Battery cell, battery device, power consuming device, and energy storage device

Abstract

The application discloses a battery monomer, a battery device, a power consumption device and an energy storage device. The battery monomer comprises a laminated core, the laminated core 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 a section of the positive pole film layer along the thickness direction of the pole piece, the area proportion of particles with a particle size greater than or equal to 1 mu m is 12%-50%; in the section of the positive pole film layer along the thickness direction of the pole piece, 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%; and the compaction density of the positive pole piece of the battery monomer under a full discharge state is 2.3 g / cm 3 -2.6 g / cm 3 .

Description

[0001] This application claims priority to International Patent Application PCT / CN2025 / 094369 entitled "Battery Cell, Battery Device, Electric Device and Energy Storage Device" filed on May 12, 2025, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of battery cells, and in particular to a battery cell, a battery device, an electric device and an energy storage device. BACKGROUND

[0003] In recent years, battery cells are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0004] With the increasing demand for the endurance mileage and cycle life of electric devices, higher requirements are also placed on the energy density and cycle performance of battery cells. However, it is difficult to simultaneously improve the above-mentioned performances in the prior art, which is a technical problem that needs to be solved in the field. SUMMARY

[0005] The present application is made in view of the above-mentioned problems, and aims to provide a battery cell with high capacity and good cycle performance.

[0006] The first aspect of the present application provides a battery cell, comprising a laminated cell, the laminated cell comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the single-sided thickness of the positive electrode film layer being 70 μm-120 μm; the positive electrode film layer comprises lithium-containing transition metal phosphate particles, at least part of the surface of the lithium-containing transition metal phosphate particles being provided with a carbon material; in the section of the positive electrode film layer along the thickness direction of the sheet, the area ratio of particles with a particle size of 1 μm or more is 12%-50%; in the section of the positive electrode film layer along the thickness direction of the sheet, the area ratio of particles with a particle size of greater than 50 nm and less than or equal to 200 nm is 3.0%-15.0%; the compaction density of the positive electrode sheet under full discharge is 2.3 g / cm 3 -2.6 g / cm 3 .

[0007] Research shows that in order to effectively improve the compaction density of the pole piece, it is necessary to introduce a certain amount of particles with a particle size greater than or equal to 1 μm in 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 in the cross section of the positive electrode film layer along the thickness direction of the pole piece is less than 12% or the area ratio of particles with a particle size of 50 nm-200 nm is less than 3%, the particle gradation will be insufficient, the compaction density will be limited, and the battery capacity will not be effectively improved. When the compaction density of the positive electrode pole piece is less than 2.3 g / cm 3 when the battery is in a full discharge state, the battery not only has difficulty in obtaining ideal capacity performance, but also hinders the formation of electron conduction network and 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 in the cross section of the positive electrode film layer along the thickness direction of the pole piece is greater than 15%, the high area ratio of small particles will increase the internal resistance of the positive electrode film layer, aggravate the heat generation of the battery during the cycle process, 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 pole piece is greater than 50% or the compaction density of the positive electrode pole piece is greater than 2.6 g / cm 3 when the battery is in a full discharge state, the compaction of large particles in the pole piece will produce obvious stress concentration effect, causing problems such as inter-particle contact failure, film layer structure loosening and active material falling off, which will have a negative impact on the cycle performance.

[0008] The embodiments of the present application improve the capacity of the battery by designing and optimizing the particle gradation of the lithium-containing transition metal phosphate positive electrode film layer in the laminated battery structure. At the same time, by reducing the area ratio of large particles and controlling the compaction density of the positive electrode pole piece, the stress concentration of large particles in the pole piece during compaction is improved, the problems of film layer structure loosening and active material falling off are effectively alleviated, and the cycle performance of the battery is improved. Further, by controlling the area ratio of small particles within a suitable range, sufficient particle filling degree is ensured, and the increase of the resistance of the positive electrode film layer caused by excessive small particles is avoided, the heat generation of the battery during the cycle process is reduced, and the dynamic performance and cycle performance of the battery are improved. At the same time, the single-sided thickness of the positive electrode film layer is within the range of 70 μm-120 μm, which is beneficial to improve the capacity of the battery monomer, so that the capacity, cycle performance and dynamic performance of the battery are improved by the coordinated design of the laminated battery and the positive electrode pole piece.

[0009] In any embodiment, 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 pole piece is 12%-50%.

[0010] The area ratio of the particles with a particle size greater than or equal to 1 mu m and less than or equal to 5 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, which is favorable for further improving the phenomenon of film layer loosening and active material falling caused by stress concentration of large particles during electrode sheet compaction on the basis of maintaining high capacity, and improving the cycle performance of the battery.

[0011] In any embodiment, the distribution uniformity of the particles with a particle size greater than or equal to 1 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is 0.2%-5%, which can be 0.2%-2%.

[0012] The distribution uniformity of the particles with a particle size greater than or equal to 1 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is within the appropriate range, and the uniformly distributed large particles can effectively reduce the stress concentration degree of local areas in the film layer, so that the stress in the film layer compaction process is uniformly dispersed in the entire area of the film layer, avoiding the local stress concentration phenomenon caused by particle agglomeration, reducing the probability of film layer falling, and improving the cycle performance of the battery.

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

[0014] The distribution uniformity of the particles with a particle size greater than or equal to 1 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is within the appropriate range, and the uniformly distributed large particles can effectively reduce the stress concentration degree of local areas in the film layer, so that the stress in the film layer compaction process is uniformly dispersed in the entire area of the film layer, avoiding the local stress concentration phenomenon caused by particle agglomeration, reducing the probability of film layer falling, and improving the cycle performance of the battery.

[0015] In any embodiment, the median number L of sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is 0.6-0.8. A50

[0016] The median number L of sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 mu m is within the above range, the large particles have good sphericity, reducing the particle bridging caused by irregular shape of large particles, reducing the void content in the electrode sheet, and reducing the stress concentration caused by irregular large particles, improving the phenomenon of film layer loosening and active material falling, and the battery monomer has high capacity and good cycle performance.

[0017] In any embodiment, the median number L of sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 mu m in the section of the positive electrode film layer along the thickness direction of the electrode sheet is 0.65-0.75. A50

[0018] ​​The median of the sphericity of the particles with a particle size greater than or equal to 1 μm is in the above range, which is conducive to reducing the stress concentration caused by the irregularity of large particles when the electrode sheet is compacted, and improving the phenomenon of film layer loosening and active material falling off.

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

[0020] The median of the sphericity of the particles with a particle size greater than or equal to 1 μm is in the above range, which can further improve the stress concentration caused by large particles when the electrode sheet is compacted, reduce the probability of film layer loosening and active material falling off, and improve the cycle life of the battery cell.

[0021] In any embodiment, in the 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 50 nm and less than or equal to 200 nm is 5.0%-15.0%.

[0022] The area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm is in the above range, the positive electrode film layer has an appropriate amount of small particles, which ensures sufficient particle packing degree, and at the same time avoids the adverse effect of excessive area ratio of small particles on the resistance of the film layer, and improves the kinetic performance of the battery on the basis of good capacity.

[0023] In any embodiment, in the 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 50 nm and less than or equal to 200 nm is 5.0%-10.0%.

[0024] The area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm is in the above range, the positive electrode film layer has a good particle size distribution, which further reduces the resistivity of the positive electrode film layer, and further improves 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 the lithium-containing transition metal phosphate particles is relatively low, and research shows that when the single-sided thickness of the positive electrode film layer is less than 70 μm, the capacity of the battery is difficult to meet market demand. The single-sided thickness of the positive electrode film layer is in the above range, which is conducive 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] The single-sided thickness of the positive electrode film layer is in the above range, which is conducive to further improving the capacity of the battery cell.

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

[0030] Increasing the single-side thickness of the positive electrode film layer is beneficial to improve the capacity of the battery. The applicant found that when the single-side thickness of the positive electrode film layer is greater than or equal to 100 μm, the positive electrode film layer is more likely to have film layer loosening and active material falling off. The embodiments of the present application reduce the area ratio of large particles and reduce the compaction density of the positive electrode film layer, which together improves the stress concentration phenomenon of large particles in the electrode sheet during compaction. At the same time, a proper amount of small particles is added, so that the electrode sheet still has good compaction density on the basis of a certain content of large particles, and the battery has good capacity and cycle performance.

[0031] In any embodiment, the positive electrode film layer further comprises a conductive agent, and the total area ratio of the agglomeration region of the conductive agent is 0.2%-6%, or optionally 1.5%-5%, based on the total area of the section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0032] The total area ratio of the agglomeration region of the conductive agent within the above range based on the total area of the section of the positive electrode film layer along the thickness direction of the electrode sheet indicates that the conductive agent is uniformly dispersed in the positive electrode film layer, which is beneficial to form a uniform conductive network and reduce local polarization and even lithium precipitation problems of the battery during the cycle process.

[0033] At the same time, the small particles of the present application can fill the gaps between large particles as a basic conductive framework, and the dispersed conductive agent agglomerates can act as long-range conduction nodes to form a hierarchical conductive structure. Since the large-size particles in the lithium-containing transition metal phosphate particles are prone to rebound, the agglomeration area of the conductive agent within the above range can also inhibit the rebound of large particles by means of uniform distribution of the conductive agent, mechanically constrain the particles and even the film layer, improve the cohesion of the film layer, reduce the film layer powder falling and active material falling off, and improve the cycle life of the battery.

[0034] In any embodiment, the conductive agent comprises carbon nanotubes, and the carbon nanotubes comprise one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes. Optionally, the conductive agent further comprises conductive carbon black.

[0035] Carbon nanotubes have a high aspect ratio, which is beneficial to bridge particles of different particle sizes in the thickness direction through their unique fiber structure, form long-range conductive paths, and improve the binding force between particles, thereby reducing local polarization and even lithium precipitation problems of the battery during the cycle process and improving the cycle life of the battery. In addition, the carbon nanotubes can reduce the rebound phenomenon of large particles in the positive electrode film layer and the falling off phenomenon of active materials in the film layer through the binding effect.

[0036] The conductive carbon black has a small size, adheres to the surface of the positive electrode particles and fills the gaps between the positive electrode particles to form a dense point-like conductive contact. In combination with the carbon nanotubes, long-range and short-range conduction is taken into account, which is conducive to further improving the conductive network in the positive electrode film layer. At the same time, the conductive agent has a large specific surface area, which is conducive to liquid absorption and liquid retention, can reduce the electrolyte extrusion phenomenon caused by the high growth rate of the expansion force of the electrode sheet in the long cycle process, and improve the long cycle life of the battery.

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

[0038] The researchers found that carbon nanotubes are prone to agglomeration due to their high surface energy, resulting in uneven dispersion in the positive electrode film layer and the inability to form an effective carbon nanotube network structure. The surface energy of the conductive carbon black and the carbon nanotubes is relatively close, and the conductive carbon black can be adsorbed on the surface of the carbon nanotubes to form a physical barrier, increase the resistance of carbon nanotube agglomeration, reduce direct contact between carbon nanotubes, and thus inhibit the agglomeration phenomenon and improve the uniformity of the distribution of carbon nanotubes in the positive electrode film layer. This helps to improve the conductivity of the positive electrode film layer and improve the dynamic performance of the battery. On the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reduces the risk of positive electrode film layer falling off, and further improves the dynamic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the conductive agent agglomeration region also causes the local ion transport path in the conductive agent agglomeration region to be blocked, and the addition of conductive carbon black can improve the lithium ion transport capacity of this region and reduce local polarization, further improving the cycle stability of the battery.

[0039] In any embodiment, the mass content C1 of the carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of the conductive carbon black satisfies: 0 < C1 ≤ 2.5%, based on the mass of the positive electrode film layer.

[0040] The mass content of the carbon nanotubes and the conductive carbon black in the above range can effectively alleviate the agglomeration of the carbon nanotubes and form a good conductive network structure, thereby effectively reducing the stress concentration of the positive electrode film layer and improving the liquid retention rate of the positive electrode film layer in the long cycle process, further reducing the risk of positive electrode film layer falling off and the degree of polarization, and improving the dynamic performance of the battery and the cycle life of the battery.

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

[0042] The polar groups (such as cyano, -CN) in the hydrogenated nitrile rubber HNBR molecule can interact (such as hydrogen bond, dipole interaction) with the hydroxyl (-OH) or metal oxide sites on the surface of the lithium-containing transition metal phosphate particles, thereby enhancing the compatibility of the particles with the solvent, reducing the interfacial tension of the particles with the solvent, and more obviously improving the interfacial tension of large particles, so that the large and small particles in the film layer are more easily uniformly dispersed, the particle aggregation caused by hydrophobicity is reduced, the dispersity of the large particles in the positive electrode film layer is improved, and the stress concentration generated in the die cutting process of the film layer is reduced.

