Battery cells, battery devices, and power-consuming devices

Abstract

The present application provides a battery cell, a battery device and an electrical device, wherein the battery cell includes a first electrode terminal and an electrode assembly; the electrode assembly includes a plurality of first electrode sheets and a plurality of second electrode sheets, the first electrode sheet and the second electrode sheet each including a coating portion and a pole ear portion, the pole ear portion being arranged on at least one side of the coating portion along a first direction, one of the first electrode sheet and the second electrode sheet being a positive electrode sheet and the other being a negative electrode sheet, the ratio of the dimension of the coating portion of the positive electrode sheet along the length direction to the dimension of the coating portion of the positive electrode sheet along the width direction is 4 to 7, and the dimension of the coating portion of the positive electrode sheet along the length direction is 300 mm to 650 mm; there are at least two first electrode terminals, at least two first electrode terminals are electrically connected to the pole ear portion of the first electrode sheet, and the first electrode sheet satisfies: n*W1 / W2 is 0.5 to 1.0.

Description

[0001] This application claims priority to patent application PCT / CN2025 / 071124, entitled “Battery Cell, Battery Device, and Electrical Device,” filed on January 7, 2025, the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] Battery cells, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy planes, and power tools. With the rapid advancements in battery technology, higher performance requirements are being placed on them. However, battery cell power performance and high-temperature cycling performance require further improvement. Summary of the Invention

[0004] The present application provides a battery cell, a battery device, and an electrical device. The power performance and high-temperature cycle performance of the battery cell of the present application can be improved.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, the battery cell comprising a housing assembly and an electrode assembly; the housing assembly comprising a housing, a first electrode terminal and a second electrode terminal, the first electrode terminal and the second electrode terminal being arranged on the housing; the electrode assembly is located within the housing, the electrode assembly comprising a plurality of first pole pieces and a plurality of second pole pieces, the first pole pieces and the second pole pieces being stacked along a thickness direction of the battery cell, the first pole pieces and the second pole pieces each comprising a coating portion and a pole ear portion, the coating portion being coated with an active material layer, the pole ear portion being arranged on at least one side of the coating portion along a first direction, the first direction being a direction parallel to a length direction of the battery cell, or a direction parallel to a width direction of the battery cell,

[0006] 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 active material layer of the positive electrode sheet includes a lithium-containing phosphate. The ratio of the length of the coating portion of the positive electrode sheet to the width of the coating portion of the positive electrode sheet is 4 to 7. The length of the coating portion of the positive electrode sheet is 300 mm to 650 mm.

[0007] There are at least two first electrode terminals, at least two of which are electrically connected to the tabs of the first electrode piece, and the second electrode terminal is electrically connected to the tabs of the second electrode piece;

[0008] The first pole piece satisfies: n*W1 / W2 is 0.5 to 1.0;

[0009] n represents the number of all the tabs on the same side of the coating portion;

[0010] W1 represents the average size of the tab portion along the second direction, where the second direction, the first direction, and the thickness direction are perpendicular to each other;

[0011] W2 represents the dimension of the coating portion along the second direction.

[0012] In the embodiment of the present application, the ratio of the size of the coating portion of the positive electrode sheet along the length direction Z to the size of the coating portion of the positive electrode sheet along the width direction Y is 4 to 7, and the size of the coating portion of the positive electrode sheet along the length direction Z is 300 mm to 650 mm. The length of the coating portion is relatively long, which is conducive to carrying relatively more positive electrode active materials and making the battery cell 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, which makes the heat generation of the positive electrode sheet high; the coating portion of the positive electrode sheet includes a lithium-containing phosphate with poor conductivity, which makes the positive electrode sheet The internal resistance is further increased, and the heat generation is aggravated; and in the embodiment of the present application, the first pole piece also satisfies n*W1 / W2 of 0.5 to 1.0, so that the connection area between the pole ear and the coating portion is relatively large, and the flow area of ​​the pole ear is relatively large, which is beneficial to reducing the DC resistance and reducing heat generation; there are at least two first electrode terminals. In other words, at least two first electrode terminals are connected to the pole ear of the first pole piece, which can further increase the flow area of ​​the first electrode terminal and the pole ear, further reduce the DC resistance, reduce heat generation, and thus help improve power performance and high-temperature cycle performance, and achieve fast charging.

[0013] 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, thereby improving the power performance and high-temperature cycle performance of the battery cell.

[0014] In some embodiments, the number of first electrode terminals is two to four. When the number of first electrode terminals is within the above range, the current capacity can be increased, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0015] In some embodiments, the housing includes a shell and an end cap, the shell housing the electrode assembly, the shell including an opening, the end cap covering the opening, the first electrode terminal disposed on the end cap, the first electrode terminal including a first electrode body and a first electrode protrusion, the first electrode body being located on a side of the end cap facing the electrode assembly, the first electrode protrusion being connected to the first electrode body and protruding toward a side facing away from the electrode assembly, and extending through the end cap. The first electrode body can enhance the connection tightness with the end cap, and the first electrode protrusion facilitates the introduction or extraction of current.

[0016] In some embodiments, the minimum cross-sectional area of ​​the first electrode protrusion parallel to the thickness of the battery cell is a first area, the area enclosed by the projected outer contour of the end cap parallel to the thickness is a second area, and 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 for improving the current carrying capacity of the first electrode terminal and the power performance and high-temperature cycling performance of the battery cell.

[0017] In some embodiments, a ratio of a dimension of the first electrode protrusion along the thickness direction to a dimension of the end cap along the thickness direction is 0.20 to 0.40.

[0018] When the first electrode protrusion meets the above conditions, the size of the first electrode protrusion accounts for a relatively high proportion, which is beneficial to improving the current capacity of the first electrode terminal and improving the power performance and high-temperature cycle performance of the battery cell.

[0019] In some embodiments, the first electrode body and the first electrode protrusion are an integrated structure. The integrated structure is more stable and has lower electron transmission resistance, which is beneficial for improving the power performance and high-temperature cycle performance of the battery cell.

[0020] In some embodiments, the housing assembly further includes a first conductive fixing member, at least partially located on a side of the end cap facing away from the electrode assembly. The first conductive fixing member surrounds the first electrode terminal and securely connects the first electrode terminal to the end cap. The first conductive fixing member can further increase the flow area between the battery cell and the external bus assembly, thereby improving the flow capacity, which is beneficial for enhancing the flow capacity of the battery device and improving the power performance and high-temperature cycling performance of the battery cell.

[0021] In some embodiments, the ratio of the thickness dimension of the first conductive fixing member to the thickness dimension of the end cap is 0.40 to 0.80. When the first conductive fixing member meets the above conditions, the size of the first conductive fixing member is relatively high, which helps to increase the flow area between the battery cell and the external bus assembly, thereby improving the flow capacity, improving the flow capacity of the battery device, and improving the power performance and high-temperature cycle performance of the battery cell.

[0022] In some embodiments, the first pole piece has at least two tabs, and the at least two tabs of the first pole piece are disposed on the same side of the coating portion along the length direction. The tabs have a strong current-carrying capacity, which helps improve the power performance and high-temperature cycling performance of the battery cell.

[0023] In some embodiments, at least two tabs of the first pole piece are respectively disposed on both sides of the coating portion along the length direction. The tabs have a strong current flow capacity, thereby improving the fast charging performance of the battery device.

[0024] In some embodiments, the pole ear portion of the first pole piece is arranged on at least one side of the coating portion along the width direction, there is only one pole ear portion on the same side of the coating portion in the first pole piece, and n*W1 / W2 is 1.0; the pole ear portion has a strong current flow capacity, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0025] In some embodiments, the first pole piece's tab is located on at least one side of the coating portion along the width direction, with at least two tabs located on the same side of the coating portion. The tabs have a strong current-carrying capacity, which helps improve the power performance and high-temperature cycling performance of the battery cell.

[0026] In some embodiments, the number of pole lugs located on the same side of the coating portion of the first pole piece is two to four. The pole lugs have a strong current-carrying capacity, which is beneficial for improving the power performance and high-temperature cycle performance of the battery cell.

[0027] In some embodiments, the battery cell further includes a first adapter, which is located between the first electrode terminal and the tab portion of the first pole piece, and connects the first electrode terminal and the tab portion of the first pole piece. The first adapter further facilitates the connection between the first tab and the first electrode terminal, and can enhance the current carrying capacity, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0028] In some embodiments, at least two first electrode terminals are disposed on at least one side of the electrode assembly along the length direction, and the first electrode tab portion is disposed on at least one side of the coating portion along the width direction. Disposing the first electrode terminals and the first electrode tab portion on opposite sides of the electrode assembly can increase widthwise spacing and improve the energy density of the battery cell.

[0029] In some embodiments, the first adapter includes a first adapter portion and a second adapter portion. The first adapter portion extends in the longitudinal direction and is connected to the tab portion of the first electrode piece. The second adapter portion is connected to the first adapter portion and protrudes from the first adapter portion in the width direction and is connected to the first electrode terminal. The first adapter portion can enhance the current carrying capacity, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0030] In some embodiments, the battery cell further includes a first conductive member positioned between the first adapter and the tab portion of the first pole piece, connecting the first adapter and the tab portion of the first pole piece. The first conductive member facilitates the connection between the first tab and the first electrode terminal, enhances current flow capacity, and improves the power performance and high-temperature cycling performance of the battery cell.

[0031] In some embodiments, the first pole piece has at least two pole lugs located on the same side of the coating portion; the first conductive member is a continuous sheet structure, connecting the at least two pole lugs. The first conductive member can enhance current flow capacity, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0032] In some embodiments, the first pole piece has at least two pole lugs located on the same side of the coating portion, and at least two first conductive members are connected to the pole lugs in a one-to-one correspondence. The first conductive members can enhance current flow capacity, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0033] In some embodiments, at least two 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 sheet is disposed on one side of the coating portion along the width direction. The first conductive member includes a first conductive portion and a second conductive portion. The first conductive portion extends along the length direction and connects the tab portion of the first electrode sheet to the first adapter. The second conductive portion is connected to the first conductive portion and protrudes from the first conductive portion along the width direction, and is connected to the second adapter portion of the first adapter. The first conductive member further facilitates the connection between the first tab and the first electrode terminal, enhances the current carrying capacity, and improves the power performance and high-temperature cycling performance of the battery cell.

[0034] In some embodiments, the thickness of the first conductive member is 0.5 mm to 2.0 mm. When the thickness of the first conductive member is within the above range, the current flow capacity can be effectively increased and the fast charging capability can be improved.

[0035] In some embodiments, there are at least two second electrode terminals; the second electrode sheet satisfies the following conditions: m*W3 / W4 is 0.5 to 1.0; m represents the number of pole lugs located on the same side of the coating portion; W3 represents the average dimension of the pole lugs along the second direction; and W4 represents the dimension of the coating portion along the second direction. The second electrode terminal has a strong current-carrying capacity, which helps improve the current-carrying capacity of the battery cell and the power performance and high-temperature cycling performance of the battery cell.

[0036] In some embodiments, the housing includes a shell and an end cap. The shell includes an opening, and the end cap covers the opening. The shell includes two first shell portions that oppose each other along the thickness direction, and a second shell portion and a third shell portion that oppose each other. The second shell portion and the third shell portion are connected by the first shell portion. The second shell portion includes a first wall and a second wall that are continuously arranged along the thickness direction, and the first and second walls are welded. The second shell portion has a relatively small area and relatively small expansion. The weld is located on the second shell portion, which can reduce the risk of leakage from the battery cell.

[0037] In some embodiments, the thickness of the housing is 0.1 mm to 0.5 mm. When the thickness of the housing is within the above range, the housing is relatively thin, which is conducive to rapid heat dissipation of the housing.

[0038] In some embodiments, the battery cell further includes a pressure relief component, which is disposed on the housing component. The area per unit capacity of the pressure relief component is 1.2 mm. 2 / Ah to 1.8mm 2 / Ah.

[0039] In the embodiment of the present application, the area per unit volume of the pressure relief component is greater than 1.2 mm 2 / Ah, can quickly release gas and improve the reliability of battery cells; and the area per unit capacity of the pressure relief component is less than or equal to 1.8mm 2 / Ah, so that the area occupied by the pressure relief component is relatively small, and the area occupied by the electrode terminals can be taken into account, so that the flow capacity is relatively high; therefore, when the battery cell of the embodiment of the present application meets the above conditions, it can take into account the improvement of the battery cell's reliability and flow capacity.

[0040] In some embodiments, there are two pressure relief assemblies, which are respectively disposed on both sides of the housing assembly, to facilitate the release of gas within the battery cell.

[0041] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate. The lithium-containing phosphate has excellent cycle stability and is conducive to improving high-temperature cycle performance.

[0042] In some embodiments, the single-side 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 , optional 275mg / 1540.25mm 2 Up to 300mg / 1540.25mm 2 The active material layer of the positive electrode plate is the positive electrode film layer. When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of ​​the positive electrode plate will not be too large, and the energy density and charge rate performance of the battery cell can be improved.

