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 an electrolyte and an electrode assembly, the electrode assembly comprises a first pole piece and a second pole piece, the first pole piece and the second pole piece comprise a coating part and a tab part, the tab part is connected to the coating part and extends out of the coating part along the length direction of the battery monomer, and the coating part is connected with the electrolyte. One of the first pole piece and the second pole piece is a positive pole piece, the ratio of the size of the coating part of the positive pole piece in the length direction to the size of the coating part of the positive pole piece in the width direction is larger than 1 and smaller than or equal to 18.5, and the size of the coating part of the positive pole piece in the length direction ranges from 265 mm to 1200 mm; the first pole piece meets the condition that n * W1 / W2 is 0.2 to 1.0; the electrolyte comprises fluorine-containing lithium sulfimide and lithium hexafluorophosphate, and the ratio of the mass content of the fluorine-containing lithium sulfimide to the mass content of the lithium hexafluorophosphate is 0.2-0.8. According to the invention, the high-temperature cycle performance and rapid charging performance of the battery monomer can be improved.

Description

[0001] This application claims the priority of the international patent application PCT / CN2025 / 071040 titled "Battery Cell, Battery Device and Electrical Device" filed on January 7, 2025, the entire content of which is incorporated herein by reference. Technical Field

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

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

[0004] This application provides a battery cell, a battery device and an electrical device, and the fast charging ability, high-temperature cycle performance, and use reliability of the battery cell of this application can be further improved.

[0005] In a first aspect, an embodiment of this application provides a battery cell. The battery cell includes an electrolyte and an electrode assembly. The electrode assembly includes a plurality of first electrode plates and a plurality of second electrode plates. The plurality of first electrode plates and the plurality of second electrode plates are stacked along the thickness direction of the battery cell. Both the first electrode plate and the second electrode plate include a coating portion and an electrode tab. The coating portion is provided with active material, and the electrode tab is connected to the coating portion and extends out of the coating portion along the length direction of the battery cell. Among them, one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other is a negative electrode plate; the size of the coating portion of the positive electrode plate along the length direction of the battery cell is a first size, the size of the coating portion of the positive electrode plate along the width direction of the battery cell is a second size, the ratio of the first size to the second size is greater than 1 and less than or equal to 18.5, and the size of the coating portion of the positive electrode plate along the length direction of the battery cell is 265 mm to 1200 mm; the first electrode plate satisfies: n*W1 / W2 is 0.2 to 1.0; n represents the number of all electrode tabs on the same side of the coating portion, n is greater than or equal to 1; W1 represents the average size of the electrode tab along the width direction; W2 represents the size of the coating portion along the width direction; the electrolyte includes lithium fluorosulfonylimide and lithium hexafluorophosphate, and based on the mass of the electrolyte, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.2 to 0.8.

[0006] Thus, when the coating part of the positive electrode plate of the embodiment of the present application meets the above range, the energy density of the battery cell can be improved; under the above electrode plate, the tab is arranged on at least one side of the coating part along the length direction of the battery cell, and the electron transfer distance on the electrode plate is relatively short, and the electron transfer rate is relatively fast, which can reduce the ohmic resistance of the electrode plate; moreover, the embodiment of the present application also improves the lithium salt component of the electrolyte. The lithium salt includes an appropriate content of lithium fluorosulfonylimide, which improves the ability of the electrolyte to conduct lithium ions. The common improvement of the active ion and electron transfer rates can effectively improve the fast charging ability of the battery cell at high energy density; the tab is arranged on at least one side of the coating part along the length direction of the battery cell, and the ohmic resistance of the electrode plate is relatively low, so that the heat generation amount of the electrode plate is relatively small; further, the appropriate size ratio of the tab makes the current-carrying area of the tab relatively high, and the resistance at the connection with the coating part is small, which can further reduce the heat generation amount of the electrode plate. Therefore, the heat accumulation inside the battery cell can be reduced, the adverse effect on lithium fluorosulfonylimide caused by heat accumulation can be reduced, the risk of lithium fluorosulfonylimide decomposing to generate gas and heat can be slowed down, and the high-temperature cycle performance and use reliability of the battery cell can be improved.

[0007] In some embodiments, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.3 to 0.5. The compound use of lithium hexafluorophosphate and lithium fluorosulfonylimide can, on the one hand, improve the conductivity of the electrolyte and the fast charging performance of the battery cell; on the other hand, it can reduce the side reactions on the negative electrode side and the risk of lithium fluorosulfonylimide decomposition, and improve the high-temperature cycle performance and use reliability of the battery cell.

[0008] In some embodiments, the mass content of lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 18%, and can be selected from 10% to 18%. When the mass content of the lithium salt is in the above range, the high-temperature cycle performance and fast charging ability of the battery cell can be improved.

[0009] In some embodiments, the mass content of lithium fluorosulfonylimide in the electrolyte is greater than 0 and less than or equal to 8%. When the mass content of lithium fluorosulfonylimide is in the above range, the high-temperature cycle performance and fast charging ability of the battery cell can be improved.

[0010] In some embodiments, the mass content of lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 12%. When the mass content of lithium hexafluorophosphate is in the above range, the high-temperature cycle performance and fast charging ability of the battery cell can be improved.

[0011] In some embodiments, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bisfluorosulfonylimide. The above materials are beneficial to improving the high-temperature cycle performance and fast charging ability of the battery cell.

[0012] In some embodiments, the conductivity of the electrolyte at room temperature is from 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.

[0013] In some embodiments, the viscosity of the electrolyte at room temperature is from 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.

[0014] In some embodiments, the density of the electrolyte at room temperature is from 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0015] In some embodiments, the electrolyte further includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent in the electrolyte is from 5% to 35%. When the mass content of the chain carboxylic ester solvent is within the above range, the fast charging ability and high temperature cycle performance of the battery cell can be improved.

[0016] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0017] The above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0018] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0019] In some embodiments, the electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is from 65% to 75%. When the mass contents of the carbonate solvent and the chain carboxylic ester solvent meet the above conditions, the stability of the electrolyte can be improved, the gas generation amount at high temperature can be reduced, and the high temperature cycle performance of the battery cell can be improved.

[0020] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0021] In some embodiments, the electrolyte includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. The mass content of the additives in the electrolyte is 0.5% to 10%. The above additives can improve the interfacial film performance on the negative electrode side. The formed interfacial film has higher stability and relatively lower impedance of the interfacial film, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycle performance.

[0022] In some embodiments, the carbonate additives include one or more of fluorinated ethylene carbonate and vinylene carbonate. The above additives can improve the performance of the solid electrolyte interface film (SEI film) on the negative electrode side. The formed interfacial film has higher stability and relatively lower impedance of the interfacial film, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycle performance.

[0023] In some embodiments, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate; the above additives are beneficial to improving the high-temperature cycle performance of the battery cell.

[0024] In some embodiments, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The above additives are beneficial to improving the high-temperature cycle performance of the battery cell.

[0025] In some embodiments, the number of tab portions of the first electrode tab is 1 to 4. When the number of tab portions is within the above range, the current-carrying capacity of the tab portions is relatively strong, which is beneficial to improving the fast charging ability of the battery cell.

[0026] In some embodiments, all the tab portions of the first electrode tab are connected to the same side of the coating portion along the length direction, and this setting method is beneficial to improving the energy density of the battery cell.

[0027] In some embodiments, the first electrode tab includes at least two tab portions, and the at least two tab portions are connected to both sides of the coating portion of the first electrode tab along the length direction. This setting method can shorten the electron transfer path and improve the fast charging ability of the battery cell.

[0028] In some embodiments, n*W1 / W2 is 0.5 to 1.0. When the tab portion meets the above requirements, the current-carrying capacity is relatively strong, which is beneficial to improving the fast charging ability of the battery cell.

[0029] In some embodiments, the ratio of the first dimension to the second dimension is from 3.5 to 8, and the dimension of the coating portion of the positive electrode tab in the length direction is from 400 mm to 600 mm. When the dimension of the positive electrode film layer is within the above range, the electron transmission path will not be too long, and the internal resistance is relatively small, which is beneficial to improving the fast charging ability and energy density of the battery cell.

[0030] In some embodiments, the active material of the positive electrode tab includes lithium-containing phosphate. The lithium-containing phosphate has relatively excellent cycle stability and can improve the high-temperature cycle performance of the battery cell.

[0031] In some embodiments, the negative electrode tab includes a negative electrode coating portion and a negative electrode tab connected to the negative electrode coating portion, and the positive electrode tab includes a positive electrode coating portion and a positive electrode tab connected to the positive electrode coating portion; the dimension of the negative electrode coating portion in the width direction is greater than the dimension of the positive electrode coating portion in the width direction, and the difference between the dimension of the negative electrode coating portion in the width direction and the dimension of the positive electrode coating portion in the width direction is from 5 mm to 11 mm; the relatively large dimension of the negative electrode coating portion can reduce the risk of lithium deposition on the negative electrode and the risk of short circuit between the positive and negative electrodes, and improve the reliability of use of the battery cell.

[0032] In some embodiments, the dimension of the negative electrode coating portion in the length direction is greater than the dimension of the positive electrode coating portion in the length direction, and the difference between the dimension of the negative electrode coating portion in the length direction and the dimension of the positive electrode coating portion in the length direction is from 5 mm to 11 mm. The relatively large dimension of the negative electrode coating portion can reduce the risk of lithium deposition on the negative electrode and the risk of short circuit between the positive and negative electrodes, and improve the reliability of use of the battery cell.

[0033] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode tab and the negative electrode tab, and the negative electrode tab includes a negative electrode coating portion and a negative electrode tab connected to the negative electrode coating portion; the dimension of the separator in the width direction is greater than the dimension of the negative electrode coating portion in the width direction, and the difference between the dimension of the separator in the width direction and the dimension of the negative electrode coating portion in the width direction is from 6 mm to 10 mm. The relatively large dimension of the separator can effectively isolate the negative electrode tab and the positive electrode tab, reduce the risk of short circuit between the negative electrode tab and the positive electrode tab, and improve the reliability of use of the battery cell.

[0034] In some embodiments, the dimension of the separator in the length direction is greater than the dimension of the negative electrode coating portion in the length direction, and the difference between the dimension of the separator in the length direction and the dimension of the negative electrode coating portion in the length direction is from 6 mm to 10 mm. The relatively large dimension of the separator can effectively isolate the negative electrode tab and the positive electrode tab, reduce the risk of short circuit between the negative electrode tab and the positive electrode tab, and improve the reliability of use of the battery cell.

