Battery cell, battery device, and electrical device

Abstract

The present application relates to a battery cell, a battery device and an electrical device. The battery cell includes an electrolyte and an electrode assembly. The electrode assembly includes a first electrode tab and a second electrode tab. The first electrode tab and the second electrode tab include a coated portion and an electrode ear portion. The electrode ear portion is connected to the coated portion and extends out of the coated portion along the length direction of the battery cell. One of the first electrode tab and the second electrode tab is a positive electrode tab. The ratio of the dimension of the coated portion of the positive electrode tab along the length direction to the dimension of the coated portion of the positive electrode tab along the width direction 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 is 265 mm to 1200 mm. The first electrode tab satisfies that n*W1 / W2 is 0.2 to 1.0. The electrolyte includes lithium fluorosulfonylimide and lithium hexafluorophosphate. The ratio of the mass content of lithium fluorosulfonylimide to the mass content of lithium hexafluorophosphate is 0.2 to 0.8. The present application can improve the high-temperature cycle performance and fast charging performance of the battery cell.

Description

[0001] This application claims the priority of 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 cars, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc. Due to the great progress made in batteries, higher requirements are put forward for the performance of batteries. However, the fast charging ability, high-temperature cycling 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 cycling 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 sheets and a plurality of second electrode sheets. The plurality of first electrode sheets and the plurality of second electrode sheets are stacked along the thickness direction of the battery cell. Both the first electrode sheet and the second electrode sheet include a coated portion and an electrode tab. The coated portion is provided with active material, and the electrode tab is connected to the coated portion and extends out of the coated portion along the length direction of the battery cell. Among them, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet; the size of the coated portion of the positive electrode sheet along the length direction of the battery cell is a first size, the size of the coated 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 coated portion of the positive electrode sheet along the length direction of the battery cell is 265 mm to 1200 mm; the first electrode sheet satisfies: n*W1 / W2 is 0.2 to 1.0; n represents the number of all electrode tabs on the same side of the coated 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 coated 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 portion of the positive electrode tab of the embodiment of the present application meets the above range, the energy density of the battery cell can be improved; under the above tab, when the tab portion is disposed on at least one side of the coating portion along the length direction of the battery cell, the electron transfer distance in the tab is relatively short, the electron transfer rate is fast, and the ohmic resistance of the tab can be reduced; moreover, the embodiment of the present application also improves the lithium salt component of the electrolyte. The lithium salt includes a proper content of lithium fluorosulfonylimide, so that the ability of the electrolyte to conduct lithium ions is improved, and the common improvement of the active ion and electron transfer rates can effectively improve the fast charging ability of the battery cell at a high energy density; the tab portion is disposed on at least one side of the coating portion along the length direction of the battery cell, and the ohmic resistance of the tab is relatively low, so that the heat generated by the tab is relatively small; further, the appropriate size ratio of the tab portion makes the current-carrying area of the tab portion relatively high, and the resistance at the connection with the coating portion is small, which can further reduce the heat generated by the tab. 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 decomposition to generate gas and heat can be slowed down, and the high-temperature cycle performance and service 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 service 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 as 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 bis(trifluoromethanesulfonyl)imide. 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 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 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 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 5% to 35%. When the mass content of the chain carboxylic ester solvent is within the above range, it can improve the fast charging ability and high-temperature cycle performance of the battery cell.

[0016] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I,

[0017] Formula I,

[0018] In Formula I,

[0019] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0020] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0021] The above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0022] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0023]

[0024] In some embodiments, the electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%. When the mass contents of the carbonate solvent and the chain carboxylic acid ester solvent meet the above conditions, the stability of the electrolyte can be improved, the gas generation amount at high temperature can be reduced, and the high-temperature cycling performance of the battery cell can be improved.

[0025] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0026] 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, which is beneficial to improving the fast charging performance of the battery cell and the high-temperature cycling performance.

[0027] 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, which is beneficial to improving the fast charging performance of the battery cell and the high-temperature cycling performance.

[0028] 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 cycling performance of the battery cell.

[0029] 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 cycling performance of the battery cell.

[0030] 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.

[0031] 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. This setting method is beneficial to improving the energy density of the battery cell.

[0032] 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 coated portion of the first electrode tab along the length direction. This arrangement can shorten the electron transmission path and improve the fast charging ability of the battery cell.

[0033] In some embodiments, n*W1 / W2 is from 0.5 to 1.0. When the tab portion meets the above requirements, the overcurrent capacity is relatively strong, which is beneficial to improving the fast charging ability of the battery cell.

[0034] In some embodiments, the ratio of the first dimension to the second dimension is from 3.5 to 8, and the dimension of the coated portion of the positive electrode tab along 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.

[0035] 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.

[0036] In some embodiments, the negative electrode tab includes a negative electrode coated portion and a negative electrode tab connected to the negative electrode coated portion, and the positive electrode tab includes a positive electrode coated portion and a positive electrode tab connected to the positive electrode coated portion; the dimension of the negative electrode coated portion along the width direction is greater than the dimension of the positive electrode coated portion along the width direction, and the difference between the dimension of the negative electrode coated portion along the width direction and the dimension of the positive electrode coated portion along the width direction is from 5 mm to 11 mm; the relatively large dimension of the negative electrode coated 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.

[0037] In some embodiments, the dimension of the negative electrode coated portion along the length direction is greater than the dimension of the positive electrode coated portion along the length direction, and the difference between the dimension of the negative electrode coated portion along the length direction and the dimension of the positive electrode coated portion along the length direction is from 5 mm to 11 mm. The relatively large dimension of the negative electrode coated 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.

[0038] 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 coated portion and a negative electrode tab connected to the negative electrode coated portion; the dimension of the separator along the width direction is greater than the dimension of the negative electrode coated 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 coated portion along 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.

[0039] In some embodiments, the size of the separator in the length direction is greater than the size of the negative electrode coating portion in the length direction, and the difference between the size of the separator in the length direction and the size of the negative electrode coating portion in the length direction is 6 mm to 10 mm. The relatively large size of the separator can effectively isolate the negative electrode plate and the positive electrode plate, reduce the risk of short circuit between the negative electrode plate and the positive electrode plate, and improve the reliability of use of the battery cell.

[0040] 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.

[0041] In a third aspect, an embodiment of the present application further provides an electrical device, and the electrical device includes the battery device according to any one of the embodiments in the second or third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0043] Figure 1 It is a schematic structural diagram of an electrical device provided by some embodiments of the present application.

[0044] Figure 2 [[ID=I19]]It is a schematic structural diagram of a battery pack provided by some embodiments of the present application;

[0045] Figure 3 It is a schematic structural diagram of a battery module provided by some embodiments of the present application;

[0046] Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application;

[0047] Figure 5 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0048] Figure 6 It is a schematic structural diagram of a first electrode plate of a battery cell provided by some embodiments of the present application;

[0049] Figure 7 It is a schematic structural diagram of a first electrode plate of a battery cell provided by some other embodiments of the present application;

[0050] Figure 8 It is a schematic structural diagram of a first electrode plate of a battery cell provided by some other embodiments of the present application;

[0051] Figure 9 It is a schematic structural diagram of the second electrode sheet of a battery cell provided by some embodiments of the present application;

[0052] Figure 10 It is a schematic structural diagram of the second electrode sheet of a battery cell provided by some other embodiments of the present application;

[0053] Figure 11 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0054] Figure 12 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0055] Figure 13 It is a schematic structural diagram of the negative electrode sheet of a battery cell provided by some embodiments of the present application;

[0056] Figure 14 It is a schematic structural diagram of the electrode assembly of a battery cell provided by some embodiments of the present application.

