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 and a negative pole piece, the positive pole piece comprises a positive pole coating part and at least two positive pole lugs, the positive pole coating part is provided with a positive pole active material layer, and the at least two positive pole lugs are connected with two sides of the positive pole coating part along the length direction; the negative pole piece and the positive pole piece are laminated along the thickness direction, each negative pole piece comprises a negative pole coating part and at least two negative pole lugs, the negative pole coating part is provided with a negative pole active material layer, the at least two negative pole lugs are connected with two sides of the negative pole coating part along the length direction, and the single-side coating weight of the positive pole active material layer is 150-370mg / 1540.25 mm < 2 >; the single-side coating weight of the negative electrode active material layer is 70 to 175 mg / 1540.25 mm < 2 >; and the size of the positive electrode coating part in the length direction is 265-655 mm. 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 / 071133, titled "Battery Cell, Battery Device and Electrical Device", filed on January 7, 2025, the entire content of which is incorporated herein by reference. Technical Field

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

[0003] Battery cells have characteristics such as high capacity and long life, and are therefore widely used in electronic devices, such as mobile phones, laptops, 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, cycle performance and energy density 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, cycle performance and energy density 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. The battery cell includes an electrode assembly. The electrode assembly includes a plurality of positive electrode plates and a plurality of negative electrode plates. Each positive electrode plate includes a positive electrode coating portion and at least two positive electrode tabs. The positive electrode coating portion is provided with a positive electrode active material layer. At least two positive electrode tabs are connected to both sides of the positive electrode coating portion along the length direction of the battery cell. The positive electrode active material layer includes lithium-containing phosphate. The plurality of negative electrode plates and the plurality of positive electrode plates are stacked along the thickness direction of the battery cell. Each negative electrode plate includes a negative electrode coating portion and at least two negative electrode tabs. The negative electrode coating portion is provided with a negative electrode active material layer. At least two negative electrode tabs are connected to both sides of the negative electrode coating portion along the length direction. The negative electrode active material layer includes a carbon-based material. Among them, the single-sided coating weight of the positive electrode active material layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; the single-sided coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; the dimension of the positive electrode coating portion along the length direction is 265 mm to 655 mm.

[0006] Therefore, when the length of the positive electrode active material layer in the embodiments of the present application meets the above range and the tabs are disposed on both sides of the coating portion along the length direction, the electron transmission distance can be shortened, the current distribution is uniform, lithium deposition is not likely to occur at the tabs, and the fast charging ability and cycle performance can be improved; when the length of the positive electrode active material layer meets the above range and the single-sided coating weight of the positive and negative electrode coating portions meets the above range, the migration path of active ions such as lithium ions in the positive electrode plate and the negative electrode plate is short, the lithium ion transmission ability can be improved, and the fast charging ability, cycle performance and energy density of the battery cell can be improved.

[0007] In some embodiments, the single-sided coating weight of the positive electrode active material 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 active material layer is within the above range, the heat generation per unit area of the positive electrode plate will not be too large, and the energy density and fast charging performance of the battery cell can be balanced.

[0008] In some embodiments, the single-sided coating weight of the negative electrode active material 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 active material layer meets the above range, it is beneficial to improve the energy density of the battery cell, and the heat generation per unit area of the negative electrode plate will not be too large, and the energy density and fast charging performance of the battery cell can be balanced.

[0009] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate. Lithium iron phosphate has excellent cycle stability and can improve the cycle performance.

[0010] In some embodiments, the lithium-containing phosphate is in granular form, and the volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm. 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, the heat generation is less, and the high-temperature cycle performance and cycle performance under fast charging of the battery cell can be improved; moreover, the particle size of the above lithium-containing phosphate is not too small, and agglomeration basically does not occur during the processing and preparation process, so that the performance of the lithium-containing phosphate is stable.

[0011] In some embodiments, the positive electrode active material layer further includes a positive electrode additive, and the positive electrode additive includes one or more of a lithium-containing ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate, and lithium ferrate. The above materials can supplement lithium ions for the positive electrode active material layer, make up for the irreversible lithium ion loss in the system, improve the capacity, and improve the cycle life of the battery cell.

[0012] In some embodiments, the volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm. When the volume average particle size of the positive electrode additive is within the above range, the dispersion in the positive electrode active material is relatively uniform, which is beneficial to uniform lithium compensation and improves the cycle life of the battery cell.

[0013] In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the positive electrode additive is 0.1% to 5%. When the mass content of the lithium compensation agent is within the above range, the cycle life of the battery cell can be improved.

[0014] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode active material layer is 0.3% to 10%. When the mass content of silicon element is within the above range, the capacity of the negative electrode active material can be improved, which is beneficial to increasing the energy density of the battery cell; moreover, during charge and discharge, the volume expansion of silicon element will not be too large, which is beneficial to maintaining the stability of the negative electrode interface film and improving the cycle performance of the battery cell.

[0015] In some embodiments, the silicon-based material includes one or more of silicon carbide and silicon oxide.

[0016] In some embodiments, the negative electrode active material layer includes a first region and a second region. The first region is disposed on the surface of the negative electrode current collector, and the thickness of the first region is 1 / 3 of the thickness of the negative electrode active material layer; the second region is connected to the side of the first region facing away from the negative electrode current collector, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode active material 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.

[0017] In some embodiments, the average particle size of the carbon-based material in the first region is 10 μm to 20 μm; when the average particle size of the carbon-based material in the first region is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material and the cycle performance of the battery cell under fast charging.

[0018] In some embodiments, the average particle size of the carbon-based material in the second region is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second region is within the above range, it is beneficial to improving the fast charging ability of the battery cell and the stability of the material, and improving the cycle performance of the battery cell under fast charging.

[0019] In some embodiments, the carbon-based material in the first region includes artificial graphite and natural graphite, and the carbon-based material in the second region includes artificial graphite. Such material settings are conducive to forming pore differences between the first region and the second region, and improving the fast charging ability of the battery cell.

[0020] In some embodiments, at least one of the first region and the second region includes a silicon-based material. The silicon-based material is conducive to improving the energy density of the battery cell.

[0021] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is disposed on the surface of the negative electrode current collector; the second negative electrode active material layer is connected to the side of the first negative electrode active material layer facing away from the negative electrode current collector. The double-layer film is conducive to improving the fast charging ability and energy density of the battery cell.

[0022] In some embodiments, the ratio of the dimension of the positive electrode coating portion in the length direction of the battery cell to the dimension of the positive electrode coating portion in the width direction of the battery cell is 2 to 12.5. When the dimension of the positive electrode active material layer meets the above range, the electron transmission path will not be too long, and the internal resistance is relatively small, which is conducive to improving the fast charging ability and energy density of the battery cell.

[0023] In some embodiments, there are at least two positive electrode tabs on the same side of the positive electrode coating portion; the current distribution between the tabs is uniform, reducing the risk of lithium deposition, and the positive electrode tabs generate less heat, which can improve the high-temperature cycling performance of the battery cell.

[0024] In some embodiments, there are at least two negative electrode tabs on the same side of the negative electrode coating portion. The current distribution between the tabs is uniform, reducing the risk of lithium deposition, and the positive electrode tabs generate less heat, which can improve the high-temperature cycling performance of the battery cell.

[0025] In some embodiments, the positive electrode plate satisfies: n×W1 / W2 is 0.2 to 1.0; n represents the number of all positive electrode tabs on the same side of the positive electrode coating portion; W1 represents the average dimension of the positive electrode tab in the width direction of the battery cell; W2 represents the dimension of the positive electrode coating portion in the width direction; when the ratio of the positive electrode tab dimension is within the above range, the overcurrent ability can be improved, the internal resistance can be reduced, the heat generation can be reduced, and the high-temperature cycling performance and the cycling performance under fast charging of the battery cell can be improved.

[0026] In some embodiments, the negative electrode plate satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all negative electrode tabs on the same side of the negative electrode coating portion; W3 represents the average dimension of the negative electrode tab in the width direction of the battery cell; W4 represents the dimension of the negative electrode coating portion in the width direction; when the ratio of the negative electrode tab dimension is within the above range, the overcurrent ability can be improved, the internal resistance can be reduced, the heat generation can be reduced, and the high-temperature cycling performance and the cycling performance under fast charging of the battery cell can be improved.

[0027] In some embodiments, the battery cell further includes a positive terminal, and there are at least two positive terminals which are respectively arranged on both sides of the positive electrode coating portion along the length direction; the positive terminals have a strong overcurrent capacity, can reduce the internal resistance of the battery cell, reduce the heat generation of the system, and improve the high-temperature cycling performance.

[0028] In some embodiments, the battery cell further includes a negative terminal, and there are at least two negative terminals which are respectively arranged on both sides of the negative electrode coating portion along the length direction; the positive terminals have a strong overcurrent capacity, can reduce the internal resistance of the battery cell, reduce the heat generation of the system, and improve the high-temperature cycling performance.

