Battery cell, battery device and electric apparatus

Abstract

Provided in the present application are a battery cell, a battery device and an electric apparatus. The battery cell comprises a casing, an electrode assembly and an electrolyte. 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 comprises a positive electrode current collector and a positive electrode film layer; the positive electrode current collector comprises a positive electrode main body portion and a positive electrode tab portion, the positive electrode tab portion extending 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 in a direction in which the positive electrode tab portion extends from the positive electrode main body portion, the dimension of the positive electrode film layer ranges from 200 mm to 700 mm. The electrolyte comprises a chain carboxylic ester, and on the basis of the total mass of the electrolyte, the mass proportion of the chain carboxylic ester ranges from 5% to 60%.

Description

Battery cells, battery devices and electrical equipment Technical Field

[0001] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical equipment. Background Technology

[0002] Batteries are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. However, individual battery cells in related technologies cannot simultaneously meet the demands for fast charging and high energy density. Summary of the Invention

[0003] A first aspect of this application provides a battery cell, the battery cell including a casing, an electrode assembly, and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film. The positive current collector includes a positive electrode body and a positive electrode tab. The positive electrode tab extends from the positive electrode body. The positive electrode film is located on at least one side of the positive electrode body and includes a lithium-containing electrolyte. The positive electrode film has a length of 200mm-700mm along the length of the positive electrode sheet, and the negative electrode sheet includes a negative current collector and a negative electrode film. The negative current collector includes a negative electrode body and a negative electrode tab, the negative electrode tab extending from the negative electrode body. The negative electrode film is located on at least one side of the positive electrode body and includes graphite. The electrolyte includes a chain carboxylic acid ester, and the mass percentage of the chain carboxylic acid ester is 5%-60% based on the total mass of the electrolyte. Therefore, by increasing the size of the positive electrode film, the energy density of the battery cell is increased. Simultaneously, by incorporating the aforementioned amount of chain carboxylic acid ester, the conductivity of the electrolyte is improved, enhancing the fast-charging performance of the battery cell, thus obtaining a battery cell with both high energy density and excellent fast-charging performance.

[0004] According to some embodiments of this application, the size of the positive electrode film is 400mm-650mm along the length of the positive electrode sheet. This further improves the energy density of the battery cell.

[0005] According to some embodiments of this application, the chain carboxylic acid ester accounts for 8%-30% of the total mass of the electrolyte. This improves the conductivity of the electrolyte while reducing the risk of gas generation in the battery cell under high-temperature conditions, resulting in a battery cell with both excellent fast-charging performance and high-temperature cycle life.

[0006] According to some embodiments of this application, the electrolyte has a conductivity of 9.5 mS / cm to 19 mS / cm at room temperature. This improves the fast-charging performance of the battery cell.

[0007] According to some embodiments of this application, the electrolyte has a conductivity of 9.7 mS / cm to 13.5 mS / cm at room temperature. This improves the lithium-ion migration rate while reducing the risk of electrolyte gas generation.

[0008] According to some embodiments of this application, the viscosity of the electrolyte at room temperature is 2 mPa·s-5 mPa·s. This improves the lithium-ion migration rate and reduces the internal resistance of the battery cells.

[0009] According to some embodiments of this application, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. This increases the migration rate of lithium ions in the electrolyte and reduces the internal resistance of the battery cells.

[0010] According to some embodiments of this application, the chain carboxylic acid ester includes compounds represented by Formula I:

[0011] R1 includes one or more of hydrogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, while R2 includes one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups. Therefore, the aforementioned chain carboxylic acid esters have relatively small molecular weights, which can improve the conductivity of the electrolyte. By combining them with long electrode plates, battery cells with high energy density, excellent fast-charging performance, and excellent high-temperature cycle life can be obtained.

[0012] According to some embodiments of this application, R1 includes one or more of hydrogen atoms, C1-C3 alkyl groups, and C1-C3 haloalkyl groups; and / or R2 includes one or more of C1-C3 alkyl groups and C1-C3 haloalkyl groups. This improves the conductivity of the electrolyte.

[0013] According to some embodiments of this application, the chain carboxylic acid ester includes One or more of these. Therefore, the aforementioned types of chain carboxylic esters have relatively small molecular weights, which can improve the conductivity of the electrolyte.

[0014] According to some embodiments of this application, the single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 -340mg / 1540.25mm 2 The option is 240mg / 1540.25mm. 2 -300mg / 1540.25mm 2This increases the energy density of individual battery cells.

[0015] According to some embodiments of this application, the positive electrode film layer has a compaction density of 2.5 g / cm³ when the battery cell is at 100% SOC. 3 -2.8g / cm 3 This increases the energy density of individual battery cells.

[0016] According to some embodiments of this application, the lithium-containing phosphate includes at least one of lithium iron phosphate and lithium manganese iron phosphate. This improves the safety and cycle performance of the battery cell.

[0017] According to some embodiments of this application, the positive electrode film layer further includes a lithium replenishing agent, and the mass percentage of the lithium replenishing agent is 0.5%-2.5% based on the total mass of the positive electrode film layer. This compensates for the loss of active lithium during the formation stage, thereby improving the energy density and cycle life of the battery cell.

[0018] According to some embodiments of this application, 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 nickel oxide, and lithium ferrite.

[0019] According to some embodiments of this application, the positive electrode and the negative electrode are stacked. This improves the utilization rate of space within the battery cell and increases the energy density of the battery cell.

[0020] According to some embodiments of this 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 a positive electrode tab. 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 a negative electrode tab. This reduces the risk of short circuits between the positive and negative electrodes and improves the safety of the battery cell.

[0021] According to some embodiments of this application, the first end cap assembly includes a positive terminal and a negative terminal, the positive electrode body portion is electrically connected to the positive terminal via the positive electrode tab, and the negative electrode body portion is electrically connected to the negative terminal via the negative electrode tab; and / or, the second end cap assembly includes a positive terminal and a negative terminal, the positive electrode body portion is electrically connected to the positive terminal via the positive electrode tab, and the negative electrode body portion is electrically connected to the negative terminal via the negative electrode tab. This improves the overcurrent capability of the battery cell.

[0022] According to some embodiments of this application, the first end cap assembly and the second end cap assembly are disposed at both ends of the housing. Along the length of the battery cell, electrode terminals of the same polarity on the first end cap assembly and the second end cap assembly are staggered. Optionally, the electrode terminals of the same polarity are diagonally arranged 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.

[0023] According to some embodiments of this application, the battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes. This improves the fast-charging performance of the battery cell.

