Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises a positive pole piece, a negative pole piece and an electrolyte, the positive pole piece comprises a positive pole current collecting part and a positive pole film layer, and the positive pole film layer comprises lithium-containing phosphate; the negative pole piece comprises a negative pole current collecting part and a negative pole film layer, and the single-side coating weight of the negative pole film layer is 80 mg / 1540.25 mm < 2 > to 135 mg / 1540.25 mm < 2 >; the negative electrode film layer comprises a carbon-based material and a silicon-based material, and the mass content of the silicon element of the silicon-based material in the negative electrode film layer is 0.3-6%; the electrolyte comprises a chain carboxylic ester solvent and an additive, the mass content of the chain carboxylic ester solvent in the electrolyte is 5%-35%, the additive comprises one or more of a carbonic ester additive, a sulfur-containing additive and a lithium salt additive, and the mass content of the additive in the electrolyte is 0.5%-10%. The rapid charging capability and the cycle performance of the battery monomer can be further improved.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 071110 filed on January 7, 2025, entitled “Battery Cell, Battery Device, and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to a battery cell, a battery device and an electric device. Background Art

[0003] Battery cells have the characteristics of high capacity and long life, so they are widely used in electronic devices such as mobile phones, laptops, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc. As batteries have made great progress, higher requirements are placed on battery performance. However, the fast charging capability and cycle performance of battery cells need to be further improved. Summary of the invention

[0004] The present application provides a battery cell, a battery device and an electrical device. The fast charging capability and cycle performance of the battery cell of the present application can be further improved.

[0005] In the first aspect, the embodiment of the present application proposes a battery cell, the battery cell includes a positive electrode sheet and a negative electrode sheet and an electrolyte, the positive electrode sheet includes a positive electrode collector and a positive electrode film layer arranged on at least one side of the positive electrode collector, the positive electrode film layer includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode collector and a negative electrode film layer arranged on at least one side of the negative electrode collector, and the single-sided coating weight of the negative electrode film layer is 80mg / 1540.25mm 2 Up to 135mg / 1540.25mm 2 The negative electrode film layer includes a carbon-based material and a silicon-based material, and the mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.3% to 6%; the electrolyte includes a chain carboxylate solvent and an additive, and the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%; the additive includes one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive, and the mass content of the additive in the electrolyte is 0.5% to 10%.

[0006] Therefore, the negative electrode plate of the embodiment of the present application includes a silicon-based material, which can make the coating thickness of the negative electrode plate relatively thin at a preset energy density. Specifically, the single-sided coating weight of the negative electrode film layer is 80 mg / 1540.25 mm 2 Up to 135mg / 1540.25mm 2. When the single-sided coating weight of the negative electrode film layer meets the above range, it is combined with an appropriate mass content of silicon-based materials to improve the energy density of the battery cell, and can also shorten the migration path of active ions in the negative electrode film layer. The migration rate of active ions in the negative electrode film layer is relatively fast, which is beneficial to reduce the polarization phenomenon under high-rate charging and improve the fast charging ability of the battery cell; and when the mass content of the chain carboxylic acid ester solvent in the electrolyte is within the above range, on the one hand, the migration rate of active ions in the electrolyte is relatively fast; on the other hand, it can alleviate the interface side reaction between the negative electrode active material and the electrolyte, reduce the high-temperature gas production, and improve the cycle performance of the battery cell; further, the electrolyte also includes additives, which can repair the solid electrolyte SEI membrane SEI membrane on the negative electrode side, and the formed SEI membrane has a relatively low impedance, which can effectively improve the fast charging ability and cycle performance of the battery cell.

[0007] In some embodiments, the mass content of silicon in the silicon-based material in the negative electrode film layer is 3% to 6%. When the mass content of silicon is within the above range, the capacity of the negative electrode active material can be increased, which is beneficial to improving the energy density of the battery cell; and during the charge and discharge process, the volume expansion of silicon will not be too large, which is beneficial to maintaining the stability of the negative electrode SEI film and improving the cycle performance of the battery cell.

[0008] In some embodiments, the silicon-based material includes one or more of silicon carbide and silicon oxide.

[0009] In some embodiments, the negative electrode film layer includes a first region and a second region, the first region is disposed on the surface of the negative electrode current collector, and the thickness of the first region is 1 / 3 of the thickness of the negative electrode film layer; the second region is connected to the side of the first region away from the negative electrode current collector, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode film layer, wherein the average particle size of the carbon-based material in the first region is greater than or equal to the average particle size of the carbon-based material in the second region. The difference in particle size between the first region and the second region can improve the fast charging performance of the battery cell.

[0010] 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, the solid-phase transmission path of lithium ions can be shortened and the fast charging performance can be improved; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material.

[0011] In some embodiments, the average particle size of the carbon-based material in the second region is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second region is within the above range, it is beneficial to improve the fast charging capability of the battery cell and improve the stability of the material.

[0012] In some embodiments, 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. The above material setting is conducive to forming a pore difference between the first region and the second region, and improving the fast charging capability of the battery cell.

[0013] In some embodiments, at least one of the first region and the second region includes a silicon-based material, which is beneficial for improving the energy density of the battery cell.

[0014] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, wherein the first negative electrode film layer is disposed on the surface of the negative electrode current collector; and the second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collector. The double-layer film layer is beneficial to improving the fast charging capability and energy density of the battery cell.

[0015] In some embodiments, the negative electrode film layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of conductive carbon and carbon nanotubes. The negative electrode conductive agent can improve the conductivity of the negative electrode film layer and improve the fast charging capability.

[0016] In some embodiments, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%; when the mass content of the conductive carbon is within the above range, the conductivity of the negative electrode film layer can be improved and the fast charging capability can be improved.

[0017] In some embodiments, the mass content of carbon nanotubes in the negative electrode film layer is 0.1% to 1%. When the mass content of carbon nanotubes is within the above range, the conductivity of the negative electrode film layer can be improved and the fast charging capability can be improved.

[0018] In some embodiments, the conductivity of the electrolyte at room temperature is 10.5 mS / cm to 13.5 mS / cm; when the conductivity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0019] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s; when the viscosity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0020] 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 high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0021] In some embodiments, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 8% to 20%. When the mass content of the chain carboxylic acid ester solvent is within the above range, the fast charging capability and cycle performance of the battery monomer can be improved.

[0022] In some embodiments, the linear carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R 1 including a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 haloalkyl group, R 2 Includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0023] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0024] In some embodiments, the linear carboxylate solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-8.

[0025] In some embodiments, the electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%.

[0026] When the mass content of carbonate solvents and chain carboxylic acid ester solvents meets the above conditions, the stability of the electrolyte can be improved, its high-temperature gas production can be reduced, and the high-temperature cycle performance can be improved.

[0027] In some embodiments, the carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0028] In some embodiments, the mass content of the additive in the electrolyte is 2% to 6%. The above mass content of the additive can effectively improve the SEI film performance on the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0029] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate.

[0030] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate.

[0031] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0032] In some embodiments, the electrolyte further comprises one or more of fluorinated sulfonyl imide lithium and lithium hexafluorophosphate. The above lithium salts are easy to dissociate, which is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and not easy to decompose, which can improve the cycle performance of the battery cell.

[0033] In some embodiments, the fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide.

[0034] In some embodiments, the mass content of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 18%, and can be 4% to 16%. The above lithium salt is beneficial to improving the cycle performance of the battery monomer.

[0035] In some embodiments, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and it is beneficial to reduce the polarization phenomenon under high-rate charging, and can take into account the improvement of the energy density and fast charging performance of the battery cell.

[0036] In a second aspect, the embodiments of the present application further provide a battery device, comprising a battery cell according to any embodiment of the first aspect of the present application.

[0037] In a third aspect, an embodiment of the present application further proposes an electrical device, which includes a battery device as in any embodiment of the second aspect or the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

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

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

[0041] The following are the descriptions of the reference numerals: X, thickness direction; Y, width direction; Z, length direction; 1. Electric device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodation space; 6. Battery module; 7. Battery cells; 10. Electrode assembly; 11. first pole piece; 111. first pole ear; 1111. first end; 112. first coating portion; 12, second pole piece; 121, second pole ear; 1211, second end; 122, second coating portion; 13. Isolation parts; 14, negative electrode plate; 141, negative electrode film layer; 142, negative electrode current collector; 1411, first negative electrode film layer; 1412, second negative electrode film layer; 141a, first region; 141b, second region; 141c, third region; 20. Shell assembly; 21. Shell; 22. End cover; 31. First electrode terminal; 32. Second electrode terminal. DETAILED DESCRIPTION

[0042] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed 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 the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the 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 described in the claims.

[0043] "Scope" disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. 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 range can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this document, and "0 to 5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0047] The term "plurality" used in the present application refers to two or more (including two).

[0048] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0049] The battery cell may be a lithium-ion battery, a sodium-lithium-ion battery, etc., which is not limited in the embodiments of the present application.

[0050] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, with the improvement of fast charging performance requirements, this can be achieved in related technologies by increasing the conductivity of the electrolyte. However, the increase in conductivity may lead to decomposition of the electrolyte at high temperatures, which increases the high-temperature gas production of the battery cells, and may deteriorate the cycle performance of the battery cells, making it impossible to improve both the fast charging performance and the cycle performance of the battery cells, especially at high energy density. It is impossible to improve both the fast charging performance and the cycle performance.

[0051] In view of the above problems, the embodiments of the present application improve the cycle performance and reliability of the battery cell by synergistically regulating the positive electrode sheet, the negative electrode sheet and the electrolyte; specifically, the negative electrode sheet of the battery cell includes a negative electrode active material containing a silicon-based material, which is conducive to improving the energy density at a thinner coating thickness; The negative electrode plate includes a silicon-based material, which is conducive to thin coating. Active ions such as lithium ions can migrate quickly in the negative electrode plate. With an appropriate amount of chain carboxylic acid ester solvent, the migration rate of lithium ions in the electrolyte can be increased, thereby increasing the liquid phase transmission rate of lithium ions, thereby improving the fast charging capability of the battery cell; However, negative electrode active materials containing silicon-based materials are more likely to undergo side reactions with the electrolyte, resulting in increased gas production, while the mass content of the chain carboxylic acid ester solvent in the embodiment of the present application is less than or equal to 35%, which can enable active ions such as lithium ions to migrate rapidly while alleviating the side reactions between the negative electrode active materials and the electrolyte and reducing gas production; the electrolyte also includes additives, which can repair the solid electrolyte interface film SEI film on the negative electrode side, further alleviate the side reactions between the negative electrode active materials and the electrolyte, and improve the cycle performance; and the impedance of the SEI film is relatively low, which is beneficial to further improve the fast charging performance of the battery cell.

