Battery cell, battery device, electric device, energy storage device, and energy storage system

Abstract

The present application relates to a battery cell, a battery device, an electric device, an energy storage device, and an energy storage system. The battery cell comprises a housing and an electrode assembly, wherein the electrode assembly comprises a main body portion and a tab portion connected to the main body portion; the capacity of the battery cell is greater than or equal to 500 Ah, and the size of the housing in a first direction is greater than or equal to 270 mm; and the battery cell satisfies the following equation: 6%≤(ST-SJ) / ST≤13%, wherein ST denotes the projection area of an accommodating cavity of the housing in a second direction, and SJ denotes the total projection area of at least one electrode assembly in the second direction when the battery cell is in a fully discharged state. The present application can improve the energy density, cycle performance and use reliability of the battery cell.

Description

Battery cells, 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, 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 improved energy density, cycle performance, and reliability. Summary of the Invention

[0005] This application provides a battery cell, a battery device, an electrical device, an energy storage device, and an energy storage system, which can improve the energy density, cycle performance, and reliability 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, and the electrode assembly includes a main body and a tab portion. The tab portion is connected to and extends beyond the main body portion, and the tab portion includes a first tab and a second tab, one of which is a positive tab and the other a negative tab.

[0007] The capacity of a single battery cell is greater than or equal to 500Ah.

[0008] The dimension of the housing along the first direction is greater than or equal to 270 mm;

[0009] The battery cell must satisfy: 6% ≤ (S) T -S J ) / S T ≤13%;

[0010] S T This represents the projected area of ​​the cavity projected along the second direction.

[0011] S J This indicates that the total projected area of ​​at least one electrode assembly is the battery cell in its fully discharged state, projected along the second direction; wherein 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 main body to the tab.

[0012] The battery cells in this embodiment employ a relatively long casing size to achieve a high-capacity system. High-capacity battery cells may face the problem of increased gas production, while the battery cells satisfy 6% ≤ (S) T -S J ) / S T The allowance of ≤13% ensures adequate internal space for the battery cell, providing reasonable gas storage space while accommodating high-capacity electrode components. This reduces the risk of battery cell swelling and improves the electrical performance and reliability of the battery cell during normal operation. Furthermore, this extra space provides a reasonable cross-sectional area for the exhaust channel, allowing for smooth exhaust in case of abnormal situations such as thermal runaway. By achieving a reasonable balance between the weight of the battery cell and the estimated amount of gas produced, the safety of the battery cell is further improved.

[0013] 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.

[0014] In some implementations, the capacity of a single battery cell is between 550 Ah and 700 Ah. When the capacity of a single battery cell is within this range, combined with an appropriate range of margin and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[0015] In some implementations, 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 margin and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[0016] In some implementations, 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 margin and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[0017] In some embodiments, the housing has a dimension of 270 mm to 800 mm along the first direction.

[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 dimensions of the casing along the second direction are 200 mm to 300 mm. When the dimensions of the casing along the second direction are 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: 88% ≤ H J / H T ≤92%; H T Indicates the dimension of the receiving cavity along the thickness direction of the battery cell; 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.

[0022] When a battery cell meets the above conditions, the electrode assembly occupies an appropriate amount of space in the thickness direction. In addition to providing high capacity, it can also provide reserved expansion space for volume expansion during the charging process, reducing the risk of battery cell bulging or even casing rupture, and improving the reliability of battery cell in long-term cycle use.

[0023] In some embodiments, the surface of the connecting body portion of the first electrode tab is the first electrode tab surface, and the ratio of the dimension of the first electrode tab surface along the first direction to the dimension of the housing along the first direction is 0.176 to 0.432.

[0024] The ratio of the tab size to the housing size in the embodiments of this application is within an appropriate range, which can improve the problem of uneven current density distribution, thereby reducing heat generation, improving temperature unevenness, weakening the degree of side reactions, thereby reducing gas generation, and improving reliability and cycle performance.

[0025] In some embodiments, when the battery cell is fully discharged, the ratio of the dimension of the first tab surface along the first direction to the dimension of the main body along the first direction is 0.179 to 0.440.

[0026] When a battery cell meets the above conditions, its cycle performance and reliability can be improved.

[0027] In some embodiments, when the battery cell is fully discharged, the ratio of the length of the first tab to the thickness of the main body is 1.2 to 2.3.

[0028] When a battery cell meets the above conditions, its cycle performance and reliability can be improved.

[0029] In some embodiments, the thickness of the positive electrode tab is 10 μm to 20 μm. When the thickness of the positive electrode tab is within the above range, it can effectively improve the overcurrent capacity of the battery cell, reduce heat generation, and improve the cycle performance and reliability of the battery cell.

[0030] In some embodiments, the thickness of the negative electrode tab is 4 μm to 8 μm. When the thickness of the negative electrode tab is within the above range, it can effectively improve the overcurrent capacity of the battery cell, reduce heat generation, and improve the cycle performance and reliability of the battery cell.

[0031] In some embodiments, the size of the first electrode tab decreases along the first direction from the main body portion to the electrode tab portion.

[0032] The above configuration results in a smaller overall volume of the first tab, which reduces the risk of the first tab obstructing gas flow and the risk of gas flowing away from the end cap and remaining in the main body. This results in better ion and electron conduction performance in the main body, reduces the internal resistance of the main body, thereby reducing heat generation, reducing gas generation, and improving the reliability of the battery cell.

[0033] In some embodiments, the surface of the connecting body portion of the second electrode tab is the second electrode tab surface, and the ratio of the dimension of the second electrode tab surface along the first direction to the dimension of the housing along the first direction is 0.176 to 0.432.

[0034] In some implementations, the thickness of each electrode assembly is 15 mm to 18 mm when the battery cell is fully discharged.

[0035] In some embodiments, the battery cell further includes a first electrode terminal and a first adapter. The first electrode terminal is disposed on the end cap, and the first adapter connects the first electrode terminal and the first tab. Along a first direction, the first adapter extends beyond the first tab, and the size difference between the first adapter and the first tab is 5mm to 30mm.

