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 casing assembly and an electrode assembly, wherein the casing assembly comprises a casing and an end cover assembly, which comprises a first electrode terminal; and the electrode assembly comprises a main body portion and a tab portion, the tab portion being connected to the main body portion and extending from the main body portion, the main body portion and the first electrode terminal being spaced apart in a first direction, the surface of the first electrode terminal facing the main body portion being a first terminal face, and a first tab being connected to the first terminal face. The battery cell satisfies: L≥270, S≥1900, and S / L is 7.0 to 9.2, where L represents the length of the casing, and the unit thereof is mm, and S represents the area of the first terminal face, and the unit thereof is mm2. The energy conversion efficiency and energy density of the battery cell can both be improved.

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 the ability to simultaneously improve energy conversion efficiency and energy density. 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 conversion efficiency and energy density of the battery cell.

[0006] In a first aspect, this application proposes a battery cell, which includes a casing assembly and an electrode assembly. The casing assembly includes a housing and an end cap assembly. The end cap assembly includes an end cap and a first electrode terminal and a second electrode terminal disposed on the end cap, and the end cap covers the housing. The electrode assembly is disposed within the housing and includes a main body portion and a tab portion. The tab portion is connected to and extends out of the main body portion. The tab portion includes a first tab and a second tab, one of which is a positive tab and the other is a negative tab.

[0007] The main body and the first electrode terminal are spaced apart along a first direction. The surface of the first electrode terminal facing the main body is the first terminal surface. The first electrode tab is connected to the first terminal surface, and the second electrode tab is connected to the second electrode terminal. The first direction is parallel to the length direction of the battery cell or parallel to the width direction of the battery cell.

[0008] The battery cell must meet the following requirements: L≥270, S≥1900, and S / L = 7.0 to 9.2. Here, L represents the length of the casing in mm, and S represents the area of ​​the first terminal face in mm². 2 .

[0009] In this embodiment, the shell is relatively long, and the electron transport path in the main body is long along the length of the battery cell. This makes it easy for uneven current density distribution to occur, causing electrons to accumulate near the tab and potentially increasing heat generation near the tab. This can lead to overheating in the area of ​​the main body near the tab, causing local side reactions and potentially exacerbating polarization problems.

[0010] The first terminal face of the first electrode terminal is connected to the first tab. The larger first terminal face increases the number of paths for electron transfer from the first electrode terminal to the first tab, or from the first tab to the first electrode terminal. This can effectively balance the current distribution along the length, reduce local overheating caused by uneven current distribution, reduce heat dissipation, and slow down the degree of side reactions and polarization, thus slowing down the rate of electrode material degradation.

[0011] The ratio of the area of ​​the first terminal face to the length of the casing is within an appropriate range. On the one hand, this ensures that the current density at the interface between the first electrode terminal and the electrode assembly is within the thermal stability threshold, which can significantly reduce Joule heating, thereby further reducing heat dissipation and improving the energy conversion efficiency of the battery cell. On the other hand, it can reduce the space occupied by the first electrode terminal, thereby increasing the energy density of the battery cell.

[0012] In some embodiments, L is between 270 and 1630. When the length of the casing is within the above range, the capacity of the battery cell can be increased; a casing of the above dimensions, combined with a first electrode terminal of appropriate size, can effectively improve the energy conversion efficiency of the battery cell.

[0013] In some embodiments, S is between 1900 and 11400. When the area of ​​the first terminal face is within the above range, it is beneficial to further improve the energy conversion efficiency of the battery cell.

[0014] In some embodiments, the main body and the first electrode terminal are spaced apart along the width direction of the battery cell; the battery cell satisfies: L1 / L is 0.15 to 0.23, where L1 represents the dimension of the first terminal face along the length direction of the battery cell, and its unit is mm.

[0015] The above ratio range can further and effectively improve the energy conversion efficiency of individual battery cells.

[0016] In some embodiments, the battery cell satisfies the following condition: S1 / L is 0.62 to 0.85, where S1 represents the minimum cross-sectional area of ​​the first electrode terminal along the thickness direction of the battery cell, and its unit is mm. 2 .

[0017] The above ratio range can further and effectively improve the energy conversion efficiency of individual battery cells.

[0018] In some embodiments, the first electrode terminal includes a first connecting portion, a second connecting portion, and a third connecting portion. The first connecting portion includes a first terminal surface and protrudes toward the main body relative to the end cover. The second connecting portion is disposed on the end cover and is connected to the first connecting portion. The third connecting portion is connected to the side of the second connecting portion away from the first connecting portion and protrudes from the end cover.

[0019] The above-mentioned structural design can improve the connection stability between the first electrode terminal and the end cap, and is conducive to the connection between the larger area of ​​the first connection part and the first tab, thereby improving the energy conversion efficiency of the battery cell.

[0020] In some embodiments, along the thickness direction of the battery cell, the minimum cross-sectional area of ​​the first connection portion is greater than or equal to the minimum cross-sectional area of ​​the second connection portion. This arrangement helps to reduce the mass of the structural components and increase the gravimetric energy density of the battery cell.

[0021] In some embodiments, the minimum cross-sectional area of ​​the first connection portion is greater than or equal to the minimum cross-sectional area of ​​the third connection portion along the thickness direction of the battery cell. This arrangement helps to reduce the mass of the structural components and increase the gravimetric energy density of the battery cell.

[0022] In some embodiments, the minimum cross-sectional area of ​​the third connection portion along the thickness direction of the battery cell is greater than or equal to the minimum cross-sectional area of ​​the second connection portion. This arrangement helps to reduce the mass of the structural components and increase the gravimetric energy density of the battery cell.

[0023] In some embodiments, the first tab extends out of the main body along a first direction. This arrangement helps reduce the assembly space of structural components and increases the energy density of the battery cell.

[0024] In some embodiments, the first tab extends out of the main body along the width direction of the battery cell.

[0025] This configuration shortens the electron transport path in the width direction, reduces heat generation, and improves the energy conversion efficiency of individual battery cells.

[0026] In some embodiments, the second tab extends out of the main body along the width direction of the battery cell.

[0027] This configuration shortens the electron transport path in the width direction, reduces heat generation, and improves the energy conversion efficiency of individual battery cells.

[0028] In some implementations, the first tab is in contact with the first terminal face. This arrangement can shorten the electron transport path, reduce heat generation, and improve the energy conversion efficiency of the battery cell.

[0029] In some embodiments, the battery cell satisfies the following: W / L is 0.16 to 0.35, where W represents the dimension of the first tab surface along the length direction of the battery cell in mm, the first tab surface is the surface of the first tab connected to the main body, and the second direction and the first direction are perpendicular to the thickness direction of the battery cell.

[0030] The area where the first tab connects to the main body is relatively large, which helps to improve the current collection efficiency in the length direction, improve the current distribution uniformity at the end of the first tab near the main body, reduce heat accumulation, and improve the energy conversion efficiency of the battery cell.

[0031] In some embodiments, the battery cell satisfies the following condition: S2 / L is 0.16 to 0.26, where S2 represents the contact area between the first tab and the first terminal face, in mm. 2 .

[0032] When a battery cell meets the above conditions, the current-carrying area of ​​the first tab is relatively large, resulting in excellent current-carrying capacity, which can reduce resistance and heat generation, thereby improving the energy conversion efficiency of the battery cell.

[0033] In some embodiments, the second electrode terminal includes a second terminal surface, which is the surface of the second electrode terminal facing the main body, and the second terminal surface is connected to the second tab; the battery cell satisfies: M / L is 7.0 to 9.2, where M represents the area of ​​the second terminal surface in mm. 2 .

[0034] The above structure can further improve the energy conversion efficiency of individual battery cells.

[0035] In some implementations, the electrode assembly has a wound structure.

[0036] 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 current collector is connected to a positive electrode tab. The positive electrode active material layer includes a positive electrode active material, which includes a phosphate-based active material. Phosphate-based active materials exhibit superior cycle stability, reducing heat generation and improving energy conversion efficiency.

[0037] In some embodiments, the powder resistivity of the positive electrode active material at a pressure of 8 MPa is ≤20 Ω / cm.

[0038] In conjunction with the aforementioned size design of the first electrode terminal and the housing, and based on the improvement of the macroscopic current distribution uniformity of the positive electrode plate by the first electrode terminal, when the powder resistivity of the phosphate active material is within the aforementioned range, it can further enhance the electron and ion transport rate, slow down the concentration polarization inside the active material particles, and allow the current to be utilized more uniformly inside the positive electrode material. This can reduce the problem of uneven local heat generation caused by slow diffusion, reduce the dissipated heat, and improve the energy conversion efficiency of the battery cell.

[0039] In some embodiments, the surface of the phosphate-active material includes a carbon material, wherein the carbon content of the carbon material is 1% to 2.5% by mass, based on the mass of the phosphate-active material.

[0040] The aforementioned carbon content can improve both the energy conversion efficiency and energy density of individual battery cells.

[0041] In some embodiments, in a cross-section along its own thickness direction, 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%.

[0042] When the positive electrode active material layer meets the above conditions, the particle size of the large particles is relatively small, which can reduce the internal resistance of the positive electrode and reduce heat generation. While improving the energy density of the battery cell, it can also improve the energy conversion efficiency of the battery cell.

[0043] In some implementations, D A 50 is from 600nm to 900nm, D A 50 indicates the particle size at which the cumulative area distribution of the particles reaches 50%.

