Battery cell, battery device, and electrical device

Abstract

The present application relates to a battery cell, a battery device, and an electrical device. The battery cell includes an electrode assembly and a housing assembly. The electrode assembly includes a plurality of first electrode plates and a plurality of second electrode plates. One of the first electrode plates and the second electrode plates is a positive electrode plate, and the other is a negative electrode plate. The first electrode plates and the second electrode plates are stacked along the thickness direction of the battery cell. Both the first electrode plates and the second electrode plates include a coating portion and an electrode tab portion. The coating portion is provided with an active material layer, and the electrode tab portion is connected to and extends out of the coating portion. The positive electrode plate includes a lithium-containing phosphate with an olivine structure; the housing assembly includes a housing and a terminal assembly provided on the housing. The terminal assembly includes at least one first electrode terminal, and the first electrode terminal is connected to the electrode tab portion of the first electrode plate. Among them, the ratio of the length of the battery cell to the thickness of the battery cell is 40 to 70; the battery cell satisfies that x1∙S1 / E is 0.2 to 0.7.

Description

[0001] This application claims the priority of the patent application PCT / CN2025 / 071111 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, and are thus widely used in electronic devices, such as mobile phones, laptop computers, battery-powered vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools, etc. Due to the great progress of batteries, higher requirements are put forward for the performance of batteries. However, the fast charging ability and energy density of battery cells need 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 and energy density 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 and a housing assembly. The electrode assembly includes a plurality of first electrode plates and a plurality of second electrode plates. One of the first electrode plates and the second electrode plates is a positive electrode plate, and the other is a negative electrode plate. The first electrode plates and the second electrode plates are stacked along the thickness direction of the battery cell. The first electrode plates and the second electrode plates each include a coating portion and a tab portion. The coating portion is provided with an active material layer, and the tab portion is connected to the coating portion and extends out of the coating portion. The active material layer of the positive electrode plate includes lithium phosphate with an olivine structure; the housing assembly includes a housing and a terminal assembly disposed on the housing. The terminal assembly includes at least one first electrode terminal, and the first electrode terminal is connected to the tab portion of the first electrode plate.

[0006] Wherein,

[0007] The ratio of the length of the battery cell to the thickness of the battery cell is 40 to 70;

[0008] The battery cell satisfies that x1∙S1 / E is 0.2 to 0.7,

[0009] x1 represents the number of the first electrode terminals;

[0010] S1 represents the minimum cross-sectional area of a single first electrode terminal perpendicular to its own thickness direction, and its unit is mm 2 ;

[0011] E represents the single-cell energy of the battery cell, and its unit is Wh.

[0012] Thus, when the battery cell in the embodiment of the present application meets the above conditions, the energy density of the battery cell is relatively high; however, the length of the battery cell is relatively long, resulting in a relatively long electron transmission path in the length direction and a relatively high internal resistance, which is not conducive to fast charging. Moreover, the positive electrode active material includes lithium-containing phosphate with relatively poor conductivity, further increasing the internal resistance of the positive electrode plate. In order for the battery cell to quickly store a relatively high monomer energy, the embodiment of the present application also improves the over-current capacity of the first electrode terminal. The battery cell also satisfies that x1∙S1 / E is greater than or equal to 0.2. The over-current area of the first electrode terminal is relatively high, and the over-current capacity is strong, which can accelerate the electron conduction ability, effectively reduce the internal resistance of the battery cell, and reduce the heat generation of the battery cell. Moreover, the thickness of the battery cell is relatively thin, which is conducive to the rapid heat dissipation of the battery cell, thereby improving the fast charging ability of the battery cell and enabling the battery cell to quickly reach the required capacity.

[0013] In some embodiments, S1 is 15 to 60; when the over-current area of the first electronic terminal is within the above range, its over-current capacity is strong, which can improve the fast charging ability of the battery cell.

[0014] In some embodiments, x1 is 1 to 4; as the number of the first electrode terminals increases, the over-current capacity of all the first electrode terminals is enhanced, which can improve the fast charging ability of the battery cell.

[0015] In some embodiments, the battery cell also satisfies that M1 / E is 0.2 to 0.6; M1 represents the area of the first connection region, and its unit is mm 2 ; the first connection region is the region where at least one first electrode terminal is connected to the tab of the first electrode plate.

[0016] Thus, when the battery cell in the embodiment of the present application meets the above conditions, the current conduction ability between the first electrode terminal and the tab of the first electrode plate is strong, which is conducive to reducing the internal resistance of the battery cell and the heat generation of the battery cell, thereby improving the fast charging ability of the battery cell and enabling the battery cell to reach the required capacity under fast charging.

[0017] In some embodiments, M1 is 60 to 120; the current conduction ability between the first electrode terminal and the first tab is strong, which is conducive to reducing the internal resistance of the battery cell and the heat generation of the battery cell, thereby improving the fast charging ability of the battery cell.

[0018] In some embodiments, E is 170 to 480. When the battery cell meets the above conditions, the energy density of the battery cell is relatively high.

[0019] In some embodiments, the first electrode terminal is disposed on at least one side of the electrode assembly along the length direction, which is beneficial to reducing the space occupied by the first electrode terminal and improving the energy density of the battery cell.

[0020] In some embodiments, there are at least two first electrode terminals, and at least two first electrode terminals are respectively arranged on both sides of the electrode assembly along the length direction; the transmission path of electrons in the length direction is shortened, which is beneficial to reducing impedance and improving the fast charging capability of the battery cell.

[0021] In some embodiments, the housing includes a shell and an end cap, the electrode assembly is accommodated in the shell, the shell includes an opening, the end cap covers the opening, and the first electrode terminal is disposed on the end cap.

[0022] In some embodiments, the first electrode terminal includes a first main body and a first protruding portion, wherein the first main body is disposed on the end cap and penetrates the end cap; the first protruding portion is disposed on the first main body and protrudes from the first main body to connect to a side of the housing facing the electrode assembly. This arrangement is conducive to increasing the current capacity of the first electrode terminal.

[0023] In some embodiments, in a direction from the first main body portion to the first protrusion portion, a dimension of the first protrusion portion is 1.5 mm to 3.0 mm.

[0024] Therefore, when the first protrusion meets the above conditions, the connection area between the first protrusion and the shell is relatively larger, the connection strength is higher, and the structure makes the structure of the battery cell more stable.

[0025] In some embodiments, the first main body and the first protrusion are an integrated structure. This arrangement is conducive to increasing the current capacity of the first electrode terminal.

[0026] In some embodiments, the first body portion is disposed on the end cover and penetrates the end cover, and a ratio of a dimension of the first body portion along a thickness direction of the battery cell to a dimension of the end cover along a thickness direction of the battery cell is 0.20 to 0.40.

[0027] Therefore, in the embodiment of the present application, when the first main body meets the above conditions, the size of the first main body is relatively high, which is beneficial to improving the current carrying capacity of the first electrode terminal, thereby improving the fast charging performance.

[0028] In some embodiments, the housing assembly further includes a first conductive fixing member, at least a portion of which is located on a side of the end cap away from the electrode assembly, and the first conductive fixing member is disposed around the outside of the first main body and fixedly connects the first main body and the end cap. The first conductive fixing member can increase the flow capacity with the external bus assembly and improve the fast charging performance.

[0029] In some embodiments, the ratio of the dimension of the first conductive fixing member in the thickness direction of the battery cell to the dimension of the end cap in the thickness direction of the battery cell is 0.40 to 0.80. The first conductive fixing member can increase the over-current capacity with the external busbar assembly and improve the fast charging performance.

[0030] In some embodiments, the tab portion of the first electrode sheet is disposed on at least one side of the coating portion along the first direction, and the first electrode sheet satisfies: n*W1 / W2 is 0.5 to 1.0; n represents the number of all tab portions on the same side of the coating portion; W1 represents the average dimension of the tab portion in 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 coating portion in the second direction. The tab portion has a relatively strong over-current capacity, which is beneficial to improving the over-current capacity of the battery device and improving the fast charging performance of the battery device.

[0031] In some embodiments, the first direction is parallel to the length direction of the battery cell.

[0032] In some embodiments, the first electrode sheet includes a plurality of tab portions. The tab portion has a relatively strong over-current capacity, which is beneficial to improving the over-current capacity of the battery device and improving the fast charging performance of the battery device.

[0033] In some embodiments, there are at least two tab portions of the first electrode sheet on the same side of the coating portion. The above arrangement makes the electron transmission path shorter, which is beneficial to improving the fast charging ability.

[0034] In some embodiments, the plurality of tab portions of the first electrode sheet are located on both sides of the coating portion along the first direction. The above arrangement makes the electron transmission path shorter, which is beneficial to improving the fast charging ability.

[0035] In some embodiments, all the tab portions of the first electrode sheet are located on the same side of the coating portion along the first direction. The tab portion has a relatively strong over-current capacity, which is beneficial to improving the over-current capacity of the battery device and improving the fast charging performance of the battery device.

[0036] In some embodiments, the terminal assembly further includes at least one second electrode terminal, and the second electrode terminal is connected to the tab portion of the second electrode sheet; wherein, the battery cell satisfies: x2∙S2 / E is 0.2 to 0.7, x2 represents the number of second electrode terminals; S2 represents the minimum cross-sectional area of a single second electrode terminal perpendicular to its own thickness direction, and its unit is mm 2 。

[0037] Thus, when the battery cell in the embodiment of the present application satisfies the above conditions, the second electrode terminal has a relatively strong over-current capacity, which can effectively reduce the internal resistance of the battery cell, reduce the heat generation of the battery cell, thereby improving the fast charging ability of the battery cell and enabling the battery cell to quickly reach the required capacity.

[0038] In some embodiments, the battery cell further satisfies that M2 / E is from 0.2 to 0.6; M2 represents the area of the second connection region, and its unit is mm 2 ; the second connection region is the region where at least one second electrode terminal is connected to the tab portion of the second electrode plate.

[0039] Thus, when the battery cell in the embodiment of the present application satisfies the above conditions, the current conduction ability between the first electrode terminal and the tab portion of the first electrode plate is strong, which is beneficial to reducing the internal resistance of the battery cell, reducing the heat generation of the battery cell, thereby improving the fast charging ability of the battery cell and enabling the battery cell to quickly reach the required capacity.

[0040] In some embodiments, the second electrode terminal is disposed on at least one side of the electrode assembly in the length direction, which is beneficial to reducing the occupied space of the second electrode terminal and improving the energy density of the battery cell.

[0041] In some embodiments, there are two second electrode terminals, and the two second electrode terminals are respectively disposed on both sides of the electrode assembly in the length direction. The transmission path of electrons in the length direction is shortened, which is beneficial to reducing the impedance and improving the fast charging ability of the battery cell.

[0042] In some embodiments, the ratio of the length of the battery cell to the thickness of the battery cell is from 40 to 70.

[0043] In some embodiments, the ratio of the width of the battery cell to the thickness of the battery cell is from 3 to 15.

[0044] In some embodiments, the thickness of the battery cell is from 10 mm to 30 mm. When the thickness of the battery cell is within the above range, the thickness of the battery cell is relatively small, which is beneficial to the rapid heat dissipation inside the battery cell and reduces the risk of thermal runaway.

[0045] In some embodiments, the lithium-containing phosphate of the olivine structure includes lithium iron phosphate. Lithium iron phosphate has relatively excellent cycle stability and can improve the cycle performance of the battery cell under fast charging.

[0046] In some embodiments, the active material layer of the positive electrode plate is a positive electrode film layer, and the single-sided coating weight of the positive electrode film 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 film layer is within the above range, the heat generation per unit area of the positive electrode plate will not be too large, and it can balance the improvement of the energy density and the charging rate performance of the battery cell.

[0047] In some embodiments, when the battery cell is in the 0% state of charge, the compaction density of the positive electrode film layer is 2.30 g / cm3 to 2.70 g / cm 3 When the tap density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active materials in the positive electrode film 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 during fast charging.

[0048] In some embodiments, the active material layer of the negative electrode sheet is a negative electrode film layer, and the single-sided coating weight of the negative electrode film 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 film 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.

[0049] In some embodiments, when the battery cell is in a 0% state of charge, the tap density of the negative electrode film layer is 1.30 g / cm 3 to 1.65 g / cm 3 . When the tap density of the negative electrode film 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 film 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.

[0050] In some embodiments, the coated portion of the negative electrode sheet includes a negative electrode current collector portion and a negative electrode film layer provided on at least one side of the negative electrode current collector portion. The negative electrode film layer includes negative electrode active materials, and the negative electrode active materials include carbon-based materials. Among them, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is provided on the surface of the negative electrode current collector portion; 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 portion. Among them, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer. In the embodiments of 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 sheet.