[0024] The second aspect of this application provides a battery device including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0025] A third aspect of this application provides an electrical device, including the battery cell provided in the first aspect of this application or the battery device provided in the second aspect of this application, wherein the battery cell or the battery device is used to provide electrical energy.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0028] Figure 1 is a schematic diagram of the positive electrode sheet according to one embodiment of this application.

[0029] Figure 2 is a schematic diagram of the electrode assembly stacking method according to an embodiment of this application.

[0030] Figure 3 is a schematic diagram of the structure of the housing according to one embodiment of this application.

[0031] Figure 4 is a schematic diagram of a first end cap assembly according to an embodiment of this application.

[0032] Figure 5 is an exploded view of the first end cap assembly in Figure 4.

[0033] Figure 6 is a structural schematic diagram of the first end cap assembly in Figure 4 from another perspective.

[0034] Figure 7 is a cross-sectional view of the first end cap assembly in Figure 6 along the AA' direction.

[0035] Figure 8 is a schematic diagram of a second end cap assembly according to an embodiment of this application.

[0036] Figure 9 is an exploded view of the second end cap assembly in Figure 8.

[0037] Figure 10 is a structural schematic diagram of the second end cap assembly in Figure 8 from another perspective.

[0038] Figure 11 is a cross-sectional view of the second end cap assembly in Figure 10 along the BB' direction.

[0039] Figure 12 is a schematic diagram of the structure of a battery cell according to an embodiment of this application.

[0040] Figure 13 is a structural schematic diagram of the first end cap assembly according to an embodiment of this application.

[0041] Figure 14 is an exploded view of the first end cap assembly in Figure 13.

[0042] Figure 15 is a structural schematic diagram of the first end cap assembly in Figure 13 from another perspective.

[0043] Figure 16 is a cross-sectional view of the first end cap assembly in Figure 15 along the CC' direction.

[0044] Figure 17 is a schematic diagram of the structure of the second end cap assembly according to an embodiment of this application.

[0045] Figure 18 is an exploded view of the second end cap assembly in Figure 17.

[0046] Figure 19 is a structural schematic diagram of the second end cap assembly in Figure 17 from another perspective.

[0047] Figure 20 is a cross-sectional view of the second end cap assembly in Figure 19 along the DD' direction.

[0048] Figure 21 is a schematic diagram of the structure of an electrode assembly according to an embodiment of this application.

[0049] Figure 22 is a schematic diagram of the structure of an electrode assembly according to another embodiment of this application.

[0050] Figure 23 is a schematic diagram of an electrical device according to an embodiment of this application.

[0051] Explanation of reference numerals in the attached drawings: 1 Battery cell; 11 Housing; 12 First end cap assembly; 13 Second end cap assembly; 121 First end cap; 1211 First opening; 1212 122 Injection hole; 123 Positive terminal; 123 First insulating component; 1231 Second opening; 124 First sealing component; 125 First positioning component; 126 Second insulating component; 127 Riveting block; 131 Second end cap; 1311 Third opening; 132 Negative terminal; 133 Third insulating component; 1331 Fourth opening; 134 Second sealing component; 135 Second positioning component; 136 Fourth insulating component; 137 Pressure relief mechanism; 2 Positive electrode plate; 21 Positive current collector; 211 Positive electrode body; 212 Positive electrode tab; 2121 First positive electrode tab; 2122 Second positive electrode tab; 22 Positive electrode film layer; 3 Negative electrode plate; 31 First negative electrode tab; 32 Second negative electrode tab; 4 Separating membrane; 20 Electrode assembly. Detailed Implementation

[0052] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0056] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0057] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing. However, current battery cells cannot simultaneously meet the demands for high energy density, fast charging, and long cycle life.

[0058] The proposed battery cell, in order to improve the energy density, increases the lithium phosphate loading by extending the coating length of the positive electrode film on the positive electrode sheet. However, as the size of the positive electrode film increases, the electron conduction path lengthens, limiting the fast-charging capability of the battery cell. By further increasing the content of chain carboxylic acid esters in the electrolyte, even with longer electrodes, the electrolyte can fully wet the positive electrode film, significantly increasing the electron and ion conduction capabilities of the positive electrode film and improving the lithium-ion transport capacity in the liquid phase, thus significantly improving the fast-charging performance of longer battery cells. However, increasing the content of chain carboxylic acid esters can also exacerbate side reactions inside the battery, causing electrolyte gas production and potentially increasing the amount of acidic substances in the electrolyte, leading to corrosion of the electrolyte interphase (SEI) film and affecting cycle life at high temperatures. This application, through comprehensive control of electrode length and solvent composition, has found a suitable content of chain carboxylic acid esters for battery cells with positive electrode film size of 200mm-700mm, enabling the battery cells to have both good fast charging capability and high temperature cycle life.

[0059] The battery cells proposed in this application can be used in electrical devices that use the battery cells as a power source or in various energy storage systems that use the battery cells as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0060] The first aspect of this application discloses a battery cell, the battery cell including a housing, an electrode assembly and an electrolyte, the electrode assembly including a positive electrode, a negative electrode and a separator located between the positive electrode and the negative electrode.

[0061] Referring to Figure 1, the positive electrode 2 includes a positive current collector 21 and a positive electrode film 22. The positive current collector 21 includes a positive electrode body portion 211 and a positive electrode tab portion 212. The positive electrode tab portion 212 extends from the positive electrode body portion 211. The positive electrode film 22 is located on at least one side of the positive electrode body portion 211. The positive electrode film 22 includes a positive electrode active material, which includes lithium phosphate. The dimension of the positive electrode film 22 along the length direction of the positive electrode 2 is 200mm-700mm.

[0062] The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative current collector includes a negative electrode body portion and a negative electrode tab portion. The negative electrode tab 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. The negative electrode film layer includes a negative electrode active material, which includes graphite.

[0063] The electrolyte comprises chain-like carboxylic acid esters, and the chain-like carboxylic acid esters account for 5%-60% of the total mass of the electrolyte.

[0064] Therefore, the battery cell proposed in this application has a longer coating length of the positive electrode film, which can increase the lithium phosphate loading on the positive electrode sheet, thereby obtaining a battery cell with higher energy density. At the same time, by adding 5%-60% of chain carboxylic acid esters to the electrolyte, the conductivity of the electrolyte can be improved. With a longer positive electrode film length, the conductivity of the electrode sheet is improved, thereby improving the fast charging performance of the battery cell.

