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

Abstract

The invention provides a battery monomer, a battery device, a power utilization device and an energy storage device. The battery monomer comprises a laminated battery cell, the laminated battery cell comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector, and the positive film layer comprises lithium-containing transition metal phosphate particles of which at least part of the surface is provided with a carbon material; in a cumulative distribution curve of a graphitization degree C value obtained by the positive electrode film layer in a surface scanning mode of a laser microscopic confocal Raman spectrometer, the median C50 of the graphitization degree is 0.95-1.20, the graphitization degree C value is IG / ID, IG represents the G peak intensity of a Raman spectrum at 1580 + / -100 cm <-1 >, ID represents the D peak intensity of the Raman spectrum at 1350 + / -100 cm <-1 >, and when the battery monomer is in a full discharge state, the battery monomer is in a non-full discharge state. And the compaction density of the positive pole piece is 2.3-2.6 g / cm < 3 >. The battery monomer provided by the invention has high capacity and good cycle performance.

Description

[0001] This application claims the priority of the PCT international application PCT / CN2025 / 094409, titled "Battery Cell, Battery Device, Electrical Device, and Energy Storage Device", filed on May 12, 2025, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of lithium-ion secondary battery cells, and particularly to a battery cell, a battery device, an electrical device, and an energy storage device. Background Art

[0003] In recent years, lithium-ion secondary battery cells have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] With the market's pursuit of the battery's endurance mileage and service life, higher requirements are put forward for battery capacity and cycling performance. However, it is difficult for the existing technology to simultaneously improve the above performances, and how to balance the two has become a technical problem urgently to be solved in this field. Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide a battery cell with both high capacity and good cycling performance.

[0006] In a first aspect of this application, a battery cell is provided. The battery cell includes a stacked electrode assembly, and the stacked electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The positive electrode film layer includes lithium-containing transition metal phosphate particles with carbon materials provided on at least part of the surface. In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 is 0.95 - 1.20. Among them, the graphitization degree C value is I G / I D , I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 100 cm -1 , and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 . When the battery cell is in a fully discharged state, the tap density of the positive electrode plate is 2.3 g / cm 3 - 2.6 g / cm 3 .

[0007] By adopting a stacked cell structure and increasing the compaction density of the positive electrode sheet, this application reduces the ineffective space inside the battery cell, improves the space utilization rate, and further enhances the volumetric energy density and capacity of the battery cell. At the same time, it regulates the median graphitization degree C 50 (reflecting the order degree of the carbon-coated material), reduces the frictional resistance between particles, enhances the sliding ability of particles in the positive electrode film layer, reduces the stress concentration in the positive electrode film layer, and reduces the risk of film layer detachment during the cycle, ultimately achieving an effective balance between high capacity and good cycle performance of the battery.

[0008] In any implementation manner, in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the median graphitization degree C 50 is 1.01 - 1.13.

[0009] When the graphitization degree of the positive electrode film layer is within the above range, it helps to further improve the sliding ability of particles in the positive electrode film layer, reduce the stress concentration in the positive electrode film layer, and reduce the risk of film layer detachment during the cycle, thereby further improving the cycle life of the battery cell.

[0010] In any implementation manner, based on the total area of particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12% - 50%, and can be optionally 12% - 40%.

[0011] When the area ratio of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the range of 12% - 50%, and further within the range of 12% - 40%, it can not only increase the compaction density of the electrode sheet, but also not increase the probability of film layer detachment, thereby improving the energy density of the battery cell while alleviating the problem of capacity drop, and taking into account the cycle life of the battery.

[0012] In any implementation manner, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm, the median sphericity L R1A1 50 is 0.6 - 0.8, and can be optionally 0.65 - 0.75, and further optionally 0.67 - 0.75.

[0013] In the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode sheet, L R1A50 is within the range of 0.65 - 0.75, and further within the range of 0.67 - 0.75, which is beneficial to further reducing the stress concentration at large particles in the positive electrode film layer of the stacked battery cell, thereby reducing the probability of film layer detachment and improving the cycle life of the battery.

[0014] In any embodiment, in the cumulative distribution curve of the coating value B obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median B of the coating value B 50 is 0.30 - 0.60, where the coating value B is I P / I D , where I P represents the intensity of the P peak of the Raman spectrum at 948 ± 100 cm -1 , and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 .

[0015] The median B of the coating value of the positive electrode film layer 50 within the above range indicates that the carbon coating material of the positive electrode active material is relatively dense and uniform, which is beneficial to improving the slip uniformity of the positive electrode film layer during rolling and reducing the stress concentration phenomenon in the positive electrode film layer; in addition, with the help of the dense and uniform carbon coating material, the large particles in the positive electrode film layer are more likely to achieve slip during compaction, thereby reducing the stress concentration phenomenon at the large particles in the positive electrode film layer, reducing the probability of film layer peeling, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0016] In any embodiment, the lithium-containing transition metal phosphate particles include the components represented by the following general formula: Li m Fe x P y O j Q q Formula I, where Q includes one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4, 0 ≤ q ≤ 0.1.

[0017] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadate phosphate, lithium manganese iron phosphate, and their modified materials.

[0018] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate and its doped and modified materials, and coated and modified materials.

[0019] In any embodiment, the iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm, and may be optionally 658 ppm - 1485 ppm.

[0020] In any embodiment, based on the total mass of the lithium-containing transition metal phosphate particles, the mass content of titanium element is 500 ppm - 8000 ppm, and optionally 1000 ppm - 3000 ppm.

[0021] In the embodiments of the present application, by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, the reaction activity of the raw materials for synthesizing the positive electrode active material is reduced, so that the positive electrode active material can achieve the control of the large particle ratio while having a high degree of graphitization, reduce the stress concentration in the positive electrode film layer, and reduce the probability of film layer shedding, taking into account the cycle life of the battery while improving the energy density of the battery.

[0022] In any embodiment, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of vanadium element is 500 ppm - 5000 ppm, and optionally 500 ppm - 3000 ppm.

[0023] The vanadium element in the positive electrode film layer can be in multiple valence states. Among them, vanadium with a +5 valence (V 5+ ) can be doped at the phosphorus element site. Due to its relatively large radius, it can cause lattice distortion and expand the diffusion channel of lithium ions, thereby improving the ionic conductivity of the positive electrode active material and the kinetic performance of the battery; vanadium with a +3 valence (V 3+ ) can be doped at the transition metal site, generating lithium vacancies through charge compensation, thereby improving the electronic conductivity of the positive electrode active material. In addition, the improvement of the distribution uniformity of vanadium element in the lithium-containing transition metal phosphate particles helps to further improve the kinetic performance of the positive electrode film layer and the reaction uniformity of the positive electrode film layer, thereby further improving the kinetic performance and cycle performance of the battery monomer.

[0024] In any embodiment, the porosity of the positive electrode film layer is 14% - 28%.

[0025] When the porosity of the positive electrode film layer is within the above range, the positive electrode film layer has good electrolyte infiltration rate and tortuosity, which is helpful for the diffusion of lithium ions in the liquid and solid phases, helps to reduce the concentration polarization of the thick electrode, and improves the kinetic performance of the battery. At the same time, it helps to alleviate the volume expansion of the positive electrode during cycling, reduce the mechanical stress of the film layer and the stress concentration phenomenon, thereby reducing the risk of film layer shedding.

[0026] In any embodiment, the resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

[0027] When the resistivity of the positive electrode film layer is within the above range, it is beneficial to reduce the electron transfer impedance, reduce the charge-discharge polarization, and improve the rate performance and cycle performance of the battery.

[0028] In any implementation, the thickness of one side of the positive electrode film layer is denoted as H, and H is 70 μm - 120 μm.

[0029] In any implementation, the thickness of one side of the positive electrode film layer is denoted as H, and H is 90 μm - 120 μm.

[0030] When the thickness of one side of the positive electrode film layer is within the above range, it helps to increase the loading amount of the positive electrode active material in the battery, improve the capacity of the battery, and at the same time take into account reducing the risk of film layer peeling off during the cycle.

[0031] In any implementation, the thickness of one side of the positive electrode film layer is denoted as H, and H is 100 μm - 120 μm.

[0032] Increasing the thickness of the positive electrode film layer helps to increase the loading amount of the positive electrode active material and improve the capacity of the battery. However, the applicant has found that when the thickness of one side of the positive electrode film layer is greater than or equal to 100 μm, during the battery cycle, the volume expansion of the positive electrode film layer is more significant, resulting in greater stress, and the stress concentration phenomenon in the positive electrode film layer is more significant, increasing the risk of film layer peeling off, which in turn affects the cycle performance of the battery. In the embodiments of the present application, by increasing the thickness of the positive electrode film layer, the capacity of the battery is increased, and at the same time, the median C value of the graphitization degree in the cumulative distribution curve of the graphitization degree obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer is controlled 50 to improve the slip ability between particles in the positive electrode film layer, thereby helping to relieve the stress concentration phenomenon of the film layer, reducing the risk of film layer peeling off, and further improving the cycle life of the battery.

[0033] In any implementation, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector. The bottom coating includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes a polyvinylidene fluoride polymer.

[0034] In any implementation, the thickness of the bottom coating is 0.5 μm - 5 μm.

[0035] The bottom coating provided by the embodiments of the present application helps to improve the adhesion between the positive electrode film layer and the positive electrode current collector and relieve the stress concentration phenomenon at large particles, thereby reducing the probability of peeling off of the positive electrode film layer and improving the cycle stability of the battery. At the same time, compared with the direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the bottom coating and the positive electrode film layer is increased, which helps to increase the area of electron transfer between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode sheet and improving the kinetic performance of the battery.

[0036] In any implementation, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber (HNBR).

[0037] After HNBR adsorbs on the surface of the particles in the slurry, its long-chain molecules will form a physical barrier around the particles, preventing the particles from approaching and aggregating with each other, and keeping the particles in a relatively independent dispersed state in the system. At the same time, HNBR can reduce the surface tension between the dispersion medium and the dispersed particles, making the particles easier to be wetted by the medium, thus promoting the dispersion of the particles in the medium. At the same time, it can also reduce the interfacial energy between the particles, reducing the aggregation phenomenon of the particles driven by the interfacial energy. Further, when the slurry dries into a film, the elastic network structure of HNBR can buffer the shrinkage stress generated by the volatilization of the solvent, reduce the re-aggregation of the conductive agent due to capillary force during this process, reduce the area ratio of the agglomeration region of the conductive agent, and improve the kinetic performance and cycle life of the battery.

[0038] In any implementation manner, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0039] When the mass content of the dispersant is within the above range, it can achieve uniform dispersion of the particles in the positive electrode film layer while maintaining a high loading amount of the positive electrode film layer, reduce the stress concentration in the positive electrode film layer, effectively alleviate the problem of battery capacity drop, and improve the cycle performance of the battery.

[0040] In any implementation manner, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is 0.5% - 2.5%, and can be optionally 1.5% - 2.5%.

[0041] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, when the area ratio of the agglomeration region of the conductive agent is within the above range, it indicates that the conductive agent in the positive electrode film layer is uniformly dispersed and is easy to form a uniform conductive network, which is particularly beneficial to reducing the problem of kinetic decline caused by the increase of the ion transport path in the film layer, reducing local polarization and even lithium deposition problems generated during the battery cycle, and improving the cycle life of the battery.

[0042] In any implementation manner, the conductive agent includes carbon nanotubes, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0043] Due to the one-dimensional structure of carbon nanotubes, a network structure can be formed in the positive electrode film layer. On the one hand, the high elastic modulus of carbon nanotubes enables their network structure to not only serve as a bridge for stress propagation but also have a binding effect on the positive electrode film layer, inhibiting the rebound of lithium-containing transition metal phosphate particles, effectively alleviating stress concentration, reducing the risk of film layer detachment, and thus improving the problem of battery capacity decline; on the other hand, the excellent electrical conductivity of carbon nanotubes makes their network structure an efficient electron transport channel. Even if there is local film layer detachment, the thick electrode can still maintain high electron transport efficiency in the in-plane direction and thickness direction, thereby delaying the occurrence of capacity decline problems and further improving the kinetic performance and cycle life of the battery.

[0044] In any implementation manner, the conductive agent further includes conductive carbon black.

[0045] Conductive carbon black has a high specific surface area and thus has good liquid retention ability. The thick electrode has a large expansion force during the cycling process, making it easy for the electrolyte to be extruded. The distribution of conductive carbon black in the positive electrode film layer is beneficial to improving the liquid retention ability of the thick electrode, further alleviating the phenomenon of capacity decline during battery cycling, and improving the cycle life of the battery.