[0044] When the positive electrode active material layer meets the above conditions, the particle size of the large particles is relatively small, which can reduce the internal resistance of the positive electrode and reduce heat generation. While improving the energy density of the battery cell, it can also improve the energy conversion efficiency of the battery cell.

[0045] In some implementations, the positive electrode active material layer satisfies: C 50 The value ranges from 0.98 to 1.20, where C 50 This indicates the median of the graphitization degree in the cumulative distribution curve of the graphitization degree C value obtained by laser microscopy confocal Raman spectroscopy in large-area scanning mode;

[0046] The degree of graphitization C is I G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0047] When the positive electrode active material layer meets the above conditions, it can improve the energy conversion efficiency of the battery cell while simultaneously improving the energy density of the battery cell.

[0048] In some embodiments, the compaction density of the positive electrode active material layer is 2.49 g / cm³. 3 Up to 2.8 g / cm 3 .

[0049] The compaction density of the positive electrode active material layer, combined with the electrode terminals with a large overcurrent area, enables the current to be distributed uniformly and with low impedance within the positive electrode active material layer. This reduces the problems of local polarization and ohmic heat concentration caused by uneven electron distribution, and can significantly improve the energy conversion efficiency of the battery cell.

[0050] In some embodiments, the main body 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 current collector is connected to a negative electrode tab, and the compaction density of the negative electrode active material layer is 1.5 g / cm³. 3 Up to 2.3 g / cm 3 .

[0051] The compaction density of the negative electrode active material layer, combined with the electrode terminals having a large overcurrent area, enables the current to be distributed uniformly and with low impedance within the negative electrode active material layer. This reduces the problems of local polarization and ohmic heat concentration caused by uneven electron distribution, and can significantly improve the energy conversion efficiency of the battery cell.

[0052] In some embodiments, the battery cell further includes an electrolyte comprising a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent comprises 8% to 75% by mass in the electrolyte.

[0053] Chain-like carboxylic acid ester solvents improve the conductivity of the electrolyte at room temperature, which is beneficial for lithium ion migration, thereby reducing ion diffusion resistance and improving the energy conversion efficiency of the battery cell.

[0054] In some embodiments, the chain carboxylic acid ester solvent comprises one or more of ethyl acetate, methyl acetate, ethyl propionate, propyl acetate, methyl propionate, and methyl butyrate.

[0055] Chain-like carboxylic acid ester solvents improve the conductivity of the electrolyte at room temperature, which is beneficial for lithium ion migration, thereby reducing ion diffusion resistance and improving the energy conversion efficiency of the battery cell.

[0056] In some embodiments, the battery cell further includes an electrolyte comprising a carbonate solvent, wherein the carbonate solvent has a mass content of 5% to 92%.

[0057] The combined use of carbonate solvents and chain carboxylic acid ester solvents is beneficial to improving the energy conversion efficiency of battery cells.

[0058] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0059] The combined use of carbonate solvents and chain carboxylic acid ester solvents is beneficial to improving the energy conversion efficiency of battery cells.

[0060] In some embodiments, the battery cell further includes an electrolyte comprising lithium fluorosulfonylimide, wherein the lithium fluorosulfonylimide content in the electrolyte is 2.5% to 6% by mass.

[0061] The aforementioned content of lithium fluorosulfonylimide can improve the ion conductivity of the electrolyte, reduce the internal resistance of the electrochemical system, and enhance the energy conversion efficiency of the battery cell.

[0062] In some embodiments, lithium fluorosulfonylimide includes one or both of lithium bisfluorosulfonylimide and lithium bistrifluoromethylsulfonylimide.

[0063] The aforementioned lithium fluorinated sulfonyl imide can improve the ion conductivity of the electrolyte, reduce the internal resistance of the electrochemical system, and enhance the energy conversion efficiency of the battery cell.

[0064] In some embodiments, the electrolyte further includes lithium hexafluorophosphate, wherein the mass ratio of lithium hexafluorophosphate to lithium fluorosulfonylimide is 2 to 4 based on the mass of the electrolyte.

[0065] In some embodiments, the battery cell further includes an electrolyte, which includes one or more of fluoroethylene carbonate (FEC) and vinylene carbonate (VC), wherein the total mass content of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) in the electrolyte is 0.5% to 6%.

[0066] The aforementioned lithium salts are beneficial for improving the lithium-ion conductivity of the electrolyte, enhancing the kinetic performance of the battery cell, and reducing the hydrofluoric acid content in the electrolyte. They also improve the film quality of the solid electrolyte interphase (SEI) film on the negative electrode side and reduce the resistance of the SEI film, thereby improving the energy conversion efficiency of the battery cell.

[0067] In some embodiments, the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature.

[0068] The high migration rate of lithium ions in this electrolyte can further reduce heat generation and internal resistance of the battery cells, thereby improving the energy conversion efficiency of the battery cells.

[0069] In some implementations, the capacity of a single battery cell is greater than or equal to 500 Ah.

[0070] The design of the aforementioned battery cells, along with the electrode terminals and tabs, can improve the energy conversion efficiency of the battery cells while increasing their energy density.

[0071] In some implementations, the capacity of a single battery cell is between 550 Ah and 700 Ah.

[0072] The design of the aforementioned battery cells, along with the electrode terminals and tabs, can improve the energy conversion efficiency of the battery cells while increasing their energy density.

[0073] In some implementations, the capacity of a single battery cell is between 800 Ah and 1200 Ah.

[0074] The design of the aforementioned battery cells, along with the electrode terminals and tabs, can improve the energy conversion efficiency of the battery cells while increasing their energy density.

[0075] In some implementations, the capacity of a single battery cell is between 2000 Ah and 3000 Ah.

[0076] The design of the aforementioned battery cells, along with the electrode terminals and tabs, can improve the energy conversion efficiency of the battery cells while increasing their energy density.

[0077] Secondly, this application proposes a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this application.

[0078] Thirdly, this application proposes an electrical device, which includes the battery device according to any embodiment of the second aspect of this application.

[0079] Fourthly, this application proposes an energy storage device, which includes the battery device according to any embodiment of the second aspect of this application.

[0080] 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

[0081] 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.

[0082] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application.

[0083] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application.

[0084] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application.

[0085] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application.

[0086] Figure 5 is an exploded view of a battery cell provided in some embodiments of this application.

[0087] Figure 6 is a schematic diagram of the end cap assembly of a battery cell provided in some embodiments of this application.

[0088] Figure 7 is a cross-sectional view of the end cap assembly shown in Figure 6 along line AA.

[0089] Figure 8 is an enlarged schematic diagram of the end cap assembly shown in Figure 7 at point I.

[0090] Figure 9 is a schematic diagram of the electrode assembly of a battery cell provided in some embodiments of this application.

[0091] Figure 10 is a schematic diagram showing the unfolded first tab and positive electrode portion of a battery cell provided in some embodiments of this application.

[0092] The accompanying drawings may not be drawn to scale.

[0093] The reference numerals in the attached drawings are explained as follows: X, thickness direction of the battery cell; Y, first direction; Z, second direction; 1, electrical device; 2, battery pack; 3, controller; 4, motor; 5, housing; 5a, first housing section; 5b, second housing section; 5c, storage space; 6, battery module; 7, battery cell; 10, electrode assembly; 11, main body section; 111, positive electrode section; 112, negative electrode section; 113, separator; 12, tab section; 121, first tab; 1210, first tab surface; 122, second tab; 20, outer casing assembly; 21, housing; 22, end cap assembly; 221, end cap; 31, first electrode terminal; 310, first terminal surface; 311, first connecting part; 312, second connecting part; 313, third connecting part; 32, second electrode terminal. Detailed Implementation

[0094] 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.

[0095] 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.

[0096] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0097] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0098] 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.

[0099] 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.

[0100] With the development of energy storage system technology, the requirements for the energy conversion efficiency (RTE) of individual battery cells in energy storage systems are constantly increasing.

[0101] Energy conversion efficiency (ECE) is the ratio of the total energy output during a complete charge-discharge cycle to the total energy input during a charge-discharge cycle. Higher ECE means less energy is consumed during energy conversion or transfer, resulting in better system performance.

[0102] When the casing of a battery cell is long, the current density distribution in the electrode may be uneven during charging, resulting in concentrated heat generation in local areas, which can cause ohmic polarization and concentration polarization, accelerate the deterioration of electrode materials, and reduce energy conversion efficiency.

[0103] When the overcurrent area of ​​the electrode terminals is small, the above situation will be further aggravated. Moreover, the Joule heat accumulation between the electrode terminals and the tabs will lead to an increased temperature rise, increase the dissipated heat, and further reduce the energy conversion efficiency. Furthermore, as the heat accumulates, it may exceed the thermal stability threshold of the battery cell, increasing the risk of thermal runaway.

[0104] In view of this, the present application proposes a battery cell with a relatively long casing, which is equipped with a large-area first electrode terminal, and the ratio of the casing size to the area of ​​the first electrode terminal is adjusted within an appropriate range. This configuration can increase the contact area between the first electrode terminal and the electrode, providing the electrode with a wider current path and lower impedance, effectively balancing the current distribution, reducing the phenomenon of current accumulation at the end and local overheating caused by path resistance difference, mitigating the degree of local side reactions, and reducing ohmic polarization and concentration polarization, thereby improving the energy conversion efficiency of the battery cell.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 modules such as an auxiliary battery management unit (SBMU) and a fusion switch.

[0113] 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.

[0114] 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.

[0115] As an example, the power distribution unit can be used to distribute power to the power modules of the energy storage device.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The battery pack 2 includes a housing and one or more battery cell assemblies, which are housed within the housing.

