Battery cell, battery device, and electrical device

Abstract

This application relates to a battery cell, a battery device, and an electrical device. The battery cell includes an electrode assembly. The electrode assembly includes a first electrode tab and a second electrode tab stacked along the thickness direction of the battery cell. Both the first electrode tab and the second electrode tab include an electrode tab body and at least one electrode ear. At least a partial region of the electrode tab body is provided with an active material layer. At least one electrode ear is connected to the electrode tab body and protrudes from the electrode tab body along a first direction. The active material layer of the positive electrode tab includes lithium-containing phosphate in an olivine structure. The dimension of the electrode tab body of the positive electrode tab along the length direction of the battery cell is 320 mm to 650 mm; the first electrode tab satisfies: a 2 +b 2 The maximum value of is 6,000 to 110,000. The fast charging ability of the battery cell of this application at high energy density can be further improved.

Description

[0001] This application claims the priority of the patent application PCT / CN2025 / 071119 titled "Battery Cell, Battery Device and Electrical Device" filed on January 7, 2025, and the entire content of this application is incorporated herein by reference. Technical Field

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

[0003] Battery cells have characteristics such as high capacity and long life, so they are widely used in electronic devices, such as mobile phones, laptops, electric bicycles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and power tools, etc. Due to the great progress of batteries, higher requirements are put forward for the performance of batteries. However, the fast charging ability of battery cells needs to be further improved. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device, and the fast charging ability of the battery cell of this application can be further improved.

[0005] In a first aspect, an embodiment of this application provides a battery cell. The battery cell includes an electrode assembly. The electrode assembly includes a first electrode tab and a second electrode tab stacked along the thickness direction of the battery cell. One of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab; both the first electrode tab and the second electrode tab include an electrode tab body and at least one tab ear. At least a part of the electrode tab body is provided with an active material layer, and at least one tab ear is connected to the electrode tab body and protrudes from the electrode tab body along a first direction;

[0006] Wherein, the active material layer of the positive electrode tab includes lithium-containing phosphate with an olivine structure, and the size of the electrode tab body of the positive electrode tab along the length direction of the battery cell is 320 mm to 650 mm;

[0007] Wherein, the first electrode tab satisfies: a 2 +b 2 The maximum value of is 6000 to 110000,

[0008] a represents, in the first electrode tab, along the first direction, the distance between any point A on the electrode tab body and the tab ear closest to point A among at least one tab ear, and its unit is mm;

[0009] b represents, in the first electrode tab, along the second direction, the distance between point A and the tab ear closest to point A among at least one tab ear is b, and its 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.

[0010] Therefore, in the embodiments of the present application, the electrode assembly is of a stacked structure, and the size of the main body of the positive electrode tab in the length direction of the battery cell is within the above range, so that the energy density of the battery cell is relatively high; in the case of relatively high energy density, the internal resistance of the tab is high, and the positive electrode active material of the present application further includes lithium-containing phosphate with an olivine structure and poor conductivity, which further increases the internal resistance; in order to reduce the internal resistance, the embodiments of the present application design the electron transmission path so that the electron transmission path in the tab is relatively short, reducing the internal resistance of the tab, thereby reducing the internal resistance of the battery cell, which is beneficial to the rapid charging of the battery cell at high energy density.

[0011] In some embodiments, the first direction is parallel to the length direction of the battery cell.

[0012] In some embodiments, there are multiple tab portions of the first tab, and the multiple tab portions are arranged on both sides of the main body of the tab along the first direction. The electron transmission path is short, which is beneficial to the rapid charging of the battery cell.

[0013] In some embodiments, a 2 +b 2 The maximum value of is 25,600 to 110,000, and can be optionally 25,600 to 90,000. The electron transmission path is short, which is beneficial to the rapid charging of the battery cell.

[0014] In some embodiments, the first direction is parallel to the width direction of the battery cell. The electron transmission path is short, which is beneficial to the rapid charging of the battery cell.

[0015] In some embodiments, at least one tab portion of the first tab is arranged on the same side of the main body of the tab along the first direction.

[0016] In some embodiments, a 2 +b 2 The maximum value of is 6,400 to 45,000, and can be optionally 6,400 to 25,000. The electron transmission path is short, which is beneficial to the rapid charging of the battery cell.

[0017] In some embodiments, the electrode assembly is of a stacked structure, and the size of the main body of the positive electrode tab in the width direction is 80 mm to 150 mm. The electron transmission path is relatively short, which is thus beneficial to the rapid charging of the battery cell.

[0018] In some embodiments, there are multiple tab portions of the first tab arranged on the same side of the main body of the tab, and the distance between two adjacent tab portions along the second direction is greater than 0 and less than or equal to 300 mm. Each tab bears less current, and the current distribution is more uniform, which is thus beneficial to the rapid charging of the battery cell.

[0019] In some embodiments, the second electrode tab satisfies: c 2 +d 2 The maximum value of is from 6000 to 110000,

[0020] wherein, c represents the distance, in the second electrode tab, along the first direction, between any point B on the electrode tab body and the electrode tab ear closest to point B among at least one electrode tab ear, with the unit of mm,

[0021] d represents the distance, along the second direction, between point B and the electrode tab ear closest to point B among at least one electrode tab ear along the second direction, with the unit of mm.

[0022] Thus, when the second electrode tab of the embodiments of the present application satisfies the above conditions, the electron transfer path is relatively short, which can effectively reduce the internal resistance of the battery cell, and each electrode tab bears less current, and the current distribution is more uniform, thereby facilitating the rapid charging of the battery cell.

[0023] In some embodiments, the electrode tab ear of the first electrode tab is disposed on at least one side of the electrode tab body along the first direction, and the first electrode tab satisfies: n*W1 / W2 is from 0.5 to 1.0; n represents the number of all electrode tab ears on the same side of the electrode tab body; W1 represents the average dimension of the electrode tab ear along the second direction, one of the first direction and the second direction 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 dimension of the electrode tab body along the second direction. The current-carrying capacity of the electrode tab ear is relatively strong, which is beneficial to improving the current-carrying capacity of the battery device and the rapid charging performance of the battery device.

[0024] In some embodiments, the battery cell further includes an electrolyte, and the electrolyte includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent in the electrolyte is from 5% to 30%. The conductivity of the above solvent system is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the rapid charging performance of the battery cell.

[0025] In some embodiments, the battery cell further includes an electrolyte, and the electrolyte includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide is from 0.5 to 4. When the lithium salt satisfies the above conditions, it is beneficial to improve the lithium ion conduction ability of the electrolyte and can improve the rapid charging performance of the battery cell.

[0026] In some embodiments, the conductivity of the electrolyte at room temperature is from 10 mS / cm to 13 mS / cm. When the conductivity of the electrolyte at room temperature, such as 25 °C, is in 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 can improve the rapid charging performance of the battery cell.

[0027] In some embodiments, the lithium-containing phosphate of olivine structure includes lithium iron phosphate. The lithium-containing phosphate has relatively excellent cycle stability, which is beneficial to improving the cycle performance.

[0028] In some embodiments, the active material layer of the positive electrode tab is a positive electrode active material layer, and the single-sided coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 ; when the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generation amount per unit area of the positive electrode tab will not be too large, and it can take into account improving the energy density and charging rate performance of the battery cell.

[0029] In some embodiments, when the battery cell is in a 0% state of charge, the tap density of the positive electrode active material layer is 2.30 g / cm 3 to 2.70 g / cm 3 . When the tap 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 since the positive electrode active materials in the positive electrode active material layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode tab can be further reduced, and the fast charging performance of the battery cell at a high energy density can be improved.

[0030] In some embodiments, the tab body of the negative electrode tab includes a negative electrode current collector part and a negative electrode active material layer provided on at least one side of the negative electrode current collector part. The negative electrode active material layer includes a carbon-based material. 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 provided on the surface of the negative electrode current collector part; the second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector part. Among them, the volume average particle diameter Dv50 of the carbon-based material of the first negative electrode film layer is greater than or equal to the volume average particle diameter Dv50 of the carbon-based material of the second negative electrode film layer. In the embodiments of the present application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode tab.

[0031] In some embodiments, the carbon-based material of the first negative electrode film layer is granular, and its volume average particle diameter Dv50 is 9.5 μm to 18.5 μm; when the volume average particle diameter Dv50 of the carbon-based material of the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance, and on the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0032] In some embodiments, the carbon-based material of the second negative electrode film layer is granular, and its volume average particle size Dv50 is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer with the above volume average particle size range cooperates with the negative electrode active material in the first negative electrode film layer, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0033] 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.

[0034] In some embodiments, the active material layer of the negative electrode sheet is a negative electrode active material layer, and the single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 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 take into account the improvement of the energy density of the battery cell, which is beneficial to improving the fast charging performance of the battery cell at high energy density.

[0035] In some embodiments, when the battery cell is in the 0% state of charge, the tap density of the negative electrode active material layer is 1.30 g / cm 3 to 1.65 g / cm 3 . When the tap 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 materials in the negative electrode active material layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet and is beneficial to improving the fast charging performance of the battery cell at high energy density.

[0036] In a second aspect, an embodiment of the present application also provides a battery device, including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0037] In a third aspect, an embodiment of the present application also provides an electrical device, and the electrical device includes the battery device according to any one of the embodiments in the second or third aspect of the present application. Description of the Drawings

[0038] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for use in the embodiments of the present application. Obviously, the accompanying drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the accompanying drawings.

[0039] Figure 1 It is a schematic structural diagram of an electrical device provided by some embodiments of the present application;

[0040] Figure 2 It is a schematic structural diagram of a battery pack provided by some embodiments of the present application;

[0041] Figure 3 It is a schematic structural diagram of a battery module provided by some embodiments of the present application;

[0042] Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application;

[0043] Figure 5 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0044] Figure 6 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some embodiments of the present application;

[0045] Figure 7 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0046] Figure 8 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some further embodiments of the present application;

[0047] Figure 9 It is a schematic structural diagram of a second electrode tab of a battery cell provided by some embodiments of the present application;

[0048] Figure 10 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0049] Figure 11 It is a schematic structural diagram of a first electrode tab of a battery cell provided by some other embodiments of the present application;

[0050] Figure 12 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0051] Figure 13 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0052] Figure 14 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0053] Figure 15 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0054] Figure 16 It is a schematic structural diagram of a first electrode sheet of a battery cell provided by some other embodiments of the present application;

[0055] Figure 17 It is a schematic structural diagram of a first electrode sheet of a battery cell provided by some other embodiments of the present application.

[0056] The drawings are not necessarily drawn to actual scale.

[0057] The description of the reference numerals is as follows:

[0058] X, thickness direction; Y, width direction; Z, length direction;

[0059] 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, first electrode sheet; 111, first electrode tab; 1111, first end; 112, first electrode sheet body; 12, second electrode sheet; 121, second electrode tab; 122, second electrode sheet body; 13, separator; 20, outer shell assembly; 21, housing; 211, first housing part; 212, second housing part; 2121, first wall; 2122, second wall; 213, third housing part; 22, end cover; 31, first electrode terminal; 32, second electrode terminal; 51, first adapter; 61, first conductive member; 611, first conductive part; 612, second conductive part. Detailed embodiments

[0060] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application that are specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0061] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0063] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0064] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0065] The "plurality" mentioned in this application means two or more (including two).