[0052] Therefore, the embodiments of the present application can comprehensively improve the cycle performance and fast charging capability of the battery cells under high energy density, and are beneficial to improving the cycle performance of the battery cells under fast charging.

[0053] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0054] Exemplarily, the power-consuming device may be a mobile phone, a portable device, a laptop computer, a battery car, an electric toy, an electric tool, a vehicle, a ship, a spacecraft, etc. Alternatively, exemplary, the power-consuming device is a spacecraft, which includes an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0055] Figure 1 1 is a schematic diagram of an exemplary electric device 1. The electric 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 electric device 1 for high power and high energy density, a battery pack or a battery module may be used.

[0056] A battery device is disposed inside the electric device 1, and the battery device can be disposed at the bottom, head, or tail of the electric device 1. The battery device can be used to power the electric device 1, for example, the battery device can be used as an operating power source for the electric device 1, and can also be used as a driving power source for the electric device 1, replacing or partially replacing fuel oil or natural gas to provide driving power for the electric device 1. Figure 1 The battery device shown in FIG. 2 is a battery pack 2 .

[0057] The electrical device 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery device to supply power to the motor 4 , for example, to meet the electrical power requirements of the electrical device 1 during startup, navigation, and driving.

[0058] A battery device may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, in parallel, or in mixed connection through a busbar.

[0059] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0060] As an example, the battery cell assembly may be a battery module (Battery Module), and the battery module is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, the battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0061] like Figure 2 As shown, in some embodiments, the battery device may be a battery pack 2 , which includes a box 5 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box 5 .

[0062] 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 .

[0063] As an example, the box body 5 includes a first box body portion 5a and a second box body portion 5b, and the box body 5 has a receiving space 5c. The first box body portion 5a and the second box body portion 5b are buckled together to form a closed space inside the box body 5 to accommodate the battery monomer assembly. The closed space here means covering or closing, which can be sealed or unsealed. The first box body portion 5a can be a top cover or a bottom plate.

[0064] 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 monomer assembly.

[0065] In some embodiments, the box 5 can be used as a part of the chassis structure of the vehicle. For example, part of the box 5 can become at least a part of the floor of the vehicle, or part of the box 5 can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0066] As an example, the battery cell assembly may be a battery module 6 , and the battery cell assembly may be accommodated in the box body 5 by fixing the battery module 6 in the box body 5 .

[0067] like Figure 3 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0068] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC, the temperature of the external environment of the battery device is room temperature, for example, 25°C.

[0069] Exemplarily, the charging step of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC may be performed as follows: Charge from 20% SOC to 25% SOC at 8.00C constant current; Charge from 25% SOC to 30% SOC at 8.00C constant current; Charge from 30% SOC to 35% SOC at 7.50C constant current; Charge from 35% SOC to 40% SOC at 6.87C constant current; Charge from 40% SOC to 45% SOC at 6.38C constant current; Charge from 45% SOC to 50% SOC at 5.95C constant current; Charge from 50% SOC to 55% SOC at 5.53C constant current; Charge from 55% SOC to 60% SOC at 5.14C constant current; 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.

[0070] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from a 20% state of charge to an 80% state of charge is 5 minutes to 30 minutes, optionally 5 minutes to 20 minutes, and the temperature of the external environment of the battery device at a 20% state of charge is room temperature, for example 25°C. Exemplarily, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min or a range consisting of any two of the above values.

[0071] like Figure 4 and Figure 5 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20 .

[0072] The housing assembly 20 has a housing cavity for accommodating the electrode assembly 10 and the electrolyte.

[0073] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0074] Exemplarily, the terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32 , one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0075] The shell can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell) or an aluminum-plastic film. In some embodiments, the shell can be a sealed structure or a non-sealed structure. As an example, when the shell is a non-sealed structure, the shell plays a role in protecting the electrode assembly 10, and a sealed bag is also included between the shell 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 shell is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0076] 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 polygonal battery, such as a hexagonal battery, etc. There is no special limitation in the present application.

[0077] In some embodiments, the housing includes an end cap 22 and a shell 21, wherein the shell 21 is provided with an opening, and the end cap 22 is provided to cover the opening. The shell 21 may be provided with one or more openings. One or more end caps 22 may also be provided.

[0078] The shape of the shell 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 shell 21 can be selected; if the electrode assembly 10 is a rectangular parallelepiped structure, a rectangular parallelepiped shell 21 can be selected. Optionally, both the electrode assembly 10 and the shell 21 are rectangular parallelepiped structures.

[0079] The electrode assembly 10 includes a first electrode sheet 11 , a second electrode sheet 12 and a separator 13 . One of the first electrode sheet 11 and the second electrode sheet 12 is a positive electrode sheet, and the other is a negative electrode sheet.

[0080] The electrode assembly 10 may be a winding structure, a laminated structure, or a mixed structure of winding and laminated structures. The electrode assembly 10 may be a laminated structure, which is beneficial to improving the energy density of the battery cell 7.

[0081] In some embodiments, the electrode assembly 10 is a wound structure. The first electrode sheet 11 and the second electrode sheet 12 are wound into a wound structure.

[0082] In other embodiments, the electrode assembly 10 is a laminated structure. As an example, a plurality of first electrode sheets 11 and a plurality of second electrode sheets 12 may be provided, respectively, and the plurality of first electrode sheets 11 and the plurality of second electrode sheets 12 are stacked.

[0083] As an example, a plurality of first pole sheets 11 may be provided, and the second pole sheet 12 may be folded to form a plurality of stacked folded segments, with one first pole sheet 11 being sandwiched between adjacent folded segments.

[0084] As an example, the first pole piece 11 and the second pole piece 12 are both folded to form a plurality of stacked folded segments.

[0085] As an example, a plurality of spacers 13 may be provided, each spacer 13 being provided between any adjacent first pole pieces 11 or second pole pieces 12 .

[0086] As an example, the spacer 13 may be disposed continuously, and disposed between any adjacent first pole pieces 11 or second pole pieces 12 by folding or winding.

[0087] In some embodiments, each electrode sheet is provided with an electrode tab, which can conduct current from the electrode assembly 10. The electrode tab includes a positive electrode tab and a negative electrode tab.

[0088] In some embodiments, the first pole piece 11 and the second pole piece 12 both include a coating portion and a pole ear portion, the coating portion is coated with an active material layer, the pole ear portion is arranged on at least one side of the coating portion along a first direction and is not coated with the active material layer, the first direction is parallel to the length direction Z of the battery cell 7, or the first direction is parallel to the width direction Y of the battery cell 7.

[0089] In the embodiment of the present application, the first direction, the second direction and the thickness direction X of the battery cell 7 are perpendicular to each other.

[0090] When the first direction is parallel to the length direction Z of the battery cell 7 , the dimension of the component in this direction can be considered as the length of the component. For example, the dimension of the coating portion along the first direction is the length of the coating portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7 .

[0091] When the first direction is parallel to the width direction Y of the battery cell 7 , the dimension of the component in this direction can be considered as the width of the component. For example, the dimension of the coating portion along the first direction is the width of the coating portion. In this case, the second direction is parallel to the length of the battery cell 7 .

[0092] In order to more clearly explain the present application, the pole ear portion of the first pole piece 11 is defined as the first pole ear 111, and the coating portion of the first pole piece 11 is defined as the first coating portion 112. The pole ear portion of the second pole piece 12 is defined as the second pole ear 121, and the coating portion of the second pole piece 12 is defined as the second coating portion 122. The electrode terminal having the same electrical properties and being electrically connected to the first pole ear 111 is the above-mentioned first electrode terminal 31, and the electrode terminal having the same electrical properties and being electrically connected to the second pole ear 121 is the above-mentioned second electrode terminal 32.

[0093] The polarities of the first electrode piece 11 and the second electrode piece 12 are opposite. When the first electrode piece 11 is a positive electrode piece, the second electrode piece 12 is a negative electrode piece, the first coating portion 112 is a positive electrode coating portion, the first electrode lug 111 is a positive electrode lug, the first electrode terminal 31 is a positive electrode terminal, the second coating portion 122 is a negative electrode coating portion, the second electrode lug 121 is a negative electrode lug, and the second electrode terminal 32 is a negative electrode terminal.

[0094] Alternatively, when the first electrode sheet 11 is a negative electrode sheet, the second electrode sheet 12 is a positive electrode sheet, the first coating portion 112 is a negative electrode coating portion, the first electrode lug 111 is a negative electrode lug, the first electrode terminal 31 is a negative electrode terminal, the second coating portion 122 is a positive electrode coating portion, the second electrode lug 121 is a positive electrode lug, and the second electrode terminal 32 is a positive electrode terminal.

[0095] The coating portion includes a current collecting portion and a film layer disposed on the current collecting portion and containing an active material. For example, the positive electrode coating portion includes a positive electrode current collecting portion and a positive electrode film layer disposed on the positive electrode current collecting portion and containing a positive electrode active material. For example, the negative electrode coating portion includes a negative electrode current collecting portion and a negative electrode film layer disposed on the negative electrode current collecting portion and containing a negative electrode active material.

[0096] like Figures 6 to 8 As shown, in some embodiments, in the first pole piece 11, the pole ear portion is disposed on at least one side of the coating portion along the first direction, and the first pole piece 11 satisfies: n*W1 / W2 is 0.2 to 1.0; n represents the number of all the lugs located on the same side of the coating portion; W1 represents the average size of the pole ear portion along the second direction; W2 represents the dimension of the coating portion along the second direction. The second direction is perpendicular to the first direction and the thickness direction X.

[0097] 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 consisting of any two of the above values. Optionally, n*W1 / W2 is 0.5 to 1.0.

[0098] When n*W1 / W2 satisfies the above range, the flow area of ​​the pole ear is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0099] W1 represents an average size of the first electrode tab 111 along the second direction.

[0100] When the first pole tab 111 is a special-shaped structure, for example, along the first direction, the size of the first pole tab 111 along the second direction gradually increases. In this case, the sizes of the first pole tab 111 along the second direction at multiple locations can be measured, thereby calculating the average size of the first pole tab 111 along the second direction. Of course, the sizes of the first pole tab 111 along the second direction at various locations can be the same value, in which case, the value can be used as the average size of the first pole tab 111.

[0101] There may be one or more first pole lugs 111 , for example, n is 1 to 4. In the case of multiple first pole lugs 111 , the average size of each first pole lug 111 may be measured respectively, and then the average size values ​​are added up and divided by the number of first pole lugs 111 to calculate the average size of the first pole lugs 111 .

