Battery cell and preparation method, battery apparatus, electric apparatus, energy storage apparatus and energy storage system

Abstract

The present application relates to a battery cell and preparation method, battery apparatus, electric apparatus, energy storage apparatus and energy storage system. The battery cell comprises a housing, an electrolyte and at least one electrode assembly. The housing comprises a casing and an end cover; the casing comprises an accommodating cavity, and the end cover covers the casing. The electrolyte is disposed in the accommodating cavity. The at least one electrode assembly is disposed in the accommodating cavity, and the electrode assembly comprises a positive electrode plate, a separator and a negative electrode plate. The capacity of the battery cell is greater than or equal to 500 Ah, the electrolyte injection coefficient of the battery cell is 1.5 g / Ah to 4 g / Ah, the electrolyte comprises vinylene carbonate, and the mass content of vinylene carbonate in the electrolyte is 1 wt% to 5 wt%. The present application can improve the energy density and cycle performance of the battery cell.

Description

Battery cells and their manufacturing methods, battery devices, electrical devices, energy storage devices and energy storage systems

[0001] References to relevant applications

[0002] This application claims priority to PCT international application PCT / CN2025 / 085921, filed on March 28, 2025, and to PCT international applications PCT / CN2025 / 140517, PCT / CN2025 / 140531, PCT / CN2025 / 140529, PCT / CN2025 / 140513, and PCT / CN2025 / 14052, filed on December 5, 2025. 7. Priority to PCT / CN2025 / 140521, PCT / CN2025 / 140532, PCT / CN2025 / 140522, PCT / CN2025 / 140453, PCT / CN2025 / 140528, PCT / CN2025 / 140456, PCT / CN2025 / 140452, and PCT / CN2025 / 140362, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to a battery cell and its preparation method, a battery device, an electrical device, an energy storage device, and an energy storage system. Background Technology

[0004] Battery cells possess characteristics such as high capacity and long lifespan, making them widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric aircraft, electric ships, and power tools. With the development of battery cell applications, higher demands are being placed on battery cell performance, such as improving energy density and cycle performance. Summary of the Invention

[0005] This application provides a battery cell and its preparation method, a battery device, an electrical device, an energy storage device, and an energy storage system, which can improve the energy density and cycle performance of the battery cell.

[0006] In a first aspect, this application proposes a battery cell, which includes a casing, an electrolyte, and at least one electrode assembly. The casing includes a housing and an end cap, the housing including a receiving cavity, and the end cap covering the housing. The electrolyte is disposed within the receiving cavity. At least one electrode assembly is disposed within the receiving cavity, the electrode assembly including a positive electrode, a separator, and a negative electrode. The separator is disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The battery cell has a capacity greater than or equal to 500 Ah, an electrolyte filling coefficient of 1.5 g / Ah to 4 g / Ah, and an electrolyte including vinylene carbonate, wherein the mass content of vinylene carbonate in the electrolyte is 1 wt% to 5 wt%.

[0007] The battery cell of the present application has a relatively high capacity. In the high-capacity system, with an appropriate range of liquid injection coefficient in the containment cavity, the liquid injection coefficient will not be too high, so that the required containment cavity volume is relatively small, which can reduce the water content in the containment cavity and weaken the side reaction. Moreover, the above-mentioned liquid injection coefficient ensures that the electrolyte can wet the electrode components, so that the lithium content in the electrolyte is within an appropriate range, thereby meeting the long life requirement of the battery cell.

[0008] Based on the aforementioned electrolyte injection coefficient, the electrolyte also includes vinylene carbonate (VC). Appropriate addition of VC allows it to decompose on the surface of the negative electrode active material layer, producing alkaline lithium salts. These alkaline lithium salts can neutralize hydrofluoric acid, reducing its content and the risk of corrosion to the negative electrode current collector. Furthermore, the remaining components from the decomposition of VC can form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode active material layer, improving the stability of the negative electrode interface, reducing gas production, and enhancing cycle performance.

[0009] In some implementations, the capacity of a single battery cell ranges from 500 Ah to 3000 Ah. The capacity of a single battery cell is relatively high.

[0010] In some embodiments, the capacity of a single battery cell is between 550 Ah and 700 Ah. When the capacity of a single battery cell is within the above range, combined with an appropriate range of electrolyte filling coefficient and vinylene carbonate, it is possible to effectively balance high energy density and cycle performance.

[0011] In some embodiments, the capacity of a single battery cell is between 800 Ah and 1200 Ah. When the capacity of a single battery cell is within this range, combined with an appropriate range of electrolyte filling coefficient and vinylene carbonate, it is possible to effectively balance high energy density and cycle performance.

[0012] In some embodiments, the capacity of a single battery cell is between 2000 Ah and 3000 Ah. When the capacity of a single battery cell is within this range, combined with an appropriate range of electrolyte filling coefficient and vinylene carbonate, it is possible to effectively balance high energy density and cycle performance.

[0013] In some implementations, the electrolyte injection coefficient of the battery cell is 2.5 g / Ah to 4 g / Ah.

[0014] When the electrolyte injection coefficient of a battery cell is within the above range, the electrode assembly can be fully wetted without the electrolyte taking up excessive space, effectively balancing the energy density and cycle performance of the battery cell.

[0015] In some embodiments, the mass content of vinylene carbonate (VC) in the electrolyte is from 1.5 wt% to 4.5 wt%.

[0016] When the mass content of vinylene carbonate is within an appropriate range, and when combined with an appropriate injection coefficient, it can effectively form a dense SEI film on the negative electrode, improve the stability of the negative electrode interface, reduce the risk of HF damaging the SEI film and the negative electrode current collector, effectively improve the stability of the negative electrode interface, and thus improve the cycle performance of the battery cell.

[0017] In some embodiments, the dimension of the housing along the first direction is greater than or equal to 270 mm, and can be selected from 270 mm to 800 mm. The first direction, the second direction, and the thickness direction of the battery cell are perpendicular to each other, and the second direction is parallel to the direction from the housing to the end cap.

[0018] When the dimensions of the casing along the first direction are within the above range, the casing size will not be too short, which is beneficial to increasing the capacity of the battery cell; moreover, the casing size will not be too long, so that the electrolyte can uniformly wet the electrode assembly during long-term cycling, reducing the risk of lithium plating at the edge of the electrode assembly, and improving long-term cycle performance and long-term reliability.

[0019] In some embodiments, the thickness of the battery cell is between 70 mm and 120 mm. A thickness within this range is beneficial for increasing the capacity of the battery cell.

[0020] In some embodiments, the dimension of the housing along the second direction is 200 mm to 300 mm, and the second direction is parallel to the direction from the housing to the end cap. When the dimension of the housing along the second direction is within the above range, it is beneficial to increase the capacity of the battery cell; moreover, the distribution of electrons in the second direction is more uniform, which can reduce the risk of lithium plating and improve cycle performance.

[0021] In some implementations, the battery cell satisfies: 6% ≤ (S T -S J ) / S T ≤13%; ST This indicates the projected area of ​​the cavity along the second direction, which is parallel to the direction from the shell to the end cap; S J This refers to the total projected area of ​​at least one electrode assembly when a battery cell is fully discharged and projected along the second direction.

[0022] (S T -S J ) / S T Within the aforementioned range, the excess space within the containment cavity is not excessive, which reduces the moisture content that may be introduced during assembly and provides reserved space for gas generation, ensuring that the gas pressure within the containment cavity is not too high, thereby improving the reliability of the battery cells during long-term cycling.

[0023] In some implementations, the battery cell satisfies: 88% ≤ H J / H T ≤92%;

[0024] H T This indicates the dimension of the receiving cavity along the thickness direction of the battery cell;

[0025] H J This refers to the total dimension of at least one electrode assembly along the thickness direction of the battery cell when the battery cell is fully discharged.

[0026] When a battery cell meets the above conditions, the electrode assembly occupies an appropriate amount of space in the thickness direction. While providing high capacity, it ensures that there is not too much extra space, which can reduce the moisture content that may be introduced during assembly. It can also provide reserved expansion space for volume expansion during charging, reduce the risk of battery cell bulging or even casing rupture, and improve the reliability of battery cell in long-term cycle use.

[0027] In some implementations, the battery cell meets the following requirement: 250cm 3 ≤V T -V J ≤2900cm 3 ,

[0028] V T This indicates the volume of the cavity.

[0029] V J This refers to the total volume of at least one electrode assembly when the battery cell is fully discharged.

[0030] The battery cells meet the above requirements, providing high capacity while ensuring adequate margin. This reduces the potential introduction of moisture during assembly and provides space for the volume expansion and / or gas generation of the electrode components, thereby reducing the risk of battery cells bulging or even casing rupture and improving the reliability of battery cells during long-term cycling.

[0031] In some embodiments, there are at least two electrode assemblies, optionally at least four, with at least two electrode assemblies stacked along the thickness direction of the battery cell.

[0032] By appropriately increasing the number of electrode components, the thickness of a single electrode component can be relatively thinner within the same volume, which can reduce excess space to a certain extent. In particular, when the electrode components are wound electrode components, the bending area can be thinned, the space occupancy rate of the electrode components can be increased, thereby reducing excess space, reducing the water content in the system, and improving the cycle performance of the battery cells.

[0033] In some embodiments, the thickness of each electrode assembly is 15 mm to 18 mm when the battery cell is fully discharged. When the thickness of the electrode assembly is within the above range, its thickness is relatively thin, which can be used for thinner battery cells, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0034] In some embodiments, the positive electrode includes a positive flat section, and the negative electrode includes a negative flat section. The positive and negative flat sections are stacked along the thickness direction of the battery cell. The electrode assembly includes 40 to 60 positive flat sections. The relatively large number of positive flat sections allows the electrode assembly to occupy more of the cavity, increasing the capacity of the battery cell and reducing excess space, thereby reducing the moisture content in the excess space.

[0035] In some embodiments, the compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 2.4g / cm³ is an optional value. 3 Up to 3.0 g / cm 3 When the compaction density of the positive electrode active material layer is within the above range, the electrode assembly can be thinned while increasing the capacity of the battery cell. This allows the electrode assembly to be adapted to thinner battery cells, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0036] In some embodiments, the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 2.5g / cm 3When the compaction density of the negative electrode active material layer is within the above range, it can reduce the thickness of the electrode assembly while increasing the capacity of the battery cell. This allows the electrode assembly to be adapted to thinner battery cells, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0037] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm. 2 Up to 0.40g / 1540.25mm 2 .

[0038] When the single-sided coating weight of the positive electrode active material layer is within the above range, it can increase the space ratio of the positive electrode active material layer and reduce the space ratio of the current collector, resulting in a higher capacity of the battery cell. Moreover, the transport resistance of lithium ions in the positive electrode active material layer is relatively small, which reduces impedance and is conducive to the rapid transport of lithium ions, thereby improving the kinetic performance and cycle performance of the battery cell.

[0039] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm. 2 Up to 0.18g / 1540.25mm 2 .

[0040] When the single-sided coating weight of the negative electrode active material layer is within the above range, it can increase the space ratio of the negative electrode active material layer and reduce the space ratio of the current collector, resulting in a higher capacity of the battery cell. The stacking of active material particles in the negative electrode active material layer is not too dense, providing expansion space for the active material particles and reducing the degree of expansion. Moreover, the transport resistance of lithium ions in the negative electrode active material layer is relatively small, reducing impedance and facilitating the rapid transport of lithium ions, thereby improving the kinetic performance and cycle performance of the battery cell.

[0041] In some implementations, the thickness of the spacer is 3 μm to 8 μm.

[0042] The relatively thin thickness of the aforementioned separator helps to reduce the thickness of the electrode assembly, thereby increasing the space occupied by the electrode assembly, reducing excess space, reducing water content, and improving the cycle performance of the battery cell.

