Battery cell, battery apparatus, electrical apparatus and energy storage apparatus

Abstract

A battery cell, a battery apparatus, an electrical apparatus and an energy storage apparatus. The battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet comprises a positive-electrode film layer; the negative electrode sheet comprises a negative-electrode film layer; the positive-electrode film layer comprises a positive-electrode active material, which positive-electrode active material comprises a lithium-containing phosphate having an olivine structure, and the compaction density of the positive-electrode film layer ranges from 2.5 g / cm3 to 3 g / cm3; the negative-electrode film layer comprises graphite, and the degree of graphitization of the negative-electrode film layer ranges from 88% to 93%; the separator comprises a base film, the thickness of which ranges from 5 μm to 9 μm; and the capacity of the battery cell is greater than or equal to 400 Ah. The battery cell has both a high capacity and a long cycle life.

Description

Battery cells, battery packs, electrical devices and energy storage devices

[0001] Cross-references

[0002] This application incorporates, in its entirety, patent application number PCT / CN2025 / 085983, filed on March 28, 2025, entitled "Lithium-ion secondary battery, battery device, power device, method for preparing positive electrode active material and method for preparing positive electrode sheet".

[0003] This application incorporates, in its entirety, patent application number PCT / CN2025 / 140527, filed on December 5, 2025, entitled “Battery Cell, Battery Device, Power Consumption Device and Energy Storage Device”. Technical Field

[0004] This application relates to the field of battery technology, specifically to a battery cell, a battery device, an electrical device, and an energy storage device. Background Technology

[0005] In recent years, the application of high-capacity battery cells in energy storage devices has become increasingly widespread. In various energy storage application scenarios, high capacity and long cycle life have become key performance indicators for evaluating energy storage batteries. This is especially true for large-scale energy storage power stations, whose large-scale, long-term operation places higher demands on battery cycle life. To effectively delay battery performance degradation and reduce replacement frequency and maintenance costs, there is an urgent need to further develop battery cells that combine high capacity and long cycle life. Summary of the Invention

[0006] This application aims to at least solve one of the technical problems existing in the background art. To this end, one object of this application is to provide a battery cell, battery device, power consumption device, and energy storage device that combines high capacity and long cycle life.

[0007] To address the aforementioned problems, an embodiment of the first aspect of this application provides a battery cell, including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The positive electrode film layer includes a positive active material, which comprises a lithium phosphate having an olivine structure. The compaction density of the positive electrode film layer is 2.5 g / cm³. 3 -3g / cm 3The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, the graphitization degree of the negative electrode film layer is 88%-93%, the separator includes a base film, the thickness of the base film is 5μm-9μm, and the capacity of the battery cell is greater than or equal to 400Ah.

[0008] High-capacity energy storage battery cells typically have a low compaction density in their positive electrode film to accommodate the large expansion forces during later cycles (e.g., beyond 8000 or 10000 cycles). However, as market demands for volumetric energy density in energy storage batteries increase, increasing the compaction density of the positive electrode film has become a growing trend. However, increasing the compaction density of the positive electrode film is accompanied by increased rigidity and rebound of the positive electrode sheet, making stress concentration due to high expansion forces in the later stages of long cycles increasingly significant. This stress concentration can lead to particle pulverization, solid electrolyte membrane rupture, increased lithium consumption, and a significant drop in capacity.

[0009] This application utilizes a separator with a base film thickness of 5μm-9μm and a high compaction density of 2.5g / cm³. 3 -3g / cm 3 The positive electrode, combined with a low-graphitization (88%-93%) negative electrode active material, achieves a balance between high-capacity (≥400Ah) battery cells and high cycle stability. Specifically, a separator with a certain thickness helps achieve high energy density while maintaining mechanical properties, reducing the risk of rupture under high expansion forces in the later stages of cycling. The low-graphitization negative electrode active material has a relatively large interlayer spacing, low intrinsic expansion, and more disordered structure to buffer expansion stress. This can offset the high rebound caused by high compaction of the positive electrode film, improve the high expansion problem of large-capacity, high-compact battery cells in the later stages of cycling, and enable large-capacity energy storage batteries to maintain good cycle life even under high energy density design.

[0010] In some embodiments, the graphitization degree of the negative electrode film is 91%-92%.

[0011] In this embodiment, the graphitization degree of the negative electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0012] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

[0013] In this embodiment, the compaction density of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0014] In some embodiments, the positive current collector includes a positive current collector portion and a positive electrode tab disposed on at least one side of the positive current collector portion. The positive electrode tab has a dimension of 15mm-45mm along a first direction, which is perpendicular to the length direction of the electrode sheet and perpendicular to the thickness direction of the electrode sheet.

[0015] In this embodiment, the size of the positive electrode tab is within the above-mentioned range, which provides a large current flow area while taking into account energy density, reducing energy loss of the battery cell during charging and discharging, and further improving the cycle life of the battery cell.

[0016] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is greater than or equal to 11m². 2 .

[0017] In some embodiments, the median C of the graphitization degree in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 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.

[0018] The applicant discovered that during the rolling process of high-voltage dense positive electrode sheets for large-capacity energy storage batteries, uneven stress distribution poses a risk of electrode sheet wrinkling and breakage. In particular, the larger size of the matching tabs in large-capacity energy storage batteries leads to a corresponding increase in the width of the blank area reserved for the tabs during coating (corresponding to the tab height after cutting), further exacerbating the problem of uneven stress on the electrode sheets during rolling. By ensuring the graphitization degree of the positive electrode film layer is within the aforementioned range, relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of particle breakage and electrode sheet failure due to stress concentration during long-life cycling, further improving the cycle life of the battery cells.

[0019] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate-containing particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate-containing particles is 0.60-0.85, and optionally 0.7-0.74.

[0020] The applicant discovered that during the rolling process of high-voltage dense positive electrode sheets for large-capacity energy storage batteries, uneven stress distribution poses a risk of wrinkling and breakage. This is particularly true for the larger tab sizes of large-capacity energy storage batteries, which, during coating, require a wider blank area (corresponding to the tab height after cutting), further exacerbating the uneven stress distribution during rolling. By ensuring the median sphericity (LA50) of the lithium phosphate particles is within the aforementioned range, balancing the interlocking force and relative slippage ability between particles, the relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of stress concentration during long cycles, leading to particle breakage and electrode failure, while also balancing the flexibility and stability of the positive electrode film, thus further improving the cycle life of the battery cells. In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area of ​​the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535.

[0021] In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area (LA90-LA10) / LA50 of the lithium phosphate particles can be selected as 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.523, 0.526, 0.528, 0.53, 0.534, 0.535, or any value range between the two.

[0022] The (LA90-LA10) / LA50 ratio reflects not only the sphericity of most particles but also the asymmetry and width of the sphericity distribution within the cathode film. A smaller value indicates a more concentrated distribution. Combined with a high sphericity median, this reflects an overall near-spherical particle shape, which is conducive to close packing, increases inter-particle contact, reduces local resistance, improves electron and ion transport efficiency, and further enhances the cycle life of the battery cell.

[0023] In some embodiments, the battery cell includes an electrolyte, which includes vinylene carbonate (VC).

[0024] In some embodiments, based on the mass of the electrolyte, the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%.

[0025] In the embodiments of this application, when the content of vinylene carbonate is within the above range, it can effectively improve the interfacial stability of the low graphitization degree negative electrode. Vinylene carbonate is preferentially reduced on the surface of the negative electrode active material, promoting the formation of a dense and uniform SEI, thereby further improving the cycle life of the battery cell.

[0026] In some embodiments, the battery cell includes an electrolyte, which includes fluoroethylene carbonate (FEC).