[0046] In any implementation manner, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

[0047] When the mass contents of carbon nanotubes and conductive carbon black are within the above ranges, the agglomeration phenomenon of carbon nanotubes can be effectively alleviated and a good conductive network structure can be formed, thereby effectively reducing stress concentration in the positive electrode film layer, increasing the liquid retention rate of the positive electrode during long-term cycling, further reducing the risk of film layer detachment and polarization degree of the electrode, improving the kinetic performance of the battery, taking into account the problem of capacity decline, and improving the cycle life of the battery.

[0048] In any implementation manner, the battery cell includes a housing, at least one stacked electrode core is accommodated in the housing, the size of the housing in the length direction is L0, the size of the housing in the width direction is W0, and the size of the housing in the thickness direction is H0, where 450 mm ≤ L0 ≤ 1300 mm, 100 mm ≤ W0 ≤ 150 mm; 14 mm ≤ H0 ≤ 22 mm.

[0049] In any implementation manner, the size L0 of the housing in the length direction satisfies: 450 mm ≤ L0 ≤ 650 mm.

[0050] When the dimension L1 of the housing in the length direction satisfies 450 mm ≤ L0 ≤ 650 mm, the length of the battery cell is relatively short, which helps to shorten the diffusion path of the current, reduce the internal resistance of the electrode sheet, thereby reducing the heat generation of the battery and improving its kinetic performance; in addition, the shorter housing length helps to shorten the diffusion path of the electrolyte during the infiltration process, improve the infiltration rate and uniformity of the electrolyte, further promote the uniformity of lithium-ion deintercalation during the cycling process, relieve the stress concentration phenomenon, reduce the risk of film layer shedding, and improve the cycling stability of the battery cell.

[0051] In any implementation, the dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

[0052] When the dimension L0 of the housing in the length direction satisfies 900 mm ≤ L0 ≤ 1300 mm, the size of the battery cell is relatively long, which helps to reduce the volume ratio of the housing in the battery cell and increase the load ratio of the active material. At the same time, the longer battery cell can reduce the number of battery cells required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of the structural components in the module, thereby improving the space utilization rate of the battery pack, and further helping to improve the volume energy density of the battery cell.

[0053] In any implementation, the material of the housing is a soft-pack material, and the soft-pack material includes an aluminum-plastic composite film. Optionally, it includes one or more of aluminum, polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE).

[0054] In any implementation, the housing includes a first sealing area, and the first sealing area is arranged at at least one end of the stacked electrode assembly extending in the width direction; the first sealing area includes a folded-edge structure extending in the length direction, and a packaging adhesive is arranged on the folded-edge structure, and the packaging adhesive is continuously arranged in the length direction and fixes the folded-edge structure.

[0055] In any implementation, the housing includes at least one second sealing area, and the second sealing area is arranged along the length direction of the housing at at least one end of the stacked electrode assembly, and the second sealing area is arranged on the tab side of the stacked electrode assembly.

[0056] In any implementation, a plurality of rubber rings surrounding in the width direction are arranged on the outer periphery of the stacked electrode assembly, and the rubber rings surrounding in the width direction are arranged at intervals in the length direction.

[0057] The spaced arrangement in the length direction of the rubber rings surrounding the cell in the width direction is beneficial to fixing the positions between the electrode sheets in the cell, reducing the probability of displacement of the cell during battery shaking. It is especially applicable to batteries with a relatively large length, and can effectively reduce the mutual displacement between the electrode sheets in the length direction, thereby avoiding lithium plating phenomenon, facilitating the maintenance of the stable spatial structure inside the battery, and thus not affecting the normal operation of the battery.

[0058] In any implementation manner, at 25 °C, the capacity of the battery cell is 105 Ah - 190 Ah, and can be optionally 150 Ah - 190 Ah.

[0059] In the second aspect of the present application, a battery device is provided, including the battery cell described in the first aspect of the present application.

[0060] In the third aspect of the present application, an electrical device is provided. The electrical device includes the battery device described in the second aspect of the present application, and the battery device is used to provide electrical energy.

[0061] In the fourth aspect of the present application, an energy storage device is provided. The energy storage device includes the battery device described in the second aspect of the present application, and the battery device is used to store electrical energy. Description of the Drawings

[0062] Figure 1 is a schematic diagram of a separator in an embodiment of the present application; Figure 2 is a schematic diagram of a separator in the prior art; Figure 3 is a schematic diagram of the surface morphology of an adhesive layer in an embodiment of the present application; Figure 4 is a schematic diagram of a soft-pack laminated battery in the present application; Figure 5 is a schematic diagram of an electrical device in an embodiment of the present application.

[0063] Description of the Reference Numerals: 5 Battery cell; 50 Housing; 20 Separator; 201 Base film; 202 Ceramic layer; 203 Adhesive layer; X Length direction; Y Width direction; Z Thickness direction. Detailed Embodiments

[0064] Hereinafter, embodiments of the battery cell, battery device, electrical device, and energy storage device of the present application will be specifically disclosed in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily long and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0065] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, 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, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0066] If there is no special instruction, all embodiments and alternative embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0067] If there is no special instruction, all technical features and alternative technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0068] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0069] In this application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0070] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0071] Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0072] In the embodiments of this application, the battery device may include one or more battery cell components for providing voltage and capacity. The battery cell components may include a plurality of pouch battery cells, and the plurality of pouch battery cells are connected in series, parallel, or in a hybrid connection through a busbar component. For example, the battery cell components are usually formed by arranging a plurality of pouch battery cells; the battery cell components can be battery modules, and the battery modules are formed by arranging and fixing a plurality of pouch battery cells to form an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0073] The battery device can be a battery pack, and the battery pack includes a box body and one or more battery cell components, and the battery cell components are accommodated in the box body. The battery cell components can be battery modules, and the battery cell components can be accommodated in the box body by fixing the battery modules in the box body; the battery cell components can also be accommodated in the box body by directly fixing a plurality of pouch battery cells to the box body.

[0074] In the embodiments of this application, the box body may include a first box body and a second box body. The first box body and the second box body are snapped together so that a closed space is formed inside the box body to accommodate the battery cell components. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body can be a top cover or a bottom plate. For example, the box body may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body to accommodate the battery cell components.

[0075] In an embodiment of the present application, the box body can be part of the chassis structure of a vehicle. For example, a part of the box body can become at least a part of the vehicle floor, or a part of the box body can become at least a part of the cross beams and longitudinal beams of the vehicle.

[0076] In an embodiment of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging to continue to be used; the battery cell can be a lithium-ion battery. The battery cell can be in a flat body shape.

[0077] The battery mentioned in the embodiment of the present application can be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application can include battery cells, battery modules, battery packs, etc.

[0078] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging.

[0079] When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, a part of the box body can become at least a part of the vehicle floor, or a part of the box body can become at least a part of the cross beams and longitudinal beams of the vehicle.

[0080] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0081] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0082] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0083] The battery cell includes an electrode assembly and an electrolyte.

[0084] The electrode assembly generally includes a positive electrode plate and a negative electrode plate. The negative electrode plate is the electrode where the reaction of absorbing or lithiating lithium ions occurs during charging and releasing or delithiating lithium during discharging, and the positive electrode plate is the electrode where the reaction of releasing or delithiating lithium ions occurs during charging and absorbing or lithiating lithium during discharging.

[0085] Although lithium-containing transition metal phosphate particles have significant advantages in terms of cycle stability as the positive electrode active material, their intrinsic specific capacity is significantly lower than that of ternary materials. The applicant has found that the capacity and energy density disadvantages can be compensated by increasing the tap density of the lithium-containing transition metal phosphate particle material and combining it with a stacked cell structure. However, this process optimization also brings new technical challenges: compared with ternary materials, the structure of lithium-containing transition metal phosphate particles is more stable and is not easily broken under high pressure. Therefore, lithium-containing transition metal phosphate particles often undergo higher pressure during the electrode pressing process to pursue an increase in tap density. Under high tap density conditions, if the slip ability of the material is insufficient, stress concentration is likely to occur due to local stress concentration during the electrode rolling process. Secondly, since the stacked cell has no corners like the wound cell, it has a relatively high energy density compared to the wound cell. However, the stacked cell is not restricted by corners like the wound cell, which makes the extrusion force on the positive electrode film in the stacked cell weaker than that in the wound cell, making it easier to exacerbate the release of the positive electrode film. The shedding of the film layer not only directly reduces the active substances participating in the electrochemical reaction but also causes the "island" effect, that is, isolated regions are formed between particles or between particles and the conductive agent, preventing the formation of good electrical contact and thus unable to participate in the charge and discharge process, resulting in a significant drop in battery capacity. In addition, the shed active substances will hinder the ion transport path, increase the battery internal resistance, cause local overheating, and even increase the risk of thermal runaway, seriously affecting the cycle life and safety of the battery.

[0086] Based on this, in the first aspect of the present application, a battery cell is provided, including a stacked cell, the stacked cell includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, the positive electrode film layer includes lithium-containing transition metal phosphate particles with carbon material provided on at least part of the surface, in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of a laser confocal Raman spectrometer, the median C of the graphitization degree 50 is 0.95 - 1.20, where the graphitization degree C value is I G / I D , I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 100 cm -1 , I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 , when the battery cell is in a fully discharged state, the tap density of the positive electrode sheet is 2.3 g / cm 3 -2.6 g / cm 3 .

[0087] The battery cell provided by the present application has high capacity while improving the problem of its capacity drop, taking into account the cycle life of the battery.

[0088] Without being bound by any theory, this may be because: adopting a laminated battery cell structure can reduce the existence of ineffective space inside the battery cell, effectively eliminating the inevitable corner voids and interlayer gaps in the winding process, making the entire battery cell structure more compact, thereby improving space utilization, increasing the volumetric energy density of the battery cell monomer, and increasing the battery capacity; in addition, the regularity of the laminated structure also creates favorable conditions for improving the high compaction density process of the electrode sheet. Under the same volume, the laminated battery cell can accommodate more electrode sheets, and with the electrode sheets of high compaction density, it further enhances the energy density and capacity output of the battery. At the same time, the applicant controls the median C of the graphitization degree in the cumulative distribution curve of the graphitization degree C value obtained by the laser confocal Raman spectrometer in the surface scanning mode of the positive electrode film layer 50 , so as to achieve a balance between battery capacity and cycle performance. The median C of the graphitization degree obtained by the laser confocal Raman spectrometer in the surface scanning mode of the positive electrode film layer 50 can reflect the graphitization degree of the carbon coating material on the surface of the lithium transition metal phosphate, that is, the degree of order of the carbon coating material on the surface of the lithium transition metal phosphate particles. The higher the graphitization degree of the lithium transition metal phosphate particles, the more orderly the arrangement of carbon atoms, forming a nearly ideal graphite layer structure. This structure can effectively reduce the friction between particles, is conducive to the relative sliding of particles along the layers when stressed, showing good slip ability, thereby helping to relieve the stress concentration phenomenon of the film layer, reducing the risk of film layer peeling, and further increasing the cycle life of the battery.

[0089] In this application, a laminated battery cell refers to a battery cell formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet together.

[0090] In this application, the positive electrode film layer contains lithium transition metal phosphate particles, but the positive electrode film layer does not simply refer to the positive electrode active material layer. Other film layers that are connected to the positive electrode active material layer and are difficult to distinguish, such as the bottom coating layer, the liquid retention layer, etc., are collectively referred to as the positive electrode film layer.

[0091] In this application, the lithium transition metal phosphate particles refer to phosphate materials containing lithium elements and transition metal elements, which can be detected by any well-known method in the art. For example, they can be detected by combining an X-ray diffractometer (XRD) with an energy spectrometer and an inductively coupled plasma mass spectrometer.

[0092] In this application, the carbon coating material provided on at least a part of the surface of the lithium transition metal phosphate particles can be detected by any well-known method in the art. As an example, by combining a transmission electron microscope and an energy spectrometer to characterize the lithium transition metal phosphate particles, the carbon coating material provided on at least a part of the surface of the lithium transition metal phosphate particles can be observed.

[0093] In this application, the fully discharged state refers to the state where the battery is placed in an oven environment at 25°C, left standing for 2 hours, and after the battery temperature remains at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then at a constant current of 0.1C to 2.0V.

[0094] The tap density of the positive electrode sheet can be tested by methods known in the art. As an example, the battery is placed in an oven environment at 25°C, left standing for 2 hours, and after the battery temperature remains at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then at a constant current of 0.1C to 2.0V. The battery is disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with a dimethyl carbonate solvent, the electrode sheet is dried, cut into small circular pieces with an area of S, and its mass is obtained as W1. The thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the above-weighted 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. Then, the tap density PD of the positive electrode sheet = (W1 - W2) / [(T1 - T2)×S].