[0125] 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.

[0126] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] A single battery cell can be the smallest unit that makes up a battery device.

[0133] 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.

[0134] 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.

[0135] As shown in Figures 4 and 5, in some embodiments, the battery cell 7 includes a housing assembly 20 and an electrode assembly 10. The housing assembly 20 includes a housing 21 and an end cap assembly 22. The end cap assembly 22 includes an end cap 221. The housing 21 includes a receiving cavity with an opening, and the end cap 221 covers the opening. The electrode assembly 10 is disposed in the receiving cavity 210.

[0136] 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.

[0137] 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.

[0138] End cap 221 covers the opening of housing 21 to isolate the internal environment of battery cell 7 from the external environment. End cap 221 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.

[0139] Optionally, the end cap assembly 22 further includes a first electrode terminal 31 and a second electrode terminal 32, both of which can be disposed on the end cap 221. The first electrode terminal 31 and the second electrode terminal 32 can be used to electrically connect with the electrode assembly 10 for outputting or inputting electrical energy of the battery cell 7.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] In some embodiments, the positive electrode can be a positive electrode plate. In some embodiments, the negative electrode can be a negative electrode plate.

[0144] As shown in Figures 4 to 8, in some embodiments, the battery cell 7 includes a housing assembly 20 and an electrode assembly 10.

[0145] The housing assembly 20 includes a housing 21 and an end cap assembly 22. The end cap assembly 22 includes an end cap 221 and a first electrode terminal 31 and a second electrode terminal 32 disposed on the end cap 221.

[0146] Electrode assembly 10 is disposed within housing 21. Electrode assembly 10 includes a main body portion 11 and electrode tab portion 12. Electrode tab portion 12 is connected to and extends out of the main body portion 11. Electrode tab portion 12 includes a first electrode tab 121 and a second electrode tab 122. One of the first electrode tab 121 and the second electrode tab 122 is a positive electrode tab, and the other is a negative electrode tab.

[0147] The main body 11 and the first electrode terminal 31 are spaced apart along the first direction Y. The surface of the first electrode terminal 31 facing the main body 11 is the first terminal surface 310. The first electrode tab 121 is connected to the first terminal surface 310, and the second electrode tab 122 is connected to the second electrode terminal 32.

[0148] The battery cell 7 meets the following requirements: L≥270, S≥1900, and S / L is 7.0 to 9.2.

[0149] L represents the length of the shell 21, and its unit is mm;

[0150] S represents the area of ​​the first terminal face 310, and its unit is mm. 2 .

[0151] The thickness direction X, width direction, and length direction of the battery cell 7 are all perpendicular to each other. When the battery cell 7 is placed vertically, the vertical direction can be parallel to the width direction or parallel to the length direction.

[0152] The first direction Y can be defined as parallel to the direction from the main body 11 to the first electrode terminal 31. For example, the first direction Y is parallel to the width direction of the battery cell 7, or the first direction Y is parallel to the length direction of the battery cell 7.

[0153] The second direction Z can be defined as being perpendicular to both the thickness direction X and the first direction Y. If the first direction Y is parallel to the width direction of the battery cell 7, then the second direction Z is parallel to the length direction of the battery cell 7. Alternatively, for example, if the first direction Y is parallel to the length direction of the battery cell 7, then the second direction Z is parallel to the width direction of the battery cell 7.

[0154] In some embodiments, the main body 11 and the first electrode terminal 31 may be spaced apart along the width direction of the battery cell 7. In other embodiments, the main body 11 and the first electrode terminal 31 may be spaced apart along the length direction of the battery cell 7.

[0155] Electrons migrate from the first electrode terminal 31 through the tab 12 to the main body 11, or from the main body 11 to the tab 12 and back to the first electrode terminal 31. However, the casing 21 is relatively long, and the electron transport path in the main body 11 is long along the length of the battery cell 7. This makes it easy for uneven current density distribution to occur, causing electrons to accumulate near the tab 12. This may also lead to increased heat generation near the tab 12, causing overheating in the area of ​​the main body 11 near the tab 12, resulting in local side reactions and potentially exacerbating polarization problems.

[0156] The first terminal surface 310 of the first electrode terminal 31 is connected to the first tab 121. The first terminal surface 310 is larger, which increases the number of paths for the first electrode terminal 31 to transfer electrons to the first tab 121 or for the first tab 121 to transfer electrons to the first electrode terminal 31. This can effectively balance the current distribution along the length, reduce the local overheating problem caused by uneven current distribution, reduce the dissipated heat, and slow down the degree of side reactions and polarization, thus slowing down the rate of electrode material degradation.

[0157] The ratio of the area of ​​the first terminal surface 310 to the length of the housing 21 is within an appropriate range. On the one hand, this ensures that the current density at the interface between the first electrode terminal 31 and the electrode assembly 10 is within the thermal stability threshold, which can significantly reduce Joule heating and further reduce the dissipated heat, thereby improving the energy conversion efficiency of the battery cell 7. On the other hand, it can reduce the space occupied by the first electrode terminal 31, thereby increasing the energy density of the battery cell 7.

[0158] In some implementations, L ≥ 270.

[0159] When the length of the casing 21 is within the above range, the size of the battery cell 7 is longer, which is beneficial to accommodate more active materials and thus increase the capacity of the battery cell 7. The casing 21 of the above size, combined with the first electrode terminal 31 of appropriate size, can effectively improve the energy conversion efficiency of the battery cell 7.

[0160] For example, the length of the housing 21 is 270mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm, 1100mm, 1200mm, 1300mm, 1400mm, 1500mm, 1600mm, 1630mm, 1650mm, or any combination of two of the above values. L in Figure 4 represents the length of the housing 21. In Figure 4, the second direction Z is parallel to the length direction of the battery cell 7.

[0161] Alternatively, L can be between 270 and 1630.

[0162] When the length of the casing 21 is within the above range, the size of the casing 21 will not be too short, which is beneficial to increasing the capacity of the battery cell 7; and the size of the casing 21 will not be too long, which is beneficial to improving the uniformity of current distribution and increasing the energy density of the battery cell 7.

[0163] In some embodiments, the area S of the first terminal face 310 is ≥1900.

[0164] When the area of ​​the first terminal surface 310 is within the above range, its area is relatively large, which is beneficial to improving the overcurrent capacity between the first electrode terminal 31 and the electrode assembly 10, reducing the Joule heat between the first electrode terminal 31 and the electrode assembly 10, and is also beneficial to balancing the current distribution on the main body 11, reducing problems such as local overheating, local side reactions, and severe polarization, and improving the energy conversion efficiency of the battery cell 7.

[0165] For example, the area of ​​the first terminal face 310 is 1900 mm². 2 2000mm 2 3000mm 2 4000mm 2 5000mm 2 6000mm 2 7000mm 2 8000mm 2 9000mm 2 10000mm 2 11000mm 2 11400mm 2 12000mm 2 Or a range consisting of any two of the above values.

[0166] Optionally, S is between 1900 and 11400.

[0167] When the area of ​​the first terminal face 310 is within the above range, it is beneficial to further improve the energy conversion efficiency of the battery cell 7.

[0168] For example, S / L is 7.0 to 9.2, such as 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2 or any range of two of the above values.

[0169] When the S / L ratio is too small, the overcurrent capacity of the first electrode terminal 31 is relatively poor, which causes current to accumulate, resulting in uneven current distribution in the main body 11 and deteriorating the energy conversion efficiency of the battery cell 7.

[0170] When the S / L ratio is too high, the overcurrent capacity of the first electrode terminal 31 is excellent, but the first electrode terminal 31 occupies a relatively large volume, which reduces the energy density of the battery cell 7.

[0171] Within an appropriate range, the S / L ratio can effectively balance the energy conversion efficiency and energy density of the battery cell 7.

[0172] In some embodiments, the main body 11 and the first electrode terminal 31 may be spaced apart along the width direction of the battery cell 7. The first electrode terminal 31 has a certain size parallel to the length direction of the battery cell 7. The battery cell 7 satisfies that L1 / L is 0.15 to 0.23, where L1 represents the size of the first terminal surface 310 along the length direction of the battery cell 7, and its unit is mm.

[0173] A gap exists between the main body 11 and the first electrode terminal 31. This gap can be used to assemble a first electrode tab 121, which is disposed between the main body 11 and the first electrode terminal 31 and connects the main body 11 and the first electrode terminal 31. Alternatively, this gap can be used to assemble an adapter that connects the first electrode terminal 31 and the first electrode tab 121.

[0174] This structure enables a low-impedance connection between the first terminal face 310 of the first electrode terminal 31 and the main body 11 over a longer section, significantly shortening the current conduction path of the main body 11 and effectively reducing the resistance from the main body 11 to the first electrode terminal 31 in the length direction. This allows the current to be collected more evenly, reducing the risk of excessive current concentration at the end of the first electrode terminal 31, reducing heat generation at the first electrode terminal 31, reducing heat dissipation, and improving the energy conversion efficiency of the battery cell 7.

[0175] By improving the uniformity of current distribution in the main body 11 along its length, the uniformity of electrochemical performance at various points in the main body 11 is enhanced, reducing the risks of local overheating, aggravated local side reactions, and lithium plating in the main body 11, reducing the risk of degradation of electrode active materials, and further improving the energy conversion efficiency of the battery cell 7.

[0176] For example, L1 / L is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, or a range of any two of the above values. Figure 8 shows L1.

