cm to 13.5 mS / cm; and / or The viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

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

16. The battery cell according to claim 1, characterized in that: The chain carboxylic acid ester solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

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

19. The battery cell according to claim 18, characterized in that: The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

20. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate includes lithium iron phosphate.

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

22. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 21.

23. An electrical device, characterized in that: Comprising a battery device as claimed in claim 22.

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