Battery cell, battery apparatus and electric apparatus

Abstract

The present application relates to a battery cell, a battery apparatus and an electric apparatus. The battery cell comprises an electrode assembly, wherein the electrode assembly comprises first electrode sheets and second electrode sheets which are stacked in the thickness direction of the battery cell; the first electrode sheets and the second electrode sheets each comprise an electrode sheet body and at least one tab portion; at least part of the region of the electrode sheet body is provided with an active material layer; the at least one tab portion is connected to the electrode sheet body and protrudes from the electrode sheet body in a first direction; the active material layer of a positive electrode sheet comprises a lithium-containing phosphate having an olivine structure; the size of the electrode sheet body of the positive electrode sheet in the length direction of the battery cell is 320 mm to 650 mm; and the first electrode sheet satisfies that the maximum value of a2+b2 is 6000 to 110,000. The fast charging capability of the battery cell of the present application under a high energy density can be further improved.

Description

Battery cells, battery packs and electrical devices Technical Field

[0001] This application relates to a battery cell, a battery device, and an electrical device. Background Technology

[0002] Battery cells possess characteristics such as high capacity and long lifespan, making them widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Due to significant advancements in battery technology, higher performance requirements have been placed on batteries. However, the fast-charging capability of battery cells needs further improvement. Summary of the Invention

[0003] This application provides a battery cell, a battery device, and an electrical device, and the fast charging capability of the battery cell in this application can be further improved.

[0004] In a first aspect, this application provides a battery cell, which includes an electrode assembly. The electrode assembly includes a first electrode and a second electrode stacked along the thickness direction of the battery cell. One of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode. Both the first electrode and the second electrode include an electrode body and at least one tab. At least a portion of the electrode body is provided with an active material layer, and at least one tab is connected to the electrode body and protrudes from the electrode body along a first direction.

[0005] The active material layer of the positive electrode includes lithium phosphate with an olivine structure, and the electrode body of the positive electrode has a length of 320 mm to 650 mm along the length of the battery cell.

[0006] Among them, the first electrode satisfies: a 2 +b 2 The maximum value is between 6,000 and 110,000.

[0007] 'a' represents the distance between any point A on the body of the first electrode and the electrode ear closest to point A in at least one electrode ear along the first direction, and its unit is mm.

[0008] b indicates that, in the first electrode, along the second direction, the distance between point A and the electrode tab closest to point A in at least one electrode tab is b, and the unit is mm. One of the second direction and the first direction is parallel to the length direction, and the other is parallel to the width direction of the battery cell.

[0009] Therefore, in this embodiment, the electrode assembly is a stacked structure, and the dimensions of the positive electrode body along the length of the battery cell are within the aforementioned range, resulting in a relatively high energy density for the battery cell. However, with a relatively high energy density, the internal resistance of the electrode is high, and the positive electrode active material in this application also includes lithium phosphate with a poor conductivity olivine structure, further increasing the internal resistance. To reduce the internal resistance, this embodiment designs the electron transport path to be relatively short within the electrode, reducing the internal resistance of the electrode and thus lowering the internal resistance of the battery cell, which is beneficial for rapid charging of the battery cell at high energy densities.

[0010] In some implementations, the first direction is parallel to the length direction of the battery cell.

[0011] In some embodiments, the first electrode has multiple tabs, which are disposed on both sides of the electrode body along a first direction. This results in a shorter electron transport path, which is beneficial for rapid charging of the battery cell.

[0012] In some implementations, a 2 +b 2 The maximum value is 25,600 to 110,000, and the selectable value is 25,600 to 90,000. The electron transport path is shorter, which is beneficial for the rapid charging of individual battery cells.

[0013] In some implementations, the first direction is parallel to the width direction of the battery cell. This results in a shorter electron transport path, which is beneficial for rapid charging of the battery cell.

[0014] In some embodiments, at least one tab of the first electrode is disposed on the same side of the electrode body along a first direction.

[0015] In some implementations, a 2 +b 2 The maximum value is 6400 to 45000, and the selectable value is 6400 to 25000. The electron transport path is shorter, which is beneficial for the rapid charging of individual battery cells.

[0016] In some embodiments, the electrode assembly has a stacked structure, with the main body of the positive electrode having a width dimension of 80mm to 150mm. This results in a relatively short electron transport path, which facilitates rapid charging of the individual battery cells.

[0017] In some embodiments, the first electrode has multiple tabs located on the same side of the electrode body, and the distance between two adjacent tabs along the second direction is greater than 0 and less than or equal to 300 mm. Each tab carries a smaller current, resulting in a more uniform current distribution, which is beneficial for the rapid charging of the battery cell.

[0018] In some implementations, the second electrode satisfies: c2 +d 2 The maximum value is between 6,000 and 110,000.

[0019] Where c represents the distance between any point B on the body of the second electrode and the electrode ear closest to point B in at least one electrode ear along the first direction, and its unit is mm.

[0020] d represents the distance along the second direction between point B and the electrode closest to point B in at least one electrode, and its unit is mm.

[0021] Therefore, when the second electrode in the embodiment of this application meets the above conditions, the electron transmission path is relatively short, which can effectively reduce the internal resistance of the battery cell, and each tab carries a smaller current and the current distribution is more uniform, which is conducive to the rapid charging of the battery cell.

[0022] In some embodiments, the tabs of the first electrode are disposed on at least one side of the electrode body along a first direction. The first electrode satisfies the following: n*W1 / W2 is 0.5 to 1.0; n represents the number of tabs located on the same side of the electrode body; W1 represents the average size of the tabs along a second direction, where one of the first and second directions is parallel to the length direction of the battery cell, and the other is parallel to the width direction of the battery cell; W2 represents the size of the electrode body along the second direction. The tabs have strong current-carrying capacity, which is beneficial for improving the current-carrying capacity of the battery device and enhancing its fast-charging performance.

[0023] In some embodiments, the battery cell further includes an electrolyte comprising a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent comprises 5% to 30% by mass in the electrolyte. The above solvent system has high conductivity, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0024] In some embodiments, the battery cell further includes an electrolyte comprising lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 0.5 to 4 based on the mass of the electrolyte. When the lithium salt meets the above conditions, it is beneficial to improve the lithium-ion conductivity of the electrolyte, thereby enhancing the fast-charging performance of the battery cell.

[0025] In some embodiments, the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature. When the conductivity of the electrolyte at room temperature, such as 25°C, is within the above range, the lithium ion migration rate in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0026] In some embodiments, the olivine-structured lithium phosphate includes lithium iron phosphate. Lithium phosphates exhibit superior cycle stability, which is beneficial for improving cycle performance.

[0027] In some embodiments, the active material layer of the positive electrode sheet is a positive active material layer, and the single-sided coating weight of the positive active material layer is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generation per unit area of ​​the positive electrode sheet will not be too large, and it can also improve the energy density and charging rate performance of the battery cell.

[0028] In some embodiments, the compaction density of the positive electrode active material layer of the battery cell at 0% charge is 2.30 g / cm³. 3 Up to 2.70 g / cm 3 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; and because the positive electrode active material layer is relatively densely packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet and improve the fast charging performance of the battery cell at high energy density.

[0029] In some embodiments, the negative electrode body includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a carbon-based material and comprises a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative current collector; the second negative electrode film layer is connected to the side of the first negative electrode film layer opposite to the negative current collector. The volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer. In the embodiments of this application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve fast charging performance, and alleviate the lithium plating problem on the surface of the negative electrode.

[0030] In some embodiments, the carbon-based material of the first negative electrode film is granular with a volume average particle size Dv50 of 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the carbon-based material of the first negative electrode film is within the above range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material.

[0031] In some embodiments, the carbon-based material of the second negative electrode film is particulate, with a volume average particle size (Dv50) of 7.8 μm to 14.3 μm. When the volume average particle size (Dv50) of the carbon-based material in the second negative electrode film is within this range, it can shorten the solid-phase transport path of lithium ions, improving fast-charging performance. Furthermore, the material is less prone to agglomeration during preparation, improving its stability. Additionally, the combination of the negative electrode active material in the second negative electrode film and the negative electrode active material in the first negative electrode film within the aforementioned volume average particle size range facilitates the creation of a gradient porosity difference between the second and first negative electrode films, reducing the tortuosity of lithium ion transport and improving the fast-charging performance of the battery cell.

[0032] In some embodiments, the carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

[0033] In some embodiments, the active material layer of the negative electrode sheet is a negative active material layer, and the single-sided coating weight of the negative active material layer is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 When the single-sided coating weight of the negative electrode active material layer is within the above range, the heat generation per unit area of ​​the negative electrode sheet will not be too large, and it can also improve the energy density of the battery cell, which is beneficial to improving the fast charging performance of the battery cell at high energy density.

[0034] In some embodiments, the compaction density of the negative electrode active material layer of the battery cell at 0% charge is 1.30 g / cm³. 3 Up to 1.65 g / cm 3 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; and because the negative electrode active material layer is relatively densely packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thus improving the fast charging performance of the battery cell at high energy density.

[0035] Secondly, embodiments of this application also propose a battery device, including a battery cell of any embodiment of the first aspect of this application.

[0036] Thirdly, embodiments of this application also propose an electrical device, which includes a battery device as described in any of the embodiments of the second or third aspects of this application. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0038] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application.

[0039] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application;

[0040] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application;

[0041] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0042] Figure 5 is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0043] Figure 6 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0044] Figure 7 is a schematic diagram of the structure of the first electrode of a battery cell provided in some other embodiments of this application;

[0045] Figure 8 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0046] Figure 9 is a schematic diagram of the structure of the second electrode of a battery cell provided in some embodiments of this application;

[0047] Figure 10 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0048] Figure 11 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0049] Figure 12 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0050] Figure 13 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0051] Figure 14 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0052] Figure 15 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0053] Figure 16 is a schematic diagram of the structure of the first electrode of a battery cell provided in some other embodiments of this application;

[0054] Figure 17 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application.

[0055] The accompanying drawings may not be drawn to scale.

[0056] The reference numerals in the attached figures are explained as follows: X, thickness direction; Y, width direction; Z, length direction; 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Receiving space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. First electrode; 111. First tab; 1111. First end; 112. First electrode body; 12. Second electrode; 121. Second tab; 122. Second electrode body; 13. Separator; 20. Housing assembly; 21. Housing; 211. First housing section; 212. Second housing section; 2121. First wall; 2122. Second wall; 213. Third housing section; 22. End cap; 31. First electrode terminal; 32. Second electrode terminal; 51. First adapter; 61. First conductive component; 611. First conductive part; 612. Second conductive part. Detailed Implementation

[0057] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0058] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all 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 stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0060] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0061] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0062] In this application, "multiple" means two or more (including two).

[0063] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0064] A battery cell includes an electrode assembly, which includes electrode plates. During charging, electrons are transported in the electrode plates. When the electron transport path is too long, the electron conductivity is low and the internal resistance is high, which is not conducive to the fast charging of the battery cell. In particular, at high energy density, the internal resistance of the battery cell increases further, which is not conducive to the fast charging of the battery cell at high energy density.

[0065] In view of the above problems, the embodiments of this application select an appropriate range of positive electrode active material layer size to make the energy density of the battery cell relatively high. Furthermore, by designing the electron transmission distance, the electron transmission path is made relatively short, which can effectively reduce the internal resistance of the battery cell, thereby facilitating the rapid charging of the battery cell at high energy density.

[0066] The battery cell described in this application is applicable to various battery devices and electrical appliances that use battery cells.

[0067] For example, the electrical device can be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, power tool, vehicle, ship, and spacecraft, etc. Alternatively, for example, the electrical device can be a spacecraft, including airplanes, rockets, space shuttles, and spacecraft, etc.

