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

Abstract

The invention discloses 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 pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, the positive pole film layer comprises lithium-containing transition metal phosphate particles, and at least part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material; in the tangent plane of the positive electrode film layer along the thickness direction of the pole piece, the area ratio of particles with the particle size greater than or equal to 1 mu m is 12%-50%; in the tangent plane of the positive electrode film layer in the thickness direction of the pole piece, the area proportion of particles with the particle size larger than 50 nm and smaller than or equal to 200 nm is 3.0%-15.0%; and when the single battery is in a full discharge state, the compaction density of the positive pole piece is 2.3 g / cm < 3 >-2.6 g / cm < 3 >.

Description

[0001] This application claims the priority of the international patent application PCT / CN2025 / 094369 titled "Battery Cell, Battery Device, Electrical Device, and Energy Storage Device" filed on May 12, 2025, and the entire content of this application is incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of 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, 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 dual increase in the market's demand for the cruising range and cycle life of electrical devices, higher requirements are also put forward for the energy density, cycle performance, etc. of battery cells. However, it is difficult to simultaneously improve the above performances in the prior art, which has become a technical problem that urgently needs 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 high capacity and good cycle performance.

[0006] In a first aspect of this application, a battery cell is provided, which includes a laminated electrode core. The laminated electrode core includes a positive electrode tab and a negative electrode tab. The positive electrode tab 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 single-side thickness of the positive electrode film layer is 70 μm - 120 μm; the positive electrode film layer includes lithium-containing transition metal phosphate particles, and at least part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material; in the cross-section of the positive electrode film layer along the thickness direction of the electrode tab, the area ratio of particles with a particle size greater than or equal to 1 μm is 12% - 50%; in the cross-section of the positive electrode film layer along the thickness direction of the electrode tab, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 3.0% - 15.0%; when the battery cell is in a fully discharged state, the tap density of the positive electrode tab is 2.3 g / cm 3 - 2.6 g / cm 3 .

[0007] Research shows that to effectively improve the compaction density of the electrode, it is necessary to introduce an appropriate amount of particles with a particle size greater than or equal to 1 μm into the positive electrode film layer. The applicant found that when the area ratio of particles with a particle size greater than or equal to 1 μm is less than 12% or the area ratio of particles with a particle size of 50 nm - 200 nm is less than 3% in the cross-section of the positive electrode film layer along the thickness direction of the electrode, it will lead to insufficient particle grading, limit the improvement of the compaction density, and thus prevent the effective increase of the battery capacity. When the battery cell is in a fully discharged state and the compaction density of the positive electrode is less than 2.3 g / cm 3 ³, the battery not only has difficulty obtaining ideal capacity performance, but also hinders the formation of the electron conduction network and the lithium-ion transport channel due to insufficient connection between particles, significantly increasing the internal resistance of the battery. When the area ratio of particles with a particle size of 50 nm - 200 nm is greater than 15% in the cross-section of the positive electrode film layer along the thickness direction of the electrode, the excessive area ratio of small particles will increase the internal resistance of the positive electrode film layer, exacerbate the heat generation during the battery cycle, and deteriorate the cycle performance. When the area ratio of particles with a particle size greater than or equal to 1 μm is greater than 50% in the cross-section of the positive electrode film layer along the thickness direction of the electrode or the compaction density of the positive electrode of the battery cell is greater than 2.6 g / cm 3 ³ when the battery cell is in a fully discharged state, obvious stress concentration effects will occur during the compaction of large particles in the electrode, causing problems such as contact failure between particles, loosening of the film layer structure, and even shedding of active materials, which have a negative impact on the cycle performance.

[0008] In the embodiment of the present application, the capacity of the battery is improved by jointly designing the laminated battery cell structure and optimizing the particle grading of the lithium-containing transition metal phosphate positive electrode film layer. At the same time, by reducing the area ratio of large particles and controlling the compaction density of the positive electrode, the stress concentration of large particles during the compaction of the laminated battery cell is improved, effectively alleviating the problems of loosening of the film layer structure and shedding of active materials, and improving the cycle performance of the battery. Further regulating the area ratio of small particles within a suitable range not only ensures sufficient particle filling but also avoids an excessive increase in the resistance of the positive electrode film layer due to too many small particles, reduces the heat generation during the battery cycle, and improves the kinetic performance and cycle performance of the battery. At the same time, the unilateral thickness of the positive electrode film layer is in the range of 70 μm - 120 μm, which is beneficial to improving the capacity of the battery cell. Therefore, through the collaborative design of the laminated battery cell and the positive electrode, the capacity, cycle performance, and kinetic performance of the battery are improved.

[0009] In any implementation manner, in the cross-section of the positive electrode film layer along the thickness direction of the electrode, the area ratio of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 50%.

[0010] When the area percentage of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial for the battery to further improve the phenomenon of film layer loosening and active material shedding caused by stress concentration easily occurring during the compaction of large particles while maintaining a high capacity, and to improve the cycle performance of the battery.

[0011] In any implementation, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area percentage of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 40%.

[0012] When the area percentage of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial for the battery to further improve the phenomenon of film layer loosening and active material shedding caused by stress concentration easily occurring during the compaction of large particles while maintaining a high capacity, and to further improve the cycle performance of the battery.

[0013] In any implementation, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size greater than or equal to 1 μm is 0.2% - 5%, and can be optionally 0.2% - 2%.

[0014] When the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within a suitable range, the uniformly distributed large particles can effectively reduce the stress concentration degree in the local area of the film layer, so that the stress during the compaction process of the film layer can be evenly dispersed throughout the entire area of the film layer, avoiding the phenomenon of local stress concentration caused by particle agglomeration, reducing the probability of film layer shedding, and improving the cycle performance of the battery.

[0015] In any implementation, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.6 - 0.8.

[0016] When the median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, the large particles have good sphericity, reducing particle bridging caused by irregular shapes of large particles, reducing the void content in the electrode sheet, and at the same time reducing the stress concentration aggravated by the irregularity of large particles, improving the phenomena of film layer loosening and active material shedding, and the battery monomer has a high capacity and good cycle performance.

[0017] In any implementation, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.65 - 0.75.

[0018] The median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, which is beneficial to reducing the stress concentration that occurs during the compaction of the electrode due to the irregularity of large particles, and improving the phenomena of film layer loosening and active material shedding.

[0019] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode, in the area cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median sphericity L A50 is 0.67 - 0.75.

[0020] The median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, which can further improve the stress concentration that occurs during the compaction of large particles in the electrode, reduce the probability of film layer loosening and active material shedding, and improve the cycle life of the battery cell.

[0021] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 15.0%.

[0022] When the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is within the above range, there are appropriate small particles in the positive electrode film layer, ensuring sufficient particle filling degree, while avoiding the adverse effect of too large an area ratio of small particles on the resistance of the film layer, and improving the kinetic performance of the battery on the basis of good capacity.

[0023] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 10.0%.

[0024] When the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is within the above range, the positive electrode film layer has good particle gradation, further reducing the resistivity of the positive electrode film layer, and further improving the kinetic performance of the battery on the basis of good capacity.

[0025] In any embodiment, the single-sided thickness of the positive electrode film layer is 70 μm - 120 μm.

[0026] The specific capacity of lithium-containing transition metal phosphate particles is relatively low. Research shows that when the single-sided thickness of the positive electrode film layer is less than 70 μm, the battery capacity is difficult to meet market demands. When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to improving the capacity of the battery cell.

[0027] In any embodiment, the single-sided thickness of the positive electrode film layer is 90 μm - 120 μm.

[0028] When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to further improving the capacity of the battery cell.

[0029] In any embodiment, the thickness of one side of the positive electrode film layer is 100 μm - 120 μm.

[0030] Increasing the thickness of one side of the positive electrode film layer is beneficial to improving the capacity of the battery. The applicant found that when the thickness of one side of the positive electrode film layer is greater than or equal to 100 μm, the positive electrode film layer is more likely to have problems such as film layer loosening and active material shedding. The examples of this application reduce the area ratio of large particles and the compaction density of the positive electrode film layer, jointly improving the phenomenon of stress concentration of large particles during the compaction of the electrode in the stacked battery cell. At the same time, an appropriate amount of small particles is added to enable the electrode to still have a good compaction density on the basis of allowing a certain content of large particles, and the battery has good capacity and cycling performance.

[0031] In any embodiment, 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, the total area ratio of the agglomeration regions of the conductive agent is 0.2% - 6%, and can be optionally 1.5% - 5%.

[0032] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode, the total area ratio of the agglomeration regions of the conductive agent within the above range indicates that the conductive agent in the positive electrode film layer is evenly dispersed, facilitating the formation of a uniform conductive network, which is beneficial to reducing local polarization and even lithium plating problems generated during the cycling of the battery.

[0033] At the same time, the appropriate amount of small particles in this application can be used as a basic conductive skeleton to fill the gaps between large particles, while the dispersed conductive agent aggregates serve as long-range conduction nodes to form a hierarchical conductive structure. Since the large-sized particles in the lithium-containing transition metal phosphate particles are prone to rebound, the uniform distribution of the conductive agent within the above range can also suppress the rebound of large particles by means of the uniform distribution of the conductive agent, forming a mechanical restraint on the particles and even the film layer, improving the internal cohesion of the film layer, reducing the phenomenon of film layer powdering and active material shedding, and improving the cycling life of the battery.

[0034] In any embodiment, 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. Optionally, the conductive agent further includes conductive carbon black.

[0035] Carbon nanotubes have the characteristic of a high aspect ratio, which is beneficial to bridging particles of different particle sizes through their unique fiber structure in the thickness direction, forming a long-range conductive path while increasing the binding force between particles, reducing local polarization and even lithium plating problems generated during the cycling of the battery, and improving the cycling life of the battery. It can also reduce the rebound phenomenon of large particles in the positive electrode film layer and the shedding phenomenon of active substances in the film layer through the binding effect.

[0036] Conductive carbon black has a small size, attaches to the surface of the positive electrode particles and fills the gaps between the positive electrode particles, forming dense dot-like conductive contacts. When used in combination with carbon nanotubes, it takes into account both long-range and short-range conductivity, which is beneficial to further improve the conductive network in the positive electrode film layer. At the same time, the conductive agent has a large specific surface area, which is beneficial to liquid absorption and liquid retention, and can reduce the phenomenon of electrolyte extrusion caused by the high growth rate of the expansion force during long-term cycling of the electrode sheet, improving the long-term cycling life of the battery.

[0037] In any embodiment, the agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0038] Researchers have 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, thereby inhibiting the agglomeration phenomenon and improving the distribution uniformity of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the 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 shedding of the positive electrode film layer, and further improving the kinetic performance and cycling 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 cycling stability of the battery.

[0039] In any embodiment, 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%.