[0051] In some embodiments, the carbon-based material of the first negative electrode film layer is granular, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm; when the volume average particle size Dv50 of the carbon-based material of the first negative electrode film 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.

[0052] 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, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved.

[0053] 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.

[0054] In some embodiments, the battery cell further includes an electrolyte, and the conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm. The migration rate of lithium ions in this electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0055] In some embodiments, the electrolyte includes a chain carboxylic ester solvent. The chain carboxylic ester solvent improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0056] In some embodiments, based on the mass of the electrolyte, the mass content of the chain carboxylic ester solvent is 5% to 30%, making the conductivity of the electrolyte relatively high and beneficial to the migration of lithium ions.

[0057] In some embodiments, 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 0.5 to 4. When the lithium salt meets the above conditions, the system is relatively stable and not easily decomposed. The lithium salt is beneficial to improving the conductivity of the electrolyte and the kinetic performance of the battery cell.

[0058] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is 1% to 15%. When the lithium salt meets the above conditions, the system is relatively stable and not easily decomposed. The lithium salt is beneficial to improving the conductivity of the electrolyte and the kinetic performance of the battery cell.

[0059] In a second aspect, an embodiment of the present application further provides a battery device, including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0060] In a third aspect, an embodiment of the present application further 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

[0061] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the drawings.

[0062] Figure 1 It is a schematic structural diagram of an electrical device provided by some embodiments of the present application;

[0063] Figure 2 It is a schematic structural diagram of a battery pack provided by some embodiments of the present application;

[0064] Figure 3 It is a schematic structural diagram of a battery module provided by some embodiments of the present application;

[0065] Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application;

[0066] Figure 5 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application;

[0067] Figure 6 It is a schematic structural diagram of an end cap, a terminal assembly and a first conductive fixing member of a battery cell provided by some embodiments of the present application;

[0068] Figure 7 is Figure 6 a top view schematic diagram of;

[0069] Figure 8 is Figure 7 a cross-sectional view taken along line A-A;

[0070] Figure 9 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0071] Figure 10 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0072] Figure 11 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0073] Figure 12 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0074] Figure 13 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application;

[0075] Figure 14It is a schematic diagram of the first electrode sheet of a battery cell provided by some embodiments of the present application;

[0076] Figure 15 It is a schematic diagram of the first electrode sheet of a battery cell provided by some other embodiments of the present application;

[0077] Figure 16 It is a schematic diagram of the first electrode sheet of a battery cell provided by some other embodiments of the present application;

[0078] Figure 17 It is a schematic diagram of the first electrode sheet of a battery cell provided by some other embodiments of the present application;

[0079] Figure 18 It is a schematic diagram of the first electrode sheet of a battery cell provided by some other embodiments of the present application.

[0080] The drawings are not necessarily drawn to actual scale.

[0081] The description of the reference numerals is as follows:

[0082] X, thickness direction; Y, width direction; Z, length direction;

[0083] 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;

[0084] 7, battery cell;

[0085] 10, electrode assembly;

[0086] 11, first electrode sheet; 111, first tab; 1111, first end; 112, first coating part;

[0087] 12, second electrode sheet; 121, second tab;

[0088] 13, separator;

[0089] 20, housing assembly;

[0090] 21, housing; 211, first housing part; 212, second housing part; 2121, first wall; 2122, second wall; 213, third housing part;

[0091] 22, end cap;

[0092] 31, first electrode terminal; 311, first protrusion; 312, first main body part;

[0093] 32, second electrode terminal;

[0094] 41, first conductive fixing part;

[0095] 51. First adapter; 511. First adapter part; 512. Second adapter part;

[0096] 61. First conductive member; 611. First conductive part; 612. Second conductive part. Detailed implementation manners

[0097] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed 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.

[0098] The "range" disclosed in the present 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 boundary of a specific range. The range defined in this way can include the end values or not include 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, 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 the present 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. Additionally, when it is stated 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.

[0099] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0100] If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0101] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0102] The term "plurality" as used in this application refers to two or more (including two).

[0103] In the embodiments of this application, the battery cell can be a secondary battery, which refers to a battery cell that can activate the active material through charging after discharging and can be used continuously.

[0104] The battery cell includes an electrode assembly and electrode terminals. In the case of relatively high energy density, the overcurrent capacity during the charging process is poor, resulting in an increase in the internal resistance of the battery cell, an increase in heat generation, and being unfavorable for the fast charging of the battery cell.

[0105] In view of the above problems, in the embodiments of this application, by adopting a battery cell with a specific size, on the one hand, more active material can be carried inside the battery cell, improving the energy density of the battery cell; on the basis of high energy density, it is beneficial for the battery cell to store relatively more monomer energy; however, the above battery cell is a long and narrow type battery, and the electron transmission path in the length direction is long, which is likely to increase the internal resistance; in order for the battery cell to quickly store a relatively high monomer energy, the embodiments of this application also improve the overcurrent capacity of the electrode terminals. For example, the total overcurrent capacity of all positive electrode terminals is improved, or the total overcurrent capacity of all negative electrode terminals is improved, so that the overcurrent capacity of the electrode terminals is relatively excellent, which can reduce the internal resistance of the battery cell, enabling electrons to migrate quickly and being beneficial for fast charging and storing capacity.

[0106] The battery cell of this application is applicable to various battery devices and electrical devices that use battery cells.

[0107] Exemplarily, the electrical device can be a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric toy, an electric tool, a vehicle, a ship, and a spacecraft, etc. Or, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, and a spaceship, etc.

[0108] Figure 1It is a schematic diagram of the electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, 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.

[0109] A battery device is arranged inside the electrical device 1, and the battery device can be arranged at the bottom, head or tail of the electrical device 1. The battery device can be used for power supply of 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 the battery pack 2.

[0110] 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 start, navigation and driving of the electrical device 1.

[0111] 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.

[0112] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0113] As an example, the battery cell assembly can be a battery module. The battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0114] As Figure 2 shown, in some embodiments, the battery device can be the battery pack 2, and the battery pack 2 includes a box body 5 and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body 5.

[0115] As an example, the battery cell assembly can also be accommodated in the box body 5 by directly fixing a plurality of battery cells to the box body 5.

[0116] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has an accommodation space 5c. The first housing portion 5a and the second housing portion 5b are snapped together so that a closed space is formed inside the housing 5 to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first housing portion 5a can be a top cover or a bottom plate.

[0117] As an example, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the housing 5 to accommodate the battery cell assembly.

[0118] In some embodiments, the housing 5 can be part of the chassis structure of a vehicle. For example, a part of the housing 5 can become at least a part of the floor of the vehicle, or a part of the housing 5 can become at least a part of the cross member and longitudinal member of the vehicle.

[0119] As an example, the battery cell assembly can be a battery module 6. The battery cell assembly can be accommodated in the housing 5 by fixing the battery module 6 in the housing 5.

[0120] As Figure 3 shown, the battery module 6 includes a plurality of battery cells 7.

[0121] In some embodiments, during the process of the battery device from 0% state of charge to 100% state of charge, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0122] In some embodiments, during the charging process of the battery device from 0% state of charge SOC to 100% state of charge SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0123] In some embodiments, during the charging process of the battery device or any battery cell 7 that makes up the battery device from 10% SOC to 80% state of charge SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0124] Exemplarily, the charging steps of the battery device or any battery cell 7 that makes up the battery device from 10% SOC to 80% SOC can be carried out in the following manner:

[0125] Charge from 10% SOC to 25% SOC at a constant current of 7.0C;

[0126] Charge from 25% SOC to 30% SOC at a constant current of 7.0C;

[0127] Charge from 30% SOC to 35% SOC at a constant current of 7.0C;

[0128] Charge from 35% SOC to 40% SOC at a constant current of 7.0C;

[0129] Charge from 40% SOC to 45% SOC at a constant current of 6.7C;

[0130] Charge from 45% SOC to 50% SOC at a constant current of 6.5C;

[0131] Charge from 50% SOC to 55% SOC at a constant current of 6.0C;

[0132] Charge from 55% SOC to 60% SOC at a constant current of 5.8C;

[0133] Charge from 60% SOC to 65% SOC at a constant current of 5.5C;

[0134] Charge from 65% SOC to 70% SOC at a constant current of 5.2C;

[0135] Charge from 70% SOC to 75% SOC at a constant current of 5.0C;

[0136] Charge from 75% SOC to 80% SOC at a constant current of 4.8C.

[0137] 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.

[0138] Such as Figures 4 to 8As shown, the battery cell 7 includes an electrode assembly 10 and a housing assembly 20. The electrode assembly 10 includes a plurality of first electrode plates 11 and a plurality of second electrode plates 12. One of the first electrode plates 11 and the second electrode plates 12 is a positive electrode plate, and the other is a negative electrode plate. The first electrode plates 11 and the second electrode plates 12 are stacked along the thickness direction X of the battery cell 7. The first electrode plates 11 and the second electrode plates 12 each include a coated portion and an electrode tab portion. The coated portion is provided with an active material layer. The electrode tab portion is connected to the coated portion and extends out of the coated portion, and is not coated with the active material layer. The active material layer of the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure.

[0139] The housing assembly 20 includes a housing and a terminal assembly. The housing houses the electrode assembly 10. The terminal assembly is disposed on the housing. The terminal assembly includes at least one first electrode terminal 31, and the first electrode terminal 31 is connected to the electrode tab portion of the first electrode plate 11.

[0140] Wherein,

[0141] The ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is 40 to 70;

[0142] The battery cell 7 satisfies that x1∙S1 / E is 0.2 to 0.7,

[0143] x1 represents the number of the first electrode terminals 31;

[0144] S1 is the minimum cross-sectional area of a single first electrode terminal 31 perpendicular to its own thickness direction, and its unit is mm 2 ;

[0145] x1∙S1 represents the minimum cross-sectional area of all the first electrode terminals 31 perpendicular to their own thickness directions, and its unit is mm 2 .

[0146] E represents the single-cell energy of the battery cell, and its unit is Wh.

[0147] Exemplarily, the formula x1∙S1 / E only performs numerical calculations without substituting units. x1∙S1 / E can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.70 or a range composed of any two of the above numerical values.

[0148] Optionally, the electrode assembly 10 further includes a separator 13, and the separator 13 is located between the first electrode plates 11 and the second electrode plates 12.

[0149] The electrode assembly 10 has a laminated structure, in which a plurality of first electrode plates 11 and a plurality of second electrode plates 12 are laminated. Compared with the wound structure, the laminated structure has no bending area, which is more conducive to increasing the coating amount of the active material on the laminated structure, enabling the battery cell 7 to have a relatively high energy density and facilitating the battery cell 7 to store more monomer energy;

[0150] The ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is 40 to 70. The length of the battery cell 7 is relatively long, resulting in a relatively long electron transmission path in the length direction and a relatively high internal resistance, which is not conducive to rapid charging. Moreover, the positive electrode active material includes lithium-containing phosphate with relatively poor conductivity, further increasing the internal resistance of the positive electrode plate;

[0151] In order for the battery cell to quickly store a relatively high monomer energy, the present application embodiment also improves the over-current capacity of the first electrode terminal. The battery cell 7 also satisfies that x1∙S1 / E is greater than or equal to 0.2. The over-current area of the first electrode terminal is relatively large, and the over-current capacity is strong, which can accelerate the electron conduction ability, effectively reduce the internal resistance of the battery cell 7, reduce the heat generation of the battery cell 7, and moreover, the thickness of the battery cell 7 is relatively thin, which is conducive to the rapid heat dissipation of the battery cell 7, thereby improving the rapid charging ability of the battery cell 7 and enabling the battery cell 7 to quickly reach the required capacity.

[0152] In the present application embodiment, the dimension of the battery cell 7 along its own length direction is the length of the battery cell 7, the dimension of the battery cell 7 along its own width direction is the width of the battery cell 7, and the dimension of the battery cell 7 along its own thickness direction is the thickness of the battery cell 7. Figure 4 The X direction shown in the figure is the thickness direction of the battery cell 7, the Y direction is the width direction of the battery cell 7, and the Z direction is the length direction of the battery cell 7.

[0153] When the ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is less than 40, the length dimension of the battery cell 7 is relatively small, which is not conducive to improving the energy density of the battery cell 7. When the ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is greater than 70, the length dimension of the battery cell 7 is too long, resulting in an overly long conduction path of electrons in the length direction and a high internal resistance, which is not conducive to improving the rapid charging of the battery cell 7.

[0154] The ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is 40 to 70, such as 40, 45, 50, 55, 60, 65, 70 or the range composed of any two of the above values. When the ratio of the length of the battery cell 7 to the thickness of the battery cell 7 is within the above range, it can balance the improvement of the energy density and rapid charging performance of the battery cell.

