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

Abstract

The invention discloses a battery monomer, a battery device, a power utilization device and an energy storage device. The single battery comprises a laminated battery cell, and the laminated battery cell comprises a positive pole piece, a negative pole piece and a diaphragm arranged between the positive pole piece and the 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 a carbon material is arranged on at least part of the surface of the lithium-containing transition metal phosphate particles; in the tangent plane of the positive electrode film layer along the thickness direction of the pole piece, the area ratio of particles with the particle size greater than or equal to 1 mu m is 12%-50%; the ceramic layers are arranged on the two sides of the base membrane, the bonding layer is arranged on the side, away from the base membrane, of the ceramic layer at least close to one side of the positive pole piece, the bonding layer is a continuous layer of a porous structure, and the bonding layer comprises a vinylidene fluoride polymer.

Description

[0001] This application claims the priority of the international application PCT / CN2025 / 094374 titled "Battery Cell, Battery Device, Electrical Device, and Energy Storage Device" filed on May 12, 2025, the entire content of which is incorporated herein by reference. Technical Field

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

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

[0004] With the dual increase in the market's demand for the cruising range and cycle life of electrical devices, higher requirements are also put forward for the capacity, cycle performance, etc. of battery cells. However, it is difficult to simultaneously improve the above performances in the prior art, which has become a technical problem urgently to be solved in this field. Summary of the Invention

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

[0006] In the first aspect of this application, a battery cell is provided, including a stacked electrode core, the stacked electrode core including a positive electrode tab, a negative electrode tab, and a separator disposed between the positive electrode tab and the negative electrode tab; the positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer including lithium-containing transition metal phosphate particles, and at least a part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material; in the cross-section of the positive electrode film layer along the thickness direction of the electrode tab, the area ratio of particles with a particle size greater than or equal to 1 μm is 12% - 50%; the separator includes a base film, ceramic layers disposed on both sides of the base film, and a bonding layer disposed on the side away from the base film of the ceramic layer at least close to the positive electrode tab side, the bonding layer being a continuous layer with a porous structure, and the bonding layer including a polyvinylidene fluoride polymer.

[0007] The applicant has 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 electrode tab is less than 12%, the insufficient particle grading will significantly limit the improvement space of the compaction density, and it is difficult to effectively improve the battery capacity. When the area ratio of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode tab is greater than 50%, the excessive large particles will cause a serious rebound phenomenon in the positive electrode film layer, leading to the breakage of the SEI film and the cracking of the film layer, increasing the short-circuit risk, and having an adverse impact on the cycle performance of the battery.

[0008] In the embodiments of the present application, the laminated battery cells are combined with a lithium-containing transition metal phosphate positive electrode film layer having a certain content of large particles to improve the battery capacity. Further, a separator with ceramic layers provided on both sides is used to increase the stiffness of the separator. At the same time, a separator with a porous continuous layer having a larger bonding area and stronger bonding force is adopted to increase the bonding effect between the separator and the positive electrode plate, improve the compactness and stiffness of the internal grouping of the laminated battery cells, make up for the deficiency of the small external binding force of the laminated battery cells, reduce the risk that the mutual extrusion in the thickness direction of the positive and negative electrode plates during the battery cell rebound evolves into misalignment in the horizontal direction, and reduce the risk of the positive and negative electrodes overlapping and thus causing a short circuit, so that on the basis of good battery capacity, the cycle performance of the battery is further improved.

[0009] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of particles with a particle size of 1 μm - 5 μm is 12% - 50%.

[0010] When the area ratio of particles with a particle size of 1 μm - 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is within the above range, it is beneficial to improve the phenomenon that large particles in the electrode plate rebound during the battery cycle while maintaining a high battery capacity, and improve the cycle performance of the battery.

[0011] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of particles with a particle size of 1 μm - 5 μm is 12% - 40%.

[0012] When the area ratio of particles with a particle size of 1 μm - 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is within the above range, it is beneficial to further improve the phenomenon that large particles in the electrode plate are prone to stress concentration and cause electrode plate rebound while maintaining a high battery capacity, reduce the probability of contact between the negative electrode film layer and the positive electrode film layer of the electrode plate and generate a short circuit, and further improve the cycle performance of the battery.

[0013] In any embodiment, the polyvinylidene fluoride polymer includes one or more of polyvinylidene fluoride homopolymer (PVDF) and copolymer of polyvinylidene fluoride and hexafluoropropylene.

[0014] In any embodiment, the single-sided thickness of the positive electrode film layer is 70 μm - 120 μm.

[0015] The specific capacity of lithium-containing transition metal phosphate particles is relatively low. Research shows that when the single-sided thickness of the positive electrode film layer is less than 70 μm, the battery capacity is difficult to meet market requirements. When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to improve the capacity of a single battery cell.

[0016] In any embodiment, the single-sided thickness of the positive electrode film layer is 90 μm - 120 μm.

[0017] When the single - side thickness of the positive electrode film layer is within the above - mentioned range, it is beneficial to further improve the battery capacity.

[0018] In any implementation manner, the single - side thickness of the positive electrode film layer is 100μm - 120μm.

[0019] Increasing the single - side thickness of the positive electrode film layer is beneficial to improving the battery capacity. The applicant found that when the single - side thickness of the positive electrode film layer is greater than or equal to 100μm, the phenomenon of particle rebound in the positive electrode film layer is more serious. The embodiments of the present application effectively alleviate the serious rebound of the thick - coated film layer in the stacked battery cells. On the basis of maintaining a high capacity, the battery has improved cycle performance.

[0020] In any implementation manner, the positive electrode film layer includes a first region. The first region is located at the top of the positive electrode film layer away from the positive electrode current collector, and the distribution uniformity of particles with a particle size greater than or equal to 1μm in the first region is 0.2% - 5%.

[0021] In any implementation manner, the positive electrode film layer includes a first region. The first region is located at the top of the positive electrode film layer away from the positive electrode current collector, and the distribution uniformity of particles with a particle size greater than or equal to 1μm in the first region is 0.2% - 3.5%.

[0022] The stress concentration degrees at the large - particle and small - particle locations in the positive electrode film layer are different. Along with the gradual release of stress during the cycling process, it leads to different degrees of rebound of the electrode sheet. In the embodiments of the present application, there are a certain amount of large particles, and at the same time, the large particles are evenly distributed in the electrode sheet, making the extrusion force of the positive electrode film layer on the separator show a uniform distribution, reducing the risks of local over - extrusion caused by uneven distribution of large particles and blockage of local lithium - ion transport pathways, which lead to an increase in the peripheral current density and easy lithium deposition. This enables the battery to further improve its cycle performance on the basis of having good capacity.

[0023] In any implementation manner, in the cross - section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative distribution curve of the spherical - like area of particles with a particle size greater than or equal to 1μm, the median L of the spherical - like degree A50 is 0.6 - 0.8.

[0024] When the median of the spherical - like degree of particles with a particle size greater than or equal to 1μm is within the above - mentioned range, the large particles have good spherical - like degree, reducing particle bridging caused by irregular shapes of large particles, reducing the void content in the electrode sheet, and at the same time reducing the stress concentration aggravated by the irregularity of large particles, reducing the rebound of the electrode sheet caused by stress release during the cycling process, enabling the battery monomer to further improve its cycle performance while having a high capacity.

[0025] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the area cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median value L of the sphericity A50 is 0.65 - 0.75.

[0026] When the median value of the sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, it is beneficial to reduce the stress concentration of large particles due to the irregularity of large particles, reduce the rebound of the electrode sheet caused by stress release during the cycling process, and improve the cycling performance of the battery.

[0027] In any embodiment, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the area cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median value L of the sphericity A50 is 0.67 - 0.75.

[0028] When the median value of the sphericity of particles with a particle size greater than or equal to 1 μm is within the above range, it can further improve the stress concentration of large particles, reduce the rebound of the electrode sheet caused by stress release during the cycling process, and further improve the cycling life of the battery cell.

[0029] In any embodiment, in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser microscopic confocal Raman spectrometer for the positive electrode film layer, the median value C of the graphitization degree 50 is greater than or equal to 0.95 and less than or equal to 1.20; wherein, the graphitization degree C value is I G / I D where I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 100 cm -1 and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 .

[0030] In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser microscopic confocal Raman spectrometer for the positive electrode film layer, the median value C of the graphitization degree 50 being within the above range can further improve the compaction density of the electrode sheet, reduce the content of large-sized particles in the positive electrode film layer, help reduce the rebound phenomenon of the film layer caused by excessive large particles while maintaining the battery capacity, and further improve the cycling performance of the battery.

[0031] In any embodiment, in the cumulative distribution curve of the coating value B obtained in the surface scanning mode of the laser microscopic confocal Raman spectrometer for the positive electrode film layer, the median value B of the coating value 50 is 0.30 - 0.60, where the coating value B is IP / ID, and IP represents the Raman spectrum at 948 ± 100 cm -1The intensity of the P peak at the position, where ID represents the Raman spectrum at 1350 ± 100 cm -1 The intensity of the D peak at the position.

[0032] The median B of the coating value of the positive electrode film layer 50 Within the above range, it indicates that the surface carbon material layer of the positive electrode active material is relatively dense and uniform, which is beneficial to improving the slip uniformity of the positive electrode film layer during the rolling process and reducing the stress concentration phenomenon in the positive electrode film layer; in addition, with the help of the dense and uniform carbon material layer, the large particles in the positive electrode film layer are more likely to achieve slip during the compaction process, thereby reducing the stress concentration phenomenon at the large particles in the positive electrode film layer and reducing the rebound caused by the stress release at the large particles during the cycling process, and improving the cycle life of the battery.

[0033] In any embodiment, the iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm, and it can be selected as 658 ppm - 1485 ppm.

[0034] The iron element dissolved in the positive electrode material mainly comes from the lithium-containing transition metal phosphate particles of the positive electrode active material. The level of the iron dissolution rate depends on the one hand on the number of lattice defects in the lithium-containing transition metal phosphate particles, and on the other hand on the integrity and density of the surface carbon material layer of the positive electrode active material. The lower the iron dissolution rate means fewer lattice defects in the lithium-containing transition metal phosphate particles, which is beneficial to reducing the corrosion of the lattice in a weak acid environment; and the more complete and dense the carbon material layer on the surface of the positive electrode active material, the more it inhibits the dissolution of iron ions in a weak acid environment. The positive electrode material with an iron dissolution rate within the above range has relatively few lattice defects and a complete and dense carbon material layer, which is beneficial to improving the compressive resistance and easy slip degree of the particles in the positive electrode film layer under a large rolling pressure, increasing the compaction density of the positive electrode film layer and reducing the stress concentration in the positive electrode film layer, improving the rebound phenomenon caused by stress concentration of large particles, and enabling the battery to further improve the cycle performance on the basis of having good capacity.

[0035] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include the components represented by the following general formula: Li m Fe x P y O j Q q Formula I, where Q includes one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4, 0 ≤ q ≤ 0.1.

[0036] In any embodiment, the lithium-containing transition metal phosphate particles include titanium element, and based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of the titanium element is 500 ppm - 8000 ppm, and can be optionally 1000 ppm - 3000 ppm.

[0037] Introducing titanium element into the lithium-containing transition metal phosphate particles requires adding a titanium source during the preparation of the positive electrode active material. The titanium source is often an inert material, and attaching to the surface of the raw material of the lithium-containing transition metal phosphate particles can play a role in reducing the reaction activity and reducing the growth of particle size. Improving the graphitization degree of the positive electrode active material often requires a higher sintering temperature or a longer sintering time, but this will also increase the size of the particles in the positive electrode film layer, increase the stress concentration in the positive electrode film layer, and increase the rebound of the electrode sheet during the cycling process. In the embodiments of the present application, by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, the reaction activity of the synthesis raw material of the positive electrode active material is reduced, so that the positive electrode active material can control the proportion of large particles while having a high graphitization degree, reduce the stress concentration in the positive electrode film layer, and improve the rebound phenomenon caused by stress concentration at the large particles, so that the battery can further improve the cycling performance on the basis of having good capacity.

[0038] At the same time, the doping of titanium element in the positive electrode active material is beneficial to causing lattice distortion, reducing the Li-O bond energy, increasing the lithium ion transmission rate, and improving the kinetic performance of the battery. The lithium ion diffusion in the positive electrode film layer is uneven, and there is often a significant lithium ion concentration gradient. In the embodiments of the present application, the solid-phase transmission rate of the positive electrode active material is improved by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, and the kinetic problems of the battery are improved.