[0065] 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 body in the direction of the length of the positive electrode current collector. Referring to L in Figure 1, it is the size of the positive electrode film layer.

[0066] As an example, the size L of the positive electrode film can be 200mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm, etc., or a range of any of the above values. This increases the lithium phosphate content on the positive electrode, resulting in a battery cell with good safety performance, good cycle performance, and high energy density.

[0067] According to some specific embodiments of this application, the size L of the positive electrode film can be 400mm-650mm along the direction extending from the positive electrode body portion along the positive electrode tab. This increases the volumetric energy density of the battery cell while reducing the electron conduction path, thereby improving the fast-charging performance of the battery cell.

[0068] According to some embodiments of this application, the electrolyte has a conductivity of 9.5 mS / cm-19 mS / cm at room temperature.

[0069] 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, or any range of the above values. This improves the rate performance of the battery cell.

[0070] According to some embodiments of this application, the electrolyte has a conductivity of 9.7 mS / cm to 13.5 mS / cm at room temperature. This improves the fast-charging performance of individual battery cells while reducing the risk of gas generation under high-temperature conditions, thus enhancing the high-temperature cycle performance of the battery cells.

[0071] In this application, after disassembling the battery cells to obtain the electrolyte, a conductivity meter is used to test the conductivity of the electrolyte at room temperature, which can be done with reference to HG-T4067-2015.

[0072] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the chain carboxylic acid ester can be 5%-60%, for example, 5%, 10%, 20%, 30%, 40%, 50%, 60%, etc., or any range of the above values. By keeping 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 gas generation in the electrolyte under high-temperature conditions can be reduced, and the high-temperature cycle life of the battery cell can be improved, thereby obtaining a battery cell with both high energy density, excellent fast-charging performance, and high-temperature cycle life.

[0073] According to some specific embodiments of this application, the mass percentage 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 gas generation in the battery cell under high-temperature conditions, thus increasing the high-temperature cycle life of the battery.

[0074] In this 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).

[0075] According to some embodiments of this application, the viscosity of the electrolyte at room temperature can be between 2 mPa·s and 5 mPa·s. For example, it can be 2 mPa·s, 2.5 mPa·s, 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, etc., or a range of any of the above values. Therefore, a lower electrolyte viscosity 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.

[0076] In this application, after disassembling the battery cells to obtain the electrolyte, the viscosity of the electrolyte is tested using a kinematic viscometer. The viscosity of the electrolyte at room temperature can be tested with reference to GB / T 10247-2008.

[0077] According to some embodiments of this application, the density of the electrolyte at room temperature can be between 1.05 g / mL and 1.35 g / mL. For example, it can be 1.05 g / mL, 1.1 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL, etc., or a range of any of the above values. This reduces the viscosity of the electrolyte, increases the migration rate of lithium ions in the electrolyte, reduces the internal resistance of the battery cell, and improves the fast-charging performance of the battery cell.

[0078] 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.

[0079] According to some embodiments of this application, the chain carboxylic acid ester may include compounds represented by Formula I:

[0080] Wherein, R1 includes one or more of hydrogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R2 includes one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

[0081] Therefore, when the mass percentage of the chain carboxylic acid esters shown in Formula I is 5%-60%, on the one hand, using the above-mentioned content of chain carboxylic acid esters 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 along the length of the electrode, improve the electron transport capability of the active material, and also improve the lithium ion migration rate in the electrolyte, thereby improving the fast charging performance of the battery cell; on the other hand, excessively high content of chain carboxylic acid esters can also increase gas generation inside the battery cell, which is not conducive to battery cycling at high temperatures. Therefore, an appropriate amount of chain carboxylic acid esters can also reduce the risk of electrolyte gas generation under high temperature conditions and improve the high temperature cycle life of the battery.

[0082] According to some embodiments of this application, R1 includes one or more of hydrogen atoms, C1-C3 alkyl groups, and C1-C3 haloalkyl groups. For example, R1 may include one or more of hydrogen atoms, methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl groups. This improves the conductivity of the electrolyte.

[0083] According to some embodiments of this application, R2 includes one or more of C1-C3 alkyl groups and C1-C3 haloalkyl groups. For example, R2 can be one or more of methyl, ethyl, propyl, fluoromethyl, fluoroethyl, and fluoropropyl. This improves the conductivity of the electrolyte.

[0084] According to some embodiments of this application, the chain carboxylic acid ester may include One or more of these. Therefore, the aforementioned types of chain carboxylic esters have relatively small molecular weights, which can improve the conductivity of the electrolyte.

[0085] According to some embodiments of this application, the single-sided coating weight of the positive electrode film can be 200 mg / 1540.25 mm. 2 -340mg / 1540.25mm 2 For example, it could 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 The values ​​can be any range of the values ​​mentioned above. Therefore, by making the size of the positive electrode film layer 200mm-700mm, and simultaneously keeping the coating weight of the positive electrode film layer within the above range, the energy density of the battery cell can be increased.

[0086] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0087] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0088] According to some specific embodiments of this application, the single-sided coating weight of the positive electrode film can be 240 mg / 1540.25 mm. 2 -300mg / 1540.25mm 2 For example, it could be 240mg / 1540.25mm. 2260mg / 1540.25mm 2 280mg / 1540.25mm 2 300mg / 1540.25mm 2 The range can be any of the values ​​mentioned above. This increases the energy density of individual battery cells.

[0089] This application provides a method for testing the weight of the positive electrode film coating: The positive electrode sheet is disassembled from the battery cell, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, and the weight of the positive current collector is measured and recorded as M0. The single-sided coating weight of the positive electrode film = (M1 - M0) / S1.

[0090] According to some embodiments of this application, the compaction density of the positive electrode film layer in the battery cell at 100% SOC can be 2.5 g / cm³. 3 -2.8g / cm 3 For example, it could be 2.5 g / cm³. 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 The values ​​can be any range of the above values. Therefore, when the compaction density of the positive electrode film is within the above range, the positive electrode sheet is more densely packed, which is beneficial to improving the energy density of the battery cell. Moreover, 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.

[0091] This application provides a method for testing the compaction density of the positive electrode film: The battery cell is charged at a constant current of 1 / 3C to 3.8V, and then charged at a constant voltage of 3.8V to 0.05C. The positive electrode sheet is disassembled from the battery cell, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode film layer on one side can be wiped off first), and cut into small circular pieces with an area of ​​S1. The weight of these pieces is recorded as M1, and their thickness H1 is measured. Then, the positive electrode film layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film = (M1-M0) / S1, the thickness of the positive electrode film = H1-H0, and the compaction density of the positive electrode film = single-sided coating weight of the positive electrode film / thickness of the positive electrode film.