[0036] The above configuration can improve the connection stability between the first adapter and the first electrode, and the current-carrying capacity between the first adapter and the first electrode is excellent, reducing internal resistance and heat generation, thereby reducing gas generation and improving the cycle performance of the battery cell.

[0037] In some embodiments, the distance between the geometric center of the first adapter and the geometric center of the first tab along the first direction is less than or equal to 2 mm.

[0038] The above configuration can reduce the resistance between the first adapter and the first tab, reduce heat generation, thereby reducing gas generation and improving the cycle performance of the battery cell.

[0039] In some embodiments, the battery cell further includes a pressure relief mechanism, which is disposed on the end cap and projected along the second direction, with a projected area of ​​200 mm². 2 Up to 3800mm 2 .

[0040] When the projected area of ​​the pressure relief mechanism is within the above range, it is less likely to be blocked by molten metal beads, which can improve the reliability of the battery cell during the pressure relief process.

[0041] In some embodiments, the main body includes a positive electrode portion, which 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. The positive electrode tab is connected to and extends out of the positive electrode current collector. The positive electrode active material layer includes a phosphate-based active material.

[0042] The aforementioned materials exhibit excellent cycle stability, which can improve the cycle performance of individual battery cells.

[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 A90 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 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.

[0048] 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 .

[0049] 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.

[0050] In some embodiments, the main body further includes a negative electrode portion, which 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. The negative electrode tab is connected to and extends beyond the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 2.5g / cm 3 .

[0051] 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.

[0052] 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 .

[0053] 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.

[0054] In some embodiments, the electrolyte includes vinylene carbonate, and the mass content of vinylene carbonate in the electrolyte is from 1 wt% to 5 wt%.

[0055] When the mass content of vinylene carbonate is within an appropriate range, 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.

[0056] In some embodiments, the electrolyte also includes fluoroethylene carbonate, wherein the fluoroethylene carbonate content in the electrolyte is 1 wt% to 3 wt%.

[0057] Fluorinated ethylene carbonate can further improve the film-forming stability of the SEI film, enhance the stability of the negative electrode interface, and improve cycle life.

[0058] 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%.

[0059] The electrolyte system described above can reduce gas production and improve the cycle performance and reliability of individual battery cells.

[0060] 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%. 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 improve the gas generation phenomenon caused by side reactions, thereby improving the cycle performance of the battery cell.

[0061] Secondly, this application proposes a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this application.

[0062] Thirdly, this application proposes an electrical device, which includes the battery device according to any embodiment of the second aspect of this application.

[0063] Fourthly, this application proposes an energy storage device, which includes the battery device according to any embodiment of the second aspect of this application.

[0064] Fifthly, this application proposes an energy storage system, which includes an energy storage device according to any embodiment of the fourth aspect of this application. Attached Figure Description

[0065] 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.

[0066] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application.

[0067] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application.

[0068] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application.

[0069] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application.

[0070] Figure 5 is an exploded view of a battery cell provided in some embodiments of this application.

[0071] Figure 6 is a schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application.

[0072] Figure 7 is a schematic diagram showing the unfolded positive electrode portion and the first electrode tab of a battery cell provided in some embodiments of this application.

[0073] Figure 8 is a cross-sectional view of a battery cell along the thickness direction provided in some embodiments of this application.

[0074] Figure 9 is a schematic diagram of the structure of a battery cell provided in some other embodiments of this application.

[0075] Figure 10 is a schematic diagram of the structure of a battery cell electrode assembly provided in some other embodiments of this application.

[0076] The accompanying drawings may not be drawn to scale.

[0077] 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; 101, main body section; 102, tab section; 1021, first tab; 10211, first tab surface; 1022, second tab; 11, positive electrode section; 111, straight section of positive electrode; 112, bent section of positive electrode; 12, negative electrode section; 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, first electrode terminal; 32, second electrode terminal; 41. First adapter; 42. Second adapter; 220. Pressure relief mechanism; 221. Recess; 222. Weak part. Detailed Implementation

[0078] 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.

[0079] 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.

[0080] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0081] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0082] 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.

[0083] 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.

[0084] 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 storage and use of battery cells, side reactions inevitably occur at the positive and negative electrode interfaces, resulting in gas production. If the gas production is too high or the internal space of the battery cell is insufficient, it may cause problems such as battery cell swelling or even casing rupture, leading to reliability issues.

[0085] Research has found that the main reasons for gas production are as follows: Firstly, during the normal charging and discharging process of a battery cell, the current generated on the current collector will converge to the electrode or diffuse from the electrode to the current collector. Since the length of the current collector is much greater than that of the electrode, there will be a drastic change in current density at the junction of the current collector and the electrode. This results in an excessively high current density near the electrode and a lower current density far from the electrode, which in turn leads to a higher temperature near the electrode. This can cause local heat generation and local heat concentration, exacerbate local side reactions, and increase the amount of gas produced.

[0086] On the other hand, large-capacity battery cells usually suffer from poor heat dissipation, which further exacerbates the side reactions of the battery cells, thereby generating more gas.

[0087] To improve the energy density of a single battery cell, the casing size is usually increased in related technologies. However, when the length of the battery cell is long, uneven current density distribution is more likely to occur along the length of the cell. This problem can exacerbate local heat generation and local heat concentration, easily triggering more side reactions, leading to increased gas production, and causing abnormal situations such as thermal runaway.

[0088] The battery cells in this application satisfy 6% ≤ (S) T -S J ) / S T A gas density of ≤13% can ensure reasonable gas storage space, mitigate battery cell expansion, and improve the electrical performance and reliability of the battery cell during normal operation. On the other hand, it can ensure reasonable exhaust channel cross-sectional area and battery cell weight, so that in abnormal situations such as thermal runaway, gas can be discharged more smoothly and the weight of the battery cell itself and the estimated amount of gas produced can reach a reasonable balance point, thereby improving the safety of the battery cell.