[0027] In some embodiments, the mass percentage of the fluoroethylene carbonate is 0.05%-10% based on the mass of the electrolyte.

[0028] In this embodiment, fluoroethylene carbonate can form a low-impedance, high-density SEI rich in LiF. When the mass percentage of the fluoroethylene carbonate is within the above range, it further improves the cycle performance of the battery cell.

[0029] In some embodiments, the battery cell includes an electrolyte, which includes propylene carbonate (PC).

[0030] In some embodiments, based on the mass of the electrolyte, the mass percentage of propylene carbonate is 2%-15%, optionally 2%-10%, and further optionally 4%-6%.

[0031] The applicant discovered that during constant power charging, battery capacity decreases in the later stages of the cycle, while the charging current remains at a high level, equivalent to an increased current rate. This increases the local overpotential at the negative electrode, easily leading to lithium metal deposition, exacerbating side reactions and cycle degradation, and worsening cycle life. In the embodiments of this application, adding propylene carbonate with a high dielectric constant within the aforementioned range can improve the lithium-ion conductivity of the electrolyte, reduce the risk of lithium deposition, and thus further improve the cycle life of the battery cells.

[0032] In some embodiments, the lithium phosphate particles include one or more of titanium, vanadium, aluminum, and magnesium.

[0033] In this embodiment, doping lithium phosphate with titanium and / or vanadium can stabilize its crystal structure, reduce lattice distortion caused by redox reactions during charging and discharging, thereby improving the structural stability of the positive electrode active material and thus increasing cycle life. Doping lithium phosphate with aluminum and / or magnesium can improve ion conduction pathways, increase lithium-ion diffusion rates, improve the rate performance of the material, reduce the risk of lithium plating in the later stages of cycling, and further improve the cycle life of the battery cell.

[0034] In some embodiments, the lithium phosphate particles include titanium, and the titanium content is 0.05%-0.1% by mass based on the total mass of the positive electrode active material.

[0035] In some embodiments, the lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.15% based on the total mass of the positive electrode active material.

[0036] In some embodiments, the battery cell includes an electrolyte, the electrolyte including a lithium-containing electrolyte salt, the lithium-containing electrolyte salt including lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0037] In this embodiment of the application, by using lithium hexafluorophosphate and lithium difluorosulfonylimide together as lithium salts, the cycle life of the battery cell can be further improved.

[0038] In some embodiments, the lithium bis(fluorosulfonyl)imide content is 2%-7% based on the total mass of the electrolyte.

[0039] In the embodiments of this application, lithium bis(fluorosulfonyl)imide can promote the formation of a dense SEI containing LiF, and when its content is within the above range, it can further improve the cycle life of the battery cell.

[0040] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and optionally 2-4.

[0041] In the embodiments of this application, when the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is within the above range, the cycle life of the battery cell is further improved.

[0042] In some embodiments, the positive electrode film further includes a conductive agent comprising carbon nanotubes, wherein the mass content of the carbon nanotubes is 0.1%-1.5% based on the total mass of the positive electrode film.

[0043] In this embodiment of the application, by adding carbon nanotubes within the above-mentioned range to the positive electrode film layer, a continuous conductive network can be formed in the film layer, which can improve the electron conduction efficiency, reduce polarization during charging and discharging, improve the local current distribution, thereby reducing the stress and side reactions of the active material, and thus improving the cycle life of the battery cell.

[0044] In some embodiments, the capacity of the battery cell is greater than or equal to 500Ah, optionally greater than or equal to 550Ah, and further optionally greater than or equal to 600Ah.

[0045] In some embodiments, the capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah.

[0046] In some embodiments, the capacity of the battery cell is 500Ah-3000Ah, and optionally 550Ah-700Ah.

[0047] The battery cells provided in this application embodiment have both long cycle life and high capacity.

[0048] In some embodiments, the volumetric energy density of the battery cell is 380Wh / L-430Wh / L.

[0049] The battery cells provided in this application have both long cycle life and high volumetric energy density.

[0050] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

[0051] An embodiment of the second aspect of this application provides a battery device including a battery cell as described in any of the embodiments of the first aspect above.

[0052] An embodiment of the third aspect of this application provides an electrical device, the electrical device including a battery device as described in any of the embodiments of the second aspect above, the battery device being used to provide electrical energy.

[0053] An embodiment of the fourth aspect of this application provides an energy storage device, the energy storage device including a battery device as described in any embodiment of the second aspect above, the battery device being used to store electrical energy.

[0054] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0055] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0056] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0057] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0058] Figure 3 is a schematic diagram of a battery module according to an embodiment of this application;

[0059] Figure 4 is a schematic diagram of a battery pack according to an embodiment of this application;

[0060] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0061] Explanation of reference numerals in the attached drawings: 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate assembly. Detailed Implementation

[0062] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0064] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0065] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0066] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0067] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0068] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0069] 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 a 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 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 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: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" 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 "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0070] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0071] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0072] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0073] Energy storage batteries are primarily used in scenarios requiring long-term storage and release of electrical energy, such as working with energy storage power stations to store or release electrical energy in emergencies, and playing roles in frequency regulation and emergency backup within the power grid. This necessitates that energy storage batteries store more electrical energy within limited resources and space to continuously and stably provide a large amount of power, thereby ensuring the reliable operation of energy storage devices and the efficient use of energy. However, research shows that increasing the capacity and volumetric energy density of energy storage batteries often exacerbates the degradation of battery cycle life. How to further improve the volumetric energy density of high-capacity battery cells while maintaining high cycle stability is a pressing technical problem that needs to be solved in this field.

[0074] To address the aforementioned problems, an embodiment of the first aspect of this application provides a battery cell, including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The positive electrode film layer includes a positive active material, which comprises a lithium phosphate having an olivine structure. The compaction density of the positive electrode film layer is 2.5 g / cm³. 3 -3g / cm 3 The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, the graphitization degree of the negative electrode film layer is 88%-93%, the separator includes a base film, the thickness of the base film is 5μm-9μm, and the capacity of the battery cell is greater than or equal to 400Ah.

[0075] High-capacity energy storage battery cells typically have a low compaction density in their positive electrode film to accommodate the large expansion forces during later cycles (e.g., beyond 8000 or 10000 cycles). However, as market demands for volumetric energy density in energy storage batteries increase, increasing the compaction density of the positive electrode film has become a growing trend. However, increasing the compaction density of the positive electrode film is accompanied by increased rigidity and rebound of the positive electrode sheet, making stress concentration due to high expansion forces in the later stages of long cycles increasingly significant. This stress concentration can lead to particle pulverization, solid electrolyte membrane rupture, increased lithium consumption, and a significant drop in capacity.

[0076] This application utilizes a separator with a base film thickness of 5μm-9μm and a high compaction density of 2.5g / cm³. 3 -3g / cm 3 The positive electrode, combined with a negative electrode active material with low graphitization (88%-93%), achieves a balance between high capacity (greater than or equal to 400Ah) battery cells and high volumetric energy density while maintaining cycle stability.

[0077] Specifically, a separator with a certain thickness helps achieve high energy density while maintaining mechanical properties, reducing the risk of rupture under high expansion forces in the later stages of cycling. Meanwhile, low-graphitization negative electrode active materials have relatively large interlayer spacing, low intrinsic expansion, and more disordered structures to buffer expansion stress. This can offset the high rebound caused by high density of the positive electrode film, improve the high expansion problem of large-capacity, high-density battery cells in the later stages of cycling, and enable large-capacity energy storage batteries to maintain good cycle life even under high energy density designs.

[0078] In this article, "lithium-containing phosphates with an olivine structure" refers to phosphate materials containing lithium with an olivine crystal structure. As examples, lithium-containing phosphates include, but are not limited to, doped and coated modified materials such as lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt iron phosphate, and lithium nickel iron phosphate.

