Battery cells, battery devices, and power-consuming devices

Abstract

The present application relates to a battery cell, a battery device and an electric device, wherein the battery cell includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet includes a positive electrode coating portion and at least two positive electrode tabs, the positive electrode coating portion is provided with a positive electrode active material layer, and the at least two positive electrode tabs are connected to both sides of the positive electrode coating portion along the length direction; the negative electrode sheet and the positive electrode sheet are stacked along the thickness direction, wherein the negative electrode sheet includes a negative electrode coating portion and at least two negative electrode tabs, the negative electrode coating portion is provided with a negative electrode active material layer, and the at least two negative electrode tabs are connected to both sides of the negative electrode coating portion along the length direction, and the single-sided coating weight of the positive electrode active material layer is 150-370 mg / 1540.25 mm 2 The single-sided coating weight of the negative electrode active material layer is 70-175 mg / 1540.25 mm 2 The positive electrode coating has a length dimension of 265-655 mm. This application can improve the fast charging capability and cycle performance of battery cells.

Description

[0001] This application claims priority to PCT International Application No. PCT / CN2025 / 071133, filed on January 7, 2025, entitled “Battery Cell, Battery Device and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

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

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

[0005] In a first aspect, an embodiment of the present application proposes a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, each positive electrode sheet includes a positive electrode coating portion and at least two positive electrode ears, the positive electrode coating portion is provided with a positive electrode active material layer, at least two positive electrode ears are connected to the positive electrode coating portion on both sides along the length direction of the battery cell, and the positive electrode active material layer includes a lithium-containing phosphate; a plurality of negative electrode sheets and a plurality of positive electrode sheets are stacked along the thickness direction of the battery cell, each negative electrode sheet includes a negative electrode coating portion and at least two negative electrode ears, the negative electrode coating portion is provided with a negative electrode active material layer, at least two negative electrode ears are connected to both sides of the negative electrode coating portion along the length direction, and the negative electrode active material layer includes a carbon-based material, wherein the single-sided coating weight of the positive electrode active material layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 The single-sided coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 ; The dimension of the positive electrode coating portion along the length direction is 265mm to 655mm.

[0006] Therefore, in the embodiment of the present application, the length of the positive electrode active material layer satisfies the above range, and the tabs are arranged on both sides of the coating portion along the length direction, which can shorten the electron transmission distance, and the current is evenly distributed, lithium plating is not likely to occur at the tabs, and the fast charging capability and cycle performance can be improved; when the length of the positive electrode active material layer satisfies the above range and the single-sided coating weight of the positive and negative electrode coating portions satisfies the above range, the migration path of active ions such as lithium ions in the positive electrode sheet and the negative electrode sheet is short, which can improve the transmission capability of lithium ions, and improve the fast charging capability and cycle performance as well as the energy density of the battery cell.

[0007] In some embodiments, the single-side coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 Up to 300mg / 1540.25mm 2 When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and both the energy density and fast charging performance of the battery cell can be improved.

[0008] In some embodiments, the single-side coating weight of the negative electrode active material layer is 95 mg / 1540.25 mm 2 Up to 142mg / 1540.25mm 2 When the single-sided coating weight of the negative electrode active material layer meets the above range, it is beneficial to improve the energy density of the battery cell, and the heat generation per unit area of ​​the negative electrode sheet will not be too large, which can take into account both the improvement of the energy density and the fast charging performance of the battery cell.

[0009] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, which has excellent cycle stability and can improve cycle performance.

[0010] In some embodiments, the lithium-containing phosphate is in a granular form, and the volume average particle size (Dv50) of the lithium-containing phosphate is between 1 μm and 2 μm. When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium ion insertion and extraction pathway in the lithium-containing phosphate is short, and heat generation is low, which can improve the high-temperature cycling performance and cycling performance of the battery cell under rapid charge. Moreover, the particle size of the lithium-containing phosphate is not too small, and agglomeration is essentially avoided during the processing and preparation process, resulting in stable performance of the lithium-containing phosphate.

[0011] In some embodiments, the positive electrode active material layer further includes a positive electrode additive, which includes one or more of lithium-containing ternary materials, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. These materials can replenish lithium ions in the positive electrode active material layer, compensating for irreversible lithium ion loss within the system, increasing capacity, and extending the cycle life of the battery cells.

[0012] In some embodiments, the volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm. When the volume average particle size of the positive electrode additive is within the above range, it is more evenly dispersed in the positive electrode active material, which is conducive to uniform lithium replenishment and improves the cycle life of the battery cell.

[0013] In some embodiments, the mass content of the positive electrode additive is 0.1% to 5% based on the mass of the positive electrode active material layer. When the mass content of the lithium supplement is within the above range, the cycle life of the battery cell can be improved.

[0014] In some embodiments, the silicon content of the silicon-based material in the negative electrode active material layer is 0.3% to 10% by mass. When the silicon content is within this range, the capacity of the negative electrode active material can be increased, which is beneficial for improving the energy density of the battery cell. Furthermore, during the charge and discharge process, the volume expansion of the silicon element is not excessive, which is beneficial for maintaining the stability of the negative electrode interface film and improving the cycle performance of the battery cell.

[0015] In some embodiments, the silicon-based material includes one or more of silicon carbide and silicon oxide.

[0016] In some embodiments, the negative electrode active material layer includes a first region and a second region. The first region is disposed on the surface of the negative electrode current collector and has a thickness that is 1 / 3 of the thickness of the negative electrode active material layer. The second region is connected to a side of the first region facing away from the negative electrode current collector and has a thickness that is 1 / 3 of the thickness of the negative electrode active material layer. The average particle size of the carbon-based material in the first region is greater than or equal to the average particle size of the carbon-based material in the second region. The difference in particle size between the first and second regions can improve the fast charging performance of the battery cell.

[0017] In some embodiments, the average particle size of the carbon-based material in the first region is 10 μm to 20 μm; when the average particle size of the carbon-based material in the first region is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material and improve the cycle performance of the battery cell under fast charging.

[0018] In some embodiments, the average particle size of the carbon-based material in the second region is 5 μm to 12 μm. When the average particle size of the carbon-based material in the second region is within the above range, it is beneficial to enhance the fast charging capability of the battery cell and enhance the stability of the material, thereby improving the cycling performance of the battery cell under fast charging.

[0019] In some embodiments, the carbon-based material in the first region includes artificial graphite and natural graphite, and the carbon-based material in the second region includes artificial graphite. This material configuration facilitates forming a pore difference between the first and second regions, thereby improving the fast charging capability of the battery cell.

[0020] In some embodiments, at least one of the first region and the second region comprises a silicon-based material, which is beneficial for improving the energy density of the battery cell.

[0021] In some embodiments, the negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is disposed on the surface of the negative electrode current collector; the second negative electrode active material layer is connected to the side of the first negative electrode active material layer facing away from the negative electrode current collector. This dual-layer membrane helps improve the fast charging capability and energy density of the battery cell.

[0022] In some embodiments, the ratio of the dimension of the positive electrode coating portion along the length direction of the battery cell to the dimension of the positive electrode coating portion along the width direction of the battery cell is 2 to 12.5. When the dimensions of the positive electrode active material layer meet the above range, the electron transmission path is not too long, the internal resistance is relatively low, and it is beneficial to improve the fast charging capability and energy density of the battery cell.

[0023] In some embodiments, there are at least two positive electrode tabs located on the same side of the positive electrode coating portion; the current distribution between the tabs is uniform, reducing the risk of lithium plating, and the positive electrode tabs generate less heat, which can improve the high-temperature cycle performance of the battery cell.

[0024] In some embodiments, there are at least two negative electrode tabs located on the same side of the negative electrode coating portion. This allows for uniform current distribution between the tabs, reducing the risk of lithium plating, and reduces heat generation in the positive electrode tabs, thereby improving the high-temperature cycling performance of the battery cell.

[0025] In some embodiments, the positive electrode sheet satisfies: n×W1 / W2 is 0.2 to 1.0; n represents the number of all positive electrode ears located on the same side of the positive electrode coating portion; W1 represents the average size of the positive electrode ear along the width direction of the battery cell; W2 represents the size of the positive electrode coating portion along the width direction; when the positive electrode ear size ratio is within the above range, it can improve the current flow capacity, reduce the internal resistance, reduce heat generation, and enhance the high temperature cycle performance and the cycle performance under fast charging of the battery cell.

[0026] In some embodiments, the negative electrode sheet satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all negative electrode ears located on the same side of the negative electrode coating portion; W3 represents the average size of the negative electrode ears along the width direction of the battery cell; W4 represents the size of the negative electrode coating portion along the width direction; when the negative electrode ear size ratio is within the above range, it can improve the current flow capacity, reduce the internal resistance, reduce heat generation, and enhance the high temperature cycle performance and the cycle performance under fast charging of the battery cell.

[0027] In some embodiments, the battery cell also includes a positive terminal, there are at least two positive terminals, and the at least two positive terminals are respectively arranged on both sides of the positive electrode coating portion along the length direction; the positive terminal has a strong current flow capacity, which can reduce the internal resistance of the battery cell, reduce system heat generation, and improve high-temperature cycle performance.

[0028] In some embodiments, the battery cell also includes a negative terminal, there are at least two negative terminals, and the at least two negative terminals are respectively arranged on both sides of the negative electrode coating portion along the length direction; the positive terminal has a strong current flow capacity, which can reduce the internal resistance of the battery cell, reduce the heat generation of the system, and improve the high-temperature cycle performance.

[0029] In some embodiments, the battery cell further includes an electrolyte, and the conductivity of the electrolyte at room temperature is 10.5 mS / cm to 13.5 mS / cm; when the conductivity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance and cycle performance of the battery cell under fast charging.

[0030] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s; when the viscosity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance and cycle performance of the battery cell under fast charging.

[0031] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. When the electrolyte density is within this range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance and cycling performance of the battery cell under fast charging.

[0032] In some embodiments, the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%. When the mass content of the chain carboxylate solvent is within the above range, the fast charging capability and cycle performance of the battery cell can be improved.

[0033] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0034] Formula I,

[0035] In Formula I,

[0036] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0037] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0038] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0039] In some embodiments, the organic solvent includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%.

[0040] When the mass content of carbonate solvents and chain carboxylate solvents meets the above conditions, the stability of the electrolyte can be improved, its high-temperature gas production can be reduced, and the high-temperature cycle performance of the battery cell can be improved.

[0041] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0042] In a second aspect, an embodiment of the present application further provides a battery device, comprising a battery cell according to any embodiment of the first aspect of the present application.

[0043] In a third aspect, an embodiment of the present application further proposes an electrical device, which includes a battery device as in any embodiment of the second aspect or the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0045] Figure 1 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0046] Figure 2 is a schematic structural diagram of a battery pack provided in some embodiments of the present application;

[0047] Figure 3 is a schematic structural diagram of a battery module provided in some embodiments of the present application;

[0048] Figure 4 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0049] Figure 5 is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0050] Figure 6 Schematic diagram of the structure of the positive electrode sheet of a battery cell provided in some embodiments of the present application;

[0051] Figure 7 Schematic diagram of the structure of the positive electrode sheet of a battery cell provided in other embodiments of the present application;

[0052] Figure 8 is a schematic structural diagram of a negative electrode sheet of a battery cell provided in some embodiments of the present application;

[0053] Figure 9 Schematic diagram of the structure of the negative electrode sheet of a battery cell provided in other embodiments of the present application;

[0054] Figure 10 is a schematic structural diagram of a battery cell provided in some other embodiments of the present application;

[0055] Figure 11 is a schematic structural diagram of a negative electrode sheet of a battery cell provided in some embodiments of the present application;

[0056] Figure 12 It is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application.

