Battery cell, battery device, and electric device

Abstract

The present application provides a battery cell, a battery device, and an electric device. The battery cell comprises first electrode terminals and an electrode assembly. The electrode assembly comprises a plurality of first electrode sheets and a plurality of second electrode sheets; each of the first electrode sheets and the second electrode sheets comprises a coated portion and a tab portion; the tab portion is arranged on at least one side of the coated portion in a first direction; one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet; the ratio of the sizes of coated portions of positive electrode sheets in the length direction to the sizes of coated portions of positive electrode sheets in the width direction is 4 to 7; and the sizes of the coated portions of the positive electrode sheets in the length direction range from 300 mm to 650 mm. There are at least two first electrode terminals; the at least two first electrode terminals are electrically connected to the tab portions of the first electrode sheets; and the first electrode sheets satisfy that the value of n*W1 / W2 ranges from 0.5 to 1.0, wherein n represents the number of all tab portions located on the same side of the coated portions, W1 represents the average size of the tab portions in a second direction, and W2 represents the sizes of the coated portions in the second direction.

Description

Battery cells, battery packs and electrical devices Technical Field

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

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

[0003] This application provides a battery cell, a battery device, and an electrical device. The battery cell of this application can improve the power performance and high-temperature cycle performance.

[0004] In a first aspect, this application provides a battery cell comprising a casing assembly and an electrode assembly. The casing assembly includes a casing, a first electrode terminal, and a second electrode terminal, which are disposed on the casing. The electrode assembly is located inside the casing and includes a plurality of first electrode plates and a plurality of second electrode plates. The first and second electrode plates are stacked along the thickness direction of the battery cell. Each first and second electrode plate includes a coating portion and a tab portion. The coating portion is coated with an active material layer, and the tab portion is disposed on at least one side of the coating portion along a first direction, which is parallel to the length direction of the battery cell or parallel to the width direction of the battery cell.

[0005] Among them, one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode. The active material layer of the positive electrode includes lithium phosphate. The ratio of the length dimension of the coating portion of the positive electrode to the width dimension of the coating portion of the positive electrode is 4 to 7. The length dimension of the coating portion of the positive electrode is 300 mm to 650 mm.

[0006] The first electrode terminal is at least two, and the at least two first electrode terminals are electrically connected to the tab portion of the first electrode plate, and the second electrode terminal is electrically connected to the tab portion of the second electrode plate.

[0007] The first electrode satisfies the following condition: n*W1 / W2 is between 0.5 and 1.0;

[0008] n represents the number of all tabs located on the same side of the coating section;

[0009] W1 represents the average dimension of the tab portion along the second direction, where the second direction, the first direction, and the thickness direction are perpendicular to each other.

[0010] W2 represents the dimension of the coated portion along the second direction.

[0011] In this embodiment, the ratio of the length Z dimension of the coating portion of the positive electrode sheet to the width Y dimension of the coating portion of the positive electrode sheet is 4 to 7, and the length Z dimension of the coating portion of the positive electrode sheet is 300 mm to 650 mm. The relatively long length of the coating portion is beneficial for carrying a relatively large amount of positive electrode active material, which is beneficial for the battery cell to have a relatively high energy density. When the length of the coating portion of the positive electrode sheet is too long, the internal resistance is high, resulting in higher heat generation of the positive electrode sheet. The coating portion of the positive electrode sheet includes lithium phosphate with poor conductivity, which makes the positive electrode sheet... The internal resistance further increases, and heat generation intensifies. In the embodiments of this application, the first electrode also satisfies that n*W1 / W2 is 0.5 to 1.0, which makes the connection area between the tab and the coating part relatively large and the current-passing area of ​​the tab relatively large, which is beneficial to reduce DC resistance and reduce heat generation. There are at least two first electrode terminals. In other words, at least two first electrode terminals are connected to the tab of the first electrode, which can further increase the current-passing area of ​​the first electrode terminals and the tab, further reduce DC resistance and reduce heat generation, thereby improving power performance and high-temperature cycling performance and achieving fast charging.

[0012] In some embodiments, at least two first electrode terminals are disposed on at least one side of the electrode assembly along its length. This arrangement can shorten the electron migration path, which is beneficial for improving the power performance and high-temperature cycling performance of the battery cell.

[0013] In some embodiments, there are two to four first electrode terminals. When the number of first electrode terminals is within the above range, the overcurrent capacity can be improved, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0014] In some embodiments, the housing includes a casing and an end cap. The casing houses the electrode assembly. The casing includes an opening, and the end cap closes to the opening. A first electrode terminal is disposed on the end cap. The first electrode terminal includes a first electrode body and a first electrode protrusion. The first electrode body is located on the side of the end cap facing the electrode assembly. The first electrode protrusion is connected to the first electrode body and protrudes toward a side opposite to the electrode assembly, penetrating the end cap. The first electrode body increases the tightness of the connection with the end cap, and the first electrode protrusion facilitates the introduction or extraction of current.

[0015] In some embodiments, the minimum cross-sectional area of ​​the first electrode protrusion parallel to the thickness direction of the battery cell is the first area, and the area enclosed by the projected outer contour of the end cap parallel to the thickness direction is the second area. The ratio of the first area to the second area is 0.02 to 0.20. When the first electrode protrusion meets the above conditions, the area ratio of the first electrode protrusion is relatively high, which is beneficial to improving the current carrying capacity of the first electrode terminal and improving the power performance and high-temperature cycle performance of the battery cell.

[0016] In some embodiments, the ratio of the dimension of the first electrode protrusion along the thickness direction to the dimension of the end cap along the thickness direction is 0.20 to 0.40.

[0017] When the first electrode protrusion meets the above conditions, the size ratio of the first electrode protrusion is relatively high, which is beneficial to improving the overcurrent capacity of the first electrode terminal and improving the power performance and high-temperature cycle performance of the battery cell.

[0018] In some embodiments, the first electrode body and the first electrode protrusion are an integral structure. An integral structure is more robust and has lower electron transport resistance, which is beneficial for improving the power performance and high-temperature cycling performance of the battery cell.

[0019] In some embodiments, the housing assembly further includes a first conductive fastener, at least a portion of which is located on the side of the end cap opposite to the electrode assembly. The first conductive fastener is disposed around the first electrode terminal and securely connects the first electrode terminal and the end cap. The first conductive fastener can further increase the current-carrying area between the battery cell and the external busbar assembly, thereby improving the current-carrying capacity, which is beneficial for improving the current-carrying capacity of the battery device and for improving the power performance and high-temperature cycle performance of the battery cell.

[0020] In some embodiments, the ratio of the dimension of the first conductive fastener along the thickness direction to the dimension of the end cap along the thickness direction is 0.40 to 0.80. When the first conductive fastener meets the above conditions, the size ratio of the first conductive fastener is relatively high, which is beneficial to increasing the current-carrying area between the battery cell 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 beneficial to improving the power performance and high-temperature cycling performance of the battery cell.

[0021] In some embodiments, the first electrode has at least two tabs; the at least two tabs of the first electrode are disposed on the same side of the coating portion along its length. The tabs have strong current-carrying capacity, which is beneficial for improving the power performance and high-temperature cycle performance of the battery cell.

[0022] In some embodiments, at least two tabs of the first electrode are respectively disposed on both sides of the coating portion along the length direction. The tabs have strong current carrying capacity, improving the fast charging performance of the battery device.

[0023] In some embodiments, the tab portion of the first electrode is disposed on at least one side of the coating portion along the width direction, and there is one tab portion of the first electrode located on the same side of the coating portion, and n*W1 / W2 is 1.0; the tab portion has a strong current carrying capacity, which is beneficial to improving the power performance and high temperature cycle performance of the battery cell.

[0024] In some embodiments, the tabs of the first electrode are disposed on at least one side of the coating portion along the width direction, and there are at least two tabs on the same side of the coating portion in the first electrode. The tabs have strong current carrying capacity, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0025] In some embodiments, there are two to four tabs on the same side of the coating portion in the first electrode. The tabs have strong current-carrying capacity, which is beneficial for improving the power performance and high-temperature cycle performance of the battery cell.

[0026] In some embodiments, the battery cell further includes a first adapter located between the first electrode terminal and the tab of the first electrode plate, connecting the first electrode terminal and the tab of the first electrode plate. The first adapter facilitates the connection between the first tab and the first electrode terminal and can improve the overcurrent capacity, thereby improving the power performance and high-temperature cycle performance of the battery cell.

[0027] In some embodiments, at least two first electrode terminals are disposed on at least one side of the electrode assembly along its length, and the tab portion of the first electrode sheet is disposed on at least one side of the coating portion along its width. The first electrode terminals and the tab portion of the first electrode sheet being disposed on opposite sides increases the space in the width direction and improves the energy density of the battery cell.

[0028] In some embodiments, the first adapter includes a first adapter portion and a second adapter portion. The first adapter portion extends along the length direction and connects to the tab portion of the first electrode. The second adapter portion is connected to the first adapter portion and protrudes from the first adapter portion along the width direction, and is connected to the first electrode terminal. The first adapter portion can improve the current carrying capacity, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0029] In some embodiments, the battery cell further includes a first conductive element located between the first adapter and the tab of the first electrode, connecting the first adapter and the tab of the first electrode. The first conductive element facilitates the connection between the first tab and the first electrode terminal and can improve the overcurrent capacity, thereby improving the power performance and high-temperature cycle performance of the battery cell.

[0030] In some embodiments, the first electrode sheet has at least two tabs located on the same side of the coating portion; the first conductive element is a continuous sheet structure, and the first conductive element connects at least two tabs. The first conductive element can improve the current carrying capacity, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0031] In some embodiments, the first electrode has at least two tabs located on the same side of the coating portion; there are at least two first conductive elements, and each first conductive element is connected to a tab in a corresponding manner. The first conductive elements can improve the current carrying capacity, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0032] In some embodiments, at least two first electrode terminals are disposed on at least one side of the electrode assembly along its length, and the tab portion of the first electrode is disposed on one side of the coating portion along its width. The first conductive element includes a first conductive portion and a second conductive portion. The first conductive portion extends along its length and connects to the tab portion of the first electrode and the first adapter. The second conductive portion is connected to the first conductive portion and protrudes from the first conductive portion along its width, and connects to the second adapter portion of the first adapter. The first conductive element facilitates the connection between the first tab and the first electrode terminals, improves current carrying capacity, and helps improve the power performance and high-temperature cycle performance of the battery cell.

[0033] In some embodiments, the thickness of the first conductive element is between 0.5 mm and 2.0 mm. When the thickness of the first conductive element is within the above range, the overcurrent capacity can be effectively improved, and the fast charging capability can be enhanced.

[0034] In some embodiments, there are at least two second electrode terminals; the second electrode sheet satisfies: m*W3 / W4 is 0.5 to 1.0; m represents the number of all tabs located on the same side of the coating portion; W3 represents the average size of the tabs along the second direction; W4 represents the size of the coating portion along the second direction. The second electrode terminals have a stronger current-carrying capacity, which is beneficial for improving the current-carrying capacity of the battery cell, and thus for improving the power performance and high-temperature cycling performance of the battery cell.

[0035] In some embodiments, the outer casing includes a housing and an end cap. The housing includes an opening, and the end cap closes to the opening. The housing includes two first housing portions, a second housing portion, and a third housing portion, which are opposite each other along the thickness direction. The second and third housing portions are connected through the first housing portions. The second housing portion includes a first wall and a second wall continuously disposed along the thickness direction, and the first and second walls are welded together. The second housing portion has a relatively small area and a relatively small degree of expansion. The weld is located on the second housing portion, which can reduce the risk of leakage from the battery cell.

[0036] In some embodiments, the thickness of the housing is between 0.1 mm and 0.5 mm. When the thickness of the housing is within the above range, the housing is relatively thin, which is beneficial for rapid heat dissipation.

[0037] In some embodiments, the battery cell further includes a pressure relief assembly disposed on the housing assembly, the pressure relief assembly having an area of ​​1.2 mm² per unit capacity. 2 / Ah to 1.8mm 2 / Ah.

[0038] In this embodiment, the area per unit capacity of the pressure relief component is greater than 1.2 mm². 2 / Ah, enabling rapid gas release and improving the reliability of individual battery cells; moreover, the area per unit capacity of the pressure relief component is less than or equal to 1.8mm². 2 / Ah, which makes the pressure relief component occupy a relatively small area, while taking into account the area occupied by the electrode terminals, resulting in a relatively high overcurrent capacity; thus, when the battery cell of the present application meets the above conditions, it can simultaneously improve the reliability and overcurrent capacity of the battery cell.

[0039] In some implementations, there are two pressure relief components, which are respectively located on both sides of the housing assembly, which is beneficial for releasing gas inside the battery cell.

[0040] In some implementations, the lithium-containing phosphate includes lithium iron phosphate. Lithium-containing phosphates exhibit superior cycle stability, which is beneficial for improving high-temperature cycle performance.

[0041] In some embodiments, the single-sided coating weight of the active material layer of the positive electrode is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 The option is 275mg / 1540.25mm. 2 Up to 300mg / 1540.25mm 2 The active material layer of the positive electrode is a positive electrode film layer. When the coating weight of the positive electrode film layer on one side is within the above range, the heat generation per unit area of ​​the positive electrode will not be too large, and it can also improve the energy density and charging rate performance of the battery cell.

[0042] In some embodiments, the compaction density of the active material layer of the positive electrode sheet is 2.30 g / cm³ when the battery cell is at 0% charge. 3 Up to 2.70 g / cm 3 2.40 g / cm³ is an optional value. 3 Up to 2.55 g / cm 3 When the compaction density of the positive electrode film is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active material in the positive electrode film is packed more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation under fast charging, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0043] In some embodiments, the coating portion of the negative electrode sheet includes a negative electrode current collector and an active material layer containing a negative electrode active material. The active material layer is disposed on at least one side of the negative electrode current collector, and the active material layer includes a negative electrode active material, which includes a carbon-based material, including artificial graphite. When the graphitization degree of the artificial graphite is within the above-mentioned range, the artificial graphite exhibits superior conductivity, which can reduce heat generation of the negative electrode sheet, reduce heat generation of the battery cell, and improve the fast charging performance of the battery cell.