[0057] The drawings are not necessarily drawn to actual scale.

[0058] The descriptions of the reference numerals are as follows:

[0059] X, thickness direction; Y, width direction; Z, length direction;

[0060] 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module;

[0061] 7, battery cell;

[0062] 10, electrode assembly;

[0063] 11, first electrode sheet; 111, first tab; 1111, first end; 112, first coating part;

[0064] 12, second electrode sheet; 121, second tab; 1211, second end; 122, second coating part;

[0065] 13, separator;

[0066] 14, negative electrode sheet; 141, negative electrode film layer; 142, negative electrode current collector; 1411, first negative electrode film layer; 1412, second negative electrode film layer; 141a, first region; 141b, second region; 141c, third region;

[0067] 20, housing assembly;

[0068] 21. Housing; 22. End cap; 31. First electrode terminal; 32. Second electrode terminal. Detailed implementation manners

[0069] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0070] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0072] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0073] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0074] "Multiple" as used in this application means two or more (including two).

[0075] 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 amount of the battery cell at high temperatures, which may cause deterioration of the high temperature cycle performance, use reliability, etc. of the battery cell.

[0076] In view of the above problems, the embodiments of this application improve the energy density of the battery cell by designing the size of the electrode sheet;

[0077] 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 this 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;

[0078] 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 amount 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 relatively small resistance at the connection with the coating part, which can further reduce the heat generation amount of the electrode sheet. Thereby, 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 use reliability of the battery cell can be reduced, and the high temperature cycle performance and use reliability of the battery cell can be improved.

[0079] The battery cell of this application is applicable to various battery devices and electrical devices that use battery cells.

[0080] 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. Alternatively, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0081] Figure 1 FIG. 4 is a schematic diagram of the 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. To meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0082] A battery device is disposed inside the electrical device 1, and the battery device can be disposed at the bottom, head or tail of the electrical device 1. The battery device can be used for power supply of the electrical device 1. For example, the battery device can be used as the operating power source of the electrical device 1, and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in FIG. 5 is the battery pack 2.

[0083] 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.

[0084] The battery device (Battery Apparatus) may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly (Battery Cell Assembly) may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel or in a hybrid connection through a busbar component.

[0085] In some embodiments, the battery cell assembly (Battery Cell Assembly) is generally formed by arranging a plurality of battery cells.

[0086] As an example, the battery cell assembly can be a battery module (Battery Module), and the battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0087] As shown in Figure 2 FIG. 6, in some embodiments, the battery device can be the battery pack 2 (battery Pack), and the battery pack 2 includes a box body 5 and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body 5.

[0088] 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.

[0089] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has a receiving space 5c. The first housing portion 5a and the second housing portion 5b are snapped together so that a closed space is formed inside the housing 5 to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first housing portion 5a can be a top cover or a bottom plate.

[0090] As an example, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the housing 5 to accommodate the battery cell assembly.

[0091] In some embodiments, the housing 5 can be part of the chassis structure of a vehicle. For example, part of the housing 5 can form at least part of the floor of the vehicle, or part of the housing 5 can form at least part of the crossbeam and longitudinal beam of the vehicle.

[0092] As an example, the battery cell assembly can be a battery module 6, and the battery cell assembly can be accommodated in the housing 5 by fixing the battery module 6 in the housing 5.

[0093] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0094] 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.

[0095] 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.

[0096] 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:

[0097] Charge at a constant current of 8.00C from 20% SOC to 25% SOC;

[0098] Charge at a constant current of 8.00C from 25% SOC to 30% SOC;

[0099] Charge at a constant current of 7.50C from 30% SOC to 35% SOC;

[0100] Charge at a constant current of 6.87C from 35% SOC to 40% SOC;

[0101] Charge at a constant current of 6.38C from 40% SOC to 45% SOC;

[0102] Charge from 45% SOC to 50% SOC at a constant current of 5.95C;

[0103] Charge from 50% SOC to 55% SOC at a constant current of 5.53C;

[0104] Charge from 55% SOC to 60% SOC at a constant current of 5.14C;

[0105] Charge from 60% SOC to 65% SOC at a constant current of 4.76C;

[0106] Charge from 65% SOC to 70% SOC at a constant current of 4.36C;

[0107] Charge from 70% SOC to 75% SOC at a constant current of 3.94C;

[0108] Charge from 75% SOC to 80% SOC at a constant current of 3.57C.

[0109] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from 20% state of charge to 80% state of charge is 5 min to 30 min, optionally 5 min to 20 min. The temperature of the external environment of the battery device at 20% state of charge is room temperature, such as 25°C. Exemplarily, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min or the range composed of any two of the above values.

[0110] As Figure 4 and Figure 5 shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20.

[0111] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0112] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0113] 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 being the positive terminal and the other being the negative terminal.

[0114] The outer casing can be a steel casing, an aluminum casing, a plastic casing (such as polypropylene), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum plastic film, etc. In some embodiments, the outer casing can be a sealed structure or a non-sealed structure. As an example, when the outer casing is a non-sealed structure, the outer casing serves to protect the electrode assembly 10, and a sealing bag is further included between the outer casing and the electrode assembly 10, and the sealing bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum plastic film. When the outer casing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0115] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, and a multi-prismatic battery. The multi-prismatic battery is, for example, a hexagonal prism battery, etc., and there is no particular limitation in this application.

[0116] In some embodiments, the outer casing includes an end cap 22 and a housing 21. The housing 21 is provided with an opening, and the end cap 22 is covered on the opening. The housing 21 can be provided with one or more openings. One or more end caps 22 can also be provided.

[0117] 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 of a cylindrical structure can be selected; if the electrode assembly 10 is a cuboid structure, a housing 21 of a cuboid structure can be selected. Optionally, both the electrode assembly 10 and the housing 21 are of cuboid structures.

[0118] 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 the positive electrode tab and the other is the negative electrode tab.

[0119] The electrode assembly 10 is a laminated structure, which is beneficial to improving the energy density of the battery cell 7.

[0120] 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 laminated.

[0121] As an example, a plurality of first electrode tabs 11 can be provided, and the second electrode tab 12 is folded to form a plurality of folded segments arranged in a laminated manner, and a first electrode tab 11 is clamped between adjacent folded segments.

[0122] As an example, both the first electrode tab 11 and the second electrode tab 12 are folded to form a plurality of folded segments arranged in a laminated manner.

[0123] As an example, a plurality of separator members 13 may be provided, which are respectively provided between any adjacent first electrode plates 11 or second electrode plates 12.

[0124] As an example, the separator members 13 may be continuously provided and are provided between any adjacent first electrode plates 11 or second electrode plates 12 by means of folding or winding.

[0125] In some embodiments, each electrode plate is provided with a tab, and the tab can conduct current out of the electrode assembly 10. The tabs include a positive tab and a negative tab.

[0126] To illustrate the present application more clearly, the tab portion of the first electrode plate 11 is defined as the first tab 111, and the coated portion of the first electrode plate 11 is defined as the first coated portion 112. The tab portion of the second electrode plate 12 is defined as the second tab 121, and the coated portion of the second electrode plate 12 is defined as the second coated portion 122. The electrode terminal having the same electric property as and electrically connected to the first tab 111 is the above-mentioned first electrode terminal 31, and the electrode terminal having the same electric property as and electrically connected to the second tab 121 is the above-mentioned second electrode terminal 32.