[0043] In some embodiments, the positive electrode active material layer includes a phosphate-based active material, and in a cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy: D A 90 is from 1400nm to 2100nm, D A 90 indicates the particle size at which the cumulative area distribution of the particles reaches 90%.

[0044] When the positive electrode active material layer meets the above conditions, the structure of the positive electrode active material is more stable and the surface activity is lower, which can reduce the degree of side reaction, reduce gas production and acid production, and improve the cycle performance of the battery cell.

[0045] In some embodiments, in a cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy: (D A 90-D A 10) / D A 50 ranges from 1.855 to 2.375, D A 90 represents the particle size (D) at which the cumulative area distribution of the particles reaches 90%. A 50 represents the particle size (D) corresponding to a cumulative area distribution of 50%. A 10 indicates the particle size at which the cumulative area distribution of the particles reaches 10%.

[0046] When the positive electrode active material layer meets the above conditions, the structure of the positive electrode active material is more stable and the surface activity is lower, which can reduce the degree of side reaction, reduce gas production and acid production, and improve the cycle performance of the battery cell.

[0047] In some embodiments, the density of the electrolyte is from 1.2 g / mL to 1.5 g / mL.

[0048] When the electrolyte density is within the above range, a suitable electrolyte injection coefficient can be used to effectively control the volume of electrolyte added, reduce the total amount of electrolyte participating in side reactions, slow down the gas and acid production caused by side reactions, and improve the cycle performance of the battery cell.

[0049] In some embodiments, the electrolyte further includes dimethyl carbonate, wherein the mass content of dimethyl carbonate in the electrolyte is from 15 wt% to 50 wt%.

[0050] The electrolyte system described above can reduce gas production and improve the long-term cycle reliability of battery cells, even with relatively limited margin.

[0051] In some embodiments, the electrolyte further includes lithium bis(fluorosulfonyl)imide, wherein the lithium bis(fluorosulfonyl)imide content in the electrolyte is 1 wt% to 5 wt%.

[0052] The addition of lithium bis(fluorosulfonyl)imide can appropriately reduce the amount of lithium hexafluorophosphate. Lithium bis(fluorosulfonyl)imide has high ionic conductivity, which can effectively improve ion conduction. It is not easily reacted with water, and its decomposition products can optimize the stability of the SEI film, further improve the gas generation phenomenon caused by side reactions, and thus improve the cycle performance of the battery cell.

[0053] In some embodiments, the electrolyte further includes fluoroethylene carbonate, which is present in a mass content of 1 wt% to 3 wt% in the electrolyte. Fluoroethylene carbonate can optimize film formation on the negative electrode side, improve interfacial stability on the negative electrode side, and enhance the cycle performance of the battery cell.

[0054] Secondly, embodiments of this application provide a method for preparing a battery cell, comprising:

[0055] At least one electrode assembly is provided, the electrode assembly including a positive electrode, an separator and a negative electrode, the separator being disposed between the positive electrode and the negative electrode, the positive electrode including a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, and the negative electrode including a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0056] A housing is provided, the housing including a shell and an end cap, the shell including a receiving cavity;

[0057] The electrode assembly is assembled into the receiving cavity, and the end cap is placed on the housing;

[0058] Electrolyte is supplied into the containment cavity to prepare a battery cell, wherein the capacity of the battery cell is greater than or equal to 500Ah, the electrolyte injection coefficient of the battery cell is 1.5g / Ah to 4g / Ah, and the electrolyte includes vinylene carbonate, the mass content of vinylene carbonate in the electrolyte is 1wt% to 5wt%.

[0059] The battery cells prepared according to the embodiments of this application can effectively improve the cycle performance of the battery cells.

[0060] In some embodiments, the step of providing at least one electrode assembly further includes:

[0061] Provide initial electrode assembly;

[0062] Pressure is applied to the initial electrode assembly along its thickness direction, ranging from 30t to 150t.

[0063] In some embodiments, the step of providing at least one electrode assembly further includes:

[0064] Provide initial electrode assembly;

[0065] The initial electrode assembly is heat-treated, optionally at a temperature of 80°C to 130°C.

[0066] Thirdly, this application proposes a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this application or battery cells prepared by a method according to any embodiment of the second aspect of this application.

[0067] Fourthly, this application proposes an electrical device, which includes the battery device according to any embodiment of the third aspect of this application.

[0068] Fifthly, this application proposes an energy storage device, which includes the battery device according to any embodiment of the third aspect of this application.

[0069] Sixthly, this application proposes an energy storage system, which includes an energy storage device according to any embodiment of the fifth aspect of this application. Attached Figure Description

[0070] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0071] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application.

[0072] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application.

[0073] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application.

[0074] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application.

[0075] Figure 5 is an exploded view of a battery cell provided in some embodiments of this application.

[0076] Figure 6 is a schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application.

[0077] Figure 7 is a cross-sectional view of a battery cell along the thickness direction provided in some embodiments of this application.

[0078] Figure 8 is a schematic diagram of the structure of a battery cell electrode assembly provided in some other embodiments of this application.

[0079] The accompanying drawings may not be drawn to scale.

[0080] The reference numerals in the attached drawings are explained as follows: X, thickness direction of the battery cell; Z, first direction; Y, second direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing section; 5b, second housing section; 5c, accommodating space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, positive electrode plate; 111, straight section of positive electrode; 112, bent section of positive electrode; 12, negative electrode plate; 121, straight section of negative electrode; 122, bent section of negative electrode; 13, separator; 20, outer shell; 21, housing; 210, accommodating cavity; 22, end cap; 31, positive terminal; 32, negative terminal. Detailed Implementation

[0081] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0082] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0083] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0086] Currently, judging from market trends, the application of individual battery cells is becoming increasingly widespread. Individual battery cells are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in energy storage systems such as energy storage containers or energy storage cabinets.

[0087] With the development of energy storage system technology, the requirements for the cycle life of battery cells in energy storage systems are constantly increasing. During the use of battery cells, lithium salts in the electrolyte, such as lithium hexafluorophosphate, are prone to side reactions with water, leading to the decomposition of lithium hexafluorophosphate to produce hydrofluoric acid. Hydrofluoric acid can easily damage the solid electrolyte interphase (SEI) film on the negative electrode surface and may corrode the current collector, thereby deteriorating the cycle and shortening the cycle life.

[0088] Research has found that moisture inside battery cells may originate from two sources: firstly, the positive electrode active material itself may carry moisture; secondly, moisture-laden air may be introduced into the battery cell during assembly. Both types of moisture can react with lithium hexafluorophosphate in the electrolyte, worsening the cycle.

[0089] Especially in energy storage systems, the capacity of individual battery cells is usually high, requiring a higher amount of positive electrode active material. The numerous cavities inside the battery cells further increase the degree of side reactions and worsen the cycle.

[0090] In view of the above problems, this application proposes a battery cell with a relatively high capacity. In the high-capacity system, with an appropriate range of liquid injection coefficient in the containment cavity, the liquid injection coefficient will not be too high, so that the required containment cavity volume is relatively small, which can reduce the water content in the containment cavity and weaken the side reaction. Moreover, the above-mentioned liquid injection coefficient ensures that the electrolyte can wet the electrode components, so that the lithium content in the electrolyte is within an appropriate range, thereby meeting the long life requirement of the battery cell.

[0091] Based on the aforementioned electrolyte injection coefficient, the electrolyte also includes vinylene carbonate (VC). Appropriate addition of VC allows it to decompose on the surface of the negative electrode active material layer, producing alkaline lithium salts. These alkaline lithium salts can neutralize hydrofluoric acid, reducing its content and the risk of corrosion to the negative electrode current collector. Furthermore, the remaining components from the decomposition of VC can form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode active material layer, improving the stability of the negative electrode interface, reducing gas production, and enhancing cycle performance.

[0092] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices, energy storage devices, or energy storage systems such as vehicles, ships, or aircraft. Systems comprising the electrical devices or energy storage devices can be composed of the battery cells and batteries disclosed in this application, which is beneficial for improving the overall performance of equipment such as battery cells, electrical devices, battery devices, energy storage devices, and energy storage systems.

[0093] The energy storage system provided in this application can be any power system that requires energy storage devices. The energy storage system may include one or more energy storage devices and a power conversion system (PCS), with the power conversion system connecting the power generation equipment and the energy storage devices. The power generation equipment generates electrical energy, which can be stored in the energy storage device through the power conversion system. For example, the power generation equipment may specifically be a solar panel, hydroelectric power generation equipment, thermal power generation equipment, wind power generation equipment, etc.

[0094] Energy storage devices can be used in energy storage power stations, wind power generation systems, solar power generation systems, mobile power systems, or temporary power supply systems. Energy storage devices can store electrical energy as needed and output it when appropriate. For example, energy storage devices can store electrical energy during off-peak hours and provide power to relevant users or electrical equipment during peak hours.

[0095] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0096] In some embodiments, the energy storage device may include a cabinet and one or more battery clusters housed within the cabinet. The battery clusters may include multiple battery units connected in series and / or in parallel via a busbar.

[0097] In some implementations, the energy storage device may include modules such as a thermal management module, a main control module, a central control module, a power distribution module, and a fire protection module.

[0098] As an example, the thermal management module may include a liquid cooling unit that supplies coolant to each battery device via piping to regulate the temperature of the individual battery cells.

[0099] As an example, the main control module can serve as the battery management unit for the battery cluster, used to monitor and manage the battery cluster. The main control module can monitor information such as the current, voltage, power, or temperature of the battery cluster. For instance, it can control the charging and discharging current and voltage of the battery cluster. The main control module includes a slave battery management unit (SBMU), a fusion switch, and other modules.

[0100] As an example, the central control module can serve as the battery management unit for an energy storage device, used to monitor and manage the device. The central control module can monitor information such as the energy storage device's current, voltage, power, state of charge, or temperature. For instance, it can control the charging and discharging current and voltage of the energy storage device. As an example, the central control module includes modules such as an Insulation Monitoring Module (IMM), a Master Battery Management Unit (MBMU), an Ethernet (ETH) module, and a fiber optic conversion module.

[0101] As an example, a fire protection system includes control panels, detectors, alarm devices, etc., used to detect, alarm, or extinguish fires in energy storage systems.

[0102] As an example, the power distribution unit can be used to distribute power to the power modules of the energy storage device.

[0103] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of this application do not impose special limitations on the above-mentioned electrical devices.

[0104] As shown in Figure 1, the electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 1, a battery pack or battery module can be used.

[0105] The electrical device 1 is equipped with a battery device inside, which can be located at the bottom, head, or tail of the electrical device 1.

[0106] The battery device (Battery Apparatus) mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0107] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0108] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0109] In some embodiments, the battery device can be a battery pack 2, for example, as shown in Figure 1, where the power device 1 has a battery pack 2 inside.

[0110] Electrical device 1 may also include controller 3 and motor 4. Controller 3 is used to control the battery device to supply power to motor 4, for example, to meet the power needs of electrical device 1 during startup, navigation and driving.

[0111] The battery pack 2 includes a housing and one or more battery cell assemblies, which are housed within the housing.

[0112] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0113] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0114] As shown in Figure 2, the battery pack 2 includes a housing 5 and individual battery cells (not shown in Figure 2), with the individual battery cells housed within the housing 5.

[0115] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with an opening on one side, and the first housing portion 5a may be a plate-like structure, covering the opening side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with an opening on one side, with the opening side of the first housing portion 5a covering the opening side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0116] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0117] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0118] In battery pack 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells are connected in both series and parallel configurations. Multiple battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed in housing 5. Alternatively, multiple battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed in housing 5.

[0119] A single battery cell can be the smallest unit that makes up a battery device.