[0155] In some embodiments, the ratio of the width to the thickness of the battery cell 7 is from 3 to 15, such as 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15 or the range composed of any two of the above values. Optionally, the ratio of the width to the thickness of the battery cell 7 is from 4 to 12. When the ratio of the width to the thickness of the battery cell 7 is within the above range, it is possible to balance the improvement of the energy density and the fast charging performance of the battery cell.

[0156] In some embodiments, the thickness of the battery cell 7 is from 10 mm to 30 mm, such as 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm or the range composed of any two of the above values. The relatively thin thickness of the battery cell 7 is beneficial to rapid heat dissipation, resulting in less heat accumulation in the system, which is beneficial to the fast charging of the battery cell 7.

[0157] In the embodiments of the present application, the single-cell energy of the battery cell 7 can characterize the electric energy stored in the battery cell 7. E = U × Q, where U represents the rated voltage of the battery cell 7, with the unit of V; Q represents the rated capacity of the battery cell 7, with the unit of Ah.

[0158] The single-cell energy of the battery cell 7 can be adjusted by the size of the battery cell, the size of the positive and negative electrode plates, the material of the positive and negative active materials, the single-sided coating weight of the positive and negative electrode film layers, the compaction density, etc.

[0159] For example, as the length of the battery cell 7 increases, the loading capacity of the active material that can be accommodated increases, the rated capacity of the battery cell 7 increases, and the single-cell energy of the battery cell 7 can be improved;

[0160] For example, as the thickness of the battery cell 7 increases, the loading capacity of the active material that can be accommodated increases, the rated capacity of the battery cell 7 increases, and the single-cell energy of the battery cell 7 can be improved;

[0161] For example, as the length of the positive electrode film layer of the positive electrode plate increases, the loading capacity of the positive active material that can be accommodated increases, the rated capacity of the battery cell 7 increases, and the single-cell energy of the battery cell 7 can be improved;

[0162] For example, as the single-sided coating weight of the positive electrode plate increases, the rated capacity of the battery cell 7 increases, and the single-cell energy of the battery cell 7 can be improved;

[0163] For example, as the compaction density of the positive electrode plate increases, the rated capacity of the battery cell 7 increases, and the single-cell energy of the battery cell 7 can be improved;

[0164] For example, if the positive electrode active material is adjusted and the rated voltage is adjusted from 3.65 V to 3.8 V, the energy of the single battery 7 increases.

[0165] Similarly, the change trend of the energy of the single battery caused by the change of the relevant parameters of the negative electrode plate is the same as that caused by the positive electrode plate, which will not be elaborated here.

[0166] In some embodiments, the energy E Wh of the single battery 7 is from 170 Wh to 480 Wh, such as 150 Wh, 200 Wh, 250 Wh, 300 Wh, 350 Wh, 400 Wh, 450 Wh, 480 Wh or the range composed of any two of the above values. For example, when the single battery 7 uses lithium-containing phosphate as the positive electrode active material and its rated voltage is 3.22 V; when the rated capacity is 100 Ah, the energy of the single battery 7 is 3.22 V × 100 Ah = 322 Wh.

[0167] To illustrate the present application more clearly, the ear part of the first electrode plate 11 is defined as the first ear 111, and the coated part of the first electrode plate 11 is defined as the first coated part 112. The ear part of the second electrode plate 12 is defined as the second ear 121, and the coated part of the second electrode plate 12 is defined as the second coated part. The electrode terminal that is electrically connected and has the same electrical property as the first ear 111 is the first electrode terminal 31, and the electrode terminal that is electrically connected and has the same electrical property as the second ear 121 is the second electrode terminal 32.

[0168] The polarities of the first electrode plate 11 and the second electrode plate 12 are opposite. When the first electrode plate 11 is the positive electrode plate, the second electrode plate 12 is the negative electrode plate, the first electrode terminal 31 is the positive terminal, and the second electrode terminal 32 is the negative terminal; or when the first electrode plate 11 is the negative electrode plate, the second electrode plate 12 is the positive electrode plate, the first electrode terminal 31 is the negative terminal, and the second electrode terminal 32 is the positive terminal.

[0169] In the embodiments of the present application, optionally, the housing assembly 20 further includes a first conductive fixing member 41. The first conductive fixing member 41 is disposed around the first electrode terminal 31. The outer contour of the first electrode terminal 31 can be circular, oval, racetrack-shaped, rectangular, etc., and the first conductive fixing member 41 is disposed around the outer contour of the first electrode terminal 31.

[0170] The part of the first electrode terminal 31 connected to the first conductive fixing member 41 is a solid structure with a preset height. Along the thickness direction of the first electrode terminal 31, the cross-sectional size of the first electrode terminal 31 perpendicular to its own thickness direction can be the same or different; when the cross-sectional size of the first electrode terminal 31 perpendicular to its own thickness direction is different, the one with the smallest area is defined as the minimum cross-sectional area. Figure 8As shown in the figure, J1 is the cross-section where the minimum cross-sectional area is located, and its area is S1.

[0171] The outer contour of the minimum cross-sectional area is the minimum contour where the first electrode terminal 31 is connected to the first conductive fixing member 41, and it is the bottleneck for current transmission between the first electrode terminal 31 and the first conductive fixing member 41; in the embodiment of the present application, x1∙S1 / E ranges from 0.2 to 0.7, so that the current-carrying capacity of the first electrode terminal 31 is relatively strong, which can effectively reduce the internal resistance of the battery cell 7, reduce the heat generation of the battery cell 7, and moreover, the thickness of the battery cell 7 is relatively thin, which is beneficial to the rapid heat dissipation of the battery cell 7, thereby improving the fast charging ability of the battery cell 7.

[0172] [Housing assembly]

[0173] In some embodiments, the battery cell 7 further includes a housing assembly 20, and the housing assembly 20 has an accommodation space for accommodating the electrode assembly 10 and the electrolyte. The housing assembly 20 includes a housing and a terminal assembly, and the terminal assembly is disposed on the housing.

[0174] The housing 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 housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly 10, and a sealing bag is further included between the housing 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 housing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0175] 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 prism battery, etc., and there is no special limitation in the present application.

[0176] In some embodiments, the housing includes an end cap 22 and a housing body 21, the housing body 21 is provided with an opening, and the end cap 22 is covered on the opening. The housing body 21 can be provided with one or more openings. One or more end caps 22 can also be provided.

[0177] The terminal assembly can be disposed on the housing body 21, or the terminal assembly is disposed on the end cap 22. Optionally, the terminal assembly is disposed on the end cap 22. When the terminal assembly is disposed on the end cap 22, the thickness direction of the terminal assembly itself is perpendicular to the thickness direction X of the battery cell 7. Figure 8 The Z direction shown in the figure is parallel to the thickness direction of the first electrode terminal 31.

[0178] The first electrode terminal 31 and the second electrode terminal 32 can be arranged on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 are arranged on the end cover 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are arranged on the end cover 22.

[0179] On the same end cover 22, the first electrode terminal 31 and the second electrode terminal 32 can be arranged simultaneously. For example, there is one end cover 22, and the first electrode terminal 31 and the second electrode terminal 32 are arranged at intervals on this end cover 22. Another example is that there are two end covers 22, the two end covers 22 are arranged oppositely, and the first electrode terminal 31 and the second electrode terminal 32 are arranged on each end cover 22.

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

[0181] 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 housing 21 with a cylindrical structure can be selected; if the electrode assembly 10 is a cuboid structure, a housing 21 with a cuboid structure can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0182] In the embodiments of the present application, the first electrode terminal 31 is at least one, and can be optionally at least two. For example, x1 represents any positive integer from 1 to 4, such as 1, 2, 3, or 4. x1∙S1 can characterize the current-carrying capacity of all the first electrode terminals 31 in the battery cell 7. As the number of the first electrode terminals 31 increases, the current-carrying capacity of all the first electrode terminals 31 is enhanced, and the fast charging ability of the battery cell can be improved.

[0183] In some embodiments, S1mm 2 is 15mm 2 to 60mm 2 ; for example, 15mm², 30mm², 35mm², 40mm², 45mm², 50mm², 55mm², 60mm² or the range composed of any two of the above values. When the current-carrying area of the first electrode terminal 31 is within the above range, its current-carrying capacity is relatively strong, and the fast charging ability of the battery cell can be improved.

[0184] In some embodiments, the first electrode terminal 31 may include a first main body portion 312 and a first protruding portion 311. The first main body portion 312 is disposed on the end cap 22 and penetrates through the end cap 22. The first protruding portion 311 is disposed on the first main body portion 312 and protrudes from the first main body portion 312 to be connected to the side of the end cap 22 facing the electrode assembly 10. It can be understood that the first protruding portion 311 is disposed around the first main body portion 312 and is connected to the side of the end cap 22 facing the electrode assembly 10. Optionally, the first conductive fixing member 41 is disposed around the first main body portion 312.

[0185] In some other embodiments, the first electrode terminal 31 may only include the first main body portion 312. The first main body portion 312 penetrates through the end cap 22 and is connected to the tab.

[0186] 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 the resistance and reducing heat generation.

[0187] Optionally, in the direction from the first main body portion 312 to the first protruding portion 311, the size of the first protruding portion 311 is 1.5 mm to 3.0 mm. When the first electrode terminal 31 is disposed on the end cap 22 of the housing, the direction from the first main body portion 312 to the first protruding portion 311 may be parallel to the width direction Y of the battery cell 7. In this case, the size of the first protruding portion 311 in the width direction Y is 1.5 mm to 3.0 mm. Figure 8 T1 shown in represents the size of the first protruding portion 311 in the width direction Y.

[0188] When the first protruding portion 311 meets the above conditions, the connection area between the first protruding portion 311 and the housing is relatively larger, the connection strength is higher, and the structure makes the structure of the battery cell 7 more stable.

[0189] Optionally, the ratio of the size of the first main body portion 312 in the thickness direction X of the battery cell 7 to the size of the end cap 22 in the thickness direction X of the battery cell 7 is 0.20 to 0.40, such as 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40 or the range composed of any two of the above values; the size of the first main body portion 312 refers to the size of the first main body portion 312 of a single first electrode terminal 31. Figure 7As shown in the figure, X3 represents the dimension of the first main body portion 312 of a single first electrode terminal 31 along the thickness direction X, which can be understood as the width of the first main body portion 312; X2 represents the dimension of the end cap 22 along the thickness direction X, which can be understood as the width of the end cap 22.

[0190] When the first main body portion 312 satisfies the above conditions, the proportion of the size of the first main body portion 312 is relatively high, which is beneficial to improving the current-carrying capacity of the first electrode terminal 31, thereby improving the fast charging performance.

[0191] The housing assembly 20 further includes a first conductive fixing member 41. At least a part of the first conductive fixing member 41 is located on the side of the end cap 22 facing away from the electrode assembly, and is used for connecting with an external busbar assembly. The first conductive fixing member 41 is disposed around the first electrode terminal 31 and fixedly connects the first electrode terminal 31 and the end cap 22.

[0192] The first conductive fixing member 41 can further increase the current-carrying area between the battery cell 7 and the external busbar assembly, thereby improving the current-carrying capacity, which is beneficial to improving the current-carrying capacity of the battery device and improving the fast charging performance of the battery device.

[0193] Optionally, a part of the first main body portion 312 protrudes from the side of the end cap 22 facing away from the electrode assembly 10, and the first conductive fixing member 41 is disposed around the first main body portion 312.

[0194] Optionally, the ratio of the dimension of the first conductive fixing member 41 along the thickness direction X of the battery cell 7 to the dimension of the end cap 22 along the thickness direction X of the battery cell 7 is 0.40 to 0.80, such as 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 or the range composed of any two of the above values. The dimension of the first conductive fixing member 41 refers to the dimension of a single first conductive fixing member 41. Figure 7 As shown in the figure, X1 represents the dimension of the first conductive fixing member 41 along the thickness direction X, which can be understood as the width of the first conductive fixing member 41.

[0195] When the first conductive fixing member 41 satisfies the above conditions, the proportion of the size of the first conductive fixing member 41 is relatively high, which is beneficial to increasing the current-carrying area between the battery cell 7 and the external busbar assembly, thereby improving the current-carrying capacity, which is beneficial to improving the current-carrying capacity of the battery device and improving the fast charging performance of the battery device.

[0196] As Figure 9 shown, in some embodiments, the terminal assembly further includes at least one second electrode terminal 32, and the second electrode terminal 32 is connected to the tab portion of the second electrode plate.

[0197] The battery cell 7 satisfies that x2∙S2 / E is from 0.2 to 0.7,

[0198] where x2 represents the number of the second electrode terminals 32;

[0199] S2 represents the minimum cross-sectional area of a single second electrode terminal 32 perpendicular to its own thickness direction, and its unit is mm 2 .