[0039] In any embodiment, the lithium-containing transition metal phosphate particles include vanadium element, and based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of the vanadium element is 500 ppm - 5000 ppm, and can be optionally 500 ppm - 3000 ppm.

[0040] The vanadium element in the positive electrode film layer can be in multiple valence states. Among them, vanadium in the +5 valence state (V 5+ ) can be doped at the phosphorus element site, and because of its larger radius, it can cause lattice distortion and expand the lithium ion diffusion channel, thereby improving the ionic conductivity of the positive electrode active material and the kinetic performance of the battery; vanadium in the +3 valence state (V 3+ ) can be doped at the transition metal site, and lithium vacancies are generated through charge compensation, thereby improving the electronic conductivity of the positive electrode active material. In addition, improving the distribution uniformity of the vanadium element in the lithium-containing transition metal phosphate particles helps to further improve the kinetic performance of the positive electrode film layer and the reaction uniformity of the positive electrode film layer, thereby further improving the kinetic performance and cycling performance of the battery cell.

[0041] The mass content of vanadium element within the above range helps to improve the kinetic performance of the positive electrode sheet and that of the lithium-containing transition metal phosphate battery. At the same time, the synergistic effect of titanium element, vanadium element and carbon nanotubes in the positive electrode film layer helps to form a good three-dimensional network, further improving the electronic conductivity and ionic conductivity of the positive electrode film layer, thereby further improving the kinetic performance of the lithium-containing transition metal phosphate battery.

[0042] In any embodiment, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the total area ratio of the agglomerated regions of the conductive agent is 0.2% - 6%, and may be optionally 1.5% - 5%.

[0043] 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 agglomerated regions of the conductive agent within the above range indicates that the conductive agent in the positive electrode film layer is evenly dispersed, facilitating the formation of a uniform conductive network, which is beneficial to reducing local polarization and even lithium plating problems generated during battery cycling.

[0044] At the same time, research shows that large-sized particles in lithium-containing transition metal phosphate particles are prone to rebound. The agglomerated area of the conductive agent within the above range can suppress the rebound of lithium-containing transition metal phosphate particles by virtue of the uniform distribution of the conductive agent, forming a mechanical restraint on the particles and even the film layer, improving the cohesive force of the film layer, reducing the damage of the SEI film and the film layer during the film layer rebound process, and improving the cycle life of the battery.

[0045] In any embodiment, the conductive agent includes carbon nanotubes, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes. Optionally, the conductive agent further includes conductive carbon black.

[0046] Carbon nanotubes have a high aspect ratio, which is conducive to overlapping multiple positive electrode particles between particles in the thickness direction, forming a long-range conductive path while increasing the binding force between particles, reducing local polarization and even lithium plating problems generated during battery cycling, and improving the cycle life of the battery; and can also reduce the rebound phenomenon of large particles in the positive electrode film layer through the binding effect, improving the cycle performance of the battery.

[0047] 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, forming dense dot-like conductive contacts. When used in combination with carbon nanotubes, it takes into account both long-range and short-range conduction, which is beneficial 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 beneficial to liquid absorption and liquid retention, and can reduce the electrolyte extrusion phenomenon caused by the high growth rate of the swelling force during long-term cycling of the electrode sheet, improving the long-term cycle life of the battery.

[0048] In any embodiment, the agglomerated region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0049] 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 unable to form an effective carbon nanotube network structure. The surface energy of conductive carbon black is relatively close to that of carbon nanotubes, and it can adsorb on the surface of carbon nanotubes to form a physical barrier, increasing the resistance to carbon nanotube agglomeration, reducing the direct contact between carbon nanotubes, thereby inhibiting the agglomeration phenomenon and improving the distribution uniformity of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the positive electrode film layer and the kinetic performance of the battery; on the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reduce the risk of shedding of the positive electrode film layer, and further improve the kinetic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the agglomerated region of the conductive agent will also cause local ion transport pathways in the agglomerated region of the conductive agent to be blocked. The combination of conductive carbon black can improve the lithium ion transport ability in this region, reduce local polarization, and further improve the cycle stability of the battery.

[0050] In any embodiment, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

[0051] When the mass contents of carbon nanotubes and conductive carbon black are within the above ranges, the agglomeration phenomenon of carbon nanotubes can be effectively alleviated and a good conductive network structure can be formed, thereby effectively reducing the stress concentration in the positive electrode film layer, increasing the liquid retention rate of the positive electrode film layer during long-term cycling, further reducing the risk of shedding of the electrode film layer and the degree of polarization, improving the kinetic performance of the battery and enhancing the cycle life of the battery.

[0052] In any embodiment, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

[0053] The polar groups (such as cyano group, -CN) in the hydrogenated nitrile rubber HNBR molecules can interact with the hydroxyl groups (-OH) or metal oxide sites on the surface of lithium-containing transition metal phosphate particles (such as hydrogen bonding, dipole interaction), enhancing the compatibility between the particles and the solvent, reducing the interfacial tension between the particles and the solvent, especially the interfacial tension of large particles, making the particles more easily and uniformly dispersed, reducing the aggregation caused by hydrophobicity, improving the dispersion of large particles in the positive electrode film layer, and reducing the stress concentration generated during the die-cutting process of the positive electrode film layer.

[0054] At the same time, when the slurry is dried to form 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 agglomerated region of the conductive agent, and improve the cycle life of the battery.

[0055] In any embodiment, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0056] When the mass content of the dispersant is within the above range, it is possible to achieve uniform dispersion of the particles in the positive electrode film layer while maintaining a high loading amount of the positive electrode film layer, and the battery has good capacity and cycling performance.

[0057] In any embodiment, when the battery cell is in a fully discharged state, the tap density of the positive electrode plate is 2.3 g / cm 3 - 2.6 g / cm 3 .

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

[0059] When the porosity of the positive electrode film layer is within the above range, on the one hand, it is beneficial to improve the liquid retention characteristics of the electrolyte, improve the ion diffusivity 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, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector. The bottom coating includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes a polyvinylidene fluoride polymer.

[0061] In any embodiment, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector, and the thickness of the bottom coating is 0.5 μm - 5 μm.

[0062] The bottom coating provided in the embodiments of the present application helps to improve the adhesion between the positive electrode film layer and the positive electrode current collector and relieve the stress concentration phenomenon at large particles, thereby reducing the probability of the positive electrode film layer falling off and improving the cycling stability of the battery. At the same time, compared with the direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the bottom coating and the positive electrode film layer increases, which helps to increase the area of electron transfer between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode plate and improving the kinetic performance of the battery.

[0063] In any embodiment, the thickness of the base film is 7 μm - 9 μm.

[0064] In any embodiment, the single-side thickness of the ceramic layer is 2 μm - 4 μm.

[0065] In any embodiment, the single-side thickness of the adhesive layer is 1 μm - 5 μm.

[0066] If the thickness of the adhesive layer is too low, the space for buffering expansion in the separator is small and the adhesive force between the separator and the electrode is low. On the one hand, after the film layer expands, the stress increases and the probability of the film layer peeling off increases, affecting the cycle life of the battery. On the other hand, the probability of positive-negative electrode short circuit increases, thus affecting the safety performance of the battery. If the thickness of the adhesive layer is too large, the space occupancy rate of the battery is large, thus affecting the volumetric energy density of the battery. In the embodiments of the present application, the thickness of the adhesive layer is within the above range, which helps to balance the cycle life, safety performance and volumetric energy density of the battery.

[0067] In any embodiment, the battery cell includes a housing, a stacked electrode assembly is accommodated in the housing, the size of the housing in the length direction is L0, the size of the housing in the width direction is W0, and the size of the housing in the thickness direction is H0, where 450 mm ≤ L0 ≤ 1300 mm, 100 mm ≤ W0 ≤ 150 mm, and 14 mm ≤ H0 ≤ 22 mm.

[0068] The housing size of the battery cell in the embodiments of the present application is within the above range, which is beneficial for the battery to achieve better capacity.

[0069] In any embodiment, the size L0 of the housing in the length direction satisfies: 450 mm ≤ L0 ≤ 650 mm.

[0070] When the size L1 of the housing in the length direction satisfies 450 mm ≤ L1 ≤ 650 mm, the length of the battery cell is shorter, which helps to shorten the diffusion path of the current, reduce the internal resistance of the electrode, thereby reducing the heat generation of the battery and improving its kinetic performance. In addition, the shorter housing length helps to shorten the diffusion path of the electrolyte during the infiltration process, improve the infiltration rate and uniformity of the electrolyte, further promote the uniformity of lithium ion deintercalation during the cycle process, relieve the stress concentration phenomenon, reduce the degree of film layer rebound, and improve the cycle stability of the battery cell.

[0071] In any embodiment, the size L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

[0072] When the size L1 of the housing in the length direction satisfies 900 mm ≤ L1 ≤ 1300 mm, the size of the battery cell is longer, which helps to reduce the volume ratio of the housing in the battery cell and increase the load ratio of the active material. At the same time, the longer battery cell can reduce the number of battery cells required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of the structural parts in the module, thereby improving the space utilization rate of the battery pack, and further helping to improve the volumetric energy density of the battery cell.

[0073] In any embodiment, the material of the housing is a soft-pack material, and the soft-pack material includes an aluminum-plastic composite film. Optionally, it includes a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) and aluminum.

[0074] The soft-pack material has a high elongation rate, so its housing is thinner, lighter, and softer, which helps to improve the space utilization rate of the battery cell and thus increase the energy density of the battery cell. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery interior, reduce the decomposition of the electrolyte and the oxidation degree of the electrode material, and thus increase the battery life.

[0075] In any embodiment, the housing includes a first sealing area, and the first sealing area is arranged at at least one end of the stacked electrode assembly extending in the width direction; the first sealing area includes a folded-edge structure extending in the length direction, and an encapsulating adhesive is arranged on the folded-edge structure, and the encapsulating adhesive is continuously arranged in the length direction and fixes the folded-edge structure.

[0076] In the embodiment of the present application, the first sealing area includes a folded-edge structure extending in the length direction to further improve the sealing strength of the first sealing area. The continuous arrangement of the encapsulating adhesive in the length direction and the fixation of the folded-edge structure can further improve the encapsulation strength compared with the discontinuous arrangement of the encapsulating adhesive in the length direction, realize the continuous reinforcement in the length direction of the sealing area, and reduce the probability that the electrode sheet breaks open the sealing area in the packaging during the cyclic rebound process.

[0077] In any embodiment, the housing includes at least one second sealing area, and the second sealing area is arranged at at least one end of the stacked electrode assembly extending in the length direction of the housing, and the second sealing area is arranged on the tab side of the stacked electrode assembly.

[0078] The second sealing area is arranged on the tab side. The tab needs to be connected to the lead-out member, and the connection strength between the lead-out member and the housing material is relatively weak, so that gas is easy to rush out from the second sealing area, which is beneficial to realize the directional pressure relief of the battery, reduce the influence on adjacent battery cells during thermal runaway, and increase the overall service life of the battery.

[0079] In any embodiment, a plurality of rubber rings surrounding in the width direction are arranged on the outer periphery of the stacked electrode assembly, and the rubber rings surrounding in the width direction are arranged at intervals in the length direction.

[0080] The interval arrangement of the rubber rings surrounding in the width direction of the electrode assembly in the length direction is beneficial to fixing the positions between the electrode sheets in the electrode assembly, reducing the probability that the electrode assembly displaces during the shaking of the battery, especially applicable to batteries with a relatively large length, and can effectively reduce the mutual displacement between the electrode sheets in the length direction and thus cause the phenomenon of lithium plating, which is beneficial to maintaining the stability of the internal space structure of the battery and thus does not affect the normal operation of the battery.

[0081] In any embodiment, at 25 °C, the capacity of the battery cell is 100 Ah - 300 Ah, optionally 110 Ah - 190 Ah, and further optionally 125 Ah - 180 Ah.

[0082] The battery cell of the embodiment of the present application has a suitable housing size to accommodate the laminated battery core, controls the proportion of large particles in the film layer of the positive electrode plate in the laminated battery core to be reasonable, and the battery cell has a relatively high capacity.

[0083] The second aspect of the present application provides a battery device, including the battery cell provided by the first aspect of the present application.

[0084] The third aspect of the present application provides an electrical device. The electrical device includes the battery device provided by the second aspect, and the battery device is used to provide electrical energy.

