Battery cells, battery devices, and power-consuming devices

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 plate and a second electrode plate. Each of the first electrode plate and the second electrode plate includes a coating portion and a lug portion. The lug portion is connected to the coating portion and extends beyond the coating portion along the width direction of the battery cell. One of the first electrode plate and the second electrode plate is a positive electrode plate. The ratio of the lengthwise dimension of the coating portion of the positive electrode plate to the widthwise dimension of the coating portion of the positive electrode plate is greater than 1 and less than or equal to 18.5. The lengthwise dimension of the coating portion of the positive electrode plate is 265 mm to 1200 mm. The first electrode plate satisfies n*W1 / W2 of 0.2 to 1.0. The electrolyte includes lithium fluorinated sulfonyl imide and lithium hexafluorophosphate, and the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 0.8. The present application can improve the high-temperature cycling performance and fast-charging performance of the battery cell.

Description

[0001] This application claims priority to international patent application PCT / CN2025 / 071127, filed on January 7, 2025, entitled “Battery Cell, Battery Device, and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] Battery cells, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy planes, and power tools. With the tremendous progress made in battery technology, higher performance requirements are being placed on them. However, the fast charging capability, high-temperature cycling performance, and operational reliability of battery cells need to be further improved. Summary of the Invention

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

[0005] In the first aspect, an embodiment of the present application proposes a battery cell, which includes an electrolyte and an electrode assembly, the electrode assembly includes a plurality of first pole pieces and a plurality of second pole pieces, the plurality of first pole pieces and the plurality of second pole pieces are stacked along the thickness direction of the battery cell, the first pole piece and the second pole piece each include a coating portion and a pole ear portion, the coating portion is provided with an active material, the pole ear portion is connected to the coating portion and extends out of the coating portion along the width direction of the battery cell, wherein one of the first pole piece and the second pole piece is a positive pole piece and the other is a negative pole piece; the size of the coating portion of the positive pole piece along the length direction of the battery cell is a first size, and the coating portion of the positive pole piece along the width direction of the battery cell is a first size. The dimension in the longitudinal direction is the second dimension, the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, and the dimension of the coated portion of the positive electrode plate along the length direction of the battery cell is 265mm to 1200mm; the first electrode plate satisfies: n*W1 / W2 is 0.2 to 1.0; n represents the number of all pole ear portions located on the same side of the coating portion, and n is greater than or equal to 1; W1 represents the average dimension of the pole ear portion along the length direction; W2 represents the dimension of the coating portion along the length direction; the electrolyte includes lithium fluorinated sulfonyl imide and lithium hexafluorophosphate, and based on the mass of the electrolyte, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 0.8.

[0006] Therefore, when the coating portion of the positive electrode plate of the embodiment of the present application meets the above range, the energy density of the battery cell can be improved; under the above-mentioned electrode plate, the pole ear portion is arranged on at least one side of the coating portion along the width direction of the battery cell, the transmission distance of electrons in the electrode plate is relatively short, the electron transmission rate is fast, and the ohmic resistance of the electrode plate can be reduced; and the embodiment of the present application also improves the lithium salt component of the electrolyte, and the lithium salt includes an appropriate content of fluorinated sulfonyl imide lithium, so that the electrolyte's ability to conduct lithium ions is improved, and the combined improvement of active ion and electron transmission rates can effectively improve the battery cell at high Fast charging capability under energy density; the pole ear portion is arranged on at least one side of the coating portion along the width direction of the battery cell, and the pole piece ohmic resistance is relatively low, so that the pole piece generates relatively less heat; further, the appropriate size ratio of the pole ear portion makes the pole ear portion have a relatively high flow area, and the resistance at the connection with the coating portion is small, which can further reduce the heat generation of the pole piece, thereby reducing the heat accumulation inside the battery cell, reducing the adverse effects of heat accumulation on fluorinated sulfonyl imide lithium, reducing the risk of fluorinated sulfonyl imide lithium decomposition to produce gas and heat, and improving the high-temperature cycle performance and reliability of the battery cell.

[0007] In some embodiments, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.3 to 0.8. The combined use of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide can, on the one hand, improve the conductivity of the electrolyte and enhance the fast charging performance of the battery cell; on the other hand, it can reduce the risk of negative electrode side reactions and decomposition of the lithium fluorinated sulfonyl imide, thereby improving the high-temperature cycling performance and reliability of the battery cell.

[0008] In some embodiments, the mass content of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 18%, and can be 10% to 18%. When the mass content of the above lithium salts is within the above range, the high-temperature cycling performance and fast charging capability of the battery cell can be improved.

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

[0011] In some embodiments, the fluorinated lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide. These materials are beneficial for improving the high-temperature cycling performance and fast charging capability 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 electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. When the electrolyte density is within this range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0015] In some embodiments, the electrolyte further comprises a linear carboxylate solvent, and the weight content of the linear carboxylate solvent in the electrolyte is 5% to 35%. When the weight content of the linear carboxylate solvent is within the above range, the fast charging capability and high-temperature cycling performance of the battery cell can be improved.

[0016] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0017] Formula I,

[0018] In Formula I,

[0019] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0020] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0021] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0022] In some embodiments, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0023]

[0024] In some embodiments, the electrolyte further includes a carbonate solvent, with the carbonate solvent comprising 65% to 75% by weight in the electrolyte. When the mass content of the carbonate solvent and the chain carboxylate solvent meet the aforementioned conditions, the electrolyte stability can be enhanced, its high-temperature gas production can be reduced, and the high-temperature cycling performance of the battery cells 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, including one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, with the weight content of the additives in the electrolyte ranging from 0.5% to 10%. These additives can improve the performance of the interface film on the negative electrode side, resulting in a more stable interface film with relatively low impedance, which is beneficial for enhancing the fast charging performance of the battery cell and improving high-temperature cycling performance.

[0027] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. These additives can improve the performance of the solid electrolyte interface (SEI) membrane on the negative electrode side, resulting in a more stable SEI membrane with relatively low impedance, which is beneficial for enhancing the fast charging performance of the battery cell and improving high-temperature cycling performance.

[0028] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate. These additives are beneficial for improving the high-temperature cycling performance of the battery cells.

[0029] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate). These additives are beneficial for improving the high-temperature cycle performance of the battery cell.

[0030] In some embodiments, the number of the pole lugs of the first pole piece is 1 to 4. When the number of the pole lugs is within the above range, the pole lugs have a stronger current flow capacity, which is beneficial to improving the fast charging capability of the battery cell.

[0031] In some embodiments, all the pole lugs of the first pole piece are connected to the same side of the coating portion along the width direction. This arrangement is beneficial for improving the energy density of the battery cell.

[0032] In some embodiments, the first pole piece includes at least two pole lugs connected to two sides of the coating portion of the first pole piece along the width direction. This arrangement can shorten the electron transmission path and improve the fast charging capability of the battery cell.

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

[0034] In some embodiments, the ratio of the first dimension to the second dimension is 3.5 to 8, and the length of the coated portion of the positive electrode sheet is 400 mm to 600 mm. When the dimensions of the positive electrode film layer are within this range, the electron transmission path is not excessively long, the internal resistance is relatively low, and this improves the fast charging capability and energy density of the battery cell.

[0035] In some embodiments, the active material of the positive electrode plate includes a lithium-containing phosphate. Lithium-containing phosphates have excellent cycle stability and can improve the high-temperature cycle performance of battery cells.

[0036] In some embodiments, the negative electrode plate includes a negative electrode coating portion and a negative electrode ear connected to the negative electrode coating portion, and the positive electrode plate includes a positive electrode coating portion and a positive electrode ear connected to the positive electrode coating portion; the size of the negative electrode coating portion along the width direction is larger than the size of the positive electrode coating portion along the width direction, and the difference between the size of the negative electrode coating portion along the width direction and the size of the positive electrode coating portion along the width direction is 5mm to 11mm; the size of the negative electrode coating portion is relatively large, which can reduce the risk of lithium plating on the negative electrode, reduce the risk of short circuit between the positive and negative electrodes, and improve the reliability of the battery cell.

[0037] In some embodiments, the negative electrode coating portion has a greater length than the positive electrode coating portion, with the difference between the lengths of the negative electrode coating portion and the positive electrode coating portion being 5 mm to 11 mm. The relatively large size of the negative electrode coating portion can reduce the risk of lithium plating at the negative electrode, reduce the risk of short circuits between the positive and negative electrodes, and improve the reliability of the battery cell.

[0038] In some embodiments, the electrode assembly further includes a separator disposed between the positive and negative electrode sheets. The negative electrode sheet includes a negative electrode coating and a negative electrode tab connected to the negative electrode coating. The separator has a width greater than the width of the negative electrode coating, with the difference between the width of the separator and the width of the negative electrode coating being 6 mm to 10 mm. The relatively large size of the separator effectively isolates the negative and positive electrode sheets, reduces the risk of shorting between the negative and positive electrode sheets, and improves the reliability of the battery cell.

[0039] In some embodiments, the separator has a larger length than the negative electrode coating portion, with the difference between the length of the separator and the length of the negative electrode coating portion being 6 mm to 10 mm. The relatively large size of the separator effectively isolates the negative electrode sheet from the positive electrode sheet, reduces the risk of shorting between the negative and positive electrode sheets, and improves the reliability of the battery cell.

[0040] In a second aspect, an embodiment of the present application further provides a battery device, comprising a battery cell according to any embodiment of the first aspect of the present application.

[0041] In a third aspect, an embodiment of the present application further proposes an electrical device, which includes a battery device as in any embodiment of the second aspect or the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

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

[0044] Figure 2 is a schematic structural diagram of a battery pack provided in some embodiments of the present application;

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

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

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

[0048] Figure 6 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0049] Figure 7 is a schematic structural diagram of a first pole piece of a battery cell provided in other embodiments of the present application;

[0050] Figure 8 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0051] Figure 9 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0052] Figure 10 is a schematic structural diagram of a second pole piece of a battery cell provided in some embodiments of the present application;

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

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

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

[0056] Figure 14 is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0057] Figure 15 This is a schematic structural diagram of the first pole piece of a battery cell provided in some other embodiments of the present application.

[0058] The drawings are not necessarily drawn to scale.