[0200] x2∙S2 represents the minimum cross-sectional area of all the second electrode terminals 32 perpendicular to their own thickness directions, and its unit is mm 2 .

[0201] In the embodiments of the present application, x2∙S2 / E is from 0.2 to 0.7. This formula only performs numerical calculations without substituting units. When the battery cell 7 satisfies the above relationship, the overcurrent capacity of the second electrode terminal 32 is relatively strong, and it can also effectively reduce the internal resistance of the battery cell 7, reduce the heat generation of the battery cell 7, and moreover, the thickness of the battery cell 7 is relatively thin, which is beneficial to the rapid heat dissipation of the battery cell 7, thereby improving the rapid charging capacity of the battery cell 7 and enabling the battery cell 7 to quickly reach the required capacity.

[0202] In some embodiments, S2mm 2 is 15mm 2 to 60mm 2 ; for example, 15mm², 30mm², 35mm², 40mm², 45mm², 50mm², 55mm², 60mm² or the range composed of any two of the above values. When the overcurrent area of the second electrode terminal 32 is within the above range, its overcurrent capacity is strong, and it can improve the rapid charging capacity of the battery cell.

[0203] In some embodiments, x2 is from 1 to 4, such as 1, 2, 3 or 4. As the number of the second electrode terminals 32 increases, the overcurrent capacity of all the second electrode terminals 32 increases, and it can improve the rapid charging capacity of the battery cell.

[0204] The part of the second electrode terminal 32 connected to the second conductive fixing member is a solid structure with a preset height. Along the thickness direction of the second electrode terminal 32, the cross-sectional size of the second electrode terminal 32 perpendicular to its own thickness direction can be the same or different; when the cross-sectional sizes of the second electrode terminals 32 perpendicular to their own thickness directions are different, the one with the smallest area is defined as the minimum cross-sectional area.

[0205] The outer contour of the minimum cross-sectional area is the minimum contour where the second electrode terminal 32 is connected to the second conductive fixing member, and it is the bottleneck for current transmission between the second electrode terminal 32 and the second conductive fixing member; in the embodiments of the present application, x2∙S2 / E is from 0.2 to 0.7, making the current-carrying capacity of the second electrode terminal 32 relatively strong, which can effectively reduce the internal resistance of the battery cell 7, reduce the heat generation of the battery cell 7, and thus improve the fast charging ability of the battery cell 7.

[0206] Exemplarily, x2∙S2 / E is 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or a range composed of any two of the above values.

[0207] In some embodiments, the second electrode terminal 32 is at least one, and optionally at least two. For example, x2 is represented as any positive integer from 1 to 4. x2∙S2 can characterize the current-carrying capacity of all the second electrode terminals 32 in the battery cell 7.

[0208] In some embodiments, the battery cell satisfies: (x1∙S1 + x2∙S2) / E is from 0.4 to 1.4,

[0209] x1 represents the number of the first electrode terminals 31; x2 represents the number of the second electrode terminals 32. Figure 9 The schematic diagram shows two first electrode terminals 31 and two second electrode terminals 32.

[0210] x1∙S1 + x2∙S2 can characterize the total current-carrying capacity of all the electrode terminals in the battery cell 7. When the battery cell satisfies the above conditions, the current-carrying capacities of the first electrode terminal 31 and the second electrode terminal 32 are relatively strong, which can effectively reduce the internal resistance of the battery cell 7, reduce the heat generation of the battery cell 7, and thus improve the fast charging ability of the battery cell 7. x1∙S1 + x2∙S2 can characterize the total current-carrying capacity of all the electrode terminals in the battery cell 7.

[0211] In some embodiments, the structural form of the second electrode terminal 32 is the same as that of the first electrode terminal 31. For example, the second electrode terminal 32 may include a second main body portion and a second protruding portion. The second main body portion penetrates the housing, and the second conductive fixing member is disposed around the second main body portion; the second protruding portion is disposed on the second main body portion and protrudes from the second main body portion to be connected to the side of the housing facing the electrode assembly 10. In other embodiments, the second electrode terminal 32 may only include the second main body portion, and the second main body portion penetrates the end cover 22 and is connected to the tab.

[0212] Optionally, in the direction from the second main body portion towards the second protruding portion, the size of the second protruding portion is 1.5 mm to 3.0 mm. When the second electrode terminal 32 is disposed on the end cap 22, the direction from the second main body portion towards the second protruding portion may be parallel to the width direction Y of the battery cell 7. In this case, the size of the second protruding portion in the width direction Y is 1.5 mm to 3.0 mm.

[0213] When the second protruding portion satisfies the above conditions, the connection area between the second protruding portion and the housing is relatively larger, the connection strength is higher, and the structure makes the structure of the battery cell 7 more stable.

[0214] Optionally, the ratio of the size of the second main body portion in the thickness direction X of the battery cell 7 to the size of the end cap 22 in the thickness direction X of the battery cell 7 is 0.20 to 0.40, such as 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40 or a range composed of any two of the above values; in the embodiment of the present application, the size of the second main body portion refers to the size of the second main body portion of a single second electrode terminal 32.

[0215] When the second main body portion satisfies the above conditions, the size ratio of the second main body portion is relatively high, which is beneficial to improving the over-current capacity of the second electrode terminal 32, thereby improving the fast charging performance.

[0216] The housing assembly 20 further includes a second conductive fixing member, which is disposed around the second electrode terminal 32 and fixedly connects the second electrode terminal 32 and the end cap 22.

[0217] The second conductive fixing member can further increase the over-current area between the battery cell 7 and the external bus bar assembly, thereby improving the over-current capacity, which is beneficial to improving the over-current capacity of the battery device and improving the fast charging performance of the battery device.

[0218] Optionally, a part of the second main body portion protrudes from the side of the end cap 22 facing away from the electrode assembly 10, and the second conductive fixing member is disposed around the second main body portion.

[0219] Optionally, the ratio of the size of the second conductive fixing member in the thickness direction X to the size of the end cap 22 in the thickness direction X is 0.40 to 0.80, such as 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 or the range composed of any two of the above values; in the embodiment of the present application, the thickness direction X refers to the thickness direction X of the battery cell 7.

[0220] When the second conductive fixing member meets the above conditions, the size ratio of the second conductive fixing member is relatively high, which is beneficial to increasing the current-carrying area between the battery cell 7 and the external busbar assembly, thereby improving the current-carrying capacity and the fast-charging performance of the battery device.

[0221] As Figure 10 shown, in some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 in the width direction Y. This arrangement can shorten the electron migration path and is beneficial to improving the fast-charging performance.

[0222] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 in the width direction Y.

[0223] Again, for example, a plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 in the width direction Y.

[0224] As Figure 11 shown, in some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 in the length direction Z.

[0225] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 in the length direction Z.

[0226] Again, for example, a plurality of first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 in the length direction Z. This arrangement can shorten the electron migration path and is beneficial to improving the fast-charging performance.

[0227] Exemplarily, there are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10 and the other is disposed on the other side of the electrode assembly 10. Or, exemplarily, there are four first electrode terminals 31, two of which are disposed on one side of the electrode assembly 10 and the other two are disposed on both sides of the electrode assembly 10.

[0228] The first tab 111 and the first electrode terminal 31 are electrically connected, 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, and 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.

[0229] 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 coating portion 112 along the width direction Y, the connection between the first tab 111 and the first electrode terminal 31 is more facilitated by the first adapter 51.

[0230] In the case where 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.

[0231] In the case where 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.

[0232] In the above embodiments, the first adapter 51 may be in a sheet structure, and of course, it may also be in other structural forms.

[0233] 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.

[0234] 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 arrangement 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.

[0235] For example, the tab portion of the first electrode sheet 11 is disposed on one side of the coating portion along the width direction Y; the first conductive member 61 is located between the first adapter 51 and the first tab 111 and connects the first adapter 51 and the first tab 111.

[0236] Optionally, there are at least two first tabs 111 and at least two first conductive members 61. The first conductive members 61 and the first tabs 111 are connected in a one-to-one correspondence. The at least two first conductive members 61 are connected to the first adapter 51. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0237] Optionally, there are at least two first tabs 111 on the same side of the first coating portion 112. The first conductive member 61 can be a continuous sheet structure that connects at least two first tabs 111.

[0238] As Figure 12 shown, when the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, optionally, the first conductive member 61 includes a first conductive portion 611 and a second conductive portion 612. The first conductive portion 611 extends along the length direction Z. The first conductive portion 611 connects the first tab 111 and the first adapter 51. The second conductive portion 612 is connected to the first conductive portion 611 and protrudes from the first conductive portion 611 along the width direction Y. The second conductive portion 612 connects the first adapter 51. This structural arrangement is beneficial to increasing the grouping space in the length direction Z and is beneficial to improving the energy density of the battery device.

[0239] It should be noted that when the battery cell 7 does not include the first adapter 51, the first tab 111 can be connected to the first electrode terminal 31 through the first conductive member 61.

[0240] Exemplarily, the first conductive member 61 has conductivity and 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.

[0241] In some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the width direction Y. This arrangement can shorten the electron migration path and is beneficial to improving the fast charging performance.

[0242] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 along the width direction Y, and there will be no mutual interference when electrically connecting to the tab portions respectively.

[0243] 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 along the width direction Y, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the width direction Y.

[0244] For another example, a plurality of 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.

[0245] 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.

[0246] For example, at least two second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the length direction Z. This setting method can 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 length direction Z, 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 length direction Z.

[0247] Exemplarily, there are two second electrode terminals 32. One of the second electrode terminals 32 is disposed on one side of the electrode assembly 10 in the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 in the length direction Z. 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 two first electrode terminals 31 are disposed on both sides of the electrode assembly 10. Figure 12 A schematic diagram showing four electrode terminals is shown.

[0248] For another example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 in 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 in the length direction Z, and there will be no mutual interference when electrically connecting to the tab portions respectively.

[0249] Exemplarily, the first electrode terminal 31 and the second electrode terminal 32 are each one. 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 with a dislocation along the width direction Y. Specifically, when all the second tabs 121 are arranged on the same side of the second coating portion along the width direction Y, and all the first tabs 111 are arranged on the same side of the first coating portion 112 along the width direction Y, the first tab 111 and the second tab 121 are respectively arranged on both sides of the coating portion along the width direction Y. The first electrode terminal 31 is arranged close to the first tab 111, and the second electrode terminal 32 is arranged close to the second tab 121. This setting method makes the electron transmission distance shorter and is more conducive to improving the fast charging ability of the battery cell 7. Figure 11 A schematic diagram showing two electrode terminals is shown.

[0250] The second tab 121 and the second electrode terminal 32 are electrically connected, and can be directly connected or indirectly connected; when the second tab 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 tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0251] For example, when the second electrode terminal 32 is arranged on at least one side of the electrode assembly 10 along the length direction Z, and the second tab 121 is arranged on at least one side of the second coating portion along the width direction Y, it is more conducive to the connection between the second tab 121 and the second electrode terminal 32 through the second adapter.

[0252] When the second tab 121 and the second electrode terminal 32 are respectively arranged 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 length 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.

[0253] When the second tab 121 and the second electrode terminal 32 are arranged on the same side of the battery cell 7, the second adapter may only include a first connection portion.

[0254] In the above embodiments, the second adapter may be a sheet-like structure, and of course, it may also be other structural forms.

[0255] In the above embodiments, the second adapter may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0256] In some embodiments, the battery cell 7 further includes a second conductive member 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, which is beneficial to improving the fast-charging performance and reducing heat generation.

[0257] For example, the tab portion of the second electrode plate 12 is disposed on one side of the coating portion 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.

[0258] Optionally, there are at least two second tabs 121 on the same side of the second coating portion. The second conductive member can be a continuous sheet structure connecting at least two second tabs 121; or there are at least two second conductive members, and the second conductive members are connected to the second tabs 121 in a one-to-one correspondence, and at least two 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.

[0259] 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, 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, and the third conductive portion connects the second adapter. This structural arrangement is beneficial to increasing the grouping space in the length direction Z and improving the energy density of the battery device.

[0260] Exemplarily, the second conductive member has conductivity and 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.

[0261] It should be noted that in the case where the battery cell 7 does not include the second adapter, the second tab 121 can be connected to the second electrode terminal 32 through the second conductive member.

[0262] 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 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.

[0263] When assembling the battery cell 7 into the box body of the battery device, the battery cell 7 is disposed inside 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 disposed opposite to the first box body part, and the second housing part 212 is disposed close to the first box body part, and the third housing part 213 is disposed 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 disposed upward, the risk of liquid leakage of the battery cell 7 is reduced.