[0066] In the embodiments of this application, the battery cell can be a secondary battery, and a secondary battery refers to a battery cell that can be activated by charging after the battery cell discharges and can be used continuously.

[0067] The battery cell includes an electrode assembly, and the electrode assembly includes electrode plates. During the charging process, electrons are transported in the electrode plates. When the transport path of the electrons is too long, the electron conductivity is relatively low and the internal resistance is relatively high, which is not conducive to the rapid charging of the battery cell. Especially when the battery cell has a high energy density, the internal resistance is further increased, which is not conducive to the rapid charging of the battery cell at high energy density.

[0068] In view of the above problems, on the one hand, in an embodiment of the present application, an appropriate range of the size of the positive electrode active material layer is selected to make the energy density of the battery cell relatively high. Furthermore, by designing the transport distance of the electrons, the electron transport path is 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.

[0069] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0070] Exemplarily, the electrical device may be a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric toy, an electric tool, a vehicle, a ship, a spacecraft, etc. Or, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0071] Figure 1 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0072] A battery device is arranged inside the electrical device 1, and the battery device can be arranged at the bottom, the head, or the tail of the electrical device 1. The battery device can be used to supply power to the electrical device 1. For example, the battery device can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in is a battery pack 2.

[0073] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery device to supply power to the motor 4. For example, it is used for the working power requirements during the startup, navigation, and driving of the electrical device 1.

[0074] The battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel, or in a hybrid connection through a busbar component.

[0075] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0076] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into an independent module. As an example, the battery module can be formed by bundling multiple battery cells with cable ties.

[0077] Such as Figure 2 shown, in some embodiments, the battery device can be a battery pack 2, which includes a box body 5 and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body 5.

[0078] As an example, the battery cell assembly can also be accommodated in the box body 5 by directly fixing multiple battery cells to the box body 5.

[0079] As an example, the box body 5 includes a first box body part 5a and a second box body part 5b. The box body 5 has an accommodation space 5c. The first box body part 5a and the second box body part 5b are snapped together so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body part 5a can be a top cover or a bottom plate.

[0080] As an example, the box body 5 can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0081] In some embodiments, the box body 5 can be part of the chassis structure of a vehicle. For example, part of the box body 5 can become at least part of the floor of the vehicle, or part of the box body 5 can become at least part of the cross beam and longitudinal beam of the vehicle.

[0082] As an example, the battery cell assembly can be a battery module 6, and the battery cell assembly can be accommodated in the box body 5 by fixing the battery module 6 to the box body 5.

[0083] Such as Figure 3 shown, the battery module 6 includes multiple battery cells 7.

[0084] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0085] In some embodiments, during the charging process of the battery device or any battery cell 7 constituting the battery device from 10% state of charge (SOC) to 80% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0086] Exemplarily, the charging steps of the battery device or any battery cell 7 constituting the battery device from 10% SOC to 80% SOC can be carried out in the following manner:

[0087] Charge from 10% SOC to 25% SOC at a constant current of 7.0C;

[0088] Charge from 25% SOC to 30% SOC at a constant current of 7.0C;

[0089] Charge from 30% SOC to 35% SOC at a constant current of 7.0C;

[0090] Charge from 35% SOC to 40% SOC at a constant current of 7.0C;

[0091] Charge from 40% SOC to 45% SOC at a constant current of 6.7C;

[0092] Charge from 45% SOC to 50% SOC at a constant current of 6.5C;

[0093] Charge from 50% SOC to 55% SOC at a constant current of 6.0C;

[0094] Charge from 55% SOC to 60% SOC at a constant current of 5.8C;

[0095] Charge from 60% SOC to 65% SOC at a constant current of 5.5C;

[0096] Charge from 65% SOC to 70% SOC at a constant current of 5.2C;

[0097] Charge from 70% SOC to 75% SOC at a constant current of 5.0C;

[0098] Charge from 75% SOC to 80% SOC at a constant current of 4.8C.

[0099] In some embodiments, the charging time of the battery device or any 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 temperature of the external environment of the battery device at 10% state of charge is room temperature, such as 25 °C. Exemplarily, the charging time of 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 the range composed of any two of the above values.

[0100] As Figures 4 to 6 shown, the battery cell 7 includes an electrode assembly 10. The electrode assembly 10 includes a first electrode tab 11 and a second electrode tab 12. One of the first electrode tab 11 and the second electrode tab 12 is a positive electrode tab, and the other is a negative electrode tab. Both the first electrode tab 11 and the second electrode tab 12 include an electrode tab body and an electrode tab ear. At least a part of the electrode tab body is provided with an active material layer. At least one electrode tab ear is connected to the electrode tab body and protrudes from the electrode tab body along a first direction, and at least a part of the electrode tab ear is not provided with an active material layer.

[0101] The active material layer of the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the size of the electrode tab body of the positive electrode tab along the length direction Z of the battery cell 7 is 320 mm to 650 mm.

[0102] Among them, the first electrode tab 11 satisfies: a 2 +b 2 The maximum value of is 6000 to 110000.

[0103] a represents, in the first electrode tab 11, along the first direction, the distance between any point A on the electrode tab body and the electrode tab ear closest to point A among at least one electrode tab ear, and its unit is mm.

[0104] b represents, in the first electrode tab 11, along the second direction, the distance between point A and the electrode tab ear closest to point A among at least one electrode tab ear is b, and its unit is mm. One of the second direction and the first direction is parallel to the length direction of the first electrode tab, and the other is parallel to the width direction of the first electrode tab.

[0105] Exemplarily, a 2 +b 2The maximum values are 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 formed by any two of the above values.

[0106] In the same first electrode tab 11, there are multiple points A, a 2 +b 2 There are multiple values of, a 2 +b 2 The maximum value of can basically characterize the longest electron transmission distance in the electrode tab. By designing the maximum value of a 2 +b 2 the electron transmission path is shortened.

[0107] In the embodiment of the present application, the electrode assembly 10 can be a stacked electrode assembly. Compared with a wound electrode assembly, it can carry more active materials, which is beneficial to improving the energy density of the battery cell 7;

[0108] If the size of the electrode tab body of the positive electrode tab along the length direction Z of the battery cell 7 is too small, the energy density of the battery cell 7 is small and cannot meet the requirements; if the size of the electrode tab body of the positive electrode tab along the length direction Z of the battery cell 7 is too large, although the energy density of the battery cell 7 is too high, the electron transmission path is long and the internal resistance is too high, which is not conducive to fast charging;

[0109] In the embodiment of the present application, the size of the electrode tab body of the positive electrode tab along the length direction Z of the battery cell 7 is within the above range, so that the energy density of the battery cell is relatively high; in the case of relatively high energy density, the internal resistance of the electrode tab is high, and the positive electrode active material of the present application also includes lithium phosphate with an olivine structure with poor conductivity, which further increases the internal resistance; in order to reduce the internal resistance, the electron transmission path is designed in the embodiment of the present application, so that the electron transmission path in the electrode tab is relatively short, reducing the internal resistance of the electrode tab, thereby reducing the internal resistance of the battery cell, which is beneficial to the fast charging of the battery cell at high energy density.

[0110] To illustrate the present application more clearly, the tab part of the first electrode tab 11 is defined as the first tab 111, and the electrode tab body of the first electrode tab 11 is defined as the first electrode tab body 112. The tab part of the second electrode tab 12 is defined as the second tab 121, and the electrode tab body of the second electrode tab 12 is defined as the second electrode tab body 122. The electrode terminal with the same electrical property as the first tab 111 and electrically connected thereto is the first electrode terminal 31, and the electrode terminal with the same electrical property as the second tab 121 and electrically connected thereto is the second electrode terminal 32.

[0111] At least a part of the region of the electrode tab body is provided with an active material layer, which can be understood as that the entire region of the electrode tab body is provided with an active material layer; alternatively, a part of the region of the electrode tab body is provided with an active material layer, and an insulating layer can be provided in another part of the region. For example, a part of the region of the electrode tab body of the positive electrode tab is provided with an active material layer, and an insulating layer is provided at the edge part of the electrode tab body.

[0112] At least a part of the region of the tab ear is not provided with an active material layer, which can be understood as that the entire region of the tab ear is not provided with an active material layer; alternatively, the main region of the tab ear is not provided with an active material layer, and a part of the region of the tab ear close to the electrode tab body is provided with an active material layer. For example, a part of the region of the tab ear of the negative electrode tab close to the electrode tab body can be provided with an active material layer to receive active ions from the positive electrode tab and reduce the risk of lithium deposition.

[0113] The polarities of the first electrode tab 11 and the second electrode tab 12 are opposite. When the first electrode tab 11 is a positive electrode tab, the second electrode tab 12 is a negative electrode tab, the first electrode terminal 31 is a positive terminal, and the second electrode terminal 32 is a negative terminal; or when the first electrode tab 11 is a negative electrode tab, the second electrode tab 12 is a positive electrode tab, the first electrode terminal 31 is a negative terminal, and the second electrode terminal 32 is a positive terminal.

[0114] The electrode assembly includes a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab. Next, taking the first electrode tab 11 as the positive electrode tab and the second electrode tab 12 as the negative electrode tab as an example for illustration. Of course, the first electrode tab 11 can also be a negative electrode tab, and the second electrode tab 12 is a positive electrode tab. The electrode tab body of the positive electrode tab includes a positive current collector part and a positive active material layer disposed on at least one side of the positive current collector part, that is, the active material layer containing the positive active material is the positive active material layer.

[0115] The dimension of the positive active material layer of the positive electrode tab in the length direction is 320 mm to 650 mm, such as 320 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm or the range composed of any two of the above values. Optionally, the dimension of the positive active material layer of the positive electrode tab in the length direction is 320 mm to 600 mm. When the dimension of the positive active material layer of the positive electrode tab in the length direction meets the above range, it can take into account improving the energy density and fast charging performance of the battery cell.

[0116] The size of the positive active material layer of the positive electrode tab along the width direction is 80 mm to 150 mm, such as 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or the range composed of any two of the above values. When the size of the positive active material layer of the positive electrode tab along the width direction meets the above range, it can take into account improving the energy density and fast charging performance of the battery cell.

[0117] In the case where the electrode assembly 10 has a stacked structure, the first electrode tab 11, the second electrode tab 12 and the separator 13 form the electrode assembly 10 through a stacking process, and the first electrode tab 11, the second electrode tab 12 and the separator 13 are stacked.

[0118] Figure 4 In the figure, 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 tab 11, the thickness direction of the second electrode tab 12, and the thickness direction of the electrode assembly are parallel.

[0119] 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 tab 11 and the width direction of the electrode assembly.

[0120] 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 tab 11 and the length direction of the electrode assembly.

[0121] In the embodiments of the present application, the first direction may be parallel to the width direction Y or the length direction Z of the battery cell 7.

[0122] Next, the related solutions where the first direction is parallel to the width direction Y of the battery cell 7 will be described.

