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

Abstract

The present application relates to a battery cell, a battery device, an electrical device, an energy storage device, and an energy storage system. The battery cell comprises: a housing; and an electrode assembly accommodated within the housing. The electrode assembly comprises an electrode body and a tab connected to each other, and the tab extends out of an end portion of the electrode body in a first direction. The electrode body comprises two first surfaces and two second surfaces. The two first surfaces are arranged opposite to each other along a second direction, and the two second surfaces are arranged opposite to each other along a third direction. The first direction, the second direction, and the third direction intersect with each other in pairs. A surface area S1 of the first surface satisfies: S1 ≥ 56000 mm2. An electrode terminal is arranged on the housing. The electrode terminal has a terminal surface facing the electrode body, the terminal surface is connected to the tab, and an area S2 of the terminal surface satisfies: S2 ≥ 1000 mm2.

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 applications PCT / CN2025 / 140517, PCT / CN2025 / 140531, PCT / CN2025 / 140529, PCT / CN2025 / 140513, PCT / CN2025 / 140527, PCT / CN2025 / 140521, PCT / CN2025 / 140532, PCT / CN2025 / 140522, PCT / CN2025 / 140453, PCT / CN2025 / 140528, PCT / CN2025 / 140456, PCT / CN2025 / 140452, PCT / CN2025 / 140362, and PCT / CN2025 / 085921, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of batteries, and in particular to a battery cell, battery device, power consumption device, energy storage device, and 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 applications for battery cells, higher demands are being placed on their performance, such as improving energy conversion efficiency. 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 of the battery cell.

[0006] In a first aspect, this application proposes a battery cell, comprising: a casing; and an electrode assembly housed within the casing. The electrode assembly includes interconnected electrode bodies and tabs, with the tabs extending from the ends of the electrode bodies in a first direction. The electrode bodies include two first surfaces and two second surfaces, the two first surfaces being disposed opposite each other along a second direction, and the two second surfaces being disposed opposite each other along a third direction. The first, second, and third directions intersect each other. The surface area S1 of the first surfaces satisfies S1 ≥ 56000 mm². 2 Electrode terminals are disposed in the housing. Each electrode terminal has a terminal surface facing the electrode body. The terminal surface is connected to an electrode tab. The area S2 of the terminal surface satisfies S2≥1000mm². 2 .

[0007] In the embodiments of this application, the battery cell includes a casing and an electrode assembly. The electrode assembly is housed within the casing and includes an electrode body and a tab extending from the electrode body at its end in a first direction X. The electrode body includes a first surface with a large surface area, enabling the battery cell to have a large capacity. The casing is provided with electrode terminals, and the tab is connected to the terminal surface of the electrode terminals to achieve electrical connection between the electrode terminals and the electrode assembly. When the area of ​​the terminal surface meets the above requirements, it can improve the overcurrent capacity between the electrode terminals and the electrode assembly, reduce Joule heat between the electrode terminals and the electrode assembly, thereby improving the energy conversion efficiency of the battery cell. It also helps to balance the temperature of the electrode terminals, improve the heat concentration problem, and help to improve the lifespan of the battery cell.

[0008] In some embodiments, the area S2 of the terminal face satisfies S2≥1900mm². 2 A larger terminal surface area is beneficial for increasing the contact area between the electrode terminals and the tabs, thereby improving the current carrying capacity between the electrode terminals and the electrode assembly, reducing Joule heating between the electrode terminals and the electrode assembly, and increasing the energy conversion efficiency of the battery cell; it also helps to balance the heat of the terminal surface and improve the problem of heat concentration causing damage to other components.

[0009] In some embodiments, the housing includes a casing and an end cap. The casing has a cavity with an opening at least at one end in a first direction. The electrode assembly is housed within the cavity, the end cap seals the opening, and electrode terminals are disposed on the end cap. The projected area S3 of the end cap and the electrode terminals in the first direction satisfies S2 ≤ 0.4 * S3. When the projected area of ​​the end cap and the electrode terminals in the first direction X satisfies the above condition, by limiting the size of the electrode terminals, the risk of interference and short circuits between the electrode terminals and other components is reduced, and the space and weight occupied by the electrode terminals are reduced, thereby increasing the energy density of the battery cell.

[0010] In some implementations, the capacity C of a single battery cell satisfies C≥500Ah. The design of the battery cell with the aforementioned capacity, along with the electrode terminals and tabs, can improve the energy conversion efficiency of the battery cell while increasing its energy density.

[0011] In some embodiments, the tab includes a first end and a second end disposed opposite to each other. The first end is connected to the electrode body, and the second end extends out of the end of the electrode body in a first direction. The dimension L1 of the first end in a third direction and the dimension L2 of the outer shell in a third direction satisfy 0.16 ≤ L1 / L2 ≤ 0.5. When the dimensions of the first end and the outer shell in the third direction Z satisfy the above condition, on the one hand, the tab and the electrode body have sufficient contact area, which can improve the connection reliability between the tab and the electrode body and reduce the contact resistance between the tab and the electrode body, thereby improving the energy conversion efficiency of the battery cell; on the other hand, it helps to reduce the manufacturing cost of the electrode assembly.

[0012] In some embodiments, the tab extends beyond the end of the electrode body in the first direction, and the extension dimension L3 of the tab satisfies 30mm ≤ L3 ≤ 40mm. In this embodiment, setting L3 to less than or equal to 40mm helps to shorten the conductive path, reduce overcurrent resistance, and improve the energy conversion efficiency of the battery cell. In this embodiment, setting L3 to greater than or equal to 30mm increases the distance between the end of the tab and the electrode body, thereby reducing the risk of the tab folding and inserting into the electrode body, leading to a short circuit within the battery cell.

[0013] In some embodiments, the dimensions L4 of the tab extending along the first direction and the central axis of the electrode body extending along the first direction in a third direction, and the dimensions L5 of the electrode body in the third direction, satisfy 3 ≤ L5 / L4 ≤ 4. When the dimensions of the electrode body in the third direction satisfy the above conditions, on the one hand, the ohmic impedance of the battery cell is reduced, and the energy conversion efficiency of the battery cell is improved; on the other hand, the problem of the tab being too close to the end of the electrode body in the third direction, which leads to the difficulty of welding the tab and the electrode body, is improved.

[0014] In some embodiments, the dimension L2 of the casing in the third direction satisfies 250mm ≤ L2 ≤ 500mm; alternatively, it can be 270mm ≤ L2 ≤ 300mm. In this embodiment, setting the dimension L2 of the casing in the third direction Z to be less than or equal to 500mm helps improve the uniformity of current density distribution, temperature distribution, and interfacial reaction. In this embodiment, setting the dimension L2 of the casing in the third direction to be greater than or equal to 250mm increases the casing size to accommodate more active material and improve the capacity of the battery cell.

[0015] In some embodiments, the dimension L6 of the casing in the first direction satisfies 0.7≤L6 / L2≤1; alternatively, it can be 0.9≤L6 / L2≤1. When the dimension of the casing in the first direction satisfies 0.7≤L6 / L2≤1, the dimensional difference between the casing in the first direction and the third direction is reduced, which helps the casing to accumulate heat to suppress heat dissipation of the battery cell, and improves the conductivity of the electrolyte in the battery cell to improve the energy conversion efficiency of the battery cell.

[0016] In some embodiments, the dimension L7 of the outer casing in the second direction satisfies 60mm≤L7≤90mm. On the one hand, increasing the dimension of the outer casing in the second direction Y helps the casing to further concentrate heat, thereby improving the conductivity of the electrolyte inside the battery cell; on the other hand, it also improves the problems of excessively large outer casing size, excessively heavy battery cells, and low energy density of battery cells.

[0017] In some embodiments, there are multiple tabs, including positive and negative tabs. The electrode body includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is disposed on at least one side of the positive current collector, and the positive current collector and the positive tab are connected. The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector, and the negative current collector and the negative tab are connected. During the charging and discharging process of a single battery cell, active ions (e.g., lithium ions) repeatedly insert and extract between the positive and negative electrodes.

[0018] In some embodiments, the areal density of the positive electrode active material layer is 0.2 / 1540.25 g / mm². 2 Up to 0.4 / 1540.25g / mm 2 When the areal density of the positive electrode active material layer meets the above conditions, the thickness of the positive electrode active material layer can be controlled within a reasonable range to balance the power performance and energy density of the battery cell.

[0019] In some embodiments, the positive electrode active material layer includes a lithium phosphate and a coating layer, the coating layer being located on at least a portion of the surface of the lithium phosphate, and the coating layer containing carbon. The carbon-containing coating layer, located on at least a portion of the surface of the lithium phosphate, can optimize the conductive network of the positive electrode active material layer, reduce contact resistance, increase ion transport rate, and improve the energy conversion efficiency of the battery cell.

[0020] 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; and / or D A 50 is 600nm to 900nm; optional is 650nm to 750nm. The D of the positive electrode active material layer... A When the above conditions are met, the particle size of the large particles is relatively small, which can reduce the internal resistance of the positive electrode and improve the kinetic performance of the battery cell while also improving the energy density of the battery cell; and / or the 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.

[0021] In some implementations, 1.855 ≤ D A 90 / D A 50≤2.375. D A 90 and D AWhen the ratio of 50 meets the above range, it helps to optimize the multi-level particle stacking structure. While increasing the compaction density of the positive electrode sheet, it constructs a gradient pore structure to maintain the continuity of the charge transport channel, so as to optimize the energy density and rate performance of the battery cell.

[0022] In some embodiments, the positive electrode active material layer satisfies the following: C50 is 0.98 to 1.20, where C50 represents the median of the graphitization degree C value in the cumulative distribution curve of graphitization degree C value obtained in the large-area scanning mode of laser microscopy confocal Raman spectroscopy; the graphitization degree C value is IG / ID, where IG represents the Raman spectrum at 1580±100 cm⁻¹. -1 The intensity of peak G at 1350 ± 100 cm⁻¹, where ID represents the Raman spectrum at 1350 ± 100 cm⁻¹. -1 The intensity of the D peak at that location. 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.

[0023] In some embodiments, the positive electrode active material layer contains titanium, with a titanium content of 500 ppm to 8000 ppm by mass; alternatively, the titanium content is 600 ppm to 1100 ppm by mass. When the titanium content in the positive electrode active material layer meets the above range, the titanium, phosphate groups, and lithium species synergistically construct a fast-ion conducting phase, optimizing the battery's kinetic performance.