[0089] Furthermore, by ensuring that the dimensions of the tabs and battery cells meet the numerical range of 0.176 to 0.432, this application can improve the problem of uneven current density distribution, improve the problem of uneven temperature, mitigate side reactions and the resulting gas generation problems, thereby improving the reliability of battery cells.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] As an example, the power distribution unit can be used to distribute power to the power modules of the energy storage device.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] The battery pack 2 includes a housing and one or more battery cell assemblies, which are housed within the housing.

[0110] 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.

[0111] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] A single battery cell can be the smallest unit that makes up a battery device.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] Optionally, the battery cell 7 also includes a positive terminal and a negative terminal, both of which can be disposed on the end cap 22. The positive and negative terminals can be used to electrically connect with the electrode assembly 10 for outputting or inputting electrical energy into the battery cell 7.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] In some embodiments, the positive electrode can be a positive electrode plate. In some embodiments, the negative electrode can be a negative electrode plate.

[0129] As shown in Figures 4 to 7, in some embodiments, the battery cell 7 includes a housing 20, at least one electrode assembly 10, and an electrolyte. The housing 20 includes a shell 21 and an end cap 22. The shell 21 includes a receiving cavity 210, and the end cap 22 covers the shell 21. The electrolyte and at least one electrode assembly 10 are disposed within the receiving cavity 210. The electrode assembly 10 includes a main body portion 101 and a tab portion 102. The tab portion 102 is connected to and extends out of the main body portion 101. The tab portion 102 includes a first tab 1021 and a second tab 1022. One of the first tab 1021 and the second tab 1022 is a positive tab, and the other is a negative tab.

[0130] The capacity of battery cell 7 is greater than or equal to 500Ah.

[0131] The dimension of the housing 21 along the first direction is greater than or equal to 270 mm.

[0132] Battery cell 7 satisfies: 6% ≤ (S) T -S J ) / S T ≤13%;

[0133] S T This indicates the projected area of ​​the cavity 210 projected along the second direction;

[0134] S J This indicates the total projected area of ​​at least one electrode assembly 10 when the battery cell 7 is fully discharged and projected along the second direction.

[0135] The first direction, the second direction, and the thickness direction of the battery cell 7 are perpendicular to each other, and the second direction is parallel to the direction from the main body 101 to the tab 102.

[0136] 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.

[0137] When the capacity of the battery cell 7 is greater than or equal to 500Ah, and can be selected from 500Ah to 3000Ah, the capacity of the embodiment of this application is relatively high. Adapting the relatively long casing 21 to the high-capacity system may lead to increased gas production in the high-capacity battery cell 7, while the battery cell 7 satisfies 6% ≤ (S T -S J ) / S T The allowance of ≤13% ensures adequate internal space for the battery cell 7. This allows for the storage of gas while accommodating the high-capacity electrode assembly 10, reducing the risk of bulging in the battery cell 7 and improving its electrical performance and reliability during normal operation. Furthermore, this allowance provides a reasonable cross-sectional area for the exhaust channel, enabling smooth exhaust in the event of thermal runaway or other abnormal conditions in the battery cell 7. By achieving a reasonable balance between the weight of the battery cell 7 and the estimated amount of gas produced, the safety of the battery cell 7 is further improved.

[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, with an appropriate range of margin and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[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, with an appropriate range of spare space and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[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, with an appropriate range of spare space and tab ratio, it can effectively balance high energy density, cycle performance, and reliability.

[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 main body 101 to the tab 102, 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 surface of the connecting body 101 of the first tab 1021 is a first tab surface 10211, and the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the housing 21 along the first direction Z is 0.176 to 0.432. Z is shown in Figure 7. 11 This indicates the dimension of the first electrode tab 10211 along the first direction Z. 11 / Z0 represents the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the housing 21 along the first direction Z.

[0154] When the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the housing 21 along the first direction Z is within the above-mentioned range, the ratio will not be too low, which can reduce the current density at the tab, help the current to be evenly distributed in the main body 101, homogenize the current density, reduce local heat, thereby weakening side reactions, reducing gas production, and improving the cycle performance and reliability of the battery cell 7; moreover, the ratio will not be too high, which can reduce the weight of mechanical structural components, so that the weight energy density of the battery cell 7 will not be too low; and it will reduce the risk of the tab forming molten beads that block the pressure relief mechanism, thereby improving the reliability of the battery cell.

[0155] For example, the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the housing 21 along the first direction Z is 0.176, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.355, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.432 or any two of the above values.

[0156] 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.

[0157] 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. 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.

[0158] 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.

[0159] 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.

[0160] 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:

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] As shown in Figure 6, in some embodiments, the battery cell 7 satisfies: 6% ≤ (S T -S J ) / S T ≤13%;

[0167] S T This represents the projected area of ​​the cavity 210 projected along the second direction Y.

[0168] 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.

[0169] 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.

[0170] 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 8 shows S... J S T area.

[0171] 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.

[0172] 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.

[0173] (S T -S J ) / S T If the size is too small, the space occupied by the electrode assembly 10 increases, and the capacity of the battery cell 7 increases; however, if the extra space is too small, the risk of the battery cell 7 bulging or even cracking increases.

[0174] (S T -S J ) / S T If the size is too large, there will be too much excess space, resulting in a low capacity and low energy density of the battery cell 7.

[0175] (S T -S J ) / S T Within an appropriate range, it can provide high capacity for battery cell 7, and also cooperate with gas generation within the system to reserve storage space for gas generation, reduce the risk of battery cell 7 swelling, and improve the reliability of battery cell 7.

[0176] For example, (S T -S J ) / S T The percentage is 6%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, or a range consisting of any two of the above values.

[0177] In some implementations, the battery cell 7 satisfies: 88% ≤ H J / H T ≤92%;

[0178] H T This indicates the dimension of the receiving cavity 210 along the thickness direction X of the battery cell 7 when the battery cell 7 is fully loaded; Figure 8 shows H. T ;

[0179] 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 8; H is shown in Figure 8. J .

[0180] 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.

[0181] 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.