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

[0058] The following are the descriptions of the reference numerals:

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

[0060] 1. Power-consuming device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space; 6. Battery module;

[0061] 7. Battery cells;

[0062] 10. Electrode assembly;

[0063] 11. Positive electrode sheet; 111. Positive electrode tab; 1111. First end; 112. Positive electrode coating portion;

[0064] 12. Negative electrode sheet; 121. Negative electrode ear; 1211. Second end; 122. Negative electrode coating portion;

[0065] 13. Isolation parts;

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

[0067] 20. Housing assembly; 21. Shell; 22. End cap; 31. Positive terminal; 32. Negative terminal. DETAILED DESCRIPTION

[0068] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0069] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0070] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0071] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0072] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0073] The term "plurality" used in this application refers to two or more (including two).

[0074] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0075] The battery cell may be a lithium-ion battery, a sodium-lithium-ion battery, etc., which is not limited in the embodiments of the present application.

[0076] With the rapid development of the battery field, the performance requirements for battery cells are gradually increasing. For example, with the increase in energy density and fast charging performance requirements, this can be achieved in related technologies by increasing the conductivity of the electrolyte. However, the increase in conductivity may cause the electrolyte to decompose at high temperatures, resulting in an increase in the high-temperature gas production of the battery cell, which may cause the cycle of the battery cell to deteriorate, and it is impossible to improve the fast charging capability, cycle performance and energy density of the battery cell at the same time.

[0077] In view of the above problems, the size of the positive electrode coating portion of the embodiment of the present application is matched with the appropriate single-side coating weight of the positive and negative electrode active materials, so that the energy density of the battery cell is relatively high;

[0078] The positive electrode active material includes a lithium-containing phosphate, which has relatively poor conductivity. When the length of the positive electrode active material layer is too long, the electron conduction resistance increases, which is not conducive to fast charging. When the size of the positive electrode coating portion is within an appropriate range and the tabs are arranged on both sides of the coating portion, the electron transmission path in the electrode sheet is shorter, which can improve the electron transmission capacity. On the other hand, when the single-sided coating weight of the positive and negative electrode active material layers is appropriate, the migration path of active ions such as lithium ions in the positive and negative electrode sheets is short, which can improve the lithium ion transmission capacity. Therefore, by improving the electron transmission capacity and ion transmission capacity, the fast charging capability and cycle performance of the battery cell under fast charging can be improved.

[0079] Since the electron transmission path is shorter, the ohmic resistance of the electrode is smaller and the heat generated is less, it can slow down the decomposition of electrolyte components caused by heat accumulation and improve the high-temperature cycle performance of the battery cell.

[0080] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0081] For example, the power-consuming device may be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, electric tool, vehicle, ship, spacecraft, etc. Alternatively, for example, the power-consuming device may be a spacecraft, including an airplane, rocket, space shuttle, and spacecraft.

[0082] Figure 1 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 1, a battery pack or battery module may be used.

[0083] A battery device is disposed within the electrical device 1, and the battery device can be disposed at the bottom, head, or tail of the electrical device 1. The battery device can be used to power the electrical device 1. For example, the battery device can serve as an operating power source for the electrical device 1, and can also serve as a driving power source for the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in FIG. 1 is a battery pack 2 .

[0084] The electric device 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery device to supply power to the motor 4 , for example, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0085] A battery device may include one or more battery cell assemblies to provide voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or in series via a busbar.

[0086] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0087] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0088] like Figure 2 As shown, in some embodiments, the battery device may be a battery pack 2 , which includes a box 5 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box 5 .

[0089] As an example, the battery cell assembly may also be housed in the box body 5 by directly fixing a plurality of battery cells to the box body 5 .

[0090] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b, which define a storage space 5c. The first housing portion 5a and the second housing portion 5b engage to form a closed space within the housing 5 for accommodating the battery cell assembly. "Enclosed" here means covered or closed, and can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0091] As an example, the box body 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0092] In some embodiments, the box 5 can be used as a part of the chassis structure of the vehicle. For example, part of the box 5 can become at least a part of the floor of the vehicle, or part of the box 5 can become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0093] As an example, the battery cell assembly may be a battery module 6 , and the battery cell assembly may be accommodated in the box body 5 by fixing the battery module 6 in the box body 5 .

[0094] like Figure 3 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0095] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% state of charge (SOC), the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0096] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC, the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0097] For example, the charging step of the battery device or any battery cell 7 constituting the battery device from 20% SOC to 80% SOC may be performed as follows:

[0098] Charge from 20% SOC to 25% SOC at 8.00C constant current;

[0099] Charge from 25% SOC to 30% SOC at 8.00C constant current;

[0100] Charge from 30% SOC to 35% SOC at 7.50C constant current;

[0101] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0102] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0103] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0104] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0105] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0106] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0107] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0108] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0109] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0110] In some embodiments, the charging time of the battery device or any battery cell 7 constituting the battery device from a 20% state of charge to an 80% state of charge is 5 minutes to 30 minutes, optionally 5 minutes to 20 minutes, and the temperature of the external environment of the battery device at a 20% state of charge is room temperature, for example, 25°C. Illustratively, the charging time of the battery device from 20% state of charge to 80% state of charge is 30 min, 29 min, 28 min, 27 min, 26 min, 25 min, 24 min, 23 min, 22 min, 21 min, 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min, or a range consisting of any two of the above values.

[0111] like Figure 4 and Figure 5 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20 .

[0112] The housing assembly 20 has a receiving cavity for receiving the electrode assembly 10 and the electrolyte.

[0113] In some embodiments, the housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0114] Illustratively, the terminal assembly includes a positive terminal 31 and a negative terminal 32 .

[0115] The outer shell can be made of steel, aluminum, plastic (e.g., polypropylene), a composite metal shell (e.g., a copper-aluminum composite shell), or an aluminum-plastic film. In some embodiments, the outer shell can be either sealed or non-sealed. For example, in a non-sealed outer shell, the outer shell protects the electrode assembly 10 and includes a sealed bag between the outer shell and the electrode assembly 10, which encapsulates the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum-plastic film. In a sealed outer shell, the sealed bag encapsulates the electrode assembly 10 and other components, such as the electrolyte.

[0116] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a polygonal battery, and a polygonal battery such as a hexagonal battery. There is no special limitation in this application.

[0117] In some embodiments, the housing includes an end cap 22 and a shell 21. The shell 21 has an opening, and the end cap 22 covers the opening. The shell 21 may have one or more openings. One or more end caps 22 may also be provided.

[0118] The shape of the housing 21 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a cylindrical housing 21 can be selected; if the electrode assembly 10 has a rectangular parallelepiped structure, a rectangular parallelepiped housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 have rectangular parallelepiped structures.

[0119] The electrode assembly 10 includes a positive electrode sheet 11 , a negative electrode sheet 12 and a separator 13 .

[0120] like Figures 4 to 6 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10, which includes a plurality of positive electrode sheets 11 and a plurality of negative electrode sheets 12. The plurality of positive electrode sheets 11 and the plurality of negative electrode sheets 12 are stacked along the thickness direction X of the battery cell. Each positive electrode sheet 11 includes a positive electrode coating portion 112 and at least two positive electrode tabs 111. The positive electrode coating portion 112 is provided with a positive electrode active material layer. At least two positive electrode tabs 111 are not coated with the positive electrode active material layer and are connected to both sides of the positive electrode coating portion 112 along the length direction Z of the battery cell. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0121] Each negative electrode sheet 12 includes a negative electrode coating portion 122 and at least two negative electrode tabs 121. The negative electrode coating portion 122 is provided with a negative electrode active material. The at least two negative electrode tabs 121 are not coated with the negative electrode active material and are connected to both sides of the negative electrode coating portion 122 along the length direction Z. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material.

[0122] Among them, the single-sided coating weight of the positive electrode active material layer is 150mg / 1540.25mm 2 Up to 370mg / 1540.25mm 2 The single-sided coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 The dimension of the positive electrode coating portion 112 along the longitudinal direction Z is 265mm to 655mm.

[0123] The electrode assembly is a laminated structure, and the size of the positive electrode active material layer can be considered to be equivalent to the size of the positive electrode coating portion. Figure 6 Z1 represents the dimension of the positive electrode coating portion 112 along the longitudinal direction Z.

[0124] The length of the positive electrode active material layer is greater than or equal to 265mm, and its coordination is greater than or equal to 150mg / 1540.25mm 2 The single-sided coating weight and the negative electrode active material layer with appropriate coating weight can effectively improve the energy density of the battery cell;

[0125] The positive electrode active material includes lithium-containing phosphate, which has relatively poor conductivity. When the length of the positive electrode active material layer is too long, the electron conduction resistance increases, which is not conducive to fast charging. However, the length of the positive electrode active material layer in the embodiment of the present application is less than or equal to 655 mm, which helps to shorten the electron conduction distance. In addition, the tabs are arranged on both sides of the coating portion along the length direction, which can further shorten the electron transmission distance and reduce the internal resistance.

[0126] The coating weight on one side of the positive electrode coating portion 112 is less than or equal to 370 mg / 1540.25 mm 2 The coating weight on one side of the negative electrode coating portion 122 is less than or equal to 175 mg / 1540.25 mm 2 , the migration path of active ions such as lithium ions in the positive and negative electrode sheets is shorter, which can improve the transmission capacity of lithium ions in the liquid phase;

[0127] Therefore, by improving the electron transmission capacity and ion transmission capacity, the fast charging capability and cycle performance of the battery cell under fast charging can be improved;

[0128] Since the electron transmission path is shorter, the ohmic resistance of the electrode is smaller and the heat generated is less, it can slow down the decomposition of electrolyte components caused by heat accumulation and improve the high-temperature cycle performance of the battery cell.

[0129] In summary, the embodiments of the present application can improve the energy density, fast charging capability, high temperature cycle performance and cycle performance under fast charging conditions of the battery cell.

[0130] The electrode assembly 10 is a laminated structure. As an example, a plurality of positive electrode sheets 11 and a plurality of negative electrode sheets 12 may be provided, and the plurality of positive electrode sheets 11 and the plurality of negative electrode sheets 12 may be alternately stacked.

[0131] As an example, a plurality of positive electrode sheets 11 may be provided, and the negative electrode sheet 12 may be folded to form a plurality of stacked folded segments, with one positive electrode sheet 11 being sandwiched between adjacent folded segments.

[0132] As an example, the positive electrode tab 11 and the negative electrode tab 12 are both folded to form a plurality of stacked folded segments.

[0133] As an example, a plurality of separators 13 may be provided, each of which is disposed between any adjacent positive electrode sheets 11 or negative electrode sheets 12 .