[0059] The following are the descriptions of the reference numerals:

[0060] X, thickness direction; Y, width direction; Z, length direction;

[0061] 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space; 6. Battery module;

[0062] 7. Battery cells;

[0063] 10. Electrode assembly;

[0064] 11. first pole piece; 111. first pole tab; 1111. first end; 112. first coating portion;

[0065] 12. Second pole piece; 121. Second pole tab; 1211. Second end; 122. Second coating portion;

[0066] 13. Isolation parts;

[0067] 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;

[0068] 20. Housing assembly;

[0069] 21. Housing; 22. End cap; 31. First electrode terminal; 32. Second electrode terminal;

[0070] 51. First adapter. DETAILED DESCRIPTION

[0071] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0072] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0073] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0074] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0075] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0076] The term "plurality" used in this application refers to two or more (including two).

[0077] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, the fast charging performance requirements for high-energy-density battery cells are gradually increasing. As the fast charging performance requirements increase, this can be achieved in related technologies by increasing the conductivity of the electrolyte. However, the increase in conductivity may cause the electrolyte to decompose at high temperatures, resulting in an increase in the high-temperature gas production of the battery cells, which may cause the high-temperature cycle performance and use reliability of the battery cells to deteriorate.

[0078] In view of the above problems, the embodiment of the present application improves the energy density of the battery cell by designing the pole piece size;

[0079] Under the above-mentioned pole piece, the pole ear portion is arranged on at least one side of the coating portion along the width direction of the battery cell. The electron transmission distance in the pole piece is relatively short, the electron transmission rate is fast, and the ohmic resistance of the pole piece can be reduced. In addition, the embodiment of the present application also improves the lithium salt component of the electrolyte. The lithium salt includes an appropriate amount of fluorinated lithium sulfonyl imide, which improves the lithium ion conductivity of the electrolyte. The combined improvement of active ion and electron transmission rate can effectively improve the fast charging capability of the battery cell at high energy density.

[0080] The pole ear portion is arranged on at least one side of the coating portion along the width direction of the battery cell, and the pole piece ohmic resistance is relatively low, so that the pole piece generates relatively less heat; further, the appropriate size ratio of the pole ear portion makes the flow area of ​​the pole ear portion relatively high, and the resistance at the connection with the coating portion is small, which can further reduce the heat generation of the pole piece, thereby reducing the heat accumulation inside the battery cell and reducing the risk of thermal runaway; reducing the risk of rapid decomposition of fluorinated sulfonyl imide lithium during thermal runaway, generating a large amount of gas and heat, and deteriorating the reliability of the battery cell, thereby improving the high-temperature cycle performance and reliability of the battery cell.

[0081] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0082] For example, the power-consuming device may be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, electric tool, vehicle, ship, spacecraft, etc. Alternatively, for example, the power-consuming device may be a spacecraft, including an airplane, rocket, space shuttle, and spacecraft.

[0083] Figure 1 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 1, a battery pack or battery module may be used.

[0084] A battery device is disposed within 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 to power the electrical device 1. For example, the battery device can serve as an operating power source for the electrical device 1, and can also serve as a driving power source for 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. 1 is a battery pack 2 .

[0085] The electric 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, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0086] A battery device may include one or more battery cell assemblies to provide voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or in series via a busbar.

[0087] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0088] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0089] like Figure 2 As shown, in some embodiments, the battery device may be a battery pack 2 , which includes a box 5 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box 5 .

[0090] As an example, the battery cell assembly may also be housed in the box body 5 by directly fixing a plurality of battery cells to the box body 5 .

[0091] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b, which define a storage space 5c. The first housing portion 5a and the second housing portion 5b engage to form a closed space within the housing 5 for accommodating the battery cell assembly. "Enclosed" here means covered or closed, and can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0092] As an example, the box body 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0093] In some embodiments, the box 5 can be used as a part of the chassis structure of the vehicle. For example, part of the box 5 can become at least a part of the floor of the vehicle, or part of the box 5 can become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0094] As an example, the battery cell assembly may be a battery module 6 , and the battery cell assembly may be accommodated in the box body 5 by fixing the battery module 6 in the box body 5 .

[0095] like Figure 3 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0096] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% state of charge (SOC), the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0097] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC, the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0098] For example, the charging step of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC may be performed as follows:

[0099] Charge from 20% SOC to 25% SOC at 8.00C constant current;

[0100] Charge from 25% SOC to 30% SOC at 8.00C constant current;

[0101] Charge from 30% SOC to 35% SOC at 7.50C constant current;

[0102] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0103] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0104] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0105] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0106] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0107] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0108] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0109] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0110] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0111] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from a 20% state of charge to an 80% state of charge is 5 minutes to 30 minutes, optionally 5 minutes to 20 minutes, and the temperature of the external environment of the battery device at a 20% state of charge is room temperature, for example, 25°C. Illustratively, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min, or a range consisting of any two of the above values.

[0112] like Figure 4 and Figure 5 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20 .

[0113] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0114] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0115] Exemplarily, the terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32 , one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0116] The outer shell can be made of steel, aluminum, plastic (e.g., polypropylene), a composite metal shell (e.g., a copper-aluminum composite shell), or an aluminum-plastic film. In some embodiments, the outer shell can be either sealed or non-sealed. For example, in a non-sealed outer shell, the outer shell protects the electrode assembly 10 and includes a sealed bag between the outer shell and the electrode assembly 10, which encapsulates the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum-plastic film. In a sealed outer shell, the sealed bag encapsulates the electrode assembly 10 and other components, such as the electrolyte.

[0117] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a polygonal battery, and a polygonal battery such as a hexagonal battery. There is no special limitation in this application.

[0118] In some embodiments, the housing includes an end cap 22 and a shell 21. The shell 21 has an opening, and the end cap 22 covers the opening. The shell 21 may have one or more openings. One or more end caps 22 may also be provided.

[0119] The shape of the housing 21 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a cylindrical housing 21 can be selected; if the electrode assembly 10 has a rectangular parallelepiped structure, a rectangular parallelepiped housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 have rectangular parallelepiped structures.

[0120] The electrode assembly 10 includes a first electrode sheet 11 , a second electrode sheet 12 and a separator 13 . One of the first electrode sheet 11 and the second electrode sheet 12 is a positive electrode sheet, and the other is a negative electrode sheet.

[0121] The electrode assembly 10 has a laminated structure, which is beneficial for improving the energy density of the battery cell 7 .

[0122] As an example, a plurality of first pole pieces 11 and a plurality of second pole pieces 12 may be provided respectively, and the plurality of first pole pieces 11 and the plurality of second pole pieces 12 may be alternately stacked.

[0123] As an example, a plurality of first pole pieces 11 may be provided, and the second pole piece 12 may be folded to form a plurality of stacked folded segments, with one first pole piece 11 being sandwiched between adjacent folded segments.

[0124] As an example, the first pole piece 11 and the second pole piece 12 are both folded to form a plurality of stacked folded segments.

[0125] As an example, a plurality of spacers 13 may be provided, each spacer being provided between any adjacent first pole pieces 11 or second pole pieces 12 .

[0126] As an example, the spacer 13 may be provided continuously, and may be provided between any adjacent first pole pieces 11 or second pole pieces 12 by folding or winding.

[0127] In some embodiments, each electrode sheet is provided with a tab, which can conduct current from the electrode assembly 10. The tabs include a positive tab and a negative tab.

[0128] For a clearer description of the present application, the tab portion of the first pole piece 11 is defined as the first pole piece 111, and the coated portion of the first pole piece 11 is defined as the first coated portion 112. The tab portion of the second pole piece 12 is defined as the second pole piece 121, and the coated portion of the second pole piece 12 is defined as the second coated portion 122. The electrode terminal having the same electrical properties as and electrically connected to the first pole piece 111 is the aforementioned first electrode terminal 31, and the electrode terminal having the same electrical properties as and electrically connected to the second pole piece 121 is the aforementioned second electrode terminal 32.

[0129] The polarities of the first electrode piece 11 and the second electrode piece 12 are opposite. When the first electrode piece 11 is a positive electrode piece, the second electrode piece 12 is a negative electrode piece, the first coating portion 112 is a positive electrode coating portion, the first electrode tab 111 is a positive electrode tab, the first electrode terminal 31 is a positive electrode terminal, the second coating portion 122 is a negative electrode coating portion, the second electrode tab 121 is a negative electrode tab, and the second electrode terminal 32 is a negative electrode terminal.

[0130] Alternatively, when the first electrode sheet 11 is a negative electrode sheet, the second electrode sheet 12 is a positive electrode sheet, the first coating portion 112 is a negative electrode coating portion, the first electrode tab 111 is a negative electrode tab, the first electrode terminal 31 is a negative electrode terminal, the second coating portion 122 is a positive electrode coating portion, the second electrode tab 121 is a positive electrode tab, and the second electrode terminal 32 is a positive electrode terminal.

[0131] The coating portion includes a current collecting portion and a film layer disposed on the current collecting portion and containing an active material. For example, the positive electrode coating portion includes a positive electrode current collecting portion and a positive electrode film layer disposed on the positive electrode current collecting portion and containing a positive electrode active material. For another example, the negative electrode coating portion includes a negative electrode current collecting portion and a negative electrode film layer disposed on the negative electrode current collecting portion and containing a negative electrode active material.

[0132] like 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 pole pieces 11 and a plurality of second pole pieces 12, the plurality of first pole pieces 11 and the plurality of second pole pieces 12 are stacked along the thickness direction X of the battery cell 7, the first pole piece 11 and the second pole piece 12 each include a coating portion and a pole ear portion, the coating portion is provided with an active material, the pole ear portion may not be coated with the active material, the pole ear portion is connected to the coating portion and extends out of the coating portion along the width direction Y of the battery cell 7,

[0133] in,

[0134] One of the first electrode piece 11 and the second electrode piece 12 is a positive electrode piece, and the other is a negative electrode piece;

[0135] The dimension of the coated portion of the positive electrode sheet along the length direction Z of the battery cell 7 is a first dimension, the dimension of the coated portion of the positive electrode sheet along the width direction Y of the battery cell 7 is a second dimension, the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, and the dimension of the coated portion of the positive electrode sheet along the length direction Z of the battery cell 7 is 265 mm to 1200 mm;

[0136] The first pole piece satisfies: n*W1 / W2 is 0.2 to 1.0;

[0137] n represents the number of all the tabs on the same side of the coating portion, and n is greater than or equal to 1;

[0138] W1 represents the average size of the pole ear along the length direction Z;

[0139] W2 represents the dimension of the coating portion along the length direction Z;

[0140] The electrolyte includes a lithium salt, which includes a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Based on the mass of the electrolyte, the ratio of the mass content of the fluorinated lithium sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 0.8.