[0182] When the battery cell 7 meets the above conditions, the electrode assembly 10 occupies an appropriate space in the thickness direction X. In addition to providing high capacity, it can also provide reserved expansion space for volume expansion during the charging process, reduce the risk of the battery cell 7 bulging or even the casing 21 cracking, and improve the reliability of the battery cell 7.

[0183] 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.

[0184] 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.

[0185] In some embodiments, there is at least one electrode assembly 10, which may optionally be at least two. 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.

[0186] In some embodiments, when the battery cell 7 is fully discharged, the thickness of each electrode assembly 10 is 15mm to 18mm, for example, 15mm, 15.5mm, 16mm, 16.5mm, 17mm, 17.5mm, 18mm, or any combination of two of the above values. Figure 8 shows H... J0 This indicates the thickness of each electrode assembly 10.

[0187] 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 and increasing the energy density of battery cells 7.

[0188] In some embodiments, when the battery cell 7 is fully discharged, the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the main body 101 along the first direction Z is 0.179 to 0.440. Figure 6 shows Z2 representing the dimension of the main body 101 along the first direction Z. 11 / Z2 represents the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the main body 101 along the first direction Z.

[0189] When the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the main body 101 along the first direction Z is within the above range, the current density at the tab can be reduced, which helps the current to be evenly distributed in the main body 101, reduces the heat generated, thereby reducing gas production and improving the cycle performance and reliability of the battery cell 7.

[0190] Furthermore, the first tab 1021 of the aforementioned dimensions will not significantly impede gas diffusion to the end cap 22, which is beneficial for gas release from the main body 101 and reduces the likelihood of localized excessive gas pressure causing reliability issues.

[0191] For example, the ratio of the dimension of the first tab surface 10211 along the first direction Z to the dimension of the main body portion 101 along the first direction Z is 0.179, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.355, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.440 or any two of the above values.

[0192] In some embodiments, when the battery cell 7 is in its fully loaded state, the ratio of the length of the first tab 1021 in its unfolded state to the thickness of the main body 101 is 1.2 to 2.3.

[0193] The first tab 1021 can be either a bent structure or a non-bent structure. When the first tab 1021 is a bent structure, after unfolding and laying the first tab 1021 flat, the dimension of the first tab 1021 along its own length direction is measured, that is, the length of the first tab 1021.

[0194] When the ratio of the length of the first tab 1021 to the thickness of the main body 101 meets the above range, the electron transport path on the first tab 1021 will not be too long, resulting in relatively small internal resistance, which will not increase heat generation and reduce the amount of gas generated by the side reaction.

[0195] Furthermore, the first electrode tab 1021 will not be too long, reducing the risk of the first electrode tab 1021 being inserted backward into the main body 101, which could lead to a local short circuit between the positive and negative electrodes.

[0196] The first tab 1021 is not too short, the first tab 1021 is not easy to break, and the first tab 1021 and the first electrode terminal are easy to assemble and connect, which improves the connection stability of the first tab 1021 and the first electrode terminal, so that the current distribution in each first tab 1021 is uniform and will not increase the current density of adjacent first tabs 1021.

[0197] For example, the ratio of the length of the first tab 1021 to the thickness of the main body 101 is 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.9, 2.1, 2.3, or a range of any two of the above values. Y1 shown in FIG. 7 represents the unfolded length of the first tab 1021. X2 shown in FIG. 6 represents the thickness of the main body 101.

[0198] In some embodiments, the thickness of the positive electrode tab is 10 μm to 20 μm, for example 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm or any combination of two of the above values.

[0199] When the thickness of the positive electrode tab is within the above range, heat generation can be reduced, and the amount of gas produced by side reactions can be decreased; specifically:

[0200] The positive electrode tab has excellent overcurrent capacity, which can reduce the current density at the positive electrode tab, reduce internal resistance, thereby reducing heat generation and further reducing the amount of gas generated by side reactions.

[0201] The positive electrode tab is not too thick, and the positive electrode tab has little interference with gas flow. Gas can flow along both ends in the first direction, which reduces the risk of gas remaining inside the main body 101. This makes the film layers inside the main body 101 relatively tight, improves the flow, increases the electron and ion conduction rate, thereby reducing internal resistance, reducing heat generation, further reducing the amount of gas generated by side reactions, and improving circulation.

[0202] When the thickness of the positive electrode tab is within the above range, in the event of thermal runaway of the battery cell 7, the risk of the positive electrode tab forming molten metal beads that block the pressure relief mechanism 220 can be reduced, thereby enabling the battery cell 7 to release pressure in a timely manner and effectively improving the reliability of the battery cell 7.

[0203] The positive electrode tab can be set to a constant size or a non-constant size.

[0204] In some implementations, the thickness of the negative electrode tab is 4 μm to 8 μm, for example, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any combination of two of the above values.

[0205] When the thickness of the negative electrode tab is within the above range, it can effectively improve the overcurrent capacity of the battery cell 7, reduce heat generation, and improve the cycle performance and reliability of the battery cell.

[0206] In some embodiments, the dimensions of the first electrode 1021 along the first direction Z are equal in the direction from the main body 101 to the electrode 102. In this case, the first electrode 1021 is set to the same size, and the dimension of the first electrode 1021 at any position along the first direction Z is the average dimension of the first electrode 1021 along the first direction Z.

[0207] In some other embodiments, the dimensions of the first electrode 1021 along the first direction Z are not equal in the direction from the main body 101 to the electrode 102. In this case, the first electrode 1021 is set with non-equal size. It is necessary to count the dimensions of the first electrode 1021 at multiple positions (e.g., more than 2) along the first direction Z, calculate the average value, and use it as the average dimension of the first electrode 1021 along the first direction Z.

[0208] Optionally, in the direction from the main body 101 to the tab 102, the size of the first tab 1021 decreases along the first direction Z.

[0209] The size Z of the first electrode surface 10211 of the first electrode ear 1021 11 The maximum area at the connection between the first electrode 1021 and the main body 101 is large, resulting in a strong current carrying capacity, which can reduce the instantaneous current density, reduce internal resistance and heat generation, thereby reducing gas generation.