[0035] In a second aspect, an embodiment of the present application further provides a battery device including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0036] In a third aspect, an embodiment of the present application further provides an electrical device, which includes a battery device according to any one of the embodiments of the second or third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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 those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0038] Figure 1 It is a schematic structural diagram of an electrical device provided by some embodiments of the present application.

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

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

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

[0042] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0043] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

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

[0046] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, a method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0047] The term "plurality" as used in this application means two or more (including two).

[0048] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, the requirements for the fast charging performance of high energy density battery cells are gradually increasing. With the improvement of the fast charging performance requirements, in related technologies, it can be achieved by increasing the conductivity of the electrolyte. However, the increase in conductivity may lead to the decomposition of the electrolyte at high temperatures, resulting in an increase in the gas generation of the battery cell at high temperatures, which may cause deterioration of the high temperature cycle performance, service reliability, etc. of the battery cell.

[0049] In view of the above problems, the embodiments of the present application design the size of the electrode sheet to improve the energy density of the battery cell; Under the above electrode sheet, the tab is arranged on at least one side of the coating part along the length direction of the battery cell. The transmission distance of electrons in the electrode sheet is relatively short, and the electron transmission rate is relatively fast, which can reduce the ohmic resistance of the electrode sheet. Moreover, the embodiments of the present application also improve the lithium salt component of the electrolyte. The lithium salt includes an appropriate content of lithium fluorosulfonylimide, which improves the ability of the electrolyte to conduct lithium ions. The combined improvement of the active ion and electron transmission rates can effectively improve the fast charging ability of the battery cell at high energy density; The tab is arranged on at least one side of the coating part along the length direction of the battery cell, and the ohmic resistance of the electrode sheet is relatively low, so that the heat generation of the electrode sheet is relatively small. Further, the appropriate size ratio of the tab results in a relatively high current-carrying area of the tab and a small resistance at the connection with the coating part, which can further reduce the heat generation of the electrode sheet. Thus, the heat accumulation inside the battery cell can be reduced, and the risk of thermal runaway can be reduced; the risk that lithium fluorosulfonylimide decomposes rapidly during thermal runaway, generating a large amount of gas and heat, and deteriorating the service reliability of the battery cell is reduced, and the high temperature cycle performance and service reliability of the battery cell are improved.

[0050] The battery cell of the present application is applicable to various battery devices and electrical devices that use battery cells.

[0051] Exemplarily, the electrical device can be a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric toy, an electric tool, a vehicle, a ship, a spacecraft, etc. Or, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0052] Figure 1 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be used.

[0053] Inside the electrical device 1, a battery device is provided, and the battery device can be arranged at the bottom, head or tail of the electrical device 1. The battery device can be used to supply power to the electrical device 1. For example, the battery device can serve as the operating power source of the electrical device 1 and also as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in

[0054] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery device to supply power to the motor 4. For example, it is used for the working power requirements during the startup, navigation and driving of the electrical device 1.

[0055] The battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel or in a hybrid connection through a busbar component.

[0056] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0057] As an example, the battery cell assembly can be a battery module, and the battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0058] As Figure 2 shown, in some embodiments, the battery device can be a battery pack 2, and the battery pack 2 includes a box body 5 and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body 5.

[0059] As an example, the battery cell assembly can also be accommodated in the box body 5 by directly fixing a plurality of battery cells to the box body 5.

[0060] As an example, the box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a and the second box body part 5b are snapped together so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly. Here, "closed" means covering or closing, which can be sealed or non-sealed. The first box body part 5a can be a top cover or a bottom plate.

[0061] As an example, the box body 5 may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0062] In some embodiments, the box body 5 can be part of the chassis structure of a vehicle. For example, part of the box body 5 can form at least part of the floor of the vehicle, or part of the box body 5 can form at least part of the cross beams and longitudinal beams of the vehicle.

[0063] As an example, the battery cell assembly can be a battery module 6, and the battery cell assembly can be accommodated in the box body 5 by fixing the battery module 6 in the box body 5.

[0064] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0065] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0066] In some embodiments, during the charging process of the battery device or any battery cell 7 that makes up the battery device from 20% SOC to 80% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0067] Exemplarily, the charging steps of the battery device or any battery cell 7 that makes up the battery device from 20% SOC to 80% SOC can be carried out in the following manner: Charge from 20% SOC to 25% SOC at a constant current of 8.00C; Charge from 25% SOC to 30% SOC at a constant current of 8.00C; Charge from 30% SOC to 35% SOC at a constant current of 7.50C; Charge from 35% SOC to 40% SOC at a constant current of 6.87C; Charge from 40% SOC to 45% SOC at a constant current of 6.38C; Charge from 45% SOC to 50% SOC at a constant current of 5.95C; Charge from 50% SOC to 55% SOC at a constant current of 5.53C; Charge from 55% SOC to 60% SOC at a constant current of 5.14C; Charge from 60% SOC to 65% SOC at a constant current of 4.76C; Charge from 65% SOC to 70% SOC at a constant current of 4.36C; Charge from 70% SOC to 75% SOC at a constant current of 3.94C; Charge from 75% SOC to 80% SOC at a constant current of 3.57C.

[0068] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from 20% state of charge to 80% state of charge is 5 min to 30 min, optionally 5 min to 20 min. The temperature of the external environment of the battery device at 20% state of charge is room temperature, such as 25 °C. Exemplarily, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min or a range composed of any two of the above values.

[0069] As Figure 4 and Figure 5 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20.

[0070] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0071] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0072] Exemplarily, the terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32. One of the first electrode terminal 31 and the second electrode terminal 32 is the positive terminal, and the other is the negative terminal.

[0073] The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite housing), or an aluminum-plastic film, etc. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly 10, and a sealed bag is further included between the housing and the electrode assembly 10 for encapsulating the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0074] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, and a multi-prismatic battery. The multi-prismatic battery is, for example, a hexagonal prism battery, etc., and there is no special limitation in this application.

[0075] In some embodiments, the outer casing includes an end cap 22 and a housing 21. The housing 21 is provided with an opening, and the end cap 22 covers the opening. The housing 21 can be provided with one or more openings. The end cap 22 can also be provided with one or more.

[0076] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a housing 21 with a cylindrical structure can be selected; if the electrode assembly 10 is a cuboid structure, a housing 21 with a cuboid structure can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0077] The electrode assembly 10 includes a first electrode tab 11, a second electrode tab 12, and a separator 13. One of the first electrode tab 11 and the second electrode tab 12 is a positive electrode tab, and the other is a negative electrode tab.

[0078] The electrode assembly 10 is a stacked structure, which is beneficial to improving the energy density of the battery cell 7.

[0079] As an example, a plurality of first electrode tabs 11 and second electrode tabs 12 can be respectively provided, and the plurality of first electrode tabs 11 and the plurality of second electrode tabs 12 are alternately stacked.

[0080] As an example, a plurality of first electrode tabs 11 can be provided, and the second electrode tab 12 is folded to form a plurality of stacked folding segments, and a first electrode tab 11 is clamped between adjacent folding segments.

[0081] As an example, both the first electrode tab 11 and the second electrode tab 12 are folded to form a plurality of stacked folding segments.

[0082] As an example, a plurality of separators 13 can be provided and are respectively arranged between any adjacent first electrode tab 11 or second electrode tab 12.

[0083] As an example, the separator 13 can be continuously provided and is arranged between any adjacent first electrode tab 11 or second electrode tab 12 by folding or winding.

[0084] In some embodiments, each electrode tab is provided with a tab. The tab can conduct current out of the electrode assembly 10. The tab includes a positive tab and a negative tab.

[0085] To more clearly illustrate the present application, the tab portion of the first electrode tab 11 is defined as the first tab 111, and the coated portion of the first electrode tab 11 is defined as the first coated portion 112. The tab portion of the second electrode tab 12 is defined as the second tab 121, and the coated portion of the second electrode tab 12 is defined as the second coated portion 122. The electrode terminal that is electrically connected and has the same electrical property as the first tab 111 is the first electrode terminal 31 described above, and the electrode terminal that is electrically connected and has the same electrical property as the second tab 121 is the second electrode terminal 32 described above.

[0086] The polarities of the first electrode tab 11 and the second electrode tab 12 are opposite. When the first electrode tab 11 is the positive electrode tab, the second electrode tab 12 is the negative electrode tab, the first coated portion 112 is the positive electrode coated portion, the first tab 111 is the positive tab, the first electrode terminal 31 is the positive terminal, the second coated portion 122 is the negative electrode coated portion, the second tab 121 is the negative tab, and the second electrode terminal 32 is the negative terminal.

[0087] Or when the first electrode tab 11 is the negative electrode tab, the second electrode tab 12 is the positive electrode tab, the first coated portion 112 is the negative electrode coated portion, the first tab 111 is the negative tab, the first electrode terminal 31 is the negative terminal, the second coated portion 122 is the positive electrode coated portion, the second tab 121 is the positive tab, and the second electrode terminal 32 is the positive terminal.

[0088] The coated portion includes a current collector portion and a film layer provided on the current collector portion and containing active material. For example, the positive electrode coated portion includes a positive electrode current collector portion and a positive electrode film layer provided on the positive electrode current collector portion and containing positive electrode active material. Another example is that the negative electrode coated portion includes a negative electrode current collector portion and a negative electrode film layer provided on the negative electrode current collector portion and containing negative electrode active material.

[0089] As Figures 4 to 6 shown, in some embodiments, the battery cell 7 includes an electrolyte and an electrode assembly 10. The electrode assembly 10 includes a plurality of first electrode tabs 11 and a plurality of second electrode tabs 12. The plurality of first electrode tabs 11 and the plurality of second electrode tabs 12 are stacked in the thickness direction X of the battery cell 7. Both the first electrode tab 11 and the second electrode tab 12 include a coated portion and a tab portion. The coated portion is provided with active material, and the tab portion may not be coated with active material. The tab portion is connected to the coated portion and extends out of the coated portion along the length direction Z of the battery cell 7. Among them, one of the first electrode tab 11 and the second electrode tab 12 is the positive electrode tab, and the other is the negative electrode tab; The dimension of the coated portion of the positive electrode tab along the length direction Z of the battery cell 7 is the first dimension, and the dimension of the coated portion of the positive electrode tab along the width direction Y of the battery cell 7 is the second dimension. The ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5. The dimension of the coated portion of the positive electrode tab along the length direction Z of the battery cell 7 is 265 mm to 1200 mm; The first electrode sheet satisfies that n*W1 / W2 is from 0.2 to 1.0; n represents the number of all tab portions located on the same side of the coating portion; n is greater than or equal to 1; W1 represents the average dimension of the tab portion along the width direction Y; W2 represents the dimension of the coating portion along the width direction Y; The electrolyte includes a lithium salt, and the lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate. Based on the mass of the electrolyte, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is from 0.2 to 0.8.