[0043] In some embodiments, the compaction density of the active material layer of the positive electrode sheet of the battery cell at 0% state of charge is 2.30 g / cm 3 to 2.70g / cm 3 , optional 2.40g / cm 3 Up to 2.55g / cm 3 When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell. Moreover, since the positive electrode active material in the positive electrode film layer is relatively densely packed, the contact resistance between particles is relatively small, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation under fast charging, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0044] In some embodiments, the coating portion of the negative electrode sheet includes a negative 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 current collector. The active material layer includes a negative electrode active material, which includes a carbon-based material, which includes artificial graphite. When the degree of graphitization of the artificial graphite is within the above range, the artificial graphite has excellent electrical conductivity, can reduce heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0045] In some embodiments, the active material layer includes a first negative electrode film layer and a second negative electrode film layer, wherein the 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 a side of the first negative electrode film layer facing 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. In the embodiments of the present application, the particles of the second negative electrode film layer have a relatively small particle size, which can shorten the solid-phase transmission path of lithium ions, improve fast charging performance, and alleviate the problem of lithium plating on the surface of the negative electrode sheet, which is beneficial for improving the power performance and high-temperature cycling performance of the battery cell.

[0046] In some embodiments, the carbon-based material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is within this range, the solid-phase transport path of lithium ions can be shortened, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0047] In some embodiments, the carbon-based material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not easily agglomerated during the preparation process, which can improve the stability of the material. On the other hand, the combination of the negative electrode active material in the second negative electrode film layer and the negative electrode active material in the first negative electrode film layer within the above volume average particle size range is conducive to constructing a gradient porosity difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, improving the fast charging performance of the battery cell, and helping to improve the power performance and high temperature cycle performance of the battery cell.

[0048] 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.

[0049] In some embodiments, the single-side 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 , optional 125mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 The active material layer of the negative electrode plate is the 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 plate will not be too large, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell, while also taking into account the improvement of the energy density of the battery cell.

[0050] In some embodiments, the compaction density of the active material layer of the negative electrode sheet of the battery cell at 0% state of charge is 1.30 g / cm 3 Up to 1.65g / cm 3 , optional 1.35g / cm 3 Up to 1.50g / cm 3 .

[0051] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active material of the negative electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0052] In some embodiments, the battery cell further includes an electrolyte, the electrolyte including an organic solvent, the organic solvent including a chain carboxylate solvent, and the electrolyte has a room temperature conductivity of 10 mS / cm to 13 mS / cm. When the electrolyte has a room temperature conductivity, such as 25°C, within the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the power performance and high-temperature cycling performance of the battery cell.

[0053] In some embodiments, the mass content of the linear carboxylate solvent is 5% to 30% based on the mass of the electrolyte. When the mass content of the linear carboxylate solvent is within this range, the viscosity of the electrolyte system is relatively low, which facilitates the migration of lithium ions. Furthermore, the mass content of the linear carboxylate solvent is not too high, which can reduce high-temperature gas production and improve high-temperature cycling performance.

[0054] In some embodiments, the electrolyte further comprises a lithium salt, wherein the lithium salt comprises one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The above lithium salt system is beneficial for improving the conductivity of the electrolyte and the dynamic performance of the battery cell.

[0055] In some embodiments, the mass content of the lithium salt is 13% to 20% based on the mass of the electrolyte. When the mass content of the lithium salt is within the above range, the lithium salt is beneficial for improving the conductivity of the electrolyte, enhancing the dynamic performance of the battery cell, and improving the power performance and high-temperature cycle performance of the battery cell.

[0056] In some embodiments, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide, based on the mass of the electrolyte, is 1.2 to 2.0. The lithium salt helps improve the conductivity of the electrolyte, enhances the kinetic performance of the battery cells, and improves the power performance and high-temperature cycling performance of the battery cells.

[0057] In some embodiments, the electrolyte further includes additives, including one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone. These additives can form a dense, uniformly thick film on the negative electrode side, effectively repairing the solid electrolyte interface (SEI) film and providing excellent protection for the negative electrode active material, thereby enhancing the rapid charging performance of the battery cell and improving high-temperature cycling performance.

[0058] In a second aspect, an embodiment of the present application further provides a battery device, comprising a battery cell according to any embodiment of the first aspect of the present application.

[0059] In a third aspect, an embodiment of the present application further proposes an electrical device, which includes a battery device as in any embodiment of the second aspect or the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0061] Figure 1 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0062] Figure 2 is a schematic structural diagram of a battery pack provided in some embodiments of the present application;

[0063] Figure 3 is a schematic structural diagram of a battery module provided in some embodiments of the present application;

[0064] Figure 4 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0065] Figure 5is a schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0066] Figure 6 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0067] Figure 7 is a schematic structural diagram of a battery cell provided in some other embodiments of the present application;

[0068] Figure 8 Schematic diagram of the structure of the end cover, the first electrode terminal and the first conductive fixing member of the battery cell provided in some embodiments of the present application;

[0069] Figure 9 yes Figure 8 Schematic top view of

[0070] Figure 10 yes Figure 9 Sectional view along line AA;

[0071] Figure 11 is a schematic structural diagram of a battery cell provided in some further embodiments of the present application;

[0072] Figure 12 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0073] Figure 13 is a schematic diagram of the exploded structure of the end cap, the first electrode terminal, and the first conductive fixing member of the battery cell provided in some embodiments of the present application;

[0074] Figure 14 is a schematic structural diagram of a first pole piece of a battery cell provided in other embodiments of the present application;

[0075] Figure 15 is a schematic structural diagram of a first pole piece of a battery cell provided in some further embodiments of the present application;

[0076] Figure 16 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0077] Figure 17 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0078] Figure 18 is a schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0079] Figure 19 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0080] Figure 20 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0081] Figure 21 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0082] Figure 22 is a schematic structural diagram of a second pole piece of a battery cell provided in some embodiments of the present application;

[0083] Figure 23 It is a schematic structural diagram of the second pole piece of a battery cell provided in other embodiments of the present application.

[0084] The drawings are not necessarily drawn to scale.

[0085] The following are the descriptions of the reference numerals:

[0086] X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing portion; 5b, second housing portion; 5c, storage space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, first pole piece; 111, first pole tab; 1111, first end; 112, first coating portion; 12, second pole piece; 121, second pole tab; 1211, second end; 122, second coating portion; 13, separator; 20, outer Shell assembly; 21. Shell; 211. First shell portion; 212. Second shell portion; 2121. First wall; 2122. Second wall; 213. Third shell portion; 22. End cover; 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 portion; 612. Second conductive portion; 70. Pressure relief assembly. DETAILED DESCRIPTION

[0087] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0088] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3,4 and 5 are listed, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0089] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0090] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0091] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0092] The term "plurality" used in this application refers to two or more (including two).

[0093] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0094] With the development of the battery field, the energy density and fast charging requirements of battery cells are gradually increasing. However, studies have found that when the battery energy density is increased, the electron transmission path may be longer and the electron distribution may be uneven, which may lead to increased internal resistance and increased heat generation; as the charging rate increases, the internal resistance increases more sharply, the heat generation further increases, the power performance and high-temperature cycle performance are poor, making it impossible for the battery cells to achieve fast charging.

[0095] In view of the above problems, the embodiments of the present application design the battery cell and improve the size of the electrode tabs, the number of electrode terminals, etc., so as to improve the power performance and high-temperature cycle performance of the battery cell.

[0096] The battery cell of the present application is applicable to various battery devices and electrical devices using the battery cell.

[0097] For example, the power-consuming device may be a mobile phone, portable device, laptop computer, electric vehicle, electric toy, electric tool, vehicle, ship, spacecraft, etc. Alternatively, for example, the power-consuming device may be a spacecraft, including an airplane, rocket, space shuttle, and spacecraft.

[0098] Figure 1 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 1, a battery pack or battery module may be used.

[0099] A battery device is disposed within the electrical device 1, and the battery device can be disposed at the bottom, head, or tail of the electrical device 1. The battery device can be used to power the electrical device 1. For example, the battery device can serve as an operating power source for the electrical device 1, and can also serve as a driving power source for the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in FIG. 1 is a battery pack 2 .

[0100] The electric device 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery device to supply power to the motor 4 , for example, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0101] A battery device may include one or more battery cell assemblies to provide voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or in series via a busbar.

[0102] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0103] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module may be formed by bundling multiple battery cells with a cable tie.

[0104] like Figure 2 As shown, in some embodiments, the battery device may be a battery pack 2 , which includes a box 5 and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the box 5 .

[0105] As an example, the battery cell assembly may also be housed in the box body 5 by directly fixing a plurality of battery cells to the box body 5 .

[0106] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b, which define a storage space 5c. The first housing portion 5a and the second housing portion 5b engage to form a closed space within the housing 5 for accommodating the battery cell assembly. "Enclosed" here means covered or closed, and can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0107] As an example, the box body 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body 5 to accommodate the battery cell assembly.

[0108] In some embodiments, the box 5 can be used as a part of the chassis structure of the vehicle. For example, part of the box 5 can become at least a part of the floor of the vehicle, or part of the box 5 can become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0109] As an example, the battery cell assembly may be a battery module 6 , and the battery cell assembly may be accommodated in the box body 5 by fixing the battery module 6 in the box body 5 .

[0110] like Figure 3 As shown, the battery module 6 includes a plurality of battery cells 7 .

[0111] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% state of charge (SOC), the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0112] In some embodiments, during the charging process of the battery device or any battery cell constituting the battery device from 10% state of charge (SOC) to 80% state of charge (SOC), the temperature of the external environment of the battery device is room temperature, for example, 25° C.

[0113] For example, the charging step of the battery device or any battery cell constituting the battery device from 10% state of charge (SOC) to 80% SOC may be performed as follows:

[0114] Charge from 10% SOC to 25% SOC at 7.0C constant current;

[0115] Charge from 25% SOC to 30% SOC at 7.0C constant current;

[0116] Charge from 30% SOC to 35% SOC at 7.0C constant current;

[0117] Charge from 35% SOC to 40% SOC at 7.0C constant current;

[0118] Charge from 40% SOC to 45% SOC at 6.7C constant current;

[0119] Charge from 45% SOC to 50% SOC at 6.5C constant current;

[0120] Charge from 50% SOC to 55% SOC at 6.0C constant current;

[0121] Charge from 55% SOC to 60% SOC at 5.8C constant current;

[0122] Charge from 60% SOC to 65% SOC at 5.5C constant current;

[0123] Charge from 65% SOC to 70% SOC at 5.2C constant current;

[0124] Charge from 70% SOC to 75% SOC at 5.0C constant current;

[0125] Charge from 75% SOC to 80% SOC at 4.8C constant current.

[0126] In some embodiments, the charging time of the battery device or any battery cell constituting the battery device from 10% state of charge to 80% state of charge is 5 min to 20 min, optionally less than or equal to 12 min, and further optionally 5 min to 8 min. The ambient temperature of the battery device at 10% state of charge is room temperature, for example, 25° C. Exemplarily, the charging time of the battery device from 10% state of charge to 80% state of charge is 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min, or a range consisting of any two of the above values.

[0127] like Figures 4 to 6 As shown, the battery cell 7 includes a shell assembly 20 and an electrode assembly 10, the shell assembly 20 includes a shell, a first electrode terminal 31 and a second electrode terminal 32, the first electrode terminal 31 and the second electrode terminal 32 are arranged on the shell; the electrode assembly 10 is located in the shell, the electrode assembly 10 includes a plurality of first pole pieces 11 and a plurality of second pole pieces 12, the first pole pieces 11 and the second pole pieces 12 are stacked along the thickness direction X of the battery cell 7, the first pole pieces 11 and the second pole pieces 12 each include a coating portion and a pole ear portion, the coating portion is coated with an active material layer, the pole ear portion is arranged on at least one side of the coating portion along the first direction and is not coated with the active material layer, the first direction is a direction parallel to the length direction Z of the battery cell 7 or the width direction Y of the battery cell 7,

[0128] One of the first electrode sheet 11 and the second electrode sheet 12 is a positive electrode sheet, and the other is a negative electrode sheet. The active material layer of the positive electrode sheet includes a lithium-containing phosphate. The ratio of the dimension of the coating portion of the positive electrode sheet along the length direction Z to the dimension of the coating portion of the positive electrode sheet along the width direction Y is 4 to 7. The dimension of the coating portion of the positive electrode sheet along the length direction Z is 300 mm to 650 mm.

[0129] There are at least two first electrode terminals 31 , and the at least two first electrode terminals 31 are electrically connected to the pole ear portion of the first pole piece 11 , and the second electrode terminal 32 is electrically connected to the pole ear portion of the second pole piece 12 ;

[0130] The first pole piece 11 satisfies: n*W1 / W2 is 0.5 to 1.0; n represents the number of all pole lugs located on the same side of the coating portion; W1 represents the average size of the pole lugs along the second direction; W2 represents the size of the coating portion along the second direction.

[0131] In the embodiment of the present application, the first direction, the second direction, and the thickness direction X of the battery cell 7 are perpendicular to each other.

[0132] When the first direction is parallel to the length direction Z of the battery cell 7, the dimension of the component in this direction can be considered as the length of the component. For example, the dimension of the coating portion along the first direction is the length of the coating portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0133] When the first direction is parallel to the width direction Y of the battery cell 7, the dimension of the component in this direction can be considered as the width of the component. For example, the dimension of the coating portion along the first direction is the width of the coating portion. In this case, the second direction is parallel to the length of the battery cell 7.