[0044] In some embodiments, the active material layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector. The second negative electrode film layer is connected to the side of the first negative electrode film layer opposite to the negative electrode current collector. The volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer. In the embodiments of this application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve fast charging performance, and improve the lithium plating problem on the surface of the negative electrode sheet, thus improving the power performance and high-temperature cycle performance of the battery cell.

[0045] In some embodiments, the carbon-based material in the first negative electrode film is particulate, with a volume average particle size Dv50 of 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film is within the above range, it can shorten the solid-phase transport path of lithium ions, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0046] In some embodiments, the carbon-based material in the second negative electrode film is particulate, with a volume average particle size (Dv50) of 7.8 μm to 14.3 μm. When the volume average particle size (Dv50) of the carbon-based material in the second negative electrode film is within this range, it can shorten the solid-phase transport path of lithium ions, improving fast-charging performance. Furthermore, the material is less prone to agglomeration during preparation, improving its stability. Additionally, the combination of the negative electrode active material in the second negative electrode film within the aforementioned volume average particle size range with the negative electrode active material in the first negative electrode film facilitates the creation of a gradient porosity difference between the second and first negative electrode films, reducing the tortuosity of lithium ion transport, improving the fast-charging performance of the battery cell, and ultimately enhancing the power performance and high-temperature cycling performance of the battery cell.

[0047] 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.

[0048] In some embodiments, the single-sided coating weight of the active material layer of the negative electrode sheet is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 The option is 125mg / 1540.25mm. 2 Up to 150mg / 1540.25mm 2 The active material layer of the negative electrode sheet is a negative electrode film layer. 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, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell, and can also improve the energy density of the battery cell.

[0049] In some embodiments, the compaction density of the active material layer of the negative electrode sheet is 1.30 g / cm³ when the battery cell is at 0% charge. 3 Up to 1.65 g / cm 3 The option is 1.35g / cm³. 3 Up to 1.50 g / cm 3 .

[0050] When the compaction density of the negative electrode film is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, since the negative electrode active material in the negative electrode film is packed more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode, thereby reducing heat generation and improving the power performance and high-temperature cycle performance of the battery cell.

[0051] In some embodiments, the battery cell further includes an electrolyte comprising an organic solvent, including chain-like carboxylic acid ester solvents, and the electrolyte having a conductivity of 10 mS / cm to 13 mS / cm at room temperature. When the conductivity of the electrolyte at room temperature, such as 25°C, is within the above range, the lithium-ion migration rate in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the power performance and high-temperature cycle performance of the battery cell.

[0052] In some embodiments, the mass content of the chain carboxylic acid ester solvent is 5% to 30% based on the mass of the electrolyte. When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively low, which is beneficial to the migration of lithium ions; moreover, the mass content of the chain carboxylic acid ester solvent is not too high, which can reduce the amount of gas generated at high temperatures and improve the high-temperature cycling performance.

[0053] In some embodiments, the electrolyte further includes a lithium salt, including one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. This lithium salt system is beneficial for improving the conductivity of the electrolyte and enhancing the kinetic performance of the battery cell.

[0054] In some embodiments, the mass content of lithium salt is 13% to 20% based on the mass of the electrolyte. When the mass content of lithium salt is within the above range, lithium salt is beneficial for improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cells, and improving the power performance and high-temperature cycling performance of the battery cells.

[0055] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 1.2 to 2.0, based on the mass of the electrolyte. Lithium salts are beneficial for improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cells, and improving the power performance and high-temperature cycling performance of the battery cells.

[0056] In some embodiments, the electrolyte further includes additives, including one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone. These additives can form a dense and uniformly thick film on the negative electrode side, effectively repairing the solid electrolyte interphase (SEI) film, providing excellent protection for the negative electrode active material, improving the fast-charging performance of the battery cell, and enhancing high-temperature cycling performance.

[0057] Secondly, embodiments of this application also propose a battery device, including a battery cell of any embodiment of the first aspect of this application.

[0058] Thirdly, embodiments of this application also propose an electrical device, which includes a battery device as described in any of the embodiments of the second or third aspects of this application. Attached Figure Description

[0059] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0060] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application.

[0061] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application;

[0062] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application;

[0063] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0064] Figure 5 is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0065] Figure 6 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0066] Figure 7 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0067] Figure 8 is a schematic diagram of the structure of the end cap, first electrode terminal and first conductive fixing member of the battery cell provided in some embodiments of this application;

[0068] Figure 9 is a top view of Figure 8;

[0069] Figure 10 is a cross-sectional view taken along line AA in Figure 9;

[0070] Figure 11 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0071] Figure 12 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0072] Figure 13 is an exploded structural diagram of the end cap, first electrode terminal and first conductive fixing member of a battery cell provided in some embodiments of this application.

[0073] Figure 14 is a schematic diagram of the structure of the first electrode of a battery cell provided in some other embodiments of this application;

[0074] Figure 15 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0075] Figure 16 is a schematic diagram of the structure of the first electrode of a battery cell provided in some other embodiments of this application;

[0076] Figure 17 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0077] Figure 18 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0078] Figure 19 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0079] Figure 20 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0080] Figure 21 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application;

[0081] Figure 22 is a schematic diagram of the structure of the second electrode of a battery cell provided in some embodiments of this application;

[0082] Figure 23 is a schematic diagram of the structure of the second electrode of a battery cell provided in some other embodiments of this application.

[0083] The accompanying drawings may not be drawn to scale.

[0084] The reference numerals in the attached drawings are explained as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing section; 5b, second housing section; 5c, accommodating space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, first electrode; 111, first tab; 1111, first end; 112, first coating section; 12, second electrode; 121, second tab; 1211, second end; 122, second coating section; 13, separator; 20, outer casing assembly; 21, housing; 211, first housing section; 2 12. Second shell portion; 2121. First wall; 2122. Second wall; 213. Third shell portion; 22. End cap; 31. First electrode terminal; 311. First electrode body; 312. First electrode protrusion; 32. Second electrode terminal; 41. First conductive fixing member; 51. First adapter; 511. First adapter portion; 512. Second adapter portion; 61. First conductive member; 611. First conductive part; 612. Second conductive part; 70. Pressure relief assembly. Detailed Implementation

[0085] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0086] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0087] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0088] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0089] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0090] In this application, "multiple" means two or more (including two).

[0091] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0092] With the development of the battery field, the requirements for energy density and fast charging of battery cells are gradually increasing. However, research has found that when increasing battery energy density, the electron transport path may be longer and the electron distribution may be uneven, which may lead to increased internal resistance and heat generation. As the charging rate increases, the increase in internal resistance intensifies, heat generation increases further, and power performance and high-temperature cycle performance are poor, making it impossible for battery cells to achieve fast charging.

[0093] In view of the above problems, the embodiments of this application design the battery cell and improve the size of the tabs, the number of electrode terminals, etc., so as to improve the power performance and high temperature cycle performance of the battery cell.

[0094] The battery cell described in this application is applicable to various battery devices and electrical appliances that use battery cells.

[0095] For example, the electrical device can be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, power tool, vehicle, ship, and spacecraft, etc. Alternatively, for example, the electrical device can be a spacecraft, including airplanes, rockets, space shuttles, and spacecraft, etc.

[0096] Figure 1 is a schematic diagram of an example electrical device 1. This electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 1, a battery pack or battery module can be used.

[0097] The electrical device 1 has a battery pack installed inside. The battery pack can be located at the bottom, head, or tail of the electrical device 1. The battery pack can be used to supply power to the electrical device 1. For example, the battery pack can be used as the operating power source for the electrical device 1, and it can also be used as the driving power source for the electrical device 1, replacing or partially replacing fuel oil or natural gas to provide driving power for the electrical device 1. The battery pack shown in Figure 1 is a battery pack 2.

[0098] Electrical device 1 may also include controller 3 and motor 4. Controller 3 is used to control the battery device to supply power to motor 4, for example, to meet the power needs of electrical device 1 during startup, navigation and driving.

[0099] A battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via busbars.

[0100] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0101] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0102] As shown in Figure 2, in some embodiments, the battery device can be a battery pack 2, which includes a housing 5 and one or more battery cell assemblies housed in the housing 5.

[0103] As an example, the battery cell assembly can also be housed in the housing 5 by directly fixing multiple battery cells to the housing 5.

[0104] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has an accommodating space 5c. The first housing portion 5a and the second housing portion 5b are fastened together to form a closed space inside the housing 5 to accommodate the battery cell assembly. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0105] As an example, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that the interior of the housing 5 forms an enclosed space to accommodate the battery cell assembly.

[0106] In some embodiments, the housing 5 can be part of the vehicle's chassis structure. For example, a portion of the housing 5 can be at least a part of the vehicle's floor, or a portion of the housing 5 can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0107] As an example, the battery cell assembly can be a battery module 6, which can be housed in the housing 5 by fixing the battery module 6 in the housing 5.

[0108] As shown in Figure 3, the battery module 6 includes multiple battery cells 7.

[0109] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the ambient temperature of the battery device is room temperature, for example, 25°C.

[0110] In some embodiments, during the charging process of the battery device or any individual battery cell comprising the battery device from 10% state of charge (SOC) to 80% SOC, the ambient temperature of the external environment in which the battery device is located is room temperature, for example, 25°C.

[0111] For example, the charging process of a battery device or any individual battery cell comprising a battery device from 10% state of charge (SOC) to 80% SOC can be performed as follows:

[0112] Charge from 10% SOC to 25% SOC at a constant current of 7.0C;

[0113] Charge from 25% SOC to 30% SOC at a constant current of 7.0C;

[0114] Charge from 30% SOC to 35% SOC at a constant current of 7.0C;

[0115] Charge from 35% SOC to 40% SOC at a constant current of 7.0C;

[0116] Charge from 40% SOC to 45% SOC at a constant current of 6.7C;

[0117] Charge from 45% SOC to 50% SOC at a constant current of 6.5C;

[0118] Charge from 50% SOC to 55% SOC at a constant current of 6.0C;

[0119] Charge from 55% SOC to 60% SOC at a constant current of 5.8C;

[0120] Charge from 60% SOC to 65% SOC at a constant current of 5.5C;

[0121] Charge from 65% SOC to 70% SOC at a constant current of 5.2C;

[0122] Charge from 70% SOC to 75% SOC at a constant current of 5.0C;

[0123] Charge from 75% SOC to 80% SOC at a constant current of 4.8C.

[0124] In some embodiments, the charging time for the battery device or any individual battery cell comprising the battery device from 10% state of charge to 80% state of charge is 5 min to 20 min, optionally less than or equal to 12 min, and further optionally 5 min to 8 min. The ambient temperature of the battery device at 10% state of charge is room temperature, for example, 25°C. Exemplarily, the charging time for the battery device from 10% state of charge to 80% state of charge is 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min, or a range of any two of the above values.

[0125] As shown in Figures 4 to 6, the battery cell 7 includes a housing assembly 20 and an electrode assembly 10. The housing assembly 20 includes a housing, a first electrode terminal 31, and a second electrode terminal 32, which are disposed on the housing. The electrode assembly 10 is located inside the housing and includes a plurality of first electrode plates 11 and a plurality of second electrode plates 12. The first electrode plates 11 and the second electrode plates 12 are stacked along the thickness direction X of the battery cell 7. Each first electrode plate 11 and the second electrode plate 12 includes a coating portion and an electrode tab portion. The coating portion is coated with an active material layer, and the electrode tab portion is disposed on at least one side of the coating portion along the first direction and is not coated with an active material layer. The first direction is a direction parallel to the length direction Z or the width direction Y of the battery cell 7.

[0126] Among them, one of the first electrode 11 and the second electrode 12 is a positive electrode and the other is a negative electrode. The active material layer of the positive electrode includes lithium phosphate. The ratio of the dimension of the coating part of the positive electrode along the length direction Z to the dimension of the coating part along the width direction Y of the positive electrode is 4 to 7. The dimension of the coating part of the positive electrode along the length direction Z is 300 mm to 650 mm.

[0127] There are at least two first electrode terminals 31, and at least two first electrode terminals 31 are electrically connected to the tab portion of the first electrode plate 11, and the second electrode terminal 32 is electrically connected to the tab portion of the second electrode plate 12.

[0128] The first electrode 11 satisfies the following: n*W1 / W2 is 0.5 to 1.0; n represents the number of all tabs located on the same side of the coating portion; W1 represents the average size of the tabs along the second direction; W2 represents the size of the coating portion along the second direction.

[0129] In the embodiments of this application, the first direction, the second direction, and the thickness direction X of the battery cell 7 are perpendicular to each other.

[0130] When the first direction is parallel to the length direction Z of the battery cell 7, the dimension of the component in that direction can be considered as the length of the component. For example, the dimension of the coating part along the first direction is the length of the coating part. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0131] When the first direction is parallel to the width direction Y of the battery cell 7, the dimension of the component in that direction can be considered as the width of the component. For example, the dimension of the coating part along the first direction is the width of the coating part. In this case, the second direction is parallel to the length of the battery cell 7.

[0132] To more clearly illustrate this application, the tab portion of the first electrode 11 is defined as the first tab 111, and the coating portion of the first electrode 11 is defined as the first coating portion 112. The tab portion of the second electrode 12 is defined as the second tab 121, and the coating portion of the second electrode 12 is defined as the second coating portion 122. The electrode terminal with the same electrical charge and electrically connected to the first tab 111 is the aforementioned first electrode terminal 31, and the electrode terminal with the same electrical charge and electrically connected to the second tab 121 is the aforementioned second electrode terminal 32.

[0133] Optionally, the battery cell 7 also includes a separator 13, which is located between the first electrode 11 and the second electrode 12.