[0029] In some embodiments, the battery cell further includes an electrolyte, and 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 can improve the fast charging performance and cycling performance under fast charging of the battery cell.

[0030] 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 can improve the fast charging performance and cycling performance under fast charging of the battery cell.

[0031] 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 can improve the fast charging performance and cycling performance under fast charging of the battery cell.

[0032] In some embodiments, the mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 35%. When the mass content of the chain carboxylic ester solvent is within the above range, the fast charging ability and cycling performance of the battery cell can be improved.

[0033] 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.

[0034] The above-mentioned chain carboxylic acid ester solvents have relatively high conductivity, which is beneficial to improving the fast charging ability of battery cells.

[0035] In some embodiments, the organic solvent includes carbonate solvents, and the mass content of the carbonate solvents in the electrolyte is 65% to 75%.

[0036] 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 at high temperature can be reduced, and the high-temperature cycling performance of the battery cell can be improved.

[0037] In some embodiments, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0038] In a second aspect, an embodiment of the present application further provides a battery device, including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0039] In a third aspect, an embodiment of the present application further provides an electrical device, and the electrical device includes the battery device according to any one of the embodiments in the second or third aspect of the present application. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0041] Figure 1 It is a schematic structural diagram of an electrical device provided by some embodiments of the present application.

[0042] 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 positive electrode sheet of a battery cell provided by some embodiments of the present application; Figure 7 It is a schematic structural diagram of a positive electrode sheet of a battery cell provided by some other embodiments of the present application; Figure 8 It is a schematic structural diagram of the negative electrode tab of a battery cell provided by some embodiments of the present application; Figure 9 It is a schematic structural diagram of the negative electrode tab of a battery cell provided by other embodiments of the present application; Figure 10 It is a schematic structural diagram of a battery cell provided by other embodiments of the present application; Figure 11 It is a schematic structural diagram of the negative electrode tab of a battery cell provided by some embodiments of the present application; Figure 12 It is a schematic structural diagram of the electrode assembly of a battery cell provided by some embodiments of the present application.

[0043] The accompanying drawings are not necessarily drawn to actual scale.

[0044] The descriptions of the reference numerals are as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, positive electrode tab; 111, positive electrode ear; 1111, first end; 112, positive electrode coating part; 12, negative electrode tab; 121, negative electrode ear; 1211, second end; 122, negative electrode coating part; 13, separator; 141, negative electrode active material layer; 142, negative electrode current collector part; 1411, first negative electrode active material layer; 1412, second negative electrode active material layer; 141a, first region; 141b, second region; 141c, third region; 20, outer shell assembly; 21, housing; 22, end cover; 31, positive terminal; 32, negative terminal. Detailed embodiments

[0045] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application that are specifically disclosed will be described in detail with appropriate reference to the accompanying 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 prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions 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.

[0046] The "ranges" disclosed in this application are 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 the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In 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.

[0047] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0048] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0049] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, if the method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. 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.

[0050] The term "a plurality of" as used in this application means two or more (including two).

[0051] 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.

[0052] 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.

[0053] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, with the improvement of energy density and 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 amount of the battery cell at high temperatures, which may cause the cycle deterioration of the battery cell and cannot balance the improvement of the fast charging ability, cycle performance, and energy density of the battery cell.

[0054] In view of the above problems, the size of the positive electrode coating part in the embodiment of the present application is matched with the appropriate single-sided coating weight of the positive and negative electrode active materials, so that the energy density of the battery cell is relatively high; The positive electrode active material includes lithium-containing phosphate, and its conductivity is relatively poor. When the length of the positive electrode active material layer is too long, the electron conduction resistance increases, which is not conducive to fast charging. When the size of the positive electrode coating part is within an appropriate range and the tabs are arranged on both sides of the coating part, the electron transmission path in the electrode sheet is short, which can improve the electron transmission ability; on the other hand, the single-sided coating weight of the positive and negative electrode active material layers is appropriate, and the migration path of active ions such as lithium ions in the positive electrode sheet and the negative electrode sheet is short, which can improve the lithium ion transmission ability. Therefore, by improving the electron transmission ability and ion transmission ability, the fast charging ability and cycle performance under fast charging of the battery cell can be improved; Since the electron transmission path is short, the ohmic resistance of the electrode sheet is small, and the heat generation is less, which can slow down the problem of electrolyte component decomposition caused by heat accumulation and improve the high-temperature cycle performance of the battery cell.

[0055] The battery cell of the present application is applicable to various battery devices and electrical devices using battery cells.

[0056] 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.

[0057] 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. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be used.

[0058] A battery device is arranged inside the electrical device 1, and the battery device can be arranged at the bottom, the head, or the tail of the electrical device 1. The battery device can be used for power supply of the electrical device 1. For example, the battery device can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.Figure 1 The battery device shown is the battery pack 2.

[0059] 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 startup, navigation, and working power requirements of the electrical device 1 during driving.

[0060] The battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. The 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.

[0061] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0062] As an example, the battery cell assembly may be a battery module. The battery module is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, the battery module may be formed by bundling a plurality of battery cells with cable ties.

[0063] As shown in Figure 2 In some embodiments, the battery device may be the battery pack 2. 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.

[0064] As an example, the battery cell assembly may also be accommodated in the box body 5 by directly fixing a plurality of battery cells to the box body 5.

[0065] 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 snapped together 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 may be a top cover or a bottom plate.

[0066] 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.

[0067] In some embodiments, the box body 5 may be part of the chassis structure of a vehicle. For example, a part of the box body 5 may become at least a part of the floor of the vehicle, or a part of the box body 5 may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0068] As an example, the battery cell assembly can be the 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.

[0069] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0070] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0071] In some embodiments, during the charging process of the battery device or any battery cell 7 that makes up the battery device from 20% SOC to 80% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0072] 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 from 20% SOC to 25% SOC at a constant current of 8.00C; Charge from 25% SOC to 30% SOC at a constant current of 8.00C; Charge from 30% SOC to 35% SOC at a constant current of 7.50C; 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.

[0073] 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 the range composed of any two of the above values.

[0074] As Figure 4 and Figure 5 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20.

[0075] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0076] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0077] Exemplarily, the terminal assembly includes a positive terminal 31 and a negative terminal 32.

[0078] 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 there is also a sealed bag between the housing and the electrode assembly 10, and the sealed bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0079] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a multi-prismatic battery, and the multi-prismatic battery is, for example, a hexagonal-prismatic battery, etc. There is no particular limitation in this application.

[0080] 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 may be provided with one or more openings. The end cap 22 may also be provided with one or more.

[0081] 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 cylindrical housing 21 can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0082] The electrode assembly 10 includes a positive electrode tab 11, a negative electrode tab 12, and a separator 13.

[0083] As Figures 4 to 6 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10. The electrode assembly includes a plurality of positive electrode tabs 11 and a plurality of negative electrode tabs 12. The plurality of positive electrode tabs 11 and the plurality of negative electrode tabs 12 are stacked in the thickness direction X of the battery cell. Each positive electrode tab 11 includes a positive electrode coating portion 112 and at least two positive electrode ears 111. The positive electrode coating portion 112 is provided with a positive electrode active material layer. The at least two positive electrode ears 111 are not coated with the positive electrode active material layer and are connected to both sides of the positive electrode coating portion 112 along the length direction Z of the battery cell. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate; Each negative electrode tab 12 includes a negative electrode coating portion 122 and at least two negative electrode ears 121. The negative electrode coating portion 122 is provided with a negative electrode active material. The at least two negative electrode ears 121 are not coated with the negative electrode active material and are connected to both sides of the negative electrode coating portion 122 along the length direction Z. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material. Among them, the single-sided coating weight of the positive electrode active material layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; the single-sided coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 ; the dimension of the positive electrode coating portion 112 along the length direction Z is 265 mm to 655 mm.

[0084] The electrode assembly is a stacked structure, and the dimension of the positive electrode active material layer can be considered equivalent to the dimension of the positive electrode coating portion. Figure 6 In [diagram] Z1 represents the dimension of the positive electrode coating portion 112 along the length direction Z.