[0079] In this paper, the compaction density of the positive electrode film can be tested using methods known in the art. As an example, at 25°C, the battery cell is discharged to the discharge cutoff voltage, the battery is disassembled, the positive electrode sheet is obtained, the residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S, obtaining a mass of W1. The thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. The compaction density of the positive electrode film is then calculated as PD = (W1 - W2) / [(T1 - T2) × S]. As an example, the steps for discharging the battery cell to the discharge cutoff voltage are as follows: the battery is discharged at 25°C with a constant power of 0.5P to the discharge cutoff voltage of 2.5V.

[0080] In some embodiments, the compaction density of the positive electrode film may be selected as 2.5 g / cm³. 3 2.51g / cm 3 2.52g / cm 3 2.53g / cm 3 2.54 g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.59g / cm 3 2.6g / cm 3 2.61 g / cm 3 2.62 g / cm 3 2.63 g / cm 3 2.64 g / cm 3 2.65g / cm 3 2.66 g / cm 3 2.67 g / cm 3 2.68g / cm 3 2.69 g / cm 3 2.7g / cm 3 2.71 g / cm 3 2.72 g / cm 3 2.73 g / cm 3 2.74 g / cm 3 2.75g / cm 3 2.76 g / cm 3 2.77 g / cm 3 2.78g / cm 3 2.79 g / cm 3 2.8g / cm 3 2.81 g / cm 3 2.82 g / cm 3 2.83 g / cm 3 2.84 g / cm 3 2.85g / cm 3 2.86 g / cm 3 2.87 g / cm 3 2.88g / cm 3 2.89 g / cm 3 2.90g / cm 3 2.91 g / cm 3 2.92g / cm 3 2.93g / cm3 2.94 g / cm 3 2.95g / cm 3 2.96 g / cm 3 2.97g / cm 3 2.98g / cm 3 2.99g / cm 3 3g / cm 3 , or the range of values ​​between any two.

[0081] In this paper, the term "graphitization degree" refers to an index measuring the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure. It reflects the integrity of the graphite crystal structure in the material, that is, the regularity of the arrangement of carbon atoms in the graphite structure. A low graphitization degree indicates that the graphite spacing is large and there is more disordered structure. Therefore, the material expands less during lithium intercalation, and the disordered structure can disperse local stress.

[0082] In this paper, the "degree of graphitization of the negative electrode film" can be tested using methods known in the art, such as X-ray diffractometer (e.g., Bruker D8 Discover), referring to GB / T 24533-2019. After discharging the battery cell to the discharge cutoff voltage, the battery is disassembled to obtain the negative electrode sheet. An ion beam is used to cut along the thickness direction of the electrode sheet, and the cross-section of the obtained negative electrode film along the thickness direction is scanned to obtain the average interlayer spacing d002 of the (002) crystal plane in the graphite material crystal structure of the negative electrode film. Then, the degree of graphitization is calculated according to the formula g = (0.344 - d002) / (0.344 - 0.3354) × 100%. In the above formula, d002 is the average interlayer spacing of the (002) crystal plane in the graphite material crystal structure, expressed in nanometers (nm).

[0083] In some embodiments, the degree of graphitization of the negative electrode film can be selected as 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, or any range between the two.

[0084] In this article, the term "cell capacity" refers to the total amount of electricity that a single cell can output under specified charge and discharge conditions (e.g., the total amount of electricity output from the charging cutoff voltage to the discharging cutoff voltage), used to characterize the energy storage capacity of a single cell, and the unit is ampere-hour (Ah).

[0085] In this paper, the capacity of a single battery cell can be tested using methods known in the art. As an example, at 25°C, the battery cell is charged to 3.65V at a constant power of 0.5P and left to stand for 30 minutes; then discharged to 2.5V at a constant power of 0.5P, and the discharge capacity A0 is recorded as the battery capacity, in Ah.

[0086] In some embodiments, the capacity of the battery cell can be selected as 400Ah, 410Ah, 420Ah, 430Ah, 440Ah, 450Ah, 460Ah, 470Ah, 480Ah, 490Ah, 500Ah, 510Ah, 520Ah, 530Ah, 540Ah, 550Ah, 560Ah, 570Ah, 580Ah, 590Ah, 600Ah, 610Ah, 620Ah, 630Ah, 640Ah, 650Ah, 660Ah, 670Ah, 680Ah, 690Ah, 700Ah, 710Ah, 720Ah, 730Ah, 740Ah, 750Ah, 760Ah, 770Ah, 7... 80Ah, 790Ah, 800Ah, 810Ah, 820Ah, 830Ah, 840Ah, 850Ah, 860Ah, 870Ah, 880Ah, 890Ah, 900Ah, 910Ah, 920Ah, 930Ah, 940Ah, 950Ah, 960Ah, 970Ah, 980Ah , 990Ah, 1000Ah, 1010Ah, 1020Ah, 1030Ah, 1040Ah, 1050Ah, 1060Ah, 1070Ah, 1080Ah, 1090Ah, 1100Ah, 1110Ah, 1120Ah, 1130Ah, 1140Ah, 1150Ah, 1160Ah , 1170Ah, 1180Ah, 1190Ah, 1200Ah, 1210Ah, 1220Ah, 1230Ah, 1240Ah, 1250Ah, 1260Ah, 1270Ah, 1280Ah, 1290Ah, 1300Ah, 1310Ah, 1320Ah, 1330Ah, 1340 Ah, 1350Ah, 1360Ah, 1370Ah, 1380Ah, 1390Ah, 1400Ah, 1410Ah, 1420Ah, 1430Ah, 1440Ah, 1450Ah, 1460Ah, 1470Ah, 1480Ah, 1490Ah, 1500Ah, 1510Ah, 152 0Ah, 1530Ah, 1540Ah, 1550Ah, 1560Ah, 1570Ah, 1580Ah, 1590Ah, 1600Ah, 1610Ah, 1620Ah, 1630Ah, 1640Ah, 1650Ah, 1660Ah, 1670Ah, 1680Ah, 1690Ah, 1 700Ah, 1710Ah, 1720Ah, 1730Ah, 1740Ah, 1750Ah, 1760Ah, 1770Ah, 1780Ah, 1790Ah, 1800Ah, 1810Ah, 1820Ah, 1830Ah, 1840Ah, 1850Ah, 1860Ah, 1870Ah,1880Ah, 1890Ah, 1900Ah, 1910Ah, 1920Ah, 1930Ah, 1940Ah, 1950Ah, 1960Ah, 1970Ah, 1980Ah, 1990Ah, 2000Ah, 2010Ah, 20 20Ah, 2030Ah, 2040Ah, 2050Ah, 2060Ah, 2070Ah, 2080Ah, 2090Ah, 2100Ah, 2110Ah, 2120Ah, 2130Ah, 2140Ah, 2150Ah, 2160A h, 2170Ah, 2180Ah, 2190Ah, 2200Ah, 2210Ah, 2220Ah, 2230Ah, 2240Ah, 2250Ah, 2260Ah, 2270Ah, 2280Ah, 2290Ah, 2300Ah, 2310Ah, 2320Ah, 2330Ah, 2340Ah, 2350Ah, 2360Ah, 2370Ah, 2380Ah, 2390Ah, 2400Ah, 2410Ah, 2420Ah, 2430Ah, 2440Ah, 245 0Ah, 2460Ah, 2470Ah, 2480Ah, 2490Ah, 2500Ah, 2510Ah, 2520Ah, 2530Ah, 2540Ah, 2550Ah, 2560Ah, 2570Ah, 2580Ah, 2590A h, 2600Ah, 2610Ah, 2620Ah, 2630Ah, 2640Ah, 2650Ah, 2660Ah, 2670Ah, 2680Ah, 2690Ah, 2700Ah, 2710Ah, 2720Ah, 2730Ah, 2 740Ah, 2750Ah, 2760Ah, 2770Ah, 2780Ah, 2790Ah, 2800Ah, 2810Ah, 2820Ah, 2830Ah, 2840Ah, 2850Ah, 2860Ah, 2870Ah, 2880Ah, 2890Ah, 2900Ah, 2910Ah, 2920Ah, 2930Ah, 2940Ah, 2950Ah, 2960Ah, 2970Ah, 2980Ah, 2990Ah, 3000Ah, or any range of values ​​between two of these.