[0120] In some embodiments, as shown in Figure 3, there are multiple battery cells 7. These multiple battery cells 7 are first connected in series, parallel, or in a mixed manner to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or in a mixed manner to form a whole, which is housed in a casing.

[0121] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6. There can be one or more busbars, each used to electrically connect at least two battery cells 7.

[0122] As shown in Figures 4 and 5, in some embodiments, the battery cell 7 includes a housing 20 and an electrode assembly 10. The housing 20 includes a shell 21 and an end cap 22. The shell 21 includes a receiving cavity 210 with an opening, and the end cap 22 covers the opening. The electrode assembly 10 is disposed in the receiving cavity 210.

[0123] The housing 21 can have various shapes, such as a cylinder or a cuboid. The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, the housing 21 can be a cylindrical structure. If the electrode assembly 10 is a cuboid structure, the housing 21 can be a cuboid structure. Optionally, the electrode assembly 10 can be a cuboid structure.

[0124] The housing 21 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and this application does not impose any special limitations on this. Optionally, the inner wall of the housing 21 may also include an insulating element, which can exist in the form of a film layer, and the insulating layer can separate the housing 21 from the electrode assembly 10. The material of the insulating layer can be selected from materials commonly used in the art, and is not particularly limited here.

[0125] The end cap 22 closes onto the opening of the housing 21 to isolate the internal environment of the battery cell 7 from the external environment. The end cap 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of this application do not impose any special limitations on this.

[0126] Optionally, the battery cell 7 also includes a positive terminal 31 and a negative terminal 32, both of which can be disposed on the end cap 22. The positive terminal 31 and the negative terminal 32 can be used to electrically connect with the electrode assembly 10 for outputting or inputting electrical energy into the battery cell 7.

[0127] In some embodiments, the battery cell 7 may also include a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 7 reaches a threshold.

[0128] There may be one or more electrode assemblies 10 located within the housing 21. The electrode assembly 10 may be a stacked structure or a wound structure.

[0129] The electrode assembly 10 includes a positive electrode and a negative electrode. During the charging and discharging process of the battery cell 7, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes. Optionally, the electrode assembly 10 also includes a separator disposed between the positive and negative electrodes, which can reduce the risk of short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0130] In some embodiments, the positive electrode can be a positive electrode plate. In some embodiments, the negative electrode can be a negative electrode plate.

[0131] As shown in Figures 4 to 6, in some embodiments, the battery cell 7 includes a casing 20, at least one electrode assembly 10, and an electrolyte. The casing 20 includes a housing 21 and an end cap 22. The housing 21 includes a receiving cavity 210, and the end cap 22 covers the housing 21. The electrode assembly 10 and the electrolyte are disposed within the receiving cavity 210. The electrode assembly 10 includes a positive electrode 11, a separator 13, and a negative electrode 12. The separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The positive electrode 11 includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode 12 includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0132] The capacity of battery cell 7 is greater than or equal to 500Ah;

[0133] The electrolyte of the battery cell 7 is 1.5 g / Ah to 4 g / Ah, and the electrolyte includes vinylene carbonate (VC), with the mass content of VC in the electrolyte being 1 wt% to 5 wt%.

[0134] A portion of the cavity 210 is used to house the electrode assembly 10, and the remaining space is surplus space. A portion of the surplus space is used to store the electrolyte, and the remaining surplus space can be used to store the gas generated during use or to provide reserved space for expansion.

[0135] When the capacity of battery cell 7 is greater than or equal to 500Ah, and can be selected from 500Ah to 3000Ah, the capacity of battery cell 7 is relatively high. In the high-capacity system, the amount of electrolyte required is relatively large, which leads to an increase in the amount of electrolyte participating in the side reaction and a higher total amount of hydrofluoric acid generated. Moreover, with the requirement of a large amount of electrolyte, a large amount of spare space is often required.

[0136] In view of this, the embodiment of this application uses an appropriate range of liquid injection coefficient in the receiving cavity 210. The liquid injection coefficient is not too high, so that the required volume of the receiving cavity 210 is relatively small, minimizing the excess space, thereby reducing the water content in the receiving cavity 210 and weakening the side reaction. Moreover, the above-mentioned liquid injection coefficient ensures that the electrolyte can wet the electrode assembly 10, so that the lithium content in the electrolyte is within an appropriate range, thereby meeting the long life requirement of the battery cell 7.

[0137] Under the aforementioned electrolyte injection coefficient, the electrolyte also includes an appropriate amount of vinylene carbonate (VC), ensuring that the absolute mass of VC is within a suitable range. This allows it to decompose on the surface of the negative electrode active material layer, producing alkaline lithium salts. These alkaline lithium salts can neutralize hydrofluoric acid, reducing its content and thus mitigating the risk of corrosion to the negative electrode current collector. Furthermore, the remaining components produced by the decomposition of VC can form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode active material layer, enhancing the stability of the negative electrode interface and improving cycle performance.

[0138] In some embodiments, the capacity of the battery cell 7 is from 500Ah to 3000Ah, specifically 500Ah, 600Ah, 700Ah, 800Ah, 900Ah, 1000Ah, 1100Ah, 1200Ah, 1300Ah, 1400Ah, 1500Ah, 1600Ah, 1700Ah, 1800Ah, 1900Ah, 2000Ah, 2100Ah, 2200Ah, 2300Ah, 2400Ah, 2500Ah, 2600Ah, 2700Ah, 2800Ah, 2900Ah, 3000Ah, or any combination of two of the above values.

[0139] In some embodiments, the capacity of the battery cell 7 is between 550 Ah and 700 Ah. When the capacity of the battery cell 7 is within the above range, its combination with an appropriate range of electrolyte injection coefficient and vinylene carbonate can effectively balance high energy density and cycle performance.

[0140] In some embodiments, the capacity of the battery cell 7 is between 800 Ah and 1200 Ah. When the capacity of the battery cell 7 is within the above range, its combination with an appropriate range of electrolyte injection coefficient and vinylene carbonate can effectively balance high energy density and cycle performance.

[0141] In some embodiments, the capacity of the battery cell 7 is between 2000 Ah and 3000 Ah. When the capacity of the battery cell 7 is within the above range, its combination with an appropriate range of electrolyte injection coefficient and vinylene carbonate can effectively balance high energy density and cycle performance.

[0142] In this embodiment, the capacity of the battery cell 7 can be adjusted by adjusting any one of the following parameters: the volume of the casing 21, the material of the positive electrode active material, the coating weight and compaction density of the positive electrode active material layer, the material of the negative electrode active material, and the coating weight and compaction density of the negative electrode active material layer.

[0143] For example, the larger the volume of the casing 21, the more active materials it can hold, and the higher the capacity of the battery cell 7.

[0144] For example, as the coating weight increases, the capacity of the battery cell 7 increases; as the compaction density increases, the capacity of the battery cell 7 also increases.

[0145] The capacity of the battery cell 7 is as known in this application and can be tested using equipment and methods known in the art. For example, at 25°C and normal pressure, the battery cell is charged at a power of 0.5P to the upper limit of the charging voltage, such as 3.65V, left to stand for 10 minutes, and then discharged at a power of 0.5P to the discharge cutoff voltage, such as 2.5V, left to stand for 10 minutes, and the above charging and discharging process is repeated twice.

[0146] The second discharge capacity is recorded as the capacity C0 of the battery cell, and the discharge voltage plateau V0 of the battery cell is also recorded.

[0147] The volumetric energy density VED of a battery cell = battery cell capacity C0 * voltage plateau V0 / battery cell volume; the volume of a battery cell = battery cell width * battery cell length * battery cell thickness.

[0148] The outer shell 20 can be a cuboid structure or a cylindrical structure.

[0149] With the outer casing 20 having a cuboid structure, the battery cell 7 also has a cuboid structure. In this case, the battery cell 7 has a preset thickness, length, and width.

[0150] The second direction Y can be defined as parallel to the direction from the housing 21 to the end cap 22, and the first direction Z can be defined as perpendicular to both the second direction Y and the thickness direction X of the battery cell 7. For example, if the second direction Y is parallel to the width direction of the battery cell 7, then the first direction Z is parallel to the length direction of the battery cell 7; or, for example, if the second direction Y is parallel to the length direction of the battery cell 7, then the first direction Z is parallel to the width direction of the battery cell 7.

[0151] In some embodiments, the dimension of the housing 21 along the first direction Z is greater than or equal to 270 mm, and can be selected from 270 mm to 800 mm. Exemplarily, the dimension of the housing 21 along the first direction Z is 270 mm, 280 mm, 290 mm, 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm, 370 mm, 380 mm, 390 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, or a range of any two of the above values. Z0 shown in Figure 4 represents the dimension of the housing 21 along the first direction Z. When the first direction Z is parallel to the length direction of the battery cell 7, the dimension of the housing 21 along the first direction Z is the length of the housing 21, and can also be the length of the battery cell 7.

[0152] When the size of the housing 21 along the first direction Z is within the above range, the size of the housing 21 will not be too short, which is beneficial to increasing the capacity of the battery cell 7; and the size of the housing 21 will not be too long, so that the electrolyte can uniformly wet the electrode assembly 10 during long-term cycling, reducing the risk of lithium plating at the edge of the electrode assembly 10, and improving long-term cycle performance and long-term reliability.

[0153] In some embodiments, the thickness of the battery cell 7 is 70 mm to 120 mm, for example, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 120 mm, or any combination of two of the above values. A thickness within this range is beneficial for increasing the capacity of the battery cell 7. X0 in Figure 4 represents the thickness of the battery cell 7.

[0154] In some embodiments, the dimension of the housing 21 along the second direction Y is 200 mm to 300 mm, for example, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 300 mm, or any combination of two of the above values, where the second direction Y is parallel to the direction from the housing 21 to the end cap 22. When the dimension of the housing 21 along the second direction Y is within the above range, it is beneficial to increase the capacity of the battery cell 7; moreover, the distribution of electrons in the second direction Y is more uniform, which can reduce the risk of lithium plating and improve cycle performance. Y0 shown in Figure 4 represents the dimension of the housing 21 along the second direction Y. When the second direction Y is parallel to the width direction of the battery cell 7, the dimension of the housing 21 along the second direction Y is the width of the housing 21.

[0155] In the embodiments of this application, the receiving cavity 210 is the internal space or hollow region of the shell 21, and the receiving cavity 210 does not include the thickness portion of the shell 21.

[0156] The upper limit voltage for charging and the lower limit voltage for discharging of battery cell 7 vary depending on the positive electrode active material. For example, when the phosphate active material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the lower limit voltage for discharging can be 2.5V. Another example is when the phosphate active material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.2V and the lower limit voltage for discharging can be 2.0V.

[0157] The following explanation uses a charging upper limit voltage of 3.65V and a discharging cutoff voltage of 2.5V as an example to illustrate the state of battery cell 7: In this embodiment, the fully discharged state and fully charged state of battery cell 7 are defined as follows:

[0158] Battery cell 7 is charged to the upper limit voltage at a constant current charging rate of 0.2C, left to stand for 10 minutes, and then charged to the upper limit voltage at a constant current charging rate of 0.05C, which corresponds to the fully charged state of battery cell 7.

[0159] Battery cell 7 is discharged at a constant current discharge rate of 0.2C to the discharge cutoff voltage, left to stand for 5 minutes, and then discharged at a constant current discharge rate of 0.05C to the discharge cutoff voltage, corresponding to the fully discharged state of battery cell 7.

[0160] During charging, lithium ions are extracted from the positive electrode active material and embedded in the negative electrode active material. As lithium ions are embedded, the negative electrode active material may expand in volume. Under full charge, the negative electrode active material expands to the highest extent, which causes the entire negative electrode active material layer to expand, resulting in the expansion of the overall structure of the electrode assembly 10, especially the volume expansion along the thickness direction.