[0040] When the mass contents of carbon nanotubes and conductive carbon black are within the above ranges, it can effectively alleviate the agglomeration phenomenon of carbon nanotubes and form a good conductive network structure, thereby effectively reducing the stress concentration in the positive electrode film layer, improving the liquid retention rate of the positive electrode film layer during long-term cycling, further reducing the risk of shedding of the electrode sheet film layer and the degree of polarization, improving the kinetic performance of the battery and improving the cycling life of the battery.

[0041] In any embodiment, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

[0042] The polar groups (such as cyano group, -CN) in the hydrogenated nitrile butadiene rubber (HNBR) molecules can interact with the hydroxyl groups (-OH) or metal oxide sites on the surface of the lithium-containing transition metal phosphate particles (such as hydrogen bonding and dipole interaction), enhancing the compatibility between the particles and the solvent, reducing the interfacial tension between the particles and the solvent, and having a more obvious improvement on the interfacial tension of large particles, making it easier for large and small particles in the film layer to be evenly dispersed, reducing particle aggregation caused by hydrophobicity, improving the dispersion of large particles in the positive electrode film layer, and reducing stress concentration generated during the die-cutting process of the film layer.

[0043] Meanwhile, when the slurry is dried into a film, the elastic network structure of HNBR can buffer the shrinkage stress generated by solvent volatilization, reduce the re-aggregation of the conductive agent due to capillary force during this process, and reduce the area ratio of the agglomeration region of the conductive agent. The uniform distribution of the conductive agent is beneficial to suppressing the rebound of large particles, forming a mechanical restraint on the particles and even the film layer, improving the cohesive force of the film layer, reducing the phenomena of film layer powder falling and active material shedding, and improving the cycle life of the battery.

[0044] In any embodiment, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0045] When the mass content of the dispersant is within the above range, it can achieve the uniform dispersion of the particles in the positive electrode film layer while maintaining a high loading amount of the positive electrode film layer, and the battery has good capacity and cycle performance.

[0046] In any embodiment, 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.

[0047] In any embodiment, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector, and the thickness of the bottom coating is 0.5 μm - 5 μm.

[0048] 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 sheet and improving the kinetic performance of the battery.

[0049] In any embodiment, 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 greater than or equal to 0.95 and less than or equal to 1.20; wherein, the graphitization degree C value is I G / ID , 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 .

[0050] 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 Within the above range, the compaction density of the electrode can be further improved by relying on the slip of the particles, without relying too much on the ratio of large and small particles in the positive electrode film layer, so that the area ratios of large and small particles are within a suitable range, which is conducive to reducing the probability of the positive electrode film layer falling off and avoiding excessive resistance of the positive electrode film layer, and helps to improve the cycle performance and kinetic performance of the battery while maintaining the battery capacity.

[0051] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include 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.

[0052] In any embodiment, the lithium-containing transition metal phosphate particles include titanium element. 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, and can be optionally 1000 ppm - 3000 ppm.

[0053] When titanium element is doped into the lithium-containing transition metal phosphate particles, the formed Ti - O - P bond has a strong bonding effect. By anchoring the phosphate groups, it reduces the shrinkage / expansion amplitude of the lattice during lithium ion deintercalation / insertion, thereby inhibiting the structural stress caused by phase change, which is beneficial to improving the cycle life of the battery; and the Ti - O - P bond can provide a more stable channel for lithium ion diffusion, reducing the migration energy barrier, which is beneficial to improving the kinetic performance of the battery.

[0054] The mass content of titanium element within the above range is beneficial to improving the lithium ion transmission rate of the positive electrode active material, reducing the risk of lithium precipitation, and improving the kinetic performance of the battery.

[0055] In any embodiment, the lithium-containing transition metal phosphate particles include vanadium element, and 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 may be 500 ppm - 3000 ppm.

[0056] When vanadium element is doped into the lithium-containing transition metal phosphate particles, it has multivalent characteristics. When pentavalent vanadium (V 5+ ) is doped into the phosphorus site, due to its larger radius, lattice distortion will be introduced, the lithium ion diffusion channel will be expanded, and the ionic conductivity of the positive electrode active material will be improved; when trivalent vanadium (V 3+ ) is doped into the transition metal site, charge is compensated by lithium vacancies or interstitial oxygen to form defect energy levels, improving the electronic conductivity of the positive electrode active material.

[0057] The mass content of vanadium element within the above range is beneficial to improving the lithium ion transport rate of the positive electrode active material, improving the electronic conductivity of the positive electrode active material, and further improving the kinetic performance of the battery through the synergistic effect with titanium element doping.

[0058] In any embodiment, the porosity of the positive electrode film layer is 14% - 28%.

[0059] The porosity of the positive electrode film layer within the above range means that the particle size grading of the positive electrode film layer is good, which is beneficial to improving the liquid retention characteristics of the electrolyte, improving the ionic diffusivity of the positive electrode film layer with large particles having a certain area ratio, and improving the kinetic performance of the battery.

[0060] In any embodiment, the resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

[0061] The resistivity of the positive electrode film layer within a suitable range is beneficial to reducing the electron transfer impedance, reducing charge-discharge polarization, and improving the kinetic performance of the battery.

[0062] In any embodiment, the battery cell further includes a separator disposed between the positive electrode plate and the negative electrode plate. 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. The adhesive layer is a continuous layer with a porous structure, and the adhesive layer includes a polyvinylidene fluoride polymer.

[0063] The diaphragm provided in the embodiment of the present application uses a continuous layer of a porous structure as a bonding layer, which has a larger bonding area than the island-shaped bonding layer in the prior art, so that the bonding between the diaphragm and the positive electrode film layer is more firm and uniform. At the same time, with the help of the pore structure in the bonding layer, it can have both the transmission efficiency of lithium ions and the dynamic performance of the battery. At the same time, compared with the wound battery, the laminated battery has a smaller pressing force between the pole pieces during the preparation of the battery, and the lithium-containing transition metal phosphate particles with a particle size greater than or equal to 1 μm will reduce the compactness of the internal components of the battery during the rebound process, increase the impedance of the battery, and increase the probability of the film layer falling off or even falling off. The diaphragm provided in the embodiment of the present application uses a continuous layer of a porous structure as a bonding layer, which is particularly suitable for laminated batteries, improves the rebound phenomenon of laminated batteries during long cycles, and improves the retention of battery capacity during long cycles.

[0064] The embodiment of the present application uses a continuous layer of a porous structure as a bonding layer to improve the bonding force between the diaphragm and the electrode while maintaining the air permeability and porosity of the diaphragm, thereby improving the stability of the electrode, further reducing the risk of powder shedding and even internal short circuit due to relative displacement between the electrode and the diaphragm, and improving the cycle stability of the battery.

[0065] In any embodiment, the battery cell includes a shell, and the laminated battery cell is accommodated in the shell. The size of the shell in the length direction is L0, the size of the shell in the width direction is W0, and the size of the shell in the thickness direction is H0, 450mm≤L0≤1300mm, 100mm≤W0≤150mm, 14mm≤H0≤22mm.

[0066] The shell size of the battery cell of the embodiment of the present application is within the above range, which is conducive to achieving a better capacity of the battery.

[0067] In any embodiment, a dimension L0 of the housing in the length direction satisfies: 450 mm ≤ L0 ≤ 650 mm.

[0068] When the dimension L0 of the shell in the length direction satisfies: 450mm≤L0≤650mm, the battery cell has a shorter length, which is beneficial to shorten the electron transmission path, reduce the internal resistance of the battery, and at the same time reduce the wetting distance of the electrolyte in the electrode pores, improve the wetting uniformity, and improve the dynamic performance of the battery; especially under fast charging conditions, it can reduce the uneven temperature rise and current density in the length direction of the electrode.

[0069] In any embodiment, a dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

[0070] When the dimension L0 of the housing in the length direction satisfies 900 mm ≤ L0 ≤ 1300 mm, the significantly increased single-cell size can effectively simplify the traditional module structure, enabling direct integration of single cells into the battery pack. The battery is fixed by structural components arranged at the ends of the large surface, significantly improving the space utilization rate, thereby increasing the overall capacity of the battery system under the same volume, reducing the number of structural components, and improving the battery energy density.

[0071] 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 a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) with aluminum.

[0072] The soft-pack material has a high elongation rate, and its housing is thin, light, and flexible, which helps to improve the space utilization rate of the battery single cell, thereby increasing the energy density of the battery single cell. However, the soft-pack material such as the aluminum-plastic composite film has poor thermal conductivity, resulting in a low heat dissipation efficiency of the soft-pack battery. Therefore, if the area ratio of small particles in the positive electrode film layer is too large, it will increase the resistivity of the positive electrode film layer, leading to excessive heat generation during the battery cycle and exacerbating the problem of poor heat dissipation of the soft-pack battery. In the embodiments of the present application, by using the soft-pack material as the housing and controlling the area ratio of small particles in the positive electrode film layer within a suitable range, the battery has a high capacity and good cycle performance.

[0073] 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 core extending in the width direction; the first sealing area includes a folded-edge structure extending in the length direction, and an encapsulation adhesive is arranged on the folded-edge structure. The encapsulation adhesive is continuously arranged in the length direction and fixes the folded-edge structure.

[0074] In the embodiments of the present application, the sealing strength of the first sealing area is further improved by the folded-edge structure extending in the length direction included in the first sealing area. The continuous arrangement of the encapsulation adhesive in the length direction and fixing the folded-edge structure can further improve the encapsulation strength compared with the discontinuous arrangement of the encapsulation adhesive in the length direction, realize continuous reinforcement in the length direction of the sealing area, and reduce the probability of the electrode sheet punching open the sealing area in the package during the cycle.

[0075] In any implementation, the housing includes at least one second sealing area, and the second sealing area is arranged at at least one end of the stacked electrode core extending along the length direction of the housing, and the second sealing area is arranged on the tab side of the stacked electrode core.

[0076] The second sealing area is arranged on the tab side. The tab needs to be connected to the lead-out piece, and the connection strength between the lead-out piece 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 influence on adjacent battery cells during thermal runaway, and improving the overall service life of the battery.

[0077] In any implementation manner, a plurality of rubber rings surrounding along the width direction are arranged on the outer periphery of the laminated battery cell, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

[0078] The spaced arrangement of the rubber rings surrounding along the width direction of the battery cell in the length direction is beneficial to fixing the positions between the electrode plates in the battery cell, reducing the probability of displacement of the battery cell during the shaking of the battery, especially applicable to batteries with a relatively large length, and can effectively reduce the mutual displacement between the electrode plates in the length direction, thereby causing the phenomenon of lithium plating, 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.

[0079] In any implementation manner, at 25 °C, the capacity of the battery monomer is 100 Ah - 300 Ah, optionally 110 Ah - 190 Ah, and further optionally 125 Ah - 180 Ah.

[0080] The battery monomer of the embodiment of the present application has a suitable housing size to accommodate the laminated battery cell, controls a reasonable large particle proportion in the film layer of the positive electrode plate in the laminated battery cell, and the battery monomer has a relatively high capacity.

[0081] The second aspect of the present application provides a battery device, including the battery monomer provided by the first aspect of the present application.