[0134] As an example, the separator 13 may be provided continuously, and may be provided between any adjacent positive electrode sheets 11 or negative electrode sheets 12 by folding or winding.

[0135] In some embodiments, each electrode sheet is provided with an electrode tab, which can conduct current from the electrode assembly 10. The electrode tabs include a positive electrode tab and a negative electrode tab.

[0136] In the embodiment of the present application, the length direction Z of the battery cell 7 , the width direction Y of the battery cell 7 , and the thickness direction X of the battery cell 7 are perpendicular to each other.

[0137] The coating portion includes a current collecting portion and a film layer disposed on the current collecting portion and containing an active material. For example, the positive electrode coating portion 112 includes a positive electrode current collecting portion and a positive electrode active material layer disposed on the positive electrode current collecting portion and containing a positive electrode active material. For another example, the negative electrode coating portion 122 includes a negative electrode current collecting portion and a negative electrode active material layer disposed on the negative electrode current collecting portion and containing a negative electrode active material.

[0138] like Figure 6 and Figure 7As shown, in some embodiments, the positive electrode sheet 11 includes at least two positive electrode tabs 111, for example, 2 to 4 positive electrode tabs 111. The multiple positive electrode tabs 111 are respectively arranged on both sides of the positive electrode coating portion 112 along the length direction Z. This arrangement can shorten the electron transmission path in the positive electrode sheet 11, which is conducive to improving the fast charging performance. For example, two positive electrode tabs 111 are located on one side of the positive electrode coating portion 112 along the length direction Z, and the other two positive electrode tabs 111 are located on the other side of the positive electrode coating portion 112 along the length direction Z.

[0139] In some embodiments, the positive electrode sheet 11 satisfies: n×W1 / W2 is 0.2 to 1.0;

[0140] n represents the number of all positive electrode tabs 111 located on the same side of the positive electrode coating portion 112;

[0141] W1 represents the average size of the positive electrode tab 111 along the width direction Y;

[0142] W2 represents the dimension of the positive electrode coating portion 112 in the width direction Y.

[0143] Figure 6 Where n is 1, Figure 7 Where n is 2.

[0144] Illustratively, n×W1 / W2 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or a range consisting of any two of the above values. Optionally, n×W1 / W2 is 0.5 to 1.0.

[0145] When n×W1 / W2 satisfies the above range, the flow area of ​​the positive electrode tab 111 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0146] W1 represents the average size of the positive electrode tab 111 along the width direction Y.

[0147] When the positive electrode tab 111 has a special-shaped structure, for example, the dimension of the positive electrode tab 111 along the width direction Y gradually increases along the length direction Z. In this case, the dimensions of the positive electrode tab 111 along the width direction Y at multiple locations can be measured to calculate the average dimension of the positive electrode tab 111 along the width direction Y. Of course, the dimensions of the positive electrode tab 111 along the width direction Y at all locations can have the same value, in which case this value can be used as the average dimension of the positive electrode tab 111.

[0148] There may be one or more positive electrode tabs 111 located on the same side, for example, n is 1 to 4. In the case of multiple positive electrode tabs 111, the average size of each positive electrode tab 111 can be measured separately, and the average size values ​​can be added up and divided by the number of positive electrode tabs 111 to calculate the average size of the positive electrode tabs 111.

[0149] The positive electrode ear 111 is connected to the positive electrode coating portion 112, and the positive electrode ear 111 includes a first end 1111 connected to the positive electrode coating portion 112. When n×W1 / W2 meets the above range, it means that the cross-section of the first end 1111 along the thickness direction of the positive electrode ear 111 itself is relatively large, and the contact area between the positive electrode ear 111 and the positive electrode coating portion 112 is relatively large. The positive electrode ear 111 has a strong current flow capacity, which can improve the fast charging performance and cycle performance of the battery cell 7.

[0150] Optionally, the current collecting portion of the positive electrode tab 111 and the positive electrode coating portion 112 is an integrated structure, so that the internal resistance of the positive electrode plate 11 is low, which can further improve the fast charging performance and cycle performance of the battery cell 7.

[0151] Optionally, there are at least two positive electrode tabs 111 on the same side of the positive electrode coating portion 112, such as two, three, four, five, six, etc. This arrangement is beneficial for uniform distribution of electrons in the positive electrode sheet 11 and improves fast charging performance.

[0152] The distance between two adjacent positive electrode tabs 111 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range consisting of any two of the above values. Figure 7 Y1 represents the distance between two adjacent positive electrode tabs 111 along the width direction Y.

[0153] like Figure 8 and Figure 9 As shown, in some embodiments, the negative electrode plate 12 includes at least two negative electrode tabs 121, for example, 2 to 4 negative electrode tabs 121. The multiple negative electrode tabs 121 are respectively arranged on both sides of the negative electrode coating portion 122 along the length direction Z. This arrangement can shorten the electron transmission path in the negative electrode plate 12, which is conducive to improving the fast charging performance.

[0154] In some embodiments, the negative electrode sheet 12 satisfies: m×W3 / W4 is 0.2 to 1.0;

[0155] m represents the number of all negative electrode tabs 121 located on the same side of the negative electrode coating portion 122;

[0156] W3 represents the average size of the negative electrode tab 121 along the width direction Y;

[0157] W4 represents the dimension of the negative electrode coating portion 122 in the width direction Y.

[0158] W3 represents the average size of the negative electrode tab 121 along the width direction Y. There may be one or more negative electrode tabs 121 on the same side. In the case of multiple negative electrode tabs 121, the size of each negative electrode tab 121 can be measured with a micrometer to calculate the average size.

[0159] The negative electrode ear 121 is connected to the negative electrode coating portion 122, and the negative electrode ear 121 includes a second end 1211 connected to the negative electrode coating portion 122. When n×W3 / W4 meets the above range, it means that the cross-section of the second end 1211 along the thickness direction of the negative electrode ear 121 itself is relatively large, and the contact area between the negative electrode ear 121 and the negative electrode coating portion 122 is relatively large. The negative electrode ear 121 has a strong current flow capacity, which can improve the fast charging performance and cycle performance of the battery cell 7.

[0160] Optionally, the negative electrode tab 121 and the current collecting portion of the negative electrode coating portion 122 are of an integrated structure, so that the internal resistance of the negative electrode plate 12 is low, which can further improve the fast charging performance and cycle performance of the battery cell 7 .

[0161] m can be 1 to 4, for example Figure 8 Where m is 1, Figure 9 Here m is 2.

[0162] Illustratively, m×W3 / W4 is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or a range consisting of any two of the above values. Optionally, m×W3 / W4 is 0.5 to 1.0.

[0163] When m×W3 / W4 satisfies the above range, the flow area of ​​the negative electrode tab 121 is relatively large, which is beneficial to improving the fast charging performance of the battery cell 7.

[0164] Optionally, there are at least two, for example, two, three, four, five, six, etc., negative electrode tabs 121 located on the same side of the negative electrode coating portion 122 along the longitudinal direction Z. This arrangement is beneficial for uniform distribution of electrons in the negative electrode sheet 12 and improves fast charging performance.

[0165] Optionally, the distance between two adjacent negative electrode tabs 121 along the width direction Y is 0 to 300 mm, such as 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, or a range consisting of any two of the above values. Figure 9 Y2 represents the distance between two adjacent negative electrode tabs 121 along the width direction Y.

[0166] like Figure 10 As shown, in some embodiments, the terminal assembly can be disposed on the housing 21 , or the terminal assembly can be disposed on the end cover 22 .

[0167] The terminal assembly includes a positive terminal 31 and a negative terminal 32 . The positive terminal 31 is connected to the positive electrode tab 111 , and the negative terminal 32 is connected to the negative electrode tab 121 .

[0168] Illustratively, the positive terminal 31 and the negative terminal 32 may be provided on the housing 21 , or the positive terminal 31 and the negative terminal 32 may be provided on the end cap 22 . Alternatively, the positive terminal 31 and the negative terminal 32 may be provided on the end cap 22 .

[0169] The positive terminal 31 and the negative terminal 32 can be provided on the same end cap 22. For example, there is one end cap 22, and the positive terminal 31 and the negative terminal 32 are provided on the end cap 22 at intervals. In another example, there are two end caps 22, and the two end caps 22 are arranged opposite each other, and each end cap 22 is provided with a positive terminal 31 and a negative terminal 32.

[0170] A positive terminal 31 and a negative terminal 32 are respectively provided on different end caps 22 . For example, there are two end caps 22 , which are arranged opposite to each other. The positive terminal 31 is provided on one of the end caps 22 , and the negative terminal 32 is provided on the other end cap 22 .

[0171] In some embodiments, there is at least one positive terminal 31 , and may be at least two, such as two, three, or four.

[0172] In some embodiments, at least one positive terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0173] Alternatively, as Figure 10 As shown, multiple positive terminals 31 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is conducive to improving the fast charging performance.

[0174] Exemplarily, there are two positive terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other positive terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplarily, there are four positive terminals 31, two of which are disposed on one side of the electrode assembly 10, and the other two positive terminals 31 are disposed on the other side of the electrode assembly 10.

[0175] In an embodiment of the present application, the positive tab 111 and the positive terminal 31 may be directly connected or indirectly connected; when the positive tab 111 and the positive terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, which is located between the positive terminal 31 and the positive tab 111 and connects the positive terminal 31 and the positive tab 111.

[0176] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0177] In other embodiments, at least one positive terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all positive terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, multiple positive terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0178] In some embodiments, there is at least one negative terminal 32 , and optionally at least two, such as two, three, or four.

[0179] In some embodiments, at least one negative terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0180] Optionally, at least two negative terminals 32 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and is conducive to improving the fast charging performance.

[0181] Figure 11 The battery cell 7 is shown to include four electrode terminals, specifically, two negative terminals 32, one of which is disposed on one side of the electrode assembly 10 along the length direction Z, and the other negative terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two positive terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other positive terminal 31 is disposed on the other side of the electrode assembly 10.

[0182] In the embodiment of the present application, the negative electrode tab 121 and the negative electrode terminal 32 can be directly connected or indirectly connected; when the negative electrode tab 121 and the negative electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter, which is located between the negative electrode terminal 32 and the negative electrode tab 121 and connects the negative electrode terminal 32 and the negative electrode tab 121.

[0183] In the above embodiments, the second transition component may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0184] In other embodiments, at least one negative terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. For example, all negative terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y, or multiple negative terminals 32 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0185] Negative electrode

[0186] The negative electrode coating portion of the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector and containing a negative active material. For example, the negative current collector has two opposing surfaces in its thickness direction, and the negative active material layer is disposed on either or both of the two opposing surfaces of the negative current collector.