[0161] During discharge, lithium ions are extracted from the negative electrode active material and embedded in the positive electrode active material. As lithium ions are extracted, the negative electrode active material shrinks in volume. Under full discharge conditions, the negative electrode active material may shrink to the greatest extent, which causes the entire negative electrode active material layer to shrink, resulting in the overall structure of the electrode assembly 10 to shrink, especially the volume shrinkage along the thickness direction is the most significant.

[0162] Due to the volume shrinkage or expansion of the electrode assembly 10, its volume differs between fully charged and fully discharged states, especially in large-capacity battery cell systems where this difference is more pronounced. To improve the performance of the battery cell 7, in this embodiment, the cycle performance and reliability of the battery cell 7 can be further improved by adjusting the proportion of excess space within the receiving cavity 210 in the fully discharged state.

[0163] As shown in Figure 7, in some embodiments, the battery cell 7 satisfies: 6% ≤ (S T -S J ) / S T ≤13%;

[0164] S T This indicates the projected area of ​​the cavity 210 along the second direction Y, which is parallel to the direction from the housing 21 to the end cap 22.

[0165] S J This indicates that the total projected area of ​​at least one electrode assembly 10 is the battery cell 7 when it is fully discharged and projected along the second direction Y.

[0166] Projecting along the second direction Y can be understood as the second direction Y being the projection normal, and the projection plane being perpendicular to the second direction Y.

[0167] The total projected area of ​​at least one electrode assembly 10 is the sum of the total projected areas of all electrode assemblies 10 inside the battery cell 7. The projected surface of an electrode assembly 10 can be considered as the area enclosed by the projected contour formed by the projection of the outer contour of the electrode assembly 10. Figure 7 shows S... J S T area.

[0168] There is a certain space between the electrode assembly 10 and the housing 21. This space can be used to store some of the free electrolyte, or to provide space for the subsequent expansion or gas generation of the electrode assembly 10.

[0169] S T -S J This represents the projected area of ​​the accommodating cavity 210 minus the total projected area of ​​all electrode assemblies 10 in the projection along the second direction Y. This value reflects the size of the space inside the battery cell 7 not occupied by the electrode assemblies 10, i.e., the size of the surplus space; (S T -S J ) / S T It can represent the proportion of surplus space.

[0170] (S T -S J ) / S T Within the aforementioned range, the excess space within the cavity 210 is not excessive, which reduces the moisture content that may be introduced during assembly and provides reserved space for gas generation, ensuring that the gas pressure within the cavity 210 is not too high, thereby improving the reliability of the battery cell 7 during long-term cycling.

[0171] For example, (S T -S J ) / S T The range is 6%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, or any two of the above values.

[0172] In some implementations, the battery cell 7 satisfies: 88% ≤ H J / H T ≤92%;

[0173] H T This indicates the dimension of the receiving cavity 210 along the thickness direction X of the battery cell 7; Figure 7 shows H. T ;

[0174] H J This indicates that, with the battery cell 7 in its fully discharged state, the total dimension of at least one electrode assembly 10 along the thickness direction X of the battery cell 7 is shown in Figure 7; H is shown in Figure 7.J .

[0175] The total dimension of at least one electrode assembly 10 along the thickness direction X of the battery cell 7 can be understood as the sum of the dimensions of all electrode assemblies 10 within the battery cell 7 along the thickness direction X, and can be further understood as the sum of the thicknesses of all electrode assemblies 10.

[0176] H J / H T It can represent the ratio of the total thickness of all electrode components 10 inside the battery cell 7 to the thickness of the receiving cavity 210. Along the thickness direction X, there is a certain amount of extra space between the electrode components 10 and the housing 21. The above ratio can also indirectly reflect the proportion of extra space in the thickness direction X.

[0177] When the battery cell 7 meets the above conditions, the electrode assembly 10 occupies an appropriate space in the thickness direction X. While providing high capacity, the excess space is not excessive. This can reduce the moisture content that may be introduced during assembly and provide reserved expansion space for volume expansion during charging. This reduces the risk of the battery cell 7 bulging or even the casing 21 cracking, and improves the reliability of the battery cell 7 in long-term cycle use.

[0178] For example, H J / H T The percentage is 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, or any two of the above values.

[0179] In some embodiments, the battery cell 7 satisfies: 250cm 3 ≤V T -V J ≤2900cm 3 ,

[0180] V T This indicates the volume of the cavity 210;

[0181] V J This indicates the total volume of at least one electrode assembly 10 when the battery cell 7 is fully discharged.

[0182] The total volume of at least one electrode assembly 10 represents the sum of the volumes of all electrode assemblies 10 within the battery cell 7.

[0183] V T -V JIt can characterize the volume of the spare space in the cavity 210 that is not occupied by the electrode assembly 10. This volume is within the above range. While providing high capacity, the spare space is appropriate, which can reduce the moisture content that may be introduced during the assembly process. It can also provide reserved space for the volume expansion and / or gas generation of the electrode assembly 10, reduce the risk of the battery cell 7 bulging or even the casing cracking, and improve the reliability of the battery cell 7 in the long-term cycle process.

[0184] In the embodiments of this application,

[0185] V T For, S T S is the product of the dimension of the receiving cavity 210 along the second direction Y. T This represents the projected area of ​​the cavity 210 along the second direction Y, which is parallel to the direction from the housing 21 to the end cap 22.

[0186] V J For, S J S is the product of the dimension of the electrode assembly 10 along the second direction Y. J This represents the total projected area of ​​at least one electrode assembly 10 projected along the second direction Y.

[0187] For example, V T -V J It can be 250cm 3 300cm 3 350cm 3 400cm 3 450cm 3 500cm 3 600cm 3 700cm 3 800cm 3 900cm 3 1000cm 3 1500cm 3 2000cm 3 2500cm 3 2900cm 3 Or a range consisting of any two of the above values.

[0188] In this embodiment, the electrode assembly 10 can be a stacked structure or a wound structure. When the electrode assembly 10 is a wound structure, the electrode assembly 10 includes a flat region and a bent region. The higher the proportion of the bent region, the higher the amount of extra space inside the battery cell 7.

[0189] In some embodiments, there is at least one electrode assembly 10, optionally at least two, optionally at least four. When there are at least two electrode assemblies 10, the at least two electrode assemblies 10 are stacked along the thickness direction X of the battery cell 7.

[0190] By appropriately increasing the number of electrode components 10, the thickness of a single electrode component 10 is relatively thinner within the same volume, which can reduce the excess space to a certain extent. In particular, when the electrode component 10 is a wound electrode component 10, the bending area can be thinned, the space occupancy rate of the electrode component 10 can be increased, thereby reducing the excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell 7.

[0191] In some embodiments, when the battery cell 7 is fully discharged, the thickness of each electrode assembly 10 is 15 mm to 18 mm, for example, 15 mm, 15.5 mm, 16 mm, 16.5 mm, 17 mm, 17.5 mm, 18 mm, or any combination of two of the above values. Figure 7 shows H... J0 This indicates the thickness of each electrode assembly 10.

[0192] When the thickness of the electrode assembly 10 is within the above range, its thickness is relatively thin, which can be applied to thinner battery cells 7, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of battery cells 7.

[0193] As shown in Figure 8, in some embodiments, when the electrode assembly 10 has a wound structure, from a structural point of view, the positive electrode 11 can be a single piece, the negative electrode 12 can be a single piece, and the separator 13 can be a single piece. The separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The positive electrode 11, the separator 13, and the negative electrode 12 are wound in one direction to form the electrode assembly 10.

[0194] The positive electrode 11 includes a positive straight section 111, and the negative electrode 12 includes a negative straight section 121. The positive straight section 111 and the negative straight section 121 are stacked along the thickness direction X of the battery cell 7.

[0195] The positive electrode straight section 111 includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the negative electrode straight section 121 includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0196] The positive electrode 11 also includes a positive electrode bending section 112, which is arranged along the winding direction of the electrode assembly 10 with the positive electrode straight section 111. The positive electrode bending section 112 is connected to the positive electrode straight section 111. The positive electrode bending section 112 includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0197] The negative electrode sheet 12 also includes a negative electrode bending section 122, which is arranged along the winding direction of the electrode assembly 10 with the negative electrode straight section 121. The negative electrode bending section 122 is connected to the negative electrode straight section 121. The negative electrode bending section 122 includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0198] In some embodiments, the electrode assembly 10 includes 40 to 60 positive electrode straight sections 111. The relatively large number of positive electrode straight sections 111 allows the electrode assembly 10 to occupy more of the receiving cavity 210, increasing the capacity of the battery cell 7 and reducing excess space, thereby reducing the moisture content of the excess space.

[0199] In some embodiments, the compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 2.4g / cm³ is an optional value. 3 Up to 3.0 g / cm 3 2.5g / cm³ is an option. 3 Up to 2.9 g / cm 3 The option is 2.54 g / cm³. 3 Up to 2.8 g / cm 3 2.6g / cm³ is an option. 3 Up to 2.7 g / cm 3 .

[0200] When the compaction density of the positive electrode active material layer is within the above range, the electrode assembly can be thinned while increasing the capacity of the battery cell. This allows the electrode assembly to be adapted to thinner battery cells, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0201] For example, the compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 2.35g / cm 3 2.4g / cm 3 2.45g / cm 3 2.5g / cm 3 2.55g / cm 3 2.60g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 Or a range consisting of any two of the above values.

[0202] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm. 2 Up to 0.40g / 1540.25mm 2 .

[0203] When the single-sided coating weight of the positive electrode active material layer is within the above range, it can increase the space ratio of the positive electrode active material layer and reduce the space ratio of the current collector, resulting in a higher capacity of the battery cell. Moreover, the transport resistance of lithium ions in the positive electrode active material layer is relatively small, which reduces impedance and is conducive to the rapid transport of lithium ions, thereby improving the kinetic performance and cycle performance of the battery cell.

[0204] For example, the single-sided coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm² or 0.30 g / 1540.25 mm². 2 0.35g / 1540.25mm 2 0.38g / 1540.25mm 2 0.40g / 1540.25mm 2 Or a range consisting of any two of the above values.

[0205] In this embodiment, the compaction density of the positive electrode active material layer can be the compaction density of the positive electrode active material layer of the battery cell in a fully discharged state; the single-sided coating weight of the positive electrode active material layer can be the single-sided coating weight of the positive electrode active material layer of the battery cell in a fully discharged state.

[0206] The compaction density and single-sided coating weight of the positive electrode active material layer can be tested using the following method: Disassemble the positive electrode sheet from a fully discharged battery cell and measure the compaction density of the positive electrode active material layer. For example, take a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, wipe off the positive electrode active material layer on one side first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its mass as M1. Measure its thickness H1. Then wipe off the positive electrode active material layer of the weighed positive electrode sheet, weigh the positive current collector, record its mass as M0, and measure its thickness H0. The single-sided coating weight of the positive electrode active material layer = (mass of the positive electrode sheet M1 - mass of the positive current collector M0) / S1; the thickness of the positive electrode active material layer = thickness of the positive electrode sheet H1 - thickness of the positive current collector H0; the compaction density of the positive electrode active material layer = single-sided coating weight of the positive electrode active material layer / thickness of the positive electrode active material layer.

[0207] In the embodiments of this application, the thickness of the positive electrode active material layer and the positive electrode current collector are known in the art and can be detected using equipment and methods known in the art. For example, the thickness of the positive electrode sheet can be measured with a micrometer, the film layer on the surface of the positive electrode current collector can be removed, and the thickness of the positive electrode current collector can be measured with a micrometer. When the positive electrode active material layer is coated on one side, the thickness of the positive electrode active material layer is the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector. When the positive electrode active material layer is coated on both sides, the thickness of the positive electrode active material layer is (the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector) / 2.

