Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises an electrode assembly, the electrode assembly comprises a plurality of positive pole pieces and a plurality of negative pole pieces, and the positive pole pieces and the negative pole pieces are stacked in the thickness direction of the battery monomer; the positive pole piece comprises a positive pole current collecting part and a positive pole film layer arranged on at least one side of the positive pole current collecting part, the ratio of the size of the positive pole film layer in the length direction of the battery monomer to the size of the positive pole film layer in the width direction of the battery monomer is 4-7, and the size of the positive pole film layer in the length direction is 300-650 mm; the positive electrode film layer includes a lithium-containing phosphate of an olivine structure and a lithium-containing iron oxide. The battery monomer provided by the invention can improve the power performance and the high-temperature cycle performance at the same time.

Description

[0001] This application claims the priority of the patent application PCT / CN2025 / 071129 entitled "Battery Cell, Battery Device and Electrical Device" filed on January 7, 2025, and the entire content of this application is incorporated herein by reference. Technical Field

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

[0003] Battery cells have characteristics such as high capacity and long life, and are therefore widely used in electronic devices, such as mobile phones, laptop computers, battery-powered vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and power tools, etc. Due to the great progress of batteries, higher requirements are put forward for the performance of batteries. However, the power performance and high-temperature cycling performance of battery cells still need to be further improved. Summary of the Invention

[0004] This application provides a battery cell, a battery device and an electrical device. The battery cell of this application can balance the improvement of power performance and high-temperature cycling performance.

[0005] In a first aspect, an embodiment of this application provides a battery cell. The battery cell includes an electrode assembly. The electrode assembly includes a plurality of positive electrode plates and a plurality of negative electrode plates. The positive electrode plates and the negative electrode plates are stacked along the thickness direction of the battery cell. The positive electrode plate includes a positive current collector portion and a positive electrode film layer disposed on at least one side of the positive current collector portion. The ratio of the size of the positive electrode film layer along the length direction of the battery cell to the size of the positive electrode film layer along the width direction of the battery cell is 4 to 7, and the size of the positive electrode film layer along the length direction is 300 mm to 650 mm; the positive electrode film layer includes a lithium-containing phosphate with an olivine structure and an iron-containing oxide of lithium.

[0006] Thus, when the positive electrode film layer of the embodiment of this application meets the above size range, the battery cell has a relatively high energy density; however, the electron transport path is relatively long, resulting in a relatively high DC resistance. The positive electrode active material further includes a lithium-containing phosphate with poor conductivity, which further increases the DC resistance; and the positive electrode plate includes an iron-containing oxide of lithium. The iron-containing oxide of lithium can release lithium ions during the charging process of the battery cell. The lithium ions migrate to the negative electrode side through the electrolyte to make up for the lithium loss in the system. As lithium is released, the iron-containing oxide of lithium forms a negatively charged group, and the negatively charged group releases oxygen. The oxygen diffuses to the surface of the negative electrode plate through the electrolyte and can participate in the formation of a solid electrolyte interface film (SEI film) with relatively low impedance, which can reduce the impedance of the solid electrolyte interface film and improve the power performance; and can play a protective role for the negative electrode plate, which is beneficial to improving the high-temperature cycling performance of the battery cell.

[0007] In some embodiments, the lithium-containing iron oxide includes lithium iron phosphate particles. During the charging process of the battery cell, lithium ions can be extracted to make up for lithium loss, which is beneficial to improving the capacity characteristics and cycling performance of the battery cell; and oxygen can be released to participate in the formation of the SEI film. While reducing the side reactions on the negative electrode side, the impedance of the SEI film is relatively low, which can take into account the improvement of the power performance and high-temperature cycling performance of the battery cell.

[0008] In some embodiments, the lithium-containing iron oxide includes Li e FeO f , where 0 < e ≤ 5 and 0 < f ≤ 4. The above materials can take into account the improvement of the power performance and high-temperature cycling performance of the battery cell.

[0009] In some embodiments, the lithium-containing iron oxide includes Li 5 FeO 4 , Li 3 FeO 3.5 and LiFeO 2 at least one of them. The above materials can take into account the improvement of the power performance and high-temperature cycling performance of the battery cell.

[0010] In some embodiments, the lithium-containing iron oxide includes a core and a carbon coating layer. The carbon coating layer is disposed on at least a part of the surface of the core, and there is a spacing between the carbon coating layer and the core. Among them, the core includes lithium iron phosphate. The spacing between the carbon coating layer and the core can provide a slow-release space for the released oxygen, realizing the gradual release of oxygen to the electrolyte and gradually participating in the construction and repair of the SEI film, which is more conducive to forming a film layer with excellent performance and reducing the impedance of the SEI film.

[0011] In some embodiments, the thickness of the carbon coating layer is 10 nm to 200 nm; when the thickness of the carbon coating layer is within the above range, the core can be more effectively protected, and it is beneficial to the construction of the spacing between the core and the carbon coating layer.

[0012] In some embodiments, the spacing is 5 nm to 50 nm; when the spacing is within the above range, it can provide a slow-release space for the released oxygen, realize the gradual release of oxygen to the electrolyte, gradually participate in the construction and repair of the SEI film, which is more conducive to forming a film layer with excellent performance and reducing the impedance of the SEI film.

[0013] In some embodiments, there are multiple lithium-containing iron oxides, and the average longest diameter of the multiple lithium-containing iron oxides is 2 μm to 5 μm. When using lithium-containing iron oxides with the above particle size, the stability of the lithium-containing iron oxides can be effectively improved while having a good oxygen release effect.

[0014] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the lithium-containing iron oxide is 0.2% to 2.5%. When using lithium-containing iron oxides within this mass range, it is possible to effectively improve the stability of the lithium-containing iron oxide while also having a good oxygen release effect.

[0015] In some embodiments, the lithium-containing phosphate includes a plurality of first phosphate particles and a plurality of second phosphate particles. The longest diameter of the first phosphate particles is greater than that of the second phosphate particles. The average longest diameter of the plurality of first phosphate particles is 1 μm to 5 μm, and the average longest diameter of the plurality of second phosphate particles is 0.1 μm to 0.5 μm. When the lithium-containing phosphate meets the above conditions, its longest diameter is relatively small, the lithium deintercalation / insertion path of lithium ions in the lithium-containing phosphate is short, the heat generation is less, it can reduce the heat in the battery cell system, slow down the decomposition of the electrolyte caused by heat accumulation, and improve the cycle performance of the battery cell.

[0016] In some embodiments, the percentage by number of the second phosphate particles in the lithium-containing phosphate is 5% to 15%. When the lithium-containing phosphate meets the above conditions, it can improve the cycle performance of the battery cell.

[0017] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, and lithium iron phosphate has excellent cycle stability and can improve the cycle performance of the battery cell.

[0018] In some embodiments, the size of the positive electrode film layer in the length direction is 400 mm to 505 mm. When the size of the positive electrode film layer in the length direction is within the above range, the electron transport path is short, which can improve the fast charging performance and power performance of the battery cell, and is beneficial to improving the energy density.

[0019] In some embodiments, the battery cell further includes an electrolyte. The electrolyte includes an organic solvent, and the organic solvent includes a carbonate solvent and a chain carboxylic ester solvent. The conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm. When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0020] In some embodiments, the carbonate solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and ethylene carbonate. The above carbonate solvents and chain carboxylic ester solvents are used in combination, which improves the conductivity of the electrolyte at room temperature, is beneficial to the migration of lithium ions, and can improve the power performance of the battery cell.

[0021] In some embodiments, based on the mass of the electrolyte, the mass content of the chain carboxylic ester solvent is 5% to 30%. When the mass content of the chain carboxylic ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions; moreover, the mass content of the chain carboxylic ester solvent is not too high, which can reduce the gas generation at high temperature and improve the cycle performance.

[0022] In some embodiments, the chain carboxylic ester solvent includes the compound shown in Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0023] The above chain carboxylic ester solvent has a relatively high conductivity, which is beneficial to improving the fast charging ability of the battery monomer.

[0024] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to Formula I-8,

[0025] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The above lithium salt system is relatively stable and not easily decomposed. The lithium salt is beneficial to improving the conductivity of the electrolyte, improving the kinetic performance of the battery monomer, and can improve the power performance of the battery monomer.

[0026] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is 13% to 20%. When the mass content of the lithium salt is within the above range, the lithium salt is beneficial to improving the conductivity of the electrolyte, improving the kinetic performance of the battery monomer, and can improve the power performance of the battery monomer.

[0027] In some embodiments, 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 lithium salt is beneficial to improving the conductivity of the electrolyte, improving the kinetic performance of the battery monomer, and can improve the power performance of the battery monomer.

[0028] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3 - propane sultone. The additive can form a dense and uniform - thickness film layer on the negative - electrode side, can effectively repair the SEI film, provide excellent protection for the negative - electrode active material, is beneficial to improving the fast - charging performance of the battery cell, and improving the high - temperature cycling performance.

[0029] In some embodiments, based on the mass of the electrolyte, the mass content of the additive is 0.5% to 6%. When the mass content of the additive is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative - electrode active material, is beneficial to improving the fast - charging performance of the battery cell, and improving the high - temperature cycling performance.

[0030] In some embodiments, based on the mass of the electrolyte, the mass content of vinylene carbonate is 0.5% to 3.0%. When the mass content of vinylene carbonate is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative - electrode active material, is beneficial to improving the fast - charging performance of the battery cell, and improving the high - temperature cycling performance.

[0031] In some embodiments, based on the mass of the electrolyte, the mass content of fluoroethylene carbonate is 0.2% to 2.5%. When the mass content of fluoroethylene carbonate is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative - electrode active material, is beneficial to improving the fast - charging performance of the battery cell, and improving the high - temperature cycling performance.

[0032] In some embodiments, based on the mass of the electrolyte, the mass content of 1,3 - propane sultone is 0.5% to 2.5%. When the mass content of 1,3 - propane sultone is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative - electrode active material, is beneficial to improving the fast - charging performance of the battery cell, and improving the high - temperature cycling performance.

[0033] In some embodiments, the single - side coating weight of the positive - electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 ; when the single - side coating weight of the positive - electrode film layer is within the above range, the heat generation per unit area of the positive - electrode sheet will not be too large, slowing down the decomposition of the electrolyte caused by heat accumulation and improving the cycling performance of the battery cell.

[0034] In some embodiments, when the battery cell is in the 0% state of charge, the compaction density of the positive - electrode film layer is 2.30 g / cm 3 to 2.70 g / cm 3When 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 since the positive electrode active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during rapid charging, slowing down the decomposition of the electrolyte caused by heat accumulation, and improving the cycle performance of the battery cell.

[0035] In some embodiments, the negative electrode sheet includes a negative electrode current collector portion and a negative electrode film layer disposed on at least one side of the negative electrode current collector portion. The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a carbon-based material, the carbon-based material includes artificial graphite, and the graphitization degree of the artificial graphite is 90% to 95%. When the graphitization degree of the artificial graphite is within the above range, the artificial graphite has excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the rapid charging performance of the battery cell.

[0036] In some embodiments, the volume average particle size of the carbon-based material is 8 μm to 13 μm. When the volume average particle size of the carbon-based material is within the above range, it is beneficial to improve the kinetic performance of the negative electrode film layer and the rapid charging performance.

[0037] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector portion; the second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector portion, 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. This kind of setting is beneficial to improve the kinetic performance of the negative electrode film layer and the rapid charging performance.

[0038] 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.

[0039] In some embodiments, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2 ; when the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be too large, slowing down the decomposition of the electrolyte caused by heat accumulation, and improving the cycle performance of the battery cell.

[0040] In some embodiments, when the battery cell is in a 0% state of charge, the compaction density of the negative electrode film layer is 1.30 g / cm 3 to 1.65 g / cm 3When 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 since the negative active materials in the negative electrode film layer are stacked relatively closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during rapid charging and slowing down the decomposition of the electrolyte caused by heat accumulation, and improving the cycling performance of the battery cell.

[0041] In some embodiments, the positive electrode sheet further includes a positive electrode tab connected to the positive electrode current collector portion, and the battery cell further includes a positive terminal connected to the positive electrode tab, and the number of positive terminals is at least two; the relatively large number of positive terminals is beneficial to improve the overcurrent capacity of the positive terminals, improve the rapid charging performance, and improve the power performance.

[0042] In some embodiments, the negative electrode sheet further includes a negative electrode tab connected to the negative electrode current collector portion in the negative electrode sheet, and the battery cell further includes a negative terminal connected to the negative electrode tab, and the number of negative terminals is at least two. The relatively large number of negative terminals is beneficial to improve the overcurrent capacity of the negative terminals, improve the rapid charging performance, and improve the power performance.

[0043] In some embodiments, at least two positive terminals are disposed on at least one side of the electrode assembly along the length direction. The relatively large number of positive terminals is beneficial to improve the overcurrent capacity of the positive terminals, improve the rapid charging performance, and improve the power performance.