[0210] The first electrode 1021 has an end face dimension Z that is away from the main body 101. 12The smaller size of the first tab 1021 reduces the overall volume of the first tab 1021, thereby reducing the risk of the first tab 1021 obstructing gas flow and reducing the risk of gas flowing away from the end cap 22 and remaining in the main body 101. This results in better ion and electron conduction performance in the main body 101, reduces the internal resistance of the main body 101, thereby reducing heat generation, reducing gas generation, and improving the reliability of the battery cell 7.

[0211] For example, the first electrode 1021 can be trapezoidal, which can be calculated by Z. 11 and Z 12 The average value is taken as the average dimension Z1 of the first electrode 1021 along the first direction Z. Of course, the first electrode 1021 can also be other structural types, such as rectangular, etc.

[0212] As shown in Figure 9, in some embodiments, the battery cell 7 further includes a first electrode terminal 31 and a first adapter 41. The first electrode terminal 31 is disposed on the end cover 22. The first adapter 41 connects the first electrode terminal 31 and the first tab 1021. Along the first direction Z, the first adapter 41 extends beyond the first tab 1021, and the size difference between the first adapter 41 and the first tab 1021 is 5mm to 30mm.

[0213] The first adapter 41 extends beyond the first tab 1021, which improves the connection stability between the first adapter 41 and the first tab 1021. Furthermore, the size of the first adapter 41 extending beyond the first tab 1021 is not excessive, resulting in excellent current-carrying capacity between the first adapter 41 and the first tab 1021, reducing internal resistance and heat generation, thereby reducing gas generation and improving the cycle performance of the battery cell 7. The first adapter 41 may extend beyond at least one side of the first tab 1021 along the first direction Z, optionally both sides.

[0214] For example, along the first direction Z, the average dimensional difference between the first adapter 41 and the first electrode 1021 is 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, or any two of the above values. In Figure 9, Z4 represents the dimension of the first adapter 41 along the first direction Z, Z1 represents the dimension of the first electrode 1021 along the first direction Z, and Z4-Z1 is the average dimensional difference between the first adapter 41 and the first electrode 1021 along the first direction Z.

[0215] In some embodiments, the first adapter 41 may be a rectangular structure or a rectangular-like structure, or a structure containing a recess, etc.

[0216] In some embodiments, the distance between the geometric center of the first adapter 41 and the geometric center of the first tab 1021 along the first direction Z is less than or equal to 2 mm.

[0217] The above-mentioned structural configuration can reduce the resistance between the first adapter 41 and the first tab 1021, reduce heat generation, thereby reducing gas generation and improving the cycle performance of the battery cell 7.

[0218] For example, the first adapter 41 is a rectangular or rectangular structure with its geometric center being the intersection of its diagonals; the first tab 1021 unfolds into a trapezoid with its geometric center being the intersection of the lines connecting the midpoints of opposite sides.

[0219] In some embodiments, the battery cell 7 further includes a second electrode terminal 32 and a second adapter 42, the second electrode terminal 32 being disposed on the end cap 22, and the second adapter 42 being connected to the second electrode terminal 32 and the second tab 1022.

[0220] In some embodiments, the structure and dimensions of the second electrode 1022 are the same as those of the first electrode 1021, and will not be described again here.

[0221] In some embodiments, the structure and dimensions of the second electrode terminal 32 are the same as those of the first electrode terminal 31, and will not be described again here.

[0222] In some embodiments, the structure and dimensions of the second adapter 42 are the same as those of the first adapter 41, and will not be described again here.

[0223] In some embodiments, the battery cell 7 also includes a pressure relief mechanism 220 disposed on the end cap 22.

[0224] When a short circuit or overcharge occurs, the electrolyte and active materials react, releasing gas and heat. The pressure relief mechanism 220 is configured to deform when the internal pressure or temperature of the housing 21 reaches a threshold, thereby connecting the internal space of the housing 21 to the external space to release the pressure or temperature within the housing 21. The deformation of the pressure relief mechanism 220 includes, but is not limited to, rupture and melting. This threshold design varies depending on design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell 7.

[0225] In this embodiment, the deformation of the pressure relief mechanism 220 can be triggered by the internal pressure of the housing 21, by the internal temperature of the housing 21, or by a combination of the internal pressure and internal temperature of the housing 21.

[0226] As an example, as gas accumulates inside the housing 21, the internal pressure of the housing 21 may reach or even exceed a pressure threshold. When the internal pressure of the housing 21 reaches the threshold, the pressure relief mechanism 220 deforms under the action of the internal pressure to connect the internal space of the housing 21 with the external space, allowing the gas inside the housing 21 to be discharged, thereby reducing the risk of battery cell 7 exploding.

[0227] As an example, when the electrolyte and active materials react and rapidly release heat, the internal temperature of the casing 21 will rise, which will also cause the internal pressure of the casing 21 to rise. When the internal temperature of the casing 21 reaches a threshold, the pressure relief mechanism 220 can deform under the action of temperature and pressure to connect the internal space of the casing 21 with the external space, allowing the gas inside the casing 21 to be discharged, thereby reducing the risk of the battery cell 7 exploding.

[0228] When the internal pressure or temperature of the housing 210 reaches a threshold, the embodiments of this application can use the deformation of the pressure relief mechanism 220 to connect the internal space of the housing 21 with the external space, thereby releasing the internal gas and internal pressure of the housing 21 and reducing the risk of the battery cell 7 exploding.

[0229] In some embodiments, the projected area of ​​the pressure relief mechanism 220 along the second direction Y is 200 mm². 2 Up to 3800mm 2 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 projection normal.

[0230] During thermal runaway, the first tab 1021 and / or the second tab 1022 are at risk of melting into molten metal beads; when the projected area of ​​the pressure relief mechanism 220 is within the above range, it is not easily blocked by molten metal beads, which can improve the reliability of the battery cell 7 during the pressure relief process.