[0087] In this document, the term "base membrane" refers to the main structural layer of the separator, which is typically composed of polyolefin materials (such as polyethylene, polypropylene, or composites thereof) and serves as the primary carrier for providing mechanical support and ion isolation. In some embodiments, a functional coating (e.g., a ceramic coating, a heat-resistant coating, or other inorganic / organic composite coating) is provided on the base membrane.

[0088] In some embodiments, the thickness of the base film can be selected as 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, or any value range between the two.

[0089] In some embodiments, the graphitization degree of the negative electrode film is 91%-92%.

[0090] In some embodiments, the graphitization degree of the negative electrode film can be selected as 91.0%, 91.1%, 91.2%, 91.3%, 91.4%, 91.5%, 91.6%, 91.7%, 91.8%, 91.9%, 92.0%, 92.1%, 92.2%, 92.3%, 92.4%, 92.5%, 92.6%, 92.7%, 92.8%, 92.9%, or any range between the two. In the embodiments of this application, the graphitization degree of the negative electrode film is within the above range, which further improves the cycle life of the large-capacity energy storage battery under high energy density design.

[0091] In some embodiments, the compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

[0092] In some embodiments, the compaction density of the positive electrode film may be selected as 2.5 g / cm³. 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm 3 2.8g / cm 3 , or the range of values ​​between any two.

[0093] In this embodiment, the compaction density of the positive electrode film is within the above-mentioned range, which further improves the cycle life of the large-capacity energy storage battery under the high energy density design.

[0094] In some embodiments, the positive current collector includes a positive current collector portion and a positive electrode tab disposed on at least one side of the positive current collector portion. The positive electrode tab has a dimension of 15mm-45mm along a first direction, which is perpendicular to the length direction of the electrode sheet and perpendicular to the thickness direction of the electrode sheet.

[0095] In this paper, the positive electrode coating plane has mutually perpendicular transverse directions (TD) and machine directions (MD). The "first direction" is parallel to TD, and the "electrode length direction" is parallel to MD, both of which are perpendicular to the electrode thickness direction. It is understandable that the "dimension of the positive electrode tab along the first direction" also refers to the dimension of the positive electrode tab along the TD.

[0096] In some embodiments, the dimensions of the positive electrode tab along the first direction can be selected as 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, 38mm, 39mm, 40mm, 41mm, 42mm, 43mm, 44mm, 45mm, or any value range between the two.

[0097] In this embodiment, the size of the positive electrode tab is within the above-mentioned range, which provides a large current flow area while taking into account energy density, reducing energy loss of the battery cell during charging and discharging, and further improving the cycle life of the battery cell.

[0098] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is greater than or equal to 11m². 2 .

[0099] In this article, a single battery cell may include one or more electrode components. "The coating area of ​​the positive electrode film in a single battery cell" refers to the sum of the coating areas of the positive electrode film in all electrode components within the single battery cell. The "coating area" of the positive electrode film is calculated by multiplying the length of the positive electrode active material covering the positive electrode current collector by its width. For double-sided coated positive electrode films, the areas on both sides of the positive electrode film need to be calculated separately and then summed to calculate the total coating area of ​​the positive electrode film.

[0100] In some embodiments, the median C of the graphitization degree in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 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.

[0101] In this paper, the graphitization degree C value of the positive electrode film can be obtained by surface scanning mode of a laser confocal Raman spectrometer. As an example, specifically, a laser confocal Raman spectrometer (high-precision Renishaw laser confocal Raman spectrometer) is used, with an excitation wavelength of 532 nm. An appropriate amount of the positive electrode film is taken and surface scanned on its surface or along the thickness direction of the electrode. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, with grid vertices as test points, a step size of 5 μm, and a total of 100 scan points. Thus, the C values ​​at different sites and the cumulative distribution curve of the C values ​​in the surface scan area are obtained.

[0102] The graphitization degree C of the positive electrode film was obtained by the ratio of the peak intensities of the G-band and D-band in the Raman spectrum. The position of the G-band peak was 1585±100 cm⁻¹. -1 Its characterization of carbon sp 2 Hybrid structure; D peak position is 1350±50 cm. -1 It characterizes a disordered structure, where disorder refers to the irregular arrangement of carbon atoms within the structure. In graphite crystals, carbon atoms in the same layer arrange themselves in an sp... 2 Hybridization forms covalent bonds, while interlayer bonding is facilitated by van der Waals forces, making the carbon in the graphite structure prone to slippage. Therefore, the C value can characterize the degree of graphitization of the positive electrode active material. It is understandable that the degree of graphitization of the lithium phosphate-containing positive electrode active material in this application mainly comes from its surface carbon coating material. Although rich in sp... 2 Hybridized carbon nanotube conductive agents also have relatively high I0 G / I D However, due to its low content and small tube diameter, its addition to the positive electrode film results in an extreme value in the Raman surface scan test of the positive electrode film, and does not affect the graphitization degree C in the positive electrode film. 50 This has an impact. Therefore, the degree of graphitization of the positive electrode film can also be used to characterize the degree of graphitization of the positive electrode active material.

[0103] The cumulative distribution curve of graphitization degree C value refers to the curve obtained by arranging at least 100 C values ​​in ascending order, with graphitization degree as the horizontal axis and the cumulative percentage as the vertical axis. 50 This represents the C value corresponding to a cumulative percentage of 50% on the vertical axis of the cumulative distribution curve of graphitization degree C. The median C value of graphitization degree. 50 Compared to point values, it can reflect the overall graphitization degree of particles in the positive electrode film, i.e., the degree of slippage; compared to the mean value, it can reduce the influence of extreme values ​​during the test and improve the confidence of the test results.

[0104] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphite-structured carbon in the positive electrode film layer, and the easier it is for particles to slip by means of the highly graphitized carbon structure in the coating material.

[0105] Those skilled in the art can control the degree of graphitization of active material particles using any known process. As an example, adjusting the carbon source (which can be a polymer carbon source, such as PEG), sintering temperature, sintering time, sintering pressure, sintering atmosphere, and nucleation process can all achieve the adjustment of the degree of graphitization of active material particles.

[0106] In some embodiments, the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value can be selected from 0.95, 0.96, 0.97, 0.98, 0.984, 0.99, 1, 1.01, 1.012, 1.015, 1.016, 1.02, 1.025, 1.03, 1.032, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.123, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or any value range between the two.

[0107] The applicant discovered that during the rolling process of high-voltage dense positive electrode sheets for large-capacity energy storage batteries, uneven stress distribution poses a risk of electrode sheet wrinkling and breakage. In particular, the larger size of the matching tabs in large-capacity energy storage batteries leads to a corresponding increase in the width of the blank area reserved for the tabs during coating (corresponding to the tab height after cutting), further exacerbating the problem of uneven stress on the electrode sheets during rolling. By ensuring the graphitization degree of the positive electrode film layer is within the aforementioned range, relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of particle breakage and electrode sheet failure due to stress concentration during long-life cycling, further improving the cycle life of the battery cells.