[0134] For a clearer description of the present application, the tab portion of the first pole piece 11 is defined as the first pole piece 111, and the coated portion of the first pole piece 11 is defined as the first coated portion 112. The tab portion of the second pole piece 12 is defined as the second pole piece 121, and the coated portion of the second pole piece 12 is defined as the second coated portion 122. The electrode terminal having the same electrical properties as and electrically connected to the first pole piece 111 is the aforementioned first electrode terminal 31, and the electrode terminal having the same electrical properties as and electrically connected to the second pole piece 121 is the aforementioned second electrode terminal 32.

[0135] Optionally, the battery cell 7 further includes an isolation member 13 , which is located between the first pole piece 11 and the second pole piece 12 .

[0136] The polarities of the first electrode piece 11 and the second electrode piece 12 are opposite. When the first electrode piece 11 is a positive electrode piece, the second electrode piece 12 is a negative electrode piece, the first electrode terminal 31 is a positive terminal, and the second electrode terminal 32 is a negative terminal; or when the first electrode piece 11 is a negative electrode piece, the second electrode piece 12 is a positive electrode piece, the first electrode terminal 31 is a negative terminal, and the second electrode terminal 32 is a positive terminal.

[0137] Figure 5 and Figure 6 , it is shown that the first direction is parallel to the width direction Y, and the second direction is parallel to the length direction Z. Figure 6 Where n*W1 is the sum of the dimensions of all first electrode tabs 111 located on the same side of the first coating portion 112 along the second direction, n is 1, and W2 represents the dimension of the first coating portion 112 along the second direction.

[0138] The electrode assembly 10 is a laminated structure, in which multiple first pole sheets 11 and multiple second pole sheets 12 are stacked. Compared with a wound structure, it is easier to increase the amount of active material coating on the laminated structure, so that the battery cell 7 has a relatively high energy density; and in an embodiment of the present application, the ratio of the size of the coated portion of the positive electrode sheet along the length direction Z to the size of the coated portion of the positive electrode sheet along the width direction Y is 4 to 7, and the size of the coated portion of the positive electrode sheet along the length direction Z is 300mm to 650mm. The length of the coating portion is relatively long, which is conducive to carrying relatively more positive electrode active materials, and is conducive to making the battery cell 7 have a relatively high energy density.

[0139] When the length of the coating portion of the positive electrode plate is too long, the internal resistance is high, which makes the heat generation of the positive electrode plate high; the coating portion of the positive electrode plate includes a lithium-containing phosphate with poor conductivity, which further increases the internal resistance of the positive electrode plate and aggravates the heat generation; with the increase of the charging rate, the above-mentioned heat generation phenomenon is further aggravated, which is not conducive to fast charging; and in the embodiment of the present application, the first electrode plate 11 also satisfies n*W1 / W2 of 0.5 to 1.0, so that the connection area between the pole ear and the coating portion is relatively large, and the flow area of ​​the pole ear is relatively large, which is conducive to reducing the 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 pole ear portion of the first electrode plate 11, which can further increase the flow area of ​​the first electrode terminal 31 and the pole ear portion, further reduce the DC resistance, reduce heat generation, and thus help improve power performance and high-temperature cycle performance, etc., and achieve fast charging.

[0140] In the embodiment of the present application, 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, Figure 6 W2 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.

[0141] If the ratio of the length of the coating portion of the positive electrode plate to the width of the coating portion is too small, for example, less than 4, the load of active material is relatively small, which is not conducive to improving the energy density of the battery cell; if the ratio of the length of the coating portion of the positive electrode plate to the width of the coating portion is too large, for example, greater than 7, the length of the positive electrode film layer is too long, the transmission path of electrons in the length direction of the positive electrode plate is too long, the resistance increases, and is not conducive to improving the power performance of the battery cell.

[0142] The ratio of the length to the width of the coating portion of the positive electrode plate in the embodiment of the present application is 4 to 7, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7 or a range consisting of any two of the above values, which can improve both the energy density and power performance of the battery cell.

[0143] If the length of the coated portion of the positive electrode plate is too short, for example, less than 300 mm, the load of active material is relatively small, which is not conducive to improving the energy density of the battery cell; if the length of the coated portion of the positive electrode plate is too long, for example, greater than 650 mm, the length of the positive electrode film layer is too long, the transmission path of electrons in the length direction of the positive electrode plate is too long, the resistance increases, and is not conducive to improving the power performance of the battery cell.

[0144] The length of the coated portion of the positive electrode sheet 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 a range consisting of any two of the foregoing values. Optionally, the length of the coated portion of the positive electrode sheet is 400 mm to 505 mm.

[0145] [Casing components]

[0146] The housing assembly 20 has a receiving space for receiving the electrode assembly 10 and the electrolyte.

[0147] In some embodiments, the housing assembly 20 includes a housing, a first electrode terminal 31 and a second electrode terminal 32 , and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the housing.

[0148] The outer shell can be made of steel, aluminum, plastic (e.g., polypropylene), a composite metal shell (e.g., a copper-aluminum composite shell), or an aluminum-plastic film. In some embodiments, the outer shell can be either sealed or non-sealed. For example, in a non-sealed outer shell, the outer shell protects the electrode assembly 10 and includes a sealed bag between the outer shell and the electrode assembly 10, which encapsulates the electrode assembly 10 and the electrolyte. Specifically, the sealed bag can be a bag-shaped insulating member or an aluminum-plastic film. In a sealed outer shell, the sealed bag encapsulates the electrode assembly 10 and other components, such as the electrolyte.

[0149] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a polygonal battery, and a polygonal battery such as a hexagonal battery. There is no special limitation in this application.

[0150] shell

[0151] In some embodiments, the housing includes an end cap 22 and a shell 21. The shell 21 has an opening, and the end cap 22 covers the opening. The shell 21 may have one or more openings. One or more end caps 22 may also be provided.

[0152] The first electrode terminal 31 and the second electrode terminal 32 may be provided on the housing 21 , or the first electrode terminal 31 and the second electrode terminal 32 may be provided on the end cover 22 . Alternatively, the first electrode terminal 31 and the second electrode terminal 32 may be provided on the end cover 22 .

[0153] The first electrode terminal 31 and the second electrode terminal 32 can be disposed on the same end cap 22. For example, there is one end cap 22, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22 at intervals. In another example, there are two end caps 22, and the two end caps 22 are disposed opposite each other, and each end cap 22 is provided with a first electrode terminal 31 and a second electrode terminal 32.

[0154] The first electrode terminal 31 and the second electrode terminal 32 are respectively provided on different end covers 22 . For example, there are two end covers 22 , which are arranged opposite to each other. The first electrode terminal 31 is provided on one of the end covers 22 , and the second electrode terminal 32 is provided on the other end cover 22 .

[0155] The shape of the housing 21 can be determined based on the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a cylindrical housing 21 can be selected; if the electrode assembly 10 has a rectangular parallelepiped structure, a rectangular parallelepiped housing 21 can be selected. Optionally, both the electrode assembly 10 and the housing 21 have rectangular parallelepiped structures.

[0156] In some embodiments, the housing 21 includes two first shell portions 211, a second shell portion 212, and a third shell portion 213. The two first shell portions 211 are opposite to each other along the thickness direction X of the battery cell 7, the second shell portion 212 and the third shell portion 213 are opposite to each other, and the second shell portion 212 and the third shell portion 213 are connected by the first shell portion 211. The second shell 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. The first wall 2121 and the second wall 2122 can be welded by tailor welding, laser welding, etc., and tailor welding can be selected. Since the area of ​​the second shell portion 212 is relatively small and the degree of expansion is relatively small, the weld is located on the second shell portion 212, which can reduce the risk of leakage of the battery cell 7.

[0157] When the battery cell 7 is assembled into the battery device's housing, it is placed within the housing, which includes a first housing portion and a second housing portion, with the first housing portion covering the second housing portion. The second housing portion 212 is positioned opposite the first housing portion, with the second housing portion 212 positioned adjacent to the first housing portion, and the third housing portion 213 positioned adjacent to the second housing portion. When the battery device is assembled into an electrical device, the first housing portion can be vertically positioned above the second housing portion. The second housing portion 212 has a weld seam, which faces upward, reducing the risk of leakage from the battery cell 7.

[0158] In some embodiments, the thickness of the housing 21 is 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, 0.30 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.40 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.50 mm, 0.51 mm, 0.52 mm, 0.53 mm, 0.54 mm, 0.55 mm, 0.56 mm, 0.57 mm, 0.58 mm, 0.59 mm, 0.60 mm, 0.61 mm, 0.62 mm, 0.63 mm, 0.64 mm, 0.65 mm, 0.66 mm, 0.67 mm, 0.68 mm, 0.69 mm, 0.70 mm, 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 a range consisting of any two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0159] When the thickness of the shell 21 is within the above range, the shell 21 is relatively thin, which is conducive to rapid heat dissipation of the shell 21.

[0160] Exemplarily, the thickness of the first shell portion 211 is 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. 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 a range consisting of any two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0161] Exemplarily, the thickness of the second shell portion 212 is 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. 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 a range consisting of any two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0162] Exemplarily, the thickness of the third shell portion 213 is 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. 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 a range consisting of any two of the above values. Optionally, the thickness of the housing 21 is 0.3mm to 0.4mm.

[0163] First electrode terminal

[0164] In some embodiments, there are at least two first electrode terminals 31 , such as two, three, or four, for example, there are two to four first electrode terminals 31 .

[0165] 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 It is shown that the first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0166] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0167] For another example, multiple first electrode terminals 31 are respectively arranged on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons and reduce the temperature rise inside the battery cell, which is beneficial to improving the fast charging performance and enhancing the power performance and cycle performance of the battery cell.

[0168] Exemplarily, there are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Alternatively, exemplary, there are four first electrode terminals 31, two of which are disposed on one side of the electrode assembly 10, and the other two are disposed on the other side of the electrode assembly 10.

[0169] like Figure 7 As shown, in other embodiments, at least one first electrode terminal 31 is arranged on at least one side of the electrode assembly 10 along the width direction Y. This arrangement can shorten the migration path of electrons, which is beneficial to improving the fast charging performance, and can reserve a surplus area for setting a first electrode terminal 31 with a larger flow area on the end cover.

[0170] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the width direction Y. For another example, the plurality of first electrode terminals 31 are disposed on both sides of the electrode assembly 10 along the width direction Y, respectively.

[0171] In the embodiment of the present application, the first electrode terminal 31 can be an integrated structure, which can be integrally formed or connected to form an integrated structure by welding or other means. The integrated structure is beneficial to reducing resistance, reducing heat generation, and improving the power performance and cycle performance of the battery cell.

[0172] like Figures 8 to 10 As shown, 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. The first electrode protrusion 312 is connected to the first electrode body 311 and protrudes toward the side away from the electrode assembly 10, and penetrates the end cap 22. Optionally, the first electrode body 311 and the first electrode protrusion 312 are an integrated structure. In other embodiments, the first electrode terminal 31 may include only the first electrode protrusion 312, which penetrates the end cap 22 and is connected to the electrode lug.

[0173] Optionally, the minimum cross-sectional area of ​​the first electrode protrusion 312 parallel to the thickness direction X is a first area, the area enclosed by the projected outer contour of the end cap 22 parallel to the thickness direction X is a second area, and 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 a range consisting of any two of the above values; in the embodiment of the present application, the thickness direction X refers to the thickness direction X of the battery cell 7. 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 overcurrent bottleneck of the first electrode terminal 31. When the first area meets the above conditions, the overcurrent capacity of the first electrode terminal 31 is strong, which is beneficial to reducing heat generation and improving the power performance and cycle performance of the battery cell.

[0174] The first electrode protrusion 312 can have multiple cross-sectional areas of different sizes along the thickness direction X. For example, if the first electrode protrusion 312 includes a first portion, a second portion, and a third portion connected in sequence, and the second portion has the smallest cross-sectional area, then the cross-sectional area of ​​the second portion is the first area. Of course, the cross-sectional area of ​​the first electrode protrusion 312 along the thickness direction X can also be the same at all locations.

[0175] Optionally, the ratio of the size of the first electrode protrusion 312 along the thickness direction X to the size 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 a range consisting of any two of the above values; in this embodiment of the application, the thickness direction X refers to the thickness direction X of the battery cell 7. The size of the first electrode protrusion 312 refers to the size of the first electrode protrusion 312 of a single first electrode terminal 31 along the thickness direction X. Figure 9 As shown, 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 cover 22 along the thickness direction X can be understood as the width of the end cover 22 .

[0176] When the first electrode protrusion 312 meets the above conditions, the size of the first electrode protrusion 312 is relatively high, which is beneficial to improving the current capacity of the first electrode terminal 31 and improving the power performance and cycle performance of the battery cell.