[0085] The length of the positive electrode active material layer is greater than or equal to 265 mm, and its combination is greater than or equal to 150 mg / 1540.25 mm2 The single-sided coating weight, and the negative electrode active material layer with an appropriate coating weight, can effectively improve the energy density of the battery cell; The positive electrode active material includes lithium-containing phosphate, which has relatively poor conductivity. When the length of the positive electrode active material layer is too long, the resistance of electron conduction increases, which is not conducive to fast charging; while in the embodiment of the present application, the length of the positive electrode active material layer is less than or equal to 655 mm, which is beneficial to shortening the electron conduction distance; moreover, the tabs are arranged on both sides of the coating part along the length direction, which can further shorten the electron transmission distance and reduce the internal resistance; The single-sided coating weight of the positive electrode coating part 112 is less than or equal to 370 mg / 1540.25 mm 2 and the single-sided coating weight of the negative electrode coating part 122 is less than or equal to 175 mg / 1540.25 mm 2 , and the migration path of active ions such as lithium ions in the positive electrode plate and the negative electrode plate is relatively short, which can improve the transmission ability of lithium ions in the liquid phase; Thus, by improving the electron transmission ability and ion transmission ability, the fast charging ability of the battery cell and the cycle performance under fast charging can be improved; Since the electron transmission path is short, the ohmic resistance of the electrode plate is small, and the heat generation is less, which can slow down the problem of electrolyte component decomposition caused by heat accumulation and improve the high-temperature cycle performance of the battery cell.

[0086] In summary, the embodiment of the present application can take into account improving the energy density, fast charging ability, high-temperature cycle performance and cycle performance under fast charging conditions of the battery cell.

[0087] The electrode assembly 10 is a stacked structure. As an example, a plurality of positive electrode plates 11 and negative electrode plates 12 can be respectively provided, and the plurality of positive electrode plates 11 and the plurality of negative electrode plates 12 are alternately stacked.

[0088] As an example, a plurality of positive electrode plates 11 can be provided, and the negative electrode plate 12 is folded to form a plurality of stacked folding segments, and a positive electrode plate 11 is clamped between adjacent folding segments.

[0089] As an example, both the positive electrode plate 11 and the negative electrode plate 12 are folded to form a plurality of stacked folding segments.

[0090] As an example, a plurality of separators 13 can be provided and are respectively arranged between any adjacent positive electrode plates 11 or negative electrode plates 12.

[0091] As an example, the separator 13 can be continuously arranged and is arranged between any adjacent positive electrode plates 11 or negative electrode plates 12 by folding or winding.

[0092] In some embodiments, each electrode tab is provided on the electrode plate, and the electrode tab can conduct the current out of the electrode assembly 10. The electrode tab includes a positive electrode tab and a negative electrode tab.

[0093] In the embodiments of the present application, the length direction Z, the width direction Y, and the thickness direction X of the battery cell 7 are perpendicular to each other in pairs.

[0094] The coating part includes a current collecting part and a film layer provided on the current collecting part and containing active materials. For example, the positive electrode coating part 112 includes a positive electrode current collecting part and a positive electrode active material layer provided on the positive electrode current collecting part and containing positive electrode active materials. Another example is that the negative electrode coating part 122 includes a negative electrode current collecting part and a negative electrode active material layer provided on the negative electrode current collecting part and containing negative electrode active materials.

[0095] Such as Figure 6 and Figure 7 As shown, in some embodiments, the positive electrode plate 11 includes at least two positive electrode tabs 111, for example, including 2 to 4 positive electrode tabs 111. The multiple positive electrode tabs 111 are respectively arranged on both sides of the positive electrode coating part 112 along the length direction Z. This arrangement can shorten the transmission path of electrons in the positive electrode plate 11, which is beneficial to improving the fast charging performance. For example, two positive electrode tabs 111 are located on one side of the positive electrode coating part 112 along the length direction Z, and the other two positive electrode tabs 111 are located on the other side of the positive electrode coating part 112 along the length direction Z.

[0096] In some embodiments, the positive electrode plate 11 satisfies that n×W1 / W2 is 0.2 to 1.0; n represents the number of all positive electrode tabs 111 on the same side of the positive electrode coating part 112; W1 represents the average size of the positive electrode tab 111 along the width direction Y; W2 represents the size of the positive electrode coating part 112 along the width direction Y.

[0097] Figure 6 where n is 1 in Figure 7 where n is 2 in

[0098] 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.

[0099] When n×W1 / W2 satisfies the above range, the current-carrying area of the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0100] W1 represents the average size of the positive electrode tab 111 along the width direction Y.

[0101] When the positive tab 111 has a special-shaped structure, for example, along the length direction Z, the dimension of the positive tab 111 in the width direction Y gradually increases. In this case, the dimensions of the positive tab 111 in the width direction Y at multiple locations can be measured, and thus the average dimension of the positive tab 111 in the width direction Y can be calculated. Of course, the dimensions of the positive tab 111 at each location in the width direction Y can be the same value, and in this case, this value can be used as the average dimension of the positive tab 111.

[0102] There can be one or more positive tabs 111 on the same side. For example, n ranges from 1 to 4. When there are multiple positive tabs 111, after measuring the average dimensions of each positive tab 111 respectively, the average dimension of the positive tabs 111 can be calculated by adding up the average dimensions and dividing by the number of positive tabs 111.

[0103] The positive tab 111 is connected to the positive coating portion 112. The positive tab 111 includes a first end 1111 connected to the positive 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 positive tab 111 itself is relatively large, the contact surface between the positive tab 111 and the positive coating portion 112 is relatively large, the current-carrying capacity of the positive tab 111 is strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0104] Optionally, the current collecting portion of the positive tab 111 and the positive coating portion 112 is an integral structure, so that the internal resistance of the positive electrode plate 11 is relatively low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0105] Optionally, there are at least two positive tabs 111 on the same side of the positive coating portion 112, such as two, three, four, five, six, etc. This setting is beneficial to the uniform distribution of electrons on the positive electrode plate 11 and is beneficial to improving the fast charging performance.

[0106] The distance between two adjacent positive tabs 111 in 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. Figure 7 In the formula, Y1 represents the distance between two adjacent positive tabs 111 in the width direction Y.

[0107] As Figure 8 and Figure 9 shown, in some embodiments, the negative electrode plate 12 includes at least two negative tabs 121, such as 2 to 4 negative tabs 121. The multiple negative tabs 121 are respectively arranged on both sides of the negative coating portion 122 along the length direction Z. This setting can shorten the transmission path of electrons on the negative electrode plate 12 and is beneficial to improving the fast charging performance.

[0108] In some embodiments, the negative electrode tab 12 satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all the negative electrode tabs 121 on the same side of the negative electrode coating portion 122; W3 represents the average dimension of the negative electrode tab 121 in the width direction Y; W4 represents the dimension of the negative electrode coating portion 122 in the width direction Y.

[0109] W3 represents the average dimension of the negative electrode tab 121 in the width direction Y. The negative electrode tabs 121 on the same side can be one or more. When there are multiple negative electrode tabs 121, the average dimension can be calculated by measuring the dimensions of each negative electrode tab 121 with a micrometer.

[0110] The negative electrode tab 121 is connected to the negative electrode coating portion 122. The negative electrode tab 121 includes a second end 1211 connected to the negative electrode 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 negative electrode tab 121 itself is relatively large, the contact surface between the negative electrode tab 121 and the negative electrode coating portion 122 is relatively large, the current-carrying capacity of the negative electrode tab 121 is relatively strong, and the fast charging performance and cycle performance of the battery cell 7 can be improved.

[0111] Optionally, the current collector portion of the negative electrode tab 121 and the negative electrode coating portion 122 is an integral structure, so that the internal resistance of the negative electrode tab 12 is relatively low, and the fast charging performance and cycle performance of the battery cell 7 can be further improved.

[0112] m can be 1 to 4. For example Figure 8 in which m is 1, Figure 9 in which m is 2.

[0113] 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 a range composed of any two of the above values. Optionally, m×W3 / W4 is 0.5 to 1.0.

[0114] When m×W3 / W4 satisfies the above range, the current-carrying area of the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0115] Optionally, there are at least two negative electrode tabs 121 on the same side of the negative electrode coating portion 122 along the length direction Z, such as two, three, four, five, six, etc. This setting is beneficial to the uniform distribution of electrons on the negative electrode tab 12 and is beneficial to improving the fast charging performance.

[0116] Optionally, the distance between two adjacent negative electrode tabs 121 in 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 a range composed of any two of the above values. Figure 9 In Figure 9 , Y2 represents the distance between two adjacent negative electrode tabs 121 in the width direction Y.

[0117] As Figure 10 shown, in some embodiments, the terminal assembly may be disposed on the housing 21, or the terminal assembly is disposed on the end cap 22.

[0118] The terminal assembly includes a positive terminal 31 and a negative terminal 32. The positive terminal 31 is connected to the positive electrode tab 111, and the negative terminal 32 is connected to the negative electrode tab 121.

[0119] Exemplarily, the positive terminal 31 and the negative terminal 32 may be disposed on the housing 21, or the positive terminal 31 and the negative terminal 32 are disposed on the end cap 22. Optionally, the positive terminal 31 and the negative terminal 32 are disposed on the end cap 22.