[0187] The upper limit voltage for charging and the cut-off voltage for discharging of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging may be 3.65V and the cut-off voltage for discharging may be 2.0V, or the upper limit voltage for charging may be 3.8V and the cut-off voltage for discharging may be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging may be 4.3V and the cut-off voltage for discharging may be 2.0V. Next, taking the upper limit voltage for charging of 3.8V and the cut-off voltage for discharging of 2.0V as an example, the state of the battery cell is described: In the embodiment of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows:

[0188] The battery cell is charged at a constant current charge rate of 0.05C to the upper limit of the charge voltage, corresponding to the state of 100% SOC of the battery cell, and the battery cell is discharged at a constant current discharge rate of 0.05C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0189] In some embodiments, the compaction density of the negative electrode active material layer of the battery cell at 100% state of charge (SOC) is 1.5 g / cm 3 to 1.7g / cm 3 For example, the compaction density of the negative electrode active material layer of the battery cell at 100% state of charge is 1.50 g / cm 3 , 1.55g / cm 3 , 1.60g / cm 3 , 1.65g / cm 3 , 1.66g / cm³, 1.68g / cm³, 1.70g / cm³ or a range consisting of any two of the above values.

[0190] When the compaction density of the negative electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, because the negative electrode active material in the negative electrode active material layer is densely packed, the contact resistance between particles is low, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle. Therefore, by adjusting the compaction density of the negative electrode active material layer to a reasonable range, the battery cell can improve the fast charging capability and cycle performance at high energy density.

[0191] In the embodiment of the present application, the single-side coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 Up to 175mg / 1540.25mm 2 For example, the single-side coating weight of the negative electrode active material layer is 70 mg / 1540.25 mm 2 , 80mg / 1540.25mm², 85mg / 1540.25mm², 90mg / 1540.25mm², 95mg / 1540.25mm², 100mg / 1540.25mm², 105mg / 1540.25mm², 110mg / 1540.25mm², 115mg / 1540.25mm², 120mg / 1540.25mm², 120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2 、130mg / 1540.25mm 2 、140mg / 1540.25mm 2 、150mg / 1540.25mm 2 、160mg / 1540.25mm 2 、170mg / 1540.25mm 2 、175mg / 1540.25mm 2 Or a range consisting of any two of the above values. Optionally, the single-sided coating weight of the negative electrode active material layer is 95 mg / 1540.25 mm 2 Up to 142mg / 1540.25mm 2 .

[0192] When the single-sided coating weight of the negative electrode active material layer meets the above range, it is beneficial to improve the energy density of the battery cell, and the migration rate of active ions in the negative electrode active material layer is faster, which is beneficial to reducing the polarization phenomenon under high-rate charging, and is beneficial to improving the fast charging capability of the battery cell at high energy density.

[0193] In the embodiments of the present application, the compaction density of the negative electrode active material layer of a battery cell at 100% state of charge (SOC) has a meaning well known in the art. Specifically, the negative electrode sheet of a battery cell at 100% state of charge (SOC) is disassembled and the compaction density of the negative electrode active material layer is measured. For example, a single-sided coated negative electrode sheet (if a double-sided coated sheet is used, the negative electrode active material layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The negative electrode active material layer of the weighed negative electrode sheet is then wiped off, and the negative electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode active material layer = (the weight of the negative electrode sheet M1 - the weight of the negative electrode current collector M0) / S1, the thickness of the negative electrode active material layer = the thickness of the negative electrode sheet H1 - the thickness of the negative electrode current collector H0, the compaction density of the negative electrode active material layer = the single-sided coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0194] In some embodiments, the negative electrode active material has a charge capacity in the range of 350 mAh / g to 540 mAh / g. For example, the negative electrode active material has a charge capacity in the range of 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, 500 mAh / g, 530 mAh / g, 540 mAh / g, or a range consisting of any two of the foregoing values.

[0195] When the charge gram capacity of the negative electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0196] In the embodiments of the present application, the gram capacity of the active material has a meaning well known in the art and can be tested using equipment and methods well known in the art. The test method for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used to test the charging gram capacity of the negative electrode active material in a half-button battery at a rate of 0.1C. A half-button battery is assembled with metallic lithium as the negative electrode and a sample electrode comprising the above-mentioned material as the positive electrode. Under the conditions of 23°C±2°C, the half-button battery is charged and discharged at a rate of 0.1C on a battery tester or other test equipment of equivalent performance to obtain the charge capacity, and then the capacity is divided by the mass of the electrode active material to obtain the charging gram capacity parameter.

[0197] In some embodiments, the negative electrode active material includes a silicon-based material. Alternatively, the silicon-based material may include elemental silicon, a silicon-carbon composite, silicon oxide SiO x At least one of (0<x≤2). For example, the silicon-carbon composite may be silicon carbide.

[0198] In some embodiments, the silicon content of the silicon-based material in the negative electrode active material layer is 0.3% to 10% by weight, for example, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two of the foregoing values. Alternatively, the silicon content of the silicon-based material in the negative electrode active material layer is 3% to 6% by weight.

[0199] When the mass content of silicon is within the above range, the capacity of the negative electrode active material can be increased, which is beneficial to improving the energy density of the battery cell. Moreover, during the charge and discharge process, the volume expansion of silicon will not be too large, which is beneficial to maintaining the stability of the negative electrode SEI film and improving the cycle performance of the battery cell at high energy density.

[0200] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the cycle performance of the battery cell.

[0201] Optionally, the carbon-based material includes at least one of artificial graphite and natural graphite.

[0202] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the aforementioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy.

[0203] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0204] For example, the present application may combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0205] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0206] like Figure 11 As shown, the negative active material layer 141 of the negative electrode plate 12 in the embodiment of the present application includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative active material layer 141 includes at least two film layers.

[0207] In the case where the negative electrode active material layer 141 is a single-layer film, the negative electrode active material in the negative electrode active material layer 141 includes a carbon-based material and an optional silicon-based material.

[0208] When the negative electrode active material layer 141 comprises at least two layers, the negative electrode active material in the negative electrode active material layer 141 includes a carbon-based material and an optional silicon-based material. The negative electrode active material layer 141 may include two layers, three layers, four layers, or even more layers.

[0209] In some embodiments, the negative electrode active material layer 141 includes a first negative electrode active material layer 1411 and a second negative electrode active material layer 1412. The first negative electrode active material layer 1411 is disposed on the surface of the negative electrode current collector 142, and the negative electrode active material in the first negative electrode active material layer 1411 includes a carbon-based material. The second negative electrode active material layer 1412 is connected to the side of the first negative electrode active material layer 1411 facing away from the negative electrode current collector 142, and the negative electrode active material in the second negative electrode active material layer 1412 includes a carbon-based material. The interface between the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 may be regular or irregular, or alternatively, there may be no distinct interface between the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412.

[0210] The negative electrode active material layer 141 comprises at least two layers, and layered coating is beneficial for improving the rapid charging performance of the battery cell. In particular, when the porosity of the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 differ, this is beneficial for improving the rapid charging performance of the battery cell.

[0211] In some embodiments, at least one of the first negative active material layer 1411 and the second negative active material layer 1412 includes a silicon-based material.

[0212] Optionally, the first negative electrode active material layer 1411 further includes a silicon-based material.

[0213] Optionally, the second negative electrode active material layer 1412 further includes a silicon-based material.

[0214] For example, the first negative electrode active material layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material and a silicon-based material. When both the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412 include silicon-based materials, this is more conducive to improving the energy density of the battery cell. Furthermore, the carbon-based materials in each layer can mitigate the volume expansion of the silicon-based materials, making the negative electrode SEI film more stable and improving cycling performance at high energy densities. Furthermore, since each layer includes silicon-based materials, the coating thickness is relatively thin, which helps shorten the lithium ion transmission path and improves fast charging performance at high energy densities.

[0215] Alternatively, the first negative electrode active material layer 1411 includes a carbon-based material and a silicon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material. When the first negative electrode active material layer 1411 includes a silicon-based material and the second negative electrode active material layer 1412 does not include a silicon-based material, the second negative electrode active material layer 1412 can alleviate the volume expansion of the first negative electrode active material layer 1411, reduce side reactions between the negative electrode active material layer 1411 and the electrolyte, and improve cycle performance at high energy density.

[0216] Alternatively, the first negative electrode active material layer 1411 includes a carbon-based material, and the second negative electrode active material layer 1412 includes a carbon-based material and a silicon-based material. When the second negative electrode active material layer 1412 includes a silicon-based material, the volume change of the silicon-based material facilitates the formation of more membrane pores, thereby improving the liquid-phase transport capability of lithium ions and enhancing the dynamic performance of the battery cell.

[0217] When the negative electrode active material layer 141 comprises at least two film layers, the cross-sectional morphology of the negative electrode active material layer 141 can be the same or similar, or can be different, along the thickness direction X of the negative electrode active material layer 141. When the electrode assembly has a laminated structure, the thickness direction of the battery cell can be parallel to the thickness direction of the electrode assembly and the thickness direction X of the negative electrode active material layer 141.

[0218] Along the thickness direction X of the negative electrode active material layer 141, the negative electrode active material layer 141 is divided into three regions, namely the first region 141a, the third region 141c and the second region 141b. The first region 141a is the region of the negative electrode active material layer 141 close to the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the first region 141a is 1 / 3 of the thickness of the negative electrode active material layer 141; the second region 141b is the region of the negative electrode active material layer 141 away from the negative electrode current collecting portion 142 along the thickness direction X, and the thickness of the second region 141b is 1 / 3 of the thickness of the negative electrode active material layer 141.

[0219] The cross-sectional morphologies of the first region 141a and the second region 141b can be the same or similar, or they can be different. The cross-sectional morphologies of the first region 141a and the third region 141c can be the same or similar, or they can be different. The cross-sectional morphologies of the second region 141b and the third region 141c can be the same or similar, or they can be different.

[0220] The first region 141a, the second region 141b, and the third region 141c may or may not have distinct interface boundaries. For example, the first negative electrode active material layer 1411 includes the first region 141a, the second negative electrode active material layer 1412 includes the second region 141b, and the third region 141c may be a portion of the first negative electrode active material layer 1411, or the third region 141c may be a portion of the second negative electrode active material layer 1412, or the third region 141c may be a portion of both the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412.

[0221] Optionally, the average particle size of the carbon-based material in the first region 141a can be greater than or equal to the average particle size of the carbon-based material in the second region 141b. Further, optionally, the average particle size of the carbon-based material in the first region 141a can be greater than the average particle size of the carbon-based material in the second region 141b. This facilitates rapid migration of lithium ions from the second region 141b to the first region 141a, thereby improving the fast charging capability of the battery cell. Of course, the average particle size of the carbon-based material in the first region 141a can be smaller than the average particle size of the carbon-based material in the second region 141b.

[0222] Optionally, the average particle size of the carbon-based material of the first negative electrode active material layer 1411 may be greater than or equal to the average particle size of the carbon-based material of the second negative electrode active material layer 1412 . Further optionally, the average particle size of the carbon-based material of the first negative electrode active material layer 1411 may be greater than the average particle size of the carbon-based material of the second negative electrode active material layer 1412 .

[0223] There is a difference in the particle size of the first negative electrode active material layer 1411 and the second negative electrode active material layer 1412, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode active material layer 1412 is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode active material layer 1412. In the embodiment of the present application, the particle size of the second negative electrode active material layer 1412 is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode plate 12, thereby improving the cycle performance under fast charging.

[0224] Optionally, the average particle size of the carbon-based material in the first region 141a is 10 μm to 20 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting of any two of the foregoing values. When the average particle size of the carbon-based material in the first region 141a is within the foregoing range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving the material's stability and cycling performance under fast charging.