[0090] Taking Figure 6 the first electrode sheet 11 in [the above] as the positive electrode sheet as an example, Z2 represents the dimension of the coating portion of the positive electrode sheet along the length direction Z of the battery cell 7, i.e., the first dimension, and W2 represents the dimension of the coating portion of the positive electrode sheet along the width direction Y of the battery cell 7, i.e., the second dimension.

[0091] When the dimension of the coating portion of the positive electrode sheet along the length direction Z of the battery cell is less than 265 mm, the amount of active material that can be carried is limited, and the energy density of the battery cell 7 is relatively low; the dimension of the coating portion of the positive electrode sheet in the embodiment of the present application is greater than or equal to 265 mm, which is beneficial to improving the energy density of the battery cell 7; As the dimension of the coating portion of the positive electrode sheet along the length direction Z further increases, the electron transmission path in the electrode sheet increases, and the ohmic resistance increases; as the ratio of the first dimension to the second dimension increases, the electron transmission path in the electrode sheet further increases, and the ohmic resistance increases, which is not conducive to fast charging; moreover, the increase in ohmic resistance may lead to an increase in heat generation, and the accumulation of heat is likely to cause the decomposition of the electrolyte, deteriorating the cycle; In one aspect, the embodiment of the present application limits the ratio of the first dimension to the second dimension to be less than or equal to 18.5, reduces the aspect ratio, and shortens the electron transmission distance in the length direction; on the other hand, the tab portion is arranged on at least one side of the coating portion along the length direction Z of the battery cell 7, which can further shorten the electron transmission distance in the electrode sheet, reduce the ohmic resistance of the electrode sheet, and improve the electron transmission rate; the embodiment of the present application also regulates the lithium salt of the electrolyte. The lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate, and the mass content ratio of the two is greater than or equal to 0.2, so that the lithium ion transference number of the electrolyte is increased, and the lithium ion conduction ability is improved; by comprehensively improving the electron transmission ability and the ion conduction ability, the fast charging ability of the battery cell at high energy density is improved; Lithium hexafluorophosphate may decompose to generate hydrofluoric acid HF. The side reaction between hydrofluoric acid and the negative electrode active material may cause an increase in gas generation during high-temperature storage; the compound use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, reduce the gas generation amount during high-temperature storage, and improve the high-temperature cycle performance; However, with the increase in the addition amount of lithium fluorosulfonylimide, the risk of thermal diffusion further increases. Specifically, the thermal decomposition temperature of the fluorosulfonylimide salt is close to the thermal runaway temperature of the battery cell 7, and lithium fluorosulfonylimide has a relatively fast thermal decomposition rate and intense heat release, which can quickly release a large amount of heat and high-temperature gases, resulting in a sharp increase in the internal heat of the battery cell 7. A large amount of heat is difficult to quickly dissipate, easily leading to thermal diffusion and deteriorating the use reliability of the battery cell 7. On the one hand, by limiting the mass content ratio of lithium fluorosulfonylimide and lithium hexafluorophosphate to be less than or equal to 0.8 in the embodiments of the present application, the risk of further heat increase caused by the decomposition of lithium fluorosulfonylimide due to heat increase can be reduced. On the other hand, the size of the electrode sheet meets the above range, and the tab is disposed on at least one side of the coating portion along the length direction Z of the battery cell. The ohmic resistance of the electrode sheet is relatively low, so that the heat generation of the electrode sheet is relatively small. Further, with an appropriate size ratio of the tab, n*W1 / W2 being greater than or equal to 0.2, the current-carrying area of the tab is relatively high, and the resistance at the connection with the coating portion is small, which can further reduce the heat generation of the electrode sheet. Thereby, the heat accumulation inside the battery cell 7 can be reduced, the adverse effect of heat accumulation on lithium fluorosulfonylimide can be reduced, and the risk of gas and heat generation caused by the decomposition of lithium fluorosulfonylimide can be slowed down, thus improving the high-temperature cycling performance and use reliability of the battery cell 7.

[0092] Therefore, the embodiments of the present application can take into account improving the fast charging performance, high-temperature cycling performance and use reliability of the high-energy density battery cell 7.

[0093] Exemplarily, n*W1 / W2 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range composed of any two of the above values. Optionally, n*W1 / W2 is from 0.5 to 1.0.

[0094] When n*W1 / W2 meets the above range, the current-carrying area of the tab is relatively large and the heat generation is small, which is beneficial to improving the fast charging performance and high-temperature cycling performance of the battery cell 7 at high energy density.

[0095] W1 represents the average size of the first tab 111 along the width direction Y. When the first tab 111 has a special-shaped structure, for example, along the length direction Z, the size of the first tab 111 along the width direction Y gradually increases. In this case, the sizes of the first tab 111 at multiple locations along the width direction Y can be measured, and thus the average size of the first tab 111 along the width direction Y can be calculated. Of course, the sizes of the first tab 111 at each location along the width direction Y can be the same value. In this case, this value can be used as the average size of the first tab 111.

[0096] The first tab 111 can be one or more. When there are multiple first tabs 111 on the same side of the first coating portion 112, for example, when n is from 1 to 4, after measuring the average size of each first tab 111 respectively, the average size of the first tabs 111 can be calculated by adding up the average sizes and dividing by the number of the first tabs 111.

[0097] The first tab 111 is connected to the first coating portion 112. The first tab 111 includes a first end 1111 connected to the first coating portion 112. When n*W1 / W2 meets the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first coating portion 112 is relatively large, the current-carrying capacity of the first tab 111 is strong, and the fast charging performance and high-temperature cycling performance of the battery cell 7 can be improved.

[0098] In some embodiments, the first electrode plate 11 includes at least one first tab 111, for example, includes 1 to 4 first tabs 111. Optionally, the first electrode plate 11 includes at least two first tabs 111, and can be four first tabs 111.

[0099] In some embodiments, one or more first tabs 111 are disposed on at least one side of the coating portion along the length direction Z.

[0100] As Figures 6 to 8 shown, the tab portions on the same side of the coating portion in the first electrode plate 11 are at least one, and the tab portion includes a first end 1111 connected to the coating portion. Figure 6 When n is 2, the sizes of the respective first tabs 111 are the same, and W1 can also represent the size of a single first tab 111. Of course, the sizes of the respective first tabs 111 can also be slightly different. W2 represents the size of the first coating portion 112 along the length direction Z. Figure 7 When n is 1, n*W1 / W2 is 1.0. Figure 8 When n is 1.

[0101] In some embodiments, the first electrode plate 11 includes at least one first tab 111, for example, includes 1 to 4 first tabs 111. Optionally, the first electrode plate 11 includes at least two first tabs 111, and can be four first tabs 111.

[0102] In some embodiments, one or more first tabs 111 are disposed on at least one side of the coating portion along the length direction Z.

[0103] One or more first 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 the first tabs 111 are disposed on the same side of the first coating portion 112 along the length direction Z.

[0104] For example, in the case where the first electrode tab 11 includes a plurality of first tab ears 111, the plurality of first tab ears 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z, which can shorten the electron transmission distance and improve the fast charging performance.

[0105] Optionally, the plurality of first tab ears 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z. This setting can shorten the transmission path of electrons in the first electrode tab 11, which is beneficial to improving the fast charging performance. For example, two first tab ears 111 are located on one side of the first coating portion 112 along the length direction Z, and two first tab ears 111 are located on the other side of the first coating portion 112 along the length direction Z.

[0106] Optionally, in the case where the plurality of first tab ears 111 are respectively disposed on at least one side of the first coating portion 112 along the length direction Z, there are at least two first tab ears 111 on the same side of the first coating portion 112 along the length direction Z, such as two, three, four, five, six, etc. This setting is beneficial to the uniform distribution of electrons in the first electrode tab 11 and is beneficial to improving the fast charging performance.

[0107] Optionally, the distance between two adjacent first tab ears 111 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range composed of any two of the above values. Figure 6 Where Y1 represents the distance between two adjacent first tab ears 111 along the width direction Y.

[0108] Such as Figure 9 and Figure 10 As shown, in some embodiments, for the second electrode tab 12: m*W3 / W4 is 0.2 to 1.0; m represents the number of all tab ear portions on the same side of the coating portion; m is greater than or equal to 1; W3 represents the average size of the tab ear portion along the width direction Y; W4 represents the size of the coating portion along the width direction Y.

[0109] Exemplarily, m*W3 / W4 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range composed of any two of the above values. Optionally, m*W3 / W4 is 0.5 to 1.0.

[0110] When m*W3 / W4 satisfies the above range, the current-carrying area of the second tab 121 is relatively large and the heat generation is less, which is beneficial to improving the fast charging performance and high-temperature cycling performance of the battery cell 7 at high energy density.

[0111] W3 represents the average dimension of the second tab 121 along the length direction Z. The second tab 121 can be one or more. For example, m is from 1 to 4. When there are multiple second tabs 121 on the same side of the second coating portion 122, the average dimension can be calculated by measuring the dimensions of each second tab 121 with a micrometer.

[0112] The second tab 121 is connected to the second coating portion 122. The second tab 121 includes a second end 1211 connected to the second coating portion 122. When m*W3 / W4 satisfies the above range, it means that the cross-section of the second end 1211 along the thickness direction of the second tab 121 itself is relatively large, the contact surface between the second tab 121 and the second coating portion 122 is relatively large, the current-carrying capacity of the second tab 121 is strong, and the fast charging performance and high-temperature cycling performance of the battery cell 7 can be improved.

[0113] Optionally, the current collector portion of the second tab 121 and the second coating portion 122 is an integral structure, so that the internal resistance of the second electrode sheet 12 is relatively low, and the fast charging performance and high-temperature cycling performance of the battery cell 7 can be further improved.

[0114] Figure 9 In [a certain case], m is 1. Figure 10 In [a certain case], m is 2.

[0115] In some embodiments, the second electrode sheet 12 includes at least one second tab 121, optionally at least two second tabs 121, and optionally four second tabs 121.

[0116] For example, one or more second tabs 121 are disposed on one side of the second coating portion 122 along the length direction Z. In this case, it can be understood that all the second tabs 121 are disposed on the same side of the second coating portion 122 along the length direction Z.

[0117] Or for example, when the second electrode sheet 12 includes multiple second tabs 121, the multiple second tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z.

[0118] Optionally, the multiple second tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z. This setting can shorten the transmission path of electrons in the second electrode sheet 12 and is beneficial to improving the fast charging performance.