[0082] The third aspect of the present application provides an electrical device, and the electrical device includes the battery device provided by the second aspect, and the battery device is used to provide electrical energy.

[0083] The fourth aspect of the present application provides an energy storage device, and the energy storage device includes the battery device provided by the second aspect, and the battery device is used to store electrical energy. Description of the Drawings

[0084] Figure 1 is a schematic diagram of a separator of an embodiment of the present application; Figure 2 is a schematic diagram of a separator of the prior art; Figure 3 is a schematic diagram of the surface topography of the adhesive layer of a separator of an embodiment of the present application; Figure 4 is a front view of a battery monomer of an embodiment of the present application; Figure 5 is a schematic diagram of an electrical device of an embodiment of the present application.

[0085] Description of the reference numerals in the drawings: 20 Diaphragm; 201 Base film; 202 Ceramic layer; 203 Adhesive layer; 5 Battery cell; 50 Housing; 51 First sealing area; 52 Second sealing area; 53 Lead-out member; X Length direction; Y Width direction; Z Thickness direction. Detailed implementation manners

[0086] 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 appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions 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.

[0087] 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 specific range. The ranges 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 specified, 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" represents 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 stating 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.

[0088] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0089] If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0090] Unless otherwise specified, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which 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.

[0091] In the present application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0092] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art.

[0093] Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various common testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of the present application. Unless otherwise specified, the test temperature of each parameter is 25 °C.

[0094] In the embodiments of the present application, the battery device may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly 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 assembly is usually formed by arranging a plurality of pouch battery cells; the battery cell assembly can be a battery module, and the battery module is 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.

[0095] The battery device can be a battery pack, and the battery pack includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body. The battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the box body by fixing the battery module in the box body; the battery cell assembly can also be accommodated in the box body by directly fixing a plurality of pouch battery cells to the box body.

[0096] In the embodiments of the present 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 assembly. Here, "closed" means covered or closed, and it 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 assembly.

[0097] 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 floor of the vehicle, or a part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0098] 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 the form of a flat body.

[0099] 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.

[0100] The battery cell is the smallest unit that makes up the battery and can independently realize the functions of charging and discharging. 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 bottom plate of the vehicle, or a part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0101] 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.

[0102] 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. In some embodiments, the above 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.

[0103] The battery cell includes an electrode assembly and an electrolyte.

[0104] 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.

[0105] Lithium-containing transition metal phosphate materials have significant advantages compared to lithium-containing transition metal oxide materials, including higher safety performance, longer cycle life, lower raw material costs, and better high-temperature stability. However, such materials also have inherent defects, especially their relatively low theoretical specific capacity, which severely restricts the improvement of battery capacity. The applicant's research found that the stacked cell has no corner area compared to the wound cell, and has a higher space utilization rate for the internal volume of the battery. Using a stacked cell is beneficial to improving the volumetric energy density of the battery. At the same time, increasing the content of large and small particles and optimizing the particle size distribution of the positive electrode active material can further improve the compaction density of the electrode sheet and increase the volumetric energy density of the battery. However, during the compaction process of the electrode sheet, stress concentration is likely to occur at large particles, resulting in contact failure between particles, loosening of the film layer structure, and even shedding of the active material; although small particles can fill voids to further improve the compaction density of the electrode sheet, an excessive amount of small particles will increase the resistance of the positive electrode film layer. Due to the lack of radial restraint in the stacked cell without the constraint of the corner area, it is more likely to exacerbate the phenomenon of film layer shedding in the electrode sheet caused by stress concentration generated by large particles. Film layer shedding will lead to a decrease in battery capacity, internal micro-short circuit, and exacerbation of electrolyte side reactions, which has an adverse impact on battery performance. How to obtain a battery with good capacity, cycle performance, and kinetic performance is a technical problem that urgently needs to be solved in this field.

[0106] In a 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, and the single-sided thickness of the positive electrode film layer is 70 μm - 120 μm; the positive electrode film layer includes lithium-containing transition metal phosphate particles, and at least part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material; 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 greater than or equal to 1 μm is 12% - 50%; 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 of 50 nm - 200 nm is 3.0% - 15.0%; when the battery cell is in a fully discharged state, the compaction density of the positive electrode sheet is 2.3 g / cm 3 - 2.6 g / cm 3 。

[0107] Research shows that to effectively improve the compaction density of the electrode, it is necessary to introduce an appropriate amount of particles with a particle size greater than or equal to 1 μm into the positive electrode film layer. The applicant found that the loss of the compaction density of the electrode caused by the reduction of the large particle content can be compensated by adding an appropriate amount of small particles. When the area ratio of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode is less than 12% or the area ratio of particles with a particle size of 50 nm - 200 nm is less than 3%, it will lead to insufficient particle grading, limit the improvement of the compaction density, and thus unable to effectively increase the battery capacity. When the battery cell is in a fully discharged state and the compaction density of the positive electrode is less than 2.3 g / cm 3 ³, the battery not only has difficulty obtaining ideal capacity performance, but also hinders the formation of the electron conduction network and lithium-ion transport channels due to insufficient connection between particles, significantly increasing the internal resistance of the battery. When the area ratio of particles with a particle size of 50 nm - 200 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode is greater than 15%, the excessive area ratio of small particles will increase the internal resistance of the positive electrode film layer, exacerbate the heat generation during the battery cycle, and deteriorate the cycle performance. When the area ratio of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode is greater than 50% or the compaction density of the positive electrode of the battery cell in the fully discharged state is greater than 2.6 g / cm 3 ³, obvious stress concentration effect will occur during the compaction of the large particles in the electrode, causing problems such as contact failure between particles, loosening of the film layer structure, and even shedding of the active material, which will have a negative impact on the cycle performance.

[0108] In the embodiment of the present application, the capacity of the battery is improved by jointly designing the laminated battery cell structure and optimizing the particle grading of the positive lithium-containing transition metal phosphate electrode film layer. At the same time, by reducing the area ratio of large particles and controlling the compaction density of the positive electrode, the stress concentration of large particles in the laminated battery cell during the electrode compaction process is improved, effectively alleviating the problems of loosening of the film layer structure and shedding of the active material, and improving the cycle performance of the battery. Further regulating the area ratio of small particles within a suitable range not only ensures sufficient particle filling degree but also avoids excessive small particles leading to an increase in the resistance of the positive electrode film layer, reducing the heat generation during the battery cycle, and improving the kinetic performance and cycle performance of the battery. At the same time, the single-side thickness of the positive electrode film layer is in the range of 70 μm - 120 μm, which is beneficial to improving the capacity of the battery cell. Therefore, through the collaborative design of the laminated battery cell and the positive electrode, the capacity, cycle performance, and kinetic performance of the battery are improved.

[0109] In the present application, a laminated battery cell refers to a battery cell formed by stacking a positive electrode, a separator, and a negative electrode together.

[0110] The lithium-containing 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 using an X-ray diffractometer (XRD) in combination with an energy spectrometer and an inductively coupled plasma mass spectrometer.

[0111] It should be noted that the positive electrode film layer contains lithium-containing transition metal phosphate particles, but the positive electrode film layer does not solely 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.

[0112] In the present application, the term "particle" refers to a particle with an identifiable complete boundary in the field of view of the positive electrode film layer at a certain magnification, such as 10,000 times. There may be defects and scratches inside the particle, but no complete boundary sufficient to divide the particle can be identified inside the particle.

[0113] 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 EM TIC 3X CP, 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. Use a field emission scanning electron microscope to collect images in the secondary electron mode at a non-edge position on the cut surface of the positive electrode film layer (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 microscope image at a magnification of 10,000 times, and analyze the particles in the electron microscope image using ImageJ software (version 1.46r, win64). The usage method of ImageJ software is as follows: Load the scanning electron microscope image 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 fully recognized by the software, or have recognition errors. The particles in the image that are not recognized by the software, not fully 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 fully 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 particle boundaries during the recognition process, resulting in recognition errors; 3. Due to the particle being too small, it fails to be recognized successfully; 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 four edges of the scanning electron microscope that cannot be fully displayed; 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 one particle, and manually mark it according to the particle boundary observed manually; In response to the presence of gap scratches inside the particles, determine whether the gap scratches penetrate the particles. If they do not penetrate the particles, then determine it as one particle and perform manual marking; In response to the gap scratches penetrating the particles, 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; In response to the contrast being not obvious and there being no sense of cracks, determine it as a scratch and mark it as one particle; In response to the contrast being strong and there being a sense of cracks, determine it as the boundary between particles and mark it as two particles. After manual marking, delete the information unrelated to the particles during the automatic image processing process, that is, the determination and marking of the particles in the picture are completed.

[0114] 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 greater than or equal to 1 μm can intuitively reflect the proportional relationship between the area of the particles in this particle size range and the total particle area, and reflect the area size of the particles in this particle size range.

[0115] It can be understood that in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, especially the particles above 50 nm mainly come from the positive electrode active material. Therefore, through the observation and statistics of the particle area in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet in the embodiments of the present application, the distribution of the lithium-containing transition metal phosphate particles in the positive electrode film layer can be accurately and objectively reflected.

[0116] 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 the 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 aggregates, 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 test cannot be equivalent to or analogized to the particle size statistically obtained in the embodiments of the present application.

[0117] In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the test method for the area proportion of particles with a particle size greater than or equal to 1 μm 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 along the thickness direction of the electrode sheet. Import the image after particle determination and identification into the ImageJ software for analysis. Complete the scale setting according to the scanning electron microscope image. Use the "Feret", "Area", "Round", and "Solidity" analysis functions to statistically analyze 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. 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 obtained "Area" parameter represents the pixel area of the particle. Since particles with a particle size less than 50 nm have large errors in the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50 nm, which will cause large errors to the statistical results. Therefore, in the particle size statistics process of this application, particles with a particle size less than 50 nm are not counted, and the particle statistical data corresponding to "Area", "Round", or "Solidity" displayed as "NaN" are deleted. Calculate the sum of the "Area" parameters of particles with a particle size greater than or equal to 1 μm and the sum of the "Area" parameters of all particles, which are used as the area of particles with a particle size greater than or equal to 1 μm and the total area of the counted particles, respectively. Divide the sum of the areas of particles with a particle size greater than or equal to 1 μm by the total area of the counted particles to obtain the area proportion of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0118] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area proportion of particles with a particle size greater than or equal to 1 μm can be 12%, 12.02%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 34.78%, 34.95%, 35%, 36%, 36.29%, 36.37%, 36.64%, 36.88%, 37%, 38%, 38.09%, 38.44%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 49.96%, 50% or any value range between any two of them.

[0119] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area proportion of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 3.0% - 15.0%.

[0120] 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 greater than 50 nm and less than or equal to 200 nm can be obtained by referring to the test method for the area ratio of particles with a particle size greater than or equal to 1 μm described above.

[0121] In some embodiments, 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 greater than 50 nm and less than or equal to 200 nm can be selected as 3%, 4%, 5%, 5.33%, 5.91%, 6%, 6.35%, 6.42%, 6.49%, 6.52%, 6.54%, 6.55%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 14.81%, 15% or the numerical range between any two of them.