[0108] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate-containing particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate-containing particles is 0.60-0.85, and optionally 0.7-0.74.

[0109] In this application, the term "particle" refers to a particle in the positive electrode film layer that has a recognizable complete boundary in the field of view at a certain magnification, such as 10,000x. Defects and scratches may exist inside the particle, but a complete boundary sufficient to divide the particle cannot be identified inside the particle.

[0110] The identification method for "the lithium phosphate-containing particles" in this paper is as follows: The positive electrode sheet is cut along its thickness direction using an argon ion beam (for example, a Leica EM TIC 3X CP device can be used, operating voltage: 6kV, operating time: 6h). After exposing the cut surface, a scanning electron microscope (for example, a Hitachi SU8230 device can be used, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) is used to observe the cut surface of the positive electrode film along its thickness direction. Images are acquired using a field emission scanning electron microscope at a non-edge location within the cut surface of the positive electrode film (after observing the electrode edge under the scanning electron microscope, the field of view is adjusted to the center of the sample) in secondary electron mode. Electron micrographs are taken at 10kx magnification, and the particles in the electron micrographs are analyzed using ImageJ software (1.46r, win64 version). The specific steps for using ImageJ software are as follows: Load the scanning electron microscope (SEM) image to be analyzed; use the Cellpose plugin to identify particles, and then perform manual corrections; use ImageJ to read and analyze data. The specific method for using the Cellpose plugin to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "run cyto3" to identify particles; manually mark particles in the image that were not identified by the software, were not fully identified, or were identified incorrectly. Particles that were not identified by the software, were not fully identified, or were identified incorrectly mainly include the following: 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 misinterpret these scratches as particle boundaries, leading to identification errors; 3. Particles that are too small and were not successfully identified; 4. Particles located at the edge of the SEM field of view, with the particle's interior penetrated by the edge, preventing a complete view of the morphology, resulting in identification errors due to partial identification replacing the whole.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.

[0111] In this paper, the test method for "sphericity of lithium phosphate particles" is as follows: Images of particles after identification and labeling are imported into ImageJ software for analysis to obtain sphericity. Scale settings are completed based on the scanning electron microscope images. According to the software manual (ImageJ User Guide IJ1.46r), the "Round" parameter obtained from the analysis represents the ratio of the pixel area of ​​the particle to the area of ​​a circle with the fitted major axis as its diameter, and can be used to characterize the sphericity of the particles. The closer the particle is to a sphere, the closer the ratio of the pixel area to the area of ​​the circle with the fitted major axis as its diameter is to 1. Therefore, the "Round" parameter obtained from the analysis is used to characterize the sphericity of the particles.

[0112] The sphericity of at least 5000 particles was arranged in ascending order. A cumulative distribution curve of the sphericity area of ​​the particles in the positive electrode film was obtained, with sphericity as the horizontal axis and cumulative area percentage as the vertical axis. LA50 is the sphericity L-value corresponding to a cumulative area percentage of 50% on the vertical axis of the cumulative distribution curve of sphericity L-value.

[0113] Those skilled in the art can control the sphericity of particles using any known process. For example, the sphericity of particles can be adjusted through processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, and adding surfactants, as well as by adjusting the parameters of each process.

[0114] Particles with a median sphericity LA50 within the above range are approximately spherical and are prone to slippage between particles under external force.

[0115] In some embodiments, in the cumulative distribution curve of the sphericity area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate particles can be selected as 0.60, 0.62, 0.64, 0.66, 0.68, 0.70, 0.72, 0.74, 0.76, 0.78, 0.80, 0.82, 0.84, 0.85, or any value range between the two.

[0116] The applicant discovered that during the rolling process of high-voltage dense positive electrode sheets for large-capacity energy storage batteries, uneven stress distribution poses a risk of wrinkling and breakage. This is particularly true for the larger tab sizes of large-capacity energy storage batteries, which, during coating, require a wider blank area (corresponding to the tab height after cutting), further exacerbating the uneven stress distribution during rolling. By ensuring the median sphericity (LA50) of the lithium phosphate particles is within the aforementioned range, balancing the interlocking force and relative slippage ability between particles, the relative slippage between positive electrode active material particles is promoted, resulting in a more uniform stress distribution. This reduces the risk of stress concentration during long cycles, leading to particle breakage and electrode failure, while also balancing the flexibility and stability of the positive electrode film, thus further improving the cycle life of the battery cells. In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area of ​​the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535.

[0117] In some embodiments, in the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area (LA90-LA10) / LA50 of the lithium phosphate particles can be selected as 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.523, 0.526, 0.528, 0.53, 0.534, 0.535, or any value range between the two.

[0118] In this paper, the test method for "sphericity concentration (LA90-LA10) / LA50" is as follows: Referring to the sphericity test method above, LA90 is the L value corresponding to 90% of the cumulative area on the vertical axis of the cumulative distribution curve of sphericity L value, and LA10 is the L value corresponding to 10% of the cumulative area on the vertical axis of the cumulative distribution curve of sphericity L value. The sphericity concentration is represented by (LA90-LA10) / LA50. (LA90-LA10) / LA50 can reflect not only the sphericity of most particles, but also the asymmetry and width of the sphericity distribution of particles in the positive electrode film layer. The smaller the value, the more concentrated the distribution. Combined with the high sphericity median, it reflects that the particles are approximately spherical overall, which is conducive to the formation of close packing, increases the contact between particles, thereby reducing local resistance, improving electron and ion transport efficiency, and further improving the cycle life of the battery cell.

[0119] In some embodiments, the battery cell includes an electrolyte, which includes vinylene carbonate (VC).

[0120] In this paper, the types and mass contents of each component in the electrolyte can be obtained by any method known to those skilled in the art. As an example, the composition and content of the electrolyte can be characterized by one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). For example, referring to GB / T 9722 2023 "General Rules for Gas Chromatography of Chemical Reagents" and / or GB / T 6041 2020 "General Rules for Mass Spectrometry Analysis Methods", gas chromatography and mass spectrometry are coupled. After gas chromatography separates the components in the sample, the components are broken into ion fragments in mass spectrometry and separated according to mass-to-charge ratio (m / z) to form specific mass spectra, obtaining qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in the chromatographic column, and detection signal spectra of each component are generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to achieve quantification, obtaining quantitative analysis of the organic components in the electrolyte. Referring to JY / T 020, the types of anions of electrolyte salts in the electrolyte are detected by ion chromatography and quantitatively analyzed. Referring to JY / T 0578 2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0121] The electrolyte referred to in this article can be either fresh electrolyte or electrolyte obtained from the disassembly of a battery cell. The electrolyte obtained from the disassembly of a battery cell can be either the free electrolyte in the battery casing or the electrolyte obtained by centrifugation from the electrodes.

[0122] In some embodiments, based on the mass of the electrolyte, the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%.

[0123] In some embodiments, based on the mass of the electrolyte, the mass percentage of vinylene carbonate can be selected as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any range between the two.

[0124] In the embodiments of this application, when the content of vinylene carbonate is within the above range, it can effectively improve the interfacial stability of the low graphitization degree negative electrode. Vinylene carbonate is preferentially reduced on the surface of the negative electrode active material, promoting the formation of a dense and uniform SEI, thereby further improving the cycle life of the battery cell.

[0125] In some embodiments, the battery cell includes an electrolyte, which includes fluoroethylene carbonate (FEC).

[0126] In some embodiments, the mass percentage of the fluoroethylene carbonate is 0.05%-10% based on the mass of the electrolyte.