[0119] Optionally, when a plurality of second tab ears 121 are disposed on at least one side of the second coating portion 122 along the length direction Z, there are at least two second tab ears 121 on the same side of the second coating portion 122 along the length direction Z, such as two, three, four, five, six, etc. This kind of setting is beneficial to the uniform distribution of electrons in the second electrode sheet 12 and is beneficial to improving the fast charging performance.

[0120] Optionally, the distance between two adjacent second tab ears 121 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or the range composed of any two of the above values.

[0121] As Figure 11 shown, in some embodiments, the terminal assembly can be disposed on the housing 21, or the terminal assembly is disposed on the end cover 22.

[0122] The terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32. The first electrode terminal 31 is connected to the first tab ear 111, and the second electrode terminal 32 is connected to the second tab ear 121.

[0123] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cover 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cover 22.

[0124] On the same end cover 22, the first electrode terminal 31 and the second electrode terminal 32 can be disposed simultaneously. For example, there is one end cover 22, and the first electrode terminal 31 and the second electrode terminal 32 are disposed at intervals on this end cover 22. Another example is that there are two end covers 22, the two end covers 22 are disposed oppositely, and each end cover 22 is provided with the first electrode terminal 31 and the second electrode terminal 32.

[0125] The first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on different end covers 22. For example, there are two end covers 22, the two end covers 22 are disposed oppositely, the first electrode terminal 31 is disposed on one of the end covers 22, and the second electrode terminal 32 is disposed on the other end cover 22.

[0126] In some embodiments, the first electrode terminal 31 is at least one, and can be optionally at least two, such as two, three or four, etc.

[0127] 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.

[0128] As Figure 11As shown, for example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0129] As Figure 12 shown, for another example, a plurality of first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0130] Exemplarily, there are two first electrode terminals 31, one of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Or, exemplarily, there are four first electrode terminals 31, two of the first electrode terminals 31 are disposed on one side of the electrode assembly 10, and the other two first electrode terminals 31 are disposed on one side of the electrode assembly 10.

[0131] In the embodiments of the present application, the first tab 111 and the first electrode terminal 31 are electrically connected, which can be directly connected or indirectly connected; when the first tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, and the first adapter 51 is located between the first electrode terminal 31 and the first tab 111 and connects the first electrode terminal 31 and the first tab 111.

[0132] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0133] 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 the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, a plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0134] In some embodiments, the second electrode terminal 32 is at least one, and may be optionally at least two, such as two, three, or four, etc.

[0135] 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.

[0136] As Figure 12 shown, for example, at least two second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0137] Figure 12It is shown that the battery cell 7 includes four electrode terminals. Specifically, there are two second electrode terminals 32. One of the second electrode terminals 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31. One of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0138] For another example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 along the length direction Z. When being respectively electrically connected to the pole ear parts, they basically do not interfere with each other.

[0139] Exemplarily, there is one first electrode terminal 31 and one second electrode terminal 32. The first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, and the second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. Optionally, the first electrode terminal 31 and the second electrode terminal 32 can be staggeredly disposed along the width direction Y. Of course, the first electrode terminal 31 and the second electrode terminal 32 can also be oppositely disposed along the length direction Z. Figure 11 It shows a schematic diagram in which the first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on both sides of the electrode assembly 10.

[0140] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32. The two first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the length direction Z.

[0141] In the embodiment of the present application, the second pole ear 121 and the second electrode terminal 32 are electrically connected, which can be directly connected or indirectly connected. When the second pole ear 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter. The second adapter is located between the second electrode terminal 32 and the second pole ear 121 and connects the second electrode terminal 32 and the second pole ear 121.

[0142] In the above embodiments, the second adapter can include a conductive polymer or a conductive metal material. The conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0143] In some other embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 in the width direction Y. For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 in the width direction Y, or a plurality of second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the width direction Y.

[0144] Negative electrode plate The coating portion of the negative electrode tab includes a negative electrode current collector portion and a negative electrode film layer disposed on at least one side of the negative electrode current collector portion and including a negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0145] The upper charge limit voltage and the discharge cut-off voltage 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 charge limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V, or the upper charge limit voltage can be 3.8V and the discharge cut-off voltage can be 2.0V; or when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.3V and the discharge cut-off voltage can be 2.0V. Next, taking the upper charge limit voltage of 3.8V and the discharge cut-off voltage of 2.0V as an example, the state of the battery cell will be described: In the embodiments of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows. The battery cell is charged at a constant current charge rate of 0.05C to the upper charge limit voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged at a constant current discharge rate of 0.05C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0146] In some embodiments, when the battery cell is in the 100% state of charge SOC, the compaction density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 . Exemplarily, the compaction density of the negative electrode film layer when the battery cell is in the 100% state of charge is 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 , 1.66 g / cm³, 1.68 g / cm³, 1.70 g / cm³ or a range composed of any two of the above values.

[0147] When the compaction density of the negative electrode film layer is within the above range, the thickness of the negative electrode film layer will not be too thick, which is beneficial to the rapid charging of the battery cell; moreover, the particle packing of the negative electrode active material will not be too tight, reducing the risk of particle crushing, which is beneficial to improving the high-temperature cycling performance of the battery cell.

[0148] In some embodiments, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 to 175 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 、80 mg / 1540.25 mm²、85 mg / 1540.25 mm²、90 mg / 1540.25 mm²、95 mg / 1540.25 mm²、100 mg / 1540.25 mm²、105 mg / 1540.25 mm²、110 mg / 1540.25 mm²、115 mg / 1540.25 mm²、120 mg / 1540.25 mm²、120 mg / 1540.25 mm 2 、122 mg / 1540.25 mm 2 、125 mg / 1540.25 mm 2 、128 mg / 1540.25 mm 2 、130 mg / 1540.25 mm 2 、140 mg / 1540.25 mm 2 、150 mg / 1540.25 mm 2 、160 mg / 1540.25 mm 2 、170 mg / 1540.25 mm 2 、175 mg / 1540.25 mm 2 or the range composed of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 to 142 mg / 1540.25 mm 2 .

[0149] When the single-sided coating weight of the negative electrode film layer meets the above range, it is beneficial to improve the energy density of the battery cell, and the migration rate of active ions in the negative electrode film layer is relatively fast, and it is beneficial to reduce the polarization phenomenon under high-rate charging, which is beneficial to improving the rapid charging ability of the battery cell.

[0150] In the embodiments of the present application, the tap density of the negative electrode film layer of the battery cell in the 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 in the 100% state of charge (SOC), and the tap 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) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, and the weight of the negative electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode sheet - the weight M0 of the negative electrode current collector) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode sheet - the thickness H0 of the negative electrode current collector, and the tap 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.

[0151] In some embodiments, the charging specific capacity of the negative electrode active material is 350 mAh / g to 500 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g or the range composed of any two of the above values.

[0152] When the charging specific capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0153] In the embodiments of the present application, the specific capacity of the active material is a well-known meaning in the art, and the equipment and methods well-known in the art can be used for testing. The testing method of the first Coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted to test the charging specific capacity of the negative electrode active material at a 0.1C rate in a half-cell. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-cell is assembled. Under the condition of 23°C ± 2°C, the half-cell is placed on a battery tester or other test equipment with the same performance, and the discharging capacity is obtained through charge and discharge at a 0.1C rate, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0154] In some embodiments, the negative electrode active material includes a silicon-based material. Optionally, the silicon-based material may include elemental silicon, silicon-carbon composite, silicon oxide SiO xAt least one of (0 < x ≤ 2). For example, the silicon-carbon composite may be silicon carbide.

[0155] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 0.3% to 10%, such as 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or the range composed of any two of the above values. Optionally, the mass content of silicon element in the silicon-based material in the negative electrode film layer is 3% to 6%.

[0156] When the mass content of silicon element is within the above range, it can improve the capacity of the negative electrode active material, which is beneficial to improving the energy density of the battery cell; moreover, during the charge and discharge process, the volume expansion of the silicon element will not be too large, which is beneficial to maintaining the stability of the negative electrode interface film and improving the high-temperature cycle performance of the battery cell.

[0157] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has high cycle stability and can improve the high-temperature cycle performance of the battery cell.

[0158] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0159] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0160] In this application, the qualitative and quantitative determination of each substance or each element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0161] For example, this application can perform X-ray powder diffraction testing and qualitative analysis on the negative electrode plate or the negative electrode active material in combination with JIS / K0131-1996 General Rules for X-ray Diffraction Analysis.

[0162] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional views taken by a scanning electron microscope (SEM). In the SEM cross-sectional view of natural graphite, there are voids between flaky structures. The SEM cross-sectional view of artificial graphite is dense and has no obvious gaps. Or they can be distinguished by the XRD spectra obtained by X-ray diffraction method. In the XRD spectrum of natural graphite, obvious 2H phase and 3R phase exist. The XRD spectrum of artificial graphite only has 2H phase.

[0163] As Figure 13 shown, in the embodiment of the present application, the negative electrode film layer 141 of the negative electrode tab 14 includes at least one layer of film layer, which can be a single-layer film layer or at least two-layer film layers. Optionally, the negative electrode film layer 141 includes at least two-layer film layers.

[0164] When the negative electrode film layer 141 adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material.

[0165] When the negative electrode film layer 141 adopts at least two-layer film layers, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material. The negative electrode film layer 141 can include two-layer film layers, three-layer film layers, four-layer film layers, or even more film layers.

[0166] 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 facing away from the negative electrode current collector 142. The negative electrode active material of the second negative electrode film layer 1412 includes a carbon-based material. The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 can be regular or irregular. Optionally, it is irregular; or there is no obvious interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0167] The negative electrode film layer 141 includes at least two-layer film layers. Layered coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences in the porosity between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, it is beneficial to improve the fast charging performance of the battery cell.

[0168] 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.

[0169] Optionally, the first negative electrode film layer 1411 further includes a silicon-based material.

[0170] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0171] Exemplarily, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 include a silicon-based material, it is more beneficial to improve the energy density of the battery cell; and it can enable each layer to relieve the volume expansion of the silicon-based material through the carbon-based material, making the negative electrode interface film more stable and improving the high-temperature cycle performance; and since each layer includes a silicon-based material, the coating thickness is relatively thin, which is beneficial to shortening the lithium-ion transmission path and improving the fast charging performance.

[0172] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material. When the first negative electrode film layer 1411 includes a silicon-based material and the second negative electrode film layer 1412 does not include a silicon-based material, the second negative electrode film layer 1412 can relieve the volume expansion of the first negative electrode film layer 1411, reduce the side reaction between the negative electrode film layer 141 and the electrolyte, and improve the high-temperature cycle performance.

[0173] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode film layer 1412 includes a silicon-based material, it is beneficial to form more film layer pores through the volume change of the silicon-based material, improve the liquid-phase transmission ability of lithium ions, and enhance the kinetic performance of the battery cell.