[0141] by Figure 6 Taking the first electrode sheet 11 as an example, W2 represents the size of the coating portion of the positive electrode sheet along the length direction Z of the battery cell 7, i.e., the first size, and Y1 represents the size of the coating portion of the positive electrode sheet along the width direction Y of the battery cell 7, i.e., the second size.

[0142] When the dimension of the coated portion of the positive electrode sheet along the length direction Z of the battery cell 7 is less than 265 mm, the amount of active material that can be carried is limited, and the energy density of the battery cell 7 is low. In the embodiment of the present application, the dimension of the coated portion of the positive electrode sheet is greater than or equal to 265 mm, which is conducive to improving the energy density of the battery cell 7.

[0143] As the size of the coated portion of the positive electrode sheet increases along the length direction Z, the electron transmission path in the sheet increases, and the ohmic resistance increases. As the ratio of the first dimension to the second dimension increases, the electron transmission path in the sheet increases, and the ohmic resistance increases, which is not conducive to fast charging. In addition, the increase in ohmic resistance may lead to increased heat generation. Heat accumulation can easily lead to electrolyte decomposition and worsen the cycle.

[0144] On the one hand, the embodiment of the present application limits the ratio of the first dimension to the second dimension to be less than or equal to 18.5, thereby reducing the aspect ratio and shortening the transmission distance of electrons in the length direction. On the other hand, the pole ear portion is arranged on at least one side of the coating portion along the width direction Y of the battery cell 7, which can further shorten the transmission distance of electrons in the pole piece, reduce the ohmic resistance of the pole piece, and improve the transmission rate of electrons. The embodiment of the present application also regulates the lithium salt of the electrolyte, wherein the lithium salt includes lithium fluorinated sulfonyl imide and lithium hexafluorophosphate, and the mass content ratio of the two is greater than or equal to 0.2, so that the lithium ion transfer number of the electrolyte is increased and the lithium ion conductivity is improved. By comprehensively improving the electron transmission capacity and ion conductivity, the fast charging capability of the battery cell at high energy density is improved.

[0145] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid (HF). The side reaction between hydrofluoric acid and the negative electrode active material may lead to increased gas production during high-temperature storage. The combination of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide can reduce the content of hydrofluoric acid, slow down the negative electrode interface side reaction, reduce the gas production during high-temperature storage, and improve high-temperature cycle performance.

[0146] However, as the amount of fluorinated lithium sulfonyl imide added increases, the risk of thermal diffusion further increases. Specifically, the thermal decomposition temperature of the fluorinated lithium sulfonyl imide salt is close to the thermal runaway temperature of the battery cell 7. In addition, the thermal decomposition rate of the fluorinated lithium sulfonyl imide is fast and the heat release is intense, which can quickly release a large amount of heat and high-temperature gas. This causes a sharp increase in the internal heat of the battery cell 7. This large amount of heat is difficult to release quickly, which easily leads to thermal diffusion and deteriorates the reliability of the battery cell 7.

[0147] On the one hand, the embodiment of the present application limits the mass content ratio of lithium fluorosulfonyl imide and lithium hexafluorophosphate to less than or equal to 0.8, thereby reducing the risk of further heat increase caused by decomposition of lithium fluorosulfonyl imide due to heat increase; on the other hand, the pole piece size meets the above range, and the pole ear portion is arranged on at least one side of the coating portion along the width direction Y of the battery cell 7, and the pole piece ohmic resistance is relatively low, so that the pole piece generates relatively less heat; further, the appropriate size ratio of the pole ear portion, n*W1 / W2 is greater than or equal to 0.2, so that the flow area of ​​the pole ear portion is relatively high, and the resistance of the connection with the coating portion is small, which can further reduce the heat generation of the pole piece, thereby reducing heat accumulation inside the battery cell 7, reducing the adverse effect of heat accumulation on the lithium fluorosulfonyl imide, and mitigating the risk of gas and heat generation by decomposition of the lithium fluorosulfonyl imide, thereby improving the high-temperature cycle performance and reliability of the battery cell 7.

[0148] Therefore, the embodiment of the present application can improve the fast charging performance, high temperature cycle performance and usage reliability of the high energy density battery cell 7.

[0149] Illustratively, n*W1 / W2 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or a range consisting of any two of the above values. Optionally, n*W1 / W2 is 0.5 to 1.0.

[0150] When n*W1 / W2 satisfies the above range, the flow area of ​​the pole ear is relatively large and the heat generation is less, which is beneficial to improving the fast charging performance and high temperature cycle performance of the battery cell 7 at high energy density.

[0151] W1 represents the average size of the first electrode tab 111 along the length direction Z,

[0152] When the first electrode tab 111 has a special-shaped structure, for example, along the width direction Y, the size of the first electrode tab 111 along the length direction Z gradually increases. In this case, the size of the first electrode tab 111 along the length direction Z at multiple locations can be measured to calculate the average size of the first electrode tab 111 along the length direction Z. Of course, the size of each location of the first electrode tab 111 along the length direction Z can be the same value, in which case this value can be used as the average size of the first electrode tab 111.

[0153] There may be one or more first pole tabs 111, for example, n is 1 to 4. When there are multiple first pole tabs 111 located on the same side of the first coating portion 112, the average size of each first pole tab 111 can be measured separately, and the average size values ​​can be added up and divided by the number of first pole tabs 111 to calculate the average size of the first pole tabs 111.

[0154] The first pole tab 111 is connected to the first coating portion 112, and the first pole 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 pole tab 111 itself is relatively large, and the contact area between the first pole tab 111 and the first coating portion 112 is relatively large. The first pole tab 111 has a strong current-carrying capacity, which can improve the fast charging performance and high-temperature cycle performance of the battery cell 7.

[0155] In some embodiments, the first pole piece 11 includes at least one first pole tab 111 , for example, 1 to 4 first pole tabs 111 . Optionally, the first pole piece 11 includes at least two first pole tabs 111 , and optionally four first pole tabs 111 .

[0156] In some embodiments, one or more first electrode tabs 111 are disposed on at least one side of the coating portion along the width direction Y.

[0157] like Figures 6 to 8 As shown, for example, one or more first pole ears 111 are arranged on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all first pole ears 111 are arranged on the same side of the first coating portion 112 along the width direction Y. This arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7. Figure 6 In FIG. 1 , n is 1, W1 represents the size of a single first electrode tab 111 , and W2 represents the size of the first coating portion 112 along the length direction Z. Figure 7 In FIG, n is 4, and the sizes of the first electrode tabs 111 are the same. W1 may also represent the size of a single first electrode tab 111. Of course, the sizes of the first electrode tabs 111 may also be slightly different. Figure 8 In this example, n is 1 and n*W1 / W2 is 1.

[0158] like Figure 9 As shown, for example, when the first electrode piece 11 includes multiple first electrode tabs 111, the multiple first electrode tabs 111 are arranged on both sides of the first coating portion 112 along the width direction Y, which can further shorten the electron transmission path and improve the fast charging capability.

[0159] Optionally, when multiple first electrode tabs 111 are disposed on at least one side of the first coating portion 112 along the width direction Y, there are at least two, for example, two, three, four, five, six, etc., first electrode tabs 111 located on the same side of the first coating portion 112 along the width direction Y; four is optional. This arrangement facilitates uniform distribution of electrons in the first electrode sheet 11 and improves fast charging performance.

[0160] Optionally, the distance between two adjacent first tabs 111 along the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range consisting of any two of the above values. Figure 9 In FIG, Z1 represents the distance between two adjacent first electrode tabs 111 along the length direction Z.

[0161] When the distance between two adjacent first electrode tabs 111 along the length direction Z meets the above range, it is beneficial for the current to be evenly distributed in the current collecting portion, which is beneficial for improving the fast charging performance.

[0162] like Figure 10 As shown, in some embodiments, for the second pole piece 12 : m*W3 / W4 is 0.2 to 1.0;

[0163] m represents the number of all the tabs on the same side of the coating portion, and m is greater than or equal to 1;

[0164] W3 represents the average size of the pole ear along the length direction Z;

[0165] W4 represents the dimension of the coating portion along the longitudinal direction Z.

[0166] Illustratively, m*W3 / W4 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or a range consisting of any two of the above values. Optionally, m*W3 / W4 is 0.5 to 1.0.

[0167] When m*W3 / W4 satisfies the above range, the flow area of ​​the second electrode 121 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.

[0168] W3 represents the average size of the second pole tab 121 along the length direction Z. There may be one or more second pole tabs 121. For example, m is 1 to 4. When there are multiple second pole tabs 121 located on the same side of the second coating portion 122, the size of each second pole tab 121 can be measured by a micrometer to calculate the average size.

[0169] The second pole tab 121 is connected to the second coating portion 122, and the second pole 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 pole tab 121 itself is relatively large, and the contact surface between the second pole tab 121 and the second coating portion 122 is relatively large. The second pole tab 121 has a strong current flow capacity, which can improve the fast charging performance and high-temperature cycle performance of the battery cell 7.

[0170] Optionally, the current collecting portion of the second electrode tab 121 and the second coating portion 122 is an integrated structure, so that the internal resistance of the second electrode sheet 12 is low, which can further improve the fast charging performance and high temperature cycle performance of the battery cell 7.

[0171] In some embodiments, the second pole piece 12 includes at least one second pole tab 121 , optionally at least two second pole tabs 121 , and optionally four second pole tabs 121 .

[0172] In some embodiments, one or more second electrode tabs 121 are disposed on at least one side of the coating portion along the width direction Y. For example, one or more second electrode tabs 121 are disposed on one side of the second coating portion 122 along the width direction Y. In this case, it can be understood that all second electrode tabs 121 are disposed on the same side of the second coating portion 122 along the width direction Y. Alternatively, for example, when the second electrode sheet 12 includes multiple second electrode tabs 121, the multiple second electrode tabs 121 are disposed on both sides of the second coating portion 122 along the width direction Y.