[0177] In some embodiments, the housing assembly 20 further includes a first conductive fixing member 41. The first conductive fixing member 41 surrounds the first electrode terminal 31 and securely connects the first electrode terminal 31 to the end cap 22. At least a portion of the first conductive fixing member 41 is located on a side of the end cap 22 facing away from the electrode assembly 10. The first conductive fixing member 41 can be used to connect to an external busbar assembly. Optionally, an insulating member can be provided between the first conductive fixing member 41 and the end cap 22 for insulation.

[0178] The first conductive fixing member 41 can further increase the flow area between the battery cell 7 and the external bus assembly, thereby improving the flow capacity, which is beneficial to improving the flow capacity of the battery device and improving the fast charging performance of the battery device.

[0179] Optionally, a portion of the first electrode protrusion 312 protrudes from a side of the end cover 22 facing away from the electrode assembly 10 , and the first conductive fixing member 41 is disposed around the outside of the first electrode protrusion 312 .

[0180] 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 a range consisting of any two of the foregoing values. In this embodiment of the present application, 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. Figure 9 X1 shown in the figure 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 ; X2 represents the dimension of the end cover 22 along the thickness direction X, which can be understood as the width of the end cover 22 .

[0181] When the first conductive fixing member 41 meets the above conditions, the size of the first conductive fixing member 41 is relatively high, which is beneficial to increasing the flow area between the battery cell 7 and the external bus assembly, thereby improving the flow capacity, which is beneficial to improving the flow capacity of the battery device and improving the fast charging performance of the battery device.

[0182] Second electrode terminal

[0183] In some embodiments, there are at least two second electrode terminals 32 , such as two, three, or four, for example, there are two to four second electrode terminals 32 .

[0184] like Figure 11As shown, 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 migration path of electrons and is conducive to improving fast charging performance.

[0185] For example, all 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 terminals 31 and the second electrode terminals 32 can be disposed on both sides of the electrode assembly 10 along the width direction Y, respectively, so that they substantially do not interfere with each other when electrically connected to the electrode tabs. Specifically, there are two first electrode terminals 31 and two second electrode terminals 32, with the two first electrode terminals 31 disposed on one side of the electrode assembly 10 along the width direction Y, and the two second electrode terminals 32 disposed on the other side of the electrode assembly 10 along the width direction Y.

[0186] For another example, multiple second electrode terminals 32 are disposed on both sides of the electrode assembly 10 along the width direction Y. This arrangement can further shorten the electron migration path, which is beneficial for improving fast charging performance. In this case, the first electrode terminal 31 and the second electrode terminal 32 are disposed on one side of the electrode assembly 10 along the width direction Y, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on the other side of the electrode assembly 10 along the width direction Y.

[0187] like Figure 12 As shown, 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.

[0188] For example, at least two second electrode terminals 32 are respectively provided on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the electron migration path and improve the fast charging performance. In this case, the first electrode terminal 31 and the second electrode terminal 32 are provided on one side of the electrode assembly 10 along the length direction Z, and the first electrode terminal 31 and the second electrode terminal 32 are provided on the other side of the electrode assembly 10 along the length direction Z.

[0189] Figure 12 The battery cell 7 is shown to include four electrode terminals. Specifically, there are two second electrode terminals 32, one of which is disposed on one side of the electrode assembly 10 along the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 along the length direction Z. There are two first electrode terminals 31, one of which is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0190] For another example, all second electrode terminals 32 are disposed on one side of the electrode assembly 10 along the longitudinal direction Z. In this case, the first electrode terminals 31 and the second electrode terminals 32 can be disposed on both sides of the electrode assembly 10 along the longitudinal direction Z, respectively. When electrically connected to the electrode tabs, they substantially do not interfere with each other. 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 longitudinal direction Z, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 along the longitudinal direction Z.

[0191] In the embodiment of the present application, the second electrode terminal 32 can be an integrated structure, which can be integrally formed or connected to form an integrated structure by welding or other means. The integrated structure is beneficial to reducing resistance, reducing heat generation, and improving the power performance and cycle performance of the battery cell.

[0192] For example, in some embodiments, the structure of the second electrode terminal 32 is similar to that of the first electrode terminal 31. For example, 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. The second electrode protrusion is connected to the second electrode body and protrudes toward the side away from the electrode assembly 10, and penetrates the end cap 22. Optionally, the second electrode body and the second electrode protrusion are an integrated structure. In other embodiments, the second electrode terminal 32 may include only the second electrode protrusion, which penetrates the end cap 22 and is connected to the electrode lug.

[0193] In some embodiments, the housing assembly 20 further includes a second conductive fixing member that surrounds the second electrode terminal 32 and securely connects the second electrode terminal 32 to the end cap 22. The structure and dimensions of the second conductive fixing member are similar to those described for the first conductive fixing member 41.

[0194] The second conductive fixing member can further increase the flow area between the battery cell 7 and the external bus assembly, thereby improving the flow capacity, which is beneficial to improving the flow capacity of the battery device and improving the fast charging performance of the battery device.

[0195] Pressure relief components

[0196] like Figure 13 As shown, 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 the pressure.

[0197] Optionally, the pressure relief assembly 70 is disposed on the housing assembly 20. Further, optionally, the pressure relief assembly 70 is disposed on the end cap 22. In the case where the housing assembly 20 includes two end caps 22 facing each other, the pressure relief assembly 70 can be one and disposed on one of the two end caps 22, or two pressure relief assemblies 70 can be provided, one on each of the two end caps 22. In other embodiments, the pressure relief assembly 70 can also be disposed on the housing.

[0198] For example, when the internal pressure or temperature of a battery cell 7 reaches a predetermined threshold, the pressure relief assembly 70 is activated to release the internal pressure or temperature. When the internal pressure or temperature of the battery cell 7 reaches the predetermined threshold, the pressure relief assembly 70 actuates or a weakened structure within 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 material of one or more of the positive electrode sheet, negative electrode sheet, electrolyte, and separator 13 in the battery cell 7.

[0199] The "activation" mentioned in this application means that the pressure relief assembly 70 is in motion or activated to a certain state, so that the internal pressure and temperature of the battery cell 7 can be released. The action generated by the pressure relief assembly 70 may include but is not limited to: the components in the pressure relief assembly 70 move to form an exhaust channel, at least a part of the pressure relief assembly 70 ruptures, breaks, is torn or opened, etc. When the pressure relief assembly 70 is actuated, the high-temperature and high-pressure substances inside the battery cell 7 will be discharged outward from the actuated part as exhaust. In this way, the pressure and temperature of the battery cell 7 can be relieved under controllable pressure or temperature, thereby avoiding potential more serious accidents.

[0200] The emissions from the battery cells 7 mentioned in the embodiments of the present application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode sheets, separator fragments, high-temperature and high-pressure gas generated by the reaction, flames, and the like.

[0201] As an example, the pressure relief assembly 70 may be integrally formed with the housing assembly 20 , for example, the pressure relief assembly 70 may be integrally formed with the end cap 22 of the housing assembly 20 .

[0202] As an example, the pressure relief assembly 70 may also be separately provided and connected to the housing assembly 20 .

[0203] 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 discharging gas inside the battery cell 7 .

[0204] [First pole piece and second pole piece]

[0205] In the embodiment of the present application, when the first electrode 11 satisfies n*W1 / W2 of 0.5 to 1.0, the first electrode 11 can be a positive electrode or a negative electrode. The electrode ear portion is used to introduce current into or lead out of the coating portion.

[0206] For example, n*W1 / W2 is 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0, or a range consisting of any two of these values. When n*W1 / W2 meets the above range, the flow area of ​​the first electrode 111 is relatively large, reducing heat generation and improving the power performance and cycle performance of the battery cell 7.

[0207] W1 represents the average size of the first electrode tab 111 along the second direction,

[0208] When the first electrode tab 111 has a special-shaped structure, for example, the size of the first electrode tab 111 along the second direction gradually increases along the first direction, in this case, the size of the first electrode tab 111 along the second direction at multiple locations can be measured to calculate the average size of the first electrode tab 111 along the second direction. Of course, the size of each location of the first electrode tab 111 along the second direction can be the same value, in which case this value can be used as the average size of the first electrode tab 111.

[0209] There may be one or more first pole tabs 111 , for example, n is 1 to 4. In the case of multiple first pole tabs 111 , the average size of each first pole tab 111 may be measured separately, and the sum of the average size values ​​may be divided by the number of first pole tabs 111 to calculate the average size of the first pole tabs 111 .

[0210] The first pole tab 111 is connected to the first coating portion 112, and the first pole tab 111 includes a first end 1111 connected to the first coating portion 112. When n*W1 / W2 satisfies the above range, it means that the cross-section of the first end 1111 along the thickness direction of the first pole tab 111 itself is relatively large, the contact area between the first pole tab 111 and the first coating portion 112 is relatively large, and the first pole tab 111 has a strong current-carrying capacity, which can improve the power performance and cycle performance of the battery cell 7.

[0211] Optionally, the first electrode tab 111 and the current collecting portion of the first coating portion 112 are an integrated structure, so that the internal resistance of the first electrode sheet 11 is low, which can further improve the power performance and cycle performance of the battery cell 7 .

[0212] like Figure 14 and Figure 15 As shown, in some embodiments, the first pole piece 11 includes one or more first pole tabs 111 , and the one or more first pole tabs 111 are disposed on at least one side of the coating portion along the width direction Y.

[0213] For example, one or more first pole ears 111 are arranged on one side of the first coating portion 112 along the width direction Y. In this case, it can be understood that all first pole ears 111 are arranged on the same side of the first coating portion 112 along the width direction Y. This arrangement is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7. Figure 14 In the figure, n is 4, the sizes of the first electrode tabs 111 can be the same, W1 can represent the size of a single first electrode tab 111, and of course the sizes of the first electrode tabs 111 can also be slightly different; W2 represents the size of the first coating portion 112 along the length direction Z. Figure 15 In this example, n is 1 and n*W1 / W2 is 1.

[0214] like Figure 16 As shown, for example, in the case where the first electrode sheet 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.

[0215] Optionally, there are at least two, for example, two, three, four, five, six, etc., first electrode tabs 111 located on the same side of the first coating portion 112 along the width direction Y; at least four can be selected. This arrangement facilitates uniform distribution of electrons on the first electrode sheet 11 and improves fast charging performance.

[0216] like Figure 17 As shown, in other embodiments, the first pole piece 11 includes one or more first pole tabs 111 ; the one or more first pole tabs 111 are disposed on at least one side of the first coating portion 112 along the length direction Z.

[0217] For example, one or more first electrode 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 first electrode tabs 111 are disposed on the same side of the first coating portion 112 along the length direction Z.

[0218] like Figure 18 As shown, for example, in the case where the first electrode sheet 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.

[0219] Optionally, a plurality of first electrode tabs 111 are respectively arranged 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 sheet 11, which is conducive to improving the fast charging performance.

[0220] Optionally, there are at least two, for example, two, three, four, five, six, etc., first electrode tabs 111 located on the same side of the first coating portion 112 along the length direction Z. This arrangement facilitates uniform distribution of electrons in the first electrode sheet 11 and improves fast charging performance.

[0221] In the embodiment of the present application, the first electrode tab 111 and the first electrode terminal 31 are electrically connected, and can be directly connected or connected as shown in FIG. Figure 19 When the first electrode 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 electrode tab 111 and connects the first electrode terminal 31 and the first electrode tab 111. When there are multiple first electrode tabs 111 and multiple first electrode terminals 31, the multiple first electrode tabs 111 can be divided into multiple groups, and each group of first electrode tabs 111 is connected to one first electrode terminal 31.

[0222] 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 electrode 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 electrode tab 111 and the first electrode terminal 31, while also improving 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 available space for the first electrode sheet 11 along the width direction Y, thereby increasing the energy density of the battery cell 7.

[0223] When the first pole tab 111 and the first electrode terminal 31 are respectively arranged on different sides of the battery cell 7, the first adapter 51 may include a first adapter portion 511 and a second adapter portion 512, the first adapter portion 511 extends along the length direction Z, the first adapter portion 511 is connected to the first pole 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.

[0224] In the case where the first electrode tab 111 and the first electrode terminal 31 are disposed on the same side of the battery cell 7 , the first adapter 51 may only include the first adapter portion 511 .

[0225] In the above embodiments, the first adapter 51 may be a sheet-like structure, and may also be other structural forms.

[0226] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0227] In some embodiments, the battery cell 7 further includes a first conductive member 61, which is located between the first adapter 51 and the first tab 111. The provision of the first conductive member 61 can increase the current flow capacity between the first tab 111 and the first adapter 51, thereby improving fast charging performance and reducing heat generation. Furthermore, the electrical connections between the first tab 111 and the first adapter 51, and between the first conductive member 61 and the first adapter 51, can be achieved through welding. The presence of the first conductive member 61 can significantly reduce the risk of failure caused by direct electrical connection between multiple first tabs 111 and the first adapter 51.

[0228] For example, the tab portion of the first electrode piece 11 is disposed on one side of the coating portion along the width direction Y; the first conductive member 61 is located between the first adapter 51 and the first tab 111 , and connects the first adapter 51 and the first tab 111 .