[0068] Figure 1 is a schematic diagram of an example electrical device 1. This electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 1, a battery pack or battery module can be used.

[0069] The electrical device 1 has a battery pack installed inside. The battery pack can be located at the bottom, head, or tail of the electrical device 1. The battery pack can be used to supply power to the electrical device 1. For example, the battery pack can be used as the operating power source for the electrical device 1, and it can also be used as the driving power source for the electrical device 1, replacing or partially replacing fuel oil or natural gas to provide driving power for the electrical device 1. The battery pack shown in Figure 1 is a battery pack 2.

[0070] Electrical device 1 may also include controller 3 and motor 4. Controller 3 is used to control the battery device to supply power to motor 4, for example, to meet the power needs of electrical device 1 during startup, navigation and driving.

[0071] A battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via busbars.

[0072] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0073] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0074] As shown in Figure 2, in some embodiments, the battery device can be a battery pack 2, which includes a housing 5 and one or more battery cell assemblies housed in the housing 5.

[0075] As an example, the battery cell assembly can also be housed in the housing 5 by directly fixing multiple battery cells to the housing 5.

[0076] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has an accommodating space 5c. The first housing portion 5a and the second housing portion 5b are fastened together to form a closed space inside the housing 5 to accommodate the battery cell assembly. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0077] As an example, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that the interior of the housing 5 forms an enclosed space to accommodate the battery cell assembly.

[0078] In some embodiments, the housing 5 can be part of the vehicle's chassis structure. For example, a portion of the housing 5 can be at least a part of the vehicle's floor, or a portion of the housing 5 can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0079] As an example, the battery cell assembly can be a battery module 6, which can be housed in the housing 5 by fixing the battery module 6 in the housing 5.

[0080] As shown in Figure 3, the battery module 6 includes multiple battery cells 7.

[0081] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the ambient temperature of the battery device is room temperature, for example, 25°C.

[0082] In some embodiments, during the charging process of the battery device or any of the battery cells 7 constituting the battery device from 10% SOC to 80% SOC, the ambient temperature of the external environment in which the battery device is located is room temperature, for example, 25°C.

[0083] For example, the charging process of the battery device or any of the battery cells 7 constituting the battery device from 10% SOC to 80% SOC can be performed as follows:

[0084] Charge from 10% SOC to 25% SOC at a constant current of 7.0C;

[0085] Charge from 25% SOC to 30% SOC at a constant current of 7.0C;

[0086] Charge from 30% SOC to 35% SOC at a constant current of 7.0C;

[0087] Charge from 35% SOC to 40% SOC at a constant current of 7.0C;

[0088] Charge from 40% SOC to 45% SOC at a constant current of 6.7C;

[0089] Charge from 45% SOC to 50% SOC at a constant current of 6.5C;

[0090] Charge from 50% SOC to 55% SOC at a constant current of 6.0C;

[0091] Charge from 55% SOC to 60% SOC at a constant current of 5.8C;

[0092] Charge from 60% SOC to 65% SOC at a constant current of 5.5C;

[0093] Charge from 65% SOC to 70% SOC at a constant current of 5.2C;

[0094] Charge from 70% SOC to 75% SOC at a constant current of 5.0C;

[0095] Charge from 75% SOC to 80% SOC at a constant current of 4.8C.

[0096] In some embodiments, the charging time for the battery device or any single battery cell 7 constituting the battery device from 10% state of charge to 80% state of charge is 5 min to 20 min, optionally less than or equal to 12 min, and further optionally 5 min to 8 min. The ambient temperature of the battery device at 10% state of charge is room temperature, for example, 25°C. Exemplarily, the charging time for the battery device from 10% state of charge to 80% state of charge is 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 any range of two of the above values.

[0097] As shown in Figures 4 to 6, the battery cell 7 includes an electrode assembly 10, which includes a first electrode 11 and a second electrode 12. One of the first electrode 11 and the second electrode 12 is a positive electrode, and the other is a negative electrode. Both the first electrode 11 and the second electrode 12 include an electrode body and a tab. At least a portion of the electrode body is provided with an active material layer. At least one tab is connected to the electrode body and protrudes from the electrode body along a first direction, and at least a portion of the tab is not provided with an active material layer.

[0098] The active material layer of the positive electrode sheet includes a positive active material, which includes a lithium phosphate with an olivine structure; the electrode body of the positive electrode sheet has a dimension of 320 mm to 650 mm along the length direction Z of the battery cell 7.

[0099] Among them, the first electrode 11 satisfies: a 2 +b 2 The maximum value is between 6,000 and 110,000.

[0100] a represents the distance between any point A of the electrode body and the electrode ear closest to point A in at least one electrode ear in the first direction of the first electrode 11, and the distance is in mm.

[0101] b indicates that, in the first electrode 11, along the second direction, the distance between point A and the electrode ear closest to point A in at least one electrode ear is b, and the unit is mm. One of the second direction and the first direction is parallel to the length direction of the first electrode, and the other is parallel to the width direction of the first electrode.

[0102] For example, a 2 +b 2The maximum value is 6000, 10000, 15000, 20000, 25000, 30000, 35000, 40000, 45000, 50000, 55000, 60000, 65000, 70000, 75000, 80000, 85000, 90000, 95000, 100000, 105000, 110000, or a range of any two of the above values.

[0103] Within the same first electrode 11, there are multiple points A, a 2 +b 2 There are multiple values ​​for a. 2 +b 2 The maximum value can basically characterize the longest electron transport distance in this electrode, by analyzing a 2 +b 2 The design maximizes the value of electrons and shortens the electron transport path.

[0104] In this embodiment, the electrode assembly 10 can be a stacked electrode assembly, which, compared to a wound electrode assembly, can carry more active material and is beneficial to improving the energy density of the battery cell 7.

[0105] The size of the positive electrode body along the length direction Z of the battery cell 7 is too small, resulting in a low energy density of the battery cell 7, which cannot meet the requirements; the size of the positive electrode body along the length direction Z of the battery cell 7 is too large, which results in a high energy density of the battery cell 7, but the electron transport path is long and the internal resistance is too high, which is not conducive to fast charging.

[0106] In this embodiment, the size of the positive electrode body along the length direction Z of the battery cell 7 is within the above-mentioned range, resulting in a relatively high energy density of the battery cell. With a relatively high energy density, the internal resistance of the electrode is high, and the positive electrode active material of this application also includes lithium phosphate with an olivine structure that has poor conductivity, further increasing the internal resistance. To reduce the internal resistance, this embodiment designs the electron transport path to be relatively short within the electrode, reducing the internal resistance of the electrode and thus reducing the internal resistance of the battery cell, which is beneficial for the rapid charging of the battery cell at high energy density.

[0107] To more clearly illustrate this application, the tab portion of the first electrode 11 is defined as the first tab 111, and the electrode body of the first electrode 11 is defined as the first electrode body 112. The tab portion of the second electrode 12 is defined as the second tab 121, and the electrode body of the second electrode 12 is defined as the second electrode body 122. The electrode terminal with the same electrical charge and electrically connected to the first tab 111 is the first electrode terminal 31, and the electrode terminal with the same electrical charge and electrically connected to the second tab 121 is the second electrode terminal 32.

[0108] At least a portion of the electrode body is provided with an active material layer, which can be understood as the entire area of ​​the electrode body being provided with an active material layer; or, a portion of the electrode body is provided with an active material layer, while an insulating layer can be provided in another portion of the electrode body. For example, a portion of the electrode body of a positive electrode is provided with an active material layer, while the edge portion of the electrode body is provided with an insulating layer.

[0109] At least a portion of the tab is not provided with an active material layer, which can be understood as the entire tab being without an active material layer; or the main area of ​​the tab is not provided with an active material layer, but a portion of the tab near the electrode body is provided with an active material layer. For example, the portion of the tab near the electrode body of the negative electrode can be provided with an active material layer to receive active ions from the positive electrode and reduce the risk of lithium plating.

[0110] The first electrode 11 and the second electrode 12 have opposite polarities. When the first electrode 11 is the positive electrode, the second electrode 12 is the negative electrode, the first electrode terminal 31 is the positive terminal, and the second electrode terminal 32 is the negative terminal; or when the first electrode 11 is the negative electrode, the second electrode 12 is the positive electrode, the first electrode terminal 31 is the negative terminal, and the second electrode terminal 32 is the positive terminal.

[0111] The electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The following explanation uses the first electrode 11 as the positive electrode and the second electrode 12 as the negative electrode as an example. Of course, the first electrode 11 can also be the negative electrode and the second electrode 12 the positive electrode. The main body of the positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector; that is, the active material layer containing the positive active material is the positive active material layer.

[0112] The length dimension of the positive electrode active material layer of the positive electrode sheet is 320 mm to 650 mm, for example, 320 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or any combination of two of the above values. Optionally, the length dimension of the positive electrode active material layer of the positive electrode sheet is 320 mm to 600 mm. When the length dimension of the positive electrode active material layer of the positive electrode sheet meets the above range, it is possible to improve both the energy density and fast charging performance of the battery cell.

[0113] The positive electrode active material layer of the positive electrode sheet has a width dimension of 80mm to 150mm, such as 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, or any combination of two of the above values. When the width dimension of the positive electrode active material layer of the positive electrode sheet meets the above range, it is possible to improve both the energy density and fast charging performance of the battery cell.

[0114] When the electrode assembly 10 has a stacked structure, the first electrode 11, the second electrode 12 and the separator 13 are stacked to form the electrode assembly 10, and the first electrode 11, the second electrode 12 and the separator 13 are stacked.

[0115] In Figure 4, X represents the thickness direction of the battery cell 7. In the case of a stacked structure, the thickness direction of the battery cell 7, the thickness direction of the first electrode 11, the thickness direction of the second electrode 12, and the thickness direction of the electrode assembly are parallel.

[0116] Y represents the width direction of the battery cell 7. In the case of a stacked structure, the width direction of the battery cell 7 is parallel to the width direction of the first electrode 11 and the width direction of the electrode assembly.

[0117] Z represents the length direction of the battery cell 7. In the case of a stacked structure, the length direction of the battery cell 7 is parallel to the length direction of the first electrode 11 and the length direction of the electrode assembly.

[0118] In this embodiment, the first direction may be parallel to the width direction Y or the length direction Z of the battery cell 7.

[0119] Next, we will explain the relevant schemes for the first direction being parallel to the width direction Y of the battery cell 11.

[0120] In some embodiments, the first electrode 11 includes one or more first tabs 111, which are disposed on at least one side of the electrode body along the width direction Y.

[0121] Any point within the first electrode body 112 is defined as point A, and point A can be arbitrarily chosen within the first electrode body 112. Any point can be a point with an area, for example, a point with an area of ​​0.01 μm. 2 The area of ​​the point is much smaller than the area of ​​the tab, and the size of the point will not interfere with the measurement of the spacing.

[0122] The first tab 111 includes a first side and a second side facing each other along a first direction. The first side is disposed close to the first electrode body 112, and the second side is disposed away from the first electrode body 112. The distance between point A and the first tab 111 along the first direction refers to the distance between point A and the first side along the first direction. In Figure 6, the first direction is parallel to the width direction Y of the battery cell 11, and 'a' represents the distance between point A and the first tab 111 along the width direction Y.

[0123] The first electrode 111 may be configured as one or more. When there are multiple first electrodes 111, the first electrode 111 that is closest to point A along the second direction refers to the first electrode 111 that has the smallest distance from point A along the second direction.

[0124] The first electrode tab 111 closest to point A is defined as the closest electrode tab. The closest electrode tab includes a first edge and a second edge that are opposite to each other along the second direction. The first edge is located close to point A, and the second edge is located away from point A. Along the second direction, the distance between point A and the first electrode tab 111 closest to point A refers to the distance between point A and the first edge along the second direction.