[0173] Optionally, one or more second electrode tabs 121 are respectively arranged on one side of the second coating portion 122 along the width direction Y. This arrangement is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0174] Optionally, when multiple second electrode tabs 121 are disposed on at least one side of the coating portion along the width direction Y, there are at least two, for example, two, three, four, five, six, etc., second electrode tabs 121 located on the same side of the second coating portion 122 along the width direction Y; four is optional. This arrangement facilitates uniform distribution of electrons in the second electrode sheet 12 and improves fast charging performance.

[0175] Optionally, the distance between two adjacent second tabs 121 along the length direction Z is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range consisting of any two of the above values.

[0176] like Figure 11 As shown, in some embodiments, the terminal assembly can be disposed on the housing 21 , or the terminal assembly can be disposed on the end cover 22 .

[0177] The terminal assembly includes a first electrode terminal 31 and a second electrode terminal 32 . The first electrode terminal 31 is connected to the first electrode tab 111 , and the second electrode terminal 32 is connected to the second electrode tab 121 .

[0178] For example, the first electrode terminal 31 and the second electrode terminal 32 may be provided on the housing 21 , or the first electrode terminal 31 and the second electrode terminal 32 may be provided on the end cover 22 . Alternatively, the first electrode terminal 31 and the second electrode terminal 32 may be provided on the end cover 22 .

[0179] The first electrode terminal 31 and the second electrode terminal 32 can be disposed on the same end cap 22. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22 at intervals. In another example, there are two end caps 22, and the two end caps 22 are disposed opposite each other, and each end cap 22 is provided with a first electrode terminal 31 and a second electrode terminal 32.

[0180] The first electrode terminal 31 and the second electrode terminal 32 are respectively provided on different end covers 22 . For example, there are two end covers 22 , which are arranged opposite to each other. The first electrode terminal 31 is provided on one of the end covers 22 , and the second electrode terminal 32 is provided on the other end cover 22 .

[0181] In some embodiments, there is at least one first electrode terminal 31 , and may be at least two, such as two, three, or four.

[0182] In some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0183] like Figure 11 As shown, for example, all first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0184] like Figure 12 As shown, for example, multiple first electrode terminals 31 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is conducive to improving the fast charging performance.

[0185] Exemplarily, there are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplary, there are four first electrode terminals 31, two of which are disposed on one side of the electrode assembly 10, and the other two are disposed on the other side of the electrode assembly 10.

[0186] In an embodiment of the present application, the first pole tab 111 and the first electrode terminal 31 are electrically connected, which can be directly or indirectly connected; when the first pole tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, which is located between the first electrode terminal 31 and the first pole tab 111, and connects the first electrode terminal 31 and the first pole tab 111.

[0187] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0188] In other embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, multiple first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0189] In some embodiments, there is at least one second electrode terminal 32 , and optionally at least two, such as two, three, or four.

[0190] 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.

[0191] like Figure 12 As shown, for example, at least two second electrode terminals 32 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is conducive to improving the fast charging performance.

[0192] Figure 12 The battery cell 7 is shown to include four electrode terminals. Specifically, there are two second electrode terminals 32, one of which is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0193] For another example, all the second electrode terminals 32 are arranged on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively arranged on both sides of the electrode assembly 10 along the length direction Z, and basically do not interfere with each other when they are electrically connected to the electrode ear parts.

[0194] For example, 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 longitudinal direction Z, and the second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the longitudinal direction Z. Optionally, the first electrode terminal 31 and the second electrode terminal 32 may be staggered along the width direction Y. Of course, the first electrode terminal 31 and the second electrode terminal 32 may also be disposed opposite each other along the longitudinal direction Z. Figure 11 A schematic diagram is shown in which the first electrode terminal 31 and the second electrode terminal 32 are respectively arranged on both sides of the electrode assembly 10.

[0195] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32 . The two first electrode terminals 31 are arranged on one side of the electrode assembly 10 along the length direction Z, and the two second electrode terminals 32 are arranged on the other side of the electrode assembly 10 along the length direction Z.

[0196] In an embodiment of the present application, the second pole tab 121 and the second electrode terminal 32 are electrically connected, which can be directly or indirectly connected; when the second pole tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, which is located between the second electrode terminal 32 and the second pole tab 121 and connects the second electrode terminal 32 and the second pole tab 121.

[0197] For example, when the second electrode terminal 32 is arranged on one side of the electrode assembly 10 along the length direction Z and the second electrode tab 121 is arranged on one side of the second coating portion 122 along the width direction Y, the second adapter is more conducive to the connection between the second electrode tab 121 and the second electrode terminal 32.

[0198] In the above embodiments, the second transition component may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0199] In other embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y, or multiple second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the width direction Y.

[0200] Negative electrode

[0201] The coating portion of the negative electrode sheet includes a negative current collector and a negative electrode film layer comprising a negative electrode active material, disposed on at least one side of the negative current collector. For example, the negative current collector has two opposing surfaces along its thickness, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative current collector.

[0202] The upper limit voltage for charging and the cut-off voltage for discharging of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging may be 3.65V and the cut-off voltage for discharging may be 2.0V, or the upper limit voltage for charging may be 3.8V and the cut-off voltage for discharging may be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging may be 4.3V and the cut-off voltage for discharging may be 2.0V. Next, taking the upper limit voltage for charging of 3.8V and the cut-off voltage for discharging of 2.0V as an example, the state of the battery cell is described: In the embodiment of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows:

[0203] The battery cell is charged at a constant current charge rate of 0.05C to the upper limit of the charge voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged at a constant current discharge rate of 0.05C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0204] In some embodiments, the negative electrode layer has a compaction density of 1.5 g / cm2 at 100% state of charge (SOC). 3 to 1.7g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.50 g / cm 3 , 1.55g / cm 3 , 1.60g / cm 3 , 1.65g / cm 3 , 1.66g / cm³, 1.68g / cm³, 1.70g / cm³ or a range consisting of any two of the above values.

[0205] 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 conducive to the rapid charging of the battery cell; and the particles of the negative electrode active material will not be stacked too densely, reducing the risk of particle crushing, which is conducive to improving the high-temperature cycle performance of the battery cell.

[0206] In some embodiments, the single-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 70 mg / 1540.25 mm 2, 80mg / 1540.25mm², 85mg / 1540.25mm², 90mg / 1540.25mm², 95mg / 1540.25mm², 100mg / 1540.25mm², 105mg / 1540.25mm², 110mg / 1540.25mm², 115mg / 1540.25mm², 120mg / 1540.25mm², 120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2 、150mg / 1540.25mm 2 、160mg / 1540.25mm 2 、170mg / 1540.25mm 2 、175mg / 1540.25mm 2 Or a range consisting of any two of the above values. Optionally, the single-sided coating weight of the negative electrode film layer is 95 mg / 1540.25 mm 2 Up to 142mg / 1540.25mm 2 .

[0207] 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 faster, which is beneficial to reduce the polarization phenomenon under high-rate charging and improve the fast charging capability of the battery cell.

[0208] In the embodiments of the present application, the compaction density of the negative electrode film layer of a battery cell at 100% state of charge (SOC) has a meaning well known in the art. Specifically, the negative electrode sheet of a battery cell at 100% state of charge (SOC) is disassembled and the compaction density of the negative electrode film layer is measured. For example, a single-sided coated negative electrode sheet (if a double-sided coated sheet is used, the negative electrode film layer on one side may be wiped off first) is punched into small discs with an area of ​​S1. These discs are weighed and recorded as M1, and their thickness H1 is measured. The negative electrode film layer of the weighed negative electrode sheet is then wiped off, and the negative electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (the weight of the negative electrode plate M1 - the weight of the negative electrode current collector M0) / S1, the thickness of the negative electrode film layer = the thickness of the negative electrode plate H1 - the thickness of the negative electrode current collector H0, the compaction density of the negative electrode film layer = the single-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0209] In some embodiments, the negative electrode active material has a charge capacity in the range of 350 mAh / g to 500 mAh / g. For example, the negative electrode active material has a charge capacity in the range of 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 consisting of any two of the foregoing values.

[0210] When the charge gram capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0211] In the embodiments of the present application, the gram capacity of the active material has a meaning well known in the art and can be tested using equipment and methods well known in the art. The test method for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used to test the charging gram capacity of the negative electrode active material in a half-button battery at a rate of 0.1C. A half-button battery is assembled with metallic lithium as the negative electrode and a sample electrode comprising the above-mentioned material as the positive electrode. Under the conditions of 23°C±2°C, the half-button battery is charged and discharged at a rate of 0.1C on a battery tester or other test equipment of equivalent performance to obtain the charge capacity, and then the capacity is divided by the mass of the electrode active material to obtain the charging gram capacity parameter.

[0212] In some embodiments, the negative electrode active material includes a silicon-based material. Alternatively, the silicon-based material may include elemental silicon, a silicon-carbon composite, silicon oxide SiO x At least one of (0<x≤2). For example, the silicon-carbon composite may be silicon carbide.

[0213] In some embodiments, the mass content of silicon in the silicon-based material in the negative electrode film layer is 0.3% to 10%, for example, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two of the foregoing values. Alternatively, the mass content of silicon in the silicon-based material in the negative electrode film layer is 3% to 6%.

[0214] When the mass content of silicon is within the above range, the capacity of the negative electrode active material can be increased, which is beneficial to improving the energy density of the battery cell; and during the charge and discharge process, the volume expansion of the silicon element will not be too large, which is beneficial to maintaining the stability of the negative electrode interface film and improving the high-temperature cycle performance of the battery cell.

[0215] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the high-temperature cycle performance of the battery cell.

[0216] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0217] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the aforementioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy.

[0218] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0219] For example, the present application may combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0220] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0221] like Figure 13 As shown, the negative electrode film layer 141 of the negative electrode plate 14 in the embodiment of the present application includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative electrode film layer 141 includes at least two film layers.

[0222] In the case where the negative electrode film layer 141 is a single-layer film layer, the negative electrode active material in the negative electrode film layer 141 includes a carbon-based material and an optional silicon-based material.

[0223] When the negative electrode film layer 141 comprises at least two 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 layers, three layers, four layers, or even more layers.