[0092] According to some embodiments of this application, the lithium-containing phosphate includes at least one of lithium iron phosphate and lithium manganese iron phosphate. This improves the cycle performance of the battery cell.

[0093] According to some embodiments of this application, the lithium-containing phosphate includes compounds represented by formula Π: Li x1 A y1 Me a M b P 1-c X c Y z Π,

[0094] 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.

[0095] According to some embodiments of this application, the positive electrode film layer further includes a lithium replenishing agent. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium replenishing 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 a range of any of the above values. Therefore, lithium ions can be replenished to the positive electrode film layer, compensating for lithium ion loss, increasing the capacity of the battery cell, and improving the energy density and cycle life of the battery cell.

[0096] According to some embodiments of this 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 nickel oxide, and lithium ferrite. This improves the energy density of the battery cell.

[0097] According to some specific embodiments of this application, the lithium replenishing agent includes lithium ferrite. During battery cycling, lithium ferrite can release oxygen free radicals, participate in the formation of the negative electrode film, further reduce the internal resistance of the battery cell, and improve the fast charging performance of the battery cell.

[0098] According to some embodiments of this application, referring to FIG2, the positive electrode 2 and the negative electrode 3 are stacked. Specifically, a separator 4 is provided between the positive electrode 2 and the negative electrode 3 to prevent short circuit between them. This improves the utilization rate of space within the battery cell and increases the energy density of the battery cell.

[0099] In some embodiments, the positive 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, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0100] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0101] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0103] 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, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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 oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. When the battery is a lithium-ion battery, lithium titanate is used; when the battery is a sodium-ion battery, sodium titanate is used. However, this application is not limited to these materials, and other conventional 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.

[0105] In some embodiments, the negative electrode active material layer may optionally 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).

[0106] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0108] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0109] According to some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative current collector includes a negative electrode body portion and a negative electrode tab portion, and the negative electrode tab portion extends from the negative electrode body portion. 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. The positive electrode body portion is electrically connected to the positive terminal through the positive electrode tab portion. And / or, the second end cap assembly includes a second end cap and at least one negative terminal. The negative electrode body portion is electrically connected to the negative terminal through the negative electrode tab portion.

[0110] Specifically, the battery cell includes a housing, 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. Referring to FIG3, the first end cap assembly and the second end cap assembly can be disposed at both ends of the housing 11 along its length direction, or at both ends of the housing 11 along its width direction. Specifically, when the housing 11 has openings at both ends along its length direction, the first end cap assembly and the second end cap assembly can be disposed at both ends of the housing 11 along its length direction and adapted to respectively cover the openings; when the housing 11 has openings at both ends along its width direction, the first end cap assembly and the second end cap assembly can be disposed at both ends of the housing 11 along its width direction and adapted to respectively cover the openings, 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 housing 11 to fit the housing 11.

[0111] In some embodiments, the first end cap assembly and the second end cap assembly may be disposed at both ends of the housing 11 along its length direction, that is, the first end cap assembly and the second end cap assembly are disposed on the smaller side of the housing 11, thereby saving space of the battery cell along the width direction, thereby accommodating wider electrodes and improving the energy density of the battery cell.

[0112] In some embodiments, the housing 11 is formed by bending and then welding, and the weld marks are integrated on the smaller side of the housing 11 extending along the length direction, which helps to reduce the problem of cracking in the weld area caused by the expansion of the battery cells along the thickness direction and improves the reliability of the housing 11.

[0113] The first and second end caps can be made independently of materials with certain hardness and strength (such as aluminum alloy), giving them higher strength and reducing deformation when subjected to compression, thus improving the safety performance of the battery cell. In some embodiments, the first and second end caps can be made of steel.

[0114] As an example, the first end cap assembly, the second end cap assembly, and the housing can be independent components.

[0115] 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 connecting body before the electrode assembly and other components are inserted into the housing. After the electrode assembly and other components are inserted into the housing 11, the second end cap assembly or the first end cap assembly covers the opening in the length or width direction of the housing.

[0116] According to some embodiments of this application, referring to Figures 4-7, the first end cap assembly 12 includes a first end cap 121 and a first electrode terminal 122.

[0117] In some embodiments, referring to the disassembled schematic diagram of the first end cap assembly 12 in FIG5, 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 riveting block 127, and is assembled into the first end cap assembly 12 shown in FIG4.

[0118] In some embodiments, Figure 7 is a cross-sectional view along the AA' direction of Figure 6. Referring to Figures 5 and 7, it can be seen that the first end cap 121 has a first opening 1211, and the first electrode terminal 122 passes through the first end cap 121. A first insulating member 123 is provided between the first end cap 121 and the first electrode terminal 122. This assembly method serves to isolate the electrical connection components inside the housing 11 from the first end cap 121, and simultaneously ensures that the first electrode terminal 122 is insulated from the first end cap 121, reducing the risk of short circuits. The first insulating member 123 has a second opening 1231, and the first electrode terminal 122 passes through the second opening 1231 and the first opening 1211 in sequence. A first sealing member 124 for insulation and sealing is provided between the first opening 1211 and the first electrode terminal 122. The first sealing member 124 is provided with a through hole so that the first electrode terminal 122 can pass through. A second insulating member 126 and a riveting 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 riveting 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 riveting block 127 in sequence. The second insulating member 126 is used to insulate the first electrode terminal 122 from the first end cover 121, and the riveting block 127 is used to fix the first electrode terminal 122 to the first end cover 121.

[0119] In some embodiments, referring to FIG5, the first end cap assembly further includes a first positioning member 125, which includes at least two members, to prevent the first electrode terminal 122 from deflecting and to increase the force strength of the first electrode terminal 122.

[0120] In some embodiments, referring to FIG5, the first end cap assembly 12 includes an injection hole 1212 for injecting electrolyte into the receiving cavity of the housing 11.

[0121] Referring to Figures 8-11, the second end cap assembly 13 includes a second end cap 131 and a second electrode terminal 132.

[0122] In some embodiments, referring to the disassembled schematic diagram of the second end cap assembly 13 in FIG9, the second end cap assembly 13 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 riveting block 127, and a second positioning member 135, and is assembled into the second end cap assembly 13 shown in FIG8.