[0102] The first pole ear 111 is connected to the first coating portion 112, and the first pole ear 111 includes a first end 1111 connected to the first coating portion 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first pole ear 111 itself is relatively large, and the contact area between the first pole ear 111 and the first coating portion 112 is relatively large. The first pole ear 111 has a strong current carrying capacity, which can improve the fast charging performance and cycle performance of the battery cell 7.

[0103] Optionally, the first pole tab 111 and the current collecting portion of the first coating portion 112 are of an integrated structure, so that the internal resistance of the first pole piece 11 is relatively low, and the cycle performance of the battery cell 7 can be further improved.

[0104] In some embodiments, the first pole piece 11 includes at least one first pole lug 111 , for example, 1 to 4 first pole lugs 111 . Optionally, the first pole piece 11 includes at least two first pole lugs 111 , and optionally four first pole lugs 111 .

[0105] In some embodiments, one or more first electrode tabs 111 are disposed on at least one side of the coating portion along the width direction Y.

[0106] like Figures 6 to 8 As shown, for example, one or more first pole ears 111 are arranged on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all the first pole ears 111 are arranged on the same side of the first coating portion 112 along the width direction Y. This arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7. Figure 6 In FIG. 1 , W1 represents the size of a single first electrode tab 111 along the length direction Z, and n is 1; W2 represents the size of the first coating portion 112 along the length direction Z. Figure 7 In FIG. 1 , n is 4, and the sizes of the first pole tabs 111 are the same. W1 may represent the size of a single first pole tab 111 . Of course, the sizes of the first pole tabs 111 may be slightly different. Figure 8 In this example, n is 1 and n*W1 / W2 is 1.

[0107] like Fig. 9 As shown, for example, in the case where the first electrode sheet 11 includes a plurality of first electrode tabs 111 , the plurality of first electrode tabs 111 are disposed on both sides of the first coating portion 112 along the width direction Y.

[0108] Optionally, when a plurality of first pole tabs 111 are disposed on at least one side of the first coating portion 112 along the width direction Y, there are at least two first pole tabs 111 located on the same side of the first coating portion 112 along the width direction Y, such as two, three, four, five, six, etc.; four are optional. This arrangement is conducive to uniform distribution of electrons in the first pole piece 11, and is conducive to improving fast charging performance.

[0109] Optionally, the distance between two adjacent first electrode tabs 111 along the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range consisting of any two of the above values. Fig. 9 In FIG. 1 , Z1 represents the distance between two adjacent first electrode tabs 111 along the length direction Z.

[0110] When the distance between two adjacent first pole tabs 111 along the length direction Z meets the above range, it is beneficial for the current to be evenly distributed in the current collecting portion, and is beneficial for improving the fast charging performance.

[0111] In some other embodiments, the first pole piece 11 includes one or more first pole tabs 111 ; the one or more first pole tabs 111 are disposed on at least one side of the first coating portion 112 along the length direction Z.

[0112] like Fig.10 As shown, for example, one or more first pole tabs 111 are disposed on one side of the first coating portion 112 along the length direction Z. In this case, it can be understood that all first pole tabs 111 are disposed on the same side of the first coating portion 112 along the length direction Z.

[0113] like Fig.11 and Fig.12 As shown, for example, in the case where the first pole sheet 11 includes a plurality of first pole tabs 111 , the plurality of first pole tabs 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z.

[0114] Optionally, a plurality of first pole tabs 111 are respectively arranged on both sides of the first coating portion 112 along the length direction Z. This arrangement can shorten the transmission path of electrons in the first pole piece 11, which is conducive to improving the fast charging performance. For example, two first pole tabs 111 are located on one side of the first coating portion 112 along the length direction Z, and the other two first pole tabs 111 are located on the other side of the first coating portion 112 along the length direction Z.

[0115] Optionally, when a plurality of first pole tabs 111 are respectively disposed on at least one side of the first coating portion 112 along the length direction Z, there are at least two first pole tabs 111 located on the same side of the first coating portion 112 along the length direction Z, for example, two, three, four, five, six, etc. This arrangement is conducive to uniform distribution of electrons in the first pole piece 11, and is conducive to improving fast charging performance.

[0116] Optionally, the distance between two adjacent first electrode tabs 111 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range consisting of any two of the above values.

[0117] like Fig.13 As shown, in some embodiments, in the second pole piece 12, the pole ear portion is disposed on at least one side of the coating portion along the first direction, and the second pole piece 12 satisfies: m*W3 / W4 is 0.2 to 1.0; m represents the number of all the lugs located on the same side of the coating portion; W3 represents the average size of the pole ear portion along the second direction; W4 represents the dimension of the coating portion along the second direction.

[0118] 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 consisting of any two of the above values. Optionally, m*W3 / W4 is 0.5 to 1.0.

[0119] When m*W3 / W4 satisfies the above range, the flow area of ​​the second electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0120] W3 represents the average size of the second pole lug 121 along the second direction. There may be one or more second pole lugs 121. For example, m is 1 to 4. When there are multiple second pole lugs 121, the size of each second pole lug 121 can be measured by a micrometer to calculate the average size.

[0121] The second pole ear 121 is connected to the second coating portion 122, and the second pole ear 121 includes a second end 1211 connected to the second coating portion 122. When n*W3 / W4 satisfies the above range, it means that the cross-section of the second end 1211 along the thickness direction of the second pole ear 121 itself is relatively large, and the contact area between the second pole ear 121 and the second coating portion 122 is relatively large. The second pole ear 121 has a strong current carrying capacity, which can improve the fast charging performance and cycle performance of the battery cell 7.

[0122] Optionally, the current collecting portion of the second pole tab 121 and the second coating portion 122 is an integrated structure, so that the internal resistance of the second pole piece 12 is relatively low, which can further improve the fast charging performance and cycle performance of the battery cell 7 .

[0123] In some embodiments, the second pole piece 12 includes at least one second pole tab 121 , and may optionally include at least two second pole tabs 121 , and may optionally include four second pole tabs 121 .

[0124] In some embodiments, one or more second pole tabs 121 are disposed on at least one side of the coating portion along the width direction Y. For example, one or more second pole tabs 121 are disposed on one side of the second coating portion 122 along the width direction Y. In this case, it can be understood that all second pole tabs 121 are disposed on the same side of the second coating portion 122 along the width direction Y. Or, for example, in the case where the second pole piece 12 includes a plurality of second pole tabs 121, the plurality of second pole tabs 121 are disposed on both sides of the second coating portion 122 along the width direction Y.

[0125] Optionally, one or more second electrode tabs 121 are respectively arranged on one side of the second coating portion 122 along the width direction Y. This arrangement is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0126] Optionally, when a plurality of second pole tabs 121 are disposed on at least one side of the coating portion along the width direction Y, there are at least two second pole tabs 121 located on the same side of the second coating portion 122 along the width direction Y, such as two, three, four, five, six, etc.; four may be selected. This arrangement is conducive to uniform distribution of electrons in the second pole piece 12, and is conducive to improving fast charging performance.

[0127] Optionally, the distance between two adjacent second electrode tabs 121 along the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range consisting of any two of the above values.

[0128] like Fig.14As shown, in other embodiments, the second pole piece 12 includes one or more second pole tabs 121; one or more second pole tabs 121 are arranged on at least one side of the second coating portion 122 along the length direction Z. For example, one or more second pole tabs 121 are arranged on one side of the second coating portion 122 along the length direction Z. In this case, it can be understood that all second pole tabs 121 are arranged on the same side of the second coating portion 122 along the length direction Z. Or, for example, in the case where the second pole piece 12 includes multiple second pole tabs 121, the multiple second pole tabs 121 are respectively arranged on both sides of the second coating portion 122 along the length direction Z.

[0129] Optionally, a plurality of second pole tabs 121 are respectively arranged on both sides of the second coating portion 122 along the length direction Z. This arrangement can shorten the transmission path of electrons in the second pole piece 12, which is beneficial to improving the fast charging performance.

[0130] Optionally, when a plurality of second pole tabs 121 are disposed on at least one side of the second coating portion 122 along the length direction Z, there are at least two second pole tabs 121 located on the same side of the second coating portion 122 along the length direction Z, such as two, three, four, five, six, etc. This arrangement is conducive to uniform distribution of electrons in the second pole piece 12, and is conducive to improving fast charging performance.

[0131] Optionally, the distance between two adjacent second electrode tabs 121 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range consisting of any two of the above values.

[0132] like Fig.15 As shown, in some embodiments, the terminal assembly can be disposed on the housing 21 , or the terminal assembly can be disposed on the end cover 22 .

[0133] The terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32 . The first electrode terminal 31 is connected to the first electrode tab 111 , and the second electrode terminal 32 is connected to the second electrode tab 121 .

[0134] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 may be disposed on the housing 21 , or the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22 . Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22 .

[0135] The first electrode terminal 31 and the second electrode terminal 32 may be disposed on the same end cap 22 at the same time. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are disposed at intervals on the end cap 22. For another example, there are two end caps 22, and the two end caps 22 are disposed opposite to each other, and each end cap 22 is provided with the first electrode terminal 31 and the second electrode terminal 32.

[0136] The first electrode terminal 31 and the second electrode terminal 32 are respectively arranged on different end covers 22 . For example, there are two end covers 22 , which are arranged opposite to each other. The first electrode terminal 31 is arranged on one of the end covers 22 , and the second electrode terminal 32 is arranged on the other end cover 22 .

[0137] In some embodiments, there is at least one first electrode terminal 31 , and may be at least two, such as two, three or four.

[0138] In some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0139] like Fig.15 As shown, for example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0140] like Fig.16 As shown, for example, a plurality of first electrode terminals 31 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0141] Exemplarily, there are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplary, there are four first electrode terminals 31, two of which are disposed on one side of the electrode assembly 10, and the other two first electrode terminals 31 are disposed on one side of the electrode assembly 10.

[0142] In the embodiment of the present application, the first pole tab 111 and the first electrode terminal 31 may be directly connected or indirectly connected; when the first pole tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, which is located between the first electrode terminal 31 and the first pole tab 111 and connects the first electrode terminal 31 and the first pole tab 111.

[0143] In the above-mentioned embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0144] In other embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, multiple first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0145] In some embodiments, there is at least one second electrode terminal 32 , and may be at least two, such as two, three, or four.

[0146] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0147] like Fig.16 As shown, for example, at least two second electrode terminals 32 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is conducive to improving the fast charging performance.

[0148] Fig.16 The battery cell 7 is shown to include four electrode terminals, specifically, there are two second electrode terminals 32, one of which is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0149] For another example, all the second electrode terminals 32 are arranged on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively arranged on both sides of the electrode assembly 10 along the length direction Z, and will not interfere with each other when they are electrically connected to the pole ear parts.