[0177] In some embodiments, the battery cell 7 satisfies: S1 / L is 0.62 to 0.85, where S1 represents the minimum cross-sectional area of ​​the first electrode terminal 31 along the thickness direction, in mm. 2 .

[0178] The first electrode terminal 31 is cut along the thickness direction X of the battery cell 7. This cut is the cross section along the thickness direction X. The first electrode terminal 31 is a solid structure, which means that the first electrode terminal 31 has multiple cross sections. The first electrode terminal 31 can adopt a structure with a constant cross section or a structure with a non-constant cross section. When the first electrode terminal 31 adopts a non-constant cross section, the minimum cross-sectional area of ​​the first electrode terminal 31 is the current bottleneck of the first electrode terminal 31 and determines the resistance of the first electrode terminal 31.

[0179] When the ratio of the minimum cross-sectional area of ​​the first electrode terminal 31 to the length of the casing 21 satisfies the above conditions, the overall current-carrying capacity of the first electrode terminal 31 is excellent, which helps to reduce the resistance of the first electrode terminal 31 and reduce the Joule heat generated by the resistance, thus reducing the risk that the first electrode terminal 31 will become a thermal bottleneck of the battery cell 7; in particular, the local heat generation during high-current charging and discharging can be mitigated. Moreover, the first electrode terminal 31 has a relatively large current-carrying area, which can also improve the thermal conductivity and heat dissipation performance of the first electrode terminal 31, helping to conduct the heat generated by the main body 11 more quickly and dissipate it evenly; especially when the battery cell 7 is long, the heat dissipation is rapid, so that when the current flows through the first electrode terminal 31, it will not cause performance degradation due to local overheating or increased resistance, thus improving the energy conversion efficiency and reliability of the battery cell 7.

[0180] In some embodiments, the first electrode terminal 31 may include a first connecting portion 311, a second connecting portion 312, and a third connecting portion 313. The first connecting portion 311 includes a first terminal surface 310 and protrudes toward the main body portion 11 relative to the end cover 221. The second connecting portion 312 is disposed on the end cover 221 and is connected to the first connecting portion 311. The third connecting portion 313 is connected to the side of the second connecting portion 312 away from the first connecting portion 311 and protrudes from the end cover 221.

[0181] The above-mentioned structural configuration can improve the connection stability between the first electrode terminal 31 and the end cap 221, and facilitate the connection between the larger area of ​​the first connection portion 311 and the first tab 121, thereby improving the energy conversion efficiency of the battery cell 7.

[0182] The first connecting part 311 is connected to the first tab 121. The area of ​​the first terminal surface 310 of the first connecting part 311 is relatively high. The contact resistance and ohmic impedance of the interface between the first terminal surface 310 and the electrode assembly 10 are relatively low. In addition, it can shorten the electron conduction path in the main body 11 and balance the path resistance, thereby improving the energy conversion efficiency of the battery cell 7.

[0183] The current-carrying capacity of the first connecting part 311, the second connecting part 312 and the third connecting part 313 can be the same or different. When the current-carrying capacity is different, the first electrode terminal 31 can adopt an expanded diameter structure. Optionally, along the thickness direction of the battery cell 7, the minimum cross-sectional area of ​​the first connecting part 311 is greater than or equal to the minimum cross-sectional area of ​​the second connecting part 312.

[0184] It can also be understood that, when projected along the first direction Y, the projection surface of the second connecting part 312 is located within the projection surface of the first connecting part 311; the first direction Y is the projection normal, and the projection surface is perpendicular to the projection normal.

[0185] The above structure extends the current collection point from a local node to a low-resistance band along the length direction, effectively shortening the current conduction path in the main body 11 and balancing the path resistance from different positions in the main body 11 to the first electrode terminal 31. This structure can fundamentally alleviate the current accumulation effect at the end of the first electrode terminal 31 near the main body 11 and improve the uniform distribution of current in the length and width directions of the main body 11.

[0186] Uniform current distribution not only makes the electrochemical reaction of active materials more consistent and improves capacity utilization, but also alleviates reliability issues such as overcharging, lithium plating and local overheating caused by excessive local current density, thereby improving both the energy conversion efficiency and reliability of the battery cell 7.

[0187] Optionally, along the thickness direction X of the battery cell 7, the minimum cross-sectional area of ​​the first connecting portion 311 is greater than or equal to the minimum cross-sectional area of ​​the third connecting portion 313. In other words, projected along the first direction Y, the projection plane of the third connecting portion 313 lies within the projection plane of the first connecting portion 311. This structure makes the first electrode terminal 31 lighter, which is beneficial to improving the energy density of the battery cell 7.

[0188] Optionally, along the thickness direction X of the battery cell 7, the minimum cross-sectional area of ​​the third connecting portion 313 is greater than or equal to the minimum cross-sectional area of ​​the second connecting portion 312. In other words, projected along the first direction Y, the projection plane of the second connecting portion 312 lies within the projection plane of the third connecting portion 313. In the battery device, two adjacent battery cells 7 can be connected by the third connecting portion 313. The relatively large minimum cross-sectional area of ​​the third connecting portion 313 results in excellent current-carrying capacity, reducing the internal resistance of the battery device and improving its energy conversion efficiency.

[0189] In some embodiments, the first electrode terminal 31 and the first tab 121 can be directly connected, that is, the first electrode terminal 31 and the first tab 121 are connected, and the surface of the first electrode terminal 31 is in contact with the surface of the first tab 121. Specifically, the first tab 121 is in contact with the first terminal surface 310. In this case, it can be directly soldered, and no adapter is required, which can reduce internal resistance, further reduce heat dissipation, and improve the energy conversion efficiency of the battery cell 7.

[0190] In other embodiments, the first electrode terminal 31 and the first tab 121 can be connected by an adapter.

[0191] In some embodiments, the tab 12 is connected to the main body 11 and can extend out of the main body 11 along the second direction Z.

[0192] In other embodiments, the tab 12 is connected to the main body 11 and can extend out of the main body 11 along the first direction Y.

[0193] In some embodiments, the first tab 121 extends from the main body 11 along the first direction Y. This arrangement helps to reduce the assembly space of structural components and increase the energy density of the battery cell 7.

[0194] In some embodiments, the second tab 122 extends out of the main body 11 along the first direction Y. This arrangement helps to reduce the assembly space of structural components and increase the energy density of the battery cell 7.

[0195] In some embodiments, when the first direction Y is parallel to the length direction of the battery cell 7, the first tab 121 extends the main body 11 along the length direction of the battery cell 7.

[0196] In some embodiments, when the first direction Y is parallel to the length direction of the battery cell 7, the second tab 122 extends out of the main body 11 along the length direction of the battery cell 7.

[0197] In some embodiments, the first tab 121 is connected to one side of the main body 11 along its length, and the second tab 122 is connected to one side of the main body 11 along its length, with the first tab 121 and the second tab 122 located on the same side. This arrangement can reduce the space occupied by the electrode terminals and increase the energy density of the battery cell 7.

[0198] When the first electrode 121 is connected to one side of the main body 11 and the second electrode 122 is connected to one side of the main body 11, the first electrode 121 and the second electrode 122 may also be located on opposite sides of the main body 11.

[0199] In some embodiments, the first tab 121 may also be connected to both sides of the main body 11.

[0200] In some embodiments, the second tab 122 may also be connected to both sides of the main body 11.

[0201] In some embodiments, when the first direction Y is parallel to the width direction of the battery cell 7, the first tab 121 extends the main body 11 along the width direction of the battery cell 7. This arrangement can shorten the electron transport path in the width direction, reduce heat generation, and improve the energy conversion efficiency of the battery cell 7.

[0202] Optionally, the first tab 121 is directly connected to the first electrode terminal 31, that is, the first tab 121 is in contact with the first terminal surface 310. This arrangement can shorten the electron transmission path, reduce heat generation, and improve the energy conversion efficiency of the battery cell 7.

[0203] In some embodiments, when the first direction Y is parallel to the width direction of the battery cell 7, the second tab 122 extends the main body 11 along the width direction of the battery cell 7. This arrangement can shorten the electron transport path in the width direction, reduce heat generation, and improve the energy conversion efficiency of the battery cell 7.

[0204] Optionally, the second electrode tab 122 is directly connected to the second electrode terminal 32, that is, the second electrode tab 122 is in contact with the second terminal surface.

[0205] In some embodiments, a first tab 121 is connected to one side of the main body 11 along the width direction, and a second tab 122 is connected to one side of the main body 11 along the width direction, with the first tab 121 and the second tab 122 located on the same side. This arrangement can reduce the space occupied by the electrode terminals and increase the energy density of the battery cell 7.

[0206] As shown in Figures 9 and 10, in some embodiments, the battery cell 7 satisfies the following: W / L is 0.16 to 0.35, where W represents the dimension of the first tab surface 1210 along the length direction of the battery cell 7, in mm, and the first tab surface 1210 is the surface of the first tab 121 connected to the main body portion 11. W is shown in Figure 10.

[0207] For example, W / L is 0.16, 0.17, 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 or a range of any two of the above values.

[0208] The area where the first tab 121 connects to the main body 11 is relatively large, which is beneficial for improving the current collection efficiency along the length direction, improving the uniformity of current distribution at the end of the first tab 121 near the main body 11, reducing heat accumulation, and improving the energy conversion efficiency of the battery cell 7; specifically:

[0209] The increased connection size between the first tab 121 and the main body 11 significantly expands the current transmission interface in the length direction, allowing the current to be efficiently collected by the larger area of ​​the main body 11. This helps to reduce the local current density at the connection between the first tab 121 and the main body 11, reduce Joule heating, and promote a more uniform distribution of current along the length direction on the main body 11, thereby improving the energy conversion efficiency of the battery cell 7.

