Battery cells, battery devices, and electrical equipment

Abstract

The present application proposes a battery cell, a battery device and an electrical equipment, wherein the battery cell includes a shell, an electrode assembly and an electrolyte, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet includes a positive electrode collector and a positive electrode film layer, the positive electrode collector includes a positive electrode body and a positive electrode ear, the positive electrode ear extends from the positive electrode body, the positive electrode film layer is located on at least one side of the positive electrode body, and the size of the positive electrode film layer along the direction in which the positive electrode ear extends from the positive electrode body is 200mm-700mm; the electrolyte includes a chain carboxylate, and the mass of the chain carboxylate accounts for 5%-50% based on the total mass of the electrolyte.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to PCT patent application PCT / CN2025 / 071087, entitled “Battery Cell, Battery Device, and Electrical Equipment,” filed on January 7, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of batteries, and in particular, to battery cells, battery devices, and electrical equipment. Background Art

[0004] Batteries are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, the battery cells used in related technologies cannot simultaneously meet the requirements of fast charging and high energy density. Summary of the Invention

[0005] The first aspect of the present application provides a battery cell, the battery cell comprising a shell, an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer, the positive electrode current collector comprises a positive electrode main body and a positive electrode ear portion, the positive electrode ear portion extends from the positive electrode main body portion, the positive electrode film layer is located on at least one side of the positive electrode main body portion, and the positive electrode film layer comprises a lithium-containing Phosphate, the positive electrode film layer has a dimension of 200mm-700mm along the length of the positive electrode sheet; the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer, the negative electrode current collector includes a negative electrode body and a negative electrode ear portion, the negative electrode ear portion extends from the negative electrode body portion, the negative electrode film layer is located on at least one side of the positive electrode body portion, and the negative electrode film layer includes graphite; the electrolyte includes a chain carboxylate, and the weight proportion of the chain carboxylate based on the total weight of the electrolyte is 5%-50%. Thus, by increasing the size of the positive electrode film layer, the energy density of the battery cell is increased, and by adding the above-mentioned content of the chain carboxylate, the conductivity of the electrolyte is increased, and the fast charging performance of the battery cell is improved, thereby obtaining a battery cell with both high energy density and excellent fast charging performance.

[0006] According to some embodiments of the present application, the size of the positive electrode film layer along the length direction of the positive electrode sheet is 400 mm to 650 mm, thereby further improving the energy density of the battery cell.

[0007] According to some embodiments of the present application, the mass proportion of the linear carboxylate is 8%-30% based on the total mass of the electrolyte. This improves the conductivity of the electrolyte while reducing the risk of gassing in the battery cell under high temperature conditions, resulting in a battery cell with both excellent fast charging performance and high-temperature cycle life.

[0008] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 9.5 mS / cm-19 mS / cm, thereby improving the fast charging performance of the battery cell.

[0009] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 9.7 mS / cm-13.5 mS / cm, thereby increasing the lithium ion migration rate while reducing the risk of electrolyte gas generation.

[0010] According to some embodiments of the present application, the viscosity of the electrolyte at room temperature is 2 mPa·s to 5 mPa·s, thereby increasing the lithium ion migration rate and reducing the internal resistance of the battery cell.

[0011] According to some embodiments of the present application, the density of the electrolyte at room temperature is 1.05 g / mL-1.35 g / mL, thereby increasing the migration rate of lithium ions in the electrolyte and reducing the internal resistance of the battery cell.

[0012] According to some embodiments of the present application, the chain carboxylate includes a compound represented by Formula I:

[0013] Formula I,

[0014] R1 includes one or more of a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and R2 includes one or more of a C1-C5 alkyl group or a C1-C5 haloalkyl group. As a result, these chain carboxylates have a relatively low molecular weight, which can improve the conductivity of the electrolyte. When combined with long electrodes, they can produce battery cells with high energy density, excellent fast-charging performance, and excellent high-temperature cycle life.

[0015] According to some embodiments of the present application, R1 includes one or more of a hydrogen atom, a C1-C3 alkyl group, or a C1-C3 haloalkyl group; and / or R2 includes one or more of a C1-C3 alkyl group or a C1-C3 haloalkyl group. This improves the conductivity of the electrolyte.

[0016] According to some embodiments of the present application, the chain carboxylate comprises Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, One or more of formula I-8. Therefore, the above-mentioned chain carboxylic acid esters have a relatively small molecular weight and can improve the conductivity of the electrolyte.

[0017] According to some embodiments of the present application, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 -340mg / 1540.25mm 2 , optional 240mg / 1540.25mm 2 -300mg / 1540.25mm 2 This increases the energy density of the battery cell.

[0018] According to some embodiments of the present application, when the battery cell is at 100% SOC, the compaction density of the positive electrode film layer is 2.5 g / cm 3 -2.8g / cm 3 This increases the energy density of the battery cell.

[0019] According to some embodiments of the present application, the lithium-containing phosphate includes at least one of lithium iron phosphate material and lithium manganese iron phosphate material, thereby improving the safety and cycle performance of the battery cell.

[0020] According to some embodiments of the present application, the positive electrode film layer also includes a lithium replenisher, which accounts for 0.5% to 2.5% of the total mass of the positive electrode film layer. This compensates for the loss of active lithium during the formation stage and improves the energy density and cycle life of the battery cell.

[0021] According to some embodiments of the present application, the lithium supplement includes one or more of lithium nickel cobalt manganese oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite.

[0022] According to some embodiments of the present application, the positive electrode sheet and the negative electrode sheet are stacked, thereby improving the utilization rate of the space inside the battery cell and increasing the energy density of the battery cell.

[0023] According to some embodiments of the present application, the battery cell includes a housing, a first end cap assembly, and a second end cap assembly. The housing, the first end cap assembly, and the second end cap assembly define a receiving cavity. The first end cap assembly includes a first end cap and at least one positive terminal, and the positive electrode body is electrically connected to the positive terminal via the positive electrode ear. And / or, the second end cap assembly includes a second end cap and at least one negative terminal, and the negative electrode body is electrically connected to the negative terminal via the negative electrode ear. This reduces the risk of short circuits between the positive and negative electrodes and improves the safety of the battery cell.

[0024] According to some embodiments of the present application, the first end cap assembly includes one positive terminal and one negative terminal, the positive electrode body is electrically connected to the positive terminal via the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal via the negative electrode ear; and / or the second end cap assembly includes one positive terminal and one negative terminal, the positive electrode body is electrically connected to the positive terminal via the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal via the negative electrode ear. Thus, the current capacity of the battery cell is improved.

[0025] According to some embodiments of the present application, the first and second end cap assemblies are disposed at opposite ends of the housing, and electrode terminals of the same polarity on the first and second end cap assemblies are staggered along the length of the battery cell. Optionally, the electrode terminals of the same polarity are disposed diagonally along the length of the battery cell. This reduces the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0026] According to some embodiments of the present application, the battery cell is configured to take 5 minutes to 10.5 minutes to charge from 10% SOC to 80% SOC, thereby improving the fast charging performance of the battery cell.

[0027] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0028] The third aspect of the present application provides an electrical device, comprising the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application, wherein the battery cell or the battery device is used to provide electrical energy.

[0029] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0031] Figure 1 This is a schematic diagram of a positive electrode sheet according to one embodiment of the present application.