[0043] Meanwhile, during the drying of the slurry into a film, the elastic network structure of the HNBR can buffer the shrinkage stress generated due to solvent evaporation, reduce the re-aggregation of the conductive agent in this process due to capillary force, reduce the area ratio of the conductive agent aggregation area, and the uniform distribution of the conductive agent is beneficial to inhibit the rebound of large particles, mechanically bind the particles and even the film layer, improve the cohesion of the film layer, reduce the phenomenon of film layer powder falling and active material falling, and improve the cycle life of the battery.

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

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

[0046] In any embodiment, the positive electrode film layer is provided with a primer layer at the bottom region close to the positive electrode current collector, the primer layer comprises a conductive agent and a binder, the conductive agent comprises carbon nanotubes and conductive carbon black, and the binder comprises a vinylidene fluoride polymer.

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

[0048] The primer layer provided by the embodiments of the present application helps to improve the adhesion of the positive electrode film layer to the positive electrode current collector and relieve the stress concentration phenomenon at the large particles, thereby reducing the probability of positive electrode film layer falling 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 primer layer and the positive electrode film layer is increased, which helps to increase the area of electron transmission 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 by the positive electrode film layer under the face scanning mode of the laser microscopic confocal Raman spectrometer, the median number C of the graphitization degree is greater than 0.95 and less than or equal to 1.20. 50 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 I D represents the intensity of the D peak of the Raman spectrum at 1350±100 cm -1 I

[0050] In the cumulative distribution curve of the graphitization degree C value of the positive electrode film layer obtained by the laser microscopic confocal Raman spectrometer in the face scanning mode, the median number C 50 The compaction density of the electrode sheet can be further improved by relying on the slippage of the particles within the above range, and it is not necessary to excessively rely on the ratio of large particles and small particles in the positive electrode film layer, so that the area ratio of large particles and small particles is within a suitable range, which is beneficial to reducing the probability of positive electrode film layer falling off while avoiding excessive resistance of the positive electrode film layer, and is helpful to improving the cycle performance and dynamic performance of the battery on the basis of maintaining the battery capacity.

[0051] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise a component represented by the following general formula: Li m Fe x P y O j Q q Formula I, wherein Q comprises one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, 0≤q≤0.1.

[0052] In any embodiment, the lithium-containing transition metal phosphate particles comprise titanium element, and the mass content of the titanium element is 500 ppm-8000 ppm, which can be optionally 1000 ppm-3000 ppm, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0053] When the titanium element is doped into the lithium-containing transition metal phosphate particles, the Ti-O-P bond formed by the titanium element has strong bonding effect, which reduces the shrinkage / expansion amplitude of the lattice when lithium ions are deintercalated, thereby inhibiting the structural stress caused by phase transition, and 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, thereby reducing the migration energy barrier and being beneficial to improving the dynamic performance of the battery.

[0054] 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 precipitation, and improving the dynamic performance of the battery.

[0055] In any embodiment, the lithium-containing transition metal phosphate particles include vanadium element, and the mass content of the vanadium element is 500-5000 ppm, optionally 500-3000 ppm, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0056] When the vanadium element is doped into the lithium-containing transition metal phosphate particles, it has the characteristics of multiple valence states. When +5 valence vanadium (V 5+ ) is doped into the phosphorus site, it will introduce lattice distortion and expand the lithium ion diffusion channel, thereby improving 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 by lithium vacancies or interstitial oxygen, thereby forming a defect energy level and improving the electronic conductivity of the positive electrode active material.

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

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

[0059] The porosity of the positive electrode film layer in the above range means that the particle size distribution in the positive electrode film layer is good, and it is beneficial to improve the liquid retention properties of the electrolyte, improve the ion diffusion of the positive electrode film layer with large particles having a certain area ratio, and improve the kinetic performance of the battery.

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

[0061] The resistivity of the positive electrode film layer in the appropriate range is beneficial to reduce the electronic transmission impedance, reduce the charge and discharge polarization, and improve the kinetic performance of the battery.

[0062] In any embodiment, the battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet, the separator includes a base film, ceramic layers disposed on both sides of the base film, and a bonding layer disposed on the side of the ceramic layer away from the base film, the bonding layer is a continuous layer of porous structure, and the bonding layer includes a vinylidene fluoride polymer.

[0063] The diaphragm provided by the embodiments of the present application takes a continuous layer with a porous structure as a bonding layer, has a larger bonding area compared to the island-shaped bonding layer in the prior art, thereby making the bonding of the diaphragm and the positive electrode film layer more firm and uniform, and at the same time, with the aid of the pore structure in the bonding layer, the transmission efficiency of lithium ions can be achieved, and the kinetic performance of the battery is considered. At the same time, the pressure between the pole pieces during the preparation process of the stacked cell is smaller than that of the wound cell, and the lithium-containing transition metal phosphate particles with a particle size greater than or equal to 1 μm will reduce the tightness of the internal components of the battery during the rebound process, increase the impedance of the battery, and increase the probability of film layer powder falling off or even falling off. The diaphragm provided by the embodiments of the present application takes a continuous layer with a porous structure as a bonding layer, which is especially suitable for stacked cells, improves the rebound phenomenon of the stacked cell during long cycle, and improves the capacity retention of the battery during long cycle.

[0064] The embodiments of the present application take a continuous layer with a porous structure as a bonding layer, improve the bonding force between the diaphragm and the pole piece while maintaining the air permeability and porosity of the diaphragm, improve the stability of the pole piece, further reduce the risk of powder falling off due to the relative displacement of the pole piece and the diaphragm, and even the risk of internal short circuit, and improve the cycle stability of the battery.

[0065] In any embodiment, the battery monomer includes a shell, the stacked 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, and 14mm≤H0≤22mm.

[0066] The size of the shell of the battery monomer of the embodiments of the present application is in the above range, which is beneficial to the battery to achieve better capacity.

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

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

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

[0070] The size L0 of the shell in the length direction satisfies: 900mm≤L0≤1300mm, the greatly increased monomer size can effectively simplify the traditional module structure, realize direct integration of the monomer battery into the battery pack, realize fixation of the battery through the structural member arranged at the large face end, significantly improve the space utilization, thereby increasing the overall capacity of the battery system under the same volume, while reducing the number of structural members and improving the battery energy density.

[0071] In any embodiment, the material of the shell is a soft package material, and the soft package material includes an aluminum plastic composite film, and optionally, one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) formed into a composite film with aluminum.

[0072] The soft package material has a high ductility, and the shell is light, thin, and soft, which helps to improve the space utilization of the battery monomer and thereby improve the energy density of the battery monomer; however, the soft package material such as the aluminum plastic composite film has poor heat conduction performance, resulting in low heat dissipation efficiency of the soft package battery, and therefore, if the area ratio of the small particles in the positive electrode film layer is too high, the resistivity of the positive electrode film layer will be increased, resulting in excessive heat generation of the battery during the cycle process and aggravating the problem of poor heat dissipation of the soft package battery. The embodiments of the present application use the soft package material as the shell and control the area ratio of the small particles in the positive electrode film layer within a suitable range, so that the battery has high capacity and good cycle performance.

[0073] In any embodiment, the shell includes a first sealing area, and the first sealing area is arranged at at least one end of the jelly-roll battery extending in the width direction; the first sealing area includes a folded edge structure extending in the length direction, and the folded edge structure is provided with encapsulation glue, and the encapsulation glue is continuously arranged and fixed on the folded edge structure in the length direction.

[0074] The embodiments of the present application further improve the sealing strength of the first sealing area by including the folded edge structure extending in the length direction in the first sealing area. The continuous arrangement and fixation of the encapsulation glue on the folded edge structure in the length direction can further improve the encapsulation strength compared to the discontinuous arrangement of the encapsulation glue in the length direction, realize continuous reinforcement of the length direction of the sealing area, and reduce the probability of the pole piece breaking through the sealing area in the package during the cycle process.

[0075] In any embodiment, the shell includes at least one second sealing area, and the second sealing area is arranged at at least one end of the jelly-roll battery extending in the length direction of the shell, and the second sealing area is arranged at the tab side of the jelly-roll battery.

[0076] The second sealing area is arranged at the side of the tab, and the tab needs to be connected with the lead-out piece. The connection strength between the lead-out piece and the shell material is relatively weak, so that the 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 the adjacent battery cells during thermal runaway, and improve the service life of the battery as a whole.

[0077] In any embodiment, the outer periphery of the jelly-roll battery cell is provided with a plurality of glue rings surrounding in the width direction, and the glue rings surrounding in the width direction are arranged at intervals in the length direction.

[0078] The interval arrangement of the glue rings surrounding in the width direction of the battery cell in the length direction is beneficial to fix the position between the jelly-roll sheets in the battery cell, reduce the probability of displacement of the battery cell during battery shaking, and is especially suitable for batteries with large length, which can effectively reduce the mutual displacement of the jelly-roll sheets in the length direction and thus cause lithium precipitation, and is beneficial to maintain the stability of the space structure inside the battery, so as to not affect the normal work of the battery.

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

[0080] The battery cell of the embodiment of the present application has a suitable shell size to accommodate the jelly-roll battery cell, controls the reasonable proportion of large particles in the film layer of the positive jelly-roll sheet in the jelly-roll battery cell, and has a high capacity.

[0081] The second aspect of the present application provides a battery device, which comprises the battery cell provided by the first aspect of the present application.

[0082] The third aspect of the present application provides a power utilization device, which comprises the battery device provided by the second aspect of the present application, and the battery device is used for providing electric energy.

[0083] The fourth aspect of the present application provides an energy storage device, which comprises the battery device provided by the second aspect of the present application, and the battery device is used for storing electric energy. BRIEF DESCRIPTION OF DRAWINGS

[0084] Figure 1 is a schematic diagram of a separator of an embodiment of the present application;

[0085] Figure 2 is a schematic diagram of a separator of the prior art;

[0086] Figure 3 is a surface topography schematic diagram of the adhesive layer of the separator of an embodiment of the present application;

[0087] Figure 4 is a front view of the battery cell of an embodiment of the present application;

[0088] Figure 5 is a schematic view of a power consuming device according to an embodiment of the present application.

[0089] Explanation of Reference Numerals:

[0090] 20 diaphragm; 201 base film; 202 ceramic layer; 203 adhesive layer; 5 battery cell; 50 case; 51 first seal area; 52 second seal area; 53 lead-out; X length direction; Y width direction; Z thickness direction. DETAILED DESCRIPTION

[0091] Hereinafter, embodiments of a battery cell, a battery device, a power consuming device, and an energy storage device according to the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are well known and repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0092] The ranges disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this manner can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0093] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0094] If not otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions shall be considered to be included in the disclosure of the present application.

[0095] If not otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0096] In the present application, the term "plurality" refers to two or more.

[0097] Unless otherwise specified, the terms used in the present application have the commonly understood meanings understood by those skilled in the art.

[0098] Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, the test methods given in the examples of the present application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0099] In the examples of the present application, the battery device can comprise one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can comprise a plurality of soft-pack battery cells connected in series, in parallel or in a mixed connection by a busbar component. For example, the battery cell assembly is usually formed by arranging a plurality of soft-pack battery cells; the battery cell assembly can be a battery module formed by arranging and fixing a plurality of soft-pack battery cells into an independent module. As an example, the battery module can be formed by binding a plurality of battery cells by a cable tie.

[0100] The battery device can be a battery pack comprising a box body and one or more battery cell assemblies 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 soft-pack battery cells in the box body.

[0101] In embodiments of the present application, the case can include a first case and a second case. The first case and the second case are coupled so that an enclosed space is formed inside the case to accommodate the battery cell assembly. The enclosed space herein means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate. For example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively coupled to the frame so that an enclosed space is formed inside the case to accommodate the battery cell assembly.

[0102] In embodiments of the present application, the case can be a part of a chassis structure of a vehicle. For example, a part of the case can be at least a part of a floor of the vehicle, or a part of the case can be at least a part of a cross beam and a longitudinal beam of the vehicle.

[0103] In embodiments of the present application, the battery cell can be a secondary battery, which means a battery cell that can be activated by charging after being discharged, and the battery cell can be a lithium ion battery. The battery cell can be in a flat shape.

[0104] The battery mentioned in embodiments 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 a battery cell, a battery module, or a battery pack, etc.

[0105] The battery cell is the smallest unit that constitutes a battery and can independently perform charging and discharging. When there are a plurality of battery cells, the plurality of battery cells are connected in series, in parallel, or in a mixed manner through a busbar. In some embodiments, the battery can be a battery module; when there are a plurality of battery cells, the plurality of battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack including a case and a battery cell, and the battery cell or the battery module is accommodated in the case. In some embodiments, the case can be a part of a chassis structure of a vehicle. For example, a part of the case can be at least a part of a floor of the vehicle, or a part of the case can be at least a part of a cross beam and a longitudinal beam of the vehicle.