[0120] On the same end cap 22, the positive terminal 31 and the negative terminal 32 may be provided simultaneously. For example, there is one end cap 22, and the positive terminal 31 and the negative terminal 32 are spaced apart on the end cap 22. Another example is that there are two end caps 22, the two end caps 22 are disposed opposite to each other, and each end cap 22 is provided with a positive terminal 31 and a negative terminal 32.

[0121] The positive terminal 31 and the negative terminal 32 are respectively disposed on different end caps 22. For example, there are two end caps 22, the two end caps 22 are disposed opposite to each other, the positive terminal 31 is disposed on one end cap 22, and the negative terminal 32 is disposed on the other end cap 22.

[0122] In some embodiments, the positive terminal 31 is at least one, and may be at least two, such as two, three, or four, etc.

[0123] In some embodiments, at least one positive terminal 31 is disposed on at least one side of the electrode assembly 10 in the length direction Z.

[0124] Optionally, as Figure 10 shown, a plurality of positive terminals 31 are respectively disposed on both sides of the electrode assembly 10 in the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0125] Exemplarily, there are two positive terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other positive terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplarily, there are four positive terminals 31, two of which are disposed on one side of the electrode assembly 10, and the other two positive terminals 31 are disposed on the other side of the electrode assembly 10.

[0126] In the embodiments of the present application, the positive tab 111 and the positive terminal 31 can be directly connected or indirectly connected; when the positive tab 111 and the positive terminal 31 are indirectly connected, the battery cell 7 can include a first adapter 51, and the first adapter 51 is located between the positive terminal 31 and the positive tab 111 and connects the positive terminal 31 and the positive tab 111.

[0127] In the above embodiments, the first adapter 51 can include a conductive polymer or a conductive metal material, and the conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0128] In other embodiments, at least one positive terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all the positive terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, a plurality of positive terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0129] In some embodiments, the negative terminal 32 is at least one, and can be optionally at least two, such as two, three, or four, etc.

[0130] In some embodiments, at least one negative terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0131] Optionally, at least two negative terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0132] Figure 11 It shows that the battery cell 7 includes four electrode terminals. Specifically, there are two negative terminals 32, one of which is disposed on one side of the electrode assembly 10 along the length direction Z, and the other negative terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two positive terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other positive terminal 31 is disposed on the other side of the electrode assembly 10.

[0133] In the embodiments of the present application, the negative tab 121 and the negative terminal 32 can be directly connected or indirectly connected; when the negative tab 121 and the negative terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, which is located between the negative terminal 32 and the negative tab 121 and connects the negative terminal 32 and the negative tab 121.

[0134] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0135] In some other embodiments, at least one negative terminal 32 is disposed on at least one side of the electrode assembly 10 in the width direction Y. For example, all the negative terminals 32 are disposed on one side of the electrode assembly 10 in the width direction Y, or multiple negative terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the width direction Y.

[0136] Negative electrode plate The negative electrode coating portion of the negative electrode plate includes a negative electrode current collector portion and a negative electrode active material layer disposed on at least one side of the negative electrode current collector portion and including a negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0137] The upper charge limit voltage and the discharge cut-off voltage of the battery cell vary according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V, or the upper charge limit voltage can be 3.8V and the discharge cut-off voltage can be 2.0V; also for example, when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.3V and the discharge cut-off voltage can be 2.0V. Next, taking the upper charge limit voltage of 3.8V and the discharge cut-off voltage of 2.0V as an example, the state of the battery cell is described as follows: 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 charge rate of 0.05C to the upper charge 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.

[0138] In some embodiments, when the battery cell is at 100% state of charge SOC, the compaction density of the negative electrode active material layer is 1.5 g / cm 3 to 1.7 g / cm 3. Exemplarily, the compaction density of the negative electrode active material layer at 100% state of charge of the battery cell 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.

[0139] When the compaction density of the negative electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the negative electrode active materials in the negative electrode active material layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle performance. Therefore, by adjusting the compaction density of the negative electrode active material layer to a reasonable range, the battery cell can improve its fast charging ability and cycle performance at high energy density.

[0140] In the embodiments of the present application, the single-sided coating weight of the negative electrode active material 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 active material 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 the range composed of any two of the above values. Optionally, the single-sided coating weight of the negative electrode active material layer is 95 mg / 1540.25 mm 2To 142 mg / 1540.25 mm 2 。

[0141] When the single-sided coating weight of the negative electrode active material layer meets the above range, it is beneficial to improve the energy density of the battery cell, and the migration rate of active ions in the negative electrode active material layer is relatively fast, which is also beneficial to reducing the polarization phenomenon under high-rate charging, and is beneficial to improving the fast charging ability of the battery cell at high energy density.

[0142] In the embodiments of the present application, the compaction density of the negative electrode active material layer of the battery cell in the 100% state of charge (SOC) is the meaning well known in the art, that is, the negative electrode pole piece is disassembled from the battery cell in the 100% state of charge (SOC), and the compaction density of the negative electrode active material layer is measured. For example, a single-sided coated negative electrode pole piece (if it is a double-sided coated pole piece, the negative electrode active material layer on one side can be wiped off first) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the negative electrode active material layer of the above-mentioned weighed negative electrode pole piece is wiped off, and the weight of the negative electrode current collector part is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode active material layer = (the weight M1 of the negative electrode pole piece - the weight M0 of the negative electrode current collector part) / S1, the thickness of the negative electrode active material layer = the thickness H1 of the negative electrode pole piece - the thickness H0 of the negative electrode current collector part, and the compaction density of the negative electrode active material layer = the single-sided coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0143] In some embodiments, the charge specific capacity of the negative electrode active material is 350 mAh / g to 540 mAh / g. Exemplarily, the charge specific capacity of the negative electrode active material is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g, 530 mAh / g, 540 mAh / g or the range composed of any two of the above values.

[0144] When the charge specific capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0145] 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 testing equipment with the same performance, and the 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.

[0146] In some embodiments, the negative active material includes silicon-based materials. Optionally, the silicon-based materials may include at least one of elemental silicon, silicon-carbon composites, and silicon oxides SiO x (where 0 < x ≤ 2). For example, the silicon-carbon composite can be silicon carbide.

[0147] In some embodiments, the mass content of silicon element in the silicon-based material in the negative active material 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 active material layer is 3% to 6%.

[0148] 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.

[0149] In some embodiments, the negative active material includes carbon-based materials. The carbon-based materials have high cycle stability and can improve the cycle performance of the battery cell.

[0150] Optionally, the carbon-based materials include at least one of artificial graphite and natural graphite.

[0151] In some embodiments, in addition to the above-mentioned carbon-based materials and optionally silicon-based materials, the negative active material may further include at least one of tin-based materials and lithium titanate. The tin-based materials may include at least one of elemental tin, tin oxides, and tin alloy materials.

[0152] In this application, the qualitative and quantitative analysis of various substances or elements can be detected by suitable equipment and methods known to those skilled in the art. 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 analysis, or several detection methods can be used in combination for qualitative or quantitative determination.

[0153] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to conduct X-ray powder diffraction test and qualitative analysis on the negative electrode plate or negative electrode active material.

[0154] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps. Or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0155] As Figure 11 shown, in the embodiment of this application, the negative electrode active material layer 141 of the negative electrode plate 12 includes at least one layer of film layer, which can be a single-layer film layer or at least two-layer film layers. Optionally, the negative electrode active material layer 141 includes at least two-layer film layers.

[0156] When the negative electrode active material layer 141 adopts a single-layer film layer, the negative electrode active material in the negative electrode active material layer 141 includes a carbon-based material and an optional silicon-based material.

[0157] When the negative electrode active material layer 141 adopts at least two-layer film layers, the negative electrode active material in the negative electrode active material layer 141 includes a carbon-based material and an optional silicon-based material. The negative electrode active material layer 141 can include two-layer film layers, three-layer film layers, four-layer film layers, or even more film layers.

[0158] In some embodiments, the negative electrode active material layer 141 includes a first negative electrode active material layer 1411 and a second negative electrode active material layer 1412. The first negative electrode active material layer 1411 is disposed on the surface of the negative electrode current collector portion 142. The negative electrode active material of the first negative electrode active material layer 1411 includes a carbon-based material. The second negative electrode active material layer 1412 is connected to the side of the first negative electrode active material layer 1411 facing away from the negative electrode current collector portion 142. The negative electrode active material of the second negative electrode active material layer 1412 includes a carbon-based material. The interface between the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 may be regular or irregular, and is optionally irregular; or there is no obvious interface between the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412.

[0159] The negative electrode active material layer 141 includes at least two film layers. Laminated coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences in the porosity between the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412, it is beneficial to improving the fast charging performance of the battery cell.

[0160] In some embodiments, at least one of the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 includes a silicon-based material.

[0161] Optionally, the first negative electrode active material layer 1411 further includes a silicon-based material.