[0134] The first electrode 11 and the second electrode 12 have opposite polarities. When the first electrode 11 is the positive electrode, the second electrode 12 is the negative electrode, the first electrode terminal 31 is the positive terminal, and the second electrode terminal 32 is the negative terminal; or when the first electrode 11 is the negative electrode, the second electrode 12 is the positive electrode, the first electrode terminal 31 is the negative terminal, and the second electrode terminal 32 is the positive terminal.

[0135] Figures 5 and 6 show that the first direction is parallel to the width direction Y, and the second direction is parallel to the length direction Z. In Figure 6, n*W1 is the sum of the dimensions of all first tabs 111 located on the same side of the first coating portion 112 along the second direction, where n is 1, and W2 represents the dimension of the first coating portion 112 along the second direction.

[0136] The electrode assembly 10 has a stacked structure, with multiple first electrodes 11 and multiple second electrodes 12 stacked together. Compared with the wound structure, it is easier to increase the amount of active material coating on the stacked structure, so that the battery cell 7 has a relatively high energy density. Moreover, in this embodiment, the ratio of the dimension of the coating portion of the positive electrode in the length direction Z to the dimension of the coating portion of the positive electrode in the width direction Y is 4 to 7, and the dimension of the coating portion of the positive electrode in the length direction Z is 300mm to 650mm. The relatively long length of the coating portion is beneficial to carrying a relatively large amount of positive electrode active material, which is beneficial to making the battery cell 7 have a relatively high energy density.

[0137] When the coating of the positive electrode is too long, the internal resistance is high, resulting in high heat generation of the positive electrode. The coating of the positive electrode includes lithium phosphate with poor conductivity, which further increases the internal resistance of the positive electrode and intensifies heat generation. As the charging rate increases, the above-mentioned heat generation phenomenon is further aggravated, which is not conducive to fast charging. In the embodiment of this application, the first electrode 11 also satisfies that n*W1 / W2 is 0.5 to 1.0, which makes the connection area between the tab and the coating relatively large and the current-carrying area of ​​the tab relatively large, which is conducive to reducing DC resistance and reducing heat generation. There are at least two first electrode terminals 31. In other words, at least two first electrode terminals 31 are connected to the tab of the first electrode 11, which can further increase the current-carrying area of ​​the first electrode terminals 31 and the tab, further reduce DC resistance and reduce heat generation, thereby improving power performance and high-temperature cycle performance, and realizing fast charging.

[0138] In this embodiment, the dimension of the coating portion of the positive electrode sheet along the length direction Z can be understood as the length of the coating portion of the positive electrode sheet. The dimension of the coating portion of the positive electrode sheet along the width direction Y can be understood as the width of the coating portion of the positive electrode sheet. When the first electrode sheet 11 is a positive electrode sheet, W2 in FIG6 represents the dimension of the coating portion of the positive electrode sheet along the length direction Z, and Y1 represents the dimension of the coating portion of the positive electrode sheet along the width direction Y.

[0139] If the ratio of the length to the width of the coating portion of the positive electrode is too small, for example, less than 4, the amount of active material loaded is relatively small, which is not conducive to improving the energy density of the battery cell. If the ratio of the length to the width of the coating portion of the positive electrode is too large, for example, greater than 7, the length of the positive electrode film is too long, the electron transport path in the length direction of the positive electrode is too long, the resistance increases, which is not conducive to improving the power performance of the battery cell.

[0140] In the embodiments of this application, the ratio of the length to the width of the coated portion of the positive electrode sheet is 4 to 7, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7 or any two of the above values, which can improve both the energy density and power performance of the battery cell.

[0141] If the length of the coating portion of the positive electrode is too small, for example, less than 300 mm, the amount of active material loaded is relatively small, which is not conducive to improving the energy density of the battery cell. If the length of the coating portion of the positive electrode is too large, for example, greater than 650 mm, the length of the positive electrode film is too long, the electron transport path in the length direction of the positive electrode is too long, the resistance increases, which is not conducive to improving the power performance of the battery cell.

[0142] The length of the coated portion of the positive electrode is 300 mm to 650 mm, for example, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 505 mm, 550 mm, 600 mm, 650 mm, or any combination of two of the above values. Optionally, the length of the coated portion of the positive electrode is 400 mm to 505 mm.

[0143] [Outer Shell Assembly]

[0144] The housing assembly 20 has a receiving space for accommodating the electrode assembly 10 and the electrolyte.

[0145] In some embodiments, the housing assembly 20 includes a housing, a first electrode terminal 31, and a second electrode terminal 32, the first electrode terminal 31 and the second electrode terminal 32 being disposed on the housing.

[0146] The outer casing can be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. In some embodiments, the outer casing can be a sealed structure or a non-sealed structure. As an example, when the outer casing is a non-sealed structure, it serves to protect the electrode assembly 10, and a sealing bag is included between the outer casing and the electrode assembly 10 to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the outer casing is a sealed structure, it is used to encapsulate the electrode assembly 10 and electrolyte components, etc.

[0147] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0148] shell

[0149] In some embodiments, the housing includes an end cap 22 and a housing 21, the housing 21 having an opening, and the end cap 22 covering the opening. The housing 21 may have one or more openings. The end cap 22 may also be provided one or more times.

[0150] The first electrode terminal 31 and the second electrode terminal 32 can be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 can be disposed on the end cover 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on the end cover 22.

[0151] On the same end cap 22, a first electrode terminal 31 and a second electrode terminal 32 can be provided simultaneously. For example, there is one end cap 22, on which the first electrode terminal 31 and the second electrode terminal 32 are provided at intervals. Or, for example, there are two end caps 22, which are arranged opposite each other, and each end cap 22 is provided with a first electrode terminal 31 and a second electrode terminal 32.

[0152] A first electrode terminal 31 and a second electrode terminal 32 are respectively provided on different end caps 22. For example, there are two end caps 22, which are arranged opposite each other. A first electrode terminal 31 is provided on one end cap 22, and a second electrode terminal 32 is provided on the other end cap 22.

[0153] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, then a cylindrical housing 21 can be selected; if the electrode assembly 10 is a cuboid structure, then a cuboid housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 are cuboid structures.

[0154] In some embodiments, the housing 21 includes two first housing portions 211, a second housing portion 212, and a third housing portion 213. The two first housing portions 211 are opposite to each other along the thickness direction X of the battery cell 7, and the second housing portions 212 and the third housing portions 213 are opposite to each other and connected by the first housing portions 211. The second housing portion 212 includes a first wall 2121 and a second wall 2122 continuously arranged along the thickness direction X, and the first wall 2121 and the second wall 2122 are welded together. The first wall 2121 and the second wall 2122 can be welded by methods such as splicing welding or laser welding, and splicing welding is optional. Since the area of ​​the second housing portion 212 is relatively small and the degree of expansion is relatively small, the weld is located on the second housing portion 212, which can reduce the risk of leakage of the battery cell 7.

[0155] When assembling the battery cell 7 into the battery device housing, the battery cell 7 is disposed inside the housing, which includes a first housing portion and a second housing portion, with the first housing portion covering the second housing portion. A second shell portion 212 is disposed opposite to the first housing portion and is positioned close to the first housing portion, while a third shell portion 213 is positioned close to the second housing portion. When assembling the battery device into the power-consuming device, the first housing portion can be vertically positioned above the second housing portion. The second shell portion 212, having a weld seam with the weld seam facing upwards, reduces the risk of leakage from the battery cell 7.

[0156] In some embodiments, the thickness of the housing 21 is from 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 is 0.3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0157] When the thickness of the housing 21 is within the above range, the housing 21 is relatively thin, which is beneficial for the rapid heat dissipation of the housing 21.

[0158] For example, the thickness of the first shell portion 211 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0159] For example, the thickness of the second shell portion 212 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0160] For example, the thickness of the third shell portion 213 is 0.1 mm to 0.5 mm, such as 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0. The thickness of the housing 21 may be 3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, 0.38mm, 0.39mm, 0.4mm, 0.41mm, 0.42mm, 0.43mm, 0.44mm, 0.45mm, 0.46mm, 0.47mm, 0.48mm, 0.49mm, 0.5mm, or any combination of two of the above values. Optionally, the thickness of the housing 21 may be from 0.3mm to 0.4mm.

[0161] First electrode terminal

[0162] In some embodiments, there are at least two first electrode terminals 31, such as two, three, or four, for example, two to four first electrode terminals 31.

[0163] In some embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z. Figure 4 shows the first electrode terminal 31 disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0164] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0165] For example, multiple first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the electron migration path and reduce the temperature rise inside the battery cell, which is beneficial to improving fast charging performance and enhancing the power performance and cycle performance of the battery cell.

[0166] For example, there are two first electrode terminals 31, one of which is located on one side of the electrode assembly 10 and the other is located on the other side of the electrode assembly 10. Alternatively, for example, there are four first electrode terminals 31, two of which are located on one side of the electrode assembly 10 and the other two are located on the other side of the electrode assembly 10.

[0167] As shown in Figure 7, in some other embodiments, at least one first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the width direction Y. This arrangement can shorten the electron migration path, which is beneficial to improving fast charging performance, and can reserve a spare area for the first electrode terminal 31 with a larger overcurrent area on the end cover.

[0168] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. Alternatively, multiple first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y.

[0169] In the embodiments of this application, the first electrode terminal 31 can be an integral structure, which can be integrally formed or connected by welding or other means to form an integral structure. The integral structure is beneficial to reduce resistance, reduce heat generation, and improve the power performance and cycle performance of the battery cell.

[0170] As shown in Figures 8 to 10, in some embodiments, the first electrode terminal 31 may include a first electrode body 311 and a first electrode protrusion 312. The first electrode body 311 is located on the side of the end cap 22 facing the electrode assembly 10, and the first electrode protrusion 312 is connected to the first electrode body 311 and protrudes toward the side opposite to the electrode assembly 10, penetrating the end cap 22. Optionally, the first electrode body 311 and the first electrode protrusion 312 are an integral structure. In other embodiments, the first electrode terminal 31 may only include the first electrode protrusion 312, which penetrates the end cap 22 and is connected to the tab portion.

[0171] Optionally, the minimum cross-sectional area of ​​the first electrode protrusion 312 parallel to the thickness direction X is the first area, and the area enclosed by the projected outer contour of the end cap 22 parallel to the thickness direction X is the second area. The ratio of the first area to the second area is 0.02 to 0.20, for example, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 or any two of the above values. In this embodiment, the thickness direction X refers to the thickness direction X of the battery cell 7. The first area refers to the minimum cross-sectional area of ​​the first electrode protrusion 312 of a single first electrode terminal 31. The first area is the bottleneck of the first electrode terminal 31. When the first area meets the above conditions, the first electrode terminal 31 has a strong current-carrying capacity, which is conducive to reducing heat generation and improving the power performance and cycle performance of the battery cell.

[0172] The first electrode protrusion 312 can have multiple cross-sectional areas of different sizes along the thickness direction X. For example, the first electrode protrusion 312 may include a first part, a second part, and a third part connected in sequence, with the second part having the smallest cross-sectional area, thus the cross-sectional area of ​​the second part is the first area. Of course, the cross-sectional area of ​​the first electrode protrusion 312 at all points along the thickness direction X can also be the same.

[0173] Optionally, the ratio of the dimension of the first electrode protrusion 312 along the thickness direction X to the dimension of the end cap 22 along the thickness direction X is 0.20 to 0.40, for example, 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 any range of two of the above values; in this embodiment, the thickness direction X refers to the thickness direction X of the battery cell 7. The dimension of the first electrode protrusion 312 refers to the dimension of the first electrode protrusion 312 of a single first electrode terminal 31 along the thickness direction X. As shown in FIG9, the dimension of the first electrode protrusion 312 along the thickness direction X can be understood as the width of the first electrode protrusion 312; the dimension of the end cap 22 along the thickness direction X can be understood as the width of the end cap 22.

[0174] When the first electrode protrusion 312 meets the above conditions, the size ratio of the first electrode protrusion 312 is relatively high, which is beneficial to improve the current carrying capacity of the first electrode terminal 31 and improve the power performance and cycle performance of the battery cell.

[0175] In some embodiments, the housing assembly 20 further includes a first conductive fastener 41, which surrounds the first electrode terminal 31 and securely connects the first electrode terminal 31 and the end cap 22. At least a portion of the first conductive fastener 41 is located on the side of the end cap 22 facing away from the electrode assembly 10. The first conductive fastener 41 can be used to connect to an external busbar assembly. Optionally, an insulating member can be provided between the first conductive fastener 41 and the end cap 22 for insulation.

[0176] 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.

[0177] Optionally, a portion of the first electrode protrusion 312 protrudes from the side of the end cap 22 away from the electrode assembly 10, and the first conductive fixing member 41 is disposed around the outside of the first electrode protrusion 312.

[0178] Optionally, the ratio of the dimension of the first conductive fixing member 41 along the thickness direction X to the dimension of the end cap 22 along the thickness direction X is 0.40 to 0.80, for example, 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 any range of two of the above values; in this embodiment, the thickness direction X refers to the thickness direction X of the battery cell 7. The dimension of the first conductive fixing member 41 refers to the dimension of a single first conductive fixing member 41 along the thickness direction X. X1 shown in FIG9 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, and 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.

[0179] When the first conductive fixing member 41 meets the above conditions, the size ratio of the first conductive fixing member 41 is relatively high, which is conducive to increasing the current flow area between the battery cell 7 and the external busbar assembly, thereby improving the current flow capacity, which is conducive to improving the current flow capacity of the battery device and improving the fast charging performance of the battery device.

[0180] Second electrode terminal

[0181] In some embodiments, there are at least two second electrode terminals 32, such as two, three, or four, for example, two to four second electrode terminals 32.

[0182] As shown in Figure 11, 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 fast charging performance.

[0183] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the width direction Y. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on both sides of the electrode assembly 10 along the width direction Y, respectively, and will not interfere with each other when electrically connected to the tab. Specifically, 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.