[0174] When the negative electrode film layer 141 adopts at least two film layers, along the thickness direction X of the negative electrode film layer 141, the cross-sectional morphology of each part of the negative electrode film layer 141 can be the same or similar, and of course, it can also be different. When the electrode assembly is of a stacked structure, the thickness direction of the battery cell can be parallel to the thickness direction of the electrode assembly and the thickness direction X of the negative electrode film layer 141.

[0175] Along the thickness direction X of the negative electrode film layer 141, the negative electrode film layer 141 is divided into three regions, namely the first region 141a, the third region 141c, and the second region 141b in sequence. The first region 141a is the region of the negative electrode film layer 141 close to the negative electrode current collector 142 along the thickness direction X, and the thickness of the first region 141a is 1 / 3 of the thickness of the negative electrode film layer 141; the second region 141b is the region of the negative electrode film layer 141 away from the negative electrode current collector 142 along the thickness direction X, and the thickness of the second region 141b is 1 / 3 of the thickness of the negative electrode film layer 141.

[0176] The cross-sectional morphology of the first region 141a and the second region 141b can be the same or similar, and of course, it can also be different. The cross-sectional morphology of the first region 141a and the third region 141c can be the same or similar, and of course, it can also be different. The cross-sectional morphology of the second region 141b and the third region 141c can be the same or similar, and of course, it can also be different.

[0177] There may or may not be an obvious layer interface between the first region 141a, the second region 141b, and the third region 141c. For example, the first negative electrode film layer 1411 includes the first region 141a, the second negative electrode film layer 1412 includes the second region 141b, the third region 141c may be a part of the first negative electrode film layer 1411, or the third region 141c may be a part of the second negative electrode film layer 1412, or the third region 141c may be a part of both the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0178] Optionally, the average particle size of the carbon-based material in the first region 141a may be greater than or equal to the average particle size of the carbon-based material in the second region 141b. Further optionally, the average particle size of the carbon-based material in the first region 141a may be greater than the average particle size of the carbon-based material in the second region 141b, which is beneficial for lithium ions to quickly migrate from the second region 141b to the first region 141a and improve the fast charging ability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a may be smaller than the average particle size of the carbon-based material in the second region 141b.

[0179] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 may be greater than or equal to the average particle size of the carbon-based material in the second negative electrode film layer 1412. Further optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 may be greater than the average particle size of the carbon-based material in the second negative electrode film layer 1412.

[0180] There is a difference in the particle size between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer 1412 is usually relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer 1412. In the embodiments of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can also improve the problem of lithium deposition on the surface of the negative electrode sheet 14.

[0181] Optionally, the average particle size of the carbon-based material in the first region 141a is 10 μm to 20 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or the range composed of any two of the above values. When the average particle size of the carbon-based material in the first region 141a is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0182] 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 in the first negative electrode film layer 1411 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0183] Optionally, the average particle size of the carbon-based material in the second region 141b is 5 μm to 12 μm, such as 5 μm, 8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm or the range composed of any two of the above values. When the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within the above range, it is beneficial to improve the fast charging ability of the battery cell and the stability of the material.

[0184] 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 in the second negative electrode film layer 1412 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer 1412 with the above average particle size range cooperates with the negative electrode active material in the first negative electrode film layer 1411, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer 1412 and the first negative electrode film layer 1411, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0185] Exemplarily, the carbon-based material in the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second region 141b includes artificial graphite. For example, the negative electrode active material in the first region 141a includes a silicon-based material, artificial graphite and natural graphite, and the negative electrode active material in the second region 141b includes a silicon-based material and artificial graphite.

[0186] Exemplarily, the carbon-based material of the first negative electrode film layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer 1412 includes artificial graphite. For example, the negative electrode active material of the first negative electrode film layer 1411 includes a silicon-based material, artificial graphite and natural graphite, and the negative electrode active material of the second negative electrode film layer 1412 includes a silicon-based material and artificial graphite.

[0187] In the embodiments of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. For example, taking the negative electrode sheet 14 as a sample, cross-section polishing is performed along the thickness direction X of the negative electrode film layer 141. For example, argon ion beam is used for cross-section polishing, and a scanning electron microscope (SEM) is used to take a cross-section to obtain an SEM cross-sectional view. The particle size of the carbon-based material in the SEM cross-section is counted, and the average particle size of the carbon-based material is calculated based on the counted quantity.

[0188] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. The embodiments of the present application do not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0189] The negative electrode conductive agent can make up for the disadvantage of insufficient conductivity of the silicon-based material, improve the conductivity of the negative electrode film layer, be beneficial to improving the kinetic performance of the battery cell, and enhancing the fast charging ability of the battery cell.

[0190] Optionally, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%, such as 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7% or the range composed of any two of the above values.

[0191] Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 0.5%.

[0192] In some embodiments, the negative electrode film layer may optionally 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%.

[0193] In some embodiments, the negative electrode film layer may optionally 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%.

[0194] In some embodiments, the negative current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0195] In some embodiments, the thickness of the negative current collector is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values.

[0196] In some embodiments, the negative electrode plate further includes a negative tab connected to the negative current collector. The thickness of the negative tab is 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range composed of any two of the above values. When the thickness of the negative tab is within the above range, it is beneficial to improve the overcurrent capacity and the fast charging capacity of the battery cell.

[0197] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0198] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application further includes a negative electrode conductive layer sandwiched between the negative current collector and the negative electrode film layer and disposed on the surface of the negative current collector. In other embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0199] Positive electrode plate In some embodiments, the battery cell further includes a positive electrode plate.

[0200] The coating portion of the positive electrode tab includes a positive current collector portion and a positive electrode film layer provided on at least one side of the positive current collector portion and including a positive electrode active material. For example, the positive current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive current collector portion.

[0201] When the battery cell includes a stacked electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode tab. The dimension of the battery cell in the length direction can be understood as the length of the battery cell, and the dimension of the positive electrode film layer in the length direction can be understood as the length of the positive electrode film layer; the width direction of the battery cell is parallel to the width direction of the positive electrode tab. The dimension of the battery cell in the width direction can be understood as the width of the battery cell, and the dimension of the positive electrode film layer in the width direction can be understood as the width of the positive electrode film layer.

[0202] In some embodiments, the dimension of the positive electrode film layer can be considered the same as the dimension of the coating portion of the positive electrode tab. The dimension of the positive electrode film layer in the length direction of the battery cell is from 265 mm to 1200 mm, such as 265 mm, 350 mm, 450 mm, 550 mm, 650 mm, 750 mm, 850 mm, 950 mm, 1050 mm, 1150 mm, 1200 mm or the range composed of any two of the above values.

[0203] In some embodiments, the dimension of the positive electrode film layer in the length direction of the battery cell is the same as the first dimension, and the dimension of the positive electrode film layer in the width direction of the battery cell is the same as the second dimension. The ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, and can be selected as 1.25 to 18.5, such as 1.25, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5 or the range composed of any two of the above values.

[0204] For example, the dimension of the positive electrode film layer in the length direction of the battery cell is from 265 mm to 655 mm, and the ratio of the dimension of the positive electrode film layer in the length direction of the battery cell to the dimension of the positive electrode film layer in the width direction of the battery cell is greater than 1 and less than or equal to 12.5, and can be selected as 1.25 to 12.5. When the positive electrode active material of the positive electrode film layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor. When the dimension of the positive electrode film layer is within the above range, the electron transport path will not be too long, the internal resistance is relatively small, the heat generation is less, which is beneficial to improving the fast charging ability and high-temperature cycle performance of the battery cell at high energy density.

[0205] Optionally, the size of the positive electrode film layer in the length direction of the battery cell is 400 mm to 600 mm, and the ratio of the size of the positive electrode film layer in the length direction of the battery cell to the size of the positive electrode film layer in the width direction of the battery cell is 3.5 to 8.

[0206] In some embodiments, the size of the negative electrode film layer in the first direction is greater than the size of the positive electrode film layer in the first direction, so that the lithium ions released from the positive electrode film layer can basically be embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of use of the battery cell. Of course, the size of the negative electrode film layer in the first direction can also be less than or equal to the size of the positive electrode film layer in the first direction.

[0207] Optionally, the size of the negative electrode film layer in the first direction is greater than the size of the positive electrode film layer in the first direction, and the difference between the size of the negative electrode film layer in the first direction and the size of the positive electrode film layer in the first direction is 5 mm to 11 mm, such as 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or the range composed of any two of the above values.

[0208] In some embodiments, the size of the negative electrode film layer in the second direction is greater than the size of the positive electrode film layer in the second direction, so that the lithium ions released from the positive electrode film layer can basically be embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of use of the battery cell. Of course, the size of the negative electrode film layer in the second direction can also be less than or equal to the size of the positive electrode film layer in the second direction.

[0209] Optionally, the size of the negative electrode film layer in the second direction is greater than the size of the positive electrode film layer in the second direction, and the difference between the size of the negative electrode film layer in the second direction and the size of the positive electrode film layer in the second direction is 5 mm to 11 mm, such as 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or the range composed of any two of the above values.

[0210] The first direction is perpendicular to the second direction. The first direction can be parallel to the length direction of the battery cell, or the first direction can be parallel to the width direction of the battery cell. When the first direction is parallel to the length direction of the battery cell, the second direction is parallel to the width direction of the battery cell. When the first direction is parallel to the width direction of the battery cell, the second direction is parallel to the length direction of the battery cell.

[0211] In some embodiments, the size of the separator in the first direction is greater than the size of the negative electrode film layer in the first direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reduce the risk of short circuit, and improve the reliability of use of the battery cell. Of course, the size of the separator in the first direction can also be less than or equal to the size of the negative electrode film layer in the first direction.

[0212] Optionally, the size of the separator in the first direction is greater than the size of the negative electrode film layer in the first direction, and the difference between the size of the separator in the first direction and the size of the negative electrode film layer in the first direction is 6 mm to 10 mm, such as 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or the range composed of any two of the above values.

[0213] In some embodiments, the size of the separator in the second direction is greater than the size of the negative electrode film layer in the second direction, so that the separator can effectively isolate the positive electrode plate and the negative electrode plate, reduce the risk of short circuit, and improve the reliability of use of the battery cell. Of course, the size of the separator in the second direction can also be less than or equal to the size of the negative electrode film layer in the second direction.

[0214] Optionally, the size of the separator in the second direction is greater than the size of the negative electrode film layer in the second direction, and the difference between the size of the separator in the second direction and the size of the negative electrode film layer in the second direction is 6 mm to 10 mm, such as 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or the range composed of any two of the above values.