[0106] In some embodiments, the battery can be an energy storage device. The energy storage device can include an energy storage container, an energy storage cabinet, etc.

[0107] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells included in the battery module can be a plurality, and the specific number can be adjusted according to the application and capacity of the battery module. In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0108] The battery cell includes an electrode assembly and an electrolyte.

[0109] The electrode assembly generally includes a positive electrode tab and a negative electrode tab, the negative electrode tab being an electrode in which a reaction of absorbing or lithiating lithium ions during charging and releasing or delithiating lithium during discharging occurs, and the positive electrode tab being an electrode in which a reaction of releasing or delithiating lithium ions during charging and absorbing or lithiating lithium during discharging occurs.

[0110] The lithium-containing transition metal phosphate material has significant advantages over the lithium-containing transition metal oxide material, including higher safety performance, longer cycle life, lower raw material cost, and more excellent high-temperature stability, but such a material also has inherent defects, especially its low theoretical specific capacity, which seriously restricts the improvement of battery capacity. The applicant found that the laminated cell has higher space utilization rate of the internal volume of the battery compared to the wound cell, and the use of the laminated cell is beneficial to improve the volume energy density of the battery, and increasing the content of large and small particles to optimize the particle size distribution of the positive active material can further improve the compaction density of the electrode tab and increase the volume energy density of the battery. However, stress concentration easily occurs at large particles during the compaction of the electrode tab, leading to the failure of the contact between particles, the loosening of the film structure, and even the shedding of the active material; although small particles can fill the gaps to further improve the compaction density of the electrode tab, excessive small particles will increase the resistance of the positive film layer. The laminated cell is more prone to the phenomenon of film layer shedding in the electrode tab caused by stress concentration generated by large particles due to the lack of radial binding force, and the film layer shedding will lead to the decrease of battery capacity, the occurrence of micro-short circuit inside, the aggravation of electrolyte side reactions, and the adverse effects on battery performance. How to obtain a battery with good capacity, cycle performance, and kinetic performance is a technical problem that needs to be solved in the field.

[0111] The first aspect of the present application provides a battery monomer, including a laminated cell, the laminated cell including a positive electrode tab and a negative electrode tab, the positive electrode tab including a positive electrode current collector and a positive film layer arranged on at least one side of the positive electrode current collector, the single-sided thickness of the positive film layer being 70 μm-120 μm; the positive film layer including lithium-containing transition metal phosphate particles, at least part of the surface of the lithium-containing transition metal phosphate particles being provided with a carbon material; in a section of the positive film layer along the thickness direction of the electrode tab, the area ratio of particles with a particle size of 1 μm or more is 12%-50%; in the section of the positive film layer along the thickness direction of the electrode tab, the area ratio of particles with a particle size of 50 nm-200 nm is 3.0%-15.0%; the compaction density of the positive electrode tab of the battery monomer under full discharge is 2.3 g / cm 3 -2.6 g / cm 3 .

[0112] Research shows that in order to effectively improve the compaction density of the pole piece, it is necessary to introduce an appropriate amount of particles with a particle size greater than or equal to 1 μm in the positive electrode film layer. The applicant found that the loss of the compaction density of the pole piece due to the decrease of the content of large particles 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 pole piece is less than 12% or the area ratio of particles with a particle size of 50 nm-200 nm is less than 3%, the particle gradation will be insufficient, the compaction density will be limited, and the effective improvement of the battery capacity will be affected. When the compaction density of the positive electrode pole piece is less than 2.3 g / cm 3 when the compaction density of the positive electrode pole piece is greater than 2.6 g / cm 3 when the compaction density of the positive electrode pole piece is greater than 2.6 g / cm

[0113] The embodiments of the present application improve the capacity of the battery by designing and optimizing the structure of the laminated battery cell and the particle gradation 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 pole piece, the stress concentration of large particles in the pole piece compaction process is improved, the problems of loose film structure and active material falling are effectively alleviated, and the cycle performance of the battery is improved. Further, the area ratio of small particles is controlled within a suitable range, which not only ensures sufficient particle filling degree, but also avoids excessive small particles leading to increased resistance of the positive electrode film layer, reduces the heat generation of the battery during the cycle process, and improves the kinetic performance and cycle performance of the battery. At the same time, the single-sided thickness of the positive electrode film layer is within the range of 70 μm-120 μm, which is beneficial to improve the capacity of the battery monomer. Therefore, by the cooperative design of the laminated battery cell and the positive electrode pole piece, the capacity, cycle performance and kinetic performance of the battery are improved.

[0114] In the present application, the laminated battery cell refers to the battery cell formed by stacking the positive electrode pole piece, the separator and the negative electrode pole piece.

[0115] The lithium-containing transition metal phosphate particles refer to phosphate materials containing lithium elements and transition metal elements, which can be detected by any known manner in the art. For example, they can be detected by X-ray diffractometer (XRD) and energy spectrum analyzer, inductively coupled plasma mass spectrometer.

[0116] 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 simply refer to the positive electrode active material layer, and other film layers connected with the positive electrode active material layer and difficult to distinguish, such as the primer layer, the liquid retaining layer, etc. are collectively referred to as the positive electrode film layer.

[0117] In the present application, the term "particle" refers to a particle having an identifiable complete boundary in the field of view of the positive electrode film layer under a certain magnification, for example, 10 thousand times. Defects and scratches can exist inside the particle, but the complete boundary sufficient to divide the particle cannot be identified inside the particle.

[0118] The particle recognition method is specifically as follows: the positive electrode film layer is cut along the thickness direction of the pole piece by an argon ion beam (as an example, the device model: Leica EM TIC 3X CP, working voltage: 6kV, working time: 6h can be selected), and the cut surface is observed by a scanning electron microscope (as an example, the device model: Hitachi SU8230, working voltage: 3kV, beam current: high, probe model: U (LA100), working distance < 5mm can be selected) after the cut surface is exposed. The cut surface of the positive electrode film layer along the thickness direction of the pole piece is observed by a field emission scanning electron microscope. The image is collected by a secondary electron mode at a non-edge position in the cut surface of the positive electrode film layer (after observing the edge of the pole piece under the scanning electron microscope, the field of view is adjusted to the center part of the sample), and the electron microscope image is taken at a magnification of 10k. The particles in the electron microscope image are analyzed by using ImageJ software (1.46r, win64 version). The use method of the ImageJ software is specifically as follows: the scanning electron microscope image to be analyzed is loaded; the Cellpose plug-in software is used to recognize the particles, and manual correction is performed on this basis; the Image J is used to read and count the data. The specific method of recognizing the particles by using the Cellpose plug-in software is as follows: the Segmantation module diameter parameter is set to 15 pixels, and the particle recognition is performed by clicking "runcyto3"; the particles in the image that are not recognized by the software or not completely recognized by the software or have errors in recognition are manually identified. The particles in the image that are not recognized by the software or not completely recognized by the software or have errors in recognition mainly include the following: 1, due to the fact that the particles are too large or the particles have scratches on the surface, the particles cannot be recognized or cannot be completely recognized; 2, during the cutting process of the argon ion beam, scratches will be generated on the surface of the particles, and the software may misjudge the scratches as the boundaries of the particles during the recognition process, thereby causing recognition errors; 3, due to the fact that the particles are too small, the particles are not successfully recognized; 4, the particles are located at the edge of the electron microscope field of view, the particles are penetrated by the edge, the morphology is not completely displayed, and the local instead of the whole is recognized, thereby causing recognition errors.For the above-mentioned unrecognizable or with recognition error particles, manual calibration is carried out, and the specific process is as follows: deleting the particles located at the edge of the scanning electron microscope, which cannot completely display the large particles; judging whether there is a gap mark in the interior of other unrecognizable or with recognition error particles, if there is no gap mark in the interior of the particles, judging that it is a particle, and manually marking it according to the particle boundary observed by manual observation; in response to the existence of the gap mark in the interior of the particle, judging whether the gap mark penetrates the particle, if not, judging that it is a particle, and manually marking it; in response to the gap mark penetrating the particle, judging whether the gap mark is linear or irregular; in response to the gap mark being irregular, judging that it is the boundary between particles, and dividing the particles along the boundary; in response to the gap mark being linear, carrying out contrast; in response to the contrast being not obvious and having no crack feeling, judging that it is a scratch, and marking it as a particle; in response to the contrast being strong and having crack feeling, judging that it is the boundary between particles, and marking it as two particles. After manual marking, the information irrelevant to the particles in the automatic processing of the image is deleted, that is, the determination and marking of the particles in the picture are completed.

[0119] The area proportion of the particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the pole piece can directly reflect the proportional relationship between the particles in this particle size section and the overall particle area, and reflect the area size of the particles in this particle size section.

[0120] It can be understood that the particles with a particle size greater than or equal to 50 nm in the section of the positive electrode film layer along the thickness direction of the pole piece mainly come from the positive electrode active material. Therefore, the distribution of the lithium-containing transition metal phosphate particles in the positive electrode film layer can be accurately and objectively reflected by observing and counting the particle area in the section of the positive electrode film layer along the thickness direction of the pole piece.

[0121] In the prior art, the particle size of the positive electrode active material is usually counted by a laser particle size analyzer through a Malvern laser diffraction method. However, the research of the applicant shows that the lithium-containing transition metal phosphate particles are easy to agglomerate, and the test results obtained by the Malvern laser diffraction method according to the laser scattering principle are often the particle sizes of the particle agglomerates, and cannot truly reflect the particle size of the particles in the positive electrode active material, and cannot 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 be improved in the processes of slurry preparation 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, and compared with the real dispersion in the pole piece, the number of large particles obtained by the test is lower than the actual value, and the number of small particles is higher than the actual value, so the particle size obtained by the Malvern laser diffraction method cannot be equal to or analogous to the particle size obtained by the counting of the embodiments of the application.

[0122] The area ratio of the particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the pole piece is tested as follows: the particles in the section of the positive electrode film layer along the thickness direction of the pole piece are identified according to the method described above, the picture after the particle identification and marking is imported into the ImageJ software for analysis, the scale is set according to the scanning electron microscope picture, and the particle size, area, sphericity and roughness of the particles in the section of the positive electrode film layer along the thickness direction of the pole piece are statistically analyzed through the analysis functions of “Feret”, “Area”, “Round” and “Solidity”. According to the software manual (ImageJ User Guide IJ 1.46r), the “Feret” parameter obtained in the analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which represents the particle size of the particle; the “Area” parameter obtained represents the pixel area of the particle. Since the particles with a particle size less than 50 nm have a large error 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 a large error in the statistical result, therefore, in the particle size statistical process of the present application, the particles with a particle size less than 50 nm are not counted, and the particle statistical data corresponding to the particles with “NaN” displayed in Area, Round or Solidity are deleted. The sum of the “Area” parameters of the particles with a particle size greater than or equal to 1 μm and the sum of the “Area” parameters of all particles are respectively taken as the area of the particles with a particle size greater than or equal to 1 μm and the total area of the counted particles. The area ratio of the particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the pole piece is calculated by dividing the sum of the areas of the particles with a particle size greater than or equal to 1 μm by the total area of the counted particles.

[0123] In some embodiments, the area ratio of the particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the pole piece 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 numerical range between any two of them.

[0124] In some embodiments, the area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm in the section of the positive electrode film layer along the thickness direction of the pole piece is 3.0%-15.0%.

[0125] The area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm in the section of the positive electrode film layer along the thickness direction of the electrode tab can be obtained by referring to the test method of the area ratio of the particles with a particle size greater than or equal to 1 μm described above.

[0126] In some embodiments, the area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm in the section of the positive electrode film layer along the thickness direction of the electrode tab 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 any numerical range between any two of them.

[0127] Theoretical studies show that, in an ideal case, spherical particles with a diameter of 314 nm can be filled into the gaps formed by the packing of spherical particles with a diameter of 1 μm, so as to improve the particle grading and the compaction density of the electrode tab. The particles with a particle size greater than 50 nm and less than or equal to 200 nm can be closely packed in the gaps between the particles with a particle size greater than or equal to 1 μm, and cooperate with them to achieve dense packing. The area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm in a suitable range is beneficial to improving the compaction density of the positive electrode tab through grading, while avoiding the increase of the internal resistance of the positive electrode film layer caused by the excessive area ratio of small particles, so as to further improve the kinetic performance of the battery while having good capacity.

[0128] In some embodiments, the compaction density of the positive electrode tab of the battery cell in the full discharge state is 2.3 g / cm 3 -2.6 g / cm 3 .