[0184] For example, multiple second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the width direction Y. This arrangement can further shorten the electron migration path and improve fast charging performance. In this case, the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on one side along the width direction Y, and the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on the other side along the width direction Y.

[0185] As shown in FIG12, in some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0186] For example, at least two second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the electron migration path and improve fast charging performance. In this case, the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on one side along the length direction Z, and the electrode assembly 10 has a first electrode terminal 31 and a second electrode terminal 32 disposed on the other side along the length direction Z.

[0187] Figure 12 shows that the battery cell 7 includes four electrode terminals. Specifically, there are two second electrode terminals 32, one of which is located on one side of the electrode assembly 10 along the length direction Z, and the other is located on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of which is located on one side of the electrode assembly 10, and the other is located on the other side of the electrode assembly 10.

[0188] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be disposed on both sides of the electrode assembly 10 along the length direction Z, respectively, and will not interfere with each other when electrically connected to the tabs. Specifically, 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 length direction Z, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the length direction Z.

[0189] In the embodiments of this application, the second electrode terminal 32 can be an integral structure, which can be integrally formed or connected by welding or other means to form an integral structure. The integral structure is beneficial to reduce resistance, reduce heat generation, and improve the power performance and cycle performance of the battery cell.

[0190] For example, in some embodiments, the second electrode terminal 32 has the same structural form as the first electrode terminal 31. For instance, the second electrode terminal 32 may include a second electrode body and a second electrode protrusion. The second electrode body is located on the side of the end cap 22 facing the electrode assembly 10, and the second electrode protrusion is connected to the second electrode body and protrudes towards the side opposite to the electrode assembly 10, penetrating the end cap 22. Optionally, the second electrode body and the second electrode protrusion are an integral structure. In other embodiments, the second electrode terminal 32 may only include the second electrode protrusion, which penetrates the end cap 22 and is connected to the tab portion.

[0191] In some embodiments, the housing assembly 20 further includes a second conductive fastener, which surrounds the second electrode terminal 32 and securely connects the second electrode terminal 32 and the end cap 22. The structure and related dimensions of the second conductive fastener are as described in the relevant description of the first conductive fastener 41.

[0192] The second conductive fixing member 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] Pressure relief components

[0194] As shown in Figure 13, in some embodiments, the battery cell 7 further includes a pressure relief assembly 70, which is used to discharge the internal gas of the battery cell 7 and release pressure.

[0195] Optionally, the pressure relief assembly 70 is disposed on the housing assembly 20. More optionally, the pressure relief assembly 70 is disposed on the end cap 22. When the housing assembly 20 includes two opposing end caps 22, the pressure relief assembly 70 can be one, disposed on one of the two end caps 22; alternatively, the pressure relief assembly 70 can be two, each disposed on one of the two end caps 22. In other embodiments, the pressure relief assembly 70 can also be disposed on the housing.

[0196] As an example, the internal pressure or temperature of the battery cell 7 is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell 7 reaches the predetermined threshold, the pressure relief assembly 70 performs an action or a weak structure provided in the pressure relief assembly 70 is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator 13 in the battery cell 7.

[0197] The term "actuation" as used in this application refers to the pressure relief assembly 70 being activated or undergoing a certain state, thereby releasing the internal pressure and temperature of the battery cell 7. The actions of the pressure relief assembly 70 may include, but are not limited to: movement of components within the pressure relief assembly 70 to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the pressure relief assembly 70, etc. When the pressure relief assembly 70 is actuated, the high-temperature, high-pressure substances inside the battery cell 7 are discharged outwards from the actuated portion as waste. This method enables pressure and temperature relief of the battery cell 7 under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0198] The emissions from the battery cell 7 mentioned in the embodiments of this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0199] As an example, the pressure relief assembly 70 can be integrally formed with the housing assembly 20, for example, the pressure relief assembly 70 can be integrally formed with the end cap 22 of the housing assembly 20.

[0200] As an example, the pressure relief assembly 70 can also be separately configured and connected to the housing assembly 20.

[0201] In some embodiments, when the housing assembly 20 is a non-sealed structure, the pressure relief assembly 70 can be configured as a through hole for venting gas inside the battery cell 7.

[0202] [First electrode and second electrode]

[0203] In this embodiment, when the first electrode 11 satisfies n*W1 / W2 being 0.5 to 1.0, the first electrode 11 can be either a positive electrode or a negative electrode. The tab is used to introduce or lead current into or out of the coating portion.

[0204] For example, n*W1 / W2 is a range of 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or any two of the above values. When n*W1 / W2 meets the above range, the current-carrying area of ​​the first tab 111 is relatively large, reducing heat generation and improving the power performance and cycle performance of the battery cell 7.

[0205] W1 represents the average size of the first electrode 111 along the second direction.

[0206] When the first electrode tab 111 has an irregular shape, for example, its size gradually increases along the second direction along the first direction. In this case, the size of the first electrode tab 111 along the second direction can be measured at multiple points, and the average size of the first electrode tab 111 along the second direction can be calculated. Of course, the size of the first electrode tab 111 along the second direction at all points can be the same value. In this case, the value can be used as the average size of the first electrode tab 111.

[0207] There can be one or more first electrodes 111, for example, n is 1 to 4. When there are multiple first electrodes 111, the average size of each first electrode 111 can be measured separately, and the average size of each first electrode 111 can be calculated by summing the average size of each first electrode 111 and dividing by the number of first electrodes 111.

[0208] The first tab 111 is connected to the first coating part 112. The first tab 111 includes a first end 1111 connected to the first coating part 112. When n*W1 / W2 meets the above range, it means that the cross section of the first end 1111 along the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first coating part 112 is relatively large, the current carrying capacity of the first tab 111 is strong, and it can improve the power performance and cycle performance of the battery cell 7.

[0209] Optionally, the current collection portion of the first tab 111 and the first coating portion 112 is an integral structure, which makes the internal resistance of the first electrode 11 lower and can further improve the power performance and cycle performance of the battery cell 7.

[0210] As shown in Figures 14 and 15, in some embodiments, the first electrode 11 includes one or more first tabs 111, which are disposed on at least one side of the coating portion along the width direction Y.

[0211] For example, one or more first tabs 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 tabs 111 are disposed on the same side of the first coating portion 112 along the width direction Y. This arrangement is beneficial to increasing the space occupied by the electrode assembly 10, thereby improving the energy density of the battery cell 7. In Figure 14, n is 4, and the size of each first tab 111 can be the same. W1 can represent the size of a single first tab 111, although the size of each first tab 111 can also be slightly different; W2 represents the size of the first coating portion 112 along the length direction Z. In Figure 15, n is 1, and n*W1 / W2 is 1.

[0212] As shown in Figure 16, for example, when the first electrode 11 includes a plurality of first electrode tabs 111, the plurality of first electrode tabs 111 are respectively disposed on both sides of the first coating portion 112 along the width direction Y.

[0213] Optionally, there may be at least two first tabs 111 located on the same side of the first coating portion 112 along the width direction Y, such as two, three, four, five, six, etc.; or optionally at least four. This arrangement is beneficial for the uniform distribution of electrons on the first electrode 11, and helps to improve fast charging performance.

[0214] As shown in FIG17, in some other embodiments, the first electrode 11 includes one or more first electrode tabs 111; the one or more first electrode tabs 111 are disposed on at least one side of the first coating portion 112 along the length direction Z.

[0215] For example, one or more first tabs 111 are disposed on one side of the first coating portion 112 along 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 along the length direction Z.

[0216] As shown in Figure 18, for example, when the first electrode 11 includes a plurality of first electrode tabs 111, the plurality of first electrode tabs 111 are respectively disposed on both sides of the first coating portion 112 along the length direction Z.

[0217] Optionally, a 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 transmission path of electrons in the first electrode 11, which is beneficial to improving fast charging performance.

[0218] Optionally, there may be at least two first tabs 111 located on the same side of the first coated portion 112 along the length direction Z, such as two, three, four, five, six, etc. This arrangement is beneficial for the uniform distribution of electrons in the first electrode 11 and helps to improve fast charging performance.

[0219] In this embodiment, the first tab 111 and the first electrode terminal 31 are electrically connected, either directly or indirectly as shown in FIG19. When the first tab 111 and the first electrode terminal 31 are indirectly connected, the battery cell 7 may include a first adapter 51, which is located between the first electrode terminal 31 and the first tab 111 and connects the first electrode terminal 31 and the first tab 111. When there are multiple first tabs 111 and multiple first electrode terminals 31, the multiple first tabs 111 can be divided into multiple groups, and each group of first tabs 111 is connected to one first electrode terminal 31.

[0220] For example, when the first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, and the first tab 111 is disposed on one side of the first coating portion 112 along the width direction Y, the first adapter 51 facilitates the connection between the first tab 111 and the first electrode terminal 31, and also improves the current carrying capacity of the battery cell 7. Disposing the first electrode terminal 31 on one side of the electrode assembly 10 along the length direction Z also increases the space utilization of the first electrode 11 along the width direction Y, thereby increasing the energy density of the battery cell 7.

[0221] When the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, the first adapter 51 may include a first adapter portion 511 and a second adapter portion 512. The first adapter portion 511 extends along the length direction Z and is connected to the first tab 111. The second adapter portion 512 is connected to the first adapter portion 511 and protrudes from the first adapter portion 511 along the width direction Y, and is connected to the first electrode terminal 31.

[0222] When the first tab 111 and the first electrode terminal 31 are located on the same side of the battery cell 7, the first adapter 51 may consist only of the first adapter portion 511.

[0223] In the above embodiments, the first adapter 51 can be a sheet-like structure, or of course, other structural forms.

[0224] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material, and the conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0225] In some embodiments, the battery cell 7 further includes a first conductive element 61 located between the first adapter 51 and the first tab 111. The first conductive element 61 increases the overcurrent capacity between the first tab 111 and the first adapter 51, which is beneficial for improving fast charging performance and reducing heat generation. Furthermore, electrical connections between the first tab 111 and the first adapter 51, and between the first conductive element 61 and the first adapter 51, can be achieved through welding. The presence of the first conductive element 61 significantly reduces the risk of failure caused by direct electrical connections between multiple first tabs 111 and the first adapter 51.

[0226] For example, the tab portion of the first electrode 11 is disposed on one side of the coating portion along the width direction Y; the first conductive element 61 is located between the first adapter 51 and the first tab 111, and connects the first adapter 51 and the first tab 111.

[0227] Optionally, there are at least two first tabs 111 located on the same side of the first coating portion 112, and at least two first conductive elements 61. The first conductive elements 61 and the first tabs 111 are connected in a one-to-one correspondence. At least two first conductive elements 61 are connected to the first adapter 51. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0228] As shown in Figure 20, optionally, there are at least two first tabs 111 located on the same side of the first coating portion 112, and the first conductive element 61 can be a continuous sheet structure connecting at least two first tabs 111.

[0229] As shown in Figure 21, when the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, optionally, the first conductive member 61 includes a first conductive portion 611 and a second conductive portion 612. The first conductive portion 611 extends along the length direction Z and connects the first tab 111 and the first adapter 51. The second conductive portion 612 is connected to the first conductive portion 611 and protrudes from the first conductive portion 611 along the width direction Y. The second conductive portion 612 is connected to the first adapter 51. This structural arrangement is beneficial for increasing the grouping space in the length direction Z and for improving the energy density of the battery device.

[0230] It should be noted that, in the absence of the first adapter 51 in the battery cell 7, the first tab 111 can be connected to the first electrode terminal 31 through the first conductive element 61.

[0231] For example, the first conductive element 61 has conductivity and may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above-mentioned metal elements.

[0232] In some embodiments, the thickness of the first conductive element 61 is from 0.5 mm to 2.0 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or any combination of two of the above values. When the thickness of the first conductive element 61 is within the above range, the current carrying capacity can be effectively improved, and the fast charging capability can be enhanced.

[0233] As shown in Figure 22, in some embodiments, the second electrode 12 satisfies: m*W3 / W4 is 0.5 to 1.0;

[0234] m represents the number of all tabs located on the same side of the coating section;

[0235] W3 represents the average size of the tab portion along the second direction;

[0236] W4 indicates the dimension of the coated portion along the second direction.

[0237] For example, m*W3 / W4 is 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range of any two of the above values.

[0238] When m*W3 / W4 meets the above range, the current-carrying area of ​​the second tab 121 is relatively large, which reduces heat generation and improves the power performance and cycle performance of the battery cell.

[0239] m can be 1 to 4.

[0240] W3 represents the average size of the second tab 121 along the second direction. There can be one or more second tabs 121. When there are multiple second tabs 121, the average size can be calculated by measuring the size of each second tab 121 with a micrometer.

[0241] The second tab 121 is connected to the second coating part 122. The second tab 121 includes a second end 1211 connected to the second coating part 122. When m*W3 / W4 meets the above range, it means that the cross section of the second end 1211 along the thickness direction of the second tab 121 itself is relatively large, the contact surface between the second tab 121 and the second coating part 122 is relatively large, the current carrying capacity of the second tab 121 is strong, and it can improve the power performance and cycle performance of the battery cell 7.

[0242] Optionally, the current collection portion of the second tab 121 and the second coating portion 122 is an integral structure, which makes the internal resistance of the second electrode 12 lower and can further improve the power performance and cycle performance of the battery cell 7.

[0243] Optionally, there are at least two second electrode terminals 32, and m*W3 / W4 is 0.5 to 1.0. When the second electrode 12 meets the above conditions, the connection area between the tab and the coating is relatively large, and the current-carrying area of ​​the tab is relatively large, which is beneficial to reduce DC resistance and heat generation. In other words, at least two second electrode terminals 32 are connected to the tab of the second electrode 12, which can further increase the current-carrying area of ​​the second electrode terminals 32 and the tab, further reduce DC resistance, reduce heat generation, and improve the power performance and cycle performance of the battery cell.