[0127] The polarities of the first electrode plate 11 and the second electrode plate 12 are opposite. When the first electrode plate 11 is a positive electrode plate, the second electrode plate 12 is a negative electrode plate, the first coated portion 112 is a positive electrode coated portion, the first tab 111 is a positive tab, the first electrode terminal 31 is a positive terminal, the second coated portion 122 is a negative electrode coated portion, the second tab 121 is a negative tab, and the second electrode terminal 32 is a negative terminal.

[0128] Or when the first electrode plate 11 is a negative electrode plate, the second electrode plate 12 is a positive electrode plate, the first coated portion 112 is a negative electrode coated portion, the first tab 111 is a negative tab, the first electrode terminal 31 is a negative terminal, the second coated portion 122 is a positive electrode coated portion, the second tab 121 is a positive tab, and the second electrode terminal 32 is a positive terminal.

[0129] The coated portion includes a current collecting portion and a film layer provided on the current collecting portion and containing an active material. For example, the positive electrode coated portion includes a positive electrode current collecting portion and a positive electrode film layer provided on the positive electrode current collecting portion and containing a positive electrode active material. Another example is that the negative electrode coated portion includes a negative electrode current collecting portion and a negative electrode film layer provided on the negative electrode current collecting portion and containing a negative electrode active material.

[0130] Such as Figures 4 to 6As 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 plates 11 and a plurality of second electrode plates 12. The plurality of first electrode plates 11 and the plurality of second electrode plates 12 are stacked along the thickness direction X of the battery cell 7. Both the first electrode plate 11 and the second electrode plate 12 include a coated portion and an electrode tab portion. The coated portion is provided with an active material, and the electrode tab portion may not be coated with the active material. The electrode 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.

[0131] Among them,

[0132] One of the first electrode plate 11 and the second electrode plate 12 is a positive electrode plate, and the other is a negative electrode plate;

[0133] The size of the coated portion of the positive electrode plate along the length direction Z of the battery cell 7 is a first size, and the size of the coated portion of the positive electrode plate along the width direction Y of the battery cell 7 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. The size of the coated portion of the positive electrode plate along the length direction Z of the battery cell 7 is 265 mm to 1200 mm;

[0134] The first electrode plate satisfies: n*W1 / W2 is 0.2 to 1.0;

[0135] n represents the number of all electrode tab portions on the same side of the coated portion; n is greater than or equal to 1;

[0136] W1 represents the average size of the electrode tab portion along the width direction Y;

[0137] W2 represents the size of the coated portion along the width direction Y;

[0138] The electrolyte includes a lithium salt. 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 0.2 to 0.8.

[0139] Taking Figure 6 the first electrode plate 11 as the positive electrode plate as an example, Z2 represents the size of the coated portion of the positive electrode plate along the length direction Z of the battery cell 7, that is, the first size, and W2 represents the size of the coated portion of the positive electrode plate along the width direction Y of the battery cell 7, that is, the second size.

[0140] When the size of the coated portion of the positive electrode plate along the length direction Z of the battery cell is less than 265 mm, the active material that can be carried is limited, and the energy density of the battery cell 7 is relatively low. The size of the coated portion of the positive electrode plate 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;

[0141] As the size of the coating portion of the positive electrode tab along the length direction Z further increases, the electron transport path in the electrode tab increases, and the ohmic resistance increases; as the ratio of the first size to the second size increases, the electron transport path in the electrode tab further increases, and the ohmic resistance increases, which is not conducive to rapid charging; moreover, the increase in ohmic resistance may lead to an increase in heat generation, and the accumulation of heat easily causes the decomposition of the electrolyte, deteriorating the cycle;

[0142] In one aspect, the embodiment of the present application limits the ratio of the first size to the second size to be less than or equal to 18.5, reduces the aspect ratio, and shortens the electron transport distance in the length direction; on the other hand, the tab portion is disposed 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 transport distance in the electrode tab, reduce the ohmic resistance of the electrode tab, and improve the electron transport 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 transport ability and ion conduction ability, the rapid charging ability of the battery cell at high energy density is improved;

[0143] Lithium hexafluorophosphate may decompose to produce 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;

[0144] However, as the addition amount of lithium fluorosulfonylimide increases, the thermal diffusion risk further increases; specifically, the thermal decomposition temperature of the fluorosulfonylimide salt is close to the thermal runaway temperature of the battery cell 7, and the thermal decomposition rate of lithium fluorosulfonylimide is fast and the heat release is intense, which can quickly release a large amount of heat and high-temperature gas, resulting in a sharp increase in the internal heat of the battery cell 7. A large amount of heat is difficult to quickly release, which easily leads to thermal diffusion and deteriorates the use reliability of the battery cell 7;

[0145] In one aspect of the embodiments of the present application, by limiting the mass content ratio of lithium fluorosulfonimide to lithium hexafluorophosphate to be less than or equal to 0.8, the risk of further heat increase caused by the decomposition of lithium fluorosulfonimide due to heat increase can be reduced; on the other hand, when 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 is 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. Thus, the heat accumulation inside the battery cell 7 can be reduced, the adverse effect of heat accumulation on lithium fluorosulfonimide can be reduced, and the risk of gas generation and heat generation caused by the decomposition of lithium fluorosulfonimide can be slowed down, thereby improving the high-temperature cycle performance and service reliability of the battery cell 7.

[0146] Thus, the embodiments of the present application can take into account improving the fast charging performance, high-temperature cycle performance, and service reliability of the high-energy-density battery cell 7.

[0147] 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.

[0148] 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 cycle performance of the battery cell 7 at high energy density.

[0149] W1 represents the average size of the first tab 111 along the width direction Y.

[0150] 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 then 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, and in this case, this value can be used as the average size of the first tab 111.

[0151] 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, n is from 1 to 4. After measuring the average sizes of the respective first tabs 111, the average size of the first tab 111 can be calculated by adding the average sizes and dividing by the number of the first tabs 111.

[0152] The first tab 111 is connected to the first coating portion 112. The first tab 111 includes a first end 1111 connected to the first coating portion 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first coating portion 112 is relatively large, the current-carrying capacity of the first tab 111 is strong, and the fast charging performance and high-temperature cycle performance of the battery cell 7 can be improved.

[0153] In some embodiments, the first electrode sheet 11 includes at least one first tab 111, for example, including 1 to 4 first tabs 111. Optionally, the first electrode sheet 11 includes at least two first tabs 111, and may be four first tabs 111.

[0154] 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.

[0155] As Figures 6 to 8 shown, the number of tab portions on the same side of the coating portion in the first electrode sheet 11 is at least one, and the tab portion includes a first end 1111 connected to the coating portion. Figure 6 In [a certain situation] where n is 2, the sizes of the respective first tabs 111 are the same, and W1 may also represent the size of a single first tab 111. Of course, the sizes of the respective first tabs 111 may also vary slightly. W2 represents the size of the first coating portion 112 along the length direction Z. Figure 7 In [a certain situation] where n is 1, n*W1 / W2 is 1.0. Figure 8 In [a certain situation] where n is 1.

[0156] In some embodiments, the first electrode sheet 11 includes at least one first tab 111, for example, including 1 to 4 first tabs 111. Optionally, the first electrode sheet 11 includes at least two first tabs 111, and may be four first tabs 111.

[0157] 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.

[0158] 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.

[0159] For example, in the case where the first electrode sheet 11 includes a plurality of first tabs 111, the plurality of first tabs 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.

[0160] Optionally, a plurality of first tabs 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z. This arrangement can shorten the transmission path of electrons in the first electrode sheet 11, which is beneficial to improving the fast charging performance. For example, two first tabs 111 are located on one side of the first coating portion 112 along the length direction Z, and two first tabs 111 are located on the other side of the first coating portion 112 along the length direction Z.