[0044] In some embodiments, at least two negative terminals are disposed on at least one side of the electrode assembly along the length direction. The relatively large number of negative terminals is beneficial to improve the overcurrent capacity of the negative terminals, improve the rapid charging performance, and improve the power performance.

[0045] In a second aspect, an embodiment of the present application further provides a battery device, including the battery cell according to any one of the embodiments in the first aspect of the present application.

[0046] In a third aspect, an embodiment of the present application further provides an electrical device, and the electrical device includes the battery device according to any one of the embodiments in the second aspect or the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the drawings without creative efforts.

[0048] Figure 1 is a schematic structural diagram of an electrical device provided by some embodiments of the present application; Figure 2It is a schematic structural diagram of a battery pack provided by some embodiments of the present application; Figure 3 It is a schematic structural diagram of a battery module provided by some embodiments of the present application; Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application; Figure 5 It is a schematic structural diagram of an electrode assembly of a battery cell provided by some embodiments of the present application; Figure 6 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by some embodiments of the present application; Figure 7 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application; Figure 8 It is a schematic structural diagram of an end cap, a first electrode terminal, and a first conductive fixing member of a battery cell provided by some embodiments of the present application; Figure 9 It is Figure 8 a top view schematic diagram of; Figure 10 It is Figure 9 a cross-sectional view taken along line A-A; Figure 11 It is a schematic structural diagram of a battery cell provided by still some other embodiments of the present application; Figure 12 It is a schematic structural diagram of a battery cell provided by yet some other embodiments of the present application; Figure 13 It is an exploded schematic structural diagram of an end cap, a first electrode terminal, and a first conductive fixing member of a battery cell provided by some embodiments of the present application; Figure 14 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by some other embodiments of the present application; Figure 15 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by still some other embodiments of the present application; Figure 16 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by yet some other embodiments of the present application; Figure 17 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by yet some other embodiments of the present application; Figure 18 It is a schematic structural diagram of a positive electrode plate of a battery cell provided by yet some other embodiments of the present application; Figure 19 It is a schematic structural diagram of a battery cell provided by yet some other embodiments of the present application; Figure 20It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application; Figure 21 It is a schematic structural diagram of a battery cell provided by some other embodiments of the present application; Figure 22 It is a schematic structural diagram of the negative electrode tab of a battery cell provided by some embodiments of the present application; Figure 23 It is a schematic structural diagram of the negative electrode tab of a battery cell provided by some other embodiments of the present application.

[0049] The drawings are not necessarily drawn to actual scale.

[0050] The description of the reference numerals is as follows: X, thickness direction; Y, width direction; Z, length direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, box body; 5a, first box body part; 5b, second box body part; 5c, accommodation space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, first tab; 111, first tab ear; 1111, first end; 112, first coating part; 12, second tab; 121, second tab ear; 1211, second end; 122, second coating part; 13, separator; 20, housing assembly; 21, housing; 211, first housing part; 212, second housing part; 2121, first wall; 2122, second wall; 213, third housing part; 22, end cap; 31, first electrode terminal; 311, first electrode body; 312, first electrode protrusion; 32, second electrode terminal; 41, first conductive fixing member; 51, first adapter; 511, first adapter part; 512, second adapter part; 61, first conductive member; 611, first conductive part; 612, second conductive part; 70, pressure relief assembly. Detailed Embodiments

[0051] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0052] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are understood to be anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all anticipated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed in this article, and "0 to 5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0054] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0055] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, and preferably in sequence. For example, if the method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0056] The "plurality" mentioned in this application refers to two or more (including two).

[0057] During the charging and discharging process of the battery cell, along with the transmission of electrons and ions, electrons and ions usually have a certain resistance during the conduction process, and the magnitude of the resistance can be represented by the direct current resistance DCR.

[0058] In the related art, the direct current resistance of the battery cell is relatively high, which is not conducive to fast charging and may cause deterioration of the cycle performance.

[0059] In view of the above problems, an embodiment of the present application provides a battery cell. The battery cell includes a long stacked electrode assembly with a specific aspect ratio. Compared with a shorter wound battery assembly, the long stacked electrode assembly enables the battery cell to have a relatively high energy density. However, the electron transport path is relatively long, resulting in a relatively high DC resistance. For a lithium-containing phosphate cathode material with an olivine structure that has relatively weak conductivity (compared with a well-conductive layered ternary material), the DC resistance is relatively higher. Moreover, the cathode material further includes a lithium-containing iron oxide. This lithium-containing iron oxide can not only release active lithium ions during the charging process of the battery cell, but also further release oxygen along with the release of lithium ions. The oxygen diffuses through the electrolyte to the surface of the negative electrode active material and can participate in the film-forming process on the surface of the negative electrode active material, enabling a solid electrolyte interface film (SEI film) with a relatively low impedance to be formed on the surface of the negative electrode active material, thereby reducing the impedance of the battery cell and being beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0060] The battery cell of the present application is applicable to various battery devices and electrical devices that use the battery cell.

[0061] Exemplarily, the electrical device can be a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric toy, an electric tool, a vehicle, a ship, a spacecraft, etc. Or, exemplarily, the electrical device is a spacecraft, and the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.

[0062] Figure 1 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0063] A battery device is provided inside the electrical device 1, and the battery device can be arranged at the bottom, the head, or the tail of the electrical device 1. The battery device can be used to supply power to the electrical device 1. For example, the battery device can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1. Figure 1 The battery device shown in is a battery pack 2.

[0064] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery device to supply power to the motor 4. For example, it is used for the working power requirements during the startup, navigation, and driving of the electrical device 1.

[0065] A Battery Apparatus may include one or more Battery Cell Assemblies for providing voltage and capacity. A Battery Cell Assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel, or in a combination of series and parallel through a busbar component.

[0066] In some embodiments, a Battery Cell Assembly is generally formed by arranging a plurality of battery cells.

[0067] As an example, the Battery Cell Assembly may be a Battery Module, and the Battery Module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the Battery Module may be formed by bundling a plurality of battery cells with cable ties.

[0068] As Figure 2 shown, in some embodiments, the Battery Apparatus may be a Battery Pack 2, and the Battery Pack 2 includes a housing 5 and one or more Battery Cell Assemblies, and the Battery Cell Assemblies are accommodated in the housing 5.

[0069] As an example, the Battery Cell Assembly may also be accommodated in the housing 5 by directly fixing a plurality of battery cells to the housing 5.

[0070] As an example, the housing 5 includes a first housing portion 5a and a second housing portion 5b, the housing 5 has an accommodation space 5c, and the first housing portion 5a and the second housing portion 5b are snapped together so that a closed space is formed inside the housing 5 to accommodate the Battery Cell Assembly. Here, "closed" means covered or closed, which may be sealed or non-sealed. The first housing portion 5a may be a top cover or a bottom plate.

[0071] As an example, the housing 5 may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the housing 5 to accommodate the Battery Cell Assembly.

[0072] In some embodiments, the housing 5 may be part of the chassis structure of a vehicle. For example, a part of the housing 5 may become at least a part of the floor of the vehicle, or a part of the housing 5 may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0073] As an example, the Battery Cell Assembly may be a Battery Module 6, and the Battery Cell Assembly may be accommodated in the housing 5 by fixing the Battery Module 6 in the housing 5.

[0074] As Figure 3 shown, the Battery Module 6 includes a plurality of battery cells 7.

[0075] In some embodiments, during the charging process of the battery device from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0076] In some embodiments, during the charging process of the battery device or any battery cell constituting the battery device from 10% SOC to 80% SOC, the temperature of the external environment where the battery device is located is room temperature, such as 25°C.

[0077] Exemplarily, the charging steps of the battery device or any battery cell constituting the battery device from 10% SOC to 80% SOC can be carried out as follows: Charge from 10% SOC to 25% SOC at a constant current of 7.0C; Charge from 25% SOC to 30% SOC at a constant current of 7.0C; Charge from 30% SOC to 35% SOC at a constant current of 7.0C; Charge from 35% SOC to 40% SOC at a constant current of 7.0C; Charge from 40% SOC to 45% SOC at a constant current of 6.7C; Charge from 45% SOC to 50% SOC at a constant current of 6.5C; Charge from 50% SOC to 55% SOC at a constant current of 6.0C; Charge from 55% SOC to 60% SOC at a constant current of 5.8C; Charge from 60% SOC to 65% SOC at a constant current of 5.5C; Charge from 65% SOC to 70% SOC at a constant current of 5.2C; Charge from 70% SOC to 75% SOC at a constant current of 5.0C; Charge from 75% SOC to 80% SOC at a constant current of 4.8C.

[0078] 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 temperature of the external environment of the battery device at 10% state of charge is room temperature, such as 25°C. Exemplarily, the charging time of the battery device from 10% state of charge to 80% state of charge is 20 min, 19 min, 18 min, 17 min, 16 min, 15 min, 14.5 min, 14 min, 13.5 min, 13 min, 12.5 min, 12 min, 11.5 min, 11 min, 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5 min or the range composed of any two of the above values.

[0079] As Figures 4 to 6 shown, the battery cell 7 includes an electrode assembly 10. The electrode assembly 10 includes a plurality of first electrode plates 11 and a plurality of second electrode plates 12. The first electrode plates 11 and the second electrode plates 12 are stacked along the thickness direction X of the battery cell 7. One of the first electrode plates 11 and the second electrode plates 12 is a positive electrode plate, and the other is a negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The ratio of the size of the positive electrode film layer along the length direction Z of the battery cell 7 to the size of the positive electrode film layer along the width direction Y of the battery cell 7 is 4 to 7, and the size of the positive electrode film layer along the length direction Z is 300 mm to 650 mm; the positive electrode film layer includes a positive electrode active material and a lithium-containing iron oxide, and the positive electrode active material includes a lithium-containing phosphate in an olivine structure.

[0080] The electrode assembly 10 has a stacked structure, and a plurality of first electrode plates 11 and a plurality of second electrode plates 12 are stacked. Compared with the wound structure, it is easier to increase the coating amount of the active material on the stacked structure, so that the battery cell 7 has a relatively high energy density; and in the embodiments of the present application, the ratio of the size of the positive electrode film layer along the length direction Z of the battery cell 7 to the size of the positive electrode film layer along the width direction Y of the battery cell 7 is 4 to 7, and the size of the positive electrode film layer along the length direction Z is 300 mm to 650 mm. The length of the positive electrode film layer is relatively long, which is beneficial to carrying a relatively large amount of positive electrode active material and is beneficial to making the battery cell 7 have a relatively high energy density.

[0081] When the battery cell 7 has the above-mentioned laminated structure, the electron transfer path is relatively long, resulting in a relatively high DC resistance. Especially when the positive electrode active material includes lithium-containing phosphate with relatively poor conductivity, the internal resistance of the battery cell is further increased. The positive electrode film layer further includes lithium-containing iron oxide. During charging, lithium ions are released from the lithium-containing iron oxide, and the lithium ions migrate to the negative electrode side through the electrolyte to compensate for the lithium loss in the system. As lithium is released, the lithium-containing iron oxide forms a negatively charged group, and the negatively charged group releases oxygen, which diffuses through the electrolyte to the surface of the negative electrode plate and can participate in the formation of a solid electrolyte interface film (SEI film) with relatively low impedance, which can reduce the impedance of the SEI film, and the SEI film can protect the negative electrode plate, which is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0082] It should be noted that the lithium-containing iron oxide may not contain phosphorus element, or the phosphorus element content is below 1000 ppm. The reason is that those skilled in the art can introduce phosphorus element into the lithium-containing iron oxide by means of doping or coating modification to improve certain physical and chemical properties of the lithium-containing iron oxide, or due to the impurity phosphorus element entering the lithium-containing iron oxide caused by the charge and discharge cycle of the battery cell.

[0083] Optionally, the battery cell 7 further includes a separator 13, and the separator 13 is located between the first electrode plate 11 and the second electrode plate 12.

[0084] In the embodiment of the present application, the dimension of the positive electrode film layer along the length direction Z of the battery cell 7 can be understood as the length of the positive electrode film layer. The dimension of the positive electrode film layer along the width direction Y of the battery cell 7 can be understood as the width of the positive electrode film layer. When the first electrode plate 11 is a positive electrode plate, Figure 6 where W2 represents the dimension of the positive electrode film layer along the length direction Z in the positive electrode plate, and Y1 represents the dimension of the positive electrode film layer along the width direction Y in the positive electrode plate.

[0085] If the ratio of the length of the positive electrode film layer to the width of the positive electrode film layer is too small, for example, less than 4, the loading of the 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 positive electrode film layer to the width of the positive electrode film layer is too large, for example, greater than 7, the length of the positive electrode film layer is too long, and the electron transfer path in the length direction of the positive electrode plate is too long, resulting in an increase in resistance, which is not conducive to improving the power performance of the battery cell.

[0086] In the embodiment of the present application, the ratio of the length of the positive electrode film layer to the width of the positive electrode film layer is 4 to 7, such as 4, 4.5, 5, 5.5, 6, 6.5, 7 or the range composed of any two of the above values, which can balance the improvement of the energy density and power performance of the battery cell.