[0125] The projection of the closest tab along the first direction partially overlaps with the projection of the first electrode body 112 along the first direction. In other words, the projection of the closest tab along the first direction lies within the projection of the first electrode body 112 along the first direction, where the first direction is parallel to the normal to the projection plane. Point A is any point in the first electrode body 112. When the projection of point A along the first direction lies within the projection of the closest tab along the first direction, the distance between point A and the closest tab along the second direction can be considered to be 0. When the projection of point A along the first direction lies outside the projection of the closest tab along the first direction, the distance between point A and the closest tab along the second direction can be considered to be greater than 0. This distance is the distance between point A and the first edge along the second direction.

[0126] For example, one or more first tabs 111 are disposed on one side of the first electrode body 112 along the width direction Y. In this case, it can be understood that all the first tabs 111 are disposed on the same side of the first electrode body 112 along the width direction Y. This arrangement is beneficial to increase the space occupied by the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0127] When all the first electrode tabs 111 are disposed on the same side of the first electrode body 112 along the width direction Y, a 2 +b 2 The maximum value is 6400 to 45000, and the selectable value is 6400 to 25000.

[0128] In Figure 6, Y1 represents the dimension of the first electrode body 112 along the width direction Y, which can also be understood as the width of the first electrode body 112.

[0129] For electrons located at the same position, there may be multiple transmission paths between them and the electrode. The distance that the electron travels along the shortest path is taken as the electron transmission distance at that point.

[0130] For electrons at different positions within the same electrode (i.e., electrons at different points A), the electron transport distance at each position is calculated, and the longest electron transport distance is selected as the maximum electron transport distance. This maximum value is represented by a. 2 +b 2 The maximum value is represented by a. 2 +b 2 The design maximizes the electron transport path, reduces internal resistance, and improves the fast charging performance of individual battery cells.

[0131] In Figure 6, for an electron located at the same point A2, there may be multiple transmission paths such as C1 and C2 (only two paths, C1 and C2, are shown in the figure, and it is not excluded that the electron may be transmitted in other ways). When the distance of C1 is greater than the distance of C2, the transmission distance of the electron located at point A2 is defined as the distance of C2; when C1 and C2 are equal, the transmission distance of the electron located at point A2 can be defined as either the distance of C1 or the distance of C2.

[0132] Specifically, since the first electrode tab 111 is disposed on the same side of the first electrode body 112, a is equal to the dimension of the first electrode body 112 along the first direction. The first direction is parallel to the width direction Y. Therefore, a is the dimension of the first electrode body 112 along the width direction Y. That is, a is equal to the width Y1 of the first electrode body 112. That is, Y1 is equal to the distance between point A2 and the electrode tab closest to point A2 in at least one electrode tab along the first direction.

[0133] The second direction is parallel to the length direction Z of the first electrode 11. b1 represents the distance between point A2 and an adjacent first electrode tab 111 along the length direction Z, and b2 represents the distance between point A2 and another adjacent first electrode tab 111 along the length direction Z. If b1 is greater than b2, then b2 represents the distance between point A2 and the electrode tab closest to point A2 in the second direction. In this case, the transmission distance of the electron located at point A2 is defined as the C2 distance.

[0134] If b1 equals b2, then either b1 or b2 can represent the distance between point A2 and the electrode closest to point A2 along the second direction. In this case, the electron transmission distance at point A2 can be defined as the C1 distance or the C2 distance.

[0135] For the same first electrode 11, there are multiple positions, such as A1 and A2.

[0136] The electron located at point A1, that is, the electron located on the edge of the first electrode body 112, has a width a equal to the width Y1 of the first electrode body 112;

[0137] b3 represents the distance between point A1 and the adjacent first pole piece 111 along the length direction Z;

[0138] C3 represents the electron transmission distance at point A1.

[0139] Taking the electron transport distance of the electron located at point A2 as C2 as an example, if C2 is greater than or equal to C3, then C2 is the longest electron transport distance in the first pole piece 11, a 2 +b 2 The maximum value is the square of C2; if C2 is less than C3, then C3 is the longest electron transport distance in the first electrode 11, a 2 +b 2 The maximum value is the square of C3.

[0140] As shown in Figure 7, for example, when the first electrode 11 includes a plurality of first electrode tabs 111, the plurality of first electrode tabs 111 are disposed on both sides of the first electrode body 112 along the width direction Y.

[0141] When multiple first electrode tabs 111 are disposed on both sides of the first electrode body 112 along the width direction Y, a 2 +b 2 The maximum value is 6400 to 45000, and the selectable value is 6400 to 25000.

[0142] In Figure 7, Y1 represents the dimension of the first electrode body 112 along the width direction Y, which can also be understood as the width of the first electrode body 112.

[0143] In Figure 7, for an electron located at the same point A2, there may be multiple transmission paths such as C1, C2, C3 and C4. When the C2 distance is the smallest, the transmission distance of the electron located at point A2 is defined as the C2 distance.

[0144] Specifically, since the first tab 111 is disposed on both sides of the first electrode body 112, a is equal to half the dimension of the first electrode body 112 along the first direction. The first direction is parallel to the width direction Y. Therefore, a is half the dimension of the first electrode body 112 along the width direction Y. That is, a is equal to the width Y1 / 2 of the first electrode body 112. That is, Y1 / 2 is equal to the distance between point A2 and the tab closest to point A2 in at least one tab along the first direction.

[0145] The second direction is parallel to the length direction Z of the first electrode 11. b1 represents the distance between point A2 and an adjacent first electrode tab 111 along the length direction Z, and b2 represents the distance between point A2 and another adjacent first electrode tab 111 along the length direction Z. If b1 is greater than b2, then b2 represents the distance between point A2 and the electrode tab closest to point A2 in the second direction. In this case, the transmission distance of the electron located at point A2 is defined as the C2 distance.

[0146] If b1 equals b2, then either b1 or b2 can represent the distance between point A2 and the electrode closest to point A2 along the second direction. In this case, the electron transmission distance at point A2 can be defined as the C1 distance or the C2 distance.

[0147] For the same first electrode 11, there are multiple positions, such as A1 and A2.

[0148] The electron located at point A1, that is, the electron located on the edge of the first electrode body 112, has a3 that is equal to the width Y1 / 2 of the first electrode body 112;

[0149] b3 represents the distance between point A1 and the adjacent first pole piece 111 along the length direction Z;

[0150] C5 represents the electron transmission distance at point A1.

[0151] Taking the electron transport distance of an electron located at point A2 as C2 as an example, if C2 is greater than or equal to C5, then C2 is the longest electron transport distance in the first pole piece 11, a 2 +b 2 The maximum value is the square of C2; if C2 is less than C5, then C5 is the longest electron transport distance in the first electrode 11, a 2 +b 2 The maximum value is the square of C5.

[0152] Whether all the first tabs 111 are located on the same side of the first electrode body 112 along the width direction Y, or all the first tabs 111 are located on opposite sides of the first electrode body 112 along the width direction Y, the number of first tabs 111 located on the same side of the first electrode body 112 can be multiple, such as two, three, four, five, six, etc.; four tabs are optional. This arrangement is beneficial for the uniform distribution of electrons on the first electrode 11, which is beneficial for improving fast charging performance.

[0153] Optionally, the distance between two adjacent tabs along the length direction Z is greater than 0 and less than or equal to 300 mm, for example, 100 mm, 120 mm, 140 mm, 150 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 250 mm, 260 mm, 280 mm, 300 mm, or any range of two of the above values. In Figure 7, Z1 represents the distance between two adjacent tabs along the length direction Z.

[0154] As shown in Figure 8, in some embodiments, the first electrode 11 satisfies: n*W1 / W2 is 0.5 to 1.0;

[0155] n represents the number of all electrode ears located on the same side of the electrode body;

[0156] W1 represents the average size of the tab portion along the second direction;

[0157] W2 represents the dimension of the electrode body along the second direction.

[0158] For example, n*W1 / W2 is 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range of any two of the above values.

[0159] In Figure 8, the first direction is parallel to the width direction Y of the battery cell 11, and n is 1. When the first direction is parallel to the length direction Z of the battery cell 11, the condition that n*W1 / W2 is 0.5 to 1.0 is also satisfied, and will not be elaborated here. When the electrode assembly 10 adopts a wound structure, the condition that n*W1 / W2 is 0.5 to 1.0 is also satisfied, and will not be elaborated here.

[0160] In this embodiment, the first electrode 11 also satisfies that n*W1 / W2 is 0.5 to 1.0, which makes the connection area between the tab and the electrode body relatively large and the overcurrent area of ​​the tab relatively large, which is beneficial to reduce DC resistance, reduce heat generation, and improve the fast charging performance of the battery cell.

[0161] W1 represents the average size of the first electrode 111 along the second direction.

[0162] When the first electrode tab 111 has an irregular shape, for example, its size gradually increases along the second direction along the first direction. In this case, the size of the first electrode tab 111 along the second direction can be measured at multiple points, and the average size of the first electrode tab 111 along the second direction can be calculated. Of course, the size of the first electrode tab 111 along the second direction at all points can be the same value. In this case, the value can be used as the average size of the first electrode tab 111.

[0163] There can be one or more first electrodes 111, for example, n is 1 to 4. When there are multiple first electrodes 111, the average size of each first electrode 111 can be measured separately, and the average size of each first electrode 111 can be calculated by summing the average size of each first electrode 111 and dividing by the number of first electrodes 111.

[0164] The first tab 111 is connected to the first electrode body 112. The first tab 111 includes a first end 1111 connected to the first electrode body 112. When n*W1 / W2 meets the above range, it means that the cross section of the first end 1111 along the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first electrode body 112 is relatively large, the current carrying capacity of the first tab 111 is strong, and it can improve the power performance and cycle performance of the battery cell 7.

[0165] Optionally, the current collection section of the first tab 111 and the first electrode body 112 is an integral structure, which makes the internal resistance of the first electrode 11 lower and can further improve the power performance and cycle performance of the battery cell 7.

[0166] As shown in Figure 9, in some embodiments, in the second electrode 12, along the first direction, the distance between any point B of the electrode body and the electrode tab closest to point B in at least one electrode tab is c, in mm. Along the second direction, the distance between point B of the second electrode 12 and the electrode tab closest to point B in at least one electrode tab along the second direction is d, in mm. One of the second direction and the first direction is parallel to the length direction of the first electrode, and the other is parallel to the width direction of the first electrode. Wherein, c... 2 +d 2 The maximum value is between 6,000 and 110,000.

[0167] When the second electrode 12 of the present application satisfies the above conditions, the electron transmission path is relatively short, which can effectively reduce the internal resistance of the battery cell, and each electrode carries a smaller current and the current distribution is more uniform, which is conducive to the rapid charging of the battery cell.

[0168] In this embodiment, the number and arrangement of the second electrode tabs 121 are the same as those of the first electrode tabs 111, and will not be described again here. The structure of the second electrode plate 12 is the same as that of the first electrode plate 11, and will not be described again here.

[0169] Next, we will explain the relevant scheme where the first direction is parallel to the length direction of the battery cell 11.

[0170] As shown in FIG10, in some embodiments, the first electrode 11 includes one or more first electrode tabs 111; the one or more first electrode tabs 111 are disposed on at least one side of the first electrode body 112 along the length direction Z.

[0171] For example, one or more first tabs 111 are disposed on one side of the first electrode body 112 along the length direction Z. In this case, it can be understood that all first tabs 111 are disposed on the same side of the first electrode body 112 along the length direction Z.

[0172] When all the first electrode tabs 111 are located on the same side of the first electrode body 112 along the length direction Z, a 2 +b 2 The maximum value is 25600 to 110000, and the selectable value is 25600 to 90000.

[0173] In Figure 10, Z2 represents the dimension of the first electrode body 112 along the length direction Z, which can also be understood as the length of the first electrode body 112.