[0032] Figure 2 This is a schematic diagram of the electrode assembly stacking method according to one embodiment of the present application.

[0033] Figure 3 It is a schematic structural diagram of a shell according to one embodiment of the present application.

[0034] Figure 4 This is a schematic diagram of a first end cover assembly according to one embodiment of the present application.

[0035] Figure 5 yes Figure 4 Exploded view of the first end cap assembly in FIG.

[0036] Figure 6 yes Figure 4 A schematic structural diagram of the first end cover assembly from another perspective.

[0037] Figure 7 yes Figure 6 A cross-sectional view of the first end cover assembly along the AA' direction.

[0038] Figure 8 This is a schematic diagram of a second end cover assembly according to one embodiment of the present application.

[0039] Figure 9 yes Figure 8 Exploded view of the second end cap assembly.

[0040] Figure 10 yes Figure 8 A schematic structural diagram of the second end cover assembly from another perspective.

[0041] Figure 11 yes Figure 10 A cross-sectional view of the second end cover assembly along direction BB'.

[0042] Figure 12 It is a schematic structural diagram of a battery cell according to one embodiment of the present application.

[0043] Figure 13 It is a structural schematic diagram of the first end cover assembly of one embodiment of the present application.

[0044] Figure 14 yes Figure 13 Exploded view of the first end cap assembly in FIG.

[0045] Figure 15 yes Figure 13 A structural schematic diagram of the first end cover assembly from another perspective.

[0046] Figure 16 yes Figure 15 Cross-sectional view of the first end cover assembly along CC' direction.

[0047] Figure 17 It is a structural schematic diagram of the second end cover assembly of one embodiment of the present application.

[0048] Figure 18 yes Figure 17 Exploded view of the second end cap assembly.

[0049] Figure 19 yes Figure 17 A schematic structural diagram of the second end cover assembly from another perspective.

[0050] Figure 20 yes Figure 19 A cross-sectional view of the second end cover assembly along the DD' direction.

[0051] Figure 21 It is a schematic structural diagram of an electrode assembly according to one embodiment of the present application.

[0052] Figure 22 It is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0053] Figure 23 It is a schematic diagram of an electrical device according to one embodiment of the present application.

[0054] Description of reference numerals:

[0055] 1 Battery cell; 11 Housing; 12 First end cap assembly; 13 Second end cap assembly; 121 First end cap; 1211 First opening; 1212 Liquid injection hole; 122 Positive terminal; 123 First insulating member; 1231 Second opening; 124 First sealing member; 125 First positioning member; 126 Second insulating member; 127 Riveted block; 131 Second end cap; 1311 Third opening; 132 Negative terminal; 133 Third insulating member; 1331 Fourth opening; 134 Second sealing member; 135 Second positioning member; 136 Fourth insulating member; 137 Pressure relief mechanism; 2 Positive electrode sheet; 21 Positive current collector; 211 Positive electrode body; 212 Positive electrode ear; 2121 First positive electrode ear; 2122 Second positive electrode ear; 22 Positive electrode film layer; 3 Negative electrode sheet; 31 First negative electrode ear; 32 Second negative electrode ear; 4 Separator; 20 Electrode assembly. DETAILED DESCRIPTION

[0056] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0057] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0060] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0061] Currently, market developments indicate that batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing. However, existing battery cells cannot simultaneously meet the requirements for high specific energy, fast charging, and long cycle times.

[0062] The battery cell proposed in this application, in order to improve the energy density of the battery cell, increases the loading capacity of the lithium-containing phosphate by extending the coating length of the positive electrode film layer on the positive electrode sheet, thereby improving the energy density of the battery cell. However, after the size of the positive electrode film layer increases, the electron conduction path increases, which limits the fast charging capability of the battery cell. By further increasing the content of the chain carboxylic acid ester in the electrolyte, the electrolyte can fully infiltrate the positive electrode film layer even for longer electrode sheets, thereby significantly increasing the electron and ion conductivity of the positive electrode film layer, and also improving the transmission capacity of lithium ions in the liquid phase, significantly improving the fast charging performance of longer battery cells. However, the increase in the content of the chain carboxylic acid ester will also aggravate the side reactions inside the battery, triggering gas production in the electrolyte, which is likely to aggravate the increase of acidic substances in the electrolyte, and then cause the problem of corrosion of the electrolyte interface film (SEI film), which has an impact on the cycle life at high temperatures. This application finds the appropriate chain carboxylate content for battery cells with a positive electrode film size of 200mm-700mm by comprehensively regulating the electrode length and solvent composition, so that the battery cells have both good fast charging capability and high-temperature cycle life.

[0063] The battery cells proposed in this application can be used in electrical devices that use the battery cells as power sources or various energy storage systems that use the battery cells as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0064] In a first aspect, the present application provides a battery cell, which includes a shell, an electrode assembly, and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet.

[0065] Among them, reference Figure 1 The positive electrode sheet 2 includes a positive electrode current collector 21 and a positive electrode film layer 22. The positive electrode current collector 21 includes a positive electrode main body 211 and a positive electrode ear 212. The positive electrode ear 212 extends from the positive electrode main body 211. The positive electrode film layer 22 is located on at least one side of the positive electrode main body 211. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate. The size of the positive electrode film layer 22 along the length direction of the positive electrode sheet 2 is 200mm-700mm.

[0066] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer. The negative electrode current collector includes a negative electrode main body and a negative electrode ear. The negative electrode ear extends from the negative electrode main body. The negative electrode film layer is located on at least one side of the positive electrode main body. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite.

[0067] The electrolyte includes a chain carboxylate, and based on the total mass of the electrolyte, the mass of the chain carboxylate accounts for 5%-50%.

[0068] Therefore, the battery cell proposed in this application has a longer coating length of the positive electrode film layer, which can increase the loading capacity of lithium phosphate on the positive electrode plate, thereby obtaining a battery cell with a higher energy density. At the same time, by adding 5%-50% of chain carboxylic acid ester to the electrolyte, the conductivity of the electrolyte can be increased. When the positive electrode film layer is longer, the conductivity of the plate is increased, thereby improving the fast charging performance of the battery cell.

[0069] In this application, the size of the positive electrode film layer refers to the size of the positive electrode film layer on at least one side of the positive electrode main body in the length direction of the positive electrode current collector. Figure 1 The L in it is the size of the positive electrode film layer.

[0070] As an example, the dimension L of the positive electrode film layer can be 200mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, etc., or any range thereof. This increases the content of lithium phosphate in the positive electrode sheet, resulting in a battery cell with excellent safety, cycle performance, and high energy density.

[0071] According to some specific embodiments of the present application, the dimension L of the positive electrode film layer along the direction in which the positive electrode tab extends from the positive electrode body can be 400 mm to 650 mm. This improves the volumetric energy density of the battery cell while reducing the electron conduction path and improving the fast charging performance of the battery cell.

[0072] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 9.5 mS / cm-19 mS / cm.

[0073] As an example, the conductivity of the electrolyte can be 9.5 mS / cm, 10 mS / cm, 12 mS / cm, 14 mS / cm, 16 mS / cm, 18 mS / cm, 19 mS / cm, etc., or can be within a range of any of the above values, thereby improving the rate performance of the battery cell.

[0074] According to some embodiments of the present application, the electrolyte has a conductivity of 9.7mS / cm-13.5mS / cm at room temperature. This improves the fast charging performance of the battery cells while reducing the risk of gassing in the battery cells under high temperature conditions, thereby improving the high-temperature cycling performance of the battery cells.