[0161] Optionally, when a plurality of first tabs 111 are respectively disposed on at least one side of the first coating portion 112 along the length direction Z, there are at least two first tabs 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 arrangement is beneficial to the uniform distribution of electrons in the first electrode sheet 11 and is beneficial to improving the fast charging performance.

[0162] Optionally, the distance between two adjacent first tabs 111 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range composed of any two of the above values. Figure 6 Where Y1 represents the distance between two adjacent first tabs 111 along the width direction Y.

[0163] Such as Figure 9 and Figure 10 As shown, in some embodiments, for the second electrode sheet 12: m*W3 / W4 is 0.2 to 1.0;

[0164] m represents the number of all tab portions on the same side of the coating portion; m is greater than or equal to 1;

[0165] W3 represents the average size of the tab portion along the width direction Y;

[0166] W4 represents the size of the coating portion along the width direction Y.

[0167] 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.

[0168] 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.

[0169] W3 represents the average dimension of the second tab 121 in the length direction Z. The second tab 121 can be one or more. For example, m ranges 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.

[0170] 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 meets 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.

[0171] 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 plate 12 is relatively low, and the fast charging performance and high-temperature cycling performance of the battery cell 7 can be further improved.

[0172] Figure 9 In this case, m is 1. Figure 10 In this case, m is 2.

[0173] In some embodiments, the second electrode plate 12 includes at least one second tab 121, optionally at least two second tabs 121, and optionally four second tabs 121.

[0174] For example, one or more second tabs 121 are arranged on one side of the second coating portion 122 in the length direction Z. In this case, it can be understood that all the second tabs 121 are arranged on the same side of the second coating portion 122 in the length direction Z.

[0175] Or for example, when the second electrode plate 12 includes multiple second tabs 121, the multiple second tabs 121 are respectively arranged on both sides of the second coating portion 122 in the length direction Z.

[0176] Optionally, the multiple second tabs 121 are respectively arranged on both sides of the second coating portion 122 in the length direction Z. This arrangement can shorten the transmission path of electrons in the second electrode plate 12, which is beneficial to improving the fast charging performance.

[0177] Optionally, when multiple second tabs 121 are arranged on at least one side of the second coating portion 122 in the length direction Z, there are at least two second tabs 121 on the same side of the second coating portion 122 in the length direction Z, such as two, three, four, five, six, etc. This arrangement is beneficial to the uniform distribution of electrons in the second electrode plate 12 and is beneficial to improving the fast charging performance.

[0178] Optionally, the distance between two adjacent second tab ears 121 in the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range composed of any two of the above values.

[0179] As Figure 11 shown, in some embodiments, the terminal assembly may be disposed on the housing 21, or the terminal assembly is disposed on the end cap 22.

[0180] 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.

[0181] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 may be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22.

[0182] On the same end cap 22, the first electrode terminal 31 and the second electrode terminal 32 can be provided simultaneously. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are spaced apart on the end cap 22. Another example is that there are two end caps 22, the two end caps 22 are oppositely arranged, and the first electrode terminal 31 and the second electrode terminal 32 are provided on each end cap 22.

[0183] The first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on different end caps 22. For example, there are two end caps 22, the two end caps 22 are oppositely arranged, the first electrode terminal 31 is disposed on one of the end caps 22, and the second electrode terminal 32 is disposed on the other end cap 22.

[0184] In some embodiments, the first electrode terminal 31 is at least one, optionally at least two, such as two, three, or four, etc.

[0185] In some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 in the length direction Z.

[0186] As Figure 11 shown, for example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 in the length direction Z.

[0187] As Figure 12 shown, another example is that a plurality of first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 in the length direction Z. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0188] 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. Alternatively, 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.

[0189] In an embodiment of the present application, the first tab 111 and the first electrode terminal 31 are electrically connected, and 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] Figure 12 It shows that the battery cell 7 includes four electrode terminals. Specifically, there are two second electrode terminals 32, one of the second electrode terminals 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0196] 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, and when electrically connected to the tab portions respectively, they will basically not interfere with each other.

[0197] 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 The schematic diagram showing that the first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on both sides of the electrode assembly 10 is shown.

[0198] 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.

[0199] In the embodiment of the present application, the second tab 121 and the second electrode terminal 32 are electrically connected, which can be directly connected or indirectly connected; when the second tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter, and the second adapter is located between the second electrode terminal 32 and the second tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0200] In the above embodiments, the second adapter can include a conductive polymer or a conductive metal material, and the conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0201] In some other embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y, or a plurality of second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the width direction Y.

[0202] Negative electrode plate

[0203] The coating portion of the negative electrode plate includes a negative current collector portion and a negative electrode film layer disposed on at least one side of the negative current collector portion and including a negative electrode active material. For example, the negative 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 current collector portion.

[0204] The upper charge limit voltage and the discharge cut-off voltage of the battery cell vary depending on the cathode active material. 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; Another example is when the phosphate material includes lithium iron manganese 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% SOC of the battery cell are defined as follows,

[0205] Charge the battery cell 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 discharge the battery cell 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.

[0206] In some embodiments, when the battery cell is at 100% SOC, the compaction density of the negative electrode film layer is 1.5 g / cm 3 to 1.7 g / cm 3 . Exemplarily, the compaction density of the negative electrode film layer of the battery cell at 100% SOC is 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 , 1.66 g / cm³, 1.68 g / cm³, 1.70 g / cm³ or the range composed of any two of the above values.

[0207] 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 fast charging of the battery cell; moreover, the particle packing of the negative electrode active material will not be overly tight, reducing the risk of particle crushing, which is beneficial to improving the high-temperature cycle performance of the battery cell.

[0208] 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 a range composed of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 to 142 mg / 1540.25 mm 2 .

[0209] 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 fast charging ability of the battery cell.

[0210] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, the negative electrode electrode sheet is disassembled from the battery cell in the 100% state of charge (SOC), and the compaction density of the negative electrode film layer is measured. For example, take the single-sided coated negative electrode electrode sheet (if it is a double-sided coated electrode sheet, one side of the negative electrode film layer can be wiped off first), punch it into small round pieces with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the negative electrode film layer of the above-mentioned weighed negative electrode electrode sheet, weigh the weight of the negative electrode current collector part, record it as M0, and measure its thickness H0. The single-sided coating weight of the negative electrode film layer = (the weight M1 of the negative electrode electrode sheet - the weight M0 of the negative electrode current collector part) / S1, the thickness of the negative electrode film layer = the thickness H1 of the negative electrode electrode sheet - the thickness H0 of the negative electrode current collector part, and the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0211] In some embodiments, the charging specific capacity of the negative electrode active material is from 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 a range composed of any two of the above values.

[0212] 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.

[0213] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art, and can be tested by the equipment and methods well-known in the art. The test method for the first Coulomb efficiency and the first discharge specific capacity in Appendix G of GB / T 24533-2019 can be adopted to test the charging specific capacity of the negative electrode active material at a rate of 0.1C in a half-cell. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-cell is assembled. Under the condition of 23°C ± 2°C, the half-cell is placed on a battery tester or other test equipment with equivalent performance, and the discharge capacity is obtained through charge and discharge at a rate of 0.1C, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0214] In some embodiments, the negative electrode active material includes a silicon-based material. Optionally, the silicon-based material may include at least one of elemental silicon, silicon-carbon composite, silicon oxide SiO x (0 < x ≤ 2). For example, the silicon-carbon composite may be silicon carbide.