[0129] In this application, the full discharge state refers to the state after the battery is placed in a 25℃ oven environment, and is allowed to stand for 2h, and the battery temperature is maintained at 25℃, and the battery is discharged at 1 / 3C constant current to 2.5V, and then discharged at 0.1C constant current to 2.0V.

[0130] The compaction density of the positive electrode tab can be tested by methods known in the art. As an example, the battery is placed in a 25℃ oven environment, and is allowed to stand for 2h, and the battery temperature is maintained at 25℃, and the battery is discharged at 1 / 3C constant current to 2.5V, and then discharged at 0.1C constant current to 2.0V, the battery is disassembled, the residual electrolyte is treated with dimethyl carbonate solvent, the tab is dried, and a small round piece with an area of S is cut, the mass W1 is obtained, and the thickness T1 of the positive electrode tab is measured using a micrometer, then the positive electrode film layer of the above weighed tab 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 tab is (W1-W2) / [(T1-T2) x S].

[0131] In some embodiments, the compaction density of the positive electrode sheet in the full discharge state 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 any numerical range between any two of the above values.

[0132] In some embodiments, 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 sheet is 12%-50%.

[0133] 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 sheet is within the above range, which is beneficial to further improve the phenomenon of film layer loosening and active material falling off caused by stress concentration of large particles during sheet compaction on the basis of maintaining high capacity, and improve the cycle performance of the battery.

[0134] In some embodiments, 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 section of the positive electrode film layer along the thickness direction of the electrode sheet is 12% to 40%.

[0135] 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 section of the positive electrode film layer along the thickness direction of the electrode sheet within the above range is beneficial to further improving the phenomenon of film layer loosening and active material falling caused by stress concentration of large particles during electrode sheet compaction on the basis of maintaining high capacity, and further improving the cycle performance of the battery.

[0136] In some embodiments, the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the electrode sheet is 0.2% to 5%, which can be 0.2% to 2%.

[0137] The distribution uniformity of particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the electrode sheet can be tested by a method known in the art. As an example, the section of the positive electrode film layer along the thickness direction of the electrode sheet is divided into three layers with equal thickness along the thickness direction of the electrode sheet, which are a lower layer close to the positive electrode current collector, an upper layer away from the positive electrode current collector, and a middle layer between the upper layer and the lower layer; 10 non-overlapping fields are selected in each of the upper layer, the middle layer and the lower layer, and scanning electron microscope images are taken at 10k magnification; the 30 scanning electron microscope images taken are respectively imported into ImageJ software for analysis, and the area percentage of particles with a particle size greater than or equal to 1 μm in the 30 images is tested to obtain 30 values; the range of the 30 values is the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the electrode sheet, wherein the range is the difference between the maximum value and the minimum value in the 30 values. The smaller the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the 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.

[0138] In some embodiments, the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the section of the positive electrode film layer along the thickness direction of the electrode sheet can be 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.

[0139] The uniformity of the distribution of particles with a particle size of 1 μm or more in the 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 in the film layer during compaction is uniformly dispersed throughout the area of the film layer, avoiding the local stress concentration phenomenon caused by particle agglomeration, reducing the probability of film layer shedding, and improving the cycle performance of the battery.

[0140] In some embodiments, in the section of the positive electrode film layer along the thickness direction of the electrode sheet, the median value L of the sphericity in the sphericity area cumulative distribution curve of the particles with a particle size of 1 μm or more is 0.6-0.8. A50

[0141] In the section of the positive electrode film layer along the thickness direction of the electrode sheet, the sphericity test method of the particles with a particle size of 1 μm or more is as follows: referring to the method described above, the particles with a particle size of 1 μm or more in the section of the positive electrode film layer along the thickness direction of the electrode sheet are identified, and the shape of the particles in the section of the positive electrode film layer along the thickness direction of the electrode sheet is analyzed using the "shape description" analysis function in ImageJ. 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 the circle with the fitted long diameter as the diameter, which can be used to characterize the sphericity of the particle. The smaller the particle, the closer the ratio of the pixel area to the area of the circle with the fitted long diameter to 1. Therefore, the "Round" parameter of the particle obtained by analysis is used to characterize the sphericity of the particle. Since the particles with a particle size of less than 50 nm have a large error 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 a large error in the statistical result, therefore, in the particle size statistical process of the present application, particles with a particle size of less than 50 nm are not counted, and the particle statistical data corresponding to the Round display "NaN" are deleted. According to the above method, in order to meet the sample number with statistical significance, not less than 10 non-overlapping scanning electron microscope images are collected for each electrode sheet. The sphericity of at least 1000 particles obtained is arranged in order from small to large, and the sphericity cumulative distribution curve of the particles in the positive electrode film layer is obtained with the sphericity as the horizontal axis and the cumulative area ratio as the vertical axis. A50 is the sphericity L value corresponding to the cumulative area ratio of 50% on the vertical axis of the particle sphericity L value cumulative distribution curve.

[0142] In some embodiments, in the section of the positive electrode film layer along the thickness direction of the electrode sheet, the median value L of the sphericity in the sphericity area cumulative distribution curve of the particles with a particle size of 1 μm or more is 0.6-0.8. A50 ​Optionally 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.705, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80 or any numerical range between any two of them.

[0143] The median of the sphericity of the particles with a particle size greater than or equal to 1 μm is in the above range, and the large particles have better sphericity, reducing particle bridging caused by irregular shapes of large particles, reducing the void content in the electrode, and reducing stress concentration caused by irregular large particles, improving the phenomenon of film layer loosening and active material falling off, and the battery monomer has high capacity and good cycle performance.

[0144] The skilled person can realize the regulation of the sphericity of the particles by any known process. As an example, the regulation of the sphericity of the particles can be realized by processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, adding surfactants, etc., and adjusting the parameters of each process.

[0145] In some embodiments, in the section of the positive electrode film layer along the thickness direction of the electrode sheet, the median L of the sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 μm is 0.65-0.75. A50

[0146] The median of the sphericity of the particles with a particle size greater than or equal to 1 μm is in the above range, which is beneficial to reduce the stress concentration caused by irregular large particles during compaction of the electrode, and improve the phenomenon of film layer loosening and active material falling off.

[0147] In some embodiments, in the section of the positive electrode film layer along the thickness direction of the electrode sheet, the median L of the sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 μm is 0.65-0.75. A50

[0148] The median of the sphericity of the particles with a particle size greater than or equal to 1 μm is in the above range, which is beneficial to reduce the stress concentration caused by irregular large particles during compaction of the electrode, and improve the phenomenon of film layer loosening and active material falling off.

[0149] In some embodiments, the area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0%-15.0%.

[0150] ​​The area ratio of the 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 an appropriate amount of small particles, which ensures sufficient particle filling degree, and at the same time avoids the adverse effect of too large area ratio of small particles on the resistance of the film layer, and the battery improves the kinetic performance of the battery on the basis of good capacity.

[0151] In some embodiments, the area ratio of the particles with a particle size greater than 50 nm and less than or equal to 200 nm is 5.0%-10.0%.

[0152] The area ratio of the 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 a good particle size distribution, which further reduces the resistivity of the positive electrode film layer, and the battery further improves the kinetic performance of the battery on the basis of good capacity.

[0153] In some embodiments, the single-sided thickness of the positive electrode film layer is 70 μm-120 μm.

[0154] The thickness of the positive electrode film layer can be detected by any 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 scanning electron microscopy. Randomly select 3 different positions for measurement, and take the average value as the thickness of the positive electrode film layer.

[0155] 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 numerical range between any two of them.

[0156] The specific capacity of the lithium-containing transition metal phosphate particles is relatively low. Studies have shown that when the single-sided thickness of the positive electrode film layer is less than 70 μm, the capacity of the battery is difficult to meet market demand. The single-sided thickness of the positive electrode film layer in the above range is beneficial to improve the capacity of the battery monomer.

[0157] In some embodiments, the single-sided thickness of the positive electrode film layer is 90 μm-120 μm.

[0158] The single-sided thickness of the positive electrode film layer in the above range is beneficial to further improve the capacity of the battery monomer.

[0159] In some embodiments, the single-sided thickness of the positive electrode film layer is 100 μm-120 μm.

[0160] Increasing the single-sided thickness of the positive electrode film layer is beneficial to improve the capacity of the battery. 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 falling off. The embodiments of the present application reduce the area ratio of large particles and the compaction density of the positive electrode film layer, which together improve the stress concentration phenomenon of large particles in the electrode sheet during compaction. At the same time, a proper amount of small particles is added, so that the electrode sheet still has good compaction density on the basis of a certain content of large particles, and the battery has good capacity and cycle performance.

[0161] In some embodiments, the positive electrode film layer further comprises a conductive agent. Based on the total area of the cross section of the positive electrode film layer along the thickness direction of the electrode sheet, the total area ratio of the agglomeration region of the conductive agent is 0.2%-6%, which can be selected as 1.5%-5%.

[0162] Based on the total area of the cross section of the positive electrode film layer along the thickness direction of the electrode sheet, the total area ratio of the agglomeration region of the conductive agent in the above range indicates that the conductive agent in the positive electrode film layer is uniformly dispersed, which is beneficial to form a uniform conductive network and reduce local polarization and even lithium precipitation problems generated during the cycle process of the battery.

[0163] At the same time, the small particles of the present application can fill the gap between the large particles as a basic conductive framework, and the dispersed conductive agent agglomerates can be used as long-range conduction nodes to form a hierarchical conductive structure. Since the large-size particles in the lithium-containing transition metal phosphate particles are prone to rebound, the agglomeration area of the conductive agent in the above range can also inhibit the rebound of the large particles by means of uniform distribution of the conductive agent, mechanically constrain the particles and even the film layer, improve the cohesion of the film layer, reduce the phenomenon of film layer powder falling and active material falling off, and improve the cycle life of the battery.

[0164] The area ratio of the agglomerated region of the conductive agent can be tested by the following method based on the total area of the section of the positive electrode film layer along the thickness direction of the electrode tab. The section of the positive electrode film layer along the thickness direction of the electrode tab is observed by scanning electron microscopy using the similar method described above, and the area of the agglomerated region of the conductive agent in the scanning electron micrograph is measured at a magnification of 3k. Since the conductive agent is generally a carbon-based material, such as conductive carbon black, carbon nanotubes, etc., the agglomerated region of the conductive agent often appears as a black agglomerate compared to other regions in the positive electrode film layer, and at a high magnification, the agglomerated conductive agent can be seen. The agglomerated region of the conductive agent refers to the range of the black region in the scanning electron micrograph where the conductive agent is obviously agglomerated. With the aid of image analysis software, such as ImageJ, the white marked region in the statistical graph is selected, and the region with a Feret display of greater than or equal to 2 μm is screened out. The sum of the areas of the above regions is the total area of the agglomerated region of the conductive agent in the scanning electron micrograph, and the area ratio of the agglomerated region of the conductive agent is characterized by dividing the total area of the agglomerated region of the conductive agent tested in the scanning electron micrograph at a magnification of 3k by the area of the scanning electron micrograph. Three non-overlapping scanning electron micrographs are randomly taken, and the average value is taken as the "total area ratio of the agglomerated region of the conductive agent based on the total area of the section of the positive electrode film layer along the thickness direction of the electrode tab".

[0165] In some embodiments, the conductive agent includes carbon nanotubes, which include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes, and optionally, the conductive agent further includes conductive carbon black.

[0166] Carbon nanotubes have a high aspect ratio characteristic, which is beneficial to bridging particles of different particle sizes in the thickness direction through their unique fiber structure, forming a long-range conductive path while improving the binding force between the particles, reducing local polarization and even lithium precipitation problems generated during the cycle 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 and reduce the shedding phenomenon of active materials in the film layer through the binding effect.

[0167] Conductive carbon black is tightly coated on the surface of the positive electrode active particles through its nanoscale size characteristics, forming a high-density point-like conductive contact. By being used in combination with carbon nanotubes, long-range conduction and short-range conduction are taken into account, further perfecting the conductive network in the positive electrode film layer. The high specific surface area of the conductive carbon black greatly improves the electrolyte adsorption capacity, effectively alleviating the consumption of electrolyte during the cycle; the mechanical toughness of the carbon nanotubes can buffer the expansion stress of the electrode tab; and the synergistic effect of the two can reduce the electrolyte extrusion phenomenon caused by the high growth rate of the expansion force of the electrode tab during long cycle, improving the long cycle life of the battery.

[0168] In some embodiments, the agglomerated region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0169] The researchers found that carbon nanotubes are prone to agglomeration due to their high surface energy, resulting in uneven distribution in the positive electrode film layer and failure to form an effective carbon nanotube network structure. The surface energy of conductive carbon black is close to that of carbon nanotubes, which can be adsorbed on the surface of carbon nanotubes to form a physical barrier, increase the resistance of carbon nanotube agglomeration, reduce direct contact between carbon nanotubes, and thus inhibit the agglomeration phenomenon and improve the 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 improve the dynamic performance of the battery; on the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reduces the risk of positive electrode film layer falling off, and further improves the dynamic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the conductive agent agglomeration area will also cause the local ion transport path of the conductive agent agglomeration area to be blocked, and the addition of conductive carbon black can improve the lithium ion transport capacity of this area, reduce local polarization, and further improve the cycle stability of the battery.