[0095] In some embodiments, when the battery cell is in the fully discharged state, the tap density of the positive electrode sheet can be selected as 2.3 g / cm 3 、2.31 g / cm 3 、2.32 g / cm 3 、2.33 g / cm 3 、2.34 g / cm 3 、2.35 g / cm 3 、2.36 g / cm 3 、2.37 g / cm 3 、2.38 g / cm 3 、2.39 g / cm 3 、2.40 g / cm 3 、2.41 g / cm 3 、2.42 g / cm 3 、2.43 g / cm 3 、2.44 g / cm 3 、2.45 g / cm 3 、2.46 g / cm 3 、2.47 g / cm 3 、2.48 g / cm 3 、2.49 g / cm 3 、2.50 g / cm 3 、2.55 g / cm 3 、2.60 g / cm 3 or any value range between any two of them.

[0096] In this application, the cumulative distribution curve of the graphitization degree C value refers to a curve obtained by arranging at least 100 obtained C values in ascending order, with the graphitization degree on the horizontal axis and the cumulative quantity ratio on the vertical axis. C 50 is the C value corresponding to the cumulative quantity ratio of 50% on the vertical axis in the cumulative distribution curve of the graphitization degree C value. The median C of the graphitization degree 50 Compared with the point value, it can reflect the overall graphitization degree of the particles in the positive electrode film layer, that is, the degree of easy slip; compared with the mean value, it can reduce the influence of extreme values during the test and improve the confidence level of the test results.

[0097] The graphitization degree C value of the positive electrode film layer can be obtained by the 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, the excitation wavelength of 532 nm is selected, an appropriate amount of the positive electrode film layer is taken, and its surface or the cross-section along the thickness direction of the electrode sheet is surface scanned. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, with the grid vertices as the test points, the step size is 5 μm, and the total number of scanning points is 100 points. Thus, the C values at different positions and the cumulative distribution curve of the C value of the surface scanning area are obtained. The positive electrode film layer in this application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery. It is inevitable that there are residual electrolyte salt particles on the surface of the positive electrode film layer disassembled from the battery. To improve the test accuracy, it is preferred to perform a surface scan on the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet to characterize the graphitization degree of the positive electrode film layer.

[0098] The graphitization degree C value of the positive electrode film layer is obtained through the peak intensity ratio of the G peak (G-band) and the D peak (D-band) of the Raman spectrum. The position of the G peak is 1580 ± 100 cm -1 , which characterizes the carbon sp 2 hybrid structure; the position of the D peak is 1350 ± 100 cm -1 , which characterizes the disordered structure, where disorder means that the carbon atoms in the structure are not regularly arranged. In a graphite crystal, the carbon atoms in the same layer form covalent bonds through sp 2 hybridization, and the intermolecular force between layers is the van der Waals force, making the carbon in the graphite structure easy to slip. Therefore, the C value can characterize the graphitization degree of the positive electrode film layer. It can be understood that the graphitization degree in the positive electrode film layer mainly comes from the carbon material treated by graphitization in the positive electrode film layer, that is, the carbon coating material of the positive electrode active material. Although the carbon nanotube conductive agent rich in sp 2 hybrid structure also has a relatively high I G / I D , but due to its small addition content and small tube diameter, its addition in the positive electrode film layer shows as an extreme value in the Raman surface scan test of the positive electrode film layer and will not affect the graphitization degree C in the positive electrode film layer50 It has an impact. Therefore, the graphitization degree of the positive electrode film layer can also be used to characterize the graphitization degree of the positive electrode active material.

[0099] Those skilled in the art can adjust the graphitization degree of the active material particles through any known process. As an example, adjusting the carbon source, sintering temperature, sintering time, sintering pressure, and sintering atmosphere can all achieve the adjustment of the graphitization degree of the active material particles.

[0100] The higher the graphitization degree of the carbon on the surface of the positive electrode active material, the higher the proportion of graphitic structural carbon in the positive electrode film layer, and the easier it is for the particles to slip through the carbon structure with a high graphitization degree in the coating layer, reducing the stress concentration phenomenon in the electrode sheet, reducing the demolding phenomenon, and improving the cycle performance of the battery.

[0101] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the median C of the graphitization degree 50 can be selected as 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20 or the numerical range between any two of them.

[0102] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the median C of the graphitization degree 50 is 1.01 - 1.13.

[0103] When the graphitization degree of the positive electrode film layer is further within the above range, it helps to further improve the ease of slippage of the particles in the positive electrode film layer, reduce the stress concentration in the positive electrode film layer, and thus further improve the long-term cycle stability of the battery cell.

[0104] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the concentration degree of the C value (C 90 - C 10 ) / C 50 is 0.01 - 0.05.

[0105] Referring to the above, by analogy, C 90 is the C value corresponding to the cumulative quantity proportion of 90% on the vertical axis in the cumulative distribution curve of the graphitization degree C value, and C 10It is the C value corresponding to the cumulative quantity ratio of 10% of the cumulative quantity on the vertical axis in the cumulative distribution curve of the graphitization degree C value. The concentration degree of the C value is represented by (C 90 - C 10 ) / C 50 . (C 90 - C 10 ) / C 50 can not only reflect the magnitudes of most C values, but also be unaffected by extreme values, and can also reflect the width of the distribution of the graphitization degree of particles in the positive electrode film layer. A small concentration degree of the C value of the positive electrode film layer indicates a narrow width of the distribution of the graphitization degree of particles in the positive electrode film layer and good concentration.

[0106] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in the surface scanning mode of a laser confocal Raman spectrometer, the concentration degree of the C value (C 90 - C 10 ) / C 50 can be optionally 0.01, 0.02, 0.023, 0.025, 0.03, 0.035, 0.036, 0.039, 0.04, 0.045, 0.05 or the numerical range between any two of them.

[0107] When the concentration degree of the C value of the positive electrode film layer is 0.01 - 0.05, it indicates a high degree of consistency in the graphitization degree of particles in the positive electrode film layer, which means that the positive electrode active material has good coating uniformity and consistency, can reduce the slippage obstruction caused by the inconsistency of the graphitization degree of particles in the positive electrode active material and the resulting local stress concentration, reduce the demolding risk, and thus improve the long-term cycle stability of the battery cell.

[0108] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in the surface scanning mode of a laser confocal Raman spectrometer, the concentration degree of the C value (C 90 - C 10 ) / C 50 is 0.02 - 0.04.

[0109] The median C 50 of the graphitization degree of the positive electrode film layer within the above range is beneficial to further improve the easy slippage degree between particles, further reduce the local stress concentration while maintaining the high kinetic performance of the battery, reduce the demolding risk, and achieve the balance between battery performance and energy density.

[0110] In some embodiments, based on the total area of particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of particles with a particle size R1 satisfying R1 ≥ 1000 nm is 12% - 50%.

[0111] 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, for example, 10,000 times. There may be defects and scratches inside the particle, but no complete boundary sufficient to divide the particle can be recognized inside the particle. The positive electrode film layer in this application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery.

[0112] The method for identifying particles is as follows: Cut the positive electrode film layer along the thickness direction of the electrode plate by an argon ion beam (as an example, the following can be selected: equipment model: Leica EMTIC3XCP, working voltage: 6 kV, working duration: 6 h). After exposing the cut surface, use a scanning electron microscope (as an example, the following can be selected: equipment model: Hitachi SU8230, working voltage: 3 kV, beam current: high, probe model: U(LA100), working distance < 5 mm) to observe the cut surface of the positive electrode film layer along the thickness direction of the electrode plate. Collect images in the secondary electron mode at a non-edge position on the cut surface of the positive electrode film layer through a field emission scanning electron microscope (after observing the edge of the electrode plate under the scanning electron microscope, adjust the field of view to the central part of the sample), take an electron micrograph at a magnification of 10,000 times, and analyze the particles in the electron micrograph with ImageJ software (version 1.46r, win64). The specific usage method of ImageJ software is as follows: Load the scanning electron micrograph to be analyzed; Use the Cellpose plug-in software in it to identify particles, and on this basis, perform manual correction; Use ImageJ to read and count data. The specific method for using the Cellpose plug-in software to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmantation module) to 15 pixels, click "runcyto3" to identify particles; Manually mark the particles in the image that are not recognized by the software, not completely recognized by the software, or have recognition errors. The particles in the image that are not recognized by the software, not completely recognized by the software, or have recognition errors mainly include the following types: 1. Due to the particle being too large or having scratches on the particle surface, the particle cannot be recognized or cannot be completely recognized; 2. During the argon ion beam cutting process, scratches will be generated on the particle surface, and the software may misjudge the scratches as the particle boundary during the recognition process, thereby generating recognition errors; 3. Due to the particle being too small, it fails to be recognized; 4. The particle is located at the edge of the electron microscope field of view, the inside of the particle is penetrated by the edge, the morphology is not fully displayed, and the local part is recognized instead of the whole, resulting in recognition errors.For the particles that are not recognized or have recognition errors as described above, manual calibration is performed, and the specific process is as follows: Delete the particles located at the edges of the scanning electron microscope that cannot fully display large particles; Determine whether there are gap scratches inside other particles that are not recognized or have recognition errors. If there are no gap scratches inside the particles, then determine it as a single particle, and manually mark it according to the particle boundary observed by the human eye; In response to the presence of gap scratches inside the particle, determine whether the gap scratches penetrate the particle. If the particle is not penetrated, then determine it as a single particle and perform manual marking; In response to the gap scratches penetrating the particle, determine whether the gap scratches are linear or irregular; In response to the gap scratches being irregular, determine it as the boundary between particles and divide the particles along this boundary; In response to the gap scratches being linear, perform contrast of the contrast; In response to the contrast being not obvious and there being no sense of crack, determine it as a scratch and mark it as a single particle; In response to the contrast being strong and there being a sense of crack, determine it as the boundary between particles and mark it as two particles. After manual marking, delete the information irrelevant to the particles during the automatic image processing process, that is, the determination and marking of the particles in the picture are completed.

[0113] It can be understood that the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, especially particles larger than 50 nm, mainly originate from the positive electrode active material. Therefore, by observing and statistically analyzing the particle area in the cross-section of the positive electrode sheet along the thickness direction of the electrode sheet in the embodiments of the present application, the distribution of lithium-containing transition metal phosphate particles in the positive electrode film layer can be accurately and objectively reflected.

[0114] In the prior art, a laser particle size analyzer is usually used to statistically analyze the particle size of the positive electrode active material by the Malvern laser diffraction method. However, the applicant's research shows that due to the easy agglomeration of lithium-containing transition metal phosphate particles, the test results obtained by the Malvern laser diffraction method based on the laser scattering principle often measure the particle size of the particle agglomerates, and cannot truly reflect the particle size of the particles in the positive electrode active material, let alone reflect the dispersion state of the positive electrode active material in the film layer, because the dispersion degree of the positive electrode active material in the film layer will increase during the processes of pulping and film forming and rolling. The test results obtained by the Malvern laser diffraction method are affected by the particle size, specific surface area, and agglomeration degree of the positive electrode active material. Compared with the actual dispersion situation in the electrode sheet, the number of large particles obtained by this test is lower than the actual value, and the number of small particles is higher than the actual value. Therefore, the particle size obtained by the Malvern laser diffraction method cannot be equivalent to or analogized to the particle size statistically obtained in the embodiments of the present application.

[0115] In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the method for testing the area ratio of particles with a particle size R1 satisfying R1≥1000nm is as follows: Refer to the method described above in this application to identify the particles in the positive electrode film layer. After the particles are determined and labeled, import the image into ImageJ software for analysis. Set the scale according to the scanning electron microscope image, and perform statistical analysis on the particle size, area, sphericity, and roughness of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet through the "Feret diameter", "Area", "Round", and "Solidity" analysis functions. According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained from the analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which characterizes the particle size of the particle; the "Area" parameter obtained represents the pixel area of the particle. Since particles with a particle size less than 50nm have large errors during the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50nm, which will cause large errors to the statistical results. Therefore, particles with a particle size less than 50nm are not counted during the particle size statistics process in this application, and the particle statistical data corresponding to "AR", "Round", or "Solidity" displayed as "NaN" are deleted. Calculate the sum of the "Area" parameters of the particles with a particle size R1 satisfying R1≥1000nm and the sum of the "Area" parameters of all particles, which are respectively used as the area of the particles with a particle size R1 satisfying R1≥1000nm and the total area of the counted particles. Divide the sum of the areas of the particles with a particle size R1 satisfying R1≥1000nm by the total area of the counted particles to obtain the area ratio of the particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0116] In some embodiments, based on the total area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size R1 satisfying R1≥1000nm can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or any numerical range between any two of them.

[0117] In some embodiments, based on the total area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size R1 satisfying R1≥1000nm is 12%-40%.

[0118] Large particles with a particle size R1 satisfying R1≥1000nm contribute to improving the compaction density of the positive electrode sheet, thereby increasing the volume energy density of the battery cell. However, researchers have found that stress concentration is likely to occur at these large particles, increasing the risk of shedding of the positive electrode film layer. Therefore, when the proportion of the area of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is in the range of 12%-50%, and further in the range of 12%-40%, it can not only improve the compaction density of the electrode sheet but also prevent the probability of film layer shedding from being too high, thereby improving the energy density of the thick-coated lithium-containing transition metal phosphate battery while alleviating the capacity plunge problem and taking into account the cycle life of the battery.