[0087] When the length of the positive electrode film layer is too small, for example, less than 300 mm, the loading of the active material is relatively small, which is not conducive to improving the energy density of the battery cell; when the length of the positive electrode film layer is too large, for example, greater than 650 mm, the length of the positive electrode film layer is too long, and the transmission path of electrons in the length direction of the positive electrode plate is too long, resulting in an increase in resistance, which is not conducive to improving the power performance of the battery cell.

[0088] The length of the positive electrode film layer 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 the range composed of any two of the above values. Optionally, the length of the positive electrode film layer is 400 mm to 505 mm. When the length of the positive electrode film layer meets the above range, it can balance the improvement of the energy density and power performance of the battery cell.

[0089] Optionally, the lithium-containing iron oxide includes lithium ferrite. The above materials can release lithium ions during the charging process of the battery cell, make up for the lithium loss of the battery cell, and improve the capacity of the battery cell; moreover, they can release oxygen to the negative electrode side to participate in the formation of the SEI film. While reducing the side reactions on the negative electrode side, the impedance of the SEI film is relatively low, which can balance the improvement of the power performance and high-temperature cycle performance of the battery cell.

[0090] Exemplarily, the lithium-containing iron oxide includes Li e FeO f , where 0 < e ≤ 5, 0 < f ≤ 4.

[0091] Exemplarily, the lithium-containing iron oxide includes Li 5 FeO 4 , Li 3 FeO 3.5 and LiFeO 2 and at least one of them.

[0092] In some embodiments, the lithium-containing iron oxide includes a core and a carbon coating layer. The core includes at least one of lithium ferrite particles or lithium nickelate particles. The carbon coating layer is disposed on at least part of the surface of the core, and there is a spacing between the carbon coating layer and the core.

[0093] The lithium-containing iron oxide including the carbon coating layer can effectively protect the core. After being coated with the carbon coating layer, the structure of the lithium-containing iron oxide is more stable, which can alleviate the side reactions between the electrolyte and the lithium-containing iron oxide, thereby further improving the cycle performance of the battery cell; moreover, the carbon coating layer can slowly release the oxygen released from the core, and the spacing between the carbon coating layer and the core can provide a slow-release space for the released oxygen, realizing the gradual release of oxygen to the electrolyte and gradually participating in the construction and repair of the SEI film, which is more conducive to forming an SEI film with excellent performance and reducing the film layer impedance. Exemplarily, the core includes lithium ferrite.

[0094] Optionally, the spacing is from 5 nm to 50 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm or any range composed of any two of them.

[0095] Optionally, the thickness of the carbon coating layer is from 10 nm to 200 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm or any range composed of any two of them. When the thickness of the carbon coating layer is within the above range, the core can be protected more effectively, and it is beneficial to construct the spacing between the core and the carbon coating layer.

[0096] In some embodiments, the average longest diameter of the lithium-containing iron oxide is from 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 range composed of any two of them. When the lithium-containing iron oxide with the above particle size is used, the stability of the lithium-containing iron oxide can be effectively improved while having a good oxygen release effect.

[0097] In the embodiments of the present application, the positive electrode sheet is cut along the thickness direction of the sheet to expose the cross-section of the positive electrode film layer; the longest diameter of the lithium-containing iron oxide particles is determined by performing a scanning electron microscope (SEM) test on the cross-section of the positive electrode film layer. For example, the "longest diameter" of the particle refers to the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle.

[0098] In the cross-section of the positive electrode film layer along its own thickness direction, the longest diameters of a plurality of, for example, 10 lithium-containing iron oxides are statistically analyzed, and the average value calculated is the average longest diameter.

[0099] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the lithium-containing iron oxide is from 0.2% to 2.5%, such as 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.5% or any range composed of any two of them.

[0100] When the lithium-containing iron oxide with the above mass range is used, the stability of the lithium-containing iron oxide can be effectively improved while having a good oxygen release effect.

[0101] In some embodiments, the positive electrode active material includes a lithium-containing phosphate having an olivine structure. In other embodiments, the positive electrode active material may also include a lithium-containing transition metal oxide, etc. Examples of the lithium-containing transition metal oxide may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0102] In the embodiments of the present application, the lithium-containing phosphate having an olivine structure may be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate having an olivine structure includes phosphate particles and a coating layer, and the coating layer coats the surface of the phosphate particles. For example, the coating layer includes elements such as carbon, which improves the conductivity of the phosphate particles, reduces the powder resistivity of the material, is beneficial to the migration rate of lithium ions, improves the fast charging ability of the battery, and reduces the heat generation of the battery cell.

[0103] In some embodiments, the phosphate particles include a compound with the general formula Li x1 A y1 Me a M b P 1-c X c Y z where 0.5 ≤ x 1 ≤ 1.3, 0 ≤ y 1 ≤ 1.3, and 0.9 ≤ x 1 + y 1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X includes one or more of Cl, C, N, and Y includes one or more of O, F. The cycle stability of the phosphate particles is relatively excellent, which is beneficial to improving the cycle performance of the battery cell.

[0104] Exemplarily, the phosphate particles include LiFePO 4 、LiMnPO 4 、LiNiPO 4 、LiCoPO 4 or more of them. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. Regarding the positive electrode active material LiFePO4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 In the enumeration of, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, regarding the positive electrode active material LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 In the enumeration of, etc., the molar content of oxygen O is only the theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will show fluctuations. The above situations are all within the protection scope of the present application.

[0105] In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art, and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry, and determined by inductively coupled plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC) and disassembling the positive electrode plate, it is cleaned with dimethyl carbonate (DMC) and dried, and then after removing impurities by high-temperature calcination, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0106] In some embodiments, the lithium-containing phosphate is granular, and the lithium-containing phosphate includes a plurality of first phosphate particles and a plurality of second phosphate particles. The longest diameter of the first phosphate particles is greater than the longest diameter of the second phosphate particles. The average longest diameter of the plurality of first phosphate particles is 1 μm to 5 μm, and the average longest diameter of the plurality of second phosphate particles is 0.1 μm to 0.5 μm.

[0107] Exemplarily, the average longest diameter of the plurality of first phosphate particles is 1 μm to 5 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the range composed of any two of the above values.

[0108] Exemplarily, the average longest diameter of the plurality of second phosphate particles is 0.1 μm to 0.5 μm, such as 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm or the range composed of any two of the above values.

[0109] When the lithium-containing phosphate satisfies the above conditions, its average longest diameter is relatively small, the lithium intercalation / deintercalation path of lithium ions in the lithium-containing phosphate is short, and the heat generation is less; moreover, the particle size of the above lithium-containing phosphate is not too small, and agglomeration basically does not occur during the processing and preparation process, so that the performance of the lithium-containing phosphate is stable.

[0110] In some embodiments, the number percentage of the second phosphate particles in the lithium-containing phosphate is 5% to 15%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or the range composed of any two of the above values.

[0111] In the embodiment of the present application, the positive electrode sheet is cut along the thickness direction of the sheet to expose the cut surface of the positive electrode film layer; by performing a scanning electron microscope (SEM) test on the cut surface of the positive electrode film layer, the magnification of the SEM can be 5000 times to determine the longest diameter of the lithium-containing iron oxide particles. For example, the "longest diameter" of the particles refers to the longest straight line passing through the center point of the particles and extending to the outer periphery of the particles.

[0112] In the cross-section of the positive electrode film layer along its own thickness direction, the longest diameters of a plurality of, for example, 50 lithium-containing phosphate particles are statistically analyzed. The particles with the longest diameter greater than or equal to 1 μm belong to the first phosphate particles, and the particles with the longest diameter less than 1 μm belong to the second phosphate particles. The average value of the longest diameters of all the first phosphate particles is calculated as the average longest diameter of the first phosphate particles, and the average value of the longest diameters of all the second phosphate particles is calculated as the average longest diameter of the second phosphate particles; In the cross-section of the positive electrode film layer along its own thickness direction, the number of all the first phosphate particles and the number of all the second phosphate particles are statistically analyzed, and the proportion of the number of the second phosphate particles is calculated as the number percentage of the second phosphate particles in the lithium-containing phosphate; during the process of preparing the positive electrode film layer, by adjusting the mass content of the second phosphate particles in the lithium-containing phosphate, the number percentage of the second phosphate particles is adjusted accordingly.

[0113] In the embodiment of the present application, both the first electrode sheet 11 and the second electrode sheet 12 include a coating portion and an electrode tab. The coating portion is coated with an active material layer, and the electrode tab is disposed 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 parallel to the length direction Z of the battery cell 7, or the first direction is parallel to the width direction Y of the battery cell 7.

[0114] 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 in pairs.

[0115] When the first direction is parallel to the length direction Z of the battery cell 7, the dimension of the component in this direction can be regarded as the length of the component. For example, the dimension of the coating portion in the first direction is the length of the coating portion. In this case, the second direction is parallel to the width direction Y of the battery cell 7.

[0116] When the first direction is parallel to the width direction Y of the battery cell 7, the dimension of the component in this direction can be regarded as the width of the component. For example, the dimension of the coating portion in the first direction is the width of the coating portion. In this case, the second direction is parallel to the length of the battery cell 7.

[0117] To illustrate the present application more clearly, the tab portion of the first electrode sheet 11 is defined as the first tab 111, and the coating portion of the first electrode sheet 11 is defined as the first coating portion 112. The tab portion of the second electrode sheet 12 is defined as the second tab 121, and the coating portion of the second electrode sheet 12 is defined as the second coating portion 122. The electrode terminal having the same electrical property as and electrically connected to the first tab 111 is the first electrode terminal 31, and the electrode terminal having the same electrical property as and electrically connected to the second tab 121 is the second electrode terminal 32.

[0118] The polarities of the first electrode sheet 11 and the second electrode sheet 12 are opposite. When the first electrode sheet 11 is the positive electrode sheet, the second electrode sheet 12 is the negative electrode sheet, the first electrode terminal 31 is the positive terminal, and the second electrode terminal 32 is the negative terminal; or when the first electrode sheet 11 is the negative electrode sheet, the second electrode sheet 12 is the positive electrode sheet, the first electrode terminal 31 is the negative terminal, and the second electrode terminal 32 is the positive terminal.

[0119] Figure 5 and Figure 6 shows that the first direction is parallel to the width direction Y and the second direction is parallel to the length direction Z.

[0120] [Housing Assembly] The housing assembly 20 has a receiving space for receiving the electrode assembly 10 and the electrolyte.

[0121] 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.

[0122] The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite housing), or an aluminum plastic film, etc. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly 10, and a sealing bag is further included between the housing and the electrode assembly 10. The sealing bag is used to encapsulate the electrode assembly 10 and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly 10 and the electrolyte.

[0123] As an example, the battery cell 7 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a multi-prismatic battery, and the multi-prismatic battery is, for example, a hexagonal prism battery, etc., and there is no special limitation in this application.

[0124] Outer shell In some embodiments, the housing includes an end cap 22 and a housing 21. The housing 21 is provided with an opening, and the end cap 22 covers the opening. The housing 21 may be provided with one or more openings. One or more end caps 22 may also be provided.

[0125] The first electrode terminal 31 and the second electrode terminal 32 may be disposed on the housing 21, or the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22. Optionally, the first electrode terminal 31 and the second electrode terminal 32 are disposed on the end cap 22.

[0126] On the same end cap 22, the first electrode terminal 31 and the second electrode terminal 32 can be disposed simultaneously. For example, the end cap 22 is one, and the first electrode terminal 31 and the second electrode terminal 32 are disposed at intervals on the end cap 22. Another example is that the end cap 22 is two, the two end caps 22 are disposed opposite to each other, and the first electrode terminal 31 and the second electrode terminal 32 are disposed on each end cap 22.

[0127] The first electrode terminal 31 and the second electrode terminal 32 are respectively disposed on different end caps 22. For example, the end cap 22 is two, the two end caps 22 are disposed opposite to each other, the first electrode terminal 31 is disposed on one of the end caps 22, and the second electrode terminal 32 is disposed on the other end cap 22.

[0128] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, the housing 21 of a cylindrical structure can be selected; if the electrode assembly 10 is a cuboid structure, the housing 21 of a cuboid structure can be selected. Optionally, both the electrode assembly 10 and the housing 21 are of cuboid structures.

[0129] In some embodiments, the housing 21 includes two first housing parts 211, a second housing part 212, and a third housing part 213. The two first housing parts 211 are opposite to each other along the thickness direction X of the battery cell 7. The second housing part 212 and the third housing part 213 are opposite to each other, and the second housing part 212 and the third housing part 213 are connected by the first housing part 211. The second housing part 212 includes a first wall 2121 and a second wall 2122 that are continuously arranged along the thickness direction X, and the first wall 2121 and the second wall 2122 are welded. The first wall 2121 and the second wall 2122 can be welded specifically by methods such as butt welding and laser welding, and butt welding is optional. Since the area of the second housing part 212 is relatively small and the degree of expansion is relatively small, and the weld seam is located on the second housing part 212, the risk of liquid leakage of the battery cell 7 can be reduced.