[0229] Optionally, there are at least two first pole ears 111 located on the same side of the first coating portion 112, and at least two first conductive members 61. The first conductive members 61 and the first pole ears 111 are connected one-to-one, and at least two first conductive members 61 are connected to the first adapter 51. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0230] like Figure 20 As shown, optionally, there are at least two first electrode tabs 111 located on the same side of the first coating portion 112 , and the first conductive member 61 may be a continuous sheet structure connecting at least two first electrode tabs 111 .

[0231] like Figure 21 As shown, when the first tab 111 and the first electrode terminal 31 are respectively arranged on different sides of the battery cell 7, the first conductive member 61 optionally 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 conductive portion 611. This structural arrangement is conducive to increasing the grouping space in the length direction Z and improving the energy density of the battery device.

[0232] It should be noted that, when the battery cell 7 does not include the first adapter 51 , the first electrode tab 111 may be connected to the first electrode terminal 31 through the first conductive member 61 .

[0233] Exemplarily, the first conductive member 61 has electrical conductivity, and may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0234] In some embodiments, the thickness of the first conductive member 61 is 0.5 mm to 2.0 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or a range consisting of any two of the foregoing values. When the thickness of the first conductive member 61 is within the foregoing range, the current carrying capacity can be effectively increased, thereby improving the fast charging capability.

[0235] like Figure 22 As shown, in some embodiments, the second pole piece 12 satisfies: m*W3 / W4 is 0.5 to 1.0;

[0236] m represents the number of all the tabs on the same side of the coating portion;

[0237] W3 represents the average size of the pole ear portion along the second direction;

[0238] W4 represents the dimension of the coating portion along the second direction.

[0239] Illustratively, 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 consisting of any two of the above values.

[0240] When m*W3 / W4 satisfies the above range, the flow area of ​​the second electrode tab 121 is relatively large, which reduces heat generation and improves the power performance and cycle performance of the battery cell.

[0241] m can be 1 to 4.

[0242] W3 represents the average size of the second electrode tab 121 along the second direction. There may be one or more second electrode tabs 121. In the case of multiple second electrode tabs 121, the size of each second electrode tab 121 can be measured by a micrometer to calculate the average size.

[0243] The second pole tab 121 is connected to the second coating portion 122, and the second pole tab 121 includes a second end 1211 connected to the second coating portion 122. When m*W3 / W4 satisfies the above range, it means that the cross-section of the second end 1211 along the thickness direction of the second pole tab 121 itself is relatively large, and the contact area between the second pole tab 121 and the second coating portion 122 is relatively large. The second pole tab 121 has a strong current-carrying capacity, which can improve the power performance and cycle performance of the battery cell 7.

[0244] Optionally, the second electrode tab 121 and the current collecting portion of the second coating portion 122 are an integrated structure, so that the internal resistance of the second electrode sheet 12 is low, which can further improve the power performance and cycle performance of the battery cell 7 .

[0245] Optionally, there are at least two second electrode terminals 32, and m*W3 / W4 is 0.5 to 1.0. When the second pole piece 12 meets the above conditions, the connection area between the pole ear and the coating portion is relatively large, and the pole ear has a relatively large flow area, which is beneficial for reducing DC resistance and heat generation. There are at least two second electrode terminals 32, in other words, at least two second electrode terminals 32 are connected to the pole ear of the second pole piece 12, which can further increase the flow area between the second electrode terminals 32 and the pole ear, further reducing DC resistance, reducing heat generation, and improving the power performance and cycle performance of the battery cell.

[0246] In some embodiments, the second pole piece 12 includes one or more second pole tabs 121, and the one or more second pole tabs 121 are arranged on at least one side of the coating portion along the width direction Y. For example, one or more second pole tabs 121 are arranged on one side of the second coating portion 122 along the width direction Y. In this case, it can be understood that all second pole tabs 121 are arranged on the same side of the second coating portion 122 along the width direction Y. Or, for example, when the second pole piece 12 includes multiple second pole tabs 121, the multiple second pole tabs 121 are arranged on both sides of the second coating portion 122 along the width direction Y.

[0247] Optionally, one or more second electrode tabs 121 are respectively arranged on one side of the second coating portion 122 along the width direction Y. This arrangement is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0248] Optionally, there are at least two second electrode 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, at least four. This arrangement facilitates uniform distribution of electrons in the second electrode sheet 12 and improves fast charging performance.

[0249] like Figure 23 As shown, in other embodiments, the second pole piece 12 includes one or more second pole tabs 121; the one or more second pole 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 pole 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 pole tabs 121 are disposed on the same side of the second coating portion 122 along the length direction Z. Alternatively, for example, when the second pole piece 12 includes multiple second pole tabs 121, the multiple second pole tabs 121 are respectively disposed on both sides of the second coating portion 122 along the length direction Z.

[0250] Optionally, a plurality of second electrode tabs 121 are respectively arranged 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 sheet 12, which is conducive to improving the fast charging performance.

[0251] Optionally, there are at least two second electrode 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, at least four. This arrangement facilitates uniform distribution of electrons in the second electrode sheet 12 and improves fast charging performance.

[0252] In an embodiment of the present application, the second pole tab 121 and the second electrode terminal 32 are electrically connected, which can be directly or indirectly connected; when the second pole 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 pole tab 121 and connects the second electrode terminal 32 and the second pole tab 121.

[0253] 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 electrode tab 121 is disposed on one side of the second coating portion 122 along the width direction Y, the second adapter facilitates the connection between the second electrode tab 121 and the second electrode terminal 32, while also improving the current carrying capacity of the battery cell 7. When the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z, the utilized space of the second electrode sheet 12 along the width direction Y can be increased, thereby improving the energy density of the battery cell 7.

[0254] When the second pole lug 121 and the second electrode terminal 32 are respectively arranged on different sides of the battery cell 7, the second adapter may include a first connecting portion and a second connecting portion, the first connecting portion extending along the length direction Z, the first connecting portion connected to the second pole lug 121, the second connecting portion connected to the first connecting portion and protruding from the first connecting portion along the width direction Y, and connected to the second electrode terminal 32.

[0255] In the case where the second electrode tab 121 and the second electrode terminal 32 are disposed on the same side of the battery cell 7 , the second adapter may include only the first connecting portion.

[0256] In the above embodiments, the second adapter may be a sheet-like structure, and may also be other structural forms.

[0257] In the above embodiments, the second transition component may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0258] In some embodiments, the battery cell 7 further includes a second conductive member located between the second adapter and the second tab 121. The provision of the second conductive member can increase the current flow capacity between the second tab 121 and the second adapter, thereby improving fast charging performance and reducing heat generation. Furthermore, the second tab 121 and the second adapter, as well as the second conductive member and the second adapter, can be electrically connected via welding. The presence of the second conductive member can significantly reduce the risk of failure caused by direct electrical connection between multiple second tabs 121 and the second adapter.

[0259] For example, the pole tab portion of the second pole piece 12 is arranged on one side of the coating portion along the width direction Y; the second conductive member is located between the second adapter and the second pole tab 121 and connects the second adapter and the second pole tab 121 .

[0260] Optionally, there are at least two second pole ears 121 located on the same side of the second coating portion 122, and the second conductive member can be a continuous sheet structure, connecting at least two second pole ears 121; or there are at least two second conductive members, the second conductive members and the second pole ears 121 are connected one-to-one, and at least two second conductive members are connected to the second adapter. This connection method is beneficial to improving the weight energy density of the battery cell 7.

[0261] When the second electrode tab 121 and the second electrode terminal 32 are respectively arranged on different sides of the battery cell 7, the second conductive member can optionally include a third conductive portion and a fourth conductive portion. The third conductive portion extends along the length direction Z and connects the electrode tab of the second electrode sheet 12 to 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 is connected to the second adapter. This structural arrangement is conducive to increasing the grouping space in the length direction Z and improving the energy density of the battery device.

[0262] Exemplarily, the second conductive member has electrical conductivity, and may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements.

[0263] It should be noted that, when the battery cell 7 does not include the second adapter, the second electrode tab 121 may be connected to the second electrode terminal 32 via the second conductive member.

[0264] Positive electrode

[0265] In order to explain the present application more clearly, the coating portion of the positive electrode sheet corresponds to the positive electrode coating portion, the ear portion corresponds to the positive electrode ear, the active material layer corresponds to the positive electrode film layer containing the positive electrode active material, and the positive electrode coating portion includes a positive electrode current collecting portion and a positive electrode film layer arranged on at least one side of the positive electrode current collecting portion.

[0266] The positive electrode sheet includes a positive current collector and a positive electrode film layer comprising a positive electrode active material and disposed on at least one surface of the positive current collector. For example, the positive current collector may have two opposing surfaces in the thickness direction of the positive current collector, and the positive electrode film layer may be disposed on one or both of the two opposing surfaces of the positive current collector.

[0267] The upper limit voltage for charging and the cut-off voltage for discharging of the battery cell vary depending on the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit voltage for charging may be 3.65V and the cut-off voltage for discharging may be 2.0V, or the upper limit voltage for charging may be 3.8V and the cut-off voltage for discharging may be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit voltage for charging may be 4.3V and the cut-off voltage for discharging may be 2.0V. Next, taking the upper limit voltage for charging of 3.65V and the cut-off voltage for discharging of 2.0V as an example, the state of the battery cell is described: In the embodiment of the present application, the 100% state of charge SOC and the 0% state of charge SOC of the battery cell are defined as follows:

[0268] The battery cell is charged at a constant current charge rate of 0.33C to the upper limit of the charge voltage, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. The battery cell is discharged at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0269] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 0% state of charge SOC is 2.30 g / cm 3 to 2.70g / cm 3 ; Optional 2.40g / cm 3 Up to 2.55g / cm 3 For example, when the battery cell is at 0% state of charge (SOC), the compaction density of the positive electrode film is 2.30 g / cm 3 , 2.32g / cm 3 , 2.35g / cm 3 , 2.38g / cm 3 , 2.40g / cm 3 , 2.42g / cm 3 , 2.45g / cm 3 , 2.48g / cm 3 , 2.50g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3, 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 Or a range consisting of any two of the above values.

[0270] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the positive electrode active material of the positive electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation under fast charging, alleviating the problem of aggravated side reactions on the negative electrode side due to heat accumulation, and improving the cycle performance of the battery cell.

[0271] In some embodiments, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 Up to 330mg / 1540.25mm 2 , optional 275mg / 1540.25mm 2 Up to 300mg / 1540.25mm 2 For example, the coating weight of the positive electrode film on one side 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.

[0272] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, which will alleviate the problem of aggravated side reactions on the negative electrode side due to heat accumulation, improve the cycle performance of the battery cell, and increase the energy density of the battery cell.

[0273] In the embodiments of the present application, the compacted density of the positive electrode film layer of a battery cell at 0% state of charge (SOC) has a meaning well known in the art. Specifically, the positive electrode sheet of a battery cell at 0% state of charge (SOC) is disassembled and the compacted density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and 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. The compacted density of the positive electrode film layer = single-sided coating weight of the positive electrode film layer / thickness of the positive electrode film layer.

[0274] In some embodiments, the positive electrode active material includes a lithium-containing phosphate with an olivine structure. In other embodiments, the positive electrode active material may also include a lithium-containing transition metal oxide, etc. Examples of lithium-containing transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof.

[0275] In the embodiment of the present application, the lithium-containing phosphate with an olivine structure can be phosphate particles, or a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate with an 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.

[0276] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y zCompounds wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A comprises one or more of Na, K, and Mg, Me comprises one or more of Mn, Fe, Co, and Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X comprises one or more of Cl, C, and N, and Y comprises one or more of O and F. Phosphate particles have excellent cycling stability, which is beneficial for improving the high-temperature cycling performance of battery cells.

[0277] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cells are accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cells is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of this application.

[0278] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0279] In some embodiments, the positive electrode film layer further includes a positive electrode additive, which includes lithium elements and can release lithium ions during the charging process of the battery cell to compensate for lithium loss, thereby improving the capacity characteristics and high-temperature cycle performance of the battery cell.

[0280] In some embodiments, the positive electrode additive includes at least one of lithium ferrite particles or lithium nickelate particles.

[0281] In some embodiments, the longest diameter of the positive electrode additive is 2 μm to 5 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any combination thereof. Using positive electrode additives with such particle sizes can effectively improve the stability of the positive electrode additive while compensating for lithium loss, thereby improving the capacity characteristics and high-temperature cycling performance of the battery cell.

[0282] In the embodiments of the present application, the positive electrode sheet is cut along its thickness to expose a longitudinal section of the positive electrode film layer. The longitudinal section of the positive electrode film layer is then subjected to scanning electron microscopy (SEM) to determine the longest diameter of the positive electrode additive particles. For example, the "longest diameter" of a particle refers to the longest straight line extending through the center of the particle and to the particle's periphery.

[0283] In the cross section of the positive electrode film layer along its own thickness direction, the longest diameters of multiple, for example, 10, lithium-containing iron oxides are counted, and their average value is calculated as the average longest diameter; the shortest diameters of multiple, for example, 10, lithium-containing iron oxides are counted, and their average value is calculated as the average shortest diameter.

[0284] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the positive electrode additive is 0.2% to 2.5%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0% or a range consisting of any two thereof.

[0285] When a positive electrode additive with a good mass range is used, the lithium loss is compensated, which is beneficial to improving the capacity characteristics and high-temperature cycle performance of the battery cell.

