Battery cell, battery device and electrical device

Abstract

Battery cell comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises several first electrode plates and several second electrode plates, wherein the several first electrode plates and the several second electrode plates are stacked along the thickness direction of the battery cell, wherein both the first electrode plates and the second electrode plates comprise a coating section and an electrode flap section, wherein the coating section contains active material, wherein the electrode flap section is connected to the coating section and extends along the longitudinal direction of the battery cell beyond the coating section, where One of the first electrode plates and the second electrode plate serve as positive electrode plates, while the others serve as negative electrode plates; wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction of the battery cell is a first dimension, while the dimension of the coating section of the positive electrode plate along the width direction is a second dimension, wherein the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction is 265 mm to 1200 mm; where the first electrode plates meet the following conditions: n*W1 / W2 is 0.2 to 1.0; where n denotes the number of all electrode flag sections on the same side of the coating section, and n is greater than or equal to 1; where W1 denotes the average dimension of the electrode flag sections along the latitude direction; where W2 denotes the dimension of the coating section along the width direction; wherein the electrolyte comprises lithium fluorosulfonylimide and lithium hexafluorophosphate, wherein the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, based on the mass of the electrolyte, is between 0.2 and 0.8.

Description

AREA OF INVENTION

[0001] The present application relates to a battery cell, a battery device and an electrical device. STATE OF THE ART

[0002] Battery cells are characterized by properties such as high capacity and long lifespan, and are therefore widely used in electronic devices such as mobile phones, laptops, e-bikes, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools, etc. Due to significant advances in battery technology, the demands on battery performance have increased. However, there is still room for improvement regarding fast charging capability, high-temperature cycle performance, and the operational reliability of battery cells. REVELATION OF THE INVENTION

[0003] The present application provides a battery cell, a battery device, and an electrical device. The fast-charging capability, high-temperature cycle performance, and operational reliability of the battery cell can be further improved in this application.

[0004] In a first aspect, the embodiments of the present application propose a battery cell comprising an electrolyte and an electrode assembly, wherein the electrode assembly comprises several first electrode plates and several second electrode plates, wherein the several first electrode plates and the several second electrode plates are stacked along the thickness direction of the battery cell, wherein both the first electrode plates and the second electrode plates comprise a coating section and an electrode flap section, wherein the coating section contains active material and the electrode flap section is connected to the coating section and extends along the longitudinal direction of the battery cell beyond the coating section, wherein one of the first electrode plates and one of the second electrode plates serve as positive electrode plates, while the others serve as negative electrode plates.The dimension of the coating section of the positive electrode plate along the longitudinal direction of the battery cell is a first dimension, while the dimension of the coating section of the positive electrode plate along the lateral direction is a second dimension, wherein the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, and wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction of the battery cell is between 265 mm and 1200 mm. The first electrode plates satisfy the following conditions: n*W1 / W2 is between 0.2 and 1.0; where n denotes the number of all electrode tab sections on the same side of the coating section and is greater than or equal to 1; where W1 denotes the average dimension of the electrode tab sections along the lateral direction; where W2 denotes the dimension of the coating section along the lateral direction.The electrolyte contains lithium fluorosulfonylimide and lithium hexafluorophosphate, wherein the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, based on the mass of the electrolyte, is between 0.2 and 0.8.

[0005] If the coating section of the positive electrode plate in the embodiments of the present application complies with the aforementioned area, the energy density of the battery cell can thus be improved. In the aforementioned electrode plate, the electrode fin section is arranged on at least one side of the coating section along the longitudinal direction of the battery cell, thereby making the electron transport path within the electrode plate relatively short, which leads to a faster electron transport rate and a reduction in the ohmic resistance of the electrode plate.Furthermore, the embodiments of the present application improve the lithium salt composition of the electrolyte, wherein the lithium salt has a suitable content of lithium fluorosulfonylimide, thereby improving the lithium ion conductivity of the electrolyte. The simultaneous improvement of both the active ion and electron transport rates effectively increases the fast-charging capability of the battery cell under high energy density conditions. Additionally, by arranging the electrode fin section on at least one side of the coating section along the longitudinal direction of the battery cell and the resulting relatively low ohmic resistance of the electrode plate, reduced heat generation in the electrode plate is achieved.Furthermore, an appropriate size ratio of the electrode fin section ensures a relatively large current-conducting area within the electrode fin section and low resistance at the interface with the coating section, which can further reduce heat generation in the electrode plate. This reduces internal heat accumulation within the battery cell, mitigates the adverse effects of heat accumulation on lithium fluorosulfonylimide, reduces the risk of gas generation and heat generation due to lithium fluorosulfonylimide decomposition, and improves the high-temperature cycle performance and operational reliability of the battery cell.

[0006] In some embodiments, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate is between 0.3 and 0.5. The combined use of lithium hexafluorophosphate and lithium fluorosulfonylimide can, on the one hand, improve the conductivity of the electrolyte and increase the fast-charging capability of the battery cell. On the other hand, it can reduce side reactions at the negative electrode and the decomposition risk of lithium fluorosulfonylimide, thereby improving the high-temperature cycle performance and operational reliability of the battery cell.

[0007] In some embodiments, the mass fraction of lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte is greater than 0 and at most 18%, and can be selected in the range of 10% to 18%. If the mass fraction of lithium salt is within this range, it can improve the high-temperature cycle performance and the fast-charging capability of the battery cell.

[0008] In some embodiments, the mass fraction of lithium fluorosulfonylimide in the electrolyte is greater than 0 and at most 8%. If the mass fraction of lithium fluorosulfonylimide is within this range, it can improve the high-temperature cycle performance and the fast-charging capability of the battery cell.

[0009] In some embodiments, the mass fraction of lithium hexafluorophosphate in the electrolyte is greater than 0 and at most 12%. If the mass fraction of lithium hexafluorophosphate is within this range, it can improve the high-temperature cycle performance and the fast-charging capability of the battery cell.

[0010] In some embodiments, lithium fluorosulfonylimide contains one or more of the following substances: lithium trifluorosulfonylimide and lithium difluorosulfonylimide. The aforementioned materials are advantageous for improving the high-temperature cycle performance and fast-charging capability of the battery cell.

[0011] In some embodiments, the electrolyte exhibits a conductivity of 10.5 mS / cm to 13.5 mS / cm at room temperature. If the electrolyte conductivity is within this 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 its fast-charging capability.

[0012] In some embodiments, the electrolyte has a viscosity of 1.5 mPa·s to 5.5 mPa·s at room temperature. If the viscosity of the electrolyte is in this 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 its fast-charging capability.

[0013] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. If the electrolyte density is in this 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 its fast-charging capability.

[0014] In some embodiments, the electrolyte further contains a linear carboxylic acid ester solvent, wherein the mass fraction of the linear carboxylic acid ester solvent in the electrolyte is between 5% and 35%. If the mass fraction of the linear carboxylic acid ester solvent is within this range, this can improve the fast-charging capability and the high-temperature cycle performance of the battery cell.

[0015] In some embodiments, the linear carboxylic acid ester solvent contains compounds represented by formula I:

[0016] In Formula I, the following applies: R1 contains hydrogen atoms, C1 to C5 alkyl groups or C1 to C5 haloalkyl groups, R2 contains C1 to C5 alkyl groups or C1 to C5 haloalkyl groups.

[0017] The linear carboxylic acid ester solvent exhibits high conductivity, which is advantageous for improving the fast-charging capability of the battery cell.

[0018] In some embodiments, the linear carboxylic acid ester solvent contains one or more compounds of formulas I-1 to I-8.

[0019] In some embodiments, the electrolyte also contains a carbonate solvent, wherein the mass fraction of the carbonate solvent in the electrolyte is between 65% and 75%. If the mass fraction of the carbonate solvent and the linear carboxylic ester solvent meets the aforementioned conditions, the stability of the electrolyte can be improved, its high-temperature gas formation reduced, and the high-temperature cycle performance of the battery cell enhanced.

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

[0021] In some embodiments, the electrolyte contains additives, wherein the additives comprise one or more of the following: carbonate additives, sulfur-containing additives, and lithium salt additives, the mass fraction of the additives in the electrolyte being between 0.5% and 10%. The additives can improve the properties of the interfacial film at the negative electrode, resulting in a more stable interfacial film with relatively low impedance, which is advantageous for improving the fast-charging capability of the battery cell and its high-temperature cycle performance.

[0022] In some embodiments, the carbonate additives contain one or more of the following substances: fluoroethylene carbonate and vinylene carbonate. These additives can improve the properties of the solid electrolyte interface layer (SEI film) at the negative electrode, resulting in a more stable interface film with relatively low impedance, which is advantageous for improving the fast-charging capability of the battery cell and its high-temperature cycle performance.

[0023] In some embodiments, the sulfur-containing additives include one or more of the following substances: ethylene sulfate, bis(ethylene sulfate), butylene sulfite, 1,3-propanesulfone, ethylene sulfite and methylenemethane disulfonate, wherein the additives are advantageous for improving the high-temperature cycle performance of the battery cell.

[0024] In some embodiments, the lithium salt additives contain one or more of the following substances: lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. These additives are advantageous for improving the high-temperature cycle performance of the battery cell.

[0025] In some embodiments, the number of electrode fin sections of the first electrode plate is 1 to 4. If the number of electrode fin sections is in this range, the current-carrying capacity of the electrode fin sections is higher, which is advantageous for improving the fast-charging capability of the battery cell.

[0026] In some embodiments, all electrode fin sections of the first electrode plate are connected along the longitudinal direction to the same side of the coating section, this arrangement being advantageous for increasing the energy density of the battery cell.

[0027] In some embodiments, the first electrode plate comprises at least two electrode flag sections, wherein the at least two electrode flag sections are connected along the longitudinal direction to both sides of the coating section of the first electrode plate. This arrangement shortens the electron transport path and improves the fast-charging capability of the battery cell.

[0028] In some embodiments, n*W1 / W2 is between 0.5 and 1.0. If the electrode flag sections meet the above-mentioned conditions, the current-carrying capacity is high, which is advantageous for improving the fast-charging capability of the battery cell.

[0029] In some embodiments, the ratio of the first dimension to the second dimension is between 3.5 and 8, and the dimension of the coating section of the positive electrode plate along the longitudinal direction is between 400 mm and 600 mm. If the dimension of the positive electrode film layer lies within this range, the electron transport path is not too long and the internal resistance is relatively low, which is advantageous for improving the fast-charging capability and the energy density of the battery cell.

[0030] In some embodiments, the active material of the positive electrode plate contains lithium phosphate. Lithium phosphates exhibit excellent cycle stability and can improve the high-temperature cycle performance of the battery cell.

[0031] In some embodiments, the negative electrode plate comprises a coating section of the negative electrode and an electrode tab of the negative electrode connected to the coating section of the negative electrode, while the positive electrode plate comprises a coating section of the positive electrode and an electrode tab of the positive electrode connected to the coating section of the positive electrode, wherein the dimension of the coating section of the negative electrode along the width direction is larger than the dimension of the coating section of the positive electrode along the width direction, and wherein the difference between the dimension of the coating section of the negative electrode along the width direction and the dimension of the coating section of the positive electrode along the width direction is between 5 mm and 11 mm.The relatively larger dimensions of the coating section of the negative electrode reduce the risk of lithium deposition on the negative electrode, reduce the risk of a short circuit between the positive and negative electrodes, and improve the operational reliability of the battery cell.

[0032] In some embodiments, the dimension of the coating section of the negative electrode along the longitudinal direction is larger than the dimension of the coating section of the positive electrode along the longitudinal direction, with the difference between the dimension of the coating section of the negative electrode along the longitudinal direction being between 5 mm and 11 mm. The relatively larger dimension of the coating section of the negative electrode reduces the risk of lithium deposition on the negative electrode, reduces the risk of a short circuit between the positive and negative electrodes, and improves the operational reliability of the battery cell.

[0033] In some embodiments, the electrode assembly further comprises a separator arranged between the positive electrode plate and the negative electrode plate, wherein the negative electrode plate comprises a coating section of the negative electrode and an electrode tab of the negative electrode connected to the coating section of the negative electrode; wherein the dimension of the separator along the width direction is larger than the dimension of the coating section of the negative electrode along the width direction, wherein the difference between the dimension of the separator along the width direction and the dimension of the coating section of the negative electrode along the width direction is between 6 mm and 10 mm.The relatively larger dimensions of the separator can effectively isolate the negative electrode plate and the positive electrode plate from each other, reducing the risk of a short circuit between the negative electrode plate and the positive electrode plate, and improving the operational reliability of the battery cell.

[0034] In some embodiments, the separator's longitudinal dimension is larger than the longitudinal dimension of the coating section of the negative electrode, with the difference between the separator's longitudinal dimension and the dimension of the coating section of the negative electrode being between 6 mm and 10 mm. The relatively larger separator dimension can effectively isolate the negative and positive electrode plates from each other, reducing the risk of a short circuit between them and improving the battery cell's operational reliability.

[0035] In a second aspect, the embodiments of the present application further propose a battery device comprising a battery cell according to any embodiment of the first aspect of the present application.

[0036] In a third aspect, the embodiments of the present application further propose an electrical device, wherein the electrical device comprises a battery device according to any embodiment of the second aspect or the third aspect. DESCRIPTION OF THE FIGURES

[0037] To more clearly illustrate the technical solutions of the embodiments of the present application, the figures used in these embodiments are briefly presented below. It is obvious that the figures described below represent only some embodiments of the present application. A person skilled in the art in this field can draw further figures based on these figures without inventive step. Fig.Figure 1 is a schematic representation of the structure of an electrical device provided by some embodiments of the present application. Fig. Figure 2 is a schematic representation of the structure of a battery pack provided by some embodiments of the present application; Fig. Figure 3 is a schematic representation of the structure of a battery module provided by some embodiments of the present application; Fig. Figure 4 is a schematic representation of the structure of a battery cell provided by some embodiments of the present application; Fig. Figure 5 is a schematic representation of the structure of the electrode assembly of a battery cell, which is provided by some embodiments of the present application; Fig.Figure 6 is a schematic representation of the structure of the first electrode plate of a battery cell, which is provided by some embodiments of the present application; Fig. Figure 7 is a schematic representation of the structure of the first electrode plate of a battery cell, which is provided by some other embodiments of the present application; Fig. Figure 8 is a schematic representation of the structure of the first electrode plate of a battery cell, which is provided by some other embodiments of the present application; Fig. Figure 9 is a schematic representation of the structure of the second electrode plate of a battery cell, which is provided by some embodiments of the present application; Fig.Figure 10 is a schematic representation of the structure of the second electrode plate of a battery cell, which is provided by some other embodiments of the present application; Fig. Figure 11 is a schematic representation of the structure of a battery cell, which is provided by some other embodiments of the present application; Fig. Figure 12 is a schematic representation of the structure of a battery cell, which is provided by some other embodiments of the present application; Fig. Figure 13 is a schematic representation of the structure of the negative electrode plate of a battery cell, which is provided by some embodiments of the present application; Fig. Figure 14 is a schematic representation of the structure of the electrode assembly of a battery cell, which is provided by some embodiments of the present application.

[0038] The figures are not necessarily to scale.

[0039] The markings in the figures are explained as follows: X: Thickness direction; Y: Width direction; Z: Length direction; 1. Electrical device; 2. Battery pack; 3. Control unit; 4. Motor; 5. Housing; 5a. First housing part; 5b. Second housing part; 5c. Receiving compartment; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. First electrode plate; 111. First electrode tab; 1111. First end; 112. First coating section; 12. Second electrode plate; 121. Second electrode tab; 1211. Second end; 122. Second coating section; 13. Separator; 14. Negative electrode plate; 141. Negative electrode film layer; 142. Negative electrode current collector; 1411. First negative electrode film layer; 1412. Second negative electrode film layer; 141a. First region; 141b. Second region; 141c. Third region; 20. Housing assembly; 21. Housing body; 22. End cover; 31. First electrode connection; 32. Second electrode connection. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0040] The embodiments of the battery cell, battery device, and electrical device of the present application are described in detail below with reference to the figures. Occasionally, however, unnecessary details may be omitted. For example, detailed explanations of generally known facts or repetitions of actually identical structures may be avoided. This is intended to avoid unnecessarily lengthening the following description and to facilitate understanding by those skilled in the art. Furthermore, the figures and the following description serve to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter of the claims.