[0231] For example, when projected along the second direction Y, the projected area of ​​the pressure relief mechanism 220 is 200 mm². 2 Up to 3800mm 2 For example, 200mm 2 300mm 2 400mm 2 500mm 2 600mm 2 700mm 2 800mm 2 900mm 2 1000mm 2 1100mm 2 1200mm 2 1300mm 21400mm 2 2000mm 2 2500mm 2 3000mm 2 3500mm 2 3800mm 2 Or a range consisting of any two of the above values.

[0232] The projected area of ​​the pressure relief mechanism 220 can be understood as the area enclosed by the projected outer contour of the pressure relief mechanism 220.

[0233] In some embodiments, the pressure relief mechanism 220 includes a weak point 222.

[0234] In some embodiments, the end cap 22 has a recess 221, the bottom wall of which is a weak portion 222. The weak portion 222 is configured to rupture when the internal pressure of the battery cell 7 reaches a threshold, so as to release the internal pressure.

[0235] After the weak point 222 ruptures, a channel is formed for internal pressure to be released. After the weak point 222 ruptures, the internal gas of the battery cell 7 will be discharged outward from the rupture site. In this way, the battery cell 7 can be depressurized under controlled pressure, thereby avoiding potential more serious accidents.

[0236] As shown in FIG10, in some embodiments, the main body 101 may include a positive electrode portion 11, a negative electrode portion 12, and an isolator 13, wherein the isolator 13 is located between the positive electrode portion 11 and the negative electrode portion 12. The positive electrode portion 11 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. The positive electrode current collector is connected to a positive electrode tab, and the positive electrode tab extends out of the positive electrode current collector. The negative electrode portion 12 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. The negative electrode current collector is connected to a negative electrode tab, and the negative electrode tab extends out of the negative electrode current collector.

[0237] In some embodiments, when the electrode assembly 10 has a wound structure, from a structural point of view, the positive electrode portion 11 can be a single piece, the negative electrode portion 12 can be a single piece, and the insulating member 13 can be a single piece. The insulating member 13 is disposed between the positive electrode portion 11 and the negative electrode portion 12. The positive electrode portion 11, the insulating member 13 and the negative electrode portion 12 are wound in one direction to form the electrode assembly 10.

[0238] The positive electrode portion 11 includes a positive electrode straight section 111, and the negative electrode portion 12 includes a negative electrode straight section 121. The positive electrode straight section 111 and the negative electrode straight section 121 are stacked along the thickness direction X of the battery cell 7.

[0239] 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.

[0240] The positive electrode portion 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.

[0241] The negative electrode portion 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.

[0242] 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 .

[0243] When the compaction density of the positive electrode active material layer is within the above range, it can reduce the thickness of the electrode assembly, improve the heat dissipation performance of the electrode assembly, thereby reducing the accumulated heat and improving the cycle performance of the battery cell, while increasing the capacity of the battery cell.

[0244] 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 / cm3 3.2g / cm 3 3.3g / cm 3 Or a range consisting of any two of the above values.

[0245] 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 .

[0246] 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 overall space occupied by the positive electrode sheet is small, which helps to provide extra space for gas production expansion, thereby improving the reliability of the battery cell.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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 .

[0252] When the compaction density of the negative electrode active material layer is within the above range, it can reduce the thickness of the electrode assembly, improve the heat dissipation performance of the electrode assembly, thereby reducing the accumulated heat and improving the cycle performance of the battery cell, while increasing the capacity of the battery cell.

[0253] 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.

[0254] 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 .

[0255] 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 overall space occupied by the negative electrode sheet is small, which helps to provide extra space for gas production expansion, thereby improving the reliability of the battery cell.

[0256] 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.

[0257] 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.

[0258] 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.

[0259] In some embodiments, the positive electrode active material layer includes a phosphate-based active material. Compared to ternary materials, phosphate-based active materials exhibit superior structural stability, thereby improving the cycle performance of the battery cell.

[0260] In some embodiments, in the cross section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy the following: (DA90-DA10) / DA50 is 1.855 to 2.375, for example 1.855, 1.9, 2, 2.1, 2.2, 2.3, 2.375 or any two of the above values.

[0261] 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.

[0262] In some embodiments, in the cross-section along the thickness direction of the positive electrode sheet, the particles of the positive electrode active material layer satisfy the following: DA90 is 1400nm to 2100nm, for example 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm or any two of the above values.

[0263] 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.

[0264] In the embodiments of this application,

[0265] D A 10 represents the particle size at which the cumulative area distribution of the particles reaches 10%.

[0266] D A 50 represents the particle size at which the cumulative area distribution of the particles reaches 50%.

[0267] D A 90 represents the particle size at which the cumulative area distribution of the particles reaches 90%.

[0268] (D A 90-D A 10) / D A 50 indicates the particle size concentration, which can characterize the distribution width of particle size.

[0269] 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.

[0270] 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.

[0271] 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.

[0272] 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.

[0273] 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.

[0274] 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.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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%.

[0279] When the mass content of vinylene carbonate is within an appropriate range, 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.

[0280] 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.

[0281] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is from 1.5 wt% to 4.5 wt%.

[0282] 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.

[0283] 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.

[0284] The electrolyte system described above can reduce gas production and improve the cycle performance and reliability of individual battery cells.

[0285] 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.

[0286] 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.

[0287] 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.

[0288] 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.

[0289] 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.

[0290] 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.

[0291] The density of the electrolyte can be the density at room temperature. When the electrolyte density is within the above range, 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.

[0292] 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.

[0293] [Positive electrode plate]

[0294] 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.

[0295] 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.

[0296] 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.

[0297] 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.

[0298] Lithium phosphate exhibits excellent stability during cycling, which can improve the lifespan of individual battery cells.

[0299] 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.

[0300] 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.

[0301] 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.

[0302] 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.

[0303] 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.

[0304] 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).

[0305] 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).

[0306] 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.

[0307] [Negative electrode plate]

[0308] 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.

[0309] 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.

[0310] 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.

[0311] 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.

[0312] 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.

[0313] 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.

[0314] 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.

[0315] 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.

[0316] 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).

[0317] 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.

[0318] [Isolation Component]

[0319] 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.