[0170] In some embodiments, 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%, based on the mass of the positive electrode film layer.

[0171] In some embodiments, 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 any numerical range between any two of them, based on the mass of the positive electrode film layer.

[0172] In some embodiments, 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 any numerical range between any two of them, based on the mass of the positive electrode film layer.

[0173] The mass content of carbon nanotubes and conductive carbon black within the above range can effectively alleviate the agglomeration of carbon nanotubes and form a good conductive network structure, thereby effectively reducing the stress concentration of the positive electrode film layer and improving the liquid retention rate of the positive electrode film layer during long-term cycling, further reducing the risk of positive electrode film layer falling off and the degree of polarization, improving the dynamic performance of the battery and improving the cycle life of the battery.

[0174] In some embodiments, the positive electrode film layer further comprises a dispersant, and the dispersant comprises hydrogenated nitrile rubber HNBR.

[0175] The polar groups (such as cyano, -CN) in the hydrogenated nitrile rubber HNBR molecule can interact (such as hydrogen bonding, dipole interaction) with the hydroxyl (-OH) or metal oxide sites on the surface of the lithium-containing transition metal phosphate particles, enhancing the compatibility of the particles with the solvent, reducing the interfacial tension of the particles with the solvent, and improving the interfacial tension of large particles more obviously, making it easier for large and small particles to disperse uniformly in the film layer, reducing particle aggregation caused by hydrophobicity, improving the dispersibility of large particles in the positive electrode film layer, and reducing stress concentration during the die cutting process of the film layer.

[0176] Meanwhile, during the drying of the slurry 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 conductive agent aggregation area, and the uniform distribution of the conductive agent helps to inhibit the rebound of large particles, mechanically binds the particles and even the film layer, improves the cohesion of the film layer, reduces the phenomenon of film powdering and active material falling off, and improves the cycle life of the battery.

[0177] In some embodiments, the mass content of the dispersant is 0.5%-2% based on the mass of the positive electrode film layer.

[0178] In some embodiments, 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 a numerical range between any two of them, based on the mass of the positive electrode film layer.

[0179] The mass content of the dispersant in the above range can achieve uniform dispersion of particles in the positive electrode film layer while maintaining a high loading capacity of the positive electrode film layer, and the battery has good capacity and cycle performance.

[0180] In some embodiments, the positive electrode film layer is provided with a bottom coating layer near the bottom region of the positive electrode current collector, and the bottom coating layer comprises a conductive agent and a binder, the conductive agent comprises carbon nanotubes and conductive carbon black, and the binder comprises a vinylidene fluoride polymer.

[0181] In some embodiments, the thickness of the bottom coating layer is 0.5μm-5μm.

[0182] In some embodiments, the thickness of the bottom coating layer can be selected as 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or a numerical range between any two of them.

[0183] The bottom coating provided by the embodiments of the present application helps to improve the adhesion of the positive electrode film layer to the positive electrode current collector and relieve the stress concentration phenomenon at large particles, thereby reducing the probability of 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 is increased, which helps to increase the area of electron transmission between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the pole piece and improving the kinetic performance of the battery.

[0184] In some embodiments, the median value C of the graphitization degree of the positive electrode film layer in the cumulative distribution curve of the graphitization degree C value obtained by the laser microscopic confocal Raman spectrometer in the face scanning mode is greater than 0.95 and less than or equal to 1.20. 50 The graphitization degree C value is I G / I D , I G represents the G peak intensity of the Raman spectrum at 1580±100 cm -1 , and I D represents the D peak intensity of the Raman spectrum at 1350±100 cm -1 .

[0185] In the present application, the graphitization degree C value of the positive electrode film layer can be obtained by the laser microscopic confocal Raman spectrometer in the face scanning mode. As an example, specifically, a laser microscopic confocal Raman spectrometer (high-precision Renishaw laser microscopic confocal Raman spectrometer) is used, the excitation wavelength of 532 nm is selected, an appropriate amount of positive electrode film layer is taken, and the surface thereof or the section thereof along the thickness direction of the pole piece is scanned in the face scanning mode. The scanning area is 45 μm x 45 μm, which is divided into 10 x 10 grids, the grid vertices are taken as the test points, the step length is 5 μm, and the total number of scanning points is 100 points. Thus, the C values of different sites and the cumulative distribution curve of the C value of the face scanning area are obtained.

[0186] The positive electrode film layer in the present application can be a freshly prepared positive electrode film layer or a positive electrode film layer obtained by disassembling a battery. The surface of the positive electrode film layer obtained by disassembling the battery inevitably has residual electrolyte salt particles. In order to improve the testing accuracy, the section of the positive electrode film layer along the thickness direction of the pole piece is preferably scanned to characterize the graphitization degree of the positive electrode film layer.

[0187] The graphitization degree C value of the positive electrode film layer is obtained by the peak intensity ratio of the G peak (G-band) and the D peak (D-band) of the Raman spectrum. The G peak position is 1580±100 cm -1 , which represents the sp 2 hybrid structure of carbon; and the D peak position is 1350±100 cm -1 , which represents the disordered structure of carbon, wherein the disorder represents that there is no regular arrangement mode between the carbon atoms in the structure.

[0188] The cumulative distribution curve of graphitization degree C value refers to a curve obtained by arranging at least 100 C values obtained in ascending order, taking graphitization degree as the horizontal axis, and taking the cumulative number ratio as the vertical axis. C 50 The median value C of graphitization degree refers to the C value corresponding to the cumulative number ratio of 50% on the vertical axis of the cumulative distribution curve of graphitization degree C value. 50 Compared with the point value, the graphitization degree of the particles in the positive electrode film layer can reflect the degree of easy sliding; compared with the average value, the influence of extreme values in the test process can be reduced, and the confidence of the test result can be improved.

[0189] A person skilled in the art can realize the regulation of the graphitization degree of the active material particles by any known process. As an example, the regulation of the carbon source, the sintering temperature, the sintering time, the sintering pressure, and the sintering atmosphere can all realize the adjustment of the graphitization degree of the active material particles.

[0190] In some embodiments, the median value C of graphitization degree in the cumulative distribution curve of graphitization degree C value obtained by the positive electrode film layer under the face scanning mode of the laser microscopic confocal Raman spectrometer is 0.95-1.05. 50 Optionally, it can be 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 any numerical range between any two of them.

[0191] The median value C of graphitization degree in the cumulative distribution curve of graphitization degree C value obtained by the positive electrode film layer under the face scanning mode of the laser microscopic confocal Raman spectrometer is 0.95-1.05. 50 Within the above range, the compaction density of the pole piece can be further improved by relying on the sliding of the particles, and it is not necessary to excessively rely on the ratio of large and small particles in the positive electrode film layer, so that the area ratio of large particles and small particles is within a suitable range, which is beneficial to reduce the probability of falling off of the positive electrode film layer while avoiding excessive resistance of the positive electrode film layer, and is helpful to improve the cycle performance and dynamic performance of the battery on the basis of maintaining the battery capacity.

[0192] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise components represented by the following general formula:

[0193] Li m Fe x P y O j Q q Formula I,

[0194] wherein Q comprises one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, 0≤q≤0.1.

[0195] In some embodiments, m can be selected from 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 numerical range between any two of them; x can be selected from 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or any numerical range between any two of them; y can be selected from 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, or any numerical range between any two of them; j can be selected from 3.5, 3.6, 3.7, 3.8, 3.9, 4, or any numerical range between any two of them; q can be selected from 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any numerical range between any two of them.

[0196] In some embodiments, the lithium-containing transition metal phosphate particles comprise titanium element, and the mass content of the titanium element is 500 ppm-8000 ppm, or 1000 ppm-3000 ppm, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0197] In some embodiments, the titanium element is uniformly distributed in the lithium-containing transition metal phosphate particles.

[0198] 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 publicly known method. As an example, the titanium element and content can be tested by inductively coupled plasma optical emission spectrometry according to Appendix C of GB / T 33822-2017.

[0199] When the titanium element is doped into the lithium-containing transition metal phosphate particles, the Ti-O-P bond formed by the titanium element has strong bonding effect, which can anchor the phosphate group and reduce the shrinkage / expansion amplitude of the lattice when lithium ions are deintercalated, thereby inhibiting the structural stress caused by phase transition and improving the cycle life of the battery; and the Ti-O-P bond can provide more stable channels for lithium ion diffusion, thereby reducing the migration energy barrier and improving the kinetic performance of the battery.

[0200] The mass content of the titanium element in the above range is beneficial to improve the lithium ion transmission rate of the positive electrode active material, reduce the risk of lithium precipitation, and improve the kinetic performance of the battery.

[0201] In some embodiments, the mass content of titanium element is selected from 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 a numerical range between any two of them, based on the total mass of lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0202] In some embodiments, the lithium-containing transition metal phosphate particles contain vanadium element, and the mass content of vanadium element is 500 ppm-5000 ppm, which is optionally 500 ppm-3000 ppm, based on the total mass of lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0203] In some embodiments, the vanadium element is uniformly distributed in the lithium-containing transition metal phosphate particles.

[0204] When vanadium element is doped into lithium-containing transition metal phosphate particles, it has the characteristics of multiple valence states. When +5 valence vanadium (V 5+ ) is doped into phosphorus sites, it will introduce lattice distortion and expand the lithium ion diffusion channel, thereby improving the ionic conductivity of the positive electrode active material. When +3 valence vanadium (V 3+ ) is doped into transition metal sites, it will form a defect energy level by compensating the charge through lithium vacancies or interstitial oxygen, thereby improving the electronic conductivity of the positive electrode active material.

[0205] The mass content of vanadium element in the above range is beneficial to improve the lithium ion transmission rate of the positive electrode active material, improve the electronic conductivity of the positive electrode active material, and further improve the kinetic performance of the battery through the synergistic effect of titanium element doping.

[0206] In some embodiments, the mass content of vanadium element is selected from 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, or a numerical range between any two of them, based on the total mass of lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0207] 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, fluorinated lithium vanadium phosphate, lithium manganese iron phosphate, and modified materials thereof.

[0208] 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 one or more of doped modified materials, coated modified materials.

[0209] In some embodiments, the porosity of the positive electrode film layer is 14%-28%.

[0210] The porosity of the positive electrode film layer can be tested in the following manner. The cross-section scanning electron microscope image of the positive electrode film layer obtained in the manner described above is imported into ImageJ software, a straight line tool is selected, a ruler length in the image is marked using the straight line, and "Analyze Set Scale" is clicked to set the ruler parameters in the software according to the ruler length in the image. A rectangular tool is selected, the part of the image outside the ruler area is selected, the selected area is copied using "Image Duplicate", the image format is adjusted using "Image Type 8 bit", "Analyze Set Measurements" is selected, and the following five options are selected: "Area", "Mean gray value", "Area Fraction", "Limit to threshold", and "Feret's diameter", wherein "Decimal places" is selected as 3, "Image"-"Adjust"-"Threshold" is selected in sequence, 0 and 100 are set in sequence in the "Threshold" box, and the porosity data in the cross-section electron microscope image can be exported using the Analyze-Measure function. The porosity picture is obtained by using "Image"-"Overlay"-"Flatten" to export, "Apply" in "Threshold" is clicked, and "Analyze"-"Analyze Particles" is clicked, and the four columns on the left are checked, and the porosity statistical data is obtained.

[0211] It can be understood that the "pores" in the cross-section of the positive electrode film layer are identified by image color difference and threshold value in the embodiments of the present application. The "pores" are not the pore data obtained by the exhaust test, and are mainly used to represent the cross-sectional area between the particles in the cross-section of the positive electrode film layer. This method is more superior to the exhaust method because the porosity obtained by the exhaust method is related to the pores between the particles and the pores in the carbon material on the surface of the lithium iron phosphate particles, and thus cannot objectively reflect the pores between the particles.

[0212] The porosity of the positive electrode film layer in the above range means that the size particle gradation in the positive electrode film layer is good, and is beneficial to improve the liquid retention properties of the electrolyte, improve the ion diffusion properties of the positive electrode film layer with a certain area ratio of large particles, and improve the kinetic performance of the battery.

[0213] In some embodiments, the porosity of the positive electrode film layer may be selected as 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or any range therebetween.

[0214] In some embodiments, the resistivity of the positive electrode film layer is 10 Ω·cm-35 Ω·cm.