[0174] In Figure 10, for an electron located at the same point A2, there may be multiple transmission paths such as C1 and C2 (only two paths, C1 and C2, are shown in the figure, and it is not excluded that the electron may be transmitted in other ways). When the distance of C1 is greater than the distance of C2, the transmission distance of the electron located at point A2 is defined as the distance of C2; when C1 and C2 are equal, the transmission distance of the electron located at point A2 can be defined as either the distance of C1 or the distance of C2.

[0175] Specifically, since the first electrode tab 111 is disposed on the same side of the first electrode body 112, a is equal to the dimension of the first electrode body 112 along the first direction. The first direction is parallel to the length direction Z. Therefore, a is the dimension of the first electrode body 112 along the length direction Z. That is, a is equal to the length Z2 of the first electrode body 112. That is, Z2 is equal to the distance between point A2 and the electrode tab closest to point A2 in at least one electrode tab along the first direction.

[0176] The second direction is parallel to the width direction Y of the first electrode 11. b1 represents the distance between point A2 and an adjacent first electrode tab 111 along the width direction Y, and b2 represents the distance between point A2 and another adjacent first electrode tab 111 along the width direction Y. If b1 is greater than b2, then b2 represents the distance between point A2 and the electrode tab closest to point A2 in the second direction. In this case, the transmission distance of the electron located at point A2 is defined as the C2 distance.

[0177] If b1 equals b2, then either b1 or b2 can represent the distance between point A2 and the electrode closest to point A2 along the second direction. In this case, the electron transmission distance at point A2 can be defined as the C1 distance or the C2 distance.

[0178] For the same first electrode 11, there are multiple positions, such as A1 and A2.

[0179] The electron located at point A1, that is, the electron located on the edge of the first electrode body 112, has a length a equal to the length Z2 of the first electrode body 112;

[0180] b3 represents the distance between point A1 and the adjacent first pole piece 111 along the width direction Y;

[0181] C3 represents the electron transmission distance at point A1.

[0182] Taking the electron transport distance of the electron located at point A2 as C2 as an example, if C2 is greater than or equal to C3, then C2 is the longest electron transport distance in the first pole piece 11, a 2 +b 2 The maximum value is the square of C2; if C2 is less than C3, then C3 is the longest electron transport distance in the first electrode 11, a 2 +b 2 The maximum value is the square of C3.

[0183] As shown in Figure 11, for example, when the first electrode 11 includes a plurality of first electrode tabs 111, the plurality of first electrode tabs 111 are respectively disposed on both sides of the first electrode body 112 along the length direction Z.

[0184] Optionally, multiple first tabs 111 are respectively disposed on both sides of the first electrode body 112 along the length direction Z. This arrangement can shorten the transmission path of electrons in the first electrode 11, which is beneficial to improving fast charging performance.

[0185] When multiple first electrode tabs 111 are disposed on both sides of the first electrode body 112 along the length direction Z, a 2 +b 2 The maximum value is 25600 to 110000, and the selectable value is 25600 to 90000.

[0186] In Figure 11, Z3 represents the dimension of the first electrode body 112 along the length direction Z, which can also be understood as the length of the first electrode body 112.

[0187] In Figure 11, for an electron located at the same point A, there may be multiple transmission paths such as C1 and C2. When the C2 distance is the smallest, the transmission distance of the electron located at point A is defined as the C2 distance.

[0188] Specifically, since the first tab 111 is disposed on both sides of the first electrode body 112, a is equal to half the dimension of the first electrode body 112 along the first direction. The first direction is parallel to the length direction Z. Therefore, a is half the dimension of the first electrode body 112 along the length direction Z. That is, a is equal to the length Z3 / 2 of the first electrode body 112. That is, Z3 / 2 is equal to the distance between point A and the tab closest to point A in at least one tab along the first direction.

[0189] There is one first electrode tab 111 located on the same side. The second direction is parallel to the width direction Y of the first electrode 11. b represents the distance between point A and the first electrode tab 111 along the width direction Y. b also represents the distance between point A and the electrode tab closest to point A in at least one electrode tab along the second direction. In this case, distances C1 and C2 are the same and can both be considered as the longest electron transmission distance in the first electrode 11. 2 +b 2 The maximum value is the square of C1.

[0190] Whether all the first tabs 111 are located on the same side of the first electrode body 112 along the width direction Y, or all the first tabs 111 are located on opposite sides of the first electrode body 112 along the width direction Y, the number of first tabs 111 located on the same side of the first electrode body 112 can be multiple, such as two, three, four, five, six, etc. This arrangement is beneficial for the uniform distribution of electrons on the first electrode 11, which is conducive to improving fast charging performance. This arrangement can further shorten the electron transport path, effectively reduce the internal resistance of the battery cell, and each tab carries a smaller current, resulting in a more uniform current distribution.

[0191] Optionally, the distance between two adjacent tabs along the width direction Y is greater than 0 and less than or equal to 300 mm, such as 100 mm, 120 mm, 140 mm, 150 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 250 mm, 260 mm, 280 mm, 300 mm, or any range of two of the above values. This arrangement can further shorten the electron transport path, effectively reduce the internal resistance of the battery cell, and each tab carries a smaller current, resulting in a more uniform current distribution. In Figure 10, Y2 represents the distance between two adjacent tabs along the width direction Y.

[0192] Electrolyte

[0193] During the charging and discharging process of a single battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive and negative electrode plates, and the electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0194] The electrolyte salt includes lithium salts, including lithium bis(fluorosulfonyl)imide, and may further include lithium hexafluorophosphate (LiPF6). These lithium salts are beneficial for improving the lithium-ion conductivity of the electrolyte and enhancing the fast-charging capability of individual battery cells.

[0195] Optionally, based on the mass of the electrolyte, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 0.5 to 4, optionally 1.2 to 2.0. Lithium salts are beneficial for improving the lithium-ion conductivity of the electrolyte and enhancing the fast-charging capability of individual battery cells.

[0196] For example, the mass content of lithium hexafluorophosphate and the mass content of lithium difluorosulfonylimide are 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3, 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9, 4.0 or any combination of the above values.

[0197] In this embodiment of the application, the mass content of lithium bis(fluorosulfonyl)imide is 1% to 15%, and optionally 3% to 12%, depending on the mass of the electrolyte.

[0198] For example, based on the mass of the electrolyte, the mass content of lithium difluorosulfonylimide is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination of two of the above values.

[0199] In some embodiments, the mass content of the lithium salt is 13% to 20% based on the mass of the electrolyte, for example, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination of two of the above values.

[0200] In some embodiments, the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature. Exemplarily, the electrolyte has a conductivity of 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, or any combination of two of these values ​​at room temperature.

[0201] When the conductivity of the electrolyte at room temperature, such as 25°C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0202] In the embodiments of this application, the conductivity of the electrolyte at room temperature, such as 25°C, is the ionic conductivity, which can be detected using equipment and methods known in the art, such as by referring to industry standard HG-T 4067-2015.

[0203] In some embodiments, the organic solvent includes carbonate solvents.

[0204] Optionally, the carbonate solvent in the electrolyte comprises 10% to 80% by mass. For example, the carbonate solvent in the organic solvent comprises 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, or any combination of two of the above values ​​by mass. The carbonate solvent at the above mass contents can further improve the conductivity of the electrolyte at room temperature, which is beneficial for lithium-ion migration and enhances the fast-charging performance of the battery cells.

[0205] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. More preferably, the carbonate solvent includes one or more of dimethyl carbonate and ethylene carbonate. Even more preferably, the carbonate solvent includes dimethyl carbonate. The combined use of the above-mentioned carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte at room temperature, which is beneficial for lithium-ion migration and enhances the fast-charging performance of the battery cells.

[0206] In some embodiments, the organic solvent includes chain carboxylic acid ester solvents.

[0207] Optionally, the chain carboxylic acid ester solvent has a mass content of 5% to 30% in the electrolyte. For example, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, or any combination of two of the above values.

[0208] When the mass content of chain carboxylic acid ester solvents is within the above range, the viscosity of the electrolyte system is relatively low, which is conducive to the migration of lithium ions and improves the fast charging performance of the battery cells.

[0209] In some embodiments, the chain carboxylic acid ester solvent includes compounds represented by Formula I.

[0210] In formula I,

[0211] R1 includes a hydrogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0212] R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

[0213] The aforementioned chain-like carboxylic acid ester solvents have high conductivity, which is beneficial for improving the fast charging capability of battery cells.

[0214] Optionally, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0215] Optionally, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. More optionally, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0216] In the above embodiments, the halogenated alkyl group includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl groups, and optionally, the halogenated alkyl group includes fluoroalkyl.

[0217] For example, the chain carboxylic acid ester solvent includes one or more compounds of formula I-1 to formula I-8.

[0218] In some embodiments, the electrolyte also contains additives, which may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0219] In some embodiments, the additive includes one or more of carbonate additives and sulfur-containing additives, optionally at least two. These additives can improve the interfacial film performance on the positive and / or negative electrode sides, which is beneficial for improving the fast-charging performance of individual battery cells and enhancing cycle performance.

[0220] In some embodiments, the additive content in the electrolyte is 0.5% to 6% by mass. Exemplarily, the additive content in the electrolyte is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6%, or a range of any two of the above values.

[0221] The aforementioned organic solvents, such as chain carboxylic acid esters, may decompose and produce acid at high temperatures, which can corrode the solid electrolyte interphase (SEI) film on the surface of the negative electrode. However, the additives can form a dense and uniformly thick SEI film on the negative electrode side, which can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the fast charging performance of the battery cell and improve cycle performance.

[0222] For example, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC), and optionally, the carbonate additives include vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0223] Vinylene carbonate (VC) can form a dense and uniformly thick SEI film on the negative electrode side, effectively repairing the SEI film and providing excellent protection for the negative electrode active material, which is beneficial to improving the fast charging performance and cycle performance of the battery cell.

[0224] Fluorinated ethylene carbonate (FEC) can form a SEI film with relatively low impedance on the negative electrode side, effectively repairing the SEI film and providing excellent protection for the negative electrode active material, which is beneficial to improving the fast charging performance and cycle performance of the battery cell.

[0225] For example, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butenyl sulfite BS, 1,3-propanesulfonate lactone PS, vinyl sulfite ES, and methylene disulfonate MMDS, optionally 1,3-propanesulfonate lactone PS.

[0226] Sulfur-containing additives can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the fast charging performance and cycle performance of battery cells.

[0227] For example, the additives include one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonyl lactone.

[0228] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is from 0.5% to 3.0%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, 3.0%, or any combination of two of the above values. When the mass content of vinylene carbonate (VC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the fast charging performance and cycle performance of the battery cell.

[0229] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is from 0.2% to 2.5%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, or any combination of two of the above values. When the mass content of fluoroethylene carbonate (FEC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the fast charging performance and cycle performance of the battery cell.

[0230] Optionally, the mass content of 1,3-propanesulfonyl lactone (PS) in the electrolyte is from 0.5% to 2.5%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, or any combination of two of the above values. When the mass content of 1,3-propanesulfonyl lactone (PS) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the fast charging performance and cycle performance of the battery cell.

[0231] In the embodiments of this application, the types and contents of inorganic components / lithium salts in the electrolyte are known in the art and can be detected using equipment and methods 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 according to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis method.

[0232] In the embodiments of this application, the types and contents of organic components in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0233] In this embodiment, after quantitative and qualitative detection of each component in the electrolyte, the components are classified. Chain-like carboxylic acid ester solvents and carbonate solvents (e.g., ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate) are considered as components of the organic solvent. The mass content of each component is calculated based on the electrolyte mass as 100%.