[0119] In some embodiments, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm, L R1A50 is 0.6 - 0.8.

[0120] In this application, in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode sheet, the method for testing the sphericity of particles with a particle size R1 satisfying R1≥1000nm is as follows: Refer to the method described above in this application to identify the particles in the cross-section of the positive electrode film layer, and use the "Shape Descriptor" analysis function in ImageJ to analyze the morphology of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet. According to the software manual (ImageJ User Guide IJ 1.46r), the "Round" parameter obtained by analysis represents the ratio of the pixel area of the particle to the area of a circle with the fitted major axis as the diameter, and can be used to characterize the sphericity of the particle. When the particle is closer to a sphere, the ratio of the pixel area to the area of a circle with the fitted major axis as the diameter is closer to 1. Therefore, the "Round" parameter of the obtained particles is used to characterize the sphericity of the particles. According to the above method, to meet the sample number with statistical significance, each electrode sheet collects at least 10 non-overlapping scanning electron microscope images of the field of view. Arrange the sphericities of at least 1000 obtained particles in ascending order, and obtain the cumulative distribution curve of the sphericity of the particles in the positive electrode film layer with the sphericity as the horizontal axis and the cumulative area proportion as the vertical axis. L A50 It is the sphericity L value corresponding to the cumulative area proportion of 50% on the vertical axis in the cumulative distribution curve of the sphericity L value of the particles.

[0121] In some embodiments, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode sheet, L R1A50It can be optionally 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.705, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80 or a numerical range between any two of them.

[0122] Those skilled in the art can adjust the sphericity of the particles through any known process. As an example, the sphericity of the particles can be adjusted by processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, adding surfactants, etc., and by adjusting the parameters of each process.

[0123] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode plate, in the cumulative area distribution curve of the sphericity of the particles with a particle size R1 satisfying R1≥1000nm, L R1A50 is 0.65 - 0.75.

[0124] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode plate, in the cumulative area distribution curve of the sphericity of the particles with a particle size R1 satisfying R1≥1000nm, L R1A50 is 0.67 - 0.75.

[0125] In the cross-section of the positive electrode film layer along the thickness direction of the positive electrode plate, in the cumulative area distribution curve of the sphericity of the particles with a particle size R1 satisfying R1≥1000nm, L R1A50 Within the range of 0.65 - 0.75, and further within the range of 0.67 - 0.75, it is beneficial to further reduce the stress concentration at the large particles in the positive electrode film layer of the thick-coated stacked cell, thereby reducing the probability of film layer peeling and improving the cycle life of the battery.

[0126] In some embodiments, in the cumulative distribution curve of the coating value B obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median coating value B 50 is 0.30 - 0.60, where the coating value B is I P / I D where I P represents the intensity of the P peak of the Raman spectrum at 948±100 cm -1 and I D represents the intensity of the D peak of the Raman spectrum at 1350±100 cm -1 .

[0127] The cumulative distribution curve of the coating value B refers to a curve obtained by arranging at least 100 obtained B values in ascending order, with the coating value on the horizontal axis and the cumulative quantity ratio on the vertical axis. In order to reduce the influence of the extreme values of the coating value in the non-particle region of the positive electrode film layer on the test results, the median B of the coating value is used. 50 Evaluate the compactness of the carbon coating material on the positive electrode active material. B 50 It is the B value corresponding to the cumulative quantity ratio of 50% on the vertical axis in the cumulative distribution curve of the coating value B.

[0128] In this application, the coating value B of the positive electrode film layer can be obtained by scanning with a laser confocal Raman spectrometer. As an example, specifically, a laser confocal Raman spectrometer (Renishaw high-precision laser confocal Raman spectrometer) is used, the excitation wavelength of 532 nm is selected, an appropriate amount of the positive electrode film layer is taken, and surface scanning is performed on its surface or the cross-section along the thickness direction of the electrode sheet. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, the grid vertices are used as test points, the step size is 5 μm, and the total number of scanning points is 100 points. Thus, the B values at different positions and the cumulative distribution curve of the B value of the surface scanning area are obtained. The positive electrode film layer in this application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery. It is inevitable that there are residual electrolyte salt particles on the surface of the positive electrode film layer disassembled from the battery. In order to improve the test accuracy, it is preferred to perform surface scanning on the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet to characterize the coating value of the positive electrode film layer.

[0129] The coating value B of the positive electrode film layer is obtained from the peak intensity ratio of the P peak (P-band) and the D peak (D-band) of the Raman spectrum. The position of the P peak is 948 ± 100 cm -1 , which characterizes the phosphate group PO4 3- The position of the D peak is 1350 ± 100 cm -1 , which characterizes the disordered structure, where disorder means that there is no regular arrangement between the carbon atoms in the structure. During the test, the excitation wavelength of 532 nm is selected, and the test depth is relatively shallow. Therefore, in the test results obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the carbon structure peak shows a higher intensity than the phosphate group structure peak.

[0130] Those skilled in the art can adjust the coating value of the active material particles through any known process. As an example, adjusting the type of carbon source, the addition amount of carbon source, sintering temperature, sintering time, sintering pressure, and sintering atmosphere can all achieve the adjustment of the coating value of the active material particles. The coating value B can reflect the compactness of the carbon coating material on the surface of the lithium-containing transition metal phosphate particles. The denser the carbon coating, the relatively lower the intensity of the phosphate group structure detected in the Raman spectrum, and the smaller the coating value B of the positive electrode film layer.

[0131] In some embodiments, the positive electrode film layer further includes a coating layer disposed on at least a part of the surface of the lithium-containing transition metal phosphate particles. In the cumulative distribution curve of the coating value B obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median B of the coating values 50 is optionally 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6 or a numerical range between any two of them.

[0132] The median B of the coating values of the positive electrode film layer 50 within the above range indicates that the carbon coating material of the positive electrode active material is relatively dense and uniform, which is beneficial to improving the slip uniformity of the positive electrode film layer during the rolling process and reducing the stress concentration phenomenon in the thick-coated positive electrode film layer; in addition, with the help of the dense and uniform carbon coating material, the large particles in the positive electrode film layer are more likely to achieve slip during the compaction process, thereby reducing the stress concentration phenomenon at the large particles in the thick-coated positive electrode film layer, reducing the probability of the positive electrode film layer peeling off, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0133] In some embodiments, the single-sided thickness H of the positive electrode film layer is 70 μm - 120 μm.

[0134] In some embodiments, the single-sided thickness H of the positive electrode film layer is 90 μm - 120 μm.

[0135] The thickness of the positive electrode film layer can be detected by any well-known method in the art. As an example, the thickness of the positive electrode film layer in the cross-section of the positive electrode sheet along the thickness direction is measured by a scanning electron microscope.

[0136] In some embodiments, the single-sided thickness H of the positive electrode film layer can be selected from 70μm, 71μm, 71.53μm, 72μm, 73μm, 74μm, 75μm, 76μm, 77μm, 78μm, 79μm, 80μm, 81μm, 82μm, 83μm, 84μm, 85μm, 86μm, 87μm, 88μm, 89μm, 90μm, 91μm, 92μm, 93μm, 94μm, 95μm, 96μm, 97μm, 98μm, 99μm, 100μm, 101μm, 102μm, 103μm, 104μm, 105μm, 105.64μm, 105.89μm, 106μm, 106.66μm, 106.79μm, 107μm, 108μm, 109μm, 110μm, 111μm, 112μm, 113μm, 114μm, 115μm, 116μm, 117μm, 118μm, 119μm, 119.12μm, 120μm or the numerical range between any two of them.

[0137] During the long cycle of the battery, if the thickness of the positive electrode film layer is too high, it will cause a large volume expansion, resulting in an increase in internal stress, making the electrode sheet prone to the risk of film layer shedding in the later stage of the cycle. When the single-sided thickness of the positive electrode film layer is within the above range, it helps to further increase the loading amount of the positive electrode active material in the battery, improve the capacity of the battery, while taking into account reducing the risk of film layer shedding and improving the cycle performance of the battery.

[0138] In some embodiments, the single-sided thickness H of the positive electrode film layer is 100μm - 120μm.

[0139] Increasing the thickness of the positive electrode film layer helps to increase the loading amount of the positive electrode active material and improve the capacity of the battery. However, the applicant has found that when the single-sided thickness of the positive electrode film layer is greater than or equal to 100μm, during the battery cycle, the volume expansion of the positive electrode film layer is more significant, resulting in greater stress, and the stress concentration phenomenon in the positive electrode film layer is more significant, increasing the risk of film layer shedding, which in turn affects the cycle performance of the battery. In the embodiments of the present application, the capacity of the battery is increased by increasing the thickness of the positive electrode film layer, and at the same time, the median C of the graphitization degree in the cumulative distribution curve of the graphitization degree C obtained in the surface scanning mode of the laser confocal Raman spectrometer of the positive electrode film layer is controlled 50 , improving the slip ability between particles in the positive electrode film layer, thereby helping to alleviate the stress concentration phenomenon of the film layer, reducing the risk of film layer shedding, and further improving the cycle life of the battery.

[0140] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include the components shown by the following general formula: Li m Fe x P yO j Q q Formula I wherein Q comprises one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br; 0.8 ≤ m ≤ 1.15; 0.9 ≤ x ≤ 1; 0.95 ≤ y ≤ 1; 3.5 ≤ j ≤ 4; 0 ≤ q ≤ 0.1.

[0141] In some embodiments, m can be optionally 0.8, 0.85, 0.9, 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15 or a numerical range between any two of them; x can be optionally 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or a numerical range between any two of them; y can be optionally 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or a numerical range between any two of them; j can be optionally 3.5, 3.6, 3.7, 3.8, 3.9, 4 or a numerical range between any two of them; q can be optionally 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or a numerical range between any two of them.

[0142] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate fluoride, lithium manganese iron phosphate and their modified materials.

[0143] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate and its doped modified materials and coated modified materials.

[0144] In some embodiments, the iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm.

[0145] The iron dissolution rate of the positive electrode material can be tested by methods well-known in the art. As an example, 7.5 g of the positive electrode material powder obtained by scraping powder from the positive electrode film layer sample is weighed and added to 100.3 g of ascorbic acid solution with a mass concentration of 0.3% (the solvent is ultrapure water). After stirring at a speed of 500 revolutions per minute for 305 minutes, the solution is quickly aspirated using a 5 mL syringe, and the solution is filtered through a 0.45 μm pore size filter head into a test tube. 1 mL of the supernatant is aspirated with a pipette and diluted 50 times in a glass volumetric flask, and then tested with an inductively coupled plasma mass spectrometer (ICP-OES) to obtain the iron element concentration in the solution. Through the formula: (ICP test iron element concentration × solution volume / mass of the solution involved in volume fixation) × 100.3 g / mass of the positive electrode material powder, the solution volume is 50 mL, and the mass of the solution involved in volume fixation is 1 g, and the iron dissolution rate of the positive electrode material is calculated.

[0146] In some embodiments, the iron dissolution rate of the positive electrode material can be 658 ppm, 700 ppm, 800 ppm, 890 ppm, 900 ppm, 1000 ppm, 1058 ppm, 1076 ppm, 1100 ppm, 1143 ppm, 1200 ppm, 1236 ppm, 1300 ppm, 1311 ppm, 1384 ppm, 1349 ppm, 1400 ppm, 1485 ppm, 1500 ppm, 1531 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1921 ppm or any numerical range between any two of them.

[0147] In some embodiments, the iron dissolution rate of the positive electrode material is 658 ppm - 1485 ppm.

[0148] The iron element dissolved in the positive electrode material mainly comes from the lithium-containing transition metal phosphate particles in the positive electrode active material. The level of the iron dissolution rate depends on the one hand on the number of lattice defects in the lithium-containing transition metal phosphate, and on the other hand on the integrity and density of the carbon coating on the surface of the positive electrode active material. The lower the iron dissolution rate means fewer lattice defects in the lithium-containing transition metal phosphate, which is beneficial to reducing the corrosion of the lattice in a weak acid environment; and the more complete and dense the carbon coating material on the surface of the positive electrode active material, the more it inhibits the dissolution of iron ions in a weak acid environment. The positive electrode material with an iron dissolution rate within the above range has relatively few lattice defects and a complete and dense carbon coating material, which is beneficial to improving the compressive resistance and ease of slippage of the particles in the positive electrode film layer under high roll pressing pressure, increasing the compaction density of the positive electrode film layer and reducing the stress concentration in the positive electrode film layer, improving the energy density of the battery and taking into account improving the problem of battery capacity drop.

[0149] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element is 500 ppm - 8000 ppm.