[0224] 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 current collector 142. The negative electrode active material of the first negative electrode film layer 1411 includes a carbon-based material. The second negative electrode film layer 1412 is connected to the side of the first negative electrode film layer 1411 facing away from the negative current collector 142. The negative electrode active material of the second negative electrode film layer 1412 includes a carbon-based material. The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 may be regular or irregular, or may be irregular; alternatively, there may be no distinct interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0225] The negative electrode film layer 141 includes at least two layers, and layered coating is beneficial to improving the fast charging performance of the battery cell. In particular, when the porosity of the first negative electrode film layer 1411 and the second negative electrode film layer 1412 are different, it is beneficial to improve the fast charging performance of the battery cell.

[0226] 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.

[0227] Optionally, the first negative electrode film layer 1411 further includes a silicon-based material.

[0228] Optionally, the second negative electrode film layer 1412 further includes a silicon-based material.

[0229] For example, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 include silicon-based materials, this is more conducive to improving the energy density of the battery cell. Furthermore, the carbon-based materials in each layer can mitigate the volume expansion of the silicon-based materials, making the negative electrode interface film more stable and improving high-temperature cycling performance. Furthermore, since each layer includes silicon-based materials, the coating thickness is relatively thin, which helps shorten the lithium ion transmission path and improves fast charging performance.

[0230] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode film layer 1412 includes a carbon-based material. When the first negative electrode film layer 1411 includes a silicon-based material and the second negative electrode film layer 1412 does not include a silicon-based material, the second negative electrode film layer 1412 can alleviate the volume expansion of the first negative electrode film layer 1411, reduce side reactions between the negative electrode film layer 1411 and the electrolyte, and improve high-temperature cycle performance.

[0231] Alternatively, the first negative electrode film layer 1411 includes a carbon-based material, and the second negative electrode film layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode film layer 1412 includes a silicon-based material, the volume change of the silicon-based material facilitates the formation of more film pores, thereby improving the liquid-phase transport capability of lithium ions and enhancing the dynamic performance of the battery cell.

[0232] When the negative electrode film layer 141 comprises at least two layers, the cross-sectional morphology of the negative electrode film layer 141 can be the same or similar at various locations along the thickness direction X of the negative electrode film layer 141, or can also be different. When the electrode assembly has a laminated 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.

[0233] 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. The first region 141a is the region of the negative electrode film layer 141 close to the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the first region 141a is 1 / 3 of the thickness of the negative electrode film layer 141; the second region 141b is the region of the negative electrode film layer 141 away from the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the second region 141b is 1 / 3 of the thickness of the negative electrode film layer 141.

[0234] The cross-sectional morphologies of the first region 141a and the second region 141b can be the same or similar, or they can be different. The cross-sectional morphologies of the first region 141a and the third region 141c can be the same or similar, or they can be different. The cross-sectional morphologies of the second region 141b and the third region 141c can be the same or similar, or they can be different.

[0235] There may or may not be a distinct interface between the first region 141a, the second region 141b, and the third region 141c. For example, the first negative electrode film layer 1411 includes the first region 141a, the second negative electrode film layer 1412 includes the second region 141b, and the third region 141c may be a portion of the first negative electrode film layer 1411, or the third region 141c may be a portion of the second negative electrode film layer 1412, or the third region 141c may be a portion of the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0236] Optionally, the average particle size of the carbon-based material in the first region 141a can be greater than or equal to the average particle size of the carbon-based material in the second region 141b. Further, optionally, the average particle size of the carbon-based material in the first region 141a can be greater than the average particle size of the carbon-based material in the second region 141b. This facilitates rapid migration of lithium ions from the second region 141b to the first region 141a, thereby improving the fast charging capability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a can be smaller than the average particle size of the carbon-based material in the second region 141b.

[0237] Optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 can be greater than or equal to the average particle size of the carbon-based material of the second negative electrode film layer 1412. Further optionally, the average particle size of the carbon-based material of the first negative electrode film layer 1411 can be greater than the average particle size of the carbon-based material of the second negative electrode film layer 1412.

[0238] There is a difference in the particle size of the first negative electrode film layer 1411 and the second negative electrode film layer 1412, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer 1412 is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer 1412. In the embodiment of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode plate 14, and can improve the high-temperature cycle performance.

[0239] Optionally, the average particle size of the carbon-based material in the first region 141a is 10 μm to 20 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting of any two of the foregoing values. When the average particle size of the carbon-based material in the first region 141a is within the foregoing range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving material stability.

[0240] 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, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving material stability.

[0241] Optionally, the average particle size of the carbon-based material in the second region 141b is 5 μm to 12 μm, for example, 5 μm, 8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the foregoing values. When the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within the foregoing range, it is beneficial to improve the fast charging capability of the battery cell and enhance the stability of the material.

[0242] Optionally, the average particle size of the carbon-based material of the second negative electrode film layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, thereby improving the fast charging performance. On the other hand, the material is less likely to agglomerate during the preparation process, thereby improving the stability of the material. On the other hand, the combination of the negative electrode active material in the second negative electrode film layer 1412 within the above average particle size range and the negative electrode active material in the first negative electrode film layer 1411 is conducive to constructing a gradient porosity 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.

[0243] For example, the carbon-based material of the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region 141b includes artificial graphite. For example, the negative electrode active material of the first region 141a includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material of the second region 141b includes a silicon-based material and artificial graphite.

[0244] Illustratively, the carbon-based material of the first negative electrode film layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer 1412 includes artificial graphite. For example, the negative electrode active material of the first negative electrode film layer 1411 includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material of the second negative electrode film layer 1412 includes a silicon-based material and artificial graphite.

[0245] In the embodiment of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the negative electrode plate 14 is used as a sample, and cross-section polishing is performed along the thickness direction X of the negative electrode film layer 141, for example, by using an argon ion beam for cross-section polishing, and the cross-section is photographed using a scanning electron microscope SEM to obtain an SEM cross-section image, and the particle size of the carbon-based material in the SEM cross-section is counted, and the average particle size of the carbon-based material is calculated based on the counted number.

[0246] In some embodiments, the negative electrode film layer may also optionally include a negative electrode conductive agent. The present embodiments do not specifically limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, the weight content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0247] Negative electrode conductive agents can make up for the insufficient conductivity of silicon-based materials, improve the conductivity of the negative electrode film layer, and help improve the dynamic performance of battery cells and enhance the fast charging capability of battery cells.

[0248] Optionally, the mass content of the conductive carbon in the negative electrode film layer is 0.4% to 0.7%, for example, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7% or a range consisting of any two of the above values.

[0249] Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the foregoing values. Optionally, the mass content of the carbon nanotubes in the negative electrode film layer is 0.1% to 0.5%.

[0250] In some embodiments, the negative electrode film layer may further include a negative electrode binder. In some embodiments, the negative electrode binder has a mass content of ≤5% based on the total weight of the negative electrode film layer.

[0251] In some embodiments, the negative electrode film layer may also optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0252] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0253] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 8.5 μm, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range consisting of any two of the above values.

[0254] In some embodiments, the negative electrode sheet further includes a negative electrode tab connected to the negative electrode current collector. The negative electrode tab has a thickness of 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range consisting of any two of these values. When the thickness of the negative electrode tab is within the above range, it is beneficial to improve the current carrying capacity and the fast charging capability of the battery cell.

[0255] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0256] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0257] Positive electrode

[0258] In some embodiments, the battery cell further includes a positive electrode tab.

[0259] The coating portion of the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector and containing a positive electrode active material. For example, the positive current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive current collector.

[0260] In the case where the battery cell includes a laminated electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode sheet, the size of the battery cell along the length direction can be understood as the length of the battery cell, and the size of the positive electrode film layer along the length direction can be understood as the length of the positive electrode film layer; the width direction of the battery cell is parallel to the width direction of the positive electrode sheet, the size of the battery cell along the width direction can be understood as the width of the battery cell, and the size of the positive electrode film layer along the width direction can be understood as the width of the positive electrode film layer.

[0261] In some embodiments, the size of the positive electrode film layer can be considered to be the same as the size of the coated portion of the positive electrode plate, and the size of the positive electrode film layer along the length direction of the battery cell is 265mm to 1200mm, for example, 265mm, 350mm, 450mm, 550mm, 650mm, 750mm, 850mm, 950mm, 1050mm, 1150mm, 1200mm or a range consisting of any two of the above values.

[0262] In some embodiments, the size of the positive electrode film layer along the length direction of the battery cell is the same as the first size, the size of the positive electrode film layer along the width direction of the battery cell is the same as the second size, and 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, for example, 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 a range consisting of any two of the above values.

[0263] For example, the dimension of the positive electrode film layer along the length of the battery cell is 265 mm to 655 mm, and the ratio of the dimension of the positive electrode film layer along the length of the battery cell to the dimension of the positive electrode film layer along the width of the battery cell is greater than 1 and less than or equal to 12.5, and can be selected from 1.25 to 12.5. When the positive electrode active material of the positive electrode film layer includes a lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the dimension of the positive electrode film layer should not be too long. When the dimension of the positive electrode film layer is within the above range, the electron transmission path is not too long, the internal resistance is relatively small, and the heat generation is low, which is conducive to improving the fast charging capability and high-temperature cycling performance of the battery cell at high energy density.

[0264] Optionally, the dimension of the positive electrode film layer along the length direction of the battery cell is 400 mm to 600 mm, and the ratio of the dimension of the positive electrode film layer along the length direction of the battery cell to the dimension of the positive electrode film layer along the width direction of the battery cell is 3.5 to 8.

[0265] In some embodiments, the dimension of the negative electrode film layer along the first direction is greater than the dimension of the positive electrode film layer along the first direction, so that lithium ions released from the positive electrode film layer can be substantially embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of the battery cell. Of course, the dimension of the negative electrode film layer along the first direction can also be less than or equal to the dimension of the positive electrode film layer along the first direction.

[0266] Optionally, the size of the negative electrode film layer along the first direction is larger than the size of the positive electrode film layer along the first direction, and the difference between the size of the negative electrode film layer along the first direction and the size of the positive electrode film layer along the first direction is 5mm to 11mm, for example, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm or a range consisting of any two of the above values.