[0024] In some embodiments, the positive electrode active material layer has a width dimension of 150 mm to 250 mm and / or a thickness dimension of 0.05 mm to 0.1 mm. When the width and thickness dimensions of the positive electrode active material layer are within these ranges, the problem of poor cell stability caused by large local temperature or performance differences in the positive electrode sheet due to poor consistency in the thickness or width of the positive electrode active material layer is mitigated.

[0025] In some embodiments, the compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 ; 2.4g / cm³ is optional. 3 Up to 3.0 g / cm 3 ; 2.5g / cm³ is optional 3 Up to 2.9 g / cm 3 ; 2.54g / cm³ is optional 3 Up to 2.8 g / cm 3 ; 2.6g / cm³ is optional 3 Up to 2.7 g / cm 3When the compaction density of the positive electrode active material layer meets the above conditions, it can optimize the microstructure inside the positive electrode active material layer and build a more efficient and stable three-dimensional electronic conductivity network, while improving the capacity of the battery cell.

[0026] In some embodiments, the areal density of the negative electrode active material layer is 0.1 / 1540.25 g / mm². 2 Up to 0.2 / 1540.25g / mm 2 When the areal density of the negative electrode active material layer meets the above conditions, on the one hand, the capacity requirement of the negative electrode is met by increasing the active material content per unit area; on the other hand, the problem of excessive active material content per unit area, which easily leads to delamination or cracking of the negative electrode sheet, is improved.

[0027] In some embodiments, the negative electrode active material layer includes graphite with a graphitization degree of 90%-95%. Highly crystalline graphite can effectively reduce structural defects, thereby improving the structural and thermal stability of the material, but it also comes at the cost of higher manufacturing costs. When the graphitization degree of the graphite in the negative electrode active material layer meets the above-mentioned range, the material cost is significantly reduced while ensuring the basic performance of the battery cell, achieving a good balance between performance and cost.

[0028] In some embodiments, the negative electrode active material layer has a width dimension of 153 mm to 257 mm and / or a thickness dimension of 0.05 mm to 0.1 mm. When the width and thickness dimensions of the negative electrode active material layer are within these ranges, the problem of poor cell stability caused by large local temperature or performance differences in the negative electrode sheet due to poor consistency in the thickness or width of the negative electrode active material layer is mitigated.

[0029] In some embodiments, the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 1.7 g / cm 3 When the compaction density of the negative electrode active material layer is within the above range, it can reduce the thickness of the electrode assembly while increasing the capacity of the battery cell. This allows the electrode assembly to be adapted to thinner battery cells, effectively reducing empty space, thereby reducing the water content in the system and improving the cycle performance of the battery cell.

[0030] In some embodiments, the electrode body further includes a separator, at least a portion of which is disposed between the positive and negative electrode plates. The separator includes a base film and a coating, the thickness of which is 2 μm to 4 μm. When the coating thickness meets the above range, on the one hand, the coating has sufficient thickness to provide thermal barrier function and improve the structural strength of the coating, thus mitigating the problem of cracking and detachment during cycling; on the other hand, it mitigates the problems of excessively thick coatings leading to long lithium-ion transport paths, low transport efficiency, low energy conversion efficiency of the battery cell, and high material cost of the battery cell.

[0031] In some embodiments, the battery cell further includes an electrolyte comprising dimethyl carbonate, wherein the mass content of dimethyl carbonate in the electrolyte is 10% to 20%. This content of dimethyl carbonate can, on the one hand, reduce the viscosity of the electrolyte and decrease the transport impedance of lithium ions in the electrolyte liquid phase, thereby improving the energy conversion efficiency of the battery cell; on the other hand, the high ionic conductivity of dimethyl carbonate helps to further improve the energy conversion efficiency of the battery cell.

[0032] In some embodiments, the electrolyte further includes lithium bisfluorosulfonylimide, wherein the lithium bisfluorosulfonylimide in the electrolyte comprises 2% to 5% by mass; optionally 2.5% to 4.5%; optionally 3% to 4%; optionally 3.3% to 3.7%. The aforementioned amounts of lithium bisfluorosulfonylimide improve the stability of the SEI film, thereby mitigating the interfacial instability caused by uneven current density and further enhancing the energy conversion efficiency of the battery cell.

[0033] In some embodiments, the electrolyte further includes vinylene carbonate, with a mass content of 0.5% to 8% in the electrolyte. This content of vinylene carbonate helps improve the stability and integrity of the SEI film, optimizes the composition of the SEI film, reduces the impedance of the SEI film, thereby improving the energy conversion efficiency of the battery cell. Furthermore, it further enhances the cycle performance and interface stability of the battery cell under conditions of localized high-temperature side reactions caused by the large size of the battery cell.

[0034] In some embodiments, the electrolyte further includes at least one of trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate, wherein the mass content of at least one of trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate in the electrolyte is from 0.03% to 0.5%. Materials within this range exhibit strong film-forming ability, which is beneficial for improving the cycle performance of the battery cell.

[0035] In some embodiments, the ratio of electrolyte mass to battery cell capacity is between 2.8 g / Ah and 3.0 g / Ah. This range of electrolyte mass-to-battery cell capacity ratios, on the one hand, ensures sufficient electrolyte wetting of the electrodes, improving the stability and integrity of the SEI film, uniform current distribution, reducing the internal resistance of the battery cell, and increasing the energy conversion efficiency of the battery cell; on the other hand, it mitigates the problems caused by excessive electrolyte, such as longer lithium-ion transport paths, increased internal resistance of the battery cell, and decreased energy conversion efficiency, as well as the problems caused by excessive electrolyte, such as increased side reactions, gas production, and increased risk of thermal runaway.

[0036] In some embodiments, the capacity of a single battery cell is C Ah, and the residual space factor of the single battery cell is from 0.18*C ml / Ah to 0.22*C ml / Ah. When the residual space factor of the single battery cell meets the above range, it helps to improve the volumetric energy density of the single battery cell and also helps to reduce the manufacturing cost of the single battery cell.

[0037] Secondly, this application proposes a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this application.

[0038] Thirdly, this application proposes an electrical device, which includes the battery device according to any embodiment of the second aspect of this application.

[0039] Fourthly, this application proposes an energy storage device, which includes a battery device according to any embodiment of the second aspect of this application.

[0040] 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

[0041] 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.

[0042] Figure 1 is a schematic diagram of the structure of an electrical device provided in some embodiments of this application;

[0043] Figure 2 is a schematic diagram of the structure of a battery pack provided in some embodiments of this application;

[0044] Figure 3 is a schematic diagram of the structure of a battery module provided in some embodiments of this application;

[0045] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0046] Figure 5 is an exploded view of a battery cell provided in some embodiments of this application;

[0047] Figure 6 is a partial structural schematic diagram of a battery cell provided in some embodiments of this application;

[0048] Figure 7 is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0049] Figure 8 is a front view of the electrode assembly of a battery cell provided in some embodiments of this application;

[0050] Figure 9 is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0051] Figure 10 is a schematic diagram of the structure of the positive electrode sheet of a battery cell provided in some embodiments of this application;

[0052] Figure 11 is a schematic diagram of the structure of the negative electrode sheet of a battery cell provided in some embodiments of this application.

[0053] The accompanying drawings may not be drawn to scale.

[0054] The reference numerals in the attached drawings are explained as follows: 1. Vehicle; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Receiving space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. Electrode body; 111. Positive electrode plate; 112. Negative electrode plate; 113. Separator; 1111. Positive current collector; 1112. Positive active material layer; 1121. Negative current collector; 1122. Negative active material layer; 114. First surface; 115. Second surface; 12. Tab; 121. Positive tab; 122. Negative tab; 123. First end; 124. Second end; 20. Outer shell; 21. Housing; 22. End cap; 30. Electrode terminal; 301. Terminal surface; X. First direction; Y. Second direction; Z. Third direction. Detailed Implementation

[0055] 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.

[0056] 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.

[0057] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0058] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] When the overcurrent area of ​​the electrode terminals is small, the Joule heat accumulation between the electrode terminals and the tabs leads to an increased temperature rise and reduces energy conversion efficiency; moreover, as heat accumulates, it may exceed the thermal stability threshold of the battery cell, increasing the risk of thermal runaway.

[0064] In view of this, the present application proposes a battery cell, which includes a casing and an electrode assembly. The electrode assembly is housed within the casing and includes an electrode body and a tab extending from the end of the electrode body in a first direction. The electrode body includes a first surface with a large surface area, so that the battery cell can have a large capacity. The casing is provided with electrode terminals, and the tab is connected to the terminal surface of the electrode terminals to realize the electrical connection between the electrode terminals and the electrode assembly. When the area of ​​the terminal surface meets the above requirements, it is beneficial to improve the overcurrent capacity between the electrode terminals and the electrode assembly, reduce the Joule heat between the electrode terminals and the electrode assembly, thereby improving the energy conversion efficiency of the battery cell; and it helps to balance the temperature of the electrode terminals, improve the heat concentration problem, and help to improve the life of the battery cell.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] In some implementations, the energy storage device is an energy storage container or an energy storage cabinet.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] As an example, the power distribution unit can be used to distribute power to the power modules of the energy storage device.

[0076] 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.

[0077] As shown in Figure 1, a battery device is installed inside the vehicle 1. The battery device can be located at the bottom, front, or rear of the vehicle 1. The battery device can be used to power the vehicle 1; for example, the battery device can serve as the operating power source for the vehicle 1.

[0078] Vehicle 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, for the power needs of vehicle 1 during starting, navigation and driving.

[0079] In some embodiments of this application, the battery device can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0080] 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.

[0081] In some implementations, a battery cell assembly is typically formed by arranging multiple battery cells.

[0082] 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.

[0083] In some embodiments, the battery device may be a battery pack 2, for example, as shown in Figure 1, where a battery pack 2 is provided inside the vehicle 1.

[0084] The battery pack 2 includes a housing and one or more battery cell assemblies, which are housed within the housing.

[0085] 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.

[0086] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0087] 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.

[0088] 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, with 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; 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] A single battery cell can be the smallest unit that makes up a battery device.

[0093] 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.

[0094] 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.

[0095] As shown in Figures 4 and 5, in some embodiments, the battery cell 7 includes a housing 20 and an electrode assembly 10. The housing 20 includes a casing 21 and an end cap 22. The casing 21 includes a receiving cavity with an opening, and the end cap 22 covers the opening. The electrode assembly 10 is disposed within the receiving cavity 210.