[0150] The types and contents of elements in the lithium-containing transition metal phosphate particles in the positive electrode film layer can be tested by any well-known method in the art. As an example, inductively coupled plasma optical emission spectrometry is used to test the titanium element and its content with reference to Appendix C of GB / T 33822-2017.

[0151] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element can be selected as 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm or any value range between any two of them.

[0152] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element is 1000 ppm - 3000 ppm.

[0153] Introducing titanium element into the lithium-containing transition metal phosphate particles requires adding a titanium source during the preparation of the positive electrode active material. The titanium source is often an inert material, and attaching to the surface of the lithium-containing transition metal phosphate particle raw material can play a role in reducing the reaction activity and reducing the growth of particle size. Improving the graphitization degree of the positive electrode active material often requires a higher sintering temperature or a longer sintering time, but this will also increase the size of the particles in the positive electrode film layer, increase the stress concentration in the positive electrode film layer, and cause the film layer peeling phenomenon of the positive electrode film layer. In the embodiments of the present application, by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, the reaction activity of the positive electrode active material synthesis raw material is reduced, so that the positive electrode active material can control the proportion of large particles while having a high graphitization degree, reduce the stress concentration in the positive electrode film layer, and reduce the probability of film layer peeling of the positive electrode film layer, taking into account the cycle life of the battery while improving the energy density of the battery.

[0154] Meanwhile, the doping of titanium element in the cathode active material is beneficial to causing lattice distortion, reducing the Li-O bond energy, increasing the lithium ion transmission rate, and improving the kinetic performance of the battery. The lithium ion diffusion in the thick coating film layer is uneven, often accompanied by a significant lithium ion concentration gradient. In the embodiments of the present application, the solid-phase transmission rate of the cathode active material is improved by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, thereby improving the kinetic problems of the thick electrode plate battery.

[0155] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the cathode film layer, the mass content of vanadium element is 500 ppm - 5000 ppm.

[0156] The types and contents of elements in the lithium-containing transition metal phosphate particles in the cathode film layer can be tested by any well-known method in the art. As an example, the inductively coupled plasma emission spectrometry is used to test the vanadium element and its content with reference to Appendix C of GB / T 33822-2017.

[0157] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the cathode film layer, the mass content of vanadium element can be selected from 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm.

[0158] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the cathode film layer, the mass content of vanadium element is 500 ppm - 3000 ppm.

[0159] The vanadium element in the cathode film layer can be in multiple valence states. Among them, vanadium with a +5 valence (V 5+ ) can be doped at the phosphorus element site. Due to its relatively large radius, it can cause lattice distortion and expand the lithium ion diffusion channel, thereby increasing the ionic conductivity of the cathode active material and improving the kinetic performance of the battery; vanadium with a +3 valence (V 3+)(It) can be doped at transition metal sites to generate lithium vacancies through charge compensation, thereby improving the electronic conductivity of the cathode active material. In addition, the improvement in the uniformity of vanadium element distribution in the lithium-containing transition metal phosphate particles helps to further improve the kinetic performance of the cathode film layer and the uniformity of the cathode film layer reaction, thereby further improving the kinetic performance and cycling performance of the battery cell.

[0160] The mass content of vanadium element within the above range helps to improve the kinetic performance of the cathode electrode sheet and the kinetic performance of the thick-coated lithium-containing transition metal phosphate battery. At the same time, the synergistic effect of titanium element, vanadium element and carbon nanotubes in the cathode film layer helps to form a good three-dimensional network, further improving the electronic conductivity and ionic conductivity of the cathode film layer, thereby further improving the kinetic performance of the thick-coated lithium-containing transition metal phosphate battery.

[0161] In some embodiments, the porosity of the cathode film layer is 14% - 28%.

[0162] In this application, the porosity of the cathode film layer can be tested in the following manner. Import the scanning electron microscope image of the cross-section of the cathode film layer obtained in the manner described above along the thickness direction of the electrode sheet into the ImageJ software. Select the straight line tool, use the straight line to mark the scale length in the picture, click "Analyze Set Scale", and set the scale parameters in the software according to the scale length in the picture. Select the rectangular tool, select the part of the picture outside the scale area, use "Image Duplicate" to copy the selected area, and use "Image Type 8 bit" to adjust the picture format; select "Analyze Set Measurements", and select the following 5 options: "Area", "Mean gray value", "Area Fraction", "Limit to threshold", "Feret’s diameter", where "Decimal places" is selected as 3. Select "Image" - "Adjust" - "Threshold" in sequence, and set 0 and 100 in the "Threshold" box selection position in sequence, then the pore data in this cross-section electron microscope image can be exported using the Analyze - Measure function. Use "Image" - "Overlay" - "Flatten" to export to obtain the pore picture; click "Apply" in "Threshold", then click "Analyze" - "Analyze Particles", and check the left four columns to obtain the pore statistical data.

[0163] It can be understood that in the embodiments of the present application, the "pores" in the cross-section of the positive electrode film layer are identified through the color difference of the picture and the threshold. This "pore" is not the pore data obtained from the exhaust test, and is mainly used to characterize the gap between particles in the cross-section of the positive electrode film layer. This method is superior to the exhaust method because the porosity obtained by the exhaust method is related to the pores between particles and the holes in the carbon coating material on the particle surface, and cannot objectively reflect the pores between particles.

[0164] In some embodiments, the porosity of the positive electrode film layer can be selected as 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or the numerical range between any two of them.

[0165] When the porosity of the positive electrode film layer is within the above range, the positive electrode film layer has good electrolyte wettability and tortuosity, which is helpful for the diffusion of lithium ions in the liquid and solid phases, helps to reduce the concentration polarization of the thick electrode, and improves the kinetic performance of the battery. At the same time, it helps to alleviate the volume expansion of the thick-coated electrode during cycling, reduces the mechanical stress of the film layer and the stress concentration phenomenon, thereby reducing the risk of film layer peeling of the thick-coated electrode.

[0166] Especially in thick-coated soft-pack batteries, the gap between the housing and the electrode is small, the volume occupancy rate of the film layer is large, the volume of the electrolyte accommodation is reduced, and when the porosity of the positive electrode film layer is within the above range, it helps to improve the liquid retention rate of the battery core and improve the kinetic performance of the battery.

[0167] In some embodiments, the resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

[0168] In some embodiments, the resistivity of the positive electrode film layer is 10 Ω·cm, 12 Ω·cm, 14 Ω·cm, 16 Ω·cm, 18 Ω·cm, 20 Ω·cm, 22 Ω·cm, 22 Ω·cm, 24 Ω·cm, 26 Ω·cm, 28 Ω·cm, 30 Ω·cm, 32 Ω·cm, 35 Ω·cm or the numerical range between any two of them.

[0169] When the resistivity of the positive electrode film layer is within the above range, it is beneficial to reduce the electron transfer impedance, reduce the charge and discharge polarization, and improve the rate performance and cycle performance of the battery.

[0170] In some embodiments, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber (HNBR).

[0171] HNBR is obtained by hydrogenating the double bonds of nitrile rubber. Its highly saturated main chain structure endows it with excellent oil resistance, heat resistance, and aging resistance, etc. This enables it to remain stable in different environments and systems when used as a dispersant, and is not prone to degradation or deterioration, thus effectively playing the dispersing role. The HNBR molecular chain contains both polar nitrile groups and non-polar hydrocarbon segments. The polar nitrile groups can interact with some polar substances or the surfaces of particles, such as adsorbing on the surfaces of the dispersed particles through hydrogen bonds, electrostatic interactions, etc.; the non-polar hydrocarbon segments have good lipophilicity and can be well extended and dispersed in non-polar or weakly polar media, enabling the particles to be evenly dispersed in the medium.

[0172] When HNBR adsorbs on the surface of the particles in the slurry, its long-chain molecules will form a physical barrier around the particles, preventing the particles from approaching and aggregating with each other, and keeping the particles in a relatively independent dispersed state in the system. At the same time, HNBR can reduce the surface tension between the dispersion medium and the dispersed particles, making the particles easier to be wetted by the medium, thereby promoting the dispersion of the particles in the medium. Meanwhile, it can also reduce the interfacial energy between the particles, reducing the aggregation phenomenon of the particles driven by the interfacial energy. Further, when the slurry dries into a film, the elastic network structure of HNBR can buffer the shrinkage stress generated by the volatilization of the solvent, reduce the re-aggregation of the conductive agent due to capillary force during this process, reduce the area ratio of the agglomerated region of the conductive agent, and improve the kinetic performance and cycle life of the battery.

[0173] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0174] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the dispersant can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2% or any numerical range between any two of them.

[0175] When the mass content of the dispersant is within the above range, it can achieve uniform dispersion of the particles in the positive electrode film layer while maintaining a high loading amount of the positive electrode film layer, reduce the stress concentration of the thick-coated lithium-containing transition metal phosphate positive electrode film layer, and effectively alleviate the problem of battery capacity drop.

[0176] In some embodiments, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomerated region of the conductive agent is 0.5% - 2.5%.

[0177] In this application, based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent can be measured by the following method. Observe the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet through a scanning electron microscope using a similar method as described above, and measure the area of the agglomeration region of the conductive agent in the scanning electron microscope image at a magnification of 3k times. Since the conductive agent is generally a carbon-based material, such as conductive carbon black, carbon nanotubes, etc., at a high magnification of the scanning electron microscope, the aggregated conductive agent can be seen, and the agglomeration region of the conductive agent often appears as a black agglomeration compared to other regions in the positive electrode film layer. With the aid of image analysis software, the agglomeration region of the conductive agent refers to the region in the scanning electron microscope image where the conductive agent is significantly aggregated and appears black. Specifically, import the scanning electron microscope image at a magnification of 3k times into ImageJ, screen out the black agglomeration regions of the conductive agent with a Feret greater than or equal to 2 μm, and record the sum of the areas of the screened regions as the area of the agglomeration region of the conductive agent. The area ratio of the agglomeration region of the conductive agent is the ratio of the area of the agglomeration region of the conductive agent to the total area of the imported scanning electron microscope image. Randomly select 3 non-overlapping scanning electron microscope images, and calculate the average value of the area ratio of the agglomeration region of the conductive agent as the "area ratio of the agglomeration region of the conductive agent based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet".

[0178] In some embodiments, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent can be selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or any value range between any two of them.

[0179] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, when the area ratio of the agglomeration region of the conductive agent is within the above range, it indicates that the conductive agent in the positive electrode film layer is evenly dispersed, which is conducive to forming a uniform conductive network. In particular, it is beneficial to reduce the problem of kinetic decline caused by the increase in the ion transport path in the thick coating film layer, reduce the local polarization and even lithium deposition problems generated during the battery cycle, and improve the cycle life of the battery.

[0180] At the same time, research shows that large-sized first particles in the lithium-containing transition metal phosphate particles are prone to rebound. When the agglomeration area of the conductive agent is within the above range, the uniform distribution of the conductive agent can inhibit the rebound of the lithium-containing transition metal phosphate particles, form a mechanical restraint on the particles and even the film layer, improve the cohesive force of the film layer, reduce the powder falling and peeling phenomena of the film layer, and improve the cycle life of the battery.

[0181] In some embodiments, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is 1.5% - 2.5%.

[0182] In the embodiments of the present application, the area ratio of the agglomeration region of the conductive agent is further within the above range, indicating that the conductive agent is more uniformly distributed in the positive electrode film layer, and the content of the conductive agent is relatively low. While improving the kinetic performance of the positive electrode film layer, it helps to reduce the occupation of the space of the positive electrode active material by excessive conductive agent, thereby further improving the volume energy density of the battery while improving the battery kinetic performance.

[0183] In some embodiments, the conductive agent includes carbon nanotubes, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0184] In the present application, the term "carbon nanotubes" refers to nanomaterials formed by curling graphene sheets bonded by carbon atoms with sp 2 hybrid bonds, which have several to dozens of coaxial hollow circular tubes. The diameter is usually in the range of several to dozens of nanometers, and the length can vary from microns to centimeters, showing a high aspect ratio. According to the number of graphene sheets, it can be divided into: single-walled carbon nanotubes (Single-walled Carbon nanotubes, SWCNTs), few-walled carbon nanotubes (Few-walled Carbon Nanotubes, FWCNTs), and multi-walled carbon nanotubes (Multi-walled Carbon nanotubes, MWCNTs). Carbon nanotubes have excellent electrical conductivity and high elastic modulus.

[0185] Due to the one-dimensional structure of carbon nanotubes, they can form a network structure in the positive electrode film layer. On the one hand, the high elastic modulus of carbon nanotubes makes its network structure not only able to serve as a bridge for stress propagation, but also has a binding effect on the thick-coated positive electrode film layer, inhibiting the rebound of lithium-containing transition metal phosphate particles, effectively alleviating stress concentration and reducing the risk of film layer peeling, thereby improving the problem of battery capacity drop; on the other hand, the excellent electrical conductivity of carbon nanotubes makes its network structure an efficient electron transport channel. Even if there is local film layer peeling, the thick electrode sheet can still maintain high electron transport efficiency in the in-plane direction and the thickness direction, thus delaying the occurrence of the capacity drop problem and further improving the kinetic performance and cycle life of the battery.