[0162] Optionally, the second negative electrode active material layer 1412 further includes a silicon-based material.

[0163] Exemplarily, the first negative electrode active material layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 include a silicon-based material, it is more beneficial to improving the energy density of the battery cell; and it can enable each layer to relieve the volume expansion of the silicon-based material through the carbon-based material, enable the negative electrode SEI film to be more stable, and improve the cycle performance under high energy density; and since each layer includes a silicon-based material, the coating thickness is relatively thin, which is beneficial to shortening the transmission path of lithium ions and improving the fast charging performance under high energy density.

[0164] Or, the first negative electrode active material layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material. When the first negative electrode active material layer 1411 includes a silicon-based material and the second negative electrode active material layer 1412 does not include a silicon-based material, the second negative electrode active material layer 1412 can relieve the volume expansion of the first negative electrode active material layer 1411, reduce the side reaction between the negative electrode active material layer 141 and the electrolyte, and improve the cycle performance under high energy density.

[0165] Alternatively, the first negative electrode active material layer 1411 includes a carbon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode active material layer 1412 includes a silicon-based material, it is beneficial to form more film layer pores through the volume change of the silicon-based material, improve the liquid-phase transport ability of lithium ions, and enhance the kinetic performance of the battery cell.

[0166] When at least two film layers are adopted for the negative electrode active material layer 141, in the thickness direction X of the negative electrode active material layer 141, the cross-sectional morphology of each part of the negative electrode active material layer 141 can be the same or similar, 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 active material layer 141.

[0167] In the thickness direction X of the negative electrode active material layer 141, the negative electrode active material 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 active material 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 active material layer 141; the second region 141b is the region of the negative electrode active material 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 active material layer 141.

[0168] 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.

[0169] 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 active material layer 1411 includes the first region 141a, the second negative electrode active material layer 1412 includes the second region 141b, and the third region 141c can be a part of the first negative electrode active material layer 1411, or the third region 141c can be a part of the second negative electrode active material layer 1412, or the third region 141c can be a part of both the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412.

[0170] Optionally, the average particle size of the carbon-based material in the first region 141a may be greater than or equal to the average particle size of the carbon-based material in the second region 141b. Further optionally, the average particle size of the carbon-based material in the first region 141a may be greater than the average particle size of the carbon-based material in the second region 141b, which is beneficial for 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 may be less than the average particle size of the carbon-based material in the second region 141b.

[0171] Optionally, the average particle size of the carbon-based material in the first negative electrode active material layer 1411 may be greater than or equal to the average particle size of the carbon-based material in the second negative electrode active material layer 1412. Further optionally, the average particle size of the carbon-based material in the first negative electrode active material layer 1411 may be greater than the average particle size of the carbon-based material in the second negative electrode active material layer 1412.

[0172] There are differences in the particle sizes of the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412, which can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode active material layer 1412 is usually relatively high, and the bottleneck of rapid charging mainly lies in the second negative electrode active material layer 1412. In the embodiments of the present application, the particle size of the second negative electrode active material layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode sheet 12 and improve the cycle performance under rapid charging.

[0173] 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 rapid 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 rapid charging.

[0174] Optionally, the average particle size of the carbon-based material in the first negative electrode active material layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material in the first negative electrode active material 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 rapid 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 rapid charging.

[0175] 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 a range composed of any two of the above values. When the average particle size of the carbon-based material in the second negative electrode active material layer 1412 is within the above range, it is beneficial to improve the rapid charging ability of the battery cell and the stability of the material, and improve the cycle performance under rapid charging.

[0176] Optionally, the average particle size of the carbon-based material in the second negative electrode active material layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second negative electrode active material 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 rapid 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. Furthermore, the negative electrode active material in the second negative electrode active material layer 1412 with the above average particle size range cooperates with the negative electrode active material in the first negative electrode active material layer 1411, which is beneficial to constructing the gradient pore difference between the second negative electrode active material layer 1412 and the first negative electrode active material layer 1411, reducing the tortuosity of lithium ion transmission, and improving the rapid charging performance of the battery cell.

[0177] Exemplarily, the carbon-based material in the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second region 141b includes artificial graphite. For example, the negative electrode active material in the first region 141a includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material in the second region 141b includes a silicon-based material and artificial graphite.

[0178] Exemplarily, the carbon-based material in the first negative electrode active material layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second negative electrode active material layer 1412 includes artificial graphite. For example, the negative electrode active material in the first negative electrode active material layer 1411 includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material in the second negative electrode active material layer 1412 includes a silicon-based material and artificial graphite.

[0179] In the embodiments of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the negative electrode plate 12 as a sample, cross-section polishing is performed along the thickness direction X of the negative electrode active material layer 141, for example, cross-section polishing is performed by using an argon ion beam, and a scanning electron microscope SEM is used to photograph the cross-section to obtain an SEM cross-sectional view. The particle size of the carbon-based material in the SEM cross-section is counted, and the average particle size of the carbon-based material is calculated according to the counted quantity. In the case where the proportion of the carbon-based material in the negative electrode film layer is relatively high, the average particle size of the carbon-based material can be used to roughly evaluate the average particle size of the negative electrode active material.

[0180] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. 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 active material layer, the mass content of the negative electrode conductive agent is ≤5%.

[0181] The negative electrode conductive agent can compensate for the disadvantage of insufficient conductivity of the negative electrode active material such as silicon-based materials, improve the conductivity of the negative electrode active material layer, and is beneficial to improving the kinetic performance of the battery cell and the fast charging ability of the battery cell at high energy density.

[0182] Optionally, the mass content of the conductive carbon in the negative electrode active material layer is 0.4% to 0.7%, such as 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7% or the range composed of any two of the above values. When the mass content of the conductive carbon is within the above mass content, the fast charging ability of the battery cell at high energy density can be improved.

[0183] Optionally, the mass content of the carbon nanotubes in the negative electrode active material layer is 0.1% to 1%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. Optionally, the mass content of the carbon nanotubes in the negative electrode active material layer is 0.1% to 0.5%. When the mass content of the carbon nanotubes is within the above mass content, the fast charging ability of the battery cell at high energy density can be improved.

[0184] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode active material layer, the mass content of the negative electrode binder is ≤5%.

[0185] In some embodiments, the negative electrode active material layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode active material layer, the mass content of the other additives is ≤2%.

[0186] In some embodiments, the negative 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).

[0187] In some embodiments, the thickness of the negative current collector is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values.

[0188] In some embodiments, the negative electrode tab further includes a negative electrode tab connected to the negative current collector. The thickness of the negative electrode tab is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values. When the thickness of the negative electrode tab is within the above range, it is beneficial to improve the overcurrent capacity and improve the fast charging capacity of the battery cell.

[0189] The negative electrode active material layer is usually formed by coating a negative electrode slurry on the negative current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0190] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode tab of the present application further includes a negative electrode conductive layer sandwiched between the negative current collector and the negative electrode active material layer and disposed on the surface of the negative current collector. In other embodiments, the negative electrode tab of the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[0191] Positive electrode plate The positive electrode coating portion of the positive electrode tab includes a positive current collector and a positive electrode active material layer disposed on at least one side of the positive current collector and including a positive electrode active material. For example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive current collector.

[0192] When the battery cell includes a stacked electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode tab, the dimension of the battery cell along the length direction can be understood as the length of the battery cell, and the dimension of the positive active material layer along the length direction can be understood as the length of the positive active material layer; the width direction of the battery cell is parallel to the width direction of the positive electrode tab, the dimension of the battery cell along the width direction can be understood as the width of the battery cell, and the dimension of the positive active material layer along the width direction can be understood as the width of the positive active material layer.

[0193] The dimension of the positive active material layer along the length direction of the positive electrode tab is from 265 mm to 655 mm, such as 265 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm or a range composed of any two of the above values. Optionally, the dimension of the positive active material layer along the length direction of the positive electrode tab is from 400 mm to 600 mm. The dimension of the positive active material layer can be equivalent to the dimension of the positive coating portion.

[0194] In some embodiments, the ratio of the dimension of the positive active material layer along the length direction of the positive electrode tab to the dimension of the positive active material layer along the width direction of the positive electrode tab is from 2 to 12.5, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 12.5 or a range composed of any two of the above values. Optionally, the ratio of the dimension of the positive active material layer along the length direction of the positive electrode tab to the dimension of the positive active material layer along the width direction of the positive electrode tab is from 4 to 8.

[0195] When the positive active material of the positive active material layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the dimension of the positive active material layer should not be too long. When the dimension of the positive active material layer meets the above range, the electron transport path will not be too long, the internal resistance is relatively small, which is beneficial to improving the fast charging ability and energy density of the battery cell.