[0127] In some embodiments, based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate can be selected as 0.05%, 0.1%, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25%, 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25%, 4.5%, 4.75%, 5%, 6%, 7%, 8%, 9%, 10%, or any range between the two.

[0128] In this embodiment, fluoroethylene carbonate can form a low-impedance, high-density SEI rich in LiF. When the mass percentage of the fluoroethylene carbonate is within the above range, it further improves the cycle performance of the battery cell.

[0129] In some embodiments, the battery cell includes an electrolyte, which includes propylene carbonate (PC).

[0130] In some embodiments, based on the mass of the electrolyte, the mass percentage of propylene carbonate is 2%-15%, optionally 2%-10%, and further optionally 4%-6%.

[0131] In some embodiments, based on the mass of the electrolyte, the mass percentage of propylene carbonate can be selected as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range between the two.

[0132] The applicant discovered that during constant power charging, battery capacity decreases in the later stages of the cycle, while the charging current remains at a high level, equivalent to an increased current rate. This increases the local overpotential at the negative electrode, easily leading to lithium metal deposition, exacerbating side reactions and cycle degradation, and worsening cycle life. In the embodiments of this application, adding propylene carbonate with a high dielectric constant within the aforementioned range can improve the lithium-ion conductivity of the electrolyte, reduce the risk of lithium deposition, and thus further improve the cycle life of the battery cells.

[0133] In some embodiments, the lithium phosphate particles include one or more of titanium, vanadium, aluminum, and magnesium.

[0134] In this embodiment, doping lithium phosphate with titanium and / or vanadium can stabilize its crystal structure, reduce lattice distortion caused by redox reactions during charging and discharging, thereby improving the structural stability of the positive electrode active material and thus increasing cycle life. Doping lithium phosphate with aluminum and / or magnesium can improve ion conduction pathways, increase lithium-ion diffusion rates, improve the rate performance of the material, reduce the risk of lithium plating in the later stages of cycling, and further improve the cycle life of the battery cell.

[0135] In some embodiments, the lithium phosphate particles include titanium, and the titanium content is 0.05%-0.1% by mass based on the total mass of the positive electrode active material.

[0136] In some embodiments, the lithium phosphate-containing particles include titanium, and the mass content of the titanium, based on the total mass of the positive electrode active material, may be selected as 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, or any range between the two.

[0137] In some embodiments, the lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.15% based on the total mass of the positive electrode active material.

[0138] In some embodiments, the lithium phosphate particles include vanadium, and the mass content of the vanadium is selected from 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, or any range between the two, based on the total mass of the positive electrode active material.

[0139] In some embodiments, the battery cell includes an electrolyte, the electrolyte including a lithium-containing electrolyte salt, the lithium-containing electrolyte salt including lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0140] In this embodiment of the application, by using lithium hexafluorophosphate and lithium difluorosulfonylimide together as lithium salts, the cycle life of the battery cell can be further improved.

[0141] In some embodiments, the lithium bis(fluorosulfonyl)imide content is 2%-7% based on the total mass of the electrolyte.

[0142] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide, based on the total mass of the electrolyte, may be selected as 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, or any range between the two.

[0143] In the embodiments of this application, lithium bis(fluorosulfonyl)imide can promote the formation of a dense SEI containing LiF, and when its content is within the above range, it can further improve the cycle life of the battery cell.

[0144] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and optionally 2-4.

[0145] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide can be selected as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, or any range between the two.

[0146] In the embodiments of this application, when the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is within the above range, the cycle life of the battery cell is further improved.

[0147] In some embodiments, the positive electrode film further includes a conductive agent comprising carbon nanotubes, wherein the mass content of the carbon nanotubes is 0.1%-1.5% based on the total mass of the positive electrode film.

[0148] In some embodiments, the positive electrode film further includes a conductive agent, the conductive agent comprising carbon nanotubes, and the mass content of the carbon nanotubes, based on the total mass of the positive electrode film, may be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or any range between the two.

[0149] In this embodiment of the application, by adding carbon nanotubes within the above-mentioned range to the positive electrode film layer, a continuous conductive network can be formed in the film layer, which can improve the electron conduction efficiency, reduce polarization during charging and discharging, improve the local current distribution, thereby reducing the stress and side reactions of the active material, and thus improving the cycle life of the battery cell.

[0150] In some embodiments, the capacity of the battery cell is greater than or equal to 500Ah, optionally greater than or equal to 550Ah, and further optionally greater than or equal to 600Ah.

[0151] In some embodiments, the capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah.

[0152] In some embodiments, the capacity of the battery cell is 500Ah-3000Ah, and optionally 550Ah-700Ah.

[0153] In some embodiments, the capacity of the battery cell can be selected as 500Ah, 600Ah, 700Ah, 800Ah, 900Ah, 1000Ah, 1200Ah, 1400Ah, 1600Ah, 1800Ah, 2000Ah, 2200Ah, 2400Ah, 2600Ah, 2800Ah, 3000Ah, or any value range between the two.

[0154] The battery cells provided in this application embodiment have both long cycle life and high capacity.

[0155] In some embodiments, the volumetric energy density of the battery cell is 380Wh / L-430Wh / L.

[0156] In this paper, the "volume energy density of a single battery cell" can be tested using methods known in the art. As an example, at 25°C, the battery cell is charged to 3.65V at a constant power of 0.5P and left to stand for 30 minutes; it is then discharged to 2.5V at a constant power of 0.5P, and the discharge energy E is recorded in Wh; the length, width, and height of the battery cell are measured using calipers, and the cell volume V0 is calculated in L; the volume energy density of the battery cell VED = discharge energy E / cell volume V0, in Wh / L.

[0157] In some embodiments, the volumetric energy density of the battery cell can be selected as 380Wh / L, 385Wh / L, 390Wh / L, 395Wh / L, 400Wh / L, 405Wh / L, 410Wh / L, 415Wh / L, 420Wh / L, 425Wh / L, 430Wh / L, or any value range between the two.

[0158] The battery cells provided in this application have both long cycle life and high volumetric energy density.

[0159] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

[0160] In some embodiments, the coating area of ​​the positive electrode film layer included in the battery cell may be 11m². 2 13m 2 15m 2 17m 2 19m 2 21m 2 23m 2 25m 2 27m 2 29m 2 31m 2 33m 2 35m 2 37m 2 39m 2 41m 2 43m 2 45m 2 47m 2 49m 2 51m 2 53m 2 55m 257m 2 59m 2 61m 2 63m 2 65m 2 67m 2 69m 2 71m 2 73m 2 75m 2 77m 2 79m 2 81m 2 83m 2 85m 2 87m 2 89m 2 91m 2 93m 2 95m 2 97m 2 99m 2 101m 2 103m 2 105m 2 107m 2 109m 2 111m 2 113m 2 115m 2 117m 2 119m 2 121m 2 123m 2 125m 2 127m 2 129m 2 131m 2 133m 2 135m 2 137m 2 139m 2 141m 2 143m 2 145m 2 147m 2 149m 2 150m 2 , or a range of values ​​between any two.

[0161] An embodiment of the second aspect of this application provides a battery device including a battery cell as described in any of the embodiments of the first aspect above.

[0162] An embodiment of the third aspect of this application provides an electrical device, the electrical device including a battery device as described in any of the embodiments of the second aspect above, the battery device being used to provide electrical energy.

[0163] An embodiment of the fourth aspect of this application provides an energy storage device, the energy storage device including a battery device as described in any embodiment of the second aspect above, the battery device being used to store electrical energy.