[0215] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode film layer is from 0.3% to 10%, such as 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range composed of any two of the above values. Optionally, the mass content of silicon element in the silicon-based material in the negative electrode film layer is from 3% to 6%.

[0216] When the mass content of silicon element is within the above range, it can improve the capacity of the anode active material, which is beneficial to increasing the energy density of the battery cell; moreover, during the charge and discharge process, the volume expansion of the silicon element will not be too large, which is beneficial to maintaining the stability of the anode interface film and improving the high-temperature cycling performance of the battery cell.

[0217] In some embodiments, the anode active material includes a carbon-based material, and the carbon-based material has relatively high cycling stability, which can improve the high-temperature cycling performance of the battery cell.

[0218] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0219] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the anode 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.

[0220] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. 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 jointly for qualitative or quantitative determination.

[0221] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to perform X-ray powder diffraction test and qualitative analysis on the anode electrode or anode active material.

[0222] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-sectional view of natural graphite, while the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, while only 2H phase exists in the XRD spectrum of artificial graphite.

[0223] As Figure 13 shown, in the embodiment of this application, the anode film layer 141 of the anode electrode 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 anode film layer 141 includes at least two-layer film layers.

[0224] When the anode film layer 141 adopts a single-layer film layer, the anode active material in the anode film layer 141 includes a carbon-based material and an optional silicon-based material.

[0225] When the negative electrode film layer 141 adopts at least two film layers, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material. The negative electrode film layer 141 may include two film layers, three film layers, four film layers, or even more film layers.

[0226] In some embodiments, the negative electrode film layer 141 includes a first negative electrode film layer 1411 and a second negative electrode film layer 1412. The first negative electrode film layer 1411 is disposed on the surface of the negative electrode current collector 142, and the negative electrode active material of the first negative electrode film layer 1411 includes a carbon-based material. The second negative electrode film layer 1412 is connected to the side of the first negative electrode film layer 1411 facing away from the negative electrode current collector 142, and the negative electrode active material of the second negative electrode film layer 1412 includes a carbon-based material. The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 may be regular or irregular, and is optionally irregular; or there is no obvious interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0227] The negative electrode film layer 141 includes at least two film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there is a difference in porosity between the first negative electrode film layer 1411 and the second negative electrode film layer 1412, it is beneficial to improving the fast charging performance of the battery cell.

[0228] 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.

[0229] Optionally, the first negative electrode film layer 1411 further includes a silicon-based material.

[0230] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0231] Exemplarily, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 include a silicon-based material, it is more beneficial to improving the energy density of the battery cell; and it can enable each layer to relieve the volume expansion of the silicon-based material through the carbon-based material, 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.

[0232] Or, 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.

[0233] Alternatively, the first negative electrode film layer 1411 comprises a carbon-based material, and the second negative electrode film layer 1412 comprises a carbon-based material and a silicon-based material. When the second negative electrode film layer 1412 comprises a silicon-based material, it is beneficial to form more film layer pores through the volume change of the silicon-based material, improve the liquid-phase transport ability of lithium ions, and enhance the kinetic performance of the battery cell.

[0234] 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.

[0235] 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.

[0236] The cross-sectional morphologies of the first region 141a and the second region 141b can be the same or similar, and of course, they can also be different. The cross-sectional morphologies of the first region 141a and the third region 141c can be the same or similar, and of course, they can also be different. The cross-sectional morphologies of the second region 141b and the third region 141c can be the same or similar, and of course, they can also be different.

[0237] There may be an obvious layer interface between the first region 141a, the second region 141b, and the third region 141c, or there may be no obvious layer interface. For example, the first negative electrode film layer 1411 comprises the first region 141a, the second negative electrode film layer 1412 comprises the second region 141b, the third region 141c can be a part of the first negative electrode film layer 1411, or the third region 141c can be a part of the second negative electrode film layer 1412, or the third region 141c can be a part of both the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0238] 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 to the rapid migration of lithium ions from the second region 141b to the first region 141a and improves the rapid charging ability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a may be smaller than the average particle size of the carbon-based material in the second region 141b.

[0239] 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.

[0240] 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 rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer 1412 is usually relatively high, and the bottleneck of rapid charging mainly lies in the second negative electrode film layer 1412. In the embodiment of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and can also improve the problem of lithium deposition on the surface of the negative electrode sheet 14.

[0241] 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 a range composed of any two of the above values. When the average particle size of the carbon-based material in the first region 141a is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the rapid charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0242] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material in the first negative electrode film layer 1411 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the rapid charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0243] Optionally, the average particle size of the carbon-based material in the second region 141b is 5 μm to 12 μm, such as 5 μm, 8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range composed of any two of the above values. When the average particle size of the carbon-based material in the second negative electrode 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.

[0244] Optionally, the average particle size of the carbon-based material in the second negative electrode film layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the 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.

[0245] 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.

[0246] Exemplarily, the carbon-based material in the first negative electrode film layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material in the second negative electrode film layer 1412 includes artificial graphite. For example, the negative electrode active material in the first negative electrode film layer 1411 includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material in the second negative electrode film layer 1412 includes a silicon-based material and artificial graphite.

[0247] In the embodiments of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has the meaning well known in the art, and can be detected by using the equipment and methods well known in the art. For example, taking the negative electrode plate 14 as a sample, cross-section polishing is performed along the thickness direction X of the negative electrode film layer 141, for example, cross-section polishing is performed by using an argon ion beam, and the cross-section is photographed by using a scanning electron microscope SEM to obtain an SEM cross-sectional view, and the particle size of the carbon-based material in the SEM cross-sectional view is statistically analyzed, and the average particle size of the carbon-based material is calculated according to the statistical quantity.

[0248] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0249] The negative electrode conductive agent can compensate for the disadvantage of insufficient conductivity of the silicon-based material, improve the conductivity of the negative electrode film layer, is beneficial to improving the kinetic performance of the battery cell, and enhancing the fast charging ability of the battery cell.

[0250] 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.

[0251] 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%.

[0252] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0253] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include a thickener, a dispersant, 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%.

[0254] In some embodiments, the negative electrode current collector part may adopt a metal foil or a composite current collector part. 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 adopted. The composite current collector part may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material 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).

[0255] In some embodiments, the thickness of the negative current collector portion is from 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.

[0256] In some embodiments, the negative electrode tab further includes a negative electrode tab connected to the negative current collector portion. The thickness of the negative electrode tab is from 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm or a range composed of any two of the above values. When the thickness of the negative electrode tab is within the above range, it is beneficial to improve the overcurrent capacity and improve the fast charging capacity of the battery cell.

[0257] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative current collector portion and 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 can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0258] The negative electrode tab does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode tab of the embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative current collector portion and the negative electrode film layer and disposed on the surface of the negative current collector portion. In other embodiments, the negative electrode tab of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0259] Positive electrode plate

[0260] In some embodiments, the battery cell further includes a positive electrode tab.

[0261] The coated portion of the positive electrode tab includes a positive current collector portion and a positive electrode film layer disposed 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 disposed on any one or both of the two opposite surfaces of the positive current collector portion.

[0262] In the case where the battery cell includes a stacked electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode 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.

[0263] In some embodiments, the size of the positive electrode film layer can be considered the same as the size of the coated portion of the positive electrode tab. The size of the positive electrode film layer in the length direction of the battery cell is 265 mm to 1200 mm, such as 265 mm, 350 mm, 450 mm, 550 mm, 650 mm, 750 mm, 850 mm, 950 mm, 1050 mm, 1150 mm, 1200 mm or the range composed of any two of the above values.