[0208] In some embodiments, the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 2.5g / cm 3 .

[0209] When the compaction density of the negative electrode active material layer is within the above range, the electrode assembly can be thinned while increasing the capacity of the battery cell. This allows the electrode assembly to be adapted to thinner battery cells, effectively reducing excess space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0210] For example, the compaction density of the negative electrode active material layer is 1.30 g / cm³. 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Or a range consisting of any two of the above values.

[0211] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm. 2 Up to 0.18g / 1540.25mm 2 .

[0212] When the single-sided coating weight of the negative electrode active material layer is within the above range, it can increase the space ratio of the negative electrode active material layer and reduce the space ratio of the current collector, resulting in a higher capacity of the battery cell. The stacking of active material particles in the negative electrode active material layer is not too dense, providing expansion space for the active material particles and reducing the degree of expansion. Moreover, the transport resistance of lithium ions in the negative electrode active material layer is relatively small, reducing impedance and facilitating the rapid transport of lithium ions, thereby improving the kinetic performance and cycle performance of the battery cell.

[0213] For example, the single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm² or 0.13 g / 1540.25 mm². 2 0.14g / 1540.25mm 2 0.15g / 1540.25mm 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 Or a range consisting of any two of the above values.

[0214] In this embodiment, the compaction density of the negative electrode active material layer can be the compaction density of the negative electrode active material layer of the battery cell in a fully discharged state, and the single-sided coating weight of the negative electrode active material layer can be the single-sided coating weight of the negative electrode active material layer of the battery cell in a fully discharged state.

[0215] The single-sided coating weight, compaction density, and thickness of the negative electrode active material layer can be tested using the same testing methods as those for the positive electrode active material layer, and will not be elaborated here.

[0216] In some embodiments, the thickness of the spacer is 3 μm to 8 μm, for example 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any combination of two of the above values.

[0217] The relatively thin thickness of the aforementioned separator helps to reduce the thickness of the electrode assembly, thereby increasing the space occupied by the electrode assembly, reducing excess space, reducing water content, and improving the cycle performance of the battery cell.

[0218] In some embodiments, the positive electrode active material layer includes a phosphate-based active material. Compared to ternary materials, phosphate-based active materials are more prone to adsorbing moisture, generating large amounts of hydrofluoric acid, which damages the SEI film. However, this application, by incorporating an appropriate amount of vinylene carbonate, enables decomposition on the surface of the negative electrode active material, generating alkaline lithium salt. The alkaline lithium salt can neutralize hydrofluoric acid, reducing the hydrofluoric acid content and lowering the risk of hydrofluoric acid corrosion to the negative electrode current collector. Furthermore, the remaining components generated from the decomposition of vinylene carbonate (VC) can form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode active material layer, improving the stability of the negative electrode interface and enhancing cycle performance.

[0219] In some embodiments, in a cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy: (D A 90-D A 10) / D A 50 is between 1.855 and 2.375, for example, 1.855, 1.9, 2, 2.1, 2.2, 2.3, 2.375 or any range of two of the above values.

[0220] When the positive electrode active material layer meets the above conditions, the structure of the positive electrode active material is more stable and the surface activity is lower, which can reduce the degree of side reaction, reduce gas production and acid production, and improve the cycle performance of the battery cell.

[0221] In some embodiments, in a cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy: D A 90 is 1400nm to 2100nm, such as 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm or any two of the above values.

[0222] When the positive electrode active material layer meets the above conditions, the structure of the positive electrode active material is more stable, which can reduce the degree of side reactions, reduce gas production and acid production, and improve the cycle performance of the battery cell.

[0223] In the embodiments of this application,

[0224] D A 10 represents the particle size at which the cumulative area distribution of the particles reaches 10%.

[0225] D A 50 represents the particle size at which the cumulative area distribution of the particles reaches 50%.

[0226] D A 90 represents the particle size at which the cumulative area distribution of the particles reaches 90%.

[0227] (D A 90-D A 10) / D A 50 indicates the particle size concentration, which can characterize the distribution width of particle size.

[0228] In the embodiments of this application, the term "particle" refers to a particle in the positive electrode active material layer that has an identifiable complete boundary in the field of view at a certain magnification, such as 10,000 times. Defects and scratches may exist inside the particle, but a complete boundary sufficient to divide the particle cannot be identified inside the particle.

[0229] It is understood that the particles in the cross-section of the positive electrode active material layer along the thickness direction of the electrode, especially particles ≤0.4μm, mainly originate from the positive electrode active material. Therefore, the embodiments of this application can accurately and objectively reflect the particle size distribution of phosphate active materials in the electrode by observing and statistically analyzing the particle size in the cross-section of the positive electrode active material layer.

[0230] The particle identification method is as follows: The positive electrode active material layer is cut along the thickness direction of the electrode sheet using an argon ion beam (for example, the equipment model can be: Leica EM TIC 3X CP, working voltage: 6kV, working time: 6h). After exposing the cut surface, a scanning electron microscope (for example, the equipment model can be: Hitachi SU8230, working voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) is used to observe the cut surface of the positive electrode active material layer along the thickness direction of the electrode sheet.

[0231] Images were acquired using a field emission scanning electron microscope (FEM) at non-edge locations within a cross-section of the positive electrode active material layer (after observing the electrode edge under the SEM, the field of view was adjusted to the center of the sample) in secondary electron mode. Electron micrographs were taken at 10kx magnification, and the particles in the electron micrographs were analyzed using ImageJ software (1.46r, Win64 version). The specific steps for using ImageJ software are as follows: load the SEM image to be analyzed; identify the particles using the Cellpose plugin software and perform manual corrections; use ImageJ to read and analyze the data.

[0232] The specific method for identifying particles using the Cellpose plugin software is as follows: Set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "run cyto3" to perform particle identification, and then manually mark the particles in the image that were not identified by the software, were not fully identified by the software, or had identification errors. The particles that were not identified by the software, were not fully identified by the software, or had identification errors mainly include the following types: 1. Particles that are too large or have scratches on their surface, making them unidentifiable or incompletely identifiable; 2. During argon ion beam cutting, scratches may be generated on the particle surface, and the software may misjudge these scratches as particle boundaries during identification, leading to identification errors; 3. Particles that are too small and were not successfully identified; 4. Particles located at the edge of the electron microscope field of view, with the interior of the particle penetrated by the edge, preventing a complete display of the morphology, and resulting in identification errors due to partial identification replacing the whole.

[0233] For the unidentified or misidentified particles mentioned above, manual calibration is performed as follows: Particles located at the edges of the scanning electron microscope that are not fully displayed are deleted; It is determined whether other unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, the particle is considered a single particle, and its boundary is manually marked based on observation; If cracks or scratches are found within the particle, it is determined whether the cracks or scratches penetrate the particle. If not, it is considered a single particle and manually marked; If the cracks or scratches penetrate the particle, it is determined whether the cracks or scratches are linear or irregular; If the cracks or scratches are irregular, they are considered the boundary between particles, and particles are divided along this boundary; If the cracks or scratches are linear, contrast is compared; If the contrast is not obvious and there is no crack-like appearance, it is considered a scratch and marked as a single particle; If the contrast is strong and there is a crack-like appearance, it is considered the boundary between particles and marked as two particles. After manual marking, irrelevant information from the automatic image processing is deleted, thus completing the particle identification and marking in the image.

[0234] The particle size calculation method for the cross-section of the positive electrode active material layer along the electrode thickness direction is as follows. After particle identification and labeling, the image is imported into ImageJ software for analysis. The scale is set based on the scanning electron microscope image. The particle size and area in the cross-section of the positive electrode active material layer along the electrode thickness direction are analyzed using the "Feret diameter," "Area," "Round," and "Solidity" analysis functions. According to the software manual (ImageJ User Guide IJ1.46r), the obtained "Feret" parameter represents the maximum spacing between all parallel lines in the two-dimensional projection of the particle, thus characterizing the particle size; and the obtained "Area" parameter represents the pixel area of ​​the particle.

[0235] Since particles smaller than 50nm have a large error in the statistical process and are difficult to identify accurately, and the particle size of positive electrode conductive agents is generally smaller than 50nm, which will cause a large error in the statistical results, particles smaller than 50nm are not counted in the particle size statistics process of this application, and the particle statistics data corresponding to AR, Round or Solidity displayed as "NaN" are deleted.

[0236] Following the above method, to ensure a statistically significant sample size, at least 10 non-overlapping scanning electron microscope (SEM) images were acquired for each electrode, and the particle size of at least 5000 particles was statistically analyzed. The particle sizes of these at least 5000 particles were arranged in ascending order. Using particle size as the horizontal axis and the cumulative area percentage calculated from the particle's "area" as the vertical axis, the cumulative area distribution curve of the particles in the positive electrode active material layer was obtained, thereby statistically calculating D. A 10. D A 50 and D A 90.

[0237] In some implementations, the electrolyte injection coefficient of the battery cell is from 1.5 g / Ah to 4 g / Ah.

[0238] If the electrolyte filling coefficient of a single battery cell is too small, the electrolyte may not adequately wet the electrode assembly, leading to localized lithium plating on the electrode assembly and worsening cycle life.

[0239] If the electrolyte injection coefficient of a single battery cell is too high, there will be too much free electrolyte, which will reduce the space occupied by the electrode assembly and result in a smaller capacity of the single battery cell. It may also lead to an increase in the total amount of lithium hexafluorophosphate that causes side reactions, thus worsening the cycle.

[0240] When the electrolyte injection coefficient of a battery cell is within the above range, the electrode assembly can be fully wetted without the electrolyte taking up excessive space, effectively balancing the energy density and cycle performance of the battery cell.

[0241] For example, the electrolyte injection coefficient of a single battery cell is 1.5 g / Ah, 2.0 g / Ah, 2.5 g / Ah, 3.0 g / Ah, 3.5 g / Ah, 4.0 g / Ah, or a range of any two of the above values. Optionally, the electrolyte injection coefficient of a single battery cell is from 2.5 g / Ah to 4 g / Ah.

[0242] In this embodiment, the electrolyte filling coefficient of a battery cell can be detected using methods known to those skilled in the art. Exemplarily, the electrolyte filling coefficient can be measured according to the following process: 1) Weigh the battery cell (M0); 2) Disassemble the battery cell, pour out the electrolyte, and remove the electrode assembly; 3) Soak and clean the electrode assembly and casing with DMC for 12 hours, cleaning at least three times; 4) Place the electrode assembly and casing in an oven until completely dry; 5) Weigh the electrode assembly and casing (M1). Therefore, the electrolyte filling coefficient of the battery cell is a = (M0 - M1) / A, where A is the rated capacity of the battery cell.

[0243] The rated capacity A of a single battery cell can be read directly from the nameplate information, or it can be obtained by testing as follows: Place the battery cell at 25°C, charge it to 3.65V with a constant current of 0.33C, let it stand for 1 minute, then charge it to 3.65V with a constant current of 0.1C, let it stand for 30 minutes; discharge it to 2.0V with a constant current of 0.33C, and record the discharge capacity at this time, which is the rated capacity A.

[0244] In some embodiments, the electrolyte includes vinylene carbonate (VC), and the mass content of VC in the electrolyte is from 1 wt% to 5 wt%.

[0245] When the mass content of vinylene carbonate is too low, vinylene carbonate cannot effectively form a film on the surface of the positive electrode active material, making the positive electrode interface unstable. The moisture and electrolyte in the positive electrode active material may still undergo side reactions leading to acid production, thereby damaging the SEI film on the negative electrode side and worsening the cycle.

[0246] When the mass content of vinylene carbonate is too high, the impedance of vinylene carbonate film formation at the positive and negative electrodes is high, the interfacial film is uneven, there is a risk of lithium plating, and the cycle is deteriorated.