[0267] In some embodiments, the dimension of the negative electrode film layer along the second direction is greater than the dimension of the positive electrode film layer along the second direction, so that lithium ions released from the positive electrode film layer can be substantially embedded in the negative electrode film layer, reducing the risk of lithium deposition on the negative electrode side and improving the reliability of the battery cell. Of course, the dimension of the negative electrode film layer along the second direction can also be less than or equal to the dimension of the positive electrode film layer along the second direction.

[0268] Optionally, the size of the negative electrode film layer along the second direction is larger than the size of the positive electrode film layer along the second direction, and the difference between the size of the negative electrode film layer along the second direction and the size of the positive electrode film layer along the second direction is 5mm to 11mm, for example, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm or a range consisting of any two of the above values.

[0269] The first direction is perpendicular to the second direction. The first direction may be parallel to the length direction of the battery cell, or the first direction may be parallel to the width direction of the battery cell. When the first direction is parallel to the length direction of the battery cell, the second direction is parallel to the width direction of the battery cell. When the first direction is parallel to the width direction of the battery cell, the second direction is parallel to the length direction of the battery cell.

[0270] In some embodiments, the size of the separator along the first direction is greater than the size of the negative electrode film layer along the first direction, so that the separator can effectively isolate the positive electrode sheet from the negative electrode sheet, reduce the risk of short circuit, and improve the reliability of the battery cell. Of course, the size of the separator along the first direction can also be less than or equal to the size of the negative electrode film layer along the first direction.

[0271] Optionally, the size of the insulating member along the first direction is larger than the size of the negative electrode film layer along the first direction, and the difference between the size of the insulating member along the first direction and the size of the negative electrode film layer along the first direction is 6 mm to 10 mm, for example, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range consisting of any two of the above values.

[0272] In some embodiments, the size of the separator along the second direction is greater than the size of the negative electrode film layer along the second direction, so that the separator can effectively isolate the positive electrode sheet from the negative electrode sheet, reduce the risk of short circuit, and improve the reliability of the battery cell. Of course, the size of the separator along the second direction can also be less than or equal to the size of the negative electrode film layer along the second direction.

[0273] Optionally, the size of the insulating member along the second direction is larger than the size of the negative electrode film layer along the second direction, and the difference between the size of the insulating member along the second direction and the size of the negative electrode film layer along the second direction is 6 mm to 10 mm, for example, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range consisting of any two of the above values.

[0274] like Figure 14 As shown, the first direction can be parallel to the length direction Z, the second direction is parallel to the width direction Y, the first electrode 11 is a positive electrode, and the second electrode 12 is a negative electrode.

[0275] The dimension of the positive electrode film layer of the first electrode piece 11 along the length direction Z is the length of the positive electrode film layer of the first electrode piece 11 , the dimension of the negative electrode film layer of the second electrode piece 12 along the length direction Z is the length of the negative electrode film layer of the second electrode piece 12 , and the dimension of the insulating member 13 along the length direction Z is the length of the insulating member 13 .

[0276] The difference between the length of the negative electrode film layer of the second electrode piece 12 and the length of the positive electrode film layer of the first electrode piece 11 is OH 11 , Figure 14 As shown in FIG, the negative electrode film layer exceeds the positive electrode film layer on both sides along the length direction Z, and each side exceeds the OH 11 Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side along the length direction Z.

[0277] The difference between the length of the separator 13 and the length of the negative electrode film layer of the second electrode piece 12 is OH 21 , Figure 14 As shown in FIG, both sides of the separator 13 along the length direction Z extend beyond the negative electrode film layer, and each side extends beyond the OH 21 Of course, the separator 13 may extend beyond the negative electrode film layer on one side along the length direction Z.

[0278] The dimension of the positive electrode film layer of the first electrode piece 11 along the width direction Y is the width of the positive electrode film layer of the first electrode piece 11, the dimension of the negative electrode film layer of the second electrode piece 12 along the width direction Y is the width of the negative electrode film layer of the second electrode piece 12, and the dimension of the insulating member 13 along the width direction Y is the width of the insulating member 13.

[0279] The difference between the width of the negative electrode film layer of the second electrode piece 12 and the width of the positive electrode film layer of the first electrode piece 11 is OH12 , Figure 14 As shown in FIG, both sides of the negative electrode film layer along the width direction Y exceed the positive electrode film layer, and each side exceeds the OH 12 Of course, the negative electrode film layer may also extend beyond the positive electrode film layer on one side along the width direction Y.

[0280] The difference between the width of the separator 13 and the width of the negative electrode film layer of the second electrode piece 12 is OH 22 , Figure 14 As shown in FIG, both sides of the separator 13 along the width direction Y extend beyond the negative electrode film layer, and each side extends beyond the OH 22 Of course, one side of the separator 13 along the width direction Y may extend beyond the negative electrode film layer.

[0281] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm 3 to 2.80g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film is 2.50 g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0282] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, because the positive electrode active material in the positive electrode film layer is densely packed, the contact resistance between particles is low, which can further reduce the resistance of the electrode sheet and thus reduce heat generation during rapid charging. Therefore, by adjusting the compaction density of the positive electrode film layer to a reasonable range, the battery cell can achieve both high energy density and rapid charging performance.

[0283] In some embodiments, the single-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2For example, the coating weight of the positive electrode film layer on one side is 150mg / 1540.25mm², 200mg / 1540.25mm², 250mg / 1540.25mm², 300mg / 1540.25mm², 350mg / 1540.25mm², 370mg / 1540.25mm² or a range consisting of any two of the above values. Optionally, the coating weight of the positive electrode film layer on one side is 200mg / 1540.25mm². 2 Up to 300mg / 1540.25mm 2 .

[0284] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and it is beneficial to reduce the polarization phenomenon under high-rate charging, and can take into account the improvement of the energy density and fast charging performance of the battery cell.

[0285] In the embodiments of the present application, the compaction density of the positive electrode film layer of a battery cell at 100% state of charge (SOC) has a meaning well known in the art. Specifically, the positive electrode sheet of a battery cell at 100% state of charge (SOC) is disassembled and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet is used, the positive electrode film layer on one side may be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and 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 of the positive electrode sheet M1 - the weight of the positive electrode collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1 - the thickness of the positive electrode collector H0, the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0286] In some embodiments, the positive electrode active material has a charge capacity in the range of 150 mAh / g to 170 mAh / g. For example, the negative electrode active material has a charge capacity in the range of 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range consisting of any two of the foregoing values.

[0287] When the charge gram capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0288] In the embodiments of the present application, the gram capacity of the positive electrode active material has a meaning well known in the art and can be tested using a gram capacity test method for negative electrode active materials.

[0289] In some embodiments, the positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate may have an olivine structure, which is structurally stable during charge and discharge, and can improve the cycle life of the battery cell.

[0290] Alternatively, the positive electrode active material may further include a lithium-containing transition metal oxide. Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof.

[0291] The lithium-containing phosphate with an olivine structure can be an unmodified lithium-containing phosphate, or a material obtained by coating and modifying it. For example, the surface of the lithium-containing phosphate is provided with a carbon-containing material, and the carbon-containing material can be coated on the surface of the lithium-containing phosphate as a coating layer, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, and being beneficial to the migration rate of lithium ions, improving the fast charging capability of the battery cell, and reducing the heat generation of the battery cell.

[0292] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a M b P 1-c X c Y z A compound wherein 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 comprises one or more of Na, K, and Mg, Me comprises one or more of Mn, Fe, Co, and Ni, M comprises 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 comprises one or more of Cl, C, and N, and Y comprises one or more of O and F. The lithium-containing phosphate has excellent cycle stability and is beneficial for improving the high-temperature cycle performance of battery cells.

[0293] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cell is accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cell is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of the present application.

[0294] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0295] In some embodiments, the lithium-containing phosphate is in granular form, and the volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm, for example, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or a range consisting of any two of the above values.

[0296] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium ion deintercalation path in the lithium-containing phosphate is 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.

[0297] In some embodiments, the positive electrode film further comprises one or more of a lithium-containing ternary material, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. These materials can serve as lithium supplements, replenishing lithium ions in the positive electrode film to compensate for irreversible lithium ion loss within the system, thereby increasing capacity and improving the energy density of the battery cell.

[0298] In some embodiments, the mass content of the lithium supplement agent is 0.1% to 5% based on the total mass of the positive electrode film layer, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing. When a lithium supplement agent within this mass range is used, lithium ions can be replenished to the positive electrode film layer to compensate for irreversible lithium ion loss in the system. Moreover, the mass content of the lithium supplement agent is not too high, so that the positive electrode discharge capacity remains high and the energy density is not substantially reduced.

[0299] In some embodiments, the volume average particle size Dv50 of the lithium supplement agent is larger than the volume average particle size Dv50 of the lithium-containing phosphate. The combination of particles of different sizes is conducive to uniform dispersion and improves the distribution uniformity of the lithium supplement agent.

[0300] In some embodiments, the volume average particle size Dv50 of the lithium supplement is 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range consisting of any two of the above.

[0301] In the embodiment of the present application, the volume average particle size Dv50 of the particles has a meaning well known in the art. The volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using equipment and methods well known in the art. After the fresh battery cell is fully discharged to 0% state of charge SOC, the positive electrode sheet is disassembled, the positive electrode collector is removed and the positive electrode film layer is retained. The positive electrode film layer is immersed in N-methylpyrrolidone NMP to wash out the binder in the positive electrode film layer, and the positive electrode active material or lithium supplement is retained as a sample. After the sample is dried, the volume average particle size Dv50 of the particles is tested by a Mastersizer2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0302] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. For example, the positive electrode conductive agent may include 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, the weight content of the positive electrode conductive agent is ≤5% based on the weight of the positive electrode film layer.

[0303] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0304] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0305] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 16 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range consisting of any two of the above values.

[0306] In some embodiments, the positive electrode sheet further includes a positive electrode tab connected to the positive electrode current collector. The positive electrode tab has a thickness of 10 μm to 16 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range consisting of any two of the foregoing values. When the thickness of the positive electrode tab is within the foregoing range, it is beneficial to increase the current capacity and improve the fast charging capability of the battery cell.

[0307] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0308] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0309] [Electrolyte]

[0310] During the charge and discharge process of a battery cell, active ions, such as lithium ions, are intercalated and released back and forth between the positive and negative electrodes. The electrolyte, which consists of an organic solvent and an electrolyte salt, conducts the active ions between the positive and negative electrodes.