[0122] Theoretical studies show that under ideal conditions, spherical particles with a diameter of 314 nm can fill the gaps formed by the accumulation of spherical particles with a diameter of 1 μm, achieving an improvement in particle grading and the compaction density of the electrode sheet. Particles with a particle size greater than 50 nm and less than or equal to 200 nm can tightly fill the gaps between particles with a size greater than or equal to 1 μm and cooperate with them to achieve dense packing. When the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is within a suitable range, it is beneficial to increase the compaction density of the positive electrode sheet through grading, while avoiding an excessive increase in the internal resistance of the positive electrode film layer due to too high an area ratio of small particles. The battery has good capacity while further improving the kinetic performance of the battery.

[0123] In some embodiments, when the battery cell is in a fully discharged state, the compaction density of the positive electrode sheet is 2.3 g / cm 3 - 2.6 g / cm 3 .

[0124] In this application, the fully discharged state means that the battery is placed in an oven environment at 25°C, left to stand for 2 h, and after the battery temperature is maintained 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.

[0125] The compaction 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 to stand for 2 h, and after the battery temperature is maintained 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 dimethyl carbonate solvent, the electrode sheet is dried, cut into small round pieces with an area of S, and its mass is W1. The thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the above weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. Then, the compaction density PD of the positive electrode sheet = (W1 - W2) / [(T1 - T2)×S].

[0126] In some embodiments, when the battery is in a fully discharged state, the compaction density of the positive electrode sheet can be selected from 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 , 2.51 g / cm 3 , 2.52 g / cm 3 , 2.53 g / cm 3 , 2.54 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.59 g / cm 3 , 2.60 g / cm 3 or a numerical range between any two of them.

[0127] In some embodiments, 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 greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 50%.

[0128] When the area ratio of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial to further improve the phenomenon of film layer loosening and active material shedding caused by stress concentration easily occurring during the compaction of large particles on the basis of maintaining a high capacity of the battery, and improve the cycle performance of the battery.

[0129] In some embodiments, 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 greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 40%.

[0130] When the area ratio of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial to further improve the phenomenon of film layer loosening and active material shedding caused by stress concentration that is likely to occur during the compaction of large particles in the electrode sheet while maintaining a high capacity of the battery, and further improve the cycle performance of the battery.

[0131] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size greater than or equal to 1 μm is 0.2% - 5%, and can be optionally 0.2% - 2%.

[0132] The test method for the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet can be tested by methods known in the art. As an example, the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is divided into three layers of equal thickness along the thickness direction of the electrode sheet, namely the lower layer close to the positive electrode current collector, the upper layer far from the positive electrode current collector, and the middle layer placed between the upper layer and the lower layer; 10 non-overlapping fields of view are respectively selected in the upper layer, the middle layer and the lower layer, and scanning electron microscope images are taken at a magnification of 10k; the 30 taken scanning electron microscope images are respectively imported into the ImageJ software for analysis, and the area ratio of particles with a particle size greater than or equal to 1 μm in the 30 images is tested, a total of 30 values; the range of the 30 obtained values is the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, where the range is the difference between the maximum value and the minimum value among the 30 values. The smaller the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the more uniform the distribution of large particles in the positive electrode film layer.

[0133] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size greater than or equal to 1 μm can be optionally 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%, 1%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 1%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 1%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5% or any numerical range between any two of them.

[0134] In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size greater than or equal to 1 μm is within an appropriate range. The uniformly distributed large particles can effectively reduce the stress concentration degree in the local area of the film layer, enabling the stress during the film layer compaction process to be evenly dispersed throughout the entire area of the film layer, avoiding the phenomenon of local stress concentration caused by particle agglomeration, reducing the probability of the film layer peeling off, and improving the cycle performance of the battery.

[0135] In some embodiments, 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 greater than or equal to 1 μm, the median L of the sphericity A50 is 0.6 - 0.8.

[0136] The method for testing the sphericity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is as follows: Refer to the method described above in this application to identify the particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, 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. Since particles with a particle size less than 50 nm 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 50 nm, which will cause large errors to the statistical results, therefore, particles with a particle size less than 50 nm are not statistically counted during the particle size statistics process in this application, and the particle statistical data corresponding to "NaN" displayed in Round is deleted. 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 ratio as the vertical axis. L A50 is the sphericity L value corresponding to the cumulative area ratio of 50% on the vertical axis in the cumulative distribution curve of the particle sphericity L value.

[0137] In some embodiments, 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 greater than or equal to 1 μm, the median L of the sphericity A50It can be 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.

[0138] The median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range. The large particles have good sphericity, reducing particle bridging caused by the irregular shape of large particles, reducing the void content in the electrode sheet, and at the same time reducing the stress concentration aggravated by the irregularity of large particles, improving the phenomena of film layer loosening and active material shedding. The battery cell has high capacity and good cycle performance.

[0139] Those skilled in the art can regulate the sphericity of particles through any known process. As an example, through processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, adding surfactants, etc., and adjusting the parameters of each process, the adjustment of the sphericity of particles can be achieved.

[0140] In some embodiments, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.65 - 0.75.

[0141] The median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, which is beneficial to reducing the stress concentration that occurs during electrode sheet compaction due to the irregularity of large particles, and improving the phenomena of film layer loosening and active material shedding.

[0142] In some embodiments, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.67 - 0.75.

[0143] The median sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, which can further improve the stress concentration that occurs during electrode sheet compaction of large particles, reduce the probability of film layer loosening and active material shedding, and improve the cycle life of the battery cell.

[0144] In some embodiments, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 15.0%.

[0145] The area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is within the above range. There are appropriate small particles in the positive electrode film layer, ensuring sufficient particle filling degree. At the same time, it avoids the adverse effect of too large an area ratio of small particles on the resistance of the film layer. On the basis of having good capacity, the battery improves the kinetic performance of the battery.

[0146] In some embodiments, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 10.0%.

[0147] The area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is within the above range. The positive electrode film layer has good particle size distribution, further reducing the resistivity of the positive electrode film layer. On the basis of having good capacity, the battery further improves the kinetic performance of the battery.

[0148] In some embodiments, the single-sided thickness of the positive electrode film layer is 70 μm - 120 μm.

[0149] 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. Randomly select 3 different positions for measurement and take the average value as the thickness of the positive electrode film layer.

[0150] In some embodiments, the single-sided thickness of the positive electrode film layer can be selected as 70 μm, 72.34 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 83 μm, 83.91 μm, 84 μm, 85 μm, 86 μm, 87 μm, 88 μm, 89 μm, 90 μm, 91 μm, 91.88 μm, 92 μm, 93 μm, 94 μm, 95 μm, 96 μm, 97 μm, 98 μm, 98.93 μm, 99 μm, 100 μm, 101 μm, 102 μm, 103 μm, 104 μm, 105 μm, 105.44 μm, 105.64 μm, 105.65 μm, 105.89 μm, 106 μm, 106.21 μm, 106.34 μm, 107 μm, 108 μm, 109 μm, 110 μm, 111 μm, 112 μm, 113 μm, 114 μm, 115 μm, 116 μm, 116.09 μm, 117 μm, 118 μm, 119 μm, 120 μm or any value range between any two of them.

[0151] The specific capacity of lithium-containing transition metal phosphate particles is relatively low. Research shows that when the single-sided thickness of the positive electrode film layer is less than 70 μm, the battery capacity is difficult to meet market demands. When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to improve the capacity of a single battery cell.

[0152] In some embodiments, the single-sided thickness of the positive electrode film layer is 90 μm - 120 μm.

[0153] When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to further improve the capacity of a single battery cell.

[0154] In some embodiments, the single-sided thickness of the positive electrode film layer is 100 μm - 120 μm.

[0155] Increasing the single-sided thickness of the positive electrode film layer is beneficial to improving the battery capacity. The applicant found that when the single-sided thickness of the positive electrode film layer is greater than or equal to 100 μm, the positive electrode film layer is more prone to film layer loosening and active material shedding. The examples of this application reduce the area ratio of large particles and the compaction density of the positive electrode film layer, jointly improving the phenomenon of stress concentration of large particles during the compaction of the electrode in the stacked battery cell. At the same time, an appropriate amount of small particles is added, so that the electrode still has a good compaction density on the basis of sacrificing a certain content of large particles, and the battery has good capacity and cycling performance.

[0156] 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, the total area ratio of the agglomeration regions of the conductive agent is 0.2% - 6%, and can be optionally 1.5% - 5%.

[0157] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode, the total area ratio of the agglomeration regions of the conductive agent within the above range indicates that the conductive agent in the positive electrode film layer is evenly dispersed and is easy to form a uniform conductive network, which is beneficial to reducing local polarization and even lithium plating problems generated during battery cycling.

[0158] At the same time, the appropriate amount of small particles in this application can be used as a basic conductive framework to fill the gaps between large particles, while the dispersed conductive agent aggregates serve as long-range conduction nodes to form a hierarchical conductive structure; since the large-sized particles in the lithium-containing transition metal phosphate particles are prone to rebound, the uniform distribution of the conductive agent within the above range of the agglomeration area of the conductive agent can also suppress the rebound of large particles, form a mechanical restraint on the particles and even the film layer, improve the internal cohesion of the film layer, reduce film layer powdering and active material shedding phenomena, and improve the cycling life of the battery.

[0159] 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 tested 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 this 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., the agglomeration region of the conductive agent often presents a black agglomerated shape compared to other regions in the positive electrode film layer. At a high magnification, the aggregated conductive agent can be seen. The agglomeration region of the conductive agent refers to the range of the region that appears black where the conductive agent is significantly aggregated in the scanning electron microscope image. With the help of image analysis software, such as ImageJ, count the area of the white marked regions in the image, and select the regions where Feret is greater than or equal to 2 μm. The sum of the areas of the above regions is the total area of the agglomeration region of the conductive agent in this scanning electron microscope image. The area ratio of the agglomeration region of the conductive agent is characterized by dividing the total area of the agglomeration region of the conductive agent obtained by testing in the scanning electron microscope image at a magnification of 3k times by the area of the scanning electron microscope image. Randomly select 3 non-overlapping scanning electron microscope images and calculate the average value as "the total 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".

[0160] 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. Optionally, the conductive agent further includes conductive carbon black.

[0161] Carbon nanotubes have the characteristic of a high aspect ratio, which is conducive to bridging particles of different particle sizes through their unique fiber structure in the thickness direction, forming a long-range conductive path while improving the binding force between particles, reducing local polarization and even lithium plating problems generated during the cycling of the battery, and improving the cycle life of the battery; and can also reduce the rebound phenomenon of large particles in the positive electrode film layer through the binding effect, and reduce the shedding phenomenon of active substances in the film layer.