[0244] In some embodiments, the second electrode 12 includes one or more second tabs 121, which are disposed on at least one side of the coating portion along the width direction Y. For example, one or more second tabs 121 are disposed on one side of the second coating portion 122 along the width direction Y. In this case, it can be understood that all second tabs 121 are disposed on the same side of the second coating portion 122 along the width direction Y. Alternatively, for example, if the second electrode 12 includes multiple second tabs 121, the multiple second tabs 121 are disposed on both sides of the second coating portion 122 along the width direction Y.

[0245] Optionally, one or more second tabs 121 are respectively disposed on one side of the second coating portion 122 along the width direction Y. This arrangement is beneficial to increase the space occupied by the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0246] Optionally, there are at least two second tabs 121 located on the same side of the second coating portion 122 along the width direction Y, such as two, three, four, five, six, etc.; optionally, there are at least four. This arrangement is beneficial for the uniform distribution of electrons on the second electrode 12, which is beneficial for improving fast charging performance.

[0247] As shown in Figure 23, in some embodiments, the second electrode 12 includes one or more second tabs 121; the one or more second tabs 121 are disposed on at least one side of the second coating portion 122 along the length direction Z. For example, the one or more second tabs 121 are disposed on one side of the second coating portion 122 along the length direction Z. In this case, it can be understood that all the second tabs 121 are disposed on the same side of the second coating portion 122 along the length direction Z. Or, for example, when the second electrode 12 includes multiple second tabs 121, the multiple second tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z.

[0248] Optionally, multiple second tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z. This arrangement can shorten the transmission path of electrons in the second electrode 12, which is beneficial to improving fast charging performance.

[0249] Optionally, there are at least two second tabs 121 located on the same side of the second coating portion 122 along the length direction Z, such as two, three, four, five, six, etc.; optionally, there are at least four. This arrangement is beneficial for the uniform distribution of electrons on the second electrode 12, which is beneficial for improving fast charging performance.

[0250] In this embodiment of the application, the second tab 121 and the second electrode terminal 32 are electrically connected, either directly or indirectly. When the second tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 may include a second adapter, which is located between the second electrode terminal 32 and the second tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0251] For example, when the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the second tab 121 is disposed on one side of the second coating portion 122 along the width direction Y, the connection between the second tab 121 and the second electrode terminal 32 is more convenient through the second adapter, and the current carrying capacity of the battery cell 7 can also be improved. Disposing the second electrode terminal 32 on one side of the electrode assembly 10 along the length direction Z also increases the utilization space of the second electrode 12 along the width direction Y, thereby increasing the energy density of the battery cell 7.

[0252] When the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, the second adapter may include a first connecting part and a second connecting part. The first connecting part extends along the length direction Z and is connected to the second tab 121. The second connecting part is connected to the first connecting part and protrudes from the first connecting part along the width direction Y and is connected to the second electrode terminal 32.

[0253] When the second tab 121 and the second electrode terminal 32 are located on the same side of the battery cell 7, the second adapter may consist only of the first connecting portion.

[0254] In the above embodiments, the second adapter can be a sheet-like structure, or of course, 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-mentioned metal elements.

[0256] In some embodiments, the battery cell 7 further includes a second conductive element located between the second adapter and the second tab 121. The second conductive element increases the current-carrying capacity between the second tab 121 and the second adapter, which improves fast-charging performance and reduces heat generation. Furthermore, electrical connections can be achieved between the second tab 121 and the second adapter, and between the second conductive element and the second adapter, through welding. The presence of the second conductive element significantly reduces the risk of failure caused by direct electrical connections between multiple second tabs 121 and the second adapter.

[0257] For example, the tab portion of the second electrode 12 is disposed on one side of the coating portion along the width direction Y; the second conductive element is located between the second adapter and the second tab 121, and connects the second adapter and the second tab 121.

[0258] Optionally, there are at least two second tabs 121 located on the same side of the second coating portion 122, and the second conductive element can be a continuous sheet structure connecting at least two second tabs 121; or there are at least two second conductive elements, and the second conductive elements and the second tabs 121 are connected in a one-to-one correspondence, and at least two second conductive elements are connected to the second adapter. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0259] When the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, the second conductive member optionally includes a third conductive portion and a fourth conductive portion. The third conductive portion extends along the length direction Z and connects to the tab portion of the second electrode 12 and the second adapter. The fourth conductive portion is connected to the third conductive portion and protrudes from the third conductive portion along the width direction Y. The third conductive portion connects to the second adapter. This structural arrangement is beneficial for increasing the packing space in the length direction Z and for improving the energy density of the battery device.

[0260] For example, the second conductive element has conductivity and may include a conductive polymer or a conductive metal material, which may include copper, aluminum, or an alloy containing the aforementioned metal elements.

[0261] It should be noted that, in the absence of the second adapter in the battery cell 7, the second tab 121 can be connected to the second electrode terminal 32 through the second conductive element.

[0262] Positive electrode sheet

[0263] To illustrate this application more clearly, the coating portion of the positive electrode sheet corresponds to the positive electrode coating portion, the tab portion corresponds to the positive electrode tab, and the active material layer corresponds to the positive electrode film layer containing the positive electrode active material. The positive electrode coating portion includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector.

[0264] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0265] The upper limit voltage for charging and the lower limit voltage for discharging a single battery cell vary depending on the positive electrode active material. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the lower limit voltage for discharging can be 2.0V, or the upper limit voltage for charging can be 3.8V and the lower limit voltage for discharging can be 2.0V. Another example is when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.3V and the lower limit voltage for discharging can be 2.0V. Taking a charging upper limit voltage of 3.65V and a discharging lower limit voltage of 2.0V as an example, the state of a single battery cell will be described as follows: In this embodiment, the 100% state of charge (SOC) and the 0% state of charge (SOC) of a single battery cell are defined as follows...

[0266] The battery cell is charged at a constant current charging rate of 0.33C to the upper limit of the charging voltage, and then charged at a constant voltage to 0.05C, which corresponds to the 100% SOC state of the battery cell. The battery cell is then discharged at a constant current discharging rate of 0.33C to the cutoff voltage, which corresponds to the 0% SOC state of the battery cell.

[0267] In some embodiments, the compaction density of the positive electrode film layer at 0% state of charge (SOC) of the battery cell is 2.30 g / cm³. 3 Up to 2.70 g / cm 3 ; 2.40 g / cm³ is optional 3 Up to 2.55 g / cm 3 For example, at 0% state of charge (SOC), the compaction density of the positive electrode film layer in a single battery cell is 2.30 g / cm³. 3 2.32 g / cm 3 2.35g / cm 3 2.38g / cm 3 2.40 g / cm 3 2.42 g / cm 3 2.45g / cm 3 2.48 g / cm 3 2.50g / cm 3 2.52g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.60g / cm 32.62 g / cm 3 2.65g / cm 3 2.68g / cm 3 2.70 g / cm 3 Or a range consisting of any two of the above values.

[0268] When the compaction density of the positive electrode film is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, since the positive active material of the positive electrode film is packed more densely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation under fast charging, alleviating the problem of aggravated negative electrode side reactions caused by heat accumulation, and improving the cycle performance of the battery cell.

[0269] In some embodiments, the single-sided coating weight of the positive electrode film is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 The option is 275mg / 1540.25mm. 2 Up to 300mg / 1540.25mm 2 For example, the single-sided coating weight of the positive electrode film is 250 mg / 1540.25 mm. 2 260mg / 1540.25mm 2 270mg / 1540.25mm 2 280mg / 1540.25mm 2 290mg / 1540.25mm 2 300mg / 1540.25mm 2 310mg / 1540.25mm 2 320mg / 1540.25mm 2 330mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0270] When the single-sided coating weight of the positive electrode film is within the above range, the heat generation per unit area of ​​the positive electrode sheet will not be too large, which alleviates the problem of aggravated side reactions on the negative electrode due to heat accumulation, improves the cycle performance of the battery cell, and can increase the energy density of the battery cell.

[0271] In this embodiment, the compaction density of the positive electrode film layer at 0% State of Charge (SOC) of a single battery cell is a well-known concept in the art. This means that the positive electrode sheet is disassembled from the battery cell at 0% SOC, and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if double-sided coated, the positive electrode film layer on one side can be wiped off first) is taken, cut into small circular pieces with an area of ​​S1, weighed, and recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1, the thickness of the positive electrode film layer = thickness of the positive electrode sheet H1 - thickness of the positive current collector H0, and the compaction density of the positive electrode film layer = single-sided coating weight of the positive electrode film layer / thickness of the positive electrode film layer.

[0272] In some embodiments, the positive electrode active material comprises a lithium phosphate with an olivine structure. In other embodiments, the positive electrode active material may also comprise lithium-containing transition metal oxides, examples of which include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0273] In this embodiment, the lithium phosphate with olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium phosphate with olivine structure includes phosphate particles and a coating layer. The coating layer is coated on the surface of the phosphate particles. For example, the coating layer includes elements such as carbon, which improves the conductivity of the phosphate particles, reduces the powder resistivity of the material, and is beneficial to the migration rate of lithium ions, thereby improving the fast charging capability of the battery and reducing the heat generation of the battery cell.

[0274] In some embodiments, the phosphate particles comprise the general formula Li x1 A y1 Me a M b P 1-c X c Y zThe compound contains the following components: 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of Cl, C, and N; and Y includes one or more of O and F. Phosphate particles exhibit excellent cycle stability, which is beneficial for improving the high-temperature cycle performance of battery cells.

[0275] For example, phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process, active ions such as Li are de-intercalated and consumed in a single battery cell, resulting in different molar contents of Li in different discharged states. In the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar contents of Li represent the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar contents of Li may change after charge-discharge cycles. In the embodiments of this application, the molar contents of oxygen (O) in the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 are only theoretical values. Lattice oxygen release can cause changes in the molar contents of oxygen (O). In reality, the molar contents of oxygen (O) may fluctuate, and all of the above situations are within the scope of protection of this application.

[0276] In this application embodiment, the element content in the positive electrode active material has a meaning known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and then calcined at high temperature to remove impurities. 0.4g of the positive electrode active material is weighed, and 10ml (50% concentration) of aqua regia is added. Then it is placed on a plate at 180°C for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0277] In some embodiments, the positive electrode film layer also includes a positive electrode additive, which includes lithium element. During the charging process of the battery cell, lithium ions can be released to compensate for lithium loss, which is beneficial to improving the capacity characteristics and high-temperature cycle performance of the battery cell.

[0278] In some embodiments, the cathode additive includes at least one of lithium ferrite particles or lithium nickelate particles.

[0279] In some embodiments, the longest diameter of the cathode additive is 2 μm to 5 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any combination thereof. When cathode additives with the above particle sizes are used, the stability of the cathode additive can be effectively improved while compensating for lithium loss, which is beneficial to improving the capacity characteristics and high-temperature cycle performance of the battery cells.

[0280] In this embodiment, the positive electrode sheet is cut along its thickness direction to expose a longitudinal section of the positive electrode film. The longest diameter of the positive electrode additive particles is determined by scanning electron microscopy (SEM) of the longitudinal section of the positive electrode film. For example, the "longest diameter" of a particle refers to the longest straight line that passes through the center point of the particle and extends to the outer periphery of the particle.

[0281] In a cross-section along the thickness direction of the positive electrode film, the longest diameter of multiple, for example, 10 lithium-containing iron oxides is counted, and their average value is calculated as the average longest diameter; the shortest diameter of multiple, for example, 10 lithium-containing iron oxides is counted, and their average value is calculated as the average shortest diameter.

[0282] In some implementations, the mass percentage of the positive electrode additive is 0.2% to 2.5% based on the total mass of the positive electrode film, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or any combination thereof.

[0283] When using cathode additives within a certain mass range, lithium loss can be compensated for, which helps to improve the capacity characteristics and high-temperature cycle performance of individual battery cells.

[0284] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0285] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include at least one selected from polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, the mass content of the positive electrode binder is ≤5% based on the mass of the positive electrode film layer.

[0286] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0287] In some embodiments, the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collector is 3 to 10, for example, 3, 4, 5, 6, 7, 8, 9, 10 or any two of the above values. Optionally, the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collector is 4 to 8.

[0288] When the ratio of the thickness of the positive electrode film layer on one side to the thickness of the positive electrode current collector is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0289] In some embodiments, the thickness of the positive current collector is 12 μm to 16 μm, optionally 13 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or any combination of two of the above values.

[0290] When the thickness of the positive current collector is within the above range, the current carrying capacity of the positive current collector is excellent, which can improve the power performance of the battery cell and enable the battery cell to have a high energy density.

[0291] In the embodiments of this application, the thickness of the positive electrode film layer and the positive electrode current collector are known in the art and can be detected using equipment and methods known in the art. For example, the thickness of the positive electrode sheet can be measured with a micrometer, the film layer on the surface of the positive electrode current collector can be removed, and the thickness of the positive electrode current collector can be measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode sheet 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 sheet minus the thickness of the positive electrode current collector) / 2.

[0292] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0293] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet 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 other embodiments, the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0294] Negative electrode sheet

[0295] To more clearly illustrate this application, the coating portion of the negative electrode sheet corresponds to the negative electrode coating portion, the tab portion corresponds to the negative electrode tab, and 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 and a negative electrode film layer disposed on at least one side of the negative electrode current collector.

[0296] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0297] In some embodiments, the compaction density of the negative electrode film layer at 0% state of charge (SOC) of the battery cell is 1.30 g / cm³. 3 Up to 1.65 g / cm 3 ; 1.35g / cm³ is optional 3 Up to 1.50 g / cm 3 For example, the compaction density of the negative electrode film layer of a single battery cell at 0% charge is 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm3 1.40g / cm 3 1.45g / cm 3 1.50g / cm 3 1.55g / cm 3 1.60g / cm 3 1.65g / cm 3 Or a range consisting of any two of the above values.

[0298] When the compaction density of the negative electrode film is within the above range, it is beneficial to improve the energy density of the battery cell. Furthermore, since the negative electrode active material in the negative electrode film is packed more densely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode, thereby reducing heat generation, alleviating the problem of aggravated negative electrode side reactions caused by heat accumulation, and improving the cycle performance of the battery cell.