[0311] In some embodiments, the electrolyte has a conductivity of 10.5 mS / cm to 13.5 mS / cm at room temperature. For example, the electrolyte has a conductivity of 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, or a range consisting of any two of the foregoing values ​​at room temperature.

[0312] 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 high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0313] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, for example, 25° C., is ionic conductivity, which can be tested using equipment and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0314] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s. For example, the viscosity of the electrolyte is 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s, or a range consisting of any two of the foregoing values.

[0315] 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 higher, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0316] In the embodiments of the present application, the viscosity of the electrolyte has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, it can be detected according to GB / T10247-2008.

[0317] In some embodiments, the density of the electrolyte at room temperature, e.g., 25° C., is between 1.05 g / mL and 1.35 g / mL. For example, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range consisting of any two of the foregoing values.

[0318] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0319] In the embodiments of the present application, the density of the electrolyte has a well-known meaning in the art and can be tested using equipment and methods well-known in the art, for example, by referring to GB / T 2013-2010.

[0320] In some embodiments, the organic solvent includes a linear carboxylate solvent.

[0321] Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylate solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, or a range consisting of any two of the above values. Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 8% to 20%.

[0322] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte is relatively low, the conductivity of the electrolyte can be improved, the internal resistance of the battery cell can be reduced, and the rapid migration of lithium ions is facilitated; and the electrolyte is compatible with the silicon-containing negative electrode, which can effectively reduce the gas production of the battery cell, reduce the impact on the interface film on the negative electrode side, and improve the fast charging capability and high-temperature cycle performance of the battery cell.

[0323] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0324] Formula I,

[0325] In Formula I,

[0326] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0327] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0328] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0329] Alternatively, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0330] Alternatively, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further alternatively, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0331] 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.

[0332] Illustratively, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0333]

[0334] In some embodiments, the organic solvent includes a carbonate-based solvent.

[0335] The use of carbonate solvents and chain carboxylate solvents improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0336] Optionally, the mass content of the carbonate solvent in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvent is 65%, 70%, 75%, or a range consisting of any two of the above values.

[0337] When the mass content of carbonate solvents and chain carboxylic acid ester solvents meets the above conditions, the stability of the electrolyte can be improved and its high-temperature gas generation can be reduced.

[0338] Illustratively, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0339] In the embodiment of the present application, the electrolyte salt includes a lithium salt, and the lithium salt includes fluorine-containing lithium sulfonyl imide and lithium hexafluorophosphate.

[0340] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF. The side reaction between hydrofluoric acid and negative electrode active materials may lead to increased gas production during high-temperature storage. The combined use of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, and reduce the gas production during high-temperature storage. The combined use is beneficial to increase the migration number of lithium ions, improve the lithium ion conductivity of the electrolyte, and can improve the high-temperature cycle performance and fast charging capability of the battery cell.

[0341] Illustratively, the fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide, and may be lithium bisfluorosulfonyl imide.

[0342] 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%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a range consisting of any two of the above values. Alternatively, 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 each component 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 contents of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate.

[0343] Illustratively, 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%.

[0344] When the mass content of lithium salt is within the above range, on the one hand, it can increase the migration number of lithium ions in the electrolyte, improve the lithium ion conductivity 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 and improve the high-temperature cycle performance of the battery cell.

[0345] Optionally, the sum of the mass content of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and can be 10% to 18%. When the mass content of the lithium salt is within the above range, the fast charging performance, high-temperature cycling performance, and reliability of the battery cell can be improved.

[0346] In an embodiment of the present application, based on the mass of the electrolyte, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 0.8, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range consisting of any two of the foregoing values. Optionally, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.3 to 0.8.

[0347] When the ratio of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide meets the above range, on the one hand, the migration number of lithium ions in the electrolyte can be increased, the lithium ion conductivity of the electrolyte can be improved, and the fast charging performance of the battery cell can be improved; on the other hand, the side reactions on the negative electrode side can be reduced, and the high-temperature cycle performance of the battery cell can be improved.

[0348] Illustratively, the mass content of lithium bis(fluorosulfonyl)imide is greater than 0 and less than or equal to 8%, and can be optionally 2% to 8%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or a range consisting of any two of the above values.

[0349] Illustratively, the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 12%, and can be optionally 1% to 12%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or a range consisting of any two of the above values.

[0350] In some embodiments, the electrolyte further includes additives, including one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. These additives can improve the performance of the interface film on the negative electrode side, resulting in a more stable interface film with relatively low impedance, which is beneficial for enhancing the fast charging performance of the battery cell and improving high-temperature cycling performance.

[0351] In some embodiments, the weight content of the additive in the electrolyte is 0.5% to 10%. For example, the weight content of the additive in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values. Alternatively, the weight content of the additive in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0352] The additives in 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.

[0353] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive contains fluoroethylene carbonate and vinylene carbonate.

[0354] Fluorinated ethylene carbonate can form an interface film rich in lithium fluoride LiF on the surface of the negative electrode, which can alleviate the side reactions on the negative electrode side, reduce high-temperature gas production, and improve the high-temperature cycle performance of the battery cell.

[0355] The combination of fluoroethylene carbonate and vinylene carbonate makes the interface film on the surface of the negative electrode more compact and has lower impedance, which can more effectively protect the negative electrode, reduce the degree of side reactions at the negative electrode interface, reduce high-temperature gas production, and improve the high-temperature cycle performance and fast charging performance of the battery cell.

[0356] Illustratively, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate.

[0357] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0358] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis method.

[0359] In the embodiment of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography.

[0360] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the components are classified. For example, chain carboxylate solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as components of the organic solvent, and the mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0361] Carbonate additives (such as fluorinated cyclic carbonates and vinylene carbonate) are used as additives for the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0362] Isolators

[0363] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0364] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical and mechanical stability can be selected.

[0365] As an example, the primary material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. The surface of the separator can also be coated with an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating.

[0366] In some embodiments, the volumetric energy density of the battery cell is between 375Wh / L and 430Wh / L. For example, the volumetric energy density of the battery cell is 375Wh / L, 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, or a range consisting of any two of these values. The volumetric energy density of the battery cell is relatively high.

[0367] In the embodiments of the present application, the volume energy density of a battery cell has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.8V and the battery discharge cut-off voltage is 2.0V.

[0368] Place the battery cell at 25°C, charge at a constant current of 0.05C to 3.8V, and discharge at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), calculate the volume of the single battery V0, unit L, and the volume energy density of the battery cell VED = (A0 × discharge platform voltage) / V0, unit Wh / L.

[0369] Example

[0370] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0371] Example 1

[0372] 1. Preparation of positive electrode sheet

[0373] The positive electrode sheet includes a positive electrode tab, a positive electrode current collector, and a positive electrode film layer disposed on both sides of the positive electrode current collector. The positive electrode current collector is made of aluminum foil. The positive electrode tab is not coated with a positive electrode film layer.

[0374] The positive electrode film layer includes lithium iron phosphate, a lithium-containing phosphate, in a mass ratio of 97.5:2:0.5, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black. The positive electrode film layer is formed by evenly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collector, and then drying and cold pressing.

[0375] The volume average particle size Dv50 of the lithium-containing phosphate was 1.5 μm.

[0376] The single-sided coating weight of the positive electrode film is 286mg / 1540.25mm 2 .

[0377] 2. Preparation of negative electrode sheet

[0378] The negative electrode sheet consists of a negative tab, a negative current collector, and negative film layers positioned on either side of the negative current collector. The negative current collector is made of copper foil. The negative tab is not coated with negative film. The placement and number of negative tabs are similar to those for the positive tabs and will not be further described.

[0379] The negative electrode film layer is formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector, drying it, and cold pressing it.

[0380] The single-sided coating weight of the negative electrode film is 132mg / 1540.25mm 2 .

[0381] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode current collecting portion, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0382] The first negative electrode film layer includes a negative electrode active material, conductive carbon, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose in a mass ratio of 96.4:0.4:2.5:0.7, and the negative electrode active material of the first negative electrode film layer includes artificial graphite;

[0383] The second negative electrode film layer includes a negative electrode active material, conductive carbon, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose in a mass ratio of 97.8:0.7:0.8:0.7. The negative electrode active material of the second negative electrode film layer includes artificial graphite.

[0384] A cross-section of the negative electrode film along its thickness showed an average particle size of 13 μm for the first negative electrode film, and 10 μm for the second negative electrode film. During the negative electrode film preparation process, the desired average particle size can be achieved by adjusting the volume average particle size of the artificial graphite multiple times.

[0385] The length of the negative electrode film layer is 5 mm greater than that of the positive electrode film layer, and the width of the negative electrode film layer is 5 mm greater than that of the positive electrode film layer.

[0386] 3. Isolation parts

[0387] The separator includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0388] The length of the separator is 6 mm greater than the length of the negative electrode film layer, and the width of the separator is 6 mm greater than the width of the negative electrode film layer.

[0389] 4. Preparation of electrolyte

[0390] The electrolyte includes an organic solvent, lithium salt and additives.

[0391] After mixing the components of the organic solvent, lithium salt and additives are added to prepare an electrolyte.

[0392] The organic solvent includes 15% of ethyl acetate, a carboxylate solvent, and 68.5% of ethylene carbonate, a carbonate solvent.

[0393] The lithium salt includes 10% lithium hexafluorophosphate and 4% lithium bis(fluorosulfonyl)imide.

[0394] Additives included 2.5% vinylene carbonate.

[0395] 1. The conductivity of the electrolyte at room temperature is 11mS / cm;

[0396] The viscosity of the electrolyte at room temperature is 2.70 mPa·s;

[0397] The density of the electrolyte at room temperature is 1.10 g / mL.

[0398] 5. Preparation of battery cells

[0399] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation to obtain an electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. The compaction density of the positive electrode film layer of the battery cell at 100% SOC is 2.63 g / cm 3 The compaction density of the negative electrode film at 0% SOC is 1.60g / cm 3 .

[0400] Comparative Example 1-1

[0401] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the number of positive electrode tabs and the percentage of the positive electrode tabs occupied in the current collecting portion were adjusted.