[0264] In some embodiments, the dimension of the battery cell 7 along the thickness direction X is 10 mm to 30 mm, such as 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.

[0265] 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.

[0266] 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 formed by any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0267] 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.

[0268] 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 formed by any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0269] 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.

[0270] 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.

[0271] Heat conduction component

[0272] In some embodiments, the battery cell 7 further includes a heat conduction member. There is a gap between the tab portion and the coating portion, and the heat conduction member is disposed in the gap between the tab portion and the coating portion. The heat conduction member can conduct the heat generated by the tab portion, quickly transfer the heat generated by the tab portion, and reduce the risk of ablation of the separator in the electrode assembly.

[0273] Optionally, the heat conduction member further contacts the housing 21, so that the heat diffuses from the housing 21.

[0274] Such as Figure 13As shown, exemplarily, the heat conduction member includes a first heat conduction member 81 disposed in the gap between the first tab 111 and the first coating portion 112, and the first heat conduction member 81 is capable of conducting the heat generated by the first tab 111.

[0275] Optionally, the first heat conduction member 81 may further be disposed in the gap between the first tab 111 and the first electrode terminal 31. When the battery cell 7 includes the first adapter 51, the first heat conduction member 81 may also be disposed in the gap between the first tab 111 and the first adapter 51, or in the gap between the second adapter portion 512 of the first adapter 51 and the coating portion.

[0276] Exemplarily, the heat conduction member includes a second heat conduction member disposed in the gap between the second tab 121 and the second coating portion, and the second heat conduction member is capable of conducting the heat generated by the second tab 121.

[0277] Optionally, the second heat conduction member may further be disposed in the gap between the second tab 121 and the second electrode terminal 32. When the battery cell 7 includes the second adapter, the second heat conduction member may also be disposed in the gap between the second tab 121 and the second adapter.

[0278] The main material of the heat conduction member includes one or more of polyimide PI and polyethylene terephthalate PET.

[0279] [First and second electrode plates]

[0280] In some embodiments, the battery cell 7 further satisfies: M1 / E is 0.2 to 0.6;

[0281] M1 represents the area of the first connection region, and its unit is mm 2 ; The first connection region is the region where at least one first electrode terminal 31 is connected to the tab portion of the first electrode plate, that is, the sum of the regions where all first electrode terminals 31 are connected to the first tab 111. When welding is used, M1 may represent the weld mark area of the first electrode terminal 31, and this weld mark area is the welding area of the first electrode terminal 31 and the first tab 11.

[0282] When the battery cell 7 satisfies the above conditions, the current conduction ability between the first electrode terminal 31 and the first tab 111 is strong, and the electron conduction ability is strong, which is beneficial to reducing the internal resistance of the battery cell 7, reducing the heat generation of the battery cell 7, thereby improving the fast charging ability of the battery cell 7 and enabling the battery cell 7 to quickly reach the required capacity.

[0283] In some embodiments, M1 mm 2 is 60 mm2 to 120 mm 2 , such as 60 mm², 70 mm², 80 mm², 90 mm², 100 mm², 110 mm², 120 mm², or a range composed of any two of the above values. The current conduction ability between the first electrode terminal 31 and the first tab 111 is relatively strong, which is beneficial to reducing the internal resistance of the battery cell 7, reducing the heat generation of the battery cell 7, and thus improving the fast charging ability of the battery cell 7.

[0284] In some embodiments, the battery cell 7 further satisfies that M2 / E is 0.2 to 0.6,

[0285] M2 represents the area of the second connection region, and its unit is mm 2 ; the second connection region is the region where at least one second electrode terminal 32 is connected to the tab portion of the second electrode plate, that is, the sum of the regions where all the second electrode terminals 32 are connected to the second tab 121.

[0286] When the battery cell 7 satisfies the above conditions, the current conduction ability between the second electrode terminal 32 and the second tab 121 is relatively strong, and the electron conduction ability is relatively strong, which is beneficial to reducing the internal resistance of the battery cell 7, reducing the heat generation of the battery cell 7, and thus improving the fast charging ability of the battery cell 7, enabling the battery cell 7 to quickly reach the required capacity.

[0287] In some embodiments, M2 mm 2 is 60 mm 2 to 120 mm 2 , such as 60 mm², 70 mm², 80 mm², 90 mm², 100 mm², 110 mm², 120 mm², or a range composed of any two of the above values. The current conduction ability between the second electrode terminal 32 and the second tab 121 is relatively strong, which is beneficial to reducing the internal resistance of the battery cell 7, reducing the heat generation of the battery cell 7, and thus improving the fast charging ability of the battery cell 7.

[0288] In some embodiments, the first tab 111 is disposed on at least one side of the first coating portion 112 along the first direction.

[0289] As Figure 14 and Figure 15 shown, in some embodiments, the first electrode plate 11 satisfies that n*W1 / W2 is 0.5 to 1.0;

[0290] n represents the number of all tab portions located on the same side of the coating portion;

[0291] W1 represents the average dimension of the tab portion along the second direction, and the first direction is perpendicular to the second direction;

[0292] W2 represents the dimension of the coating portion along the second direction.

[0293] 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.

[0294] In the embodiment of the present application, the first pole piece 11 further satisfies that n*W1 / W2 is from 0.5 to 1.0, so that the connection area between the pole ear part and the coating part is relatively large, and the current-carrying area of the pole ear part is relatively large, which is beneficial to reducing the DC resistance and reducing heat generation; the first electrode terminal 31 is at least two. In other words, at least two first electrode terminals 31 are connected to the pole ear part of the first pole piece 11, which can further increase the current-carrying area of the first electrode terminal 31 and the pole ear part, further reduce the DC resistance and reduce heat generation, thereby facilitating fast charging.

[0295] W1 represents the average dimension of the first pole ear 111 along the second direction.

[0296] When the first pole ear 111 is of a special-shaped structure, for example, along the first direction, the dimension of the first pole ear 111 along the second direction gradually increases. In this case, the dimensions of the first pole ear 111 at multiple positions along the second direction can be measured, and thus the average dimension of the first pole ear 111 along the second direction can be calculated. Of course, the dimensions of the first pole ear 111 at each position along the second direction can be the same value, and in this case, this value can be used as the average dimension of the first pole ear 111.

[0297] The first pole ear 111 can be one or more. For example, n is from 1 to 4. When there are multiple first pole ears 111, after measuring the average dimensions of each first pole ear 111 respectively, the average dimension of the first pole ear 111 can be calculated by adding up the average dimensions and dividing by the number of the first pole ears 111.

[0298] The first pole ear 111 is connected to the first coating part 112. The first pole ear 111 includes a first end 1111 connected to the first coating part 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first pole ear 111 itself is relatively large, the contact surface between the first pole ear 111 and the first coating part 112 is relatively large, and the current-carrying capacity of the first pole ear 111 is strong, which can improve the power performance and cycling performance of the battery cell 7.

[0299] Optionally, the current collector part of the first pole ear 111 and the first coating part 112 is an integral structure, so that the internal resistance of the first pole piece 11 is relatively low, which can further improve the power performance and cycling performance of the battery cell 7.

[0300] Optionally, W2 is from 300 mm to 650 mm, such as 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or a range formed by any two of the above values.

[0301] Optionally, n*W1 is from 150 mm to 650 mm, such as 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or a range formed by any two of the above values.

[0302] In the embodiments of the present application, the first direction, the second direction, and the thickness direction X of the battery cell 7 are perpendicular to each other in pairs. The first direction may be parallel to the length direction of the battery cell 7 or parallel to the width direction of the battery cell 7.

[0303] When the first direction is parallel to the length direction Z of the battery cell 7, the dimension of the component in this direction can be regarded as the length of the component. For example, the dimension of the coating portion in the first direction is the length of the coating portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0304] When the first direction is parallel to the width direction Y of the battery cell 7, the dimension of the component in this direction can be regarded as the width of the component. For example, the dimension of the coating portion in the first direction is the width of the coating portion. In this case, the second direction is parallel to the length of the battery cell 7.

[0305] Figure 14 and Figure 15 shows that the first direction is parallel to the width direction Y and the second direction is parallel to the length direction Z. Figure 14 In, n is 1, and W1 can also represent the dimension of a single first tab 111, and W2 represents the dimension of the first coating portion 112 in the second direction. Figure 15 In, n is 4, and the dimensions of each first tab 111 are the same. W1 can represent the dimension of a single first tab 111. Of course, the dimensions of each first tab 111 can also be slightly different.

[0306] When the first electrode sheet 11 is a positive electrode sheet, the dimension of the coating portion of the positive electrode sheet in the length direction Z of the battery cell 7 is the first dimension, and the dimension of the coating portion of the positive electrode sheet in the width direction Y of the battery cell 7 Figure 14 In, W2 represents the dimension of the coating portion of the positive electrode sheet in the length direction Z, and Y1 represents the dimension of the coating portion of the positive electrode sheet in the width direction Y.

[0307] The ratio of the length to the width of the coating portion of the positive electrode tab is 4 to 7, such as 4, 4.5, 5, 5.5, 6, 6.5, 7, or a range composed of any two of the above values, which can balance the improvement of the energy density and fast charging performance of the battery cell.

[0308] In some embodiments, the length of the coating portion of the positive electrode tab is 300 mm to 650 mm, such as 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, or a range composed of any two of the above values. Optionally, the length of the coating portion of the positive electrode tab is 400 mm to 500 mm. When the length of the coating portion of the positive electrode tab satisfies the above range, it can balance the improvement of the energy density and fast charging performance of the battery cell.

[0309] Next, the related solutions where the first direction is parallel to the width direction Y of the first tab 11 will be described.

[0310] As Figure 15 shown, in some embodiments, the first 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 coating portion along the width direction Y.

[0311] For example, one or more first tab ears 111 are disposed on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all the first tab ears 111 are disposed on the same side of the first coating portion 112 along the width direction Y. This kind of arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0312] When all the first tab ears 111 are disposed on the same side of the first coating portion 112 along the width direction Y, the size of the first coating portion 112 along the width direction Y is 80 mm to 150 mm.

[0313] Figure 15 In [diagram], Y1 represents the size of the first coating portion 112 along the width direction Y, and it can also be understood as the width of the first coating portion 112.

[0314] As Figure 16 shown, for example, when the first tab 11 includes a plurality of first tab ears 111, the plurality of first tab ears 111 are disposed on both sides of the first coating portion 112 along the width direction Y.

[0315] When the plurality of first tab ears 111 are disposed on both sides of the first coating portion 112 along the width direction Y, the size of the first coating portion 112 along the width direction Y is 80 mm to 150 mm.

[0316] Figure 16In this case, Y1 represents the dimension of the first coating portion 112 in the width direction Y, which can also be understood as the width of the first coating portion 112.

[0317] Whether all the first tabs 111 are disposed on the same side of the first coating portion 112 in the width direction Y, or all the first tabs 111 are respectively disposed on both sides of the first coating portion 112 in the width direction Y, at least two first tabs 111 on the same side of the first coating portion 112 can be selected, such as two, three, four, five, six, etc.; four can be selected. This setting is beneficial to the uniform distribution of electrons in the first electrode sheet 11 and is beneficial to improving the fast charging performance.

[0318] This setting method can further shorten the electron transmission path, effectively reduce the internal resistance of the battery cell, and each tab bears a small current, and the current distribution is more uniform.

[0319] 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 16 In this case, Z1 represents the distance between two adjacent tab portions in the length direction Z.

[0320] Next, the related solutions in which the first direction is parallel to the length direction of the first electrode sheet 11 will be described.

[0321] As Figure 17 shown, in some embodiments, the first electrode sheet 11 includes one or more first tabs 111; one or more first tabs 111 are disposed on at least one side of the first coating portion 112 in the length direction Z.

[0322] For example, one or more first tabs 111 are disposed on one side of the first coating portion 112 in the length direction Z. In this case, it can be understood that all the first tabs 111 are disposed on the same side of the first coating portion 112 in the length direction Z.

[0323] When all the first tabs 111 are disposed on the same side of the first coating portion 112 in the length direction Z, the dimension of the first coating portion 112 in the length direction Z is 300 mm to 650 mm.

[0324] Figure 17 In this case, Z2 represents the dimension of the first coating portion 112 in the length direction Z, which can also be understood as the length of the first coating portion 112.

[0325] As Figure 18As 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 respectively disposed on both sides of the first coating portion 112 along the length direction Z.

[0326] Optionally, the plurality of first tabs 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z. This arrangement can shorten the electron transmission path in the first electrode tab 11, which is beneficial to improving the fast charging performance.

[0327] In the case where the plurality of first tabs 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z, the dimension of the first coating portion 112 along the length direction Z is 300 mm to 650 mm.