[0215] The resistivity of the positive electrode film layer can be tested by the following method: specifically: using a resistance tester (Suzhou Lidian) to test under a standard pressure of 25MPa, randomly selecting 8 test points on the film layer of the positive electrode piece during the test, maintaining the pressure at each test point for 15s, and obtaining the resistivity of the test point; the average value of the 8 resistivities is used as the resistivity of the positive electrode film layer.

[0216] In some embodiments, the resistivity of the positive electrode film layer may be 10Ω·cm, 11Ω·cm, 12Ω·cm, 13Ω·cm, 14Ω·cm, 15Ω·cm, 16Ω·cm, 17Ω·cm, 18Ω·cm, 19Ω·cm, 20Ω·cm, 21Ω·cm, 22Ω·cm, 23Ω·cm, 24Ω·cm, 25Ω·cm, 26Ω·cm, 27Ω·cm, 28Ω·cm, 29Ω·cm, 29.72Ω·cm, 29.88Ω·cm, 30Ω·cm, 30.55Ω·cm, 30.73Ω·cm, 31Ω·cm, 31.5Ω·cm, 32Ω·cm, 32.2Ω·cm, 33Ω·cm, 33.67Ω·cm, 34Ω·cm, 34.98Ω·cm, 35Ω·cm, or any range therebetween.

[0217] The resistivity of the positive electrode film layer is within an appropriate range, which is beneficial to reducing the electron transfer impedance, reducing the charge and discharge polarization, and improving the battery's kinetic performance.

[0218] In some embodiments, as Figure 1 As shown, the battery cell also includes a separator 20 arranged between the positive electrode plate and the negative electrode plate, the separator 20 includes a base film 201 and a ceramic layer 202 arranged on both sides of the base film 201 and a bonding layer 203 arranged on at least one side of the ceramic layer 202 away from the base film 201, the bonding layer 203 is a continuous layer of a porous structure, and the bonding layer 203 includes a vinylidene fluoride polymer.

[0219] In some embodiments, the vinylidene fluoride polymer includes vinylidene fluoride homopolymer (PVDF) and copolymers of vinylidene fluoride and other monomers, for example, copolymers of vinylidene fluoride and hexafluoropropylene.

[0220] likeFigure 2 As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak.

[0221] As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak. Figure 3 As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak. As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak. As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak. As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak. As shown in the prior art, the adhesive layer of the separator often uses water-based PVDF, which often presents an island structure in the separator, which is beneficial to provide a gap for the swelling of the battery and is convenient for manufacturing; however, the adhesive area of the adhesive layer of such a separator is low, and the adhesive force is weak.

[0222] The separator provided in the embodiments of the present application uses a porous continuous layer as the adhesive layer, which has a larger bonding area than the island-shaped adhesive layer in the prior art, thereby making the bonding of the separator and the positive film layer more firm and uniform, and at the same time, the porous structure in the adhesive layer can also improve the transmission efficiency of lithium ions and the kinetic performance of the battery. Meanwhile, the pressure between the electrode sheets in the preparation process of the stacked battery is smaller than that of the wound battery, and the lithium-containing transition metal phosphate particles with a particle size greater than or equal to 1 μm can reduce the tightness of the internal components of the battery during the rebound process, increase the impedance of the battery, and increase the probability of powder falling and even falling off of the film layer. The separator provided in the embodiments of the present application uses a porous continuous layer as the adhesive layer, which is particularly suitable for stacked batteries, improves the rebound phenomenon of the stacked battery during long-term cycling, and improves the capacity retention of the battery during long-term cycling. In addition, the stacked battery is prone to relative displacement between the electrode sheet and the separator during the process of dragging the outer electrode sheet and welding the tab, which makes the film layer prone to powder falling, and even the positive and negative electrodes are prone to mutual lapping, which increases the risk of internal short circuit.

[0223] The embodiments of the present application use a porous continuous layer as the adhesive layer, which improves the adhesion between the separator and the electrode sheet while maintaining the air permeability and porosity of the separator, improves the stability of the electrode sheet, further reduces the risk of powder falling and even internal short circuit due to the relative displacement between the electrode sheet and the separator, and improves the cycle stability of the battery.

[0224] In some embodiments, as Figure 4 As shown, the battery cell 5 includes a shell 50, and the laminated battery core is accommodated in the shell 50. The size of the shell 50 in the length direction (X direction) is L0, the size of the shell in the width direction (Y direction) is W0, and the size of the shell in the thickness direction (Z direction) is H0. 450mm≤L0≤1300mm, 100mm≤W0≤150mm; 14mm≤H0≤22mm.

[0225] 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.

[0226] 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 any range therebetween.

[0227] In some embodiments, W0 can be selected as 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or any range of values ​​therebetween.

[0228] In some embodiments, H0 can be selected as 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, or any range of values ​​therebetween.

[0229] In some embodiments, a length L0 of the housing satisfies: 450 mm ≤ L0 ≤ 650 mm.

[0230] When the length dimension L0 of the shell satisfies the following conditions: 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, and reducing the infiltration distance of the electrolyte in the electrode pores, thereby improving the infiltration uniformity and 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.

[0231] In some embodiments, the length L0 of the shell satisfies: 900mm≤L0≤1300mm.

[0232] When the length L0 of the shell satisfies: 900mm≤L0≤1300mm, the greatly increased monomer size can effectively simplify the traditional module structure, realize direct integration of the monomer battery into the battery pack, realize fixation of the battery through the structural member arranged at the large face end, significantly improve the space utilization, thereby increasing the overall capacity of the battery system under the same volume, while reducing the number of structural members, improving the battery energy density, and further improving the capacity of the battery.

[0233] In some embodiments, as shown in Figure 4 The shell 50 is made of a soft package material, which includes an aluminum plastic composite film, and optionally, one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) composite film formed with aluminum.

[0234] The soft package material has a high ductility, and the shell is light, thin, and soft, which helps to improve the space utilization of the battery monomer, thereby improving the energy density of the battery monomer. However, the soft package material such as the aluminum plastic composite film has poor heat conduction performance, resulting in low heat dissipation efficiency of the soft package battery. Therefore, if the area ratio of small particles in the positive electrode film layer is too high, the resistivity of the positive electrode film layer will increase, resulting in excessive heat generation of the battery during the cycling process, and aggravating the problem of poor heat dissipation of the soft package battery. The embodiments of the present application use a soft package material as the shell and control the area ratio of small particles in the positive electrode film layer within a suitable range, so that the battery has high capacity and good cycling performance.

[0235] In some embodiments, continuing to refer to Figure 4 The shell 50 includes a first sealing area 51 arranged at at least one end of the laminated core 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 the folded edge structure is provided with encapsulation glue, which is continuously arranged and fixed to the folded edge structure in the length direction (X direction).

[0236] The folded edge structure refers to a reinforcing structure formed by folding the encapsulation area, and the number of folds is not limited. For example, it can be a single folded edge structure folded once, or a double folded edge structure folded on both sides.

[0237] During the cycling process of the electrode tab, the SEI film will thicken, and therefore, large rebound and gas production will occur during the long cycling process. The sealing area of the soft package core is used to seal the electrode assembly, but the strength of the sealing area is limited and is easily broken by the large rebound and high gas production in the film layer.

[0238] The first sealing area is further improved in sealing strength by the fold structure extending along the length direction in the first sealing area. The continuous arrangement of the encapsulation adhesive along the length direction and the fixing of the fold structure can further improve the encapsulation strength, realize continuous reinforcement of the length direction of the sealing area, and reduce the probability of the pole piece breaking the sealing area in the package during the cycle process.

[0239] In some embodiments, the shell 50 comprises at least one second sealing area 52 arranged at at least one end of the jelly-roll along the length direction of the shell, and the second sealing area 52 is arranged at the tab side of the jelly-roll.

[0240] It can be understood that the positive tab and the negative tab can be arranged on the same side of the jelly-roll, as shown in FIG. 1A; or can be arranged on the opposite side of the jelly-roll. Figure 4

[0241] In some embodiments, the battery monomer 5 further comprises a lead-out piece 53 connected with the tab of the battery monomer, for example, the lead-out piece 53 can be welded with the tab, the lead-out piece 53 is a conductive piece, at least part of the lead-out piece 53 is located outside the shell 50, the lead-out piece 53 is used as the electrode lead-out end of the battery monomer 5, and the lead-out piece 53 is used for facilitating the electrical connection of the battery monomer 5 with other battery monomers 5 or other components. For example, the lead-out piece 53 can be in a sheet shape.

[0242] Correspondingly, the lead-out piece 53 also comprises a positive lead-out piece and a negative lead-out piece, the positive lead-out piece is connected with the positive tab, and the negative lead-out piece is connected with the negative tab.

[0243] The second sealing area is arranged at the tab side, the tab needs to be connected with the lead-out piece, the connection strength of the lead-out piece with the shell material is relatively weak, so that the gas is easy to be broken out from the second sealing area, which is beneficial to realize the directional pressure relief of the battery, reduce the influence on the adjacent jelly-roll during the thermal runaway, and improve the service life of the whole battery.

[0244] In some embodiments, the jelly-roll is provided with a plurality of glue rings surrounding along the width direction, and the glue rings surrounding along the width direction are arranged at intervals along the length direction.

[0245] The interval arrangement of the glue rings surrounding along the width direction of the jelly-roll along the length direction is beneficial to fix the positions of the pole pieces in the jelly-roll, reduce the probability of displacement of the jelly-roll during the shaking process of the battery, and is especially suitable for the battery with a large length, can effectively reduce the mutual displacement of the pole pieces along the length direction and cause the lithium precipitation phenomenon, and is beneficial to keep the space structure of the battery stable, so as to not affect the normal work of the battery.

[0246] ​In some embodiments, the capacity of the battery cell is 100 Ah-300 Ah, optionally 110 Ah-190 Ah, further optionally 125 Ah-180 Ah at 25℃.

[0247] In the present application, the capacity of the battery cell is the meaning known in the art, which can be tested by the method known in the art. As an example, at 25℃, charge to 3.65V at 0.5C charge rate of the nominal capacity of the battery cell, then constant voltage charge to 0.05C at 3.65V, stand for 10 min, then discharge to 2.5V at 1C discharge rate, stand for 10 min, the capacity C during the discharging process is calculated by the formula C=Ixt, unit Ah.

[0248] In some embodiments, the capacity of the battery cell is 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 any numerical range between any two of them at 25℃.

[0249] The battery cell of the embodiments of the present application has a reasonable large particle ratio in the film layer of the positive electrode plate in the jelly-roll cell by controlling the size of the suitable shell to accommodate the jelly-roll cell, and has a higher capacity.

[0250] In some embodiments, the positive current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be adopted. The composite current collector can include a high polymer material base layer and a metal layer formed on at least one surface of the high polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a high polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0251] In some embodiments, the negative current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be adopted. The composite current collector can include a high polymer material base layer and a metal layer formed on at least one surface of the high polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a high polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0252] In some embodiments, the negative electrode film layer comprises a negative electrode active material. As an example, the negative electrode active material can comprise at least one of the following materials: artificial graphite, natural graphite, soft carbon, and hard carbon. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination with two or more.

[0253] In some embodiments, the negative electrode film layer can also optionally comprise a binder. The binder can be selected from at least one of the following: 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).

[0254] In some embodiments, the negative electrode film layer can also optionally comprise other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0255] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0256] The second aspect of the present application provides a battery device comprising the battery cell provided by the first aspect of the present application.

[0257] The battery device disclosed in the embodiments of the present application can be used in a power consumption device using the battery device as a power source or a variety of 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 is not limited to, mobile phones, tablets, notebook computers, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, and the like. Among them, the electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric plane toys, and the like, and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, and the like.

[0258] In addition, the present application also provides a power consumption device using the battery device as a power source, wherein the power consumption device comprises 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 a power source of the power consumption device, or can be used as an energy storage unit of the power consumption device.

[0259] As the power consumption device, the battery cell, the battery module, or the battery pack can be selected according to the use requirements thereof.

[0260] Figure 5 It is an electric device as an example. The electric device disclosed in the embodiment of the present application can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery device is provided inside the vehicle, and the battery device can be provided at the bottom, head or tail of the vehicle. The battery device can be used to power the vehicle. For example, the battery device can be used as an operating power source for the vehicle. The vehicle may also include a controller and a motor, and the controller is used to control the battery device to power the motor, for example, for the working power requirements of the vehicle during starting, navigation and driving. In some embodiments of the present application, the battery device can be used not only 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.

[0261] An embodiment of the present application also provides an energy storage device that uses a battery device as a power source. The energy storage device may 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.