[0085] The fourth aspect of the present application provides an energy storage device. The energy storage device includes the battery device provided by the second aspect, and the battery device is used to store electrical energy. Description of the Drawings

[0086] Figure 1 is a schematic diagram of a separator of an embodiment of the present application; Figure 2 is a schematic diagram of a separator of the prior art; Figure 3 is a schematic diagram of the surface topography of the adhesive layer of a separator of an embodiment of the present application; Figure 4 is a schematic diagram of a positive electrode plate of an embodiment of the present application; Figure 5 is a front view of a battery cell of an embodiment of the present application; Figure 6 is a schematic diagram of an electrical device of an embodiment of the present application.

[0087] Description of the Reference Numerals: 10 Positive electrode plate; 101 Positive current collector; 102 Positive film layer; 102a First surface; 102b Second surface; 1021 First region; 20 Separator; 201 Base film; 202 Ceramic layer; 203 Adhesive layer; 5 Battery cell; 50 Housing; 51 First sealing area; 52 Second sealing area; 53 Lead-out piece; X Length direction; Y Width direction; Z Thickness direction. Detailed Embodiments

[0088] Hereinafter, embodiments of the battery cell, battery device, power consumption device, and energy storage device of the present application will be specifically described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there may be cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0089] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include or exclude the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" represents that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0090] Unless otherwise specified, all embodiments and alternative embodiments of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0091] Unless otherwise specified, all technical features and alternative technical features of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0092] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0093] In this application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0094] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0095] Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various common testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of this application. Unless otherwise specified, the test temperature of each parameter is 25 °C.

[0096] In the embodiments of this application, the battery device may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of pouch battery cells, and the plurality of pouch battery cells are connected in series, parallel or in a combined series-parallel manner through a busbar component. For example, the battery cell assembly is usually formed by arranging a plurality of pouch battery cells; the battery cell assembly can be a battery module, and the battery module is formed by arranging and fixing a plurality of pouch battery cells to form an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with cable ties.

[0097] The battery device can be a battery pack, and the battery pack includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body. The battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the box body by fixing the battery module in the box body; the battery cell assembly can also be accommodated in the box body by directly fixing a plurality of pouch battery cells to the box body.

[0098] In the embodiments of this application, the box body may include a first box body and a second box body. The first box body and the second box body are buckled together so that a closed space is formed inside the box body to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body can be a top cover or a bottom plate. For example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0099] In an embodiment of the present application, the box body can be part of the chassis structure of a vehicle. For example, a part of the box body can form at least a part of the vehicle floor, or a part of the box body can form at least a part of the cross beams and longitudinal beams of the vehicle.

[0100] In an embodiment of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging so as to continue to be used; the battery cell can be a lithium-ion battery. The battery cell can be in the shape of a flat body.

[0101] The battery mentioned in the embodiment of the present application can be a single physical module including one or more battery cells to provide a higher voltage and capacity. For example, the battery mentioned in the present application can include battery cells, battery modules, battery packs, etc.

[0102] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging. When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, a part of the box body can form at least a part of the vehicle floor, or a part of the box body can form at least a part of the cross beams and longitudinal beams of the vehicle.

[0103] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0104] In some embodiments, battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0105] A battery cell includes an electrode assembly and an electrolyte.

[0106] The electrode assembly generally includes a positive electrode tab and a negative electrode tab. The negative electrode tab is the electrode where the reaction of absorbing or lithiating lithium ions occurs during charging and releasing or delithiating lithium during discharging, and the positive electrode tab is the electrode where the reaction of releasing or delithiating lithium ions occurs during charging and occluding or lithiating lithium during discharging.

[0107] Compared with lithium-containing transition metal oxide materials, lithium-containing transition metal phosphate materials have the advantages of high safety, long cycle life, low cost, and stable high-temperature performance. However, the specific capacity of lithium-containing transition metal phosphate materials is low, which is not conducive to improving the battery capacity. The applicant's research found that compared with wound electrodes, stacked electrodes have no corner areas and higher space utilization of the internal volume of the battery. Using stacked electrodes is beneficial to further improve the volumetric energy density of the battery. At the same time, a certain content of large particles is beneficial to increasing the grading of the film layer, improving the compaction density of the electrode sheet, and further increasing the volumetric energy density of the battery. However, due to the absence of corner areas in wound electrodes, stacked electrodes have higher capacity, but also lack radial binding force, resulting in weak interfacial shear force between the positive and negative electrode sheets and the separator, and are prone to relative sliding under long cycles or mechanical shocks, increasing the risk of short circuit. At the same time, stress concentration is likely to occur at the large particles in the film layer during the compaction process of the electrode sheet. During the cycle, the stress gradually releases, causing the film layer to rebound. In the case of stacked electrodes lacking external binding force, the film layer rebound is more likely to cause misalignment between the positive and negative electrode sheets and the separator, further increasing the risk of local short circuit of the battery and deteriorating the cycle performance of the battery. How to obtain a battery with both good capacity and cycle performance is a technical problem that urgently needs to be solved in this field.

[0108] In a first aspect of the present application, a battery cell is provided. The battery cell includes a stacked electrode, and the stacked electrode includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes lithium-containing transition metal phosphate particles, and at least a part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material. In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of particles with a particle size greater than or equal to 1 μm is 12% - 50%. Wherein the structure of the separator is as Figure 1 shown. The separator 20 includes a base film 201, ceramic layers 202 disposed on both sides of the base film 201, and a bonding layer 203 disposed on the side of the ceramic layer 202 away from the base film 201 and at least close to the positive electrode sheet. The bonding layer 203 is a continuous layer with a porous structure, and the bonding layer 203 includes a polyvinylidene fluoride polymer.

[0109] 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 electrode sheet is less than 12%, the lack of particle grading will significantly limit the improvement space of the compaction density, and it is difficult to effectively improve the battery capacity. When the area ratio of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is greater than 50%, excessive large particles will cause serious rebound of the positive electrode film layer, trigger the breakage of the SEI film and cracking of the film layer, increase the risk of short circuit, and have an adverse impact on the cycle performance of the battery.

[0110] In the embodiments of the present application, the laminated battery cell is combined with a lithium-containing transition metal phosphate positive electrode film layer having a certain content of large particles to improve the battery capacity. Further, a separator with ceramic layers on both sides is used to increase the stiffness of the separator. At the same time, a separator with a porous continuous layer having a larger bonding area and stronger bonding force is adopted to increase the bonding effect between the separator and the positive electrode sheet, improve the compactness and stiffness of the internal grouping of the laminated battery cell, make up for the deficiency of the small external binding force of the laminated battery cell, reduce the risk that the mutual extrusion in the thickness direction of the positive and negative electrode sheets during the battery cell rebound evolves into misalignment in the horizontal direction, and reduce the risk of short circuit caused by the overlap of the positive and negative electrodes. Thus, on the basis of good battery capacity, the cycle performance of the battery is further improved.

[0111] In the present application, a laminated battery cell refers to a battery cell formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet together.

[0112] In the present application, 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. Other film layers that are connected to the positive electrode active material layer and are difficult to distinguish, such as the bottom coating layer, the liquid retention layer, etc., are collectively referred to as the positive electrode film layer.

[0113] Lithium-containing transition metal phosphate refers to a phosphate material containing lithium elements and transition metal elements, and can be detected by any well-known method in the art. For example, it can be detected by using an X-ray diffractometer (XRD) in combination with an energy spectrometer and an inductively coupled plasma mass spectrometer.

[0114] In the present application, the term "particle" refers to a particle with an identifiable complete boundary in the field of view of the positive electrode film layer at a certain magnification, such as 10,000 times. There may be defects and scratches inside the particle, but no complete boundary sufficient to divide the particle can be identified inside the particle.

[0115] The method for identifying particles is as follows: Cut the positive electrode film layer along the thickness direction of the electrode plate by an argon ion beam (as an example, the equipment model can be: Leica EM TIC 3X CP, working voltage: 6 kV, working duration: 6 h). After exposing the cut surface, use a scanning electron microscope (as an example, the equipment model can be: Hitachi SU8230, working voltage: 3 kV, beam current: high, probe model: U(LA100), working distance <5 mm) to observe the cut surface of the positive electrode film layer along the thickness direction of the electrode plate. Use a field emission scanning electron microscope to collect images in the secondary electron mode at a non-edge position on the cut surface of the positive electrode film layer (after observing the edge of the electrode plate under the scanning electron microscope, adjust the field of view to the central part of the sample), take an electron microscope image at a magnification of 10,000 times, and analyze the particles in the electron microscope image using ImageJ software (version 1.46r, win64). The specific usage method of ImageJ software is as follows: Load the scanning electron microscope image to be analyzed; Use the Cellpose plug-in software in it to identify particles, and perform manual correction on this basis; Use ImageJ to read and count data. The specific method for using the Cellpose plug-in software to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmantation module) to 15 pixels, click "runcyto3" to identify particles; Manually mark the particles in the image that are not recognized by the software, not completely recognized by the software, or have recognition errors. The particles in the image that are not recognized by the software, not completely recognized by the software, or have recognition errors mainly include the following types: 1. Due to the particle being too large or having scratches on the particle surface, the particle cannot be recognized or cannot be completely recognized; 2. During the argon ion beam cutting process, scratches will be generated on the particle surface, and the software may misjudge the scratches as the particle boundary during the recognition process, resulting in recognition errors; 3. Due to the particle being too small, it fails to be recognized; 4. The particle is located at the edge of the electron microscope field of view, and the inside of the particle is penetrated by the edge, and the morphology cannot be completely displayed, and the local part is recognized instead of the whole, resulting in recognition errors.For the particles that are not recognized or have recognition errors as described above, manual calibration is performed, and the specific process is as follows: Delete the particles located at the edges of the scanning electron microscope that cannot be fully displayed; Determine whether there are gap scratches inside other unrecognized or misrecognized particles. If there are no gap scratches inside the particles, then determine it as one particle, and manually mark it according to the particle boundary observed manually; In response to the presence of gap scratches inside the particle, determine whether the gap scratches penetrate the particle. If they do not penetrate the particle, then determine it as one particle and perform manual marking; In response to the gap scratches penetrating the particle, determine whether the gap scratches are linear or irregular; In response to the gap scratches being irregular, determine it as the boundary between particles and divide the particles along this boundary; In response to the gap scratches being linear, perform contrast; In response to the contrast being not obvious and there being no sense of crack, determine it as a scratch and mark it as one particle; In response to the contrast being strong and there being a sense of crack, determine it as the boundary between particles and mark it as two particles. After manual marking, delete the information unrelated to the particles in the automatic image processing process, that is, the determination and marking of the particles in the picture are completed.

[0116] In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size greater than or equal to 1 μm can intuitively reflect the proportional relationship between the area of the particles in this particle size range and the total particle area, and reflect the area size of the particles in this particle size range.

[0117] It can be understood that in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, especially the particles above 50 nm mainly come from the positive electrode active material. Therefore, by observing and statistically analyzing the particle area in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet in the embodiments of the present application, the distribution of the lithium-containing transition metal phosphate particles in the positive electrode film layer can be accurately and objectively reflected.

[0118] In the prior art, a laser particle size analyzer is usually used to statistically analyze the particle size of the positive electrode active material by the Malvern laser diffraction method. However, the applicant's research shows that due to the easy agglomeration of the lithium-containing transition metal phosphate particles, the test results obtained by the Malvern laser diffraction method based on the laser scattering principle often measure the particle size of the particle aggregates, and cannot truly reflect the particle size of the particles in the positive electrode active material, let alone reflect the dispersion state of the positive electrode active material in the film layer, because the dispersion degree of the positive electrode active material in the film layer will increase during the processes of pulping and film forming and rolling. The test results obtained by the Malvern laser diffraction method are affected by the particle size, specific surface area, and agglomeration degree of the positive electrode active material. Compared with the actual dispersion situation in the electrode sheet, the number of large particles obtained by this test is lower than the actual value, and the number of small particles is higher than the actual value. Therefore, the particle size obtained by the Malvern laser diffraction method test cannot be equivalent to or analogized to the particle size statistically obtained in the embodiments of the present application.

[0119] In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the method for testing the area proportion of particles with a particle size greater than or equal to 1 μm is as follows: Refer to the method described above in this application to identify the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet. Import the image after the particles are determined and marked into the ImageJ software for analysis. Complete the scale setting according to the scanning electron microscope image, and perform statistical analysis on the particle size, area, sphericity, and roughness of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet through the "Feret", "Area", "Round", and "Solidity" analysis functions. According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained by analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which characterizes the particle size of the particle; the obtained "Area" parameter represents the pixel area of the particle. Since particles with a particle size less than 50 nm have large errors in the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50 nm, which will cause large errors in the statistical results. Therefore, in the particle size statistics process of this application, particles with a particle size less than 50 nm are not counted, and the particle statistical data corresponding to "Area", "Round", or "Solidity" displayed as "NaN" are deleted. Calculate the sum of the "Area" parameters of the particles with a particle size greater than or equal to 1 μm and the sum of the "Area" parameters of all particles, which are respectively used 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. Divide 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 to obtain the area proportion of the particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0120] In some embodiments, the area proportion of the particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet can be 12%, 12.02%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 34.78%, 34.95%, 35%, 36%, 36.29%, 36.37%, 36.64%, 36.88%, 37%, 38%, 38.09%, 38.44%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 49.96%, 50% or any value range between any two of them.