[0123] In some embodiments, the first electrode tab 11 includes one or more first tab ears 111, and one or more first tab ears 111 are disposed on at least one side of the tab body along the width direction Y.

[0124] Any point in the first electrode tab body 112 is defined as point A, and point A is arbitrarily taken in the first electrode tab body 112. Any point may be a point with an area. For example, the area of the point is 0.01 μm 2 , the area of the point is much smaller than the area of the tab ear, and the size of the point basically does not interfere with the measurement of the spacing.

[0125] The first tab ear 111 includes a first side and a second side that are opposite to each other along the first direction. The first side is disposed close to the first electrode tab body 112, and the second side is disposed away from the first electrode tab body 112. The spacing between point A and the first tab ear 111 along the first direction refers to the spacing between point A and the first side along the first direction.Figure 6 Among them, the first direction is parallel to the width direction Y of the battery cell 7, and a represents the distance between point A and the first tab 111 in the width direction Y.

[0126] The first tab 111 may be provided as one or more. In the case where there are multiple first tabs 111, the first tab 111 closest to point A in the second direction refers to the first tab 111 with the smallest distance from point A in the second direction.

[0127] The first tab 111 closest to point A is defined as the closest tab. The closest tab includes a first edge and a second edge that are opposite to each other in the second direction. The first edge is arranged close to point A, and the second edge is arranged away from point A. In the second direction, the distance between point A and the first tab 111 closest to point A refers to the distance between point A and the first edge in the second direction.

[0128] The projection of the closest tab in the first direction partially overlaps with the projection of the first tab body 112 in the first direction. In other words, the projection of the closest tab in the first direction is located within the projection of the first tab body 112 in the first direction, where the first direction is parallel to the normal of the projection plane. Point A is any point in the first tab body 112. When the projection of point A in the first direction is located within the projection of the closest tab in the first direction, it can be considered that the distance between point A and the closest tab in the second direction is 0. When the projection of point A in the first direction is located outside the projection of the closest tab in the first direction, it can be considered that the distance between point A and the closest tab in the second direction is greater than 0, and this distance is the distance between point A and the first edge in the second direction.

[0129] For example, one or more first tabs 111 are arranged on one side of the first tab body 112 in the width direction Y. In this case, it can be understood that all the first tabs 111 are arranged on the same side of the first tab body 112 in the width direction Y. This kind of arrangement is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0130] In the case where all the first tabs 111 are arranged on the same side of the first tab body 112 in the width direction Y, a 2 +b 2 The maximum value of is 6400 to 45000, and can be selected as 6400 to 25000.

[0131] Figure 6 Among them, Y1 represents the dimension of the first tab body 112 in the width direction Y, and can also be understood as the width of the first tab body 112.

[0132] For electrons located at the same position, there may be multiple transmission paths between them and the tabs. The distance of the electrons transmitted along the shortest path is statistically used as the electron transmission distance at this point.

[0133] For electrons at different positions in the same electrode (i.e., electrons at different A points), the electron transmission distances at each position are statistically analyzed, and the longest electron transmission distance is selected as the maximum value of the electron transmission distance. This maximum value is represented by the maximum value of a 2 +b 2 By designing the maximum value of a 2 +b 2 the electron transmission path is shortened, the internal resistance is reduced, and the fast charging performance of the battery cell is improved.

[0134] Figure 6 In [reference], for electrons located at the same point A2, there may be multiple transmission paths such as C1 and C2 (only C1 and C2 are shown in the figure, and it does not exclude that electrons may also be transmitted in other ways). When the distance of C1 is greater than the distance of C2, the transmission distance of the electrons located at point A2 is defined as the distance of C2; when C1 is equal to C2, the transmission distance of the electrons located at point A2 can be defined as the distance of C1 or C2.

[0135] Specifically, since the first tab 111 is provided 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, and the first direction is parallel to the width direction Y. Then 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 tab closest to point A2 among at least one tab along the first direction.

[0136] 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 tab 111 along the length direction Z, and b2 represents the distance between point A2 and the other adjacent first tab 111 along the length direction Z. If b1 is greater than b2, then b2 represents the distance between point A2 and the tab closest to point A2 among at least one tab along the second direction. In this case, the transmission distance of the electrons located at point A2 is defined as the distance of C2;

[0137] If b1 is equal to b2, then either b1 or b2 can represent the distance between point A2 and the tab closest to point A2 among at least one tab along the second direction. In this case, the transmission distance of the electrons located at point A2 can be defined as the distance of C1 or C2.

[0138] For the same first electrode 11, there are multiple positions, such as A1 and A2,

[0139] For the electrons located at point A1, that is, the electrons located on the edge of the first electrode body 112, a is equal to the width Y1 of the first electrode body 112;

[0140] b3 represents the distance between point A1 and the adjacent first tab 111 in the length direction Z.

[0141] C3 represents the electron transfer distance at point A1.

[0142] Taking the electron transfer distance of the electron at point A2 as C2 as an example, if C2 is greater than or equal to C3, then C2 is the longest electron transfer distance in the first electrode tab 11, and the maximum value of a 2 +b 2 is the square of C2; if C2 is less than C3, then C3 is the longest electron transfer distance in the first electrode tab 11, and the maximum value of a 2 +b 2 is the square of C3.

[0143] As Figure 7 shown, for example, in the case where the first electrode tab 11 includes a plurality of first tabs 111, the plurality of first tabs 111 are arranged on both sides of the first electrode tab body 112 in the width direction Y.

[0144] In the case where the plurality of first tabs 111 are arranged on both sides of the first electrode tab body 112 in the width direction Y, the maximum value of a 2 +b 2 is from 6400 to 45000, and can be optionally from 6400 to 25000.

[0145] Figure 7 In, Y1 represents the dimension of the first electrode tab body 112 in the width direction Y, and can also be understood as the width of the first electrode tab body 112.

[0146] Figure 7 In, for the electrons at the same point A2, there may be multiple transmission paths such as C1, C2, C3, and C4. In the case where the C2 distance is the smallest, the transmission distance of the electrons at point A2 is defined as the C2 distance.

[0147] Specifically, since the first tab 111 is arranged on both sides of the first electrode tab body 112, a is equal to half of the dimension of the first electrode tab body 112 in the first direction, and the first direction is parallel to the width direction Y. Then a is half of the dimension of the first electrode tab body 112 in the width direction Y, that is, a is equal to Y1 / 2 of the first electrode tab body 112, that is, Y1 / 2 is equal to the distance between point A2 and the tab portion closest to point A2 in at least one tab portion in the first direction.

[0148] The second direction is parallel to the length direction Z of the first pole piece 11. b1 represents the distance between point A2 and an adjacent first pole ear 111 along the length direction Z, and b2 represents the distance between point A2 and another adjacent first pole ear 111 along the length direction Z. If b1 is greater than b2, then b2 represents the distance between point A2 and the pole ear part closest to point A2 among at least one pole ear part along the second direction. In this case, the transmission distance of the electron located at point A2 is defined as the C2 distance;

[0149] If b1 is equal to b2, then either b1 or b2 can represent the distance between point A2 and the pole ear part closest to point A2 among at least one pole ear part along the second direction. In this case, the electron transmission distance located at point A2 can be defined as the C1 distance or the C2 distance.

[0150] For the same first pole piece 11, there are multiple positions, such as A1 and A2.

[0151] The electron located at point A1, that is, the electron located on the edge of the first pole piece body 112, a3 is equal to half of the width Y1 of the first pole piece body 112;

[0152] b3 represents the distance between point A1 and the adjacent first pole ear 111 along the length direction Z;

[0153] C5 represents the electron transmission distance located at point A1.

[0154] Taking the electron transmission distance of the 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 transmission distance in the first pole piece 11, and the maximum value of a 2 +b 2 is the square of C2; if C2 is less than C5, then C5 is the longest electron transmission distance in the first pole piece 11, and the maximum value of a 2 +b 2 is the square of C5.

[0155] Whether all the first pole ears 111 are arranged on the same side of the first pole piece body 112 along the width direction Y, or all the first pole ears 111 are respectively arranged on both sides of the first pole piece body 112 along the width direction Y, multiple first pole ears 111 on the same side of the first pole piece body 112 can be selected, such as two, three, four, five, six, etc.; four can be selected. This kind of arrangement is beneficial to the uniform distribution of electrons in the first pole piece 11 and is beneficial to improving the fast charging performance.

[0156] Optionally, the distance between two adjacent tab portions in the length direction Z 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 a range composed of any two of the above values. Figure 7 In Figure 7 , Z1 represents the distance between two adjacent tab portions in the length direction Z.

[0157] As Figure 8 shown, in some embodiments, the first electrode tab 11 satisfies: n*W1 / W2 is 0.5 to 1.0;

[0158] n represents the number of all tab portions on the same side of the electrode tab body;

[0159] W1 represents the average dimension of the tab portion in the second direction;

[0160] W2 represents the dimension of the electrode tab body in the second direction.

[0161] Exemplarily, 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 composed of any two of the above values.

[0162] Figure 8 In Figure 8 , the first direction is parallel to the width direction Y of the battery cell 7, and n is 1. When the first direction is parallel to the length direction Z of the battery cell 7, the condition that n*W1 / W2 is 0.5 to 1.0 is also satisfied, which 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, which will not be elaborated here.

[0163] In the embodiments of the present application, the first electrode tab 11 also satisfies that n*W1 / W2 is 0.5 to 1.0, so that the connection area between the tab portion and the electrode tab body is relatively large, the current-carrying area of the tab portion is relatively large, which is beneficial to reducing the DC resistance and heat generation, and is beneficial to improving the fast charging performance of the battery cell.

[0164] W1 represents the average dimension of the first tab 111 in the second direction,

[0165] When the first tab 111 has a special-shaped structure, for example, in the first direction, the dimension of the first tab 111 in the second direction gradually increases. In this case, the dimensions of the first tab 111 at multiple positions in the second direction can be measured, and thus the average dimension of the first tab 111 in the second direction can be calculated. Of course, the dimensions of each part of the first tab 111 in the second direction can be the same value. In this case, this value can be used as the average dimension of the first tab 111.

[0166] The first tab 111 can be one or more. For example, when n ranges from 1 to 4, in the case where there are multiple first tabs 111, after measuring the average dimension of each first tab 111 respectively, the average dimension of the first tab 111 can be calculated by adding the average dimensions and then dividing by the number of the first tabs 111.

[0167] The first tab 111 is connected to the first tab body 112. The first tab 111 includes a first end 1111 connected to the first tab body 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first tab body 112 is relatively large, the current-carrying capacity of the first tab 111 is strong, and the power performance and cycle performance of the battery cell 7 can be improved.

[0168] Optionally, the current collector part of the first tab 111 and the first tab body 112 is an integral structure, so that the internal resistance of the first tab 11 is relatively low, and the power performance and cycle performance of the battery cell 7 can be further improved.

[0169] As Figure 9 shown, in some embodiments, in the second tab 12, along the first direction, the distance between any point B on the tab body and the tab part closest to point B among at least one tab part is c, and its unit is mm. Along the second direction, in the second tab 12, the distance between point B and the tab part closest to point B among at least one tab part along the second direction is d, and its unit is mm. One of the second direction and the first direction is parallel to the length direction of the first tab, and the other is parallel to the width direction of the first tab. Among them, c 2 +d 2 has a maximum value of 6000 to 110000.