[0150] Exemplarily, there is one first electrode terminal 31 and one second electrode terminal 32, the first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, and the second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. Optionally, the first electrode terminal 31 and the second electrode terminal 32 may be staggered along the width direction Y. Of course, the first electrode terminal 31 and the second electrode terminal 32 may also be disposed opposite to each other along the length direction Z. Fig.15 A schematic diagram showing that the first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on both sides of the electrode assembly 10 .

[0151] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32 . The two first electrode terminals 31 are arranged on one side of the electrode assembly 10 along the length direction Z, and the two second electrode terminals 32 are arranged on the other side of the electrode assembly 10 along the length direction Z.

[0152] In the embodiment of the present application, the second pole tab 121 and the second electrode terminal 32 can be directly connected or indirectly connected; when the second pole tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter, which is located between the second electrode terminal 32 and the second pole tab 121 and connects the second electrode terminal 32 and the second pole tab 121.

[0153] For example, when the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z and the second electrode tab 121 is disposed on one side of the second coating portion 122 along the width direction Y, the second adapter is more conducive to the connection between the second electrode tab 121 and the second electrode terminal 32 .

[0154] In the above-mentioned embodiments, the second transition component 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-mentioned metal elements.

[0155] In other embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y, or a plurality of second electrode terminals 32 are disposed on both sides of the electrode assembly 10 along the width direction Y, respectively.

[0156] In some embodiments, the battery cell includes a positive electrode sheet, a negative electrode sheet and an electrolyte, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative current collector, and the single-side coating weight of the negative electrode film layer is 80 mg / 1540.25 mm 2 Up to 135mg / 1540.25mm 2 The negative electrode film layer includes a negative electrode active material, which includes a carbon-based material and a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.3% to 6%; the electrolyte includes an organic solvent and an additive, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%, and the additive includes one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive, and the mass content of the additive in the electrolyte is 0.5% to 10%.

[0157] The mass content of silicon in the negative electrode active material is greater than or equal to 0.3%, which is conducive to improving the energy density at a thinner coating thickness; The migration path of active ions such as lithium ions in the negative electrode film layer is short, and lithium ions can migrate quickly in the negative electrode plate; and the mass content of the chain carboxylic acid ester solvent in the electrolyte is greater than or equal to 5%, so that the migration rate of lithium ions in the electrolyte is faster, thereby improving the liquid phase transmission rate of lithium ions, thereby improving the fast charging ability of the battery cell; However, as the mass content of silicon and the mass content of chain carboxylic acid ester solvents increase, the interface reaction between silicon-based materials and electrolytes intensifies, gas production increases, and may damage the SEI film on the negative electrode side; therefore, the embodiment of the present application further regulates the mass content of silicon to be less than or equal to 6%, and the mass content of chain carboxylic acid ester solvents in the electrolyte to be less than or equal to 35%, so as to alleviate the interface side reaction between the negative electrode active material and the electrolyte, reduce gas production, and improve the cycle performance of the battery cell; Furthermore, the electrolyte also includes an additive. When the mass content of the additive is greater than or equal to 0.5%, the additive can repair the SEI film on the negative electrode side, and when the mass content of the additive is less than or equal to 10%, the impedance of the formed SEI film is relatively low, which can effectively improve the fast charging capability of the battery cell.

[0158] At the same time, the negative electrode plate of the embodiment of the present application includes a silicon-based material, which can make the coating thickness of the negative electrode plate relatively thin at a preset energy density. Specifically, the single-sided coating weight of the negative electrode film layer is 80 mg / 1540.25 mm 2 Up to 135mg / 1540.25mm 2 When the single-sided coating weight of the negative electrode film layer meets the above range, it is combined with an appropriate mass content of silicon-based materials to improve the energy density of the battery cell, and can also shorten the migration path of active ions in the negative electrode film layer. The migration rate of active ions in the negative electrode film layer is faster, which is beneficial to reduce the polarization phenomenon under high-rate charging and improve the fast charging capability of the battery cell.

[0159] Therefore, the embodiments of the present application can improve the cycle performance and fast charging capability of the battery cell under high energy density, and are conducive to improving the cycle performance under fast charging.

[0160] Negative electrode The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector and including a negative electrode active material. For example, the negative current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0161] The upper limit voltage for charging and the cut-off voltage for discharging of the battery cell are different according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the cut-off voltage for discharging can be 2.0V, or the upper limit voltage for charging can be 3.8V and the cut-off voltage for discharging can be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.3V and the cut-off voltage for discharging can be 2.0V. Next, taking the upper limit voltage for charging being 3.8V and the cut-off voltage for discharging being 2.0V as an example, the state of the battery cell is explained: In the embodiment 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 limit voltage of the charge, 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.

[0162] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge SOC is 1.5 g / cm 3 Up to 1.7g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.50 g / cm 3 , 1.55g / cm 3 , 1.60g / cm 3 , 1.65g / cm 3 , 1.66g / cm³, 1.68g / cm³, 1.70g / cm³ or a range consisting of any two of the above values.

[0163] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active materials in the negative electrode film layer are densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation and improving the cycle. Therefore, by adjusting the compaction density of the negative electrode film layer to a reasonable range, the battery cell can improve the fast charging capability and cycle performance at high energy density.

[0164] In some embodiments, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 70 mg / 1540.25 mm 2, 80mg / 1540.25mm², 85mg / 1540.25mm², 90mg / 1540.25mm², 95mg / 1540.25mm², 100mg / 1540.25mm², 105mg / 1540.25mm², 110mg / 1540.25mm², 115mg / 1540.25mm², 120mg / 1540.25mm², 120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2 、150mg / 1540.25mm 2 、160mg / 1540.25mm 2 、170mg / 1540.25mm 2 、175mg / 1540.25mm 2 Or a range consisting of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 Up to 142mg / 1540.25mm 2 .

[0165] When the single-sided coating weight of the negative electrode film layer meets the above range, it is combined with an appropriate mass content of silicon-based materials to help improve the energy density of the battery cell. In addition, the migration rate of active ions in the negative electrode film layer is faster, which is beneficial to reducing the polarization phenomenon under high-rate charging, and is beneficial to improving the fast charging capability of the battery cell at high energy density.

[0166] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge SOC is a well-known meaning in the art, that is, the negative electrode sheet is disassembled from the battery cell at 100% state of charge SOC, and the compaction density of the negative electrode film layer is measured. For example, a single-sided coated negative electrode sheet (if it is a double-sided coated sheet, the negative electrode film layer on one side can be wiped off first), punched into a small disc with an area of ​​S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative electrode collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (the weight of the negative electrode pole piece M1 - the weight of the negative electrode current collector M0) / S1, the thickness of the negative electrode film layer = the thickness of the negative electrode pole piece H1 - the thickness of the negative electrode current collector H0, the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0167] In some embodiments, the charge gram capacity of the negative electrode active material is 350 mAh / g to 540 mAh / g. Exemplarily, the charge gram capacity of the negative electrode active material is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g, 530 mAh / g, 540 mAh / g, or a range consisting of any two of the above values.

[0168] When the charge gram capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0169] In the embodiments of the present application, the gram capacity of the active material has a meaning well known in the art and can be tested using equipment and methods well known in the art. The test method for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used to test the charging gram capacity of the negative electrode active material in a half-button battery at a rate of 0.1C. A half-button battery is assembled with metallic lithium as the negative electrode and a sample electrode comprising the above material as the positive electrode. Under the conditions of 23°C±2°C, the half-button battery is charged and discharged at a rate of 0.1C on a battery tester or other test equipment of equivalent performance to obtain the charge capacity, and then the capacity is divided by the mass of the active material in the electrode to obtain the charging gram capacity parameter.

[0170] In some embodiments, the negative electrode active material includes a silicon-based material. Optionally, the silicon-based material may include elemental silicon, a silicon-carbon composite, a silicon oxide SiO x At least one of (0<x≤2). For example, the silicon-carbon composite may be silicon carbide.

[0171] In some embodiments, the mass content of silicon in the silicon-based material in the negative electrode film layer is 0.15% to 6%.

[0172] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.3% to 6%.

[0173] In these embodiments, the present application discloses that the mass content of silicon in the negative electrode film layer in the silicon-based material is, for example, 0.15%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range consisting of any two of the above values. Optionally, the mass content of silicon in the negative electrode film layer in the silicon-based material is 3% to 6%.

[0174] When the mass content of silicon is within the above range, the capacity of the negative electrode active material can be improved, which is beneficial to improving the energy density of the battery cell; and during the charge and discharge process, the volume expansion of the silicon-based material will not be too large, which is beneficial to maintaining the stability of the negative electrode SEI film and improving the cycle performance of the battery cell at high energy density.

[0175] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the cycle performance of the battery cell.

[0176] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0177] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the above-mentioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy material.

[0178] The qualitative and quantitative properties of each substance or element in this application can be detected by appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0179] For example, the present application may combine JIS / K0131-1996 X-ray diffraction analysis method general rules to perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0180] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flaky structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0181] like Fig.17 As shown, the negative electrode film layer 141 of the negative electrode plate 14 in the embodiment of the present application includes at least one film layer, which may be a single film layer or at least two film layers. Optionally, the negative electrode film layer 141 includes at least two film layers.

[0182] In the case where the negative electrode film layer 141 is a single-layer film layer, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material.

[0183] When the negative electrode film layer 141 has at least two layers, the negative electrode active material in the negative electrode film layer 141 includes carbon-based materials and optional silicon-based materials. The negative electrode film layer 141 may include two layers, three layers, four layers, or even more layers.

[0184] In some embodiments, the negative electrode film layer 141 includes a first negative electrode film layer 1411 and a second negative electrode film layer 1412, the first negative electrode film layer 1411 is disposed on the surface of the negative electrode current collector 142, the negative electrode active material of the first negative electrode film layer 1411 includes a carbon-based material, the second negative electrode film layer 1412 is connected to the side of the first negative electrode film layer 1411 away from the negative electrode current collector 142, and the negative electrode active material of the second negative electrode film layer 1412 includes a carbon-based material. The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 is regular or irregular, optionally irregular; or there is no obvious interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0185] The negative electrode film layer 141 includes at least two film layers, and the layered coating is beneficial to improving the fast charging performance of the battery cell. In particular, when there is a difference in porosity between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, it is beneficial to improving the fast charging performance of the battery cell.

[0186] In some embodiments, at least one of the first negative electrode film layer 1411 and the second negative electrode film layer 1412 includes a silicon-based material.

[0187] Optionally, the first negative electrode film layer 1411 also includes a silicon-based material.