[0162] Conductive carbon black tightly coats the surface of the positive electrode active particles through its nano-scale size characteristics, forming a high-density dot-like conductive contact. By using it in combination with carbon nanotubes, both long-range conduction and short-range conduction are taken into account, further improving the conductive network in the positive electrode film layer. The high specific surface area of conductive carbon black greatly improves the electrolyte adsorption capacity, effectively alleviating the electrolyte consumption during the cycling process; the mechanical toughness of carbon nanotubes can buffer the expansion stress of the electrode sheet; the synergistic effect of the two can reduce the electrolyte extrusion phenomenon caused by the high growth rate of the expansion force during long cycling of the electrode sheet, and improve the long cycle life of the battery.

[0163] In some embodiments, the agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0164] Researchers found that due to their 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 energy of conductive carbon black is relatively close to that of carbon nanotubes, which can adsorb on the surface of carbon nanotubes to form a physical barrier, increase the resistance to carbon nanotube agglomeration, reduce the direct contact between carbon nanotubes, thereby inhibiting the agglomeration phenomenon and improving the distribution uniformity of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the 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, reduce the risk of the positive electrode film layer peeling off, and further improve the kinetic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the agglomeration area of the conductive agent will also cause blockage of the local ion transport path in the conductive agent agglomeration area. The combination of conductive carbon black can improve the lithium ion transport ability in this area, reduce local polarization, and further improve the cycle stability of the battery.

[0165] 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%.

[0166] In some embodiments, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes can be selected as 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 the numerical range between any two of them.

[0167] In some embodiments, based on the mass of the positive electrode film layer, the mass content C2 of conductive carbon black can be selected as 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 the numerical range between any two of them.

[0168] 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 the stress concentration in the positive electrode film layer, increasing the liquid retention rate of the positive electrode film layer during long-term cycling, further reducing the risk of the electrode film layer peeling off and the degree of polarization, improving the kinetic performance of the battery and the cycle life of the battery.

[0169] In some embodiments, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber (HNBR).

[0170] The polar groups (such as cyano group, -CN) in the HNBR molecule can interact with the hydroxyl groups (-OH) or metal oxide sites on the surface of the lithium-containing transition metal phosphate particles (such as hydrogen bonding, dipole interaction), enhancing the compatibility between the particles and the solvent, reducing the interfacial tension between the particles and the solvent, and having a more obvious improvement on the interfacial tension of large particles, making it easier for large and small particles in the film layer to be evenly dispersed, reducing particle aggregation caused by hydrophobicity, improving the dispersion of large particles in the positive electrode film layer, and reducing stress concentration generated during the die-cutting process of the film layer.

[0171] Meanwhile, when the slurry is dried into a film, the elastic network structure of HNBR can buffer the shrinkage stress generated by solvent evaporation, 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, the uniform distribution of the conductive agent is conducive to suppressing the rebound of large particles, forming a mechanical restraint on the particles and even the film layer, improving the cohesion of the film layer, reducing the phenomena of film layer powder falling and active material shedding, and improving the cycle life of the battery.

[0172] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0173] 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%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the numerical range between any two of them.

[0174] 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, and the battery has good capacity and cycle performance.

[0175] 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 a polyvinylidene fluoride polymer.

[0176] In some embodiments, the thickness of the bottom coating is 0.5 μm - 5 μm.

[0177] 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 the numerical range between any two of them.

[0178] 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 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.

[0179] In some embodiments, 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 greater than or equal to 0.95 and less than or equal to 1.20; wherein, 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 .

[0180] In the present application, 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 (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 its surface or the cross-section along the thickness direction of the electrode is surface-scanned. The scanning area is 45 μm×45 μm, which is divided into 10×10 grids. The grid vertices are used 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.

[0181] The positive electrode film layer in the present application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery. The surface of the positive electrode film layer disassembled from a battery inevitably has residual electrolyte salt particles. In order 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 to characterize the graphitization degree of the positive electrode film layer.

[0182] The graphitization degree C value of the positive electrode film layer is obtained from 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 of carbon, where disorder means that the carbon atoms in the structure are arranged without a regular pattern.

[0183] 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.

[0184] 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.

[0185] In some embodiments, 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 can be optionally 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 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.

[0186] 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 Within the above range, the compaction density of the electrode sheet can be further improved by relying on the slip of the particles, without relying too much on the ratio of large and small particles in the positive electrode film layer, making the area ratios of large and small particles within a suitable range, which is beneficial to reducing the probability of the positive electrode film layer falling off while avoiding too large resistance of the positive electrode film layer, and helps to improve the cycle performance and kinetic performance of the battery on the basis of maintaining the battery capacity.

[0187] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include the components represented by 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.

[0188] In some embodiments, m can be selected as 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 any value range between any two of them; x can be selected as 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or any value range between any two of them; y can be selected as 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or any value range between any two of them; j can be selected as 3.5, 3.6, 3.7, 3.8, 3.9, 4 or any value range between any two of them; q can be selected as 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or any value range between any two of them.

[0189] In some embodiments, the lithium-containing transition metal phosphate particles include titanium element. Based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of the titanium element is 500 ppm - 8000 ppm, and can be optionally 1000 ppm - 3000 ppm.

[0190] In some embodiments, the titanium element is uniformly distributed in the lithium-containing transition metal phosphate particles.

[0191] 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, the inductively coupled plasma emission spectrometry is used to test the titanium element and its content with reference to Appendix C of GB / T 33822 - 2017.

[0192] When the titanium element is doped into the lithium-containing transition metal phosphate particles, the formed Ti - O - P bond has a strong bonding effect. By anchoring the phosphate groups, it reduces the shrinkage / expansion amplitude of the lattice during lithium ion deintercalation / insertion, thereby inhibiting the structural stress caused by phase change, which is beneficial to improving the cycle life of the battery; and the Ti - O - P bond can provide a more stable channel for lithium ion diffusion, reducing the migration energy barrier, which is beneficial to improving the kinetic performance of the battery.

[0193] The mass content of the titanium element within the above range is beneficial to improving the lithium ion transmission rate of the positive electrode active material, reducing the risk of lithium deposition, and improving the kinetic performance of the battery.

[0194] 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 optionally 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm or the numerical range between any two of them.

[0195] In some embodiments, the lithium-containing transition metal phosphate particles include vanadium element. 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 can be optionally 500 ppm - 3000 ppm.

[0196] In some embodiments, the vanadium element is uniformly distributed in the lithium-containing transition metal phosphate particles.

[0197] When vanadium element is doped into the lithium-containing transition metal phosphate particles, it has multivalent characteristics. When +5 valence vanadium (V 5+ ) is doped into the phosphorus site, due to its larger radius, it will introduce lattice distortion, expand the lithium ion diffusion channel, and improve the ionic conductivity of the positive electrode active material; when +3 valence vanadium (V 3+ ) is doped into the transition metal site, it compensates the charge through lithium vacancies or interstitial oxygen to form defect energy levels, and improves the electronic conductivity of the positive electrode active material.

[0198] The mass content of vanadium element within the above range is beneficial to improving the lithium ion transmission rate of the positive electrode active material, improving the electronic conductivity of the positive electrode active material, and further improving the kinetic performance of the battery through the synergistic effect with titanium element doping.

[0199] 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 vanadium element can be optionally 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm or the numerical range between any two of them.

[0200] 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 fluorophosphate, lithium manganese iron phosphate and their modified materials.

[0201] 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, coated modified materials.

[0202] In some embodiments, the porosity of the positive electrode film layer is 14% - 28%.

[0203] The porosity of the positive electrode film layer can be tested in the following manner. Import the scanning electron microscope image of the cross-section of the positive electrode film layer obtained in the manner described above along the thickness direction of the electrode 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. Then, in sequence, select "Image" - "Adjust" - "Threshold", and set 0 and 100 in the "Threshold" box selection position in turn. Then the pore data in the cross-section electron microscope image can be exported using the Analyze - Measure function. Use "Image" - "Overlay" - "Flatten" to export and 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.

[0204] 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 picture color difference and threshold. This "pore" is not the pore data obtained from the exhaust test, and is mainly used to characterize the cross-sectional area 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 also related to the pores in the carbon material on the surface of the lithium iron phosphate particles, thus unable to objectively reflect the pores between particles.

[0205] The porosity of the positive electrode film layer within the above range means that the size particle grading in the positive electrode film layer is better, which is beneficial to improving the liquid retention characteristics of the electrolyte, improving the ion diffusivity of the positive electrode film layer with large particles having a certain area ratio, and improving the kinetic performance of the battery.

[0206] In some embodiments, the porosity of the positive electrode film layer can be selected from 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or the numerical range between any two of them.

[0207] In some embodiments, the resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

[0208] The resistivity of the positive electrode film layer can be tested by the following method. Specifically: use a resistance tester (Suzhou Lidian) to test under the standard pressure condition of 25 MPa. When testing, randomly select 8 test points on the film layer of the positive electrode plate, keep the pressure for 15 s at each test point to obtain the resistivity of this test point; take the average value of the 8 resistivities as the resistivity of the positive electrode film layer.

[0209] In some embodiments, the resistivity of the positive electrode film layer can be selected from 10 Ω·cm, 11 Ω·cm, 12 Ω·cm, 13 Ω·cm, 14 Ω·cm, 15 Ω·cm, 16 Ω·cm, 17 Ω·cm, 18 Ω·cm, 19 Ω·cm, 20 Ω·cm, 21 Ω·cm, 22 Ω·cm, 23 Ω·cm, 24 Ω·cm, 25 Ω·cm, 26 Ω·cm, 27 Ω·cm, 28 Ω·cm, 29 Ω·cm, 29.72 Ω·cm, 29.88 Ω·cm, 30 Ω·cm, 30.55 Ω·cm, 30.73 Ω·cm, 31 Ω·cm, 31.5 Ω·cm, 32 Ω·cm, 32.2 Ω·cm, 33 Ω·cm, 33.67 Ω·cm, 34 Ω·cm, 34.98 Ω·cm, 35 Ω·cm or the numerical range between any two of them.

[0210] When the resistivity of the positive electrode film layer is within a suitable range, it is beneficial to reduce the electron transfer impedance, reduce the charge-discharge polarization, and improve the kinetic performance of the battery.

[0211] In some embodiments, as Figure 1 shown, the battery cell further includes a separator 20 disposed between the positive electrode plate and the negative electrode plate. The separator 20 includes a base film 201, ceramic layers 202 disposed on both sides of the base film 201, and an adhesive layer 203 disposed on the side of at least one of the ceramic layers 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 polymer.

[0212] In some embodiments, the polyvinylidene fluoride polymer includes a polyvinylidene fluoride homopolymer (PVDF) and a copolymer of polyvinylidene fluoride and other monomers. For example, a copolymer of polyvinylidene fluoride and hexafluoropropylene.

[0213] AsFigure 2 As shown, in the prior art, aqueous PVDF is often used as the bonding layer of the diaphragm, which often presents an island structure in the diaphragm. On the one hand, this is beneficial for providing gaps for the expansion of the battery cell, and on the other hand, it is easy to manufacture; however, such a diaphragm bonding layer has a low bonding area and weak bonding force.