[0286] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0287] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0288] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0289] In some embodiments, the ratio of the thickness of the positive electrode film layer on a single 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 a range consisting of any two of the foregoing values. Alternatively, the ratio of the thickness of the positive electrode film layer on a single side to the thickness of the positive electrode current collector is 4 to 8.

[0290] When the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collecting portion is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0291] In some embodiments, the thickness of the positive electrode current collector is 12 μm to 16 μm, optionally 13 μm to 15 μm. For example, the thickness of the positive electrode current collector is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, or a range consisting of any two of the above values.

[0292] When the thickness of the positive electrode current collecting portion is within the above range, the positive electrode current collecting portion has a relatively excellent current-carrying capacity, can improve the power performance of the battery cell, and can enable the battery cell to have a higher energy density.

[0293] In the embodiment of the present application, the thickness of the positive electrode film layer and the positive electrode current collecting portion has a meaning well known in the art and can be detected by using equipment and methods well known in the art. For example, a caliper is used to measure the thickness of the positive electrode sheet, the film layer on the surface of the positive electrode current collecting portion is removed, and the thickness of the positive electrode current collecting portion is measured with a caliper. 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 collecting portion. 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 collecting portion) / 2.

[0294] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0295] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0296] Negative electrode

[0297] In order to explain the present application more clearly, the coating portion of the negative electrode sheet corresponds to the negative electrode coating portion, the ear portion corresponds to the negative electrode ear, 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 collecting portion and a negative electrode film layer arranged on at least one side of the negative electrode current collecting portion, and the negative electrode coating portion includes a negative electrode current collecting portion and a negative electrode film layer arranged on at least one side of the negative electrode current collecting portion.

[0298] The negative electrode sheet includes a negative current collector and a negative electrode film layer comprising a negative electrode active material disposed on at least one surface of the negative current collector. For example, the negative current collector may have two opposing surfaces in the thickness direction of the negative current collector, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative current collector.

[0299] In some embodiments, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge (SOC) is 1.30 g / cm 3 Up to 1.65g / cm 3 ; Optional 1.35g / cm 3 Up to 1.50g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge is 1.3 g / cm 3 , 1.32g / cm 3, 1.35g / cm 3 , 1.40g / cm 3 , 1.45g / cm 3 , 1.50g / cm 3 , 1.55g / cm 3 , 1.60g / cm 3 , 1.65g / cm 3 Or a range consisting of any two of the above values.

[0300] When the compaction density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active material of the negative electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation, alleviating the problem of aggravated side reactions on the negative electrode side due to heat accumulation, and improving the cycle performance of the battery cell.

[0301] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 0% state of charge SOC has a meaning well known in the art and can be detected using equipment and methods well known in the art, and its detection method is the same as the compaction density test method of the positive electrode film layer mentioned above.

[0302] In some embodiments, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 Up to 180mg / 1540.25mm 2 , optional 125mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side 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 / 1540.25mm 2 、170mg / 1540.25mm 2 、175mg / 1540.25mm 2 、180mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0303] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, thereby alleviating the problem of aggravated side reactions on the negative electrode side due to heat accumulation, improving the cycle performance of the battery cell, and being able to simultaneously improve the energy density of the battery cell.

[0304] In the embodiment of the present application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the single-sided coating weight test method of the film layer described above.

[0305] In some embodiments, the negative electrode active material includes a carbon-based material, which has high cycling stability and can improve the high-temperature cycling performance of the battery cell. The positive electrode active material of this application is primarily an olivine-structured lithium-containing phosphate system, and the negative electrode active material is primarily a carbon-based material system. The combination of the two results in excellent high-temperature cycling performance for the battery cell.

[0306] Optionally, the carbon-based material includes artificial graphite, which has excellent electrical conductivity, can reduce the heat generation of the negative electrode plate, reduce the heat generation of the battery cell, and can improve the power performance and cycle performance of the battery cell.

[0307] In some embodiments, the carbon-based material may also include natural graphite. Specifically, the carbon-based material may include artificial graphite, or the carbon-based material may include both artificial and natural graphite. Natural graphite has relatively good electrical conductivity, which further reduces heat generation and improves the power performance and cycle performance of the battery cell.

[0308] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate, in addition to the aforementioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy. Alternatively, the silicon-based material may include at least one of elemental silicon, silicon oxide, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy.

[0309] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0310] For example, the present application may combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0311] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0312] In the embodiment of the present 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.

[0313] In the case where the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material. In the case of a single-layer film layer, the volume average particle size Dv50 of the carbon-based material is 8μm to 13μm, and can be optionally 9.5μm to 11.5μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 8μm, 8.5μm, 8.8μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10μm, 10.2μm, 10.5μm, 10.8μm, 11μm, 11.2μm, 11.5μm, 11.8μm, 12μm, 12.2μm, 12.5μm, 12.8μm, 13μm or a range consisting of any two of the above values.

[0314] In the case where the negative electrode film layer comprises at least two film layers, the negative electrode active material in the negative electrode film layer comprises a carbon-based material. The negative electrode film layer may comprise two film layers, three film layers, four film layers, or even more film layers.

[0315] 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 being disposed on a surface of a negative electrode current collector, the carbon-based material in the first negative electrode film layer including artificial graphite, the second negative electrode film layer being connected to a side of the first negative electrode film layer facing away from the negative electrode current collector, the carbon-based material in the second negative electrode film layer including artificial graphite, and the artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer may 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, they may have different particle sizes or different degrees of graphitization.

[0316] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and may optionally be irregular.

[0317] The negative electrode film comprises at least two layers, and layered coating is beneficial for improving the rapid charging performance of the battery cell. In particular, when the first and second negative electrode film layers are different, the pore differences between the negative electrode film layers can be created, reducing the tortuosity of lithium-ion transport, improving the rapid charging performance of the battery cell, and enhancing the cycling performance and power performance of the battery cell.

[0318] 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, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer, which is beneficial for improving the dynamic performance of the negative electrode film layer, improving the rapid charging performance of the battery cell, and thus improving the power performance of the battery cell.

[0319] There is a difference in the particle size of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiment of the present application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium plating on the surface of the negative electrode sheet, thereby improving the cycle performance of the battery cell.

[0320] Optionally, the carbon-based material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm, and 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, a 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 optionally 9.5 μm to 14.6 μm.

[0321] When the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material.

[0322] Optionally, the carbon-based material in the second negative electrode film layer is in granular form, and its volume average particle size Dv50 is 7.8 μm to 14.3 μm, and optionally 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 7.8μm, 8.0μm, 8.2μm, 8.5μm, 8.8μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10μm, 10.2μm, 10.5μm, 10.8μm, 11μm, 11.3μm, 11.2μm, 11.5μm, 11.8μm, 12μm, 12.2μm, 12.5μm, 12.8μm, 13μm, 13.2μm, 13.5μm, 13.8μm, 14μm, 14.1μm, 14.3μm or a range consisting of any two of the above values. When the second negative electrode film layer includes a carbon-based material, a 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 optionally 7.8 μm to 11.3 μm.

[0323] When the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material; on the other hand, the combination of the negative electrode active material in the second negative electrode film layer within the above volume average particle size range and the negative electrode active material in the first negative electrode film layer is beneficial to constructing a gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, improving the fast charging performance of the battery cell, and improving the power performance and cycle performance of the battery cell.

[0324] In the embodiment of the present application, the volume average particle size Dv50 of the negative electrode active material has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the negative electrode active material is used as a sample and the Dv50 and Dv10 of the particles are tested using a Mastersizer 2000E laser particle size analyzer in accordance with the test standard GB / T 19077-2016.

[0325] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0326] Illustratively, 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.

[0327] In other embodiments, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is greater than the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer. Further optionally, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is greater than the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer, which is beneficial to improving the compaction density of the negative electrode film layer.

[0328] The difference in particle size between the first negative electrode film layer and the second negative electrode film layer can improve the fast charging performance of the battery cell.

[0329] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. For 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 weight content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0330] In some embodiments, the negative electrode film layer may further include a negative electrode binder. In some embodiments, the negative electrode binder has a mass content of ≤5% based on the total weight of the negative electrode film layer.

[0331] In some embodiments, the negative electrode film layer may also optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0332] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0333] In some embodiments, the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collector is 8 to 14, such as 8, 9, 10, 11, 12, 13, 14, or a range consisting of any two of the foregoing values. Alternatively, the ratio of the thickness of the negative electrode film layer on one side to the thickness of the negative electrode current collector is 10 to 12.

[0334] When the ratio of the thickness of the single-side negative electrode film layer to the thickness of the negative electrode current collecting portion is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0335] In some embodiments, the thickness of the negative electrode current collector is 5 μm to 10 μm, optionally 6 μm to 8 μm. For example, the thickness of the negative electrode current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or a range consisting of any two of the above values.

[0336] When the thickness of the negative electrode current collecting portion is within the above range, the negative electrode current collecting portion has a relatively excellent current-carrying capacity, thereby improving the power performance of the battery cell and enabling the battery cell to have a higher energy density.

[0337] In the embodiment of the present application, the thickness of the negative electrode current collector has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, a solvent is used to wash away the film layer on the surface of the negative electrode current collector, and the thickness of the negative electrode current collector is measured with a micrometer.

[0338] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0339] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0340] Isolators

[0341] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0342] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical and mechanical stability can be selected.

[0343] As an example, the primary material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. The surface of the separator can also be coated with an inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating.

[0344] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transport ions and isolate the positive and negative electrodes.

[0345] electrolyte

[0346] In some embodiments, the battery cell further includes an electrolyte.

[0347] During the charge and discharge process of a battery cell, active ions such as lithium ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays the role of conducting active ions between the positive electrode and the negative electrode.

[0348] In an embodiment of the present application, the organic solvent includes a carbonate solvent and a chain carboxylate solvent, and the electrolyte has a room temperature conductivity of 10 mS / cm to 13 mS / cm. For example, the room temperature conductivity of the electrolyte 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 a range consisting of any two of these values.

[0349] When the conductivity of the electrolyte at room temperature, for example, 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.

[0350] In the embodiment of the present application, the conductivity of the electrolyte at room temperature, for example, 25° C., is ionic conductivity, which can be tested using equipment and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0351] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not particularly limited and can be selected according to actual needs.

[0352] In some embodiments, the organic solvent further includes a carbonate solvent.

[0353] Optionally, the mass content of the carbonate solvent in the electrolyte is 10% to 80%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, or a range consisting of any two of the above values. The above mass content of carbonate solvent can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions; and the mass content of carbonate solvent is not too high, which can reduce high-temperature gas production and improve high-temperature cycle performance.

[0354] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Further, optionally, the carbonate solvent includes one or more of dimethyl carbonate and ethyl methyl carbonate. The combination of the above carbonate solvents and chain carboxylate solvents improves the conductivity of the electrolyte at room temperature, facilitates lithium ion migration, and improves the power performance of the battery cell.

[0355] Illustratively, 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%.

[0356] In some embodiments, the organic solvent includes a linear carboxylate solvent.

[0357] Optionally, the mass content of the chain carboxylate solvent in the electrolyte is 5% to 30%. Exemplarily, the mass content of the chain carboxylate solvent is 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the above values.

[0358] When the mass content of the chain carboxylate solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is conducive to the migration of lithium ions; and the mass content of the chain carboxylate solvent is not too high, which can reduce high-temperature gas production and improve high-temperature cycle performance.

[0359] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0360] Formula I,

[0361] In Formula I,

[0362] R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0363] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0364] The above-mentioned chain carboxylic acid ester solvent has a high electrical conductivity, which is beneficial to improving the fast charging capability of the battery cell and improving the power performance of the battery cell.

[0365] Alternatively, R1 includes a hydrogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0366] Alternatively, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further alternatively, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0367] In each of the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0368] Illustratively, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0369]

[0370] When the mass content of the chain carboxylic acid ester solvent is 5% to 30%, the unit capacity area of ​​the pressure relief component is 1.2mm 2 / Ah to 1.8mm 2 / Ah.

[0371] For example, the unit volume area of ​​the pressure relief component is 1.2 mm 2 / Ah, 1.3mm 2 / Ah, 1.4mm 2 / Ah, 1.5mm 2 / Ah, 1.6mm2 / Ah, 1.7mm 2 / Ah, 1.8mm 2 / Ah or a range consisting of any two of the above values.

[0372] As the capacity of the battery cell increases, the injection volume of the battery cell increases, the amount of chain carboxylic acid ester solvent added increases, the risk of gas production increases, and the amount of gas production may increase; in the embodiment of the present application, the area per unit capacity of the pressure relief component is greater than 1.2mm 2 / Ah, can quickly release gas and improve the reliability of battery cells; and the area per unit capacity of the pressure relief component is less than or equal to 1.8mm 2 / Ah, so that the area occupied by the pressure relief component is relatively small, and the area occupied by the electrode terminals can be taken into account, so that the flow capacity is relatively high; therefore, when the battery cell of the embodiment of the present application meets the above conditions, it can take into account the improvement of the battery cell's reliability and flow capacity, and improve the power performance of the battery cell.