[0130] When assembling the battery cell 7 into the box body of the battery device, the battery cell 7 is disposed in the box body. The box body includes a first box body part and a second box body part, and the first box body part covers the second box body part; wherein, the second housing part 212 is disposed opposite to the first box body part, and the second housing part 212 is disposed close to the first box body part, and the third housing part 213 is disposed close to the second box body part. When assembling the battery device into the electrical device, the first box body part can be located above the second box body part in the vertical direction. Since the second housing part 212 has a weld seam and the weld seam is disposed upward, the risk of liquid leakage of the battery cell 7 is reduced.

[0131] In some embodiments, the thickness of the housing 21 is from 0.1 mm to 0.5 mm. For example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or the range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0132] When the thickness of the housing 21 is within the above range, the housing 21 is relatively thin, which is beneficial to the rapid heat dissipation of the housing 21.

[0133] Exemplarily, the thickness of the first housing part 211 is from 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0134] Exemplarily, the thickness of the second housing part 212 is from 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0135] Exemplarily, the thickness of the third housing portion 213 is from 0.1 mm to 0.5 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm, 0.3 mm, 0.31 mm, 0.32 mm, 0.33 mm, 0.34 mm, 0.35 mm, 0.36 mm, 0.37 mm, 0.38 mm, 0.39 mm, 0.4 mm, 0.41 mm, 0.42 mm, 0.43 mm, 0.44 mm, 0.45 mm, 0.46 mm, 0.47 mm, 0.48 mm, 0.49 mm, 0.5 mm or a range composed of any two of the above values. Optionally, the thickness of the housing 21 is from 0.3 mm to 0.4 mm.

[0136] First electrode terminal In some embodiments, there are at least two first electrode terminals 31, such as two, three, four, etc.

[0137] 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 shows that the first electrode terminal 31 is disposed on at least one side of the electrode assembly 10 along the length direction Z.

[0138] For example, all the first electrode terminals 31 are disposed on one side of the electrode assembly 10 along the length direction Z.

[0139] Again, for example, a plurality of first electrode terminals 31 are respectively disposed on both sides of the electrode assembly 10 along the length direction Z. This arrangement can shorten the migration path of electrons, reduce the temperature rise inside the battery cell, is beneficial to improving the fast charging performance, and enhancing the power performance and cycle performance of the battery cell.

[0140] Exemplarily, there are two first electrode terminals 31, one of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10. Or, exemplarily, there are four first electrode terminals 31, two of the first electrode terminals 31 are disposed on one side of the electrode assembly 10, and the other two first electrode terminals 31 are disposed on the other side of the electrode assembly 10.

[0141] Such as Figure 7As 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 current flow area on the end cover.

[0142] 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.

[0143] In the embodiment of the present application, the first electrode terminal 31 can be an integrated structure, which can be integrally formed or connected by welding or other means to form an integrated structure. The integrated structure is beneficial for reducing resistance, reducing heat generation, and improving the power performance and cycle performance of the battery cell.

[0144] 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 only include the first electrode protrusion 312, the first electrode protrusion 312 penetrates the end cap 22, and is connected to the pole ear.

[0145] Optionally, the minimum cross-sectional area of ​​the first electrode protrusion 312 parallel to the thickness direction X is the first area, the area enclosed by the projected outer contour of the end cover 22 parallel to the thickness direction X is the 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 current bottleneck of the first electrode terminal 31. When the first area meets the above conditions, the first electrode terminal 31 has a strong current capacity, which is beneficial to reduce heat generation and improve the power performance and cycle performance of the battery cell.

[0146] The first electrode protrusion 312 may have a plurality of cross-sectional areas of different sizes along the thickness direction X. For example, the first electrode protrusion 312 includes a first part, a second part, and a third part connected in sequence, and the cross-sectional area of the second part is the smallest, so the cross-sectional area of the second part is the first area. Of course, the cross-sectional areas of the first electrode protrusion 312 at various positions along the thickness direction X may also be the same.

[0147] 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, such as 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40 or the range composed of any two of the above values; in the embodiment of the present 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. As Figure 9 shown, the size of the first electrode protrusion 312 along the thickness direction X can be understood as the width of the first electrode protrusion 312; the size of the end cap 22 along the thickness direction X can be understood as the width of the end cap 22.

[0148] When the first electrode protrusion 312 meets the above conditions, the size ratio of the first electrode protrusion 312 is relatively high, which is beneficial to improving the overcurrent capacity of the first electrode terminal 31 and enhancing the power performance and cycle performance of the battery cell.

[0149] In some embodiments, the housing assembly 20 further includes a first conductive fixing member 41. The first conductive fixing member 41 is disposed around the first electrode terminal 31 and fixedly connects the first electrode terminal 31 and the end cap 22. At least a part of the first conductive fixing member 41 is located on the side of the end cap 22 facing away from the electrode assembly 10. The first conductive fixing member 41 can be used to connect with an external busbar assembly. Optionally, an insulating member may be disposed between the first conductive fixing member 41 and the end cap 22 for insulation.

[0150] The first conductive fixing member 41 can further increase the overcurrent area between the battery cell 7 and the external busbar assembly, thereby improving the overcurrent capacity, which is beneficial to improving the overcurrent capacity of the battery device and enhancing the fast charging performance of the battery device.

[0151] Optionally, a part of the first electrode protrusion 312 protrudes from the side of the end cap 22 facing away from the electrode assembly 10, and the first conductive fixing member 41 is disposed around the first electrode protrusion 312.

[0152] Optionally, the ratio of the size of the first conductive fixing member 41 in the thickness direction X to the size of the end cap 22 in the thickness direction X is 0.40 to 0.80, such as 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80 or the range composed of any two of the above values; in the embodiment of the present application, the thickness direction X refers to the thickness direction X of the battery cell 7. The size of the first conductive fixing member 41 refers to the size of a single first conductive fixing member 41 in the thickness direction X. Figure 9 X shown in 1 represents the size of the first conductive fixing member 41 in the thickness direction X, which can be understood as the width of the first conductive fixing member 41, X 2 represents the size of the end cap 22 in the thickness direction X, which can be understood as the width of the end cap 22.

[0153] When the first conductive fixing member 41 meets the above conditions, the size ratio of the first conductive fixing member 41 is relatively high, which is beneficial to increasing the current-carrying area between the battery cell 7 and the external busbar assembly, thereby improving the current-carrying capacity and the fast-charging performance of the battery device.

[0154] Second electrode terminal In some embodiments, there are at least two second electrode terminals 32, such as two, three, four, etc.

[0155] Such as Figure 11 shown, in some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 in the width direction Y. This setting method can shorten the electron migration path and is beneficial to improving the fast-charging performance.

[0156] For example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 in the width direction Y. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 in the width direction Y, and there will be basically no interference when they are respectively electrically connected to the tab portions. 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 in the width direction Y, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 in the width direction Y.

[0157] For another example, a plurality of second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the width direction Y. This arrangement can further shorten the migration path of electrons and is beneficial to improving the fast charging performance. In this case, a first electrode terminal 31 and a second electrode terminal 32 are disposed on one side of the electrode assembly 10 in the width direction Y, and a first electrode terminal 31 and a second electrode terminal 32 are disposed on the other side of the electrode assembly 10 in the width direction Y.

[0158] As Figure 12 shown, in some embodiments, at least one second electrode terminal 32 is disposed on at least one side of the electrode assembly 10 in the length direction Z.

[0159] For example, at least two second electrode terminals 32 are respectively disposed on both sides of the electrode assembly 10 in the length direction Z. This arrangement can shorten the migration path of electrons and is beneficial to improving the fast charging performance. In this case, a first electrode terminal 31 and a second electrode terminal 32 are disposed on one side of the electrode assembly 10 in the length direction Z, and a first electrode terminal 31 and a second electrode terminal 32 are disposed on the other side of the electrode assembly 10 in the length direction Z.

[0160] Figure 12 It is shown that the battery cell 7 includes four electrode terminals. Specifically, there are two second electrode terminals 32. One of the second electrode terminals 32 is disposed on one side of the electrode assembly 10 in the length direction Z, and the other second electrode terminal 32 is disposed on the other side of the electrode assembly 10 in the length direction Z. There are two first electrode terminals 31. One of the first electrode terminals 31 is disposed on one side of the electrode assembly 10, and the other first electrode terminal 31 is disposed on the other side of the electrode assembly 10.

[0161] For another example, all the second electrode terminals 32 are disposed on one side of the electrode assembly 10 in the length direction Z. In this case, the first electrode terminal 31 and the second electrode terminal 32 can be respectively disposed on both sides of the electrode assembly 10 in the length direction Z, and there will be no mutual interference when electrically connecting to the tab portions respectively. 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 in the length direction Z, and the two second electrode terminals 32 are disposed on the other side of the electrode assembly 10 in the length direction Z.

[0162] In the embodiments of the present application, the second electrode terminal 32 can be an integral structure, which can be integrally formed or can be formed into an integral structure by means of welding or the like. The integral structure is beneficial to reducing the resistance, reducing heat generation, and improving the power performance and cycle performance of the battery cell.

[0163] For example, in some embodiments, the second electrode terminal 32 has the same structural form as 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 through the end cap 22. Optionally, the second electrode body and the second electrode protrusion are of an integral structure. In other embodiments, the second electrode terminal 32 may only include the second electrode protrusion, which penetrates through the end cap 22 and is connected to the tab.

[0164] In some embodiments, the housing assembly 20 further includes a second conductive fixing member, which is disposed around the second electrode terminal 32 and fixedly connects the second electrode terminal 32 and the end cap 22. The structural form and related dimensions of the second conductive fixing member are as described for the first conductive fixing member 41.

[0165] The second conductive fixing member can further increase the current-carrying area between the battery cell 7 and the external busbar assembly, thereby improving the current-carrying capacity, which is beneficial to improving the current-carrying capacity of the battery device and enhancing the fast charging performance of the battery device.

[0166] Pressure relief component As Figure 13 shown, in some embodiments, the battery cell 7 further includes a pressure relief assembly 70 for discharging the internal gas of the battery cell 7 and relieving the pressure.

[0167] 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. When the housing assembly 20 includes two end caps 22 opposite to each other, the pressure relief assembly 70 may be one and disposed on one of the two end caps 22, or the pressure relief assembly 70 may be provided as two and disposed on the two end caps 22 respectively. In other embodiments, the pressure relief assembly 70 may also be disposed on the housing.

[0168] As an example, it is actuated to relieve the internal pressure or temperature when the internal pressure or temperature of the battery cell 7 reaches a predetermined threshold. When the internal pressure or temperature of the battery cell 7 reaches the predetermined threshold, the pressure relief assembly 70 performs an action or a weak structure provided in the pressure relief assembly 70 is damaged, thereby forming an opening or channel for the internal pressure or temperature to be relieved. This threshold design varies according to different design requirements. The threshold may depend on one or several of the materials of the positive electrode plate, negative electrode plate, electrolyte, and separator 13 in the battery cell 7.

[0169] The internal pressure and temperature of the battery cell 7 can be released. The actions generated by the pressure relief component 70 may include, but are not limited to: the components in the pressure relief component 70 move to form an exhaust passage, at least a part of the pressure relief component 70 ruptures, breaks, is torn or opened, etc. When the pressure relief component 70 is actuated, the high-temperature and high-pressure substances inside the battery cell 7 will be discharged outward from the actuated part as emissions. In this way, the battery cell 7 can be depressurized and temperature-relieved under controlled pressure or temperature, thereby avoiding potential more serious accidents.

[0170] The emissions from the battery cell 7 mentioned in the embodiments of the present application include, but are not limited to: electrolytes, dissolved or split positive and negative electrode sheets, fragments of separators, high-temperature and high-pressure gases generated by reactions, flames, etc.

[0171] As an example, the pressure relief component 70 can be integrally formed with the housing component 20. For example, the pressure relief component 70 is integrally formed with the end cap 22 of the housing component 20.

[0172] As an example, the pressure relief component 70 can also be separately provided and connected to the housing component 20.

[0173] The "actuation" mentioned in the present application refers to that the pressure relief component 70 generates an action or is activated to a certain state, so that in some embodiments of the battery, when the housing component 20 is a non-sealed structure, the pressure relief component 70 can be set as a through hole for discharging the gas inside the battery cell 7.

[0174] [First electrode sheet and second electrode sheet] In some embodiments, the first electrode sheet 11 satisfies: n*W1 / W2 is 0.5 to 1.0; n represents the number of all tab ears located on the same side of the coating part; W1 represents the average size of the tab ear along the second direction; W2 represents the size of the coating part along the second direction.

[0175] When the first electrode sheet 11 satisfies that n*W1 / W2 is 0.5 to 1.0, the first electrode sheet 11 can be a positive electrode sheet or a negative electrode sheet.