[0328] Figure 18 In, Z3 represents the dimension of the first coating portion 112 along the length direction Z, which can also be understood as the length of the first coating portion 112.

[0329] Whether all the first tabs 111 are disposed on the same side of the first coating portion 112 along the width direction Y, or all the first tabs 111 are respectively disposed on both sides of the first coating portion 112 along the width direction Y, at least two of the first tabs 111 on the same side of the first coating portion 112 can be selected, such as two, three, four, five, six, and so on. This arrangement is beneficial to the uniform distribution of electrons in the first electrode tab 11 and is beneficial to improving the fast charging performance.

[0330] Optionally, the distance between two adjacent tab portions 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 a range composed of any two of the above values. This arrangement 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 17 In, Y2 represents the distance between two adjacent tab portions along the width direction Y.

[0331] In the embodiment of the present application, the number and arrangement of the second tabs 121 are the same as those of the first tabs 111, which will not be elaborated here. The structure of the second electrode tab 12 is the same as that of the first electrode tab 11, which will not be elaborated here.

[0332] [Electrolyte]

[0333] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and removed back and forth between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting active ions between the positive electrode tab and the negative electrode tab.

[0334] 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 salt is beneficial to increasing the total number of lithium ion migrations in the electrolyte, improving the lithium ion conductivity, and enhancing the kinetic performance of the battery cell.

[0335] 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 increasing the total number of lithium ion migrations in the electrolyte, improving the lithium ion conductivity, and enhancing the kinetic performance of the battery cell.

[0336] Exemplarily, the mass content of lithium hexafluorophosphate and the mass content of lithium bis(fluorosulfonyl)imide are 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3, 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9, 4.0 or the range composed of any two of the above values.

[0337] 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%. When the lithium salt meets the above conditions, it is beneficial to increasing the total number of lithium ion migrations in the electrolyte, improving the lithium ion conductivity, and enhancing the kinetic performance of the battery cell.

[0338] 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.

[0339] 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. When the mass content of the lithium salt is within the above range, the lithium salt is beneficial to increasing the conductivity of the electrolyte and enhancing the kinetic performance of the battery cell.

[0340] 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.

[0341] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0342] 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.

[0343] In some embodiments, the organic solvent includes carbonate solvents.

[0344] 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 increase the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions; moreover, the mass content of the carbonate solvent is not too high, which can reduce the gas generation amount at high temperature and improve the high-temperature cycle performance.

[0345] 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 chain carboxylic ester solvent are used in combination, which increases the conductivity of the electrolyte at room temperature and is beneficial to the migration of lithium ions.

[0346] In some embodiments, the organic solvent includes chain carboxylic ester solvents.

[0347] 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.

[0348] 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; moreover, the mass content of the chain carboxylic ester solvent is not too high, which can reduce the gas generation amount at high temperature and improve the high-temperature cycle performance.

[0349] In some embodiments, the chain carboxylic ester solvent includes the compound shown in Formula I.

[0350] Formula I

[0351] In Formula I,

[0352] R1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group,

[0353] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0354] The above chain carboxylic ester solvents have relatively high conductivity, which is beneficial to improving the fast charging ability of battery monomers.

[0355] Optionally, R1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0356] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0357] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0358] Exemplarily, the chain carboxylic ester solvents include one or more of the compounds shown in Formula I-1 to the compounds shown in Formula I-8,

[0359]

[0360] In some embodiments, the electrolyte further contains an additive. The additive can include a negative electrode film-forming additive, or can include a positive electrode film-forming additive, and can also include an additive that can improve certain battery performances, such as an additive for improving the overcharging performance of the battery, an additive for improving the high-temperature performance of the battery, an additive for improving the low-temperature power performance of the battery, etc.

[0361] In some embodiments, the additive includes one or more of a carbonate additive and a sulfur-containing additive, 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 monomers and improving the cycling performance.

[0362] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 6%. Exemplarily, the mass content of the additive 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.

[0363] The above-mentioned organic solvents, such as chain carboxylic acid ester solvents, may decompose to produce acids at high temperatures, corroding the interface film on the surface of the negative electrode. The additive can form a dense and uniform-thickness film layer on the negative electrode side, effectively repair the interface film, provide excellent protection for the negative electrode active material, be beneficial to improving the fast charging performance of the battery cell, and improving the cycle performance.

[0364] 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).

[0365] 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 methanedisulfonate (MMDS), and may be 1,3-propane sultone (PS).

[0366] Exemplarily, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

[0367] 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 a range composed of any two of the above values.

[0368] 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.

[0369] 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.

[0370] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, qualitative or quantitative analysis of the inorganic components / lithium salts in the electrolyte can be carried out by ion chromatography analysis method with reference to the standard JY / T 020-1996 General Rules for Ion Chromatography Analysis Method. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, or the 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 disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography analysis method.

[0371] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, qualitative and quantitative analysis of the organic components in the electrolyte can be carried out by gas chromatography with reference to GB / T 9722-2006 General Rules for Gas Chromatography of Chemical Reagents.

[0372] In the embodiments of the present application, after the components in the electrolyte are quantitatively and qualitatively detected, the components are classified. Chain carboxylic ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as the component components of the organic solvent. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0373] Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate) and sulfur-containing additives are used as additives in the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0374] Positive electrode plate

[0375] To illustrate the present application more clearly, the coating part of the positive electrode tab corresponds to the positive electrode coating part, the tab part corresponds to the positive electrode tab, the active material layer corresponds to the positive electrode film layer containing the positive electrode active material, and the positive electrode coating part includes a positive electrode current collector part and a positive electrode film layer provided on at least one side of the positive electrode current collector part.

[0376] The positive electrode tab includes a positive electrode current collector part and a positive electrode film layer provided on at least one surface of the positive electrode current collector part and including the positive electrode active material. For example, the positive electrode current collector part has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector part.

[0377] The upper charging limit voltage and the lower discharging cut-off voltage of the battery cell vary according to the different cathode active materials. For example, when the phosphate-based material includes lithium iron phosphate, the upper charging limit voltage can be 3.65V and the lower discharging cut-off voltage can be 2.0V, or the upper charging limit voltage can be 3.8V and the lower discharging cut-off voltage can be 2.0V; Another example is that when the phosphate-based material includes lithium manganese iron phosphate, the upper charging limit voltage can be 4.3V and the lower discharging cut-off voltage can be 2.0V. Next, taking the upper charging limit voltage of 3.65V and the lower discharging 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.

[0378] Charge the battery cell at a constant current charging rate of 0.33C to the upper charging limit voltage, and then charge 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 discharging rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0379] In some embodiments, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film layer is 2.30 g / cm 3 to 2.70 g / cm 3 ; It can be optionally 2.40 g / cm 3 to 2.55 g / cm 3 . Exemplarily, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film 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.

[0380] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the single-cell energy of the battery cell and increase the energy density; moreover, since the positive active materials in the positive electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing the heat generation during fast charging and enhancing the fast charging ability of the battery cell.

[0381] In some embodiments, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 , and can be optionally 275 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film 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.

[0382] When the single-sided coating weight of the positive electrode film layer is within the above range, it is beneficial to improve the single-cell energy of the battery cell and increase the energy density; the heat generation per unit area of the positive electrode sheet will not be too large, and the fast charging ability of the battery cell can be enhanced.

[0383] In the embodiments of the present application, the tap density of the positive electrode film layer of the battery cell at 0% state of charge (SOC) has the meaning well-known in the art, that is, the positive electrode sheet of the battery cell at 0% SOC is disassembled, and the tap density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film 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 film layer of the above-mentioned weighed positive electrode sheet is wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode sheet - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode sheet - the thickness H0 of the positive electrode current collector, and the tap density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0384] In some embodiments, the positive electrode active material includes lithium-containing phosphate in 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.

[0385] In the embodiments of the present application, the lithium-containing phosphate in an olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate in an olivine structure includes phosphate particles and a coating layer, and the coating layer is coated on the surface of the phosphate particles. For example, the coating layer includes elements such as carbon, which improves the conductivity of the phosphate particles, reduces the powder resistivity of the material, 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.

[0386] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y zA compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A 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 cyclic stability of the phosphate particles is relatively excellent, which is beneficial to improving the cyclic performance of the battery cell.

[0387] 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. 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. 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 show fluctuations, and the above situations are all within the protection scope of the present application.

[0388] In the embodiments of the present application, the content of elements in the cathode active material has the meaning well-known in the art and can be detected by devices 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 atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the cathode electrode sheet, it is cleaned with dimethyl carbonate (DMC) and dried, and then after high-temperature calcination to remove impurities, 0.4 g of the cathode 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.

[0389] In some embodiments, the lithium-containing phosphate is granular. The lithium-containing phosphate includes a first phosphate particle and a second phosphate particle. The longest diameter of the first phosphate particle is greater than that of the second phosphate particle. The longest diameter of the first phosphate particle is 1 μm to 5 μm, and the longest diameter of the second phosphate particle is 0.1 μm to 0.5 μm.

[0390] Exemplarily, the longest diameter of the first phosphate particle is 1 μm to 5 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the range composed of any two of the above values.

[0391] Exemplarily, the longest diameter of the second phosphate particle is 0.1 μm to 0.5 μm, such as 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm or the range composed of any two of the above values.

[0392] When the lithium-containing phosphate meets the above conditions, its longest diameter is relatively small, the lithium deintercalation / insertion path of lithium ions in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the lithium-containing phosphate stable.

[0393] In some embodiments, the quantity percentage of the second phosphate particle in the lithium-containing phosphate is 5% to 35%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or the range composed of any two of the above values. When the quantity percentage of the second phosphate particle in the lithium-containing phosphate meets the above range, it is beneficial to shorten the migration path of lithium ions.

[0394] In some embodiments, the positive electrode film layer further includes a positive electrode additive. The positive electrode additive may include lithium element and can release lithium ions during the charging process of the battery cell to make up for lithium loss, which is beneficial to improving the capacity characteristics and cycle performance of the battery cell.

[0395] In some embodiments, the positive electrode additive includes at least one of lithium ferrite particles or lithium nickelate particles.

[0396] 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.

[0397] In the embodiments of the present application, the positive electrode sheet is cut along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer; by performing a scanning electron microscope (SEM) test on the longitudinal section of the positive electrode film layer, the longest diameter and the shortest diameter of the positive electrode additive particles and the longest diameter of the lithium-containing phosphate are determined. For example, the "longest diameter" of a particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle;

[0398] In the cross-section of the positive electrode film layer along its own thickness direction, the longest diameters of multiple, for example, 10 iron oxides containing lithium are counted, and the average value thereof is the average longest diameter.

[0399] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the positive electrode additive is 0.2% to 2%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% or any range composed of any two of them. When using a positive electrode additive within a mass range, lithium can be effectively supplemented.

[0400] In some embodiments, the positive electrode film 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. As an 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 film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0401] In some embodiments, the positive electrode film 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. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0402] In some embodiments, the positive electrode current collector part may adopt a metal foil or a composite current collector part. As an 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 part 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 of the metal material layer may include at least one of aluminum, aluminum 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).

[0403] In some embodiments, the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector 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 film layer to the thickness of the positive electrode current collector is 4 to 8.

[0404] When the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0405] In some embodiments, the thickness of the positive electrode current collector is 12 μm to 16 μm, and can be optionally 13 μm to 15 μm. Exemplarily, the thickness of the positive electrode current collector is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or the range composed of any two of the above values.

[0406] When the thickness of the positive electrode current collector is within the above range, the current-carrying capacity of the positive electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0407] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive electrode current collector 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, a micrometer is used to measure the thickness of the positive electrode plate, the film layer on the surface of the positive electrode current collector is removed, and a micrometer is used to measure the thickness of the positive electrode current collector. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode plate minus the thickness of the positive electrode current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode plate minus the thickness of the positive electrode current collector) / 2.

[0408] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode 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.

[0409] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In some other embodiments, the positive electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0410] Negative electrode plate

[0411] To more clearly illustrate the present application, the coating portion of the negative electrode tab corresponds to the negative electrode coating portion, the tab portion corresponds to the negative electrode tab, the active material layer corresponds to the negative electrode film layer containing the negative electrode active material, the negative electrode coating portion includes a negative electrode current collector portion and a negative electrode film layer disposed on at least one side of the negative electrode current collector portion, and the negative electrode coating portion includes a negative electrode current collector portion and a negative electrode film layer disposed on at least one side of the negative electrode current collector portion.

[0412] The negative electrode tab includes a negative electrode current collector portion and a negative electrode film layer disposed on at least one surface of the negative electrode current collector portion and including the negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0413] In some embodiments, when the battery cell is at 0% state of charge (SOC), the tap density of the negative electrode film layer is 1.30 g / cm 3 to 1.65 g / cm 3 ; optionally 1.35 g / cm 3 to 1.50 g / cm 3 . Exemplarily, when the battery cell is at 0% state of charge, the tap density of the negative electrode film layer 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.