[0225] Optionally, the average particle size of the carbon-based material of the first negative electrode active material layer 1411 is 10 μm to 20 μm. When the average particle size of the carbon-based material of the first negative electrode active material layer 1411 is within this range, the solid-phase transport path of lithium ions can be shortened, thereby improving fast charging performance. Furthermore, the material is less likely to agglomerate during the preparation process, thereby improving material stability and cycling performance under fast charging.

[0226] Optionally, the average particle size of the carbon-based material in the second region 141b is 5 μm to 12 μm, for example, 5 μm, 8 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range consisting of any two of the foregoing values. When the average particle size of the carbon-based material in the second negative active material layer 1412 is within the foregoing range, it is beneficial to enhance the fast charging capability of the battery cell and improve the stability of the material, thereby improving the cycling performance under fast charging.

[0227] Optionally, the average particle size of the carbon-based material of the second negative electrode active material layer 1412 is 5 μm to 12 μm. When the average particle size of the carbon-based material of the second negative electrode active material layer 1412 is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, thereby improving the fast charging performance. On the other hand, the material is less likely to agglomerate during the preparation process, thereby improving the stability of the material. On another hand, the combination of the negative electrode active material in the second negative electrode active material layer 1412 and the negative electrode active material in the first negative electrode active material layer 1411 within the above average particle size range is conducive to establishing a gradient porosity difference between the second negative electrode active material layer 1412 and the first negative electrode active material layer 1411, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0228] For example, the carbon-based material of the first region 141a includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region 141b includes artificial graphite. For example, the negative electrode active material of the first region 141a includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material of the second region 141b includes a silicon-based material and artificial graphite.

[0229] Illustratively, the carbon-based material of the first negative electrode active material layer 1411 includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode active material layer 1412 includes artificial graphite. For example, the negative electrode active material of the first negative electrode active material layer 1411 includes a silicon-based material, artificial graphite, and natural graphite, and the negative electrode active material of the second negative electrode active material layer 1412 includes a silicon-based material and artificial graphite.

[0230] In the embodiment of the present application, the average particle size of the carbon-based material in the first region 141a and the second region 141b has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the negative electrode sheet 12 is used as a sample, and a cross-section is polished along the thickness direction X of the negative electrode active material layer 141, for example, using an argon ion beam for cross-section polishing. The cross-section is photographed using a scanning electron microscope (SEM) to obtain an SEM cross-sectional image. The particle size of the carbon-based material in the SEM cross-section is counted, and the average particle size of the carbon-based material is calculated based on the counted number. In the case where the proportion of carbon-based material in the negative electrode film layer is relatively high, the average particle size of the carbon-based material can be used to roughly estimate the average particle size of the negative electrode active material.

[0231] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode conductive agent. The present embodiments do not particularly limit the type of negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of conductive carbon and carbon nanotubes. In some embodiments, the weight content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode active material layer.

[0232] Negative electrode conductive agents can make up for the shortcomings of insufficient conductivity of negative electrode active materials such as silicon-based materials, improve the conductivity of the negative electrode active material layer, and help improve the dynamic performance of battery cells and improve the fast charging capability of battery cells at high energy density.

[0233] Optionally, the conductive carbon content in the negative electrode active material layer is 0.4% to 0.7% by weight, such as 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, or a range consisting of any two of these values. The conductive carbon content within these ranges can improve the fast charging capability of the battery cell at high energy density.

[0234] Optionally, the carbon nanotube content in the negative electrode active material layer is 0.1% to 1% by weight, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range consisting of any two of the foregoing values. Optionally, the carbon nanotube content in the negative electrode active material layer is 0.1% to 0.5% by weight. Carbon nanotube content within the above-mentioned ranges can improve the fast charging capability of battery cells at high energy densities.

[0235] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. In some embodiments, the negative electrode binder has a mass content of ≤5% based on the total weight of the negative electrode active material layer.

[0236] In some embodiments, the negative electrode active material layer may optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode active material layer.

[0237] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0238] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 8.5 μm, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range consisting of any two of the above values.

[0239] In some embodiments, the negative electrode sheet further includes a negative electrode tab connected to the negative electrode current collector. The negative electrode tab has a thickness of 4 μm to 8.5 μm, such as 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or a range consisting of any two of these values. When the thickness of the negative electrode tab is within the above range, it is beneficial to improve the current carrying capacity and the fast charging capability of the battery cell.

[0240] The negative electrode active material layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0241] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[0242] Positive electrode

[0243] The positive electrode coating portion of the positive electrode sheet includes a positive current collector and a positive electrode active material layer disposed on at least one side of the positive current collector and containing a positive electrode active material. For example, the positive current collector has two opposing surfaces in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two opposing surfaces of the positive current collector.

[0244] In the case where the battery cell includes a laminated electrode assembly, the length direction of the battery cell is parallel to the length direction of the positive electrode sheet, the size of the battery cell along the length direction can be understood as the length of the battery cell, and the size of the positive electrode active material layer along the length direction can be understood as the length of the positive electrode active material layer; the width direction of the battery cell is parallel to the width direction of the positive electrode sheet, the size of the battery cell along the width direction can be understood as the width of the battery cell, and the size of the positive electrode active material layer along the width direction can be understood as the width of the positive electrode active material layer.

[0245] The positive electrode active material layer has a length along the length of the positive electrode sheet of 265 mm to 655 mm, for example, 265 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or a range consisting of any two of the foregoing values. Alternatively, the positive electrode active material layer has a length along the length of the positive electrode sheet of 400 mm to 600 mm. The size of the positive electrode active material layer may be equivalent to the size of the positive electrode coating portion.

[0246] In some embodiments, the ratio of the dimension of the positive electrode active material layer along the length direction of the positive electrode sheet to the dimension of the positive electrode active material layer along the width direction of the positive electrode sheet is 2 to 12.5, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 12.5, or a range consisting of any two of the foregoing values. Alternatively, the ratio of the dimension of the positive electrode active material layer along the length direction of the positive electrode sheet to the dimension of the positive electrode active material layer along the width direction of the positive electrode sheet is 4 to 8.

[0247] In the case where the positive electrode active material of the positive electrode active material layer includes lithium-containing phosphate, the conductivity of the lithium-containing phosphate is relatively poor, and the size of the positive electrode active material layer should not be too long. When the size of the positive electrode active material layer meets the above range, the electron transmission path will not be too long and the internal resistance will be relatively small, which is conducive to improving the fast charging capability and energy density of the battery cell.

[0248] In some embodiments, the length of the negative electrode active material layer is greater than the length of the positive electrode active material layer, so that lithium ions released from the positive electrode active material layer can be substantially embedded in the negative electrode active material layer, reducing the risk of lithium ion deposition at the negative electrode and improving the reliability of the battery cell. Of course, the length of the negative electrode active material layer can also be less than or equal to the length of the positive electrode active material layer.

[0249] Optionally, the difference between the length dimension of the negative electrode active material layer and the length dimension of the positive electrode active material layer is 5 mm to 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 consisting of any two of the above values.

[0250] In some embodiments, the negative electrode active material layer has a greater width than the positive electrode active material layer, allowing substantially all lithium ions released from the positive electrode active material layer to be embedded in the negative electrode active material layer, mitigating the risk of lithium ion deposition at the negative electrode and improving the reliability of the battery cell. Of course, the width of the negative electrode active material layer may also be less than or equal to the width of the positive electrode active material layer.

[0251] Optionally, the difference between the size of the negative electrode active material layer along the width direction and the size of the positive electrode active material layer along the width direction is 5 mm to 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 consisting of any two of the above values.

[0252] In some embodiments, the separator's length is greater than the negative electrode active material layer's length, enabling the separator to effectively isolate the positive and negative electrode sheets, reducing the risk of short circuits and improving the reliability of the battery cell. Of course, the separator's length may also be less than or equal to the negative electrode active material layer's length.

[0253] Optionally, the difference between the length dimension of the separator and the length dimension of the negative electrode active material layer is 6 mm to 10 mm, for example, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range consisting of any two of the above values.

[0254] In some embodiments, the separator's width is greater than the negative electrode active material layer's width, enabling the separator to effectively isolate the positive and negative electrode sheets, reducing the risk of short circuits and improving the reliability of the battery cell. Of course, the separator's width can also be less than or equal to the negative electrode active material layer's width.

[0255] Optionally, the difference between the width dimension of the separator and the width dimension of the negative electrode active material layer is 6 mm to 10 mm, for example, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm or a range consisting of any two of the above values.

[0256] like Figure 12 As shown, the dimension of the positive active material layer of the positive electrode sheet 11 along the length direction Z is the length of the positive active material layer of the positive electrode sheet 11, the dimension of the negative active material layer of the negative electrode sheet 12 along the length direction Z is the length of the negative active material layer of the negative electrode sheet 12, and the dimension of the separator 13 along the length direction Z is the length of the separator 13.

[0257] The difference between the length of the negative active material layer of the negative electrode sheet 12 and the length of the positive active material layer of the positive electrode sheet 11 is OH 11 , Figure 12 As shown in FIG, both sides of the negative electrode active material layer along the length direction Z exceed the positive electrode active material layer, and each side exceeds the OH 11Of course, the negative electrode active material layer may also extend beyond the positive electrode active material layer on one side along the length direction Z.

[0258] The difference between the length of the separator 13 and the length of the negative electrode active material layer of the negative electrode sheet 12 is OH 21 , Figure 12 As shown in FIG, both sides of the separator 13 along the length direction Z extend beyond the negative electrode active material layer, and each side extends beyond the OH 21 Of course, one side of the separator 13 along the length direction Z may extend beyond the negative electrode active material layer.

[0259] The dimension of the positive active material layer of the positive electrode sheet 11 along the width direction Y is the width of the positive active material layer of the positive electrode sheet 11, the dimension of the negative active material layer of the negative electrode sheet 12 along the width direction Y is the width of the negative active material layer of the negative electrode sheet 12, and the dimension of the separator 13 along the width direction Y is the width of the separator 13.

[0260] The difference between the width of the negative electrode active material layer of the negative electrode sheet 12 and the width of the positive electrode active material layer of the positive electrode sheet 11 is OH 12 , Figure 12 As shown in FIG, both sides of the negative electrode active material layer along the width direction Y exceed the positive electrode active material layer, and each side exceeds the OH 12 Of course, one side of the negative electrode active material layer along the width direction Y may also extend beyond the positive electrode active material layer.

[0261] The difference between the width of the separator 13 and the width of the negative electrode active material layer of the negative electrode sheet 12 is OH 22 , Figure 12 As shown in FIG, both sides of the separator 13 along the width direction Y extend beyond the negative electrode active material layer, and each side extends beyond the OH 22 Of course, one side of the separator 13 in the width direction Y may extend beyond the negative electrode active material layer.

[0262] In some embodiments, the compaction density of the positive electrode active material layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm 3 to 2.80g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode active material layer is 2.50 g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3, 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.75g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0263] When the compaction density of the positive electrode active material layer is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, because the positive electrode active material in the positive electrode active material layer is densely packed, the contact resistance between particles is low, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and improving the cycle. Therefore, by adjusting the compaction density of the positive electrode active material layer to a reasonable range, the battery cell can improve the fast charging capability and cycle performance at high energy density.