[0123] In some embodiments, Figure 11 is a cross-sectional view of Figure 10 along the BB' direction. Referring to Figures 9 and 11, a third opening 1311 is provided on the second end cap 131. The second electrode terminal 132 penetrates the second end cap 131. A third insulating member 133 is provided between the second end cap 131 and the second electrode terminal 132. This assembly method serves to isolate the electrical connection components inside the housing 11 from the second end cap 131, and simultaneously ensures that the second electrode terminal 132 is insulated from the second end cap 131, reducing the risk of short circuits. A fourth opening 1331 is provided on the third insulating member 133. The second electrode terminal 132 passes through the fourth opening 1331 and the third opening 1311 in sequence. A second sealing member 134 for insulation and sealing is provided between the third opening 1311 and the second electrode terminal 132. The second sealing member 134 is provided with a through hole so that the second electrode terminal 132 can pass through. A fourth insulating member 136 and a riveting 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 riveting block 127 are also provided with through holes. The second electrode terminal 132 passes through the through holes of the fourth insulating member 136 and the riveting block 127 in sequence. The fourth insulating member 136 is used to insulate the second electrode terminal 132 from the second end cover 131, and the riveting block 127 is used to fix the second electrode terminal 132 to the second end cover 131.

[0124] In some embodiments, referring to FIG9, the second end cap assembly 13 further includes a second positioning member 135, which includes at least two members, to prevent the second electrode terminal 132 from deflecting and to increase the force strength of the second electrode terminal 132.

[0125] According to some embodiments of this application, referring to Figures 8-11, a pressure relief mechanism 137 is provided on the second end cover 131. When the internal pressure of the housing exceeds a threshold, the pressure relief mechanism 137 can release the internal pressure of the housing.

[0126] As an example, the pressure relief mechanism 137 and the second end cap 131 are two separate components, molded separately and then assembled together. The pressure relief mechanism 137 can be a component such as an explosion-proof plate, explosion-proof valve, or safety valve, and can be installed on the second end cap 131 by means of bonding, welding, or other methods. When the internal pressure of the battery cell reaches a threshold, the pressure relief mechanism 137 opens at least part of the pressure relief hole, and the internal pressure of the battery cell is released through the pressure relief hole to relieve the internal pressure of the battery cell.

[0127] According to some embodiments of this application, the first end cap assembly includes a positive terminal and a negative terminal, the positive terminal body is electrically connected to the positive terminal via the positive terminal tab, and the negative terminal body is electrically connected to the negative terminal via the negative terminal tab.

[0128] According to some embodiments of this 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 tab, and the negative electrode body is electrically connected to the negative terminal via the negative electrode tab. This improves the overcurrent capability of the battery cell.

[0129] Referring to FIG12, the first end cap assembly 12 and the second end cap assembly 13 are disposed at both ends of the housing 11 along its length direction. The first end cap assembly 12 includes a positive terminal and a negative terminal, and the second end cap assembly includes a positive terminal and a negative terminal.

[0130] Specifically, referring to Figures 13-16, the first end cap assembly 12 includes a first end cap 121 and two electrode terminals with opposite polarities (first electrode terminal 122 and second electrode terminal 132), wherein when the first electrode terminal 122 is the positive terminal, the second electrode terminal 132 is the negative terminal; and when the first electrode terminal 122 is the negative terminal, the second electrode terminal is the positive terminal.

[0131] In some embodiments, referring to the disassembled schematic diagram of the first end cap assembly 12 in FIG14, the first end cap assembly 12 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 riveting blocks 127 and four first positioning members 125, and is assembled into the first end cap assembly shown in FIG13.

[0132] In some embodiments, Figure 16 is a cross-sectional view of Figure 15 along the CC' direction. Referring to Figures 14 and 16, it can be seen that the first end cap 121 has two first openings 1211. The first electrode terminal 122 and the second electrode terminal 132 respectively penetrate the first end cap 121. A first insulating member 123 is provided between the first end cap 121 and the first electrode terminal 122 and the second electrode terminal 132. This assembly method serves to isolate the electrical connection components inside the housing 11 from the first end cap 121, and simultaneously ensures that the first electrode terminal 122, the second electrode terminal 132, and the first end cap 121 are insulated from each other, reducing the risk of short circuits. The first insulating member 123 has two second openings 1231, through which the first electrode terminal 122 and the second electrode terminal 132 sequentially pass. 231 and the first opening 1211, the first opening 1211 and the first electrode terminal 122 and the second electrode terminal 132 are both provided with a first sealing member 124 for insulation and sealing. The first sealing member 124 is provided with a through hole so that the first electrode terminal 122 and the second electrode terminal 132 can pass through. On the side of the first end cover 121 away from the electrode assembly, there are two second insulating members 126 and two riveting blocks 127. The second insulating members 126 and the riveting 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 members 126 and the riveting blocks 127 in sequence. The second insulating members 126 are used to insulate the electrode terminals from the first end cover 121, and the riveting blocks 127 are used to fix the electrode terminals to the first end cover 121.

[0133] Referring to Figures 17-20, the second end cap assembly 13 includes a second end cap 131 and two electrode terminals with opposite polarities (a first electrode terminal 122 and a second electrode terminal 132). When the first electrode terminal 122 is the positive terminal, the second electrode terminal 132 is the negative terminal; when the first electrode terminal 122 is the negative terminal, the second electrode terminal is the positive terminal.

[0134] In some embodiments, referring to the disassembled schematic diagram of the second end cap assembly 13 in FIG18, the second end cap assembly 13 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 riveting block 127, and a second positioning member 135, and is assembled into the second end cap assembly 13 shown in FIG17.

[0135] In some embodiments, Figure 20 is a cross-sectional view of Figure 19 along the DD' direction. Referring to Figures 18 and 20, it can be seen that the second end cap 131 has two third openings 1311. The first electrode terminal 122 and the second electrode terminal 132 pass through the second end cap 131. A third insulating member 133 is provided between the second end cap 131 and the first electrode terminal 122 and the second electrode terminal 132. This assembly method serves to isolate the electrical connection components inside the housing 11 from the second end cap 131, and simultaneously ensures that the first electrode terminal 122 and the second electrode terminal 132 are insulated from the second end cap 131, reducing the risk of short circuits. The third insulating member 133 has two fourth openings 1331, through which the first electrode terminal 122 and the second electrode terminal 132 sequentially pass. 1. A third opening 1311 is provided between the third opening 1311 and the first electrode terminal 122 and the second electrode terminal 132, and a second sealing member 134 is provided for insulation and sealing. The second sealing member 134 is provided with a through hole so that the first electrode terminal 122 and the second electrode terminal 132 can pass through. Two fourth insulating members 136 and two riveting blocks 127 are provided on the side of the second end cover 131 away from the electrode assembly. The fourth insulating members 136 and the riveting 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 members 136 and the riveting blocks 127 in sequence. The fourth insulating members 136 are used to insulate the electrode terminals from the second end cover 131, and the riveting blocks 127 are used to fix the electrode terminals to the second end cover 131.