[0186] In some embodiments, the conductive agent further includes conductive carbon black.

[0187] Conductive carbon black has a relatively high specific surface area and thus has good liquid retention ability. The thick electrode has a large swelling force during cycling, making it easy for the electrolyte to be extruded. The distribution of conductive carbon black in the positive electrode film layer is beneficial to improving the liquid retention ability of the thick electrode, further alleviating the phenomenon of capacity drop during battery cycling, and improving the cycle life of the battery.

[0188] In some embodiments, the agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0189] Researchers found that due to its high surface energy, carbon nanotubes are prone to agglomeration, resulting in uneven dispersion in the positive electrode film layer and unable to form an effective carbon nanotube network structure. The surface energies of conductive carbon black and carbon nanotubes are relatively close, and it can adsorb on the surface of carbon nanotubes to form a physical barrier, increasing the resistance to carbon nanotube agglomeration, reducing the direct contact between carbon nanotubes, and thus inhibiting the agglomeration phenomenon. This improves the uniformity of the distribution of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the thick-coated positive electrode film layer and the kinetic performance of the battery; on the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reducing the risk of peeling of the thick-coated positive electrode film layer and further improving the kinetic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the agglomeration region of the conductive agent will also cause local blockage of the ion transport path in the agglomeration region of the conductive agent. The combination of conductive carbon black can improve the lithium ion transport ability in this region, reduce local polarization, and further improve the cycle stability of the battery. In some embodiments, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

[0190] In some embodiments, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes can be selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or any numerical range between any two of them.

[0191] In some embodiments, based on the mass of the positive electrode film layer, the mass content C2 of conductive carbon black can be selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or any numerical range between any two of them.

[0192] When the mass contents of the carbon nanotubes and the conductive carbon black are within the above ranges, the agglomeration phenomenon of the carbon nanotubes can be effectively alleviated, and a good conductive network structure can be formed, thereby effectively reducing the stress concentration in the positive electrode film layer, improving the liquid retention rate of the positive electrode sheet during long-term cycling, further reducing the risk of film layer shedding and the degree of polarization of the electrode sheet, improving the kinetic performance of the battery, taking into account the problem of capacity drop, and improving the cycle life of the battery.

[0193] In some embodiments, the battery cell further includes a separator 20 disposed between the positive electrode sheet and the negative electrode sheet. The separator 20 includes a base film 201, a ceramic layer 202 disposed on at least one side of the base film 201, and an adhesive layer 203 disposed on the side of the ceramic layer 202 away from the base film 201. The adhesive layer 203 is a continuous layer with a porous structure, and the adhesive layer 203 includes a polyvinylidene fluoride-based polymer.

[0194] In some embodiments, the battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, a ceramic layer disposed on both sides of the base film, and an adhesive layer disposed on the side of at least one ceramic layer away from the base film.

[0195] The ceramic layer disposed on both sides of the base film is beneficial to improving the stiffness of the soft-pack battery and reducing local stress concentration.

[0196] In some embodiments, the battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, a ceramic layer disposed on both sides of the base film, and an adhesive layer disposed on the sides of the ceramic layers away from the base film.

[0197] In some embodiments, the polyvinylidene fluoride-based polymer includes one or more of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0198] In some embodiments, the polyvinylidene fluoride-based polymer includes polyvinylidene fluoride (PVDF).

[0199] In the prior art, the adhesive layer of the separator usually uses aqueous PVDF, which presents an island structure in the separator, as Figure 2 shown. On the one hand, this is beneficial to providing a gap for the expansion of the battery cell, and on the other hand, it is convenient for manufacturing; however, the contact area between such a separator adhesive layer and the electrode sheet is small, and the adhesive force is weak.

[0200] The separator provided in the embodiment of the present application uses a continuous layer with a porous structure as the adhesive layer, as Figure 1 and Figure 3 shown. Compared with the adhesive layer in the prior art, its bonding area with the electrode sheet is larger, so that the bonding between the separator and the electrode sheet is more firm and uniform; further, when the positive electrode film layer rebounds, it is beneficial to maintain the interfacial contact between the separator and the positive electrode film layer, and reduce the occurrence probability of film layer shedding.

[0201] It can be understood that during the manufacturing of the electrode sheet or the cycling process, the continuous adhesive layer may break and deform into a blocky structure due to contact or extrusion stress with the positive electrode sheet or the negative electrode sheet. The continuous structure referred to in this application means that at the microscopic level, such as observed under a scanning electron microscope or an optical microscope, the adhesive layer of the separator is continuous. In order to reflect the true morphology of the separator, during the sampling process, it is preferably sampled in the area where the adhesive layer of the separator in the battery does not adhere to the positive electrode sheet or the negative electrode sheet. As an example, sampling is performed at the position of the separator beyond the positive electrode sheet and the negative electrode sheet; or sampling is performed on the separator near the surface of the electrode assembly. The adhesion between this separator sampling area and the positive electrode sheet or the negative electrode sheet is less, and it can better reflect the true state of the separator.

[0202] Compared with wound battery cells, the extrusion between the separator and the electrode sheet in laminated battery cells is smaller, and relative displacement is likely to occur between the separator and the electrode sheet, thus disturbing the film layer, and the film layer is prone to powder falling or peeling off; in addition, it may also cause the positive and negative electrodes to overlap with each other, increasing the risk of internal short circuit in the battery cell. Therefore, the separator provided in the embodiments of this application is particularly suitable for laminated battery cells. The increased adhesion between the porous adhesive layer and the electrode sheet helps to improve the adhesion between the separator and the electrode sheet and reduce the relative displacement between the separator and the electrode sheet, which not only helps to reduce the disturbance to the positive electrode film layer and reduce the probability of film layer peeling off, but also helps to reduce the risk of short circuit caused by the overlap of the positive and negative electrodes.

[0203] In summary, when the polyvinylidene fluoride-based polymer in the adhesive layer of the embodiments of this application is selected from the above materials, it helps to form a continuous and uniform porous adhesive layer. First, the adhesion between this adhesive layer and the electrode sheet is improved and evenly distributed, which helps to reduce the stress concentration phenomenon in the thick-coated lithium-containing transition metal phosphate positive electrode film layer and reduce the risk of film layer peeling off, thereby helping to further improve the cycle life of the battery; second, the adhesive layer stably adheres to the positive electrode sheet or the negative electrode sheet, which helps to reduce the direct contact between the positive electrode sheet and the negative electrode sheet caused by the relative displacement between the electrode sheet and the separator and reduce the risk of internal short circuit, helping to improve the battery safety performance; second, the porous adhesive layer helps to maintain the porosity of the separator and reserve space for the expansion of the battery cell, further improving the cycle life of the battery.

[0204] In some embodiments, the material of the base film may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene (PE), and polypropylene (PP).

[0205] In some embodiments, the ceramic layer includes one or more of aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), silicon oxide (SiO2), and boron nitride (BN).

[0206] The ceramic particles have flame retardancy and a relatively high hardness value, and are not easily deformed by heat, so they have excellent dimensional stability. The low thermal conductivity of the ceramic material can further prevent the expansion of some thermal runaway points in the battery to form an overall thermal runaway, thereby improving the safety performance of the battery cell.

[0207] In some embodiments, the thickness of the base film in the separator is 7 - 9 μm.

[0208] In some embodiments, the thickness of the base film in the separator can be selected from 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or the numerical range between any two of them.

[0209] In some embodiments, the thickness of one side of the ceramic layer in the separator is 2 - 4 μm.

[0210] In some embodiments, the thickness of one side of the ceramic layer in the separator can be selected from 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or the numerical range between any two of them.

[0211] In some embodiments, the thickness of one side of the adhesive layer in the separator is 1 - 5 μm.

[0212] In some embodiments, the thickness of one side of the adhesive layer in the separator can be selected from 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the numerical range between any two of them.

[0213] In this application, "thickness" has the meaning well-known in the art and can be measured using methods and instruments known in the art. As an example, a high-precision micrometer (such as Mitutoyo 293 - 100 type with an accuracy of 0.1 μm) can be used for testing.

[0214] If the thickness of the adhesive layer is too low, the void space in the separator is small and the adhesive force between the separator and the electrode is low. On the one hand, the stress increases after the film layer expands and the probability of the film layer peeling off increases, affecting the cycle life of the battery; on the other hand, the probability of positive-negative lap short circuit increases, thus affecting the safety performance of the battery. If the thickness of the adhesive layer is too large, it occupies a large space in the battery, thus affecting the volume energy density of the battery. In the embodiments of this application, the thickness of the adhesive layer within the above range helps to balance the cycle life, safety performance and volume energy density of the battery.

[0215] In some embodiments, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector. The bottom coating includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes polyvinylidene fluoride (PVDF).

[0216] In some embodiments, the thickness of the bottom coating is 0.5 μm - 5 μm.

[0217] In some embodiments, the thickness of the bottom coating can be selected as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a numerical range between any two of them.

[0218] The bottom coating provided in the embodiments of the present application helps to improve the adhesion between the positive electrode film layer and the positive electrode current collector and relieve the stress concentration phenomenon at large particles, thereby reducing the probability of the positive electrode film layer falling off and improving the cycle stability of the battery. At the same time, compared with the direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the bottom coating and the positive electrode film layer increases, which helps to increase the area of electron transfer between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode and improving the kinetic performance of the battery.

[0219] In some embodiments, as Figure 4 shown, the battery cell 5 includes a housing 50, the laminated battery core is accommodated in the housing 50, the size of the housing 50 in the length direction X is L0, the size of the housing 50 in the width direction Y is W0, and the size of the housing 50 in the thickness direction Z is H0, wherein, 480 mm ≤ L0 ≤ 720 mm, 100 mm ≤ W0 ≤ 150 mm; 14 mm ≤ H0 ≤ 22 mm.

[0220] In some embodiments, L0 can be selected as 480 mm, 490 mm, 500 mm, 510 mm, 520 mm, 530 mm, 540 mm, 550 mm, 560 mm, 570 mm, 580 mm, 590 mm, 600 mm, 610 mm, 620 mm, 630 mm, 640 mm, 650 mm, 660 mm, 670 mm, 680 mm, 690 mm, 700 mm, 710 mm, 720 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, 1000 mm, 1050 mm, 1100 mm, 1150 mm, 1200 mm, 1250 mm, 1300 mm, or a numerical range between any two of them.

[0221] In some embodiments, W0 can be selected as 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or a numerical range between any two of them.

[0222] In some embodiments, H0 can be selected as 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, or a numerical range between any two of them.

[0223] In some embodiments, the size of the housing in the length direction is L0, and 450 mm ≤ L0 ≤ 650 mm.

[0224] When the dimension L0 of the housing in the length direction satisfies 450 mm ≤ L0 ≤ 650 mm, the length of the battery cell is shorter, which helps to shorten the diffusion path of the current, reduce the internal resistance of the electrode sheet, thereby reducing the heat generation of the battery and improving its kinetic performance; in addition, the shorter housing length helps to shorten the diffusion path of the electrolyte during the infiltration process, improve the infiltration rate and uniformity of the electrolyte, further promote the uniformity of lithium ion deintercalation during the cycling process, relieve the stress concentration phenomenon, reduce the risk of film layer shedding, and improve the cycling stability of the battery cell.

[0225] In some embodiments, the dimension of the housing in the length direction is L0, and 900 mm ≤ L0 ≤ 1300 mm.

[0226] When the dimension L0 of the housing in the length direction satisfies 900 mm ≤ L0 ≤ 1300 mm, the size of the battery cell is longer, which helps to reduce the volume ratio of the housing in the battery cell and increase the load ratio of the active material. At the same time, the longer battery cell can reduce the number of battery cells required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of the structural parts in the module, thereby improving the space utilization rate of the battery pack, and further helping to improve the volumetric energy density of the battery cell.

[0227] In some embodiments, as Figure 4 shown, the material of the housing 50 is a soft-pack material, and the soft-pack material includes an aluminum-plastic composite film. Optionally, it includes a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) and aluminum.

[0228] The applicant found that the soft-pack material is lighter in mass than hard-shell materials such as aluminum shells and steel shells, which is beneficial to further improve the energy density of the lithium-containing transition metal phosphate battery. In addition, the soft-pack material has a high elongation rate, so its housing is thinner, lighter, and more flexible, which helps to improve the space utilization rate of the battery cell, thereby increasing the energy density of the battery cell. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery interior, reduce the decomposition of the electrolyte and the oxidation degree of the electrode material, thereby extending the battery life. In some embodiments, continuing to refer to Figure 4 , the housing 50 includes a first sealing area 51, and the first sealing area 51 is disposed at at least one end of the stacked electrode assembly extending in the width direction; the first sealing area 51 includes a folded edge structure extending in the length direction, and a packaging adhesive is disposed on the folded edge structure, and the packaging adhesive is continuously disposed along the length direction and fixes the folded edge structure.