[0041] The “range” disclosed in this application is defined by a lower bound and an upper bound. The specified range is determined by selecting a lower bound and an upper bound, the selected lower and upper bounds defining the limits of the respective range. The range thus defined can include or exclude limits and can be combined arbitrarily. That is, any lower bound can be combined with any upper bound to form a range. For example, if the ranges 60 to 120 and 80 to 110 are listed for a particular parameter, it is assumed that the ranges 60 to 110 and 80 to 120 are also anticipated. If, in addition, the minimum range values ​​1 and 2 and the maximum range values ​​3, 4, and 5 are listed, then the following ranges are all anticipated: 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 range of values ​​“a to b” denotes an abbreviated representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the range of values ​​“0 to 5” means that all real numbers between “0 and 5” are fully listed in this application, where “0 to 5” is merely an abbreviated representation of these combinations of numbers. Furthermore, when it is specified that a parameter is an integer ≥ 2, this means that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise stated, all embodiments and optional embodiments of this application may be combined to form new technical solutions.

[0043] Unless otherwise stated, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise stated, all steps of this application may be performed sequentially or in any order, with sequential order being preferred. For example, if a procedure includes steps (a) and (b), this means that the procedure may include steps (a) and (b) consecutively or steps (b) and (a) consecutively. For example, if it is mentioned that the procedure may also include step (c), this means that step (c) may be inserted into the procedure in any order. For example, the procedure may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0045] In the present application, the term "several" refers to two or more (including two).

[0046] With the rapid development of the battery industry, the performance requirements for battery cells are constantly increasing. For example, the demands on the fast-charging capability of high-energy-density battery cells are continuously rising. To meet these requirements, the conductivity of the electrolyte can be increased. However, increased conductivity at high temperatures can lead to electrolyte degradation. This, in turn, increases gas formation in the battery cells and can impair their high-temperature cycle performance and operational reliability.

[0047] In view of the problems mentioned above, the embodiments of the present application improve the energy density of the battery cell by designing the dimensions of the electrode plate.

[0048] In the aforementioned electrode plate, the electrode fin section is arranged on at least one side of the coating section along the longitudinal direction of the battery cell, resulting in a relatively short electron transport path within the electrode plate. This leads to a faster electron transport rate and a reduction in the ohmic resistance of the electrode plate. Furthermore, the embodiments of the present application improve the lithium salt composition of the electrolyte, wherein the lithium salt has a suitable content of lithium fluorosulfonylimide. This improves the lithium ion conductivity of the electrolyte, and the simultaneous improvement of both the active ion and electron transport rates effectively increases the fast-charging capability of the battery cell under high energy density conditions.

[0049] By positioning the electrode fin section on at least one side of the coating section along the longitudinal direction of the battery cell, and by resulting in a relatively low ohmic resistance of the electrode plate, heat generation within the electrode plate is reduced. Furthermore, an appropriate size ratio of the electrode fin section ensures a relatively large current-conducting area within the electrode fin section and low resistance at the interface with the coating section, which can further reduce heat generation. This reduces internal heat accumulation within the battery cell and lowers the risk of thermal runaway.This reduces the risk of lithium fluorosulfonylimide rapidly decomposing in the event of thermal runaway, generating large amounts of gas and heat and thereby degrading the operational reliability of the battery cell, thus improving the high-temperature cycle performance as well as the operational reliability of the battery cell.

[0050] The battery cell described in this application is applicable to various battery devices and electrical devices that use battery cells.

[0051] For example, the electrical device could be a mobile phone, a portable device, a laptop, an electric bicycle, an electric toy, a power tool, a vehicle, a ship, or an aircraft or spacecraft, etc. Alternatively, the electrical device could be, for example, an aircraft or spacecraft, where aircraft and spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0052] Fig.Figure 1 is a schematic representation of an exemplary electrical device 1. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device 1, a battery pack or battery module can be used.

[0053] The electrical device 1 is equipped with an internal battery unit, which may be located at the bottom, top, or end of the electrical device 1. The battery unit can be used to power the electrical device 1. For example, the battery unit can serve as the operating power source for the electrical device 1 and also as the driving power source for the electrical device 1, wholly or partially replacing heating oil or natural gas to provide driving energy for the electrical device 1. The in Fig.The battery device shown in 1 is battery pack 2.

[0054] The electrical device 1 can also include a control unit 3 and a motor 4, wherein the control unit 3 serves to control the battery device in order to supply power to the motor 4, for example to meet the energy requirements of the electrical device 1 during the starting process, navigation and driving.

[0055] A battery apparatus can comprise one or more battery cell assemblies that provide voltage and capacity. A battery cell assembly can comprise multiple battery cells, with the multiple battery cells connected via a busbar in series, parallel, or a mixed configuration.

[0056] In some embodiments, a battery cell assembly is typically formed by the arrangement of several battery cells.

[0057] For example, a battery cell assembly can be a battery module, where the battery module consists of several battery cells arranged and secured to form an independent module. For example, a battery module can be formed by bundling several battery cells together with cable ties.

[0058] As in Fig. As shown in Figure 2, in some embodiments the battery device may be a battery pack 2, wherein the battery pack 2 comprises a housing 5 and one or more battery cell assemblies, the battery cell assemblies being housed in the housing 5.

[0059] For example, the battery cell assembly can also be housed in the casing 5 by attaching several battery cells directly to the casing 5.

[0060] For example, the housing 5 comprises a first housing part 5a and a second housing part 5b, wherein the housing 5 has a receiving space 5c, the first housing part 5a and the second housing part 5b interlocking to form a closed space within the housing 5 that receives the battery cell assembly. Here, "closed" refers to covering or sealing, which may be either sealed or unsealed. The first housing part 5a may be a top cover or a bottom plate.

[0061] For example, housing 5 can comprise a top cover, a frame, and a base plate. The top cover and the base plate are each connected to the frame, thereby forming an enclosed space within housing 5 to accommodate the battery cell assembly.

[0062] In some designs, the housing 5 can be part of the chassis structure. For example, part of the housing 5 can be at least part of the vehicle floor, or part of the housing 5 can be at least part of the vehicle's cross members and longitudinal members.

[0063] For example, the battery cell assembly can be a battery module 6, wherein the battery cell assembly can be housed in the casing 5 by attaching the battery module 6 to the casing 5.

[0064] As in Fig. As shown in Figure 3, the battery module 6 comprises several battery cells 7.

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

[0066] In some embodiments, the temperature of the external environment in which the battery device is located during the charging process of the battery device or of any battery cell 7 of which the battery device consists, is from 20% SOC to 80% SOC at room temperature, for example 25°C.

[0067] For example, the charging process of the battery device or any battery cell 7 of which the battery device consists, from 20% SOC to 80% SOC can be carried out as follows: Charging from 20% SOC to 25% SOC with a constant current of 8.00 C; Charging from 25% SOC to 30% SOC with a constant current of 8.00 C; Charging from 30% SOC to 35% SOC with a constant current of 7.50 C; Charging from 35% SOC to 40% SOC with a constant current of 6.87 C; Charging from 40% SOC to 45% SOC with a constant current of 6.38 C; Charging from 45% SOC to 50% SOC with a constant current of 5.95 C; Charging from 50% SOC to 55% SOC with a constant current of 5.53 C; Charging from 55% SOC to 60% SOC with a constant current of 5.14 C; Charging from 60% SOC to 65% SOC with a constant current of 4.76 C; Charging from 65% SOC to 70% SOC with a constant current of 4.36 C; Charging from 70% SOC to 75% SOC with a constant current of 3.94 C; Charging from 75% SOC to 80% SOC with a constant current of 3.57C.

[0068] In some embodiments, the charging time of the battery device or of any battery cell 7 of which the battery device consists, from 20% state of charge to 80% state of charge is 5 to 30 minutes, optionally 5 to 20 minutes, and the temperature of the external environment of the battery device at 20% state of charge is room temperature, for example 25 °C. For example, the charging time of the battery device from 20% charge to 80% charge is 30 minutes, 29 minutes, 28 minutes, 27 minutes, 26 minutes, 25 minutes, 24 minutes, 23 minutes, 22 minutes, 21 minutes, 20 minutes, 19 minutes, 18 minutes, 17 minutes, 16 minutes, 15 minutes, 14.5 minutes, 14 minutes, 13.5 minutes, 13 minutes, 12.5 minutes, 12 minutes, 11.5 minutes, 11 minutes, 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5 minutes, or a range formed by any two of the aforementioned values.

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

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

[0071] In some embodiments, the housing assembly comprises 20 housings and a connection assembly, wherein the connection assembly is arranged on the housing.

[0072] For example, the connection assembly comprises a first electrode connection 31 and a second electrode connection 32, wherein one of the first electrode connection 31 and second electrode connection 32 is the positive connection and the other is the negative connection.

[0073] The housing can be made of steel, aluminum, plastic (e.g., polypropylene), composite metal (e.g., copper-aluminum composite), or aluminum-plastic foil, etc. In some designs, the housing can have a sealed or unsealed structure. For example, if the housing has an unsealed structure, it serves to protect the electrode assembly 10, with an additional sealing bag located between the housing and the electrode assembly 10, encapsulating both the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a pouch-shaped insulating element or an aluminum-plastic foil. If the housing has a sealed structure, it serves to encapsulate the components, such as the electrode assembly 10 and the electrolyte.

[0074] For example, the battery cell 7 can be cylindrical, prismatic, pouch, or otherwise shaped, wherein the prismatic battery cells include cuboid, sheet-shaped, and multiprismatic battery cells, the multiprismatic battery cells being, for example, hexagonal prismatic battery cells. The present application is not subject to any particular restrictions.

[0075] In some embodiments, the housing comprises an end cover 22 and a housing body 21, wherein the housing body 21 has an opening and the end cover 22 covers the opening. The housing body 21 may have one or more openings. One or more end covers 22 may also be provided.

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

[0077] The electrode assembly 10 comprises first electrode plates 11, second electrode plates 12 and separators 13, wherein one type of first electrode plates 11 and second electrode plates 12 are positive electrode plates, and the other type are negative electrode plates.

[0078] The electrode assembly 10 has a stacked structure, which is advantageous for increasing the energy density of the battery cell 7.

[0079] For example, several first electrode plates 11 and several second electrode plates 12 can be arranged, and several first electrode plates 11 and several second electrode plates 12 can be stacked alternately.

[0080] For example, several first electrode plates 11 can be arranged, and a second electrode plate 12 can be folded to create several stacked folded segments, with a first electrode plate 11 embedded between adjacent folded segments.

[0081] For example, both the first electrode plate 11 and the second electrode plate 12 can be folded in such a way that several stacked folded segments are created.

[0082] For example, several separators 13 can be arranged, each positioned between adjacent first electrode plates 11 or second electrode plates 12.

[0083] For example, the separator 13 can be continuously arranged by folding or winding between any two adjacent first electrode plates 11 or second electrode plates 12.

[0084] In some embodiments, each electrode plate is provided with electrode tabs that can conduct current from the electrode assembly 10. The electrode tabs comprise positive electrode tabs and negative electrode tabs.

[0085] To illustrate this application more clearly, the electrode tail section of the first electrode plate 11 is defined as the first electrode tail 111, and the coating section of the first electrode plate 11 is defined as the first coating section 112. The electrode tail section of the second electrode plate 12 is defined as the second electrode tail 121, and the coating section of the second electrode plate 12 is defined as the second coating section 122. The electrode terminal that has the same electrical polarity as the first electrode tail 111 and is electrically connected to it is the first electrode terminal 31, and the electrode terminal that has the same electrical polarity as the second electrode tail 121 and is electrically connected to it is the second electrode terminal 32.

[0086] The first electrode plate 11 and the second electrode plate 12 have opposite polarities. If the first electrode plate 11 is the positive electrode plate, then the second electrode plate 12 is the negative electrode plate, the first coating section 112 is the positive coating section, the first electrode tab 111 is the positive electrode tab, and the first electrode terminal 31 is the positive terminal; the second coating section 122 is the negative coating section, the second electrode tab 121 is the negative electrode tab, and the second electrode terminal 32 is the negative terminal.

[0087] Or, if the first electrode plate 11 is the negative electrode plate, then the second electrode plate 12 is the positive electrode plate, the first coating section 112 is the negative coating section, the first electrode tab 111 is the negative electrode tab, the first electrode terminal 31 is the negative terminal, the second coating section 122 is the positive coating section, the second electrode tab 121 is the positive electrode tab, and the second electrode terminal 32 is the positive terminal.

[0088] The coating section comprises a current collector and a film layer containing active material arranged on the current collector. For example, the positive coating section comprises a positive current collector and a positive film layer containing active material arranged on the positive current collector. Another example is the positive coating section comprising a positive current collector and a positive film layer containing active material arranged on the positive current collector.

[0089] As in Fig. 4 to Fig.As shown in Figure 6, the battery cell 7 in some embodiments comprises electrolytes and an electrode assembly 10, wherein the electrode assembly 10 comprises several first electrode plates 11 and several second electrode plates 12, the several first electrode plates 11 and the several second electrode plates 12 being stacked along the thickness direction X of the battery cell 7, both the first electrode plates 11 and the second electrode plates 12 comprising a coating section and an electrode flag section, the coating section containing active material, while the electrode flag section may be free of active material, the electrode flag section being connected to the coating section and extending along the longitudinal direction Z of the battery cell 7 beyond the coating section. where One type of first electrode plates 11 and second electrode plates 12 serves as positive electrode plates, while the other type serves as negative electrode plates; wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction Z of the battery cell 7 is a first dimension, while the dimension of the coating section of the positive electrode plate along the lateral direction Y is a second dimension, wherein the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction Z of the battery cell is between 265 mm and 1200 mm; where the first electrode plates meet the following conditions: n*W1 / W2 is between 0.2 and 1.0; where n denotes the number of all electrode flag sections on the same side of the coating section; where n is greater than or equal to 1; where W1 denotes the average dimension of the electrode flag sections along the latitude direction Y; where W2 denotes the dimension of the coating section along the width direction Y; wherein the electrolyte contains lithium salts, wherein the lithium salts comprise lithium fluorosulfonylimide and lithium hexafluorophosphate, wherein the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, based on the mass of the electrolyte, is between 0.2 and 0.8.

[0090] Using the first electrode plate 11 as an example in Fig.6, which serves as positive electrode plate 11, Z2 denotes the dimension of the coating section of the positive electrode plate along the longitudinal direction Z of the battery cell 7, i.e. the first dimension, while W2 denotes the dimension of the coating section of the positive electrode plate along the lateral direction Y of the battery cell 7, i.e. the second dimension.

[0091] If the dimension of the coating section of the positive electrode plate along the longitudinal direction Z of the battery cell is less than 265 mm, it can only accommodate a limited amount of active material, resulting in a low energy density of the battery cell 7. In the embodiments of the present application, the dimension of the coating section of the positive electrode plate is at least 265 mm, which is advantageous for increasing the energy density of the battery cell 7.

[0092] As the dimensions of the coating section of the positive electrode plate increase along the longitudinal direction Z, the electron transport path in the electrode plate lengthens, thereby increasing the ohmic resistance. With an increasing ratio of the first dimension to the second dimension, the electron transport path in the electrode plate lengthens further, leading to increased ohmic resistance and hindering fast charging. Furthermore, the increased ohmic resistance can lead to increased heat generation, and the accumulation of this heat can easily lead to electrolyte degradation, thus degrading cycle performance.