[0188] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0189] Exemplarily, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 include silicon-based materials, it is more conducive to improving the energy density of the battery cell; and each layer can alleviate the volume expansion of the silicon-based material through the carbon-based material, which can make the negative electrode SEI film more stable and improve the cycle performance under high energy density; and because each layer includes silicon-based materials, the coating thickness is relatively thin, which is conducive to shortening the transmission path of lithium ions and improving the fast charging performance under high energy density.

[0190] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material. When the first negative electrode film layer 1411 includes a silicon-based material and the second negative electrode film layer 1412 does not include a silicon-based material, the second negative electrode film layer 1412 can alleviate the volume expansion of the first negative electrode film layer 1411, reduce the side reaction between the negative electrode film layer 141 and the electrolyte, and improve the cycle performance under high energy density.

[0191] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode film layer 1412 includes a silicon-based material, it is advantageous to form more film pores through the volume change of the silicon-based material, improve the liquid phase transmission capacity of lithium ions, enhance the dynamic performance of the battery cell, and improve the cycle performance under high energy density.

[0192] When the negative electrode film layer 141 has at least two layers, the cross-sectional shape of the negative electrode film layer 141 may be the same or similar at various locations along the thickness direction X of the negative electrode film layer 141, or may be different. When the electrode assembly is a laminated structure, the thickness direction of the battery cell may be parallel to the thickness direction of the electrode assembly and the thickness direction X of the negative electrode film layer 141.

[0193] Along the thickness direction X of the negative electrode film layer 141, the negative electrode film layer 141 is divided into three regions, namely the first region 141a, the third region 141c and the second region 141b, wherein the first region 141a is a region of the negative electrode film layer 141 close to the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the first region 141a is 1 / 3 of the thickness of the negative electrode film layer 141; the second region 141b is a region of the negative electrode film layer 141 away from the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the second region 141b is 1 / 3 of the thickness of the negative electrode film layer 141.

[0194] The cross-sectional morphology of the first region 141a and the second region 141b can be the same or similar, or different. The cross-sectional morphology of the first region 141a and the third region 141c can be the same or similar, or different. The cross-sectional morphology of the second region 141b and the third region 141c can be the same or similar, or different.

[0195] There may or may not be obvious interface between the first region 141a, the second region 141b and the third region 141c. For example, the first negative electrode film layer 1411 includes the first region 141a, the second negative electrode film layer 1412 includes the second region 141b, and the third region 141c may be a part of the first negative electrode film layer 1411, or the third region 141c may be a part of the second negative electrode film layer 1412, or the third region 141c may be a part of the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0196] 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 conducive to the rapid migration of lithium ions from the second region 141b to the first region 141a, thereby improving the rapid charging capability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a may be smaller than the average particle size of the carbon-based material in the second region 141b.

[0197] Optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 can be greater than or equal to the average particle size of the carbon-based material of the second negative electrode film layer 1412. Further optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 can be greater than the average particle size of the carbon-based material of the second negative electrode film layer 1412.

[0198] There is a difference in the particle size of the first negative electrode film layer 1411 and the second negative electrode film layer 1412, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer 1412 is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer 1412. In the embodiment of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which can shorten the solid phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium chromatography on the surface of the negative electrode plate 14, thereby improving the cycle performance under high energy density.

[0199] Optionally, the average particle size of the carbon-based material in the first region 141a is 10 μm to 20 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting 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, the solid phase transmission path of lithium ions can be shortened and the fast charging performance can be improved. On the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material and improve the cycle performance under high energy density.

[0200] Optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material of the first negative electrode film layer 1411 is within the above range, on the one hand, the solid phase transmission path of lithium ions can be shortened to improve the fast charging performance, and on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material.

[0201] 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 consisting of any two of the above values. When the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within the above range, the stability of the material is improved, which is beneficial to improving the fast charging capability and cycle performance of the battery cell at high energy density.

[0202] Optionally, the average particle size of the carbon-based material of the second negative electrode film layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material of the second negative electrode film layer 1412 is within the above range, on the one hand, the solid phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved. On the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer 1412 within the above average particle size range and the negative electrode active material in the first negative electrode film layer 1411 cooperate, which is conducive to constructing the gradient pore difference between the second negative electrode film layer 1412 and the first negative electrode film layer 1411, reducing the tortuosity of lithium ion transmission, and improving the fast charging capability of the battery cell at high energy density.

[0203] Exemplarily, the carbon-based material of the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region 141b includes artificial graphite. For example, the negative electrode active material of the first region 141a includes silicon-based material, artificial graphite and natural graphite, and the negative electrode active material of the second region 141b includes silicon-based material and artificial graphite.

[0204] Exemplarily, the carbon-based material of the first negative electrode film layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer 1412 includes artificial graphite. For example, the negative electrode active material of the first negative electrode film layer 1411 includes silicon-based material, artificial graphite and natural graphite, and the negative electrode active material of the second negative electrode film layer 1412 includes silicon-based material and artificial graphite.

[0205] In the embodiment of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b is a well-known meaning in the art, and can be detected by using equipment and methods well-known in the art, such as taking the negative electrode plate 14 as a sample, performing cross-section polishing along the thickness direction X of the negative electrode film layer 141, such as using an argon ion beam for cross-section polishing, using a scanning electron microscope SEM to photograph the cross section, obtaining a SEM cross-sectional view, and counting the particle size of the carbon-based material in the SEM cross section, and calculating the average particle size of the carbon-based material based on the counted number. In the case where the proportion of carbon-based materials in the negative electrode film layer is 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.

[0206] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application embodiment has no particular restrictions on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0207] Negative electrode conductive agents can make up for the insufficient conductivity of silicon-based materials, improve the conductivity of the negative electrode film layer, and help improve the dynamic performance of battery cells and the fast charging capability of battery cells at high energy density.

[0208] Optionally, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%, such as 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7% or a range consisting of any two of the above values. The mass content of the conductive carbon at the above mass content can improve the fast charging capability of the battery cell at high energy density.

[0209] Optionally, the mass content of carbon nanotubes in the negative electrode film layer is 0.1% to 1%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range consisting of any two of the above values. Optionally, the mass content of carbon nanotubes in the negative electrode film layer is 0.1% to 0.5%. The mass content of carbon nanotubes at the above mass content can improve the fast charging capability of battery cells at high energy density.

[0210] In some embodiments, the negative electrode film layer may further include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0211] In some embodiments, the negative electrode film layer may further include other additives. As an example, the other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0212] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a 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).

[0213] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 8.5 μm, for example, 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 consisting of any two of the above values.

[0214] In some embodiments, the negative electrode plate further includes a negative electrode ear connected to the negative electrode current collector, and the thickness of the negative electrode ear 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 consisting of any two of the above values. When the thickness of the negative electrode ear is within the above range, it is beneficial to improve the current capacity and improve the fast charging capability of the battery cell.

[0215] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0216] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0217] Positive electrode In some embodiments, the battery cell further includes a positive electrode tab.

[0218] The positive electrode sheet includes a positive current collector and a positive electrode film 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 thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0219] In the case where the battery cell includes a stacked electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode sheet, the size of the battery cell along the length direction can be understood as the length of the battery cell, and the size of the positive electrode film layer along the length direction can be understood as the length of the positive electrode film layer; the width direction of the battery cell is parallel to the width direction of the positive electrode sheet, the size of the battery cell along the width direction can be understood as the width of the battery cell, and the size of the positive electrode film layer along the width direction can be understood as the width of the positive electrode film layer.

[0220] In some embodiments, the dimension of the positive electrode film layer along the length direction of the positive electrode sheet is 265 mm to 655 mm.

[0221] In some embodiments, the ratio of the size of the positive electrode film layer along the length direction of the positive electrode sheet to the size of the positive electrode film layer along the width direction of the positive electrode sheet is greater than 1 and less than or equal to 12.5, and can be selected from 2 to 12.5. In the case where the positive electrode active material of the positive electrode film layer includes a lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the size of the positive electrode film layer should not be too long. When the size of the positive electrode film layer is within the above range, the electron transmission path will not be too long, and the internal resistance is relatively small, which is conducive to improving the fast charging capability and energy density of the battery cell at high energy density.

[0222] Optionally, the dimension of the positive electrode film layer along the length direction of the positive electrode sheet is 400 mm to 600 mm, and the ratio of the dimension of the positive electrode film layer along the length direction of the positive electrode sheet to the dimension of the positive electrode film layer along the width direction of the positive electrode sheet is 4 to 8.

[0223] In some embodiments, the size of the negative electrode film layer along the first direction is greater than the size of the positive electrode film layer along the first direction, so that the lithium ions released from the positive electrode film layer can be basically embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of the battery cell. Of course, the size of the negative electrode film layer along the first direction can also be less than or equal to the size of the positive electrode film layer along the first direction.

[0224] Optionally, the difference between the size of the negative electrode film layer along the first direction and the size of the positive electrode film layer along the first direction is 5mm to 11mm, for example, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm or a range consisting of any two of the above values.

[0225] In some embodiments, the size of the negative electrode film layer along the second direction is greater than the size of the positive electrode film layer along the second direction, so that the lithium ions released from the positive electrode film layer can be basically embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of the battery cell. Of course, the size of the negative electrode film layer along the second direction can also be less than or equal to the size of the positive electrode film layer along the second direction.

[0226] Optionally, the difference between the size of the negative electrode film layer along the second direction and the size of the positive electrode film layer along the second direction is 5mm to 11mm, for example, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm or a range consisting of any two of the above values.

[0227] The first direction is perpendicular to the second direction, and the first direction may be parallel to the length direction of the battery cell, or the first direction may be parallel to the width direction of the battery cell. When the first direction is parallel to the length direction of the battery cell, the second direction is parallel to the width direction of the battery cell. When the first direction is parallel to the width direction of the battery cell, the second direction is parallel to the length direction of the battery cell.

[0228] In some embodiments, the size of the separator along the first direction is larger than the size of the negative electrode film layer along the first direction, so that the separator can effectively isolate the positive electrode sheet and the negative electrode sheet, reduce the risk of short circuit, and improve the reliability of the battery cell. Of course, the size of the separator along the first direction can also be less than or equal to the size of the negative electrode film layer along the first direction.

[0229] Optionally, the difference between the size of the isolation member along the first direction and the size of the negative electrode film layer along the first direction is 6 mm to 10 mm, for example, 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 consisting of any two of the above values.

[0230] In some embodiments, the size of the separator along the second direction is greater than the size of the negative electrode film layer along the second direction, so that the separator can effectively isolate the positive electrode sheet and the negative electrode sheet, reduce the risk of short circuit, and improve the reliability of the battery cell. Of course, the size of the separator along the second direction can also be less than or equal to the size of the negative electrode film layer along the second direction.