[0176] Exemplarily, n*W1 / W2 is 0.5, 0.55, 0.6, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 1.0 or a range composed of any two of the above values.

[0177] When n*W1 / W2 satisfies the above range, the current-carrying area of the first tab ear 111 is relatively large, reducing heat generation and improving the power performance and cycle performance of the battery cell.

[0178] W1 represents the average dimension of the first tab 111 in the second direction. When the first tab 111 has a special-shaped structure, for example, in the first direction, the dimension of the first tab 111 in the second direction gradually increases. In this case, the dimensions of the first tab 111 in the second direction at multiple locations can be measured, and thus the average dimension of the first tab 111 in the second direction can be calculated. Of course, the dimensions of the first tab 111 at each location in the second direction can be the same value, and in this case, this value can be used as the average dimension of the first tab 111.

[0179] There can be one or more first tabs 111. For example, n ranges from 1 to 4. When there are multiple first tabs 111, after measuring the average dimensions of each first tab 111 respectively, the average dimension of the first tab 111 can be calculated by adding up the average dimensions and dividing by the number of first tabs 111.

[0180] The first tab 111 is connected to the first coating portion 112. The first 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 in the thickness direction of the first tab 111 itself is relatively large, the contact surface between the first tab 111 and the first coating portion 112 is relatively large, the current-carrying capacity of the first tab 111 is strong, and the power performance and cycling performance of the battery cell 7 can be improved.

[0181] Optionally, the current collector portion of the first tab 111 and the first coating portion 112 is an integral structure, so that the internal resistance of the first electrode sheet 11 is relatively low, and the power performance and cycling performance of the battery cell 7 can be further improved.

[0182] As Figure 14 and Figure 15 shown, in some embodiments, the first electrode sheet 11 includes one or more first tabs 111, and the one or more first tabs 111 are disposed on at least one side of the coating portion in the width direction Y.

[0183] For example, one or more first tabs 111 are disposed on one side of the first coating portion 112 in the width direction Y. In this case, it can be understood that all the first tabs 111 are disposed on the same side of the first coating portion 112 in the width direction Y. This kind of arrangement is beneficial to increasing the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7. Figure 14 In, n is 4, and the dimensions of each first tab 111 can be the same. W1 can represent the dimension of a single first tab 111. Of course, the dimensions of each first tab 111 can also be slightly different; W2 represents the dimension of the first coating portion 112 in the length direction Z. Figure 15 In, n is 1, and n*W1 / W2 is 1.

[0184] AsFigure 16 As shown, for example, when the first electrode tab 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 in the width direction Y.

[0185] Optionally, there are at least two first electrode tabs 111 on the same side of the first coating portion 112 in the width direction Y, such as two, three, four, five, six, etc.; it can be at least four. This setting is beneficial to the uniform distribution of electrons in the first electrode tab 11 and is beneficial to improving the fast charging performance.

[0186] Such as Figure 17 As shown, in some other embodiments, the first electrode tab 11 includes one or more first electrode tabs 111; the one or more first electrode tabs 111 are disposed on at least one side of the first coating portion 112 in the length direction Z.

[0187] For example, one or more first electrode tabs 111 are disposed on one side of the first coating portion 112 in the length direction Z. In this case, it can be understood that all the first electrode tabs 111 are disposed on the same side of the first coating portion 112 in the length direction Z.

[0188] Such as Figure 18 As shown, for example, when the first electrode tab 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 in the length direction Z.

[0189] Optionally, the plurality of first electrode tabs 111 are respectively disposed on both sides of the first coating portion 112 in the length direction Z. This setting can shorten the transmission path of electrons in the first electrode tab 11 and is beneficial to improving the fast charging performance.

[0190] Optionally, there are at least two first electrode tabs 111 on the same side of the first coating portion 112 in the length direction Z, such as two, three, four, five, six, etc. This setting is beneficial to the uniform distribution of electrons in the first electrode tab 11 and is beneficial to improving the fast charging performance.

[0191] In the embodiments of the present application, the first electrode tab 111 is electrically connected to the first electrode terminal 31, which can be directly connected or indirectly connected as Figure 19 shown; 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, and the first adapter 51 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 a plurality of first electrode tabs 111 and a plurality of first electrode terminals 31, the plurality of first electrode tabs 111 can be divided into multiple groups, and each group of first electrode tabs 111 is respectively connected to one first electrode terminal 31.

[0192] For example, when the first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, and the first tab 111 is disposed on one side of the first coating portion 112 along the width direction Y, the connection between the first tab 111 and the first electrode terminal 31 is more facilitated by the first adapter 51, and at the same time, the overcurrent capacity of the battery cell 7 can be improved. When the first electrode terminal 31 is disposed on one side of the electrode assembly 10 along the length direction Z, the utilization space of the first electrode plate 11 along the width direction Y can also be increased, and the energy density of the battery cell 7 can be improved.

[0193] When the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, the first adapter 51 may include a first adapter portion 511 and a second adapter portion 512. The first adapter portion 511 extends along the length direction Z, the first adapter portion 511 is connected to the first tab 111, the second adapter portion 512 is connected to the first adapter portion 511 and protrudes from the first adapter portion 511 along the width direction Y, and is connected to the first electrode terminal 31.

[0194] When the first tab 111 and the first electrode terminal 31 are disposed on the same side of the battery cell 7, the first adapter 51 may only include the first adapter portion 511.

[0195] In the above embodiments, the first adapter 51 may be a sheet-like structure, and of course, it may also be in other structural forms.

[0196] In the above embodiments, the first adapter 51 may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0197] In some embodiments, the battery cell 7 further includes a first conductive member 61. The first conductive member 61 is located between the first adapter 51 and the first tab 111. The setting of the first conductive member 61 can increase the overcurrent capacity between the first tab 111 and the first adapter 51, which is beneficial to improving the fast charging performance and reducing heat generation; and the electrical connection 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 by welding. The presence of the first conductive member 61 can significantly reduce the failure risk caused by the direct electrical connection of multiple first tabs 111 and the first adapter 51.

[0198] For example, the tab portion of the first electrode plate 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.

[0199] Optionally, there are at least two first tabs 111 located on the same side of the first coating portion 112, and there are at least two first conductive members 61. The first conductive members 61 and the first tabs 111 are connected in a one-to-one correspondence. 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.

[0200] As Figure 20 shown, optionally, there are at least two first tabs 111 located on the same side of the first coating portion 112, and the first conductive member 61 can be a continuous sheet structure connecting at least two first tabs 111.

[0201] As Figure 21 shown, in the case where the first tab 111 and the first electrode terminal 31 are respectively disposed on different sides of the battery cell 7, optionally, the first conductive member 61 includes a first conductive portion 611 and a second conductive portion 612. The first conductive portion 611 extends along the length direction Z. The first conductive portion 611 connects the first tab 111 and the first adapter 51. The second conductive portion 612 is connected to the first conductive portion 611 and protrudes from the first conductive portion 611 along the width direction Y. The second conductive portion 612 connects the first adapter 51. This structural arrangement is beneficial to increasing the grouping space in the length direction Z and beneficial to improving the energy density of the battery device.

[0202] It should be noted that in the case where the battery cell 7 does not include the first adapter 51, the first tab 111 can be connected to the first electrode terminal 31 through the first conductive member 61.

[0203] Exemplarily, the first conductive member 61 has electrical conductivity, and it can include a conductive polymer or a conductive metal material. The conductive metal material can include copper, aluminum, or an alloy containing the above metal elements, etc.

[0204] In some embodiments, the thickness of the first conductive member 61 is 0.5 mm to 2.0 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm or a range composed of any two of the above values. When the thickness of the first conductive member 61 is within the above range, the overcurrent capacity can be effectively improved and the fast charging capacity can be improved.

[0205] As Figure 22 shown, in some embodiments, the second pole piece 12 satisfies: m * W3 / W4 is 0.5 to 1.0; m represents the number of all tab portions located on the same side of the coating portion; W3 represents the average dimension of the tab portion along the second direction; W4 represents the dimension of the coating portion along the second direction.

[0206] Exemplarily, 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 composed of any two of the above values.

[0207] When m*W3 / W4 satisfies the above range, the current-carrying area of the second tab 121 is relatively large, reducing heat generation and improving the power performance and cycling performance of the battery cell.

[0208] m can be from 1 to 4.

[0209] W3 represents the average dimension of the second tab 121 along the second direction. The second tab 121 can be one or more. In the case where the second tab 121 is multiple, the average dimension can be calculated by measuring the dimensions of each second tab 121 with a micrometer.

[0210] The second tab 121 is connected to the second coating portion 122. The second 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 tab 121 itself is relatively large, the contact surface between the second tab 121 and the second coating portion 122 is relatively large, the current-carrying capacity of the second tab 121 is strong, and the power performance and cycling performance of the battery cell 7 can be improved.

[0211] Optionally, the current collector portion of the second tab 121 and the second coating portion 122 is an integral structure, making the internal resistance of the second electrode sheet 12 relatively low and further improving the power performance and cycling performance of the battery cell 7.

[0212] Optionally, there are at least two second electrode terminals 32, and m*W3 / W4 is from 0.5 to 1.0. When the second electrode sheet 12 satisfies the above conditions, the connection area between the tab portion and the coating portion is relatively large, the current-carrying area of the tab portion is relatively large, which is beneficial to reducing the DC resistance and heat generation; there are at least two second electrode terminals 32, in other words, at least two second electrode terminals 32 are connected to the tab portion of the second electrode sheet 12, which can further increase the current-carrying area of the second electrode terminals 32 and the tab portion, further reducing the DC resistance and heat generation, and improving the power performance and cycling performance of the battery cell.

[0213] In some embodiments, the second electrode tab 12 includes one or more second tabs 121, and the one or more second tabs 121 are disposed on at least one side of the coating portion in the width direction Y. For example, the one or more second tabs 121 are disposed on one side of the second coating portion 122 in the width direction Y. In this case, it can be understood that all the second tabs 121 are disposed on the same side of the second coating portion 122 in the width direction Y. Or for example, in the case where the second electrode tab 12 includes a plurality of second tabs 121, the plurality of second tabs 121 are disposed on both sides of the second coating portion 122 in the width direction Y.

[0214] Optionally, the one or more second tabs 121 are respectively disposed on the same side of the second coating portion 122 in the width direction Y. This setting is beneficial to increase the occupied space of the electrode assembly 10, thereby improving the energy density of the battery cell 7.

[0215] Optionally, there are at least two second tabs 121 on the same side of the second coating portion 122 in the width direction Y, such as two, three, four, five, six, etc.; it can be selected as at least four. This setting is beneficial to the uniform distribution of electrons in the second electrode tab 12 and is beneficial to improving the fast charging performance.

[0216] As Figure 23 shown, in some other embodiments, the second electrode tab 12 includes one or more second tabs 121; the one or more second tabs 121 are disposed on at least one side of the second coating portion 122 in the length direction Z. For example, the one or more second tabs 121 are disposed on one side of the second coating portion 122 in the length direction Z. In this case, it can be understood that all the second tabs 121 are disposed on the same side of the second coating portion 122 in the length direction Z. Or for example, in the case where the second electrode tab 12 includes a plurality of second tabs 121, the plurality of second tabs 121 are respectively disposed on both sides of the second coating portion 122 in the length direction Z.

[0217] Optionally, the plurality of second tabs 121 are respectively disposed on both sides of the second coating portion 122 in the length direction Z. This setting can shorten the transmission path of electrons in the second electrode tab 12 and is beneficial to improving the fast charging performance.

[0218] Optionally, there are at least two second tabs 121 on the same side of the second coating portion 122 in the length direction Z, such as two, three, four, five, six, etc.; it can be selected as at least four. This setting is beneficial to the uniform distribution of electrons in the second electrode tab 12 and is beneficial to improving the fast charging performance.

[0219] In the embodiments of the present application, the second tab 121 and the second electrode terminal 32 can be directly connected or indirectly connected; when the second tab 121 and the second electrode terminal 32 are indirectly connected, the battery cell 7 can include a second adapter, and the second adapter is located between the second electrode terminal 32 and the second tab 121 and connects the second electrode terminal 32 and the second tab 121.

[0220] For example, when the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z, and the second tab 121 is disposed on one side of the second coating portion 122 along the width direction Y, the connection between the second tab 121 and the second electrode terminal 32 is more facilitated by the second adapter, and at the same time, the overcurrent capacity of the battery cell 7 can be improved. When the second electrode terminal 32 is disposed on one side of the electrode assembly 10 along the length direction Z, the utilization space of the second electrode sheet 12 in the width direction Y can also be increased, and the energy density of the battery cell 7 can be improved.

[0221] In the case where the second tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, the second adapter may include a first connection portion and a second connection portion. The first connection portion extends along the length direction Z, the first connection portion connects the second tab 121, the second connection portion is connected to the first connection portion and protrudes from the first connection portion along the width direction Y, and is connected to the second electrode terminal 32.

[0222] In the case where the second tab 121 and the second electrode terminal 32 are disposed on the same side of the battery cell 7, the second adapter may only include a first connection portion.