[0093] The embodiments of the present application limit, on the one hand, the ratio of the first dimension to the second dimension to a maximum of 18.5, thereby reducing the aspect ratio and shortening the electron transport path along the longitudinal direction; on the other hand, the electrode fin section is arranged on at least one side of the coating section along the longitudinal direction Z of the battery cell 7, thereby further shortening the electron transport path in the electrode plate, reducing the ohmic resistance of the electrode plate, and improving the electron transport rate. The embodiments of the present application also regulate the lithium salts of the electrolyte, wherein the lithium salts contain lithium fluorosulfonylimide and lithium hexafluorophosphate, the mass ratio of the two being greater than or equal to 0.2, thereby increasing the lithium ion migration number of the electrolyte and improving the lithium ion conductivity.The comprehensive improvement of electron transport capability and ion conductivity enhances the fast-charging capability of the battery cell at high energy density.

[0094] Lithium hexafluorophosphate can decompose, forming hydrofluoric acid (HF). The side reaction between the hydrofluoric acid and the active material of the negative electrode can lead to increased gas formation during storage at high temperatures. The combined use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the hydrofluoric acid content, slow down the side reaction at the negative electrode interface, decrease gas formation during storage at high temperatures, and improve high-temperature cycle performance.

[0095] However, the risk of heat spread increases further with the increasing proportion of lithium fluorosulfonylimide. More precisely, the thermal decomposition temperature of the fluorosulfonylimide salt is close to the thermal runaway temperature of battery cell 7. Furthermore, lithium fluorosulfonylimide exhibits a rapid decomposition rate and intense heat generation. This rapidly releases large quantities of heat and hot gas, leading to a significant increase in the internal temperature within battery cell 7. This large amount of heat is difficult to dissipate quickly, which can easily lead to heat spread and impair the operational reliability of battery cell 7.

[0096] The embodiments of the present application limit, on the one hand, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate to a maximum of 0.8, thereby reducing the risk of further heat generation due to the decomposition of lithium fluorosulfonylimide through increased heat generation; on the other hand, the dimensions of the electrode plate comply with the aforementioned range and the electrode fin section is arranged on at least one side of the coating section along the longitudinal direction Z of the battery cell 7, resulting in a relatively low ohmic resistance of the electrode plate, which leads to reduced heat generation in the electrode plate.Furthermore, an appropriate electrode fin size ratio, where n*W1 / W2 is greater than or equal to 0.2, ensures a relatively large current-conducting area within the electrode fin section and low resistance at the junction with the coating section, which can further reduce heat generation in the electrode plate. This reduces internal heat accumulation within battery cell 7, mitigates the adverse effects of heat accumulation on lithium fluorosulfonylimide, reduces the risk of gas and heat generation due to lithium fluorosulfonylimide decomposition, and improves the high-temperature cycle performance and operational reliability of battery cell 7.

[0097] Therefore, the embodiments of the present application can simultaneously improve the fast charging capability, the high-temperature cycle performance and the operational reliability of the high-energy-density battery cell 7.

[0098] For example, 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 formed by any two of these values. Optionally, n*W1 / W2 can be between 0.5 and 1.0.

[0099] If n*W1 / W2 stays within the above range, the current conduction area within the electrode flag section is relatively large and the heat generation is low, which improves the fast charging capability and the high-temperature cycle performance of the high-energy-density battery cell 7.

[0100] W1 denotes the average dimension of the first electrode flag 111 along the latitude direction Y.

[0101] If the first electrode flag 111 has an irregular structure, for example, if its dimensions gradually increase along the lateral direction Y over the longitudinal direction Z, the dimensions of the first electrode flag 111 can be measured at several points along the lateral direction Y, and the average dimension of the first electrode flag 111 along the lateral direction Y can be calculated from these measurements. Of course, the dimensions of the first electrode flag 111 can also be the same at all points along the lateral direction Y. In this case, the value can be used as the average dimension of the first electrode flag 111.

[0102] There may be one or more first electrode tabs 111. If several first electrode tabs 111 are located on the same side of the first coating section 112, for example, if n is in the range of 1 to 4, the average dimension of each first electrode tab 111 can be measured. These average dimensions are then added together, and the sum is divided by the total number of first electrode tabs 111 to obtain the average dimension of the first electrode tabs 111.

[0103] The first electrode tab 111 is connected to the first coating section 112, the first electrode tab 111 having a first end 1111 that is connected to the first coating section 112. If n*W1 / W2 adheres to the above-mentioned range, this means that the cross-section of the first end 1111 is relatively large along the thickness direction of the first electrode tab 111, the contact area between the first electrode tab 111 and the first coating section 112 is relatively large, and the current-carrying capacity of the first electrode tab 111 is high, which can improve the fast-charging capability and the high-temperature cycle performance of the battery cell 7.

[0104] In some embodiments, the first electrode plate 11 comprises at least one first electrode tab 111, for example one to four first electrode tabs 111. Optionally, the first electrode plate 11 comprises at least two first electrode tabs 111 and optionally four first electrode tabs 111.

[0105] In some embodiments, one or more first electrode fins 111 are arranged on at least one side of the coating section along the longitudinal direction Z.

[0106] As in Fig. 6 to Fig. As shown in Figure 8, the first electrode plate 11 has at least one electrode fin section on the same side as the coating section, and the electrode fin section comprises a first end 1111 that is connected to the coating section. Fig.6, where n equals 2, and the dimensions of each first electrode tab 111 are identical. W1 can also represent the dimension of a single first electrode tab 111. Of course, the dimensions of the individual first electrode tabs 111 can also differ slightly from one another. W2 denotes the dimension of the first coating section 112 along the longitudinal direction Z. Fig. 7 is where n equals 1 and n*W1 / W2 equals 1.0. In Fig. 8 is n equal to 1.

[0107] In some embodiments, the first electrode plate 11 comprises at least one first electrode tab 111, for example one to four first electrode tabs 111. Optionally, the first electrode plate 11 comprises at least two first electrode tabs 111 and optionally four first electrode tabs 111.

[0108] In some embodiments, one or more first electrode tabs 111 are arranged on at least one side of the coating section along the longitudinal direction Z. One or more first electrode tabs 111 are arranged on one side of the first coating section 112 along the longitudinal direction Z. In this case, it can be assumed that all first electrode tabs 111 are arranged on the same side of the first coating section 112 along the longitudinal direction Z.

[0109] For example, if the first electrode plate 11 includes several first electrode tabs 111, these several first electrode tabs 111 are arranged on both sides of the first coating section 112 along the longitudinal direction Z, thereby shortening the electron transport path and improving the fast charging capability.

[0110] Optionally, several first electrode tabs 111 are arranged on both sides of the first coating section 112 along the longitudinal direction Z. This arrangement can shorten the electron transport path in the first electrode plate 11, thus improving the fast-charging capability. For example, two first electrode tabs 111 are arranged on one side of the first coating section 112 along the longitudinal direction Z, and two first electrode tabs 111 are arranged on the other side of the first coating section 112 along the longitudinal direction Z.

[0111] Optionally, if several first electrode tabs 111 are arranged on at least one side of the first coating section 112 along the longitudinal direction Z, the first electrode tabs 111 arranged on the same side of the first coating section 112 along the longitudinal direction Z comprise at least two, for example two, three, four, five, six, etc. This arrangement facilitates a uniform distribution of electrons in the first electrode plate 11, which improves the fast-charging capability.

[0112] Optionally, the distance between two adjacent first electrode flags 111 along the lateral direction Y is 0 to 300 mm, for example 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range formed by any two of the aforementioned values. Fig. 6 denotes Y1 as the distance between two adjacent first electrode tails 111 along the latitude direction Y.

[0113] As in Fig. 9 and Fig. As shown in Figure 10, in some embodiments the following applies to the second electrode plate 12: m*W3 / W4 is between 0.2 and 1.0; where m denotes the number of all electrode flag sections on the same side of the coating section; where m is greater than or equal to 1; where W3 denotes the average dimension of the electrode flag sections along the latitude direction Y; where W4 denotes the dimension of the coating section along the width direction Y.

[0114] For example, m*W3 / W4 is equal to 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 formed by any two of these values. Optionally, m*W3 / W4 can be in the range of 0.5 to 1.0.

[0115] If m*W3 / W4 adheres to the above-mentioned range, the current conduction area within the electrode flag section is relatively large and the heat generation is low, which improves the fast charging capability and the high-temperature cycle performance of the high-energy-density battery cell 7.

[0116] W3 denotes the average dimension of the second electrode tab 121 along the longitudinal direction Z. One or more second electrode tabs 121 may be present, for example, if m is in the range of 1 to 4. If several second electrode tabs 121 are located on the same side of the second coating section 122, the average dimension can be calculated by measuring the dimension of each second electrode tab 121 with a micrometer.

[0117] The second electrode tab 121 is connected to the second coating section 122, the second electrode tab 121 having a second end 1211 that is connected to the second coating section 122. If m*W3 / W4 adheres to the above-mentioned range, this means that the cross-section of the second end 1211 is relatively large along the thickness direction of the second electrode tab 121, the contact area between the second electrode tab 121 and the second coating section 122 is relatively large, and the current-carrying capacity of the second electrode tab 121 is high, which can improve the fast-charging capability and the high-temperature cycle performance of the battery cell 7.

[0118] Optionally, the second electrode tab 121 and the current collector of the second coating section 122 can be designed as an integral component, thereby reducing the internal resistance of the second electrode plate 12, which can further improve the fast charging capability and the high temperature cycle performance of the battery cell 7.

[0119] In Fig. 9 is m equal to 1. In Fig. 10 is m equal to 2.

[0120] In some embodiments, the second electrode plate 12 comprises at least one second electrode tab 121, optionally at least two second electrode tabs 121 and optionally four second electrode tabs 121.

[0121] For example, one or more second electrode tabs 121 are arranged on one side of the second coating section 122 along the longitudinal direction Z. In this case, it can be assumed that all second electrode tabs 121 are arranged on the same side of the second coating section 122 along the longitudinal direction Z.

[0122] If, on the other hand, the second electrode plate 12 has several second electrode tabs 121, these several second electrode tabs 121 are arranged on both sides of the second coating section 122 along the longitudinal direction Z.

[0123] Optionally, several second electrode tabs 121 are arranged on both sides of the second coating section 122 along the longitudinal direction Z. This arrangement can shorten the transport path of the electrons in the second electrode plate 12, which improves the fast-charging capability.

[0124] Optionally, if several second electrode tabs 121 are arranged on at least one side of the second coating section 122 along the longitudinal direction Z, the second electrode tabs 121 arranged on the same side of the second coating section 122 along the longitudinal direction Z comprise at least two, for example two, three, four, five, six, etc. This arrangement facilitates a uniform distribution of electrons in the second electrode plate 12, which improves the fast-charging capability.

[0125] Optionally, the distance between two adjacent second electrode flags 121 along the width direction Y is 0 to 300 mm, for example 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm or a range formed by any two of the aforementioned values.

[0126] As in Fig.As shown in Figure 11, in some embodiments the connection assembly can be arranged on the housing body 21, or the connection assembly can be arranged on the end cover 22.

[0127] The connection assembly comprises a first electrode connection 31 and a second electrode connection 32, wherein the first electrode connection 31 is connected to the first electrode tab 111 and the second electrode connection 32 is connected to the second electrode tab 121.

[0128] For example, the first electrode connection 31 and the second electrode connection 32 can be arranged on the housing body 21, or the first electrode connection 31 and the second electrode connection 32 can be arranged on the end cover 22. Optionally, the first electrode connection 31 and the second electrode connection 32 are arranged on the end cover 22.

[0129] The first electrode connection 31 and the second electrode connection 32 can be arranged simultaneously on the same end cover 22. For example, there can be a single end cover 22, with the first electrode connection 31 and the second electrode connection 32 arranged at a certain distance from each other on this end cover 22. Or, for example, there can be two end covers 22, with the two end covers 22 facing each other, each with both a first electrode connection 31 and a second electrode connection 32 arranged on it.

[0130] A first electrode connection 31 and a second electrode connection 32 are arranged on various end covers 22. For example, there are two end covers 22, with the two end covers 22 opposite each other, with a first electrode connection 31 arranged on one end cover 22 and a second electrode connection 32 arranged on the other.

[0131] In some embodiments, at least one first electrode connection 31 is provided, optionally at least two, for example two, three or four etc.

[0132] In some embodiments, at least one first electrode connection 31 is arranged on at least one side of the electrode assembly 10 along the longitudinal direction Z.

[0133] For example, in Fig. As shown in Figure 11, all first electrode connections 31 are arranged on one side of the electrode assembly 10 along the longitudinal direction Z.

[0134] For example, in Fig. As shown in Figure 12, several first electrode connections 31 are arranged on both sides of the electrode assembly 10 along the longitudinal direction Z. This arrangement can shorten the electron migration path, which improves the fast charging capability.

[0135] For example, two first electrode terminals 31 are provided, with one of the first electrode terminals 31 being arranged on one side of the electrode assembly 10 and the other first electrode terminal 31 being arranged on the other side of the electrode assembly 10. Or, for example, four first electrode terminals 31 are provided, with two of the first electrode terminals 31 being arranged on one side of the electrode assembly 10 and the other two first electrode terminals 31 being arranged on the other side of the electrode assembly 10.

[0136] In the embodiments of the present application, the first electrode tab 111 and the first electrode terminal 31 are electrically connected either directly or indirectly. If the first electrode tab 111 and the first electrode terminal 31 are connected indirectly, the battery cell 7 may comprise a first transition piece 51, wherein the first transition piece 51 is arranged between the first electrode terminal 31 and the first electrode tab 111 and connects the first electrode terminal 31 and the first electrode tab 111.

[0137] In the embodiments mentioned above, the first transition piece 51 can consist of electrically conductive polymer or electrically conductive metal material, wherein the electrically conductive metal material can comprise copper, aluminum or an alloy containing the aforementioned metal elements.

[0138] In some other embodiments, at least one first electrode connection 31 is arranged on at least one side of the electrode assembly 10 along the width direction Y. For example, all first electrode connections 31 are arranged on one side of the electrode assembly 10 along the width direction Y. For example, several first electrode connections 31 are arranged on both sides of the electrode assembly 10 along the width direction Y.

[0139] In some embodiments, at least one second electrode connection 32 is provided, optionally at least two, for example two, three or four etc.

[0140] In some embodiments, at least one second electrode connection 32 is arranged on at least one side of the electrode assembly 10 along the longitudinal direction Z.

[0141] For example, in Fig.As shown in Figure 12, at least two second electrode connections 32 are arranged on both sides of the electrode assembly 10 along the longitudinal direction Z. This arrangement can shorten the electron migration path, which improves the fast-charging capability.

[0142] Fig. Figure 12 shows that the battery cell 7 has four electrode terminals. More precisely, there are two second electrode terminals 32, one of which is located on one side of the electrode assembly 10 along the longitudinal direction Z, and the other is located on the opposite side of the electrode assembly 10 along the longitudinal direction Z. There are also two first electrode terminals 31, one of which is located on one side of the electrode assembly 10, and the other is located on the opposite side of the electrode assembly 10.

[0143] For example, all second electrode terminals 32 are arranged on one side of the electrode assembly 10 along the longitudinal direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can each be arranged on both sides of the electrode assembly 10 along the longitudinal direction Z, and if they are each electrically connected to the electrode flag section, they do not interfere with each other.