[0414] When the tap density of the negative electrode film layer is within the above range, it is beneficial to improve the energy of the battery cell and the energy density; and since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode tab can be further reduced, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0415] In the embodiments of the present application, the tap density of the negative electrode film layer at 0% state of charge (SOC) of the battery cell has the meaning well known in the art, and can be detected by using the equipment and methods well known in the art, and its detection method is the same as the tap density test method of the positive electrode film layer described above.

[0416] In some embodiments, the single-sided coating weight of the negative electrode film 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 film 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.

[0417] When the single-sided coating weight of the negative electrode film layer is within the above range, it is beneficial to improve the monomer energy of the battery cell and the energy density; and the heat generation per unit area of the negative electrode plate will not be too large, which can improve the fast charging ability of the battery cell.

[0418] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer 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 as described in the single-sided coating weight test method of the film layer above.

[0419] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has high cycle stability, which 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 cycle performance of the battery cell is relatively excellent.

[0420] Optionally, the carbon-based material includes artificial graphite, and the graphitization degree of the artificial graphite is 90% to 95%, optionally 92% to 95%. Exemplarily, the graphitization degree of the artificial graphite is 90%, 90.5%, 91%, 91.5%, 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95% or a range composed of any two of the above values.

[0421] When the graphitization degree of the artificial graphite is within the above range, the artificial graphite has excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and can improve the fast charging performance of the battery cell.

[0422] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include artificial graphite, or the carbon-based material may include artificial graphite and natural graphite.

[0423] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, 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.

[0424] In this application, the qualitative and quantitative determination of each substance or each element 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 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.

[0425] 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.

[0426] Artificial graphite and natural graphite can be distinguished by the SEM cross-section diagram taken by scanning electron microscope (SEM). There are voids between the flaky structures in the SEM cross-section diagram of natural graphite, and the SEM cross-section diagram of artificial graphite is dense and has no obvious gaps, or 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.

[0427] In the embodiments of this application, the negative electrode film layer includes at least one layer of film layer, and a single-layer film layer can be used, or at least two layers of film layers can be used. Optionally, the negative electrode film layer includes at least two layers of film layers.

[0428] When the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material. When a single-layer film layer is adopted, 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 a range composed of any two of the above values.

[0429] When the negative electrode film layer adopts at least two layers of film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0430] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is 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 can 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 can be the particle size difference or the graphitization degree difference.

[0431] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0432] The negative electrode film layer includes at least two layers of film layers. Layered 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 film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0433] 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 film layer.

[0434] 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 fast charging, the overpotential of the second negative electrode film layer is usually relatively high, 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 transmission path of lithium ions, improve the fast charging performance, and can also improve the problem of lithium deposition on the surface layer of the negative electrode sheet.

[0435] Optionally, the carbon-based material of the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 9.0 μm to 18.5 μm, and can be optionally from 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 from 9.0 μm to 18.5 μm, and can be optionally from 9.0 μm to 14.6 μm.

[0436] 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.

[0437] Optionally, the carbon-based material of the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, and can be optionally from 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 from 7.8 μm to 14.3 μm, and can be optionally from 7.8 μm to 11.3 μm.

[0438] 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 transport path of lithium ions and improve the fast charging performance.

[0439] 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.

[0440] 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 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer.

[0441] Optionally, the carbon-based material of the first negative electrode film layer further includes natural graphite.

[0442] 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.

[0443] 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 film layer.

[0444] 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.

[0445] Optionally, the carbon-based material of the second 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. 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.

[0446] Optionally, the carbon-based material of the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm. When the volume average particle size Dv50 of the carbon-based material of the first negative electrode film layer is within the above range, the solid-phase transmission path of lithium ions can be shortened, and the fast charging performance can be improved.

[0447] 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.

[0448] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. 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 film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0449] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0450] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include a thickener, a dispersant, etc., for example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0451] In some embodiments, the negative electrode current collector portion may be a metal foil or a composite current collector portion. 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 portion 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).

[0452] In some embodiments, the ratio of the thickness of the single-sided negative electrode film 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 the range composed of any two of the above values. Optionally, the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector portion is 10 to 12.

[0453] When the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0454] In some embodiments, the thickness of the negative electrode current collector is 5 μm to 10 μm, and can be optionally 6 μm to 8 μm. Exemplarily, the thickness of the negative electrode current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or the range composed of any two of the above values.

[0455] When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a high energy density.

[0456] In the embodiments of the present application, the thickness of the negative electrode current collector 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 electrode current collector is washed away with a solvent, and the thickness of the negative electrode current collector is measured with a micrometer.

[0457] The negative electrode film layer is usually formed by coating a negative electrode paste on the negative electrode current collector and then drying and cold pressing. The negative electrode paste is usually formed by dispersing negative electrode active materials, 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.

[0458] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0459] Separator

[0460] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode plate and the negative electrode plate.

[0461] In some embodiments, the separator is a separator film. The present application does not particularly limit the type of the separator film, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0462] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or 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.

[0463] 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.

[0464] In some embodiments, the volumetric energy density of the battery cell is from 385 Wh / L to 450 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 385 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.

[0465] 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 using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration,

[0466] The battery cell is placed at 25 °C, 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 terminals and excluding the insulating film outside the outer shell), calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0467] In some embodiments, the volumetric energy density of the battery cell can be adjusted by the following optional methods:

[0468] From the perspective of the active material, positive and negative electrode active materials with high specific capacity can be used. For example, for the positive electrode active material, a lithium-containing phosphate material with a higher gram capacity is used. For example, physically mix positive electrode active materials with a higher gram capacity, such as ternary materials, to improve the energy density; for example, for the negative electrode active material, graphite with a higher gram capacity is used. For example, physically mix negative electrode active materials with a higher gram capacity, such as silicon-based materials, etc.;

[0469] From the perspective of the electrolyte, reducing the amount of electrolyte injection, or using an electrolyte that supports a higher energy density, etc.;

[0470] From the perspective of the electrode design, the compaction density and coating weight of the positive electrode or negative electrode can be adjusted, or the thickness of the positive current collector or negative current collector can be adjusted, etc.;

[0471] In terms of the separator, the thickness of the separator can be adjusted, etc.;

[0472] In terms of the structural design, first, the proportion of non-active substances such as battery components can be reduced. For example, making the battery casing thinner while ensuring its safety and mechanical properties, so that more active substances can be accommodated in the same space, improving the energy density. For example, adjusting the space occupancy ratio of the electrode assembly in the housing cavity of the casing.

[0473] Example

[0474] 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.

[0475] Example 1

[0476] 1. Preparation of the positive electrode

[0477] The positive electrode includes a positive current collector and positive electrode layers provided on both sides of the positive current collector. The positive current collector is an aluminum foil with a thickness of 13.5 μm.

[0478] The positive electrode layers include a lithium-containing phosphate, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black with a mass ratio of 96:2:2. The positive electrode layers are formed by uniformly coating a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive current collector and then drying and cold pressing.

[0479] The lithium-containing phosphate includes lithium iron phosphate.

[0480] The single-sided coating weight of the positive electrode layers is 300 mg / 1540.25 mm 2 。

[0481] The length of the positive electrode layers is 500 mm, and the ratio of the length to the width of the positive electrode layers is 5.25.

[0482] 2. Preparation of the negative electrode sheet

[0483] The negative electrode sheet includes a negative current collector part and negative electrode film layers provided on both sides of the negative current collector part. The negative current collector part is a copper foil with a thickness of 6 μm.

[0484] The negative electrode film layers are formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) on the surface of the negative current collector part and then drying and cold pressing.

[0485] The single-sided coating weight of the negative electrode film layer is 130 mg / 1540.25 mm 2 。

[0486] The negative electrode film layers include 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 current collector part, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0487] The first negative electrode film layer includes a carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose 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.

[0488] The second negative electrode film layer includes a carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose 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.

[0489] 3. Separator

[0490] The separator includes a base film, which is a polyethylene film layer with a thickness of 7 μm and a porosity of 42%.

[0491] 4. Preparation of the electrolyte

[0492] The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0493] The organic solvent includes 10% chain carboxylic ester solvent (ethyl acetate) and 75% carbonate solvent (diethyl carbonate, dimethyl carbonate, 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.

[0494] Based on the mass of the electrolyte, the mass content of the additive is 1.5%, which includes vinylene carbonate VC.

[0495] The lithium salt includes 8.5% lithium hexafluorophosphate LiPF6 and 5% lithium bis(fluorosulfonyl)imide.

[0496] The conductivity of the electrolyte at room temperature is 12 mS / cm.

[0497] 5. Preparation of Battery Cell

[0498] Stack the above positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging shell, inject electrolyte after drying, and go through processes such as vacuum packaging, standing, formation, and shaping to obtain a battery cell. The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.5 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.45 g / cm 3 ,

[0499] The outer shell assembly further includes a housing, an end cap, a positive terminal, and a negative terminal. The housing accommodates the electrode assembly and the electrolyte. The housing includes an opening, and the end cap covers the opening. The positive terminal and the negative terminal are arranged on the end cap;

[0500] The length of the battery cell is 525 mm, the thickness of the battery cell is 10 mm, the width is 100 mm, and the ratio of the length to the thickness is 52.5.

[0501] Comparative Examples 1 to 3

[0502] Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the minimum cross-sectional areas of the positive terminal and the negative terminal are adjusted,

[0503] Among them, in Comparative Examples 1 and 2, the dimensions of the battery cell are also adjusted,

[0504] The ratio of the length to the width of the positive electrode sheet in Comparative Example 1 is 2;

[0505] The length of the battery cell is 225 mm, the thickness of the battery cell is 10 mm, the width is 100 mm, and the ratio of the length to the thickness is 22.5.

[0506] The ratio of the length to the width of the positive electrode sheet in Comparative Example 2 is 8;

[0507] The length of the battery cell is 825 mm, the thickness of the battery cell is 10 mm, the width is 100 mm, and the ratio of the length to the thickness is 82.5.

[0508] Examples 2-1 to 2-3

[0509] Prepare a battery cell using a method similar to that of Example 1. Different from Example 1, the minimum cross-sectional areas of the positive terminal and the negative terminal are adjusted.

[0510] Example 3

[0511] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the numbers of the positive terminal and the negative terminal were adjusted.

[0512] Examples 4-1 and 4-2

[0513] The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the welding mark areas of the positive terminal and the positive tab were adjusted.

[0514] The parameters are shown in Table 1.

[0515] Table 1

[0516]

[0517] In Table 1,

[0518] x1 represents the number of positive terminals;

[0519] x2 represents the number of negative terminals;

[0520] S1 represents the minimum cross-sectional area of a single positive terminal perpendicular to its own thickness direction, and its unit is mm 2 ;

[0521] S2 represents the minimum cross-sectional area of a single negative terminal perpendicular to its own thickness direction, and its unit is mm 2 ;

[0522] M1 represents the welding mark area of all positive terminals and the positive tab, and its unit is mm 2 ;

[0523] M2 represents the welding mark area of all negative terminals and the negative tab, and its unit is mm 2 ;

[0524] In Example 1, the size T1 of the first protrusion of the positive terminal was 2 mm, and the size T of the second protrusion of the negative terminal was 2 mm. As Figure 9 shown, two positive terminals were respectively arranged on both sides of the electrode assembly along the length direction of the battery single cell, and two negative terminals were respectively arranged on both sides of the electrode assembly along the length direction of the battery single cell.

[0525] Except for Example 3, the other examples and comparative examples adopted the same arrangement of electrode terminals as in Example 1.

[0526] In Example 3, as Figure 11 shown, there was one positive terminal, and the positive terminal was arranged on one side of the electrode assembly along the length direction of the battery single cell. There was one negative terminal, and the negative terminal was respectively arranged on the other side of the electrode assembly along the length direction of the battery single cell.

[0527] Performance test

[0528] 1. DC internal resistance DCR test of battery cell

[0529] The method in GB / T 31467 "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEV" can be referred to.

[0530] For example, at 25 °C, charge the battery cell at a constant current of 0.33 C to 3.65 V, let it stand for 1 min, then charge it at a constant current of 0.05 C to 3.65 V, let it stand for 30 min, discharge it at a constant current of 0.33 C to 2.5 V, record the discharge capacity A0 at this time, with the unit of Ah, and then charge it at a constant current of 0.33 C for 0.5A0 Ah to adjust the SOC to 50%.

[0531] 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 , and the discharge DCR data of the lithium-ion battery is calculated through the following formula, R 放电 =∆U 放电 / ∆I 放电 ,

[0532] where, ∆U 放电 represents the voltage change within 10 s at the start of discharge, and ∆I 放电 represents the current value within 10 s at the start of discharge.