[0196] In some embodiments, the dimension of the negative active material layer along the length direction is greater than the dimension of the positive active material layer along the length direction, so that the lithium ions released from the positive active material layer can basically be embedded in the negative active material layer, reducing the risk of lithium deposition on the negative electrode side and improving the use reliability of the battery cell. Of course, the dimension of the negative active material layer along the length direction can also be less than or equal to the dimension of the positive active material layer along the length direction.

[0197] Optionally, the difference between the dimension of the negative electrode active material layer in the length direction and the dimension of the positive electrode active material layer in the length 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.

[0198] In some embodiments, the dimension of the negative electrode active material layer in the width direction is greater than the dimension of the positive electrode active material layer in the width direction, so that the lithium ions released from the positive electrode active material layer can basically be embedded in the negative electrode active material layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of use of the battery cell. Of course, the dimension of the negative electrode active material layer in the width direction can also be less than or equal to the dimension of the positive electrode active material layer in the width direction.

[0199] Optionally, the difference between the dimension of the negative electrode active material layer in the width direction and the dimension of the positive electrode active material layer in the width 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.

[0200] In some embodiments, the dimension of the separator in the length direction is greater than the dimension of the negative electrode active material layer in the length direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reducing the risk of short circuit and improving the reliability of use of the battery cell. Of course, the dimension of the separator in the length direction can also be less than or equal to the dimension of the negative electrode active material layer in the length direction.

[0201] Optionally, the difference between the dimension of the separator in the length direction and the dimension of the negative electrode active material layer in the length 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 the range composed of any two of the above values.

[0202] In some embodiments, the dimension of the separator in the width direction is greater than the dimension of the negative electrode active material layer in the width direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reducing the risk of short circuit and improving the reliability of use of the battery cell. Of course, the dimension of the separator in the width direction can also be less than or equal to the dimension of the negative electrode active material layer in the width direction.

[0203] Optionally, the difference between the dimension of the separator in the width direction and the dimension of the negative electrode active material layer in the width 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.

[0204] As Figure 12 shown, the dimension of the positive electrode active material layer of the positive electrode tab 11 in the length direction Z is the length of the positive electrode active material layer of the positive electrode tab 11, the dimension of the negative electrode active material layer of the negative electrode tab 12 in the length direction Z is the length of the negative electrode active material layer of the negative electrode tab 12, and the dimension of the separator 13 in the length direction Z is the length of the separator 13.

[0205] The difference between the length of the negative electrode active material layer of the negative electrode tab 12 and the length of the positive electrode active material layer of the positive electrode tab 11 is OH 11 , Figure 12 as shown in 11 , both sides of the negative electrode active material layer in the length direction Z exceed the positive electrode active material layer, and each side exceeds OH

[0206] The difference between the length of the separator 13 and the length of the negative electrode active material layer of the negative electrode tab 12 is OH 21 , Figure 12 as shown in 21 , both sides of the separator 13 in the length direction Z exceed the negative electrode active material layer, and each side exceeds OH

[0207] The dimension of the positive electrode active material layer of the positive electrode tab 11 in the width direction Y is the width of the positive electrode active material layer of the positive electrode tab 11, the dimension of the negative electrode active material layer of the negative electrode tab 12 in the width direction Y is the width of the negative electrode active material layer of the negative electrode tab 12, and the dimension of the separator 13 in the width direction Y is the width of the separator 13.

[0208] The difference between the width of the negative electrode active material layer of the negative electrode tab 12 and the width of the positive electrode active material layer of the positive electrode tab 11 is OH 12 , Figure 12 as shown in 12 , both sides of the negative electrode active material layer in the width direction Y exceed the positive electrode active material layer, and each side exceeds OH

[0209] The difference between the width of the separator 13 and the width of the negative electrode active material layer of the negative electrode tab 12 is OH 22 ,Figure 12 As shown, both sides of the separator 13 in the width direction Y exceed the negative electrode active material layer, and each side exceeds OH 22 / 2. Of course, the separator 13 may exceed the negative electrode active material layer on one side in the width direction Y.

[0210] In some embodiments, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode active material layer is 2.50 g / cm 3 to 2.80 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode active material 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.

[0211] When the tap density of the positive electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive electrode active materials in the positive electrode active material layer are stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle performance. Therefore, by adjusting the tap density of the positive electrode active material layer to a reasonable range, the battery cell can improve its fast charging ability and cycle performance at high energy density.

[0212] In some embodiments, the single-sided coating weight of the positive electrode active material 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 active material 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 active material layer is 200 mg / 1540.25 mm2 to 300 mg / 1540.25 mm 2 。

[0213] When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generation amount per unit area of the positive electrode sheet will not be too large, reducing the risk of exacerbation of 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.

[0214] In the embodiments of the present application, the compaction density of the positive electrode active material layer of the battery cell in the 100% state of charge (SOC) is a meaning well known in the art, that is, disassembling the positive electrode sheet of the battery cell in the 100% state of charge (SOC) and measuring the compaction density of the positive electrode active material layer. For example, taking a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first), punching it into small circular pieces with an area of S1, weighing it, recording it as M1, and measuring its thickness H1. Then wipe off the positive electrode active material layer of the above-mentioned weighed positive electrode sheet, weigh the weight of the positive electrode current collector part, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode active material layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector part) / S1, the thickness of the positive electrode active material layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive electrode current collector part, and the compaction density of the positive electrode active material layer = the single-sided coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0215] 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.

[0216] 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.

[0217] In the embodiments of the present application, the specific capacity of the positive electrode active material is a meaning well known in the art, and the test method for the specific capacity of the negative electrode active material can be used for detection.

[0218] 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 the charge and discharge process and can improve the cycle life of the battery cell.

[0219] Optionally, the positive electrode active material may further include a lithium-containing transition metal oxide. Examples of the lithium-containing transition metal oxide may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0220] The lithium-containing phosphate in the olivine structure may 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, facilitating the migration rate of lithium ions, improving the fast charging ability of the battery cell, and reducing the heat generation of the battery cell.

[0221] 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, Mg, Me includes one or more of Mn, Fe, Co, 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, Ce, X includes one or more of Cl, C, N, and Y includes one or more of O, F. The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0222] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO 4 、LiMnPO 4 、LiNiPO 4 、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 is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 、LiMnPO 4 、LiNiPO 4, LiCoPO 4 In the enumeration of, for example, 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 positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active material LiFePO

[0223] 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, and 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 made up to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0224] In some embodiments, the lithium-containing phosphate is granular, and the volume average particle size Dv50 of the lithium-containing phosphate is from 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm or a range composed of any two of the above values.

[0225] 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, making the performance of the lithium-containing phosphate stable.

[0226] In some embodiments, the positive electrode active material layer further includes a positive electrode additive, and the positive electrode additive includes one or more of a lithium-containing ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as a lithium supplement agent, which can supplement lithium ions to the positive electrode active material layer, make up for the irreversible lithium ion loss in the system, improve the capacity, and improve the energy density of the battery cell.

[0227] In some embodiments, based on the mass of the positive electrode active material 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 the range composed of any two of the above. When using a lithium supplement agent in a mass range, it can supplement lithium ions to the positive electrode active material layer, make up for the irreversible lithium ion loss in the system, and the mass content of the lithium supplement agent 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.

[0228] 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 distribution uniformity of the positive electrode additive.

[0229] 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.

[0230] 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 equipment and methods well known in the art. After fully discharging the fresh battery cell 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.

[0231] In some embodiments, the positive electrode active material 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 active material layer, the mass content of the positive electrode conductive agent is ≤5%.

[0232] In some embodiments, the positive electrode active material 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 resin. In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the positive electrode binder is ≤5%.

[0233] In some embodiments, the positive electrode current collector portion may be a metal foil or a composite current collector. As an example of the metal foil, at least one of foils of aluminum, aluminum 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 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).

[0234] In some embodiments, the thickness of the positive electrode current collector portion 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.

[0235] In some embodiments, the positive electrode plate further includes a positive electrode tab connected to the positive electrode current collector portion. The thickness of the positive electrode tab 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 tab is within the above range, it is beneficial to improve the overcurrent capacity and improve the fast charging capacity of the battery cell.

[0236] The positive electrode active material layer is usually formed by coating a positive electrode slurry on the positive electrode current collector portion and 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.

[0237] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of the embodiment of the present application further includes a positive electrode conductive layer disposed on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode active material layer. In some other embodiments, the positive electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode active material layer.

[0238] [Electrolyte] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The electrolyte includes an organic solvent and an electrolyte salt.

[0239] In some embodiments, the conductivity of the electrolyte at room temperature is from 10.5 mS / cm to 13.5 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm or a range composed of any two of the above values.

[0240] 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.

[0241] In the embodiment 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 equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0242] 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 a range composed of any two of the above values.

[0243] 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.