[0247] When the mass content of vinylene carbonate is within an appropriate range, and when combined with an appropriate injection coefficient, it can effectively form a dense SEI film on the negative electrode, improve the stability of the negative electrode interface, reduce the risk of HF damaging the SEI film and the negative electrode current collector, effectively improve the stability of the negative electrode interface, and thus improve the cycle performance of the battery cell.

[0248] For example, the mass content of vinylene carbonate (VC) in the electrolyte is 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, or any combination of two of the above values.

[0249] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is from 1.5 wt% to 4.5 wt%.

[0250] In some embodiments, the density of the electrolyte is from 1.2 g / mL to 1.5 g / mL, for example 1.20 g / mL, 1.25 g / mL, 1.30 g / mL, 1.35 g / mL, 1.40 g / mL, 1.45 g / mL, 1.50 g / mL, or any combination of two of the above values.

[0251] The density of the electrolyte can be the density at room temperature. When the electrolyte density is within the above range, and an appropriate electrolyte injection coefficient is used, the volume of electrolyte added can be effectively controlled, the total amount of electrolyte participating in side reactions can be reduced, the amount of gas and acid produced by side reactions can be slowed down, and the cycle performance of the battery cell can be improved.

[0252] In the embodiments of this application, the density of the electrolyte has a meaning known in the art and can be detected using equipment and methods known in the art, such as referring to GB / T 2013-2010 for testing.

[0253] In some embodiments, the electrolyte further includes dimethyl carbonate (DMC), wherein the mass content of DMC in the electrolyte is from 15 wt% to 50 wt%, for example, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, or any combination of two of the above values.

[0254] The electrolyte system described above can reduce gas production and improve the long-term cycle reliability of battery cells, even with relatively limited margin.

[0255] In some embodiments, the electrolyte further includes fluoroethylene carbonate, wherein the mass content of fluoroethylene carbonate in the electrolyte is from 1 wt% to 3 wt%, for example, 1 wt%, 2 wt%, 3 wt%, or any combination of two of the above values. Fluoroethylene carbonate can further improve the film-forming stability of the SEI film, enhance the stability of the negative electrode interface, and improve cycle life.

[0256] In some embodiments, the electrolyte further includes ethylene carbonate, wherein the ethylene carbonate content in the electrolyte is from 15 wt% to 30 wt%, for example, 15 wt%, 20 wt%, 30 wt%, or any combination of two of the above values. Ethylene carbonate can further enhance the film-forming properties and high-temperature stability of the electrolyte, improve the stability of the negative electrode interface, and enhance cycle performance.

[0257] In some embodiments, the electrolyte further includes one or more of diethyl carbonate and methyl ethyl carbonate, wherein the total mass content of diethyl carbonate and methyl ethyl carbonate in the electrolyte is 10 wt% to 20 wt%, for example, 10 wt%, 15 wt%, 20 wt%, or any combination of the above data. The combination of these components with dimethyl carbonate can further improve the high-temperature stability of the electrolyte and reduce side reactions at localized high temperatures.

[0258] In some embodiments, the electrolyte may also include carboxylic acid esters. Exemplarily, carboxylic acid ester solvents include one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0259] In some embodiments, the electrolyte further includes lithium bis(fluorosulfonyl)imide, wherein the mass content of lithium bis(fluorosulfonyl)imide in the electrolyte is 1 wt% to 5 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any combination of two of the above data. The addition of lithium bis(fluorosulfonyl)imide can appropriately reduce the amount of lithium hexafluorophosphate used. Lithium bis(fluorosulfonyl)imide has high ionic conductivity, which can effectively improve ion conduction capacity. It is not easily reactive with water, and its decomposition products can optimize the stability of the SEI film, further improving the gas generation phenomenon caused by side reactions, thereby improving the cycle performance of the battery cell.

[0260] In some embodiments, the electrolyte further includes lithium hexafluorophosphate, wherein the mass content of lithium hexafluorophosphate in the electrolyte is 10 wt% to 15 wt%, for example, 10 wt%, 12 wt%, 15 wt%, or any combination of two of the above data. Lithium hexafluorophosphate is beneficial for improving the conductivity of the electrolyte and has good solubility in organic solvents, making the electrolyte system more stable. Its combination with lithium fluorosulfonylimide further enhances long-term reliability.

[0261] This application also provides a method for preparing a single battery cell, comprising:

[0262] Step S10: Provide at least one electrode assembly, the electrode assembly including a positive electrode sheet, an separator and a negative electrode sheet, the separator being disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, and the negative electrode sheet including a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0263] Step S20: Provide a housing, the housing including a shell and an end cap, the shell including a receiving cavity;

[0264] Step S30: Assemble the electrode assembly into the receiving cavity and place the end cap on the housing;

[0265] Step S40: Electrolyte is supplied into the cavity to prepare a battery cell.

[0266] in,

[0267] The capacity of a single battery cell is greater than or equal to 500Ah.

[0268] The electrolyte filling coefficient of the battery cell is 1.5 g / Ah to 4 g / Ah, and the electrolyte includes vinylene carbonate (VC), with the mass content of VC in the electrolyte being 1 wt% to 5 wt%.

[0269] The battery cells prepared according to the embodiments of this application can effectively improve the cycle performance of the battery cells.

[0270] In some implementations, step S10 may include:

[0271] Step S11, provide the initial electrode assembly;

[0272] Step S12: Apply pressure to the initial electrode assembly along the thickness direction of the initial electrode assembly, with a pressure of 30t to 150t.

[0273] The initial electrode assembly includes a positive electrode, an insulator, and a negative electrode. The positive electrode of the initial electrode assembly is basically the same as the positive electrode of the electrode assembly, the insulator of the initial electrode assembly is basically the same as the insulator of the electrode assembly, and the negative electrode of the initial electrode assembly is basically the same as the negative electrode of the electrode assembly.

[0274] After the initial electrode assembly is pressure treated, the gap between the positive electrode plate and the separator is reduced, and the gap between the negative electrode plate and the separator is reduced, thereby reducing the thickness of the initial electrode assembly and forming an electrode assembly. The resulting electrode assembly is relatively thin, which can improve the space utilization of the electrode assembly, reduce excess space, and reduce the introduction of moisture.

[0275] For example, the pressure is 30t, 40t, 50t, 60t, 70t, 80t, 90t, 100t, 110t, 120t, 130t, 140t, 150t, or a range consisting of any two of the above values.

[0276] In some embodiments, the step of providing at least one electrode assembly further includes:

[0277] Step S11, provide the initial electrode assembly;

[0278] Step S13: Heat treatment of the initial electrode assembly. Optionally, the heat treatment temperature is 80°C to 130°C, such as 80°C, 100°C, 110°C, 130°C, or any combination of two of the above values.

[0279] After heat treatment of the initial electrode assembly, the current collector in the electrode assembly has better ductility, which is more conducive to thinning the electrode assembly during the pressurization process. This can improve the space utilization of the electrode assembly, reduce excess space, and reduce the introduction of moisture.

[0280] Step S13 can be performed after step S12.

[0281] [Positive electrode plate]

[0282] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector and including a positive active material. For example, the positive current collector has two sides opposite to each other in its thickness direction, and the positive active material layer is disposed on either or both sides of the positive current collector.

[0283] In some embodiments, the positive electrode active material includes one or more of phosphate-based active materials and transition metal oxides. Optionally, the positive electrode active material includes a phosphate-based active material. The phosphate-based active material has an olivine structure.

[0284] Phosphate-based active materials may include, but are not limited to, one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate, or modified versions of the above. These materials exhibit excellent cycle stability and can improve the lifespan of individual battery cells. Modification includes coating modification or doping modification. In the case of coating modification, a carbon layer can be used for coating. In the case of doping modification, dopant elements can be introduced into the material.

[0285] In some embodiments, lithium phosphates include those with the general formula Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 The material has the following properties: 0.5≤x1≤1.3, 0≤y1≤1.3, 0.5≤x1+y1≤1.3, 0.9≤a1≤1.5, 0≤b1≤0.5, 0.9≤a1+b1≤1.5, 0≤c1≤0.5, 3≤z1≤5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Hf, Ge, and Ce; X includes one or more of Cl, C, and N; and Y includes one or more of O and F.

[0286] Lithium phosphate exhibits excellent stability during cycling, which can improve the lifespan of individual battery cells.

[0287] During the charging and discharging process, active ions such as Li undergo insertion / extraction and consumption, resulting in varying molar Li content in a single battery cell at different discharge states. In the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar Li content represents the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery system. In the embodiments of this application, the molar oxygen content in the examples of positive electrode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 is only a theoretical value. Lattice oxygen release can cause changes in the molar oxygen content; in reality, the molar oxygen content may fluctuate. All of these situations fall within the scope of protection of this application.

[0288] In this application embodiment, the element content in the positive electrode active material has a meaning known in the art and can be detected using equipment and methods known in the art. For example, referring to EPA 6010D-2014, it can be tested by inductively coupled plasma atomic emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After discharging the battery cell to a fully discharged state, the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and then calcined at high temperature to remove impurities. 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. Then it is placed on a plate at 180°C for 30min. After digestion on the plate, the volume is adjusted to 100mL, and quantitative testing is performed using the standard curve method.

[0289] In some embodiments, the positive electrode active material layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, superconducting carbon, conductive graphite, acetylene black, Ketjen black, carbon dots, graphene, and carbon nanofibers. The positive electrode conductive agent can improve the conductivity of the positive electrode active material layer, which is beneficial for improving the fast charging capability of the battery cell.

[0290] Optionally, based on the mass of the positive electrode active material layer, the mass content of the positive electrode conductive agent is less than or equal to 5%. When the mass content of the positive electrode conductive agent is within the above range, it can increase the mass ratio of other substances, such as the positive electrode active material, while improving the conductivity of the positive electrode active material layer, thereby balancing the fast charging capability and energy density of the battery cell.

[0291] In some embodiments, the positive electrode active material layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, the mass content of the positive electrode binder is less than or equal to 5% based on the mass of the positive electrode active material layer.

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

[0293] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. Examples of the metal material layer include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of the polymer substrate include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0294] The positive electrode sheet does not exclude additional functional layers besides the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of this application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of this application further includes a protective layer covering the surface of the positive electrode active material layer.

[0295] [Negative electrode plate]

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

[0297] In some embodiments, the negative electrode active material includes a carbon-based material, which includes graphite particles. The graphite particles exhibit high stability during cycling, thereby improving the lifespan of the battery cell. Exemplarily, the graphite particles include one or more of artificial graphite and natural graphite, with artificial graphite being a preferred option.

[0298] In some embodiments, the negative electrode active material includes a silicon-based material. The introduction of a silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0299] Optionally, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon materials, and silicon-nitrogen materials. These materials have high specific capacity, which is beneficial for improving the energy density of individual battery cells.

[0300] In some embodiments, the negative electrode active material layer further includes a negative electrode binder, which includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass content of the negative electrode binder is less than or equal to 5% based on the total weight of the negative electrode active material layer.

[0301] In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass content of the negative electrode conductive agent is less than or equal to 5% based on the total weight of the negative electrode active material layer.

[0302] In some embodiments, the negative electrode active material layer further includes other additives. As examples, other additives may include thickeners, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of other additives is ≤2% based on the total weight of the negative electrode active material layer.

[0303] The negative electrode active material layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0304] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, the metal material layer may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0305] The negative electrode sheet does not exclude additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode active material layer.

[0306] [Isolation Component]

[0307] In some embodiments, the separator can be a separator membrane. The separator membrane is disposed between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode.

[0308] In some embodiments, the separating membrane comprises a porous base membrane.

[0309] In some embodiments, the base film includes one or more of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0310] Alternatively, the polyolefin includes one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0311] In some implementations, the separator can be a base membrane.