[0262] Example

[0263] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0264] Example 1

[0265] (1) Preparation of positive electrode active materials

[0266] Lithium carbonate, iron phosphate, titanium dioxide, vanadium pentoxide, sucrose, glucose, and polyethylene glycol are added to deionized water and mixed in a premixing tank, wherein the ratio of lithium carbonate and iron phosphate is such that the molar ratio of lithium to iron is 1.02:1.0, and 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 uniform mixing, a mixed raw material with a solid content of 38% is obtained;

[0267] Among them, the particle size Dv of lithium carbonate 50 The particle size of the iron phosphate particles is 6 μm; the morphology of the iron phosphate particles is spherical; both titanium dioxide and vanadium pentoxide are nanoparticles; the purity of sucrose is ≥98%; the water content of glucose is <0.5%; and the weight-average molecular weight of polyethylene glycol is 1500.

[0268] The mixed raw materials are ground in a sand mill twice, coarse grinding for 1 h and then fine grinding, and the slurry temperature is controlled to be less than 40 DEG C during the grinding process, to obtain a mixed slurry; the particle size Dv50 of the solid particles in the mixed slurry is 0.40 pm, and the mixed slurry is spray dried to obtain a dried precursor powder, and the particle size Dv50 of the dried precursor powder is 55.50 pm.

[0269] The precursor powder is sintered in two stages in a nitrogen atmosphere to obtain a positive electrode active material: heating from 25 DEG C to 460 DEG C at a heating rate of 2 DEG C / min (first heating stage), holding for 3 h; heating from 460 DEG C to 780 DEG C at a heating rate of 5 DEG C / min (second heating stage), holding for 12 h; wherein the gas flow rate in the heating stage is greater than that in the holding stage, and the ratio is 1.5:1, and the total gas flow rate is 1350 cm 3 / h, and then cooling; and airflow crushing to obtain a lithium iron phosphate positive electrode active material with a carbon material on the surface, wherein the particle size Dv50 is 1.6 pm, and the mass content of Ti element is 1050 ppm and the mass content of V element is 950 ppm based on the total mass of the positive electrode active material.

[0270] The above Dv10, Dv50 and Dv90 refer to the data obtained by Malvern laser scattering method.

[0271] (2) Preparation of the positive electrode tab

[0272] The above positive electrode active material with a mass ratio of 93.9%, a conductive agent with a mass ratio of 2%, and a binder polyvinylidene fluoride with a mass ratio of 3% are mixed in a solvent N-methyl pyrrolidone, and then a dispersant HNBR with a mass ratio of 1.1% is added, and the mixture is fully mixed, stirred and dispersed in a stirring tank to form a positive electrode slurry; after the stirring process is completed, the positive electrode slurry is transported to a coating process; wherein the mass ratios of the positive electrode active material, the conductive agent, the binder and the dispersant are calculated based on the total mass of the solids in the positive electrode slurry; the conductive agent includes conductive carbon black with a mass ratio of 1.33% and single-walled carbon nanotubes with a mass ratio of 0.67%, the specific surface area of the conductive carbon black is 85 m 2 / g, and the oil absorption value is 200 ml / 100 g, the average length of the single-walled carbon nanotubes is 30 pm, 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%;

[0273] The positive electrode slurry is transferred and coated onto an aluminum foil current collector and dried, and then hot-pressed to obtain a positive electrode tab with a single-sided thickness of 105.64 pm and a compacted density of 2.36 g / cm 3 . The transfer coating speed is 20 m / min.

[0274] 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. Before entering the hot roller compaction for the first time, the electrode is heated at 40°C.

[0275] The compaction density here refers to the compaction density of the battery cell when it is fully discharged. The test method is shown below.

[0276] 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%.

[0277] The positive electrode sheets are striped 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.

[0278] (3) Preparation of negative electrode sheet

[0279] 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, the negative electrode slurry is obtained. The negative electrode slurry is coated on the base copper foil, and the negative electrode sheet is obtained after drying, compacting, slitting and sheeting.

[0280] 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.

[0281] (4) Diaphragm

[0282] Polyvinylidene fluoride (PVDF) was dissolved in N-methylpyrrolidone (NMP) and stirred thoroughly. Polyethylene glycol (PEG) was then added as a pore-forming agent and thoroughly stirred to produce a bonding layer solution. This bonding layer solution was then applied to the aforementioned base film with ceramic layers on both sides. After pre-evaporation at 80°C and drying at 110°C, the solution was immersed in deionized water to dissolve the PEG, resulting in a separator with a porous bonding layer on both sides. The base film had a thickness of 8μm, the ceramic layer on one side had a thickness of 3μm, and the bonding layer on one side had a thickness of 1μm.

[0283] (5) Electrolyte

[0284] 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 uniformly.

[0285] Lithium hexafluorophosphate was added again, dissolved in the organic solvent, so that the concentration of lithium hexafluorophosphate was 1.05 mol / L, and vinylene carbonate (VC) was added and stirred uniformly to obtain the electrolyte of Example 1.

[0286] The mass content of dimethyl carbonate was 26%, the mass content of methyl ethyl carbonate was 43.3%, the mass content of ethylene carbonate was 17.3%, and the mass content of vinylene carbonate was 0.9%, based on the total mass of the electrolyte.

[0287] (6) Preparation of the battery

[0288] The positive electrode sheet, the separator and the negative electrode sheet were stacked in order by using a lamination machine, and the separator could isolate the positive electrode and the negative electrode to obtain a laminated cell. The laminated cell was subjected to a glue sticking process to tightly wrap the cell. The laminated cell after glue sticking was placed in an outer package, and the outer package was a soft package material of aluminum plastic film. The aluminum plastic film was composed of an inner layer of polypropylene, an intermediate layer of aluminum foil and an outer layer of nylon. The aluminum plastic film outer package was obtained by a pit forming machine and trimming to obtain a target shape and size. Then, the aluminum plastic film was heat sealed to meet the sealing tension of the aluminum plastic film ≥ 25 N / 8 mm. The battery was vacuum baked, placed, injected with electrolyte, packaged, and then subjected to hot pressing and cold pressing operations. The temperature of hot pressing was 45℃, the time was 2 minutes, and the pressure was 90 kg / cm 2 . The temperature of cold pressing was 25℃, the time was 2 minutes, and the pressure was 90 kg / cm 2 . Finally, the battery monomer was obtained through processes such as formation, vacuum exhaust and edge cutting. 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.

[0289] The preparation method of Example 2-3 was basically the same as that of Example 1, except that the preparation method of the positive electrode active material and the positive electrode sheet was adjusted, and the specific adjustments were as follows:

[0290] Example 2

[0291] The preparation method of Example 2 was basically the same as that of Example 1, except that the preparation process of the positive electrode active material and the hot pressing process of the positive electrode sheet were slightly different. The difference points included:

[0292] (1) The carbon source in the mixed raw materials was sucrose and glucose, and the mass of sucrose was 2wt% compared to the mass of iron phosphate, and the mass of glucose was 4wt% compared to the mass of iron phosphate;

[0293] (2) The temperature rising sintering process was different. The precursor powder was sintered at least twice in a nitrogen atmosphere, and the first sintering temperature was 765℃ and the holding time was 8 hours to obtain a preliminary sintered product.

[0294] 1.5 wt% (based on the mass of the calcined product) of glucose, 3.0 wt% (based on the mass of the calcined product) of polyethylene glycol, titanium dioxide and vanadium pentoxide were added to the primary calcined product, and after being ground evenly, the product was divided into two groups for secondary grinding. The grinding parameters of the two groups were different, and the D of the particles after the first group was controlled. V 50 is 2.2 μm, and the D of the second group of milled particles is V The first and second groups of ground particles were mixed in a mass ratio of 30:70, spray-dried, and sintered for the second time. The second sintering temperature was 815°C and kept at this temperature for 10 hours.

[0295] The mass content of the Ti element was 1050 ppm, and the mass content of the V element was 950 ppm, based on the total mass of the positive electrode active material.

[0296] (3) The positive electrode slurry was transferred and coated onto the current collector aluminum foil and dried. After hot pressing, the positive electrode film layer had a single-side thickness of 106.34 μm and a compaction density of 2.37 g / cm 3 The drying temperature is 95°C and the drying speed is 2.0 m / min.

[0297] The hot pressing process involves three hot roller pressing steps, with increasing pressures of 35 tons, 55 tons, and 70 tons, respectively. The hot roller temperature is 65°C, and the electrode is heated to 50°C before the first hot roller compaction. The compaction density here refers to the compaction density of the battery cell at full discharge. The testing method is described below.

[0298] Example 3

[0299] The preparation method of Example 3 is basically the same as that of Example 1, except that the sintering process of the positive electrode active material and the hot pressing process of the positive electrode sheet are different. Specifically:

[0300] (1) The precursor powder was subjected to two-stage temperature rising sintering in a nitrogen atmosphere to obtain the positive electrode active material: the temperature was raised from 25°C to 440°C at a heating rate of 2°C / min (the first heating stage) and kept at this temperature for 2.5 hours; the temperature was raised from 440°C to 760°C at a heating rate of 5°C / min (the second heating stage) and kept at this temperature for 11 hours; and the air flow crushing intensity was then increased to obtain the lithium iron phosphate positive electrode active material with carbon material on the surface.

[0301] (2) The positive electrode slurry was transferred and coated onto the current collector aluminum foil and dried. After hot pressing, the positive electrode film layer had a single-side thickness of 105.65 μm and a compaction density of 2.36 g / cm 3 The transfer coating speed is 20 m / min.

[0302] The hot-pressing process includes three times of hot-rolling processes, and the hot-rolling pressures are sequentially increased, and the hot-rolling pressures are sequentially 45 tons, 60 tons and 80 tons; the hot-rolling temperature is 60 DEG C; before entering the first hot-rolling process, the positive plate is heated, and the heating temperature is 40 DEG C.

[0303] The preparation method of the example 4-8 is basically the same as that of the example 1, and the difference lies in that the preparation method of the positive plate is adjusted, and the specific method is as follows:

[0304] Example 4

[0305] The positive electrode slurry of the example 1 is transferred and coated on the current collector aluminum foil and dried, the positive plate with the single side thickness of 91.88 μm of the positive electrode film layer is obtained by adjusting the pressure size, the calendering speed, the roll gap, the pressure holding time, the calendering times and the coating area density in the hot-pressing process; the compaction density of the positive plate is 2.36 g / cm 3 The compaction density here refers to the compaction density under the full discharge state of the battery monomer, and the test method is described below. The number of layers of the stack is kept unchanged, and the thickness of the battery monomer is adaptively adjusted according to the thickness of the positive electrode film layer.

[0306] Example 5

[0307] The positive electrode slurry of the example 1 is transferred and coated on the current collector aluminum foil and dried, the positive plate with the single side thickness of 91.88 μm of the positive electrode film layer is obtained by adjusting the pressure size, the calendering speed, the roll gap, the pressure holding time, the calendering times and the coating area density in the hot-pressing process; the compaction density of the positive plate is 2.36 g / cm 3 The compaction density here refers to the compaction density under the full discharge state of the battery monomer, and the test method is described below. The number of layers of the stack is kept unchanged, and the thickness of the battery monomer is adaptively adjusted according to the thickness of the positive electrode film layer.

[0308] Example 6

[0309] The positive electrode slurry of the example 1 is transferred and coated on the current collector aluminum foil and dried, the positive plate with the single side thickness of 91.88 μm of the positive electrode film layer is obtained by adjusting the pressure size, the calendering speed, the roll gap, the pressure holding time, the calendering times and the coating area density in the hot-pressing process; the compaction density of the positive plate is 2.36 g / cm 3 The compaction density here refers to the compaction density under the full discharge state of the battery monomer, and the test method is described below. The number of layers of the stack is kept unchanged, and the thickness of the battery monomer is adaptively adjusted according to the thickness of the positive electrode film layer.

[0310] Example 7

[0311] The positive electrode slurry of Example 1 was transferred and coated onto the current collector aluminum foil and dried, and a positive electrode sheet with a single-sided thickness of 83.91 pm of the positive electrode film layer was obtained by adjusting the pressure size, rolling speed, roll gap, holding time, rolling times, and coating surface density in the hot-pressing process; the compaction density of the positive electrode sheet was 2.36 g / cm 3 The compaction density here refers to the compaction density under the full discharge state of the battery monomer, and the test method is described below. The number of layers of the stack was kept unchanged, and the thickness of the battery monomer was adaptively adjusted according to the thickness of the positive electrode film layer.

[0312] Example 8

[0313] The positive electrode slurry of Example 1 was transferred and coated onto the current collector aluminum foil and dried, and a positive electrode sheet with a single-sided thickness of 83.91 pm of the positive electrode film layer was obtained by adjusting the pressure size, rolling speed, roll gap, holding time, rolling times, and coating surface density in the hot-pressing process; the compaction density of the positive electrode sheet was 2.36 g / cm 3 The compaction density here refers to the compaction density under the full discharge state of the battery monomer, and the test method is described below. The number of layers of the stack was kept unchanged, and the thickness of the battery monomer was adaptively adjusted according to the thickness of the positive electrode film layer.