[0170] When the second tab 12 in the embodiment of the present application meets the above conditions, the electron transmission path is relatively short, the internal resistance of the battery cell can be effectively reduced, and each tab bears less current and the current distribution is more uniform, which is beneficial to the fast charging of the battery cell.

[0171] In the embodiment of the present application, the number and arrangement method of the second tab 121 are the same as those of the first tab 111, which will not be elaborated here. The structure of the second tab 12 is the same as that of the first tab 11, which will not be elaborated here.

[0172] Next, the related solutions where the first direction is parallel to the length direction of the battery cell 7 will be described.

[0173] As Figure 10As shown, in some embodiments, the first electrode tab 11 includes one or more first tab ears 111; the one or more first tab ears 111 are disposed on at least one side of the first electrode tab body 112 along the length direction Z.

[0174] For example, the one or more first tab ears 111 are disposed on one side of the first electrode tab body 112 along the length direction Z. In this case, it can be understood that all the first tab ears 111 are disposed on the same side of the first electrode tab body 112 along the length direction Z.

[0175] In the case where all the first tab ears 111 are disposed on the same side of the first electrode tab body 112 along the length direction Z, a 2 +b 2 The maximum value of is 25,600 to 110,000, and can be optionally 25,600 to 90,000.

[0176] Figure 10 In, Z2 represents the dimension of the first electrode tab body 112 along the length direction Z, and can also be understood as the length of the first electrode tab body 112.

[0177] Figure 10 In, for electrons located at the same point A2, there may be multiple transmission paths such as C1 and C2 (only C1 and C2 are shown in the figure, and it does not exclude that electrons may also be transmitted in other ways). In the case where the distance of C1 is greater than the distance of C2, the transmission distance of the electrons located at point A2 is defined as the distance of C2; in the case where C1 is equal to C2, the transmission distance of the electrons located at point A2 can be defined as the distance of C1 or the distance of C2.

[0178] Specifically, since the first tab ear 111 is disposed on the same side of the first electrode tab body 112, a is equal to the dimension of the first electrode tab body 112 along the first direction, and the first direction is parallel to the length direction Z. Then a is the dimension of the first electrode tab body 112 along the length direction Z, that is, a is equal to the length Z2 of the first electrode tab body 112, that is, Z2 is equal to the distance between point A2 and the tab ear closest to point A2 among at least one tab ear part along the first direction.

[0179] The second direction is parallel to the width direction Y of the first electrode tab 11. b1 represents the distance between point A2 and an adjacent first tab ear 111 along the width direction Y, and b2 represents the distance between point A2 and another adjacent first tab ear 111 along the width direction Y. If b1 is greater than b2, then b2 represents the distance between point A2 and the tab ear closest to point A2 among at least one tab ear part along the second direction. In this case, the transmission distance of the electrons located at point A2 is defined as the distance of C2;

[0180] If b1 is equal to b2, then either b1 or b2 can represent the distance between point A2 and the ear tab closest to point A2 among at least one ear tab in the second direction. In this case, the electron transmission distance at point A2 can be defined as the C1 distance or the C2 distance.

[0181] For the same first pole piece 11, there are multiple positions, such as A1 and A2.

[0182] The electron at point A1, that is, the electron on the edge of the first pole piece body 112, a is equal to the length Z2 of the first pole piece body 112.

[0183] b3 represents the distance between point A1 and the adjacent first ear tab 111 in the width direction Y.

[0184] C3 represents the electron transmission distance at point A1.

[0185] Taking the electron transmission distance of the electron at point A2 as C2 as an example, if C2 is greater than or equal to C3, then C2 is the longest electron transmission distance in the first pole piece 11, and the maximum value of a 2 +b 2 is the square of C2; if C2 is less than C3, then C3 is the longest electron transmission distance in the first pole piece 11, and the maximum value of a 2 +b 2 is the square of C3.

[0186] As Figure 11 shown, for example, in the case where the first pole piece 11 includes multiple first ear tabs 111, the multiple first ear tabs 111 are respectively arranged on both sides of the first pole piece body 112 along the length direction Z.

[0187] Optionally, the multiple first ear tabs 111 are respectively arranged on both sides of the first pole piece body 112 along the length direction Z. This arrangement can shorten the transmission path of electrons in the first pole piece 11, which is beneficial to improving the fast charging performance.

[0188] In the case where the multiple first ear tabs 111 are arranged on both sides of the first pole piece body 112 along the length direction Z, the maximum value of a 2 +b 2 is 25600 to 110000, and can be optionally 25600 to 90000.

[0189] Figure 11 In, Z3 represents the dimension of the first pole piece body 112 along the length direction Z, and can also be understood as the length of the first pole piece body 112.

[0190] Figure 11Among them, for electrons located at the same point A, there may be multiple transmission paths such as C1 and C2. When the distance of C2 is the smallest, the transmission distance of the electrons located at point A is defined as the distance of C2.

[0191] Specifically, since the first tab 111 is provided on both sides of the first tab body 112, a is equal to half of the dimension of the first tab body 112 along the first direction, and the first direction is parallel to the length direction Z. Then a is half of the dimension of the first tab body 112 along the length direction Z, that is, a is equal to Z3 / 2 of the first tab body 112, that is, Z3 / 2 is equal to the distance between point A and the tab part closest to point A among at least one tab part along the first direction.

[0192] There is one first tab 111 on the same side. The second direction is parallel to the width direction Y of the first tab 11. b represents the distance between point A and the first tab 111 along the width direction Y. b represents the distance between point A and the tab part closest to point A among at least one tab part along the second direction. In this case, the distances of C1 and C2 are the same, and both can be used as the longest electron transmission distance in the first tab 11, a 2 +b 2 The maximum value of is the square of C1.

[0193] Whether all the first tabs 111 are provided on the same side of the first tab body 112 along the width direction Y or all the first tabs 111 are respectively provided on both sides of the first tab body 112 along the width direction Y, multiple first tabs 111 on the same side of the first tab body 112 can be selected, such as two, three, four, five, six, etc. This setting is beneficial to the uniform distribution of electrons in the first tab 11 and is beneficial to improving the fast charging performance. This setting method can further shorten the electron transmission path, effectively reduce the internal resistance of the battery cell, and each tab bears less current, and the current distribution is more uniform.

[0194] Optionally, the distance between adjacent two tab parts 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 the range composed of any two of the above values. This setting method can further shorten the electron transmission path, effectively reduce the internal resistance of the battery cell, and each tab bears less current, and the current distribution is more uniform. Figure 10 In it, Y2 represents the distance between adjacent two tab parts along the width direction Y.

[0195] [Electrolyte]

[0196] During the charging and discharging process of the battery cell, active ions such as lithium ions are inserted into and extracted from between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0197] The electrolyte salt includes a lithium salt, the lithium salt includes lithium bis(fluorosulfonyl)imide, and may further include lithium hexafluorophosphate LiPF6. The above lithium salts are beneficial to improving the lithium ion conduction ability of the electrolyte and the rapid charging ability of the battery cell.

[0198] Optionally, based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide is 0.5 to 4, and may be 1.2 to 2.0. The lithium salt is beneficial to improving the lithium ion conduction ability of the electrolyte and the rapid charging ability of the battery cell.

[0199] Exemplarily, the mass content ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 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 the range composed of any two of the above values.

[0200] In the embodiments of the present application, based on the mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 1% to 15%, and may be 3% to 12%.

[0201] Exemplarily, based on the mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or the range composed of any two of the above values.

[0202] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is 13% to 20%, such as 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or the range composed of any two of the above values.

[0203] In some embodiments, the conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 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 the range composed of any two of the above values.

[0204] 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 rapid charging performance of the battery cell.

[0205] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using the equipment and methods well-known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0206] In some embodiments, the organic solvent includes carbonate solvents.

[0207] Optionally, the mass content of the carbonate solvent in the electrolyte is 10% to 80%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80% or the range composed of any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, facilitate the migration of lithium ions, and enhance the fast charging performance of the battery cell.

[0208] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further optionally, the carbonate solvent includes one or more of dimethyl carbonate and ethylene carbonate. More optionally, the carbonate solvent includes dimethyl carbonate. The above carbonate solvent and the chain carboxylic ester solvent are used in combination, which improves the conductivity of the electrolyte at room temperature, facilitates the migration of lithium ions, and enhances the fast charging performance of the battery cell.

[0209] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0210] Optionally, the mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 30%. Exemplarily, the mass content of the chain carboxylic ester solvent is 5%, 10%, 15%, 20%, 25%, 30% or the range composed of any two of the above values.

[0211] When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions and enhances the fast charging performance of the battery cell.

[0212] In some embodiments, the chain carboxylic ester solvent includes the compound shown in Formula I,

[0213] Formula I,

[0214] In Formula I,

[0215] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0216] R2 includes a C1-C5 alkyl or a C1-C5 haloalkyl.

[0217] The above-mentioned chain carboxylic ester solvents have relatively high conductivity, which is beneficial to improving the fast charging ability of battery cells.

[0218] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl or a C1-C3 haloalkyl. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl or a C1-C2 haloalkyl.

[0219] Optionally, R2 includes a C1-C3 alkyl or a C1-C3 haloalkyl. Further optionally, R2 includes a C1-C2 alkyl or a C1-C2 haloalkyl.

[0220] In the above embodiments, the haloalkyl includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl. Optionally, the haloalkyl includes fluoroalkyl.

[0221] Exemplarily, the chain carboxylic ester solvents include one or more of the compounds shown in Formula I-1 to Formula I-8.

[0222]

[0223] In some embodiments, the electrolyte further contains additives. The additives can include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0224] In some embodiments, the additives include one or more of carbonate additives and sulfur-containing additives, and can be selected as at least two. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of battery cells and improving the cycle performance.

[0225] In some embodiments, the mass content of the additives in the electrolyte is 0.5% to 6%. Exemplarily, the mass content of the additives 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 composed of any two of the above values.

[0226] The above-mentioned organic solvents, such as chain carboxylic acid ester solvents, may decompose to produce acid at high temperatures, corroding the solid electrolyte interface film (SEI film) on the surface of the negative electrode. However, the additive can form a dense and uniform-thickness SEI film on the negative electrode side, effectively repair the SEI film, provide excellent protection for the negative electrode active material, be conducive to improving the fast charging performance of the battery cell, and improve the cycle performance.

[0227] Exemplarily, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Optionally, the carbonate additives include vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0228] Vinylene carbonate (VC) can form a dense and uniform-thickness SEI film on the negative electrode side, effectively repair the SEI film, provide excellent protection for the negative electrode active material, be conducive to improving the fast charging performance and cycle performance of the battery cell.

[0229] Fluoroethylene carbonate (FEC) can form an SEI film with relatively low impedance on the negative electrode side, effectively repair the SEI film, provide excellent protection for the negative electrode active material, be conducive to improving the fast charging performance and cycle performance of the battery cell.