[0264] In some embodiments, the size of the positive electrode film layer in the length direction of the battery cell is the same as the first size, and the size of the positive electrode film layer in the width direction of the battery cell is the same as the 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 can be optionally 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.

[0265] For example, the size of the positive electrode film layer in the length direction of the battery cell is 265 mm to 655 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 greater than 1 and less than or equal to 12.5, and can be optionally 1.25 to 12.5. When the positive electrode active material in the positive electrode film layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the size of the positive electrode film layer should not be too long. When the size of the positive electrode film layer is within the above range, the electron transport path will not be too long, 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.

[0266] 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.

[0267] 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 use reliability of the battery cell. Of course, the size of the negative electrode film layer in the first direction can also be less than or equal to the size of the positive electrode film layer in the first direction.

[0268] 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. 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 a range composed of any two of the above values.

[0269] 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.

[0270] 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. The difference between the size of the negative electrode film layer in the second direction and the size of the positive electrode film layer in the second direction is 5 mm to 11 mm, such as 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, or a range composed of any two of the above values.

[0271] 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.

[0272] 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, reducing the risk of short circuit and improving 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.

[0273] 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. The difference between the size of the separator in the first direction and the size of the negative electrode film layer in the first direction is 6 mm to 10 mm, such as 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, or a range composed of any two of the above values.

[0274] 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.

[0275] 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.

[0276] 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,

[0277] 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.

[0278] 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 as shown in, 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.

[0279] 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 in, 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.

[0280] The size of the positive electrode film layer of the first electrode plate 11 in the width direction Y is the width 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 width direction Y is the width of the negative electrode film layer of the second electrode plate 12, and the size of the separator 13 in the width direction Y is the width of the separator 13.

[0281] The difference between the width of the negative electrode film layer of the second electrode plate 12 and the width of the positive electrode film layer of the first electrode plate 11 is OH12 , Figure 14 shows that on both sides of the negative electrode film layer along the width direction Y, it extends beyond the positive electrode film layer, and the extension on each side is OH 12 / 2. Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side along the width direction Y.

[0282] 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 shows that on both sides of the separator 13 along the width direction Y, it extends beyond the negative electrode film layer, and the extension on each side is OH 22 / 2. Of course, the separator 13 may extend beyond the negative electrode film layer on one side along the width direction Y.

[0283] In some embodiments, when the battery cell is in the 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 in the 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.

[0284] When the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive active material of the positive electrode film layer is stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during fast charging. Therefore, by adjusting the tap density of the positive electrode film layer to a reasonable range, the battery cell has both high energy density and fast charging performance.

[0285] 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 2Exemplarily, 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 .

[0286] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode plate 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.

[0287] 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 plate 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, for a single-sided coated positive electrode plate (if it is a double-sided coated plate, one side of the positive electrode film layer can be wiped off first), it is punched into small round 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 plate is wiped off, and the weight of the positive electrode current collector is weighed and 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 plate - 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 plate - 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.

[0288] In some embodiments, the charging specific capacity of the positive electrode active material is 150 mAh / g to 170 mAh / g. Exemplarily, the charging specific capacity of the 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.

[0289] When the charging specific capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0290] 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 using the testing method of the specific capacity of the negative electrode active material.

[0291] 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 processes and can improve the cycle life of the battery cell.

[0292] Optionally, the positive electrode active material can further include lithium-containing transition metal oxides. Examples of the lithium-containing transition metal oxides can include but are not limited to at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0293] 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 serve as a coating layer to coat the surface of the lithium-containing phosphate, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, facilitating the migration rate of lithium ions, improving the fast charging ability of the battery cell, and reducing the heat generation of the battery cell.

[0294] 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 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of Cl, C, and N, and Y includes one or more of O and F. The lithium-containing phosphate has relatively excellent cycle stability, which is beneficial to improving the high-temperature cycle performance of the battery cell.

[0295] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction of active ions such as Li will occur, along with consumption. The molar content of Li in the battery cell is different when the battery cell is discharged to different states. In the listing of cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the listing of cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value. Lattice oxygen release will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will show fluctuations. All the above situations are within the protection scope of the present application.

[0296] In the embodiments of the present application, the content of elements in the cathode active material has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the cathode plate, it is cleaned with dimethyl carbonate (DMC) and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the cathode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0297] In some embodiments, the lithium-containing phosphate is granular, and the volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm, such as 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm or a range composed of any two of the above values.

[0298] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium insertion and extraction path of lithium ions in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the lithium-containing phosphate stable.

[0299] In some embodiments, the positive electrode film layer further includes one or more of a lithium-containing ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as a lithium supplementing agent, which can supplement lithium ions to the positive electrode film layer, make up for the irreversible lithium ion loss in the system, improve the capacity, and improve the energy density of the battery cell.

[0300] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lithium supplementing 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 supplementing agent within a mass range, it can supplement lithium ions to the positive electrode film layer, make up for the irreversible lithium ion loss in the system, and the mass content of the lithium supplementing agent is not too high, so that the discharge specific capacity of the positive electrode is still relatively high, and the energy density is basically not reduced.

[0301] In some embodiments, the volume average particle size Dv50 of the lithium supplementing 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 distribution uniformity of the lithium supplementing agent.

[0302] In some embodiments, the volume average particle size Dv50 of the lithium supplementing 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.

[0303] 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 equipment and methods well known in the art. After fully discharging the fresh battery cell to 0% state of charge (SOC), disassemble the positive electrode plate, remove the positive electrode current collector part and retain the positive electrode film layer, immerse the positive electrode film layer in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer, and retain the positive electrode active material or lithium supplementing 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.

[0304] 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%.

[0305] 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%.

[0306] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one of foils of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0307] In some embodiments, the thickness of the positive electrode 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.

[0308] In some embodiments, the positive electrode plate further includes a positive electrode tab connected to the positive electrode current collector. The thickness of the positive electrode tab is 10 μm to 16 μm, such as 10 μm, 10.5 μm,

11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range composed of any two of the above values. When the thickness of the positive electrode tab is within the above range, it is beneficial to improve the overcurrent capacity and the fast charging capacity of the battery cell.

[0309] [[ID=12]]The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode 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.

[0310] The positive electrode tab does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiment of the present application further includes a positive electrode conductive layer disposed on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode film layer. In other embodiments, the positive electrode tab of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0311] [Electrolyte]

[0312] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting active ions between the positive electrode tab and the negative electrode tab. The electrolyte includes an organic solvent and an electrolyte salt.

[0313] 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.

[0314] 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.

[0315] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using 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.

[0316] 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.

[0317] 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.

[0318] In the embodiment of the present application, the viscosity of the electrolyte has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, it can be detected according to GB / T10247-2008.

[0319] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 1.05 g / mL to 1.35 g / mL. Exemplarily, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range composed of any two of the above values.

[0320] 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.

[0321] 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.

[0322] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0323] Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is from 5% to 35%. Exemplarily, the mass content of the chain carboxylic ester solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, or a range composed of any two of the above values. Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is from 8% to 20%.

[0324] When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte is small, which can improve the conductivity of the electrolyte, reduce the internal resistance of the battery cell, and is beneficial to the rapid migration of lithium ions; and the electrolyte is compatible with the silicon-containing negative electrode, which can effectively reduce the gas generation amount of the battery cell, reduce the influence on the interfacial film on the negative electrode side, and improve the fast charging ability and high-temperature cycle performance of the battery cell.

[0325] In some embodiments, the chain carboxylic ester solvent includes a compound represented by Formula I,

[0326] Formula I,

[0327] In Formula I,

[0328] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0329] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0330] The above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery cell.