[0075] In this application, after disassembling the battery cells to obtain the electrolyte, a conductivity meter is used. The conductivity of the electrolyte at room temperature can be tested with reference to HG-T 4067-2015.

[0076] According to some embodiments of the present application, the mass proportion of the chain carboxylic acid ester can be 5%-50% based on the total mass of the electrolyte, for example, 5%, 10%, 20%, 30%, 40%, 50%, etc., or can be a range consisting of any of the above values. By setting the content of the chain carboxylic acid ester within the above range, on the one hand, the viscosity of the electrolyte can be reduced, the internal resistance of the battery cell can be reduced, the migration rate of lithium ions can be increased, and the fast charging performance of the battery cell can be improved; on the other hand, the risk of gassing of the electrolyte under high temperature conditions can be reduced, and the high temperature cycle life of the battery cell can be increased, thereby obtaining a battery cell with high energy density, excellent fast charging performance, and high temperature cycle life.

[0077] According to some specific embodiments of the present application, the mass proportion of the chain carboxylic acid ester can be 8%-30% based on the total mass of the electrolyte. This improves the fast charging performance of the battery cell while reducing the risk of gassing of the battery cell under high temperature conditions, thereby increasing the high-temperature cycle life of the battery.

[0078] In the present application, after disassembling the battery cell to obtain the electrolyte, the qualitative and quantitative detection of the chain carboxylic acid ester can be performed by gas chromatography-ion chromatography (GC-IC).

[0079] According to some embodiments of the present application, the viscosity of the electrolyte at room temperature may be 2mPa·s-5mPa·s. For example, it may be 2mPa·s, 2.5mPa·s, 3mPa·s, 3.5mPa·s, 4mPa·s, 4.5mPa·s, 5mPa·s, etc., or may be a range consisting of any of the above values. As a result, the viscosity of the electrolyte is relatively low, which can increase the migration rate of lithium ions, reduce the internal resistance of the battery cell, and improve the fast charging performance of the battery cell.

[0080] In the present application, after disassembling the battery cells to obtain the electrolyte, the viscosity of the electrolyte is tested by a kinematic viscometer. The viscosity of the electrolyte at room temperature can be tested with reference to GB / T 10247-2008.

[0081] According to some embodiments of the present application, the density of the electrolyte at room temperature can be 1.05g / mL-1.35g / mL. For example, it can be 1.05g / mL, 1.1g / mL, 1.15g / mL, 1.2g / mL, 1.25g / mL, 1.3g / mL, 1.35g / mL, etc., or it can be a range composed of any of the above values. Thus, the viscosity of the electrolyte is reduced, the migration rate of lithium ions in the electrolyte is increased, the internal resistance of the battery cell is reduced, and the fast charging performance of the battery cell is improved.

[0082] In this application, after disassembling the battery cell to obtain the electrolyte, the density of the electrolyte is tested using a liquid density meter. The density of the electrolyte at room temperature can be tested with reference to GB / T 2013-2010.

[0083] According to some embodiments of the present application, the chain carboxylate may include a compound represented by Formula I:

[0084] Formula I,

[0085] Wherein, R1 includes one or more of a hydrogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R2 includes one or more of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

[0086] Therefore, when the mass proportion of the chain carboxylate represented by Formula I is 5%-50%, on the one hand, the use of the chain carboxylate of the above type and content can improve the wetting ability of the electrolyte in the electrode film layer, especially in longer battery cells, improve the wetting uniformity of the electrolyte in the length direction of the electrode, improve the electron transmission ability of the active material, and in addition, can also increase the lithium ion migration rate in the electrolyte, thereby improving the fast charging performance of the battery cell; on the other hand, too high a content of chain carboxylate also increases the gas production inside the battery cell, which is not conducive to the cycle of the battery at high temperature. Therefore, an appropriate amount of chain carboxylate can also reduce the risk of gas production of the electrolyte under high temperature conditions and improve the high temperature cycle life of the battery.

[0087] According to some embodiments of the present application, R1 includes one or more of a hydrogen atom, a C1-C3 alkyl group, or a C1-C3 haloalkyl group. For example, R1 may include one or more of a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, or a fluoropropyl group. This improves the conductivity of the electrolyte.

[0088] According to some embodiments of the present application, R2 includes one or more of a C1-C3 alkyl group and a C1-C3 haloalkyl group. For example, R2 can be one or more of a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, and a fluoropropyl group. This improves the conductivity of the electrolyte.

[0089] According to some embodiments of the present application, the chain carboxylic acid ester may include Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, One or more of formula I-8. Therefore, the above-mentioned chain carboxylic acid esters have a relatively small molecular weight and can improve the conductivity of the electrolyte.

[0090] According to some embodiments of the present application, the single-sided coating weight of the positive electrode film layer can be 200 mg / 1540.25 mm 2 -340mg / 1540.25mm 2 , for example, it can be 200mg / 1540.25mm 2 、230mg / 1540.25mm 2 、260mg / 1540.25mm 2 、290mg / 1540.25mm 2 、320mg / 1540.25mm 2 、340mg / 1540.25mm 2 Thus, by setting the size of the positive electrode film layer to 200 mm to 700 mm and setting the coating weight of the positive electrode film layer to the above range, the energy density of the battery cell can be increased.

[0091] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0092] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0093] According to some specific embodiments of the present application, the single-sided coating weight of the positive electrode film layer can be 240 mg / 1540.25 mm 2 -300mg / 1540.25mm 2 For example, it can be 240mg / 1540.25mm 2 、260mg / 1540.25mm2 、280mg / 1540.25mm 2 、300mg / 1540.25mm 2 The energy density of the battery cell can be increased by using any of the above numerical values.

[0094] This application provides a method for testing the coating weight of the positive electrode film layer: A battery cell is disassembled to remove the positive electrode sheet. For example, a single-sided coated positive electrode sheet (for double-sided coated sheets, the positive electrode film layer on one side can be wiped off first) is punched into small discs with an area of S1. These discs are weighed and recorded as M1. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0. The single-sided coating weight of the positive electrode film layer = (M1 - M0) / S1.

[0095] According to some embodiments of the present application, when the battery cell is at 100% SOC, the compaction density of the positive electrode film layer can be 2.5 g / cm 3 -2.8g / cm 3 For example, it can be 2.5g / cm 3 , 2.55g / cm 3 , 2.6g / cm 3 , 2.65g / cm 3 , 2.7g / cm 3 , 2.75g / cm 3 , 2.8g / cm 3 etc., or can be within a range consisting of any of the above values. Therefore, when the compaction density of the positive electrode film layer is within the above range, the positive electrode sheets are densely stacked, which is beneficial to improving the energy density of the battery cell. In addition, the contact resistance between particles is small, which can further reduce the internal resistance of the battery cell, reduce the heat generation of the battery cell, and improve the high-temperature performance of the battery cell.

[0096] The present application provides a method for testing the compaction density of the positive electrode film layer: charge to 3.8V at a constant current of 1 / 3C, charge to 0.05C at a constant voltage of 3.8V, disassemble the battery cell to obtain the positive electrode sheet, for example, take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), punch it into a small disc with an area of S1, weigh it, record it as M1, and measure its thickness H1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the weight of the positive electrode current collector, record it as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode film layer = (M1- M0) / S1, the thickness of the positive electrode film layer = H1- H0, and the compaction 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.