[0210] Especially when the length of the casing 21 is long, the length of the main body 11 is also long. In this embodiment, the connection size between the first tab 121 and the main body 11 is increased, which can compensate for the current distribution gradient that is aggravated by the increase in the size of the main body 11, and homogenize the current distribution, thereby reducing the tendency of local overcharging, lithium plating and thermal runaway, and improving the reliability of the battery cell 7 and the reliability of the battery under high rate charge and discharge.

[0211] In some embodiments, the battery cell 7 satisfies the following condition: S2 / L is 0.16 to 0.26, where S2 represents the contact area between the first tab 121 and the first terminal surface 310, and its unit is mm. 2 .

[0212] For example, S2 / L is 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26 or a range consisting of any two of the above values.

[0213] In the case where the first tab 121 is directly connected to the first electrode terminal 31, for example by soldering, S2 represents the solder area of ​​the first tab 121.

[0214] When the battery cell 7 meets the above conditions, the current-carrying area of ​​the first tab 121 is relatively large, resulting in excellent current-carrying capacity, which can reduce resistance and heat generation, thereby improving the energy conversion efficiency of the battery cell 7.

[0215] The relatively large current-passing area of ​​the first tab 121 is beneficial to reduce the current density at the connection between the first tab 121 and the first electrode terminal 31 and improve the uniformity of current distribution on the main body 11.

[0216] Specifically,

[0217] Because the current path of the electrode in the battery cell 7 is relatively long in the length direction, it is easy for a current convergence effect to form in the connection area between the first tab 121 and the main body 11, resulting in excessively high local current density, causing abnormal heating and uneven temperature distribution. However, the embodiment of this application can effectively expand the current transmission interface by relatively increasing the area where the first tab 121 is connected to the first electrode terminal 31, significantly reducing the current density in the area where the first tab 121 intersects with the electrode, thereby reducing Joule heat accumulation, suppressing local overheating, and thus improving the energy conversion efficiency of the battery cell 7.

[0218] The relatively large current-carrying area of ​​the first tab 121 helps to collect and release current more evenly on the electrode in the second direction Z, alleviates the current distribution gradient caused by the increase in the size of the electrode in the second direction Z, reduces the risk of local lithium plating and side reactions, and further improves the energy conversion efficiency of the battery cell 7.

[0219] The relatively large current-carrying area of ​​the first tab 121 can enhance the mechanical connection strength and thermal conductivity between the tab and the current collector. Under abnormal conditions such as overcharging, short circuit or thermal runaway, it can better conduct heat, delay the propagation of thermal runaway, and provide more stable structural support for internal gas generation, thereby improving the reliability of the battery cell 7.

[0220] The dimensions and structural configuration of the second electrode 122 are the same as those of the first electrode 121, and will not be repeated here.

[0221] The size and structure of the second electrode terminal 32 are the same as those of the first electrode terminal 31. In some embodiments, the second electrode terminal 32 includes a second terminal surface, which is the surface of the second electrode terminal 32 facing the main body portion 11. The second terminal surface is connected to the second electrode tab 122.

[0222] Battery cell 7 meets the following requirements: M / L is 7.0 to 9.2, where M represents the area of ​​the second terminal face in mm².2 .

[0223] The above structure can further improve the energy conversion efficiency of the battery cell 7.

[0224] In some embodiments, the electrode assembly 10 may be a wound structure. Optionally, the electrode assembly 10 may include a plurality of first tabs 121 and a plurality of second tabs 122.

[0225] In other embodiments, the electrode assembly 10 may be a stacked structure.

[0226] In the embodiments of this application, when the first electrode tab 121 is the positive electrode tab, the first electrode terminal 31 is the positive terminal; the second electrode tab 122 is the negative electrode tab, and the second electrode terminal 32 is the negative terminal. Alternatively, when the first electrode tab 121 is the negative electrode tab, the second electrode tab 122 is the positive electrode tab.

[0227] In this embodiment, the main body 11 may include a positive electrode portion 111, a negative electrode portion 112, and an insulating member 113, with the insulating member 113 located between the positive electrode portion 111 and the negative electrode portion 112. The positive electrode portion 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 positive electrode current collector is connected to a positive electrode tab. The negative electrode portion 112 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, and the negative electrode current collector is connected to a negative electrode tab.

[0228] In some embodiments, the capacity of the battery cell 7 is greater than or equal to 500Ah, and can be selected from 500Ah to 3000Ah. For example, the capacity of the battery cell 7 is 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 a range of any two of the above values.

[0229] With a longer casing 21, it is easier to accommodate a relatively larger amount of active material, thereby increasing the capacity of the battery cell 7 and giving the battery cell 7 a higher energy density. Moreover, the design of the battery cell 7 with the aforementioned capacity, along with the electrode terminals, tabs, etc., can improve the energy conversion efficiency of the battery cell 7 while increasing its energy density.

[0230] When the capacity of a single battery cell 7 is high, when the battery cell 7 is applied to battery devices, power devices, energy storage devices, and energy storage systems, it is beneficial to reduce the mechanical components between battery cells 7, improve the space utilization rate of battery devices, power devices, energy storage devices, and energy storage systems, and increase the overall energy density.

[0231] 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, in conjunction with the design of the electrode terminals, tabs, etc., the energy conversion efficiency of the battery cell 7 can be improved while increasing the energy density of the battery cell 7.

[0232] 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, in conjunction with the design of the electrode terminals, tabs, etc., the energy conversion efficiency of the battery cell 7 can be improved while increasing the energy density of the battery cell 7.

[0233] 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, in conjunction with the design of the electrode terminals, tabs, etc., the energy conversion efficiency of the battery cell 7 can be improved while increasing the energy density of the battery cell 7.

[0234] In this embodiment of the application, the capacity of the battery cell 7 can be adjusted by adjusting any of the following parameters: the volume of the casing assembly 20, 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.

[0235] For example, the larger the volume of the housing component 20, the more active material it can accommodate, and the higher the capacity of the battery cell 7.

[0236] 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.

[0237] The capacity of a single battery cell 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.

[0238] 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.

[0239] The mass energy density (MED) of a single battery cell is calculated as: (C0) * (Voltage plateau) / (Mass of the single battery cell).

[0240] In some embodiments, the compaction density of the positive electrode active material layer is 2.49 g / cm³. 3 Up to 2.8 g / cm 3 .

[0241] When the compaction density of the positive electrode active material layer is within the above-mentioned range, it can optimize the internal microstructure of the positive electrode active material layer and construct a more efficient and stable three-dimensional electronic conductivity network, while improving the capacity of the battery cell. Specifically, an appropriate compaction density increases the contact points between the positive electrode active material and the optional conductive agent and positive electrode current collector, significantly reducing the contact resistance between particles and the interfacial transport impedance. On the other hand, it can optimize the pore structure of the positive electrode active material layer, achieving optimization of the electronic conduction path while ensuring the lithium-ion transport channel.

[0242] Moreover, the aforementioned compaction density works in conjunction with the larger area of ​​the first terminal face of the first electrode terminal, allowing current to be uniformly injected into the positive current collector from the external circuit. The aforementioned compaction density enables the current to be uniformly and with low impedance distributed to the positive active material within the positive active material layer, thereby fundamentally reducing the problems of local polarization and ohmic heat concentration caused by uneven electronic conductivity, and significantly improving the energy conversion efficiency of the battery cell.

[0243] For example, the compaction density of the positive electrode active material layer is 2.49 g / cm³. 3 2.5g / cm 3 2.55g / cm 3 2.60g / cm 3 2.65g / cm 3 2.7g / cm 3 2.8g / cm 3 Or a range consisting of any two of the above values.

[0244] 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; or the compaction density of the positive electrode active material layer can be measured by measuring the compaction density of the positive electrode active material layer after cold pressing during the preparation of the positive electrode sheet.

[0245] The upper limit of charging voltage and the lower limit of discharging voltage of a single battery cell vary depending on the positive electrode active material. For example, when the active material is phosphate, including lithium iron phosphate, the upper limit of charging voltage can be 3.65V and the lower limit of discharging voltage can be 2.0V. Another example is when the active material is phosphate, including lithium manganese iron phosphate, the upper limit of charging voltage can be 4.2V and the lower limit of discharging voltage can be 2.0V.

[0246] The following explanation uses a charging upper limit voltage of 3.65V and a discharging cutoff voltage of 2.0V as an example to illustrate the state of a single battery cell: In this embodiment, the fully discharged state and fully charged state of a single battery cell are defined as follows:

[0247] The battery cell is charged at a constant current charging rate of 0.33C to the upper limit of the charging voltage, and then charged at a constant voltage to 0.05C, which corresponds to the full charge state of battery cell 7, corresponding to 100% state of charge (SOC).

[0248] The battery cell is discharged at a constant current discharge rate of 0.33C to the discharge cutoff voltage, which corresponds to the fully discharged state of battery cell 7 and the 0% state of charge (SOC).

[0249] The compaction density 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, record its mass as M1, and 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 1.5 g / cm³. 3 Up to 2.3 g / cm 3 1.5g / cm³, 1.6g / cm³ 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 Or a range consisting of any two of the above values.

[0252] 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 the empty space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0253] For example, the compaction density of the negative electrode active material layer is 1.5 g / cm³. 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 Or a range consisting of any two of the above values.