[0164] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0165] [Positive electrode plate]

[0166] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0167] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0168] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0169] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0170] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0171] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0172] [Negative electrode plate]

[0173] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0174] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0175] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0176] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0177] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0178] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0179] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0180] [Electrolytes]

[0181] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0182] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0183] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0184] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0185] [Isolation membrane]

[0186] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0187] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0188] The embodiments of this application do not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0189] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover assembly 53. The housing 51 and the cover assembly 53 enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover assembly 53 is capable of covering the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator may be formed into an electrode assembly 52 via a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0190] This application also provides a battery device, which includes the battery cell provided in this application. In some embodiments, the battery device is one or more of a battery module and a battery pack.

[0191] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0192] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0193] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0194] As an example, a battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0195] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0196] This application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application.

[0197] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0198] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0199] I. Implementation Examples

[0200] Example 1

[0201] (1) Preparation of positive electrode sheet

[0202] Preparation of positive electrode active materials:

[0203] Lithium dihydrogen phosphate, ferrous oxalate, polyethylene glycol, and titanium dioxide were mixed evenly in methanol and then ground to obtain a mixed raw material. The ratio of lithium dihydrogen phosphate to ferrous oxalate resulted in an atomic molar ratio of lithium to iron of 1.03.

[0204] The spray-dried slurry yields a dried precursor powder, which is light yellow in appearance and uniform in color.

[0205] The precursor powder was placed in a sintering furnace and heated from 25°C to 350°C at a rate of 2°C / min under a nitrogen atmosphere and held at that temperature for 3 hours. Then, the temperature was increased to a second temperature of 770°C at a rate of 5°C / min and held at that temperature for 10 hours. After the process, the temperature was lowered and cooled.

[0206] The obtained material was crushed using an airflow pulverization method with a staged frequency of 22Hz and a pulverizing airflow of 0.55MPa to obtain carbon-coated lithium iron phosphate cathode active material.

[0207] The prepared positive electrode active material has a carbon content of 1.177% by mass, a lithium iron antisite defect concentration of 0.53%, and a powder tap density of 1.19 g / cm³. 3 The compacted density of the powder under 3T pressure is 2.57 g / cm³. 3 The powder resistivity at 8 MPa is 6.3 Ω·cm; the discharge capacity at a 1C discharge rate is 142.3 mAh / g; there is a discharge plateau in the voltage range of 2.5V to 2.9V, and the discharge capacity of the 3.2V discharge plateau accounts for 92.1%.

[0208] The above-mentioned positive electrode active materials, lithium iron phosphate, carbon nanotubes, conductive carbon black, polyvinylidene fluoride, and lithium carboxymethyl cellulose, were mixed in a mass ratio of 97.5%:0.1%:0.5%:1.6%:0.3%, and then N-methylpyrrolidone solvent was added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was transferred and coated onto a current collector aluminum foil, dried, hot-pressed, die-cut, and slit to obtain the positive electrode sheet.

[0209] (2) Preparation of negative electrode sheet

[0210] A negative electrode slurry was prepared by mixing graphite (anode active material), carbon nanotubes (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) in a ratio of 96.5%:0.6%:2%:0.9%, adding deionized water, and stirring. The slurry was then coated onto both sides of a copper foil. After coating both sides, the foil was dried, compacted, slit, and sheeted to obtain the negative electrode sheet.

[0211] (3) Separating membrane

[0212] The separator membrane includes a base membrane and coatings disposed on both sides of the base membrane. The base membrane is a polyethylene membrane with a thickness of 5 μm; the coatings include alumina and polyvinylidene fluoride (PVDF), and the thickness of the coating on one side is 1 μm.

[0213] (4) Preparation of electrolyte

[0214] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC) are mixed evenly, and 3% lithium bis(fluorosulfonyl)imide (LiFSI) and 9% lithium hexafluorophosphate (LiPF6) are added.

[0215] Based on the total mass of the electrolyte, the mass percentages of each component are as follows: DMC 26.4%, EMC 23.4%, EC 27.28%, PC 4.4%, FEC 3.52%, VC 3%, LiFSI 3%, and LiPF6 9%.

[0216] 5) Preparation of battery cells

[0217] The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the anode and cathode. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and after processes such as encapsulation, formation, and degassing, a lithium-ion battery is finally obtained.

[0218] Battery disassembly and testing revealed:

[0219] The battery cell has a capacity of 410 Ah and a volumetric energy density of 390 Wh / L; the positive electrode film has a compaction density of 2.56 g / cm³. 3 The tab's dimension along the first direction is 28 mm; the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The median LA50 of the sphericity of lithium phosphate particles is 0.72; the concentration of sphericity of lithium phosphate particles (LA90-LA10) / LA50 is 0.528; and the graphitization degree of the negative electrode film is 91.5%.

[0220] Examples 2-5 and Comparative Examples 1-2

[0221] The battery cells of Examples 2-5 and Comparative Examples 1-2 are similar to those of Example 1, except that the graphitization degree of the negative electrode film is different, as shown in Table 1 below.

[0222] Example 6 and Comparative Example 3

[0223] The battery cells of Example 6 and Comparative Example 3 are similar to those of Example 1, except that the compaction density of the positive electrode film is different, as shown in Table 2 below.

[0224] Examples 7-10

[0225] The battery cells in Examples 7-10 are similar to those in Example 1, except that the positive electrode active material is different, as shown in Table 4 below.

[0226] Examples 11-14

[0227] The battery cells in Examples 11-14 are similar to those in Example 1, except that the height of the positive electrode tab of the battery cell is different, as shown in Table 5 below.

[0228] Example 15

[0229] The battery cell of Example 15 is similar to that of Example 1, except that the size of the battery cell is different. The capacity of the battery cell of Example 15 is 1200Ah.

[0230] Examples 16-19

[0231] The battery cells in Examples 16-19 are similar to those in Example 1, except that the electrolyte is different, as shown in Table 6 below.

[0232] Example 20

[0233] The battery cell of Example 20 is similar to that of Example 1, except that the positive electrode film of the battery cell of Example 20 does not include carbon nanotubes. Specifically, the positive electrode film includes: lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and lithium carboxymethyl cellulose in a mass ratio of 97.5%:0.6%:1.6%:0.3%.

[0234] II. Battery Performance Testing

[0235] (1) Battery cycle performance test

[0236] At 45℃, the battery cells were discharged at a constant power of 0.5P until the voltage of the battery cells reached 2.5V, and then allowed to stand for 30 minutes. Then, the battery cells were subjected to charge-discharge cycle tests at a constant power of 0.5P: In the first charge-discharge cycle, the battery cells were charged at a constant power of 0.5P to 3.65V, allowed to stand for 30 minutes, and then discharged at a constant power of 0.5P to 2.5V. The discharge capacity Q1 was recorded. Subsequently, after the battery cells were allowed to stand for 30 minutes, the first charge-discharge cycle was repeated. This cycle was repeated, and the discharge capacity Qn of each cycle was recorded. The number of cycles n when Qn decayed to 80% of Q1 was recorded.

[0237] (2) Battery capacity and volumetric energy density testing

[0238] At 25℃, the battery cell is charged to 3.65V at a constant power of 0.5P and left to stand for 30 minutes; it is then discharged to 2.5V at a constant power of 0.5P, and the discharge capacity A0 is recorded as the battery capacity in Ah. At the same time, the discharge energy E is recorded in Wh. The length, width, and height of the battery cell are measured with calipers, and the cell volume V0 is calculated in L. The volumetric energy density of the battery cell VED = discharge energy E / cell volume V0, in Wh / L.

[0239] (3) DCR testing method

[0240] At 25℃, the voltage is charged to 3.65V at a constant current of 0.33C, then charged at a constant voltage to a current of 0.05C, and then discharged to 50% SOC at 0.33C. After resting for 2 hours, the voltage is pulsed at 0.5C for 30 seconds. The voltage is recorded before and after the pulse discharge, and the DCR is calculated. The calculation formula is DCR = (voltage before pulse discharge - voltage after pulse discharge) / pulse current.