[0223] In the above embodiments, the second adapter may be a sheet-like structure, and of course, it may also be other structural forms.

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

[0225] In some embodiments, the battery cell 7 further includes a second conductive member, and the second conductive member is located between the second adapter and the second tab 121. The arrangement of the second conductive member can increase the overcurrent capacity between the second tab 121 and the second adapter, which is beneficial to improving the fast charging performance and reducing heat generation; and the electrical connection between the second tab 121 and the second adapter and between the second conductive member and the second adapter can be achieved by welding. The presence of the second conductive member can significantly reduce the failure risk caused by the direct electrical connection of multiple second tabs 121 and the second adapter.

[0226] For example, the tab portion of the second electrode tab 12 is disposed on one side of the coating portion in the width direction Y; the second conductive member is located between the second adapter and the second electrode tab 121 and connects the second adapter and the second electrode tab 121.

[0227] Optionally, there are at least two second electrode tabs 121 on the same side of the second coating portion 122. The second conductive member may be a continuous sheet structure that connects at least two second electrode tabs 121; or there are at least two second conductive members, and the second conductive members and the second electrode tabs 121 are connected in a one-to-one correspondence. 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.

[0228] When the second electrode tab 121 and the second electrode terminal 32 are respectively disposed on different sides of the battery cell 7, optionally, the second conductive member includes a third conductive portion and a fourth conductive portion. The third conductive portion extends along the length direction Z. The third conductive portion connects the tab portion of the second electrode tab 12 and the second adapter. The fourth conductive portion is connected to the third conductive portion and protrudes from the third conductive portion in the width direction Y. The third conductive portion connects the second adapter. This structural setting is beneficial to increasing the grouping space in the length direction Z and is beneficial to improving the energy density of the battery device.

[0229] Exemplarily, the second conductive member has conductivity, and it may include a conductive polymer or a conductive metal material. The conductive metal material may include copper, aluminum, or an alloy containing the above metal elements, etc.

[0230] 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 through the second conductive member.

[0231] Positive electrode tab To more clearly illustrate the present application, the coating portion of the positive electrode tab corresponds to the positive electrode coating portion, the tab portion corresponds to the positive electrode tab, the active material layer corresponds to the positive electrode film layer containing the positive electrode active material, and the positive electrode coating portion includes a positive electrode current collector portion and a positive electrode film layer provided on at least one side of the positive electrode current collector portion.

[0232] The positive electrode tab includes a positive electrode current collector portion and a positive electrode film layer provided on at least one surface of the positive electrode current collector portion and including the positive electrode active material. For example, the positive electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector portion.

[0233] The upper charge limit voltage and the discharge cut-off voltage of the battery cell vary depending on the cathode active material. For example, when the phosphate material includes lithium iron phosphate, the upper charge limit voltage can be 3.65V and the discharge cut-off voltage can be 2.0V, or the upper charge limit voltage can be 3.8V and the discharge cut-off voltage can be 2.0V; Another example is when the phosphate material includes lithium manganese iron phosphate, the upper charge limit voltage can be 4.3V and the discharge cut-off voltage can be 2.0V. Next, taking the upper charge limit voltage of 3.65V and the discharge cut-off voltage of 2.0V as an example, the state of the battery cell will be described: In the embodiments 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, Charge the battery cell at a constant current charge rate of 0.33C to the upper charge limit voltage, and then charge it at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell. Discharge the battery cell at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0234] In some embodiments, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film layer is 2.30 g / cm 3 to 2.70 g / cm 3 ; It can be optionally 2.40 g / cm 3 to 2.55 g / cm 3 . Exemplarily, when the battery cell is in the 0% state of charge (SOC), the compaction density of the cathode film layer is 2.30 g / cm 3 , 2.32 g / cm 3 , 2.35 g / cm 3 , 2.38 g / cm 3 , 2.40 g / cm 3 , 2.42 g / cm 3 , 2.45 g / cm 3 , 2.48 g / cm 3 , 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 or a range composed of any two of the above values.

[0235] 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 since the positive active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation during rapid charging and alleviating the problem of intensified side reactions on the negative electrode side caused by heat accumulation, and improving the cycle performance of the battery cell.

[0236] In some embodiments, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 , and can be optionally 275 mg / 1540.25 mm 2 to 300 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 290 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 310 mg / 1540.25 mm 2 , 320 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0237] 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 sheet will not be too large, alleviating the problem of intensified side reactions on the negative electrode side caused by heat accumulation, improving the cycle performance of the battery cell, and being able to improve the energy density of the battery cell.

[0238] In the embodiments of the present application, the tap density of the positive electrode film layer of the battery cell at 0% state of charge (SOC) has the meaning well-known in the art, that is, the positive electrode plate of the battery cell at 0% SOC is disassembled, and the tap density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode plate (if it is a double-sided coated plate, the positive electrode film layer on one side can be wiped off first) is punched into small round pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the above-mentioned weighed positive electrode plate is wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the tap density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0239] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The embodiments of the present application do not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0240] 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 the 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 fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0241] In some embodiments, the positive electrode current collector may be made of a metal foil or a composite current collector. As an example of the metal foil, at least one of foils made of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0242] In some embodiments, the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is 3 to 10, such as 3, 4, 5, 6, 7, 8, 9, 10 or the range composed of any two of the above values. Optionally, the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is 4 to 8.

[0243] When the ratio of the thickness of the single-sided positive electrode film layer to the thickness of the positive electrode current collector is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0244] In some embodiments, the thickness of the positive electrode current collector is 12 μm to 16 μm, and can be optionally 13 μm to 15 μm. Exemplarily, the thickness of the positive electrode current collector is 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm or the range composed of any two of the above values.

[0245] When the thickness of the positive electrode current collector is within the above range, the current-carrying capacity of the positive electrode current collector is relatively excellent, which can improve the power performance of the battery cell and enable the battery cell to have a high energy density.

[0246] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive electrode current collector have the meanings well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the thickness of the positive electrode plate is measured with a micrometer, the film layer on the surface of the positive electrode current collector is removed, and the thickness of the positive electrode current collector is measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode plate minus the thickness of the positive electrode current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode plate minus the thickness of the positive electrode current collector) / 2.

[0247] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0248] The positive electrode plate does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode plate of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In some other embodiments, the positive electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0249] Negative electrode tab To more clearly illustrate the present application, the coating portion of the negative electrode tab corresponds to the negative electrode coating portion, the tab portion corresponds to the negative electrode tab, the active material layer corresponds to the negative electrode film layer containing the negative electrode active material, the negative electrode coating portion includes a negative electrode current collector portion and a negative electrode film layer provided on at least one side of the negative electrode current collector portion, and the negative electrode coating portion includes a negative electrode current collector portion and a negative electrode film layer provided on at least one side of the negative electrode current collector portion.

[0250] The negative electrode tab includes a negative electrode current collector portion and a negative electrode film layer provided on at least one surface of the negative electrode current collector portion and including the negative electrode active material. For example, the negative electrode current collector portion has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector portion.

[0251] In some embodiments, when the battery cell is at 0% state of charge (SOC), the tap density of the negative electrode film layer is 1.30 g / cm 3 to 1.65 g / cm 3 ; optionally 1.35 g / cm 3 to 1.50 g / cm 3 . Exemplarily, when the battery cell is at 0% state of charge, the tap density of the negative electrode film layer is 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.45 g / cm 3 , 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 or a range composed of any two of the above values.

[0252] When the tap density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode tab can be further reduced, thereby reducing heat generation and alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, and improving the cycling performance of the battery cell.

[0253] In the embodiments of the present application, the tap density of the negative electrode film layer at 0% state of charge (SOC) of the battery cell has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art, and its detection method is the same as the tap density test method of the positive electrode film layer described above.

[0254] In some embodiments, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 to 180 mg / 1540.25 mm 2, optionally 125 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 Exemplarily, the single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 、122 mg / 1540.25 mm 2 、125 mg / 1540.25 mm 2 、128 mg / 1540.25 mm 2 、130 mg / 1540.25 mm 2 、132 mg / 1540.25 mm 2 、135 mg / 1540.25 mm 2 、137 mg / 1540.25 mm 2 、140 mg / 1540.25 mm 2 、145 mg / 1540.25 mm 2 、150 mg / 1540.25 mm 2 、155 mg / 1540.25 mm 2 、160 mg / 1540.25 mm 2 、165 mg / 1540.25 mm 2 、170 mg / 1540.25 mm 2 、175 mg / 1540.25 mm 2 、180 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0255] 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 tab will not be too large, alleviating the problem of aggravated side reactions on the negative electrode side caused by heat accumulation, improving the cycling performance of the battery cell, and being able to balance the improvement of the energy density of the battery cell.

[0256] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art, and the detection method is as described in the single-sided coating weight test method of the film layer above.

[0257] In some embodiments, the negative electrode active material includes a carbon-based material, and the carbon-based material has high cycling stability and can improve the cycling performance of the battery cell. The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used in combination, the battery cell has excellent cycling performance.

[0258] Optionally, the carbon-based material includes artificial graphite, and the graphitization degree of the artificial graphite is 90% to 95%, optionally 92% to 95%. Exemplarily, the graphitization degree of the artificial graphite is 90%, 90.5%, 91%, 91.5%, 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95% or a range composed of any two of the above values.

[0259] When the graphitization degree of the artificial graphite is within the above range, the artificial graphite has excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and can improve the power performance and cycling performance of the battery cell.

[0260] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include artificial graphite, or the carbon-based material may include artificial graphite and natural graphite. The electrical conductivity of natural graphite is relatively good, which is beneficial to further reducing heat generation and can improve the power performance and cycling performance of the battery cell.

[0261] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material. Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0262] In this application, the qualitative and quantitative determination of each substance or each element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change some detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0263] For example, this application can perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or the negative electrode active material in combination with the general rules of X-ray diffraction analysis method of JIS / K0131-1996.

[0264] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by scanning electron microscope (SEM). There are voids between flaky structures in the SEM cross-section of natural graphite, and the SEM cross-section of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0265] In the embodiments 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.

[0266] When the negative electrode film layer is a single film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material. When a single film layer is used, the volume average particle size Dv50 of the carbon-based material is 8 μm to 13 μm, and can be optionally 9.5 μm to 11.5 μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 8 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm or a range composed of any two of the above values.

[0267] When the negative electrode film layer includes at least two film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material. The negative electrode film layer can include two film layers, three film layers, four film layers, or even more film layers.

[0268] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector. The carbon-based material in the first negative electrode film layer includes artificial graphite. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer includes artificial graphite. The artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer can be the same or different. When the artificial graphite in the first negative electrode film layer and the artificial graphite in the second negative electrode film layer are different, it can be the difference in particle size or the difference in graphitization degree.

[0269] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0270] The negative electrode film layer includes at least two film layers. Layered coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, it is possible to construct pore differences in the negative electrode film layer, reduce the tortuosity of lithium ion transport, improve the fast charging performance of the battery cell, and improve the cycle performance and power performance of the battery cell.

[0271] 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 to improving the kinetic performance of the negative electrode film layer, improving the fast charging performance of the battery cell, and thus improving the power performance of the battery cell.

[0272] There are differences in the particle sizes of the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size of the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode sheet and improve the cycle performance of the battery cell.

[0273] Optionally, the carbon-based material in the first negative electrode film layer is in the form of particles, and its volume average particle size Dv50 is from 9.5 μm to 18.5 μm, and can be optionally from 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 the range composed of any two of the above values. When the first negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is from 9.5 μm to 18.5 μm, and can be optionally from 9.5 μm to 14.6 μm.

[0274] 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 easily agglomerated during the preparation process, which can improve the stability of the material.

[0275] Optionally, the carbon-based material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the carbon-based material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm or a range composed of any two of the above values. When the second negative electrode film layer includes a carbon-based material, the volume average particle size Dv50 of the carbon-based material in the second negative electrode film layer is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm.

[0276] 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 prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the negative electrode active material in the second negative electrode film layer with the above volume average particle size range cooperates with the negative electrode active material in the first negative electrode film layer, which is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, improving the fast charging performance of the battery cell, and improving the power performance and cycle performance of the battery cell.

[0277] In the embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the negative electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 of the particles is tested by a Mastersizer 2000E laser particle size analyzer, etc.

[0278] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0279] Exemplarily, the carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

[0280] In some 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 being greater than the volume average particle size Dv50 of the carbon-based material in the first negative electrode film layer is beneficial to improving the compaction density of the negative electrode film layer.

[0281] The difference in the particle sizes of the first negative electrode film layer and the second negative electrode film layer can improve the fast charging performance of the battery cell.

[0282] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0283] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0284] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include a thickening agent, a dispersing agent, etc. For example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0285] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0286] In some embodiments, the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is 8 to 14, such as 8, 9, 10, 11, 12, 13, 14 or the range composed of any two of the above values. Optionally, the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is 10 to 12.