[0234] Carbonate additives (such as vinylene carbonate and fluoroethylene carbonate) and sulfur-containing additives are used as additives in the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0235] [Outer Shell Assembly]

[0236] In some embodiments, the battery cell 7 further includes a housing assembly 20 having a receiving space for accommodating the electrode assembly 10 and the electrolyte.

[0237] In some embodiments, the housing assembly 20 includes a housing, a first electrode terminal 31, and a second electrode terminal 32, the first electrode terminal 31 and the second electrode terminal 32 being disposed on the housing.

[0238] The outer casing can be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. In some embodiments, the outer casing can be a sealed structure or a non-sealed structure. As an example, when the outer casing is a non-sealed structure, it serves to protect the electrode assembly 10, and a sealing bag is included between the outer casing and the electrode assembly 10 to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the outer casing is a sealed structure, it is used to encapsulate the electrode assembly 10 and electrolyte components, etc.

[0239] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0240] shell

[0241] In some embodiments, the housing includes an end cap 22 and a housing 21, the housing 21 having an opening, and the end cap 22 covering the opening. The housing 21 may have one or more openings. The end cap 22 may also be provided one or more times.

[0242] The first electrode terminal 31 and the second electrode terminal 32 can be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 can be disposed on the end cover 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on the end cover 22.

[0243] On the same end cap 22, a first electrode terminal 31 and a second electrode terminal 32 can be provided simultaneously. For example, there is one end cap 22, on which the first electrode terminal 31 and the second electrode terminal 32 are provided at intervals. Or, for example, there are two end caps 22, which are arranged opposite each other, and each end cap 22 is provided with a first electrode terminal 31 and a second electrode terminal 32.

[0244] A first electrode terminal 31 and a second electrode terminal 32 are respectively provided on different end caps 22. For example, there are two end caps 22, which are arranged opposite each other. A first electrode terminal 31 is provided on one end cap 22, and a second electrode terminal 32 is provided on the other end cap 22.

[0245] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, then a cylindrical housing 21 can be selected; if the electrode assembly 10 is a cuboid structure, then a cuboid housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0246] In some embodiments, the housing 21 includes two first housing portions 211, a second housing portion 212, and a third housing portion 213. The two first housing portions 211 are opposite to each other along the thickness direction X of the battery cell 7, and the second housing portions 212 and the third housing portions 213 are opposite to each other and connected by the first housing portions 211. The second housing portion 212 includes a first wall 2121 and a second wall 2122 continuously arranged along the thickness direction X, and the first wall 2121 and the second wall 2122 are welded together. The first wall 2121 and the second wall 2122 can be welded by methods such as splicing welding or laser welding, and splicing welding is optional. Since the area of ​​the second housing portion 212 is relatively small and the degree of expansion is relatively small, the weld is located on the second housing portion 212, which can reduce the risk of leakage of the battery cell 7.

[0247] When assembling the battery cell 7 into the battery device housing, the battery cell 7 is disposed inside the housing, which includes a first housing portion and a second housing portion, with the first housing portion covering the second housing portion. A second shell portion 212 is disposed opposite to the first housing portion and is positioned close to the first housing portion, while a third shell portion 213 is positioned close to the second housing portion. When assembling the battery device into the power-consuming device, the first housing portion can be vertically positioned above the second housing portion. The second shell portion 212, having a weld seam with the weld seam facing upwards, reduces the risk of leakage from the battery cell 7.

[0248] In some embodiments, the dimension of the battery cell 7 along the thickness direction X is 10 mm to 30 mm, for example 10 mm, 12 mm, 14 mm, 15 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 25 mm, 26 mm, 28 mm, 30 mm or any combination of two of the above values.

[0249] The dimension of the battery cell 7 along the thickness direction X can characterize the thickness of the battery cell 7; in other words, the thickness of the battery cell 7 is between 10 mm and 30 mm. When the thickness of the battery cell 7 is within the above range, the thickness of the battery cell 7 is relatively small, which is conducive to rapid heat dissipation inside the battery cell 7 and reduces the risk of thermal runaway.

[0250] In some embodiments, the thickness of the housing 21 is from 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 is 0.3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0251] When the thickness of the housing 21 is within the above range, the housing 21 is relatively thin, which is beneficial for the rapid heat dissipation of the housing 21.

[0252] For example, the thickness of the first shell portion 211 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0253] For example, the thickness of the second shell portion 212 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0254] For example, the thickness of the third shell portion 213 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0255] First electrode terminal

[0256] In some embodiments, the battery cell 7 further includes a first electrode terminal 31, which is connected to a first tab 111.

[0257] In some embodiments, there is at least one first electrode terminal 31, and there may be multiple terminals, such as two, three, or four.

[0258] As shown in Figure 12, in some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. This arrangement can shorten the electron migration path and is beneficial to improving fast charging performance.

[0259] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y.

[0260] For example, a plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0261] As shown in FIG13, in some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0262] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0263] For example, multiple first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the electron migration path and is beneficial to improving fast charging performance.

[0264] For example, there are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10 and the other is disposed on the other side of the electrode assembly 10. Alternatively, for example, there are four first electrode terminals 31, two of which are disposed on one side of the electrode assembly 10 and the other two are disposed on both sides of the electrode assembly 10.

[0265] The first tab 111 and the first electrode terminal 31 are electrically connected, either directly or indirectly. When the first tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, which is located between the first electrode terminal 31 and the first tab 111 and connects the first electrode terminal 31 and the first tab 111.

[0266] For example, when the first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z, and the first electrode tab 111 is disposed on at least one side of the first electrode body 112 along the width direction Y, the connection between the first electrode tab 111 and the first electrode terminal 31 is more facilitated by the first adapter 51.

[0267] When the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, the first adapter 51 may include a first adapter portion 511 and a second adapter portion 512. The first adapter portion 511 extends along the length direction Z and is connected to the first tab 111. The second adapter portion 512 is connected to the first adapter portion 511 and protrudes from the first adapter portion 511 along the width direction Y, and is connected to the first electrode terminal 31.

[0268] When the first tab 111 and the first electrode terminal 31 are located on the same side of the battery cell 7, the first adapter 51 may consist only of the first adapter portion 511.

[0269] In the above embodiments, the first adapter 51 can be a sheet-like structure, or of course, other structural forms.

[0270] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0271] In some embodiments, the battery cell 7 further includes a first conductive element 61 located between the first adapter 51 and the first tab 111. The first conductive element 61 can increase the overcurrent capacity between the first tab 111 and the first adapter 51, which is beneficial to improving fast charging performance and reducing heat generation.

[0272] For example, the tab of the first electrode 11 is disposed on one side of the electrode body along the width direction Y; the first conductive element 61 is located between the first adapter 51 and the first tab 111, and connects the first adapter 51 and the first tab 111.

[0273] Optionally, there are multiple first conductive elements 61, and each first conductive element 61 is connected to a first electrode tab 111 in a one-to-one correspondence. Multiple first conductive elements 61 are connected to a first adapter 51. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0274] As shown in Figure 14, optionally, there are multiple first electrode tabs 111 located on the same side of the first electrode body 112, and the first conductive element 61 can be a continuous sheet structure connecting multiple first electrode tabs 111.

[0275] When the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, optionally, the first conductive member 61 includes a first conductive portion 611 and a second conductive portion 612. The first conductive portion 611 extends along the length direction Z and connects the first tab 111 and the first adapter 51. The second conductive portion 612 is connected to the first conductive portion 611 and protrudes from the first conductive portion 611 along the width direction Y. The second conductive portion 612 is connected to the first adapter 51. This structural arrangement is beneficial for increasing the packing space in the length direction Z and for improving the energy density of the battery device.

[0276] It should be noted that, in the absence of the first adapter 51 in the battery cell 7, the first tab 111 can be connected to the first electrode terminal 31 through the first conductive element 61.

[0277] For example, the first conductive element 61 has conductivity and may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0278] In some embodiments, the thickness of the first conductive element 61 is from 0.5 mm to 2.0 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or any combination of two of the above values. When the thickness of the first conductive element 61 is within the above range, the current carrying capacity can be effectively improved, and the fast charging capability can be enhanced.

[0279] In the embodiments of this application, the first electrode terminal 31 can be an integral structure, which can be integrally formed or connected by means of welding to form an integral structure. An integral structure is beneficial to reduce resistance and reduce heat generation.

[0280] Second electrode terminal

[0281] In some embodiments, the battery cell further includes a second electrode terminal 32, which is connected to the second tab 121.

[0282] In some embodiments, there is at least one second electrode terminal 32, and there may be multiple terminals, such as two, three, or four.

[0283] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. This arrangement can shorten the electron migration path and improve fast charging performance.

[0284] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on both sides of the electrode assembly 10 along the width direction Y, respectively, and will not interfere with each other when they are electrically connected to the tabs respectively.

[0285] For example, there are two first electrode terminals 31 and two second electrode terminals 32. The two first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the width direction Y. Figure 14 shows a schematic diagram of the first electrode terminals 31 and the second electrode terminals 32 disposed on both sides of the electrode assembly 10 along the width direction Y.

[0286] For example, multiple second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the width direction Y. This arrangement can further shorten the electron migration path and improve fast charging performance. In this case, the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on one side along the width direction Y, and the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on the other side along the width direction Y.

[0287] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0288] For example, multiple second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the electron migration path and improve fast charging performance. In this case, the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on one side along the length direction Z, and the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on the other side along the length direction Z.

[0289] For example, there are two second electrode terminals 32, one of which is located on one side of the electrode assembly 10 along the length direction Z, and the other is located on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of which is located on one side of the electrode assembly 10, and the other is located on the other side of the electrode assembly 10. Figure 14 shows a schematic diagram of four electrode terminals.

[0290] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on both sides of the electrode assembly 10 along the length direction Z, respectively, and will not interfere with each other when they are electrically connected to the tabs.

[0291] As shown in Figure 15, exemplarily, there is one first electrode terminal 31 and one second electrode terminal 32. The first electrode terminal 31 and the second electrode terminal 32 are located on both sides of the electrode assembly along the length direction Z, and the first electrode terminal 31 and the second electrode terminal 32 are staggered along the width direction Y. Specifically, when all the second tabs 121 are located on the same side of the second electrode body 122 along the width direction Y, and all the first tabs 111 are located on the same side of the first electrode body 112 along the width direction Y, the first tabs 111 and the second tabs 121 are located on both sides of the electrode body along the width direction Y, with the first electrode terminal 31 positioned close to the first tab 111 and the second electrode terminal 32 positioned close to the second tab 121. This arrangement results in a shorter electron transmission distance, which is more conducive to improving the fast charging capability of the battery cell 7.

[0292] The second tab 121 is electrically connected to the second electrode terminal 32, either directly or indirectly. When the second tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, which is located between the second electrode terminal 32 and the second tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0293] For example, when the second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z, and the second electrode tab 121 is disposed on at least one side of the second electrode body 122 along the width direction Y, the connection between the second electrode tab 121 and the second electrode terminal 32 is more facilitated by the second adapter.

[0294] When the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, the second adapter may include a first connecting part and a second connecting part. The first connecting part extends along the length direction Z and is connected to the second tab 121. The second connecting part is connected to the first connecting part and protrudes from the first connecting part along the width direction Y and is connected to the second electrode terminal 32.

[0295] When the second tab 121 and the second electrode terminal 32 are located on the same side of the battery cell 7, the second adapter may consist only of the first connecting portion.

[0296] In the above embodiments, the second adapter can be a sheet-like structure, or of course, other structural forms.

[0297] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0298] In some embodiments, the battery cell 7 further includes a second conductive element located between the second adapter and the second tab 121. The arrangement of the second conductive element can increase the overcurrent capacity between the second tab 121 and the second adapter, which is beneficial to improving fast charging performance and reducing heat generation.