[0241] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0242] The parameters of the battery cells prepared in Examples 1-20 and Comparative Examples 1-3 were tested according to the methods described herein, and the results are shown in Tables 1-7 below.

[0243] This application provides a battery cell including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The positive electrode film layer includes a positive active material, which includes a lithium phosphate containing an olivine structure. The compaction density of the positive electrode film layer is 2.5 g / cm³. 3 -3g / cm 3 The negative electrode film layer includes a negative electrode active material, which includes graphite. The graphitization degree of the negative electrode film layer is 88%-93%. The separator layer includes a base film with a thickness of 5μm-9μm. The capacity of the battery cell is greater than or equal to 400Ah. Through the above technical solution, a high-capacity (greater than or equal to 400Ah) battery cell is achieved while maintaining high volumetric energy density and cycle stability.

[0244] Table 1

[0245] Table 2

[0246] Table 3

[0247] According to Tables 1-3 above, comparing Examples 1-6 and 15 with Comparative Examples 1-3 shows that when the compaction density of the positive electrode film is 2.5 g / cm³... 3 -3g / cm 3 When the graphitization degree of the negative electrode film is 88%-93% and the thickness of the base film is 5μm-9μm, high-capacity (greater than or equal to 400Ah) battery cells are achieved while maintaining high volumetric energy density and cycle stability.

[0248] According to Table 1 above, comparing Examples 1 and 3-4 with Examples 2 and 5, it can be seen that when the graphitization degree of the negative electrode film is 91%-92%, it better balances the volumetric energy density and cycle stability of large-capacity battery cells.

[0249] Table 4

[0250] According to Table 4 above, comparing Example 1 with Examples 7-10, it can be seen that when the median graphitization degree C50 of the positive electrode film is 0.98-1.15 and the concentration of the spheroidity of the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.535, the cycle performance of the battery cell is further improved.

[0251] Table 5

[0252] As shown in Table 5 above, when the size of the positive electrode tab along the first direction is 24mm-32mm, the volumetric energy density and cycle performance of the high-capacity battery are better balanced.

[0253] Table 6

[0254] According to Table 6 above, comparing Example 1 with Examples 16-17, it can be seen that when the mass percentage of vinylene carbonate (VC) is 0.6%-4%, the cycle performance of the battery cell is further improved.

[0255] According to Table 6 above, comparing Example 1 with Examples 18-19, it can be seen that when the mass percentage of propylene carbonate (PC) is 4%-6%, the cycle performance of the battery cell is further improved.

[0256] Table 7

[0257] According to Table 7 above, comparing Example 1 with Example 20, it can be seen that when the positive electrode film layer includes carbon nanotubes, the cycle performance of the battery cell is further improved.

[0258] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate with an olivine structure. The compaction density of the positive electrode film layer is 2.5 g / cm³. 3 -3g / cm 3 , The negative electrode film layer includes a negative electrode active material, which includes graphite, and the graphitization degree of the negative electrode film layer is 88%-93%. The separator includes a base film with a thickness of 5 μm-9 μm. The capacity of the battery cell is greater than or equal to 400Ah.

2. The battery cell according to claim 1, characterized in that, The graphitization degree of the negative electrode film is 91%-92%.

3. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the positive electrode film is 2.5 g / cm³. 3 -2.8g / cm 3 .

4. The battery cell according to any one of claims 1 to 3, characterized in that, The positive current collector includes a positive current collector portion and a positive electrode tab disposed on at least one side of the positive current collector portion. The positive electrode tab has a dimension of 15mm-45mm along a first direction, which is perpendicular to the length direction of the electrode sheet and also perpendicular to the thickness direction of the electrode sheet.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The coating area of ​​the positive electrode film layer contained in the battery cell is greater than or equal to 11m². 2 .

6. The battery cell according to any one of claims 1 to 5, characterized in that, In the cumulative graphitization distribution curve of the positive electrode film obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode, the median C of the graphitization degree is... 50 The value is 0.95-1.20, and can be selected as 0.98-1.15, where C 50 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.

7. The battery cell according to any one of claims 1 to 6, characterized in that, In the cumulative distribution curve of the sphericity area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the median LA50 of the sphericity of the lithium phosphate particles is 0.60-0.85, and can be selected as 0.7-0.

74.

8. The battery cell according to any one of claims 1 to 7, characterized in that, In the cumulative distribution curve of the spheroidal area of ​​the lithium phosphate particles in the cross section along the thickness direction of the positive electrode sheet, the concentration of spheroidal area of ​​the lithium phosphate particles (LA90-LA10) / LA50 is 0.45-0.

535.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The battery cell includes an electrolyte, which includes vinylene carbonate.

10. The battery cell according to claim 9, characterized in that, Based on the mass of the electrolyte, the mass percentage of vinylene carbonate is 0.5%-8%, optionally 0.6%-4%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The battery cell includes an electrolyte, which includes fluoroethylene carbonate.

12. The battery cell according to claim 11, characterized in that, Based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate is 0.05%-10%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes an electrolyte, which includes propylene carbonate.

14. The battery cell according to claim 13, characterized in that, Based on the mass of the electrolyte, the mass percentage of propylene carbonate is 2%-15%, optionally 2%-10%, and further optionally 4%-6%.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The lithium phosphate particles include one or more of the following elements: titanium, vanadium, aluminum, and magnesium.

16. The battery cell according to claim 15, characterized in that, The lithium phosphate particles include titanium, and the mass content of the titanium is 0.05%-0.1% based on the total mass of the positive electrode active material.

17. The battery cell according to claim 15 or 16, characterized in that, The lithium phosphate particles include vanadium, and the vanadium content is 0.05%-0.15% based on the total mass of the positive electrode active material.

18. The battery cell according to any one of claims 1 to 17, characterized in that, The battery cell includes an electrolyte, which includes a lithium-containing electrolyte salt, including lithium hexafluorophosphate and lithium difluorosulfonylimide.

19. The battery cell according to claim 18, characterized in that, Based on the total mass of the electrolyte, the mass content of the lithium bis(fluorosulfonyl)imide is 2%-7%.

20. The battery cell according to claim 18 or 19, characterized in that, The mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is 1-5, and can be selected as 2-4.

21. The battery cell according to any one of claims 1 to 20, characterized in that, The positive electrode film layer also includes a conductive agent, which includes carbon nanotubes, and the mass content of the carbon nanotubes is 0.1%-1.5% based on the total mass of the positive electrode film layer.

22. The battery cell according to any one of claims 1 to 21, characterized in that, The capacity of the battery cell is greater than or equal to 500Ah, optionally greater than or equal to 550Ah, and further optionally greater than or equal to 600Ah.

23. The battery cell according to any one of claims 1 to 22, characterized in that, The capacity of the battery cell is less than or equal to 3000Ah, optionally less than or equal to 1500Ah, and further optionally less than or equal to 1000Ah.

24. The battery cell according to any one of claims 1 to 23, characterized in that, The capacity of the battery cell is 500Ah-3000Ah, and can be selected as 550Ah-700Ah.

25. The battery cell according to any one of claims 1 to 24, characterized in that, The volumetric energy density of the battery cell is 380Wh / L-430Wh / L.

26. The battery cell according to any one of claims 1 to 25, characterized in that, The coating area of ​​the positive electrode film layer contained in the battery cell is 11m². 2 -150m 2 11m is optional 2 -120m 2 Further options include 11m. 2 -100m 2 .

27. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1 to 26.

28. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 27, the battery device being used to provide electrical energy.

29. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 27, the battery device being used to store electrical energy.

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