[0231] Optionally, the difference between the size of the isolation member along the second direction and the size of the negative electrode film layer along the second direction is 6 mm to 10 mm, for example, 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 consisting of any two of the above values.

[0232] like Fig.18 As shown, the first direction can be parallel to the length direction Z, the second direction is parallel to the width direction Y, the first pole piece 11 is a positive pole piece, and the second pole piece 12 is a negative pole piece. The dimension of the positive electrode film layer of the first pole piece 11 along the length direction Z is the length of the positive electrode film layer of the first pole piece 11 , the dimension of the negative electrode film layer of the second pole piece 12 along the length direction Z is the length of the negative electrode film layer of the second pole piece 12 , and the dimension of the insulating member 13 along the length direction Z is the length of the insulating member 13 .

[0233] The difference between the length of the negative electrode film layer of the second electrode sheet 12 and the length of the positive electrode film layer of the first electrode sheet 11 is OH 11 , Fig.18 As shown in FIG. 1 , both sides of the negative electrode film layer along the length direction Z exceed the positive electrode film layer, and each side exceeds the OH 11 Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side along the length direction Z.

[0234] The difference between the length of the separator 13 and the length of the negative electrode film layer of the second electrode sheet 12 is OH 21 , Fig.18 As shown in FIG. 1 , both sides of the separator 13 along the length direction Z extend beyond the negative electrode film layer, and each side extends beyond the OH 21 Of course, one side of the separator 13 along the length direction Z may extend beyond the negative electrode film layer.

[0235] The dimension of the positive electrode film layer of the first electrode piece 11 along the width direction Y is the width of the positive electrode film layer of the first electrode piece 11 , the dimension of the negative electrode film layer of the second electrode piece 12 along the width direction Y is the width of the negative electrode film layer of the second electrode piece 12 , and the dimension of the insulating member 13 along the width direction Y is the width of the insulating member 13 .

[0236] The difference between the width of the negative electrode film layer of the second electrode sheet 12 and the width of the positive electrode film layer of the first electrode sheet 11 is OH 12 , Figure 8 As shown in FIG. 1 , both sides of the negative electrode film layer along the width direction Y extend beyond the positive electrode film layer, and each side extends beyond the OH 12 Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side along the width direction Y.

[0237] The difference between the width of the separator 13 and the width of the negative electrode film layer of the second electrode sheet 12 is OH 22 , Fig.18 As shown in FIG. 1 , both sides of the separator 13 along the width direction Y extend beyond the negative electrode film layer, and each side extends beyond the OH 22 Of course, one side of the separator 13 along the width direction Y may extend beyond the negative electrode film layer.

[0238] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC is 2.50 g / cm 3 Up to 2.80g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.50 g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0239] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active materials in the positive electrode film layer are densely packed, the contact resistance between particles is small, which can further reduce the resistance of the pole piece, thereby reducing heat generation and improving the cycle. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell can improve the fast charging capability and cycle performance at high energy density.

[0240] In some embodiments, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2. Exemplarily, the single-sided coating weight of the positive electrode film layer is 150mg / 1540.25mm², 200mg / 1540.25mm², 250mg / 1540.25mm², 300mg / 1540.25mm², 350mg / 1540.25mm², 370mg / 1540.25mm² or a range consisting of any two of the above values. Optionally, the single-sided coating weight of the positive electrode film layer is 200mg / 1540.25mm 2 Up to 300mg / 1540.25mm 2 .

[0241] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, which will reduce the risk of aggravated side reactions due to heat accumulation, and is beneficial to improving the fast charging capability and cycle performance of the battery cell at high energy density.

[0242] In the embodiment of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge SOC is a well-known meaning in the art, that is, the positive electrode sheet is disassembled from the battery cell at 100% state of charge SOC, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punched into a small disc with an area of ​​S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive electrode collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight of the positive electrode plate M1 - the weight of the positive electrode collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode plate H1 - the thickness of the positive electrode collector H0, the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0243] In some embodiments, the charge gram capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g. Exemplarily, the charge gram capacity of the positive electrode active material is 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range consisting of any two of the above values.

[0244] When the charge gram capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0245] In the embodiments of the present application, the gram capacity of the positive electrode active material has a meaning well known in the art and can be detected by using a gram capacity test method for negative electrode active materials.

[0246] In some embodiments, the positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate may be an olivine structure, which is structurally stable during the charge and discharge process and can improve the cycle life of the battery cell.

[0247] Alternatively, the positive electrode active material may further include a lithium-containing transition metal oxide. Examples of lithium-containing transition metal oxides 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.

[0248] The lithium-containing phosphate with an olivine structure can be an unmodified lithium-containing phosphate, or a material obtained by coating and modifying it. For example, the surface of the lithium-containing phosphate is provided with a carbon-containing material, and the carbon-containing material can be coated on the surface of the lithium-containing phosphate as a coating layer, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, and facilitating the migration rate of lithium ions, improving the fast charging capability of the battery cell, and reducing the heat generation of the battery cell.

[0249] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a M b P 1-c X c Y z Compounds, where 0.5≤x 1 ≤1.3,0≤y 1 ≤1.3, and 0.9≤x 1 +y 1 ≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of Cl, C, and N, and Y includes one or more of O and F. The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0250] Exemplarily, the lithium-containing phosphate includes LiFePO 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4One or more of the following. During the charging and discharging process, the battery cells are accompanied by the deintercalation and consumption of active ions such as Li. The molar content of Li in the battery cells is different when they are discharged to different states. 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 In the examples of the present invention, 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 used in the battery system, the molar content of Li may change after charge and discharge cycles. 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 In the enumeration of etc., the molar content of oxygen O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In reality, the molar content of oxygen O will fluctuate. The above situations are all within the protection scope of the present application.

[0251] In the embodiment of the present application, the content of elements in the positive electrode active material has a well-known meaning in the art, and can be detected by equipment and methods well-known in the art, for example, with reference to EPA 6010D-2014, tested by inductively coupled plasma atomic emission spectrometry, and measured by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After the battery cell is discharged to 0% state of charge SOC, the positive electrode sheet is disassembled, washed and dried with dimethyl carbonate DMC, and calcined at high temperature to remove impurities, 0.4g of positive electrode active material is weighed, and 10ml (50% concentration) of aqua regia is added thereto. Then place it on a plate at 180°C for 30min. After digestion on the plate, the volume is fixed to 100mL, and the standard curve method is used for quantitative testing.

[0252] 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, for example, 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 consisting of any two of the above values.

[0253] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium ion deintercalation path in the lithium-containing phosphate is shorter, and the heat generated is less; and the particle size of the above lithium-containing phosphate will not be too small, and basically no agglomeration will occur during the processing and preparation process, so that the performance of the lithium-containing phosphate is stable.

[0254] In some embodiments, the positive electrode film layer further includes a positive electrode additive, and the positive electrode additive includes one or more of lithium-containing ternary materials, lithium phosphate, lithium dihydrogen 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. The above materials can be used as lithium supplements to supplement lithium ions for the positive electrode film layer, compensate for irreversible lithium ion losses in the system, increase capacity, and increase the energy density of the battery cell.

[0255] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode additive is 0.1% to 5%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range composed of any two of the above. When a positive electrode additive of a mass range is used, lithium ions can be supplemented for the positive electrode film layer to compensate for the irreversible lithium ion loss in the system, and the mass content of the positive electrode additive is not too high, so that the positive electrode discharge gram capacity is still high, and the energy density is basically not reduced.

[0256] 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 conducive to uniform dispersion and improves the distribution uniformity of the lithium supplement.

[0257] 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 a range consisting of any two of the above.

[0258] In the embodiment of the present application, the volume average particle size Dv50 of the particles has a meaning well known in the art, and the volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using equipment and methods well known in the art. After the fresh battery cell is fully discharged to 0% state of charge SOC, the positive electrode plate is disassembled, the positive electrode current collector is removed and the positive electrode film layer is retained, the positive electrode film layer is immersed in N-methylpyrrolidone NMP, the binder in the positive electrode film layer is washed out, and the positive electrode active material or lithium supplement is retained as a sample. After the sample is dried, the volume average particle size Dv50 of the particles is tested by a Mastersizer2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0259] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0260] In some embodiments, the positive electrode film layer may also optionally include a positive electrode binder. The present application embodiment has no particular restrictions on the type of positive electrode binder. 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 fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0261] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy may be used. The composite current collector 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).

[0262] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 16 μm, for example, 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 consisting of any two of the above values.

[0263] In some embodiments, the positive electrode sheet further includes a positive electrode ear connected to the positive current collector, and the thickness of the positive electrode ear is 10 μm to 16 μm, for example, 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 consisting of any two of the above values. When the thickness of the positive electrode ear is within the above range, it is beneficial to improve the current capacity and the fast charging capability of the battery cell.

[0264] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0265] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiment of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In 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 film layer.

[0266] [Electrolyte] During the charge and discharge process of a battery cell, active ions such as lithium ions are inserted and removed back and forth between the positive electrode and the negative electrode, and the electrolyte plays a role in conducting the active ions between the positive electrode and the negative electrode. The electrolyte includes an organic solvent and an electrolyte salt.

[0267] In some embodiments, the conductivity of the electrolyte at room temperature is 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 consisting of any two of the above values.

[0268] 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.

[0269] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, such as 25° C., is ionic conductivity, which can be detected using equipment and methods known in the art, such as testing with reference to industry standard HG-T 4067-2015.

[0270] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s. For example, 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 consisting of any two of the above values.

[0271] 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.

[0272] In the embodiments of the present application, the viscosity of the electrolyte has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, it can be detected according to GB / T10247-2008.

[0273] In some embodiments, the density of the electrolyte at room temperature, such as 25° C., is 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 consisting of any two of the above values.

[0274] 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.

[0275] In the embodiments of the present application, the density of the electrolyte has a well-known meaning in the art and can be tested using equipment and methods well-known in the art, for example, by referring to GB / T 2013-2010 for testing.

[0276] In some embodiments, the organic solvent includes a linear carboxylic acid ester solvent.

[0277] Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylate solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35% or a range consisting of any two of the above values. Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 8% to 20%.

[0278] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte is small, the conductivity of the electrolyte can be improved, the internal resistance of the battery cell can be reduced, and the rapid migration of lithium ions is beneficial; and the electrolyte and the silicon-containing negative electrode are compatible, which can effectively reduce the gas production of the battery cell, reduce the impact on the SEI film on the negative electrode side, and improve the fast charging capability and cycle performance of the battery cell.

[0279] In some embodiments, the linear carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R 1 including a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 haloalkyl group, R 2 Includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0280] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0281] Optionally, R 1Including hydrogen atoms, C1 to C3 alkyl or C1 to C3 haloalkyl. Further optionally, R 1 Includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group or a C1 to C2 halogenated alkyl group.