[0121] In some embodiments, the polyvinylidene fluoride polymer includes one or more of polyvinylidene fluoride homopolymer (PVDF) and copolymer of polyvinylidene fluoride and hexafluoropropylene.

[0122] Such as Figure 2As shown, in the prior art, aqueous PVDF is often used as the bonding layer of the diaphragm, which often presents an island structure in the diaphragm. On the one hand, this is beneficial for providing gaps for the expansion of the battery cell, and on the other hand, it is easy to manufacture; however, such a diaphragm bonding layer has a low bonding area and weak bonding force.

[0123] like Figure 3 As shown, it is a schematic diagram of the surface morphology of the bonding layer 203 of the diaphragm of the embodiment of the present application. The bonding layer of the diaphragm of the embodiment of the present application has a certain pore structure in its continuous structure, and the ceramic layer arranged between the base film and the bonding layer can be observed through the pore structure. It can be understood that when a continuous layer with a porous structure is used as a bonding layer, it may become a block due to contact with the positive electrode sheet or the negative electrode sheet or force extrusion during the manufacturing or circulation of the electrode sheet. The continuous layer referred to in this application does not require that the bonding layer is continuous throughout the battery; but refers to a continuous layer of a uniform porous structure at the microscopic level, such as when observed under a microscope, rather than an island structure. In order to feedback the true morphology of the diaphragm, during the sampling process, it is preferred to sample in the area where the diaphragm bonding layer in the battery has less bonding with the positive electrode sheet or the negative electrode sheet. As an example, sampling is performed at the diaphragm position where the projection exceeds the positive electrode sheet and the negative electrode sheet; or sampling is performed at the diaphragm near the surface of the electrode assembly. The diaphragm sampled in this way can better reflect the true state of the diaphragm.

[0124] The diaphragm provided in the embodiment of the present application uses a continuous layer of a porous structure as a bonding layer, which has a larger bonding area than the island-shaped bonding layer in the prior art, so that the bonding between the diaphragm and the positive electrode film layer is more firm and uniform. At the same time, with the help of the pore structure in the bonding layer, it can have both the transmission efficiency of lithium ions and the dynamic performance of the battery. Compared with the wound battery, the laminated battery has a smaller pressing force between the pole pieces during the preparation of the battery, and the lithium-containing transition metal phosphate particles with a particle size greater than or equal to 1 μm will damage the SEI film and the pole piece film layer during the rebound process. At the same time, the mutual extrusion of the positive and negative pole pieces in the thickness direction is easy to cause the relative dislocation of the positive and negative pole pieces in the horizontal direction. The diaphragm provided in the embodiment of the present application is provided with a ceramic layer on both sides, and a continuous layer of a porous structure is used as a bonding layer, which is particularly suitable for laminated batteries, which is beneficial to reduce the rebound phenomenon of the laminated battery during a long cycle and improve the battery capacity during a long cycle.

[0125] The embodiment of the present application uses a continuous layer of a porous structure as a bonding layer to improve the bonding force between the diaphragm and the electrode while maintaining the air permeability and porosity of the diaphragm, thereby improving the stability of the electrode, further reducing the risk of internal short circuit caused by electrode rebound, and improving the cycle stability of the battery.

[0126] In some embodiments, the material of the base film may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene (PE), and polypropylene (PP).

[0127] In the present application, the ceramic layer comprises ceramic particles, and the ceramic particles comprise one or more of Al2O3, AlO(OH), SiO2, TiO2, MgO, CaO, ZnO2, ZrO2, and SnO2.

[0128] The ceramic particles have flame retardancy and a relatively high hardness value, and are not easily deformed by heat, so they have excellent dimensional stability. The ceramic layer is disposed on both sides of the base film, which is beneficial to improving the stiffness of the battery, reducing the rebound of the electrode sheet, and reducing the probability of contact between the negative electrode film layer and the positive electrode film layer and short circuit generation during the rebound of the electrode sheet.

[0129] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size of 1 μm - 5 μm is 12% - 50%.

[0130] When the area ratio of the particles with a particle size of 1 μm - 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial to improve the rebound phenomenon of large particles in the electrode sheet during the battery cycle while maintaining a high capacity, and to improve the cycle performance of the battery.

[0131] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size of 1 μm - 5 μm is 12% - 40%.

[0132] When the area ratio of the particles with a particle size of 1 μm - 5 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is within the above range, it is beneficial to further improve the rebound phenomenon of the electrode sheet caused by stress concentration of large particles in the electrode sheet while maintaining a high capacity, reduce the probability of contact between the negative electrode film layer and the positive electrode film layer of the electrode sheet and short circuit generation, and further improve the cycle performance of the battery.

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

[0134] As Figure 4 shown, the single-side thickness H of the positive electrode film layer refers to the distance between the first surface 102a of the positive electrode film layer 102 away from the positive electrode current collector 101 and the second surface 102b opposite to the first surface 102a. 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. Other film layers that are connected to the positive electrode active material layer and are difficult to distinguish, such as the bottom coating layer, the liquid retention layer, etc., are collectively referred to as the positive electrode film layer.

[0135] The thickness of the positive electrode film layer can be detected by any well-known method in the art. As an example, the thickness of the positive electrode film layer in the cross-section of the positive electrode sheet along the thickness direction is measured by a scanning electron microscope. Randomly select 3 different positions for measurement and calculate the average value as the thickness of the positive electrode film layer.

[0136] In some embodiments, the single-sided thickness of the positive electrode film layer can be selected from 70μm, 72.34μm, 71μm, 72μm, 73μm, 74μm, 75μm, 76μm, 77μm, 78μm, 79μm, 80μm, 81μm, 82μm, 83μm, 83.91μm, 84μm, 85μm, 86μm, 87μm, 88μm, 89μm, 90μm, 91μm, 91.88μm, 92μm, 93μm, 94μm, 95μm, 96μm, 97μm, 98μm, 98.93μm, 99μm, 100μm, 101μm, 102μm, 103μm, 104μm, 105μm, 105.44μm, 105.64μm, 105.65μm, 105.89μm, 106μm, 106.21μm, 106.34μm, 107μm, 108μm, 109μm, 110μm, 111μm, 112μm, 113μm, 114μm, 115μm, 116μm, 116.09μm, 117μm, 118μm, 119μm, 120μm or the numerical range between any two of them.

[0137] The specific capacity of the lithium-containing transition metal phosphate particles is relatively low. Research shows that when the single-sided thickness of the positive electrode film layer is less than 70μm, it is difficult for the battery capacity to meet the market demand. When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to improve the capacity of the single battery.

[0138] In some embodiments, the single-sided thickness of the positive electrode film layer is 90μm - 120μm.

[0139] When the single-sided thickness of the positive electrode film layer is within the above range, it is beneficial to further improve the battery capacity.

[0140] In some embodiments, the single-sided thickness of the positive electrode film layer is 100μm - 120μm.

[0141] Increasing the single-sided thickness of the positive electrode film layer is beneficial to improving the battery capacity. The applicant found that when the single-sided thickness of the positive electrode film layer is greater than or equal to 100μm, the phenomenon of particle rebound in the positive electrode film layer is more serious. The embodiments of the present application effectively alleviate the serious rebound of the thick-coated film layer in the laminated battery cell. On the basis of maintaining a high capacity, the battery has improved cycling performance.

[0142] In some embodiments, such as Figure 4As shown, the positive electrode plate 10 includes a positive electrode current collector 101 and a positive electrode film layer 102 disposed on at least one side of the positive electrode current collector 101. The positive electrode film layer 102 includes a first region 1021. The first region 1021 is located at the top of the positive electrode film layer 102 away from the positive electrode current collector 101. The distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region 1021 is 0.2% - 5%, and can be optionally 0.2% - 3.5%.

[0143] In this application, the first region of the positive electrode film layer refers to the region located at the top of the positive electrode film layer away from the current collector. As an example, the region within a thickness range of 20 μm from the first surface 102a of the positive electrode film layer is denoted as the first region of the positive electrode film layer.

[0144] The test method for the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region can be tested by methods known in the art. As an example, obtain a cross-sectional view of the positive electrode film layer along the thickness direction, observe the cross-section of the first region of the positive electrode film layer through a scanning electron microscope at a magnification of 3k times by a similar method as described above, continue to observe the electron microscope image at 3k times at a magnification of 10k times, select 10 non-overlapping fields of view, and take 10 scanning electron microscope images; import the 10 taken scanning electron microscope images into ImageJ software for analysis, test the area ratio of particles with a particle size greater than or equal to 1 μm in the 10 images, obtaining a total of 10 values; the range of the 10 obtained values is the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region, where the range is the difference between the maximum and minimum values among the 10 values. In the first region, the smaller the distribution uniformity of particles with a particle size greater than or equal to 1 μm, the more uniform the distribution of large particles in the positive electrode film layer.

[0145] In some embodiments, the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region can be optionally 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 1%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 1%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5% or any numerical range between any two of them.

[0146] The stress concentration degrees at large particles and small particles in the positive electrode film layer are different. Along with the gradual release of stress during the cycling process, it causes the electrode sheet to have different degrees of rebound. In the embodiments of the present application, there are large particles with a certain content, and at the same time, the large particles are evenly distributed in the electrode sheet, so that the extrusion force of the positive electrode film layer on the separator shows a uniform distribution, reducing the risk of local over-extrusion caused by uneven distribution of large particles and blockage of local lithium ion transport channels, which leads to an increase in the peripheral current density and is prone to lithium plating. This enables the battery to further improve the cycling performance of the battery on the basis of having good capacity.

[0147] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the area cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median value L of the sphericity A50 is 0.6 - 0.8.

[0148] The method for testing the sphericity of particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is as follows: Refer to the method described above in the present application to identify the particles with a particle size greater than or equal to 1 μm in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, and use the "Shape Descriptor" analysis function in ImageJ to analyze the morphology of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet. According to the software manual (ImageJ User Guide IJ 1.46r), the "Round" parameter obtained by the analysis represents the ratio of the pixel area of the particle to the area of a circle with the fitted major axis as the diameter, and can be used to characterize the sphericity of the particle. When the particle is closer to a sphere, the ratio of the pixel area to the area of a circle with the fitted major axis as the diameter is closer to 1. Therefore, the "Round" parameter of the obtained particle is used to characterize the sphericity of the particle. Since particles with a particle size less than 50 nm have large errors in the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50 nm, which will cause large errors in the statistical results, therefore, particles with a particle size less than 50 nm are not statistically counted in the particle size statistics process of the present application, and the particle statistical data corresponding to "NaN" displayed by Round is deleted. According to the above method, to meet the sample number with statistical significance, each electrode sheet collects at least 10 non-overlapping scanning electron microscope images of the field of view. Arrange the sphericities of at least 1000 obtained particles in ascending order, and obtain the sphericity cumulative distribution curve of the particles in the positive electrode film layer with the sphericity as the horizontal axis and the cumulative area ratio as the vertical axis. L A50 is the sphericity L value corresponding to the cumulative area ratio of 50% on the vertical axis in the particle sphericity L value cumulative distribution curve.

[0149] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the area cumulative distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median value L of the sphericity A50It can be optionally 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.705, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80 or a numerical range between any two of them.

[0150] The median of the sphericity of particles with a particle size greater than or equal to 1 μm is within the above range. The large particles have better sphericity, reducing particle bridging caused by the irregular shape of large particles, reducing the void content in the electrode sheet, and at the same time reducing the stress concentration aggravated by the irregularity of large particles, and reducing the rebound of the electrode sheet caused by stress release during the cycling process, so that the battery cell has high capacity while further improving its cycling performance.

[0151] Those skilled in the art can adjust the sphericity of particles through any known process. As an example, through processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, adding surfactants, etc., and adjusting the parameters of each process, the adjustment of the sphericity of particles can be achieved.

[0152] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median sphericity L A50 is 0.65 - 0.75.