[0230] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methyl disulfonate (MMDS), and can be optionally 1,3-propane sultone (PS).

[0231] The sulfur-containing additives can effectively repair the SEI film, provide excellent protection for the negative electrode active material, be conducive to improving the fast charging performance and cycle performance of the battery cell.

[0232] Exemplarily, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

[0233] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 3.0%, such as 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 the range composed of any 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 be conducive to improving the fast charging performance and cycle performance of the battery cell.

[0234] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.2% to 2.5%, such as 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 a range composed of any 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 is beneficial to improving the fast charging performance and cycle performance of the battery cell.

[0235] Optionally, the mass content of 1,3 - propane sultone (PS) in the electrolyte is 0.5% to 2.5%, such as 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 a range composed of any two of the above values. When the mass content of 1,3 - propane sultone (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 is beneficial to improving the fast charging performance and cycle performance of the battery cell.

[0236] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte have the meanings well - known in the art, and can be detected by equipment and methods well - known in the art. For example, reference can be made to the standard JY / T 020 - 1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a discharged battery (discharged to the lower cut - off voltage so that the charged state of the battery is about 0% SOC) can be reverse - disassembled, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0237] In the embodiments of the present application, the types and contents of organic components in the electrolyte have the meanings well - known in the art, and can be detected by equipment and methods well - known in the art. For example, reference can be made to GB / T 9722 - 2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0238] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified. Chain - like carboxylic ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of organic solvents. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0239] Use carbonate additives (such as vinylene carbonate, fluorinated ethylene carbonate) and sulfur-containing additives as additives for the electrolyte, and calculate the mass content of each component based on the mass of the electrolyte being 100%.

[0240] [Outer shell assembly]

[0241] In some embodiments, the battery cell 7 further includes an outer shell assembly 20, and the outer shell assembly 20 has an accommodation space for accommodating the electrode assembly 10 and the electrolyte.

[0242] In some embodiments, the outer shell assembly 20 includes an outer shell, a first electrode terminal 31, and a second electrode terminal 32, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the outer shell.

[0243] The outer shell can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum plastic film, etc. In some embodiments, the outer shell can be a sealed structure or a non-sealed structure. As an example, when the outer shell is a non-sealed structure, the outer shell serves to protect the electrode assembly 10, and a sealing bag is further included between the outer shell and the electrode assembly 10, and the sealing bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum plastic film. When the outer shell is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0244] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a multi-prismatic battery, and the multi-prismatic battery is, for example, a hexagonal-prismatic battery, etc., and there is no particular limitation in this application.

[0245] Outer shell

[0246] In some embodiments, the outer shell includes an end cap 22 and a housing 21, the housing 21 is provided with an opening, and the end cap 22 covers the opening. The housing 21 can be provided with one or more openings. One or more end caps 22 can also be provided.

[0247] 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 are disposed on the end cap 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22.

[0248] The first electrode terminal 31 and the second electrode terminal 32 can be provided on the same end cap 22 at the same time. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are provided at intervals on the end cap 22. Another example is that there are two end caps 22, the two end caps 22 are arranged opposite to each other, and the first electrode terminal 31 and the second electrode terminal 32 are provided on each end cap 22.

[0249] The first electrode terminal 31 and the second electrode terminal 32 are respectively provided on different end caps 22. For example, there are two end caps 22, the two end caps 22 are arranged opposite to each other, the first electrode terminal 31 is provided on one of the end caps 22, and the second electrode terminal 32 is provided on the other end cap 22.

[0250] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing 21 can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0251] In some embodiments, the housing 21 includes two first housing parts 211, a second housing part 212 and a third housing part 213. The two first housing parts 211 are opposite to each other along the thickness direction X of the battery cell 7. The second housing part 212 and the third housing part 213 are opposite to each other, and the second housing part 212 and the third housing part 213 are connected by the first housing part 211. The second housing part 212 includes a first wall 2121 and a second wall 2122 that are continuously arranged along the thickness direction X, and the first wall 2121 and the second wall 2122 are welded. The first wall 2121 and the second wall 2122 can be welded by specific methods such as butt welding and laser welding, and butt welding is optional. Since the area of the second housing part 212 is relatively small and the degree of expansion is relatively small, and the weld seam is located on the second housing part 212, the risk of liquid leakage of the battery cell 7 can be reduced.

[0252] When assembling the battery cell 7 into the box body of the battery device, the battery cell 7 is arranged in the box body. The box body includes a first box body part and a second box body part, and the first box body part covers the second box body part; wherein, the second housing part 212 is arranged opposite to the first box body part, and the second housing part 212 is arranged close to the first box body part, and the third housing part 213 is arranged close to the second box body part. When assembling the battery device into the electrical device, the first box body part can be located above the second box body part in the vertical direction. Since the second housing part 212 has a weld seam and the weld seam is arranged upward, the risk of liquid leakage of the battery cell 7 is reduced.

[0253] In some embodiments, the dimension of the battery cell 7 in the thickness direction X is from 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 a range composed of any two of the above values.

[0254] The dimension of the battery cell 7 in the thickness direction X can characterize the thickness of the battery cell 7. In other words, the thickness of the battery cell 7 is from 10 mm to 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 beneficial to the rapid heat dissipation inside the battery cell 7 and reduces the risk of thermal runaway.

[0255] 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, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm, or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0256] When the thickness of the housing 21 is within the above range, the housing 21 is relatively thin, which is beneficial to the rapid heat dissipation of the housing 21.

[0257] Exemplarily, the thickness of the first housing portion 211 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, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0258] Exemplarily, the thickness of the second housing portion 212 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, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0259] Exemplarily, the thickness of the third housing portion 213 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, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0260] First electrode terminal

[0261] In some embodiments, the battery cell 7 further includes a first electrode terminal 31, and the first electrode terminal 31 is connected to the first tab 111.

[0262] In some embodiments, the first electrode terminal 31 is at least one, and may be multiple, such as two, three, or four, etc.

[0263] As Figure 12 shown, 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 setting method can shorten the electron migration path and is beneficial to improving the fast charging performance.

[0264] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y.

[0265] Again, for example, multiple first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0266] As Figure 13 shown, 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.

[0267] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0268] Again, for example, multiple first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This setting method can shorten the electron migration path and is beneficial to improving the fast charging performance.

[0269] Exemplarily, there are two first electrode terminals 31. One of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplarily, there are four first electrode terminals 31. Two of the first electrode terminals 31 are disposed on one side of the electrode assembly 10, and the other two first electrode terminals 31 are disposed on both sides of the electrode assembly 10.

[0270] The first tab 111 is electrically connected to the first electrode terminal 31, which can be directly connected or indirectly connected. When the first tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51. The first adapter 51 is located between the first electrode terminal 31 and the first tab 111 and connects the first electrode terminal 31 and the first tab 111.

[0271] 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 tab 111 is disposed on at least one side of the first tab body 112 along the width direction Y, it is more beneficial to connect the first tab 111 and the first electrode terminal 31 through the first adapter 51.

[0272] 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. The first adapter portion 511 connects 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.

[0273] When the first tab 111 and the first electrode terminal 31 are disposed on the same side of the battery cell 7, the first adapter 51 may only include the first adapter portion 511.

[0274] In the above embodiments, the first adapter 51 may be a sheet-like structure, and of course, it may also be in other structural forms.

[0275] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0276] In some embodiments, the battery cell 7 further includes a first conductive member 61. The first conductive member 61 is located between the first adapter 51 and the first tab 111. The setting of the first conductive member 61 can increase the current-carrying capacity between the first tab 111 and the first adapter 51, which is beneficial to improving the fast charging performance and reducing heat generation.

[0277] For example, the tab portion of the first electrode tab 11 is disposed on one side of the electrode tab body along the width direction Y; the first conductive member 61 is located between the first adapter member 51 and the first electrode tab 111 and connects the first adapter member 51 and the first electrode tab 111.

[0278] Optionally, there are multiple first conductive members 61. The first conductive members 61 and the first electrode tabs 111 are connected in a one-to-one correspondence, and the multiple first conductive members 61 are connected to the first adapter member 51. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0279] As Figure 14 shown, optionally, there are multiple first electrode tabs 111 on the same side of the first electrode tab body 112, and the first conductive member 61 can be a continuous sheet structure that connects the multiple first electrode tabs 111.

[0280] When the first electrode 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, the first conductive portion 611 connects the first electrode tab 111 and the first adapter member 51, the second conductive portion 612 is connected to the first conductive portion 611, and the second conductive portion 612 protrudes from the first conductive portion 611 along the width direction Y, and the second conductive portion 612 connects the first adapter member 51. This structural setting is beneficial to increasing the grouping space in the length direction Z and beneficial to improving the energy density of the battery device.

[0281] It should be noted that when the battery cell 7 does not include the first adapter member 51, the first electrode tab 111 can be connected to the first electrode terminal 31 through the first conductive member 61.

[0282] Exemplarily, the first conductive member 61 has conductivity, and it can include a conductive polymer or a conductive metal material. The conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0283] In some embodiments, the thickness of the first conductive member 61 is 0.5 mm to 2.0 mm, such as 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 a range composed of any two of the above values. When the thickness of the first conductive member 61 is within the above range, the overcurrent capacity can be effectively improved and the fast charging capacity can be improved.

[0284] In the embodiments of the present application, the first electrode terminal 31 may be an integral structure, which may be integrally formed or formed into an integral structure by means such as welding. The integral structure is beneficial to reducing resistance and heat generation.

[0285] Second electrode terminal

[0286] In some embodiments, the battery cell further includes a second electrode terminal 32, and the second electrode terminal 32 is connected to the second tab 121.

[0287] In some embodiments, there is at least one second electrode terminal 32, and multiple second electrode terminals 32 are optional, such as two, three, or four.

[0288] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 in the width direction Y. This setting method can shorten the migration path of electrons and is beneficial to improving the fast charging performance.

[0289] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 in the width direction Y. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 in the width direction Y, and there will be no mutual interference when they are respectively electrically connected to the tab portions.

[0290] Exemplarily, there are two first electrode terminals 31 and two second electrode terminals 32. The two first electrode terminals 31 are disposed on one side of the electrode assembly 10 in the width direction Y, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 in the width direction Y. Figure 14 The schematic diagram shows that the first electrode terminal 31 and the second electrode terminal 32 are disposed on both sides of the electrode assembly 10 in the width direction Y.

[0291] Again, for example, multiple second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the width direction Y. This setting method can further shorten the migration path of electrons and is beneficial to improving the fast charging performance. In this case, the first electrode terminal 31 and the second electrode terminal 32 are disposed on one side of the electrode assembly 10 in the width direction Y, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the other side of the electrode assembly 10 in the width direction Y.

[0292] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 in the length direction Z.

[0293] For example, a plurality of 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 migration path of electrons and is beneficial to improving the fast charging performance. In this case, a first electrode terminal 31 and a second electrode terminal 32 are disposed on one side of the electrode assembly 10 along the length direction Z, and a first electrode terminal 31 and a second electrode terminal 32 are disposed on the other side of the electrode assembly 10 along the length direction Z.