[0299] For example, the tab of the second electrode 12 is disposed on one side of the electrode body along the width direction Y; the second conductive element is located between the second adapter and the second tab 121, and connects the second adapter and the second tab 121.

[0300] Optionally, there are multiple second tabs 121 located on the same side of the second electrode body 122, and the second conductive element can be a continuous sheet structure connecting multiple second tabs 121; or there are multiple second conductive elements, and the second conductive elements and the second tabs 121 are connected in a one-to-one correspondence, and multiple second conductive elements are connected to the second adapter. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0301] When the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, the second conductive member optionally includes a third conductive portion and a fourth conductive portion. The third conductive portion extends along the length direction Z and connects to the tab portion of the second electrode 12 and the second adapter. The fourth conductive portion is connected to the third conductive portion and protrudes from the third conductive portion along the width direction Y. The third conductive portion connects to the second adapter. This structural arrangement is beneficial for increasing the packing space in the length direction Z and for improving the energy density of the battery device.

[0302] For example, the second conductive element has conductivity and may include a conductive polymer or a conductive metal material, which may include copper, aluminum, or an alloy containing the aforementioned metal elements.

[0303] It should be noted that, in the absence of the second adapter in the battery cell 7, the second tab 121 can be connected to the second electrode terminal 32 through the second conductive element.

[0304] Positive electrode sheet

[0305] To illustrate this application more clearly, the electrode body of the positive electrode sheet is referred to as the positive electrode sheet body, the tab portion as the positive electrode tab, and the active material layer as the positive electrode active material layer containing positive electrode active material. The positive electrode sheet body includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0306] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector and comprising a positive active material. For example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0307] The upper limit voltage for charging and the lower limit voltage for discharging a single battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the lower limit voltage for discharging can be 2.0V, or the upper limit voltage for charging can be 3.8V and the lower limit voltage for discharging can be 2.0V. Another example is when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.3V and the lower limit voltage for discharging can be 2.0V. Taking a charging upper limit voltage of 3.65V and a discharging lower limit voltage of 2.0V as an example, the state of a single battery cell will be described as follows: In this embodiment, the 100% state of charge (SOC) and the 0% state of charge (SOC) of a single battery cell are defined as follows...

[0308] The battery cell is charged at a constant current charging rate of 0.33C to the upper limit of the charging voltage, and then charged at a constant voltage to 0.05C, which corresponds to the 100% SOC state of the battery cell. The battery cell is then discharged at a constant current discharging rate of 0.33C to the cutoff voltage, which corresponds to the 0% SOC state of the battery cell.

[0309] In some embodiments, the compaction density of the positive electrode active material layer at 0% state of charge (SOC) of the battery cell is 2.30 g / cm³. 3 Up to 2.70 g / cm 3 ; 2.40 g / cm³ is optional 3 Up to 2.55 g / cm 3 For example, at 0% state of charge (SOC), the compaction density of the positive electrode active material layer in a single battery cell is 2.30 g / cm³. 3 2.32 g / cm 3 2.35g / cm 3 2.38g / cm 3 2.40 g / cm 3 2.42 g / cm 3 2.45g / cm 3 2.48 g / cm 3 2.50g / cm 3 2.52g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.60g / cm3 2.62 g / cm 3 2.65g / cm 3 2.68g / cm 3 2.70 g / cm 3 Or a range consisting of any two of the above values.

[0310] 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, since the positive electrode active material layer is densely packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation under fast charging, alleviating the problem of aggravated negative electrode side reactions caused by heat accumulation, and improving the cycle performance of the battery cell.

[0311] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 The option is 275mg / 1540.25mm. 2 Up to 300mg / 1540.25mm 2 For example, the single-sided coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm. 2 260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 320mg / 1540.25mm 2 330mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0312] When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generation per unit area of ​​the positive electrode sheet will not be too large, which alleviates the problem of aggravated side reactions on the negative electrode due to heat accumulation, improves the cycle performance of the battery cell, and can increase the energy density of the battery cell.

[0313] In this embodiment, the compaction density of the positive electrode active material layer of a battery cell at 0% state of charge (SOC) is a well-known concept in the art. That is, the positive electrode sheet is disassembled from the battery cell at 0% SOC, and the compaction density of the positive electrode active material layer is measured. For example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first) is cut into a small circular piece with an area of ​​S1, its weight is weighed and recorded as M1, and its thickness H1 is measured. Then, the positive electrode active material layer of the weighed positive electrode sheet is wiped off, the weight of the positive 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 = (weight of the positive electrode sheet M1 - weight of the positive electrode current 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 current collector H0, and 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.

[0314] In some embodiments, the positive electrode active material comprises a lithium phosphate with an olivine structure. In other embodiments, the positive electrode active material may also comprise lithium-containing transition metal oxides, examples of which include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0315] In this embodiment, the lithium phosphate with olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium phosphate with olivine structure includes phosphate particles and a coating layer. The coating layer is coated on the surface of the phosphate particles. For example, the coating layer includes elements such as carbon, which improves the conductivity of the phosphate particles, reduces the powder resistivity of the material, and is beneficial to the migration rate of lithium ions, thereby improving the fast charging capability of the battery and reducing the heat generation of the battery cell.

[0316] In some embodiments, the phosphate particles comprise the general formula Li x1 A y1 Me a M b P 1-c X c Y zThe compound contains the following components: 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; and Y includes one or more of O and F. Phosphate particles exhibit excellent cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0317] For example, phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process, active ions such as Li are de-intercalated and consumed in a single battery cell, resulting in different molar contents of Li in different discharged states. In the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar contents of Li represent the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li may change after charge-discharge cycles. In the embodiments of this application, the molar contents of oxygen (O) in the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 are only theoretical values. Lattice oxygen release can cause changes in the molar contents of oxygen (O). In reality, the molar contents of oxygen (O) may fluctuate, and all of the above situations are within the scope of protection of this application.

[0318] In this application embodiment, the element content in the positive electrode active material has a meaning known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA6010D-2014, it is tested 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 then calcined at high temperature to remove impurities. 0.4g of the positive electrode active material is weighed, and 10ml (50% concentration) of aqua regia is added. Then it is placed on a plate at 180°C for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0319] In some embodiments, the positive electrode active material layer also includes a positive electrode additive, which may also include lithium elements. During the charging process of the battery cell, lithium ions can be released to compensate for lithium loss, which is beneficial to improving the capacity characteristics and cycle performance of the battery cell.

[0320] In some embodiments, the average longest diameter of the cathode additive is 2 μm to 5 μm, for example, 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any combination thereof. When cathode additives with the above particle size are used, lithium loss can be effectively compensated while effectively improving the stability of the cathode additive.

[0321] In this embodiment, the positive electrode sheet is cut along its thickness direction to expose the longitudinal section of the positive electrode active material layer. Scanning electron microscopy (SEM) is used to test the longitudinal section of the positive electrode active material layer to determine the longest diameter of the positive electrode additive particles and the longest diameter of the lithium phosphate-containing particles. For example, the "longest diameter" of a particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0322] In a cross-section along the thickness of the positive electrode active material layer, the longest diameters of multiple, for example, 10 lithium-containing iron oxides are counted, and their average value is the average longest diameter.

[0323] In some embodiments, the mass percentage of the cathode additive, based on the total mass of the cathode active material layer, is 0.2% to 2%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or any combination thereof. Using cathode additives within this mass range effectively compensates for lithium loss.

[0324] In some embodiments, the positive electrode active material layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode active material layer.

[0325] In some embodiments, the positive electrode active material layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode active material layer.

[0326] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0327] In some embodiments, the ratio of the thickness of the single-sided positive electrode active material layer to the thickness of the positive electrode current collector is 3 to 10, for example, 3, 4, 5, 6, 7, 8, 9, 10, or any two of the above values. Optionally, the ratio of the thickness of the single-sided positive electrode active material layer to the thickness of the positive electrode current collector is 4 to 8.

[0328] When the ratio of the thickness of the positive electrode active material layer on one side to the thickness of the positive electrode current collector is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0329] In some embodiments, the thickness of the positive current collector is 12 μm to 16 μm, optionally 13 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or any combination of two of the above values.

[0330] When the thickness of the positive electrode current collector is within the above range, the current carrying capacity of the positive electrode current collector is excellent, and it can enable the battery cell to have a high energy density.

[0331] In the embodiments of this application, the thickness of the positive electrode active material layer and the positive electrode current collector are known in the art and can be detected using equipment and methods known in the art. For example, the thickness of the positive electrode sheet can be measured with a micrometer, the film layer on the surface of the positive electrode current collector can be removed, and the thickness of the positive electrode current collector can be measured with a micrometer. When the positive electrode active material layer is coated on one side, the thickness of the positive electrode active material layer is the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector. When the positive electrode active material layer is coated on both sides, the thickness of the positive electrode active material layer is (the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector) / 2.

[0332] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0333] The positive electrode sheet does not exclude additional functional layers besides the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of this 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 this application further includes a protective layer covering the surface of the positive electrode active material layer.

[0334] Negative electrode sheet

[0335] To more clearly illustrate this application, the electrode body of the negative electrode sheet corresponds to the negative electrode sheet body, the tab portion corresponds to the negative electrode tab, and the active material layer corresponds to the negative electrode active material layer containing negative electrode active material. The negative electrode sheet body includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0336] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector and comprising a negative active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative active material layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0337] In some embodiments, the compaction density of the negative electrode active material layer at 0% state of charge (SOC) of the battery cell is 1.30 g / cm³. 3 Up to 1.65 g / cm 3 ; 1.35g / cm³ is optional 3 Up to 1.50 g / cm 3For example, the compaction density of the negative electrode active material layer of the battery cell at 0% charge is 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.40g / cm 3 1.45g / cm 3 1.50g / cm 3 1.55g / cm 3 1.60g / cm 3 1.65g / cm 3 Or a range consisting of any two of the above values.

[0338] 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, since the negative electrode active material layer is densely packed, the contact resistance between particles is small, which can further reduce the resistance of the electrode, thereby reducing heat generation, alleviating the problem of aggravated negative electrode side reactions caused by heat accumulation, and improving the cycle performance of the battery cell.

[0339] In the embodiments of this application, the compaction density of the negative electrode active material layer of the battery cell at 0% state of charge (SOC) is a term known in the art and can be detected using equipment and methods known in the art, such as the compaction density test method of the positive electrode active material layer described above.

[0340] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 The option is 125mg / 1540.25mm. 2 Up to 150mg / 1540.25mm 2 For example, the single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm. 2 122mg / 1540.25mm 2 125mg / 1540.25mm 2 128mg / 1540.25mm 2 130mg / 1540.25mm 2 132mg / 1540.25mm 2 135mg / 1540.25mm 2 137mg / 1540.25mm 2 140mg / 1540.25mm 2 145mg / 1540.25mm 2150mg / 1540.25mm 2 155mg / 1540.25mm 2 160mg / 1540.25mm 2 165mg / 1540.25mm 2 170mg / 1540.25mm 2 175mg / 1540.25mm 2 180mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0341] When the single-sided coating weight of the negative electrode active material layer is within the above range, the heat generation per unit area of ​​the negative electrode sheet will not be too large, which alleviates the problem of aggravated negative electrode side reactions caused by heat accumulation, improves the cycle performance of the battery cell, and can also improve the energy density of the battery cell.

[0342] In the embodiments of this application, the single-sided coating weight of the negative electrode active material layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as the single-sided coating weight test method of the film layer described above.

[0343] In some embodiments, the negative electrode active material includes a carbon-based material, which has high cycle stability and can improve the cycle performance of the battery cell. The positive electrode active material of this application is mainly a lithium phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. The combination of these two materials results in excellent cycle performance of the battery cell.

[0344] Optionally, the carbon-based material includes artificial graphite, which has excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the fast charging performance of the battery cell.