[0153] The median of the sphericity of particles with a particle size greater than or equal to 1 μm being within the above range is beneficial to reducing the stress concentration of large particles aggravated by the irregularity of large particles, reducing the rebound of the electrode sheet caused by stress release during the cycling process, and improving the cycling performance of the battery.

[0154] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median sphericity L A50 is 0.67 - 0.75.

[0155] The median of the sphericity of particles with a particle size greater than or equal to 1 μm being within the above range can further improve the stress concentration of large particles, reduce the rebound of the electrode sheet caused by stress release during the cycling process, and further improve the cycling life of the battery cell.

[0156] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the positive electrode film layer, the median graphitization degree C 50 is greater than or equal to 0.95 and less than or equal to 1.20; wherein, the graphitization degree C value is I G / I D ,IG 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 .

[0157] In this application, the graphitization degree C value of the positive electrode film layer can be obtained through the surface scanning mode of a laser confocal Raman spectrometer. As an example, specifically, a laser confocal Raman spectrometer (high-precision Renishaw laser confocal Raman spectrometer) is used, with an excitation wavelength of 532 nm. An appropriate amount of the positive electrode film layer is taken, and its surface or the cross-section along the thickness direction of the electrode is scanned. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids. The grid vertices are used as the test points, with a step size of 5 μm and a total number of 100 scanning points. Thus, the C values at different positions and the cumulative distribution curve of the C value in the scanned area are obtained.

[0158] The positive electrode film layer in this application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery. It is inevitable that there are residual electrolyte salt particles on the surface of the positive electrode film layer disassembled from the battery. To improve the test accuracy, it is preferred to perform a surface scan on the cross-section of the positive electrode film layer along the thickness direction of the electrode to characterize the graphitization degree of the positive electrode film layer.

[0159] The graphitization degree C value of the positive electrode film layer is obtained through the peak intensity ratio of the G peak (G-band) and D peak (D-band) of the Raman spectrum. The G peak is located at 1580 ± 100 cm -1 , which characterizes the carbon sp 2 hybrid structure; the D peak is located at 1350 ± 100 cm -1 , which characterizes the disordered structure of carbon, where disorder means that there is no regular arrangement among the carbon atoms in the structure.

[0160] The cumulative distribution curve of the graphitization degree C value refers to the curve obtained by arranging at least 100 C values obtained in ascending order, with the graphitization degree on the horizontal axis and the cumulative quantity ratio on the vertical axis. C 50 is the C value corresponding to the cumulative quantity ratio of 50% on the vertical axis in the cumulative distribution curve of the graphitization degree C value. The median C of the graphitization degree 50 Compared with the point value, it can reflect the overall graphitization degree of the particles in the positive electrode film layer, that is, the ease of slippage; compared with the mean value, it can reduce the influence of extreme values during the test and improve the confidence level of the test results.

[0161] Those skilled in the art can adjust the graphitization degree of the active material particles through any known process. As an example, adjusting the carbon source, sintering temperature, sintering time, sintering pressure, and sintering atmosphere can all achieve the adjustment of the graphitization degree of the active material particles.

[0162] In some embodiments, in the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 can be optionally 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20 or the numerical range between any two of them.

[0163] In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median C of the graphitization degree 50 Within the above range, the compaction density of the electrode sheet can be further improved, so that the content of large-sized particles in the positive electrode film layer can be reduced, which helps to reduce the rebound phenomenon caused by excessive large particles in the film layer on the basis of maintaining the battery capacity, and further improves the cycling performance of the battery.

[0164] In some embodiments, in the cumulative distribution curve of the coating value B obtained in the surface scanning mode of a laser confocal Raman spectrometer for the positive electrode film layer, the median B of the coating value 50 is 0.30 - 0.60, where the coating value B is I P / I D where I P represents the intensity of the P peak of the Raman spectrum at 948 ± 100 cm -1 and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 .

[0165] The cumulative distribution curve of the coating value B refers to the curve obtained by arranging at least 100 obtained B values in ascending order, with the coating value as the horizontal axis and the cumulative quantity ratio as the vertical axis. In order to reduce the influence of the extreme values of the coating value caused by the non-particle region in the positive electrode film layer on the test results, the median B of the coating value is used 50 to evaluate the compactness of the carbon material layer on the positive electrode active material. B 50 is the B value corresponding to the cumulative quantity ratio of 50% on the vertical axis in the cumulative distribution curve of the coating value B.

[0166] In this application, the coating value B of the positive electrode film layer can be obtained by scanning with a laser confocal Raman spectrometer. As an example, specifically, a laser confocal Raman spectrometer (Renishaw high-precision laser confocal Raman spectrometer) is used. The excitation wavelength of 532 nm is selected. An appropriate amount of the positive electrode film layer is taken and surface scanning is performed on its surface or on the cross-section along the thickness direction of the electrode plate. The scanning area is 45 μm × 45 μm, which is divided into 10 × 10 grids. The grid vertices are used as test points, the step size is 5 μm, and the total number of scanning points is 100 points. Thus, the B values at different positions and the cumulative distribution curve of the B value in the surface scanning area are obtained. The positive electrode film layer in this application can be either a freshly prepared positive electrode film layer or a positive electrode film layer disassembled from a battery. It is inevitable that there are residual electrolyte salt particles on the surface of the positive electrode film layer disassembled from the battery. To improve the test accuracy, it is preferred to perform surface scanning on the cross-section of the positive electrode film layer along the thickness direction of the electrode plate to characterize the coating value of the positive electrode film layer.

[0167] The coating value B of the positive electrode film layer is obtained from the peak intensity ratio of the P peak (P-band) and the D peak (D-band) of the Raman spectrum. The position of the P peak is 948 ± 100 cm -1 , which characterizes the phosphate root PO4 3- structure; the position of the D peak is 1350 ± 100 cm -1 , which is one of the characteristic peaks of carbon materials and characterizes the defects or disordered structures in the sp 2 hybridized carbon atom lattice. During the test, an excitation wavelength of 532 nm is selected, and the test depth is relatively shallow, only the surface of the particles. Therefore, in the test results obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the carbon structure peak shows a higher intensity than the phosphate root structure peak.

[0168] Those skilled in the art can adjust the coating value of the active material particles through any known process. As an example, adjusting the type of carbon source, the amount of carbon source added, the sintering temperature, the sintering time, the sintering pressure, and the sintering atmosphere can all adjust the coating value of the active material particles. The coating value B can reflect the compactness of the carbon material layer on the surface of the lithium-containing transition metal phosphate particles. The denser the carbon material layer, the relatively lower the intensity of the phosphate root structure detected in the Raman spectrum, and the smaller the coating value B of the positive electrode film layer.

[0169] In some embodiments, the positive electrode film layer further includes a coating layer provided on at least a part of the surface of the lithium-containing transition metal phosphate particles. In the cumulative distribution curve of the coating value B obtained by the positive electrode film layer in the surface scanning mode of the laser confocal Raman spectrometer, the median B of the coating value 50It can be optionally 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.355, 0.36, 0.368, 0.369, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.446, 0.45, 0.456, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6 or a numerical range between any two of them.

[0170] The median B of the coating value of the positive electrode film layer 50 Within the above range, it indicates that the carbon material layer of the positive electrode active material is relatively dense and uniform, which is beneficial to improving the slip uniformity of the positive electrode film layer during the rolling process and reducing the stress concentration phenomenon in the positive electrode film layer; in addition, with the help of the dense and uniform carbon material layer, the large particles in the positive electrode film layer are more likely to achieve slip during the compaction process, thereby reducing the stress concentration phenomenon at the large particles in the positive electrode film layer and reducing the rebound caused by the stress release at the large particles during the cycle, and improving the cycle life of the battery.

[0171] In some embodiments, the iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm.

[0172] The iron dissolution rate of the positive electrode material can be tested by methods well-known in the art. As an example, weigh 7.5 g of the positive electrode material powder obtained by scraping powder from the positive electrode film layer sample, add it to 100.3 g of ascorbic acid solution with a mass concentration of 0.3% (the solvent is ultrapure water), stir at a speed of 500 revolutions per minute for 305 minutes, then quickly use a 5 mL syringe to rapidly extract the solution, filter the solution through a 0.45 μm pore size filter head into a test tube, pipette 1 mL of the supernatant with a pipette gun, add it to a glass volumetric flask and dilute it 50 times, and test it with an inductively coupled plasma mass spectrometer (ICP - OES) to obtain the iron element concentration in the solution. Through the formula: (ICP - tested iron element concentration × solution volume / mass of the solution participating in the volume fixing) × 100.3 g / mass of the positive electrode material powder, the solution volume is 50 mL, and the mass of the solution participating in the volume fixing is 1 g, calculate the iron dissolution rate of the positive electrode material.

[0173] In some embodiments, the iron dissolution rate of the positive electrode material can be 658 ppm, 700 ppm, 800 ppm, 890 ppm, 900 ppm, 1000 ppm, 1058 ppm, 1076 ppm, 1100 ppm, 1143 ppm, 1200 ppm, 1236 ppm, 1300 ppm, 1311 ppm, 1384 ppm, 1349 ppm, 1400 ppm, 1485 ppm, 1500 ppm, 1531 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1921 ppm, or the numerical range between any two of them.

[0174] In some embodiments, the iron dissolution rate of the positive electrode material is 658 ppm - 1485 ppm.

[0175] The iron element dissolved in the positive electrode material mainly comes from the lithium-containing transition metal phosphate particles of the positive electrode active material. The level of the iron dissolution rate depends on the one hand on the number of lattice defects of the lithium-containing transition metal phosphate particles, and on the other hand on the integrity and density of the carbon material layer on the surface of the positive electrode active material. The lower the iron dissolution rate means fewer lattice defects in the lithium-containing transition metal phosphate particles, which is beneficial to reducing the corrosion of the lattice in a weak acid environment; and the more complete and dense the carbon material layer on the surface of the positive electrode active material, the more it inhibits the dissolution of iron ions in a weak acid environment. The positive electrode material with an iron dissolution rate within the above range has relatively few lattice defects and a complete and dense carbon material layer, which is beneficial to improving the compressive resistance and easy slip degree of the particles in the positive electrode film layer under a large rolling pressure, increasing the compaction density of the positive electrode film layer and reducing the stress concentration in the positive electrode film layer, improving the rebound phenomenon caused by stress concentration of large particles, and enabling the battery to further improve the cycle performance of the battery on the basis of having good capacity.

[0176] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include the components shown by the following general formula: Li m Fe x P y O j Q q Formula I wherein, Q includes one or more of Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4, 0 ≤ q ≤ 0.1.

[0177] In some embodiments, m can be optionally 0.8, 0.85, 0.9, 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15 or a numerical range between any two of them; x can be optionally 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0 or a numerical range between any two of them; y can be optionally 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or a numerical range between any two of them; j can be optionally 3.5, 3.6, 3.7, 3.8, 3.9, 4 or a numerical range between any two of them; q can be optionally 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or a numerical range between any two of them.

[0178] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate and their modified materials.

[0179] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate and its doped modified materials, coated modified materials.

[0180] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element is 500 ppm - 8000 ppm.

[0181] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element is 1000 ppm - 3000 ppm.

[0182] The types and contents of elements in the lithium-containing transition metal phosphate particles in the positive electrode film layer can be tested by any well-known method in the art. As an example, the inductively coupled plasma emission spectrometry is used to test the titanium element and its content with reference to Appendix C of GB / T 33822-2017.

[0183] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element can be optionally 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm or a numerical range between any two of them.

[0184] Introducing titanium element into the lithium-containing transition metal phosphate particles requires adding a titanium source during the preparation of the positive electrode active material. The titanium source is often an inert material, and attaching to the surface of the raw material of the lithium-containing transition metal phosphate particles can play a role in reducing the reaction activity and reducing the growth of particle size. Improving the graphitization degree of the positive electrode active material often requires a higher sintering temperature or a longer sintering time, but this will also increase the size of the particles in the positive electrode film layer, increase the stress concentration in the positive electrode film layer, and increase the rebound of the electrode during cycling. In the embodiments of the present application, by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, the reaction activity of the synthesis raw material of the positive electrode active material is reduced, so that the positive electrode active material can control the proportion of large particles while having a high graphitization degree, reduce the stress concentration in the positive electrode film layer, improve the rebound phenomenon caused by stress concentration at the large particles, and further improve the cycling performance of the battery on the basis of having good capacity.