[0294] Exemplarily, there are two second electrode terminals 32. One second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31. One first electrode terminal 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Figure 14 A schematic diagram showing four electrode terminals is shown.

[0295] For another example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 along the length direction Z, and when electrically connected to the pole ear portions respectively, they will not interfere with each other.

[0296] As Figure 15 shown, 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 respectively 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 arranged in a staggered manner along the width direction Y. Specifically, in the case where all the second pole ears 121 are disposed on the same side of the second pole piece body 122 along the width direction Y, and all the first pole ears 111 are disposed on the same side of the first pole piece body 112 along the width direction Y, the first pole ear 111 and the second pole ear 121 are respectively disposed on both sides of the pole piece body along the width direction Y. The first electrode terminal 31 is disposed close to the first pole ear 111, and the second electrode terminal 32 is disposed close to the second pole ear 121. This arrangement makes the electron transmission distance shorter and is more conducive to improving the fast charging ability of the battery cell 7.

[0297] The second pole ear 121 and the second electrode terminal 32 can be electrically connected directly or indirectly; when the second pole ear 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, and the second adapter is located between the second electrode terminal 32 and the second pole ear 121 and connects the second electrode terminal 32 and the second pole ear 121.

[0298] For example, when the second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the longitudinal direction Z, and the second tab 121 is disposed on at least one side of the second electrode plate body 122 along the width direction Y, the connection between the second tab 121 and the second electrode terminal 32 is more facilitated by the second adapter.

[0299] In the case where 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 connection portion and a second connection portion. The first connection portion extends along the longitudinal direction Z, the first connection portion connects the second tab 121, the second connection portion is connected to the first connection portion and protrudes from the first connection portion along the width direction Y, and is connected to the second electrode terminal 32.

[0300] In the case where the second tab 121 and the second electrode terminal 32 are disposed on the same side of the battery cell 7, the second adapter may only include a first connection portion.

[0301] In the above embodiments, the second adapter may be in a sheet structure, and of course, it may also be in other structural forms.

[0302] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0303] In some embodiments, the battery cell 7 further includes a second conductive member. The second conductive member is located between the second adapter and the second tab 121. The provision of the second conductive member can increase the current-carrying capacity between the second tab 121 and the second adapter, is beneficial to improving the fast charging performance, and reduces heat generation.

[0304] For example, the tab portion of the second electrode plate 12 is disposed on one side of the electrode plate body along the width direction Y; the second conductive member is located between the second adapter and the second tab 121, and connects the second adapter and the second tab 121.

[0305] Optionally, there are multiple second tabs 121 on the same side of the second electrode plate body 122. The second conductive member may be a continuous sheet structure connecting the multiple second tabs 121; or there are multiple second conductive members, the second conductive members and the second tabs 121 are connected in one-to-one correspondence, and the multiple second conductive members are connected to the second adapter. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0306] When the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, optionally, the second conductive member includes a third conductive portion and a fourth conductive portion. The third conductive portion extends along the length direction Z and connects the tab portion of the second electrode plate 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 the second adapter. Such a structural arrangement is beneficial to improving the grouping space in the length direction Z and is beneficial to improving the energy density of the battery device.

[0307] Exemplarily, the second conductive member 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 metal elements, etc.

[0308] It should be noted that when the battery cell 7 does not include the second adapter, the second tab 121 may be connected to the second electrode terminal 32 through the second conductive member.

[0309] Positive electrode plate

[0310] To more clearly illustrate the present application, the electrode plate body of the positive electrode plate corresponds to the positive electrode plate body, the tab portion corresponds to the positive electrode tab, the active material layer corresponds to the positive electrode active material layer containing the positive electrode active material, and the positive electrode plate body includes a positive electrode current collector portion and a positive electrode active material layer provided on at least one side of the positive electrode current collector portion.

[0311] The positive electrode plate includes a positive electrode current collector portion and a positive electrode active material layer provided on at least one surface of the positive electrode current collector portion and including the positive electrode active material. For example, the positive electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector portion.

[0312] The upper charge limit voltage and the lower discharge cut-off voltage of the battery cell vary according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage may be 3.65V and the lower discharge cut-off voltage may be 2.0V, or the upper charge limit voltage may be 3.8V and the lower discharge cut-off voltage may be 2.0V; again, for example, when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage may be 4.3V and the lower discharge cut-off voltage may be 2.0V. Next, taking the upper charge limit voltage of 3.65V and the lower discharge cut-off voltage of 2.0V as an example, the state of the battery cell will be described: In the embodiment of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows.

[0313] Charge the battery cell at a constant current charge rate of 0.33C to the upper charge voltage limit, then charge it at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. Discharge the battery cell at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0314] In some embodiments, when the battery cell is at 0% state of charge (SOC), the tap density of the positive electrode active material layer is 2.30 g / cm 3 to 2.70 g / cm 3 ; optionally 2.40 g / cm 3 to 2.55 g / cm 3 . Exemplarily, when the battery cell is at 0% state of charge (SOC), the tap density of the positive electrode active material layer is 2.30 g / cm 3 , 2.32 g / cm 3 , 2.35 g / cm 3 , 2.38 g / cm 3 , 2.40 g / cm 3 , 2.42 g / cm 3 , 2.45 g / cm 3 , 2.48 g / cm 3 , 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 or a range composed of any two of the above values.

[0315] When the tap 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 since the positive electrode active materials in the positive electrode active material layer are stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation during fast charging and alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, and improving the cycle performance of the battery cell.

[0316] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2, optionally 275 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode active material layer is 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0317] When the single-sided coating weight of the positive electrode active material layer is within the above range, the heat generation amount per unit area of the positive electrode plate will not be too large, alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, improving the cycling performance of the battery cell, and being able to increase the energy density of the battery cell.

[0318] In the embodiments of the present application, the compaction density of the positive electrode active material layer of the battery cell in the 0% state of charge (SOC) has the meaning well known in the art, that is, the positive electrode plate is disassembled from the battery cell in the 0% state of charge (SOC) to measure the compaction density of the positive electrode active material layer. For example, a single-sided coated positive electrode plate (if it is a double-sided coated plate, the positive electrode active material layer on one side can be wiped off first) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode active material layer of the above weighed positive electrode plate is wiped off, and the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode active material layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode active material layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the compaction density of the positive electrode active material layer = the single-sided coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0319] In some embodiments, the positive electrode active material includes lithium-containing phosphate with an olivine structure. In other embodiments, the positive electrode active material may also include lithium-containing transition metal oxides, etc. Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0320] In the embodiments of the present application, the lithium-containing phosphate in the olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate in the olivine structure includes phosphate particles and a coating layer, and the coating layer coats 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, is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, and reduces the heat generation of the battery cell.

[0321] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of Cl, C, and N, and Y includes one or more of O and F. The phosphate particles have excellent cycle stability, which is beneficial to improving the cycle performance of the battery cell.

[0322] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0323] In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode plate, it is cleaned with dimethyl carbonate (DMC) and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0324] In some embodiments, the positive electrode active material layer further includes a positive electrode additive, and the positive electrode additive may further include lithium element, which can release lithium ions during the charging process of the battery cell to make up for lithium loss, and is beneficial to improving the capacity characteristics and cycle performance of the battery cell.

[0325] In some embodiments, the average longest diameter of the positive electrode additive is 2 μm to 5 μm, such as 2 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the range composed of any two of them. When using the positive electrode additive with the above particle size, the stability of the positive electrode additive can be effectively improved while effectively making up for lithium loss.

[0326] In the embodiments of the present application, the positive electrode plate is cut along the thickness direction of the plate to expose the longitudinal section of the positive electrode active material layer; by performing scanning electron microscopy (SEM) testing on the longitudinal section of the positive electrode active material layer, the longest diameter of the positive electrode additive particles and the longest diameter of the lithium-containing phosphate are determined. For example, the "longest diameter" of the particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0327] In the cross-section of the positive electrode active material layer along its own thickness direction, the longest diameters of multiple, for example, 10 iron oxides containing lithium are statistically analyzed, and the average value thereof is calculated as the average longest diameter.

[0328] In some embodiments, based on the total mass of the positive electrode active material layer, the mass ratio of the positive electrode additive is 0.2% to 2%, such as 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% or the range composed of any two of them. When using the positive electrode additive within the mass range, lithium loss can be effectively made up.

[0329] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode conductive agent. There is no particular limitation on the type of the positive electrode conductive agent in the embodiments of the present application. By way of example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the positive electrode conductive agent is ≤5%.

[0330] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. There is no particular limitation on the type of the positive electrode binder in the embodiments of the present application. By way of example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode active material layer, the mass content of the positive electrode binder is ≤5%.

[0331] In some embodiments, the positive electrode current collector portion may be a metal foil or a composite current collector. By way of example of the metal foil, at least one foil of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. By way of example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. By way of example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0332] 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 portion is 3 to 10, such as 3, 4, 5, 6, 7, 8, 9, 10 or the range composed of 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 portion is 4 to 8.

[0333] When the ratio of the thickness of the single-sided positive electrode active material layer to the thickness of the positive electrode current collector portion is within the above range, the rapid charging ability and energy density of the battery cell can be improved.

[0334] In some embodiments, the thickness of the positive electrode current collector portion is 12 μm to 16 μm, and may be optionally 13 μm to 15 μm. Exemplarily, the thickness of the positive electrode current collector portion is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or the range composed of any two of the above values.

[0335] When the thickness of the positive current collector portion is within the above range, the current-carrying capacity of the positive current collector portion is relatively excellent, and the battery cell can have a high energy density.

[0336] In the embodiments of the present application, the thicknesses of the positive active material layer and the positive current collector portion have the meanings well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the thickness of the positive electrode sheet is measured with a micrometer, the film layer on the surface of the positive current collector portion is removed, and the thickness of the positive current collector portion is measured with a micrometer. When the positive active material layer is coated on one side, the thickness of the positive active material layer is the thickness of the positive electrode sheet minus the thickness of the positive current collector portion. When the positive active material layer is coated on both sides, the thickness of the positive active material layer is (the thickness of the positive electrode sheet minus the thickness of the positive current collector portion) / 2.

[0337] The positive active material layer is usually formed by coating a positive electrode paste on the positive current collector portion and then drying and cold pressing. The positive electrode paste is usually formed by dispersing a positive active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0338] The positive electrode sheet does not exclude other additional functional layers in addition to the positive active material layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive conductive layer sandwiched between the positive current collector portion and the positive active material layer and disposed on the surface of the positive current collector portion. In some other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive active material layer.

[0339] Negative electrode plate

[0340] To more clearly illustrate the present application, the main body of the negative electrode sheet corresponds to the main body of the negative electrode sheet, the tab corresponds to the negative tab, the active material layer corresponds to the negative active material layer containing the negative active material, and the main body of the negative electrode sheet includes a negative current collector portion and a negative active material layer disposed on at least one side of the negative current collector portion. The main body of the negative electrode sheet includes a negative current collector portion and a negative active material layer disposed on at least one side of the negative current collector portion.

[0341] The negative electrode sheet includes a negative current collector portion and a negative active material layer disposed on at least one surface of the negative current collector portion and including a negative active material. For example, the negative current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative active material layer is disposed on any one or both of the two opposite surfaces of the negative current collector portion.