[0299] In the embodiments of this application, the compaction density of the negative electrode film layer of a single battery cell at 0% state of charge (SOC) has a well-known meaning in the art and can be detected using well-known equipment and methods in the art, such as the compaction density test method of the positive electrode film layer described above.

[0300] In some embodiments, the single-sided coating weight of the negative electrode film is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 The option is 125mg / 1540.25mm. 2 Up to 150mg / 1540.25mm 2 For example, the single-sided coating weight of the negative electrode film is 120 mg / 1540.25 mm. 2 122mg / 1540.25mm 2 125mg / 1540.25mm 2 128mg / 1540.25mm 2 130mg / 1540.25mm 2 132mg / 1540.25mm 2 135mg / 1540.25mm 2 137mg / 1540.25mm 2 140mg / 1540.25mm 2 145mg / 1540.25mm 2 150mg / 1540.25mm 2 155mg / 1540.25mm 2 160mg / 1540.25mm 2 165mg / 1540.25mm2 170mg / 1540.25mm 2 175mg / 1540.25mm 2 180mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0301] When the single-sided coating weight of the negative electrode film is within the above range, the heat generation per unit area of ​​the negative electrode sheet will not be too large, which alleviates the problem of aggravated negative electrode side reactions caused by heat accumulation, improves the cycle performance of the battery cell, and can also improve the energy density of the battery cell.

[0302] In the embodiments of this application, the single-sided coating weight of the negative electrode film layer has a meaning known in the art and can be detected using equipment and methods known in the art, such as the single-sided coating weight test method of the film layer described above.

[0303] In some embodiments, the negative electrode active material includes a carbon-based material, which has high cycle stability and can improve the high-temperature cycle performance of the battery cell. The positive electrode active material of this application is mainly a lithium phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. The combination of these two materials results in excellent high-temperature cycle performance of the battery cell.

[0304] Optionally, the carbon-based material includes artificial graphite, which has excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the power performance and cycle performance of the battery cell.

[0305] In some embodiments, the carbon-based material may also include natural graphite. Specifically, the carbon-based material may include artificial graphite, or it may include both artificial and natural graphite. Natural graphite has relatively good electrical conductivity, which helps to further reduce heat generation and improve the power performance and cycle performance of the battery cell.

[0306] In some embodiments, the negative electrode active material may include, in addition to the aforementioned carbon-based materials and optionally silicon-based materials, at least one of tin-based materials and lithium titanate. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloy materials. Optionally, silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.

[0307] The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adaptively modify certain testing steps / instrument parameters from the perspective of testing accuracy to obtain more accurate results. One testing method can be used for qualitative or quantitative analysis, or several testing methods can be used in combination for qualitative or quantitative determination.

[0308] For example, this application can combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis to perform X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials.

[0309] Artificial graphite and natural graphite can be distinguished by SEM cross-sectional images taken by scanning electron microscope (SEM). Natural graphite has gaps between the sheet-like structures in its SEM cross-section, while artificial graphite has a dense structure with no obvious gaps. Alternatively, they can be distinguished by XRD patterns obtained by X-ray diffraction. Natural graphite has obvious 2H and 3R phases in its XRD pattern, while artificial graphite only has the 2H phase in its XRD pattern.

[0310] In the embodiments of this application, the negative electrode film layer includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0311] When a single-layer negative electrode film is used, the negative electrode active material in the negative electrode film includes a carbon-based material. When a single-layer film is used, the volume average particle size Dv50 of the carbon-based material is 8 μm to 13 μm, optionally from 9.5 μm to 11.5 μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 8 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, or a range consisting of any two of the above values.

[0312] When the negative electrode film layer uses at least two film layers, the negative electrode active material in the negative electrode film layer includes carbon-based materials. The negative electrode film layer may include two film layers, three film layers, four film layers, or even more film layers.

[0313] 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, and the carbon-based material in the first negative electrode film layer includes artificial graphite. The second negative electrode film layer is connected to the side of the first negative electrode film layer opposite to the negative electrode current collector, and the carbon-based material in the second negative electrode film layer also includes artificial graphite. The artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer can be the same or different. When the artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer are different, it can be due to different particle sizes or different degrees of graphitization.

[0314] The interface between the first negative electrode film and the second negative electrode film can be regular or irregular, and can optionally be irregular.

[0315] The negative electrode film consists of at least two layers, and layered coating is beneficial for improving the fast charging performance of the battery cell. In particular, when there are differences between the first and second negative electrode films, it can create porosity differences in the negative electrode films, reduce the tortuosity of lithium-ion transport, improve the fast charging performance of the battery cell, and enhance the cycle performance and power performance of the battery cell.

[0316] In some embodiments, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer. Further optionally, having a larger volume average particle size Dv50 in the first negative electrode film layer than in the second negative electrode film layer is beneficial for improving the kinetic performance of the negative electrode film layer, enhancing the fast-charging performance of the battery cell, and thus improving the power performance of the battery cell.

[0317] The difference in particle size between the first and second negative electrode films can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film is usually higher, and the bottleneck of fast charging is mainly the second negative electrode film. However, in the embodiments of this application, the particle size of the second negative electrode film is relatively small, which can shorten the solid-phase transport path of lithium ions, improve fast charging performance, improve the lithium deposition problem on the surface of the negative electrode sheet, and improve the cycle performance of the battery cell.

[0318] Optionally, the carbon-based material in the first negative electrode film layer is particulate, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm, optionally 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the carbon-based material in the first negative electrode film layer is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm, or a range consisting of any two of the above values. When the first negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is 9.5 μm to 18.5 μm, and can be selected as 9.5 μm to 14.6 μm.

[0319] When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film is within the above range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material.

[0320] Optionally, the carbon-based material in the second negative electrode film is particulate, with a volume average particle size Dv50 of 7.8 μm to 14.3 μm, optionally 7.8 μm to 11.3 μm. For example, the volume average particle size Dv50 of the carbon-based material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range of any two of the above values. When the second negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is 7.8 μm to 14.3 μm, and can be selected as 7.8 μm to 11.3 μm.

[0321] When the volume average particle size Dv50 of the carbon-based material in the second negative electrode film is within the above-mentioned range, it can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material. Furthermore, the combination of the negative electrode active material in the second negative electrode film within the above-mentioned volume average particle size range with the negative electrode active material in the first negative electrode film is conducive to building a gradient porosity difference between the second negative electrode film and the first negative electrode film, reducing the tortuosity of lithium ion transport, improving the fast charging performance of the battery cell, and improving the power performance and cycle performance of the battery cell.

[0322] In the embodiments of this application, the volume average particle size Dv50 of the negative electrode active material has a well-known meaning in the art and can be detected using well-known equipment and methods in the art. For example, the negative electrode active material can be used as a sample, and the particle Dv50 and Dv10 can be tested using a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T19077-2016.

[0323] Optionally, the carbon-based material in the first negative electrode film layer may also include natural graphite.

[0324] For example, the carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

[0325] In other embodiments, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film is greater than that in the first negative electrode film. Further optionally, having a larger volume average particle size Dv50 in the second negative electrode film than in the first negative electrode film is beneficial for increasing the compaction density of the negative electrode film.

[0326] The difference in particle size between the first and second negative electrode films can improve the fast charging performance of individual battery cells.

[0327] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0328] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0329] In some embodiments, the negative electrode film layer may optionally include other additives. As examples, other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2% based on the total weight of the negative electrode film layer.

[0330] In some embodiments, the negative current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one foil made of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. A composite current collector may include a polymer base material and a metal material layer formed on at least one surface of the polymer base material. As an example, the metal material layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer base material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0331] In some embodiments, the ratio of the thickness of the single-sided negative electrode film to the thickness of the negative electrode current collector is 8 to 14, for example, 8, 9, 10, 11, 12, 13, 14 or any two of the above values. Optionally, the ratio of the thickness of the single-sided negative electrode film to the thickness of the negative electrode current collector is 10 to 12.

[0332] When the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collector is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0333] In some embodiments, the thickness of the negative current collector is 5 μm to 10 μm, optionally 6 μm to 8 μm. Exemplarily, the thickness of the negative current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any range of two of the above values.

[0334] 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, which improves the power performance of the battery cell and enables the battery cell to have a high energy density.

[0335] In the embodiments of this application, the thickness of the negative electrode current collector has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the film layer on the surface of the negative electrode current collector can be washed away with a solvent, and the thickness of the negative electrode current collector can be measured with a micrometer.

[0336] The negative electrode film is typically formed by coating a negative electrode slurry onto the negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0337] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet 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 sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0338] Isolation component

[0339] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0340] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0341] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0342] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0343] electrolyte

[0344] In some implementations, the battery cell also includes an electrolyte.

[0345] During the charging and discharging process of a single battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive and negative electrode plates, and the electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0346] In this embodiment, the organic solvent includes carbonate solvents and chain carboxylic acid ester solvents, and the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature. Exemplarily, the electrolyte conductivity 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 any range of two of the above values.

[0347] 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, reducing the degree of side reactions on the negative electrode side, and improving the power performance and cycle performance of the battery cell.

[0348] In the embodiments of this application, the conductivity of the electrolyte at room temperature, such as 25°C, is the ionic conductivity, which can be detected using equipment and methods known in the art, such as by referring to industry standard HG-T 4067-2015.

[0349] Electrolytes consist of organic solvents and electrolyte salts. The types of organic solvents and electrolyte salts are not specifically limited and can be selected according to actual needs.

[0350] In some embodiments, the organic solvent also includes carbonate solvents.

[0351] Optionally, the carbonate solvent in the electrolyte comprises 10% to 80% by mass. For example, the carbonate solvent in the organic solvent comprises 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, or any combination of two of the above values ​​by mass. The carbonate solvent at the above mass contents can further improve the conductivity of the electrolyte at room temperature, which is beneficial for lithium-ion migration; moreover, the mass content of the carbonate solvent is not too high, which can reduce high-temperature gas generation and improve high-temperature cycling performance.

[0352] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. More preferably, the carbonate solvent includes one or more of dimethyl carbonate and methyl ethyl carbonate. The combined use of the above-mentioned carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte at room temperature, which is beneficial for lithium-ion migration and improves the power performance of the battery cell.

[0353] For example, the carbonate solvent includes one or more of dimethyl carbonate and ethyl methyl carbonate, and the mass content of the carbonate solvent is 10% to 80%.

[0354] In some embodiments, the organic solvent includes chain carboxylic acid ester solvents.

[0355] Optionally, the chain carboxylic acid ester solvent has a mass content of 5% to 30% in the electrolyte. For example, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30%, or any combination of two of the above values.

[0356] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively low, which is conducive to the migration of lithium ions; moreover, the mass content of the chain carboxylic acid ester solvent will not be too high, which can reduce the amount of gas generated at high temperature and improve the high temperature cycling performance.

[0357] In some embodiments, the chain carboxylic acid ester solvent includes compounds represented by Formula I.

[0358] In formula I,

[0359] R1 includes a hydrogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group.

[0360] R2 includes C1 to C5 alkyl or C1 to C5 haloalkyl.

[0361] The aforementioned chain-like carboxylic acid ester solvents have high conductivity, which is beneficial for improving the fast charging capability of battery cells and enhancing their power performance.

[0362] Optionally, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0363] Optionally, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. More optionally, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0364] In the above embodiments, the halogenated alkyl group includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl groups, and optionally, the halogenated alkyl group includes fluoroalkyl.

[0365] For example, the chain carboxylic acid ester solvent includes one or more compounds of formula I-1 to formula I-8.

[0366] With a chain carboxylic acid ester solvent content of 5% to 30%, the area per unit capacity of the pressure relief assembly is 1.2 mm². 2 / Ah to 1.8mm 2 / Ah.

[0367] For example, the area per unit capacity of the pressure relief assembly is 1.2 mm². 2 / Ah, 1.3mm 2 / Ah, 1.4mm 2 / Ah, 1.5mm 2 / Ah, 1.6mm 2 / Ah, 1.7mm 2 / Ah, 1.8mm 2 / Ah or a range consisting of any two of the above values.

[0368] As the capacity of a single battery cell increases, the amount of electrolyte injected into the cell also increases, leading to an increase in the amount of chain-like carboxylic acid ester solvents added, which in turn increases the risk and potential amount of gas generation. However, in the embodiments of this application, the area per unit capacity of the pressure relief component is greater than 1.2 mm². 2 / Ah, enabling rapid gas release and improving the reliability of individual battery cells; moreover, the area per unit capacity of the pressure relief component is less than or equal to 1.8mm². 2 / Ah, which makes the pressure relief component occupy a relatively small area, can take into account the area occupied by the electrode terminals, and makes the overcurrent capacity relatively high; therefore, when the battery cell of the present application meets the above conditions, it can take into account both the reliability of the battery cell and the overcurrent capacity, and improve the power performance of the battery cell.

[0369] In some embodiments, the electrolyte salt includes a lithium salt, which includes one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate (LiPF6). The aforementioned lithium salt system is relatively stable and not easily decomposed. Lithium salts are beneficial for improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cell, and improving the power performance of the battery cell. The fluorosulfonyl imide salt includes monofluorosulfonyl imide salts, difluorosulfonyl imide salts, etc., and difluorosulfonyl imide salts are optional.

[0370] In some embodiments, the mass content of lithium salt is 13% to 20% based on the mass of the electrolyte, for example, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination of two of the above values. When the mass content of lithium salt is within the above range, the lithium salt helps to improve the conductivity of the electrolyte and improve the power performance of the battery cell.

[0371] Optionally, based on the mass of the electrolyte, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is between 1.2 and 2.0. When the lithium salt meets the above conditions, the system is relatively stable and not easily decomposed. The lithium salt is beneficial for improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cells, and improving the power performance of the battery cells. When the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide meets the above range, it can also reduce the content of hydrofluoric acid, mitigate the side reactions at the negative electrode interface, and help improve the high-temperature cycle life of the battery cells.