[0136] According to some embodiments of this application, the first end cap assembly and the second end cap assembly are disposed at both ends of the housing, and the 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.

[0137] According to some embodiments of this application, the electrode terminals of the same polarity are arranged diagonally along the length of the battery cell.

[0138] Therefore, the temperature rise of individual battery cells can be reduced during charging, thereby reducing the impedance of individual battery cells.

[0139] Referring to Figure 21, the electrode assembly 20 includes four tabs. Two tabs extend from one end of the electrode assembly 20 along its length, namely a first positive tab 2121 and a first negative tab 31. Two tabs extend from the other end of the electrode assembly 20 along its length, namely a second positive tab 2122 and a second negative tab 32. The first positive tab 2121 is electrically connected to a first electrode terminal 122 on the first end cap. The first negative tab 31 is electrically connected to a 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. The second negative tab 32 is electrically connected to the second electrode terminal 132 on the second end cap 131. Thus, electrode terminals of different polarities are diagonally arranged along the length of the battery cell, which can reduce the temperature rise of the battery cell during charging, thereby reducing the impedance of the battery cell.

[0140] Referring to Figure 22, the electrode assembly 20 includes four tabs. Two tabs extend from one end of the electrode assembly 20 along its length, namely a first positive tab 2121 and a first negative tab 31. Two tabs extend from the other end of the electrode assembly 20 along its length, namely a second positive tab 2122 and a second negative tab 32. The two positive tabs at both ends of the electrode assembly 20 along its length are asymmetrically arranged, as are the two negative tabs at both ends. 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 diagonally arranged along the length of the battery cell, which improves the current carrying capacity of the battery cell and reduces the wiring within the battery cell, making assembly easier.

[0141] According to some embodiments of this application, the battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes. This improves the fast-charging performance of the battery cell.

[0142] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0143] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0144] The second aspect of this application provides a battery device including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0145] A third aspect of this application provides an electrical device, including the battery cell described in the first aspect of this application or the battery device described in the second aspect of this application, wherein the battery cell or the battery device is used 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 and satellites, energy storage systems, etc.

[0146] As for the electrical equipment, battery modules or battery packs can be selected according to its usage requirements.

[0147] Figure 23 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0148] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0149] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0150] Example 1

[0151] 1. Positive electrode sheet

[0152] The positive electrode sheet includes a positive current collector aluminum foil, with a positive electrode film layer on both surfaces. At 100% SOC, the compacted density is 2.65 g / cm³. 3 The coating weight of the single-sided positive electrode film is 290 mg / 1540.25 mm. 2The positive electrode film has a size of 200 mm. Based on the total mass of the single-sided positive electrode film, the positive electrode film includes lithium iron phosphate material with a mass ratio of 95.8%, lithium supplementer Li5FeO4 with a mass ratio of 0.9%, conductive agent carbon black with a mass ratio of 1.1%, and binder polyvinylidene fluoride (PVDF). The lithium iron phosphate surface has a carbon coating layer, and based on the total mass of lithium iron phosphate, the carbon coating layer accounts for 1.18% of the mass.

[0153] 2. Negative electrode plate

[0154] The negative electrode sheet includes a negative current collector copper foil, with a negative electrode film layer on both surfaces of the copper foil, and a compaction density of 1.56 g / cm³. 3 The coating weight of the single-sided negative electrode film is 138 mg / 1540.25 mm. 2 Based on the total mass of the single-sided negative electrode film, the negative electrode film comprises 96% artificial graphite, 1.1% conductive carbon black, 1.4% binder styrene-butadiene rubber (SBR), and 1.5% thickener sodium carboxymethyl cellulose (CMC-Na).

[0155] 3. Electrolyte

[0156] The electrolyte comprises 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 difluorooxalate borate (LiDFOB). Based on the total mass of the electrolyte, EC accounts for 28.9% of the mass, DMC accounts for 45.4%, ethyl acetate accounts for 8.3%, lithium hexafluorophosphate accounts for 8.3%, LiFSI accounts for 4.2%, VC accounts for 3%, FEC accounts for 1%, ES accounts for 0.5%, and LiDFOB accounts for 0.5%. The electrolyte has a density of 1.22 g / mL, a viscosity of 3.19 mPa·s, and a conductivity of 11 mS / cm.

[0157] 4. Separating membrane

[0158] Polypropylene film, 12μm thick.

[0159] 5. Battery cell

[0160] The battery cell includes a casing, 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 opposite ends of the casing along its length. The structure of the first end cap assembly is shown in Figure 4, and the structure of the second end cap assembly is shown in Figure 8. Each of the first and second end cap assemblies includes an electrode terminal. The electrode assembly and the electrolyte are disposed within the cavity formed by the casing and the end cap assembly. The electrode assembly is a stacked electrode assembly, which is made by stacking the aforementioned positive electrode sheet, separator, and negative electrode sheet. Along the length 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.

[0161] The battery casing has a length of 245mm, a width of 104.5mm, and a thickness of 15.7mm.

[0162] Performance testing

[0163] 1. Charging time

[0164] The time required to charge a single battery cell from 10% SOC to 80% SOC is calculated, and the specific charging process is as follows:

[0165] Charge from 0% SOC to 10% SOC at a constant current of 1C; charge from 10% SOC to 30% SOC at a constant current of 7.0C; charge from 30% SOC to 35% SOC at a constant current of 6.2C; charge from 35% SOC to 40% SOC at a constant current of 5.7C; charge from 40% SOC to 45% SOC at a constant current of 5.2C; charge from 45% SOC to 50% SOC at a constant current of 4.8C; charge from 50% SOC to 50% SOC at a constant current of 4.6C. Charge to 55% SOC at OC; charge from 55% SOC to 60% SOC at a constant current of 4.4C; charge from 60% SOC to 65% SOC at a constant current of 4.2C; charge from 65% SOC to 70% SOC at a constant current of 3.9C; charge from 70% SOC to 75% SOC at a constant current of 3.5C; charge from 75% SOC to 80% SOC at a constant current of 3.0C. The total charging time is the sum of the charging times for each segment.