[0185] At the same time, the doping of titanium element in the positive electrode active material is beneficial to causing lattice distortion, reducing the Li-O bond energy, increasing the lithium ion transmission rate, and improving the kinetic performance of the battery. The lithium ion diffusion in the positive electrode film layer is uneven, often accompanied by a significant lithium ion concentration gradient. In the embodiments of the present application, the solid-phase transmission rate of the positive electrode active material is improved by adding a high content of titanium element to the lithium-containing transition metal phosphate particles, and the kinetic problems of the battery are improved.

[0186] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of vanadium element is 500 ppm - 5000 ppm.

[0187] The types and contents of elements in the lithium-containing transition metal phosphate particles in the positive electrode film layer can be tested by any well-known method in the art. As an example, the inductively coupled plasma emission spectrometry is used to test the vanadium element and its content with reference to Appendix C of GB / T 33822-2017.

[0188] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of the vanadium element can be optionally 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm.

[0189] In some embodiments, based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of the vanadium element is 500 ppm - 3000 ppm.

[0190] The vanadium element in the positive electrode film layer can be in multiple valence states. Among them, vanadium with a +5 valence (V 5+ ) can be doped at the phosphorus element site. Due to its relatively large radius, it can cause lattice distortion and expand the diffusion channels of lithium ions, thereby improving the ionic conductivity of the positive electrode active material and enhancing the kinetic performance of the battery; vanadium with a +3 valence (V 3+ ) can be doped at the transition metal site, and lithium vacancies are generated through charge compensation, thereby improving the electronic conductivity of the positive electrode active material. In addition, the improvement of the uniformity of the distribution of the vanadium element in the lithium-containing transition metal phosphate particles helps to further improve the kinetic performance of the positive electrode film layer and the reaction uniformity of the positive electrode film layer, thereby further enhancing the kinetic performance and cycling performance of the battery cell.

[0191] The mass content of the vanadium element within the above range helps to improve the kinetic performance of the positive electrode sheet and the kinetic performance of the lithium-containing transition metal phosphate battery. At the same time, the synergistic effect of titanium element, vanadium element and carbon nanotubes in the positive electrode film layer helps to form a good three-dimensional network, further improving the electronic conductivity and ionic conductivity of the positive electrode film layer, thereby further improving the kinetic performance of the lithium-containing transition metal phosphate battery.

[0192] In some embodiments, the positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the total area of the agglomeration regions of the conductive agent accounts for 0.2% - 6%, optionally 1.5% - 5%.

[0193] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the fact that the total area of the agglomeration regions of the conductive agent is within the above range indicates that the conductive agent in the positive electrode film layer is uniformly dispersed, facilitating the formation of a uniform conductive network, which is beneficial to reducing local polarization and even lithium plating problems generated during battery cycling.

[0194] Meanwhile, research shows that large-sized particles in lithium-containing transition metal phosphates are prone to rebound. When the agglomeration area of the conductive agent is within the above range, it can suppress the rebound of lithium-containing transition metal phosphate particles by virtue of the uniform distribution of the conductive agent, form a mechanical restraint on the particles and even the film layer, improve the cohesive force of the film layer, reduce the damage of the SEI film and the film layer during the film layer rebound process, and improve the cycle life of the battery.

[0195] Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration regions of the conductive agent can be tested by the following method. Observe the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet through a scanning electron microscope by using a similar method as described above, and measure the area of the agglomeration regions of the conductive agent in the scanning electron microscope image at a magnification of 3k times. Since the conductive agent is generally a carbon-based material, such as conductive carbon black, carbon nanotubes, etc., the agglomeration regions of the conductive agent often appear as black agglomerations compared to other regions in the positive electrode film layer. At a high magnification, aggregated conductive agents can be seen. The agglomeration regions of the conductive agent refer to the range of regions in the scanning electron microscope image where the conductive agent is significantly aggregated and appears black. With the help of image analysis software, such as ImageJ, count the white marked regions in the image, screen out the regions where the Feret is greater than or equal to 2μm. The "Feret" parameter obtained represents the maximum distance between all parallel lines in the two-dimensional projection of the region; its total area is the total area of the agglomeration regions of the conductive agent in the scanning electron microscope image. The area ratio of the agglomeration regions of the conductive agent is characterized by dividing the total area of the agglomeration regions of the conductive agent obtained by testing in the scanning electron microscope image at a magnification of 3k times by the area of the scanning electron microscope image. Randomly select 3 non-overlapping scanning electron microscope images and calculate the average value as the "total area ratio of the agglomeration regions of the conductive agent based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet".

[0196] In some embodiments, the conductive agent includes carbon nanotubes, and the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes. Optionally, the conductive agent further includes conductive carbon black.

[0197] Carbon nanotubes have a high aspect ratio, which is conducive to overlapping multiple positive electrode particles in the thickness direction between particles, forming a long-range conductive path while increasing the binding force between particles, reducing local polarization and even lithium plating problems generated during battery cycling, and improving the cycle life of the battery; it can also reduce the rebound phenomenon of large particles in the positive electrode film layer through the binding effect, improving the cycle performance of the battery.

[0198] Conductive carbon black has a small size, adheres to the surface of positive electrode particles and fills the gaps between positive electrode particles, forming dense dot-like conductive contacts. When used in combination with carbon nanotubes, it takes into account both long-range and short-range conductivity, which is beneficial to further improve the conductive network in the positive electrode film layer. At the same time, the conductive agent has a large specific surface area, which is conducive to liquid absorption and liquid retention, and can reduce the phenomenon of electrolyte extrusion caused by the high growth rate of the swelling force during long cycling of the electrode sheet, improving the long cycle life of the battery.

[0199] In some embodiments, the agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0200] 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 unable to form an effective carbon nanotube network structure. The surface energy of conductive carbon black and carbon nanotubes is relatively close, and it can adsorb on the surface of carbon nanotubes to form a physical barrier, increasing the resistance to carbon nanotube agglomeration, reducing the direct contact between carbon nanotubes, thereby inhibiting the agglomeration phenomenon and improving the distribution uniformity of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the positive electrode film layer and the kinetic performance of the battery; on the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reducing the risk of peeling of the positive electrode film layer, and further improving the kinetic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the agglomeration region of the conductive agent will also cause local ion transport path blockage in the agglomeration region of the conductive agent. The combination of conductive carbon black can improve the lithium ion transport ability in this region, reduce local polarization, and further improve the cycle stability of the battery.

[0201] In some embodiments, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

[0202] In some embodiments, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or the numerical range between any two of them.

[0203] In some embodiments, based on the mass of the positive electrode film layer, the mass content C2 of the conductive carbon black can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or the numerical range between any two of them.

[0204] When the mass contents of the carbon nanotubes and the conductive carbon black are within the above ranges, the agglomeration phenomenon of the carbon nanotubes can be effectively alleviated and a good conductive network structure can be formed, thereby effectively reducing the stress concentration of the positive electrode film layer, improving the liquid retention rate of the positive electrode film layer during long-term cycling, further reducing the risk of the electrode film layer peeling off and the degree of polarization, improving the kinetic performance of the battery and improving the cycle life of the battery.

[0205] In some embodiments, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

[0206] The polar groups (such as cyano group, -CN) in the hydrogenated nitrile rubber HNBR molecules can interact with the hydroxyl groups (-OH) or metal oxide sites on the surface of the lithium-containing transition metal phosphate particles (such as hydrogen bonding, dipole interaction), enhancing the compatibility between the particles and the solvent, reducing the interfacial tension between the particles and the solvent, especially the interfacial tension of large particles, making the particles more easily and uniformly dispersed, reducing the aggregation caused by hydrophobicity, improving the dispersibility of large particles in the positive electrode film layer, and reducing the stress concentration generated during the die-cutting process of the positive electrode film layer.

[0207] At the same time, when the slurry is dried into a film, the elastic network structure of HNBR can buffer the shrinkage stress generated by the volatilization of the solvent, reduce the re-aggregation of the conductive agent due to capillary force during this process, reduce the area ratio of the agglomeration region of the conductive agent, and improve the cycle life of the battery.

[0208] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

[0209] In some embodiments, based on the mass of the positive electrode film layer, the mass content of the dispersant can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the numerical range between any two of them.

[0210] When the mass content of the dispersant is within the above range, it is possible to achieve uniform dispersion of the particles in the positive electrode film layer while maintaining a high loading amount of the positive electrode film layer, and the battery has good capacity and cycling performance.

[0211] In some embodiments, when the battery cell is in a fully discharged state, the tap density of the positive electrode plate is 2.3 g / cm 3 - 2.6 g / cm 3 .

[0212] In this application, the fully discharged state means that the battery is placed in an oven environment at 25°C, left standing for 2 h, and after the battery temperature remains at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then at a constant current of 0.1C to 2.0V.

[0213] The tap density of the positive electrode plate can be tested by methods known in the art. As an example, the battery is placed in an oven environment at 25°C, left standing for 2 h, and after the battery temperature remains at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then at a constant current of 0.1C to 2.0V. The battery is disassembled to obtain the positive electrode plate, the residual electrolyte is treated with dimethyl carbonate solvent, the electrode plate is dried, cut into small circular pieces with an area of S, and its mass is W1. The thickness T1 of the positive electrode plate is measured using a micrometer. Then, the positive electrode film layer of the above-weighted electrode plate is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. Then, the tap density PD of the positive electrode plate = (W1 - W2) / [(T1 - T2)×S].

[0214] In some embodiments, when the battery is in a fully discharged state, the tap density of the positive electrode plate can be selected as 2.3 g / cm 3 , 2.31 g / cm 3 , 2.32 g / cm 3 , 2.33 g / cm 3 , 2.34 g / cm 3 , 2.35 g / cm 3 , 2.36 g / cm 3 , 2.37 g / cm 3 , 2.38 g / cm 3 , 2.39 g / cm 3 , 2.40 g / cm 3 , 2.41 g / cm 3 , 2.42 g / cm 3 , 2.43 g / cm 3 , 2.44 g / cm 3 , 2.45 g / cm 3 , 2.46 g / cm 3 , 2.47 g / cm 3 , 2.48 g / cm3 , 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 the numerical range between any two of them.

[0215] In some embodiments, the porosity of the positive electrode film layer is 14% - 28%.

[0216] The porosity of the positive electrode film layer can be tested in the following manner. Import the scanning electron microscope image of the cross-section of the positive electrode film layer obtained in the manner described above along the thickness direction of the electrode sheet into the ImageJ software. Select the straight line tool, use the straight line to mark the scale length in the picture, click "Analyze Set Scale", and set the scale parameters in the software according to the scale length in the picture. Select the rectangular tool, select the part of the picture outside the scale area, use "Image Duplicate" to copy the selected area, and use "Image Type 8 bit" to adjust the picture format; select "Analyze Set Measurements", and select the following 5 options: "Area", "Mean gray value", "Area Fraction", "Limit to threshold", "Feret’s diameter", where "Decimal places" is selected as 3, and successively select "Image" - "Adjust" - "Threshold", and set 0 and 100 in turn at the position of the "Threshold" box, then the pore data in the cross-section electron microscope image can be exported using the Analyze - Measure function. Use "Image" - "Overlay" - "Flatten" to export and obtain the pore picture; click "Apply" in "Threshold", then click "Analyze" - "Analyze Particles", and check the left four columns to obtain the pore statistical data.

[0217] It can be understood that in the embodiments of the present application, the "pores" in the cross-section of the positive electrode film layer are identified through the color difference of the picture and the threshold. This "pore" is not the pore data obtained from the exhaust test, and is mainly used to characterize the cross-sectional area between the particles in the cross-section of the positive electrode film layer. This method is superior to the exhaust method because the porosity obtained by the exhaust method is related to the pores between the particles and also related to the pores in the carbon material on the surface of the lithium iron phosphate particles, so it is impossible to objectively reflect the pores between the particles.

[0218] On the one hand, when the porosity of the positive electrode film layer is within the above range, it is beneficial to improve the liquid retention characteristics of the electrolyte, improve the ion diffusivity of the positive electrode film layer with large particles having a certain area ratio, and improve the kinetic performance of the battery.

[0219] In some embodiments, the porosity of the positive electrode film layer can be selected as 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or the numerical range between any two of them.

[0220] In some embodiments, a bottom coating is provided in the bottom region of the positive electrode film layer close to the positive electrode current collector. The bottom coating includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes a polyvinylidene fluoride polymer.

[0221] In some embodiments, the thickness of the bottom coating is 0.5 μm - 5 μm.

[0222] In some embodiments, the thickness of the bottom coating can be selected as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the numerical range between any two of them.