[0342] In some embodiments, at 0% state of charge (SOC) of the battery cell, the tap density of the negative active material layer is 1.30 g / cm 3 to 1.65 g / cm3 ; Optionally, it is 1.35 g / cm 3 to 1.50 g / cm 3 . Exemplarily, the compaction density of the negative electrode active material layer of the battery cell at 0% state of charge is 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 or a range composed of any two of the above values.

[0343] 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 since the negative electrode active materials in the negative electrode active material layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation and alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, and improving the cycle performance of the battery cell.

[0344] In the embodiments of the present application, the compaction density of the negative electrode active material layer of the battery cell at 0% state of charge (SOC) has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. The detection method is the same as the compaction density test method of the positive electrode active material layer described above.

[0345] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 , optionally 125 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode active material layer is 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2, 140 mg / 1540.25 mm 2 , 145 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 , 175 mg / 1540.25 mm 2 , 180 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0346] 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 excessive, alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, improving the cycle performance of the battery cell, and being able to balance the improvement of the energy density of the battery cell.

[0347] In the embodiments of the present application, the single-sided coating weight of the negative electrode active material layer has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. The detection method is the same as the single-sided coating weight test method of the film layer described above.

[0348] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has relatively high cycle stability and can improve the cycle performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used in combination, the battery cell has relatively excellent cycle performance.

[0349] Optionally, the carbon-based material includes artificial graphite. The artificial graphite has relatively excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0350] In some embodiments, the carbon-based material may also include natural graphite. Specifically, the carbon-based material may include artificial graphite, or the carbon-based material may include artificial graphite and natural graphite. The natural graphite has relatively good electrical conductivity, which is beneficial to further reducing heat generation and can improve the power performance and cycle performance of the battery cell.

[0351] In some embodiments, in addition to the above-mentioned carbon-based materials and optional silicon-based materials, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material. Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0352] The qualitative and quantitative determination of each substance or element in this application can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0353] For example, this application can combine the general rules of X-ray diffraction analysis method in JIS / K0131-1996 to perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or the negative electrode active material.

[0354] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by scanning electron microscope (SEM). There are voids between the flaky structures in the SEM cross-section of natural graphite, while the SEM cross-section of artificial graphite is dense and has no obvious gaps, or they can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0355] In the embodiments of this application, the negative electrode active material layer includes at least one film layer, which can be a single-layer film layer or at least two-layer film layers. Optionally, the negative electrode active material layer includes at least two-layer film layers.

[0356] When the negative electrode active material layer adopts a single-layer film layer, the negative electrode active material in the negative electrode active material layer includes carbon-based materials. When adopting a single-layer film layer, the volume average particle size Dv50 of the carbon-based material is 8 μm to 13 μm, and can be 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 the range composed of any two of the above values.

[0357] When the negative electrode active material layer adopts 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 film layers, three film layers, four film layers, or even more film layers.

[0358] 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. 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 facing away from the negative electrode current collector. The carbon-based material of the second negative electrode film layer includes artificial graphite. The artificial graphite of the first negative electrode film layer and the artificial graphite of the second negative electrode film layer may be the same or different. When the artificial graphite of the first negative electrode film layer and the artificial graphite of the second negative electrode film layer are different, it may be the particle size or the graphitization degree that is different.

[0359] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and is optionally irregular.

[0360] The negative electrode active material layer includes at least two film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, it is possible to construct pore differences in the negative electrode active material layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0361] In some embodiments, 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. Further optionally, the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is greater than the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer, which is beneficial to improving the kinetic performance of the negative electrode active material layer.

[0362] There are differences in the particle sizes of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present 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 the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0363] Optionally, the carbon-based material of the first negative electrode film layer is granular, and its volume average particle size Dv50 is 9.0 μm to 18.5 μm, and can be 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 layer 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 composed 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 of the first negative electrode film layer is 9.0 μm to 18.5 μm, and can be optionally 9.0 μm to 14.6 μm.

[0364] When the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0365] Optionally, the carbon-based material of the second negative electrode film layer is granular, and its volume average particle size Dv50 is 7.8 μm to 14.3 μm, and can be optionally 7.8 μm to 11.3 μm. Exemplarily, 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 composed 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 of the second negative electrode film layer is 7.8 μm to 14.3 μm, and can be optionally 7.8 μm to 11.3 μm.

[0366] When the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is within the above range, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance.

[0367] When the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transport path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer with the above volume average particle size range cooperates with the negative electrode active material in the first negative electrode film layer, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell.

[0368] In the embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material has the meaning well known in the art, and can be detected by using the equipment and methods well known in the art. For example, taking the negative electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 of the particles is tested by a Mastersizer 2000E type laser particle size analyzer, etc.

[0369] Optionally, the carbon-based material of the first negative electrode film layer further includes natural graphite.

[0370] Exemplarily, 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.

[0371] In some other embodiments, the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer is greater than the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer. Further optionally, the volume average particle size Dv50 of the carbon-based material of the second negative electrode film layer being greater than the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is beneficial to improving the compaction density of the negative electrode active material layer.

[0372] The difference in particle sizes between the first negative electrode film layer and the second negative electrode film layer can improve the fast charging performance of the battery cell.

[0373] Exemplarily, 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.

[0374] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode conductive agent. The embodiments of the present application do not particularly limit the type of the 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, based on the total weight of the negative electrode active material layer, the mass content of the negative electrode conductive agent is ≤5%.

[0375] In some embodiments, the negative electrode active material layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode active material layer, the mass content of the negative electrode binder is ≤5%.

[0376] In some embodiments, the negative electrode active material layer may further optionally include other additives. As an example, the other additives may include thickeners, dispersants, etc., for example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode active material layer, the mass content of the other additives is ≤2%.

[0377] In some embodiments, the negative electrode current collector portion may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0378] 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 portion is 8 to 14, such as 8, 9, 10, 11, 12, 13, 14 or a range composed of 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 portion is 10 to 12.

[0379] When the ratio of the thickness of the single-sided negative electrode active material layer to the thickness of the negative electrode current collector portion is within the above range, the rapid charging ability and energy density of the battery cell can be improved.

[0380] In some embodiments, the thickness of the negative electrode current collector portion is 5 μm to 10 μm, and may be optionally 6 μm to 8 μm. Exemplarily, the thickness of the negative electrode current collector portion 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 a range composed of any two of the above values.

[0381] When the thickness of the negative electrode current collector portion is within the above range, the current-carrying capacity of the negative electrode current collector portion is relatively excellent, and the battery cell can have a high energy density.

[0382] In the embodiments of the present application, the thickness of the negative current collector part has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the film layer on the surface of the negative current collector part is washed off with a solvent, and the thickness of the negative current collector part is measured with a micrometer.

[0383] The negative active material layer is usually formed by coating a negative electrode paste on the negative current collector part and then drying and cold pressing. The negative electrode paste is usually formed by dispersing negative active substances, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0384] The negative electrode sheet does not exclude other additional functional layers in addition to the negative active material layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative electrode conductive layer sandwiched between the negative current collector part and the negative active material layer and disposed on the surface of the negative current collector part. In some other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative active material layer.

[0385] Separator

[0386] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0387] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0388] As an example, the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane 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 can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator membrane.

[0389] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and simultaneously functions to transport ions and isolate the positive and negative electrodes.

[0390] In some embodiments, the volumetric energy density of the battery cell is from 350 Wh / L to 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 composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0391] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art, and can be detected by devices and methods well-known in the art. For example, taking the upper charging limit voltage of the battery as 3.65 V and the discharge cut-off voltage of the battery as 2.0 V as an example for illustration,

[0392] The battery cell is placed at 25 °C and charged at a constant current of 0.33 C to 3.65 V, then charged at a constant voltage to 0.05 C, and discharged at a constant current of 0.33 C to 2.0 V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminal and excluding the insulating film outside the outer shell), and calculate the volume V0 of the single battery, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0393] Example

[0394] The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0395] Example 1

[0396] 1. Preparation of the positive electrode sheet

[0397] The positive electrode sheet includes a positive electrode tab, a positive electrode current collector portion, and positive electrode active material layers provided on both sides of the positive electrode current collector portion. The positive electrode current collector portion is an aluminum foil with a thickness of 13 μm.

[0398] The positive electrode active material layer comprises a lithium-containing phosphate, lithium ferrite as a positive electrode additive, polyvinylidene fluoride (PVDF) as a binder, and acetylene black as a conductive agent, with a mass ratio of 96:1:2:1. The positive electrode active material layer is a film layer formed by uniformly coating both sides of the positive electrode current collector portion with a positive electrode slurry (solvent: N-methylpyrrolidone NMP), followed by drying and cold pressing.

[0399] The lithium-containing phosphate includes lithium iron phosphate.

[0400] The single-sided coating weight of the positive electrode active material layer is 300 mg / 1540.25 mm 2 。

[0401] 2. Preparation of the negative electrode plate

[0402] The negative electrode plate includes a negative electrode tab, a negative electrode current collector portion, and negative electrode active material layers provided on both sides of the negative electrode current collector portion. The negative electrode current collector portion is a copper foil with a thickness of 6 μm.

[0403] The negative electrode active material layer is a film layer formed by uniformly coating the surface of the negative electrode current collector portion with a negative electrode slurry (solvent: deionized water), followed by drying and cold pressing.

[0404] The single-sided coating weight of the negative electrode active material layer is 130 mg / 1540.25 mm 2 。

[0405] 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 portion, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0406] The first negative electrode film layer comprises a carbon-based material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent, with 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 with a mass ratio of 1:1, and the volume average particle size of the carbon-based material is 9.0 μm;

[0407] The second negative electrode film layer comprises a carbon-based material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent, with a mass ratio of 96.5:1:1.5:1. The carbon-based material of the second negative electrode film layer includes artificial graphite, and the volume average particle size of the carbon-based material is 8.0 μm.

[0408] 3. Separator

[0409] The separator includes a base film, which is a polyethylene film layer with a thickness of 7 μm and a porosity of 42%.

[0410] 4. Preparation of the electrolyte

[0411] The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0412] The organic solvent includes 10% of chain carboxylic acid ester solvents (ethyl acetate) and 75% of carbonate solvents (diethyl carbonate, dimethyl carbonate, and ethylene carbonate with a mass ratio of 1:1:1). The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0413] Based on the mass of the electrolyte, the mass content of the additive is 1.5%, which includes vinylene carbonate VC.

[0414] The lithium salt includes 8.5% of lithium hexafluorophosphate LiPF6 and 5% of lithium bis(fluorosulfonyl)imide.

[0415] The conductivity of the electrolyte at room temperature is 12 mS / cm.

[0416] 5. Preparation of the battery cell

[0417] Stack the above positive electrode plate, separator, and negative electrode plate in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and obtain the battery cell through processes such as vacuum packaging, standing, forming, and shaping. The compaction density of the positive electrode active material layer of the battery cell at 0% SOC is 2.5 g / cm 3 , and the compaction density of the negative electrode active material layer at 0% SOC is 1.45 g / cm 3 .