[0166] 2. High-temperature cycle life

[0167] At an ambient temperature of 45℃, the battery cell is charged to 3.8V using Stepcharge, then charged at a constant voltage to 0.05C, left to rest for 30 minutes, and then discharged at a constant current of 0.5C to 2.5V, left to rest for 30 minutes. This constitutes one charge-discharge cycle. The above charge-discharge cycle is repeated until the capacity of the battery cell is 80% of its initial capacity. The number of charge-discharge cycles is the high-temperature cycle life of the battery cell.

[0168] The Stepcharge charging steps are as follows:

[0169] Charge from 0% SOC to 10% SOC at a constant current of 1C; charge from 10% SOC to 30% SOC at a constant current of 7.0C; charge from 30% SOC to 35% SOC at a constant current of 6.2C; charge from 35% SOC to 40% SOC at a constant current of 5.7C; charge from 40% SOC to 45% SOC at a constant current of 5.2C; charge from 45% SOC to 50% SOC at a constant current of 4.8C; charge from 50% SOC at a constant current of 4.6C. Charge to 55% SOC; charge from 55% SOC to 60% SOC at a constant current of 4.4C; charge from 60% SOC to 65% SOC at a constant current of 4.2C; charge from 65% SOC to 70% SOC at a constant current of 3.9C; charge from 70% SOC to 75% SOC at a constant current of 3.5C; charge from 75% SOC to 80% SOC at a constant current of 3.0C; charge from 80% SOC to 100% SOC at a constant current of 0.33C.

[0170] 3. Energy density

[0171] At 25℃, charge the battery cell at a constant current of 0.33C to 3.8V, then charge it at a constant voltage of 3.8V to 0.05C, and let it stand for 30 minutes. Discharge the battery cell at a constant current of 0.33C to 2.0V and record the discharge capacity A0 (Ah). Calculate the discharge plateau voltage (V). Measure the length, width, and height of the battery cell using calipers and calculate the cell volume V0 (L). The volumetric energy density of the battery cell, VED, is calculated as (A0 × discharge plateau voltage) ÷ V0 ÷ 1000 (Wh / L).

[0172] In this application, the length of the battery cell minus the size of the positive electrode film 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.

[0173] Example 2

[0174] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 400 mm.

[0175] Example 3

[0176] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 500 mm.

[0177] Example 4

[0178] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 650 mm.

[0179] Example 5

[0180] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 700 mm.

[0181] Comparative Example 1

[0182] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 150 mm.

[0183] Comparative Example 2

[0184] The preparation method of the battery cell is the same as in Example 1, except that the size of the positive electrode film is 800 mm.

[0185] The detailed differences and test structures of the battery cells in Examples 2-5 and Comparative Examples 1-2 are shown in Table 1.

[0186] Table 1

[0187] As can be seen from Examples 1-5 and Comparative Examples 1 and 2, by making the size of the positive electrode film layer 200mm-700mm and using an electrolyte containing chain carboxylic acid esters, the energy density, fast charging performance, and cycle performance of the battery cell can be improved simultaneously. If the size of the positive electrode film layer is too small, although the charging time is short, the energy density of the battery cell is low; if the size of the positive electrode film layer is too large, although the energy density of the battery cell is high, the battery cell temperature rises faster and the internal resistance is larger due to the longer electrode length, which will shorten the cycle life of the battery cell.

[0188] Example 6

[0189] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of ethyl acetate is 5%, the mass percentage of EC is 28.9%, and the mass percentage of DMC is 48.6%.

[0190] Example 7

[0191] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of ethyl acetate is 6.6%, the mass percentage of EC is 28.9%, and the mass percentage of DMC is 47%.

[0192] Example 8

[0193] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of ethyl acetate is 24.8%, the mass percentage of EC is 28.9%, and the mass percentage of DMC is 28.9%.

[0194] Example 9

[0195] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of ethyl acetate is 40.8%, the mass percentage of EC is 28.5%, the mass percentage of DMC is 12.2%, and the mass percentage of VC in the additive is 4%.

[0196] Example 10

[0197] The preparation method of the battery cell is the same as in Example 4, except that the mass ratio of ethyl acetate is 56.4%, the mass ratio of EC is 24.2%, the mass ratio of VC in the additive is 5%, and DMC is not present.

[0198] Example 11

[0199] The preparation method of the battery cell is the same as in Example 4, except that the carboxylic acid ester is methyl acetate.

[0200] Comparative Example 3

[0201] The preparation method of the battery cell is the same as in Example 4, except that the mass ratio of ethyl acetate is 61.9%, the mass ratio of EC is 20.6%, and DMC is not present.

[0202] Comparative Example 4

[0203] The preparation method of the battery cell is the same as in Example 4, except that the electrolyte does not contain chain carboxylic acid esters, the mass ratio of EC is 29.6%, the mass ratio of DMC is 54.9%, and the mass ratio of VC in the additive is 1%.

[0204] Table 2 shows the detailed differences between the individual battery cells in Examples 6-11, Comparative Example 3, and Comparative Example 4, as well as the test results.

[0205] Table 2

[0206] As can be seen from the comparison between Examples 6-10 and Comparative Examples 3 and 4, by adjusting the content of carboxylic acid esters 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 content of carboxylic acid esters is too high, it is easy to cause electrolyte gas generation under high temperature conditions, releasing acid to corrode the SEI film, which will reduce the high temperature cycle life of the battery cell.

[0207] Examples 6-10, compared with Comparative Example 1, show that the energy density of the battery cells is also improved. Compared with Comparative Example 2, it can be seen that the energy density of the battery cells is also improved.

[0208] As can be seen from Example 11, different types of carboxylic acid esters can all improve the ionic conductivity of the electrolyte.

[0209] Example 12

[0210] The preparation method of the battery cell is the same as in Example 4, except that the compaction density of the positive electrode film is 2.5 g / cm³. 3 .

[0211] Example 13

[0212] The preparation method of the battery cell is the same as in Example 4, except that the compaction density of the positive electrode film is 2.6 g / cm³. 3 .

[0213] Example 14

[0214] The preparation method of the battery cell is the same as in Example 4, except that the compaction density of the positive electrode film is 2.7 g / cm³. 3 .

[0215] Example 15

[0216] The preparation method of the battery cell is the same as in Example 4, except that the coating weight of the positive electrode sheet is 220 mg / 1540.25 mm. 2 .

[0217] Example 16

[0218] The preparation method of the battery cell is the same as in Example 4, except that the coating weight of the positive electrode sheet is 260 mg / 1540.25 mm. 2 .