[0096] The housing 21 can have various shapes, such as 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 has a cuboid structure, the housing 21 can also have a cuboid structure. Optionally, the electrode assembly 10 can have a cuboid structure.

[0097] 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.

[0098] The end cap 22 closes onto the opening of the housing 21 to isolate the internal environment of the battery cell 7 from the external environment. The end cap 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of this application do not impose any special limitations on this.

[0099] Optionally, electrode terminals 30 can be disposed on end cap 22. The electrode terminals can be electrically connected to electrode assembly 10 for outputting or inputting electrical energy of battery cell 7.

[0100] 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.

[0101] As shown in Figures 4 to 8, in some embodiments, the battery cell 7 includes a housing 20 and an electrode assembly 10. The electrode assembly 10 is housed within the housing 20 and includes an electrode body 11 and a tab 12 connected to each other. The tab 12 extends from the electrode body 11 at its end in a first direction X. The electrode body 11 includes two first surfaces 114 and two second surfaces 115. The two first surfaces 114 are arranged opposite each other along a second direction Y, and the two second surfaces 115 are arranged opposite each other along a third direction Z. The first direction X, the second direction Y, and the third direction Z intersect each other. The surface area S1 of the first surface 114 satisfies S1≥56000mm². 2 Electrode terminals 30 are disposed on the housing 20. Electrode terminals 30 have terminal surfaces 301 facing the electrode body 11. Terminal surfaces 301 are connected to electrode tabs 12. The area S2 of terminal surfaces 301 satisfies S2≥1000mm². 2 .

[0102] In the embodiment of this application, the battery cell 7 includes a housing 20 and an electrode assembly 10. The electrode assembly 10 is housed within the housing 20 and includes an electrode body 11 and a tab 12 extending from the end of the electrode body 11 in a first direction X. The electrode body 11 includes a first surface 114 with a large surface area, so that the battery cell 7 can have a large capacity. The housing 20 is provided with electrode terminals 30, and the tab 12 is connected to the terminal surface 301 of the electrode terminals 30 to realize the electrical connection between the electrode terminals 30 and the electrode assembly 10. When the area of ​​the terminal surface 301 meets the above requirements, it can improve the overcurrent capacity between the electrode terminals 30 and the electrode assembly 10, reduce the Joule heat between the electrode terminals 30 and the electrode assembly 10, thereby improving the energy conversion efficiency of the battery cell 7; and help to balance the temperature of the electrode terminals 30, improve the heat concentration problem, and help to improve the life of the battery cell 7.

[0103] Optionally, the first direction X is parallel to the height direction of the battery cell 7, the second direction Y is parallel to the thickness direction of the battery cell 7, and the third direction Z is parallel to the length direction of the battery cell 7; or the first direction X is parallel to the length direction of the battery cell 7, the second direction Y is parallel to the thickness direction of the battery cell 7, and the third direction Z is parallel to the height direction of the battery cell 7. The height direction, thickness direction, and length direction of the battery cell 7 are all perpendicular to each other.

[0104] The number of tabs 12 is multiple, including positive tab 121 and negative tab 122. Optionally, both positive tab 121 and negative tab 122 extend from the same end of the electrode body 11 in the first direction X; or positive tab 121 and negative tab 122 extend from both ends of the electrode body 11 in the first direction X.

[0105] Optionally, there may be multiple electrode terminals 30. At least one electrode terminal 30 is connected to the positive electrode tab 121, and at least one electrode terminal 30 is connected to the negative electrode tab 122. Optionally, there may be two electrode terminals 30. The two electrode terminals 30 may be located at the same end of the housing 20 in the first direction X, or the two electrode terminals 30 may be located at opposite ends of the housing 20 in the first direction X.

[0106] The electrode body 11 includes a first surface 114, the surface area S1 of the first surface 114 being ≥ 56000 mm². 2 The larger first surface 114 indicates that the electrode body 11 has a larger first direction X dimension and / or a third direction Z dimension, so that the electrode body 11 has sufficient size to accommodate more active material, so that the battery cell 7 has a larger capacity.

[0107] For example, the surface area S1 of the first surface 114 is 56000 mm². 2 57000mm 2 58000mm 2 59000mm 2 60000mm 2 61000mm 2 62000mm 2 63000mm 2 64000mm 2 65000mm 2 66000mm 2 67000mm 2 68000mm 2 69000mm 2 70000mm 2 Or a range consisting of any two of the above values.

[0108] The area S2 of terminal face 301 is ≥ 1000 mm² 2 The area S2 of the terminal face 301 can be selected as ≥1900mm². 2 A larger terminal surface 301 is beneficial for increasing the contact area between the electrode terminal 30 and the tab 12, thereby improving the current carrying capacity between the electrode terminal 30 and the electrode assembly 10, reducing Joule heating between the electrode terminal 30 and the electrode assembly 10, and increasing the energy conversion efficiency of the battery cell 7; it also helps to balance the heat of the terminal surface 301 and improve the problem of heat concentration causing damage to other components.

[0109] For example, the area S2 of the terminal surface 301 is 1000 mm². 2 1100mm 2 1200mm 2 1300mm2 1400mm 2 1500mm 2 1600mm 2 1700mm 2 1800mm 2 1900mm 2 2000mm 2 2100mm 2 2200mm 2 2300mm 2 2400mm 2 2500mm 2 Or a range consisting of any two of the above values.

[0110] For example, a sealing ring is provided between the electrode terminal 30 and the housing 20, and the electrode tab 12 is welded to the terminal surface 301. The problem of damage to other components may be fatigue of the welding point of the electrode tab 12 and aging of the sealing ring.

[0111] Optionally, the tab 12 is in contact with the terminal surface 301. In this case, the tab 12 is directly connected to the electrode terminal 30, eliminating the need for an adapter. This reduces internal resistance, further reduces the heat generated, and improves the energy conversion efficiency of the battery cell 7.

[0112] For example, the tab 12 is welded to the terminal surface 301, and the area of ​​the terminal surface 301 is greater than or equal to the welding area. It is easy to understand that the larger the area of ​​the terminal surface 301, the larger the welding area can be set; a larger welding area means a larger contact area between the electrode terminal 30 and the tab 12. A larger contact area helps to reduce the contact resistance between the two, thereby improving the overcurrent capacity between the electrode terminal 30 and the tab 12, slowing down heat generation, reducing energy loss, and increasing the energy conversion efficiency of the battery cell 7.

[0113] Optionally, the number of electrode terminals 30 is two, and the area of ​​the terminal surface 301 of both electrode terminals 30 is greater than or equal to 1000 mm². 2 This is to reduce the impact of the overcurrent capacity of the electrode terminal 30 of the smaller terminal surface 301 on the performance of the battery cell.

[0114] In some embodiments, the housing 20 includes a housing 21 and an end cap 22. The housing 21 has a cavity with an opening at least at one end in a first direction X. The electrode assembly 10 is housed in the cavity, and the end cap 22 covers the opening. An electrode terminal 30 is disposed on the end cap 22, and the projected area S3 of the end cap 22 and the electrode terminal 30 in the first direction X satisfies S2 ≤ 0.4 * S3. When the projected area of ​​the end cap 22 and the electrode terminal 30 in the first direction X satisfies the above condition, by limiting the size of the electrode terminal 30, the risk of interference and short circuit between the electrode terminal 30 and other components is reduced, and the space and weight occupied by the electrode terminal are reduced, thereby increasing the energy density of the battery cell 7.

[0115] For example, the area of ​​terminal face 301 is 0.1×S3, 0.2×S3, 0.3×S3, 0.4×S3, or a range of any two of the above values.

[0116] The electrode terminal 30 is disposed on the end cover 22. The orthogonal projection area of ​​the end cover 22 and the electrode terminal 30 in the first direction X refers to the orthogonal projection area of ​​the whole formed by the electrode terminal 30 and the end cover 22 in the first direction X.

[0117] During the cycling process of a battery cell, terminal facet 301 can provide more parallel current paths. However, due to limitations in the manufacturing process, the impedances of these current paths differ. In this embodiment, setting S2 to be less than or equal to 0.4*S3 reduces the difficulty of controlling the current paths on terminal facet 301, reduces the impedance differences between multiple current paths, improves the uniformity of current distribution, and enhances the energy conversion efficiency of the battery cell 7. Furthermore, setting S2 to be less than or equal to 0.4*S3 in this embodiment also reduces the length of the overcurrent path between the tab and the low-impedance current path on the terminal facet, reduces the overcurrent resistance of the electrode terminal and the tab, and further enhances the energy conversion efficiency of the battery cell 7.

[0118] In some embodiments, the capacity C Ah of the battery cell 7 satisfies C≥500. The battery cell 7 with the above-mentioned capacity, in conjunction with the design of the electrode terminals 30, tabs 12, etc., can improve the energy conversion efficiency of the battery cell 7 while increasing its energy density.

[0119] For example, the capacity C of the battery cell 7 is 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000 or any two of the above values.

[0120] 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 number of battery cells 7, improve consistency, reduce mechanical components that cannot provide energy, improve the space utilization of battery devices, power devices, energy storage devices, and energy storage systems, and increase the overall energy density.

[0121] 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 20, the material of the positive electrode active material, the surface density and compaction density of the positive electrode active material layer, the material of the negative electrode active material, and the surface density and compaction density of the negative electrode active material layer.

[0122] For example, the larger the volume of the casing 20, the more active material it can accommodate, and the higher the capacity of the battery cell 7.

[0123] For example, as the areal density increases, the capacity of the battery cell 7 increases; as the compaction density increases, the capacity of the battery cell 7 also increases.

[0124] The capacity of battery cell 7 is as known in this application and can be tested using equipment and methods known in the art. For example, at 25°C and normal pressure, battery cell 7 is charged at a power of 0.25P to the upper limit of the charging voltage, for example, 3.65V, and left to stand for 10 minutes. Then, it is discharged at a power of 0.25P to the discharge cutoff voltage, for example, 2.5V, and left to stand for 10 minutes. The above charge and discharge process is repeated 3 times. The discharge capacity of the third discharge is recorded as the capacity C0 of battery cell 7.

[0125] In some embodiments, the capacity of the battery cell 7 is C Ah, and the residual space coefficient of the battery cell 7 is from 0.18*C ml / Ah to 0.22*C ml / Ah. When the residual space coefficient of the battery cell 7 meets the above range, it helps to improve the volumetric energy density of the battery cell 7 and also helps to reduce the manufacturing cost of the battery cell 7.