[0223] The bottom coating provided by the embodiments of the present application helps to improve the adhesion between the positive electrode film layer and the positive electrode current collector and relieve the stress concentration phenomenon at the large particles, thereby reducing the probability of the positive electrode film layer falling off and improving the cycle stability of the battery. At the same time, compared with the direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the bottom coating and the positive electrode film layer increases, which helps to increase the area of electron transfer between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode sheet and improving the kinetic performance of the battery.

[0224] In some embodiments, the thickness of the base film in the separator is 7 μm - 9 μm.

[0225] In some embodiments, the thickness of the base film in the separator can be selected as 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or the numerical range between any two of them.

[0226] In some embodiments, the thickness of the ceramic layer on one side of the separator is 2 μm - 4 μm.

[0227] In some embodiments, the thickness of the ceramic layer on one side of the separator can be selected as 2μm, 2.5μm, 3μm, 3.5μm, 4μm, or the numerical range between any two of them.

[0228] In some embodiments, the thickness of the adhesive layer on one side of the separator is 1μm - 5μm.

[0229] In some embodiments, the thickness of the adhesive layer on one side of the separator can be selected as 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or the numerical range between any two of them.

[0230] If the thickness of the adhesive layer is too low, the space for buffer expansion in the separator is small and the adhesion between the separator and the electrode is low. On the one hand, after the film layer expands, the stress increases and the probability of the film layer peeling off increases, affecting the cycle life of the battery; on the other hand, the probability of positive-negative short circuit increases, thus affecting the safety performance of the battery. If the thickness of the adhesive layer is too large, the space occupancy rate of the battery is large, thus affecting the volume energy density of the battery. In the embodiments of the present application, when the thickness of the adhesive layer is within the above range, it helps to balance the cycle life, safety performance and volume energy density of the battery.

[0231] In some embodiments, as Figure 5 shown, the battery cell 5 includes a housing 50, the stacked electrode assembly is accommodated in the housing 50, the size of the housing 50 in the length direction X is L1, the size of the housing 50 in the width direction Y is W1, and the size of the housing 50 in the thickness direction Z is H1, where 480mm ≤ L1 ≤ 720mm, 100mm ≤ W1 ≤ 150mm; 14mm ≤ H1 ≤ 22mm.

[0232] In some embodiments, L1 can be selected as 480mm, 490mm, 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 600mm, 610mm, 620mm, 630mm, 640mm, 650mm, 660mm, 670mm, 680mm, 690mm, 700mm, 710mm, 720mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm, 1250mm, 1300mm, or the numerical range between any two of them.

[0233] In some embodiments, W1 can be selected as 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, or the numerical range between any two of them.

[0234] In some embodiments, H1 can be optionally 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm or a numerical range between any two of them.

[0235] When the housing size of the battery cell in the embodiment of the present application is within the above range, it is beneficial for the battery to achieve a better capacity.

[0236] In some embodiments, the size of the housing in the length direction is L1, and 450mm ≤ L1 ≤ 650mm.

[0237] When the size L1 of the housing in the length direction satisfies 450mm ≤ L1 ≤ 650mm, the length of the battery cell is shorter, which helps to shorten the diffusion path of the current, reduce the internal resistance of the electrode sheet, thereby reducing the heat generation of the battery and improving its kinetic performance; in addition, the shorter housing length helps to shorten the diffusion path of the electrolyte during the infiltration process, improve the infiltration rate and uniformity of the electrolyte, further promote the uniformity of lithium-ion deintercalation during the cycling process, relieve the stress concentration phenomenon, reduce the degree of film layer rebound, and improve the cycling stability of the battery cell.

[0238] In some embodiments, the size of the housing in the length direction is L1, and 900mm ≤ L1 ≤ 1300mm.

[0239] When the size L1 of the housing in the length direction satisfies 900mm ≤ L1 ≤ 1300mm, the size of the battery cell is longer, which helps to reduce the volume ratio of the housing in the battery cell and increase the load ratio of the active material. At the same time, the longer battery cell can reduce the number of battery cells required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of the structural parts in the module, thereby improving the space utilization rate of the battery pack, and further helping to improve the volume energy density of the battery cell.

[0240] In some embodiments, as Figure 5 shown, the material of the housing 50 is a soft-pack material, and the soft-pack material includes an aluminum-plastic composite film.

[0241] In some embodiments, the material of the housing includes a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), polyethylene (PE) and aluminum.

[0242] The soft-pack material has a high elongation rate, so its housing is thinner, lighter and softer, which helps to improve the space utilization rate of the battery cell, thereby increasing the energy density of the battery cell. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery interior, reduce the decomposition of the electrolyte and the oxidation degree of the electrode material, thereby increasing the battery life.

[0243] In some embodiments, with continued reference to Figure 5 , the housing 50 includes a first sealing region 51 disposed at at least one end of the stacked battery cells extending in the width direction (Y direction); the first sealing region 51 includes a folded edge structure extending in the length direction (X direction), and a packaging adhesive is disposed on the folded edge structure, and the packaging adhesive is continuously disposed in the length direction (X direction) and fixes the folded edge structure.

[0244] The folded edge structure refers to a strengthened structure formed by folding the packaging area, and the number of folds is not limited. As an example, it can be a single-folded edge structure folded once, or a double-folded edge structure folded on both sides.

[0245] During the cycling of the electrode sheet, the SEI film on the positive electrode film layer will thicken. Therefore, large rebound and gas generation will occur during long-term cycling. The sealing region of the soft-pack battery cell is used to seal the electrode assembly, but the strength of the sealing region is limited and is easily opened by the large rebound and high gas generation in the film layer.

[0246] In the embodiment of the present application, the sealing strength of the first sealing region is further improved by including a folded edge structure extending in the length direction in the first sealing region. The continuous arrangement of the packaging adhesive in the length direction and fixing the folded edge structure can further improve the packaging strength compared with the discontinuous arrangement of the packaging adhesive in the length direction, realize continuous reinforcement in the length direction of the sealing region, and reduce the probability that the electrode sheet breaks through the sealing region in the packaging during the cyclic rebound process.

[0247] In some embodiments, the housing 50 includes at least one second sealing region 52, the second sealing region 52 is disposed at at least one end of the stacked battery cells along the length direction of the housing, and the second sealing region 52 is disposed on the tab side of the stacked battery cells.

[0248] It can be understood that the positive electrode tab and the negative electrode tab can be disposed on the same side of the stacked battery cells, as Figure 5 shown; or they can be disposed on opposite sides of the stacked battery cells.

[0249] In some embodiments, the battery cell 5 further includes a lead-out member 53, the lead-out member 53 is connected to the tab of the battery cell. For example, the lead-out member 53 can be connected to the tab by welding. The lead-out member 53 is a conductive member, and at least a part of the lead-out member 53 is located outside the housing 50. The lead-out member 53 serves as the electrode lead-out end of the battery cell 5, and the lead-out member 53 is used to facilitate the electrical connection between the battery cell 5 and other battery cells 5 or other components. For example, the lead-out member 53 can be in the shape of a sheet.

[0250] Correspondingly, the lead-out member 53 also includes a positive electrode lead-out member and a negative electrode lead-out member. The positive electrode lead-out member is connected to the positive electrode tab, and the negative electrode lead-out member is connected to the negative electrode tab.

[0251] The second sealing area is arranged on the tab side. The tab needs to be connected to the lead-out component, and the connection strength between the lead-out component and the housing material is relatively weak, making it easy for gas to rush out from the second sealing area, which is beneficial to achieving the directional pressure relief of the battery, reducing the impact on adjacent battery cells during thermal runaway, and improving the overall service life of the battery.

[0252] In some embodiments, a plurality of rubber rings surrounding along the width direction are arranged on the outer periphery of the laminated battery cell, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

[0253] The spaced arrangement of the rubber rings surrounding along the width direction of the battery cell in the length direction is beneficial to fixing the positions between the electrode plates in the battery cell, reducing the probability of displacement of the battery cell during the shaking of the battery. It is especially suitable for batteries with a larger length, and can effectively reduce the mutual displacement between the electrode plates in the length direction, thereby causing the phenomenon of lithium plating, which is beneficial to maintaining the stability of the internal space structure of the battery, and thus does not affect the normal operation of the battery.

[0254] In some embodiments, at 25 °C, the capacity of the battery cell is 100 Ah - 300 Ah, optionally 110 Ah - 190 Ah, and further optionally 125 Ah - 180 Ah.

[0255] In this application, the capacity of the battery cell has the meaning well-known in the art, and can be tested by the methods known in the art. As an example, at 25 °C, the battery cell is charged at a charging rate of 0.5C of the nominal capacity of the battery cell to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, left standing for 10 min, and then discharged at a discharge rate of 1C to 2.5V, left standing for 10 min. The capacity C during the discharge process is calculated by the formula C = I * t, and the unit is Ah.

[0256] In some embodiments, at 25 °C, the capacity of the battery cell can be optionally 100 Ah, 125 Ah, 130 Ah, 135 Ah, 140 Ah, 145 Ah, 150 Ah, 155 Ah, 160 Ah, 165 Ah, 170 Ah, 175 Ah, 180 Ah, 185 Ah, 190 Ah, 300 Ah or the numerical range between any two of them.

[0257] The battery cell of the embodiment of this application has a higher capacity by means of a suitable housing size to accommodate the laminated battery cell and controlling a reasonable large particle proportion in the film layer of the positive electrode plate in the laminated battery cell.

[0258] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0259] In some embodiments, the negative current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0260] In some embodiments, the negative electrode film layer includes a negative electrode active material. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0261] In some embodiments, the negative electrode film layer may also optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0262] In some embodiments, the negative electrode film layer may also optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0263] In some embodiments, the negative electrode sheet can be prepared in the following manner: dispersing the above components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0264] The second aspect of the present application provides a battery device, including the battery cell provided by the first aspect of the present application.

[0265] The battery device disclosed in the embodiments of the present application can be used in electrical devices that use the battery device as a power source or various energy storage systems that use the battery device as an energy storage element. In addition to being used in vehicles, the battery device can also be used in, but not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0266] In addition, the present application also provides an electrical device that uses the battery device as a power source. The electrical device includes at least one of the battery cell, battery module, or battery pack provided by the present application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device.

[0267] As the electrical device, the battery cell, battery module, or battery pack can be selected according to its usage requirements.

[0268] Figure 6 This is an electrical device as an example. The electrical device disclosed in the embodiments of the present application can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A battery device is arranged inside the vehicle, and the battery device can be arranged at the bottom, head, or tail of the vehicle. The battery device can be used for power supply of the vehicle. For example, the battery device can be used as the operating power source of the vehicle. The vehicle can also include a controller and a motor. The controller is used to control the battery device to supply power to the motor. For example, it is used for the working power requirements during the start, navigation, and driving of the vehicle. In some embodiments of the present application, the battery device can not only be used as the operating power source of the vehicle, but also be used as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0269] The embodiments of the present application also provide an energy storage device that uses the battery device as a power source. The energy storage device can be, but not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0270] Embodiment The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation of the present application. For those where specific technologies or conditions are not indicated in the embodiments, the technologies or conditions described in the literature in this field or the product specifications shall be followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchases.

[0271] Example 1 (1) Preparation of the positive electrode active material Lithium carbonate, iron phosphate, titanium dioxide, vanadium pentoxide, sucrose, glucose, and polyethylene glycol were added to deionized water and mixed in a premixing tank. Among them, the ratio of lithium carbonate to iron phosphate was such that the molar ratio of lithium to iron was 1.02:1.0. Based on the total mass of the mixed raw materials, the mass content of sucrose was 2%, the mass content of glucose was 4%, and the mass content of polyethylene glycol was 5%. After mixing evenly, a mixed raw material with a solid content of 38% was obtained; Among them, the particle size Dv 50 of lithium carbonate was 6 μm; the morphology of the iron phosphate particles was spherical-like; both titanium dioxide and vanadium pentoxide were nanoparticles; the purity of sucrose was ≥98%; the mass content of water in glucose was <0.5%; the weight-average molecular weight of polyethylene glycol was 1500.

[0272] The mixed raw material was ground twice in a sand mill, first coarsely ground for 1 h and then finely ground. During the grinding process, the temperature of the slurry was controlled to be less than 40 °C to obtain a mixed slurry; the particle size Dv50 of the solid particles in the mixed slurry was 0.40 μm, and spray drying was performed to obtain a dried precursor powder, and its particle size Dv50 after drying was 55.50 μm.