[0264] In some embodiments, the single-side coating weight of the positive electrode active material layer is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 For example, the coating weight of the positive electrode active material layer on one side is 150 mg / 1540.25 mm², 200 mg / 1540.25 mm², 250 mg / 1540.25 mm², 300 mg / 1540.25 mm², 350 mg / 1540.25 mm², 370 mg / 1540.25 mm², or a range consisting of any two of the above values. Optionally, the coating weight of the positive electrode active material layer on one side is 200 mg / 1540.25 mm². 2 Up to 300mg / 1540.25mm 2 .

[0265] When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, which will reduce the risk of aggravated side reactions due to heat accumulation, and is beneficial to improving the fast charging capability and cycle performance of the battery cell at high energy density.

[0266] In the embodiments of the present application, the compaction density of the positive electrode active material layer of a battery cell at 100% state of charge (SOC) has a meaning well known in the art. Specifically, the positive electrode sheet of a battery cell at 100% state of charge (SOC) is disassembled and the compaction density of the positive electrode active material layer is measured. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet is used, the positive electrode active material layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The positive electrode active material layer of the weighed positive electrode sheet is then wiped off, and the positive electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode active material layer = (the weight of the positive electrode sheet M1 - the weight of the positive electrode collector M0) / S1, the thickness of the positive electrode active material layer = the thickness of the positive electrode sheet H1 - the thickness of the positive electrode collector H0, the compaction density of the positive electrode active material layer = the single-sided coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0267] In some embodiments, the positive electrode active material has a charge capacity in the range of 150 mAh / g to 170 mAh / g. For example, the charge capacity in the range of 150 mAh / g, 155 mAh / g, 160 mAh / g, 165 mAh / g, 170 mAh / g, or a range consisting of any two of the foregoing values.

[0268] When the charge gram capacity of the positive electrode active material is within the above range, the energy density of the battery cell is relatively high.

[0269] In the embodiments of the present application, the gram capacity of the positive electrode active material has a meaning well known in the art and can be tested using a gram capacity test method for negative electrode active materials.

[0270] In some embodiments, the positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate may have an olivine structure, which is structurally stable during charge and discharge, and can improve the cycle life of the battery cell.

[0271] Alternatively, the positive electrode active material may further include a lithium-containing transition metal oxide. Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof.

[0272] The lithium-containing phosphate with an olivine structure can be an unmodified lithium-containing phosphate, or a material obtained by coating and modifying it. For example, the surface of the lithium-containing phosphate is provided with a carbon-containing material, and the carbon-containing material can be coated on the surface of the lithium-containing phosphate as a coating layer, thereby improving the conductivity of the lithium-containing phosphate, reducing the powder resistivity of the material, and being beneficial to the migration rate of lithium ions, improving the fast charging capability of the battery cell, and reducing the heat generation of the battery cell.

[0273] In some embodiments, the lithium-containing phosphate comprises a general formula of Li x1 A y1 Me a M b P 1-c X c Y z A compound wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A comprises one or more of Na, K, and Mg, Me comprises one or more of Mn, Fe, Co, and Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X comprises one or more of Cl, C, and N, and Y comprises one or more of O and F. The lithium-containing phosphate has excellent cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0274] Exemplarily, the lithium-containing phosphate includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cell is accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cell is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of the present application.

[0275] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0276] In some embodiments, the lithium-containing phosphate is in granular form, and the volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm, for example, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or a range consisting of any two of the above values.

[0277] When the lithium-containing phosphate meets the above conditions, its particle size is relatively small, the lithium ion deintercalation path in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the lithium-containing phosphate stable.

[0278] In some embodiments, the positive electrode active material layer further includes a positive electrode additive, which includes one or more of lithium-containing ternary materials, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. These materials can serve as lithium supplements, replenishing lithium ions in the positive electrode active material layer to compensate for irreversible lithium ion loss within the system, thereby increasing capacity and improving the energy density of the battery cell.

[0279] In some embodiments, the mass content of the positive electrode additive is 0.1% to 5%, based on the mass of the positive electrode active material layer, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing. When a lithium supplement agent within this mass range is used, lithium ions can be replenished to the positive electrode active material layer to compensate for irreversible lithium ion loss in the system. Moreover, the mass content of the lithium supplement agent is not too high, so that the positive electrode discharge capacity remains high and the energy density is not substantially reduced.

[0280] In some embodiments, the volume average particle size Dv50 of the positive electrode additive is larger than the volume average particle size Dv50 of the lithium-containing phosphate. The combination of particles of different sizes is conducive to uniform dispersion and improves the distribution uniformity of the positive electrode additive.

[0281] In some embodiments, the volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm, such as 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range consisting of any two of the foregoing.

[0282] In the embodiment of the present application, the volume average particle size Dv50 of the particles has a meaning well known in the art. The volume average particle size Dv50 of the particles refers to the particle size corresponding to 50% in the volume distribution. It can be detected by using equipment and methods well known in the art. After the fresh battery cell is fully discharged to 0% state of charge SOC, the positive electrode sheet is disassembled, the positive electrode collector is removed and the positive electrode film layer is retained. The positive electrode film layer is immersed in N-methylpyrrolidone NMP to wash out the binder in the positive electrode film layer, and the positive electrode active material or lithium supplement is retained as a sample. After the sample is dried, the volume average particle size Dv50 of the particles is tested by a Mastersizer2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0283] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the weight content of the positive electrode conductive agent is ≤5% based on the weight of the positive electrode active material layer.

[0284] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the positive electrode binder is ≤5%.

[0285] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0286] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 16 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range consisting of any two of the above values.

[0287] In some embodiments, the positive electrode sheet further includes a positive electrode tab connected to the positive electrode current collector. The positive electrode tab has a thickness of 10 μm to 16 μm, for example, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range consisting of any two of the foregoing values. When the thickness of the positive electrode tab is within the foregoing range, it is beneficial to increase the current capacity and improve the fast charging capability of the battery cell.

[0288] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0289] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode active material layer. For example, in certain embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode active material layer.

[0290] [Electrolyte]

[0291] During the charge and discharge process of a battery cell, active ions, such as lithium ions, are intercalated and released back and forth between the positive and negative electrodes. The electrolyte, which consists of an organic solvent and an electrolyte salt, conducts the active ions between the positive and negative electrodes.

[0292] In some embodiments, the electrolyte has a conductivity of 10.5 mS / cm to 13.5 mS / cm at room temperature. For example, the electrolyte has a conductivity of 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, or a range consisting of any two of the foregoing values ​​at room temperature.

[0293] When the conductivity of the electrolyte at room temperature, such as 25° C., is within the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0294] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, for example, 25° C., is ionic conductivity, which can be tested using equipment and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0295] In some embodiments, the viscosity of the electrolyte at room temperature is 1.5 mPa·s to 5.5 mPa·s. For example, the viscosity of the electrolyte is 1.5 mPa·s, 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s, or a range consisting of any two of the foregoing values.

[0296] When the viscosity of the electrolyte at room temperature, such as 25° C., is within the above range, the migration rate of lithium ions in the electrolyte is higher, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0297] In the embodiments of the present application, the viscosity of the electrolyte has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, it can be detected according to GB / T10247-2008.

[0298] In some embodiments, the density of the electrolyte at room temperature, e.g., 25° C., is between 1.05 g / mL and 1.35 g / mL. For example, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, or a range consisting of any two of the foregoing values.

[0299] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell and improve the fast charging performance of the battery cell.

[0300] In the embodiments of the present application, the density of the electrolyte has a well-known meaning in the art and can be tested using equipment and methods well-known in the art, for example, by referring to GB / T 2013-2010.

[0301] In some embodiments, the organic solvent includes a linear carboxylate solvent.

[0302] Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%. Exemplarily, the mass content of the chain carboxylate solvent is 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, or a range consisting of any two of the above values. Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 8% to 20%.

[0303] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte is relatively low, the conductivity of the electrolyte can be improved, the internal resistance of the battery cell can be reduced, and the rapid migration of lithium ions is facilitated; and the electrolyte is compatible with the silicon-containing negative electrode, which can effectively reduce the gas production of the battery cell, reduce the impact on the interface film on the negative electrode side, and improve the fast charging capability and cycle performance of the battery cell.

[0304] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0305] Formula I,

[0306] In Formula I,

[0307] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0308] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0309] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0310] Alternatively, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0311] Alternatively, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further alternatively, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0312] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0313] Illustratively, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0314]

[0315] In some embodiments, the organic solvent includes a carbonate-based solvent.

[0316] The use of carbonate solvents and chain carboxylate solvents can improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0317] Optionally, the mass content of the carbonate solvent in the electrolyte is 65% to 75%. Exemplarily, the mass content of the carbonate solvent is 65%, 70%, 75%, or a range consisting of any two of the above values.

[0318] When the mass content of carbonate solvents and chain carboxylic acid ester solvents meets the above conditions, the stability of the electrolyte can be improved, the gas production can be reduced, and the cycle performance can be improved.

[0319] Illustratively, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0320] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorinated lithium sulfonyl imide and a lithium hexafluorophosphate. Alternatively, the lithium salt includes a fluorinated lithium sulfonyl imide and a lithium hexafluorophosphate.

[0321] Lithium hexafluorophosphate may decompose to produce hydrofluoric acid HF. The side reaction between hydrofluoric acid and the negative electrode, especially the silicon-containing negative electrode, may lead to increased gas production during high-temperature storage. The combined use of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, reduce the gas production during high-temperature storage, and improve the cycle performance of the battery cell. In addition, the migration number of lithium ions increases, and the lithium ion conductivity increases, which can improve the fast charging capability of the battery cell.

[0322] Illustratively, the fluorine-containing lithium sulfonyl imide includes one or more of lithium trifluorosulfonyl imide and lithium bisfluorosulfonyl imide, and may be lithium bisfluorosulfonyl imide.

[0323] In some embodiments, the weight content of the lithium salt is greater than 0 and less than or equal to 18% based on the weight of the electrolyte, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or a range consisting of any two of the foregoing values. Optionally, the weight content of the lithium salt is 4% to 16%.

[0324] Illustratively, the sum of the mass content of lithium bis(fluorosulfonyl)imide and the mass content of lithium hexafluorophosphate is greater than 0 and less than or equal to 18%, and can be optionally 4% to 16%.

[0325] In some embodiments, based on the mass of the electrolyte, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.2 to 1.5, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two of the foregoing values. Alternatively, the ratio of the mass content of the lithium fluorinated sulfonyl imide to the mass content of the lithium hexafluorophosphate is 0.4 to 0.8.

[0326] When the ratio of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide meets the above range, on the one hand, the content of hydrofluoric acid can be reduced, the side reactions at the negative electrode interface can be slowed down, and the gas production during high-temperature storage can be reduced; on the other hand, the organic component content of the interface film formed at the negative electrode interface is appropriate, which can also reduce the gas production during high-temperature storage and improve the cycle performance.