[0126] The residual space factor is the ratio of the residual volume to the rated capacity of the battery cell 7. The residual volume can be the volume remaining in the battery cell 7 after removing all solid and liquid components (including positive electrode plates, negative electrode plates, separator, mechanical parts, electrolyte, etc.). The residual volume can be measured by filling the remaining space with liquid while keeping the casing unchanged, or by using methods such as laser scanning / nuclear magnetic resonance technology. For example, after the battery cell 7 is finished, electrolyte is injected into the casing until the entire cavity is filled; the volume of the subsequently injected electrolyte is the residual volume.

[0127] For example, the residual space coefficient of the battery cell 7 is 0.18*C ml / Ah, 0.19*C ml / Ah, 0.20*C ml / Ah, 0.21*C ml / Ah, 0.22*C ml / Ah, or a range of any two of the above values.

[0128] In some embodiments, the tab 12 includes a first end 123 and a second end 124 disposed opposite to each other. The first end 123 is connected to the electrode body 11, and the second end 124 extends out of the end of the electrode body 11 in the first direction X. The first end 123 has a dimension L1 in the third direction Z, and the outer shell 20 has a dimension L2 in the third direction Z, satisfying 0.16≤L1 / L2≤0.5.

[0129] When the dimensions of the first end 123 and the outer casing 20 in the third direction Z meet the above conditions, on the one hand, the tab 12 and the electrode body 11 have sufficient contact area, which can improve the connection reliability of the tab 12 and the electrode body 11 and reduce the contact resistance of the tab 12 and the electrode body 11, thereby improving the energy conversion efficiency of the battery cell 7; on the other hand, it helps to reduce the manufacturing cost of the electrode assembly 10.

[0130] For example, L1 / L2 is 0.16, 0.2, 0.3, 0.33, 0.4, 0.5 or a range consisting of any two of the above values.

[0131] In some embodiments, the tab 12 extends from the end of the electrode body 11 in the first direction X, and the extension dimension L3 of the tab 12 satisfies 30mm≤L3≤40mm.

[0132] In this embodiment, L3 is set to less than or equal to 40mm, which helps to shorten the conductive path, reduce overcurrent resistance, and improve the energy conversion efficiency of the battery cell 7. In this embodiment, L3 is set to greater than or equal to 30mm, which increases the distance between the tab end and the electrode body, thereby reducing the risk of the tab folding and inserting into the electrode body, causing a short circuit inside the battery cell 7.

[0133] The extension dimension L3 of the tab 12 is the dimension along the X direction after the tab 12 is flattened.

[0134] For example, the extension dimension L3 of the tab 12 is 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, 38mm, 39mm, 40mm or any range of two of the above values.

[0135] When the extension dimension of the tab 12 is short, the end of the tab 12 that is away from the electrode body 11 is close to the electrode body 11. Under the action of external force, the tab 12 can be easily folded and inserted into the electrode body 11, piercing the separator 113, causing the positive electrode 111 and the negative electrode 112 to conduct, resulting in a short circuit in the battery cell 7.

[0136] In some embodiments, the central axis N1 of the tab 12 extending along the first direction X and the central axis N2 of the electrode body 11 extending along the first direction X are in the third direction Z with dimension L4, and the dimension L5 of the electrode body 11 is in the third direction Z, satisfying 3≤L5 / L4≤4.

[0137] In these embodiments, when the electrode body 11 meets the above conditions in the third direction Z, on the one hand, the ohmic impedance of the battery cell 7 is reduced and the energy conversion efficiency of the battery cell 7 is improved; on the other hand, the problem that the tab 12 is too close to the end of the electrode body 11 in the third direction Z, which makes the welding of the tab 12 and the electrode body 11 difficult is improved.

[0138] For example, L5 / L4 is 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0 or a range consisting of any two of the above values.

[0139] In this embodiment, the electrode assembly 10 is designed with a sampling bias tab 12. On the one hand, this increases the distance between the tab 12 and the central axis of the electrode body 11 in the third direction Z, thereby reducing the equivalent parallel resistance of the electrode body 11 and reducing the impedance of the battery cell 7 to improve its energy conversion efficiency. On the other hand, it also increases the distance between the tab 12 and the edge portion of the electrode body 11, improving the problem that the current collector at the edge portion is prone to wrinkling and tearing during the welding process of the tab 12 and the electrode body 11, resulting in poor stability of the tab 12. It also improves the problem that the current is excessively concentrated in the narrow area between the tab 12 and the edge due to the tab 12 being too close to the edge of the electrode body 11, resulting in excessively high local temperature of the electrode body 11.

[0140] In some embodiments, the dimension L2 of the housing 20 in the third direction Z satisfies 250mm≤L2≤500mm; optionally, it is 270mm≤L2≤300mm.

[0141] In this embodiment, the dimension L2 of the outer casing 20 in the third direction Z is set to be less than or equal to 500 mm, which helps to improve the uniformity of current density distribution, temperature distribution, and interface reaction. In this embodiment, the dimension L2 of the outer casing 20 in the third direction Z is set to be greater than or equal to 250 mm, increasing the outer casing size to accommodate more active materials and increase the capacity of the battery cell 7.

[0142] For example, the size L2 of the housing 20 in the third direction Z is 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, 360mm, 370mm, 380mm, 390mm, 400mm, 450mm, 500mm or any combination of two of the above values.

[0143] The dimension of the casing 20 along the third direction Z is the length of the battery cell 7. When the dimension of the casing 20 along the third direction Z is within the above range, the size of the battery cell 7 is longer, which is beneficial for accommodating more active materials, thereby increasing the capacity of the battery cell 7; the casing 20 of the above dimensions, combined with the electrode terminals 30 of appropriate size, can effectively improve the energy conversion efficiency of the battery cell 7.

[0144] Optionally, the housing 20 has a dimension L6 of 200 mm to 250 mm in the first direction X.

[0145] For example, the size L6 of the housing 20 in the first direction X is 200mm, 210mm, 220mm, 230mm, 240mm, 250mm or any combination of two of the above values.

[0146] In some embodiments, the dimension L6 of the housing 20 in the first direction X satisfies 0.7 ≤ L6 / L2 ≤ 1. Optionally, it can be 0.9 ≤ L6 / L2 ≤ 1.

[0147] When the size of the outer casing 20 in the first direction X satisfies 0.7≤L6 / L2≤1, the size difference between the outer casing 20 in the first direction X and the third direction Z is reduced, which helps the outer casing 20 to accumulate heat, suppress heat dissipation of the battery cell 7, and improve the conductivity of the electrolyte in the battery cell 7, thereby improving the energy conversion efficiency of the battery cell 7.

[0148] For example, L6 / L2 is 0.7, 0.75, 0.8, 0.85, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or a range of any two of the above values.

[0149] Optionally, the housing 20 has a dimension L6 of 175 mm to 500 mm in the first direction X; optionally, it is 243 mm to 270 mm.

[0150] For example, the size L6 of the housing 20 in the first direction X is 175mm, 200mm, 225mm, 230mm, 240mm, 243mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 350mm, 400mm, 450mm, 500mm or any combination of two of the above values.

[0151] With the same internal volume, a cuboid has a larger surface area than a cube. The cube, with its smaller surface area, is more likely to accumulate internal heat. Therefore, in this embodiment, the difference between the outer casing 20 in the first direction (X-dimensional) and the third direction (Z-dimensional) is reduced, making the outer casing 20 closer to a heat-accumulating cube. This suppresses heat dissipation from the battery cell 7 and mitigates the problems of increased electrolyte viscosity, decreased conductivity, increased internal resistance, and decreased energy conversion efficiency of the battery cell 7 due to excessively low battery cell 7 temperature.

[0152] In some embodiments, the size L7 of the outer casing 20 in the second direction Y satisfies 60mm≤L7≤90mm. On the one hand, increasing the size of the outer casing 20 in the second direction Y helps the outer casing 20 to further accumulate heat, thereby improving the conductivity of the electrolyte in the battery cell 7. On the other hand, it also improves the problems of the outer casing 20 being too large, the battery cell 7 being too heavy, and the battery cell 7 having low energy density.

[0153] For example, the size L7 of the housing 20 in the first direction X is 60mm, 70mm, 80mm, 90mm or any combination of two of the above values.

[0154] As shown in Figures 9 to 11, in some embodiments, there are multiple tabs 12, including positive tabs 121 and negative tabs 122. The electrode body 11 includes a positive electrode plate 111 and a negative electrode plate 112. The positive electrode plate 111 includes a positive current collector 1111 and a positive active material layer 1112. The positive active material layer 1112 is provided on at least one side of the positive current collector 1111. The positive current collector 1111 and the positive tab 121 are connected. The negative electrode plate 112 includes a negative current collector 1121 and a negative active material layer 1122. The negative active material layer 1122 is disposed on at least one side of the negative current collector 1121. The negative current collector 1121 and the negative tab 122 are connected. During the charging and discharging process of the battery cell 7, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive and negative electrodes.

[0155] Optionally, the positive current collector 1111 and the positive electrode tab 121 are prepared separately and welded together; or the positive current collector 1111 and the positive electrode tab 121 are integrally formed, and the positive current collector 1111 and the positive electrode tab 121 are cut from the same foil material.

[0156] Optionally, the electrode assembly 10 located within the housing 20 can be one or more.

[0157] Optionally, the electrode body 11 can be a stacked structure or a wound structure.

[0158] In some embodiments, the electrode body 11 further includes a separator 113, at least a portion of which is disposed between the positive electrode 111 and the negative electrode 112. The separator 113 includes a base film and a coating, the thickness of which is 2 μm to 4 μm.

[0159] When the coating thickness meets the above range, on the one hand, the coating has sufficient thickness to play a role in thermal barrier and improve the structural strength of the coating, thus improving the problem of cracking and detachment during cycling; on the other hand, it improves the problem of excessive coating thickness, which leads to long lithium-ion transport paths, low transport efficiency, low energy conversion efficiency of battery cell 7, and high material cost of battery cell 7.

[0160] The separator 113 is disposed between the positive electrode 111 and the negative electrode 112 to reduce the risk of short circuit between the positive electrode 111 and the negative electrode 112, while allowing active ions to pass through.

[0161] Optionally, the coating includes a PCCS (Polymer Ceramic Coating System) coating, which combines the high thermal stability of the ceramic component with the interfacial bonding properties of the polymer component. A single coating application achieves the effects of both a ceramic and polymer coating, reducing processing costs.

[0162] In the embodiments of this application, the thickness of the coating has a meaning known in the art and can be detected using equipment and methods known in the art, such as measuring the thickness of the coating using a micrometer.