[0244] In the embodiment of the present application, the viscosity of the electrolyte has the meaning well-known in the art and can be detected by using equipment and methods well-known in the art. For example, it can be detected in accordance with GB / T10247-2008.

[0245] 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 a range composed of any two of the above values.

[0246] 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.

[0247] 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 equipment and methods well-known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0248] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0249] Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is from 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 a range composed of any two of the above values. Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is from 8% to 20%.

[0250] When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte is relatively 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 impact on the interfacial film on the negative electrode side, and improve the fast charging ability and cycle performance of the battery cell.

[0251] 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.

[0252] The above chain carboxylic ester solvent has relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0253] Optionally, R 1Includes 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.

[0254] Optionally, R 2 Includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2 Includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0255] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0256] Exemplarily, the chain carboxylic acid ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8,

[0257] In some embodiments, the organic solvent includes a carbonate solvent.

[0258] The carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0259] Optionally, the mass content of the carbonate solvent in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvent is 65%, 70%, 75%, or a range composed of any two of the above values.

[0260] When the mass contents of the carbonate solvent and the chain carboxylic acid ester solvent meet the above conditions, the stability of the electrolyte can be improved, the gas generation amount can be reduced, and the cycle performance can be improved.

[0261] Exemplarily, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0262] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0263] 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. The compound use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, reduce the gas generation amount during high-temperature storage, and can improve the cycle performance of the battery cell; and the transference number of lithium ions increases, the lithium ion conduction ability increases, and the fast charging ability of the battery cell can be improved.

[0264] Exemplarily, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide, and may be lithium bis(fluorosulfonyl)imide optionally.

[0265] 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 the range composed of any two of the above values. Optionally, the mass content of the lithium salt is 4% to 16%.

[0266] Exemplarily, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and may be 4% to 16% optionally.

[0267] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of the lithium fluorosulfonylimide to the mass content of the lithium hexafluorophosphate is 0.2 to 1.5, such as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or the range composed of any two of the above values. Optionally, the ratio of the mass content of the lithium fluorosulfonylimide to the mass content of the lithium hexafluorophosphate is 0.4 to 0.8.

[0268] When the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide satisfies the above range, on the one hand, the content of hydrofluoric acid can be reduced, the side reaction at the negative electrode interface can be slowed down, and the gas generation amount during high-temperature storage can be reduced; on the other hand, the content of the organic component of the interface film formed at the negative electrode interface is appropriate, and the gas generation amount during high-temperature storage can also be reduced, and the cycle performance can be improved.

[0269] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. 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.

[0270] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 10%. Exemplarily, the mass content of the additive in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. Optionally, the mass content of the additive in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0271] The additives with the above mass contents can effectively improve the interfacial film properties on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycling performance.

[0272] In some embodiments, the carbonate additives include one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive comprises fluoroethylene carbonate and vinylene carbonate.

[0273] Fluoroethylene carbonate can form a solid electrolyte interface film (SEI film) rich in lithium fluoride (LiF) on the surface of the negative electrode, which can relieve the volume expansion of silicon, improve the lifespan of the silicon-containing system, and reduce the gas generation amount 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 amount at high temperatures.

[0274] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate.

[0275] Optionally, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

[0276] 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 devices and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0277] 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 devices 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.

[0278] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, the components are classified. Chain carboxylic acid ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as constituent components of the organic solvent. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0279] Fluorinated cyclic carbonates, vinylene carbonate, etc. are used as additives to the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0280] Separator In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0281] In some embodiments, the separator is a separator membrane. The present application does not have any particular limitation on the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0282] 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 any particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without any 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.

[0283] In some embodiments, the volumetric energy density of the battery cell is 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 any range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0284] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.8 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration. The battery cell is placed at 25°C and charged at a constant current of 0.05C to 3.8V, then discharged at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the shell), and calculate the volume V0 of the single cell, unit: L. The volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0285] Example 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.

[0286] Example 1 1. Preparation of the positive electrode sheet The positive electrode sheet includes a positive electrode tab, a positive electrode current collector part, and positive electrode active material layers provided on both sides of the positive electrode current collector part. The positive electrode current collector part is aluminum foil. There are two positive electrode tabs, which are respectively connected to both sides of the positive electrode current collector part along the length direction.

[0287] The positive electrode active material 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 active material layer is a film layer formed by uniformly coating the positive electrode slurry (solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collector part and then drying and cold pressing.

[0288] 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, and the mass content of the positive electrode additive in the positive electrode active material layer is 1.85%. The single-sided coating weight of the positive electrode active material layer is 284 mg / 1540.25 mm 2 . The length of the positive electrode active material layer is 592 mm.

[0289] 2. Preparation of the negative electrode sheet The negative electrode sheet includes a negative electrode tab, a negative electrode current collector part, and negative electrode active material layers provided on both sides of the negative electrode current collector part. The negative electrode current collector part is copper foil. There are two negative electrode tabs, which are respectively connected to both sides of the negative electrode current collector part along the length direction.

[0290] The negative electrode active material layer is a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative electrode current collector part and then drying and cold-pressing it.

[0291] The single-sided coating weight of the negative electrode active material layer is 135 mg / 1540.25 mm 2 。

[0292] The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is located on the surface of the negative electrode current collector part, and the second negative electrode active material layer is located on the surface of the first negative electrode active material layer.

[0293] The first negative electrode active material layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.3:0.5:2.5:0.7. The negative electrode active material of the first negative electrode active material layer includes artificial graphite and silicon carbide; The second negative electrode active material layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickening agent sodium carboxymethyl cellulose with a mass ratio of 97.8:0.7:0.8:0.7. The negative electrode active material of the second negative electrode active material layer includes artificial graphite and silicon carbide; 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.

[0294] The ratio of the thickness of the first negative electrode active material layer to the thickness of the second negative electrode active material layer is 1; the conductive agents of the first negative electrode active material layer and the second negative electrode active material layer both include conductive carbon and carbon nanotubes, and the mass ratio of conductive carbon to carbon nanotubes in the first negative electrode active material layer and the second negative electrode active material layer is both 5:1.

[0295] The mass content of silicon element in the negative electrode active material layer is 3.0%. The charging specific capacity of the negative electrode active material is 420 mAh / g.

[0296] 3. Separator The separator includes a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0297] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive. The components of the organic solvent are mixed, and the lithium salt and the additive are added to prepare the electrolyte.

[0298] The organic solvent includes 15% chain carboxylic acid ester solvent (ethyl acetate) and 68.5% carbonate solvent (ethylene carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte solution.

[0299] Based on the mass of the electrolyte solution, the mass content of the additive is 2.5% vinylene carbonate VC.

[0300] The lithium salt includes 10% lithium hexafluorophosphate LiPF 6 and 4% lithium bis(fluorosulfonyl)imide.

[0301] 5. Preparation of battery cells Stack the above-mentioned positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging shell, inject the electrolyte solution 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 active material layer of the battery cell at 100% SOC is 2.62 g / cm 3 , and the compaction density of the negative electrode active material layer at 0% SOC is 1.30 g / cm 3 .

[0302] Comparative Example 1-1 and Comparative Example 1-2 Prepare battery cells using a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the positive electrode active material layer and the negative electrode active material layer is adjusted.

[0303] Examples 2-1 to 2-4 Prepare battery cells using a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the positive electrode active material layer and the negative electrode active material layer is adjusted.

[0304] Examples 2-5 and 2-6 Prepare battery cells using a method similar to that of Example 1. Different from Example 1, the compaction density of the positive electrode active material layer and the negative electrode active material layer is adjusted.

[0305] Performance test 1. DC resistance DCR test of battery cells The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0306] 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, and discharge it at a constant current of 0.33 C to 2.0 V, and record the discharge capacity A at this time0 , in Ah, and then charge it at a constant current of 0.33C with 0.5A 0 Ah, and adjust the SOC to 50%.

[0307] After leaving the battery cell at 25°C for 2 h, discharge it at a current of 4C for 10 s, and record ∆U 放电 , ∆I 放电 , and obtain 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 represents the voltage change within 10 s at the start of discharge, and ∆I 放电 represents the current value within 10 s at the start of discharge.

[0308] 2. High-temperature cycling performance test of the battery cell In an environment of 60±5°C, charge the battery cell at a constant current of 1C until the charge cut-off voltage, 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 until the discharge cut-off voltage. This is one charge-discharge cycle.

[0309] The discharge capacity 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 cycling n times, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of the battery cell = Cn / C1×100%, and 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.

[0310] 3. Normal-temperature cycling performance test of the battery cell 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; 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.

[0311] 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.

[0312] 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.

[0313] 4. Fast charging time test for 20% to 80% SOC of the battery cell Under the environment of 25±5℃, 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 4.76C constant current; Charge from 65% SOC to 70% SOC at 4.36C constant current; Charge from 70% SOC to 75% SOC at 3.94C constant current; Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0314] The test results are shown in Table 1.