[0144] For example, a first electrode connection 31 and a second electrode connection 32 are provided, wherein the first electrode connection 31 is arranged on one side of the electrode assembly 10 along the longitudinal direction Z and the second electrode connection 32 is arranged on the other side of the electrode assembly 10 along the longitudinal direction Z. Optionally, the first electrode connection 31 and the second electrode connection 32 can be offset from each other along the lateral direction Y. Of course, the first electrode connection 31 and the second electrode connection 32 can also be arranged directly opposite each other along the longitudinal direction Z. Fig. Figure 11 shows a schematic representation in which the first electrode connection 31 and the second electrode connection 32 are each arranged on both sides of the electrode assembly 10.

[0145] For example, two first electrode terminals 31 and two second electrode terminals 32 are provided, wherein the two first electrode terminals 31 are arranged on one side of the electrode assembly 10 along the longitudinal direction Z and the two second electrode terminals 32 are arranged on the other side of the electrode assembly 10 along the longitudinal direction Z.

[0146] In the embodiments of the present application, the second electrode tab 121 and the second electrode terminal 32 are electrically connected either directly or indirectly. If the second electrode tab 121 and the second electrode terminal 32 are connected indirectly, the battery cell 7 may include a second transition piece, wherein the first transition piece is arranged between the second electrode terminal 32 and the second electrode tab 121 and connects the second electrode terminal 32 and the second electrode tab 121.

[0147] In the embodiments mentioned above, the second transition piece can consist of electrically conductive polymer or electrically conductive metal material, wherein the electrically conductive metal material can comprise copper, aluminum or an alloy containing the aforementioned metal elements.

[0148] In some other embodiments, at least one second electrode connection 32 is arranged on at least one side of the electrode assembly 10 along the width direction Y. For example, all second electrode connections 32 are arranged on one side of the electrode assembly 10 along the width direction Y, or several second electrode connections 32 are arranged on both sides of the electrode assembly 10 along the width direction Y. Negative electrode plate

[0149] The coating section of the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer, which is arranged on at least one side of the negative electrode current collector and contains the active material of the negative electrode. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is arranged on one or both of these opposing surfaces of the negative electrode current collector.

[0150] The upper charge voltage and the lower discharge voltage of a battery cell vary depending on the active material of the positive electrode. For example, for phosphate-based materials, including lithium iron phosphate, the upper charge voltage can be 3.65 V and the discharge voltage 2.0 V, or alternatively, the upper charge voltage can be 3.8 V and the discharge voltage 2.0 V. Alternatively, for phosphate-based materials, including lithium iron manganese phosphate, the upper charge voltage can be 4.3 V and the discharge voltage 2.0 V. The state of the battery cell is explained below using the example of an upper charge voltage of 3.8 V and a lower discharge voltage of 2.0 V: In the embodiments of the present application, the 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows: The state in which the battery cell has been charged at a constant current of 0.05C up to the upper charging cut-off voltage corresponds to the 100% state of charge (SOC). The state in which the battery cell has been discharged at a constant current of 0.05C up to the lower discharge cut-off voltage corresponds to the 0% state of charge (SOC).

[0151] In some embodiments, the compression density of the negative electrode film layer of the battery cell at 100% state of charge (SOC) is between 1.5 g / cm³. 3 and 1.7 g / cm³ 3 For example, the compression density of the negative electrode film layer of the battery cell at 100% state of charge (SOC) is 1.50 g / cm³. 3 , 1.55 g / cm³ 3 , 1.60 g / cm³ 3 , 1.65 g / cm³ 3 , 1.66 g / cm³ 3 , 1.68 g / cm³ 3 , 1.70 g / cm³ 3 or a range formed by any two of the aforementioned values.

[0152] If the compression density of the negative electrode film layer is within this range, the thickness of the negative electrode film layer is not too great, which promotes the fast charging capability of the battery cell; furthermore, the particle packing of the active material of the negative electrode is not too dense, which reduces the risk of particle crushing and improves the high-temperature cycle performance of the battery cell.

[0153] In some embodiments, the one-sided coating weight of the negative electrode film layer is between 70 mg / 1540.25 mm². 2 and 175 mg / 1540.25 mm 2 For example, the one-sided coating weight of the negative electrode film layer is 70 mg / 1540.25 mm². 2 , 80 mg / 1540.25 mm 2 , 85 mg / 1540.25 mm 2 , 90 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2, 115 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 122 mg / 1540.25 mm 2 125 mg / 1540.25 mm 2 128 mg / 1540.25 mm 2 130 mg / 1540.25 mm 2 140 mg / 1540.25 mm 2 150 mg / 1540.25 mm 2 160 mg / 1540.25 mm 2 170 mg / 1540.25 mm 2 175 mg / 1540.25 mm 2 or a range formed by any two of the aforementioned values. Optionally, the one-sided coating weight of the negative electrode film layer is between 95 mg / 1540.25 mm². 2 and 142 mg / 1540.25 mm 2 .

[0154] If the coating weight of the negative electrode film layer on one side remains within the aforementioned range, this improves the energy density of the battery cell. Furthermore, the migration rate of active ions in the negative electrode film layer is higher, which mitigates the polarization phenomenon during fast charging and improves the fast-charging capability of the battery cell.

[0155] In the embodiments of the present application, the compression density of the negative electrode film layer of a battery cell at 100% state of charge (SOC) has the generally known meaning in this field. Specifically, this means that the battery cell is disassembled at 100% SOC to remove the negative electrode plate and measure the compression density of the negative electrode film layer. For example, a single-sided coated negative electrode plate (in the case of a double-sided coated electrode plate, the coating on one side can be wiped off beforehand) is cut into a small circular piece with an area S1, weighed and recorded as M1, and its thickness H1 is measured. Subsequently, the negative electrode film layer is wiped off the weighed negative electrode plate, the negative electrode current collector is weighed and recorded as M0, and its thickness H0 is measured.The one-sided coating weight of the negative electrode film layer = (weight of the negative electrode plate M1 - 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 and the compression density of the negative electrode film layer = the one-sided coating weight of the negative electrode film layer / the thickness of the negative electrode film layer.

[0156] In some embodiments, the charging capacity per gram of the active material of the negative electrode is between 350 mAh / g and 500 mAh / g. For example, the charging capacity per gram of the active material of the negative electrode is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g, or a range formed by any two of the aforementioned values.

[0157] If the charging capacity per gram of the active material of the negative electrode is in this range, the energy density of the battery cell is relatively high.

[0158] In the embodiments of the present application, the capacity per gram of active material has the generally known meaning in this field and can be tested using generally known equipment and methods. The test methods for first coulomb efficiency and first discharge capacity according to Annex G of the Chinese national standard GB / T 24533-2019 can be used to test the charge capacity per gram of the active material of the negative electrode in a half-button cell at a rate of 0.1 C. A half-button cell is constructed with lithium metal as the negative electrode and a sample electrode containing the aforementioned material as the positive electrode. The half-button cell is charged and discharged at a rate of 0.1 C at 23 °C ± 2 °C on a battery tester or equivalent testing equipment to determine the button cell capacity.The capacity is then divided by the mass of the active material of the electrode plate to obtain the parameter of the charging capacity per gram.

[0159] In some embodiments, the active material of the negative electrode comprises silicon-based materials. Optionally, silicon-based materials may contain at least one of the following: elemental silicon, silicon-carbon composites, or silicon dioxide (SiO₂). x (0 < x ≤ 2). Silicon-carbon composites can be, for example, silicon carbide.

[0160] In some embodiments, the mass fraction of silicon from silicon-based materials in the negative electrode film layer is between 0.3% and 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 formed by any two of the aforementioned values. Optionally, the mass fraction of silicon from silicon-based materials in the negative electrode film layer is between 3% and 6%.

[0161] If the mass fraction of silicon is within this range, the capacity of the active material of the negative electrode can be increased, which improves the energy density of the battery cell. Furthermore, the volume expansion of the silicon during the charging and discharging process is not too great, which maintains the stability of the interface film of the negative electrode and improves the high-temperature cycle performance of the battery cell.

[0162] In some embodiments, the active material of the negative electrode comprises carbon-based materials, with carbon-based materials exhibiting high cycle stability and potentially improving the high-temperature cycle performance of the battery cell.

[0163] Optionally, carbon-based materials contain at least one of synthetic graphite and one of natural graphite.

[0164] In some embodiments, the active material of the negative electrode may, in addition to the carbon-based materials and optional silicon-based materials mentioned above, comprise at least one of the tin-based materials and lithium titanate. Silicon-based materials may include one of the following: elemental tin, tin oxides, and tin alloys.

[0165] The qualitative and quantitative determination of the individual substances or elements in the present application can be carried out using suitable equipment and procedures known to those skilled in the art. Relevant test methods can be found in national and international testing standards, national and international company standards, etc. Furthermore, those skilled in the art can adjust certain test steps or equipment parameters with regard to test accuracy in order to obtain more precise test results. A single test method can be used for the qualitative or quantitative determination, or several test methods can be used in combination for the qualitative or quantitative determination.

[0166] For example, in this application, the X-ray powder diffraction test of negative electrode plates or negative active material can be performed in accordance with JIS / K0131-1996 "General Rules for X-ray diffraction analysis" and a qualitative analysis can be carried out.

[0167] Artificial and natural graphite can be distinguished using SEM cross-sectional images obtained with a scanning electron microscope (SEM). Natural graphite exhibits gaps between its platelet-like structures in SEM cross-sections, while artificial graphite has a dense structure without discernible gaps. Alternatively, they can also be distinguished using X-ray diffraction (XRD) patterns. Natural graphite shows distinct 2H and 3R phases in its XRD pattern, while artificial graphite exhibits only the 2H phase.

[0168] As in Fig.As shown in Figure 13, the negative electrode film layer 141 of the negative electrode plate 14 in the embodiments of this application comprises at least one film layer, which may consist of a single film layer or of at least two film layers. Optionally, the negative electrode film layer 141 comprises at least two film layers.

[0169] If the negative electrode film layer 141 is a single layer, the active material of the negative electrode in the negative electrode film layer 141 comprises carbon-based materials and optionally silicon-based materials.

[0170] If the negative electrode film layer 141 consists of at least two film layers, the active material of the negative electrode in the negative electrode film layer 141 comprises carbon-based materials and optionally silicon-based materials. The negative electrode film layer 141 can comprise two, three, four, or even more film layers.

[0171] In some embodiments, the negative electrode film layer 141 comprises a first negative electrode film layer 1411 and a second negative electrode film layer 1412, wherein the first negative electrode film layer 1411 is arranged on the surface of the negative electrode current collector 142, wherein the active material of the negative electrode in the first negative electrode film layer 1411 comprises carbon-based materials, and wherein the second negative electrode film layer 1412 is attached to the side of the first negative electrode film layer 1411 opposite the negative electrode current collector 142, and wherein the active material of the negative electrode in the second negative electrode film layer 1412 also comprises carbon-based materials.The interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 can be regular or irregular, with an irregular interface also being optional; alternatively, there may be no apparent interface between the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0172] The negative electrode film layer 141 comprises at least two film layers, and the multilayer coating can improve the fast-charging capability of the battery cell. In particular, if the porosity of the first negative electrode film layer 1411 and the second negative electrode film layer 1412 differs, this can also improve the fast-charging capability of the battery cell.

[0173] In some embodiments, at least one of the first negative electrode film layer 1411 and the second negative electrode film layer 1412 comprises silicon-based materials.

[0174] Optionally, the first negative electrode film layer 1411 can also contain silicon-based materials.

[0175] Optionally, the second negative electrode film layer 1412 can also contain silicon-based materials.

[0176] For example, the first negative electrode film layer 1411 contains carbon-based and silicon-based materials, and the second negative electrode film layer 1412 contains carbon-based and silicon-based materials. When both the first negative electrode film layer 1411 and the second negative electrode film layer 1412 contain silicon-based materials, the energy density of the battery cell is improved. Furthermore, the addition of carbon-based materials to each layer reduces the volume expansion of the silicon-based materials, thereby making the negative electrode interface more stable and improving high-temperature cycle performance. Since each layer contains silicon-based materials, the coating thickness is relatively small, which shortens the lithium-ion transport path and improves fast-charging capability.

[0177] Alternatively, the first negative electrode film layer 1411 contains carbon-based and silicon-based materials, and the second negative electrode film layer 1412 contains carbon-based materials. If the first negative electrode film layer 1411 contains silicon-based materials and the second negative electrode film layer 1412 does not contain silicon-based materials, the second negative electrode film layer 1412 can reduce 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.

[0178] Alternatively, the first negative electrode film layer 1411 contains carbon-based materials, and the second negative electrode film layer 1412 contains carbon-based and silicon-based materials. In the case that the second negative electrode film layer 1412 contains silicon-based materials, it is advantageous to create more film pores by changing the volume of the silicon-based materials, thereby improving the liquid-phase transport capability of lithium ions and increasing the dynamic performance of the battery cell.

[0179] In the case that the negative electrode film layer 141 consists of at least two film layers, the cross-sectional shapes of the negative electrode film layer 141 can be the same or similar at different locations along the thickness direction X of the negative electrode film layer 141, or of course, they can also be different. If the electrode assembly has a stacked structure, the thickness direction of the battery cell can run parallel to the thickness direction of the electrode assembly and to the thickness direction X of the negative electrode film layer 141.

[0180] Along the thickness direction X of the negative electrode film layer 141, the electrode film layer 141 is divided into three regions: a first region 141a, a third region 141c, and a second region 141b, in that order. The first region 141a is the portion of the negative electrode film layer 141 that is closest to the negative electrode current collector 142 along the thickness direction X, and the first region 141a is one-third as thick as the negative electrode film layer 141. The second region 141b is the portion of the negative electrode film layer 141 that is furthest away from the negative electrode current collector 142 along the thickness direction X, and the second region 141b is one-third as thick as the negative electrode film layer 141.

[0181] The cross-sectional shapes of the first area 141a and the second area 141b can be the same or similar, or of course different. The cross-sectional shapes of the first area 141a and the third area 141c can be the same or similar, or of course different. The cross-sectional shapes of the second area 141b and the third area 141c can be the same or similar, or of course different.

[0182] There may be clear layer boundaries between the first region 141a, the second region 141b, and the third region 141c, or there may be no clear layer boundary. For example, the first negative electrode film layer 1411 comprises a first region 141a, the second negative electrode film layer 1412 comprises a second region 141b, and the third region 141c may either be part of the first negative electrode film layer 1411, or the third region 141c may be part of the second negative electrode film layer 1412, or the third region 141c may be part of both the first negative electrode film layer 1411 and the second negative electrode film layer 1412.

[0183] Optionally, the average particle size of the carbon-based material in the first area 141a can be greater than or equal to the average particle size of the carbon-based material in the second area 141b. Furthermore, optionally, the average particle size of the carbon-based material in the first area 141a can be larger than the average particle size of the carbon-based material in the second area 141b, which promotes the rapid migration of lithium ions from the second area 141b to the first area 141a and improves the fast-charging capability of the battery cell. Of course, the average particle size of the carbon-based material in the first area 141a can also be smaller than the average particle size of the carbon-based material in the second area 141b.

[0184] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 can be greater than or equal to the average particle size of the carbon-based material in the second negative electrode film layer 1412. Furthermore, optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 can be larger than the average particle size of the carbon-based material in the second negative electrode film layer 1412.

[0185] The difference in particle size between the first negative electrode film layer 1411 and the second negative electrode film layer 1412 can improve the fast-charging capability of the battery cell. More precisely, during the fast-charging process, the overpotential in the second negative electrode film layer 1412 is typically high, with this second negative electrode film layer 1412 being the main bottleneck for fast charging. However, in the embodiments of the present application, the particle size of the second negative electrode film layer 1412 is relatively small, which shortens the transport path for solid-state lithium ions, improves the fast-charging capability, and reduces the problem of lithium deposition on the surface of the negative electrode plate 14.