[0214] like Figure 3 As shown, it is a schematic diagram of the surface morphology of the bonding layer 203 of the diaphragm of the embodiment of the present application. The bonding layer of the diaphragm of the embodiment of the present application has a certain pore structure in its continuous structure, and the ceramic layer arranged between the base film and the bonding layer can be observed through the pore structure. It can be understood that when a continuous layer with a porous structure is used as a bonding layer, it may become a block due to contact with the positive electrode sheet or the negative electrode sheet or force extrusion during the manufacturing or circulation of the electrode sheet. The continuous layer referred to in this application does not require that the bonding layer is continuous throughout the battery; but refers to a continuous layer of a uniform porous structure at the microscopic level, such as when observed under a microscope, rather than an island structure. In order to feedback the true morphology of the diaphragm, during the sampling process, it is preferred to sample in the area where the diaphragm bonding layer in the battery has less bonding with the positive electrode sheet or the negative electrode sheet. As an example, sampling is performed at the diaphragm position where the projection exceeds the positive electrode sheet and the negative electrode sheet; or sampling is performed at the diaphragm near the surface of the electrode assembly. The diaphragm sampled in this way can better reflect the true state of the diaphragm.

[0215] The diaphragm provided in the embodiment of the present application uses a continuous layer of a porous structure as a bonding layer, which has a larger bonding area than the island-shaped bonding layer in the prior art, so that the bonding between the diaphragm and the positive electrode film layer is more firmly and evenly, and at the same time, with the help of the pore structure in the bonding layer, it can have both the transmission efficiency of lithium ions and the dynamic performance of the battery. At the same time, compared with the wound battery, the laminated battery has a smaller pressing force between the pole pieces during the preparation of the battery, and the lithium-containing transition metal phosphate particles with a particle size greater than or equal to 1 μm will reduce the compactness of the internal components of the battery during the rebound process, increase the impedance of the battery, and increase the probability of the film layer falling off or even falling off. The diaphragm provided in the embodiment of the present application uses a continuous layer of a porous structure as a bonding layer, which is particularly suitable for laminated batteries, improves the rebound phenomenon of laminated batteries during long cycles, and improves the retention of battery capacity during long cycles. In addition, the laminated battery is prone to relative displacement between the pole piece and the diaphragm in the process of dragging the outer pole piece and welding the pole ear, which makes the film layer prone to falling off, and even the positive and negative poles overlap each other, resulting in the risk of internal short circuit.

[0216] The embodiment of the present application uses a continuous layer of a porous structure as a bonding layer to improve the bonding force between the diaphragm and the electrode while maintaining the air permeability and porosity of the diaphragm, thereby improving the stability of the electrode, further reducing the risk of powder shedding and even internal short circuit due to relative displacement between the electrode and the diaphragm, and improving the cycle stability of the battery.

[0217] In some embodiments, such as Figure 4 shown, the battery cell 5 includes a housing 50, the laminated battery cell is accommodated in the housing 50, the size of the housing 50 in the length direction (X direction) is L0, the size of the housing in the width direction (Y direction) is W0, and the size of the housing in the thickness direction (Z direction) is H0, 450mm ≤ L0 ≤ 1300mm, 100mm ≤ W0 ≤ 150mm; 14mm ≤ H0 ≤ 22mm.

[0218] When the housing size of the battery cell in the embodiment of the present application is within the above range, it is beneficial for the battery to achieve better capacity.

[0219] In some embodiments, L0 can be selected as 450mm, 460mm, 470mm, 480mm, 490mm, 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 600mm, 610mm, 620mm, 630mm, 640mm, 650mm, 660mm, 670mm, 680mm, 690mm, 700mm, 710mm, 720mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm, 1250mm, 1300mm or the numerical range between any two of them.

[0220] In some embodiments, W0 can be selected as 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or the numerical range between any two of them.

[0221] In some embodiments, H0 can be selected as 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm or the numerical range between any two of them.

[0222] In some embodiments, the size L0 of the housing in the length direction satisfies: 450mm ≤ L0 ≤ 650mm.

[0223] When the size L0 of the housing in the length direction satisfies: 450mm ≤ L0 ≤ 650mm, the battery cell has a shorter length, which is beneficial to shortening the electron transmission path, reducing the internal resistance of the battery, while reducing the wetting distance of the electrolyte in the pores of the electrode, improving the wetting uniformity, and improving the kinetic performance of the battery; especially under fast charging conditions, it can reduce the uneven temperature rise and uneven current density in the length direction of the electrode sheet.

[0224] In some embodiments, the dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

[0225] When the dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm, the significantly increased monomer size can effectively simplify the traditional module structure, realize the direct integration of the single battery into the battery pack, fix the battery through the structural member arranged at the end of the large surface, significantly improve the space utilization rate, thereby increase the overall capacity of the battery system under the same volume, reduce the number of structural members at the same time, improve the battery energy density, and further improve the capacity of the battery.

[0226] In some embodiments, such 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.

[0227] The soft-pack material has a high elongation rate, and its housing is thin, light, and soft, which helps to improve the space utilization rate of the battery monomer, thereby improving the energy density of the battery monomer; however, the soft-pack material such as the aluminum-plastic composite film has poor thermal conductivity, resulting in low heat dissipation efficiency of the soft-pack battery. Therefore, if the area ratio of small particles in the positive electrode film layer is too large, it will increase the resistivity of the positive electrode film layer, resulting in excessive heat generation during the battery cycle and exacerbating the heat dissipation problem of the soft-pack battery. In the embodiments of the present application, by using the soft-pack material as the housing and controlling the area ratio of small particles in the positive electrode film layer within a suitable range, the battery has high capacity and good cycle performance.

[0228] 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 arranged at at least one end of the stacked electrode assembly extending in the width direction (Y direction); the first sealing area 51 includes a folded-edge structure extending in the length direction (X direction), and an encapsulation adhesive is arranged on the folded-edge structure, and the encapsulation adhesive is continuously arranged in the length direction (X direction) and fixes the folded-edge structure.

[0229] The folded-edge structure refers to a strengthened structure formed by folding the encapsulation area, and the number of folding times is not limited. As an example, it can be a single-folded-edge structure folded once, or a double-folded-edge structure folded on both sides.

[0230] During the cycling of the electrode sheet, the SEI film will thicken. Therefore, large rebound and gas generation will occur during long 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 rebound 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, realizes the continuous reinforcement in the length direction of the sealing area, and reduces the probability of the pole piece punching open the sealing area in the package during cycling.

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

[0233] It can be understood that the positive tab and the negative tab can be arranged on the same side of the stacked electrode assembly, as Figure 4 shown; they can also be arranged on different sides of the stacked electrode assembly.

[0234] In some embodiments, the battery cell 5 further includes a lead-out member 53, 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, at least 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 between the battery cell 5 and 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 lead-out member and a negative lead-out member, the positive lead-out member is connected to the positive tab, and the negative lead-out member is connected to the negative tab.

[0236] 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 realize the directional pressure relief of the battery, reduce the influence on adjacent battery cells during thermal runaway, and improve 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 electrode assembly, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

[0238] The spaced arrangement of the rubber rings surrounding along the width direction of the battery cell in the length direction is beneficial to fixing the positions of the pole pieces in the battery cell, reducing the probability of the battery cell displacement during the battery shaking, especially suitable for batteries with a relatively large length, and can effectively reduce the mutual displacement of the pole pieces in the length direction, thereby causing lithium deposition 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 100 Ah - 300 Ah, optionally 110 Ah - 190 Ah, and further optionally 125 Ah - 180 Ah.

[0240] 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, it is charged at a charging rate of 0.5C of the nominal capacity of the battery cell to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, left standing for 10 min, 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.

[0241] In some embodiments, at 25 °C, the capacity of the battery cell can be optionally 100 Ah, 125 Ah, 130 Ah, 135 Ah, 140 Ah, 145 Ah, 150 Ah, 155 Ah, 160 Ah, 165 Ah, 170 Ah, 175 Ah, 180 Ah, 185 Ah, 190 Ah, 300 Ah or the numerical range between any two of them.

[0242] The battery cell of the embodiment of the present application has a suitable housing size to accommodate the stacked electrode assembly, controls the reasonable proportion of large particles in the film layer of the positive electrode sheet in the stacked electrode assembly, and the battery cell has a high capacity.

[0243] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can 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 current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can 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 can 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 can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0246] In some embodiments, the negative electrode film layer may further 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 further optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0248] In some embodiments, the negative electrode plate can be prepared by the following method: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, the conductive agent, the 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 cell provided by 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, the electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0251] In addition, the present application also provides an electrical device using the battery device as a power source. The electrical device includes at least one of the battery cell, the battery module, or the battery pack provided by the present application. The battery cell, the battery module, or the battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device.

[0252] As the electrical device, the battery cell, the battery module, or the battery pack can be selected according to its usage requirements.

[0253] Figure 5 It 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 arranged 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 may further include a controller and a motor, and 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.

[0254] The embodiments of the present application further provide an energy storage device using a battery device as a power source. The energy storage device can be, but is 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.

[0255] 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 to the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0256] Embodiment 1 (1) Preparation of the positive electrode active material Lithium carbonate, iron phosphate, titanium dioxide, vanadium pentoxide, sucrose, glucose and polyethylene glycol are added to deionized water and mixed in a premixing tank. Among them, the ratio of lithium carbonate to iron phosphate is such that the molar ratio of lithium to iron is 1.02:1.0. Based on the total mass of the mixed raw materials, the mass content of sucrose is 2%, the mass content of glucose is 4%, and the mass content of polyethylene glycol is 5%. After mixing evenly, a mixed raw material with a solid content of 38% is obtained; Among them, the particle size Dv of lithium carbonate 50 is 6 μm; the morphology of the iron phosphate particles is spherical-like; both titanium dioxide and vanadium pentoxide are nanoparticles; the purity of sucrose ≥ 98%; the mass content of water in glucose < 0.5%; the weight average molecular weight of polyethylene glycol is 1500.

[0257] The mixed raw materials are ground twice in a sand mill. After coarse grinding for 1 h, fine grinding is carried out. During the grinding process, the temperature of the slurry is controlled to be less than 40 °C to obtain a mixed slurry; the particle size Dv50 of the solid particles in the mixed slurry is 0.40 μm, and spray drying is carried out to obtain a dried precursor powder, and its particle size Dv50 after drying is 55.50 μm.

[0258] The precursor powder is subjected to two-stage temperature-raising sintering in a nitrogen atmosphere to obtain a cathode active material: heating from 25 °C to 460 °C at a heating rate of 2 °C / min (the first heating stage) and holding for 3 h; heating from 460 °C to 780 °C at a heating rate of 5 °C / min (the second heating stage) and holding for 12 h; wherein, the ventilation volume in the heating stage is greater than that in the constant temperature stage, and the ratio is 1.5:1, and the total ventilation volume is 1350 cm 3 / h, and then cooling after completion; airflow crushing is carried out to obtain a lithium iron phosphate cathode active material with a surface having carbon material and a particle size Dv50 of 1.6 μm. Among them, based on the total mass of the cathode active material, the mass content of Ti element is 1050 ppm, and the mass content of V element is 950 ppm.