[0315] Table 1

[0316] The coating weight of the positive and negative active material 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 active material 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 active material 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.

[0317] Increasing the coating weight of the positive and negative active material layers is beneficial to improving the volume energy density of the battery cell. As the single-sided coating weight of the positive active material 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.

[0318] The single-sided coating weight of the positive electrode active material 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 active material 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.

[0319] 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.

[0320] Embodiments 2-5 and 2-6 can effectively improve the volume energy density of the battery cell by setting the compaction density of the positive and negative electrode active material layers within an appropriate range, and can effectively improve the cycle performance of the battery cell under high energy density and fast charging.

[0321] Comparative Example 2-1 and Comparative Example 2-2 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the length of the positive electrode active material layer was adjusted.

[0322] Comparative Example 2-3 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the positive electrode tab was disposed on one side of the positive electrode coating portion in the length direction, and the negative electrode tab was disposed on one side of the negative electrode coating portion in the length direction.

[0323] Example 3-1 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the length and the single-sided coating weight of the positive electrode active material layer were adjusted.

[0324] Example 3-2 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the length of the positive electrode active material layer was adjusted.

[0325] The test results are shown in Table 2.

[0326] Table 2

[0327] The length of the positive electrode active material layer of Comparative Example 2-1 was small, resulting in a small energy density of the battery single cell; the length of the positive electrode active material layer of Comparative Example 2-2 was long, and the electron transport path was long, resulting in a high internal resistance and poor cycling performance of the battery single cell.

[0328] The positive electrode tab of Comparative Example 2-3 was disposed on one side of the positive electrode coating portion in the length direction, and the electron transport path in the positive electrode coating portion was long, resulting in a high internal resistance and poor cycling performance of the battery single cell.

[0329] However, for Example 3-1 and Example 3-2 of the present application, the length of the positive electrode active material layer was within an appropriate range, and the energy density of the battery single cell was relatively high; the positive electrode tabs were disposed on both sides of the positive electrode coating portion in the length direction, which could shorten the electron transport path in the length direction of the positive electrode coating portion, reduce the internal resistance of the battery single cell, improve the fast charging ability, and was beneficial to the improvement of the cycling performance under fast charging conditions; due to the reduction of the internal resistance, the heat generation was reduced, which could alleviate the decomposition of the electrolyte components caused by heat accumulation, thereby improving the high temperature cycling performance.

[0330] Example 4-1 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the volume average particle size Dv50 of the lithium-containing phosphate was adjusted.

[0331] Example 4-2 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the material of the positive electrode additive was adjusted.

[0332] Example 4-3 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the volume average particle size Dv50 of the positive electrode additive was adjusted.

[0333] Example 4-4 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the mass content of the positive electrode additive in the positive electrode active material layer was adjusted.

[0334] The test results are shown in Table 3.

[0335] Table 3

[0336] The smaller the volume average particle size of the lithium-containing phosphate in Example 1 and Example 4-1, the more beneficial it is to increase the active surface, increase the contact area with the conductive agent, etc., improve the conductive performance, reduce the internal resistance of the battery single cell, and improve the cycle performance under fast charging conditions; and due to the reduction of the internal resistance, the heat generation is reduced, which can alleviate the decomposition of the electrolyte components caused by heat accumulation, thereby improving the high-temperature cycle performance.

[0337] The positive electrode additive can be used as a lithium supplement agent to make up for the lithium loss in the battery single cell. The positive electrode additive can include various materials such as lithium ferrite and lithium nickelate. When the volume average particle size of the positive electrode additive in Examples 4-1 to 4-4 meets 8 μm to 10 μm, it can effectively release lithium ions for lithium supplementation and improve the cycle life of the battery single cell; as the particle size increases, the active surface decreases, and the interface for side reactions with the electrolyte at high temperature decreases, and the high-temperature cycle performance is improved. As the addition amount of the positive electrode additive increases, the lithium supplementation effect is improved. When the mass content of the positive electrode additive is 0.1% to 5%, the cycle life of the battery single cell can be effectively improved.

[0338] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as limitations on the implementation manners of the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the implementation manners of the present application.

Claims

1. A battery cell, characterized in that: An electrode assembly is included, wherein the electrode assembly includes: A plurality of positive electrode sheets, each of which comprises a positive electrode coating portion and at least two positive electrode tabs, the positive electrode coating portion is provided with a positive electrode active material layer, the at least two positive electrode tabs are connected to both sides of the positive electrode coating portion along the length direction of the battery cell, and the positive electrode active material layer comprises a lithium-containing phosphate; A plurality of negative electrode sheets, wherein the plurality of negative electrode sheets and the plurality of positive electrode sheets are stacked along the thickness direction of the battery cell, each of the negative electrode sheets comprises a negative electrode coating portion and at least two negative electrode tabs, the negative electrode coating portion is provided with a negative electrode active material layer, the at least two negative electrode tabs are connected to both sides of the negative electrode coating portion along the length direction, and the negative electrode active material layer comprises a carbon-based material, The negative electrode sheet satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all negative electrode ears located on the same side of the negative electrode coating portion; W3 represents the average size of the negative electrode ear along the width direction of the battery cell; W4 represents the dimension of the negative electrode coating portion along the width direction; in, The single-sided coating weight of the positive electrode active material layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 ; The single-sided coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 ; The positive electrode coating portion has a dimension in the length direction of 265 mm to 655 mm.

2. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the positive electrode active material 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 active material 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 lithium-containing phosphate includes lithium iron phosphate.

4. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate is in a granular form, and a volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm.

5. The battery cell according to claim 1, characterized in that: The positive electrode active material layer also includes a positive electrode additive, which includes one or more of a lithium-containing ternary material, lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate and lithium ferrite.

6. The battery cell according to claim 5, characterized in that: The volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm.

7. The battery cell according to claim 5, characterized in that: The mass content of the positive electrode additive is 0.1% to 5% based on the mass of the positive electrode active material layer.

8. The battery cell according to claim 1, characterized in that: The negative electrode active material layer further includes a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode active material layer is 0.3% to 10%.

9. The battery cell according to claim 8, characterized in that: The silicon-based material includes one or more of silicon carbide and silicon oxide.

10. The battery cell according to claim 1, characterized in that: The negative electrode coating portion further includes a negative electrode current collecting portion, and the negative electrode active material layer includes: A first region is disposed on the surface of the negative electrode current collecting portion, wherein the thickness of the first region is 1 / 3 of the thickness of the negative electrode active material layer; and A second region is connected to a side of the first region away from the negative electrode current collecting portion, and a thickness of the second region is 1 / 3 of a thickness of the negative electrode active material 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.

11. The battery cell according to claim 10, 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.

12. The battery cell according to claim 10, 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.

13. The battery cell according to claim 1, characterized in that: The negative electrode coating portion further includes a negative electrode current collecting portion, and the negative electrode active material layer includes: A first negative electrode active material layer is disposed on the surface of the negative electrode current collecting portion; The second negative electrode active material layer is connected to a side of the first negative electrode active material layer away from the negative electrode current collecting portion.

14. The battery cell according to claim 1, characterized in that: A ratio of a dimension of the positive electrode coating portion along the length direction to a dimension of the positive electrode coating portion along a width direction of the battery cell is 2 to 12.

5.

15. The battery cell according to claim 1, characterized in that: There are at least two positive electrode ears located on the same side of the positive electrode coating portion; and / or There are at least two negative electrode ears located on the same side of the negative electrode coating portion.

16. The battery cell according to claim 1, characterized in that: The positive electrode sheet satisfies: n×W1 / W2 is 0.2 to 1.0; n represents the number of all positive electrode ears located on the same side of the positive electrode coating portion; W1 represents the average size of the positive electrode tab along the width direction of the battery cell; W2 represents the dimension of the positive electrode coating portion along the width direction.

17. The battery cell according to claim 1, characterized in that: The battery cell further includes at least two positive terminals, and the at least two positive terminals are respectively disposed on both sides of the positive electrode coating portion along the length direction.

18. The battery cell according to claim 1, characterized in that: The battery cell further includes at least two negative electrode terminals, and the at least two negative electrode terminals are respectively disposed on both sides of the negative electrode coating portion along the length direction.

19. The battery cell according to claim 1, characterized in that: The battery cell also includes an electrolyte, 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.

20. The battery cell according to claim 1, characterized in that The battery cell further includes an electrolyte, and the electrolyte further includes a chain carboxylate solvent, wherein the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%.

21. The battery cell according to claim 20, 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.

22. The battery cell according to claim 19, characterized in that: The electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%.

23. The battery cell according to claim 22, characterized in that: The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

24. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 23.

25. An electrical device, characterized in that: Comprising a battery device as claimed in claim 24.

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