[0186] Optionally, the average particle size of the carbon-based material in the first region 141a is between 10 µm and 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 defined by any two of these values. If the average particle size of the carbon-based material in the first region 141a is within this range, it can, on the one hand, shorten the transport path for solid-state lithium ions and improve fast charging capability; on the other hand, the material is less prone to agglomeration during the manufacturing process, which can improve the material's stability.

[0187] Optionally, the average particle size of the carbon-based material in the first negative electrode film layer 1411 is between 10 µm and 20 µm. If the average particle size of the carbon-based material in the first negative electrode film layer 1411 is within this range, this can, on the one hand, shorten the transport path for solid-state lithium ions and improve the fast-charging capability, and on the other hand, the material is less prone to agglomeration during the manufacturing process, which can improve the material's stability.

[0188] Optionally, the average particle size of the carbon-based material in the second region 141b is between 5 µm and 12 µm, for example, 5 µm, 8 µm, 10 µm, 10.5 µm, 11 µm, 11.5 µm, 12 µm, or a range formed by any two of these values. If the average particle size of the carbon-based material in the second negative electrode film layer 1412 is within this range, it can improve the fast-charging capability of the battery cell and the stability of the material.

[0189] Optionally, the average particle size of the carbon-based material in the second negative electrode film layer 1412 is between 5 µm and 12 µm.If the average particle size of the carbon-based material in the second negative electrode film layer 1412 lies within this range, this can, firstly, shorten the transport path for solid-state lithium ions and improve the fast-charging capability; secondly, the material is less prone to agglomeration during the manufacturing process, which can improve the stability of the material; and thirdly, the combination of the active material of the negative electrode in the second electrode film layer 1412 and the active material of the negative electrode in the first electrode film layer 1411, which lies within the range of the above-mentioned average particle size, promotes the formation of a gradient in pore size differences between the second electrode film layer 1412 and the first electrode film layer 1411, which reduces the tortuosity of lithium ion transport and improves the fast-charging capability of the battery cell.

[0190] For example, the carbon-based material in the first region 141a contains at least one synthetic and one natural graphite, and the carbon-based material in the second region 141b contains synthetic graphite. For example, the active material of the negative electrode in the first region 141a contains silicon-based materials, synthetic graphite, and natural graphite, and the active material of the negative electrode in the second region 141b contains silicon-based materials and synthetic graphite.

[0191] For example, the carbon-based material in the first negative electrode film layer 1411 contains at least one synthetic graphite and one natural graphite, and the carbon-based material in the second negative electrode film layer 1412 contains synthetic graphite. For example, the active material of the negative electrode in the first negative electrode film layer 1411 contains silicon-based materials, synthetic graphite, and natural graphite, and the active material of the negative electrode in the second negative electrode film layer 1412 contains silicon-based materials and synthetic graphite.

[0192] In the embodiments of the present application, the average particle size of the carbon-based material in the first region 141a and in the second region 141b has a generally known meaning in this field and can be tested using generally known equipment and methods. For example, the negative electrode plate 14 is used as a sample, and its cross-section is polished along the thickness direction X of the negative electrode film layer 141, for example by argon ion beam polishing. The cross-section is recorded with a scanning electron microscope (SEM) to obtain an SEM cross-section. The particle size of the carbon-based material in the SEM cross-section is measured, and the average particle size of the carbon-based material is calculated based on the number of particles measured.

[0193] In some embodiments, the negative electrode film layer may optionally contain a conductive material for the negative electrode. The embodiments of the present application are not subject to any particular restrictions regarding the type of conductive material for the negative electrode. For example, the conductive material for the negative electrode may comprise at least one of the following: conductive carbon and carbon nanotubes. In some embodiments, the mass fraction of the conductive material for the negative electrode is ≤5%, based on the total weight of the negative electrode film layer.

[0194] The conductive medium for the negative electrode can compensate for the insufficient conductivity of silicon-based materials, which improves the conductivity of the negative electrode film layer and helps to improve the dynamic performance of the battery cell and increase the fast-charging capability of the battery cell.

[0195] Optionally, the mass fraction of conductive carbon in the negative electrode film layer is between 0.4% and 0.7%, for example 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, or a range formed by any two of the aforementioned values.

[0196] Optionally, the mass fraction of carbon nanotubes in the negative electrode film layer is between 0.1% and 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 formed by any two of the aforementioned values. Optionally, the mass fraction of carbon nanotubes in the negative electrode film layer is between 0.1% and 0.5%.

[0197] In some embodiments, the negative electrode film layer may optionally contain a binder for the negative electrode. In some embodiments, the mass fraction of the binder for the negative electrode is ≤5%, based on the total weight of the negative electrode film layer.

[0198] In some embodiments, the negative electrode film layer may optionally contain additional excipients. For example, these excipients may include thickeners, dispersants, etc., such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass fraction of these additional excipients for the negative electrode is ≤2%, based on the total weight of the negative electrode film layer.

[0199] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be made of at least one of the following materials: copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy. The composite current collector can comprise a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal in the metal material layer can comprise at least one of the following: copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer substrate layer can contain at least one of the following: polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0200] In some embodiments, the thickness of the negative electrode current collector is between 4 µm and 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 formed by any two of the aforementioned values.

[0201] In some embodiments, the negative electrode plate further comprises a negative electrode flap connected to the negative electrode current collector, and the thickness of the negative electrode flap is between 4 µm and 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 formed by any two of these values. Having the thickness of the negative electrode flap within this range is advantageous for improving the current-carrying capacity and enhances the fast-charging capability of the battery cell.

[0202] The negative electrode film layer is typically produced by applying a negative electrode paste to the negative electrode current collector, followed by drying and cold rolling. The negative electrode paste is typically prepared by dispersing and thoroughly mixing negative active material, optional conductor, optional binder, and other optional excipients in a solvent. N-methylpyrrolidone (NMP) or deionized water can be used as the solvent, but these are not the only options.

[0203] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. In some embodiments, the negative electrode plate of the embodiments in the present application, for example, additionally comprises a negative conductive layer, which is embedded between the negative electrode current collector and the negative electrode film layer and arranged on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate of the embodiments in the present application additionally comprises a protective layer that covers the surface of the negative electrode film layer. Positive electrode plate

[0204] In some embodiments, the battery cell also includes a positive electrode plate.

[0205] The coating section of the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer, which is arranged on at least one side of the positive electrode current collector and contains active material of the positive electrode. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is arranged on one or both of these opposing surfaces of the positive electrode current collector.

[0206] If the battery cell comprises a stacked electrode assembly, the longitudinal direction of the battery cell is parallel to the longitudinal direction of the positive electrode plate. The dimension of the battery cell along the longitudinal direction can be understood as its length, and the dimension of the positive electrode plate along the longitudinal direction can be understood as its length. The lateral direction of the battery cell is parallel to the lateral direction of the positive electrode plate. The dimension of the battery cell along the lateral direction can be understood as its width, and the dimension of the positive electrode plate along the lateral direction can be understood as its width.

[0207] In some embodiments, the dimensions of the positive electrode film layer can be considered identical to the dimensions of the coating section of the positive electrode plate. The dimension of the positive electrode film layer along the longitudinal direction of the battery cell is between 265 mm and 1200 mm, for example 265 mm, 350 mm, 450 mm, 550 mm, 650 mm, 750 mm, 850 mm, 950 mm, 1050 mm, 1150 mm, 1200 mm, or a range formed by any two of the aforementioned values.

[0208] In some embodiments, the dimension of the positive electrode film layer along the longitudinal direction of the battery cell is equal to the first dimension, and the dimension of the positive electrode film layer along the lateral direction of the battery cell is equal to the second dimension. The ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5 and can be chosen in the range of 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 formed by any two of the aforementioned values.

[0209] For example, the dimension of the positive electrode film layer along the longitudinal direction of the battery cell is between 265 mm and 655 mm, and the ratio of the dimension of the positive electrode film layer along the longitudinal direction of the battery cell to the dimension of the positive electrode film layer along the transverse direction of the battery cell is greater than 1 and less than or equal to 12.5 and can be selected in the range of 1.25 to 12.5. If the active material of the positive electrode in the positive electrode film layer contains lithium phosphate, the conductivity of lithium phosphate is relatively low, which is why the dimension of the positive electrode film layer should not be too large.If the dimensions of the positive electrode film layer are within this range, the electron transport path is not too long, the internal resistance is relatively low, and heat generation is lower, which improves the fast charging capability and the high-temperature cycle performance of the high-energy-density battery cell.

[0210] Optionally, the dimension of the positive electrode film layer along the longitudinal direction of the battery cell is between 400 mm and 600 mm, and the ratio of the dimension of the positive electrode film layer along the longitudinal direction of the battery cell to the dimension of the positive electrode film layer along the transverse direction of the battery cell is 3.5 to 8.

[0211] In some embodiments, the dimension of the negative electrode film layer along the first direction is larger than the dimension of the positive electrode film layer along the first direction, so that almost all lithium ions released from the positive electrode film layer can be incorporated into the negative electrode film layer. This reduces the risk of lithium deposition from the negative electrode and improves the operational reliability of the battery cell. Of course, the dimension of the negative electrode film layer along the first direction can also be smaller than or equal to the dimension of the positive electrode film layer along the first direction.

[0212] Optionally, the dimension of the negative electrode film layer along the first direction is larger than the dimension of the positive electrode film layer along the first direction, wherein the difference between the dimension of the negative electrode film layer along the first direction and the dimension of the positive electrode film layer along the first direction is between 5 mm and 11 mm, for example 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or a range formed by any two of the aforementioned values.

[0213] In some embodiments, the dimension of the negative electrode film layer along the second direction is larger than the dimension of the positive electrode film layer along the second direction, so that almost all lithium ions released from the positive electrode film layer can be incorporated into the negative electrode film layer. This reduces the risk of lithium deposition from the negative electrode and improves the operational reliability of the battery cell. Of course, the dimension of the negative electrode film layer along the second direction can also be smaller than or equal to the dimension of the positive electrode film layer along the second direction.

[0214] Optionally, the dimension of the negative electrode film layer along the second direction is larger than the dimension of the positive electrode film layer along the second direction, wherein the difference between the dimension of the negative electrode film layer along the second direction and the dimension of the positive electrode film layer along the second direction is between 5 mm and 11 mm, for example 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm or a range formed by any two of the aforementioned values.

[0215] The first direction is perpendicular to the second direction. The first direction can be parallel to the longitudinal direction of the battery cell, or it can be parallel to the transverse direction of the battery cell. If the first direction is parallel to the longitudinal direction of the battery cell, the second direction is parallel to the transverse direction of the battery cell. Conversely, if the first direction is parallel to the transverse direction of the battery cell, the second direction is parallel to the longitudinal direction of the battery cell.

[0216] In some embodiments, the separator's dimension along the first direction is larger than the dimension of the negative electrode film layer along the first direction, so that the separator can effectively insulate the positive and negative electrodes, reducing the risk of a short circuit and improving the battery cell's operational reliability. Of course, the separator's dimension along the first direction can also be smaller than or equal to the dimension of the negative electrode film layer along the first direction.

[0217] Optionally, the dimension of the separator along the first direction is larger than the dimension of the negative electrode film layer along the first direction, wherein the difference between the dimension of the separator along the first direction and the dimension of the negative electrode film layer along the first direction is between 6 mm and 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 formed by any two of the aforementioned values.

[0218] In some embodiments, the separator's dimension along the second direction is larger than the dimension of the negative electrode film layer along the second direction, so that the separator can effectively insulate the positive and negative electrodes, reducing the risk of a short circuit and improving the battery cell's operational reliability. Of course, the separator's dimension along the second direction can also be smaller than or equal to the dimension of the negative electrode film layer along the second direction.

[0219] Optionally, the dimension of the separator along the second direction is larger than the dimension of the negative electrode film layer along the second direction, wherein the difference between the dimension of the separator along the second direction and the dimension of the negative electrode film layer along the second direction is between 6 mm and 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 formed by any two of the aforementioned values.

[0220] As in Fig. As shown in Figure 14, it is assumed for illustration that the first direction is parallel to the longitudinal direction Z, the second direction is parallel to the lateral direction Y, the first electrode plate 11 is the positive electrode plate and the second electrode plate 12 is the negative electrode plate.

[0221] The dimension of the positive electrode film layer of the first electrode plate 11 along the longitudinal direction Z is the length of the positive electrode film layer of the first electrode plate 11, the dimension of the negative electrode film layer of the second electrode plate 12 along the longitudinal direction Z is the length of the negative electrode film layer of the second electrode plate 12, and the dimension of the separator 13 along the longitudinal direction Z is the length of the separator 13.

[0222] The difference between the length of the negative electrode film layer of the second electrode plate 12 and the length of the positive electrode film layer of the first electrode plate 11 is called OH. 11 described. As in Fig. As shown in Figure 14, the negative electrode film layer extends beyond the positive electrode film layer on both sides along the longitudinal direction Z, with the excess length on each side being OH. 11 / 2. Of course, the negative electrode film layer can also extend beyond the positive electrode film layer on only one side along the longitudinal direction Z.

[0223] The difference between the length of the separator 13 and the length of the negative electrode film layer of the second electrode plate 12 is called OH. 21 described. As in Fig. As shown in 14, the separator 13 projects beyond the negative electrode film layer on both sides along the longitudinal direction Z, with the excess length on each side being OH 21 / 2. Naturally, the separator 13 can only extend beyond the negative electrode film layer on one side along the longitudinal direction Z.

[0224] The dimension of the positive electrode film layer of the first electrode plate 11 along the lateral direction Y is the width of the positive electrode film layer of the first electrode plate 11, the dimension of the negative electrode film layer of the second electrode plate 12 along the lateral direction Y is the width of the negative electrode film layer of the second electrode plate 12, and the dimension of the separator 13 along the lateral direction Y is the width of the separator 13.

[0225] The difference between the width of the negative electrode film layer of the second electrode plate 12 and the width of the positive electrode film layer of the first electrode plate 11 is called OH. 12 described. As in Fig. As shown in 14, the negative electrode film layer extends beyond the positive electrode film layer on both sides along the width direction Y, with the excess length on each side being OH 12 / 2. Of course, the negative electrode film layer can also extend beyond the positive electrode film layer on only one side along the width direction Y.

[0226] The difference between the width of the separator 13 and the width of the negative electrode film layer of the second electrode plate 12 is called OH. 22 described. As in Fig. As shown in 14, the separator 13 projects beyond the negative electrode film layer on both sides along the width direction Y, with the excess length on each side OH 22 / 2. Naturally, the separator 13 can only extend beyond the negative electrode film layer on one side along the width direction Y.

[0227] In some embodiments, the compression density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is between 2.50 g / cm³. 3 and 2.80 g / cm² 3For example, the compression density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm³. 3 , 2.52 g / cm³ 3 , 2.55 g / cm³ 3 , 2.56 g / cm³ 3 , 2.57 g / cm³ 3 , 2.58 g / cm³ 3 , 2.60 g / cm³ 3 , 2.62 g / cm³ 3 , 2.65 g / cm³ 3 , 2.68 g / cm³ 3 , 2.70 g / cm³ 3 , 2.75 g / cm³ 3 , 2.80 g / cm³ 3 or a range formed by any two of the aforementioned values.

[0228] If the compression density of the positive electrode film layer lies within this range, it is advantageous for improving the energy density of the battery cell; and since the active material of the positive electrode is more densely packed in the positive electrode film layer, the contact resistance between the particles is lower, which can further reduce the resistance of the electrode plate and thus reduce heat generation during fast charging. Consequently, adjusting the compression density of the positive electrode film layer to a reasonable range allows the battery cell to exhibit both high energy density and good fast-charging capability.