[0259] The above Dv10, Dv50, and Dv90 refer to the data obtained by testing with the Malvern laser scattering method.

[0260] (2)Preparation of the cathode electrode Mix 93.9% by mass of the above cathode active material, 2% by mass of a conductive agent, and 3% by mass of a binder polyvinylidene fluoride in a solvent N-methylpyrrolidone, and then add 1.1% by mass of a dispersant HNBR, and mix well in a stirring tank, stir and disperse to prepare a cathode slurry; after completing the stirring process, transfer the cathode slurry to the coating process; wherein, the mass ratios of the cathode active material, the conductive agent, the binder, and the dispersant are calculated based on the total mass of the solids in the cathode slurry; the conductive agent includes 1.33% by mass of conductive carbon black and 0.67% by mass of single-walled carbon nanotubes. The specific surface area of the conductive carbon black is 85 m 2 / g, the oil absorption value is 200 ml / 100 g, the average length of the single-walled carbon nanotubes is 30 μm, the specific surface area is 300 m 2 / g, and the mass content of metal impurities in the single-walled carbon nanotubes is <1 wt%; Transfer and coat the cathode slurry onto a current collector aluminum foil and dry it, and after hot pressing, obtain a cathode film layer with a single-sided thickness of 105.64 μm and a tap density of 2.36 g / cm 3 of the cathode electrode. Among them, the transfer coating speed is 20 m / min.

[0261] The hot pressing process includes three hot roller pressing processes. The hot roller pressing pressure increases successively, and the hot roller pressure is 40 tons, 60 tons, and 80 tons respectively; the hot roller temperature is 60°C, and the pole piece is heated before entering the hot roller compaction for the first time, and the heating temperature is 40°C.

[0262] The compaction density here refers to the compaction density of the battery cell when it is fully discharged. The test method is shown below.

[0263] Among them, the median graphitization degree of the positive electrode film is C 50 is 1.005; the porosity of the positive electrode film layer is 16.1%; the iron dissolution rate of the positive electrode material is 974ppm; the total area of ​​the agglomerated region of the conductive agent accounts for 1.99%; in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size greater than or equal to 1μm is 1.85%.

[0264] The positive electrode sheets are stripped and punched into specified shapes, and the punched positive electrode sheets are sorted by weight using a weighing sorting machine for stacking by a stacking machine.

[0265] (3) Preparation of negative electrode sheet Natural graphite, conductive carbon black, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC) are mixed evenly in a weight percentage of 95:1:2:2, and deionized water is added. After stirring and dispersion, a negative electrode slurry is obtained. The negative electrode slurry is coated on a base copper foil, and after drying, compacting, slitting and sheeting, a negative electrode sheet is obtained.

[0266] The negative electrode sheets are stripped and punched into specified shapes, and the punched negative electrode sheets are sorted by weight using a weighing sorting machine for stacking by a stacking machine.

[0267] (4) Diaphragm Dissolve polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP), stir evenly, add polyethylene glycol (PEG) as a pore-forming agent, and stir and mix thoroughly to obtain a bonding layer solution. Apply the bonding layer solution to the base film with ceramic layers on both sides, pre-volatilize at 80°C and dry at 110°C, and then immerse in deionized water to dissolve PEG to obtain a diaphragm with a bonding layer with a porous structure on both sides. The thickness of the base film is 8μm, the thickness of the ceramic layer on one side is 3μm, and the thickness of the bonding layer on one side is 1μm.

[0268] (5) Electrolyte In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were mixed evenly.

[0269] Lithium hexafluorophosphate was further added and dissolved in an 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 is 26%, the mass content of ethyl methyl carbonate is 43.3%, the mass content of ethylene carbonate is 17.3%, and the mass content of vinylene carbonate is 0.9%.

[0271] (6)Preparation of the battery The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence using a laminator. The separator should be able to isolate the positive and negative electrodes to obtain a laminated battery cell. The laminated battery cell was subjected to gluing treatment to tightly wrap the battery cell. The glued laminated battery cell was placed in an outer package, and the outer package was a soft package material, an aluminum-plastic film, which was composed of an inner layer of polypropylene, a middle layer of aluminum foil, and an outer layer of nylon. Among them, the aluminum-plastic film outer package was obtained by punching and trimming with 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 the electrolyte, and sealing, 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 monomer was obtained. The size of the battery monomer 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 2-3 were basically the same as those of Example 1, except that the positive active material and the preparation method of the positive electrode sheet were adjusted, specifically as follows: Example 2 The preparation method of Example 2 was basically the same as that of Example 1, except that there were slight differences in the preparation process of the positive active material and the hot pressing process of the positive electrode sheet. The specific differences included: (1)The carbon source in the mixed raw materials was sucrose and glucose. The mass of sucrose was 2 wt% compared to the mass of iron phosphate, and the mass of glucose was 4 wt% compared to the mass of iron phosphate; (2)The process of heating and sintering was different. The precursor powder was sintered at least twice in a nitrogen atmosphere. The first sintering temperature was 765 °C, and the holding time was 8 hours to obtain a preliminarily sintered product.

[0273] Add 1.5 wt% (based on the mass of the as-fired product) glucose, 3.0 wt% (based on the mass of the as-fired product) polyethylene glycol, titanium dioxide, and vanadium pentoxide to the as-fired product. After grinding evenly, divide it into two groups for secondary grinding. The grinding parameters of the two groups are different, and control the D of the particles after grinding in the first group V of 2.2 μm for D V 50, and the D of the particles after grinding in the second group

[0274] is 0.4 μm for D

[0275] 50. Mix the ground particles of the first group and the second group according to a mass ratio of 30:70, and spray dry, followed by a second sintering. The temperature of the second sintering is 815 °C, and keep it warm for 10 hours. 3 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.

[0276] The hot pressing process includes three hot roll pressing processes, and the hot roll pressing pressure increases successively. The hot roll pressures are 35 tons, 55 tons, and 70 tons in sequence; the hot roll temperature is 65 °C. Before the first entry into the hot roll compaction, heat the electrode sheet, and the heating temperature is 50 °C. Here, the compaction density refers to the compaction density under the full discharge state of the battery cell, and its test method is as follows.

[0277] Example 3 The preparation method of Example 3 is basically the same as that of Example 1, except that there are differences in the sintering process of the positive electrode active material and the hot pressing process of the positive electrode sheet. Specifically: (1) Perform two-stage temperature-raising sintering on the precursor powder in a nitrogen atmosphere to obtain the positive electrode active material: heat from 25 °C to 440 °C at a heating rate of 2 °C / min (the first heating stage), and keep it warm for 2.5 h; heat from 440 °C to 760 °C at a heating rate of 5 °C / min (the second heating stage), and keep it warm for 11 h; then increase the airflow crushing intensity to obtain the lithium iron phosphate positive electrode active material with carbon material on the surface.

[0278] (2) Transfer and coat the positive electrode slurry onto the current collector aluminum foil and dry it. After hot pressing, a positive electrode sheet with a single-sided thickness of the positive electrode film layer of 105.65 μm and a compaction density of 2.36 g / cm 3 is obtained. Among them, the transfer coating speed is 20 m / min.

[0279] The hot pressing process includes three hot rolling processes, with the hot rolling pressure increasing in sequence. The hot rolling pressures are 45 tons, 60 tons, and 80 tons respectively; the hot roller temperature is 60 °C. Before the first entry into hot rolling compaction, the electrode sheet is heated, and the heating temperature is 40 °C.

[0280] The preparation methods of Examples 4-8 are basically the same as that of Example 1, except that the preparation method of the positive electrode sheet is adjusted, specifically as follows: Example 4 The positive electrode slurry of Example 1 was transferred and coated on the current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes, and controlling the coating surface density in the hot pressing process, a positive electrode sheet with a single-sided thickness of 91.88 μm of the positive electrode film layer was obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is as follows. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0281] Example 5 The positive electrode slurry of Example 1 was transferred and coated on the current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes, and controlling the coating surface density in the hot pressing process, a positive electrode sheet with a single-sided thickness of 116.09 μm of the positive electrode film layer was obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is as follows. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0282] Example 6 The positive electrode slurry of Example 1 was transferred and coated on the current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes, and controlling the coating surface density in the hot pressing process, a positive electrode sheet with a single-sided thickness of 72.34 μm of the positive electrode film layer was obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is as follows. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0283] Example 7 The positive electrode slurry of Example 1 was transferred and coated on the current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes, and controlling the coating surface density in the hot pressing process, a positive electrode sheet with a single-sided thickness of 83.91 μm of the positive electrode film layer was obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3。The compaction density here refers to the compaction density of the battery cell under the fully discharged state, and its test method is described below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0284] Example 8 Transfer and coat the positive electrode slurry of Example 1 onto the current collector aluminum foil and dry it. By adjusting the pressure, rolling speed, roll gap, pressure holding time, rolling times in the hot pressing process, and controlling the coating surface density, a positive electrode plate with a unilateral thickness of 98.93 μm of the positive electrode film layer is obtained by hot pressing; the compaction density of the positive electrode plate is 2.52 g / cm 3 。The compaction density here refers to the compaction density of the battery cell under the fully discharged state, and its test method is described below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0285] Example 9 The preparation method of Example 9 is basically the same as that of Example 1, except that the preparation method of the positive electrode active material and the preparation method of the positive electrode plate are adjusted, which are specifically as follows: First, prepare a precursor solution under argon protection. Mix FeSO4·7H2O, LiOH·H2O, and H3PO4 in deionized water, and add 0.5 wt% ascorbic acid as an antioxidant; then adjust the pH to 5.0, and add 0.1 mol / L citric acid as a crystal growth inhibitor and 1 wt% PEG - 4000 as a dispersant. Transfer the mixed solution to a high-pressure reaction kettle and react at 180 °C for 6 hours; after the reaction product is centrifuged and washed, it is dried in vacuum at 80 °C, and finally annealed in an argon atmosphere at 350 °C for 2 hours to obtain lithium iron phosphate material with an average particle size of 160 nm.

[0286] Mix the above-prepared lithium iron phosphate material and the positive electrode active material of Example 1 according to a mass ratio of 10:90 to obtain the positive electrode active material of Example 9.

[0287] Transfer and coat the positive electrode slurry onto the current collector aluminum foil and dry it. By adjusting the pressure, rolling speed, roll gap, pressure holding time, rolling times in the hot pressing process, and controlling the coating surface density, a positive electrode plate with a unilateral thickness of 105.65 μm of the positive electrode film layer is obtained by hot pressing; the compaction density of the positive electrode plate is 2.36 g / cm 3 。The compaction density here refers to the compaction density of the battery cell under the fully discharged state, and its test method is described below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0288] Example 10 The preparation method of Example 10 is basically the same as that of Example 9, except that the preparation method of the positive electrode plate is adjusted, which is specifically as follows: The positive electrode active material of Example 9 was prepared using the same method for preparing the positive electrode sheet as in Example 1, and a positive electrode sheet with a single-sided thickness of 105.65 μm of the positive electrode film layer was obtained; the tap density of the positive electrode sheet was 2.32 g / cm 3 . Here, the tap density refers to the tap density under the fully discharged state of the battery cell, and the test method is as follows.