[0345] In some embodiments, the carbon-based material may also include natural graphite. Specifically, the carbon-based material may include artificial graphite, or it may include both artificial and natural graphite. Natural graphite has relatively good electrical conductivity, which helps to further reduce heat generation and improve the power performance and cycle performance of the battery cell.

[0346] In some embodiments, the negative electrode active material may include, in addition to the aforementioned carbon-based materials and optionally silicon-based materials, at least one of tin-based materials and lithium titanate. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloy materials. Optionally, silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.

[0347] The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adaptively modify certain testing steps / instrument parameters from the perspective of testing accuracy to obtain more accurate results. One testing method can be used for qualitative or quantitative analysis, or several testing methods can be used in combination for qualitative or quantitative determination.

[0348] For example, this application can combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis to perform X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials.

[0349] Artificial graphite and natural graphite can be distinguished by SEM cross-sectional images taken by scanning electron microscope (SEM). Natural graphite has gaps between the sheet-like structures in its SEM cross-section, while artificial graphite has a dense structure with no obvious gaps. Alternatively, they can be distinguished by XRD patterns obtained by X-ray diffraction. Natural graphite has obvious 2H and 3R phases in its XRD pattern, while artificial graphite only has the 2H phase in its XRD pattern.

[0350] In the embodiments of this application, the negative electrode active material layer includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative electrode active material layer includes at least two film layers.

[0351] When a single-layer film is used for the negative electrode active material layer, the negative electrode active material in the negative electrode active material layer includes a carbon-based material. When a single-layer film is used, the volume average particle size Dv50 of the carbon-based material is 8 μm to 13 μm, optionally 9.5 μm to 11.5 μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 8 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, or a range consisting of any two of the above values.

[0352] When the negative electrode active material layer employs at least two film layers, the negative electrode active material in the negative electrode active material layer includes a carbon-based material. The negative electrode active material layer may include two, three, four, or even more film layers.

[0353] In some embodiments, the negative electrode active material layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector, and the carbon-based material of the first negative electrode film layer includes artificial graphite. The second negative electrode film layer is connected to the side of the first negative electrode film layer opposite to the negative electrode current collector, and the carbon-based material of the second negative electrode film layer also includes artificial graphite. The artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer can be the same or different. When the artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer are different, it can be due to different particle sizes or different degrees of graphitization.

[0354] The interface between the first negative electrode film and the second negative electrode film can be regular or irregular, and can optionally be irregular.

[0355] The negative electrode active material layer comprises at least two film layers, and layered coating is beneficial for improving the fast charging performance of the battery cell. In particular, when there is a difference between the first and second negative electrode film layers, it can create a porosity difference in the negative electrode active material layer, reduce the tortuosity of lithium-ion transport, and improve the fast charging performance of the battery cell.

[0356] In some embodiments, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer. Further optionally, having a larger volume average particle size Dv50 in the first negative electrode film layer than in the second negative electrode film layer is beneficial for improving the kinetic performance of the negative electrode active material layer.

[0357] The difference in particle size between the first and second negative electrode film layers can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging is mainly the second negative electrode film layer. However, in the embodiments of this application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve fast charging performance, and improve the problem of lithium deposition on the surface of the negative electrode sheet.

[0358] Optionally, the carbon-based material of the first negative electrode film is particulate, and its volume average particle size Dv50 is 9.0 μm to 18.5 μm, optionally 9.0 μm to 14.6 μm. Exemplarily, the volume average particle size of the carbon-based material of the second negative electrode film is 9.0 μm, 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, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, or a range consisting of any two of the above values. When the first negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is from 9.0 μm to 18.5 μm, and can be selected from 9.0 μm to 14.6 μm.

[0359] When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film is within the above range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material.

[0360] Optionally, the carbon-based material of the second negative electrode film is particulate, with a volume average particle size Dv50 of 7.8 μm to 14.3 μm, optionally 7.8 μm to 11.3 μm. For example, the volume average particle size Dv50 of the carbon-based material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range of any two of the above values. When the second negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is 7.8 μm to 14.3 μm, and can be selected as 7.8 μm to 11.3 μm.

[0361] When the volume average particle size Dv50 of the carbon-based material in the second negative electrode film is within the above range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance.

[0362] When the volume average particle size Dv50 of the carbon-based material in the second negative electrode film is within the above-mentioned range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during preparation, which can improve the stability of the material. Furthermore, the combination of the negative electrode active material in the second negative electrode film and the negative electrode active material in the first negative electrode film within the above-mentioned volume average particle size range is conducive to building a gradient porosity difference between the second negative electrode film and the first negative electrode film, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell.

[0363] In the embodiments of this application, the volume average particle size Dv50 of the negative electrode active material has a well-known meaning in the art and can be detected using well-known equipment and methods in the art. For example, the negative electrode active material can be used as a sample, and the Dv50 of the particles can be tested using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T19077-2016.

[0364] Alternatively, the carbon-based material of the first negative electrode film may also include natural graphite.

[0365] For example, the carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

[0366] In other embodiments, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film is greater than that in the first negative electrode film. Further optionally, having a larger volume average particle size Dv50 in the second negative electrode film than in the first negative electrode film is beneficial for increasing the compaction density of the negative electrode active material layer.

[0367] The difference in particle size between the first and second negative electrode films can improve the fast charging performance of individual battery cells.

[0368] For example, the carbon-based material of the second negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the first negative electrode film layer includes artificial graphite.

[0369] In some embodiments, the negative electrode active material layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative 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 mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode active material layer.

[0370] In some embodiments, the negative electrode active material layer may optionally include a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode active material layer.

[0371] In some embodiments, the negative electrode active material layer may optionally include other additives. As examples, other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2% based on the total weight of the negative electrode active material layer.

[0372] In some embodiments, the negative current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil made of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0373] In some embodiments, the ratio of the thickness of the single-sided negative electrode active material layer to the thickness of the negative electrode current collector is 8 to 14, for example, 8, 9, 10, 11, 12, 13, 14 or any two of the above values. Optionally, the ratio of the thickness of the single-sided negative electrode active material layer to the thickness of the negative electrode current collector is 10 to 12.

[0374] When the ratio of the thickness of the single-sided negative electrode active material layer to the thickness of the negative electrode current collector is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0375] In some embodiments, the thickness of the negative current collector is 5 μm to 10 μm, optionally 6 μm to 8 μm. Exemplarily, the thickness of the negative current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any range of two of the above values.

[0376] When the thickness of the negative electrode current collector is within the above range, the current carrying capacity of the negative electrode current collector is excellent, and it can enable the battery cell to have a high energy density.

[0377] In the embodiments of this application, the thickness of the negative electrode current collector has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the film layer on the surface of the negative electrode current collector can be washed away with a solvent, and the thickness of the negative electrode current collector can be measured with a micrometer.

[0378] The negative electrode active material layer is typically formed by coating a negative electrode slurry onto the negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0379] The negative electrode sheet does not exclude additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application further includes a negative electrode 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 this application further includes a protective layer covering the surface of the negative electrode active material layer.

[0380] Isolation component

[0381] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0382] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0383] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and 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 single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0384] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0385] In some embodiments, the volumetric energy density of the battery cell is between 350 Wh / L and 450 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 350 Wh / L, 375 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 450 Wh / L, or a range of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0386] In the embodiments of this application, the volumetric energy density of a single battery cell has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the following description uses a battery charging upper limit voltage of 3.65V and a battery discharging cutoff voltage of 2.0V as an example.

[0387] Place the battery cell at 25°C and charge it to 3.65V with a constant current of 0.33C, then charge it to 0.05C with a constant voltage, and discharge it to 2.0V with a constant current of 0.33C. Record the discharge capacity A0 at this point, in Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing). Calculate the volume of the battery cell V0, in L. The volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0388] Example

[0389] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0390] Example 1

[0391] 1. Preparation of positive electrode sheet

[0392] The positive electrode includes a positive electrode tab, a positive current collector, and a positive active material layer disposed on both sides of the positive current collector. The positive current collector is an aluminum foil with a thickness of 13μm.

[0393] The positive electrode active material layer includes lithium phosphate, lithium iron ferrite additive, polyvinylidene fluoride (PVDF) binder, and acetylene black conductive agent in a mass ratio of 96:1:2:1. The positive electrode active material layer is a film layer formed by uniformly coating the positive electrode slurry (solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collector, and then drying and cold pressing it.

[0394] Lithium-containing phosphates include lithium iron phosphate.

[0395] The single-sided coating weight of the positive electrode active material layer is 300 mg / 1540.25 mm. 2 .

[0396] 2. Preparation of negative electrode sheet

[0397] The negative electrode sheet includes a negative electrode tab, a negative electrode current collector, and a negative electrode active material layer disposed on both sides of the negative electrode current collector. The negative electrode current collector is a copper foil with a thickness of 6μm.

[0398] The negative electrode active material layer is a film layer formed by uniformly coating the negative electrode slurry (solvent is deionized water) onto the surface of the negative electrode current collector, and then drying and cold pressing it.

[0399] The single-sided coating weight of the negative electrode active material layer is 130 mg / 1540.25 mm. 2 .

[0400] The negative electrode active material layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode current collector, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0401] The first negative electrode film layer includes carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:1:1.5:1. The carbon-based material of the first negative electrode film layer includes artificial graphite and natural graphite in a mass ratio of 1:1, and the volume average particle size of the carbon-based material is 9.0 μm.

[0402] The second negative electrode film layer includes carbon-based materials, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:1:1.5:1. The carbon-based materials of the second negative electrode film layer include artificial graphite, and the volume average particle size of the carbon-based materials is 8.0 μm.

[0403] 3. Isolation components

[0404] The separator includes a base film, which is a 7μm polyethylene film layer with a porosity of 42%.

[0405] 4. Preparation of electrolyte

[0406] The electrolyte consists of organic solvents, lithium salts, and additives.

[0407] The organic solvents include 10% chain carboxylic acid ester solvents (ethyl acetate) and 75% carbonate solvents (diethyl carbonate, dimethyl carbonate, and ethylene carbonate in a mass ratio of 1:1:1). The mass content of each component in the organic solvents is calculated based on the mass of the electrolyte.

[0408] Based on the mass of the electrolyte, the additive content is 1.5% by mass, which includes vinylene carbonate (VC).

[0409] The lithium salt comprises 8.5% lithium hexafluorophosphate (LiPF6) and 5% lithium difluorosulfonylimide.

[0410] The electrolyte has a conductivity of 12 mS / cm at room temperature.

[0411] 5. Preparation of battery cells

[0412] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, resulting in a stacked electrode assembly. This assembly is then placed in an outer packaging shell, dried, and injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained. The compaction density of the positive electrode active material layer at 0% SOC is 2.5 g / cm³. 3 The compaction density of the negative electrode active material layer at 0% SOC is 1.45 g / cm³. 3 .

[0413] Comparative Example 1, Examples 2 to 9

[0414] Battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 is that the parameters of the positive electrode tab and the positive electrode active material layer in the positive electrode sheet were adjusted, as shown in Table 1.

[0415] Performance testing

[0416] 1. DC internal resistance (DCR) test of individual battery cells

[0417] You can refer to the methods in GB / T 31467 "Performance Test Specification for High-Power Lithium-ion Power Batteries for HEVs".

[0418] For example, at 25°C, charge a single battery cell to 3.65V with a constant current of 0.33C, let it stand for 1 minute, then charge it to 3.65V with a constant current of 0.05C, let it stand for 30 minutes, and then discharge it to 2.5V with a constant current of 0.33C. Record the discharge capacity A0 at this point in Ah. Then charge it to 0.5A0Ah with a constant current of 0.33C and adjust the SOC to 50%.