[0373] In some embodiments, the electrolyte salt includes a lithium salt, which includes one or more of a fluorinated sulfonyl imide salt and lithium hexafluorophosphate (LiPF6). These lithium salt systems are relatively stable and resistant to decomposition. Lithium salts are beneficial for improving the conductivity of the electrolyte, the dynamic performance of the battery cells, and the power performance of the battery cells. Fluorinated sulfonyl imide salts include monofluorosulfonyl imide salts and bisfluorosulfonyl imide salts, with bisfluorosulfonyl imide salts being an option.

[0374] In some embodiments, the lithium salt content is 13% to 20% by weight of the electrolyte, such as 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or a range consisting of any two of these values. When the lithium salt content is within the above range, the lithium salt helps increase the conductivity of the electrolyte and improve the power performance of the battery cell.

[0375] Optionally, based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium bis(fluorosulfonyl)imide is 1.2 to 2.0. When the lithium salt meets the above conditions, the system is relatively stable and not easy to decompose. The lithium salt is beneficial to improving the conductivity of the electrolyte, improving the kinetic performance of the battery cell, and improving the power performance of the battery cell. When the ratio of the mass content of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide meets the above range, it can also reduce the content of hydrofluoric acid, slow down the side reactions at the negative electrode interface, and help improve the high-temperature cycle life of the battery cell.

[0376] Illustratively, the mass content of lithium hexafluorophosphate and the mass content of lithium bis(fluorosulfonyl)imide are 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or a range consisting of any two of the above values.

[0377] Illustratively, based on the mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 1% to 15%, optionally 3% to 12%.

[0378] For example, based on the mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the foregoing values. When the mass content of lithium bis(fluorosulfonyl)imide is within the foregoing range, the hydrofluoric acid content can be reduced, the negative electrode interface side reactions can be slowed down, and the gas production during high-temperature storage can be reduced, which is beneficial for improving the high-temperature cycle life of the battery cell.

[0379] In some embodiments, the electrolyte further includes additives, including one or more of carbonate additives and sulfur-containing additives, and optionally at least two. These additives can improve the SEI film performance on the positive and / or negative electrode sides, thereby enhancing the rapid charging performance of the battery cell and improving high-temperature cycling performance.

[0380] In some embodiments, the weight content of the additive in the electrolyte is 0.5% to 6%. For example, the weight content of the additive in the electrolyte is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6%, or a range consisting of any two of the above values.

[0381] The above-mentioned organic solvents, such as chain carboxylic acid ester solvents, may decompose and produce acid at high temperatures, corroding the SEI film on the surface of the negative electrode. The additives can form a dense and uniform film layer on the negative electrode side, which can effectively repair the SEI film and provide excellent protection for the negative electrode active materials, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycle performance.

[0382] Illustratively, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Optionally, the carbonate additive includes both 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, thereby improving the power performance and high-temperature cycling performance of the battery cell.

[0383] Fluoroethylene carbonate FEC can form a SEI film with relatively low impedance on the negative electrode side, can effectively repair the SEI film, and provide 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.

[0384] For example, the sulfur-containing additive includes one or more of vinyl sulfate (DTD), vinyl disulfate (2-DTD), butylene sulfite (BS), 1,3-propane sultone (PS), vinyl sulfite (ES), and methylene dimethyl disulfonate (MMDS), with 1,3-propane sultone (PS) being an option. Sulfur-containing additives can effectively repair the SEI film, providing excellent protection for the negative electrode active material, and improving the power performance and high-temperature cycling performance of the battery cells.

[0385] Illustratively, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

[0386] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 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 a range consisting of any two of the foregoing values. When the mass content of vinylene carbonate (VC) in the electrolyte is within the foregoing range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and improve the power performance and high-temperature cycling performance of the battery cell.

[0387] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 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 a range consisting of any two of the foregoing values. When the mass content of fluoroethylene carbonate (FEC) in the electrolyte is within the foregoing range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and improve the power performance and high-temperature cycling performance of the battery cell.

[0388] Optionally, the mass content of 1,3-propane sultone (PS) in the electrolyte is 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 a range consisting of any two of these values. When the mass content of 1,3-propane sultone (PS) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and improve the power performance and high-temperature cycling performance of the battery cell.

[0389] In the embodiments of the present application, the types and contents of the inorganic components / lithium salts in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis method.

[0390] In the embodiment of the present application, the types and contents of the organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic components in the electrolyte by gas chromatography.

[0391] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the components are classified, and the chain carboxylate solvent and carbonate solvent (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as components of the organic solvent. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0392] Carbonate additives (such as vinylene carbonate and fluoroethylene carbonate) and sulfur-containing additives are used as additives for the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0393] In some embodiments, the volumetric energy density of the battery cell is between 375Wh / L and 450Wh / L. For example, the volumetric energy density of the battery cell is 375Wh / L, 380Wh / L, 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, 450Wh / L, or a range consisting of any two of these values. The volumetric energy density of the battery cell is relatively high.

[0394] In the embodiments of the present application, the volume energy density of a battery cell has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V.

[0395] Place the battery cell at 25°C, charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage to 0.05C, and discharge at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), calculate the volume of the single battery V0, unit L, and the volume energy density of the battery cell VED = (A0 × discharge platform voltage) / V0, unit Wh / L.

[0396] Example

[0397] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0398] Example 1

[0399] 1. Preparation of positive electrode sheet

[0400] The positive electrode sheet includes a positive current collector and positive electrode films disposed on both sides of the positive current collector. The positive current collector is made of 13μm thick aluminum foil. The ratio of the thickness of the positive electrode film on one side to the thickness of the positive current collector is 5.5.

[0401] The positive electrode film layer includes lithium-containing phosphate, positive electrode additives, 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 evenly coating the positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive electrode current collecting part, and then drying and cold pressing.

[0402] Lithium-containing phosphates include lithium iron phosphate.

[0403] The positive electrode additive includes lithium ferrite, and the mass content of the positive electrode additive in the positive electrode film layer is 1.5%.

[0404] The single-sided coating weight of the positive electrode film is 282mg / 1540.25mm 2 .

[0405] The length of the positive electrode film layer is 502 mm, and the ratio of the length to the width of the positive electrode film layer is 5.4.

[0406] 2. Preparation of negative electrode sheet

[0407] The negative electrode sheet includes a negative current collecting portion and negative electrode film layers arranged on both sides of the negative current collecting portion. The negative current collecting portion is a copper foil with a thickness of 6 μm. The ratio of the thickness of the single-sided negative electrode film layer to the negative electrode current collecting portion is 10.3.

[0408] The negative electrode film layer is formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector, drying it, and cold pressing it.

[0409] The single-sided coating weight of the negative electrode film is 134mg / 1540.25mm 2 .

[0410] 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 collecting portion, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0411] The first negative electrode film layer includes a carbon-based material, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a 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.

[0412] The second negative electrode film layer includes a carbon-based material, a conductive agent acetylene black, a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose in a mass ratio of 96.5:1:1.5:1. The carbon-based material of the second negative electrode film layer includes artificial graphite, and the volume average particle size of the carbon-based material is 9.5 μm.

[0413] 3. Isolation film

[0414] The isolation film includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0415] 4. Preparation of electrolyte

[0416] The electrolyte comprises an organic solvent, a lithium salt and an additive. The components of the organic solvent are mixed, and the lithium salt and the additive are added to prepare the electrolyte.

[0417] The organic solvent includes 10% chain carboxylic acid ester solvent (ethyl acetate) and 70% carbonate solvent (10% dimethyl carbonate DMC, 25% ethyl methyl carbonate EMC, 10% diethyl carbonate DEC, 25% ethylene carbonate EC). The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0418] Based on the mass of the electrolyte, the additives include 2.5% vinylene carbonate VC, 1% fluoroethylene carbonate FEC, and 2.5% 1,3-propane sultone PS.

[0419] The lithium salt includes 8.5% lithium hexafluorophosphate LiPF6 and 5.5% lithium bis(fluorosulfonyl)imide.

[0420] The conductivity of the electrolyte at room temperature is 12 mS / cm.

[0421] 5. Preparation of battery cells

[0422] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a housing, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. The compacted density of the positive electrode film layer of the battery cell at 0% SOC is 2.55 g / cm 3 The compaction density of the negative electrode film at 0% SOC is 1.4g / cm 3 .

[0423] in,

[0424] The outer shell includes an end cap and a shell. The shell is 0.35mm thick and made of aluminum. The end cap is also provided with a pressure relief component, a positive terminal and a negative terminal. The unit capacity area of ​​the pressure relief component is 2mm. 2 / Ah.

[0425] Comparative Example 1-1 and Comparative Example 1-2

[0426] A battery cell was prepared using a method similar to that of Example 1. Unlike Example 1, Comparative Example 1-1 adjusted the number of positive terminals; and unlike Example 1, Comparative Example 1-2 adjusted the number of positive electrode tabs.

[0427] Example 1-1 and Example 1-2

[0428] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the size of the positive terminal was adjusted.

[0429] Example 1-3 to Example 1-6

[0430] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the number and / or arrangement positions of the positive electrode tabs were adjusted.

[0431] Performance Testing

[0432] 1. Power density test of battery cells

[0433] At 25°C, charge the battery cell to 3.65 V at a constant current of 0.33 C, let it rest for 10 min, then charge it to 3.65 V at a constant current of 0.33 C, let it rest for 30 min, and discharge it to 2.0 V at a constant current of 0.33 C. Record the discharge capacity C0 and discharge energy E0 at this time.

[0434] Charge the battery cell at a constant current of 0.33C to a cut-off voltage of 3.65V and leave it for 10 minutes; discharge it at a constant current of 0.33C0 for 90 minutes to adjust the battery cell to 50% SOC, record the voltage U1 at this time, then discharge it with a 4C0 pulse for 10 seconds, and record the voltage after discharge as U2. The corresponding DC resistance R=(U1-U2) / 4C0, power W=discharge cut-off voltage*(U1-discharge cut-off voltage) / R, and power density P=W / E0.

[0435] 2. High temperature cycle performance of battery cells

[0436] At 45°C, charge the battery cell to 3.65V at a constant current of 0.5C, then charge it to 0.05C at a constant voltage, let it stand for 10 minutes, and then discharge it to 2.0V at a constant current of 1C. This is one charge and discharge cycle, and record the first-cycle discharge capacity. Let it stand for 10 minutes and repeat the above charge and discharge cycle until the battery cell discharge capacity decays to 80% of the first-cycle discharge capacity. Stop the test and record the number of cycles.

[0437] The test results are shown in Table 1.

[0438] Table 1

[0439]

[0440] In Table 1, in the embodiment where the positive electrode terminal is exposed at the short side and the positive electrode tab is exposed at the long side, the battery cell further includes a first conductive member, and the thickness of the first conductive member is 1.0 mm.

[0441] S1 represents the ratio of the first area to the second area, where the first area is the projection of the first electrode protrusion of the positive terminal parallel to the thickness direction, and the second area is the projection of the end cap parallel to the thickness direction.

[0442] S2 represents the ratio of the size of the first electrode protrusion of the positive terminal along the thickness direction of the battery cell to the size of the end cover along the thickness direction of the battery cell; for example Figure 9 In the embodiment, the dimension of the end cover along the thickness direction of the battery cell can be considered as the width of the end cover; 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;

[0443] S3 represents the ratio of the dimension of the first conductive fixing member along the thickness direction of the battery cell to the dimension of the end cover along the thickness direction of the battery cell; for example Figure 9 In the embodiment, the dimension of the first conductive fixing member along the thickness direction of the battery cell is X1, which can be considered as the width of the first conductive fixing member; the dimension of the end cover along the thickness direction of the battery cell can be considered as the width X2 of the end cover.

[0444] The number of positive terminals refers to the total number of positive terminals in the same battery cell.

[0445] The positive terminal is located on the short side, which means that the positive terminal is located on at least one side of the electrode assembly along the length direction.

[0446] The positive terminals are located on the same side along the length of the electrode assembly.

[0447] The positive terminals are located on both sides of the short side, which means that multiple positive terminals are located on both sides of the electrode assembly along the length direction.

[0448] The positive terminals are on both sides of the short side, one on each side, which means that there are two positive terminals, and the two positive terminals are located on both sides of the electrode assembly along the length direction; Figure 12 As shown in .

[0449] The positive terminal is located on the long side, which means that the positive terminal is located on at least one side of the electrode assembly along the width direction.

[0450] The number of positive electrode tabs refers to the total number of positive electrode tabs in the same positive electrode sheet.

[0451] The positive electrode tab is located on at least one side of the positive electrode current collecting portion along the length direction;

[0452] The positive electrode tabs are on the same side along the length direction, which means that all the positive electrode tabs are located on the same side of the positive electrode current collector. Figure 17 As shown in .

[0453] The positive electrode tabs are located on both sides of the short side, which means that multiple positive electrode tabs are located on both sides of the positive electrode current collecting part along the length direction;

[0454] The positive electrode tabs are protruding from both sides of the short side, one on each side, which means that there are two positive electrode tabs, and the two positive electrode tabs are respectively located on both sides of the positive electrode current collecting part along the length direction; Figure 18 As shown in .