[0097] According to some embodiments of the present application, the lithium-containing phosphate includes at least one of a lithium iron phosphate material and a lithium iron manganese phosphate material, thereby improving the cycle performance of the battery cell.

[0098] According to some embodiments of the present application, the lithium-containing phosphate includes a compound shown in Formula II:

[0099] Li x1 A y1 Me a M b P 1-c X c Y z Formula II,

[0100] Wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, P, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or two of O and F.

[0101] According to some embodiments of the present application, the positive electrode film layer further includes a lithium supplement agent, and based on the total mass of the positive electrode film layer, the mass proportion of the lithium supplement agent can be 0.5%-2.5%. For example, it can be 0.5%, 0.7%, 1%, 1.3%, 1.6%, 1.85%, 2.2%, 2.5%, etc., or it can be a range composed of any of the above values. In this way, lithium ions can be supplemented to the positive electrode film layer to compensate for the loss of lithium ions, increase the capacity of the battery cell, and improve the energy density and cycle life of the battery cell.

[0102] According to some embodiments of the present application, the lithium supplement may include one or more of lithium nickel cobalt manganese oxide, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite, thereby increasing the energy density of the battery cell.

[0103] According to some specific embodiments of the present application, the lithium supplement includes lithium ferrite. During the battery cycle, lithium ferrite can release oxygen free radicals to participate in the negative electrode film formation, further reduce the internal resistance of the battery cell, and improve the fast charging performance of the battery cell.

[0104] According to some embodiments of the present application, reference Figure 2 The positive electrode sheet 2 and the negative electrode sheet 3 are stacked. Specifically, a separator 4 is provided between the positive electrode sheet 2 and the negative electrode sheet 3 to prevent short circuit between the positive electrode sheet 2 and the negative electrode sheet 3. This improves the utilization of the space within the battery cell and increases the energy density of the battery cell.

[0105] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode film layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0107] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0109] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0110] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. When the battery is a lithium-ion battery, lithium titanate is used as the titanate; when the battery is a sodium-ion battery, sodium titanate is used as the titanate. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0111] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0112] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0113] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0114] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0115] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer, the negative electrode current collector includes a negative electrode main body and a negative electrode ear, and the negative electrode ear extends from the negative electrode main body; the battery cell includes a shell, a first end cover assembly and a second end cover assembly, the shell, the first end cover assembly and the second end cover assembly define a accommodating cavity, the first end cover assembly includes a first end cover and at least one positive terminal, the positive electrode main body is electrically connected to the positive terminal through the positive electrode ear; and / or, the second end cover assembly includes a second end cover and at least one negative terminal, the negative electrode main body is electrically connected to the negative terminal through the negative electrode ear.

[0116] Specifically, the battery cell includes a shell, a first end cap assembly and a second end cap assembly. The first end cap assembly includes a first end cap, and the second end cap assembly includes a second end cap. Figure 3 , the first end cap assembly and the second end cap assembly can be arranged at both ends of the shell 11 along its length direction, or the first end cap assembly and the second end cap assembly can be arranged at both ends of the shell 11 along its width direction. Specifically, when the shell 11 has openings at both ends along its length direction, the first end cap assembly and the second end cap assembly can be arranged at both ends of the shell 11 along its length direction and are suitable for covering the openings respectively; when the shell 11 has openings at both ends along its width direction, the first end cap assembly and the second end cap assembly can be arranged at both ends of the shell 11 along its width direction and are suitable for covering the openings respectively, so as to isolate the internal environment of the battery cell from the external environment. The shapes of the first end cap assembly and the second end cap assembly can be adapted to the shape of the shell 11 to match the shell 11.

[0117] In some embodiments, the first end cover assembly and the second end cover assembly can be arranged at both ends of the shell 11 along its length direction, that is, the first end cover assembly and the second end cover assembly are arranged on the smaller side surfaces of the shell 11, thereby saving space of the battery cell along the width direction, thereby accommodating wider pole pieces and improving the energy density of the battery cell.

[0118] In some embodiments, the shell 11 is formed by bending and then welding, and the weld marks are integrated on the smaller side surfaces of the shell 11 extending along the length direction, which helps to reduce the problem of cracking in the welding area caused by expansion of the battery cell along the thickness direction and improve the reliability of the shell 11.

[0119] The first and second end caps can be independently made of a material with a certain degree of hardness and strength (such as an aluminum alloy). This provides the first and second end caps with greater strength, reduces deformation when squeezed, and improves the safety of the battery cell. In some embodiments, the first and second end caps can be steel shells.

[0120] As an example, the first end cover assembly, the second end cover assembly, and the housing may be independent components.

[0121] As an example, the first end cap assembly, the second end cap assembly, and the housing can also be integrated. Specifically, the first end cap assembly or the second end cap assembly and the housing can form a common connection before the electrode assembly and other components are placed in the housing. After the electrode assembly and other components are placed in the housing 11, the second end cap assembly or the first end cap assembly is then used to cover the opening of the housing along the length or width direction.

[0122] According to some embodiments of the present application, reference Figure 4-Figure 7 The first end cap assembly 12 includes a first end cap 121 and a first electrode terminal 122 .

[0123] In some embodiments, reference Figure 5 The first end cap assembly 12 includes a first cover plate 121, a first electrode terminal 122, a first insulating member 123, a first sealing member 124, a first positioning member 125, a second insulating member 126 and a rivet block 127, and is assembled into Figure 4 A first end cap assembly 12 is shown.

[0124] In some embodiments, Figure 7 yes Figure 6 Schematic diagram of the cross section along the AA' direction, combined with Figure 5 and Figure 7It can be seen that a first opening 1211 is provided on the first end cover 121, and the first electrode terminal 122 passes through the first end cover 121. A first insulating member 123 is provided between the first end cover 121 and the first electrode terminal 122. This assembly method is used to isolate the electrical connection components in the housing 11 from the first end cover 121, and at the same time, the first electrode terminal 122 is insulated from the first end cover 121 to reduce the risk of short circuit. A second opening 1231 is provided on the first insulating member 123, and the first electrode terminal 122 is sequentially passed through the second opening 1231 and the first opening 1211. The first opening 1211 and the first electrode terminal 122 are connected to each other. A first sealing member 124 for insulation and sealing is provided between the terminals 122. A through hole is provided on the first sealing member 124 so that the first electrode terminal 122 can pass through. A second insulating member 126 and a rivet block 127 are provided on the side of the first end cover 121 away from the electrode assembly. The second insulating member 126 and the rivet block 127 are also provided with through holes. The first electrode terminal 122 passes through the through holes of the second insulating member 126 and the rivet block 127 in sequence, wherein the second insulating member 126 is used to insulate the first electrode terminal 122 from the first end cover 121, and the rivet block 127 is used to fix the first electrode terminal 122 on the first end cover 121.

[0125] In some embodiments, reference Figure 5 The first end cap assembly further includes a first positioning member 125 , and the first positioning member 125 includes at least two members to prevent the first electrode terminal 122 from deflecting and improve the force strength of the first electrode terminal 122 .

[0126] In some embodiments, reference Figure 5 The first end cover assembly 12 includes a liquid injection hole 1212 for injecting electrolyte into the accommodating cavity of the shell 11.