[0287] When the ratio of the thickness of the single-sided negative electrode film layer to the thickness of the negative electrode current collector is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0288] In some embodiments, the thickness of the negative electrode current collector is 5 μm to 10 μm, and can be optionally 6 μm to 8 μm. Exemplarily, the thickness of the negative electrode current collector is 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or a range composed of any two of the above values.

[0289] When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, which improves the power performance of the battery cell and enables the battery cell to have a high energy density.

[0290] In the embodiments of the present application, the thickness of the negative electrode current collector has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the film layer on the surface of the negative electrode current collector is washed away with a solvent, and the thickness of the negative electrode current collector is measured with a micrometer.

[0291] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, optional conductive agents, optional binders, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0292] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the embodiments of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0293] Separator In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode plate and the negative electrode plate.

[0294] In some embodiments, the separator is a separator film. The present application does not particularly limit the type of the separator film, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0295] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0296] Electrolyte In some embodiments, the battery cell further includes an electrolyte.

[0297] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting the active ions between the positive electrode plate and the negative electrode plate.

[0298] In the embodiments of the present application, the organic solvent includes a carbonate solvent and a chain carboxylic acid ester solvent, and the conductivity of the electrolyte at room temperature is 10 mS / cm to 13 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm or a range composed of any two of the above values.

[0299] When the conductivity of the electrolyte at room temperature, such as 25 °C, is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, reducing the degree of side reactions on the negative electrode side, and improving the power performance and cycling performance of the battery cell.

[0300] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is the ionic conductivity, and it can be detected by using equipment and methods well known in the art. For example, it can be tested with reference to the industry standard HG-T 4067-2015.

[0301] 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.

[0302] In some embodiments, the organic solvent further includes a carbonate solvent.

[0303] 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 composed of any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions; moreover, the mass content of the carbonate solvent is not too high, which can reduce the gas generation at high temperature and improve the high-temperature cycle performance.

[0304] 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 above carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is beneficial to the migration of lithium ions and improves the power performance of the battery monomer.

[0305] Exemplarily, 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%.

[0306] In some embodiments, the organic solvent includes a chain carboxylic acid ester solvent.

[0307] Optionally, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 5% to 30%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 5%, 10%, 15%, 20%, 25%, 30% or a range composed of any two of the above values.

[0308] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions; moreover, the mass content of the chain carboxylic acid ester solvent is not too high, which can reduce the gas generation at high temperature and improve the cycle performance.

[0309] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R 1 includes a hydrogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R 2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0310] The above chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging ability of the battery monomer and improving the power performance of the battery monomer.

[0311] Optionally, R 1 includes a hydrogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0312] Optionally, R 2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R 2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0313] 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.

[0314] Exemplarily, the chain carboxylic ester solvents include one or more of the compounds represented by Formula I-1 to Formula I-8,

[0315] When the mass content of the chain carboxylic ester solvents is 5% to 30%, the area per unit capacity of the pressure relief component is 1.2 mm 2 / Ah to 1.8 mm 2 / Ah.

[0316] Exemplarily, the area per unit capacity of the pressure relief component is 1.2 mm 2 / Ah, 1.3 mm 2 / Ah, 1.4 mm 2 / Ah, 1.5 mm 2 / Ah, 1.6 mm 2 / Ah, 1.7 mm 2 / Ah, 1.8 mm 2 / Ah or a range composed of any two of the above values.

[0317] As the capacity of the battery cell increases, the liquid injection amount of the battery cell increases, the addition amount of the chain carboxylic ester solvents increases, the gas generation risk increases, and the gas generation amount may increase; while in the embodiments of the present application, the area per unit capacity of the pressure relief component is greater than 1.2 mm 2 / Ah, which can quickly release gas and improve the use reliability of the battery cell; moreover, the area per unit capacity of the pressure relief component is less than or equal to 1.8 mm 2 / Ah, so that the pressure relief component occupies a relatively small area, can take into account the area occupied by the electrode terminals, and has a relatively high overcurrent capacity; thus, when the battery cell of the embodiment of the present application meets the above conditions, it can take into account improving the use reliability and overcurrent capacity of the battery cell and improve the power performance of the battery cell.

[0318] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes a fluorosulfonylimide salt and lithium hexafluorophosphate LiPF 6 or one or more of them. The above lithium salt system is beneficial to improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cell, and improving the power performance of the battery cell. The fluorosulfonylimide salt includes a monofluorosulfonylimide salt, a difluorosulfonylimide salt, etc., and can be selected as the difluorosulfonylimide salt.

[0319] In some embodiments, based on the mass of the electrolyte, the mass content of the lithium salt is 13% to 20%, such as 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or a range composed of any two of the above values. When the mass content of the lithium salt is within the above range, the lithium salt is beneficial to improving the conductivity of the electrolyte and improving the power performance of the battery cell.

[0320] Optionally, based on the mass of the electrolyte, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium difluorosulfonylimide is 1.2 to 2.0. When the lithium salt meets the above conditions, the lithium salt is beneficial to improving the conductivity of the electrolyte, enhancing the kinetic performance of the battery cell, and improving the power performance of the battery cell. When the ratio of the mass contents of lithium hexafluorophosphate and lithium difluorosulfonylimide meets the above range, it can also reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, and is beneficial to improving the high-temperature cycle life of the battery cell.

[0321] Exemplarily, the mass content of lithium hexafluorophosphate and the mass content of lithium difluorosulfonylimide are 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 or a range composed of any two of the above values.

[0322] Exemplarily, based on the mass of the electrolyte, the mass content of lithium difluorosulfonylimide is 1% to 15%, and can be selected as 3% to 12%.

[0323] Exemplarily, based on the mass of the electrolyte, the mass content of lithium difluorosulfonylimide is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or a range composed of any two of the above values. When the mass content of lithium difluorosulfonylimide is within the above range, it can reduce the content of hydrofluoric acid, slow down the side reaction at the negative electrode interface, can reduce the gas generation amount during high-temperature storage, and is beneficial to improving the high-temperature cycle life of the battery cell.

[0324] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of carbonate additives and sulfur-containing additives, and may be optionally at least two. The above additives can improve the performance of the SEI film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the high-temperature cycle performance.

[0325] In some embodiments, the mass content of the additive in the electrolyte is 0.5% to 6%. Exemplarily, the mass content of the additive in the electrolyte is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6% or a range composed of any two of the above values.

[0326] The above organic solvents, such as chain carboxylic acid ester solvents, may decompose to produce acid at high temperatures, corroding the SEI film on the surface of the negative electrode. However, the additive can form a dense and uniform-thickness film layer on the negative electrode side, which can effectively repair the SEI film, provide excellent protection for the negative electrode active material, be beneficial to improving the fast charging performance of the battery cell, and improve the high-temperature cycle performance.

[0327] Exemplarily, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Optionally, the carbonate additives include vinylene carbonate (VC) and fluoroethylene carbonate (FEC). Vinylene carbonate (VC) can form a dense and uniform-thickness SEI film on the negative electrode side, which can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0328] Fluoroethylene carbonate (FEC) can form an SEI film with relatively low impedance on the negative electrode side, which can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0329] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methanedisulfonate (MMDS), and may be optionally 1,3-propane sultone (PS). The sulfur-containing additives can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and are beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0330] Exemplarily, the additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

[0331] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 3.0%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5%, 3.0% or the range composed of any two of the above values. When the mass content of vinylene carbonate (VC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0332] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.2% to 2.5%, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5% or the range composed of any two of the above values. When the mass content of fluoroethylene carbonate (FEC) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0333] Optionally, the mass content of 1,3 - propane sultone (PS) in the electrolyte is 0.5% to 2.5%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.5% or the range composed of any two of the above values. When the mass content of 1,3 - propane sultone (PS) in the electrolyte is within the above range, it can effectively repair the SEI film, provide excellent protection for the negative electrode active material, and is beneficial to improving the power performance and high-temperature cycle performance of the battery cell.

[0334] In the embodiments of the present application, the types and contents of inorganic components / lithium salts in the electrolyte have the meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, reference can be made to the standard JY / T 020 - 1996 General Rules for Ion Chromatographic Analysis Methods to qualitatively or quantitatively analyze the inorganic components / lithium salts in the electrolyte by ion chromatography. In the embodiments of the present application, newly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a discharged battery (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0335] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by 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 qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography.

[0336] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified. Chain carboxylic acid ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated. Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate) and sulfur-containing additives are used as additives in the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0337] In some embodiments, the volumetric energy density of the battery cell is from 375 Wh / L to 450 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 375 Wh / L, 380 Wh / L, 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 450 Wh / L or a range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0338] In the embodiments of the present application, the volumetric energy density of the battery cell has a meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, taking the upper charge cut-off voltage of the battery as 3.65 V and the discharge cut-off voltage of the battery as 2.0 V as an example for illustration. The battery cell is placed at 25°C and charged at a constant current of 0.33C to 3.65 V, then charged at a constant voltage to 0.05C, and discharged at a constant current of 0.33C to 2.0 V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and excluding the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volumetric energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0339] Embodiment The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are all commercially available.

[0340] Example 1 1. Preparation of the positive electrode sheet The positive electrode sheet includes a positive current collector portion and positive electrode film layers provided on both sides of the positive current collector portion. The positive current collector portion is an aluminum foil with a thickness of 13 μm.

[0341] The positive electrode film layer includes a lithium-containing phosphate, a lithium-containing iron oxide, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black with a mass ratio of 95.5:1.5:2:1. The positive electrode film layer is a film layer formed by uniformly coating a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) on both sides of the positive current collector portion and then drying and cold pressing.

[0342] The lithium-containing phosphate includes a plurality of first phosphate particles and a plurality of second phosphate particles. Both the first phosphate particles and the second phosphate particles are lithium iron phosphate particles. The mass content of the second phosphate particles in the lithium-containing phosphate is 15 ± 2%. By adjusting the mass content of the second phosphate particles, the required percentage by number of the second phosphate particles is obtained.

[0343] In the cross-section in the thickness direction of the positive electrode film layer, the average longest diameter of the plurality of first phosphate particles is 2 μm, the average longest diameter of the plurality of second phosphate particles is 0.3 μm, and the percentage by number of the second phosphate particles in the lithium-containing phosphate is 15%.

[0344] The lithium-containing iron oxide is a plurality of particles, each particle includes an oxide core portion and a carbon coating layer provided on the surface of the oxide core portion, and the oxide core portion includes lithium ferrite particles.

[0345] In the cross-section in the thickness direction of the positive electrode film layer, the distance between the carbon coating layer and the oxide core portion is 15 nm, the thickness of the carbon coating layer is 20 nm, the average longest diameter of the lithium-containing iron oxide is 4 μm, and the mass content of the lithium-containing iron oxide in the positive electrode film layer is 1.5%.

[0346] The single-sided coating weight of the positive electrode film layer is 282 mg / 1540.25 mm 2 .

[0347] 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.

[0348] 2. Preparation of the negative electrode sheet The negative electrode sheet includes a negative electrode current collector part and negative electrode film layers arranged on both sides of the negative electrode current collector part. The negative electrode current collector part is a copper foil with a thickness of 6 μm.

[0349] The negative electrode film layer is a film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector part and then drying and cold pressing.

[0350] The single-sided coating weight of the negative electrode film layer is 134 mg / 1540.25 mm 2 。

[0351] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative electrode current collector part, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0352] The first negative electrode film layer includes a carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.5:1:1.5:1. The carbon-based material of the first negative electrode film layer includes artificial graphite. The volume average particle size of the carbon-based material is 11.3 μm, and the graphitization degree of the artificial graphite is 93%.

[0353] The second negative electrode film layer includes a carbon-based material, conductive agent acetylene black, negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose with a mass ratio of 96.5:1:1.5:1. The carbon-based material of the second negative electrode film layer includes artificial graphite. The volume average particle size of the carbon-based material is 9.5 μm, and the graphitization degree of the artificial graphite is 93%.

[0354] 3. Separator The separator includes a base film, which is a polyethylene film layer with a thickness of 7 μm and a porosity of 42%.

[0355] 4. Preparation of the electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive.

[0356] Mix the components of the organic solvent, add the lithium salt and the additive, and prepare them into an electrolyte.

[0357] 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.

[0358] Based on the quality of the electrolyte, the additives include 2.5% vinylene carbonate (VC), 1% fluoroethylene carbonate (FEC), and 2.5% 1,3 - propane sultone.

[0359] The lithium salt includes 8.5% lithium hexafluorophosphate LiPF 6 and 5.5% lithium bis(fluorosulfonyl)imide.

[0360] The conductivity of the electrolyte at room temperature is 12 mS / cm.

[0361] 5. Preparation of Battery Cells Stack the above - mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. Place the electrode assembly in an outer packaging shell, inject the electrolyte after drying, and through processes such as vacuum packaging, standing, forming, and shaping, obtain the battery cell. The compaction density of the positive electrode film layer of the battery cell at 0% SOC is 2.55 g / cm 3 , and the compaction density of the negative electrode film layer at 0% SOC is 1.4 g / cm 3 .