[0163] In some embodiments, the areal density of the positive electrode active material layer 1112 is 0.2 / 1540.25 g / mm². 2 Up to 0.4 / 1540.25g / mm 2 .

[0164] When the areal density of the positive electrode active material layer 1112 meets the above conditions, the thickness of the positive electrode active material layer 1112 is controlled within a reasonable range to balance the power performance and energy density of the battery cell 7.

[0165] Optionally, the areal density is greater than or equal to 0.2 / 1540.25 g / mm². 2In this case, a thicker positive electrode active material layer 1112 ensures sufficient mass of active material per unit area of ​​the current collector, thereby improving the specific energy and volumetric energy density of the battery cell 7. Furthermore, a thicker positive electrode sheet 111 helps reduce the number of electrode components 10 within the battery cell 7, improving the internal space utilization of the battery cell 7 and reducing the manufacturing cost of the battery cell 7.

[0166] Surface density less than or equal to 0.4 / 1540.25 g / mm² 2 In this case, the positive electrode active material layer 1112 is relatively thin. The thinner active material layer can shorten the lithium ion transport path, reduce ohmic polarization and diffusion polarization, and thus exhibit better rate characteristics during high-rate charge and discharge.

[0167] For example, the areal density of the positive electrode active material layer 1112 is 0.2 / 1540.25 g / mm². 2 0.25 / 1540.25g / mm 2 0.3 / 1540.25g / mm 2 0.35 / 1540.25g / mm 2 0.4 / 1540.25g / mm 2 Or a range consisting of any two of the above values.

[0168] In some embodiments, the positive electrode active material layer 1112 has a width dimension of 150 mm to 250 mm and / or a thickness dimension of 0.05 mm to 0.1 mm.

[0169] In these embodiments, when the width and thickness of the positive electrode active material layer 1112 are within the above-mentioned range, the problem of poor cell stability caused by large local temperature or performance differences in the positive electrode sheet 111 due to poor consistency in the thickness or width of the positive electrode active material layer 1112 is improved.

[0170] For example, the positive electrode active material layer 1112 has a width dimension of 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm or any combination of two of the above values.

[0171] For example, the thickness dimension of the positive electrode active material layer 1112 is 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm or any combination of two of the above values.

[0172] In some embodiments, the compaction density of the positive electrode active material layer 1112 is 2.3 g / cm³. 3 Up to 3.3 g / cm3 2.4g / cm³ is an optional value. 3 Up to 3.0 g / cm 3 2.5g / cm³ is an option. 3 Up to 2.9 g / cm 3 The option is 2.54 g / cm³. 3 Up to 2.8 g / cm 3 2.6g / cm³ is an option. 3 Up to 2.7 g / cm 3 .

[0173] In these embodiments, when the compaction density of the positive electrode active material layer 1112 meets the above conditions, it can optimize the internal microstructure of the positive electrode active material layer 1112 and construct a more efficient and stable three-dimensional electronic conductive network while improving the capacity of the battery cell 7.

[0174] For example, the compaction density of the positive electrode active material layer 1112 is 2.3 g / cm³. 3 2.32 g / cm 3 2.34 g / cm 3 2.36 g / cm 3 2.38g / cm 3 2.4g / cm 3 2.42 g / cm 3 2.44 g / cm 3 2.46 g / cm 3 2.48 g / cm 3 2.5g / cm 3 2.52g / cm 3 2.54 g / cm 3 2.56 g / cm 3 2.58g / cm 3 2.60g / cm 3 2.62 g / cm 3 2.64 g / cm 3 2.66 g / cm 3 2.68g / cm 3 2.7g / cm 3 2.72 g / cm 3 2.74 g / cm 3 2.76 g / cm 3 2.78g / cm 3 2.8g / cm 3 2.82 g / cm 3 2.84 g / cm 3 2.86 g / cm 3 2.88g / cm3 2.9g / cm 3 2.92g / cm 3 2.94 g / cm 3 2.96 g / cm 3 2.98g / cm 3 3g / cm 3 3.02g / cm 3 3.04 g / cm 3 3.06 g / cm 3 3.08g / cm 3 3.1g / cm 3 3.12g / cm 3 3.14 g / cm 3 3.16 g / cm 3 3.18 g / cm 3 3.2g / cm 3 3.22g / cm 3 3.24 g / cm 3 3.26 g / cm 3 3.28g / cm 3 3.3g / cm 3 Or a range consisting of any two of the above values.

[0175] Specifically, an appropriate compaction density increases the contact points between the positive electrode active material and the conductive agent and the positive electrode current collector 1111, 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 1112, achieving optimization of the electron conduction path while ensuring the lithium ion transport channel.

[0176] Moreover, the aforementioned compaction density, in conjunction with the larger terminal surface 301, allows current to be uniformly injected into the positive current collector 1111 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 1112, 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 7.

[0177] In this embodiment, the areal density and compaction density of the positive electrode active material layer 1112 can be the compaction density of the positive electrode active material layer 1112 of the battery cell 7 in a fully discharged state.

[0178] The upper limit voltage for charging and the lower limit voltage for discharging of battery cell 7 vary depending on the positive electrode active material. For example, when the phosphate active material includes lithium iron phosphate, the upper limit voltage for charging can be 3.65V and the lower limit voltage for discharging can be 2.0V. Another example is when the phosphate active material includes lithium manganese iron phosphate, the upper limit voltage for charging can be 4.2V and the lower limit voltage for discharging can be 2.0V.

[0179] 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 battery cell 7: In this embodiment, the fully discharged state and fully charged state of battery cell 7 are defined as follows:

[0180] Battery cell 7 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).

[0181] The battery cell 7 is discharged at a constant current discharge rate of 0.33C to the discharge cutoff voltage, which corresponds to the fully discharged state of the battery cell 7 and the 0% state of charge (SOC).

[0182] The areal density and compaction density of the positive electrode active material layer 1112 can be tested using the following method: Disassemble the positive electrode sheet 111 from the fully discharged battery cell 7, and measure the compaction density of the positive electrode active material layer 1112. For example, take a single-sided coated positive electrode sheet 111 (if it is a double-sided coated sheet, wipe off the positive electrode active material layer 1112 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 1112 of the weighed positive electrode sheet 111, weigh the positive electrode current collector 1111, record its mass as M0, and measure its thickness H0. The surface density of the positive electrode active material layer 1112 is (M1-M0) / S1, the thickness of the positive electrode active material layer 1112 is H1-H0, and the compaction density of the positive electrode active material layer 1112 is the surface density of the positive electrode active material layer 1112 / the thickness of the positive electrode active material layer 1112.

[0183] In the embodiments of this application, the thicknesses of the positive electrode active material layer 1112 and the positive electrode current collector 1111 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 111 can be measured using a micrometer, the film layer on the surface of the positive electrode current collector 1111 can be removed, and the thickness of the positive electrode current collector 1111 can be measured using a micrometer. When the positive electrode active material layer 1112 is coated on one side, the thickness of the positive electrode active material layer 1112 is the thickness of the positive electrode sheet 111 minus the thickness of the positive electrode current collector 1111. When the positive electrode active material layer 1112 is coated on both sides, the thickness of the positive electrode active material layer 1112 is (the thickness of the positive electrode sheet 111 minus the thickness of the positive electrode current collector 1111) / 2.

[0184] In the embodiments of this application, the width of the positive electrode active material layer 1112 has a meaning known in the art and can be detected using equipment and methods known in the art, such as using calipers or micrometers to measure the width of the positive electrode active material layer 1112.

[0185] In some embodiments, the areal density of the negative electrode active material layer 1122 is 0.1 / 1540.25 g / mm². 2 Up to 0.2 / 1540.25g / mm 2 .

[0186] When the areal density of the negative electrode active material layer 1122 meets the above conditions, on the one hand, the capacity requirement of the negative electrode is met by increasing the active material content per unit area; on the other hand, the problem of excessive active material content per unit area, which makes the negative electrode sheet 112 prone to delamination or cracking is improved.

[0187] For example, the areal density of the negative electrode active material layer 1122 is 0.1 / 1540.25 g / mm². 2 0.12 / 1540.25g / mm 2 0.15 / 1540.25g / mm 2 0.2 / 1540.25g / mm 2 Or a range consisting of any two of the above values.

[0188] In this embodiment, the areal density of the negative electrode active material layer 1122 can be the areal density of the negative electrode active material layer 1122 of the battery cell 7 in a fully discharged state. The areal density of the negative electrode active material layer 1122 can be tested using the same testing method as the positive electrode active material layer 1112, which will not be elaborated here.

[0189] In some embodiments, the negative electrode active material layer 1122 has a width dimension of 153 mm to 257 mm and / or a thickness dimension of 0.05 mm to 0.1 mm.

[0190] When the width and thickness of the negative electrode active material layer 1122 are within the above range, the problem of poor cell stability caused by large local temperature or performance differences in the negative electrode sheet 112 due to poor consistency in the thickness or width of the negative electrode active material layer 1122 is improved.

[0191] For example, the negative electrode active material layer 1122 has a width dimension of 153mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 257mm or any combination of two of the above values.

[0192] For example, the thickness dimension of the negative electrode active material layer 1122 is 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm or any range of two of the above values.

[0193] The width and thickness of the negative electrode active material layer 1122 can be tested using the same testing method as the positive electrode active material layer 1112, and will not be elaborated here.

[0194] In some embodiments, the compaction density of the negative electrode active material layer 1122 is 1.3 g / cm³. 3 Up to 1.7 g / cm 3 .

[0195] When the compaction density of the negative electrode active material layer 1122 is within the above range, the electrode assembly 10 can be thinned while increasing the capacity of the battery cell 7. This allows the electrode assembly 10 to be adapted to the thinner battery cell 7, effectively reducing the free space, thereby reducing the water content in the system and improving the cycle performance of the battery cell 7.

[0196] For example, the compaction density of the negative electrode active material layer 1122 is 1.3 g / cm³. 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 Or a range consisting of any two of the above values.

[0197] In this embodiment, the compaction density of the negative electrode active material layer 1122 can be the compaction density of the negative electrode active material layer 1122 of the battery cell 7 in a fully discharged state.

[0198] The compaction density of the negative electrode active material layer 1122 can be tested using the same testing method as the positive electrode active material layer 1112, which will not be elaborated here.

[0199] In some embodiments, the positive electrode active material layer includes a lithium phosphate and a coating layer, the coating layer being located on at least a portion of the surface of the lithium phosphate, and the coating layer containing carbon elements.