[0127] refer to Figures 8-11 The second end cap assembly 13 includes a second end cap 131 and a second electrode terminal 132 .

[0128] In some embodiments, reference Figure 9 The second end cap assembly 13 is a disassembled schematic diagram of the second end cap assembly 13, which includes a second end cap 131, a second electrode terminal 132, a third insulating member 133, a second sealing member 134, a fourth insulating member 136, a rivet block 127 and a second positioning member 135, and is assembled into Figure 8 The second end cap assembly 13 is shown.

[0129] In some embodiments, Figure 11 yes Figure 10 Schematic diagram of the cross section along the BB' direction, combined with Figure 9 and Figure 11 It can be seen that a third opening 1311 is provided on the second end cover 131, and the second electrode terminal 132 passes through the second end cover 131. A third insulating member 133 is provided between the second end cover 131 and the second electrode terminal 132. This assembly method is used to isolate the electrical connection components in the housing 11 from the second end cover 131, and at the same time, the second electrode terminal 132 is in an insulated state from the second end cover 131 to reduce the risk of short circuit. A fourth opening 1331 is provided on the third insulating member 133, and the second electrode terminal 132 is sequentially passed through the fourth opening 1331 and the third opening 1311. The third opening 1311 and the second electrode terminal 132 are connected to each other. A second sealing member 134 for insulation and sealing is provided between the terminals 132, and a through hole is provided on the second sealing member 134 so that the second electrode terminal 132 can pass through. A fourth insulating member 136 and a rivet block 127 are provided on the side of the second end cover 131 away from the electrode assembly. The fourth insulating member 136 and the rivet block 127 are also provided with through holes, and the second electrode terminal 132 passes through the through holes of the fourth insulating member 136 and the rivet block 127 in turn, wherein the fourth insulating member 136 is used to insulate the second electrode terminal 132 from the second end cover 131, and the rivet block 127 is used to fix the second electrode terminal 132 on the second end cover 131.

[0130] In some embodiments, reference Figure 9 The second end cap assembly 13 further includes a second positioning member 135 , which includes at least two second positioning members 135 to prevent the second electrode terminal 132 from deflecting and improve the force strength of the second electrode terminal 132 .

[0131] According to some embodiments of the present application, reference Figures 8-11 The second end cover 131 is provided with a pressure relief mechanism 137 . When the pressure inside the shell exceeds a threshold, the pressure relief mechanism 137 can release the pressure inside the shell.

[0132] As an example, the pressure relief mechanism 137 and the second end cap 131 are two separate components that are molded separately and then assembled together. The pressure relief mechanism 137 can be a component such as a rupture disk, explosion-proof valve, or safety valve, and can be attached to the second end cap 131 by bonding, welding, or other methods. When the internal pressure of the battery cell reaches a threshold, the pressure relief mechanism 137 opens at least a portion of the pressure relief holes, allowing the exhaust gas inside the battery cell to be discharged through the pressure relief holes, thereby relieving the internal pressure of the battery cell.

[0133] According to some embodiments of the present application, the first end cap assembly includes a positive terminal and a negative terminal, the positive electrode body is electrically connected to the positive terminal through the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal through the negative electrode ear.

[0134] According to some embodiments of the present application, the second end cap assembly includes a positive terminal and a negative terminal, the positive electrode body is electrically connected to the positive terminal via the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal via the negative electrode ear, thereby improving the current capacity of the battery cell.

[0135] refer to Figure 12 The first end cover assembly 12 and the second end cover assembly 13 are arranged at both ends of the shell 11 along its length direction. The first end cover assembly 12 includes a positive terminal and a negative terminal, and the second end cover assembly includes a positive terminal and a negative terminal.

[0136] Specifically, refer to Figure 13-16 The first end cap assembly 12 includes a first end cap 121 and two electrode terminals with opposite polarities (a first electrode terminal 122 and a second electrode terminal 132), wherein when the first electrode terminal 122 is a positive terminal, the second electrode terminal 132 is a negative terminal; when the first electrode terminal 122 is a negative terminal, the second electrode terminal is a positive terminal.

[0137] In some embodiments, reference Figure 14 The first end cap assembly 12 is a disassembled schematic diagram of the first end cap assembly 12, which includes a first end cap 121, a first electrode terminal 122, a second electrode terminal 132, a first insulating member 123, two first sealing members 124, two second insulating members 126, two rivet blocks 127 and four first positioning members 125, and is assembled into Figure 13 The first end cap assembly is shown.

[0138] In some embodiments, Figure 16 yes Figure 15 Schematic diagram of the cross section along CC' direction, combined with Figure 14 and Figure 16It can be seen that two first openings 1211 are provided on the first end cover 121, and the first electrode terminal 122 and the second electrode terminal 132 respectively pass through the first end cover 121. A first insulating member 123 is provided between the first end cover 121 and the first electrode terminal 122 and the second electrode terminal 132. This assembly method is used to isolate the electrical connection components in the housing 11 from the first end cover 121, and at the same time, the first electrode terminal 122, the second electrode terminal 132 and the first end cover 121 are insulated to reduce the risk of short circuit. Two second openings 1231 are provided on the first insulating member 123, and the first electrode terminal 122 and the second electrode terminal 132 are respectively passed through the corresponding second openings 1231 and the first opening 1211. The first A first sealing member 124 for insulation and sealing is provided between the opening 1211 and the first electrode terminal 122 and the second electrode terminal 132. A through hole is provided on the first sealing member 124 so that the first electrode terminal 122 and the second electrode terminal 132 can pass through. Two second insulating members 126 and two rivet blocks 127 are provided on the side of the first end cover 121 away from the electrode assembly. The second insulating member 126 and the rivet blocks 127 are also provided with through holes. The first electrode terminal 122 and the second electrode terminal 132 pass through the corresponding through holes on the second insulating member 126 and the rivet blocks 127 in sequence, wherein the second insulating member 126 is used to insulate the electrode terminal from the first end cover 121, and the rivet blocks 127 are used to fix the electrode terminal to the first end cover 121.

[0139] refer to Figures 17-20 The second end cap assembly 13 includes a second end cap 131 and two electrode terminals (a first electrode terminal 122 and a second electrode terminal 132) with opposite polarities. When the first electrode terminal 122 is a positive terminal, the second electrode terminal 132 is a negative terminal; when the first electrode terminal 122 is a negative terminal, the second electrode terminal is a positive terminal.

[0140] In some embodiments, reference Figure 18 The second end cap assembly 13 is a disassembled schematic diagram of the second end cap assembly 13, which includes a second end cap 131, a first electrode terminal 122, a second electrode terminal 132, a third insulating member 133, two second sealing members 134, a fourth insulating member 136, a rivet block 127 and a second positioning member 135, and is assembled into Figure 17 The second end cap assembly 13 is shown.