[0327] In some embodiments, the electrolyte further includes additives, including one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. These additives can improve the performance of the interface film on the negative electrode side, resulting in a more stable interface film with relatively low impedance, which is beneficial for enhancing the fast charging performance of the battery cell and improving the cycling performance.

[0328] In some embodiments, the weight content of the additive in the electrolyte is 0.5% to 10%. For example, the weight content of the additive in the electrolyte is 0.5%, 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values. Alternatively, the weight content of the additive in the electrolyte is 2% to 6%, and further optionally 2% to 5%.

[0329] The additives in the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0330] In some embodiments, the carbonate additive includes one or more of fluoroethylene carbonate and vinylene carbonate. Optionally, the additive contains fluoroethylene carbonate and vinylene carbonate.

[0331] Fluorinated ethylene carbonate can form a solid electrolyte interface film SEI film rich in lithium fluoride LiF on the surface of the negative electrode, which can alleviate the volume expansion of silicon, improve the life of the silicon-containing system, and reduce high-temperature gas production.

[0332] The combined use of fluoroethylene carbonate and vinylene carbonate makes the interface film on the negative electrode surface more compact, which can more effectively protect the silicon-containing negative electrode, reduce the degree of side reactions at the negative electrode interface, and reduce high-temperature gas production.

[0333] Illustratively, the sulfur-containing additive includes one or more of vinyl sulfate, vinyl bissulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylene disulfonate.

[0334] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

[0335] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis method.

[0336] In the embodiment of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography.

[0337] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the components are classified, and the chain carboxylate solvent and carbonate solvent (ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as components of the organic solvent. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0338] Carbonate additives (such as fluorinated cyclic carbonates and vinylene carbonate) are used as additives for the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0339] Isolators

[0340] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0341] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical and mechanical stability can be selected.

[0342] As an example, the primary material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. The surface of the separator can also be coated with an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating.

[0343] In some embodiments, the volumetric energy density of the battery cell is between 350Wh / L and 430Wh / L. For example, the volumetric energy density of the battery cell is 350Wh / L, 370Wh / L, 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, or a range consisting of any two of these values. The volumetric energy density of the battery cell is relatively high.

[0344] In the embodiments of the present application, the volume energy density of a battery cell has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.8V and the battery discharge cut-off voltage is 2.0V.

[0345] Place the battery cell at 25°C, charge at a constant current of 0.05C to 3.8V, and discharge at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), calculate the volume of the single battery V0, unit L, and the volume energy density of the battery cell VED = (A0 × discharge platform voltage) / V0, unit Wh / L.

[0346] Example

[0347] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0348] Example 1

[0349] 1. Preparation of positive electrode sheet

[0350] The positive electrode sheet includes a positive electrode tab, a positive electrode current collector, and a positive electrode active material layer disposed on both sides of the positive electrode current collector. The positive electrode current collector is made of aluminum foil. There are two positive electrode tabs, one connected to each side of the positive electrode current collector along the length direction.

[0351] The positive electrode active material layer includes lithium iron phosphate, a lithium-containing phosphate, in a mass ratio of 95:1.85:2:1.15, lithium ferrite, a positive electrode additive, polyvinylidene fluoride (PVDF), a binder, and acetylene black, a conductive agent. The positive electrode active material layer is a film layer formed by evenly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collector, and then drying and cold pressing.

[0352] The volume average particle size Dv50 of the lithium-containing phosphate is 1.5 μm. The charge capacity of the positive electrode active material is 161 mAh / g. The volume average particle size Dv50 of the positive electrode additive is 9.5 μm, and the mass content of the positive electrode additive in the positive electrode active material layer is 1.85%. The single-sided coating weight of the positive electrode active material layer is 284 mg / 1540.25 mm 2 The length of the positive electrode active material layer is 592 mm.

[0353] 2. Preparation of negative electrode sheet

[0354] The negative electrode sheet includes a negative electrode tab, a negative electrode current collector, and negative electrode active material layers arranged on both sides of the negative electrode current collector. The negative electrode current collector is copper foil. There are two negative electrode tabs, one connected to each side of the negative electrode current collector along the length direction.

[0355] The negative electrode active material layer is a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector, drying it, and cold pressing it.

[0356] The single-side coating weight of the negative electrode active material layer is 135 mg / 1540.25 mm 2 .

[0357] The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is located on the surface of the negative electrode current collector, and the second negative electrode active material layer is located on the surface of the first negative electrode active material layer.

[0358] The first negative electrode active material layer includes a negative electrode active material, a conductive agent, a negative electrode binder (styrene-butadiene rubber), and a thickener (sodium carboxymethyl cellulose) in a mass ratio of 96.3:0.5:2.5:0.7, wherein the negative electrode active material of the first negative electrode active material layer includes artificial graphite and silicon carbide;

[0359] The second negative electrode active material layer includes a negative electrode active material, a conductive agent, a negative electrode binder (styrene-butadiene rubber), and a thickener (sodium carboxymethyl cellulose) in a mass ratio of 97.8:0.7:0.8:0.7, and the negative electrode active material of the second negative electrode active material layer includes artificial graphite and silicon carbide;

[0360] A cross-section of the negative electrode film along its thickness showed an average particle size of 13 μm for the first negative electrode film, and 10 μm for the second negative electrode film. During the negative electrode film preparation process, the desired average particle size can be achieved by adjusting the volume average particle size of the artificial graphite multiple times.

[0361] The ratio of the thickness of the first negative electrode active material layer to the thickness of the second negative electrode active material layer is 1; the conductive agents of the first negative electrode active material layer and the second negative electrode active material layer both include conductive carbon and carbon nanotubes, and the mass ratio of the conductive carbon and carbon nanotubes in the first negative electrode active material layer and the second negative electrode active material layer is 5:1.

[0362] The mass content of silicon in the negative electrode active material layer is 3.0%. The charge capacity of the negative electrode active material is 420 mAh / g.

[0363] 3. Isolation parts

[0364] The separator includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0365] 4. Preparation of electrolyte

[0366] The electrolyte comprises an organic solvent, a lithium salt and an additive. The components of the organic solvent are mixed, and the lithium salt and the additive are added to prepare the electrolyte.

[0367] The organic solvent includes 15% of a chain carboxylate solvent (ethyl acetate) and 68.5% of a carbonate solvent (ethylene carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0368] Based on the mass of the electrolyte, the mass content of the additive is 2.5% of vinylene carbonate VC.

[0369] The lithium salt includes 10% lithium hexafluorophosphate LiPF6 and 4% lithium bis(fluorosulfonyl)imide.

[0370] 5. Preparation of battery cells

[0371] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. The compaction density of the positive electrode active material layer of the battery cell at 100% SOC is 2.62 g / cm 3 The compaction density of the negative electrode active material layer at 0% SOC is 1.30 g / cm 3 .

[0372] Comparative Example 1-1 and Comparative Example 1-2

[0373] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the coating weights on one side of the positive electrode active material layer and the negative electrode active material layer were adjusted.

[0374] Example 2-1 to Example 2-4

[0375] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the coating weights on one side of the positive electrode active material layer and the negative electrode active material layer were adjusted.

[0376] Example 2-5 and Example 2-6

[0377] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the compaction density of the positive electrode active material layer and the negative electrode active material layer was adjusted.

[0378] Performance Testing

[0379] 1. DC resistance DCR test of battery cells

[0380] You can refer to the methods in GB / T 31467 "Performance test specification for high-power lithium-ion power batteries for HEV".

[0381] For example, at 25°C, charge the battery cell to 3.65V at a constant current of 0.33C, let it stand for 1 min, then charge it to 3.65V at a constant current of 0.1C, let it stand for 30 min, and discharge it to 2.0V at a constant current of 0.33C. Record the discharge capacity A0 at this time in Ah, and then charge it at a constant current of 0.33C for 0.5A0Ah, and adjust the SOC to 50%.

[0382] After the battery cell is placed at 25℃ for 2 hours, it is discharged at a current of 4C for 10 seconds and ∆U is recorded. 放电 , ∆I 放电 , the discharge DCR data of the battery cell is calculated by the following formula, R 放电 =∆U 放电 / ∆I 放电 ,

[0383] Where ∆U 放电 Indicates the voltage change within 10s after the discharge starts, ∆I 放电 Indicates the current value within 10 seconds after the start of discharge.

[0384] 2. High temperature cycle performance test of battery cells

[0385] In an environment of 60±5℃, the battery cell is charged at a constant current of 1C to the charge cut-off voltage, then charged at a constant voltage to a cut-off current of 0.05C, and then discharged at a constant current of 1C to the discharge cut-off voltage. This is one charge and discharge cycle.

[0386] The discharge capacity of this battery cell is recorded as the discharge capacity C1 of the first cycle of the lithium-ion battery cell. Repeat this cycling process for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery cell = Cn / C1 × 100%. Record the number of cycles at which the cycle capacity retention rate reaches 80%. For accuracy, take the average of five replicate samples as the test result.

[0387] 3. Room temperature cycle performance test of battery cells

[0388] At 25±5℃, charge the battery cells with Stercharge constant current:

[0389] Charge from 0% SOC to 20% SOC at 0.33C constant current;

[0390] Charge from 20% SOC to 25% SOC at 8C constant current;

[0391] Charge from 25% SOC to 30% SOC at 8C constant current;

[0392] Charge from 30% SOC to 35% SOC at 7.5C constant current;

[0393] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0394] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0395] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0396] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0397] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0398] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0399] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0400] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0401] Charge from 75% SOC to 80% SOC at 3.57C constant current;

[0402] Charge from 80% SOC to 85% SOC at 2C constant current;

[0403] Charge from 90% SOC to 95% SOC at 1C constant current;

[0404] Charge from 95% SOC to 98% SOC at 0.5C constant current;

[0405] Charge from 98% SOC to 100% SOC at 0.25C constant current.

[0406] Charging cut-off voltage at 0.1C constant current;

[0407] Then, the battery is discharged at a constant current of 1C until the discharge cut-off voltage is reached. This is one charge and discharge cycle.

[0408] The discharge capacity of this battery cell is recorded as the discharge capacity C1 of the first cycle. Repeat this cycle for the same battery cell. After n cycles, record the discharge capacity Cn of the nth cycle. The cycle capacity retention rate of this battery cell = Cn / C1 × 100%. Record the number of cycles at which the cycle capacity retention rate reaches 80%. For accuracy, take the average of five replicate samples as the test result.

[0409] 4. Fast charging time test of battery cells from 20% to 80% SOC

[0410] At 25±5℃, charge the battery cells with Stercharge constant current:

[0411] Charge from 0% SOC to 20% SOC at 0.33C constant current;

[0412] Charge from 20% SOC to 25% SOC at 8C constant current;

[0413] Charge from 25% SOC to 30% SOC at 8C constant current;

[0414] Charge from 30% SOC to 35% SOC at 7.5C constant current;

[0415] Charge from 35% SOC to 40% SOC at 6.87C constant current;

[0416] Charge from 40% SOC to 45% SOC at 6.38C constant current;

[0417] Charge from 45% SOC to 50% SOC at 5.95C constant current;

[0418] Charge from 50% SOC to 55% SOC at 5.53C constant current;

[0419] Charge from 55% SOC to 60% SOC at 5.14C constant current;

[0420] Charge from 60% SOC to 65% SOC at 4.76C constant current;

[0421] Charge from 65% SOC to 70% SOC at 4.36C constant current;

[0422] Charge from 70% SOC to 75% SOC at 3.94C constant current;

[0423] Charge from 75% SOC to 80% SOC at 3.57C constant current.