[0229] The hemming structure refers to a reinforcing structure formed by folding the encapsulation area, and the number of folds is not limited. As an example, it can be a single-fold hemming structure with one fold, or a double-fold hemming structure with two folds on both sides.

[0230] During the cycling of the electrode sheet, the SEI film on the positive electrode film layer will thicken. Therefore, large rebounds and gas generation will occur during long-term cycling. The sealing area of the soft-pack battery cell is used to seal the electrode assembly, but the strength of the sealing area is limited and it is easy to be opened by the large rebounds and high gas generation in the film layer.

[0231] In the embodiment of the present application, the first sealing area includes a hemming structure extending along the length direction, which further improves the sealing strength of the first sealing area. The encapsulating adhesive is continuously arranged along the length direction and fixes the hemming structure, which can further improve the encapsulation strength compared with the discontinuous arrangement of the encapsulating adhesive along the length direction, realize continuous reinforcement in the length direction of the sealing area, and reduce the probability of the thick-coated electrode sheet breaking through the sealing area in the packaging during cycling.

[0232] In some embodiments, the housing 50 includes at least one second sealing area 52, and the second sealing area 52 is arranged at at least one end of the stacked battery cell along the length direction of the housing, and the second sealing area 52 is arranged on the tab side of the stacked battery cell.

[0233] It can be understood that the positive electrode tab and the negative electrode tab can be arranged on the same side of the stacked battery cell, as Figure 1 shown; or they can be arranged on different sides of the stacked battery cell.

[0234] In some embodiments, the battery cell 5 further includes a lead-out member 53, and the lead-out member 53 is connected to the tab of the battery cell. For example, the lead-out member 53 can be welded to the tab. The lead-out member 53 is a conductive member, and at least a part of the lead-out member 53 is located outside the housing 50. The lead-out member 53 serves as the electrode lead-out end of the battery cell 5, and the lead-out member 53 is used to facilitate the electrical connection of the battery cell 5 to other battery cells 5 or other components. For example, the lead-out member 53 can be in the shape of a sheet.

[0235] Correspondingly, the lead-out member 53 also includes a positive electrode lead-out member and a negative electrode lead-out member. The positive electrode lead-out member is connected to the positive electrode tab, and the negative electrode lead-out member is connected to the negative electrode tab.

[0236] In some embodiments, the second sealing area is arranged on the tab side. The tab needs to be connected to the lead-out member, and the connection strength between the lead-out member and the housing material is relatively weak, so that gas is easy to rush out from the second sealing area, which is beneficial to realizing the directional pressure relief of the battery, reducing the impact on adjacent battery cells during thermal runaway, and improving the overall service life of the battery.

[0237] In some embodiments, a plurality of rubber rings surrounding along the width direction are arranged on the outer periphery of the stacked battery cell, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

[0238] The spaced arrangement in the length direction of the rubber rings surrounding the battery cell in the width direction of the battery cell is beneficial to fixing the positions between the electrode plates in the battery cell, reducing the probability of displacement of the battery cell during battery shaking, and is particularly suitable for batteries with a relatively large length, and can effectively reduce the mutual displacement in the length direction between the electrode plates, thereby causing lithium plating phenomenon, and is beneficial to maintaining the stability of the internal space structure of the battery, so as not to affect the normal operation of the battery.

[0239] In some embodiments, at 25 °C, the capacity of the battery cell is 95 Ah - 300 Ah.

[0240] In some embodiments, at 25 °C, the capacity of the battery cell is 150 Ah - 180 Ah.

[0241] In the present application, the capacity of the battery cell has the meaning well-known in the art, and can be tested by methods known in the art. As an example, at 25 °C, the battery is charged at a charging rate of 0.5C of the nominal capacity of the battery to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, left standing for 10 min, and then discharged at a discharge rate of 1C to 2.5V, left standing for 10 min, and the capacity C during the discharge process is calculated by the formula C = I * t, with the unit of Ah.

[0242] In some embodiments, at 25 °C, the capacity of the battery cell can be selected from 95 Ah, 100 Ah, 105 Ah, 107 Ah, 110 Ah, 115 Ah, 120 Ah, 125 Ah, 130 Ah, 135 Ah, 140 Ah, 145 Ah, 150 Ah, 155 Ah, 160 Ah, 161 Ah, 162 Ah, 163 Ah, 164 Ah, 165 Ah, 170 Ah, 175 Ah, 180 Ah, 182 Ah, 185 Ah, 190 Ah, 200 Ah, 210 Ah, 220 Ah, 230 Ah, 240 Ah, 250 Ah, 270 Ah, 280 Ah, 290 Ah, 300 Ah or the numerical range between any two of them.

[0243] In some embodiments, the positive current collector can be made of a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0244] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0245] In some embodiments, the negative electrode film layer includes a negative electrode active material. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0246] In some embodiments, the negative electrode film layer may also 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).

[0247] In some embodiments, the negative electrode film layer may also optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0248] In some embodiments, the negative electrode plate may be prepared by the following method: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0249] The second aspect of the present application provides a battery device, including the battery monomer provided in the first aspect of the present application.

[0250] The battery device disclosed in the embodiments of the present application can be used in electrical equipment using the battery device as a power source or various energy storage systems using the battery device as an energy storage element. In addition to being used in vehicles, the battery device can also be used in, but not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, and so on. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0251] In a third aspect of the present application, there is provided an electrical device using a battery device as a power source. The electrical device includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as the power source of the electrical device or as the energy storage unit of the electrical device. As the electrical device, the battery cells, battery modules, or battery packs can be selected according to its usage requirements.

[0252] Figure 5 is an electrical device as an example. The electrical device disclosed in the embodiments of the present application can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A battery device is provided inside the vehicle, and the battery device can be provided at the bottom, head, or tail of the vehicle. The battery device can be used for power supply of the vehicle. For example, the battery device can be used as the operating power source of the vehicle. The vehicle can also include a controller and a motor. The controller is used to control the battery device to supply power to the motor. For example, it is used for the working power requirements during the start, navigation, and driving of the vehicle. In some embodiments of the present application, the battery device can not only be used as the operating power source of the vehicle, but also as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0253] In a fourth aspect of the present application, there is provided an energy storage device using a battery device as a power source. The energy storage device can be, but not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0254] Embodiment Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specification are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial procurement.

[0255] Embodiment 1 (1) Preparation of the positive electrode active material Lithium dihydrogen phosphate, iron oxalate, carbon source, titanium dioxide, and vanadium pentoxide are mixed evenly and ground in methanol to obtain a mixed raw material. Among them, the ratio of lithium dihydrogen phosphate to iron oxalate is such that the molar ratio of lithium to iron is 1.025:1.0; the carbon source includes polyethylene glycol with a weight average molecular weight of 500, polyethylene glycol with a weight average molecular weight of 2000, and polyethylene glycol with a weight average molecular weight of 4000 in a mass ratio of 2:6:2; the particle size D 10 is 6.5 μm, the particle size D 50 is 62 μm, the particle size D 90 is 108 μm, and the mass content of Fe element in iron oxalate is 30.5%, and the mass content of trivalent iron element is 0.03%.

[0256] The mixed raw material is ball-milled multiple times in a ball mill and demagnetized to obtain a mixed slurry. The number of grinding times and time are controlled, and the particle size Dv of the ground mixed slurry 50 is 3.15 μm.

[0257] The mixed slurry is spray-dried to obtain a dry precursor powder material, and the appearance of the dry precursor powder material is light yellow and the color is uniform.

[0258] The precursor powder is placed in a sintering furnace, heated from 25°C to 360°C at a rate of 2°C / min in a nitrogen atmosphere and held at this temperature for 3.5 h, then heated to a second temperature of 785°C at a rate of 5°C / min and held at this temperature for 10 h, and then cooled after completion. Among them, based on the total mass of the positive electrode active material, the mass content of Ti element is 1050 ppm, and the mass content of V element is 950 ppm.

[0259] The obtained material is crushed by the method of air flow crushing at a classification frequency of 21 Hz and a wind volume with a crushing air pressure of 0.54 MPa to obtain a carbon-coated lithium iron phosphate positive electrode active material.

[0260] The above D10, D50, D90, Dv50 refer to the data obtained by testing through the Malvern laser scattering method.

[0261] (2) Preparation of the positive electrode sheet The above positive electrode active material, conductive agent, and binder polyvinylidene fluoride are mixed in a mass ratio of 94.1:1.9:3 in the solvent N-methylpyrrolidone, and then a dispersant HNBR with a mass ratio of 1% is added, and they are fully mixed in a stirring tank, stirred, and dispersed to form a positive electrode slurry; after the stirring process is completed, the positive electrode slurry is transported to the coating process; the conductive agent includes conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 0.9:1, the specific surface area of the conductive carbon black is 80 m 2 / g, the oil absorption value is 180 mL / 100 g, the average length of the carbon nanotubes is 20 μm, and the specific surface area is 280 m2 / g; The positive electrode slurry is applied to an aluminum foil by extrusion coating and dried, and then cold-pressed to obtain a positive electrode film layer with a single-sided thickness H of 105.64 μm and a compaction density of 2.36 g / cm 3 for the positive electrode plate. Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell.

[0262] The positive electrode plate is slit and punched into a specified shape, and the punched positive electrode plates are classified by weight through a weighing sorter for stacking by a stacker.

[0263] Among them, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, in the cumulative area distribution curve of the sphericity of the particles with a particle size R1 satisfying R1≥1000 nm, the median L of the sphericity R1A50 is 0.72; the median C of the graphitization degree of the positive electrode film layer 50 is 1.12; the concentration degree (C 90 -C 10 ) / C 50 is 0.025; based on the total area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the particles with a particle size R1 satisfying R1≥1000 nm is 35.28%; the median B of the coating value B of the positive electrode film layer 50 is 0.441; the iron dissolution rate of the positive electrode material is 976 ppm; based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the agglomeration region of the conductive agent is 1.91%; the porosity of the positive electrode film layer is 15.06%; the sheet resistivity of the positive electrode film layer is 31.0 Ω·cm.

[0264] (2) Preparation of the negative electrode plate A mixture of artificial graphite and natural graphite (weight ratio 1:1), conductive agent conductive carbon black, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC) are mixed evenly according to a weight percentage of 96:0.5:2.0:1.5 and deionized water is added. After stirring and dispersing, a negative electrode slurry is obtained. The negative electrode slurry is coated on a substrate copper foil, and after drying, cold pressing, slitting and sheet making, a negative electrode plate is obtained.

[0265] The negative electrode plate is slit and punched into a specified shape, and the punched negative electrode plates are classified by weight through a weighing sorter for stacking by a stacker.

[0266] (3) Separator Polyvinylidene fluoride (PVDF) was dissolved in N-methylpyrrolidone (NMP). After stirring evenly, polyethylene glycol (PEG) was added as a pore-forming agent and stirred thoroughly to obtain a binder layer solution. The binder layer solution was coated on the base film with ceramic layers on both sides. After pre-volatilization at 80 °C and drying at 110 °C, it was immersed in deionized water to dissolve PEG, obtaining a separator with a porous binder layer.

[0267] Among them, the thickness of the base film was 8 μm, the thickness of the single-sided ceramic layer was 3 μm, and the thickness of the single-sided binder layer was 1 μm.

[0268] (4) Electrolyte In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were mixed evenly.

[0269] Then lithium hexafluorophosphate was added and dissolved in the organic solvent to make the concentration of lithium hexafluorophosphate 1.05 mol / L, and vinylene carbonate (VC) was added and stirred evenly to obtain the electrolyte of Example 1.

[0270] Among them, based on the total mass of the electrolyte, the mass content of dimethyl carbonate was 26%, the mass content of ethyl methyl carbonate was 43.3%, the mass content of ethylene carbonate was 17.3%, and the mass content of vinylene carbonate was 0.9%.

[0271] (5) Preparation of the battery: The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence using a stacking machine. The separator should be able to isolate the positive and negative electrodes to obtain a stacked cell core. The stacked cell core was subjected to gluing treatment to tightly wrap the cell core. The glued stacked cell core was placed in an outer package, and the outer package was a soft package material aluminum-plastic film, which was composed of an inner layer of polypropylene, a middle layer of aluminum foil, and an outer layer of nylon composite. Among them, the aluminum-plastic film outer package was formed and trimmed by a punching and forming machine to obtain the target shape and size. Then the aluminum-plastic film was heat-sealed to meet the requirement that the sealing tensile strength of the aluminum-plastic film ≥ 25 N / 8 mm. The battery was subjected to vacuum baking, standing, injecting electrolyte, and packaging, and then hot pressing and cold pressing operations were performed on the soft package battery. The temperature of hot pressing was 45 °C, the time was 2 minutes, and the pressure was 90 kg / cm 2 , and the temperature of cold pressing was 25 °C, the time was 2 minutes, and the pressure was 90 kg / cm 2 . Finally, after processes such as formation, vacuum exhaust, and trimming, a battery cell was obtained. The size of the battery cell in the length direction was 600 mm, the size in the width direction was 125 mm, and the size in the thickness direction was 20 mm.