[0229] In some embodiments, the one-sided coating weight of the positive electrode film layer is between 150 mg / 1540.25 mm². 2 and 370 mg / 1540.25 mm 2For example, the one-sided coating weight of the positive electrode film layer is 150 mg / 1540.25 mm². 2 , 200 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 350 mg / 1540.25 mm 2 , 370 mg / 1540.25 mm 2 or a range formed by any two of the aforementioned values. Optionally, the one-sided coating weight of the positive electrode film layer is between 200 mg / 1540.25 mm². 2 and 300 mg / 1540.25 mm 2 .

[0230] If the one-sided coating weight of the positive electrode film layer is in this range, the heat generation per unit area of ​​the positive electrode film layer is not too high, which can mitigate the polarization phenomenon during fast charging and also improve the energy density and fast-charging capability of the battery cell.

[0231] In the embodiments of the present application, the compression density of the positive electrode film layer of a battery cell at 100% state of charge (SOC) has the generally known meaning in this field. Specifically, this means that the battery cell is disassembled at 100% SOC to remove the positive electrode plate and measure the compression density of the positive electrode film layer. For example, a single-sided coated positive electrode plate (in the case of a double-sided coated electrode plate, the coating on one side can be wiped off beforehand) is cut into a small circular piece with an area S1, weighed and recorded as M1, and its thickness H1 is measured. Subsequently, the positive electrode film layer is wiped off the weighed positive electrode plate, the positive electrode current collector is weighed and recorded as M0, and its thickness H0 is measured.The one-sided coating weight of the positive electrode film layer = (weight of the positive electrode plate M1 - weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode plate H1 - the thickness of the positive electrode current collector H0 and the compression density of the positive electrode film layer = the one-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0232] In some embodiments, the charging capacity per gram of the active material of the positive electrode is between 150 mAh / g and 170 mAh / g. For example, the charging capacity per gram of the active material of the negative electrode is 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range formed by any two of the aforementioned values.

[0233] If the charging capacity per gram of the active material of the positive electrode is in this range, the energy density of the battery cell is relatively high.

[0234] In the embodiments of the present application, the capacity per gram of the active material of the positive electrode has the generally known meaning in this field and can be determined using the test method for determining the capacity per gram of the active material of the negative electrode.

[0235] In some embodiments, the active material of the positive electrode contains lithium phosphate. Lithium phosphates can have an olivine structure, which is structurally stable during charging and discharging and can improve the cycle life of the battery cell.

[0236] Optionally, the active material of the positive electrode can also comprise lithium-containing transition metal oxides. Examples of lithium-containing transition metal oxides include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0237] The lithium phosphate with an olivine structure can be either unmodified lithium phosphate or a material modified by coating. For example, the surface of the lithium phosphate can be coated with a carbon-containing material. This carbon-containing material acts as a coating on the surface of the lithium phosphate, thereby improving the conductivity of the lithium phosphate, reducing the powder resistance of the material, promoting the migration rate of lithium ions, optimizing the fast-charging capability of the battery cell, and reducing heat generation in the battery cell.

[0238] In some embodiments, the lithium phosphate comprises compounds of the general formula Li x1 A y1 Me a M3P 1-c X c Y z, where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3 and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5 and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A comprises one or more of the elements Na, K and Mg, Me comprises one or more of the elements Mn, Fe, Co and Ni, M comprises one or more of the elements 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 Lithium phosphates comprise X, one or more of the elements Cl, C, and N, and Y comprises one or more of the elements O and F. Lithium phosphates exhibit excellent cycle stability, which is advantageous for improving the high-temperature cycle performance of the battery cell.

[0239] For example, lithium phosphates comprise one or more of the following substances: LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process of the battery cell, active ions such as lithium are stored, released, and consumed. The molar content of lithium varies in different discharge states. When listing the active material of the positive electrode, such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the stated molar content of lithium refers to the initial state of the material, i.e., the state before installation in the cell. After the active material of the positive electrode has been integrated into the battery system and has undergone charge-discharge cycles, the molar content of lithium may change. In the embodiments of the present application, when listing the active material of the positive electrode, such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the stated molar content of oxygen (O) refers only to the theoretical value.The release of oxygen from the crystal lattice leads to a change in the molar content of oxygen (O). In practice, the molar content of oxygen (O) is subject to fluctuations. All these matters fall within the scope of protection of this application.

[0240] In the embodiments of the present application, the elemental content of the active material of the positive electrode has a generally known significance in this field and can be tested using generally known instruments and methods. For example, it can be analyzed according to EPA 6010D-2014 by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After the battery cell has been discharged to 0% state of charge (SOC), the positive electrode plate is removed, cleaned with dimethyl carbonate (DMC), dried, and then freed from impurities by high-temperature calcination. Subsequently, 0.4 g of the active material of the positive electrode is weighed out and mixed with 10 ml of aqua regia (50% concentration). The mixture is then placed on a hot plate heated to 180 °C for 30 minutes.After digestion on the hot plate, the volume is adjusted to 100 ml and a quantitative analysis is performed using the standard curve method.

[0241] In some embodiments, the lithium phosphate is in particulate form, and the volume mean particle size Dv50 of the lithium phosphate is between 1 µm and 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 formed by any two of the aforementioned values.

[0242] If the lithium phosphate meets the above conditions, its particle size is relatively small, the insertion / removal path of the lithium ions in the lithium phosphate is short, and the heat generation is low; furthermore, the particle size of the aforementioned lithium phosphate is not too small, which minimizes agglomeration during processing and manufacturing, thus stabilizing the performance of the lithium phosphate.

[0243] In some embodiments, the positive electrode film layer further comprises one or more of the following materials: lithium-containing ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. These materials can be used as lithium supplements to replenish lithium ions in the positive electrode film layer, compensate for irreversible lithium ion losses in the system, increase capacity, and boost the energy density of the battery cell.

[0244] In some embodiments, the mass fraction of the lithium supplement, based on the total weight of the positive electrode film layer, is between 0.1% and 5%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range formed by any two of these values. When the lithium supplement is used in this mass fraction range, it can supply the positive electrode film layer with additional lithium ions and thus compensate for irreversible lithium ion losses in the system. Furthermore, the mass fraction of the lithium supplement is not too high, so the discharge capacity per gram of the positive electrode remains high and the energy density is not substantially reduced.

[0245] In some embodiments, the volume-average particle size Dv50 of the lithium supplement is larger than the volume-average particle size Dv50 of the lithium phosphate. Combining particles of different sizes achieves a uniform dispersion and improves the distribution uniformity of the lithium supplement.

[0246] In some embodiments, the volume-average particle size Dv50 of the lithium supplement is between 8 µm and 10 µm, for example 8 µm, 8.5 µm, 9 µm, 9.5 µm, 10 µm or a range formed by any two of the aforementioned values.

[0247] In the embodiments of the present application, the volume-average particle size Dv50 has the generally known meaning in this field. The volume-average particle size Dv50 denotes the particle size that corresponds to 50% of the volume distribution. It can be determined using generally known instruments and methods. After the new battery cell has been discharged to 0% state of charge (SOC), the positive electrode plate and the positive electrode current collector are removed to obtain the positive electrode film layer. The positive electrode film layer is immersed in N-methylpyrrolidone (NMP) to wash out the binder in the positive electrode film layer. The active material of the positive electrode, or the lithium additive, is taken as a sample. After drying the sample, the volume-average particle size Dv50 is determined according to the test standard GB / T 19077-2016 using a Mastersizer 2000E laser particle size analyzer.

[0248] In some embodiments, the positive electrode film layer may optionally contain a conductive material for the positive electrode. For example, the conductive material for the positive electrode may contain at least one of the following: superconducting carbon, conductive graphite, carbon black, carbon black, Ketjen black, carbon nanoparticles, carbon nanotubes, graphene, or carbon nanofibers. In some embodiments, the mass fraction of the conductive material for the positive electrode is ≤ 5%, based on the weight of the positive electrode film layer.

[0249] In some embodiments, the positive electrode film layer may optionally contain a binder for the positive electrode. The embodiments of the present application are not subject to any particular restrictions regarding the type of binder for the positive electrode. For example, the binder for the positive electrode may comprise at least one of the following substances: polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene propylene terpolymer, vinylidene fluoride-hexafluoropropylene tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, the mass fraction of the binder for the positive electrode is ≤ 5%, based on the weight of the positive electrode film layer.

[0250] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be made of at least one of the following materials: aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector can comprise a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal in the metal material layer can comprise at least one of the following: aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer substrate layer can contain at least one of the following: polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0251] In some embodiments, the thickness of the positive electrode current collector is between 10 µm and 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 formed by any two of the aforementioned values.

[0252] In some embodiments, the positive electrode plate further comprises a positive electrode tab connected to the positive electrode current collector, and the thickness of the positive electrode tab is between 10 µm and 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 formed by any two of these values. Having the thickness of the positive electrode tab within this range is advantageous for improving the current-carrying capacity and enhances the fast-charging capability of the battery cell.

[0253] The positive electrode film layer is typically produced by applying a positive electrode paste to the positive electrode current collector, followed by drying and cold rolling. The positive electrode paste is typically prepared by dispersing and thoroughly mixing positive active material, optional conductor, optional binder, and other components in a solvent. N-methylpyrrolidone (NMP) can be used as the solvent, but is not limited to this.

[0254] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. In some embodiments, the positive electrode plate of the embodiments in the present application, for example, additionally comprises a positive conductive layer, which is embedded between the positive electrode current collector and the positive electrode film layer and arranged on the surface of the positive electrode current collector. In some other embodiments, the positive electrode plate of the embodiments in the present application additionally comprises a protective layer that covers the surface of the positive electrode film layer. electrolyte

[0255] During the charging and discharging process of a battery cell, active ions such as lithium ions move back and forth between the positive and negative electrode plates, being incorporated into and released from the electrode materials. The electrolyte acts as the medium for this ion transport between the positive and negative electrode plates. The electrolyte consists of an organic solvent and an electrolyte salt.

[0256] In some embodiments, the electrolyte has a conductivity of 10.5 mS / cm to 13.5 mS / cm at room temperature. For example, the conductivity of the electrolyte at room temperature is 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, or a range formed by any two of the aforementioned values.

[0257] If the conductivity of the electrolyte at room temperature, for example 25 °C, is in this 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 capability of the battery cell.

[0258] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, for example 25 °C, is the ionic conductivity, which can be determined using generally known equipment and methods, for example according to the industry standard HG-T 4067-2015.

[0259] In some embodiments, the viscosity of the electrolyte at room temperature is between 1.5 mPa·s and 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 formed by any two of the aforementioned values.

[0260] If the viscosity of the electrolyte at room temperature, for example 25 °C, is in this 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 capability of the battery cell.

[0261] In the embodiments of the present application, the viscosity of the electrolyte has the generally known meaning in this field and can be determined using generally known equipment and methods, for example according to GB / T10247-2008.

[0262] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature, for example 25 °C. 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 formed by any two of the aforementioned values.

[0263] If the density of the electrolyte is in this 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 capability of the battery cell.

[0264] In the embodiments of the present application, the density of the electrolyte has the generally known meaning in this field and can be determined using generally known equipment and methods, for example according to GB / T 2013-2010.

[0265] In some embodiments, the organic solvent comprises a chain carboxylic acid ester solvent.

[0266] Optionally, the mass fraction of the linear carboxylic acid ester solvent in the electrolyte is between 5% and 35%. For example, the mass fraction of the linear carboxylic acid ester solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, or a range formed by any two of these values. Optionally, the mass fraction of the linear carboxylic acid ester solvent in the electrolyte is between 8% and 20%.

[0267] If the mass fraction of the linear carboxylic acid ester solvent is within this range, the viscosity of the electrolyte is lower. This improves the electrolyte's conductivity, reduces the internal resistance of the battery cell, and promotes rapid lithium ion migration. Furthermore, the electrolyte is compatible with the silicon-containing negative electrode, effectively reducing gas formation within the battery cell, minimizing the impact on the electrode-side interface film, and improving the battery cell's fast-charging capability and high-temperature cycle performance.

[0268] In some embodiments, the linear carboxylic acid ester solvent contains compounds represented by formula I:

[0269] In Formula I, the following applies: R1 contains hydrogen atoms, C1 to C5 alkyl groups or C1 to C5 haloalkyl groups, R2 contains C1 to C5 alkyl groups or C1 to C5 haloalkyl groups.

[0270] The linear carboxylic acid ester solvent exhibits high conductivity, which is advantageous for improving the fast-charging capability of the battery cell.

[0271] Optionally, R1 contains hydrogen atoms, C1 to C3 alkyl groups, or C1 to C3 haloalkyl groups. Furthermore, R1 optionally contains hydrogen atoms, halogen atoms, C1 to C2 alkyl groups, or C1 to C2 haloalkyl groups.

[0272] Optionally, R2 contains C1 to C3 alkyl groups or C1 to C3 haloalkyl groups. Furthermore, R2 optionally contains C1 to C2 alkyl groups or C1 to C2 haloalkyl groups.

[0273] In the embodiments mentioned above, haloalkyl groups comprise one or more of the following groups: fluoroalkyl groups, chloroalkyl groups, bromoalkyl groups and iodoalkyl groups; optionally, the haloalkyl groups also include fluoroalkyl groups.

[0274] For example, the linear carboxylic acid ester solvent contains one or more compounds of formula I-1 to I-8.

[0275] In some embodiments, the organic solvent comprises carbonate solvents.

[0276] The combined use of the carbonate solvent and the linear carboxylic acid ester solvent improves the conductivity of the electrolyte, which promotes the migration of lithium ions.

[0277] Optionally, the mass fraction of the carbonate solvent in the electrolyte is between 65% and 75%. For example, the mass fraction of the carbonate solvent is 65%, 70%, 75%, or a range formed by any two of the aforementioned values.

[0278] If the mass fraction of the carbonate solvent and the linear carboxylic acid ester solvent meets the aforementioned conditions, the stability of the electrolyte can be improved and its high-temperature gas formation reduced.

[0279] For example, the carbonate solvent contains one or more of the following substances: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0280] In the embodiments of the present application, the electrolyte salt comprises a lithium salt, wherein the lithium salt comprises one or more of the following substances: lithium fluorosulfonylimide and lithium hexafluorophosphate. Optionally, the lithium salt contains lithium fluorosulfonylimide and lithium hexafluorophosphate.

[0281] Lithium hexafluorophosphate can decompose, forming hydrofluoric acid (HF). The side reaction between the hydrofluoric acid and the active material of the negative electrode can lead to increased gas formation during storage at high temperatures. The combined use of lithium hexafluorophosphate and lithium fluorosulfonylimide can reduce the hydrofluoric acid content, slow down the side reaction at the negative electrode interface, and decrease gas formation during storage at high temperatures. This combined use increases the lithium ion migration number, improves the lithium ion conductivity of the electrolyte, and optimizes the high-temperature cycle performance and fast-charging capability of the battery cell.

[0282] For example, lithium fluorosulfonylimide comprises one or more of the following substances: lithium trifluorosulfonylimide and lithium difluorosulfonylimide, optionally also lithium difluorosulfonylimide.

[0283] In some embodiments, the mass fraction of the lithium salt, based on the weight of the electrolyte, is greater than 0 and at most 18%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a range formed by any two of these values. Optionally, the mass fraction of the lithium salt is between 10% and 18%. Furthermore, optionally, the mass fraction of the lithium salt is between 10% and 15%. The mass fraction of a lithium salt is equal to the sum of the mass fractions of its components. For example, if the lithium salt is lithium difluorosulfonylimide and lithium hexafluorophosphate, then the mass fraction of the lithium salt is the sum of the mass fractions of lithium difluorosulfonylimide and lithium hexafluorophosphate.

[0284] For example, the sum of the mass fractions of lithium difluorosulfonylimide and lithium hexafluorophosphate is greater than 0 and less than or equal to 18% and can be chosen in the range of 10% to 18%.