[0533] The test results are shown in Table 2.

[0534] Table 2

[0535]

[0536] In Table 2,

[0537] E represents the energy of the battery cell, with the unit of Wh, and the energy E of each example and comparative example is 225 Wh.

[0538] In Comparative Example 1 and Comparative Example 3, the overcurrent area of the electrode terminal is relatively small, resulting in insufficient overcurrent capacity and larger internal resistance of the battery cell, which is not conducive to fast charging at high energy density.

[0539] In Comparative Example 2, although the overcurrent capacity of the electrode terminal is strong, the ratio of the length to the width of the positive electrode plate in Comparative Example 2 is too large, and the length of the battery cell is relatively large, resulting in a longer migration path of electrons in the length direction of the positive electrode plate and larger internal resistance, which is not conducive to fast charging at high energy density.

[0540] In the embodiments of the present application, by adjusting the over-current area of the first electrode terminal, such as the positive electrode terminal, so that x1∙S1 / E is greater than or equal to 0.2, the over-current capacity of the positive electrode terminal is improved, the internal resistance of the battery cell is reduced, which is beneficial to improving the fast charging ability of the battery cell with high energy density.

[0541] In Embodiment 1, Embodiments 2-1 to 2-3, the larger the over-current area of the electrode terminal, the stronger the over-current capacity, which is more beneficial to reducing the internal resistance of the battery cell. However, the over-current area of the electrode terminal is limited by the assembly space, so that x1∙S1 / E is less than or equal to 0.7 and x2∙S2 / E is less than or equal to 0.7.

[0542] Embodiment 3 uses one negative electrode terminal, and Embodiment 2-3 uses two negative electrode terminals. The over-current area of the negative electrode terminal in Embodiment 3 is basically the same as that of each negative electrode terminal in Embodiment 2-3. In other words, the over-current area of the negative electrode terminal in Embodiment 3 is smaller than the total over-current area of the two negative electrode terminals in Embodiment 2-3. The over-current capacity of the negative electrode terminal in Embodiment 3 is less than the total over-current capacity of the negative electrode terminals in Embodiment 2-3, and the internal resistance of Embodiment 3 is relatively high. However, since Embodiment 3 uses one positive electrode terminal and the over-current area of one positive electrode terminal is basically the same as the total over-current area of the two positive electrode terminals in Embodiment 2-3, the over-current capacities of the positive electrode terminals in Embodiment 3 and Embodiment 2-3 are basically the same. The over-current capacity of the positive electrode terminal is relatively strong, so that the overall over-current capacity of the battery cell is relatively strong, which is beneficial to fast charging.

[0543] In Embodiment 1, Embodiments 4-1 and 4-2, by adjusting the welding mark area between the electrode terminal and the pole ear part, the over-current capacity between the electrode terminal and the pole ear part is adjusted. As the welding mark area increases, the over-current capacity becomes stronger, the internal resistance becomes smaller, which is more beneficial to improving the fast charging ability of the battery cell with high energy density.

[0544] Embodiments 5-1 and 5-2

[0545] The battery cells are prepared by a method similar to that of Embodiment 1. Different from Embodiment 1, the size of the battery cell is adjusted.

[0546] The test results are shown in Table 3.

[0547] Table 3

[0548]

[0549] In each of the embodiments and comparative examples, the width of the battery cell is 100 mm, the thickness is 10 mm, and the ratio of the width to the thickness is 10.

[0550] In Comparative Example 1, not only is the over-current capacity of the electrode terminal insufficient, but also due to the short size of the battery cell, the energy density of the battery cell is small.

[0551] Compared with Comparative Example 2, the aspect ratio of the positive electrode film layer in the embodiment of the present application is 4 to 7, and the size of the battery cell is within an appropriate range, which can enable the battery cell to have a relatively high energy density; and in cooperation with the appropriate number and suitable position setting of the electrode terminals, for example, two positive electrode terminals are respectively arranged on both sides of the electrode assembly along the length direction, which can effectively shorten the electron transmission path, improve the over-current capacity, reduce the internal resistance, and enhance the fast charging ability of the battery cell.

[0552] Examples 6-1 to 6-2

[0553] A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the single-sided coating weight of the positive and negative electrode film layers was adjusted.

[0554] Examples 6-3 to 6-4

[0555] A battery cell was prepared by a method similar to that of Example 1. Different from Example 1, the compaction density of the positive and negative electrode film layers was adjusted.

[0556] The test results are shown in Table 4.

[0557] Table 4

[0558]

[0559] The single-sided coating weight of the positive and negative electrode film layers was adjusted. When the single-sided coating weight is relatively high, it is beneficial to improve the single-cell energy of the battery cell and enhance the energy density; however, due to the increased migration path of lithium ions in the positive and negative electrode film layers, the DCR deteriorates slightly.

[0560] The single-sided coating weight of the positive and negative electrode film layers in Examples 6-1 and 6-2 is within an appropriate range. For example, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 , and the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 , enabling the battery cell to balance relatively high single-cell energy and low DCR, which is beneficial to balance the improvement of the fast charging performance and energy density of the battery cell.

[0561] The compaction density of the positive and negative electrode film layers was adjusted. When the compaction density is relatively high, it is beneficial to improve the single-cell energy of the battery cell and enhance the energy density; however, due to the possible increase in the migration resistance of lithium ions in the positive and negative electrode film layers, the DCR deteriorates slightly.

[0562] The single-sided coating weights of the positive and negative electrode film layers in Example 6-3 and Example 6-4 are within an appropriate range. For example, the compaction density of the positive electrode film layer is 2.30 g / cm 3 to 2.70 g / cm 3 , and the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.65 g / cm 3 , enabling the battery cell to balance high single-cell energy and low DCR, which is beneficial for balancing the improvement of the fast charging performance and energy density of the battery cell.

[0563] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the implementation manners of the present application, and changes, substitutions, and modifications to the embodiments can be made without departing from the spirit, principles, and scope of the implementation manners of the present application.

Claims

1. A battery cell, characterized in that, The battery cell comprises: An electrode assembly, comprising a plurality of first pole sheets and a plurality of second pole sheets, wherein one of the first pole sheet and the second pole sheet is a positive pole sheet and the other is a negative pole sheet, the first pole sheet and the second pole sheet are stacked along the thickness direction of the battery cell, the first pole sheet and the second pole sheet each comprise a coating portion and a pole ear portion, the coating portion is provided with an active material layer, the pole ear portion is connected to the coating portion and extends out of the coating portion, and the active material layer of the positive pole sheet comprises a lithium-containing phosphate having an olivine structure; and A housing assembly comprises a housing and a terminal assembly disposed on the housing, wherein the terminal assembly comprises at least one first electrode terminal, wherein the first electrode terminal is connected to the pole ear portion of the first pole piece, in, The ratio of the length of the battery cell to the thickness of the battery cell is 40 to 70; The battery cell satisfies: x1∙S1 / E is 0.2 to 0.7, x1 represents the number of the first electrode terminals; S1 represents the minimum cross-sectional area of a single said first electrode terminal perpendicular to its own thickness direction, with the unit of mm 2 ; E represents the single cell energy of the battery cell, and its unit is Wh.

2. The battery cell according to claim 1, wherein S1 is 15 to 60.

3. The battery cell according to claim 1 or 2, characterized in that, x1 is 1 to 4.

4. The battery cell according to claim 1, characterized in that, The battery cell also satisfies: M1 / E is 0.2 to 0.6, M1 represents the area of the first connection region, with the unit of mm 2 , and the first connection region is the region where the first electrode terminal is connected to the tab portion of the first electrode plate.

5. The battery cell according to claim 4, characterized in that, M1 is 60 to 120.

6. The battery cell according to claim 1, wherein E is 170 to 480.

7. The battery cell according to claim 1, wherein The first electrode terminal is disposed on at least one side of the electrode assembly along a length direction of the battery cell.

8. The battery cell according to claim 7, wherein There are at least two first electrode terminals, and the at least two first electrode terminals are respectively arranged on both sides of the electrode assembly along the length direction.

9. The battery cell according to claim 1, wherein, The housing comprises a shell and an end cover, the shell contains the electrode assembly, the shell comprises an opening, the end cover covers the opening, and the first electrode terminal is arranged on the end cover; The first electrode terminal comprises: A first main body portion, disposed on the end cover and penetrating the end cover; and The first protrusion is arranged on the first main body and protrudes from the first main body to be connected with a side of the end cover facing the electrode assembly.

10. The battery cell according to claim 9, characterized in that, In a direction from the first main body to the first protrusion, a size of the first protrusion is 1.5 mm to 30 mm.

11. The battery cell according to claim 9 or 10, characterized in that, The first main body and the first protruding portion are an integrated structure.

12. The battery cell according to claim 9, wherein A ratio of a dimension of the first body portion along a thickness direction of the battery cell to a dimension of the end cover along a thickness direction of the battery cell is 0.20 to 0.

40.

13. The battery cell according to claim 9, characterized in that, The shell assembly also includes a first conductive fixing member, at least part of which is located on a side of the end cover away from the electrode assembly, and the first conductive fixing member is disposed around the outside of the first main body and fixedly connects the first main body and the end cover.

14. The battery cell according to claim 13, characterized in that, A ratio of a dimension of the first conductive fixing member along a thickness direction of the battery cell to a dimension of the end cover along a thickness direction of the battery cell is 0.40 to 0.

80.

15. The battery cell according to claim 1, characterized in that, The pole ear portion of the first pole piece is arranged on at least one side of the coating portion along the first direction, and the first pole piece satisfies: n*W1 / W2 is 0.5 to 1.0; n represents the number of all the pole lugs located on the same side of the coating portion; W1 represents an average size of the pole ear portion along a second direction, wherein one of the first direction and the second direction is parallel to a length direction of the battery cell, and the other is parallel to a width direction of the battery cell; W2 represents a dimension of the coating portion along the second direction.

16. The battery cell according to claim 15, wherein, The first direction is parallel to a length direction of the battery cell.

17. The battery cell according to claim 1, wherein There are at least two pole lug portions in the first pole piece located on the same side of the coating portion.

18. The battery cell according to claim 16 or 17, characterized in that, The first pole piece has a plurality of pole ear portions, and the plurality of pole ear portions of the first pole piece are located on both sides of the coating portion along the first direction; or All the pole lug portions of the first pole piece are located on the same side of the coating portion along the first direction.

19. The battery cell according to claim 1, wherein The terminal assembly further includes at least one second electrode terminal, and the second electrode terminal is connected to the pole ear portion of the second pole piece; Wherein, the battery cell satisfies: x2∙S2 / E is 0.2 to 0.7, x2 represents the number of the second electrode terminals; S2 represents the minimum cross-sectional area of a single said second electrode terminal perpendicular to its own thickness direction, and its unit is mm 2 .

20. The battery cell according to claim 1, characterized in that, The ratio of the width of the battery cell to the thickness of the battery cell is 3 to 15; and / or The thickness of the battery cell is 10 mm to 30 mm.

21. The battery cell according to claim 1, characterized in that, The olivine-structured lithium-containing phosphate includes lithium iron phosphate.

22. The battery cell according to claim 1, 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 in the 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 .

23. The battery cell according to claim 1, wherein, 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 in a 0% state of charge, the compaction density of the active material layer of the negative electrode plate is 1.30 g / cm 3 to 1.65 g / cm 3 .

24. The battery cell according to claim 1, wherein The coating portion of the negative electrode sheet includes a negative electrode current collecting portion and a negative electrode film layer disposed on at least one side of the negative electrode current collecting portion, wherein the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a carbon-based material, wherein the negative electrode film layer includes: A first negative electrode film layer is disposed on the surface of the negative electrode current collecting portion; and A second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion, 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.

25. The battery cell according to claim 24, characterized in that: The carbon-based material of the first negative electrode film layer is in a granular form, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm; and / or; 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.

26. The battery cell according to claim 24 or 25, characterized in that, 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.

27. The battery cell according to claim 1, wherein, The battery cell further includes an electrolyte, wherein the conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm.

28. The battery cell according to claim 27, wherein The electrolyte includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent is 5% to 30% based on the mass of the electrolyte.

29. The battery cell according to claim 27 or 28, characterized in that, The electrolyte includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Based on the mass of the electrolyte, the ratio of the mass content of the lithium hexafluorophosphate to the mass content of the lithium bis(fluorosulfonyl)imide is 0.5 to 4.

30. A battery device, characterized in that, The battery device comprises the battery cell according to any one of claims 1 to 29.

31. An electric device, characterized in that, The electrical device comprises the battery device as claimed in claim 30.

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