[0320] In some embodiments, the separating membrane comprises a porous base membrane.

[0321] 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.

[0322] Alternatively, the polyolefin includes one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0323] In some implementations, the separator can be a base membrane.

[0324] 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.

[0325] 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.

[0326] 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.

[0327] Electrolyte

[0328] In some implementations, the battery cell includes an electrolyte.

[0329] 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.

[0330] 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.

[0331] 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.

[0332] 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.

[0333] 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".

[0334] Example

[0335] 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.

[0336] Example 1

[0337] 1. Preparation of positive electrode sheet

[0338] 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.

[0339] 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.

[0340] 2. Preparation of negative electrode sheet

[0341] 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.

[0342] 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.

[0343] 3. Separating membrane

[0344] 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 6 μm, and the alumina ceramic coating on one side has a thickness of 1 μm.

[0345] 4. Preparation of electrolyte

[0346] The electrolyte consists of organic solvents, lithium salts, and additives.

[0347] 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.

[0348] 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.

[0349] Based on the total mass of the electrolyte, the additives also include 3% vinylene carbonate V and 2% FEC by mass.

[0350] Based on the total mass of the electrolyte, the lithium salt comprises 12 wt% lithium hexafluorophosphate (LiPF6) and 3 wt% lithium bisfluorosulfonylimide (LiFSI).

[0351] 5. Preparation of battery cells

[0352] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation, thus obtaining an electrode assembly. The electrode assembly is placed in a housing, with the positive and negative terminals set on the housing. After baking, electrolyte is injected (multiple injections can be performed if necessary). After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0353] The first direction is parallel to the length direction of the battery cell, and the second direction is parallel to the width direction of the battery cell.

[0354] The first tab is the positive tab, and the second tab is the negative tab. The thickness of the second tab is 6μm. The other dimensions of the second tab are the same as those of the positive tab, and will not be described again here.

[0355] The positive electrode tab is connected to the electrode terminal through a positive electrode adapter, and the negative electrode tab is connected to the negative terminal through a negative electrode adapter. Along the length of the battery cell, the positive electrode adapter extends beyond the positive electrode tab, and the size difference between the two is 8mm. The distance between the geometric center of the positive electrode adapter and the geometric center of the positive electrode tab is 1mm.

[0356] The end cap of the outer casing is also equipped with a pressure relief mechanism. The projection area of ​​the pressure relief mechanism along the second direction is 300 mm². 2 .

[0357] Performance testing

[0358] 1. Cycle performance test of individual battery cells

[0359] 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.

[0360] After allowing the charge and discharge cycles to stand for 30 minutes, calculate the capacity retention rate after each cycle.

[0361] 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%.

[0362] The higher the capacity retention rate, the better the cycle performance of the battery cell.

[0363] 2. Battery cell volume expansion test

[0364] Before the cycle test of a single battery cell, the thickness of the battery cell is measured as the initial thickness.

[0365] 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.

[0366] The volume expansion rate of a single battery cell is 100% × (post-cycle thickness - initial thickness) / initial thickness.

[0367] 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.

[0368] Examples 1-1 and 1-2

[0369] The example was prepared using a method similar to that of Example 1, except that the dimensions of the first tab surface along the first direction (i.e., the length direction of the battery cell) were adjusted.

[0370] Examples 1-3 and Examples 1-4

[0371] The example was prepared using a method similar to that of Example 1, except that the length of the first tab after unfolding was adjusted.

[0372] Examples 1-5 and Examples 1-6

[0373] The example was prepared using a method similar to that of Example 1, except that the thickness of the first tab was adjusted.

[0374] The test results are shown in Table 1.

[0375] Table 1

[0376] When the ratio of the size of a single first tab to the size of the casing in Examples 1, 1-1, and 1-2 is within the above range, the current density at the tab can be reduced, which helps the current to be evenly distributed in the main body, reduces the heat generated, thereby weakening side reactions, reducing gas production, and improving the cycle performance and reliability of the battery cell.

[0377] In Examples 1-3 and 1-4, when the ratio of the length of the first tab after unfolding to the thickness of the electrode assembly meets the above range, the electron transport path on the first tab will not be too long, resulting in relatively low internal resistance, no increase in heat generation, reduced side reactions, and improved cycle performance and reliability of the battery cell.

[0378] In Examples 1-5 and Examples 1-6, when the thickness of the first tab is within the above range, the risk of the first tab forming molten metal beads that block the pressure relief mechanism can be reduced in the event of thermal runaway of the battery cell, thereby enabling the battery cell to release pressure in a timely manner.

[0379] Example 2-0

[0380] 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.

[0381] Examples 2-1 and 2-2

[0382] 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.

[0383] Comparative Example 2-1 and Example 2-3

[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 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.

[0385] Examples 2-4 and 2-5

[0386] 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.

[0387] Comparative Example 2-2, Example 2-6 and Example 2-7

[0388] 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.

[0389] The test results are shown in Table 2.

[0390] Table 2

[0391] In Example 1,

[0392] The projected area S of the cavity along the second direction T 19656mm 2 The thickness H of the cavity T It is 72mm.

[0393] 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 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.

[0394] If the length of a single battery cell is too short, such as in Comparative Example 2-1, the capacity of the single battery cell will be too low, failing to meet the requirements for long cycle life.

[0395] In contrast, in Comparative Example 2-2, insufficient margin may worsen the cycle and cause excessive expansion of the battery cell volume, which is detrimental to improving reliability.

[0396] 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 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.

[0397] Comparative Example 3-1, Comparative Example 3-2, Examples 3-1 to 3-3

[0398] 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,

[0399] If the mass content of the additive increases by N%, the mass content of dimethyl carbonate decreases by N%.

[0400] If the mass content of the additive decreases by N%, the mass content of dimethyl carbonate increases by N%.

[0401] The test results are shown in Table 3.

[0402] Table 3

[0403] In Table 3, VC represents vinylene carbonate; FEC represents fluoroethylene carbonate; and DMC represents dimethyl carbonate.