[0362] Comparative Example 1 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, The positive electrode film layer includes lithium - containing phosphate, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black with a mass ratio of 95.5:2.5:2. The positive electrode film layer is formed by uniformly coating the two sides of the positive electrode current collector part with positive electrode slurry (solvent is N - methylpyrrolidone NMP), followed by drying and cold pressing.

[0363] Examples 2 - 1 and 2 - 2 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the average longest diameter of the iron oxide containing lithium is adjusted.

[0364] Examples 3 - 1 and 3 - 2 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the thickness of the carbon coating layer of the iron oxide containing lithium and the distance between the carbon coating layer and the core part are adjusted.

[0365] Examples 4 - 1 to 4 - 3 Prepare the battery cell using a method similar to that of Example 1. Different from Example 1, the mass content of the iron oxide containing lithium in the positive electrode film layer is adjusted.

[0366] Examples 6 - 1 to 6 - 3 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the average longest diameter of the lithium-containing phosphate was adjusted.

[0367] Example 7 The battery single cells were prepared by a method similar to that of Example 1. Different from Example 1, the mass content of the second phosphate particles of the lithium-containing phosphate in the lithium-containing phosphate was adjusted to 5% ± 2%.

[0368] Performance test 1. DC internal resistance DCR and power density test of the battery single cell At 25 °C, the battery single cell was charged to 3.65 V at a constant current of 0.33 C, left standing for 10 min, then charged to 3.65 V at a constant current of 0.33 C again, left standing for 30 min, and discharged at a constant current of 0.33 C to 2.0 V. The discharge capacity C0 and discharge energy E0 at this time were recorded. The battery single cell was charged at a constant current of 0.33C to the cut-off voltage of 3.65V and left standing for 10min; discharged at a constant current of 0.33C0 for 90min to adjust the battery single cell to 50% SOC. The voltage U1 at this time was recorded, and then discharged with a 4C0 pulse for 10s. The voltage after discharge was recorded as U2. Then 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.

[0369] 2. High-temperature cycling performance of the battery single cell At 45 °C, the battery single cell was charged to 3.65 V at a constant current of 0.5C, then charged at a constant voltage to 0.05C, left standing for 10min, and then discharged at a constant current of 1C to 2.0V. This was one charge-discharge cycle, and the first-cycle discharge capacity was recorded; left standing for 10min, and the above charge-discharge cycle was repeated until the discharge capacity of the battery single cell decayed to 80% of the first-cycle discharge capacity and the test was stopped, and the number of cycles was recorded.

[0370] The test results are shown in Table 1.

[0371] Table 1

[0372] In Comparative Example 1, side reactions were likely to occur on the negative electrode side, deteriorating the cycling performance.

[0373] Compared with Comparative Example 1, in Example 1, an iron oxide containing lithium was added to the positive electrode film layer. Oxygen could be released during the charge and discharge process of the battery single cell. The oxygen participated in the formation of the SEI film on the surface of the negative electrode, which could improve the protection of the negative electrode side, reduce the side reactions at the negative electrode interface, and improve the high-temperature cycling performance; moreover, the impedance of the SEI film was relatively low, which was beneficial to reducing the DC internal resistance of the battery single cell and improving the power performance.

[0374] Compared with Example 1, in Examples 2-1 to 5, the average longest diameter of the lithium-containing iron oxide is within an appropriate range, such as 2 μm to 5 μm, which can effectively release oxygen to the negative electrode side, improve the performance of the SEI film, effectively protect the negative electrode active material, reduce the side reactions at the negative electrode interface, and improve the high-temperature cycle performance; moreover, the impedance of the SEI film is relatively low, which is beneficial to reducing the DC internal resistance of the battery cell and improving the power performance.

[0375] The thickness of the carbon coating layer on the surface of the lithium-containing iron oxide is within an appropriate range, such as 10 nm to 200 nm. The carbon coating layer can reduce the risk of side reactions between lithium ferrite and the electrolyte, and can achieve gradual oxygen release, improving the power performance and high-temperature cycle performance of the battery cell.

[0376] The spacing on the surface of the lithium-containing iron oxide is within an appropriate range, such as 5 nm to 50 nm, which can provide a storage space for oxygen, achieve gradual oxygen release, and can effectively improve the power performance and high-temperature cycle performance of the battery cell.

[0377] In Examples 6-1 to 7, the longest diameter of the lithium-containing phosphate is within an appropriate range, or the percentage of the number of second phosphate particles with small particle sizes is within an appropriate range, which can improve its own conductivity and effectively improve the power performance and high-temperature cycle performance of the battery cell.

[0378] Examples 8-1 to 8-3 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the components of the electrolyte were adjusted.

[0379] The test results are shown in Table 2.

[0380] Table 2

[0381] DEC represents diethyl carbonate; DMC represents dimethyl carbonate; EMC represents ethyl methyl carbonate; EC represents ethylene carbonate; VC represents vinylene carbonate; FEC represents fluoroethylene carbonate; PS represents 1,3-propane sultone; LiPF 6 represents lithium hexafluorophosphate; LiFSI represents lithium bis(fluorosulfonyl)imide.

[0382] In the examples, the mass content of the chain carboxylic ester solvent is within an appropriate range, such as 5% to 30%, which can effectively improve the conductivity of the electrolyte and enhance the migration rate of lithium ions; moreover, since the mass content of the chain carboxylic ester solvent is not too high, there are fewer side reactions at the negative electrode side, which can improve the high-temperature cycle performance and power performance and enhance the fast charging ability.

[0383] When the mass content of lithium salt is within an appropriate range, such as 13% to 20%, it is beneficial to improve the conductivity of the electrolyte, improve the kinetic properties of the battery cells, improve the fast charging capability, and improve the high temperature cycle performance and power performance.

[0384] When the mass content of the additive is within an appropriate range, such as 0.5% to 6%, it can form a dense and uniformly thick film layer on the negative electrode side, effectively repair the SEI film, provide excellent protection for the negative electrode active materials, and help improve the fast charging performance of the battery cell and improve the high temperature cycle performance.

[0385] Example 9-1 to Example 9-3 A battery cell was prepared by 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 and negative electrode film layers were adjusted.

[0386] Example 10-1 and Example 10-2 A battery cell was prepared by a method similar to that of Example 1, except that the size of the positive electrode film layer was adjusted.

[0387] Comparative Example 2 and Comparative Example 3 A battery cell was prepared by a method similar to that of Example 1, except that the size of the positive electrode film layer was adjusted.

[0388] The test results are shown in Table 3.

[0389] Table 3

[0390] The length of the positive electrode film layer of Comparative Example 2 is shorter, and less active material can be carried, resulting in a lower energy density of the battery cell.

[0391] The length of the positive electrode film layer of Comparative Example 3 is relatively large, and the aspect ratio is relatively large, so that the transmission path of electrons in the positive electrode plate is relatively long, and the resistance may be too large, which is not conducive to fast charging.

[0392] It can be seen from Examples 9-1 to 10-2 that when the size of the positive electrode film layer is within an appropriate range, the electron transmission path will not be too long, the electron transmission rate will be relatively fast, and the internal resistance of the battery cell will not be too high; By matching the size of the positive electrode film layer and adopting a single-sided coating weight within an appropriate range, the transmission path of lithium ions can be further shortened, the electronic and ion conduction rates can be simultaneously improved, the internal resistance can be reduced, and it is conducive to fast charging. It can also improve the volume energy density, power performance and high-temperature cycle performance of the battery cell.

[0393] The compaction density of the positive and negative electrode film layers in the embodiment is within an appropriate range, which can improve the volume energy density, power performance and high temperature cycle performance of the battery cell.

[0394] Although the illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the implementation of the present application, and changes, substitutions, and modifications can be made to the embodiments without departing from the spirit, principles, and scope of the implementation of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises an electrode assembly, wherein the electrode assembly comprises a plurality of positive electrode sheets and a plurality of negative electrode sheets, wherein the positive electrode sheets and the negative electrode sheets are stacked along a thickness direction of the battery cell. The positive electrode sheet comprises a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the ratio of the size of the positive electrode film layer along the length direction of the battery cell to the size of the positive electrode film layer along the width direction of the battery cell is 4 to 7, and the size of the positive electrode film layer along the length direction is 300 mm to 650 mm; The positive electrode film layer includes lithium-containing phosphate with an olivine structure and lithium-containing iron oxide.

2. The battery cell according to claim 1, characterized in that: The lithium-containing iron oxide includes lithium ferrite.

3. The battery cell according to claim 1 or 2, characterized in that: The lithium-containing iron oxide includes Li e FeO f ,0<e≤5,0 <f≤4。 4. The battery cell according to claim 1, characterized in that: The lithium-containing iron oxides include Li5FeO4, Li3FeO 3.5 and at least one of LiFeO2.

5. The battery cell according to claim 1, characterized in that: The lithium-containing iron oxide comprises a core portion and a carbon coating layer, wherein the carbon coating layer is disposed on at least a portion of the surface of the core portion, a distance is provided between the carbon coating layer and the core portion, and the core portion comprises lithium ferrite.

6. The battery cell according to claim 5, characterized in that: The thickness of the carbon coating layer is 10 nm to 200 nm; and / or the spacing is 5 nm to 50 nm.

7. The battery cell according to claim 1, characterized in that: There are a plurality of lithium-containing iron oxides, and an average longest diameter of the plurality of lithium-containing iron oxides is 2 μm to 5 μm.

8. The battery cell according to claim 1, characterized in that: Based on the mass of the positive electrode film layer, the mass content of the lithium-containing iron oxide is 0.2% to 2.5%.

9. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate includes a plurality of first phosphate particles and a plurality of second phosphate particles, the longest diameter of the first phosphate particles is greater than the longest diameter of the second phosphate particles, the average longest diameter of the plurality of first phosphate particles is 1 μm to 5 μm, and the average longest diameter of the plurality of second phosphate particles is 0.1 μm to 0.5 μm.

10. The battery cell according to claim 9, characterized in that: The amount percentage of the second phosphate particles in the lithium-containing phosphate is 5% to 15%.

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

12. The battery cell according to claim 1, characterized in that: The length of the positive electrode film layer is 400 mm to 505 mm.

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

14. The battery cell according to claim 13, characterized in that: The carbonate solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate and ethylene carbonate.

15. The battery cell according to claim 13 or 14, characterized in that: Based on the mass of the electrolyte, the mass content of the chain carboxylic acid ester solvent is 5% to 30%.

16. The battery cell according to claim 13, characterized in that: The chain carboxylic acid ester solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

17. The battery cell according to claim 13, 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.

18. The battery cell according to claim 17, characterized in that: Based on the mass of the electrolyte, the mass content of the lithium salt is 13% to 20%.

19. The battery cell according to claim 17 or 18, characterized in that: 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.

20. The battery cell according to claim 13, 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.

21. The battery cell according to claim 20, characterized in that: Based on the mass of the electrolyte, the mass content of the additive is 0.5% to 6%.

22. The battery cell according to claim 20 or 21, characterized in that: Based on the mass of the electrolyte, the mass content of the vinylene carbonate is 0.5% to 3.0%; and / or Based on the mass of the electrolyte, the mass content of the fluoroethylene carbonate is 0.2% to 2.5%; and / or The mass content of the 1,3-propane sultone is 0.5% to 2.5% based on the mass of the electrolyte.

23. The battery cell according to claim 1, characterized in that: The single-sided coating weight of the positive electrode film layer is 250 mg / 1540.25 mm 2 Up to 330mg / 1540.25mm 2 ; and / or The compaction density of the positive electrode film layer of the battery cell at 0% charge state is 2.30 g / cm 3 Up to 2.70g / cm 3 .

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

25. The battery cell according to claim 24, 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.

26. The battery cell according to claim 24 or 25, characterized in that: The carbon-based material of the first negative electrode film layer includes at least one of artificial graphite and natural graphite, and the carbon-based material of the second negative electrode film layer includes artificial graphite.

27. The battery cell according to claim 24, characterized in that: The single-sided coating weight of the negative electrode film layer is 120 mg / 1540.25 mm 2 Up to 180mg / 1540.25mm 2 and / or, The compaction density of the negative electrode film layer of the battery cell at 0% charge state is 1.30 g / cm 3 Up to 1.65g / cm 3 .

28. The battery cell according to claim 1, characterized in that: The positive electrode sheet further includes a positive electrode tab connected to the positive current collecting portion, and the battery cell further includes a positive terminal connected to the positive electrode tab, and the number of the positive terminals is at least two; and / or The negative electrode plate further includes a negative electrode tab connected to the negative current collecting portion of the negative electrode plate, and the battery cell further includes a negative electrode terminal connected to the negative electrode tab, and there are at least two negative electrode terminals.

29. The battery cell according to claim 28, characterized in that: At least two of the positive terminals are disposed on at least one side of the electrode assembly along the length direction; and / or At least two of the negative terminals are disposed on at least one side of the electrode assembly along the length direction.

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

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

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