[0254] 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.

[0255] The 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, which will not be elaborated here.

[0256] In some embodiments, the positive electrode active material layer includes one or more of phosphate-based active materials and layered transition metal oxides. Optionally, the positive electrode active material layer includes phosphate-based active materials, which offer superior cycle stability, reduce heat generation, and improve energy conversion efficiency.

[0257] In some embodiments, the powder resistivity of the positive electrode active material at a pressure of 8 MPa is ≤20 Ω / cm.

[0258] In conjunction with the aforementioned size design of the first electrode terminal and the housing, and based on the improvement of the macroscopic current distribution uniformity of the positive electrode sheet by the first electrode terminal, when the powder resistivity of the phosphate active material is within the aforementioned range, it can further enhance the electron and ion transport rate, slow down the concentration polarization inside the active material particles, and allow the current to be utilized more uniformly inside the positive electrode material. This can reduce the problem of uneven local heat generation caused by slow diffusion, reduce the dissipated heat, and improve the energy conversion efficiency of the battery cell.

[0259] For example, the powder resistivity of phosphate-based active materials at a pressure of 8 MPa is 20 Ω / cm, 18 Ω / cm, 15 Ω / cm, 12 Ω / cm, 10 Ω / cm, 8 Ω / cm, 5 Ω / cm, 4 Ω / cm, 3 Ω / cm, 2 Ω / cm, 1 Ω / cm, or any combination of two of the above values.

[0260] The powder resistivity of the positive electrode active material can be measured using methods and equipment known in the art. For example, it can be measured using a powder resistivity meter (Suzhou Jingge, ST2722 type) according to GB / T 33822-2017. Specifically, a certain amount of positive electrode active material (e.g., 1g) is weighed and added to the feeding chamber of the powder resistivity meter, a pressure of 8MPa is applied, and the forward and reverse resistivity of the positive electrode active material are measured separately. The average value of the two is taken as the powder resistivity of the positive electrode active material.

[0261] In some embodiments, the surface of the phosphate-active material includes a carbon material, wherein the carbon content of the carbon material is 1% to 2.5% by mass, based on the mass of the phosphate-active material.

[0262] Carbon materials can form a coating layer on the surface of phosphate-based active materials. This coating layer is also part of the phosphate-based active material, which can be considered as having a core-shell structure, with the shell being the carbon coating layer. When calculating the mass content of carbon, it is calculated based on the total mass of the phosphate-based active material as 100%, and the overall structure includes both the core and the shell.

[0263] The carbon content improves the overall conductivity of phosphate-based active materials. On the one hand, the carbon content optimizes the conductive network of the positive electrode active material layer and reduces contact resistance. On the other hand, the carbon content is not too high, which allows for a higher proportion of positive electrode active material, which is beneficial to improving the capacity of the positive electrode sheet, thereby improving the energy conversion efficiency and energy density of the battery cell.

[0264] For example, the mass content of carbon element in the carbon material is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any range of two of the above values.

[0265] The mass content of carbon can be measured using methods and equipment known in the art. For example, referring to GB / T 21023-2006 "Determination of Total Carbon and Sulfur Content in Iron and Steel - Infrared Absorption Method After Combustion in High-Frequency Induction Furnace", the carbon content was determined using the Dekai HCS infrared carbon and sulfur analyzer.

[0266] 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 represents 1400nm to 2100nm, such as 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm, or any range of two of the above values. Optionally, D A 90 refers to the range of 1600nm to 1850nm.

[0267] When the positive electrode active material layer meets the above conditions, the particle size of the large particles is relatively small, which can reduce the internal resistance of the positive electrode and reduce heat generation. While improving the energy density of the battery cell, it can also improve the energy conversion efficiency of the battery cell.

[0268] 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 50 represents 600nm to 900nm, such as 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, or any range of two of the above values. Optionally, D A 50 refers to 650nm to 750nm.

[0269] D of the particles in the positive electrode active material layer A Within the above range, the particle size is small, the kinetic performance is excellent, and the particle tolerance is strong, which is beneficial for the positive electrode sheet to withstand higher pressure and is conducive to improving the energy density and kinetic performance of the battery cell.

[0270] In the embodiments of this application,

[0271] D A 50 represents the particle size at which the cumulative area distribution of the particles reaches 50%.

[0272] D A 90 indicates the particle size at which the cumulative area distribution of the particles reaches 90%.

[0273] 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.

[0274] 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.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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.

[0279] 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.

[0280] 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.

[0281] 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 50 and D A 90.

[0282] In some implementations, the positive electrode active material layer satisfies C 50 The range is from 0.98 to 1.20, for example, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or a range consisting of any two of the above values. Optionally, C 50 It ranges from 0.98 to 1.15, and can be further selected from 1.02 to 1.10.

[0283] C 50 This indicates the median of the graphitization degree in the cumulative distribution curve of the graphitization degree C value obtained by laser microscopy confocal Raman spectroscopy in large-area scanning mode;

[0284] The degree of graphitization C is I G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0285] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the easier it is for the particles to slip by means of the highly graphitized carbon structure in the coating material, thereby increasing the electrode compaction density, thus increasing the positive electrode capacity and improving the energy density of the battery cell.

[0286] Moreover, highly graphitized carbon can form a highly efficient three-dimensional electron conduction network, significantly reducing the interfacial charge transfer impedance of the positive electrode, reducing energy loss, and improving the energy conversion efficiency of the battery cell.

[0287] [Positive electrode plate]

[0288] 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.

[0289] 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. The above structure exhibits superior cycle stability and can improve cycle performance.

[0290] 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.

[0291] 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.

[0292] Lithium phosphate exhibits excellent stability during cycling, which can improve the lifespan of individual battery cells.

[0293] 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.

[0294] In this embodiment, the elemental content in the positive electrode active material is defined in a way 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 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with dimethyl carbonate (DMC), dried, and then calcined at high temperature to remove impurities. 0.4 g of the positive electrode active material is weighed and 10 ml (50% concentration) of aqua regia is added. It is then placed on a plate at 180°C for 30 min. After digestion on the plate, the volume is adjusted to 100 mL, and quantitative testing is performed using a standard curve method.

[0295] 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.

[0296] 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.

[0297] 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.

[0298] 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).

[0299] 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).

[0300] 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.

[0301] [Negative electrode plate]

[0302] 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.

[0303] 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.

[0304] 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.

[0305] 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.

[0306] 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.

[0307] 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.

[0308] 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.

[0309] 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.

[0310] 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).

[0311] 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.

[0312] [Isolation Component]

[0313] 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.

[0314] In some embodiments, the separating membrane comprises a porous base membrane.

[0315] 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.

[0316] Alternatively, the polyolefin includes one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0317] In some implementations, the separator can be a base membrane.

[0318] 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.

[0319] 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.

[0320] 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.

[0321] Electrolyte

[0322] In some implementations, the battery cell includes an electrolyte.

[0323] 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.

[0324] In some embodiments, the electrolyte includes a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent comprises 8% to 75% by mass in the electrolyte. The chain-like carboxylic acid ester solvent improves the conductivity of the electrolyte at room temperature, which is beneficial for lithium ion migration, thereby reducing ion diffusion resistance and improving the energy conversion efficiency of the battery cell.

[0325] For example, the mass content of the chain carboxylic acid ester solvent in the electrolyte is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or any combination of two of the above values.

[0326] For example, the chain carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, ethyl propionate, propyl acetate, methyl propionate, and methyl butyrate.

[0327] In some embodiments, the electrolyte includes a carbonate solvent, wherein the carbonate solvent accounts for 5% to 92% by mass in the electrolyte.

[0328] The combined use of carbonate solvents and chain carboxylic acid ester solvents can reduce the viscosity of the electrolyte, which is beneficial for wetting the positive and negative electrode active material layers, increasing the migration rate of lithium ions, reducing the transport impedance of lithium ions in the electrolyte phase, and improving the energy conversion efficiency of the battery cell. Furthermore, lithium salts exhibit superior solubility in carbonate solvents, which further facilitates the dissociation of lithium ions from the lithium salt, increasing the ionic conductivity of the electrolyte and further enhancing the energy conversion efficiency of the battery cell.

[0329] For example, the mass content of carbonate solvent in the electrolyte is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, or any combination of two of the above values.

[0330] For example, carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0331] In some embodiments, the electrolyte comprises lithium fluorosulfonylimide. Optionally, the lithium fluorosulfonylimide comprises one or both of lithium bisfluorosulfonylimide and lithium bistrifluoromethylsulfonylimide. These materials can improve the ion conductivity of the electrolyte, reduce the internal resistance of the electrochemical system, and enhance the energy conversion efficiency of the battery cell.

[0332] In some embodiments, the lithium fluorosulfonylimide content in the electrolyte is 2.5% to 6% by mass. This content of lithium fluorosulfonylimide can improve the ion conductivity of the electrolyte, reduce the internal resistance of the electrochemical system, and enhance the energy conversion efficiency of the battery cell.

[0333] For example, the mass content of lithium fluorosulfonylimide in the electrolyte is 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, or any range of two of the above values.

[0334] In some embodiments, the electrolyte further includes lithium hexafluorophosphate, wherein the mass ratio of lithium hexafluorophosphate to lithium fluorosulfonylimide is 2 to 4, optionally 2.2 to 3.8, further optionally 2.3 to 3.6, and even more preferably 2.4 to 3.4, based on the mass of the electrolyte. The aforementioned lithium salt is beneficial for improving the lithium-ion conductivity of the electrolyte, enhancing the kinetic performance of the battery cell, and reducing the hydrofluoric acid content in the electrolyte, thereby improving the film formation quality of the solid electrolyte interphase (SEI) film on the negative electrode side and reducing the resistance of the SEI film, thus improving the energy conversion efficiency of the battery cell.