[0141] In some embodiments, Figure 20 yes Figure 19 Schematic diagram of the cross section along the DD' direction, combined with Figure 18 and Figure 20 It can be seen that two third openings 1311 are provided on the second end cover 131, and the first electrode terminal 122 and the second electrode terminal 132 pass through the second end cover 131. A third insulating member 133 is provided between the second end cover 131 and the first electrode terminal 122 and the second electrode terminal 132. This assembly method is used to isolate the electrical connection components in the housing 11 from the second end cover 131, while making the first electrode terminal 122, the second electrode terminal 132 and the second end cover 131 in an insulated state to reduce the risk of short circuit. Two fourth openings 1331 are provided on the third insulating member 133, and the first electrode terminal 122 and the second electrode terminal 132 are sequentially passed through the corresponding fourth openings 1331 and the third opening 1311. The third opening A second sealing member 134 for insulation and sealing is provided between 1311 and the first electrode terminal 122 and the second electrode terminal 132. A through hole is provided on the second sealing member 134 so that the first electrode terminal 122 and the second electrode terminal 132 can pass through. Two fourth insulating members 136 and two rivet blocks 127 are provided on the side of the second end cover 131 away from the electrode assembly. The fourth insulating member 136 and the rivet blocks 127 are also provided with through holes. The first electrode terminal 122 and the second electrode terminal 132 pass through the corresponding through holes on the fourth insulating member 136 and the rivet blocks 127 in sequence, wherein the fourth insulating member 136 is used to insulate the electrode terminal from the second end cover 131, and the rivet block 127 is used to fix the electrode terminal to the second end cover 131.

[0142] According to some embodiments of the present application, the first end cover assembly and the second end cover assembly are arranged at both ends of the shell, and the electrode terminals of the same polarity on the first end cover assembly and the second end cover assembly are staggered along the length direction of the battery cell.

[0143] According to some embodiments of the present application, the electrode terminals of the same polarity are arranged diagonally along the length direction of the battery cell.

[0144] As a result, the temperature rise of the battery cells can be reduced during charging, thereby reducing the impedance of the battery cells.

[0145] refer to Figure 21The electrode assembly 20 includes four tabs. Two tabs extend from one end of the electrode assembly 20 in the longitudinal direction: a first positive tab 2121 and a first negative tab 31. Two tabs extend from the other end of the electrode assembly 20 in the longitudinal direction: a second positive tab 2122 and a second negative tab 32. The first positive tab 2121 is electrically connected to the first electrode terminal 122 on the first end cap, the first negative tab 31 is electrically connected to the second electrode terminal 132 on the first end cap, the second positive tab 2122 is electrically connected to the first electrode terminal 122 on the second end cap 131, and the second negative tab 32 is electrically connected to the second electrode terminal 132 on the second end cap 131. Thus, the electrode terminals of different polarities are arranged diagonally along the longitudinal direction of the battery cell, which can reduce the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0146] refer to Figure 22 The electrode assembly 20 includes four tabs. Two tabs extend from one longitudinal end of the electrode assembly 20: a first positive tab 2121 and a first negative tab 31. Two tabs extend from the other longitudinal end of the electrode assembly 20: a second positive tab 2122 and a second negative tab 32. The two positive tabs at the two longitudinal ends of the electrode assembly 20 are asymmetrically arranged, as are the two negative tabs at the two longitudinal ends of the electrode assembly 20. The first positive tab 2121 is electrically connected to the first electrode terminal 122 on the first end cap, the first negative tab 31 is electrically connected to the second electrode terminal 132 on the first end cap, the second positive tab 2122 is electrically connected to the first electrode terminal 122 on the second end cap 131, and the second negative tab 32 is electrically connected to the second electrode terminal 132 on the second end cap 131. Thus, electrode terminals of the same polarity are arranged diagonally along the longitudinal direction of the battery cell, which improves the current carrying capacity of the battery cell and reduces wiring within the battery cell, making assembly easier.

[0147] According to some embodiments of the present application, the battery cell is configured to take 5 minutes to 10.5 minutes to charge from 10% SOC to 80% SOC, thereby improving the fast charging performance of the battery cell.

[0148] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0149] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. 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.

[0150] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0151] In a third aspect, the present application provides an electrical device comprising the battery cell described in the first aspect or the battery device described in the second aspect, wherein the battery cell or the battery device is configured to provide electrical energy. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0152] As the electrical device, a battery module or a battery pack can be selected according to its usage requirements.

[0153] Figure 23 This is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module can be used.

[0154] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0155] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0156] Example 1

[0157] 1. Positive electrode

[0158] The positive electrode sheet includes a positive electrode current collector aluminum foil with a positive electrode film layer on both surfaces. At 100% SOC, the compaction density is 2.65g / cm 3 The coating weight of the single-sided positive electrode film is 290mg / 1540.25mm 2The size of the positive electrode film layer is 200mm. Based on the total mass of the single-sided positive electrode film layer, the positive electrode film layer includes 95.8% lithium iron phosphate material, 0.9% lithium supplement Li5FeO4, 1.1% conductive agent carbon black, and 2.2% binder polyvinylidene fluoride (PVDF). The surface of the lithium iron phosphate has a carbon coating layer. Based on the total mass of the lithium iron phosphate, the mass proportion of the carbon coating layer is 1.18%.

[0159] 2. Negative electrode

[0160] The negative electrode sheet includes a negative electrode current collector copper foil with a negative electrode film layer on both surfaces, with a compaction density of 1.56g / cm 3 The coating weight of the single-sided negative electrode film is 138mg / 1540.25mm 2 Based on the total mass of the single-sided negative electrode film layer, the negative electrode film layer includes 96% artificial graphite, 1.1% conductive agent carbon black, 1.4% binder styrene-butadiene rubber (SBR), and 1.5% thickener sodium carboxymethyl cellulose (CMC-Na).

[0161] 3. Electrolyte

[0162] The electrolyte includes solvents, electrolyte salts and additives. The solvents include ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl acetate. The electrolyte salts are lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide (LiFSI). The additives include vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES) and lithium difluorooxalatoborate (LiDFOB). Based on the total mass of the electrolyte, the mass proportion of EC is 28.9%, the mass proportion of DMC is 45.4%, the mass proportion of ethyl acetate is 8.3%, the mass proportion of lithium hexafluorophosphate is 8.3%, the mass proportion of LiFSI is 4.2%, the mass proportion of VC is 3%, the mass proportion of FEC is 1%, the mass proportion of ES is 0.5%, and the mass proportion of LiDFOB is 0.5%. The density of the electrolyte is 1.22 g / mL, the viscosity is 3.19 mPa·s, and the conductivity is 11 mS / cm.

[0163] 4. Isolation film

[0164] Polypropylene film, thickness 12 μm.

[0165] 5. Battery cells

[0166] The battery cell includes a shell, a first end cap assembly, a second end cap assembly, an electrode assembly and an electrolyte. The first end cap assembly and the second end cap assembly are located at both ends of the shell in the length direction. The structure of the first end cap assembly is referenced. Figure 4 , the structural reference of the second end cover assembly Figure 8, that is, the first end cover assembly and the second end cover assembly each include an electrode terminal, the electrode assembly and the electrolyte are arranged in the accommodating cavity formed by the shell and the end cover assembly, the electrode assembly is a laminated electrode assembly, which is made by stacking the above-mentioned positive electrode sheet, isolation membrane, and negative electrode sheet. Along the length direction of the electrode assembly, a positive electrode tab extends from one end and a negative electrode tab extends from the other end. The positive electrode tab is electrically connected to the positive terminal, and the negative electrode tab is electrically connected to the negative terminal.

[0167] The battery case has a shell length of 245 mm, a width of 104.5 mm, and a thickness of 15.7 mm.