[0285] If the mass fraction of the lithium salt is in this range, this can, on the one hand, increase the lithium ion migration number of the electrolyte, improve the lithium ion conductivity of the electrolyte and increase the fast charging capability of the battery cell; on the other hand, this can reduce the side reactions at the negative electrode and improve the high-temperature cycle performance of the battery cell.

[0286] Optionally, the sum of the mass fractions of lithium difluorosulfonylimide and lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and can be selected within the range of 10% to 18%. If the mass fraction of lithium salt is within this range, it can improve the fast-charging capability, high-temperature cycle performance, and operational reliability of the battery cell.

[0287] In some embodiments, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, based on the weight of the electrolyte, is between 0.2 and 0.8, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or a range formed by any two of these values. Optionally, the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate is between 0.3 and 0.8.

[0288] If the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide adheres to the above-mentioned range, this can, on the one hand, increase the lithium ion migration number of the electrolyte, improve the lithium ion conductivity of the electrolyte and increase the fast-charging capability of the battery cell; on the other hand, this can reduce the side reactions at the negative electrode and improve the high-temperature cycle performance of the battery cell.

[0289] For example, the mass fraction of lithium difluorosulfonylimide is greater than 0 and less than or equal to 8% and can be chosen in the range of 2% to 8%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range formed by any two of the aforementioned values.

[0290] For example, the mass fraction of lithium hexafluorophosphate is greater than 0 and less than or equal to 12% and can be chosen in the range of 1% to 12%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or a range formed by any two of the aforementioned values.

[0291] In some embodiments, the electrolyte also contains additives, comprising one or more of the following: carbonate additives, sulfur-containing additives, and lithium salt additives. These additives can improve the properties of the interfacial film at the negative electrode, resulting in a more stable interfacial film with relatively low impedance, which is advantageous for improving the fast-charging capability of the battery cell and its high-temperature cycle performance.

[0292] In some embodiments, the mass fraction of the additives in the electrolyte is between 0.5% and 10%. For example, the mass fraction of the additives in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range formed by any two of these values. Optionally, the mass fraction of the additive in the electrolyte is between 2% and 6%, and furthermore, a range from 2% to 5% is possible.

[0293] If the mass fraction of the above-mentioned additive is within the specified range, this can effectively improve the properties of the interfacial film on the side of the positive and / or negative electrode, which is advantageous for improving the fast charging capability of the battery cell and the high-temperature cycle performance.

[0294] In some embodiments, the carbonate additives contain one or more of the following substances: fluoroethylene carbonate and vinylene carbonate; optionally, the additives contain fluoroethylene carbonate and vinylene carbonate.

[0295] Fluoroethylene carbonate can form an interfacial film on the surface of the negative electrode that is rich in lithium fluoride (LiF). This can mitigate side reactions at the negative electrode, reduce gas formation at high temperatures, and improve the high-temperature cycle performance of the battery cell.

[0296] The combined use of fluoroethylene carbonate and vinylene carbonate results in a denser interfacial film on the surface of the negative electrode with lower impedance, which better protects the negative electrode, reduces the extent of side reactions at the interface of the negative electrode, reduces gas formation at high temperature, and improves the high-temperature cycle performance and fast-charging capability of the battery cell.

[0297] For example, the sulfur-containing additives contain one or more of the following substances: ethylene sulfate, bis(ethylene sulfate), butylene sulfite, 1,3-propanesulfone, ethylene sulfite and methylenemethane disulfonate.

[0298] Optionally, the lithium salt additives contain one or more of the following substances: lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate and lithium bis(oxalato)borate.

[0299] In the embodiments of the present application, the type and concentration of the inorganic components / lithium salts in the electrolyte have a generally known significance in this field and can be determined using generally known equipment and methods. For example, the inorganic components / lithium salts in the electrolyte can be analyzed qualitatively or quantitatively by ion chromatography in accordance with the standard JY / T020-1996 "General Rules for Ion Chromatography". In the embodiments of the present application, a freshly prepared electrolyte or the free electrolyte from a new battery can be used as a sample. Alternatively, a completely discharged battery (discharged to the lower discharge cut-off voltage, so that the state of charge of the battery is approximately 0%) can be reversibly disassembled, and the free electrolyte obtained from the battery can be used as a sample for analysis by ion chromatography.

[0300] In the embodiments of the present application, the type and content of the organic components in the electrolyte have a generally known significance in this field and can be determined using generally known equipment and methods. For example, the organic components in the electrolyte can be analyzed qualitatively and quantitatively by gas chromatography in accordance with GB / T9722-2006 "General rules for the gas chromatography of chemical reagents".

[0301] In the embodiments of the present application, the components of the electrolyte are classified according to quantitative and qualitative determination. Chain carboxylic acid ester solvents and carbonate solvents (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are considered components of the organic solvent. Assuming that the total mass of the electrolyte is 100%, the mass fraction of each component is calculated.

[0302] Carbonate additives (such as fluoroethylene carbonate and vinylene carbonate) are considered additives in the electrolyte. Assuming the total mass of the electrolyte is 100%, the mass fraction of each component is calculated. separator

[0303] In some embodiments, the electrode assembly further comprises a separator, wherein the separator is arranged between the positive electrode plate and the negative electrode plate.

[0304] In some embodiments, the separator is a separator film. The present application is not subject to any particular restrictions regarding the type of separator film. Any generally known porous separator film with good chemical and mechanical stability can be used.

[0305] The main material for the separator film can be, for example, at least one of the following: fiberglass, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator film can be a single-layer film or a multi-layer composite film, without any particular restrictions. If the separator film is a multi-layer composite film, the materials of the individual layers can be the same or different, without any particular restrictions. The separator can be a separate component located between the positive and negative electrodes, or it can be applied to the surfaces of the positive and negative electrodes. Coatings of inorganic particles, organic particles, or organic / inorganic composites can also be applied to the surface of the separator film.

[0306] In some embodiments, the volumetric energy density of the battery cell ranges from 375 Wh / L to 430 Wh / L. For example, the volumetric energy density of the battery cell is 375 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, or a range formed by any two of these values. The battery cell exhibits a high volumetric energy density.

[0307] In the embodiments of the present application, the volumetric energy density of the battery cell has the generally known meaning in this field and can be determined using generally known devices and methods. In the following, an upper charging cut-off voltage of 3.8 V and a discharging cut-off voltage of 2.0 V are used as examples.

[0308] The battery cell is charged to 3.8 V at 25 °C with a constant current of 0.05 C. It is then discharged to 2.0 V with a constant current of 0.33 C. The discharge capacity extracted in this step is recorded as A0 (in Ah). The length, width, and height of the battery cell are measured with calipers (generally, the external dimensions of the casing are used, excluding the height of the electrode terminals and the insulating film outside the casing). From this, the volume of the battery cell V0 (in L) is calculated. The volumetric energy density of the battery cell VED = (A0 × discharge voltage plateau) / V0 (in Wh / L). Examples of implementation

[0309] The following exemplary embodiments describe in detail the content of the invention disclosed by the embodiments of this application. These exemplary embodiments serve only for illustration, since various modifications and changes within the scope of the content disclosed by the embodiments of this application are obvious to those skilled in the art. Unless otherwise stated, all proportions, percentages, and ratios given in the following exemplary embodiments refer to weight; all reagents used in the exemplary embodiments are commercially available or are synthesized by conventional methods and can be used directly without further preparation; and the equipment used in the exemplary embodiments is commercially available. Example 11. Production of the positive electrode plate

[0310] The positive electrode plate comprises a positive electrode tail, a positive electrode current collector, and positive electrode film layers arranged on both sides of the positive electrode current collector. The positive electrode current collector is made of aluminum foil. The positive electrode tail is not coated with the positive electrode film layer.

[0311] The positive electrode film layer consists of lithium iron phosphate, the binder polyvinylidene fluoride (PVDF), and the conductor acetylene carbon black in a mass ratio of 97.5:2:0.5. The positive electrode film layer is produced by applying a positive electrode paste (solvent: N-methylpyrrolidone NMP) evenly to both sides of the positive electrode current collector, then drying and cold rolling.

[0312] The volume average particle size Dv50 of lithium phosphate is 1.5 µm.

[0313] The one-sided coating weight of the positive electrode film layer is 286 mg / 1540.25 mm². 2 . 2. Production of the negative electrode plate

[0314] The negative electrode plate comprises a negative electrode tail, a negative electrode current collector, and negative electrode film layers arranged on both sides of the negative electrode current collector. The negative electrode current collector is made of copper foil. The negative electrode tail is not coated with the negative electrode film layer. The arrangement and number of negative electrode tails are the same as those of the positive electrode tails and are therefore not described again.

[0315] The negative electrode film layer is produced by applying a negative electrode paste (solvent: deionized water) evenly to the surface of the negative electrode current collector and then drying and cold rolling.

[0316] The one-sided coating weight of the negative electrode film layer is 132 mg / 1540.25 mm². 2 .

[0317] The negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, wherein the first negative electrode film layer is arranged on the surface of the negative electrode current collector, and wherein the second negative electrode film layer is arranged on the surface of the first negative electrode film layer.

[0318] The first negative electrode film layer consists of the active material of the negative electrode, conductive carbon, the binder styrene-butadiene rubber for the negative electrode, and the thickening agent sodium carboxymethylcellulose in a mass ratio of 96.4:0.4:2.5:0.7. The active material of the negative electrode of the first negative electrode film layer contains synthetic graphite.

[0319] The second negative electrode film layer consists of the active material of the negative electrode, conductive carbon, the binder styrene-butadiene rubber for the negative electrode, and the thickening agent sodium carboxymethylcellulose in a mass ratio of 97.8:0.7:0.8:0.7. The active material of the negative electrode of the first negative electrode film layer contains synthetic graphite.

[0320] The cross-section along the thickness direction of the negative electrode film layer shows that the average particle size of the synthetic graphite in the first negative electrode film layer is 13 µm and the average particle size of the synthetic graphite in the second negative electrode film layer is 10 µm. During the fabrication of the negative electrode film layer, the film layer with the desired average particle size can be obtained by repeatedly adjusting the volume-average particle size of the synthetic graphite.

[0321] The length of the negative electrode film layer is 5 mm longer than the length of the positive electrode film layer, and the width of the negative electrode film layer is 5 mm greater than the width of the positive electrode film layer. 3. Separator

[0322] The separator comprises a base film, the base film being made of a 7 µm thick polyethylene film with a porosity of 42%.

[0323] The length of the separator is 6 mm longer 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. 4. Preparation of the electrolyte

[0324] The electrolyte comprises an organic solvent, lithium salts, and additives.

[0325] The individual components of the organic solvent are mixed, then the lithium salt and additives are added to produce the electrolyte.

[0326] The organic solvent consists of: 15% carboxylic acid ester solvent ethyl acetate and 68.5% carbonate solvent ethylene carbonate.

[0327] The lithium salts consist of: 10% lithium hexafluorophosphate and 4% lithium difluorosulfonylimide.

[0328] The additive contains 2.5% vinylene carbonate.

[0329] The conductivity of the electrolyte at room temperature is 11 mS / cm;

[0330] The viscosity of the electrolyte at room temperature is 2.70 mPa·s;

[0331] The density of the electrolyte at room temperature is 1.10 g / mL. 5. Production of battery cells

[0332] The positive electrode plate, the separator, and the negative electrode plate are stacked sequentially, with the separator positioned between the positive and negative electrode plates to provide insulation. This creates the electrode assembly. This assembly is then placed in an outer casing, dried, and filled with electrolyte. After vacuum sealing, storage, conditioning, and adjustment, a battery cell is obtained. The compression density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.63 g / cm³. 3 The compression density of the negative electrode film layer at 0% SOC is 1.60 g / cm³. 3 . Comparison example 1-1

[0333] A battery cell was manufactured using a method similar to that of embodiment 1. The difference from embodiment 1 lay in adjusting the number of positive electrode tabs and the percentage they occupy on the current collector. Exemplary embodiments 2-1 to 2-3

[0334] A battery cell was manufactured using a method similar to that of embodiment 1. The difference from embodiment 1 lay in adjusting the number of positive electrode tabs and the percentage they occupy on the current collector. Comparative example 2-1 and 2-2

[0335] A battery cell was manufactured using a method similar to that of embodiment 1. The difference from embodiment 1 lay in adjusting the length of the positive electrode film layer of the positive electrode plate. Exemplary embodiments 3-1 to 3-4

[0336] A battery cell was manufactured using a method similar to that of embodiment 1. The difference compared to embodiment 1 lay in adjusting the length of the positive electrode film layer of the positive electrode plate. Performance tests: 1. Test of the DC resistance (DCR) of the battery cell

[0337] The test can be carried out according to the method in GB / T 31467 “Test procedure for the performance of high-performance lithium-ion batteries for HEVs”.

[0338] For example, at 25 °C, a battery cell is charged to 3.65 V with a constant current of 0.33 C, left to rest for 1 minute, then charged again to 3.65 V with a constant current of 0.1 C, left to rest for 30 minutes, and subsequently discharged to 2.0 V with a constant current of 0.33 C. The discharge capacity taken in this step is recorded as A0 (in Ah). It is then charged with a constant current of 0.33 C for 0.5 A0 Ah to set the state of charge (SOC) to 50%.

[0339] The battery cell is stored at 25 °C for 2 hours. Afterwards, it is discharged for 10 seconds at a current of 4C, and the value of ΔU is measured. Entiadung and ΔI Entiadung is recorded. The DCR discharge data of lithium-ion batteries can be calculated using the following formula: R Entladung = ΔU Entladung / ΔI Entladung .

[0340] Here, ΔU denotes Entladungthe voltage change within 10 seconds after the start of the discharge and ΔI Entladung denotes the current value within 10 seconds after the start of the discharge. 3. Testing the high-temperature cycle performance of the battery cell

[0341] At 60 ± 5 °C, the battery cell is charged with a constant current of 1 C up to the upper charging cut-off voltage, then charged with a constant voltage up to the final current of 0.05 C, and finally discharged with a constant current of 1 C up to the discharge cut-off voltage. This is one charge-discharge cycle.

[0342] The discharge capacity recorded during this cycle is designated as the discharge capacity C1 for the first cycle of the lithium-ion battery cell. The same cycle is repeated for the same battery cell. After n cycles, the discharge capacity Cn of the nth cycle is recorded. The capacity retention rate of the battery cell = Cn / C1 × 100%. The number of cycles at which the capacity retention rate reaches 80% is recorded. To ensure accuracy, the mean of five parallel samples is used as the test result.

[0343] The test results are shown in Table 1. Table 1 Positive electrode plate Battery performance Positive electrode film layer Positive electrode tail High temperature 80% SOH Cycle count / cl DCR / mΩ Volumetric energy density / Wh / L Length / mm aspect ratio Total number position n ∗ W1 / W2 Example 1 592 6,0 4 On both short sides, 2 each Fig. 10 0,6 1286 0,486 384 Example 2-1 2 On both short sides, one each Fig. 9 0,2 1162 0,493 384 Example 2-2 2 On both short sides, one each Fig. 7 1 1341 0,442 384 Example 2-3 2 On one short side, 2 on one side, like Fig. 6 0,5 1140 0,505 384 Example 3-1 265 1,3 4 On both short sides, 2 each Fig. 10 0,6 1395 0,446 375 Example 3-2 400 3,5 1342 0,454 380 Example 3-3 1200 18,5 1147 0,507 393 Example 3-4 700 9,0 1245 0,502 387 Comparison example 1-1 592 6,0 2 On one short side, 2 on one side, like Fig. 6 0,05 997 0,563 384 Comparison example 2-1 200 1,0 4 On both short sides, 2 each Fig. 10 0,6 1446 0,420 372 Comparison example 2-2 1300 20,0 1098 0,547 394

[0344] In Table 1: “Positive electrode flags on short side” means that the positive electrode flags are arranged on at least one side of the positive electrode current collector along the longitudinal direction. “Positive electrode tails on one short side” means that all positive electrode tails are arranged on the same side of the positive electrode current collector along the longitudinal direction. “Positive electrode flags on both short sides” means that the positive electrode flags are arranged on both sides of the positive electrode current collector along the longitudinal direction. “Positive electrode tabs on both short sides, 2 each” means that there are a total of 4 positive electrode tabs, two positive electrode tabs are arranged on one side of the positive electrode current collector along the longitudinal direction, and the other two electrode tabs are arranged on the other side of the positive electrode current collector along the longitudinal direction.