[0335] For example, the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium fluorosulfonylimide is 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4 or any range of two of the above values.

[0336] In some embodiments, the electrolyte further includes one or more of fluoroethylene carbonate (FEC) and vinylene carbonate (VC), wherein the total mass content of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) in the electrolyte is 0.5% to 6%.

[0337] The above-mentioned additives can optimize the composition of the SEI film, reduce the impedance of the SEI film, and thus improve the energy conversion efficiency of the battery cell.

[0338] In some embodiments, the electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature. The high migration rate of lithium ions in this electrolyte further reduces heat generation and the internal resistance of the battery cells, thereby improving the energy conversion efficiency of the battery cells.

[0339] For example, the conductivity of the electrolyte at room temperature is 10 mS / cm, 10.2 mS / cm, 10.4 mS / cm, 10.6 mS / cm, 10.8 mS / cm, 11 mS / cm, 11.2 mS / cm, 11.4 mS / cm, 11.6 mS / cm, 11.8 mS / cm, 12 mS / cm, 12.2 mS / cm, 12.4 mS / cm, 12.6 mS / cm, 12.8 mS / cm, 13 mS / cm, or any combination of two of the above values.

[0340] The electrolyte system has high conductivity, which allows lithium ions to shuttle rapidly between the positive and negative electrode active material layers, thus increasing the migration rate of lithium ions.

[0341] The electrolyte system described above has good compatibility with the positive electrode active material described above, and together they can construct a highly efficient ion transport channel, thereby achieving comprehensive optimization of charge transport within the battery cell and improving the energy conversion efficiency of the battery cell.

[0342] In this embodiment, the conductivity of the electrolyte is ionic conductivity, specifically the conductivity at room temperature, which can be detected using equipment and methods known in the art, such as referring to industry standard HG-T 4067-2015. In this embodiment, the room temperature is 20°C to 35°C, for example, 25°C.

[0343] In some implementations, the electrolyte may also include functional additives.

[0344] 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.

[0345] 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.

[0346] 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.

[0347] 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".

[0348] Example

[0349] 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.

[0350] Example 1

[0351] 1. Preparation of positive electrode sheet

[0352] 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.

[0353] The positive electrode active material layer comprises a film layer formed by uniformly coating a positive electrode slurry (with N-methylpyrrolidone NMP as the solvent) onto the surface of the positive electrode current collector, followed by drying and cold pressing. The positive electrode active material layer includes 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 98:1:1.

[0354] The surface of lithium iron phosphate is coated with a carbon layer, with carbon content of 1.3% by mass. The powder resistivity is 9.5 Ω / cm.

[0355] D A 50 is 700nm, D A 90 represents 1800nm.

[0356] 2. Preparation of negative electrode sheet

[0357] 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.

[0358] The negative electrode active material layer comprises a film layer formed by uniformly coating a 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 Super P, and binder SBR in a mass ratio of 96:2:2.

[0359] 3. Separating membrane

[0360] The separator membrane includes a base membrane and an alumina ceramic coating disposed on both sides of the base membrane. The base membrane is polyethylene (PE).

[0361] 4. Preparation of electrolyte

[0362] The electrolyte consists of organic solvents, lithium salts, and additives.

[0363] The components of each organic solvent are mixed, and then electrolyte lithium salt and additives are added to prepare an electrolyte.

[0364] Based on the total mass of the electrolyte, the organic solvents include 12% ethylene carbonate, 12.5% ​​diethyl carbonate, 42% ethyl acetate, and 20% propyl acetate.

[0365] Additives include vinylene carbonate (VC);

[0366] Lithium salts include lithium hexafluorophosphate (LiPF6) and lithium difluorosulfonylimide.

[0367] 5. Preparation of battery cells

[0368] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus obtaining the electrode assembly.

[0369] The electrode tabs of the electrode assembly are directly laser-welded to the electrode terminals of the end cap, placed into the housing and the end cap is welded, then the electrolyte is injected, and after vacuum sealing, settling, formation and shaping, the battery cell is finally obtained.

[0370] The positive terminal includes a first connecting part, a second connecting part, and a third connecting part.

[0371] The negative electrode tab can be designed with a similar size to the positive electrode tab.

[0372] The negative terminal can be designed with a similar size to the positive terminal.

[0373] Examples 2-1 and 2-2

[0374] Battery cells were prepared using a method similar to that of Example 1, except that the size of the positive terminal was adjusted.

[0375] Comparative Example 1 and Comparative Example 2

[0376] Battery cells were prepared using a method similar to that of Example 1, except that the size of the positive terminal was adjusted.

[0377] Examples 2-3 to Examples 2-5

[0378] Battery cells were prepared using a method similar to that of Example 1, except that the length of the casing was adjusted.

[0379] Performance testing

[0380] 1. Energy conversion efficiency test of individual battery cells

[0381] Under normal pressure, charge the battery cell at a power of 0.5P to the upper limit of the charging voltage, for example, 3.65V, let it stand for 10 minutes, and then discharge it at a power of 0.5P to the discharge cutoff voltage, for example, 2.5V, let it stand for 10 minutes, and repeat the above charging and discharging process twice.

[0382] The discharge energy during the second constant power charge-discharge process is denoted as the discharge energy Q0 of the battery cell, and the charging energy during the second constant power charge-discharge process is denoted as the charging energy Q1 of the battery cell. The energy conversion efficiency of the battery cell = discharge energy Q0 / charging energy Q1.

[0383] The test results are shown in Table 1.

[0384] Table 1

[0385] In Table 1,

[0386] The base area of ​​the positive terminal refers to the area of ​​the first terminal face of the positive terminal.

[0387] The bottom length of the positive terminal refers to the length of the first terminal face of the positive terminal.

[0388] When the S / L ratio is too small, such as in Comparative Example 1, the bottom area of ​​the positive terminal is small, the current carrying capacity of the positive terminal is relatively poor, which causes current to accumulate, the current distribution in the electrode plates is uneven, and the energy conversion efficiency of the battery cell is low.

[0389] When the S / L ratio is too large, such as in Comparative Example 2, the positive terminal has a superior overcurrent capability. Although this can improve the energy conversion efficiency to some extent, the positive terminal occupies a relatively large volume, which reduces the energy density of the battery cell.

[0390] In Examples 1, 2-1 to 2-5, the S / L ratio is within an appropriate range, which can effectively improve the capacity of the battery cell while also improving energy conversion efficiency and energy density.

[0391] The dimension L1mm of the first terminal face of the first electrode terminal along the length direction of the battery cell is 40.5-374.9mm.

[0392] In Examples 1, 2-1 to 2-5, the L1 / L ratio is within an appropriate range, which can further and effectively improve the capacity of the battery cell while also improving energy conversion efficiency and energy density.

[0393] Examples 3-1 to 3-2

[0394] Battery cells were prepared using a method similar to that of Example 1, except that the minimum cross-sectional area of ​​the positive terminal was adjusted.

[0395] Examples 4-1 to 4-2

[0396] Battery cells were prepared using a method similar to that of Example 1, except that the minimum cross-sectional area of ​​the positive terminal was adjusted.

[0397] Examples 5-1 and 5-2

[0398] Battery cells were prepared using a method similar to that of Example 1, except that the welding area of ​​the positive electrode tab and the positive terminal was adjusted.

[0399] The test results are shown in Table 2.

[0400] Table 2

[0401] In Table 2,

[0402] The length of each shell is 285mm, the capacity of each embodiment is basically the same, and the mass energy density of each embodiment is basically the same.

[0403] In each embodiment, the minimum cross-sectional area of ​​the positive terminal is the minimum cross-sectional area of ​​the second connection portion of the positive terminal along the thickness direction of the battery cell.

[0404] The minimum cross-sectional area of ​​the first electrode terminal is S1mm. 2 The diameter ranges from 167.4 to 1385.5 mm. 2 .

[0405] When the S1 / L ratio meets the above conditions, the overall overcurrent capacity of the positive terminal is excellent, which helps to reduce the resistance of the positive terminal and reduce the Joule heat generated by the resistance. Moreover, the positive terminal can also improve the thermal conductivity and heat dissipation performance, which helps to conduct heat faster and dissipate it evenly. Especially when the casing is long, the heat dissipation is fast, so that when the current flows through the positive terminal, it will not cause performance degradation due to local overheating or increased resistance, thus improving the energy conversion efficiency of the battery cell.

[0406] The dimension W mm of the first tab surface along the length of the battery cell is 43.2-570.5 mm.

[0407] When the W / L ratio meets the above conditions, the area where the positive electrode tab connects to the main body is relatively large, which is beneficial to improve the current collection efficiency in the length direction, improve the current distribution uniformity at the end of the tab near the main body, reduce heat accumulation, and improve the energy conversion efficiency of the battery cell.

[0408] The contact area between the first tab and the first electrode terminal is S2mm. 2 That is, the welding area between the two is 43.2-423.8 mm. 2 .

[0409] When the S2 / L ratio meets the above conditions, the current-carrying area of ​​the positive electrode tab is relatively large, resulting in excellent current-carrying capacity, which can reduce resistance and heat generation, thereby improving the energy conversion efficiency of the battery cell.