[0200] In these embodiments, the carbon-containing coating layer is located on at least a portion of the surface of the lithium phosphate-containing material, which can optimize the conductive network of the positive electrode active material layer, reduce contact resistance, increase ion transport rate, and improve the energy conversion efficiency of the battery cell.

[0201] Specifically, carbon materials can form a coating layer on the surface of lithium phosphate active materials. This helps improve the contact between active material particles, reduce interparticle contact resistance, increase the conductivity of the positive electrode active material layer, and lower the internal resistance of the battery cell. The carbon material coating layer forms a continuous conductive network, thereby reducing obstruction of electron transport paths and creating smoother electron transport paths. Electrons can release energy more efficiently during discharge, thus improving the energy conversion efficiency of the battery cell. It also helps optimize ion transport paths, increase ion transport rates, reduce energy loss, and ultimately improve the energy conversion efficiency of the battery cell.

[0202] 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 represents the range of 1400nm to 2100nm. For example, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm, or any range of two of these values. Optionally, D A 90 refers to the range of 1600nm to 1850nm.

[0203] In these embodiments, 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 improve the dynamic performance of the battery cell while improving the energy density of the battery cell.

[0204] In some embodiments, in a cross-section along its own thickness direction, the particles of the positive electrode active material layer satisfy: D A 50 represents 600nm to 900nm; it can also be 650nm to 750nm. For example, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, or any range of two of the above values.

[0205] In these embodiments, the 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.

[0206] In some embodiments, 1.855 ≤ D A 90 / D A 50≤2.375.

[0207] In the solution of this application embodiment, D A 90 and D A When the ratio of 50 meets the above range, it helps to optimize the multi-level particle stacking structure. While increasing the compaction density of the positive electrode sheet, it constructs a gradient pore structure to maintain the continuity of the charge transport channel, so as to optimize the energy density and rate performance of the battery cell.

[0208] For example, D A 90 / D A 50 can be 1.855, 1.9, 2.0, 2.1, 2.2, 2.3, 2.375, or a range of any two of the above values.

[0209] In the embodiments of this application, D A 90 and D A When the ratio of 50 meets the above range, it helps to optimize the multi-level particle stacking structure. While increasing the compaction density of the positive electrode sheet, it constructs a gradient pore structure to maintain the continuity of the charge transport channel, so as to optimize the energy density and rate performance of the battery cell.

[0210] D A 50 indicates the particle size at which the cumulative area distribution of the particles reaches 50%.

[0211] D A 90 indicates the particle size at which the cumulative area distribution of the particles reaches 90%.

[0212] In the embodiments of this application, the term "particle" refers to a particle in the field of view of the positive electrode active material layer at a certain magnification, such as 10,000 times, which has a identifiable complete boundary. The particle may have defects or scratches inside, but the particle cannot be identified as having a complete boundary sufficient to divide the particle.

[0213] 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.

[0214] The specific method for particle identification 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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 IJ 1.46r), 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.

[0219] 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.

[0220] 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.

[0221] In some embodiments, 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.

[0222] 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;

[0223] 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 the D peak at that location. 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.

[0224] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphitic carbon in the positive electrode film layer. This makes it easier for particles to slip during rolling, thanks to the highly graphitized carbon structures in the coating material. With proper particle gradation in the electrode, even under low rolling pressure, the electrode compaction density can be further improved. Furthermore, highly graphitized carbon can form a highly efficient three-dimensional electron conduction network, significantly reducing the interfacial charge transfer resistance of the positive electrode, minimizing energy loss, and improving the energy conversion efficiency of the battery cell.

[0225] In some embodiments, the positive electrode active material layer contains titanium, and the mass content of titanium in the positive electrode active material layer is 500ppm-8000ppm.

[0226] When the mass content of titanium in the positive electrode active material layer meets the above range, titanium, phosphate groups, and lithium species synergistically construct a fast ion conductor phase, which optimizes the kinetic performance of the battery.

[0227] Optionally, the mass content of titanium in the positive electrode active material layer is 600ppm-1100ppm.

[0228] For example, the mass content of titanium in the positive electrode active material layer is 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm or any two of the above values.

[0229] Optionally, the elements in the positive electrode active material layer and the content of each element can be determined using an argon ion cross-section polisher (model JEOLIB-19530CP) and a scanning electron microscope (model Zeiss Sigma 300) (equipped with an X-ray energy dispersive spectrometer (EDS, model Oxford X-Max-50mm2)).

[0230] For example, the positive electrode sheet of a fully discharged battery cell is disassembled, and the longitudinal cross-section of the positive electrode active material layer is obtained by using an ion section polisher. The cross-section of the positive electrode active material layer is scanned by a scanning electron microscope to test the titanium content.

[0231] In some embodiments, the negative electrode active material layer comprises graphite, with a graphitization degree of 90%-95%.

[0232] Highly crystalline graphite can effectively reduce structural defects, thereby improving the structural and thermal stability of materials, but it also comes at the cost of higher manufacturing costs. When the graphitization degree of the graphite in the negative electrode active material layer meets the above-mentioned range, the material cost is significantly reduced while ensuring the basic performance of the battery cell, achieving a good balance between performance and cost.

[0233] For example, the graphitization degree of graphite is 90%, 91%, 92%, 93%, 94%, 95%, or any range of two of the above values.

[0234] In this embodiment, the method for testing the degree of graphitization of graphite can be as follows: scrape off the negative electrode active material layer powder from the negative electrode sheet, perform testing using an X-ray diffractometer (XRD), and calculate the 002 interplanar spacing (d) using the Bragg equation. 002 =nλ / sinθ), degree of graphitization P = (1-(d 002 -0.3354) / (0.344-0.3354))×100%.

[0235] [Positive electrode plate]

[0236] 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 comprising a positive active material. For example, the positive current collector has two sides opposite each other in its thickness direction, and the positive active material layer is disposed on either or both sides of the positive current collector.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] Lithium phosphate exhibits excellent stability during cycling, which can improve the lifespan of individual battery cells.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] 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 improve the conductivity of the positive electrode active material layer and increase the mass ratio of other substances, such as the positive electrode active material, thereby balancing the fast charging capability and energy density of the battery cell.

[0245] 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.

[0246] 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, optionally a conductive agent, optionally a binder, and any other components in a solvent and stirring until homogeneous. The solvent may include, but is not limited to, N-methylpyrrolidone (NMP).

[0247] 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).

[0248] 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.

[0249] [Negative electrode plate]

[0250] 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 comprising 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 or both sides of the negative current collector.

[0251] 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.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] 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.

[0256] In some embodiments, the negative electrode active material layer also 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.

[0257] 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, optionally a conductive agent, optionally a 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.

[0258] 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).

[0259] 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.

[0260] [Isolation Component]

[0261] 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.

[0262] In some embodiments, the separating membrane comprises a porous base membrane.

[0263] 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.

[0264] Alternatively, the polyolefin includes one or more of polyethylene, polypropylene, and polyvinylidene fluoride.

[0265] In some implementations, the separator can be a base membrane.

[0266] In some embodiments, the separator further includes a coating disposed on at least one side of the base film. The coating may include inorganic particles to improve the heat resistance of the separator and enhance the reliability of the battery cells. Optionally, the coating is disposed on both sides of the base film. Specifically, the coating is disposed on both sides of the base film along the thickness direction of the separator itself.

[0267] 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.

[0268] 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.

[0269] Electrolyte

[0270] In some embodiments, the battery cell further includes an electrolyte comprising dimethyl carbonate, wherein the mass content of dimethyl carbonate in the electrolyte is 10% to 20%.

[0271] The dimethyl carbonate content mentioned above can, on the one hand, reduce the viscosity of the electrolyte and reduce the transport impedance of lithium ions in the electrolyte liquid phase, thereby improving the energy conversion efficiency of the battery cell; on the other hand, the high ionic conductivity of dimethyl carbonate helps to further improve the energy conversion efficiency of the battery cell.

[0272] For example, the mass content of dimethyl carbonate in the electrolyte is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination of two of the above values.

[0273] Optionally, the electrolyte also includes ethylene carbonate and diethyl carbonate. In the embodiments of this application, dimethyl carbonate, which has a lower viscosity, is added to the ethylene carbonate and diethyl carbonate solvent to reduce the overall viscosity of the solvent, increase the diffusion rate of lithium ions, and further improve the energy conversion efficiency of the battery cell.

[0274] In some embodiments, the electrolyte further includes lithium bisfluorosulfonylimide, wherein the lithium bisfluorosulfonylimide in the electrolyte comprises 2% to 5% by mass; optionally 2.5% to 4.5%; optionally 3% to 4%; optionally 3.3% to 3.7%.

[0275] The aforementioned content of lithium bisfluorosulfonylimide enhances the stability of the SEI film, thereby mitigating the interfacial instability caused by uneven current density and further improving the energy conversion efficiency of the battery cell.

[0276] For example, the mass content of lithium bisfluorosulfonylimide in the electrolyte 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%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or any combination of two of the above values.

[0277] Optionally, the electrolyte may also include lithium hexafluorophosphate. The combined use of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide is beneficial to improving the lithium-ion conduction capacity of the electrolyte, enhancing the kinetic performance of the battery cell, and reducing the hydrofluoric acid content in the electrolyte. This improves the film formation quality of the solid electrolyte interphase (SEI) film on the negative electrode side and reduces the resistance of the SEI film, thereby improving the energy conversion efficiency of the battery cell.

[0278] In some embodiments, the electrolyte further includes vinylene carbonate, wherein the mass content of vinylene carbonate in the electrolyte is 1% to 3%.

[0279] The aforementioned content of vinylene carbonate helps improve the stability and integrity of the SEI film, optimizes the composition of the SEI film, and reduces the impedance of the SEI film, thereby improving the energy conversion efficiency of the battery cell. Furthermore, under the condition of local high-temperature side reactions caused by the large size of the battery cell, it further improves the cycle performance and interface stability of the battery cell.

[0280] Optionally, the mass content of vinylene carbonate in the electrolyte is 1.6% to 3%.

[0281] Optionally, the mass content of vinylene carbonate in the electrolyte is 1.7% to 2.4%.

[0282] For example, the mass content of vinylene carbonate in the electrolyte is 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.5%, 3.0%, or any range of two of the above values.

[0283] In some embodiments, the electrolyte further includes at least one selected from trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate, wherein the mass content of at least one selected from trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate in the electrolyte is from 0.03% to 0.5%. Materials within this range exhibit strong film-forming ability, which is beneficial for improving the cycle performance of the battery cell.