[0345] In comparative example 1-1, the dimensions of the positive electrode plate are within a suitable range, resulting in a relatively high energy density of the battery cell. Although the positive electrode tabs are arranged along the longitudinal direction on one side of the positive electrode current collector, thus shortening the electron transport path, the dimensions of the positive electrode tabs are relatively small. The ratio n ∗ W1 / W2 is less than 0.2, more precisely 0.15. This results in a relatively small conduction area of ​​the positive electrode leads, leading to low current-carrying capacity, high resistance, increased heat generation, and a higher risk of electrolyte degradation. This impairs the high-temperature cycle performance and fast charging of the battery cell.

[0346] In embodiment 1 and embodiments 2-1 to 2-3, the positive electrode tabs are arranged along the longitudinal direction on at least one side of the positive electrode current collector. The dimensions of the positive electrode tabs are relatively large and occupy a significant portion of the positive electrode current collector. The ratio n*W1 / W2 is greater than or equal to 0.2. This results in a larger current-conducting area of ​​the positive electrode tabs, higher current-carrying capacity, lower internal resistance, and reduced heat generation. Consequently, the internal heat of the battery cell is effectively reduced, and the high-temperature cycle performance and fast-charging capability of the battery cell are improved.

[0347] As the proportion of positive electrode tails on the positive electrode current collector increases, the ratio n also increases. ∗W1 / W2, which improves the current-carrying capacity of the positive electrode tabs. In embodiment 2-2, the ratio n*W1 / W2 is, for example, 1, and the dimension of the positive electrode tabs along the longitudinal direction is equal to the dimension of the positive electrode current collector along the longitudinal direction. In this case, the current-carrying capacity of the positive electrode tabs is higher, which further reduces the internal resistance, reduces heat generation, and improves the high-temperature cycle performance and fast-charging capability of the battery cell.

[0348] Comparison example 2-1 has a relatively short length of the positive electrode film layer, resulting in a lower energy density of the battery cell. Although the shorter electron transport path results in lower DC resistance (DCR) and less heat generation, thus improving the fast-charging capability and high-temperature cycle performance of the battery cell, the lower energy density of the battery cell does not meet the production requirements.

[0349] Comparative example 2-2 exhibits a relatively long positive electrode film layer. Although the energy density of the battery cell is relatively high, the electron transport path is too long, which increases the ohmic resistance of the positive electrode plate. This, in turn, leads to a higher internal resistance of the battery cell and greater heat generation, which impairs the high-temperature cycle performance and fast-charging capability.

[0350] As the length of the positive electrode film layer increases, the energy density of the battery cell improves; however, this also increases the ohmic resistance of the positive electrode plate, leading to increased heat generation, which negatively impacts the high-temperature cycle performance and fast-charging capability of the battery cell. In embodiments 3-1 to 3-4, the length and aspect ratio of the positive electrode film layer are suitable, resulting in a relatively high energy density of the battery cell. Under high energy density conditions, the length-to-width ratio of the positive electrode film layer is set to a maximum of 18.5. This prevents the positive electrode film layer from being too long, shortening the electron transport path along the longitudinal direction and reducing the ohmic resistance of the electrode.In combination with an n*W1 / W2 ratio of at least 0.2 for the electrode tabs, the positive electrode tabs exhibit excellent current-carrying capacity. This effectively reduces internal resistance and heat generation, and improves the high-temperature cycle performance and fast-charging capability of the battery cell. Particularly with a positive electrode film layer aspect ratio of 3.5 to 8 and a coating section dimension of the positive electrode plate along the longitudinal direction of 400 mm to 600 mm, it is advantageous to improve both the high-temperature cycle performance and the fast-charging capability of the high-energy-density battery cell. Comparative example 3-1

[0351] A battery cell was manufactured using a method similar to that of embodiment 1. The difference from embodiment 1 was the adjustment of the electrolyte composition, and no lithium difluorosulfonylimide was added. Exemplary embodiments 4-1 to 4-7

[0352] A battery cell was manufactured using a method similar to that of embodiment 1. The difference compared to embodiment 1 lay in the adjustment of the electrolyte composition.

[0353] In embodiments 4-1 to 4-4, the mass fraction of lithium difluorosulfonylimide was adjusted.

[0354] In embodiment 4-5, lithium difluorosulfonylimide was replaced by lithium trifluorosulfonylimide, while the mass fraction remained unchanged.

[0355] In embodiments 4-6 and 4-7, the mass fraction of lithium hexafluorophosphate was adjusted. In embodiment 4-6, the mass fraction of lithium hexafluorophosphate was 11.67%, and in embodiment 4-7, the mass fraction of lithium hexafluorophosphate was 7.78%.

[0356] The test results are shown in Table 2. Table 2 electrolyte Battery cell Lithium salts Conductivity mS / cm Viscosity mPa·s Density g / mL High temperature 80% SOH cycle count / cls Fast charging DCR / mΩ Lithium fluorosulfonylimide A2 / A I A1+A2 / % material A2 / % Example 4-1 LiFSI 2,00 0,2 12 11,4 2,62 1,09 1177 0,512 Example 4-2 LiFSI 3,00 0,3 13 11,3 2,66 1,10 1250 0,503 Example 4-3 LiFSI 5,00 0,5 15 10,9 2,74 1,10 1312 0,470 Example 4-4 LiFSI 8,00 0,8 18 10,7 2,90 1,11 1341 0,454 Example 4-5 LiTFSI 4,00 0,4 14 11,0 2,71 1,10 1283 0,490 Example 4-6 LiFSI 2,33 0,2 14 11,3 2,65 1,09 1221 0,507 Example 4-7 LiFSI 6,22 0,8 14 10,8 2,76 1,11 1314 0,469 Comparative example 3-1 / / / / 11,7 2,52 1,08 1041 0,558

[0357] In Table 2: LiFSI stands for lithium difluorosulfonylimide; LiTFSI stands for lithium trifluorosulfonylimide; A1 denotes the mass fraction of lithium hexafluorophosphate, A2 denotes the mass fraction of lithium fluorosulfonylimide.

[0358] In comparative example 3-1, the amount of lithium fluorosulfonylimide added was too low, resulting in relatively poor lithium ion conductivity of the electrolyte, which impairs lithium ion migration and fast charging.

[0359] With increasing mass fraction of lithium fluorosulfonylimide, the lithium ion migration number of the electrolyte increases, which improves lithium ion conductivity and reduces the fast-charge DCR. Furthermore, it contributes to the formation of a SEI film on the negative electrode, containing lithium sulfonate and lithium fluoride. This improves the protection of the negative electrode and increases the high-temperature cycle performance of the battery cell. For example, the battery cells in embodiments 4-1 to 4-5 exhibit excellent high-temperature cycle performance and fast-charge capability at a mass fraction of lithium difluorosulfonylimide of at least 2%.

[0360] While adding too much lithium fluorosulfonylimide (e.g., 10% or more) can lower the DCR of the battery cell and improve high-temperature cycle performance, lithium fluorosulfonylimide decomposes rapidly during thermal runaway, generating large amounts of gas and heat. This leads to a sharp increase in the internal temperature of the battery cell, which is difficult to dissipate, thus impairing the battery cell's operational reliability.

[0361] In embodiment 4-5, lithium trifluorosulfonylimide and lithium difluorosulfonylimide are used as lithium fluorosulfonylimide in combination with lithium hexafluorophosphate, which can effectively improve the high-temperature cycle performance and fast-charging capability of the battery cell.

[0362] In embodiments 4-6 and 4-7, the mass fraction of lithium hexafluorophosphate changes synchronously. The lower the mass fraction of lithium hexafluorophosphate, the lower the RF content and the less damage to the SEI film. The lithium salt also contains lithium fluorosulfonylimide, which improves the protection of the negative electrode and enhances the high-temperature cycle performance of the battery cell.

[0363] Although the illustrative embodiments have been shown and described here, those skilled in the art should understand that the aforementioned embodiments must not be interpreted as limiting this application. Rather, changes, substitutions, and modifications to these embodiments may be made without departing from the spirit, principles, and scope of the embodiments of the present application. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] JIS / K0131-1996

[0166] Industry standard HG-T 4067-2015

[0258] GB / T10247-2008

[0261] GB / T 2013-2010

[0264] Standard JY / T020-1996

[0299] GB / T9722-2006 “General rules for gas chromatography of chemical reagents

[0300]

Claims

[1] Battery cell comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises several first electrode plates and several second electrode plates, wherein the several first electrode plates and the several second electrode plates are stacked along the thickness direction of the battery cell, wherein both the first electrode plates and the second electrode plates comprise a coating section and an electrode flap section, wherein the coating section contains active material, wherein the electrode flap section is connected to the coating section and extends along the longitudinal direction of the battery cell beyond the coating section, where One of the first electrode plates and the second electrode plate serve as positive electrode plates, while the others serve as negative electrode plates; wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction of the battery cell is a first dimension, while the dimension of the coating section of the positive electrode plate along the width direction is a second dimension, wherein the ratio of the first dimension to the second dimension is greater than 1 and less than or equal to 18.5, wherein the dimension of the coating section of the positive electrode plate along the longitudinal direction is 265 mm to 1200 mm; where the first electrode plates meet the following conditions: n*W1 / W2 is 0.2 to 1.0; where n denotes the number of all electrode flag sections on the same side of the coating section, and n is greater than or equal to 1; where W1 denotes the average dimension of the electrode flag sections along the latitude direction; where W2 denotes the dimension of the coating section along the width direction; wherein the electrolyte comprises lithium fluorosulfonylimide and lithium hexafluorophosphate, wherein the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate, based on the mass of the electrolyte, is between 0.2 and 0.

8. [2] Battery cell according to claim 1, wherein the mass ratio of lithium fluorosulfonylimide to lithium hexafluorophosphate is between 0.3 and 0.

8. [3] Battery cell according to claim 1 or 2, wherein the mass fraction of lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte is more than 0 and at most 18%. [4] Battery cell according to claim 3, wherein the mass fraction of lithium fluorosulfonylimide and lithium hexafluorophosphate in the electrolyte is between 10% and 18%. [5] Battery cell according to any one of claims 1 to 4, wherein the mass fraction of lithium fluorosulfonylimide in the electrolyte is more than 0 and at most 8%; and / or where the mass fraction of lithium hexafluorophosphate in the electrolyte is more than 0 and at most 12%. [6] Battery cell according to any one of claims 1 to 5, wherein lithium fluorosulfonylimide contains one or more of the following substances: lithium trifluorosulfonylimide and lithium difluorosulfonylimide. [7] Battery cell according to any one of claims 1 to 6, wherein the conductivity of the electrolyte at room temperature is between 10.5 mS / cm and 13.5 mS / cm; and / or wherein the viscosity of the electrolyte at room temperature is between 1.5 mPa·s and 5.5 mPa·s; and / or where the density of the electrolyte at room temperature is between 1.05 g / mL and 1.35 g / mL. [8] Battery cell according to any one of claims 1 to 7, wherein the electrolyte further contains a linear carboxylic acid ester solvent, wherein the mass fraction of the linear carboxylic acid ester solvent in the electrolyte is between 5% and 35%. [9] Battery cell according to claim 8, wherein the linear carboxylic acid ester solvent contains compounds represented by formula I: In formula I: R1 contains hydrogen atoms, C1 to C5 alkyl groups or C1 to C5 haloalkyl groups, R2 contains C1 to C5 alkyl groups or C1 to C5 haloalkyl groups. [10] Battery cell according to claim 9, wherein the linear carboxylic acid ester solvent contains one or more compounds of formulas I-1 to I-8. [11] Battery cell according to any one of claims 1 to 10, wherein the electrolyte further comprises a carbonate solvent, wherein the carbonate solvent comprises one or more of the following substances: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. [12] Battery cell according to any one of claims 1 to 11, wherein the electrolyte contains additives, the additives comprising one or more of the following additives: carbonate additives, sulfur-containing additives and lithium salt additives, wherein the mass fraction of the additives in the electrolyte is between 0.5% and 10%. [13] Battery cell according to claim 12, wherein the carbonate additives contain one or more of the following substances: fluoroethylene carbonate and vinylene carbonate; and / or wherein the sulfur-containing additives contain one or more of the following substances: ethylene sulfate, bis(ethylene sulfate), butylene sulfite, 1,3-propanesulfone, ethylene sulfite and methylenemethane disulfonate; and / or wherein the lithium salt additives contain one or more of the following substances: lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate and lithium bis(oxalato)borate. [14] Battery cell according to any one of claims 1 to 13, wherein the number of electrode flag sections of the first electrode plate is between 1 and 4. [15] Battery cell according to any one of claims 1 to 14, wherein all electrode fin sections of the first electrode plate are connected along the longitudinal direction to the same side of the coating section; or wherein the first electrode plate comprises at least two electrode fin sections, wherein the at least two electrode fin sections are connected along the longitudinal direction to both sides of the coating section of the first electrode plate. [16] Battery cell according to any one of claims 1 to 15, wherein n*W1 / W2 is 0.5 to 1.

0. [17] Battery cell according to any one of claims 1 to 16, wherein the ratio of the first dimension to the second dimension is between 3.5 and 8 and the dimension of the coating section of the positive electrode plate along the longitudinal direction is between 400 mm and 600 mm. [18] Battery cell according to any one of claims 1 to 17, wherein the active material of the positive electrode plate contains lithium phosphate. [19] Battery cell according to any one of claims 1 to 18, wherein the negative electrode plate comprises a coating section of the negative electrode and an electrode tail of the negative electrode that is connected to the coating section of the negative electrode, while the positive electrode plate comprises a coating section of the positive electrode and an electrode tail of the positive electrode that is connected to the coating section of the positive electrode; wherein the dimension of the coating section of the negative electrode along the width direction is larger than the dimension of the coating section of the positive electrode along the width direction, wherein the difference between the dimension of the coating section of the negative electrode along the width direction and the dimension of the coating section of the positive electrode along the width direction is between 5 mm and 11 mm; and / or wherein the dimension of the coating section of the negative electrode along the longitudinal direction is larger than the dimension of the coating section of the positive electrode along the longitudinal direction, wherein the difference between the dimension of the coating section of the negative electrode along the longitudinal direction and the dimension of the coating section of the positive electrode along the longitudinal direction is between 5 mm and 11 mm. [20] Battery cell according to any one of claims 1 to 19, wherein the electrode assembly further comprises a separator, wherein the separator is arranged between the positive electrode plate and the negative electrode plate, wherein the negative electrode plate comprises a coating section of the negative electrode and an electrode tab of the negative electrode which is connected to the coating section of the negative electrode; wherein the dimension of the separator along the width direction is larger than the dimension of the coating section of the negative electrode along the width direction, wherein the difference between the dimension of the separator along the width direction and the dimension of the coating section of the negative electrode along the width direction is between 6 mm and 10 mm; and / or wherein the dimension of the separator along the longitudinal direction is larger than the dimension of the coating section of the negative electrode along the longitudinal direction, wherein the difference between the dimension of the separator along the longitudinal direction and the dimension of the coating section of the negative electrode along the longitudinal direction is between 6 mm and 10 mm. [21] Battery device comprising a battery cell according to any one of claims 1 to 20. [22] Electrical device comprising the battery device according to claim 21.

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