[0215] As Figure 14 shown, taking the first direction parallel to the length direction Z, the second direction parallel to the width direction Y, the first electrode plate 11 as the positive electrode plate, and the second electrode plate 12 as the negative electrode plate as an example for illustration, The size of the positive electrode film layer of the first electrode plate 11 in the length direction Z is the length of the positive electrode film layer of the first electrode plate 11, the size of the negative electrode film layer of the second electrode plate 12 in the length direction Z is the length of the negative electrode film layer of the second electrode plate 12, and the size of the separator 13 in the length direction Z is the length of the separator 13.

[0216] The difference between the length of the negative electrode film layer of the second electrode plate 12 and the length of the positive electrode film layer of the first electrode plate 11 is OH 11 , Figure 14 It is shown in that both sides of the negative electrode film layer in the length direction Z exceed the positive electrode film layer, and each side exceeds OH 11 / 2. Of course, the negative electrode film layer can also exceed the positive electrode film layer on one side in the length direction Z.

[0217] The difference between the length of the separator 13 and the length of the negative electrode film layer of the second electrode plate 12 is OH 21 ,Figure 14 As shown, both sides of the separator 13 in the length direction Z exceed the negative electrode film layer, and each side exceeds OH 21 / 2. Of course, the separator 13 can exceed the negative electrode film layer on one side in the length direction Z.

[0218] The dimension of the positive electrode film layer of the first electrode sheet 11 in the width direction Y is the width of the positive electrode film layer of the first electrode sheet 11, the dimension of the negative electrode film layer of the second electrode sheet 12 in the width direction Y is the width of the negative electrode film layer of the second electrode sheet 12, and the dimension of the separator 13 in the width direction Y is the width of the separator 13.

[0219] 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 14 As shown, both sides of the negative electrode film layer in the width direction Y exceed the positive electrode film layer, and each side exceeds OH 12 / 2. Of course, the negative electrode film layer can also exceed the positive electrode film layer on one side in the width direction Y.

[0220] 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 , Figure 14 As shown, both sides of the separator 13 in the width direction Y exceed the negative electrode film layer, and each side exceeds OH 22 / 2. Of course, the separator 13 can exceed the negative electrode film layer on one side in the width direction Y.

[0221] In some embodiments, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the tap density of the positive electrode film layer is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.75 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0222] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive electrode active materials in the positive electrode film layer are stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell has both high energy density and fast charging performance.

[0223] In some embodiments, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm², 200 mg / 1540.25 mm², 250 mg / 1540.25 mm², 300 mg / 1540.25 mm², 350 mg / 1540.25 mm², 370 mg / 1540.25 mm² or a range composed of any two of the above values. Optionally, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 .

[0224] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode sheet is not too large, which is beneficial to reducing the polarization phenomenon under high-rate charging, and can take into account improving the energy density and fast charging performance of the battery cell.

[0225] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, the positive electrode sheet is disassembled from the battery cell in the 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, one side of the positive electrode film layer can be wiped off first) is punched into small circular pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the above-mentioned weighed positive electrode sheet is wiped off, the weight of the positive electrode current 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 M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive electrode current collector, and the 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.

[0226] In some embodiments, the charge specific capacity of the positive electrode active material is from 150 mAh / g to 170 mAh / g. Exemplarily, the charge specific capacity of the negative electrode active material is 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range composed of any two of the above values.

[0227] When the charge specific capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0228] In the embodiments of the present application, the specific capacity of the positive electrode active material has the meaning well-known in the art and can be detected by the testing method of the specific capacity of the negative electrode active material.

[0229] In some embodiments, the positive electrode active material includes lithium-containing phosphate. The lithium-containing phosphate can have an olivine structure, which is stable in structure during charge and discharge, and can improve the cycle life of the battery cell.

[0230] Optionally, the positive electrode active material may further include lithium-containing transition metal oxide. Examples of the lithium-containing transition metal oxide may include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0231] The lithium-containing phosphate with an olivine structure can be an unmodified lithium-containing phosphate or a material obtained by coating modification thereof. For example, a carbon-containing material is provided on the surface of the lithium-containing phosphate, and the carbon-containing material can be used as a coating layer to coat on the surface of the lithium-containing phosphate, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, being beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery cell, and reducing the heat generation of the battery cell.

[0232] In some embodiments, the lithium-containing phosphate includes a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1≤1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of Cl, C, and N, and Y includes one or more of O and F. The lithium-containing phosphate has excellent cycle stability, which is beneficial to improving the high-temperature cycle performance of the battery cell.

[0233] Exemplarily, the lithium-containing phosphate includes LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 or one or more thereof. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycling, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active materials LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 etc., the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will show fluctuations, and the above situations are all within the protection scope of the present application.

[0234] In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode sheet, it is cleaned with dimethyl carbonate (DMC) and dried, then after impurity removal by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0235] In some embodiments, the lithium-containing phosphate is granular, and the volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm or the range composed of any two of the above values.

[0236] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium deintercalation / insertion path of lithium ions in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and basically no agglomeration occurs during the processing and preparation process, so that the performance of the lithium-containing phosphate is stable.

[0237] In some embodiments, the positive electrode film layer further includes one or more of lithium-containing ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, lithium citrate, lithium nickelate and lithium ferrate. The above materials can be used as lithium supplement agents, which can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and improve the energy density of the battery cell.

[0238] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lithium supplement agent is 0.1% to 5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or the range composed of any two of the above. When using a lithium supplement agent within the mass range, it can supplement lithium ions for the positive electrode film layer and make up for the irreversible loss of lithium ions in the system, and the mass content of the lithium supplement agent is not too high, so that the discharge specific capacity of the positive electrode is still high and the energy density is basically not reduced.

[0239] In some embodiments, the volume average particle size Dv50 of the lithium supplement agent is greater than the volume average particle size Dv50 of the lithium-containing phosphate. The combination of particles of different sizes is beneficial to uniform dispersion and improves the uniformity of the distribution of the lithium supplement agent.

[0240] In some embodiments, the volume average particle size Dv50 of the lithium supplement agent is 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or the range composed of any two of the above.

[0241] In the embodiments of the present application, the volume average particle size Dv50 of the particles has the meaning well known in the art. The volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using the equipment and methods well known in the art. After fully discharging the fresh battery cell to 0% state of charge (SOC), disassemble the positive electrode sheet, remove the positive electrode current collector part and retain the positive electrode film layer. Immerse the positive electrode film layer in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, and retain the positive electrode active material or the lithium supplement agent as a sample. After drying the sample, according to the test standard GB / T 19077-2016, test the volume average particle size Dv50 of the particles by a Mastersizer 2000E laser particle size analyzer.

[0242] 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%.

[0243] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0244] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0245] In some embodiments, the thickness of the positive current collector is 10 μm to 16 μm, such as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range composed of any two of the above values.

[0246] In some embodiments, the positive electrode tab further includes a positive electrode ear connected to the positive current collector. The thickness of the positive electrode ear is 10 μm to 16 μm, such as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range composed of any two of the above values. When the thickness of the positive electrode ear is within the above range, it is beneficial to improve the overcurrent capacity and the fast charging capacity of the battery cell.

[0247] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive current collector and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0248] The positive electrode tab does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the present application further includes a positive electrode conductive layer sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector. In some other embodiments, the positive electrode tab of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0249] [Electrolyte] During the charging and discharging process of the battery cell, active ions such as lithium ions are intercalated and deintercalated back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The electrolyte includes an organic solvent and an electrolyte salt.

[0250] In some embodiments, the conductivity of the electrolyte at room temperature is from 10.5 mS / cm to 13.5 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm or the range composed of any two of the above values.

[0251] 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.

[0252] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using the equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0253] In some embodiments, the viscosity of the electrolyte at room temperature is from 1.5 mPa·s to 5.5 mPa·s. Exemplarily, the viscosity of the electrolyte is 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s or the range composed of any two of the above values.

[0254] 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.

[0255] In the embodiments of the present application, the viscosity of the electrolyte has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, it can be detected according to GB / T10247-2008.

[0256] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 1.05 g / mL to 1.35 g / mL. Exemplarily, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL or the range composed of any two of the above values.

[0257] 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.

[0258] In the embodiments of the present application, the density of the electrolyte has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0259] In some embodiments, the organic solvent includes chain carboxylic acid ester solvents.

[0260] Optionally, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35% or the range composed of any two of the above values. Optionally, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 8% to 20%.

[0261] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte is small, which can improve the conductivity of the electrolyte, reduce the internal resistance of the battery cell, and is beneficial to the rapid migration of lithium ions; and the electrolyte is compatible with the silicon-containing negative electrode, which can effectively reduce the gas generation amount of the battery cell, reduce the influence on the interface film on the negative electrode side, and improve the fast charging ability and high-temperature cycle performance of the battery cell.

[0262] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0263] The above chain carboxylic acid ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0264] Optionally, R 1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0265] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2It includes C1-C2 alkyl or C1-C2 haloalkyl.

[0266] In each of the above embodiments, the haloalkyl includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl. Optionally, the haloalkyl includes fluoroalkyl.

[0267] Exemplarily, the chain carboxylic acid ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8.

[0268] In some embodiments, the organic solvent includes carbonate solvents.

[0269] The carbonate solvents and the chain carboxylic acid ester solvents are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0270] Optionally, the mass content of the carbonate solvents in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvents is 65%, 70%, 75% or the range composed of any two of the above values.

[0271] When the mass contents of the carbonate solvents and the chain carboxylic acid ester solvents meet the above conditions, the stability of the electrolyte can be improved and its gas generation amount at high temperature can be reduced.

[0272] Exemplarily, the carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0273] In the embodiments of the present application, the electrolyte salt includes lithium salts, and the lithium salts include one or more of lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salts include lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0274] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF, and the side reaction between hydrofluoric acid and the negative electrode active material may cause an increase in gas generation during high-temperature storage; the compound use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, and reduce the gas generation amount at high-temperature storage; the compound use is beneficial to improving the transference number of lithium ions, enhancing the lithium ion conduction ability of the electrolyte, and can improve the high-temperature cycle performance and fast charging ability of the battery monomer.

[0275] Exemplarily, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide, and may be lithium bis(fluorosulfonyl)imide.

[0276] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is greater than 0 and less than or equal to 18%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or the range composed of any two of the above values. Optionally, the mass content of the lithium salt is 10% to 18%. Further optionally, the mass content of the lithium salt is 10% to 15%. The mass content of the lithium salt is the sum of the mass contents of the components of the lithium salt. For example, if the lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, the mass content of the lithium salt is the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate.

[0277] Exemplarily, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and can be optionally 10% to 18%.