[0312] In some embodiments, the separator further includes a functional layer disposed on at least one side of the base film. The functional layer may include inorganic particles to improve the heat resistance of the separator and enhance the reliability of the battery cells. Optionally, the functional layer is disposed on both sides of the base film. Specifically, the functional layer is disposed on both sides of the base film along the thickness direction of the separator itself.

[0313] For example, the inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. These inorganic particles can improve the heat resistance of the functional layer and enhance the reliability of the battery cell.

[0314] Optionally, the functional layer may further include an adhesive. The adhesive may include one or more of fluorinated adhesives or polyacrylic adhesives. Specifically, the fluorinated adhesive includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. The polyacrylic adhesive includes one or more of polyacrylic acid and fluorinated acrylate resins.

[0315] Electrolyte

[0316] In some implementations, the battery cell includes an electrolyte.

[0317] During the charging and discharging process of a single battery cell, active ions such as lithium ions are inserted and extracted back and forth between the positive and negative electrode plates, and the electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0318] In some implementations, the electrolyte may also include functional additives.

[0319] Adding certain substances, such as additives, to the electrolyte can have a significant impact. Because these additives participate in film formation on the surface of active materials, their content in the electrolyte of a single battery cell varies depending on the formation process, the battery's lifespan, and its storage condition. Therefore, the additive content in freshly prepared electrolyte may differ from that in electrolyte obtained from reverse-engineered batteries. However, those skilled in the art can determine the approximate range of the relevant substances' content in the fresh electrolyte based on the battery cell's performance characteristics (e.g., cycle count) and residual content. Similarly, those skilled in the art can determine the approximate range of the additive content in non-freshly prepared (i.e., reverse-engineered) electrolytes based on the additive content in freshly prepared electrolytes, considering the battery cell's performance requirements and storage environment.

[0320] Therefore, the additive content mentioned in the technical solution of this application can be the content of additives actively added to fresh electrolyte, or the content of residual additives detected by reverse detection based on the actual battery state.

[0321] In the embodiments of this application, the types and contents of inorganic components / lithium salts in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by referring to standards JY / T 0575-2020 "General Rules for Ion Chromatography Analysis" and GB / T 6040-2019 "General Rules for Infrared Spectroscopy Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a fully discharged battery cell (discharged to the discharge cutoff voltage so that the charge state of the battery cell is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be used as a sample for detection.

[0322] In the embodiments of this application, the types and contents of organic components in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T 9722-2023 "General Rules for Gas Chromatography of Chemical Reagents".

[0323] Example

[0324] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0325] Example 1

[0326] 1. Preparation of positive electrode sheet

[0327] The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is disposed on both sides of the positive current collector, which is an aluminum foil.

[0328] The positive electrode active material layer comprises a film layer formed by uniformly coating the surface of the positive electrode current collector with a positive electrode slurry (solvent being N-methylpyrrolidone NMP) and then drying and cold pressing it. The positive electrode active material layer comprises lithium iron phosphate as the positive electrode active material, polyvinylidene fluoride (PVDF) as the binder, and acetylene black as the conductive agent in a weight ratio of 97:2:1.

[0329] 2. Preparation of negative electrode sheet

[0330] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on both sides of the negative electrode current collector, and the negative electrode current collector is copper foil.

[0331] The negative electrode active material layer comprises a film layer formed by uniformly coating the negative electrode slurry (solvent is water) onto the surface of the negative electrode current collector, followed by drying and cold pressing. The negative electrode active material layer comprises artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a mass ratio of 97:0.5:1.5:1.

[0332] 3. Separating membrane

[0333] The separator includes a base film and an alumina ceramic coating disposed on both sides of the base film. The base film is made of polyethylene (PE), the separator has a thickness of 7.5 μm, and the alumina ceramic coating on one side has a thickness of 1 μm.

[0334] 4. Preparation of electrolyte

[0335] The electrolyte consists of organic solvents, lithium salts, and additives.

[0336] The components in an organic solvent are mixed in a mass ratio, and then lithium salt and additives are added to the mixed solvent to prepare an electrolyte.

[0337] Based on the total mass of the electrolyte, the organic solvents include 20 wt% ethylene carbonate EC, 40 wt% dimethyl carbonate DMC, and 20 wt% ethyl methyl carbonate EMC.

[0338] Based on the total mass of the electrolyte, the additives also include 3% vinylene carbonate V and 2% FEC by mass.

[0339] Based on the total mass of the electrolyte, the lithium salt comprises 12 wt% lithium hexafluorophosphate (LiPF6) and 3 wt% lithium bisfluorosulfonylimide (LiFSI).

[0340] 5. Preparation of battery cells

[0341] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus forming an electrode assembly. This assembly is then placed in a housing, with the positive and negative terminals positioned on the housing. After baking, electrolyte is injected (multiple injections may be performed if necessary). Following vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained. The first direction is parallel to the length of the battery cell, and the second direction is parallel to the width of the battery cell.

[0342] Performance testing

[0343] 1. Cycle performance test of individual battery cells

[0344] At 25°C, the battery cells were subjected to charge-discharge cycle tests on a charge-discharge tester. They were charged at a 0.5C rate to the upper limit cutoff voltage, for example, 3.65V, and left to stand for 30 minutes. Then, they were charged at a 0.05C rate to the upper limit cutoff voltage. Finally, they were discharged at a 0.5C rate to the lower limit cutoff voltage, for example, 2.5V, and left to stand for 30 minutes. Then, they were discharged at a 0.05C rate to the lower limit cutoff voltage.

[0345] After allowing the charge and discharge cycles to stand for 30 minutes, calculate the capacity retention rate after each cycle.

[0346] The capacity retention rate after the cycle is: Capacity retention rate after the 10,000th cycle = (Discharge capacity after the 10,000th cycle / Discharge capacity in the first cycle) × 100%.

[0347] The higher the capacity retention rate, the better the cycle performance of the battery cell.

[0348] 2. Battery cell volume expansion test

[0349] Before the cycle test of a single battery cell, the thickness of the battery cell is measured as the initial thickness.

[0350] After a single battery cell has been cycled 10,000 times, the thickness of the battery cell is measured, and this is the thickness after cycling.

[0351] The volume expansion rate of a single battery cell is 100% × (post-cycle thickness - initial thickness) / initial thickness.

[0352] The higher the volume expansion rate of a battery cell, the more gas is produced, and the higher the risk of the battery cell bulging; the lower the volume expansion rate of a battery cell, the less gas is produced, and the higher the reliability of the battery cell.

[0353] Comparative Example 1-1, Comparative Example 1-2, Example 1-1 and Example 1-2

[0354] Battery cells were prepared using a method similar to that of Example 1, except that the liquid injection coefficient was adjusted.

[0355] The test results are shown in Table 1.

[0356] Table 1

[0357] If the liquid injection coefficient is too low, such as in Comparative Example 1-1, the electrode assembly may not be sufficiently wetted, its capacity may not be fully utilized, and it may lead to local lithium plating and cycle failure.

[0358] When the electrolyte injection coefficient is too high, such as in Comparative Examples 1-2, a relatively large volume of receiving cavity is usually required. When the volume of the receiving cavity is basically the same as in Example 1, as the electrolyte injection coefficient increases excessively, there is a risk of electrolyte overflow. Moreover, it increases the thickness of the solid electrolyte interface film on the surface of the negative electrode, increases the impedance, deteriorates the cycle, and causes the cycle to drop.

[0359] The electrolyte injection coefficients of Examples 1, 1-1, and 1-2 are between 1.5 and 4 g / Ah. The battery cells have basically the same capacity and volumetric energy density. Moreover, the required cavity volume for the battery cells is not too high, minimizing excess space, thereby reducing the water content in the cavity, weakening side reactions, and improving the cycle performance of the battery cells. Furthermore, the addition of an appropriate amount of vinylene carbonate can further improve the stability of the negative electrode interface, reduce gas production, reduce the volume expansion rate of the battery cells, and improve the cycle performance of the battery cells.

[0360] Comparative Example 2-1, Comparative Example 2-2, Examples 2-1 to 2-3

[0361] Battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 was that the additives and dimethyl carbonate content of the electrolyte in Example 2-1 were adjusted; for example,

[0362] If the mass content of the additive increases by N%, the mass content of dimethyl carbonate decreases by N%.

[0363] If the mass content of the additive decreases by N%, the mass content of dimethyl carbonate increases by N%.

[0364] The test results are shown in Table 2.

[0365] Table 2

[0366] In Table 2, VC represents vinylene carbonate; FEC represents fluoroethylene carbonate; and DMC represents dimethyl carbonate.

[0367] The battery cells in the various embodiments and comparative examples in Table 2 have basically the same capacity and volumetric energy density.

[0368] When the content of vinylene carbonate (VC) is too low, or even when VC is not added to the electrolyte (e.g., in Comparative Example 2-1), the side reactions on the negative electrode side are severe, resulting in significant gas production. Furthermore, the hydrofluoric acid in the system continuously corrodes the negative electrode current collector, worsening the cycle and causing a cycle failure. Even if the electrolyte includes a certain amount, such as 2 wt% FEC, the interfacial stability of the negative electrode remains poor when VC is not present, leading to severe side reactions on the negative electrode side.

[0369] Excessive VC content in vinylene carbonate, such as in Comparative Example 2-2, increases the impedance of the SEI film on the negative electrode side, potentially worsening cycling and increasing the volume expansion rate.

[0370] Lithium hexafluorophosphate generates hydrofluoric acid (HF) in the electrolyte system, which corrodes the negative electrode current collector. In the embodiments of this application, under an appropriate range of electrolyte injection coefficient, an appropriate amount of vinylene carbonate (VC) is added, so that the absolute mass of VC is within an appropriate range. VC can effectively neutralize hydrofluoric acid and form a dense SEI film on the negative electrode side, effectively protecting the negative electrode, improving the stability of the negative electrode interface, reducing gas generation, reducing the volume expansion rate of the battery cell, and improving the cycle performance of the battery cell.

[0371] When the electrolyte includes vinylene carbonate and fluoroethylene carbonate, it can also effectively improve the stability of the negative electrode interface and improve the cycle.

[0372] Examples 3-1 to 3-5

[0373] Battery cells were prepared using a method similar to that of Example 1, except that the electrolyte formulation was adjusted, as shown in Table 3.

[0374] Table 3

[0375] In Table 3, LiPF6 represents lithium hexafluorophosphate and LiFSI represents lithium difluorosulfonylimide.

[0376] In Table 3, the capacity of each embodiment is basically the same as that of Embodiment 1, and the energy density of each embodiment is basically the same as that of Embodiment 1.

[0377] The electrolyte in Example 1 has a density of 1.3 g / mL at room temperature.

[0378] The electrolyte in Examples 3-3 has a density of 1.28 g / mL at room temperature.

[0379] In Example 1, the mass content of dimethyl carbonate is within a certain range. Combined with a certain range of ethylene carbonate and ethyl methyl carbonate, it can effectively improve the high-temperature stability of the battery cell, reduce local side reactions at high temperatures, reduce gas production, and improve the cycle performance of the battery cell.

[0380] The addition of lithium bis(fluorosulfonyl)imide can appropriately reduce the amount of lithium hexafluorophosphate. Lithium bis(fluorosulfonyl)imide has high ionic conductivity, which can effectively improve ion conduction. It is not easily reacted with water, and its decomposition products can optimize the stability of the SEI film, further improve the gas generation phenomenon caused by side reactions, and thus improve the cycle performance of the battery cell.

[0381] Example 4-0

[0382] Battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 is that the dimensions of the battery cells were adjusted. The length of the battery cell casing was 270 mm, the thickness of the battery cell was 70 mm, the width of the casing was 200 mm, and the capacity of the battery cell was 510 Ah.