[0168] Performance Testing

[0169] 1. Charging time

[0170] Calculate the time it takes to charge a battery cell from 10% SOC to 80% SOC. The specific charging process is as follows:

[0171] Charge from 0% SOC to 10% SOC at 1C constant current; charge from 10% SOC to 30% SOC at 7.0C constant current; charge from 30% SOC to 35% SOC at 6.2C constant current; charge from 35% SOC to 40% SOC at 5.7C constant current; charge from 40% SOC to 45% SOC at 5.2C constant current; charge from 45% SOC to 50% SOC at 4.8C constant current; charge from 50% SOC to 50% SOC at 4.6C constant current. Charge from 55% SOC to 55% SOC at a constant current of 4.4C; charge from 55% SOC to 60% SOC at a constant current of 4.2C; charge from 60% SOC to 65% SOC at a constant current of 3.9C; charge from 65% SOC to 70% SOC at a constant current of 3.5C; charge from 70% SOC to 75% SOC at a constant current of 3.0C; and charge from 75% SOC to 80% SOC. The total time of each charging period is the charging time.

[0172] 2. High temperature cycle life

[0173] At an ambient temperature of 45°C, the battery cell is charged to 3.8V with step charge, charged to 0.05C with constant voltage, left for 30 minutes, discharged to 2.5V with 0.5C constant current, and left for 30 minutes. This is one charge and discharge cycle. Repeat the above charge and discharge cycles until the capacity of the battery cell is 80% of the initial capacity. The number of charge and discharge cycles is the high-temperature cycle life of the battery cell.

[0174] Step charge charging steps are:

[0175] Charge from 0% SOC to 10% SOC at 1C constant current; charge from 10% SOC to 30% SOC at 7.0C constant current; charge from 30% SOC to 35% SOC at 6.2C constant current; charge from 35% SOC to 40% SOC at 5.7C constant current; charge from 40% SOC to 45% SOC at 5.2C constant current; charge from 45% SOC to 50% SOC at 4.8C constant current; charge from 50% SOC to 50% SOC at 4.6C constant current Charge to 55% SOC; charge from 55% SOC to 60% SOC at 4.4C constant current; charge from 60% SOC to 65% SOC at 4.2C constant current; charge from 65% SOC to 70% SOC at 3.9C constant current; charge from 70% SOC to 75% SOC at 3.5C constant current; charge from 75% SOC to 80% SOC at 3.0C constant current; charge from 80% SOC to 100% SOC at 0.33C constant current.

[0176] 3. Energy density

[0177] At 25°C, charge at a constant current of 0.33C to 3.8V, then charge at a constant voltage of 3.8V to 0.05C and let it stand for 30 minutes; discharge at a constant current of 0.33C to 2.0V, record the discharge capacity A0 at this time, unit: Ah, calculate the discharge platform voltage, unit: V; use calipers to measure the length, width and height of the battery cell, calculate the volume of the single cell V0, unit: L; the volume energy density of the battery cell VED = (A0 × discharge platform voltage) ÷ V0 ÷ 1000, unit: Wh / L.

[0178] In this application, the length of the battery cell minus the size of the positive electrode film layer is 45 mm, the width of the battery cell is 104.5 mm, the thickness of the battery cell is 15.7 mm, the discharge capacity A0 is 62.3 Ah, and the discharge platform voltage is 3.2 V.

[0179] Example 2

[0180] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 400 mm.

[0181] Example 3

[0182] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 500 mm.

[0183] Example 4

[0184] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 650 mm.

[0185] Example 5

[0186] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 700 mm.

[0187] Comparative Example 1

[0188] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 150 mm.

[0189] Comparative Example 2

[0190] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode film layer is 800 mm.

[0191] The detailed differences and test structures of the battery cells in Examples 2 to 5 and Comparative Examples 1 and 2 are shown in Table 1.

[0192] Table 1

[0193]

[0194] Comparing Examples 1-5 with Comparative Examples 1 and 2 shows that by adjusting the positive electrode film size to 200mm-700mm and using an electrolyte containing a chain carboxylate, the energy density, fast-charging performance, and cycle performance of the battery cell can be simultaneously improved. If the positive electrode film size is too small, the charging time is shortened, but the energy density of the battery cell is low. If the positive electrode film size is too large, although the battery cell energy density is high, the longer electrode length leads to a faster temperature rise in the battery cell and a higher internal resistance, shortening the cycle life of the battery cell.

[0195] Example 6

[0196] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 5%, the mass proportion of EC is 28.9%, and the mass proportion of DMC is 48.6%.

[0197] Example 7

[0198] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 6.6%, the mass proportion of EC is 28.9%, and the mass proportion of DMC is 47%.

[0199] Example 8

[0200] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 24.8%, the mass proportion of EC is 28.9%, and the mass proportion of DMC is 28.9%.

[0201] Example 9

[0202] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 40.8%, the mass proportion of EC is 28.5%, the mass proportion of DMC is 12.2%, and the mass proportion of VC in the additive is 4%.

[0203] Example 10

[0204] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 56.4%, the mass proportion of EC is 24.2%, the mass proportion of VC in the additive is 5%, and DMC is not included.

[0205] Example 11

[0206] The preparation method of the battery monomer is the same as that of Example 4, except that the carboxylate is methyl acetate.

[0207] Comparative Example 3

[0208] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of ethyl acetate is 61.9%, the mass proportion of EC is 20.6%, and DMC is not included.

[0209] Comparative Example 4

[0210] The preparation method of the battery cell is the same as that of Example 4, except that the electrolyte does not contain chain carboxylate, the mass proportion of EC is 29.6%, the mass proportion of DMC is 54.9%, and the mass proportion of VC in the additive is 1%.

[0211] The detailed differences and test results of the battery cells in Examples 6 to 11, Comparative Example 3, and Comparative Example 4 are shown in Table 2.

[0212] Table 2

[0213]

[0214] It can be seen from the comparison between Examples 6 to 10 and Comparative Examples 3 and 4 that by adjusting the content of carboxylic acid ester in the electrolyte, an electrolyte with higher conductivity can be obtained, thereby shortening the charging time and improving the fast charging performance of the battery. However, when the carboxylic acid ester content is too high, it is easy to cause the electrolyte to produce gas under high temperature conditions, releasing acid to corrode the SEI film, which will reduce the high-temperature cycle life of the battery cell.

[0215] Compared with Comparative Example 1, it can be seen that the energy density of the battery cells of Examples 6 to 10 is also improved. Compared with Comparative Example 2, it can be seen that the energy density of the battery cells is also improved.

[0216] It can be seen from Example 11 that different types of carboxylates can all improve the ionic conductivity of the electrolyte.

[0217] Example 12

[0218] The preparation method of the battery cell is the same as that of Example 4, except that the compaction density of the positive electrode film layer is 2.5 g / cm 3 .

[0219] Example 13

[0220] The preparation method of the battery cell is the same as that of Example 4, except that the compaction density of the positive electrode film layer is 2.6 g / cm 3 .

[0221] Example 14

[0222] The preparation method of the battery cell is the same as that of Example 4, except that the compaction density of the positive electrode film layer is 2.7 g / cm 3 .

[0223] Example 15

[0224] The preparation method of the battery cell is the same as that of Example 4, except that the coating weight of the positive electrode sheet is 220 mg / 1540.25 mm 2 .

[0225] Example 16

[0226] The preparation method of the battery cell is the same as that of Example 4, except that the coating weight of the positive electrode sheet is 260 mg / 1540.25 mm 2 .