[0282] Optionally, R 2 Including C1 to C3 alkyl or C1 to C3 haloalkyl. Further optionally, R 2 Includes C1 to C2 alkyl or C1 to C2 halogenated alkyl.

[0283] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0284] Illustratively, the chain carboxylate solvent includes one or more of the compounds represented by Formula I-1 to the compounds represented by Formula I-8,

[0285] In some embodiments, the organic solvent includes a carbonate-based solvent.

[0286] The use of carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte, facilitates the migration of lithium ions, and improves the fast charging capability of the battery cells.

[0287] 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 consisting of any two of the above values.

[0288] When the mass content of carbonate solvents and chain carboxylic acid ester solvents meets the above conditions, the stability of the electrolyte can be improved, the gas production can be reduced, and the cycle performance can be improved.

[0289] Illustratively, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0290] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Alternatively, the lithium salt includes a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate.

[0291] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF. The side reaction between hydrofluoric acid and the negative electrode, especially the silicon-containing negative electrode, may lead to increased gas production during high-temperature storage. The combined use of lithium hexafluorophosphate and fluorinated lithium sulfonyl imide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, reduce the gas production during high-temperature storage, and improve the cycle performance of the battery cell. In addition, the migration number of lithium ions increases, and the lithium ion conductivity capacity increases, which can improve the fast charging capability of the battery cell.

[0292] Illustratively, the fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide, and may be lithium bisfluorosulfonyl imide.

[0293] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is greater than 0 and less than or equal to 18%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a range consisting of any two of the above values. Optionally, the mass content of the lithium salt is 4% to 16%.

[0294] 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%.

[0295] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of the fluorinated sulfonyl imide lithium 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 a range consisting of any two of the above values. Optionally, the ratio of the mass content of the fluorinated sulfonyl imide lithium to the mass content of the lithium hexafluorophosphate is 0.4 to 0.8.

[0296] When the ratio of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide meets the above range, on the one hand, the content of hydrofluoric acid can be reduced, the side reactions at the negative electrode interface can be slowed down, and the gas production during high-temperature storage can be reduced; on the other hand, the organic component content of the SEI film formed at the negative electrode interface is appropriate, which can also reduce the gas production during high-temperature storage and improve the cycle performance.

[0297] 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-mentioned additive can improve the SEI film performance on the negative electrode side, and the formed SEI film has higher stability and relatively low impedance, which is conducive to improving the fast charging performance of the battery cell and improving the cycle performance.

[0298] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 10%. For example, 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 a range consisting 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%.

[0299] The additives in the above mass content can effectively improve the SEI film performance on the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0300] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive includes fluoroethylene carbonate and vinylene carbonate.

[0301] Fluorinated ethylene carbonate can form a SEI film rich in lithium fluoride LiF on the surface of the negative electrode, which can alleviate the volume expansion of silicon, improve the life of the silicon-containing system, and reduce high-temperature gas production. The use of fluoroethylene carbonate and vinylene carbonate together makes the SEI film on the negative electrode surface more compact, which can more effectively protect the silicon-containing negative electrode, reduce the degree of side reactions at the negative electrode interface, and reduce high-temperature gas production.

[0302] Exemplarily, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate.

[0303] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0304] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte are well-known in the art, and can be detected by equipment and methods well-known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, a free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower limit cut-off voltage so that the battery is charged at about 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery is used as a sample, and the ion chromatography analysis method is used for detection.

[0305] In the embodiments of the present application, the types and contents of organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of organic components in the electrolyte by gas chromatography.

[0306] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the components are classified, and the chain carboxylic acid ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are taken as the components of the organic solvent. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0307] The carbonate additive (such as fluorinated cyclic carbonate, vinylene carbonate) is used as an additive for the electrolyte, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0308] Isolation In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0309] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical stability and mechanical stability can be selected.

[0310] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without special restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surface 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.

[0311] In some embodiments, the volume energy density of the battery cell is 350Wh / L to 430Wh / L. For example, the volume energy density of the battery cell is 350Wh / L, 370Wh / L, 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, or a range consisting of any two of the above values. The volume energy density of the battery cell is relatively high.

[0312] In the embodiments of the present application, the volume energy density of a battery cell has a well-known meaning in the art and can be detected by using well-known equipment and methods in the art. For example, the battery charging upper limit voltage is 3.8V and the battery discharge cut-off voltage is 2.0V. Place the battery cell at 25°C, charge to 3.8V at a constant current of 0.05C, and discharge to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the battery shell size, excluding the electrode terminal height and the insulating film outside the shell), calculate the volume of the single battery V0, unit L, and the volume energy density of the battery cell VED=(A0×discharge platform voltage) / V0, unit Wh / L.

[0313] Example The following examples more specifically describe the contents disclosed in the embodiments of the present application, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and changes are made within the scope of the disclosure of the embodiments of the present application. 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 processing, and the instruments used in the examples are commercially available.

[0314] Example 1 1. Preparation of positive electrode sheet The positive electrode plate comprises a positive electrode current collecting part and a positive electrode film layer arranged on both sides of the positive electrode current collecting part, and the positive electrode current collecting part is an aluminum foil.

[0315] The positive electrode film layer includes lithium iron phosphate, a lithium-containing phosphate with a mass ratio of 95:1.85:2:1.15, lithium ferrite, a positive electrode additive, polyvinylidene fluoride (PVDF), a binder, and acetylene black, a conductive agent. The positive electrode film layer is formed by evenly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collecting part, and then drying and cold pressing.

[0316] The volume average particle size Dv50 of the lithium-containing phosphate was 1.5 μm. The charge gram capacity of the positive electrode active material was 161 mAh / g.

[0317] The volume average particle size Dv50 of the positive electrode additive was 9.5 μm.

[0318] The single-sided coating weight of the positive electrode film is 313mg / 1540.25mm 2 .

[0319] The length of the positive electrode film layer is 592 mm.

[0320] 2. Preparation of negative electrode sheet The negative electrode plate comprises a negative electrode current collecting part and a negative electrode film layer arranged on both sides of the negative electrode current collecting part, and the negative electrode current collecting part is a copper foil.

[0321] The negative electrode film layer is formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector, and then drying and cold pressing.

[0322] The single-sided coating weight of the negative electrode film is 135mg / 1540.25mm 2 .

[0323] The negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, wherein the first negative electrode film layer is located on the surface of the negative electrode current collecting portion, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0324] The first negative electrode film layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose in a mass ratio of 96.3:0.5:2.5:0.7, the negative electrode active material of the first negative electrode film layer includes artificial graphite and silicon carbide, and the average particle size of the artificial graphite is 13 μm; The second negative electrode film layer includes a negative electrode active material, a conductive agent, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose in a mass ratio of 97.8:0.7:0.8:0.7, the negative electrode active material of the second negative electrode film layer includes artificial graphite and silicon carbide, and the average particle size of the artificial graphite is 10 μm; The average particle size of the artificial graphite in the first negative electrode film layer was measured to be 13 μm in the cross section along the thickness direction of the negative electrode film layer; the average particle size of the artificial graphite in the second negative electrode film layer was 10 μm. In the process of preparing the negative electrode film layer, the film layer with the desired average particle size can be obtained by adjusting the volume average particle size of the artificial graphite multiple times.

[0325] The ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 1; the conductive agents of the first negative electrode film layer and the second negative electrode film layer both include conductive carbon and carbon nanotubes, and the mass ratio of the conductive carbon and carbon nanotubes in the first negative electrode film layer and the second negative electrode film layer is 5:1.

[0326] The charge capacity of the negative electrode active material is 420 mAh / g.

[0327] 3. Isolation parts The separator includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0328] 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.

[0329] The organic solvent includes 15% chain carboxylic acid ester solvent (ethyl acetate) and 68.5% carbonate solvent (including ethylene carbonate and dimethyl carbonate, the mass ratio of the two is 2:3). The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte. Based on the mass of the electrolyte, the mass content of the additive is 2.5% (including 1.5% vinylene carbonate VC and 1% fluoroethylene carbonate FEC).

[0330] Lithium salt includes 10% lithium hexafluorophosphate LiPF 6 and 4% lithium bis(fluorosulfonyl)imide.

[0331] 5. Preparation of battery cells The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and a laminated electrode assembly is obtained. The electrode assembly is placed in an outer packaging shell, and after drying, an electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.62g / cm 3 The compaction density of the negative electrode film layer at 0% SOC is 1.30g / cm 3 .

[0332] Comparative Example 1-1 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the negative electrode film layer did not contain silicon-based materials, and the single-sided coating weights of the positive electrode film layer and the negative electrode film layer were adjusted.

[0333] Comparative Example 1-2 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the mass content of silicon and the single-sided coating weight of the positive electrode film layer were adjusted. A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the mass content of silicon element and the single-side coating weight of the positive electrode film layer were adjusted.

[0334] Embodiment 2-5 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the mass content of silicon element and the single-sided coating weight of the positive electrode film layer and the negative electrode film layer were adjusted.

[0335] Example 3 A battery cell was prepared by a method similar to that of Example 1, except that the material of the silicon-based material was adjusted.

[0336] Performance Testing 1. DC resistance DCR test of battery cells You can refer to the methods in GB / T 31467 "Performance test specification for high-power lithium-ion power batteries for HEV".

[0337] For example, at 25°C, charge the battery to 3.65 V at a constant current of 0.33 C, let it stand for 1 min, then charge it to 3.65 V at a constant current of 0.1 C, let it stand for 30 min, and discharge it to 2.0 V at a constant current of 0.33 C. Record the discharge capacity A at this time. 0 , unit is Ah, then charge at 0.33C constant current 0.5A 0 Ah, adjust SOC to 50%.

[0338] After the battery cell is placed at 25℃ for 2 h, it is discharged at 4C for 10 s and ∆U is recorded. 放电 , ∆I 放电 , the discharge DCR data of the battery cell is calculated by the following formula, R 放电 =∆U 放电 / ∆I 放电 , Among them, ∆U 放电 Indicates the voltage change within 10s after the discharge starts, ∆I 放电 Indicates the current value within 10 seconds after the discharge starts.

[0339] 2. High temperature cycle performance test of battery cells In an environment of 60±5℃, the battery cell is charged at a constant current of 1C to the charge cut-off voltage, then charged at a constant voltage to a cut-off current of 0.05C, and then discharged at a constant current of 1C to the discharge cut-off voltage. This is a charge and discharge cycle.

[0340] The discharge capacity of this time is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycle step for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of 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.