[0419] After placing the battery cell at 25°C for 2 hours, it was discharged at a constant current of 4C for 10 seconds, and ΔU was recorded.放电 ΔI 放电 The discharge DCR data of lithium-ion batteries can be calculated using the following formula, R. 放电 =ΔU 放电 / ΔI 放电 ,

[0420] Wherein, ΔU 放电 ΔI represents the voltage change within 10 seconds of the start of discharge. 放电 This indicates the current value within 10 seconds of the start of discharge.

[0421] The test results are shown in Table 1.

[0422] Table 1

[0423] In Table 1, the positive electrode tab is disposed on at least one side of the positive current collector along the first direction, and the negative electrode tab adopts a similar arrangement as the positive electrode tab.

[0424] a represents the distance between the electron and the nearest electrode along the first direction; b represents the distance between the electron and the nearest electrode along the second direction; c represents the distance between the electron and the nearest electrode. 2 =a 2 +b 2 c 2 The maximum value is a 2 +b 2 The maximum value, i.e., a 2 +b 2 The maximum value can characterize the square of the longest electron transport distance in the positive electrode.

[0425] In all embodiments and comparative examples, the electrode assembly is a stacked electrode assembly, and the tabs of the positive and negative electrode sheets are arranged in the same way. The width of the positive active material layer in the positive electrode sheet is 100 mm.

[0426] "Positive electrode tab exiting on the short side" means that the positive electrode tab is located on at least one side of the positive current collector along the length direction; "positive electrode tab exiting on one side of the short side" means that all positive electrode tabs are located on the same side of the positive current collector along the length direction; "positive electrode tab exiting on both sides of the short side" means that multiple positive electrode tabs are located on both sides of the positive current collector along the length direction, and when there are two positive electrode tabs, one positive electrode tab is located on each side of the positive current collector.

[0427] "Positive electrode tabs are located on the long side" means that the positive electrode tabs are located on at least one side of the positive current collector along the width direction; "positive electrode tabs are located on one side of the long side" means that all positive electrode tabs are located on the same side of the positive current collector along the width direction.

[0428] A full tab refers to a positive electrode tab whose size W1 is 1 to the size W2 of the positive current collector, i.e., n*W1 / W2 is 1 and n is 1.

[0429] In Comparative Example 1, the positive electrode active material layer is longer and has a higher energy density; however, the positive electrode tab is located on one side of the positive electrode current collector along the length direction, and 'a' is equal to the length of the positive electrode current collector, that is, 'a' is equal to the length of the positive electrode active material layer. Since the positive electrode tab is a full tab, its width is the same as the width of the positive electrode active material layer, therefore, 'b' is 0. This arrangement makes the electron transport path longer in the length direction, resulting in higher internal resistance of the battery cell, which is not conducive to fast charging at high energy density.

[0430] In Comparative Example 2, the length of the positive electrode active material layer is too long. Although the energy density is high, the positive electrode tab is located on one side of the positive electrode current collector along the length direction. 'a' equals the length of the positive electrode current collector, which is equal to the length of the positive electrode active material layer. Since the positive electrode tab is a full tab, its width is the same as the width of the positive electrode active material layer. Therefore, 'b' is 0. This configuration results in a longer electron transport path along the length direction, leading to higher internal resistance in the battery cell, which is not conducive to fast charging at high energy density.

[0431] In Comparative Example 3, the positive electrode tab is located on one side of the positive current collector along the length direction, and a is equal to the length of the positive current collector, that is, a is equal to the length of the positive active material layer. Since the positive electrode tab is a full tab, its width is the same as the width of the positive active material layer. Therefore, b is 0. Although this setting makes the electron transport path shorter, the length of the positive active material layer is shorter, which is not conducive to improving the energy density of the battery cell.

[0432] In Examples 6 to 9, the positive electrode tabs are located on both sides of the positive current collector along the length direction, and a is equal to half of the positive current collector. Since the positive electrode tabs are full tabs, their width is the same as the width of the positive active material layer, therefore, b is 0. This arrangement ensures that the electron transport path in the length direction is not too long. The shorter electron transport path can reduce the internal resistance of the battery cell and is beneficial for fast charging under high energy density.

[0433] In Examples 1 to 5, the positive electrode tab is located on one side of the positive electrode current collector along the width direction. Because the width of the positive electrode active material layer is relatively short, the electron transport path in the width direction is shorter, effectively reducing the internal resistance of the battery cell and facilitating fast charging at high energy density. With a 2 +b 2 The decrease in the maximum value of a further shortens the electron transport path, which can more effectively reduce the internal resistance of the battery cell; however, as a 2 +b 2 The decrease in the maximum value may lead to a corresponding decrease in the energy density of the battery cells, making it impossible to meet the demand for high energy density; therefore, in the embodiment a of this application... 2 +b 2The maximum value is 6,000 to 110,000, which can effectively balance improving the energy density of individual battery cells and fast charging performance, and is conducive to achieving fast charging at high energy density.

[0434] As shown in Figure 16, in Example 1, there are two positive electrode tabs, which are located on the same side of the positive current collector along the width direction, where a is 100mm; the length dimension of each positive electrode tab is 125mm, W1 is 125mm, n is 2, and W2 is 500mm, i.e., n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 200mm, so b is half of the distance, which is 100mm.

[0435] As shown in Figure 17, in Example 2, there are four positive electrode tabs, which are located on the same side of the positive current collector along the width direction, where a is 100mm; the length dimension of each positive electrode tab is 100mm, W1 is 100mm, n is 4, and W2 is 500mm, i.e., n*W1 / W2 is 0.8; the distance Z1 between two adjacent positive electrode tabs is 25mm, so b is half of the distance (corresponding to point A2), or half of the remaining size of the positive current collector after subtracting the size occupied by the positive electrode tabs and then subtracting the size occupied by the distance (corresponding to point A1), which is 12.5mm.

[0436] As shown in Figure 8, in Example 3, there is one positive electrode tab, W1 is 500mm, n is 1, W2 is 500mm, that is, n*W1 / W2 is 1, a is 100mm, and b is 0.

[0437] In Example 4, there are two positive electrode tabs, which are located on the same side of the positive current collector along the width direction, and a is 100mm; the length dimension of each positive electrode tab is 162.5mm, W1 is 162.5mm, n is 2, W2 is 650mm, that is, n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 200mm, then b is half of the distance, which is 100mm.

[0438] In Example 5, there are two positive electrode tabs, which are located on the same side of the positive current collector along the width direction, and a is 80mm; the dimension of each positive electrode tab along the length direction is 80mm, W1 is 80mm, n is 2, W2 is 320mm, that is, n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 90mm, then b is half of the distance, which is 45mm.

[0439] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the implementation of the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the implementation of the present application.

Claims

1. A battery cell, comprising an electrode assembly, the electrode assembly including a first electrode and a second electrode stacked along the thickness direction of the battery cell, wherein one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode, both the first electrode and the second electrode include an electrode body and at least one tab, at least a portion of the electrode body is provided with an active material layer, and the at least one tab is connected to the electrode body and protrudes from the electrode body along a first direction. The active material layer of the positive electrode sheet includes a lithium phosphate with an olivine structure, and the electrode sheet body has a dimension of 320 mm to 650 mm along the length of the battery cell. in, The first electrode satisfies: a 2 +b 2 The maximum value is between 6,000 and 110,000. 'a' represents the distance between any point A of the electrode body and the electrode ear closest to point A in the at least one electrode ear in the first electrode sheet along the first direction, and its unit is mm; b indicates that, in the first electrode, along the second direction, the distance between point A and the electrode closest to point A in the at least one electrode tab is b, and the unit is mm. The second direction and the first direction are either parallel to the length direction or parallel to the width direction of the battery cell.

2. The battery cell according to claim 1, wherein, The first direction is parallel to the length direction of the battery cell.

3. The battery cell according to claim 2, wherein, The first electrode has multiple tabs, which are respectively disposed on both sides of the electrode body along the first direction.

4. The battery cell according to claim 2 or 3, wherein, a 2 +b 2 The maximum value is between 25,600 and 110,000.

5. The battery cell according to claim 4, wherein, a 2 +b 2 The maximum value is between 25,600 and 90,000.

6. The battery cell according to claim 1, wherein, The first direction is parallel to the width direction of the battery cell.

7. The battery cell according to claim 6, wherein, The at least one tab of the first electrode is disposed on the same side of the electrode body along the first direction.

8. The battery cell according to claim 6 or 7, wherein, a 2 +b 2 The maximum value is between 6400 and 45000.

9. The battery cell according to claim 8, wherein, a 2 +b 2 The maximum value is between 6400 and 25000.

10. The battery cell according to any one of claims 1 to 9, wherein, The main body of the positive electrode sheet has a dimension of 80mm to 150mm along the width direction.

11. The battery cell according to any one of claims 1 to 10, wherein, The first electrode has multiple tabs located on the same side of the electrode body, and the distance between two adjacent tabs along the second direction is greater than 0 and less than or equal to 300 mm.

12. The battery cell according to any one of claims 1 to 11, wherein, The second electrode satisfies: c 2 +d 2 The maximum value is between 6,000 and 110,000. in, c represents the distance, in the second electrode, along the first direction, between any point B of the electrode body and the electrode ear closest to point B in the at least one electrode ear, and its unit is mm. d represents the distance along the second direction between point B and the electrode portion closest to point B in the at least one electrode portion, and its unit is mm.

13. The battery cell according to any one of claims 1 to 12, wherein, The first electrode satisfies the following condition: n*W1 / W2 is between 0.5 and 1.0; n represents the number of all electrode ears located on the same side of the electrode body; W1 represents the average size of the tab portion along the second direction; W2 represents the dimension of the electrode body along the second direction.

14. The battery cell according to any one of claims 1 to 13 further includes an electrolyte, said electrolyte comprising a chain-like carboxylic acid ester solvent, said chain-like carboxylic acid ester solvent having a mass content of 5% to 30% in the electrolyte.

15. The battery cell according to any one of claims 1 to 14, further comprising an electrolyte, the electrolyte further comprising lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the mass content of the lithium hexafluorophosphate to the mass content of the lithium difluorosulfonylimide is 0.5 to 4 based on the mass of the electrolyte.

16. The battery cell according to claim 14 or 15, wherein, The electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature.

17. The battery cell according to any one of claims 1 to 16, wherein, The lithium phosphates with the olivine structure include lithium iron phosphate.

18. The battery cell according to claim 17, wherein, The single-sided coating weight of the active material layer of the positive electrode sheet is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 ; and / or When the battery cell is at 0% charge, the compaction density of the active material layer of the positive electrode is 2.30 g / cm³. 3 Up to 2.70 g / cm 3 .

19. The battery cell according to any one of claims 1 to 18, wherein, The negative electrode sheet body includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a carbon-based material and comprises: A first negative electrode film layer is disposed on the surface of the negative electrode current collector; and The second negative electrode film layer is connected to the side of the first negative electrode film layer that is away from the negative electrode current collector. Wherein, the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer.

20. The battery cell according to claim 19, wherein, The carbon-based material of the first negative electrode film is granular, with a volume average particle size Dv50 of 9.5 μm to 18.5 μm; and / or The carbon-based material of the second negative electrode film is granular, with a volume average particle size Dv50 of 7.8 μm to 14.3 μm.

21. The battery cell according to claim 19 or 20, wherein, The carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

22. The battery cell according to any one of claims 1 to 21, wherein, The single-sided coating weight of the active material layer of the negative electrode sheet is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 ; and / or When the battery cell is at 0% charge, the compaction density of the active material layer of the negative electrode is 1.30 g / cm³. 3 Up to 1.65 g / cm 3 .

23. A battery device comprising a battery cell as claimed in any one of claims 1 to 22.

24. An electrical device comprising the battery device as described in claim 23.

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