[0219] Example 17

[0220] The preparation method of the battery cell is the same as in Example 4, except that the coating weight of the positive electrode sheet is 300 mg / 1540.25 mm. 2 .

[0221] Example 18

[0222] The preparation method of the battery cell is the same as in Example 4, except that the coating weight of the positive electrode sheet is 340 mg / 1540.25 mm. 2 .

[0223] The detailed differences and test results of the battery cells in Examples 12-18 are shown in Table 3.

[0224] Table 3

[0225] As can be seen from Examples 12-18, by adjusting the compaction density and coating weight of the positive electrode film, the charging time and energy density of the battery cell can be optimized, resulting in a battery cell with both excellent fast charging performance and high energy density.

[0226] Example 19

[0227] The preparation method of the battery cell is the same as in Example 4, except that the lithium supplement is lithium nickelate.

[0228] Example 20

[0229] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of Li5FeO4 is 0.5% and the mass percentage of lithium iron phosphate material is 96.2%.

[0230] Example 21

[0231] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of Li5FeO4 is 1.5% and the mass percentage of lithium iron phosphate material is 95.2%.

[0232] Example 22

[0233] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of Li5FeO4 is 2.5% and the mass percentage of lithium iron phosphate material is 94.2%.

[0234] Example 23

[0235] The preparation method of the battery cell is the same as in Example 4, except that the mass percentage of Li5FeO4 is 2.8% and the mass percentage of lithium iron phosphate material is 93.9%.

[0236] The detailed differences and test results of the battery cells in Examples 19-23 are shown in Table 4.

[0237] Table 4

[0238] As can be seen from Examples 20-23, by adjusting the content of lithium replenishing agent in the positive electrode film layer, the charging time, cycle life and energy density of the battery cell can be optimized simultaneously, resulting in a battery cell with excellent overall performance.

[0239] As can be seen from Example 19, different types of lithium supplements can all achieve the effect of lithium supplementation.

[0240] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a casing, an electrode assembly, and an electrolyte, wherein the electrode assembly includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode, wherein, The positive electrode sheet includes a positive current collector and a positive electrode film layer. The positive current collector includes a positive electrode body portion and a positive electrode tab portion. The positive electrode tab portion extends from the positive electrode body portion. The positive electrode film layer is located on at least one side of the positive electrode body portion. The positive electrode film layer includes lithium phosphate. The dimension of the positive electrode film layer along the length direction of the positive electrode sheet is 200mm-700mm. The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative current collector includes a negative electrode body portion and a negative electrode tab portion. The negative electrode tab 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. The negative electrode film layer includes graphite. The electrolyte comprises chain-like carboxylic acid esters, and the chain-like carboxylic acid esters account for 5%-60% of the total mass of the electrolyte.

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

3. The battery cell according to claim 1 or 2, wherein, Based on the total mass of the electrolyte, the chain carboxylic acid ester accounts for 8%-30% of the mass.

4. The battery cell according to any one of claims 1-3, wherein, The electrolyte has a conductivity of 9.5 mS / cm to 19 mS / cm at room temperature.

5. The battery cell according to any one of claims 1-4, wherein, The electrolyte has a conductivity of 9.7 mS / cm to 13.5 mS / cm at room temperature.

6. The battery cell according to any one of claims 1-5, wherein, The viscosity of the electrolyte at room temperature is 2 mPa·s-5 mPa·s.

7. The battery cell according to any one of claims 1-6, wherein, The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

8. The battery cell according to any one of claims 1-7, wherein, The chain-like carboxylic acid esters include compounds represented by Formula I: Wherein, R1 includes one or more of hydrogen atoms, C1-C5 alkyl groups, and C1-C5 haloalkyl groups, and R2 includes one or more of C1-C5 alkyl groups and C1-C5 haloalkyl groups.

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

10. The battery cell according to any one of claims 1-9, wherein, The chain carboxylic acid ester includes One or more of them.

11. The battery cell according to any one of claims 1-10, wherein, The single-sided coating weight of the positive electrode film is 200 mg / 1540.25 mm. 2 -340mg / 1540.25mm 2 The option is 240mg / 1540.25mm. 2 -300mg / 1540.25mm 2 .

12. The battery cell according to any one of claims 1-11, wherein, When the battery cell is at 100% SOC, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

13. The battery cell according to any one of claims 1-12, wherein, The lithium-containing phosphate includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

14. The battery cell according to any one of claims 1-13, wherein, The positive electrode film layer also includes a lithium replenishing agent, and the mass percentage of the lithium replenishing agent is 0.5%-2.5% based on the total mass of the positive electrode film layer.

15. The battery cell according to claim 14, 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 metamanganate, lithium tartrate, trilithium citrate, lithium nickel oxide, and lithium ferrite.

16. The battery cell according to any one of claims 1-15, wherein, The positive electrode and the negative electrode are stacked.

17. The battery cell according to any one of claims 1-16, wherein, 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. The positive electrode body is electrically connected to the positive terminal via a positive electrode tab; and / or The second end cap assembly includes a second end cap and at least one negative terminal, wherein the negative electrode body is electrically connected to the negative terminal via the negative electrode tab.

18. The battery cell according to claim 17, wherein, The first end cap assembly includes a positive terminal and a negative terminal, the positive terminal body being electrically connected to the positive terminal via the positive terminal tab, and the negative terminal body being electrically connected to the negative terminal via the negative terminal tab; and / or, The second end cap assembly includes a positive terminal and a negative terminal. The positive terminal body is electrically connected to the positive terminal via the positive terminal tab, and the negative terminal body is electrically connected to the negative terminal via the negative terminal tab.

19. The battery cell according to claim 18, wherein, The first end cap assembly and the second end cap assembly are disposed at both ends of the housing. Along the length direction of the battery cell, the electrode terminals of the same polarity on the first end cap assembly and the second end cap assembly are staggered. Optionally, the electrode terminals of the same polarity are diagonally arranged along the length direction of the battery cell.

20. The battery cell according to any one of claims 1-19, wherein, The battery cell is configured to charge from 10% SOC to 80% SOC in 5-10.5 minutes.

21. A battery device, wherein, The battery device includes any one of the battery cells according to claims 1-20, and the battery device is at least one of a battery module, a battery pack, and an energy storage device.

22. An electrical appliance, wherein, Includes a battery cell according to any one of claims 1-20 or a battery device according to claim 21, wherein the battery cell or the battery device is used to provide electrical energy.

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