[0341] 3. Normal temperature cycle performance test of battery cells At 25±5℃, charge the battery cells with Stercharge constant current: Charge from 0% SOC to 20% SOC at 0.33C constant current; Charge from 20% SOC to 25% SOC at 8C constant current; Charge from 25% SOC to 30% SOC at 8C constant current; Charge from 30% SOC to 35% SOC at 7.5C constant current; Charge from 35% SOC to 40% SOC at 6.87C constant current; Charge from 40% SOC to 45% SOC at 6.38C constant current; Charge from 45% SOC to 50% SOC at 5.95C constant current; Charge from 50% SOC to 55% SOC at 5.53C constant current; Charge from 55% SOC to 60% SOC at 5.14C constant current; 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.

[0342] Charge from 80% SOC to 85% SOC at 2C constant current; Charge from 90% SOC to 95% SOC at 1C constant current; Charge from 95% SOC to 98% SOC at 0.5C constant current; Charge at 0.25C constant current from 98% SOC to 100% SOC or 3.8V cut-off (when reaching 3.8V can also be used as the cut-off condition, whichever comes first). Then discharge at 1C constant current to the discharge cut-off voltage of 2.8V. This is one charge and discharge cycle.

[0343] 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%, 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.

[0344] 4. Volume energy density test Place the battery cell at room temperature, charge it to 3.8V at a constant current of 0.05C, and discharge it to 2.0V at a constant current of 0.33C. 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 cell, excluding the height of the electrode terminals and the insulating film outside the outer shell), and calculate the volume V0 of the single cell. Unit L, volume energy density of battery cell VED = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0345] The test results are shown in Table 1.

[0346] Table 1

[0347] Comparative Example 1-1 does not add silicon-based materials. At a higher energy density, the coating weight of the negative electrode film layer is relatively high, and the migration resistance of active ions on the negative electrode side is relatively large, which is not conducive to fast charging.

[0348] In Comparative Example 1-2, the amount of silicon-based material added is relatively high, which makes the side reaction on the negative electrode side more serious, aggravates the gas production, especially the high-temperature gas production, and worsens the cycle.

[0349] Silicon-based materials Silicon-based materials In Examples 1, 2, 2-1 to 2-4 of the present application, the mass content of the silicon-based materials is regulated so that the mass content of the silicon-based materials is within an appropriate range. Since the gram capacity of the silicon material is greater than that of the graphite material, the volume energy density of the battery cell can be reduced significantly at a lower coating weight than that of Comparative Example 1-1, and the cycle performance and fast charging performance of the battery cell at high energy density can be effectively improved. For example, in Example 2-5, when the mass content of silicon is 3%, the single-sided coating weight of the negative electrode film layer is 80 mg / 1540.25 mm 2 , so that the volume energy density of the battery cell will not be too low, and because the coating thickness of the negative electrode film layer is thin, the lithium ion migration path is shorter, which is beneficial to improving the fast charging ability of the battery cell; and because the overall coating amount of the negative electrode film layer is low, the total amount of negative electrode active materials participating in the side reaction can be reduced, which can improve the cycle performance under fast charging conditions and high temperature cycle performance.

[0350] As the mass content of the silicon-based material increases, the charge gram capacity of the negative electrode active material increases. For example, in Example 2-3, the charge gram capacity of the negative electrode active material can reach 534 mAh / g.

[0351] This application is applicable to silicon-based materials of different materials, such as silicon-carbon materials and silicon-oxygen materials, which can effectively improve the cycle performance of battery cells and are conducive to improving the fast charging performance of battery cells; compared with the silicon-oxygen materials of Example 3, the volume expansion of the silicon-carbon material in Example 1 during the charge and discharge process is relatively small, and the cycle performance is relatively excellent. A battery cell was prepared by a method similar to that of Example 1, except that the components of the electrolyte were adjusted.

[0352] Example 4-1 and Example 4-2 A battery cell was prepared by a method similar to that of Example 1, except that the components of the electrolyte were adjusted.

[0353] Example 4-3 and Example 4-4 A battery cell was prepared by a method similar to that of Example 2-3, except that the components of the electrolyte were adjusted.

[0354] The test results are shown in Table 2.

[0355] Table 2

[0356] In Table 2, the mass content of the chain carboxylic acid ester solvent in Comparative Example 2-1 is relatively small, which makes the conductivity of the electrolyte low, the DCR of the battery cell high, and the lithium ion transmission resistance relatively large, which is not conducive to fast charging; In Comparative Example 2-2, the mass content of the chain carboxylic acid ester solvent is relatively high, and the conductivity of the electrolyte is high, which is beneficial to reducing the DCR of the battery cell; however, the side reaction between the above solvent and the negative electrode active material is relatively serious, and the gas production is aggravated, especially the high temperature gas production is aggravated, which worsens the cycle.

[0357] The mass content of the chain carboxylic acid ester solvent in the embodiment of the present application is within an appropriate range, which can effectively improve the conductivity of the electrolyte, improve the transmission capacity of lithium ions, and enhance the fast charging performance of the battery cell; and the electrolyte components are relatively stable, which can improve the cycle performance; it should be noted that the change of the electrolyte components has little effect on the energy density, and the energy density is not reflected in the table.

[0358] Comparative Example 3-1 and Comparative Example 3-2 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the components of the electrolyte were adjusted, mainly the content of the carboxylate.

[0359] Example 5-1 to Example 5-4 A battery cell was prepared by a method similar to that of Example 1. The difference from Example 1 was that the components of the electrolyte were adjusted, mainly the content of the additives.

[0360] The test results are shown in Table 3.

[0361] Table 3

[0362] In Table 3, VC stands for vinylene carbonate; FEC stands for fluoroethylene carbonate; PS stands for 1,3-propane sultone; The change in the additive content in Table 3 also brings about a change in the content of the carbonate solvent in the corresponding electrolyte, and the total mass content of each component in the electrolyte is 100%.

[0363] In comparative example 3-1, no film-forming additives were added, resulting in more serious side reactions on the negative electrode side and poor cycle performance; in comparative example 3-2, the additive content was too high, resulting in a higher SEI film impedance on the negative electrode side, which was not conducive to fast charging.

[0364] In the embodiments of the present application, the mass content of the additive is appropriate, and a dense SEI film can be formed on the negative electrode side. The film layer impedance is relatively low, which can alleviate interfacial side reactions, reduce gas production, and improve the fast charging capability and cycle performance of the battery cell at high energy density.

[0365] In Example 5-1, Example 1, and Example 5-2, as the content of vinylene carbonate VC increases, the formed SEI film becomes denser, and the protection performance on the negative electrode side is more excellent, which can effectively improve the cycle performance, but the film layer impedance increases, which reduces the fast charging performance; Example 5-3 uses fluoroethylene carbonate FEC to protect the negative electrode side. Fluoroethylene carbonate FEC can form a SEI film with relatively low impedance on the negative electrode side, reduce the internal resistance of the battery cell, and improve the fast charging capability of the battery cell; however, the protective effect of the SEI film formed by fluoroethylene carbonate FEC on the negative electrode active material is weaker than the protective effect of the SEI film formed by vinylene carbonate VC on the negative electrode active material. Compared with Example 1, Example 5-3 has a higher risk of side reactions on the negative electrode side and a slightly worse cycle performance.

[0366] In Example 5-4, vinylene carbonate VC and 1,3-propane sultone are used in combination, which can not only form an excellent SEI film on the negative electrode side, but also reduce impedance and improve the fast charging performance of the battery cell, which is beneficial to the improvement of the cycle performance under fast charging conditions.

[0367] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the embodiments of the present application, and that the embodiments may be changed, substituted and modified without departing from the spirit, principle and scope of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: include: A positive electrode sheet, comprising a positive current collecting portion and a positive electrode film layer disposed on at least one side of the positive current collecting portion, wherein the positive electrode film layer comprises a lithium-containing phosphate; A negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, wherein the single-side coating weight of the negative electrode film layer is 80 mg / 1540.25 mm 2 Up to 135mg / 1540.25mm 2 ; The negative electrode film layer comprises a carbon-based material and a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode film layer is 0.3% to 6%; and An electrolyte comprises a chain carboxylate solvent and an additive, wherein the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%, and the additive comprises one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive, and the mass content of the additive in the electrolyte is 0.5% to 10%.

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

3. The battery cell according to any one of claims 1 to 2, characterized in that: The silicon-based material includes one or more of silicon carbide and silicon oxide.

4. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer comprises: A first region is provided on the surface of the negative electrode current collecting portion, and a thickness of the first region is 1 / 3 of a thickness of the negative electrode film layer; and The second region is connected to the side of the first region away from the negative electrode current collector, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode film layer. in, An average particle size of the carbon-based material in the first region is greater than or equal to an average particle size of the carbon-based material in the second region.

5. The battery cell according to claim 4, 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.

6. The battery cell according to claim 4, 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.

7. The battery cell according to claim 4, characterized in that: At least one of the first region and the second region includes a silicon-based material.

8. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer comprises: A first negative electrode film layer is disposed on the surface of the negative electrode current collecting portion; and The second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion.

9. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode film layer includes a negative electrode conductive agent, and the negative electrode conductive agent includes one or more of conductive carbon and carbon nanotubes.

10. The battery cell according to claim 9, characterized in that: The mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%; and / or The mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%.

11. The battery cell according to any one of claims 1 to 2, characterized in that: The conductivity of the electrolyte at room temperature is 10.5 mS / cm to 13.5 mS / cm; and / or The viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

12. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the chain carboxylic acid ester solvent in the electrolyte is 8% to 20%.

13. The battery cell according to any one of claims 1 to 2, 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.

14. The battery cell according to claim 13, characterized in that: The chain carboxylic acid ester solvent includes one or more of the compounds represented by formula I-1 to the compounds represented by formula I-8, 。 15. The battery cell according to any one of claims 1 to 2, 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%.

16. The battery cell according to claim 15, characterized in that: The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

17. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the additive in the electrolyte is 2% to 6%.

18. The battery cell according to any one of claims 1 to 2, characterized in that: The carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate; and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite and methylene disulfonate; and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium bis(oxalatoborate).

19. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further comprises one or more of fluorinated lithium sulfonyl imide and lithium hexafluorophosphate.

20. The battery cell according to claim 19, characterized in that: The fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide.

21. The battery cell according to claim 19, characterized in that: The mass content of the fluorinated lithium sulfonyl imide and the lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 18%.

22. The battery cell according to claim 21, characterized in that: The mass content of the fluorinated lithium sulfonyl imide and the lithium hexafluorophosphate in the electrolyte is 4% to 16%.

23. The battery cell according to any one of claims 1 to 2, characterized in that: The single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 .

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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