[0418] Comparative Example 1, Examples 2 to 9

[0419] Battery cells were prepared using a method similar to that of Example 1. Different from Example 1, the parameters of the positive electrode tab and the positive electrode active material layer in the positive electrode plate were adjusted, as specifically shown in Table 1.

[0420] Performance test

[0421] 1. DC internal resistance DCR test of the battery cell

[0422] The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0423] For example, at 25 °C, the battery cell is charged to 3.65 V at a constant current of 0.33 C, left standing for 1 min, then charged to 3.65 V at a constant current of 0.05 C, left standing for 30 min, discharged at a constant current of 0.33 C to 2.5 V, and the discharge capacity A0 at this time is recorded, with the unit of Ah. Then, it is charged at a constant current of 0.33 C for 0.5A0 Ah to adjust the SOC to 50%.

[0424] After leaving the battery cell at 25 °C for 2 h, discharge it at a constant current of 4C for 10 s, and record ∆U 放电 , ∆I 放电 . The discharge DCR data of the lithium-ion battery is calculated by the following formula, R 放电 = ∆U 放电 / ∆I 放电 ,

[0425] where ∆U 放电 represents the voltage change within 10 s from the start of discharge, and ∆I 放电 represents the current value within 10 s from the start of discharge.

[0426] The test results are shown in Table 1.

[0427] Table 1

[0428]

[0429] In Table 1, the positive electrode tab is disposed on at least one side of the positive electrode current collector portion along the first direction, and the negative electrode tab is disposed in a manner similar to that of the positive electrode tab.

[0430] a represents the distance between the electron and the closest tab along the first direction; b represents the distance between the electron and the closest tab along the second direction; c represents the distance between the electron and the closest tab, and c 2 = a 2 + b 2 , and the maximum value of c 2 is the maximum value of a 2 + b 2 , that is, the maximum value of a 2 + b 2 can characterize the square of the longest transmission distance of electrons in the positive electrode sheet.

[0431] In each of the examples and comparative examples, the electrode assembly is a stacked electrode assembly, and the tabs of the positive electrode sheet and the negative electrode sheet are arranged in the same way. The width of the positive electrode active material layer in the positive electrode sheet is 100 mm.

[0432] The positive electrode tab is on the short side, which means that the positive electrode tab is disposed on at least one side of the positive electrode current collector portion along the length direction; the positive electrode tab is on one short side, which means that all the positive electrode tabs are disposed on the same side of the positive electrode current collector portion along the length direction; the positive electrode tab is on both short sides, which means that multiple positive electrode tabs are disposed on both sides of the positive electrode current collector portion along the length direction. When there are two positive electrode tabs, one positive electrode tab is disposed on each side of the positive electrode current collector portion;

[0433] The positive electrode tab is on the long side, which means that the positive electrode tab is disposed on at least one side of the positive electrode current collector portion along the width direction; the positive electrode tab is on one long side, which means that all the positive electrode tabs are disposed on the same side of the positive electrode current collector portion along the width direction.

[0434] The full tab refers to the ratio of the size W1 of the positive tab to the size W2 of the positive current collector being 1, that is, n*W1 / W2 is 1, and n is 1.

[0435] In Comparative Example 1, the length of the positive active material layer is relatively long and the energy density is relatively high. However, the positive tab is located on one side of the positive current collector in the length direction, 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 tab is a full tab and its width is the same as the width of the positive active material layer, b is 0. This setting results in a relatively long electron transmission path in the length direction, leading to a relatively high internal resistance of the battery cell and being unfavorable for fast charging at high energy density.

[0436] In Comparative Example 2, the length of the positive active material layer is too long and although the energy density is relatively high. However, the positive tab is located on one side of the positive current collector in the length direction, 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 tab is a full tab and its width is the same as the width of the positive active material layer, b is 0. This setting results in a relatively long electron transmission path in the length direction, leading to a relatively high internal resistance of the battery cell and being unfavorable for fast charging at high energy density.

[0437] In Comparative Example 3, the positive tab is located on one side of the positive current collector in the length direction, 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 tab is a full tab and its width is the same as the width of the positive active material layer, b is 0. Although this setting results in a relatively short electron transmission path, the length of the positive active material layer is relatively short, which is unfavorable for improving the energy density of the battery cell.

[0438] In Examples 6 to 9, the positive tabs are located on both sides of the positive current collector in the length direction, a is equal to half of the positive current collector. Since the positive tabs are full tabs and their widths are the same as the width of the positive active material layer, b is 0. This setting ensures that the electron transmission path in the length direction is not too long, the electron transmission path is relatively short, which can reduce the internal resistance of the battery cell and is favorable for fast charging at high energy density.

[0439] In Examples 1 to 5, the positive tabs are located on one side of the positive current collector in the width direction. Since the width dimension of the positive active material layer is relatively short, the electron transmission path in the width direction is relatively short, which can effectively reduce the internal resistance of the battery cell and is favorable for fast charging at high energy density. As a 2 +b 2 decreases, the electron transmission path is further shortened, which can more effectively reduce the internal resistance of the battery cell. However, as a 2 +b 2The decrease in the maximum value may cause the energy density of the battery cell to decrease synchronously, unable to meet the requirements of high energy density; therefore, in the embodiments of the present application, a 2 +b 2 has a maximum value of 6,000 to 110,000, which can effectively balance the improvement of the energy density of the battery cell and the fast charging performance, and is beneficial to achieving fast charging at high energy density.

[0440] As Figure 16 shown, in Example 1, there are two positive electrode tabs, and the two positive electrode tabs are located on the same side of the positive electrode current collector along the width direction. a is 100 mm; the dimension of each positive electrode tab along the length direction is 125 mm, W1 is 125 mm, n is 2, W2 is 500 mm, that is, n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 200 mm, then b is half of the distance, which is 100 mm.

[0441] As Figure 17 shown, in Example 2, there are four positive electrode tabs, and the four positive electrode tabs are located on the same side of the positive electrode current collector along the width direction. a is 100 mm; the dimension of each positive electrode tab along the length direction is 100 mm, W1 is 100 mm, n is 4, W2 is 500 mm, that is, n*W1 / W2 is 0.8; the distance Z1 between two adjacent positive electrode tabs is 25 mm, then b is half of the distance (corresponding to point A2), or half of the remaining dimension obtained by subtracting the dimension occupied by the positive electrode tabs from the positive electrode current collector and then subtracting the distance (corresponding to point A1), both of which are 12.5 mm.

[0442] As Figure 8 shown, in Example 3, there is one positive electrode tab, W1 is 500 mm, n is 1, W2 is 500 mm, that is, n*W1 / W2 is 1, a is 100 mm, and b is 0.

[0443] In Example 4, there are two positive electrode tabs, and the two positive electrode tabs are located on the same side of the positive electrode current collector along the width direction. a is 100 mm; the dimension of each positive electrode tab along the length direction is 162.5 mm, W1 is 162.5 mm, n is 2, W2 is 650 mm, that is, n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 200 mm, then b is half of the distance, which is 100 mm.

[0444] In Example 5, there are two positive electrode tabs, and the two positive electrode tabs are located on the same side of the positive electrode current collector along the width direction. a is 80 mm; the dimension of each positive electrode tab along the length direction is 80 mm, W1 is 80 mm, n is 2, W2 is 320 mm, that is, n*W1 / W2 is 0.5; the distance Z1 between two adjacent positive electrode tabs is 90 mm, then b is half of the distance, which is 45 mm.

[0445] Although the illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on 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, characterized in that, The battery cell includes an electrode assembly, the electrode assembly includes a first electrode tab and a second electrode tab stacked along the thickness direction of the battery cell, one of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab. Both the first electrode tab and the second electrode tab include an electrode tab body and at least one tab ear. At least a part of the electrode tab body is provided with an active material layer. The at least one tab ear is connected to the electrode tab body and protrudes from the electrode tab body along a first direction. The active material layer of the positive electrode tab includes lithium-containing phosphate with an olivine structure. The size of the electrode tab body along the length direction of the battery cell is 320 mm to 650 mm. Among them, the first electrode sheet satisfies: a 2 +b 2 The maximum value of is 6,000 to 110,000, a represents, in the first electrode tab, along the first direction, the distance between any point A on the electrode tab body and the tab ear closest to point A among the at least one tab ear, and its unit is mm. b represents, in the first electrode tab, along a second direction, the distance between point A and the tab ear closest to point A among the at least one tab ear is b, and its 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.

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 There are multiple tab ears on the first electrode tab, and the multiple tab ears are respectively arranged on both sides of the electrode tab body along the first direction.

4. The battery cell according to claim 2 or 3, characterized in that, a 2 +b 2 The maximum value is from 25,600 to 110,000.

5. The battery cell according to claim 4, wherein, a 2 +b 2 The maximum value is from 25,600 to 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 ear of the first electrode tab is arranged on the same side of the electrode tab body along the first direction.

8. The battery cell according to claim 6 or 7, characterized in that, a 2 +b 2 The maximum value is from 6,400 to 45,000.

9. The battery cell according to claim 8, characterized in that, a 2 +b 2 The maximum value is from 6,400 to 25,000.

10. The battery cell according to claim 1, characterized in that, The size of the electrode tab body of the positive electrode tab along the width direction is 80 mm to 150 mm.

11. The battery cell according to claim 1, wherein There are multiple tab ears arranged on the same side of the electrode tab body in the first electrode tab, and the distance between two adjacent tab ears along the second direction is greater than 0 and less than or equal to 300 mm.

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

13. The battery cell according to claim 1, characterized in that, The first electrode tab satisfies: n*W1 / W2 is 0.5 to 1.

0. n represents the number of all tab ears located on the same side of the electrode tab body. W1 represents the average size of the tab ear along the second direction. W2 represents the size of the electrode tab body along the second direction.

14. The battery cell according to claim 1, wherein The battery cell further includes an electrolyte, the electrolyte includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent in the electrolyte is 5% to 30%.

15. The battery cell according to claim 1, characterized in that, The battery cell further includes an electrolyte, and the electrolyte further includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide is 0.5 to 4.

16. The battery cell according to claim 14 or 15, characterized in that, The conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm.

17. The battery cell according to claim 1, characterized in that, The lithium-containing phosphate with an olivine structure includes 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 to 330 mg / 1540.25 mm 2 ; and / or When the battery cell is at 0% state of charge, the tap density of the active material layer of the positive electrode sheet is 2.30 g / cm 3 to 2.70 g / cm 3 .

19. The battery cell according to claim 1, wherein, The electrode body of the negative electrode plate 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. The negative active material layer includes: A first negative electrode film layer disposed on the surface of the negative current collector; and A second negative electrode film layer connected to a side of the first negative electrode film layer facing away from the negative current collector, wherein 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.

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

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

22. The battery cell according to claim 1, characterized in that, The single-sided coating weight of the active material layer of the negative electrode sheet is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 ; and / or When the battery cell is at 0% state of charge, the tap density of the active material layer of the negative electrode plate is 1.30 g / cm 3 to 1.65 g / cm 3 .

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

24. An electrical device, characterized in that, The electrical device includes the battery device according to claim 23.

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