[0284] For example, the mass content of the above material in the electrolyte is 0.03%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any range of two of the above values.

[0285] Optionally, trimethylsilyl phosphate additive can be added to the electrolyte. Trimethylsilyl phosphate decomposes under high temperature or thermal runaway conditions, releasing flame-retardant compounds, thereby effectively reducing the risk of battery cell ignition. Simultaneously, its decomposition products form a protective film inside the battery cell, preventing flame spread and further heat accumulation. Trimethylsilyl phosphate exhibits good thermal stability, remaining stable within the normal operating temperature range of the battery cell and not affecting its normal performance. Furthermore, trimethylsilyl phosphate has good compatibility with other materials and electrolyte components in the battery, reducing the risk of adverse effects on the battery's electrochemical performance (such as capacity, energy density, and cycle life).

[0286] 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.

[0287] 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.

[0288] 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.

[0289] 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".

[0290] In some embodiments, the ratio of the mass of the electrolyte to the capacity of the battery cell is from 2.8 g / Ah to 3.0 g / Ah.

[0291] The electrolyte mass to battery cell capacity ratio within the aforementioned range, on the one hand, ensures that the electrolyte fully wets the electrode, improving the stability and integrity of the SEI film, uniform current distribution, reducing the internal resistance of the battery cell, and improving the energy conversion efficiency of the battery cell; on the other hand, it improves the problems caused by excessive electrolyte, such as longer lithium-ion transport paths, increased internal resistance of the battery cell, and decreased energy conversion efficiency of the battery cell, as well as the problems caused by excessive electrolyte, such as increased side reactions, increased gas production, and increased risk of thermal runaway.

[0292] For example, the ratio of electrolyte mass to battery cell capacity is 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, or any combination of two of the above values.

[0293] The mass of the electrolyte can be tested using methods known in the art. For example, the battery cell is weighed and its mass is recorded as M0; the battery cell is disassembled, and the electrolyte is poured out; the internal electrode assembly is removed, and the positive electrode, negative electrode, separator, and mechanical parts (such as the insulating film covering the electrode assembly) are separated. The positive electrode, negative electrode, separator, and mechanical parts are then immersed in dimethyl carbonate (DMC) for 24-48 hours, repeated at least three times. The aforementioned positive electrode, negative electrode, separator, and mechanical parts are placed in a 100°C oven for at least 24 hours until completely dried. The dried positive electrode, negative electrode, separator, and mechanical parts are weighed and their mass is recorded as M1; thus, the mass of the electrolyte inside the battery cell is obtained as M0-M1.

[0294] Example

[0295] 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.

[0296] Example 1-1

[0297] 1. Preparation of positive electrode sheet

[0298] 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.

[0299] The positive electrode active material layer comprises a film formed by uniformly coating a positive electrode slurry (using 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.

[0300] Lithium iron phosphate has a carbon layer coated on its surface.

[0301] The areal density of the positive electrode active material layer is 0.25 g / 1540.25 mm. 2 Compacted density 2.75 g / cm³ 3 The mass content of titanium in the positive electrode active material layer is 2000 ppm.

[0302] 2. Preparation of negative electrode sheet

[0303] 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.

[0304] The negative electrode active material layer comprises a film layer formed by uniformly coating the negative electrode slurry (solvent is water) onto the surface of the negative electrode current collector, and then drying and cold pressing it. The negative electrode active material layer comprises artificial graphite, conductive agent Super P, and binder SBR in a mass ratio of 96:2:2.

[0305] The areal density of the negative electrode active material layer is 0.18 g / 1540.25 mm. 2 The compacted density is 1.6 g / cm³. 3 .

[0306] 3. Isolation components

[0307] The separator includes a base film and a polymer ceramic (PCCS) coating disposed on both sides of the base film. The base film is polyethylene (PE).

[0308] 4. Preparation of electrolyte

[0309] The electrolyte consists of organic solvents, lithium salts, and additives.

[0310] The components in an organic solvent are mixed in a mass ratio, and then lithium salt and additives are added to the mixed solvent to prepare an electrolyte.

[0311] Based on the total mass of the electrolyte, the organic solvents include ethylene carbonate EC (30 wt%), dimethyl carbonate DMC (20 wt%), and diethyl carbonate DEC (30 wt%).

[0312] Based on the total mass of the electrolyte, the additives also include 3% vinylene carbonate and 2% fluoroethylene carbonate (FEC) by mass.

[0313] Based on the total mass of the electrolyte, the lithium salt comprises 12 wt% lithium hexafluorophosphate (LiPF6) and 3 wt% lithium bisfluorosulfonylimide (LiFSI).

[0314] 5. Preparation of battery cells

[0315] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator placed between the positive and negative electrode to provide isolation, thus obtaining the electrode assembly.

[0316] The electrode tabs of the electrode assembly are directly laser-welded to the electrode terminals of the end cap, placed into the outer shell, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, the battery cell is finally obtained.

[0317] The surface area of ​​the first surface of the electrode body is 60000 mm². 2 The terminal surface area of ​​the electrode terminal is 1000 mm². 2 The first end of the electrode has a width dimension (i.e., electrode width dimension) of 87 mm. The extension dimension of the electrode is 35 mm. The dimension in a third direction between the central axis of the electrode extending in the first direction and the central axis of the electrode body extending in the first direction is 83 mm. The length dimension of the outer shell is 300 mm, and the height dimension of the outer shell is 285 mm. The first direction is parallel to the height direction of the outer shell, and the third direction is parallel to the length direction of the outer shell, the width direction of the electrode, and the length direction of the electrode body.

[0318] Comparative Example 1

[0319] Battery cells were prepared using a method similar to that of Example 1-1, except that the terminal surface area of ​​the electrode terminals was adjusted.

[0320] Examples 1-2

[0321] Battery cells were prepared using a method similar to that of Example 1-1, except that the terminal surface area of ​​the electrode terminals was adjusted.

[0322] Examples 2-1 and 2-2

[0323] Battery cells were prepared using a method similar to that of Example 1-1, except that the ratio of the casing height to the casing length was adjusted.

[0324] Examples 3-1 and 3-2

[0325] Battery cells were prepared using a method similar to that of Example 1-1, except that the ratio of the width of the first end of the tab to the length of the outer casing was adjusted.

[0326] Examples 3-3 and 3-4

[0327] Battery cells were prepared using a method similar to that of Example 1-1, except that the extension dimensions of the tabs were adjusted.

[0328] Examples 3-5 and 3-6

[0329] The battery cell was prepared using a method similar to that in Example 1-1. The difference from Example 1-1 is that the ratio of the dimension of the central axis of the tab extending in the first direction to the dimension of the length of the electrode body in the third direction was adjusted.

[0330] Examples 4-1 and 4-2

[0331] Battery cells were prepared using a method similar to that in Example 1-1, except that the areal density of the positive active material layer of the positive electrode sheet was adjusted.

[0332] Examples 4-3 and 4-4

[0333] Battery cells were prepared using a method similar to that in Example 1-1, except that the compaction density of the positive active material layer of the positive electrode sheet was adjusted.

[0334] Examples 4-5 and 4-6

[0335] Battery cells were prepared using a method similar to that in Example 1-1, except that the titanium content of the positive electrode active material layer of the positive electrode sheet was adjusted.

[0336] Examples 5-1 and 5-2

[0337] Battery cells were prepared using a method similar to that in Example 1-1. The difference from Example 1-1 was that the mass content of dimethyl carbonate, ethylene carbonate, and diethyl carbonate in the electrolyte was adjusted. When the mass content of dimethyl carbonate increased by N%, the mass content of ethylene carbonate and diethyl carbonate decreased by N%.

[0338] Examples 5-3 and 5-4

[0339] Battery cells were prepared using a method similar to that in Example 1-1. The difference from Example 1-1 was that the mass content of lithium difluorosulfonyl imide and lithium hexafluorophosphate in the electrolyte was adjusted. When the mass content of lithium difluorosulfonyl imide increased by N%, the mass content of lithium hexafluorophosphate decreased by N%.

[0340] Examples 5-5 and 5-6

[0341] Battery cells were prepared using a method similar to that in Example 1-1. The difference from Example 1-1 was that the mass content of vinylene carbonate and fluoroethylene carbonate in the electrolyte was adjusted. When the mass content of vinylene carbonate increased by N%, the mass content of fluoroethylene carbonate decreased by N%.

[0342] Performance testing

[0343] 1. Energy conversion efficiency test of individual battery cells

[0344] 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.

[0345] 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.

[0346] The test results are shown in Table 1.

[0347] Table 1

[0348] When the terminal surface area is small, such as in Comparative Example 1, the current-carrying capacity between the electrode terminals and the electrode assembly is poor, the Joule heat generated between the electrode terminals and the electrode assembly is large, and the energy conversion efficiency of the battery cell is low.

[0349] In Examples 1-1 and 1-2, when the terminal surface area is within an appropriate range, the current-carrying capacity between the electrode terminals and the electrode assembly is good, the Joule heat generated between the electrode terminals and the electrode assembly is low, and the energy conversion efficiency of the battery cell is high. Furthermore, within an appropriate range, the larger the terminal surface area, the higher the energy conversion efficiency of the battery cell.

[0350] In Examples 1-1, 2-1, and 2-2, when L6 / L2 is within an appropriate range, it helps the casing to accumulate heat to suppress heat dissipation from individual battery cells, thereby improving the energy conversion efficiency of individual battery cells. By increasing the value of L6 / L2 within an appropriate range, it helps to further enhance the heat accumulation capacity of the casing and improve the energy conversion efficiency of individual battery cells.

[0351] The test results are shown in Table 2.

[0352] Table 2

[0353] In Examples 1-1, 3-1, and 3-2, when L1 / L2 is within an appropriate range, the contact resistance between the tab and the electrode body can be reduced, thereby improving the energy conversion efficiency of the battery cell. By increasing the value of L1 / L2 within an appropriate range, it is helpful to further reduce the contact resistance between the tab and the electrode body and improve the energy conversion efficiency of the battery cell.

[0354] In Examples 1-1, 3-3, and 3-4, the tab extension size, when within an appropriate range, can shorten the conductive path, reduce overcurrent resistance, and improve the energy conversion efficiency of the battery cell. Reducing the tab extension size within an appropriate range helps to further reduce overcurrent resistance and improve the energy conversion efficiency of the battery cell.