[0455] The positive electrode tab is located on at least one side of the positive electrode current collecting portion along the width direction;

[0456] The positive electrode tabs are on the same side along the width direction of the positive electrode current collector. Figure 15 As shown in .

[0457] n*W1 / W2 refers to the ratio of the size of all the positive electrode tabs located on the same side of the positive electrode current collecting portion along the second direction to the size of the positive electrode current collecting portion along the second direction.

[0458] From the comparison between the comparative example and the embodiment, it can be seen that the number of positive terminals in the embodiment of the present 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 conducive to improving the volume energy density and power performance of the battery cell as well as the high-temperature cycle performance.

[0459] As the number of positive terminals increases, for example, to four, the current capacity increases accordingly. However, due to the limited assembly space on the end cap, the number of positive terminals cannot be increased indefinitely.

[0460] In Comparative Example 1-1, although the size of the positive electrode tab accounts for a relatively high proportion, the number of positive terminals is too small, which may lead to poor overcurrent capability, large DC impedance of the battery cell, and high internal temperature rise, which is not conducive to the power density and high-temperature cycle performance of the battery cell.

[0461] Compared to Comparative Example 1-1, Examples 1 and 1-1 through 1-6 have two positive terminals, resulting in superior current capacity, lower DC impedance of the battery cells, and lower temperature rise, which improves the power density and high-temperature cycling performance of the battery cells. The positive terminals can be located on the same side or on either side of the battery cell. As long as the number of positive terminals meets the requirements, both improve the power density and high-temperature cycling performance of the battery cells.

[0462] In Comparative Examples 1-2, although there are two positive terminals on the same side of the battery cell, since the positive electrode tabs are on the same side, the size of the positive electrode tabs is too small, which may lead to poor overcurrent capability and a large DC impedance of the battery cell, thereby reducing the power density of the battery cell. In addition, the internal temperature rise of the battery cell is high, which deteriorates the high-temperature cycle performance.

[0463] Compared with Comparative Examples 1-2, the positive electrode tabs of Examples 1-6 have a higher size ratio, a lower DC impedance of the battery cell, and a lower temperature rise of the battery cell, which can improve the power density and high-temperature cycle performance of the battery cell.

[0464] Compared with Example 1, Example 1-1 and Example 1-2 adjust the minimum cross-sectional ratio of the first electrode protrusion. The higher the minimum cross-sectional ratio, the stronger the current capacity and the lower the temperature rise of the battery cell, which is beneficial to improving the power density and high-temperature cycle performance of the battery cell.

[0465] Compared with Examples 1-5, the size ratio of the positive electrode tab in Example 1 is increased. The higher the size ratio, the better the current capacity and the smaller the temperature rise, which is beneficial to improving the power density and high-temperature cycle performance of the battery cell.

[0466] Example 2-1

[0467] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the single-sided coating weight and compaction density of the positive electrode film layer and the negative electrode film layer were adjusted.

[0468] Example 2-2 and Example 2-3

[0469] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the size of the positive electrode film layer was adjusted.

[0470] Comparative Example 2-1 and Comparative Example 2-2

[0471] A battery cell was prepared using a method similar to that in Example 1. The difference from Example 1 was that the size of the positive electrode film layer was adjusted. The size of the negative electrode film layer was adjusted accordingly. The length of the negative electrode film layer was 5 mm greater than the length of the positive electrode film layer, and the width of the negative electrode film layer was 5 mm greater than the width of the positive electrode film layer.

[0472] The test results are shown in Table 2.

[0473] Table 2

[0474]

[0475] The length of the positive electrode film layer of Comparative Example 2-1 is shorter, and the amount of active material that can be carried is less, resulting in a lower energy density of the battery cell.

[0476] The positive electrode film layer of Comparative Example 2-2 is longer and has a larger aspect ratio, which makes the electron transmission path in the positive electrode plate longer and the resistance may be too large, thereby deteriorating the power performance and high-temperature cycle performance of the battery cell.

[0477] It can be seen from Examples 2-1 to 2-3 that when the size of the positive electrode film layer is within an appropriate range, or the single-sided coating weight and compaction density of the film layer are within an appropriate range, the volume energy density, power performance and high-temperature cycle performance of the battery cell can be improved.

[0478] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the embodiments of the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: A housing assembly comprising 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 is located in the housing, the electrode assembly includes a plurality of first pole sheets and a plurality of second pole sheets, the first pole sheets and the second pole sheets are stacked along the thickness direction of the battery cell, the first pole sheet and the second pole sheet each include a coating portion and a pole ear portion, the coating portion is provided with an active material layer, and the pole ear portion is provided on at least one side of the coating portion along a first direction, the first direction being a direction parallel to the length direction or the width direction of the battery cell, One of the first and second electrode sheets is a positive electrode sheet, and the other is a negative electrode sheet; the active material layer of the positive electrode sheet includes a lithium-containing phosphate; the ratio of the dimension of the coating portion of the positive electrode sheet along the length direction to the dimension of the coating portion of the positive electrode sheet along the width direction is 4 to 7; and the dimension of the coating portion of the positive electrode sheet along the length direction is 300 mm to 650 mm; There are at least two first electrode terminals, at least two of which are electrically connected to the tabs of the first pole piece, and the second electrode terminal is electrically connected to the tabs of the second pole piece; The first pole piece satisfies: n*W1 / W2 is 0.5 to 1.0; n represents the number of all the tabs located on the same side of the coating portion; W1 represents the average size 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 size of the coating portion along the second direction; There are at least two second electrode terminals; The second pole piece satisfies: m*W3 / W4 is 0.5 to 1.0; m represents the number of all the tabs located on the same side of the coating portion; W3 represents the average size of the pole ear portion along the second direction; W4 represents the dimension of the coating portion along the second direction.

2. The battery cell according to claim 1, wherein: At least two 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, characterized in that: There are two to four first electrode terminals.

4. The battery cell according to claim 1, wherein: The housing includes a shell and an end cover, the shell accommodates the electrode assembly, the shell includes an opening, the end cover covers the opening, and the first electrode terminal is disposed on the end cover; 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 cover 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 passes through the end cover.

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

40.

6. The battery cell according to claim 4 or 5, characterized in that: The first electrode body and the first electrode protrusion are an integrated structure.

7. The battery cell according to claim 4, characterized in that The housing assembly further includes a first conductive fixing member, at least a portion of which is located on a side of the end cover facing away from the electrode assembly. The first conductive fixing member is disposed around the outside of the first electrode terminal and fixedly connects the first electrode terminal and the end cover.

8. The battery cell according to claim 7, characterized in that A ratio of a dimension of the first conductive fixing member along a thickness direction of the battery cell to a dimension of the end cover along the thickness direction of the battery cell is 0.40 to 0.

80.

9. The battery cell according to claim 1, characterized in that The first pole piece has at least two pole lugs; At least two pole lugs of the first pole piece are arranged on the same side of the coating portion along the length direction; or The at least two pole tabs of the first pole piece are respectively arranged on two sides of the coating portion along the length direction.

10. The battery cell according to claim 1, characterized in that The pole ear portion of the first pole piece is provided on at least one side of the coating portion along the width direction. There is one pole ear portion on the same side of the coating portion in the first pole piece, and n*W1 / W2 is 1.0; or There are at least two pole lugs in the first pole piece located on the same side of the coating portion.

11. The battery cell according to claim 10, characterized in that The number of pole lugs located on the same side of the coating portion in the first pole piece is two to four.

12. The battery cell according to claim 1, wherein The battery cell further includes a first adapter, which is located between the first electrode terminal and the pole ear portion of the first pole piece and connects the first electrode terminal and the pole ear portion of the first pole piece.

13. The battery cell according to claim 12, characterized in that: 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 pole ear portion of the first pole piece is disposed on at least one side of the coating portion along the width direction.

14. The battery cell according to claim 13, characterized in that The first adapter comprises: a first transition portion extending along the length direction, the first transition portion being connected to the pole ear portion of the first pole piece; and The second transition portion is connected to the first transition portion, protrudes from the first transition portion along the width direction, and is connected to the first electrode terminal.

15. The battery cell according to claim 12, characterized in that The battery cell further includes a first conductive member, which is located between the first adapter and the pole ear portion of the first pole piece and connects the first adapter and the pole ear portion of the first pole piece.

16. The battery cell according to claim 15, characterized in that There are at least two pole lugs located on the same side of the coating portion in the first pole piece; The first conductive member is a continuous sheet structure, and the first conductive member connects the at least two electrode lugs; or There are at least two first conductive members, and the first conductive members are connected to the pole lugs in a one-to-one correspondence.

17. The battery cell according to claim 15 or 16, characterized in that: The first conductive member includes: a first conductive portion extending along the length direction, the first conductive portion connecting the pole ear portion of the first pole piece and the first adapter; and The second conductive portion is connected to the first conductive portion and protrudes from the first conductive portion along the width direction. The second conductive portion is connected to the second adapter portion of the first adapter.

18. The battery cell according to claim 15, characterized in that The thickness of the first conductive member is 0.5 mm to 2.0 mm.

19. The battery cell according to claim 1, characterized in that The housing includes a shell and an end cover, the shell includes an opening, the end cover covers the opening, the shell accommodates the electrode assembly, and the shell includes: two first shell portions facing each other along the thickness direction; and The second shell portion and the third shell portion are opposite to each other, the second shell portion and the third shell portion are connected through the first shell portion, the second shell portion includes a first wall and a second wall continuously arranged along the thickness direction, and the first wall and the second wall are welded.

20. The battery cell according to claim 19, characterized in that The thickness of the shell is 0.1 mm to 0.5 mm.

21. The battery cell according to claim 1, characterized in that It also includes a pressure relief component, which is arranged on the housing component, and the unit capacity area of ​​the pressure relief component is 1.2mm 2 / Ah to 1.8mm 2 / Ah.

22. The battery cell according to claim 21, characterized in that There are two pressure relief components, and the two pressure relief components are respectively arranged on both sides of the shell component.

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

24. The battery cell according to claim 1, characterized in that The single-side 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 .

25. The battery cell according to claim 24, characterized in that The single-side coating weight of the active material layer is 275 mg / 1540.25 mm 2 Up to 300mg / 1540.25mm 2 .

26. The battery cell according to claim 1, characterized in that The battery cell is at 0% state of charge, and the compaction density of the active material layer of the positive electrode sheet is 2.30 g / cm 3 to 2.70g / cm 3 .

27. The battery cell according to claim 26, characterized in that The battery cell is at 0% state of charge, and the compaction density of the active material layer of the positive electrode sheet is 2.40 g / cm 3 Up to 2.55g / cm 3 .

28. The battery cell according to claim 1, characterized in that The coating portion of the negative electrode sheet includes a negative current collecting portion and an active material layer disposed on at least one side of the negative current collecting portion. The active material layer includes a negative active material. The negative active material includes a carbon-based material. The carbon-based material includes artificial graphite.

29. The battery cell according to claim 28, characterized in that The active material layer of the negative electrode plate includes: A first negative electrode film layer is provided on the surface of the negative electrode current collecting portion; and A second negative electrode film layer is connected to a side of the first negative electrode film layer away from the negative electrode current collecting portion, The volume average particle size Dv50 of the carbon-based material 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.

30. The battery cell according to claim 29, characterized in that 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.

31. The battery cell according to claim 29 or 30, characterized in that: The carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

32. The battery cell according to claim 28, characterized in that The single-side coating weight of the active material layer of the negative electrode plate is 120 mg / 1540.25 mm 2 Up to 180mg / 1540.25mm 2 .

33. The battery cell according to claim 32, characterized in that The single-side coating weight of the active material layer of the negative electrode plate is 125 mg / 1540.25 mm 2 Up to 150mg / 1540.25mm 2 .

34. The battery cell according to claim 28, wherein: The battery cell is at a 0% state of charge, and the compaction density of the active material layer of the negative electrode plate is 1.30 g / cm 3 Up to 1.65g / cm 3 .

35. The battery cell according to claim 34, characterized in that The battery cell is at a 0% state of charge, and the compaction density of the active material layer of the negative electrode plate is 1.35 g / cm 3 Up to 1.50g / cm 3 .

36. The battery cell according to claim 1, characterized in that The battery cell further includes an electrolyte, the electrolyte includes a chain carboxylate solvent, and the conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm.

37. The battery cell according to claim 36, characterized in that Based on the mass of the electrolyte, the mass content of the chain carboxylate solvent is 5% to 30%.

38. The battery cell according to claim 36 or 37, characterized in that: The electrolyte further includes a lithium salt, and the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate.

39. The battery cell according to claim 38, characterized in that The mass content of the lithium salt is 13% to 20% based on the mass of the electrolyte.

40. The battery cell according to claim 38, wherein Based on the mass of the electrolyte, the ratio of the mass content of the lithium hexafluorophosphate to the mass content of the lithium bis(fluorosulfonyl)imide is 1.2 to 2.

0.

41. The battery cell according to claim 36, characterized in that The electrolyte further includes an additive, wherein the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

42. A battery device, characterized in that: The battery device includes the battery cell according to any one of claims 1 to 41.

43. An electrical device, characterized in that: The electrical device comprises the battery device as claimed in claim 42.

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