[0314] Example 9

[0315] 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 sheet are adjusted, as follows:

[0316] First, a precursor solution was prepared under argon protection, FeSO4·7H2O, LiOH·H2O and H3PO4 were mixed in deionized water, and 0.5wt% ascorbic acid was added as an antioxidant; then the pH was adjusted to 5.0, 0.1 mol / L citric acid was added as a crystal grain growth inhibitor, and 1wt% PEG-4000 was added as a dispersant, and the mixed solution was transferred to a high-pressure reaction kettle, and reacted at 180°C for 6 hours; the reaction product was washed by centrifugation and dried at 80°C under vacuum, and finally annealed at 350°C in an argon atmosphere for 2 hours to obtain a lithium iron phosphate material with an average particle size of 160 nm.

[0317] The lithium iron phosphate material prepared above was mixed with the positive electrode active material of Example 1 in a mass ratio of 10:90 to obtain the positive electrode active material of Example 9.

[0318] The positive electrode slurry was transferred and coated onto the current collector aluminum foil and dried, and a positive electrode sheet with a single-sided thickness of 105.65 pm of the positive electrode film layer was obtained by adjusting the pressure size, rolling speed, roll gap, holding time, rolling times, and coating surface density in the hot-pressing process; the compaction density of the positive electrode sheet was 2.36 g / cm3 The compaction density here refers to the compaction density of the battery monomer in the full discharge state, and the test method is described below. The thickness of the battery monomer is adjusted adaptively according to the thickness of the positive electrode film layer while the number of layers of the laminated sheet remains unchanged.

[0319] Example 10

[0320] The preparation method of Example 10 is basically the same as that of Example 9, except that the preparation method of the positive electrode sheet is adjusted, which is as follows:

[0321] The positive electrode active material of Example 9 is prepared by using the same positive electrode sheet preparation method as that of Example 1, and a positive electrode sheet with a single-sided thickness of 105.65 μm of the positive electrode film layer is obtained. The compaction density of the positive electrode sheet is 2.32 g / cm 3 The compaction density here refers to the compaction density of the battery monomer in the full discharge state, and the test method is described below.

[0322] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the preparation method of the positive electrode active material is adjusted, which is as follows:

[0323] Comparative Example 1

[0324] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the preparation method of the positive electrode active material is adjusted, which is as follows:

[0325] The precursor powder is subjected to two-stage temperature rising sintering in a nitrogen atmosphere to obtain the positive electrode active material: the temperature is raised from 25°C to 500°C at a rate of 2°C / min (first temperature rising stage), and the temperature is kept for 3.5 h; the temperature is raised from 500°C to 800°C at a rate of 5°C / min (second temperature rising stage), and the temperature is kept for 13 h; and then the lithium iron phosphate positive electrode active material with carbon material on the surface is obtained by reducing the airflow crushing intensity.

[0326] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the preparation method of the positive electrode active material is adjusted, which is as follows:

[0327] Comparative Example 2

[0328] First, the precursor solution is prepared under argon protection, FeSO4·7H2O, LiOH·H2O and H3PO4 are mixed in deionized water, and 0.5wt% ascorbic acid is added as an antioxidant; then the pH is adjusted to 5.0, 0.1mol / L citric acid is added as a crystal grain growth inhibitor, and 1wt% PEG-4000 is added as a dispersant, and the mixed solution is transferred to a high-pressure reaction kettle, and reacted at 180°C for 6 hours; the reaction product is washed by centrifugation, dried at 80°C under vacuum, and finally annealed at 350°C in an argon atmosphere for 2 hours to obtain a lithium iron phosphate material with an average particle size of 160 nm.

[0329] The lithium iron phosphate material prepared above was mixed with the positive electrode active material of Example 1 at a mass ratio of 12:88 to obtain the positive electrode active material of Comparative Example 2.

[0330] It can be understood that the positive electrode sheet preparation processes of Example 1, Example 10 and Comparative Example 2 are consistent; the positive electrode sheet preparation processes of Example 9 and Example 10 are different although the same positive electrode active material preparation process is used.

[0331] Test method:

[0332] 1. Capacity of battery monomer

[0333] At 25°C, the battery monomer was charged at a charge rate of 0.5C of the nominal capacity to 3.65V, then charged at 3.65V to 0.05C, and then discharged at a discharge rate of 1C to 2.5V, and then rested for 10 min. The capacity C during discharging was calculated by the formula C=Ixt, and the unit was Ah.

[0334] 2. Cycle number corresponding to capacity decay to 85%

[0335] At 25°C, the battery monomer was charged at a charge rate of 0.5C of the nominal capacity to 3.65V, then charged at 3.65V to 0.05C, and then discharged at a discharge rate of 1C to 2.5V, and then rested for 10 min. The above one charge-discharge was one cycle, and the test was stopped until the battery capacity decayed to 85% of the nominal capacity, which was recorded as the cycle number @ 85% SOH.

[0336] Test results

[0337] Table 1

[0338]

[0339] As can be seen from the comparison of the examples and comparative examples, in the section of the positive electrode film layer along the thickness direction of the sheet, the area ratio of particles with a particle size greater than or equal to 1μm is 12%-50%, the area ratio of particles with a particle size greater than 50nm and less than or equal to 200nm is 3.0%-15.0%, and the compaction density of the positive electrode sheet is 2.3g / cm 3 -2.6g / cm 3 when the battery monomer has good capacity, the phenomenon of stress concentration of large particles in the compaction process of the sheet is alleviated, the positive electrode film layer has a low resistivity, and the cycle performance and dynamic performance of the battery are improved.

[0340] As can be seen from the comparison of Example 2 and Examples 1 and 3, in the 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 is 12%-40%, which is beneficial to further improve the phenomenon of stress concentration of large particles in the electrode sheet compaction process, reduce the probability of film layer loosening and active material falling off, and improve the cycle performance of the battery on the basis of maintaining high capacity.

[0341] As can be seen from the comparison of Example 9 and Examples 1-3, in the 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 50 nm and less than or equal to 200 nm is 5%-10%, which is beneficial to reduce the resistivity of the positive electrode film layer and improve the dynamic performance of the battery on the basis of maintaining high capacity and good cycle performance.

[0342] As can be seen from the comparison of Example 5 and Examples 1-4 and 6-9, in the section of the positive electrode film layer along the thickness direction of the electrode sheet, the median number L A50 of sphericity in the sphericity area cumulative distribution curve of the particles with a particle size greater than or equal to 1 μm is 0.67-0.75, which further improves the phenomenon of stress concentration of large particles in the electrode sheet compaction process, reduces the probability of film layer loosening and active material falling off, and improves the cycle performance of the battery.

[0343] As can be seen from the comparison of 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.

[0344] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: It includes a laminated battery cell, and the laminated battery cell includes a positive electrode 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 90μm - 120μm; 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 1μm and less than or equal to 5μm 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 50nm and less than or equal to 200nm is 3.0% - 15.0%; The battery cell is in a fully charged state, and the compaction density of the positive electrode sheet is 2.3 g / cm 3 -2.6g / 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 1μm and less than or equal to 5μm is 12% - 40%.

3. The battery cell according to any one of claims 1 to 2, 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 1μm is 0.2% - 5%.

4. The battery cell according to claim 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 1μm is 0.2% - 2%.

5. The battery cell according to any one of claims 1 to 2, characterized in that: In the cross section of the positive electrode film along the thickness direction of the electrode, in the cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median of the sphericity L A50 It is 0.6-0.

8.

6. The battery cell according to claim 5, characterized in that In the cross section of the positive electrode film along the thickness direction of the electrode, in the cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median of the sphericity L A50 It is 0.65-0.

75.

7. The battery cell according to claim 6, characterized in that In the cross section of the positive electrode film along the thickness direction of the electrode, in the cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median of the sphericity L A50 It is 0.67-0.

75.

8. The battery cell according to any one of claims 1 to 2, 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 50nm and less than or equal to 200nm is 5.0% - 15.0%.

9. The battery cell according to claim 8, 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 50nm and less than or equal to 200nm is 5.0% - 10.0%.

10. The battery cell according to claim 1, characterized in that The single-sided thickness of the positive electrode film layer is 100μm - 120μm.

11. The battery cell according to any one of claims 1 to 2, 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%.

12. The battery cell according to claim 11, 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%.

13. The battery cell according to claim 11, 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.

14. The battery cell according to claim 13, characterized in that The conductive agent further includes conductive carbon black.

15. The battery cell according to claim 11, characterized in that The agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

16. The battery cell according to claim 15, characterized in that Based on the mass of the positive electrode film layer, the mass content C1 of the carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of the conductive carbon black satisfies: 0 < C2 ≤ 2.5%.

17. The battery cell according to any one of claims 1 to 2, characterized in that: The positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

18. The battery cell according to claim 17, characterized in that Based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

19. The battery cell according to any one of claims 1 to 2, 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 0.5μm - 5μm.

20. The battery cell according to any one of claims 1 to 2, characterized in that: In the cumulative distribution curve of the graphitization degree C of the positive electrode film obtained in the surface scanning mode of the laser microconfocal Raman spectrometer, the median value of the graphitization degree C 50 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 Indicates that the Raman spectrum is at 1580±100cm -1 The G peak intensity at I D Indicates that the Raman spectrum is at 1350±100cm -1 The D peak intensity at .

21. The battery cell according to any one of claims 1 to 2, characterized in that: The lithium-containing transition metal phosphate particles in the positive electrode film layer include the components shown by the following general formula: Li m Fe x P 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, and Br, 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0≤q≤0.

1.

22. The battery cell according to any one of claims 1 to 2, 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 the titanium element is 500ppm-8000ppm.

23. The battery cell according to claim 22, 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 the titanium element is 1000ppm-3000ppm.

24. The battery cell according to any one of claims 1 to 2, 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 the vanadium element is 500ppm-5000ppm.

25. The battery cell according to claim 24, 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 the vanadium element is 500ppm-3000ppm.

26. The battery cell according to any one of claims 1-2, characterized in that: The porosity of the positive electrode film layer is 14%-28%.

27. The battery cell according to any one of claims 1 to 2, characterized in that: The resistivity of the positive electrode film layer is 10Ω·cm-35Ω·cm.

28. The battery cell according to any one of claims 1 to 2, characterized in that: The battery cell also includes a separator arranged between the positive electrode plate and the negative electrode plate, the separator includes a base film and a ceramic layer arranged on both sides of the base film and an adhesive layer arranged on at least one side of the ceramic layer away from the base film side, the adhesive layer is a continuous layer of a porous structure, and the adhesive layer includes a vinylidene fluoride polymer.

29. The battery cell according to any one of claims 1 to 2, characterized in that: The battery cell includes a shell, and the laminated battery core 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, and 14mm≤H0≤22mm.

30. The battery cell according to claim 29, characterized in that The length dimension L0 of the shell satisfies: 450 mm ≤ L0 ≤ 650 mm.

31. The battery cell according to claim 29, characterized in that The length dimension L0 of the shell satisfies: 900 mm ≤ L0 ≤ 1300 mm.

32. The battery cell according to claim 29, characterized in that The housing satisfies at least one of the following conditions: (1) The shell is made of a soft-pack material, which includes an aluminum-plastic composite film; (2) The housing includes a first sealing area, which is provided at at least one end of the laminated battery cell extending in the width direction; the first sealing area includes a folding structure extending in the length direction, and a packaging glue is provided on the folding structure, and the packaging glue is continuously provided in the length direction and fixes the folding structure; (3) The shell includes at least one second sealing area, which is arranged at at least one end of the laminated battery core along the length direction of the shell, and the second sealing area is arranged on the tab side of the laminated battery core.

33. The battery cell according to claim 32, characterized in that The aluminum-plastic composite film comprises 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.

34. The battery cell according to any one of claims 1 to 2, characterized in that: A plurality of rubber rings surrounding along the width direction are provided on the outer periphery of the laminated battery core, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

35. The battery cell according to any one of claims 1 to 2, characterized in that: At 25° C., the capacity of the battery cell is 100Ah-190Ah.

36. The battery cell according to claim 35, characterized in that At 25° C., the capacity of the battery cell is 110Ah-190Ah.

37. The battery cell according to claim 36, characterized in that At 25° C., the capacity of the battery cell is 125Ah-180Ah.

38. A battery device, characterized in that: The invention comprises a battery cell according to any one of claims 1 to 37.

39. An electrical device, characterized in that: The electrical device comprises the battery device as claimed in claim 38, and the battery device is used to provide electrical energy.

40. An energy storage device, characterized in that: The energy storage device includes the electrical device as described in claim 39, and the electrical device is used to store electrical energy.

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