[0424] The test results are shown in Table 1.

[0425] Table 1

[0426]

[0427] The coating weight of the positive and negative active material layers of Comparative Example 1-1 is relatively small, and the volume energy density of the battery cell is low; the coating weight of the positive and negative active material layers of Comparative Example 1-2 is relatively high. Although the volume energy density of the battery cell is high, the migration resistance of lithium ions in the positive and negative active material layers is large, which is not conducive to the rapid charging of the battery cell under high energy density; and the side reactions on the negative electrode side are aggravated, and the cycle is deteriorated, especially the cycle under fast charging is deteriorated.

[0428] Increasing the coating weight of the positive and negative active material layers is beneficial to improving the volumetric energy density of the battery cell. As the coating weight of the positive active material layer on one side increases, the energy density of the battery cell increases, but the DCR of the battery cell also increases, which is not conducive to fast charging of the battery cell.

[0429] The coating weight of the positive electrode active material layer on one side of the embodiment 2-1 to embodiment 2-4 of the present application is 150 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm2 ; The single-sided coating weight of the negative electrode active material layer is 70mg / 1540.25mm 2 Up to 175mg / 1540.25mm 2 ; This makes the energy density of the battery cell relatively high, and the migration resistance of lithium ions will not be too large, which can effectively improve the cycle performance under fast charging conditions and high-temperature cycle performance.

[0430] Furthermore, the charging time of the battery cells of the embodiments from 20% SOC to 80% SOC is relatively short, for example, 7 minutes for embodiment 1 and 14 minutes for embodiments 2-4. The charging time is relatively short, and a fast charging effect can be achieved.

[0431] By setting the compaction density of the positive and negative electrode active material layers within an appropriate range, Examples 2-5 and 2-6 can effectively improve the volume energy density of the battery cell and can effectively improve the cycle performance of the battery cell under high energy density and fast charging.

[0432] Comparative Example 2-1 and Comparative Example 2-2

[0433] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode active material layer was adjusted.

[0434] Comparative Examples 2-3

[0435] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the positive electrode tab was arranged on one side of the positive electrode coating portion along the length direction, and the negative electrode tab was arranged on one side of the negative electrode coating portion along the length direction.

[0436] Example 3-1

[0437] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the length and single-side coating weight of the positive electrode active material layer were adjusted.

[0438] Example 3-2

[0439] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the length of the positive electrode active material layer was adjusted.

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

[0441] Table 2

[0442]

[0443] The length of the positive electrode active material layer of Comparative Example 2-1 is relatively short, resulting in a lower energy density of the battery cell; the length of the positive electrode active material layer of Comparative Example 2-2 is relatively long, and the electron transmission path is relatively long, resulting in a higher internal resistance of the battery cell and poor cycle performance.

[0444] The positive electrode tab of Comparative Example 2-3 is arranged on one side of the positive electrode coating portion along the length direction. The electron transmission path in the positive electrode coating portion is long, resulting in poor internal resistance and cycle of the battery cell.

[0445] The length of the positive electrode active material layer of Examples 3-1 and 3-2 of the present application is within an appropriate range, and the energy density of the battery cell is relatively high; the positive electrode ears are arranged on both sides of the positive electrode coating portion along the length direction, which can shorten the transmission path of electrons in the length direction of the positive electrode coating portion, reduce the internal resistance of the battery cell, improve the fast charging capability, and is conducive to the improvement of the cycle performance under fast charging conditions; due to the reduction in internal resistance, the heat generation is reduced, which can alleviate the decomposition of electrolyte components caused by heat accumulation, thereby improving high-temperature cycle performance.

[0446] Example 4-1

[0447] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size Dv50 of the lithium-containing phosphate was adjusted.

[0448] Example 4-2

[0449] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the material of the positive electrode additive was adjusted.

[0450] Example 4-3

[0451] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the volume average particle size Dv50 of the positive electrode additive was adjusted.

[0452] Example 4-4

[0453] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the mass content of the positive electrode additive in the positive electrode active material layer was adjusted.

[0454] The test results are shown in Table 3.

[0455] Table 3

[0456]

[0457] The smaller the volume average particle size of the lithium-containing phosphate in Example 1 and Example 4-1, the more conducive it is to increasing the active surface, increasing the contact area with the conductive agent, etc., improving the conductive performance, reducing the internal resistance of the battery cell, and improving the cycle performance under fast charging conditions; and since the internal resistance is reduced, the heat generation is reduced, which can alleviate the decomposition of electrolyte components caused by heat accumulation, thereby improving high-temperature cycle performance.

[0458] Positive electrode additives can be used as lithium replenishers to compensate for lithium loss in battery cells. Positive electrode additives can include various materials such as lithium ferrite and lithium nickelate. When the volume average particle size of the positive electrode additives in Examples 4-1 to 4-4 meets the requirements of 8μm to 10μm, they can effectively release lithium ions to replenish lithium and improve the cycle life of the battery cells. As the particle size increases, the active surface area decreases, and the interface for side reactions with the electrolyte at high temperatures is reduced, thereby improving high-temperature cycle performance. As the amount of positive electrode additive added increases, the lithium replenishment effect improves. When the mass content of the positive electrode additive is 0.1% to 5%, the cycle life of the battery cells can be effectively improved.

[0459] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the embodiments of the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: An electrode assembly is included, the electrode assembly comprising: A plurality of positive electrode sheets, each of the positive electrode sheets comprising a positive electrode coating portion and at least two positive electrode tabs, the positive electrode coating portion being provided with a positive electrode active material layer, the at least two positive electrode tabs being connected to opposite sides of the positive electrode coating portion along the length direction of the battery cell, the positive electrode active material layer comprising a lithium-containing phosphate; A plurality of negative electrode sheets, wherein the plurality of negative electrode sheets and the plurality of positive electrode sheets are stacked along the thickness direction of the battery cell, each of the negative electrode sheets comprises a negative electrode coating portion and at least two negative electrode tabs, the negative electrode coating portion is provided with a negative electrode active material layer, the at least two negative electrode tabs are connected to both sides of the negative electrode coating portion along the length direction, and the negative electrode active material layer comprises a carbon-based material. The negative electrode sheet satisfies: m×W3 / W4 is 0.2 to 1.0; m represents the number of all negative electrode ears located on the same side of the negative electrode coating portion; W3 represents the average size of the negative electrode tab along the width direction of the battery cell; W4 represents the dimension of the negative electrode coating portion along the width direction; in, The single-side coating weight of the positive electrode active material layer is 200 mg / 1540.25 mm 2 Up to 300mg / 1540.25mm 2 ; The single-side coating weight of the negative electrode active material layer is 95 mg / 1540.25 mm 2 Up to 142mg / 1540.25mm 2 ; The positive electrode coating portion has a dimension along the length direction of 265 mm to 655 mm.

2. The battery cell according to claim 1, wherein: The lithium-containing phosphate includes lithium iron phosphate.

3. The battery cell according to claim 1, wherein: The lithium-containing phosphate is in a granular form, and a volume average particle size Dv50 of the lithium-containing phosphate is 1 μm to 2 μm.

4. The battery cell according to claim 1, wherein: The positive electrode active material layer also includes a positive electrode additive, which includes one or more of lithium-containing ternary materials, lithium phosphate, dilithium 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 ferrite.

5. The battery cell according to claim 4, characterized in that The volume average particle size Dv50 of the positive electrode additive is 8 μm to 10 μm.

6. The battery cell according to claim 4, characterized in that The positive electrode additive may be present in an amount of 0.1% to 5% by mass based on the mass of the positive electrode active material layer.

7. The battery cell according to claim 1, characterized in that The negative electrode active material layer further includes a silicon-based material, and the mass content of silicon element of the silicon-based material in the negative electrode active material layer is 0.3% to 10%.

8. The battery cell according to claim 7, characterized in that The silicon-based material includes one or more of silicon carbide and silicon oxide.

9. The battery cell according to claim 1, characterized in that The negative electrode coating portion further includes a negative electrode current collecting portion, and the negative electrode active material layer includes: a first region disposed on the surface of the negative electrode current collecting portion, wherein the thickness of the first region is 1 / 3 of the thickness of the negative electrode active material layer; and The second region is connected to the side of the first region away from the negative electrode current collecting portion, and the thickness of the second region is 1 / 3 of the thickness of the negative electrode active material layer. in, An average particle size of the carbon-based material in the first region is greater than or equal to an average particle size of the carbon-based material in the second region.

10. The battery cell according to claim 9, characterized in that The average particle size of the carbon-based material in the first region is 10 μm to 20 μm; and / or The average particle size of the carbon-based material in the second region is 5 μm to 12 μm.

11. The battery cell according to claim 9, characterized in that The carbon-based material of the first region includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second region includes artificial graphite.

12. The battery cell according to claim 1, wherein The negative electrode coating portion further includes a negative electrode current collecting portion, and the negative electrode active material layer includes: a first negative electrode active material layer, disposed on the surface of the negative electrode current collecting portion; The second negative electrode active material layer is connected to a side of the first negative electrode active material layer away from the negative electrode current collecting portion.

13. The battery cell according to claim 1, characterized in that A ratio of a dimension of the positive electrode coating portion along the length direction to a dimension of the positive electrode coating portion along a width direction of the battery cell is 2 to 12.

5.

14. The battery cell according to claim 1, characterized in that There are at least two positive electrode tabs located on the same side of the positive electrode coating portion; and / or There are at least two negative electrode ears located on the same side of the negative electrode coating portion.

15. The battery cell according to claim 1, characterized in that The positive electrode sheet satisfies: n×W1 / W2 is 0.2 to 1.0; n represents the number of all positive electrode ears located on the same side of the positive electrode coating portion; W1 represents the average size of the positive electrode tab along the width direction of the battery cell; W2 represents the dimension of the positive electrode coating portion along the width direction.

16. The battery cell according to claim 1, characterized in that The battery cell further includes at least two positive terminals, and the at least two positive terminals are respectively disposed on both sides of the positive electrode coating portion along the length direction.

17. The battery cell according to claim 1, characterized in that The battery cell further includes at least two negative electrode terminals, and the at least two negative electrode terminals are respectively disposed on both sides of the negative electrode coating portion along the length direction.

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

19. The battery cell according to claim 1, characterized in that The battery cell further includes an electrolyte, and the electrolyte further includes a chain carboxylate solvent. The mass content of the chain carboxylate solvent in the electrolyte is 5% to 35%.

20. The battery cell according to claim 19, characterized in that The chain carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

21. The battery cell according to claim 18, characterized in that The electrolyte further includes a carbonate solvent, and the mass content of the carbonate solvent in the electrolyte is 65% to 75%.

22. The battery cell according to claim 21, characterized in that The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

23. A battery device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 22.

24. An electrical device, characterized in that: Comprising the battery device of claim 23.

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