[0278] When the mass content of the lithium salt is within the above range, on the one hand, it can improve the transference number of lithium ions in the electrolyte, enhance the lithium ion conduction ability of the electrolyte, and improve the fast charging performance of the battery cell; on the other hand, it can reduce the side reactions on the negative electrode side and improve the high-temperature cycle performance of the battery cell.

[0279] Optionally, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and can be optionally 10% to 18%. When the mass content of the lithium salt is within the above range, it can improve the fast charging performance, high-temperature cycle performance and service reliability of the battery cell.

[0280] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of lithium fluorosulfonylimide and the mass content of lithium hexafluorophosphate is 0.2 to 0.8, such as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or the range composed of any two of the above values. Optionally, the ratio of the mass content of lithium fluorosulfonylimide and the mass content of lithium hexafluorophosphate is 0.3 to 0.8.

[0281] When the ratio of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide satisfies the above range, on the one hand, it can improve the transference number of lithium ions in the electrolyte, enhance the lithium ion conduction ability of the electrolyte, and improve the fast charging performance of the battery cell; on the other hand, it can reduce the side reactions on the negative electrode side and improve the high-temperature cycle performance of the battery cell.

[0282] Exemplarily, the mass content of lithium bis(fluorosulfonyl)imide is greater than 0 and less than or equal to 8%, and can be optionally 2% to 8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or the range composed of any two of the above values.

[0283] Exemplarily, the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 12%, optionally 1% to 12%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or a range composed of any two of the above values.

[0284] In some embodiments, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. The above additives can improve the interfacial film performance on the negative electrode side, the formed interfacial film has higher stability, and the impedance of the interfacial film is relatively low, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycling performance.

[0285] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 10%. Exemplarily, the mass content of the additive in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. Optionally, the mass content of the additive in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0286] The additive with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycling performance.

[0287] In some embodiments, the carbonate additives include one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive includes fluoroethylene carbonate and vinylene carbonate.

[0288] Fluoroethylene carbonate can form an interfacial film rich in lithium fluoride LiF on the negative electrode surface, which can alleviate the side reactions on the negative electrode side, reduce the gas generation amount at high temperature, and improve the high-temperature cycling performance of the battery cell. When fluoroethylene carbonate and vinylene carbonate are used in combination, the interfacial film on the negative electrode surface has better compactness and lower impedance, can more effectively protect the negative electrode-containing part, reduce the degree of negative electrode interface side reactions, reduce the gas generation amount at high temperature, and improve the high-temperature cycling performance and fast charging performance of the battery cell.

[0289] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate.

[0290] Optionally, the lithium salt additives include one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0291] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte have meanings well-known in the art and can be detected by devices and methods well-known in the art. For example, reference can be made to the General Rules for Ion Chromatography Analysis (JY / T 020-1996) to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, or the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0292] In the embodiments of the present application, the types and contents of organic components in the electrolyte have meanings well-known in the art and can be detected by devices and methods well-known in the art. For example, reference can be made to the General Rules for Gas Chromatography of Chemical Reagents (GB / T 9722-2006) to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0293] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, the components are classified. Chain carboxylic ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0294] Fluorinated cyclic carbonates and vinylene carbonate, etc., which are carbonate additives, are used as additives in the electrolyte, and the mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0295] Separator In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode plate and the negative electrode plate.

[0296] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0297] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0298] In some embodiments, the volumetric energy density of the battery cell is from 375 Wh / L to 430 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 375 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L or a range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0299] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.8 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration, The battery cell is placed at 25 °C, charged at a constant current of 0.05 C to 3.8 V, discharged at a constant current of 0.33 C to 2.0 V, and the discharge capacity A0 at this time is recorded, unit: Ah. The length, width, and height of the battery cell are measured using a caliper (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminal and excluding the insulating film outside the outer shell), and the volume V0 of the single battery cell is calculated, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0300] Embodiment The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0301] Example 1 1. Preparation of the positive electrode plate The positive electrode plate includes a positive electrode tab, a positive electrode current collector portion, and positive electrode film layers provided on both sides of the positive electrode current collector portion. The positive electrode current collector portion is aluminum foil. No positive electrode film layer is coated on the positive electrode tab.

[0302] The positive electrode film layer comprises lithium-containing phosphate lithium iron phosphate, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black with a mass ratio of 97.5:2:0.5. The positive electrode film layer is formed by uniformly coating both sides of the positive electrode current collector part with positive electrode slurry (solvent: N-methylpyrrolidone NMP), followed by drying and cold pressing.

[0303] The volume average particle size Dv50 of the lithium-containing phosphate is 1.5 μm.

[0304] The single-sided coating weight of the positive electrode film layer is 286 mg / 1540.25 mm 2 。

[0305] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative electrode tab, a negative electrode current collector part, and negative electrode film layers provided on both sides of the negative electrode current collector part. The negative electrode current collector part is a copper foil. The negative electrode film layer is not coated on the negative electrode tab. The setting position and number of the negative electrode tabs are the same as those of the positive electrode tabs, which will not be elaborated here.

[0306] The negative electrode film layer is formed by uniformly coating the surface of the negative electrode current collector part with negative electrode slurry (solvent: deionized water), followed by drying and cold pressing.

[0307] The single-sided coating weight of the negative electrode film layer is 132 mg / 1540.25 mm 2 。

[0308] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode current collector part, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0309] The first negative electrode film layer comprises negative electrode active material, conductive carbon, negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.4:0.4:2.5:0.7. The negative electrode active material of the first negative electrode film layer includes artificial graphite; The second negative electrode film layer comprises negative electrode active material, conductive carbon, negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 97.8:0.7:0.8:0.7. The negative electrode active material of the first negative electrode film layer includes artificial graphite.

[0310] In the cross-section along the thickness direction of the negative electrode film layer, the average particle size of the artificial graphite in the first negative electrode film layer is measured to be 13 μm; the average particle size of the artificial graphite in the second negative electrode film layer is 10 μm. During the preparation of the negative electrode film layer, the film layer with the desired average particle size can be obtained by adjusting the volume average particle size of the artificial graphite multiple times.

[0311] The length of the negative electrode film layer is 5 mm larger than that of the positive electrode film layer, and the width of the negative electrode film layer is 5 mm larger than that of the positive electrode film layer.

[0312] 3. Separator The separator includes a base film, which is a polyethylene film layer with a thickness of 7 μm and a porosity of 42%.

[0313] The length of the separator is 6 mm greater than that of the negative electrode film layer, and the width of the separator is 6 mm greater than that of the negative electrode film layer.

[0314] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0315] After mixing the components of the organic solvent, the lithium salt and the additive are added to prepare the electrolyte.

[0316] The organic solvent includes 15% carboxylic ester solvent ethyl acetate and 68.5% carbonate solvent ethylene carbonate.

[0317] The lithium salt includes 10% lithium hexafluorophosphate and 4% lithium bis(fluorosulfonyl)imide.

[0318] The additive includes 2.5% vinylene carbonate.

[0319] The conductivity of the electrolyte at room temperature is 11 mS / cm; The viscosity of the electrolyte at room temperature is 2.70 mPa·s; The density of the electrolyte at room temperature is 1.10 g / mL.

[0320] 5. Preparation of battery cell The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining an electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with the electrolyte. 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 2.63 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.60 g / cm 3 .

[0321] Comparative Example 1-1 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the number of positive electrode tabs and the percentage occupying the current collector were adjusted.

[0322] Examples 2-1 to 2-3 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the number of positive electrode tabs and the percentage occupying the current collector were adjusted.

[0323] Comparative Examples 2-1 and 2-2 The battery single cells were prepared by a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode film layer in the positive electrode sheet was adjusted.

[0324] Examples 3-1 to 3-4 The battery single cells were prepared by a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode film layer in the positive electrode sheet was adjusted.

[0325] Performance test 1. DC Resistance DCR Test of Battery Single Cells The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0326] For example, at 25 °C, the battery single cell was charged to 3.65 V at a constant current of 0.33 C, left standing for 1 min, then charged to 3.65 V at a constant current of 0.1 C, left standing for 30 min, and discharged at a constant current of 0.33 C to 2.0 V. Record the discharge capacity A at this time 0 , in the unit of Ah, and then charged at a constant current of 0.33 C for 0.5 A 0 Ah, and adjust the SOC to 50%.

[0327] After the battery single cell was placed at 25 °C for 2 h, it was discharged at a current of 4 C for 10 s, and ∆U was recorded 放电 , ∆I 放电 , and the discharge DCR data of the lithium-ion battery was calculated through the following formula, R 放电 = ∆U 放电 / ∆I 放电 , where ∆U 放电 represents the voltage change within the first 10 s of discharge, and ∆I 放电 represents the current value within the first 10 s of discharge.

[0328] 3. High-Temperature Cycling Performance Test of Battery Single Cells In an environment of 60 ± 5 °C, the battery single cell was charged at a constant current of 1 C to the cut-off upper limit voltage, then charged at a constant voltage to the cut-off current of 0.05 C, and then discharged at a constant current of 1 C to the discharge cut-off voltage. This was one charge-discharge cycle.

[0329] The discharge capacity this time was recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery single cell. Repeat this cycle step for the same battery single cell. After cycling n times, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery single cell = Cn / C1 * 100%, and record the number of cycles when the capacity retention rate is 80%. For accuracy, take the average value of 5 parallel samples as the test result.

[0330] The test results are shown in Table 1.

[0331] Table 1

[0332] In Table 1, The short side of the positive tab exits, which means that the positive tab is arranged on at least one side of the positive current collector along the length direction; The short side of the positive tab exits from one side, which means that the positive tab is arranged on one side of the positive current collector along the length direction, and all the positive tabs are located on the same side; The short side of the positive tab exits from both sides, which means that the positive tab is arranged on both sides of the positive current collector along the length direction.

[0333] The short side of the positive tab exits from both sides, with 2 exiting from each side, and there are a total of 4 positive tabs. Two positive tabs are arranged on one side of the positive current collector along the length direction, and the other two positive tabs are arranged on the other side of the positive current collector along the length direction.

[0334] In Comparative Example 1-1, the size of the positive electrode plate is within an appropriate range, and the energy density of the battery cell is relatively high; although the positive tab is arranged on one side of the positive current collector along the length direction, which can shorten the electron transmission path, the size of the positive tab is relatively small, n*W1 / W2 is less than 0.2, being 0.15, the current-carrying area of the positive tab is relatively small, resulting in poor current-carrying capacity of the positive tab, high resistance, increased heat generation, and an increased risk of decomposition of the electrolyte components, which is not conducive to the high-temperature cycling and fast charging of the battery cell.