[0372] For example, the mass content of lithium hexafluorophosphate and the mass content of lithium difluorosulfonylimide are 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or any two of the above values.

[0373] For example, the mass content of lithium bisfluorosulfonylimide is 1% to 15%, optionally 3% to 12%, depending on the mass of the electrolyte.

[0374] For example, based on the mass of the electrolyte, the mass content of lithium difluorosulfonylimide is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination of two of the above values. When the mass content of lithium difluorosulfonylimide is within the above range, the content of hydrofluoric acid can be reduced, the side reactions at the negative electrode interface can be mitigated, the gas generation during high-temperature storage can be reduced, and the high-temperature cycle life of the battery cell can be improved.

[0375] In some embodiments, the electrolyte further includes additives, which may include one or more of carbonate additives and sulfur-containing additives, optionally at least two. These additives can improve the SEI film performance on the positive and / or negative electrode sides, thereby enhancing the fast-charging performance of the battery cell and improving high-temperature cycle performance.

[0376] In some embodiments, the additive content in the electrolyte is 0.5% to 6% by mass. Exemplarily, the additive content in the electrolyte is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6%, or a range of any two of the above values.

[0377] The aforementioned organic solvents, such as chain carboxylic acid esters, may decompose and produce acid at high temperatures, corroding the SEI film on the surface of the negative electrode. However, the additives can form a dense and uniformly thick film on the negative electrode side, effectively repairing the SEI film, providing excellent protection for the negative electrode active material, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycle performance.

[0378] For example, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Optionally, the carbonate additive includes vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Vinylene carbonate (VC) can form a dense and uniformly thick SEI film on the negative electrode side, effectively repairing the SEI film and providing excellent protection for the negative electrode active material, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0379] Fluorinated ethylene carbonate (FEC) can form a SEI film with relatively low impedance on the negative electrode side, effectively repairing the SEI film and providing excellent protection for the negative electrode active material, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0380] For example, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butenyl sulfite BS, 1,3-propanesulfonate lactone PS, vinyl sulfite ES, and methylene disulfonate MMDS, with 1,3-propanesulfonate lactone PS being optional. The sulfur-containing additive can effectively repair the SEI film, providing excellent protection for the negative electrode active material and contributing to improved power performance and high-temperature cycle performance of the battery cell.

[0381] For example, the additives include one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propanesulfonyl lactone.

[0382] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is from 0.5% to 3.0%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, 3.0%, or any combination of two of the above values. When the mass content of vinylene carbonate (VC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the power performance and high-temperature cycle performance of the battery cell.

[0383] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is from 0.2% to 2.5%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, or any combination of two of the above values. When the mass content of fluoroethylene carbonate (FEC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the power performance and high-temperature cycle performance of the battery cell.

[0384] Optionally, the mass content of 1,3-propanesulfonyl lactone (PS) in the electrolyte is from 0.5% to 2.5%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, or any combination of two of the above values. When the mass content of 1,3-propanesulfonyl lactone (PS) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and help improve the power performance and high-temperature cycle performance of the battery cell.

[0385] In the embodiments of this application, the types and contents of inorganic components / lithium salts in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method according to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a battery that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection by ion chromatography analysis method.

[0386] In the embodiments of this application, the types and contents of organic components in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0387] In this embodiment, after quantitative and qualitative detection of each component in the electrolyte, the components are classified. Chain-like carboxylic acid ester solvents and carbonate solvents (e.g., ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate) are considered as components of the organic solvent. The mass content of each component is calculated based on the electrolyte mass as 100%.

[0388] Carbonate additives (such as vinylene carbonate and fluoroethylene carbonate) and sulfur-containing additives are used as additives in the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0389] In some embodiments, the volumetric energy density of the battery cell is between 375 Wh / L and 450 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 375 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 450 Wh / L, or a range of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0390] In the embodiments of this application, the volumetric energy density of a single battery cell has a meaning known in the art and can be detected using equipment and methods known in the art. For example, the following description uses a battery charging upper limit voltage of 3.65V and a battery discharging cutoff voltage of 2.0V as an example.

[0391] Place the battery cell at 25°C and charge it to 3.65V with a constant current of 0.33C, then charge it to 0.05C with a constant voltage, and discharge it to 2.0V with a constant current of 0.33C. Record the discharge capacity A0 at this point, in Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing). Calculate the volume of the battery cell V0, in L. The volumetric energy density of the battery cell VED = (A0 × discharge plateau voltage) / V0, in Wh / L.

[0392] Example

[0393] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0394] Example 1

[0395] 1. Preparation of positive electrode sheet

[0396] The positive electrode includes a positive current collector and positive electrode film layers disposed on both sides of the positive current collector. The positive current collector is an aluminum foil with a thickness of 13 μm. The thickness ratio of the positive electrode film layer on one side to the thickness of the positive current collector is 5.5.

[0397] The positive electrode film layer comprises lithium phosphate, positive electrode additive, binder polyvinylidene fluoride (PVDF) and conductive agent acetylene black in a mass ratio of 95.5:1.5:2:1. The positive electrode film layer is formed by uniformly coating the positive electrode slurry (solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collector, and then drying and cold pressing it.

[0398] Lithium-containing phosphates include lithium iron phosphate.

[0399] The cathode additive includes lithium ferrite, and the mass content of the cathode additive in the cathode film is 1.5%.

[0400] The single-sided coating weight of the positive electrode film is 282 mg / 1540.25 mm. 2 .

[0401] The length of the positive electrode film is 502 mm, and the ratio of the length to the width of the positive electrode film is 5.4.

[0402] 2. Preparation of negative electrode sheet

[0403] The negative electrode includes a negative current collector and negative electrode film layers disposed on both sides of the negative current collector. The negative current collector is a copper foil with a thickness of 6μm, and the ratio of the thickness of the negative electrode film layer on one side to that of the negative current collector is 10.3.

[0404] The negative electrode film is formed by uniformly coating the negative electrode slurry (with deionized water as the solvent) onto the surface of the negative electrode current collector, followed by drying and cold pressing.

[0405] The single-sided coating weight of the negative electrode film is 134 mg / 1540.25 mm. 2 .

[0406] 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 located on the surface of the negative electrode current collector, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0407] The first negative electrode film layer includes carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:1:1.5:1. The carbon-based material of the first negative electrode film layer includes artificial graphite, and the volume average particle size of the carbon-based material is 11.3 μm.

[0408] The second negative electrode film layer includes carbon-based materials in a mass ratio of 96.5:1:1.5:1, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The carbon-based materials of the second negative electrode film layer include artificial graphite, and the volume average particle size of the carbon-based materials is 9.5 μm.

[0409] 3. Separating membrane

[0410] The separator includes a base membrane, which is a 7μm polyethylene film layer with a porosity of 42%.

[0411] 4. Preparation of electrolyte

[0412] The electrolyte consists of an organic solvent, a lithium salt, and additives. The components of the organic solvent are mixed, and then the lithium salt and additives are added to prepare the electrolyte.

[0413] The organic solvents include 10% chain carboxylic acid ester solvents (ethyl acetate) and 70% carbonate solvents (10% dimethyl carbonate DMC, 25% ethyl methyl carbonate EMC, 10% diethyl carbonate DEC, and 25% ethylene carbonate EC). The mass content of each component in the organic solvents is calculated based on the mass of the electrolyte.

[0414] Based on the quality of the electrolyte, the additives include 2.5% vinylene carbonate (VC), 1% fluoroethylene carbonate (FEC), and 2.5% 1,3-propanesulfonyl lactone (PS).

[0415] The lithium salt comprises 8.5% lithium hexafluorophosphate (LiPF6) and 5.5% lithium difluorosulfonylimide.

[0416] The electrolyte has a conductivity of 12 mS / cm at room temperature.

[0417] 5. Preparation of battery cells

[0418] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, resulting in a stacked electrode assembly. This assembly is then placed in a housing, dried, and injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained. The compaction density of the positive electrode film layer at 0% SOC is 2.55 g / cm³. 3 The compaction density of the negative electrode film at 0% SOC is 1.4 g / cm³. 3 .

[0419] in,

[0420] The housing includes an end cap and a casing. The casing is 0.35 mm thick and made of aluminum. The end cap also has a pressure relief assembly, a positive terminal, and a negative terminal. The pressure relief assembly has a unit capacity area of ​​2 mm². 2 / Ah.

[0421] Comparative Example 1-1 and Comparative Example 1-2

[0422] Battery cells were prepared using a method similar to that of Example 1. The difference between Comparative Example 1-1 and Example 2 is that the number of positive terminals was adjusted.

[0423] Examples 1-1 and 1-2

[0424] Battery cells were prepared using a method similar to that of Example 1, except that the size of the positive terminal was adjusted.

[0425] Examples 1-3 to Examples 1-6

[0426] Battery cells were prepared using a method similar to that of Example 1, except that the number and / or placement of the positive electrode tabs were adjusted.

[0427] Performance testing

[0428] 1. Power density test of individual battery cells

[0429] At 25℃, the battery cell was charged to 3.65V with a constant current of 0.33C, left to stand for 10 minutes, charged to 3.65V with a constant current of 0.33C, left to stand for 30 minutes, and discharged to 2.0V with a constant current of 0.33C. The discharge capacity C0 and discharge energy E0 at this time were recorded.

[0430] Charge the battery cell at a constant current of 0.33C to the cutoff voltage of 3.65V and let it rest for 10 minutes; discharge it at a constant current of 0.33C0 for 90 minutes to adjust the battery cell to 50% SOC, and record the voltage U1 at this time. Then discharge it with a pulse of 4C0 for 10 seconds and record the voltage after discharge as U2. The corresponding DC resistance R = (U1-U2) / 4C0, the power W = discharge cutoff voltage * (U1-discharge cutoff voltage) / R, and the power density P = W / E0.

[0431] 2. High-temperature cycle performance of individual battery cells

[0432] At 45℃, the battery cell is charged to 3.65V at a constant current of 0.5C, then charged to 0.05C at a constant voltage, left to stand for 10 minutes, and then discharged to 2.0V at a constant current of 1C. This constitutes one charge-discharge cycle, and the discharge capacity of the first cycle is recorded. After standing for 10 minutes, the above charge-discharge cycle is repeated until the discharge capacity of the battery cell decreases to 80% of the discharge capacity of the first cycle, at which point the test is stopped, and the number of cycles is recorded.

[0433] The test results are shown in Table 1.

[0434] Table 1

[0435] In Table 1, in the embodiment where the positive terminal is output from the short side and the positive electrode tab is output from the long side, the battery cell also includes a first conductive element with a thickness of 1.0 mm.

[0436] S1 represents the ratio of the first area to the second area. The first area is the projection surface of the first electrode protrusion of the positive terminal parallel to the thickness direction, and the second area is the projection surface of the end cap parallel to the thickness direction.

[0437] S2 represents the ratio of the dimension of the first electrode protrusion of the positive terminal along the thickness direction of the battery cell to the dimension of the end cap along the thickness direction of the battery cell; for example, in Figure 9, the dimension of the end cap along the thickness direction of the battery cell can be considered as the width of the end cap; the dimension of the first electrode protrusion along the thickness direction of the battery cell can be considered as the width of the first electrode protrusion.

[0438] S3 represents the ratio of the dimension of the first conductive fastener along the thickness direction of the battery cell to the dimension of the end cap along the thickness direction of the battery cell; for example, in Figure 9, the dimension of the first conductive fastener along the thickness direction of the battery cell is X1, which can be considered as the width of the first conductive fastener; the dimension of the end cap along the thickness direction of the battery cell can be considered as the width of the end cap X2.

[0439] The number of positive terminals refers to the total number of positive terminals in the same battery cell.

[0440] The positive terminal is located on the short side, meaning that the positive terminal is located on at least one side of the electrode assembly along its length.

[0441] "Positive terminals are located on the same side of the short side" means that all positive terminals are located on the same side of the electrode assembly along its length.

[0442] "Positive terminals located on both sides of the short side" means that multiple positive terminals are located on both sides of the electrode assembly along its length.

[0443] The positive terminal has two outlets on the short side, one on each side, meaning there are two positive terminals, located on opposite sides of the electrode assembly along its length, as shown in Figure 12.

[0444] "Positive terminal with long side out" means that the positive terminal is located on at least one side of the electrode assembly along the width direction.

[0445] The number of positive electrode tabs refers to the total number of positive electrode tabs in the same positive electrode plate.

[0446] The term "positive electrode tab on the short side" means that the positive electrode tab is located on at least one side of the positive electrode current collector along its length.

[0447] "Positive electrode tabs are located on the same side of the short side" means that all positive electrode tabs are located on the same side of the positive electrode current collector along the length direction, as shown in Figure 17.

[0448] "Positive electrode tabs are located on both sides of the short side" means that multiple positive electrode tabs are located on both sides of the positive electrode current collector along the length direction.

[0449] The positive electrode tabs are located on both sides of the short side, one on each side, meaning there are two positive electrode tabs, located on both sides of the positive current collector along the length direction, as shown in Figure 18.

[0450] "Positive electrode tab with long side out" means that the positive electrode tab is located on at least one side of the positive electrode current collector along the width direction;

[0451] "Positive electrode tabs are located on the same side along the width of the positive electrode current collector" means that all positive electrode tabs are located on the same side along the width of the positive electrode current collector; as shown in Figure 15.

[0452] n*W1 / W2 refers to the ratio of the dimensions of all positive electrode tabs along the second direction on the same side of the positive electrode current collector to the dimensions of the positive electrode current collector along the second direction.

[0453] As can be seen from the comparison of the comparative examples and the embodiments, the number of positive terminals in the embodiments of this application is at least two, and the size ratio of the positive electrode tab is within an appropriate range, for example, n*W1 / W2 is 0.5 to 1, which is beneficial to simultaneously improve the volumetric energy density and power performance of the battery cell as well as its high-temperature cycle performance.