[0289] The preparation method of Comparative Example 1 was basically the same as that of Example 1, except that the preparation method of the positive electrode active material was adjusted, specifically as follows: Comparative Example 1 The preparation method of Comparative Example 1 was basically the same as that of Example 1, except that the sintering process of the positive electrode active material was different. Specifically: The precursor powder was sintered by two-stage heating in a nitrogen atmosphere to obtain the positive electrode active material: heated from 25 °C to 500 °C at a heating rate of 2 °C / min (the first heating stage) and held for 3.5 h; heated from 500 °C to 800 °C at a heating rate of 5 °C / min (the second heating stage) and held for 13 h; and then the gas flow pulverization intensity was reduced to obtain the lithium iron phosphate positive electrode active material with carbon material on the surface.

[0290] The preparation method of Comparative Example 2 was basically the same as that of Example 1, except that the preparation method of the positive electrode active material was adjusted, specifically as follows: Comparative Example 2 First, a precursor solution was prepared under argon protection. FeSO4·7H2O, LiOH·H2O, and H3PO4 were mixed in deionized water, and 0.5 wt% ascorbic acid was added as an antioxidant; then the pH was adjusted to 5.0, and 0.1 mol / L citric acid was added as a grain growth inhibitor and 1 wt% PEG-4000 as a dispersant. The mixed solution was transferred to a high-pressure reaction kettle and reacted at 180 °C for 6 hours; after the reaction product was centrifuged and washed, it was dried in vacuum at 80 °C, and finally annealed in an argon atmosphere at 350 °C for 2 hours to obtain a lithium iron phosphate material with an average particle size of 160 nm.

[0291] The lithium iron phosphate material prepared above was mixed with the positive electrode active material of Example 1 in a mass ratio of 12:88 to obtain the positive electrode active material of Comparative Example 2.

[0292] It can be understood that the preparation processes of the positive electrode sheets of Example 1, Example 10, and Comparative Example 2 are the same; Example 9 and Example 10 use the same preparation process for the positive electrode active material, and their positive electrode sheet preparation processes are different.

[0293] Test method: 1. Capacity of the battery cell At 25°C, charge at a charging rate of 0.5C based on the nominal capacity of the battery cell until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 1C until 2.5V, let it stand for 10 minutes, and calculate the capacity C during the discharge process through the formula C = I×t, with the unit of Ah.

[0294] 2. The number of cycles corresponding to the capacity attenuation to 85% At 25°C, charge at a charging rate of 0.5C based on the nominal capacity of the battery cell until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 1C until 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 attenuates to 85% of the nominal capacity, which is recorded as the number of cycles @85% SOH.

[0295] Test results Table 1

[0296] It can be seen from the comparison between the examples and the comparative examples that 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 greater than or equal to 1μm is 12% - 50%, and the area ratio of particles with a particle size greater than 50nm and less than or equal to 200nm is 3.0% - 15.0%. When the battery cell is in the full discharge state, the compaction density of the positive electrode sheet is 2.3 g / cm 3 - 2.6 g / cm 3 At this time, while the battery cell maintains good capacity, it alleviates the phenomenon of stress concentration of large particles during the compaction of the electrode sheet. The positive electrode film layer has a lower resistivity, improving the cycle performance and kinetic performance of the battery.

[0297] It can be seen from the comparison between Example 2 and Examples 1 and 3 that 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 greater than or equal to 1μm is 12% - 40%, which is beneficial to further improving the phenomenon of stress concentration of large particles during the compaction of the electrode sheet on the basis of maintaining high capacity of the battery, reducing the probability of film layer loosening and active material shedding, and improving the cycle performance of the battery.

[0298] It can be seen from the comparison between Example 9 and Examples 1 - 3 that 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 greater than 50nm and less than or equal to 200nm is 5% - 10%, which is beneficial to reducing the resistivity of the positive electrode film layer and improving the kinetic performance of the battery on the basis of maintaining high capacity and good cycle performance of the battery.

[0299] As can be seen from the comparison between Example 5 and Examples 1-4, 6-9, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.67-0.75, which further improves the phenomenon of stress concentration of large particles during the compaction of the electrode sheet, reduces the probability of film layer loosening and active material shedding, and improves the cycle performance of the battery.

[0300] As can be seen from the comparison between Examples 6 and 7 and Examples 4 and 5, the single-sided thickness of the positive electrode film layer is 90 μm-120 μm, which is beneficial to further improve the capacity of the battery.

[0301] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes a laminated battery cell, and the laminated battery cell includes a positive electrode tab and a negative electrode tab. The positive electrode tab 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 single-sided thickness of the positive electrode film layer is 70 μm - 120 μm. The positive electrode film layer includes lithium-containing transition metal phosphate particles, and at least part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material. In the cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than or equal to 1 μm is 12% - 50%. In the cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 3.0% - 15.0%. 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 cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 50%.

3. The battery cell according to claim 2, wherein, In the cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than or equal to 1 μm and less than or equal to 5 μm is 12% - 40%.

4. The battery cell according to any one of claims 1 to 3, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the tab, the distribution uniformity of particles with a particle size greater than or equal to 1 μm is 0.2% - 5%.

5. The battery cell according to claim 4, wherein In the cross-section of the positive electrode film layer along the thickness direction of the tab, the distribution uniformity of particles with a particle size greater than or equal to 1 μm is 0.2% - 2%.

6. The battery cell according to any one of claims 1-3, 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 greater than or equal to 1 μm, the median sphericity L A50 is 0.6 - 0.

8.

7. The battery cell according to claim 6, 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 greater than or equal to 1 μm, the median L of the sphericity A50 is 0.65 - 0.

75.

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 greater than or equal to 1 μm, the median value L of the sphericity A50 is 0.67 - 0.

75.

9. The battery cell according to any one of claims 1 to 3, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 15.0%.

10. The battery cell according to claim 9, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the tab, the area ratio of particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0% - 10.0%.

11. The battery cell according to any one of claims 1-3, characterized in that, The single-sided thickness of the positive electrode film layer is 90 μm - 120 μm.

12. The battery cell according to claim 11, wherein, The single-sided thickness of the positive electrode film layer is 100 μm - 120 μm.

13. The battery cell according to any one of claims 1-3, characterized in that, 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 tab, the total area ratio of the agglomeration regions of the conductive agent is 0.2% - 6%.

14. The battery cell according to claim 13, characterized in that, 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 tab, the total area ratio of the agglomeration regions of the conductive agent is 1.5% - 5%.

15. The battery cell according to claim 13, 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.

16. The battery cell according to claim 15, characterized in that, The conductive agent further includes conductive carbon black.

17. The battery cell according to claim 13, characterized in that, The agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

18. The battery cell according to claim 17, wherein, 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%.

19. The battery cell according to any one of claims 1-3, characterized in that, The positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

20. The battery cell according to claim 19, characterized in that, Based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

21. The battery cell according to any one of claims 1-3, characterized in that, The positive electrode film layer is provided with a bottom coating in the bottom region close to the positive electrode 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.

22. The battery cell according to any one of claims 1-3, 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 median C of the graphitization degree 50 is greater than or equal to 0.95 and less than or equal to 1.20; wherein, 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 .

23. The battery cell according to any one of claims 1-3, characterized in that, The lithium-containing transition metal phosphate particles in the positive electrode film layer include components represented by the following general formula: Li m Fe x P y O j Q q Formula I Wherein, 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.

24. The battery cell according to any one of claims 1-3, characterized in that, The lithium-containing transition metal phosphate particles include titanium element. 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.

25. The battery cell according to claim 24, characterized in that, The lithium-containing transition metal phosphate particles include titanium element. 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.

26. The battery cell according to any one of claims 1-3, characterized in that, The lithium-containing transition metal phosphate particles include vanadium element. 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.

27. The battery cell according to claim 26, wherein, The lithium-containing transition metal phosphate particles include vanadium element. 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.

28. The battery cell according to any one of claims 1-3, characterized in that, The porosity of the positive electrode film layer is 14% - 28%.

29. The battery cell according to any one of claims 1-3, characterized in that, The resistivity of the positive electrode film layer is 10 Ω·cm - 35 Ω·cm.

30. The battery cell according to any one of claims 1-3, characterized in that, The battery cell further includes a separator disposed between the positive electrode plate and the negative electrode plate. The separator includes a base film, a ceramic layer disposed on both sides of the base film, and a bonding layer disposed on the side of at least one of the ceramic layers away from the base film. The bonding layer is a continuous layer with a porous structure, and the bonding layer includes a polyvinylidene fluoride polymer.

31. The battery cell according to any one of claims 1-3, characterized in that, The battery cell includes a housing. The stacked electrode core 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. 450 mm ≤ L0 ≤ 1300 mm, 100 mm ≤ W0 ≤ 150 mm, 14 mm ≤ H0 ≤ 22 mm.

32. The battery cell according to claim 31, wherein, The dimension L0 of the housing in the length direction satisfies: 450 mm ≤ L0 ≤ 650 mm.

33. The battery cell according to claim 31, wherein The dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

34. The battery cell according to claim 31, wherein, The housing satisfies at least one of the following conditions: (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 electrode core extending in the width direction; the first sealing area includes a folded edge structure extending in the length direction, and an encapsulation adhesive is disposed on the folded edge structure. The encapsulation adhesive is continuously disposed in the length direction and fixes the folded edge structure; (3) The housing includes at least one second sealing area, which is arranged at at least one end of the laminated battery cell along the length direction of the housing, and the second sealing area is arranged on the tab side of the laminated battery cell.

35. The battery cell according to claim 34, characterized in that, The aluminum-plastic composite film includes a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), polyethylene (PE) and aluminum.

36. The battery cell according to any one of claims 1-3, characterized in that, A plurality of rubber rings surrounding along the width direction are arranged on the outer periphery of the laminated battery cell, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

37. The battery cell according to any one of claims 1-3, characterized in that, At 25 °C, the capacity of the battery monomer is 100 Ah - 300 Ah.

38. The battery cell according to claim 37, wherein At 25 °C, the capacity of the battery monomer is 110 Ah - 190 Ah.

39. The battery cell according to claim 38, wherein, At 25 °C, the capacity of the battery monomer is 125 Ah - 180 Ah.

40. A battery device, characterized in that, It includes the battery monomer according to any one of claims 1-39.

41. An electrical device, characterized in that, The electrical device includes the battery device according to claim 40, and the battery device is used to provide electrical energy.

42. An energy storage device, characterized in that, The energy storage device includes the electrical device according to claim 41, and the electrical device is used to store electrical energy.

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