[0410] Examples 6-1 and 6-2

[0411] Battery cells were prepared using a method similar to that in Example 1, except that the compaction density of the positive electrode active material layer and the negative electrode active material layer was adjusted.

[0412] The test results are shown in Table 3.

[0413] Table 3

[0414] The current is uniformly injected into the positive and negative current collectors from the external circuit. The compaction density of the positive and negative active material layers and the electrode terminals with a large current flow area work together to enable the current to be uniformly and with low impedance distributed to the positive and negative active materials inside the positive and negative active material layers. This reduces the problems of local polarization and ohmic heat concentration caused by uneven electron distribution, and can significantly improve the energy conversion efficiency of the battery cell.

[0415] Examples 7-1 to 7-4

[0416] Battery cells were prepared using a method similar to that of Example 1, except that the electrolyte formulation was adjusted.

[0417] With the increase of the total content of LiFSI and LiPF6, the total mass content of the corresponding organic solvent decreases;

[0418] When the total content of LiFSI and LiPF6 decreases, the total mass content of the corresponding organic solvent increases;

[0419] As the mass content of VC increases, the total mass content of the corresponding organic solvents decreases.

[0420] When the mass content of VC decreases, the total mass content of the corresponding organic solvents increases.

[0421] The test results are shown in Table 4.

[0422] Table 4

[0423] In Table 4, LiPF6 / LiFSI represents the ratio of the mass content of LiPF6 to the mass content of LiFSI.

[0424] In Examples 7-1 and 7-2, LiFSI and LiPF6 are beneficial for improving the lithium-ion conduction capability of the electrolyte, enhancing the kinetic performance of the battery cell, reducing the hydrofluoric acid content in the electrolyte, improving the film formation quality of the solid electrolyte interphase (SEI) film on the negative electrode side, and reducing the resistance of the SEI film on the solid electrolyte interphase, thereby improving the energy conversion efficiency of the battery cell.

[0425] In Examples 7-3 and 7-4, additives such as VC can optimize the composition of the SEI film, reduce the impedance of the SEI film, and thus improve the energy conversion efficiency of the battery cell.

[0426] 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: A housing assembly includes a housing and an end cap assembly, the end cap assembly including an end cap and a first electrode terminal and a second electrode terminal disposed on the end cap, the end cap covering the housing; as well as An electrode assembly is disposed within the housing. 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, one of which is a positive electrode tab and the other is a negative electrode tab. in, The main body and the first electrode terminal are spaced apart along a first direction. The surface of the first electrode terminal facing the main body is a first terminal surface. The first tab is connected to the first terminal surface, and the second tab is connected to the second electrode terminal. The first direction is parallel to the length direction of the battery cell, or the first direction is parallel to the width direction of the battery cell. The battery cell meets the following requirements: L≥270, S≥1900, and S / L is between 7.0 and 9.

2. L represents the length of the shell, and its unit is mm; S represents the area of ​​the first terminal face, and its unit is mm. 2 .

2. The battery cell according to claim 1, wherein, L is between 270 and 1630; and / or S is between 1900 and 11400.

3. The battery cell according to claim 1 or 2, wherein, The main body and the first electrode terminal are spaced apart along the width direction of the battery cell; The battery cell satisfies the following condition: L1 / L is 0.15 to 0.23, where L1 represents the dimension of the first terminal face along the length direction of the battery cell, and its unit is mm.

4. The battery cell according to any one of claims 1 to 3, wherein, The battery cell satisfies the following condition: S1 / L is 0.62 to 0.85, where S1 represents the minimum cross-sectional area of ​​the first electrode terminal along the thickness direction of the battery cell, and its unit is mm. 2 .

5. The battery cell according to any one of claims 1 to 4, wherein, The first electrode terminal includes: A first connecting portion includes a first terminal face, and the first connecting portion protrudes toward the main body relative to the end cap; A second connecting portion is disposed on the end cap, and the second connecting portion is connected to the first connecting portion; and The third connecting portion is connected to the side of the second connecting portion opposite to the first connecting portion, and the third connecting portion protrudes from the end cap.

6. The battery cell according to claim 5, wherein, Along the thickness direction of the battery cell, the minimum cross-sectional area of ​​the first connection portion is greater than or equal to the minimum cross-sectional area of ​​the second connection portion; and / or Along the thickness direction of the battery cell, the minimum cross-sectional area of ​​the first connecting portion is greater than or equal to the minimum cross-sectional area of ​​the third connecting portion; and / or Along the thickness direction of the battery cell, the minimum cross-sectional area of ​​the third connection portion is greater than or equal to the minimum cross-sectional area of ​​the second connection portion.

7. The battery cell according to any one of claims 1 to 6, wherein, The first electrode extends out of the main body along the first direction.

8. The battery cell according to claim 7, wherein, The first tab extends out of the main body along the width direction of the battery cell; and / or The second tab extends out of the main body along the width direction of the battery cell.

9. The battery cell according to claim 7 or 8, wherein, The first electrode tab is in contact with the first terminal face.

10. The battery cell according to any one of claims 7 to 9, wherein, The battery cell meets the following requirements: W / L is 0.16 to 0.

35. W represents the dimension of the first tab surface along the length direction of the battery cell, and its unit is mm. The first tab surface is the surface of the first tab connected to the main body. The second direction and the first direction are perpendicular to the thickness direction of the battery cell.

11. The battery cell according to claim 9 or 10, wherein, The battery cell satisfies the following condition: S2 / L is 0.16 to 0.26, where S2 represents the contact area between the first tab and the first terminal surface, in mm. 2 .

12. The battery cell according to any one of claims 1 to 11, wherein, The second electrode terminal includes a second terminal surface, which is the surface of the second electrode terminal facing the main body, and the second terminal surface is connected to the second electrode tab; The battery cell meets the following requirements: M / L is 7.0 to 9.2, where M represents the area of ​​the second terminal facet in mm. 2 .

13. The battery cell according to any one of claims 1 to 12, wherein, The electrode assembly has a wound structure.

14. The battery cell according to any one of claims 1 to 13, 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 current collector is connected to the positive electrode tab. The positive electrode active material layer includes a positive electrode active material, which includes a phosphate active material.

15. The battery cell according to claim 14, wherein, The resistivity of the positive electrode active material at a pressure of 8 MPa is ≤20 Ω / cm.

16. The battery cell according to claim 14 or 15, wherein, The surface of the phosphate-based active material includes a carbon material, wherein the carbon content of the carbon material is 1% to 2.5% by mass, based on the mass of the phosphate-based active material.

17. The battery cell according to any one of claims 14 to 16, wherein, In a cross-section along its thickness direction, the particles of the positive electrode active material layer satisfy the following conditions: 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 50 is from 600nm to 900nm, D A 50 indicates the particle size at which the cumulative area distribution of the particles reaches 50%.

18. The battery cell according to any one of claims 14 to 17, wherein, The positive electrode active material layer satisfies: C 50 The range is from 0.98 to 1.

20. Among them, C 50 This indicates the median of the graphitization degree in the cumulative distribution curve of the graphitization degree C value obtained by laser microscopy confocal Raman spectroscopy in large-area scanning mode; The degree of graphitization C is I G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

19. The battery cell according to any one of claims 14 to 18, wherein, The compaction density of the positive electrode active material layer is 2.49 g / cm³. 3 Up to 2.8 g / cm 3 .

20. The battery cell according to any one of claims 1 to 19, wherein, The main body 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 current collector is connected to the negative electrode tab, and the compaction density of the negative electrode active material layer is 1.5 g / cm³. 3 Up to 2.3 g / cm 3 .

21. The battery cell according to any one of claims 1 to 20, wherein, The battery cell also includes an electrolyte, which comprises a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent has a mass content of 8% to 75% in the electrolyte.

22. The battery cell according to claim 21, wherein, The chain-like carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, ethyl propionate, propyl acetate, methyl propionate, and methyl butyrate.

23. The battery cell according to any one of claims 1 to 22, wherein, The battery cell also includes an electrolyte, which comprises a carbonate solvent, wherein the carbonate solvent has a mass content of 5% to 92%.

24. The battery cell according to claim 23, wherein, The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

25. The battery cell according to any one of claims 1 to 24, wherein, The battery cell also includes an electrolyte, which includes lithium fluorosulfonylimide, and the lithium fluorosulfonylimide in the electrolyte has a mass content of 2.5% to 6%.

26. The battery cell according to claim 25, wherein, The fluorinated sulfonyl imide lithium includes one or both of lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonyl imide.

27. The battery cell according to claim 25 or 26, wherein, The electrolyte also includes lithium hexafluorophosphate, and the ratio of the mass content of lithium hexafluorophosphate to the mass content of lithium fluorosulfonylimide is 2 to 4 based on the mass of the electrolyte.

28. The battery cell according to any one of claims 1 to 27, wherein, The battery cell further includes an electrolyte, which includes one or more of fluoroethylene carbonate and vinylene carbonate, wherein the total mass content of fluoroethylene carbonate and vinylene carbonate in the electrolyte is 0.5% to 6%.

29. The battery cell according to any one of claims 21 to 28, wherein, The electrolyte has a conductivity of 10 mS / cm to 13 mS / cm at room temperature.

30. The battery cell according to any one of claims 1 to 29, wherein, The capacity of the battery cell is greater than or equal to 500Ah.

31. The battery cell according to any one of claims 1 to 30, 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.

32. A battery device comprising a battery cell according to any one of claims 1 to 31.

33. An electrical device comprising the battery device according to claim 32.

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

35. An energy storage system comprising the energy storage device according to claim 34.

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