[0331] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl group, or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group, or a C1-C2 haloalkyl group.

[0332] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0333] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0334] Exemplarily, the chain carboxylic acid ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8.

[0335]

[0336] In some embodiments, the organic solvent includes a carbonate solvent.

[0337] The carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0338] Optionally, the mass content of the carbonate solvent in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvent is 65%, 70%, 75%, or a range composed of any two of the above values.

[0339] When the mass contents of the carbonate solvent and the chain carboxylic acid ester solvent meet the above conditions, the stability of the electrolyte can be improved, and its high-temperature gas generation amount can be reduced.

[0340] Exemplarily, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0341] In the embodiments of the present application, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0342] Lithium hexafluorophosphate may decompose to produce 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, and reduce the high-temperature storage gas generation amount. The compound use is beneficial to increasing the transference number of lithium ions, improving the lithium ion conduction ability of the electrolyte, and can improve the high-temperature cycling performance and fast charging ability of the battery monomer.

[0343] Exemplarily, the lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide, and may be lithium bis(fluorosulfonyl)imide optionally.

[0344] 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.

[0345] Exemplarily, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and may be 10% to 18% optionally.

[0346] 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.

[0347] 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 may be 10% to 18% optionally. 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.

[0348] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of the lithium fluorosulfonylimide to the mass content of the lithium hexafluorophosphate is 0.2 to 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 the lithium fluorosulfonylimide to the mass content of the lithium hexafluorophosphate is 0.3 to 0.8. [[ID=?]]

[0349] 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.

[0350] Exemplarily, the mass content of lithium bis(fluorosulfonyl)imide is greater than 0 and less than or equal to 8%, 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.

[0351] 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 the range composed of any two of the above values.

[0352] 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 cycle performance.

[0353] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 10%. Exemplarily, the mass content of the additive in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. Optionally, the mass content of the additive in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0354] 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 cycle performance.

[0355] In some embodiments, the carbonate additives include one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive contains fluoroethylene carbonate and vinylene carbonate.

[0356] 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 cycle performance of the battery cell.

[0357] 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 cycle performance and fast charging performance of the battery cell.

[0358] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate, bis(ethylene sulfate), butene sultone, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate.

[0359] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

[0360] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatography Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography analysis methods. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be reverse-disassembled, and the free electrolyte obtained from the battery can be taken as a sample, and detected by ion chromatography analysis methods.

[0361] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0362] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified, and chain carboxylic ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0363] Carbonate additives (such as fluorinated cyclic carbonates and vinylene carbonate) are used as additives to the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0364] Separator

[0365] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0366] 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.

[0367] 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 any particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without any particular limitation. The separator can be a single component located between the positive and negative electrodes, or can be 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.

[0368] 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.

[0369] 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,

[0370] 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 terminals and excluding the insulating film outside the outer shell), and the volume V0 of the single battery cell is calculated, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0371] Embodiment

[0372] The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are all commercially available.

[0373] Example 1

[0374] 1. Preparation of the positive electrode sheet

[0375] The positive electrode plate includes a positive electrode tab, a positive current collector portion, and positive electrode film layers provided on both sides of the positive current collector portion. The positive current collector portion is an aluminum foil. The positive electrode tab is not coated with the positive electrode film layer.

[0376] The positive electrode film layer includes 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 a film layer formed by uniformly coating the positive electrode slurry (solvent is N-methylpyrrolidone NMP) on both sides of the positive current collector portion and then drying and cold pressing.

[0377] The volume average particle size Dv50 of the lithium-containing phosphate is 1.5 μm.

[0378] The single-sided coating weight of the positive electrode film layer is 286 mg / 1540.25 mm 2 。

[0379] 2. Preparation of the negative electrode plate

[0380] The negative electrode plate includes a negative electrode tab, a negative current collector portion, and negative electrode film layers provided on both sides of the negative current collector portion. The negative current collector portion is a copper foil. The negative electrode tab is not coated with the negative electrode film layer. The setting position and number of the negative electrode tabs are the same as those of the positive electrode tabs and will not be elaborated here.

[0381] The negative electrode film layer is a film layer formed by uniformly coating the negative electrode slurry (solvent is deionized water) on the surface of the negative current collector portion and then drying and cold pressing.

[0382] The single-sided coating weight of the negative electrode film layer is 132 mg / 1540.25 mm 2 。

[0383] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative current collector portion, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0384] The first negative electrode film layer includes a negative electrode active material, conductive carbon, negative electrode binder styrene-butadiene rubber, and thickener 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;

[0385] The second negative electrode film layer includes a negative electrode active material, conductive carbon, negative electrode binder styrene-butadiene rubber, and thickener 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.

[0386] In the cross-section along the thickness direction of the negative electrode film layer, the average particle size of the artificial graphite in the first negative electrode film layer is 13 μm; the average particle size of the artificial graphite in the second negative electrode film layer is 10 μm. During the preparation of the negative electrode film layer, the film layer with the required average particle size can be obtained by adjusting the volume average particle size of the artificial graphite multiple times.

[0387] 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.

[0388] 3. Separator

[0389] The separator includes a base film, and the base film is a 7-μm polyethylene film layer with a porosity of 42%.

[0390] The length of the separator is 6 mm larger than that of the negative electrode film layer, and the width of the separator is 6 mm larger than that of the negative electrode film layer.

[0391] 4. Preparation of electrolyte

[0392] The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0393] After mixing the components of the organic solvent, a lithium salt and an additive are added to prepare the electrolyte.

[0394] The organic solvent includes 15% carboxylic ester solvent ethyl acetate and 68.5% carbonate solvent ethylene carbonate.

[0395] The lithium salt includes 10% lithium hexafluorophosphate and 4% lithium bis(fluorosulfonyl)imide.

[0396] The additive includes 2.5% vinylene carbonate.

[0397] The conductivity of the electrolyte at room temperature is 11 mS / cm;

[0398] The viscosity of the electrolyte at room temperature is 2.70 mPa·s;

[0399] The density of the electrolyte at room temperature is 1.10 g / mL.

[0400] 5. Preparation of battery cell

[0401] Stack the above-mentioned positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role, obtaining an electrode assembly. Place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, formation, and shaping. 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 .

[0402] Comparative Example 1-1

[0403] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the number of positive tabs and the percentage occupying the current collector were adjusted.

[0404] Examples 2-1 to 2-3

[0405] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the number of positive tabs and the percentage occupying the current collector were adjusted.

[0406] Comparative Examples 2-1 and 2-2

[0407] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the length of the positive electrode film layer in the positive electrode plate was adjusted.

[0408] Examples 3-1 to 3-4

[0409] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the length of the positive electrode film layer in the positive electrode plate was adjusted.

[0410] Performance test

[0411] 1. DC Resistance DCR Test of Battery Single Cell

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

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

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

[0415] 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.

[0416] 3. High-temperature cycling performance test of battery cells

[0417] Under the environment of 60±5°C, charge the battery cell at a constant current of 1C until the upper cut-off voltage, then charge at a constant voltage until the cut-off current of 0.05C, and then discharge at a constant current of 1C until the discharge cut-off voltage. This is one charge-discharge cycle.

[0418] The discharge capacity this time is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycle step for the same battery cell. After cycling n times, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery cell = Cn / C1*100%. 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.

[0419] The test results are shown in Table 1.

[0420] Table 1

[0421]

[0422] In Table 1,

[0423] 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;

[0424] The short side of the positive tab exits on one side, which means that the positive tab is arranged on one side of the positive current collector along the length direction, and all positive tabs are located on the same side;

[0425] The short side of the positive tab exits on both sides, which means that the positive tab is arranged on both sides of the positive current collector along the length direction.