[0335] In Example 1, Examples 2-1 to 2-3, the positive tab is arranged on at least one side of the positive current collector along the length direction, the size of the positive tab is relatively large, the size ratio of the positive tab in the positive current collector is relatively large, n*W1 / W2 is greater than or equal to 0.2, resulting in a relatively high current-carrying area of the positive tab, strong current-carrying capacity, small internal resistance, less heat generation, and can effectively reduce the internal heat of the battery cell, improving the high-temperature cycling stability and fast charging ability of the battery cell.

[0336] As the size ratio of the positive tab in the positive current collector increases, n*W1 / W2 increases, and the current-carrying capacity of the positive tab is enhanced. For example, in Example 2-2, n*W1 / W2 is 1, and the size of the positive tab along the length direction is the same as the size of the positive current collector along the length direction. In this case, the current-carrying capacity of the positive tab is relatively excellent, which can further reduce the internal resistance, reduce heat generation, and improve the high-temperature cycling stability and fast charging ability of the battery cell.

[0337] The length of the positive electrode film layer of Comparative Example 2-1 is short, resulting in a small energy density of the battery cell. Although the electron transport path is short, the DCR of the battery cell is small, the heat generation is less, which is beneficial to the fast charging of the battery cell and the improvement of the high-temperature cycling performance. However, the energy density of the battery cell is small and does not meet the production requirements.

[0338] The length of the positive electrode film layer of Comparative Example 2-2 is long. Although the energy density of the battery cell is relatively high, the electron transport path is too long, the ohmic resistance of the positive electrode plate increases, resulting in an increase in the internal resistance of the battery cell and a relatively high heat generation, deteriorating the high-temperature cycling and fast charging capabilities.

[0339] As the length of the positive electrode film layer increases, the energy density of the battery cell is improved. However, the ohmic resistance of the positive electrode plate increases and the heat generation increases, which is not conducive to the improvement of the high-temperature cycling performance and fast charging performance of the battery cell. The lengths and aspect ratios of the positive electrode film layers of Examples 3-1 to 3-4 are appropriate, resulting in a relatively high energy density of the battery cell. In the case of high energy density, the ratio of the length to the width of the positive electrode film layer is set to be less than or equal to 18.5, so that the length of the positive electrode film layer is not too long, which is beneficial to reducing the electron transport distance in the length direction and reducing the ohmic resistance of the electrode plate. Further combined with an ear ratio of n*W1 / W2 greater than or equal to 0.2, the current-carrying capacity of the positive electrode ear is relatively excellent, which can effectively reduce the internal resistance, reduce the heat generation, and improve the high-temperature cycling performance and fast charging performance of the battery cell. Especially when the aspect ratio of the positive electrode film layer is 3.5 to 8 and the size of the coated portion of the positive electrode plate in the length direction is 400 mm to 600 mm, it is beneficial to simultaneously improve the high-temperature cycling performance and fast charging performance of the battery cell under high energy density.

[0340] Comparative Example 3-1 A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted and lithium bis(fluorosulfonyl)imide was not added.

[0341] Examples 4-1 to 4-7 A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted.

[0342] In Examples 4-1 to 4-4, the mass content of lithium bis(fluorosulfonyl)imide was adjusted; In Example 4-5, lithium bis(fluorosulfonyl)imide was replaced with lithium bis(trifluoromethanesulfonyl)imide, and the mass content remained unchanged.

[0343] In Examples 4-6 and 4-7, the mass content of lithium hexafluorophosphate was adjusted. The mass content of lithium hexafluorophosphate in Example 4-6 was 11.67%, and the mass content of lithium hexafluorophosphate in Example 4-7 was 7.78%.

[0344] The test results are shown in Table 2.

[0345] Table 2

[0346] In Table 2, LiFSI represents lithium bis(fluorosulfonyl)imide; LiTFSI represents lithium tris(fluorosulfonyl)imide; A 1 represents the mass content of hexafluorophosphoric acid, and A 2 represents the mass content of lithium fluorosulfonylimide.

[0347] In Comparative Example 3-1, the addition amount of lithium fluorosulfonylimide is too small, resulting in relatively poor lithium-ion conduction ability of the electrolyte, which is not conducive to lithium-ion migration and fast charging.

[0348] With the increase of the mass content of lithium fluorosulfonylimide, the lithium-ion transference number of the electrolyte increases, the lithium-ion conduction ability is enhanced, and the fast-charging DCR can be reduced; moreover, it participates in the formation of an SEI film containing lithium sulfonate, lithium fluoride, etc. on the negative electrode side, which can improve the protection of the negative electrode side and is beneficial to improving the high-temperature cycle performance of the battery cell; for example, in Examples 4-1 to 4-5, when the mass content of lithium bis(fluorosulfonyl)imide is greater than or equal to 2%, the high-temperature cycle performance and fast-charging performance of the battery cell are relatively excellent.

[0349] However, when the addition amount of lithium fluorosulfonylimide is too much, for example, greater than or equal to 10%, although the DCR of the battery cell can be reduced and the high-temperature cycle performance can be improved, in the case of thermal runaway, lithium fluorosulfonylimide can decompose rapidly in a short time, generating a large amount of gas and heat, resulting in a sharp increase in the internal heat of the battery cell, and a large amount of heat is difficult to release quickly, deteriorating the use reliability of the battery cell.

[0350] In Example 4-5, lithium tris(fluorosulfonyl)imide and lithium bis(fluorosulfonyl)imide, as lithium fluorosulfonylimide, are used in combination with lithium hexafluorophosphate, and both can effectively improve the high-temperature cycle performance and fast-charging performance of the battery cell.

[0351] In Examples 4-6 and 4-7, the mass content of lithium hexafluorophosphate changes synchronously. The less the mass content of lithium hexafluorophosphate, the less the HF content, and the less the damage to the SEI film. The lithium salt also includes lithium fluorosulfonylimide, which can improve the protection of the negative electrode side and is beneficial to improving the high-temperature cycle performance of the battery cell.

[0352] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be construed as limitations on the implementation of the present application, and that changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principles, and scope of the implementation of the present application.

Claims

1. A battery cell, characterized in that: Including electrode assembly and electrolyte, The electrode assembly includes a plurality of first pole sheets and a plurality of second pole sheets, the plurality of first pole sheets and the plurality of second pole sheets are stacked along the thickness direction of the battery cell, the first pole sheet and the second pole sheet each include a coating portion and a pole ear portion, the coating portion is provided with active material, the pole ear portion is connected to the coating portion and extends out of the coating portion along the length direction of the battery cell, in, One of the first pole piece and the second pole piece is a positive pole piece, and the other is a negative pole piece; The size of the coating portion of the positive electrode sheet along the length direction of the battery cell is a first size, the size of the coating portion of the positive electrode sheet along the width direction of the battery cell is a second size, the ratio of the first size to the second size is greater than 1 and less than or equal to 18.5, and the size of the coating portion of the positive electrode sheet along the length direction is 265 mm to 1200 mm; The first pole piece satisfies: n*W1 / W2 is 0.2 to 1.0; n represents the number of all the pole lugs located on the same side of the coating portion, and n is greater than or equal to 1; W1 represents the average size of the pole ear portion along the width direction; W2 represents the dimension of the coating portion along the width direction; The electrolyte includes fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Based on the mass of the electrolyte, the ratio of the mass content of the fluorinated lithium sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 0.

8.

2. The battery cell according to claim 1, characterized in that: The ratio of the mass content of the fluorine-containing lithium sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.3 to 0.

8.

3. The battery cell according to claim 1 or 2, 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%.

4. The battery cell according to claim 3, characterized in that: The mass content of the fluorinated lithium sulfonyl imide and the lithium hexafluorophosphate in the electrolyte is 10% to 18%.

5. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the fluorinated sulfonyl imide lithium in the electrolyte is greater than 0 and less than or equal to 8%; and / or The mass content of the lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 12%.

6. The battery cell according to any one of claims 1 to 2, characterized in that: The fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide.

7. 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.

8. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%.

9. The battery cell according to claim 8, 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.

10. The battery cell according to claim 9, 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, 。 11. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

12. The battery cell according to any one of claims 1 to 2, characterized in that: The electrolyte includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives and lithium salt additives. The mass content of the additives in the electrolyte is 0.5% to 10%.

13. The battery cell according to claim 12, 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).

14. The battery cell according to any one of claims 1 to 2, characterized in that: The number of the pole lugs of the first pole piece is 1 to 4.

15. The battery cell according to any one of claims 1 to 2, characterized in that: All the pole lugs of the first pole piece are connected to the same side of the coating portion along the length direction; or The first pole piece includes at least two pole ear portions, and the at least two pole ear portions are connected to two sides of the coating portion of the first pole piece along the length direction.

16. The battery cell according to any one of claims 1 to 2, characterized in that: n*W1 / W2 is 0.5 to 1.

0.

17. The battery cell according to any one of claims 1 to 2, characterized in that: The ratio of the first size to the second size is 3.5 to 8, and the size of the coating portion of the positive electrode sheet along the length direction is 400 mm to 600 mm.

18. The battery cell according to any one of claims 1 to 2, characterized in that: The active material of the positive electrode plate includes lithium-containing phosphate.

19. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode sheet comprises a negative electrode coating portion and a negative electrode tab connected to the negative electrode coating portion, and the positive electrode sheet comprises a positive electrode coating portion and a positive electrode tab connected to the positive electrode coating portion; The dimension of the negative electrode coating portion along the width direction is greater than the dimension of the positive electrode coating portion along the width direction, and the difference between the dimension of the negative electrode coating portion along the width direction and the dimension of the positive electrode coating portion along the width direction is 5 mm to 11 mm; and / or The dimension of the negative electrode coating portion along the length direction is greater than that of the positive electrode coating portion along the length direction, and the difference between the dimension of the negative electrode coating portion along the length direction and the dimension of the positive electrode coating portion along the length direction is 5 mm to 11 mm.

20. The battery cell according to any one of claims 1 to 2, characterized in that: The electrode assembly further includes a separator, the separator is disposed between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet includes a negative electrode coating portion and a negative electrode ear connected to the negative electrode coating portion; The dimension of the separator along the width direction is greater than the dimension of the negative electrode coating portion along the width direction, and the difference between the dimension of the separator along the width direction and the dimension of the negative electrode coating portion along the width direction is 6 mm to 10 mm; and / or The dimension of the separator along the length direction is greater than the dimension of the negative electrode coating portion along the length direction, and the difference between the dimension of the separator along the length direction and the dimension of the negative electrode coating portion along the length direction is 6 mm to 10 mm.

21. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 20.

22. An electrical device, characterized in that: Comprising a battery device as claimed in claim 21.

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