[0355] In Examples 1-1, 3-5, and 3-6, L5 / L4, when within an appropriate range, can reduce the ohmic impedance of a single battery cell and improve its energy conversion efficiency. Increasing the value of L5 / L4 within an appropriate range can further improve the energy conversion efficiency of the battery cell.

[0356] The test results are shown in Table 3.

[0357] Table 3

[0358] In Examples 1-1, 4-1, and 4-2, the areal density of the positive electrode active material layer of the positive electrode sheet within an appropriate range can shorten the lithium ion transport path, reduce ohmic polarization and diffusion polarization, thereby improving the energy conversion efficiency of the battery cell; further improving the energy conversion efficiency of the battery cell can be achieved by reducing the areal density of the positive electrode sheet within an appropriate range.

[0359] In Examples 1-1, 4-3, and 4-4, the compaction density of the positive electrode active material layer of the positive electrode sheet is within an appropriate range, which increases the contact points between the positive electrode active material and the conductive agent and the positive electrode current collector, reduces the contact resistance between particles and the interfacial transmission impedance, and improves the energy conversion efficiency of the battery cell. By increasing the compaction density of the positive electrode sheet within an appropriate range, the energy conversion efficiency of the battery cell can be further improved.

[0360] In Examples 1-1, 4-5, and 4-6, the mass content of titanium in the positive electrode active material layer is within an appropriate range. Titanium, phosphate groups, and lithium species synergistically construct a fast-ion conductor phase, which optimizes the kinetic performance of the battery and improves the energy conversion efficiency of the battery cell. By increasing the titanium content within an appropriate range, the energy conversion efficiency of the battery cell can be further improved.

[0361] The test results are shown in Table 4.

[0362] Table 4

[0363] DMC stands for dimethyl carbonate; LiFSI stands for lithium bis(fluorosulfonyl)imide; VC stands for vinylene carbonate.

[0364] In Examples 1-1, 5-1, and 5-2, when the DMC content is within an appropriate range, DMC can reduce the overall viscosity of the electrolyte and increase the diffusion rate of lithium ions, thereby improving the energy conversion efficiency of the battery cell. By increasing the DMC content within an appropriate range, the electrolyte viscosity can be further reduced, thereby improving the energy conversion efficiency of the battery cell.

[0365] In Examples 1-1, 5-3, and 5-4, the LiFSI content within an appropriate range is beneficial for improving the lithium-ion conductivity 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 SEI film at the solid electrolyte interface on the negative electrode side, and reducing the resistance of the SEI film at the solid electrolyte interface, thereby improving the energy conversion efficiency of the battery cell. By increasing the LiFSI content within an appropriate range, the energy conversion efficiency of the battery cell can be further improved.

[0366] In Examples 1-1, 5-5, and 5-6, the VC content within an appropriate range 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. By increasing the VC content within an appropriate range, the energy conversion efficiency of the battery cell can be further improved.

[0367] 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: shell; An electrode assembly, housed within the housing, includes interconnected electrode bodies and electrode tabs. The electrode tabs extend from the end of the electrode body in a first direction. The electrode body includes two first surfaces and two second surfaces. The two first surfaces are arranged opposite each other along a second direction, and the two second surfaces are arranged opposite each other along a third direction. The first direction, the second direction, and the third direction intersect each other. The surface area S1 of the first surfaces satisfies S1≥56000mm². 2 , An electrode terminal is disposed on the housing, the electrode terminal having a terminal surface facing the electrode body, the terminal surface being connected to the electrode tab, and the area S2 of the terminal surface satisfying S2≥1000mm². 2 .

2. The battery cell according to claim 1, wherein, The area S2 of the terminal face satisfies S2≥1900mm². 2 .

3. The battery cell according to claim 1 or 2, wherein, The housing includes a shell and an end cap. The shell has a cavity with an opening at least one end in a first direction. The electrode assembly is housed in the cavity. The end cap covers the opening. The electrode terminal is disposed on the end cap. The projected area S3 of the end cap and the electrode terminal in the first direction satisfies S2≤0.4*S3.

4. The battery cell according to any one of claims 1-3, wherein, The capacity C of the battery cell satisfies C≥500Ah.

5. The battery cell according to any one of claims 1-4, wherein, The electrode tab includes a first end and a second end disposed opposite to each other. The first end is connected to the electrode body, and the second end extends out of the end of the electrode body in the first direction. The first end has a dimension L1 in the third direction, and the outer shell has a dimension L2 in the third direction, satisfying 0.16≤L1 / L2≤0.

5.

6. The battery cell according to any one of claims 1-5, wherein, The tab extends from the end of the electrode body in the first direction, and the extension dimension L3 of the tab satisfies 30mm≤L3≤40mm.

7. The battery cell according to any one of claims 1-6, wherein, The central axis of the electrode tab extending along the first direction and the central axis of the electrode body extending along the first direction are in the third direction at a dimension L4, and the dimension of the electrode body in the third direction is L5, satisfying 3≤L5 / L4≤4.

8. The battery cell according to any one of claims 1-7, wherein, The outer casing has a third-direction dimension L2 that satisfies 250mm≤L2≤500mm; alternatively, it can be 270mm≤L2≤300mm.

9. The battery cell according to claim 8, wherein, The dimension L6 of the outer shell in the first direction satisfies 0.7≤L6 / L2≤1; it can be optionally 0.9≤L6 / L2≤1.

10. The battery cell according to claim 8, wherein, The dimension L7 of the outer shell in the second direction satisfies 60mm≤L7≤90mm.

11. The battery cell according to any one of claims 1-10, wherein, The electrode tabs are multiple, including positive electrode tabs and negative electrode tabs. The electrode body includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is disposed on at least one side of the positive current collector. The positive current collector is connected to the positive electrode tab. The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector. The negative current collector is connected to the negative electrode tab.

12. The battery cell according to claim 11, wherein, The compaction density of the positive electrode active material layer is 2.3 g / cm³. 3 Up to 3.3 g / cm 3 ; 2.4g / cm³ is optional. 3 Up to 3.0 g / cm 3 ; 2.5g / cm³ is optional 3 Up to 2.9 g / cm 3 ; 2.54g / cm³ is optional 3 Up to 2.8 g / cm 3 ; 2.6g / cm³ is optional 3 Up to 2.7 g / cm 3 .

13. The battery cell according to claim 11 or 12, wherein, The areal density of the positive electrode active material layer is 0.2 / 1540.25 g / mm². 2 Up to 0.4 / 1540.25g / mm 2 .

14. The battery cell according to any one of claims 11-13, wherein, The positive electrode active material layer includes a lithium phosphate and a coating layer, wherein the coating layer is located on at least a portion of the surface of the lithium phosphate and the coating layer contains carbon.

15. The battery cell according to any one of claims 11-14, wherein, In a cross-section along its thickness direction, the particles of the positive electrode active material layer satisfy: D A 90 is from 1400nm to 2100nm; and / or D A 50 is 600nm to 900nm; optional is 650nm to 750nm.

16. The battery cell according to claim 15, wherein, 1.855≤D A 90 / D A 50≤2.375。 17. The battery cell according to claim 14, wherein, The positive electrode active material layer satisfies the following conditions: C50 is 0.98 to 1.

20. Wherein, C50 represents the median of the degree of graphitization in the cumulative distribution curve of the degree of graphitization C value obtained by laser microscopy confocal Raman spectroscopy in large-area scanning mode; The degree of graphitization C is IG / ID, where IG represents the Raman spectrum at 1580±100 cm⁻¹. -1 The intensity of peak G at 1350 ± 100 cm⁻¹, where ID represents the Raman spectrum at 1350 ± 100 cm⁻¹. -1 The intensity of peak D at that location.

18. The battery cell according to any one of claims 11-17, wherein, The positive electrode active material layer contains titanium, and the mass content of titanium in the positive electrode active material layer is 500ppm-8000ppm; optionally, the mass content of titanium in the positive electrode active material layer is 600ppm-1100ppm.

19. The battery cell according to any one of claims 11-18, wherein, The positive electrode active material layer has a width dimension of 150 mm to 250 mm and / or a thickness dimension of 0.05 mm to 0.1 mm.

20. The battery cell according to any one of claims 11-19, wherein, The areal density of the negative electrode active material layer is 0.1 / 1540.25 g / mm². 2 Up to 0.2 / 1540.25g / mm 2 .

21. The battery cell according to any one of claims 11-20, wherein, The negative electrode active material layer includes graphite, and the graphite has a graphitization degree of 90%-95%.

22. The battery cell according to any one of claims 11-21, wherein, The negative electrode active material layer has a width dimension of 153 mm to 257 mm and / or a thickness dimension of 0.05 mm to 0.1 mm.

23. The battery cell according to any one of claims 11-22, wherein, The compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 Up to 1.7 g / cm 3 .

24. The battery cell according to any one of claims 11-23, wherein, The electrode body further includes an insulating element, at least a portion of which is disposed between the positive electrode and the negative electrode. The insulating element includes a base film and a coating, the thickness of which is 2 μm to 4 μm.

25. The battery cell according to any one of claims 1-24, wherein, The battery cell also includes an electrolyte, which includes dimethyl carbonate, and the mass content of dimethyl carbonate in the electrolyte is 10% to 20%.

26. The battery cell according to claim 25, wherein, The electrolyte further includes lithium bisfluorosulfonylimide, wherein the lithium bisfluorosulfonylimide in the electrolyte comprises 2% to 5% by mass; optionally 2.5% to 4.5%; optionally 3% to 4%; optionally 3.3% to 3.7%.

27. The battery cell according to claim 25, wherein, The electrolyte also includes vinylene carbonate, wherein the mass content of vinylene carbonate in the electrolyte is 1% to 3%.

28. The battery cell according to claim 25, wherein, The electrolyte further includes at least one of trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate, wherein the mass content of at least one of trimethylfluorosilane, trimethylsilyl phosphate, and tri(trimethylsilane)borate in the electrolyte is from 0.03% to 0.5%.

29. The battery cell according to any one of claims 25-28, wherein, The ratio of the mass of the electrolyte to the capacity of the battery cell is 2.8 g / Ah to 3.0 g / Ah.

30. The battery cell according to any one of claims 1-29, wherein, The capacity of the battery cell is C Ah, and the residual space coefficient of the battery cell is from 0.18*C ml / Ah to 0.22*C ml / Ah.

31. A battery device comprising a battery cell as described in any one of claims 1-30.

32. An electrical device comprising the battery device as described in claim 31.

33. An energy storage device comprising the battery device of claim 31.

34. An energy storage system comprising the energy storage device as described in claim 33.

Images