[0402] Example 2-1 to Example 2-3

[0403] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the number of positive electrode tabs and the percentage of the positive electrode tabs occupied in the current collecting portion were adjusted.

[0404] Comparative Example 2-1 and Comparative Example 2-2

[0405] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode film layer of the positive electrode sheet was adjusted.

[0406] Example 3-1 to Example 3-4

[0407] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode film layer of the positive electrode sheet was adjusted.

[0408] Performance Testing

[0409] 1. DC resistance DCR test of battery cells

[0410] You can refer to the methods in GB / T 31467 "Performance test specification for high-power lithium-ion power batteries for HEV".

[0411] For example, at 25°C, charge the battery cell to 3.65V at a constant current of 0.33C, let it stand for 1 min, then charge it to 3.65V at a constant current of 0.1C, let it stand for 30 min, and discharge it to 2.0V at a constant current of 0.33C. Record the discharge capacity A0 at this time in Ah, and then charge it at a constant current of 0.33C for 0.5A0Ah, and adjust the SOC to 50%.

[0412] After the battery cell is placed at 25 ℃ for 2 hours, it is discharged at a current of 4C for 10 seconds and ∆U is recorded. 放电 , ∆I 放电 , the discharge DCR data of the battery cell is calculated by the following formula, R 放电 =∆U 放电 / ∆I 放电 ,

[0413] Where ∆U 放电 Indicates the voltage change within 10s after the discharge starts, ∆I 放电 Indicates the current value within 10 seconds after the start of discharge.

[0414] 3. High temperature cycle performance test of battery cells

[0415] In an environment of 60±5℃, the battery cell is charged at a constant current of 1C to the cut-off upper limit voltage, then charged at a constant voltage to the cut-off current of 0.05C, and then discharged at a constant current of 1C to the discharge cut-off voltage. This is one charge and discharge cycle.

[0416] The discharge capacity of this battery cell is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycling process for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery cell = Cn / C1*100%. Record the number of cycles at which the capacity retention rate reaches 80%. For accuracy, take the average of five replicate samples as the test result.

[0417] The test results are shown in Table 1.

[0418] Table 1

[0419]

[0420] In Table 1,

[0421] The positive electrode tab is arranged on the long side, which means that the positive electrode tab is arranged on at least one side of the positive electrode current collecting part along the width direction;

[0422] The positive electrode tab is located on one side along the long side, which means that the positive electrode tab is arranged on one side of the positive electrode current collecting part along the width direction, and all positive electrode tabs are located on the same side;

[0423] The positive electrode tabs are arranged on both sides of the long side, which means that the positive electrode tabs are arranged on both sides of the positive electrode current collecting part along the width direction.

[0424] The positive electrode ears are arranged on both sides of the long side, with 2 on each side, for a total of 4 positive electrode ears. Two positive electrode ears are arranged on one side of the positive electrode current collecting part along the width direction, and the other two positive electrode ears are arranged on the other side of the positive electrode current collecting part along the width direction.

[0425] 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 electrode ear is arranged on one side of the positive electrode collecting portion along the width direction, which can shorten the electron transmission path, the size of the positive electrode ear is relatively small, n*W1 / W2 is less than 0.2, and is 0.15. The flow area of ​​the positive electrode ear is relatively small, which makes the flow capacity of the positive electrode ear poor, the resistance is high, the heat generation is increased, and the risk of decomposition of the electrolyte components is increased, which is not conducive to high-temperature cycling and fast charging of the battery cell.

[0426] In Example 1, Example 2-1 to Example 2-3, the positive electrode ear is arranged on at least one side of the positive electrode current collecting part along the width direction. The size of the positive electrode ear is relatively large, and the size of the positive electrode ear in the positive electrode current collecting part accounts for a large proportion. n*W1 / W2 is greater than or equal to 0.2, so that the positive electrode ear has a higher flow area, stronger flow capacity, smaller internal resistance, and less heat generation, which can effectively reduce the internal heat of the battery cell and improve the high-temperature cycle stability and fast charging capability of the battery cell.

[0427] As the proportion of the positive electrode tab in the positive electrode current collecting part increases, n*W1 / W2 increases, and the current flow 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 collecting part along the length direction. In this case, the current flow 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 capability of the battery cell.

[0428] The length of the positive electrode film layer of Comparative Example 2-1 is shorter. Although the electron transmission path is shorter, the DCR of the battery cell is smaller and the heat generation is less, which is conducive to the rapid charging of the battery cell and the improvement of high-temperature cycle performance; however, the energy density of the battery cell is relatively small and does not meet production requirements.

[0429] The length of the positive electrode film layer of Comparative Example 2-2 is longer. Although the energy density of the battery cell is relatively high, the electron transmission path is too long, and the ohmic resistance of the positive electrode plate increases, which increases the internal resistance of the battery cell and generates higher heat, thereby deteriorating the high-temperature cycle and fast charging capabilities.

[0430] As the length of the positive electrode film increases, the energy density of the battery cell is improved; however, the ohmic resistance of the positive electrode tab increases, and heat generation increases, which is not conducive to improving the high-temperature cycling performance and rapid charging performance of the battery cell. The length and aspect ratio of the positive electrode film layers of Examples 3-1 and 3-4 are appropriate, resulting in a relatively high energy density of the battery cell. In the case of high energy density, the ratio of the length to the width of the positive electrode film layer is set to be less than or equal to 18.5, so that the length of the positive electrode film layer is not too long, which is beneficial to reducing the transmission distance of electrons in the longitudinal direction and reducing the ohmic resistance of the tab. Furthermore, with the tab ratio of n*W1 / W2 being greater than or equal to 0.2, the positive tab has excellent current capacity, which can effectively reduce internal resistance, reduce heat generation, and improve the high-temperature cycling performance and rapid charging performance of the battery cell. In particular, when the aspect ratio of the positive electrode film layer is 3.5 to 8 and the length dimension of the coated portion of the positive electrode tab is 400mm to 600mm, it is beneficial to improve both the high-temperature cycling performance and rapid charging performance of the battery cell at high energy density.

[0431] Comparative Example 3-1

[0432] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the components of the electrolyte were adjusted and lithium bis(fluorosulfonyl)imide was not added.

[0433] Example 4-1 to Example 4-7

[0434] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the components of the electrolyte were adjusted.

[0435] In Example 4-1 to Example 4-4, the mass content of lithium bis(fluorosulfonyl)imide was adjusted;

[0436] In Example 4-5, lithium bis(fluorosulfonyl)imide was replaced by lithium trifluorosulfonylimide, and the mass content remained unchanged.

[0437] 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%.

[0438] The test results are shown in Table 2.

[0439] Table 2

[0440]

[0441] In Table 2,

[0442] LiFSI stands for lithium bis(fluorosulfonyl)imide;

[0443] LiTFSI stands for lithium trifluorosulfonyl imide;

[0444] A1 represents the mass content of hexafluorophosphoric acid, and A2 represents the mass content of fluorinated lithium sulfonyl imide.

[0445] In Comparative Example 3-1, the amount of fluorinated lithium sulfonyl imide added is too small, resulting in relatively poor lithium ion conductivity of the electrolyte, which is not conducive to lithium ion migration and fast charging.

[0446] As the mass content of fluorinated lithium sulfonyl imide increases, the lithium ion migration number of the electrolyte increases, the lithium ion conductivity is enhanced, and the fast charging DCR can be reduced; and the formation of an SEI film containing lithium sulfonate, lithium fluoride, etc. on the negative electrode side can enhance the protection of the negative electrode side, which is beneficial to improving the high-temperature cycle performance of the battery cell; for example, in Examples 4-1 to 4-5, when the mass content of lithium bis(fluorosulfonyl)imide is greater than or equal to 2%, the high-temperature cycle performance and fast charging performance of the battery cell are relatively excellent.

[0447] However, when the amount of fluorinated lithium sulfonyl imide added is too much, for example greater than or equal to 10%, although it can reduce the DCR of the battery cell and improve the high-temperature cycle performance, the fluorinated lithium sulfonyl imide can decompose rapidly in a short period of time in the case of thermal runaway, generating a large amount of gas and heat, resulting in a sharp increase in the internal heat of the battery cell. The large amount of heat is difficult to release quickly, which deteriorates the reliability of the battery cell.

[0448] In Examples 4-5, lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide are used as fluorinated lithium sulfonyl imide, and their combination with lithium hexafluorophosphate can effectively improve the high-temperature cycle performance and fast charging performance of the battery cell.

[0449] In Examples 4-6 and 4-7, the mass content of lithium hexafluorophosphate changes synchronously. The lower the mass content of lithium hexafluorophosphate, the lower the HF content, and the less damage to the SEI film. The lithium salt also includes lithium fluorinated sulfonyl imide, which can enhance the protection of the negative electrode side and is beneficial to improving the high-temperature cycle performance of the battery cell.

[0450] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the embodiments of the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the embodiments of the present application.

Claims

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

8.

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

8.

3. The battery cell according to any one of claims 1 to 2, characterized in that: The mass content of the fluorinated lithium sulfonyl imide and the lithium hexafluorophosphate in the electrolyte is greater than 0 and less than or equal to 18%.

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

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

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

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

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

9. The battery cell according to claim 8, characterized in that The chain carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

10. The battery cell according to claim 9, characterized in that The chain carboxylate solvent includes one or more compounds represented by 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 additives, which include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. The mass content of the additives in the electrolyte is 0.5% to 10%.

13. The battery cell according to claim 12, characterized in that: The carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate; and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite and methylene disulfonate; and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium bis(oxalatoborate).

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

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

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

0.

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

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

19. The battery cell according to any one of claims 1 to 2, characterized in that: The negative electrode sheet 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 negative electrode coating portion has a larger dimension along the longitudinal direction than the positive electrode coating portion, and a difference between the dimension along the longitudinal direction of the negative electrode coating portion and the dimension along the longitudinal direction of the positive electrode coating portion is 5 mm to 11 mm.

20. The battery cell according to any one of claims 1 to 2, characterized in that: The electrode assembly further includes a separator, the separator being disposed between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet including 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 separator has a larger dimension along the length direction than the negative electrode coating portion, and a difference between the dimension of the separator and the dimension of the negative electrode coating portion along the length direction is 6 mm to 10 mm.

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

22. An electrical device, characterized in that: Comprising the battery device of claim 21.

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