[0426] The short side of the positive tab exits on both sides, with 2 exiting on 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.

[0427] 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 electrolyte components, which is not conducive to the high-temperature cycling and fast charging of the battery cell.

[0428] In Example 1, Example 2-1 to Example 2-3, the positive electrode tab is disposed on at least one side of the positive electrode current collector portion along the length direction. The size of the positive electrode tab is relatively large, and the proportion of the size of the positive electrode tab in the positive electrode current collector portion is relatively large. n*W1 / W2 is greater than or equal to 0.2, so that the current-carrying area of the positive electrode tab is relatively high, the current-carrying capacity is relatively strong, the internal resistance is relatively small, the heat generation is small, and the heat inside the battery cell can be effectively reduced, improving the high-temperature cycle stability and fast charging ability of the battery cell.

[0429] As the proportion of the size of the positive electrode tab in the positive electrode current collector portion increases, n*W1 / W2 increases, and the current-carrying capacity of the positive electrode tab is enhanced. For example, in Example 2-2, n*W1 / W2 is 1, and the size of the positive electrode tab along the length direction is the same as the size of the positive electrode current collector portion along the length direction. In this case, the current-carrying capacity of the positive electrode tab is relatively excellent, which can further reduce the internal resistance, reduce heat generation, and improve the high-temperature cycle stability and fast charging ability of the battery cell.

[0430] The length of the positive electrode film layer in Comparative Example 2-1 is relatively short, resulting in a relatively small energy density of the battery cell. Although the electron transport path is relatively short, the DCR of the battery cell is relatively small, the heat generation is small, which is beneficial to the fast charging and high-temperature cycle performance of the battery cell. However, the energy density of the battery cell is relatively small, which does not meet the production requirements.

[0431] The length of the positive electrode film layer in Comparative Example 2-2 is relatively 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, a relatively high heat generation, and deterioration of the high-temperature cycle and fast charging ability.

[0432] 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 cycle performance and fast charging performance of the battery cell. The length and aspect ratio of the positive electrode film layer in Example 3-1 to Example 3-4 are appropriate, so that the energy density of the battery cell is relatively high. In the case of high energy density, the ratio of the length to the width of the positive electrode film layer is 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 the tab ratio of n*W1 / W2 greater than or equal to 0.2, the current-carrying capacity of the positive electrode tab is relatively excellent, which can effectively reduce the internal resistance, reduce heat generation, and improve the high-temperature cycle 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 coating portion of the positive electrode plate along the length direction is 400 mm to 600 mm, it is beneficial to simultaneously improve the high-temperature cycle performance and fast charging performance of the battery cell under high energy density.

[0433] Comparative Example 3-1

[0434] The battery single cells were 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.

[0435] Examples 4-1 to 4-7

[0436] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted.

[0437] In Examples 4-1 to 4-4, the mass content of lithium bis(fluorosulfonyl)imide was adjusted;

[0438] In Example 4-5, lithium bis(fluorosulfonyl)imide was replaced by lithium bis(trifluoromethanesulfonyl)imide, and the mass content remained unchanged.

[0439] 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%.

[0440] The test results are shown in Table 2.

[0441] Table 2

[0442]

[0443] In Table 2,

[0444] LiFSI represents lithium bis(fluorosulfonyl)imide;

[0445] LiTFSI represents lithium bis(trifluoromethanesulfonyl)imide;

[0446] A1 represents the mass content of lithium hexafluorophosphate, and A2 represents the mass content of lithium fluorosulfonylimide.

[0447] In Comparative Example 3-1, the addition amount of lithium fluorosulfonylimide was too small, resulting in relatively poor lithium ion conduction ability of the electrolyte, which was not conducive to lithium ion migration and fast charging.

[0448] 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 charge 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 single 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 charge performance of the battery single cell are relatively excellent.

[0449] However, when the addition amount of lithium fluorosulfonylimide is excessive, for example, greater than or equal to 10%, although it can reduce the DCR of the battery cell and improve the high-temperature cycling performance, in the case of thermal runaway, lithium fluorosulfonylimide can decompose rapidly within a short time, generating a large amount of gas and heat, resulting in a sharp increase in the internal heat of the battery cell. A large amount of heat is difficult to release quickly, deteriorating the reliability of the battery cell during use.

[0450] In Examples 4-5, lithium trifluoromethanesulfonimide and lithium bis(fluorosulfonyl)imide are used as lithium fluorosulfonylimide, and when they are used in combination with lithium hexafluorophosphate, they can effectively improve the high-temperature cycling performance and fast charging performance of the battery cell.

[0451] 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 degree of damage to the SEI film. The lithium salt also includes lithium fluorosulfonylimide, which can enhance the protection of the negative electrode side and is beneficial to improving the high-temperature cycling performance of the battery cell.

[0452] 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 modes of the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the implementation modes of the present application.

Claims

1. A battery cell, characterized in that, It includes an electrode assembly and an electrolyte solution. 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 materials, 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. Wherein, 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, and 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 is 265 mm to 1200 mm. The first electrode plate satisfies that 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, and 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 solution includes lithium fluorosulfonylimide and lithium hexafluorophosphate. Based on the mass of the electrolyte solution, the ratio of the mass content of lithium fluorosulfonylimide to the mass content of 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 lithium fluorosulfonylimide to the mass content of 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 lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte solution 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 lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte solution is 10% to 18%.

5. The battery cell according to any one of claims 1 to 2, characterized in that, The mass content of lithium fluorosulfonylimide in the electrolyte solution is greater than 0 and less than or equal to 8%; and / or The mass content of lithium hexafluorophosphate in the electrolyte solution 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 lithium fluorosulfonylimide includes one or more of lithium trifluoromethanesulfonylimide and lithium bis(fluorosulfonyl)imide.

7. The battery cell according to any one of claims 1 to 2, wherein The conductivity of the electrolyte solution at room temperature is 10.5 mS / cm to 13.5 mS / cm; and / or The viscosity of the electrolyte solution at room temperature is 1.5 mPa·s to 5.5 mPa·s; and / or The density of the electrolyte solution at room temperature is 1.05 g / mL to 1.35 g / mL.

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

9. The battery cell according to claim 8, characterized in that, The chain carboxylic 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 haloalkyl group. R2 includes a C1 to C5 alkyl group or a C1 to C5 haloalkyl group.

10. The battery cell according to claim 9, characterized in that, The chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to 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 an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The mass content of the additive in the electrolyte is 0.5% to 10%.

13. The battery cell according to claim 12, wherein The carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate; and / or The sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite, and methylene methanedisulfonate; and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, and lithium bis(oxalate) borate.

14. The battery cell according to any one of claims 1 to 2, characterized in that, The number of the tab portions of the first electrode sheet is 1 to 4.

15. The battery cell according to any one of claims 1 to 2, characterized in that, All the tab portions of the first electrode sheet are connected to the same side of the coating portion along the length direction; or The first electrode sheet includes at least two tab portions, and at least two tab portions are connected to both sides of the coating portion of the first electrode sheet 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 dimension to the second dimension is 3.5 to 8, and the dimension 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 sheet includes lithium-containing phosphate.

19. The battery cell according to any one of claims 1 to 2, wherein The negative electrode sheet includes a negative electrode coating portion and a negative electrode tab connected to the negative electrode coating portion, and the positive electrode sheet 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 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 the dimension 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, wherein The electrode assembly further includes a separator 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 tab 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, Comprising a battery cell as described in any one of claims 1 to 20.

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

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