[0227] Example 17

[0228] The preparation method of the battery cell is the same as that of Example 4, except that the coating weight of the positive electrode sheet is 300 mg / 1540.25 mm 2 .

[0229] Example 18

[0230] The preparation method of the battery cell is the same as that of Example 4, except that the coating weight of the positive electrode sheet is 340 mg / 1540.25 mm 2 .

[0231] The detailed differences and test results of the battery cells in Examples 12 to 18 are shown in Table 3.

[0232] Table 3

[0233]

[0234] It can be seen from Examples 12 to 18 that by adjusting the compaction density and coating weight of the positive electrode film layer, the charging time and energy density of the battery cell can be optimized, and a battery cell with both excellent fast charging performance and high energy density can be obtained.

[0235] Example 19

[0236] The preparation method of the battery cell is the same as that of Example 4, except that the lithium supplement is lithium nickelate.

[0237] Example 20

[0238] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of Li5FeO4 is 0.5%, and the mass proportion of lithium iron phosphate material is 96.2%.

[0239] Example 21

[0240] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of Li5FeO4 is 1.5%, and the mass proportion of lithium iron phosphate material is 95.2%.

[0241] Example 22

[0242] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of Li5FeO4 is 2.5%, and the mass proportion of lithium iron phosphate material is 94.2%.

[0243] Example 23

[0244] The preparation method of the battery cell is the same as that of Example 4, except that the mass proportion of Li5FeO4 is 2.8%, and the mass proportion of lithium iron phosphate material is 93.9%.

[0245] The detailed differences and test results of the battery cells in Examples 19 to 23 are shown in Table 4.

[0246] Table 4

[0247]

[0248] It can be seen from Examples 20 to 23 that by adjusting the content of the lithium supplement in the positive electrode film layer, the charging time, cycle life and energy density of the battery cell can be optimized simultaneously, thereby obtaining a battery cell with excellent comprehensive performance.

[0249] It can be seen from Example 19 that different types of lithium supplements can all achieve the effect of lithium supplementation.

[0250] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell comprising a housing, an electrode assembly, and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, wherein: The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer, the positive electrode current collector includes a positive electrode main body and a positive electrode ear portion, the positive electrode ear portion extends from the positive electrode main body, the positive electrode film layer is located on at least one side of the positive electrode main body, the positive electrode film layer includes a lithium-containing phosphate, and the size of the positive electrode film layer along the length direction of the positive electrode sheet is 200 mm to 700 mm; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer, the negative electrode current collector includes a negative electrode main body and a negative electrode ear portion, the negative electrode ear portion extends from the negative electrode main body, the negative electrode film layer is located on at least one side of the positive electrode main body, and the negative electrode film layer includes graphite; The electrolyte includes a chain carboxylate, and based on the total mass of the electrolyte, the mass of the chain carboxylate accounts for 5%-50%.

2. The battery cell according to claim 1, wherein: Along the length direction of the positive electrode plate, the size of the positive electrode film layer is 400mm-650mm.

3. The battery cell according to claim 1, wherein: Based on the total mass of the electrolyte, the mass proportion of the chain carboxylic acid ester is 8%-30%.

4. The battery cell according to claim 1, wherein: The conductivity of the electrolyte at room temperature is 9.5 mS / cm-19 mS / cm.

5. The battery cell according to claim 1, wherein The conductivity of the electrolyte at room temperature is 9.7 mS / cm-13.5 mS / cm. The battery cell according to claim 1 , wherein: The viscosity of the electrolyte at room temperature is 2 mPa·s-5 mPa·s.

7. The battery cell according to claim 1, wherein: The density of the electrolyte at room temperature is 1.05 g / mL-1.35 g / mL.

8. The battery cell according to claim 1, wherein The chain carboxylic acid ester includes a compound shown in Formula I: Formula I, Wherein, R1 includes one or more of a hydrogen atom, a C1-C5 alkyl group, and a C1-C5 haloalkyl group, and R2 includes one or more of a C1-C5 alkyl group and a C1-C5 haloalkyl group.

9. The battery cell according to claim 8, wherein: R1 includes one or more of a hydrogen atom, a C1-C3 alkyl group, and a C1-C3 haloalkyl group; and / or R2 includes one or more of C1-C3 alkyl and C1-C3 haloalkyl.

10. The battery cell according to claim 1, wherein The chain carboxylic acid ester includes Formula I-1, Formula I-2, Formula I-3, Formula I-4, Formula I-5, Formula I-6, Formula I-7, One or more of formula I-8.

11. The battery cell according to claim 1, wherein The single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 -340mg / 1540.25mm 2 .

12. The battery cell according to claim 1, wherein The single-sided coating weight of the positive electrode film layer is 240 mg / 1540.25 mm 2 -300mg / 1540.25mm 2 .

13. The battery cell according to claim 1, wherein When the battery cell is in the state of 100% SOC, the compaction density of the positive electrode film layer is 2.5g / cm 3 -2.8g / cm 3 .

14. The battery cell according to claim 1, wherein The lithium-containing phosphate includes at least one of lithium iron phosphate material and lithium manganese iron phosphate material.

15. The battery cell according to claim 1, wherein The positive electrode film layer further includes a lithium supplement agent, and based on the total mass of the positive electrode film layer, the mass proportion of the lithium supplement agent is 0.5%-2.5%.

16. The battery cell according to claim 15, wherein: The lithium supplement includes one or more of lithium nickel cobalt manganese oxide, lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganese oxide, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite.

17. The battery cell according to claim 1, wherein The positive electrode sheet and the negative electrode sheet are stacked.

18. The battery cell according to claim 1, wherein The battery cell includes a shell, a first end cap assembly, and a second end cap assembly, wherein the shell, the first end cap assembly, and the second end cap assembly define a receiving cavity, the first end cap assembly includes a first end cap and at least one positive terminal, and the positive electrode body is electrically connected to the positive terminal through the positive electrode ear; and / or, The second end cap assembly includes a second end cap and at least one negative electrode terminal, and the negative electrode body is electrically connected to the negative electrode terminal through the negative electrode ear.

19. The battery cell according to claim 18, wherein: The first end cap assembly includes a positive terminal and a negative terminal, the positive electrode body is electrically connected to the positive terminal through the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal through the negative electrode ear; and / or, The second end cap assembly includes a positive terminal and a negative terminal. The positive electrode body is electrically connected to the positive terminal through the positive electrode ear, and the negative electrode body is electrically connected to the negative terminal through the negative electrode ear.

20. The battery cell according to claim 19, wherein The first end cap assembly and the second end cap assembly are arranged at both ends of the shell, and electrode terminals of the same polarity on the first end cap assembly and the second end cap assembly are staggered along the length direction of the battery cell.

21. The battery cell according to claim 20, wherein: The electrode terminals of the same polarity are arranged diagonally along the length direction of the battery cell.

22. The battery cell according to any one of claims 1 to 21, wherein: The battery cells are configured to be charged from 10% SOC to 80% SOC in a time range of 5 min to 10.5 min.

23. A battery device, wherein: The battery device comprises the battery cell according to any one of claims 1 to 22, wherein the battery device is at least one of a battery module and a battery pack.

24. An electrical device, wherein: The battery cell according to any one of claims 1 to 22 or the battery device according to claim 23 is used to provide electrical energy.

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