[0272] The preparation methods of Examples 2-10 are basically the same as that of Example 1, except that the preparation method of the positive electrode active material is adjusted as follows: Example 2 The preparation method of Example 2 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the second temperature is adjusted to 765 °C.

[0273] Example 3 The preparation method of Example 3 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the second temperature is adjusted to 735 °C.

[0274] Example 4 The preparation method of Example 4 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a weight average molecular weight of 500 and polyethylene glycol with a weight average molecular weight of 2000 at a mass ratio of 2:8.

[0275] Example 5 The preparation method of Example 5 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a weight average molecular weight of 500.

[0276] Example 6 The preparation method of Example 6 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a weight average molecular weight of 2000.

[0277] Example 7 The preparation method of Example 7 is basically the same as that of Example 3, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a weight average molecular weight of 500 and glucose at a mass ratio of 2:8.

[0278] Example 8 The preparation method of Example 8 is basically the same as that of Example 1, except that during the preparation of the positive electrode plate, the coating weight is adjusted, and parameters such as the hot roll pressing pressure, hot roll temperature, transfer coating speed, and heating temperature before the first entry into the hot roll compaction are adaptively adjusted to adjust the compaction density of the positive electrode plate.

[0279] Example 9 The preparation method of Example 9 is basically the same as that of Example 1, except that during the preparation of the positive electrode plate, the coating weight is adjusted so that the single-sided thickness H of the positive electrode film layer obtained by cold pressing is 119.12 μm; and the thickness of the battery is appropriately adjusted while keeping the number of positive electrode plates, separators, and negative electrode plates unchanged.

[0280] Example 10 The preparation method of Example 10 is basically the same as that of Example 1, except that when preparing the positive electrode sheet, the coating weight is adjusted so that the thickness H of the positive electrode film layer obtained by cold pressing on one side is 71.53 μm; and the thickness of the battery is appropriately adjusted while keeping the number of positive electrode sheets, separators and negative electrode sheets unchanged.

[0281] Comparative Example 1 The preparation method of Comparative Example 1 is basically the same as that of Example 7, except that in the preparation of the positive electrode active material, the carbon source is replaced with glucose.

[0282] Test method: 1. Capacity of the lithium-ion secondary battery monomer At 25 °C, charge at a charging rate of 0.5C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 1C to 2.5V, let it stand for 10 minutes, and calculate the capacity C during the discharge process through the formula C = I * t, and the unit is Ah.

[0283] 2. Number of cycles corresponding to the capacity decay to 80% At 25 °C, charge at a charging rate of 0.5C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 1C to 2.5V, let it stand for 10 minutes. The above one charge and discharge is one cycle, and the test is stopped until the battery capacity decays to 80% of the nominal capacity, which is recorded as the number of cycles @80% SOH.

[0284] Test results The test results of the above examples and comparative examples are shown in Table 1.

[0285] Table 1 Preparation parameters of each example and comparative example

[0286] It can be seen from the comparison between Examples 1-10 and Comparative Example 1 that the battery monomer includes a stacked cell, the stacked cell includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, the positive electrode film layer includes lithium-containing transition metal phosphate particles with carbon materials provided on at least part of the surface, and in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 is 0.95 - 1.20, where the graphitization degree C value is I G / I D , I G represents the intensity of the G peak in the Raman spectrum at 1580 ± 100 cm -1 , I DIndicates the intensity of the D peak at 1350±100 cm in the Raman spectrum. When the battery cell is in a fully discharged state, the compaction density of the positive electrode sheet is 2.3 g / cm -1 -2.6 g / cm 3 . While maintaining a good capacity, the battery cell helps to improve the cycle life during long-term cycling of the battery. 3 .

[0287] As can be seen from the comparison between Example 1, Examples 4-6 and Example 7, in the cumulative distribution curve of the graphitization degree C value obtained by the laser confocal Raman spectrometer in the surface scanning mode of the positive electrode film layer, the median C of the graphitization degree 50 is further preferably 1.01-1.13, which helps to further improve the cycle life during long-term cycling of the battery cell.

[0288] As can be seen from the comparison between Examples 1-10 and Comparative Example 1, in the cumulative distribution curve of the graphitization degree C value obtained by the laser confocal Raman spectrometer in the surface scanning mode of the positive electrode film layer, the concentration of the C value (C 90 -C 10 ) / C 50 is 0.01-0.05, which helps to further improve the cycle life during long-term cycling of the battery cell.

[0289] As can be seen from Examples 1-3, in the cross-section of the positive electrode film layer along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000 nm, L R1A50 is in the range of 0.67-0.75, and the battery cell has a good cycle life during long-term cycling.

[0290] As can be seen from Examples 1-9, the unilateral thickness H of the positive electrode film layer is in the range of 70 μm-120 μm. While maintaining a good capacity, the battery cell helps to improve the cycle life during long-term cycling of the battery.

[0291] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and achieving the same effects as the technical idea within the technical scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments and other embodiments constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that, It includes a laminated battery cell, and the laminated battery cell includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The positive electrode film layer includes lithium-containing transition metal phosphate particles with carbon materials provided on at least part of the surface. The single-side thickness of the positive electrode film layer is denoted as H, and H is 70 μm - 120 μm; In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 is 0.95 - 1.20, Among them, the graphitization degree C value is I G / I D , I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 100 cm -1 , I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 , When the battery cell is in a fully discharged state, the compaction density of the positive electrode plate is 2.3 g / cm 3 -2.6 g / cm 3 .

2. The battery cell according to claim 1, wherein In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 is 1.01 - 1.

13.

3. The battery cell according to claim 1, wherein, In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the concentration degree of the C value (C 90 -C 10 ) / C 50 is 0.01 - 0.

05.

4. The battery cell according to claim 3, characterized in that, In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the concentration degree of the C value (C 90 -C 10 ) / C 50 is 0.02 - 0.

04.

5. The battery cell according to claim 1, characterized in that, Based on the total area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the particles with a particle size R1 satisfying R1 ≥ 1000 nm is 12% - 50%.

6. The battery cell according to claim 5, wherein, Based on the total area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the particles with a particle size R1 satisfying R1 ≥ 1000 nm is 12% - 40%.

7. The battery cell according to claim 5, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm, the median L R1A1 50 is 0.6 - 0.

8.

8. The battery cell according to claim 7, wherein In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm, the median L R1A1 50 is 0.65 - 0.

75.

9. The battery cell according to claim 7, wherein In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size R1 satisfying R1≥1000nm, the median value L R1A1 50 is 0.67 - 0.

75.

10. The battery cell according to claim 1, characterized in that, In the cumulative distribution curve of the coating value B obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median B of the coating value B 50 is 0.30 - 0.60, where the coating value B is I P / I D , where I P represents the intensity of the P peak of the Raman spectrum at 948 ± 100 cm -1 , and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 .

11. The battery cell according to claim 1, wherein The lithium-containing transition metal phosphate particles include the components shown in the following general formula: Li m Fe x P y O j Q q Formula I Among them, Q includes one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4, 0 ≤ q ≤ 0.

1.

12. The battery cell according to claim 1, characterized in that, The positive electrode film layer includes a positive electrode material, and the iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm.

13. The battery cell according to claim 12, characterized in that, The iron dissolution rate of the positive electrode material is 658 ppm - 1485 ppm.

14. The battery cell according to claim 1, wherein Based on the total mass of the lithium-containing transition metal phosphate particles, the mass content of titanium element is 500 ppm - 8000 ppm.

15. The battery cell according to claim 14, characterized in that, Based on the total mass of the lithium-containing transition metal phosphate particles, the mass content of titanium element is 1000 ppm - 3000 ppm.

16. The battery cell according to claim 1, wherein Based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of vanadium element is 500 ppm - 5000 ppm.

17. The battery cell according to claim 16, characterized in that, Based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of vanadium element is 500 ppm - 3000 ppm.

18. The battery cell according to claim 1, characterized in that, The porosity of the positive electrode film layer is 14% - 28%.

19. The battery cell according to claim 1, wherein, The resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

20. The battery cell according to claim 1, characterized in that, The single-side thickness of the positive electrode film layer is denoted as H, and H is 90 μm - 120 μm.

21. The battery cell according to claim 1, characterized in that, The single-side thickness of the positive electrode film layer is denoted as H, and H is 100 μm - 120 μm.

22. The battery cell according to claim 1, wherein, The positive electrode film layer is provided with a bottom coating in the bottom area close to the positive current collector, and the bottom coating satisfies at least one of the following conditions: (1) The bottom coating includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes a polyvinylidene fluoride polymer; (2) The thickness of the bottom coating is 0.5 μm - 5 μm.

23. The battery cell according to claim 1, wherein, The positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber.

24. The battery cell according to claim 1, wherein, Based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

25. The battery cell according to claim 1, wherein The positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the agglomeration regions of the conductive agent is 0.5% - 2.5%.

26. The battery cell according to claim 25, wherein Based on the total area of the cross-section of the positive electrode film layer in the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is 1.5% - 2.5%.

27. The battery cell according to claim 25, characterized in that, The conductive agent includes carbon nanotubes, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

28. The battery cell according to claim 27, characterized in that, The conductive agent further includes conductive carbon black.

29. The battery cell according to claim 25, wherein The agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

30. The battery cell according to claim 18, wherein, Based on the mass of the positive electrode film layer, the mass content C1 of the carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of the conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

31. The battery cell according to claim 1, wherein The battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, ceramic layers disposed on both sides of the base film, and an adhesive layer disposed on the side away from the base film of at least one of the ceramic layers. The adhesive layer is a continuous layer with a porous structure, and the adhesive layer includes a vinylidene fluoride-based polymer.

32. The battery cell according to claim 31, wherein, The separator satisfies at least one of the following conditions: (1) The thickness of the base film is 7 - 9 μm; (2) The thickness of one side of the ceramic layer is 2 - 4 μm; (3) The thickness of one side of the adhesive layer is 1 - 5 μm.

33. The battery cell according to claim 1, characterized in that, The battery cell includes a housing, and at least one of the stacked sheet electrodes is accommodated in the housing. The dimension of the housing in the length direction is L0, the dimension of the housing in the width direction is W0, and the dimension of the housing in the thickness direction is H0, where 450 mm ≤ L0 ≤ 1300 mm, 100 mm ≤ W0 ≤ 150 mm; 14 mm ≤ H0 ≤ 22 mm.

34. The battery cell according to claim 33, wherein The dimension L0 of the housing in the length direction satisfies: 450 mm ≤ L0 ≤ 650 mm.

35. The battery cell according to claim 33, characterized in that, The dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

36. The battery cell according to claim 35, wherein (1) The material of the housing is a soft package material, and the soft package material includes an aluminum-plastic composite film; (2) The housing includes a first sealing area, and the first sealing area is disposed at at least one end of the stacked sheet electrode extending in the width direction; the first sealing area includes a folded edge structure extending in the length direction, and a packaging adhesive is disposed on the folded edge structure. The packaging adhesive is continuously disposed in the length direction and fixes the folded edge structure; (3) The housing includes at least one second sealing area, and the second sealing area is disposed along the length direction of the housing at at least one end of the stacked sheet electrode. The second sealing area is disposed on the tab side of the stacked sheet electrode.

37. The battery cell according to claim 36, wherein The soft package material includes one or more of aluminum, polypropylene, polybutylene terephthalate, polybutylene succinate, nylon, polyethylene terephthalate, and polyethylene.

38. The battery cell according to claim 1, characterized in that, A plurality of rubber rings surrounding in the width direction are disposed on the outer periphery of the stacked sheet electrode, and the rubber rings surrounding in the width direction are spaced apart in the length direction.

39. The battery cell according to claim 1, wherein At 25 °C, the capacity of the battery cell is 105 Ah - 190 Ah.

40. The battery cell according to claim 39, wherein, At 25 °C, the capacity of the battery cell is 150 Ah - 190 Ah.

41. A battery device, characterized in that, Comprising a battery cell as described in any one of claims 1 to 40.

42. An electrical device, characterized in that, The electrical device comprises a battery device as described in claim 41, the battery device being used for providing electric energy.

43. A energy storage device, characterized in that, The energy storage device comprises a battery device as described in claim 41, the battery device being used for storing electric energy.

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