[0454] As the number of positive terminals increases, for example to four, the current carrying capacity increases accordingly. However, due to the limited assembly space on the end cap, the number of positive terminals cannot be increased indefinitely.

[0455] In Comparative Example 1-1, although the size of the positive electrode tab is relatively large, the number of positive terminals is too small, which may lead to poor overcurrent capacity, large DC resistance of the battery cell, and high internal temperature rise, which is detrimental to the power density and high temperature cycle performance of the battery cell.

[0456] Compared to Comparative Example 1-1, Examples 1, 1-1 to 1-6 have two positive terminals, resulting in superior overcurrent capability, lower DC resistance of the battery cells, and lower temperature rise, thus improving the power density and high-temperature cycling performance of the battery cells. The positive terminals can be located on the same side or separately on opposite sides of the battery cell; as long as the number of positive terminals meets the requirements, both methods can improve the power density and high-temperature cycling performance of the battery cells.

[0457] In Comparative Examples 1-2, although there are two positive terminals on the same side of the battery cell, the positive electrode tabs are located on the same side, resulting in a small proportion of the positive electrode tab size. This may lead to poor overcurrent capacity, high DC resistance of the battery cell, reduced power density, and high internal temperature rise of the battery cell, which deteriorates high-temperature cycling performance.

[0458] Compared to Comparative Examples 1-2, Examples 1-6 have a higher positive electrode tab size ratio, lower DC resistance of the battery cell, and lower temperature rise of the battery cell, which can improve the power density and high-temperature cycle performance of the battery cell.

[0459] Compared to Example 1, Examples 1-1 and 1-2 adjust the minimum cross-sectional area ratio of the first electrode protrusion. The higher the minimum cross-sectional area ratio, the stronger the current carrying capacity and the less the temperature rise of the battery cell, which is beneficial to improving the power density and high-temperature cycle performance of the battery cell.

[0460] Compared to Examples 1-5, the positive electrode tab of Example 1- has an increased size ratio. The higher the size ratio, the better the current carrying capacity and the smaller the temperature rise, which is beneficial to improving the power density and high-temperature cycle performance of the battery cell.

[0461] Example 2-1

[0462] Battery cells were prepared using a method similar to that in Example 1, except that the single-sided coating weight and compaction density of the positive and negative electrode films were adjusted.

[0463] Examples 2-2 and 2-3

[0464] Battery cells were prepared using a method similar to that of Example 1, except that the size of the positive electrode film was adjusted.

[0465] Comparative Example 2-1 and Comparative Example 2-2

[0466] Battery cells were prepared using a method similar to that in Example 1. The difference from Example 1 was that the size of the positive electrode film was adjusted. Corresponding to the adjustment of the size of the positive electrode film, the size of the negative electrode film was also adjusted. The length of the negative electrode film was 5 mm greater than the length of the positive electrode film, and the width of the negative electrode film was 5 mm greater than the width of the positive electrode film.

[0467] The test results are shown in Table 2.

[0468] Table 2

[0469] The positive electrode film of Comparative Example 2-1 is shorter in length and can support less active material, resulting in a lower energy density of the battery cell.

[0470] The positive electrode film in Comparative Example 2-2 is longer and has a larger aspect ratio, which makes the electron transport path in the positive electrode longer, potentially resulting in excessive resistance and deteriorating the power performance and high-temperature cycling performance of the battery cell.

[0471] As can be seen from Examples 2-1 to 2-3, when the size of the positive electrode film is within an appropriate range, or when the single-sided coating weight and compaction density of the film are within an appropriate range, it is possible to improve the volumetric energy density, power performance and high-temperature cycle performance of the battery cell.

[0472] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the implementation of the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the implementation of the present application.

Claims

1. A single battery cell, comprising: The housing assembly includes a housing, a first electrode terminal, and a second electrode terminal, wherein the first electrode terminal and the second electrode terminal are disposed on the housing; An electrode assembly, located within the housing, includes multiple first electrode plates and multiple second electrode plates. The first and second electrode plates are stacked along the thickness direction of the battery cell. Each first and second electrode plate includes a coating portion and a tab portion. The coating portion is provided with an active material layer, and the tab portion is disposed on at least one side of the coating portion along a first direction, which is a direction parallel to the length or width direction of the battery cell. Wherein, one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode. The active material layer of the positive electrode includes lithium phosphate. The ratio of the dimension of the coating portion of the positive electrode along the length direction to the dimension of the coating portion of the positive electrode along the width direction is 4 to 7. The dimension of the coating portion of the positive electrode along the length direction is 300 mm to 650 mm. The first electrode terminal is at least two, and the at least two first electrode terminals are electrically connected to the tab portion of the first electrode plate, and the second electrode terminal is electrically connected to the tab portion of the second electrode plate; The first electrode satisfies the following condition: n*W1 / W2 is between 0.5 and 1.0; n represents the number of all tabs located on the same side of the coating portion; W1 represents the average dimension of the tab portion along the second direction, where the second direction, the first direction, and the thickness direction are perpendicular to each other. W2 represents the dimension of the coated portion along the second direction.

2. The battery cell according to claim 1, wherein, At least two of the first electrode terminals are disposed on at least one side of the electrode assembly along the length direction.

3. The battery cell according to claim 1 or 2, wherein, The first electrode terminal has two to four.

4. The battery cell according to any one of claims 1 to 3, wherein, The housing includes a shell and an end cap. The shell houses the electrode assembly. The shell includes an opening. The end cap closes to the opening. The first electrode terminal is disposed on the end cap. The first electrode terminal includes a first electrode body and a first electrode protrusion. The first electrode body is located on the side of the end cap facing the electrode assembly. The first electrode protrusion is connected to the first electrode body and protrudes toward the side away from the electrode assembly, and penetrates the end cap.

5. The battery cell according to claim 4, wherein, The minimum cross-sectional area of ​​the first electrode protrusion parallel to the thickness direction of the battery cell is the first area; the area enclosed by the projected outer contour of the end cap parallel to the thickness direction of the battery cell is the second area; and the ratio of the first area to the second area is 0.02 to 0.20; and / or The ratio of the dimension of the first electrode protrusion along the thickness direction of the battery cell to the dimension of the end cap along the thickness direction is 0.20 to 0.

40.

6. The battery cell according to claim 4 or 5, wherein, The first electrode body and the first electrode protrusion are an integral structure.

7. The battery cell according to any one of claims 4 to 6, wherein, The housing assembly further includes a first conductive fastener, at least a portion of which is located on the side of the end cap away from the electrode assembly. The first conductive fastener is disposed around the first electrode terminal and is fixedly connected to the first electrode terminal and the end cap.

8. The battery cell according to claim 7, wherein, The ratio of the dimension of the first conductive fastener along the thickness direction of the battery cell to the dimension of the end cap along the thickness direction of the battery cell is 0.40 to 0.

80.

9. The battery cell according to any one of claims 1 to 8, wherein, The first electrode has at least two tabs; At least two tabs of the first electrode are disposed on the same side of the coated portion along the length direction; or At least two tabs of the first electrode are respectively disposed on both sides of the coating portion along the length direction.

10. The battery cell according to any one of claims 1 to 9, wherein, The tab portion of the first electrode is disposed on at least one side of the coated portion along the width direction. In the first electrode, there is one tab located on the same side of the coated portion, and n*W1 / W2 is 1.0; or The first electrode has at least two tabs located on the same side of the coated portion.

11. The battery cell according to claim 10, wherein, The first electrode has two to four tabs located on the same side as the coating portion.

12. The battery cell according to any one of claims 1 to 11, wherein the battery cell further comprises a first adapter, the first adapter being located between the first electrode terminal and the tab portion of the first electrode sheet, and connecting the first electrode terminal and the tab portion of the first electrode sheet.

13. The battery cell according to claim 12, wherein, At least two of the first electrode terminals are disposed on at least one side of the electrode assembly along the length direction, and the tab portion of the first electrode is disposed on at least one side of the coating portion along the width direction.

14. The battery cell according to claim 13, wherein, The first adapter includes: A first adapter portion extends along the length direction, and the first adapter portion connects to the tab portion of the first electrode plate; and The second adapter is connected to the first adapter and protrudes from the first adapter along the width direction, and is connected to the first electrode terminal.

15. The battery cell according to any one of claims 12 to 14, wherein the battery cell further comprises a first conductive element, the first conductive element being located between the first adapter and the tab portion of the first electrode, and connecting the first adapter and the tab portion of the first electrode.

16. The battery cell according to claim 15, wherein, The first electrode sheet has at least two tabs located on the same side of the coated portion; The first conductive element is a continuous sheet structure, and the first conductive element is connected to the at least two tabs; or There are at least two first conductive elements, and each first conductive element is connected to a corresponding tab.

17. The battery cell according to claim 15 or 16, wherein, The first conductive element includes: A first conductive portion extends along the length direction, and the first conductive portion connects the tab portion of the first electrode and the first adapter; and The second conductive part is connected to the first conductive part and protrudes from the first conductive part along the width direction. The second conductive part is connected to the second adapter part of the first adapter.

18. The battery cell according to any one of claims 15 to 17, wherein, The thickness of the first conductive element is 0.5 mm to 2.0 mm.

19. The battery cell according to any one of claims 1 to 18, wherein, The second electrode terminal has at least two; The second electrode satisfies the following condition: m*W3 / W4 is 0.5 to 1.0; m represents the number of all tabs located on the same side of the coating portion; W3 represents the average dimension of the tab portion along the second direction; W4 represents the dimension of the coated portion along the second direction.

20. The battery cell according to any one of claims 1 to 19, wherein, The housing includes a shell and an end cap. The shell includes an opening, and the end cap closes to the opening. The shell houses the electrode assembly. The shell includes: Two first shell portions opposite each other along the thickness direction; and A second shell portion and a third shell portion opposite to each other, the second shell portion and the third shell portion being connected through the first shell portion, the second shell portion including a first wall and a second wall continuously disposed along the thickness direction, the first wall and the second wall being welded.

21. The battery cell according to claim 20, wherein, The thickness of the shell is 0.1 mm to 0.5 mm.

22. The battery cell according to any one of claims 1 to 21, further comprising a pressure relief assembly, the pressure relief assembly being disposed on the housing assembly, the pressure relief assembly having an area per unit capacity of 1.2 mm². 2 / Ah to 1.8mm 2 / Ah.

23. The battery cell according to claim 22, wherein, There are two pressure relief components, which are respectively disposed on both sides of the outer shell component.

24. The battery cell according to any one of claims 1 to 23, wherein, The lithium-containing phosphate includes lithium iron phosphate.

25. The battery cell according to any one of claims 1 to 24, wherein, The single-sided coating weight of the active material layer of the positive electrode sheet is 250 mg / 1540.25 mm. 2 Up to 330mg / 1540.25mm 2 .

26. The battery cell according to claim 25, wherein, The single-sided coating weight of the active material layer is 275 mg / 1540.25 mm. 2 Up to 300mg / 1540.25mm 2 .

27. The battery cell according to any one of claims 1 to 26, wherein, When the battery cell is at 0% charge, the compaction density of the active material layer of the positive electrode is 2.30 g / cm³. 3 Up to 2.70 g / cm 3 .

28. The battery cell according to claim 27, wherein, When the battery cell is at 0% charge, the compaction density of the active material layer of the positive electrode is 2.40 g / cm³. 3 Up to 2.55 g / cm 3 .

29. The battery cell according to any one of claims 1 to 28, wherein, The coating portion of the negative electrode sheet includes a negative electrode current collector and an active material layer disposed on at least one side of the negative electrode current collector. The active material layer includes a negative electrode active material, which includes a carbon-based material, and the carbon-based material includes artificial graphite.

30. The battery cell according to claim 29, wherein, The active material layer of the negative electrode sheet includes: A first negative electrode film layer is disposed on the surface of the negative electrode current collector; and The second negative electrode film layer is connected to the side of the first negative electrode film layer that is away from the negative electrode current collector. Wherein, the volume average particle size Dv50 of the carbon-based material 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.

31. The battery cell according to claim 30, wherein, The volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is 9.5 μm to 18.5 μm; and / or The volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is 7.8 μm to 14.3 μm.

32. The battery cell according to claim 30 or 31, wherein, The carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

33. The battery cell according to any one of claims 29 to 32, wherein, The single-sided coating weight of the active material layer of the negative electrode sheet is 120 mg / 1540.25 mm. 2 Up to 180mg / 1540.25mm 2 .

34. The battery cell according to claim 33, wherein, The single-sided coating weight of the active material layer of the negative electrode sheet is 125 mg / 1540.25 mm. 2 Up to 150mg / 1540.25mm 2 .

35. The battery cell according to any one of claims 29 to 34, wherein, When the battery cell is at 0% charge, the compaction density of the active material layer of the negative electrode is 1.30 g / cm³. 3 Up to 1.65 g / cm 3 .

36. The battery cell according to claim 35, wherein, When the battery cell is at 0% charge, the compaction density of the active material layer of the negative electrode is 1.35 g / cm³. 3 Up to 1.50 g / cm 3 .

37. The battery cell according to any one of claims 1 to 36, wherein the battery cell further comprises an electrolyte comprising a chain-like carboxylic acid ester solvent, and the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature.

38. The battery cell according to claim 37, wherein, Based on the mass of the electrolyte, the mass content of the chain carboxylic acid ester solvent is 5% to 30%.

39. The battery cell according to claim 37 or 38, wherein, The electrolyte also includes a lithium salt, which includes one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate.

40. The battery cell according to claim 39, wherein, Based on the mass of the electrolyte, the lithium salt has a mass content of 13% to 20%.

41. The battery cell according to claim 39 or 40, wherein, Based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium difluorosulfonylimide is 1.2 to 2.

0.

42. The battery cell according to any one of claims 37 to 41, wherein, The electrolyte also includes additives, which include one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone.

43. A battery device comprising a battery cell as claimed in any one of claims 1 to 42.

44. An electrical device comprising the battery device as described in claim 43.

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