[0383] Examples 4-1 and 4-2

[0384] The battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 is that the size of the battery cells was adjusted, and the projected area of ​​the electrode assembly along the width direction of the battery cells was adjusted accordingly.

[0385] Example 4-3

[0386] The battery cells were prepared using a method similar to that of Example 1. The difference from Example 1 is that the size of the battery cells and the thickness of the electrode assembly were adjusted, and the projected area of ​​the electrode assembly along the width direction of the battery cells was adjusted accordingly.

[0387] Examples 4-4 and 4-5

[0388] The battery cell was prepared using a method similar to that in Example 1. The thickness of the electrode assembly was basically the same as in Example 1. The difference from Example 1 was that the dimensions of the electrode assembly along the length of the battery cell were adjusted, and the projection area of ​​the electrode assembly along the width of the battery cell was adjusted accordingly.

[0389] Examples 4-6 and 4-7

[0390] The battery cell was prepared using a method similar to that in Example 1. The dimensions of the electrode assembly along the length of the battery cell were basically the same as in Example 1. The difference from Example 1 was that the thickness of the electrode assembly was adjusted, and the projection along the width of the battery cell was adjusted accordingly, as was the projected area of ​​the electrode assembly.

[0391] The test results are shown in Table 4.

[0392] Table 4

[0393] In Example 1,

[0394] The projected area S of the cavity along the second direction T 19656mm 2 The thickness H of the cavity T The diameter is 72mm, and the volume of the cavity is V. T 4108cm 3 ,

[0395] The battery cell includes four electrode components, each with a projected area of ​​4493 mm² along the second direction. 2 The total projected area S of the four electrode components along the second direction J 17972mm 2 The total volume V of the four electrode assemblies J 3576cm 3 The thickness of each electrode assembly is 16.14 mm, and the total thickness H of the four electrode assemblies is... J It is 64.56mm. Calculations show that V... T -V J It is 532cm 3 .

[0396] In Example 4-3, V T -V J 2827cm 3 .

[0397] If the length of a single battery cell is too short, such as in Comparative Example 4-1, the capacity of the single battery cell will be too low, failing to meet the requirements for long cycle life.

[0398] Increasing the length of the battery cell, i.e., increasing the length of the casing, is beneficial for increasing the capacity of the battery cell. In a high-capacity system, with appropriate extra space, i.e. (S T -S J ) / S T Within an appropriate range, and / or V T -V J Within an appropriate range, and / or H J / H T Within an appropriate range, it can leave suitable margins for the system during long-term cycling, thereby improving the cycle performance of individual battery cells.

[0399] Examples 5-1 and 5-2

[0400] Battery cells were prepared using a method similar to that of Example 1, except that the compaction density of the positive and negative electrodes was adjusted.

[0401] In Example 5-1, in the cross-section along the thickness direction of the positive electrode sheet, the positive electrode active material layer satisfies: D A 90 is 2000nm, (D A 90-D A 10) / D A 50 is 2.25;

[0402] In Example 5-2, the particle size of the positive electrode active material layer is basically the same as that of the particles in Example 1.

[0403] Example 5-3

[0404] Battery cells were prepared using a method similar to that of Example 1, except that the coating weight on one side of the positive and negative electrodes was adjusted.

[0405] The test results are shown in Table 5.

[0406] Table 5

[0407] In Example 1, in the cross-section along the thickness direction of the positive electrode sheet, the positive electrode active material layer satisfies: D A 90 is 1500nm, (D A 90-D A 10) / D A 50 is 1.93.

[0408] Within a certain range, the compaction density of the positive and negative electrode active material layers decreases. Although the capacity of the battery cell decreases moderately as the compaction density decreases, it is more conducive to cycling and reduces gas production. However, due to the reduction in the excess space in the battery cell, the volume expansion rate may increase moderately.

[0409] Therefore, setting the compaction density of the positive electrode active material layer within an appropriate range can effectively balance high capacity, excellent cycle performance, and low volume expansion rate.

[0410] Within a certain range, the single-sided coating weight of the positive and negative electrode active material layers decreases. Although the capacity of the battery cell decreases moderately as the single-sided coating weight decreases, it is more conducive to cycling, reduces gas production, and increases the excess space in the battery cell, which helps to reduce the increase in volume expansion rate.

[0411] Therefore, by setting the single-sided coating weight of the positive electrode active material layer within an appropriate range, it is possible to effectively balance high capacity, excellent cycle performance, and low volume expansion rate.

[0412] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A single battery cell, comprising: An outer casing includes a housing and an end cap, the housing including a receiving cavity, and the end cap covering the housing; Electrolyte is disposed within the receiving cavity; as well as At least one electrode assembly is disposed within the receiving cavity. The electrode assembly includes a positive electrode, an separator, and a negative electrode. The separator is disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. in, The capacity of the battery cell is greater than or equal to 500Ah. The electrolyte of the battery cell is 1.5 g / Ah to 4 g / Ah, and the electrolyte includes vinylene carbonate, the mass content of which is 1 wt% to 5 wt%.

2. The battery cell according to claim 1, wherein, The capacity of the individual battery cells ranges from 500Ah to 3000Ah.

3. The battery cell according to claim 1 or 2, wherein, The capacity of the battery cell is 550Ah to 700Ah, or The capacity of the battery cell is 800Ah to 1200Ah, or The capacity of the battery cell is between 2000Ah and 3000Ah.

4. The battery cell according to any one of claims 1 to 3, wherein, The electrolyte injection coefficient of the battery cell is from 2.5 g / Ah to 4 g / Ah.

5. The battery cell according to any one of claims 1 to 4, wherein, The vinylene carbonate (VC) in the electrolyte contains 1.5 wt% to 4.5 wt% by mass.

6. The battery cell according to any one of claims 1 to 5, wherein, The housing has a dimension of 270 mm or more along the first direction. The first direction, the second direction, and the thickness direction of the battery cell are perpendicular to each other. The second direction is parallel to the direction from the housing to the end cap.

7. The battery cell according to claim 6, wherein, The dimensions of the housing along the first direction are 270 mm to 800 mm.

8. The battery cell according to any one of claims 1 to 7, wherein, The thickness of the battery cell is 70mm to 120mm.

9. The battery cell according to any one of claims 1 to 8, wherein, The housing has a dimension of 200 mm to 300 mm along a second direction, which is parallel to the direction from the housing toward the end cap.

10. The battery cell according to any one of claims 1 to 9, wherein, The battery cell satisfies: 6% ≤ (S) T -S J ) / S T ≤13%; S T This indicates the projected area of ​​the receiving cavity projected along a second direction, which is parallel to the direction from the housing to the end cap; S J This indicates the total projected area of ​​the at least one electrode assembly when the battery cell is fully discharged and projected along the second direction.

11. The battery cell according to any one of claims 1 to 10, wherein, The battery cell satisfies: 88% ≤ H J / H T ≤92%; H T This indicates the dimension of the receiving cavity along the thickness direction of the battery cell; H J This refers to the total dimension of the at least one electrode assembly along the thickness direction of the battery cell when the battery cell is fully discharged.

12. The battery cell according to any one of claims 1 to 11, wherein, The battery cell meets the following requirement: 250cm 3 ≤V T -V J ≤2900cm 3 , V T This indicates the volume of the receiving cavity; V J This refers to the total volume of the at least one electrode assembly when the battery cell is fully discharged.

13. The battery cell according to any one of claims 1 to 12, wherein, The electrode assembly comprises at least two electrodes, which are stacked along the thickness direction of the battery cell.

14. The battery cell according to any one of claims 1 to 13, wherein, The electrode assembly comprises at least four electrodes.

15. The battery cell according to any one of claims 1 to 14, wherein, When the battery cell is fully discharged, the thickness of each electrode assembly is 15mm to 18mm.

16. The battery cell according to any one of claims 1 to 15, wherein, The positive electrode sheet includes a positive flat section, and the negative electrode sheet includes a negative flat section. The positive flat section and the negative flat section are stacked along the thickness direction of the battery cell. The electrode assembly includes 40 to 60 positive flat sections.

17. The battery cell according to any one of claims 1 to 16, wherein, The compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 ; and / or the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 2.5g / cm 3 .

18. The battery cell according to any one of claims 1 to 17, wherein, The compaction density of the positive electrode active material layer is 2.4 g / cm³. 3 Up to 3.0 g / cm 3 .

19. The battery cell according to any one of claims 1 to 18, wherein, The single-sided coating weight of the positive electrode active material layer is 0.28g / 1540.25mm. 2 Up to 0.40g / 1540.25mm 2 .

20. The battery cell according to any one of claims 1 to 19, wherein, The single-sided coating weight of the negative electrode active material layer is 0.12g / 1540.25mm. 2 Up to 0.18g / 1540.25mm 2 .

21. The battery cell according to any one of claims 1 to 20, wherein, The thickness of the insulating element is 3 μm to 8 μm.

22. The battery cell according to any one of claims 1 to 21, wherein, The positive electrode active material layer includes a phosphate-based active material, and in a cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy the following: D A 90 is from 1400nm to 2100nm, D A 90 represents the particle size at which the cumulative area distribution of the particles reaches 90%; and / or (D A 90-D A 10) / D A 50 ranges from 1.855 to 2.375, D A 90 represents the particle size (D) at which the cumulative area distribution of the particles reaches 90%. A 50 represents the particle size (D) corresponding to a cumulative area distribution of 50%. A 10 indicates the particle size at which the cumulative area distribution of the particles reaches 10%.

23. The battery cell according to any one of claims 1 to 22, wherein, The electrolyte has a density of 1.2 g / mL to 1.5 g / mL.

24. The battery cell according to any one of claims 1 to 23, wherein, The electrolyte also includes dimethyl carbonate, wherein the mass content of dimethyl carbonate in the electrolyte is from 15 wt% to 50 wt%.

25. The battery cell according to any one of claims 1 to 24, wherein, The electrolyte also includes lithium bisfluorosulfonylimide, wherein the lithium bisfluorosulfonylimide in the electrolyte has a mass content of 1 wt% to 5 wt%.

26. The battery cell according to any one of claims 1 to 25, wherein, The electrolyte also includes fluoroethylene carbonate, wherein the fluoroethylene carbonate content in the electrolyte is 1 wt% to 3 wt%.

27. A method for preparing a battery cell, comprising: At least one electrode assembly is provided, the electrode assembly including a positive electrode, an separator and a negative electrode, the separator being disposed between the positive electrode and the negative electrode, the positive electrode including a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, and the negative electrode including a negative current collector and a negative active material layer disposed on at least one side of the negative current collector; A housing is provided, the housing including a shell and an end cap, the shell including a receiving cavity; The electrode assembly is assembled into the receiving cavity, and the end cap is placed on the housing; Electrolyte is supplied into the cavity to prepare a battery cell. in, The capacity of the battery cell is greater than or equal to 500Ah. The electrolyte of the battery cell is 1.5 g / Ah to 4 g / Ah, and the electrolyte includes vinylene carbonate, the mass content of which is 1 wt% to 5 wt%.

28. The method according to claim 27, wherein, The step of providing at least one electrode assembly further includes: Provide initial electrode assembly; Pressure is applied to the initial electrode assembly along its thickness direction, the pressure being 30t to 150t.

29. The method according to claim 27 or 28, wherein, The step of providing at least one electrode assembly further includes: Provide initial electrode assembly; The initial electrode assembly is heat-treated, optionally at a temperature of 80°C to 130°C.

30. A battery device comprising a battery cell according to any one of claims 1 to 26, or a battery cell prepared by the method according to any one of claims 27 to 29.

31. An electrical device comprising the battery device according to claim 30.

32. An energy storage device comprising the battery device according to claim 30.

33. An energy storage system comprising the energy storage device according to claim 32.

Images