[0404] The battery cells in the various embodiments and comparative examples in Table 3 have basically the same capacity and volumetric energy density.

[0405] 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.

[0406] 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.

[0407] Examples 4-1 to 4-5

[0408] Battery cells were prepared using a method similar to that of Example 1, except that the electrolyte formulation was adjusted, as shown in Table 4.

[0409] Table 4

[0410] In Table 4, LiPF6 represents lithium hexafluorophosphate and LiFSI represents lithium difluorosulfonylimide.

[0411] In Table 4, 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.

[0412] The electrolyte in Example 1 has a density of 1.3 g / mL at room temperature.

[0413] The electrolyte in Examples 4-3 has a density of 1.28 g / mL at room temperature.

[0414] 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.

[0415] 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.

[0416] Examples 5-1 and 5-2

[0417] 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.

[0418] 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;

[0419] 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.

[0420] Example 5-3

[0421] 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.

[0422] The test results are shown in Table 5.

[0423] Table 5

[0424] 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.

[0425] 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.

[0426] 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.

[0427] 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.

[0428] 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.

[0429] 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 main body and an electrode tab. The electrode tab is connected to and extends beyond the main body. The electrode tab includes a first electrode tab and a second electrode tab, wherein one of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab. in, The capacity of the battery cell is greater than or equal to 500Ah, and the dimension of the casing along the first direction is greater than or equal to 270mm; The battery cell satisfies: 6% ≤ (S) T -S J ) / S T ≤13%; S T This represents the projected area of ​​the receiving cavity when projected along the second direction. S J This indicates that the total projected area of ​​the at least one electrode assembly is the projection of the battery cell in its fully discharged state along the second direction; wherein 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 main body to the tab.

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 dimensions of the housing along the first direction are 270 mm to 800 mm.

5. The battery cell according to any one of claims 1 to 4, wherein, The thickness of the battery cell is 70mm to 120mm.

6. The battery cell according to any one of claims 1 to 5, wherein, The dimensions of the housing along the second direction are 200 mm to 300 mm.

7. The battery cell according to any one of claims 1 to 6, 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.

8. The battery cell according to any one of claims 1 to 7, wherein, The surface of the first electrode tab that connects to the main body is called the first electrode tab surface, and the ratio of the dimension of the first electrode tab surface along the first direction to the dimension of the housing along the first direction is 0.176 to 0.

432.

9. The battery cell according to any one of claims 1 to 8, wherein, The surface of the first tab that connects to the main body is called the first tab surface. When the battery cell is fully discharged, the ratio of the dimension of the first tab surface along the first direction to the dimension of the main body along the first direction is 0.179 to 0.

440.

10. The battery cell according to any one of claims 1 to 9, wherein, When the battery cell is fully loaded, the ratio of the length of the first tab in the unfolded state to the thickness of the main body is 1.2 to 2.

3.

11. The battery cell according to any one of claims 1 to 10, wherein, The thickness of the positive electrode tab is 10 μm to 20 μm; and / or the thickness of the negative electrode tab is 4 μm to 8 μm.

12. The battery cell according to any one of claims 1 to 11, wherein, In the direction from the main body to the tab, the size of the first tab decreases along the first direction.

13. The battery cell according to any one of claims 1 to 12, wherein, The surface of the second electrode ear that connects to the main body is called the second electrode ear surface, and the ratio of the dimension of the second electrode ear surface along the first direction to the dimension of the housing along the first direction is 0.176 to 0.

432.

14. The battery cell according to any one of claims 1 to 13, wherein, When the battery cell is fully discharged, the thickness of each electrode assembly is 15mm to 18mm.

15. The battery cell according to any one of claims 1 to 14, wherein, The battery cell further includes a first electrode terminal and a first adapter. The first electrode terminal is disposed on the end cap. The first adapter connects the first electrode terminal and the first tab. Along the first direction, the first adapter extends beyond the first tab, and the size difference between the first adapter and the first tab is 5mm to 30mm.

16. The battery cell according to claim 15, wherein, Along the first direction, the distance between the geometric center of the first adapter and the geometric center of the first electrode tab is less than or equal to 2 mm.

17. The battery cell according to any one of claims 1 to 16, wherein, The battery cell also includes a pressure relief mechanism, which is disposed on the end cap and projected along the second direction. The projected area of ​​the pressure relief mechanism is 200 mm². 2 Up to 3800mm 2 .

18. The battery cell according to any one of claims 1 to 17, wherein, The main body includes a positive electrode portion, which 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. The positive electrode tab is connected to and extends out of the positive electrode current collector. The positive electrode active material layer includes a phosphate active material.

19. The battery cell according to claim 18, wherein, 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%.

20. The battery cell according to claim 18 or 19, wherein, The compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 .

21. The battery cell according to claim 20, wherein, The compaction density of the positive electrode active material layer is 2.4 g / cm³. 3 Up to 3g / cm 3 .

22. The battery cell according to any one of claims 18 to 21, 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 .

23. The battery cell according to any one of claims 1 to 22, wherein, The main body also includes a negative electrode portion, which comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode tab is connected to and extends beyond the negative electrode current collector, and the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 2.5g / cm 3 .

24. The battery cell according to claim 23, 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 .

25. The battery cell according to any one of claims 1 to 24, wherein, The electrolyte includes vinylene carbonate, and the mass content of vinylene carbonate in the electrolyte is from 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. The battery cell according to any one of claims 1 to 26, wherein, The electrolyte also includes dimethyl carbonate, wherein the mass content of dimethyl carbonate in the electrolyte is from 15 wt% to 50 wt%.

28. The battery cell according to any one of claims 1 to 27, wherein, The electrolyte also includes lithium bisfluorosulfonylimide, wherein the lithium bisfluorosulfonylimide in the electrolyte has a mass content of 1 wt% to 5 wt%.

29. A battery device comprising a battery cell according to any one of claims 1 to 28.

30. An electrical device comprising the battery device according to claim 29.

31. An energy storage device comprising the battery device according to claim 29.

32. An energy storage system comprising the energy storage device according to claim 31.

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