[0273] The precursor powder was sintered in a nitrogen atmosphere by two-stage heating to obtain the positive electrode active material: heated from 25 °C to 460 °C at a heating rate of 2 °C / min (the first heating stage) and held for 3 h; heated from 460 °C to 780 °C at a heating rate of 5 °C / min (the second heating stage) and held for 12 h; among them, the ventilation volume during the heating stage was greater than that during the constant temperature stage, and the ratio was 1.5:1, and the total ventilation volume was 1350 cm 3 / h, and then cooled after completion; the lithium iron phosphate positive electrode active material with a carbon material on the surface and a particle size Dv50 of 1.6 μm was obtained by airflow pulverization. Among them, based on the total mass of the positive electrode active material, the mass content of Ti element was 1050 ppm, and the mass content of V element was 950 ppm.

[0274] The above Dv10, Dv50, and Dv90 refer to the data obtained by testing with the Malvern laser scattering method.

[0275] (2) Preparation of the positive electrode plate Mix the above-mentioned cathode 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% in the solvent N-methylpyrrolidone, and then add a dispersant HNBR with a mass ratio of 1.1%, and mix well in a stirring tank. Stirring includes first stirring and second stirring. The stirring speed of the first stirring is 600 rpm and the stirring time is 30 min. The stirring speed of the second stirring is 1600 rpm and the stirring time is 260 min. After dispersion, a cathode slurry is prepared; after the stirring process is completed, the cathode slurry is transported to the coating process; among them, the mass ratios of the cathode active material, the conductive agent, the binder, and the dispersant are calculated based on the total mass of the solids in the cathode slurry; the conductive agent includes 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 85m 2 / g, the oil absorption value is 200 ml / 100 g, the average length of the single-walled carbon nanotubes is 30 μm, the specific surface area is 300m 2 / g, and the mass content of metal impurities in the single-walled carbon nanotubes < 1 wt%; Transfer coat the cathode slurry onto the current collector aluminum foil and dry it. After hot pressing, the single-sided thickness of the cathode film layer is 105.64 μm and the tap density is 2.36 g / cm 3 of the cathode pole piece. Among them, the transfer coating speed is 20 m / min.

[0276] The hot pressing process includes three hot roll pressing processes, and the hot roll pressing pressure increases in sequence. The hot roll pressures are 40 tons, 60 tons, and 80 tons in sequence; the hot roll temperature is 60 °C. Before the first entry into the hot roll compaction, the pole piece is heated, and the heating temperature is 40 °C.

[0277] Here, the tap density refers to the tap density under the fully discharged state of the battery cell, and its test method is as follows.

[0278] Among them, the median C 50 of the graphitization degree of the cathode film layer is 1.005; the porosity of the cathode film layer is 16.1%; the iron dissolution rate of the cathode material is 974 ppm; the total area ratio of the agglomeration regions of the conductive agent is 1.99%.

[0279] Cut the cathode pole piece into strips and punch it into a specified shape, and classify the punched cathode pole pieces by weight through a weighing and sorting machine for the laminator to stack.

[0280] (3) Preparation of the anode pole piece Natural graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed evenly according to a weight percentage of 95:1:2:2, and deionized water is added. After stirring and dispersing, a negative electrode slurry is obtained. The negative electrode slurry is coated on a substrate copper foil, and after drying, compaction, slitting, and sheet making, a negative electrode plate is obtained.

[0281] The negative electrode plate is slit and punched into a specified shape, and the punched negative electrode plates are sorted by weight through a weighing and sorting machine for stacking by a stacker.

[0282] (4) Separator Polyvinylidene fluoride (PVDF) is dissolved in N-methylpyrrolidone (NMP), and after stirring evenly, polyethylene glycol (PEG) is added as a pore-forming agent and stirred thoroughly to obtain a bonding layer solution. The bonding layer solution is coated on the base film with ceramic layers on both sides, pre-volatilized at 80 °C and dried at 110 °C, and then immersed in deionized water to dissolve PEG, obtaining a separator with porous bonding layers on both sides. Among them, the thickness of the base film is 8 μm, the thickness of the single-sided ceramic layer is 3 μm, and the thickness of the single-sided bonding layer is 1 μm.

[0283] (5) Electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) are mixed evenly.

[0284] Then lithium hexafluorophosphate is added and dissolved in the organic solvent to make the concentration of lithium hexafluorophosphate 1.05 mol / L, and vinylene carbonate (VC) is added and stirred evenly to obtain the electrolyte of Example 1.

[0285] Among them, based on the total mass of the electrolyte, the mass content of dimethyl carbonate is 26%, the mass content of ethyl methyl carbonate is 43.3%, the mass content of ethylene carbonate is 17.3%, and the mass content of vinylene carbonate is 0.9%.

[0286] (6) Preparation of the battery Use a laminator to stack the positive electrode sheet, separator, and negative electrode sheet in sequence. The separator should be able to isolate the positive and negative electrodes to obtain a laminated battery cell. Apply adhesive to the laminated battery cell to tightly wrap the cell. Place the laminated battery cell with adhesive into the outer package, which is a soft package material of aluminum-plastic film. The aluminum-plastic film is composed of an inner layer of polypropylene, a middle layer of aluminum foil, and an outer layer of nylon composite. Among them, the aluminum-plastic film outer package is obtained through a punching and forming machine and trimming to obtain the target shape and size. Then, perform heat sealing on the aluminum-plastic film to meet the requirement that the sealing tensile strength of the aluminum-plastic film ≥ 25 N / 8 mm. The battery is subjected to vacuum baking, standing, injecting electrolyte, and encapsulation, and then perform hot pressing and cold pressing operations on the soft package battery. The temperature of hot pressing is 45 °C, the time is 2 minutes, and the pressure is 90 kg / cm 2 , and the temperature of cold pressing is 25 °C, the time is 2 minutes, and the pressure is 90 kg / cm 2 . Finally, through processes such as formation, vacuum exhaust, and trimming, a battery single body is obtained. The size of the battery single body in the length direction is 600 mm, the size in the width direction is 125 mm, and the size in the thickness direction is 20 mm.

[0287] The preparation methods of Examples 2-5 are basically the same as those of Example 1, except that the preparation methods of the positive active material and the positive electrode sheet are adjusted, specifically as follows: Example 2 (1)Preparation of positive active material: Mix lithium dihydrogen phosphate, iron oxalate, polyethylene glycol with a weight average molecular weight of 1000, polyethylene glycol with a weight average molecular weight of 1500, titanium dioxide, and vanadium pentoxide evenly in methanol and grind to obtain a mixed raw material. Among them, the ratio of lithium dihydrogen phosphate to iron oxalate makes the molar ratio of lithium to iron 1.02:1.0. The particle size D 10 of iron oxalate is 6.2 μm, the particle size D 50 is 60.8 μm, the particle size D 90 is 106.5 μm, the mass content of Fe element in iron oxalate is 30.6%, and the mass content of trivalent iron element is 0.03%.

[0288] Perform multiple ball milling and demagnetization on the mixed raw material in a ball mill to obtain a mixed slurry. Control the number of grinding times and time, and the particle size Dv 50 of the ground mixed slurry is 3.1 μm.

[0289] Spray-dry the mixed slurry to obtain a dry precursor powder. The appearance of the dry precursor powder material is light yellow and the color is uniform.

[0290] Place the precursor powder in a sintering furnace. Under a nitrogen atmosphere, heat it from 25°C to 360°C at a rate of 2°C / min and hold at this temperature for 3.5 h. Then heat it to the second temperature of 775°C at a rate of 5°C / min and hold at this temperature for 10 h. After that, cool it down. Among them, based on the total mass of the cathode active material, the mass content of Ti element is 1050 ppm, and the mass content of V element is 950 ppm.

[0291] Adopt the method of airflow crushing to crush the obtained material with an air volume at a classification frequency of 22 Hz and a crushing air pressure of 0.55 MPa to obtain a lithium iron phosphate cathode active material with carbon material on its surface.

[0292] The above D10, D50, D90, Dv50 refer to the data obtained by testing through the Malvern laser scattering method.

[0293] (2)Preparation of the cathode electrode Mix 93.9% by mass of the above cathode active material, 2% by mass of the conductive agent, and 3% by mass of the binder polyvinylidene fluoride in the solvent N-methylpyrrolidone. Then add 1.1% by mass of the dispersant HNBR and mix well in a stirring tank, stir and disperse to make a cathode slurry; after completing the stirring process, transfer the cathode slurry to the coating process; among them, the mass ratios of the cathode active material, conductive agent, binder, and dispersant are calculated based on the total mass of the solids in the cathode slurry; the conductive agent includes 1.33% by mass of conductive carbon black and 0.67% by mass of single-walled carbon nanotubes. The specific surface area of the conductive carbon black is 85 m 2 / g, the oil absorption value is 200 ml / 100 g, the average length of the single-walled carbon nanotubes is 30 μm, the specific surface area is 300 m 2 / g, and the mass content of metal impurities in the single-walled carbon nanotubes is <1 wt%; Transfer and coat the cathode slurry onto the current collector aluminum foil and dry it. After hot pressing, a cathode electrode with a single-sided thickness of 105.89 μm and a tap density of 2.36 g / cm 3 is obtained. Among them, the stirring includes pre-stirring and main stirring. The stirring speed of pre-stirring is lower than that of main stirring. The revolution speed of pre-stirring is 25 rpm, the rotation speed is 500 rpm, and the pre-stirring time is 15 min.

[0294] The hot pressing process includes three hot roll pressing processes, and the hot roll pressing pressure increases in sequence. The hot roll pressures are 35 tons, 55 tons, and 75 tons in sequence; the hot roll temperature is 65°C. Before the first entry into the hot roll compaction, heat the electrode, and the heating temperature is 50°C. Here, the tap density refers to the tap density in the fully discharged state of the battery cell, and its test method is as follows.

[0295] The positive electrode sheet is slit and punched into a specified shape, and the punched positive electrode sheets are classified by weight through a weighing and sorting machine for laminating by a laminator.

[0296] Example 3 (1)Preparation of positive electrode active material Lithium carbonate, iron phosphate, sucrose, glucose, titanium dioxide, and vanadium pentoxide are added to water and mixed in a premixing tank at a rotation speed of 1800 rpm. Among them, the ratio of lithium carbonate to iron phosphate is such that the molar ratio of iron to phosphorus is 0.975, the mass content of glucose compared to iron phosphate is 3.8%, and the mass content of sucrose compared to iron phosphate is 1.9%; The mixed raw materials are ground twice in a sand mill. The first grinding is carried out under the conditions of using zirconia balls with a diameter of 0.6 mm and a rotation speed of 500 rpm for 1 h, and the pressure in the grinding chamber is less than 0.3 MPa. Then the second grinding is carried out to obtain a mixed slurry, and the particle size D of the mixed slurry V50 is 0.43 μm; The mixed slurry is spray-dried to obtain a precursor powder, The precursor powder is sintered to obtain a lithium iron phosphate positive electrode material. The sintering process includes: First sintering: The precursor powder is sintered in a nitrogen atmosphere, heated from 25°C to 765°C at a heating rate of 5°C / min, and kept warm for 10 h. After cooling, a first sintering product is obtained; Grinding and mixing: 0.5% of sucrose, 1% of glucose, and 3.0% of polyethylene glycol based on the total mass of the first sintering product are added to the first sintering product. It is divided into two groups for grinding (the third grinding). Among them, when the particle size D of the particles in the first group V50 reaches 1.0 μm, the grinding stops (grinding conditions: 550 rpm, grinding time 1 h) to obtain a first group of grinding products; when the particle size D of the particles in the second group V50 reaches 0.40 μm, the grinding stops (grinding conditions: 500 rpm, grinding time 4 h) to obtain a second group of grinding products; the first group of grinding products and the second group of grinding products are mixed according to a mass ratio of 72:28 to obtain a mixed intermediate product; the mixed intermediate product is spray-dried; Second sintering: The dried mixed intermediate product is sintered in a nitrogen atmosphere, heated from 25°C to 800°C at a heating rate of 5°C / min, and kept warm for 10 h. After cooling, a second sintering product is obtained.

[0297] After sintering, it is cooled to below 100 °C, and the second sintered product is crushed by air jet milling to obtain a lithium iron phosphate cathode active material with carbon material on its surface. Among them, the classification frequency of air jet milling is 25 Hz, and the crushing air pressure is 0.55 MPa. Among them, based on the total mass of the cathode active material, the mass content of Ti element is 1050 ppm, and the mass content of V element is 950 ppm.

[0298] (2) Preparation of the cathode electrode Mix 93.9% by mass of the above-mentioned cathode active material, 2% by mass of the conductive agent, and 3% by mass of the binder polyvinylidene fluoride in the solvent N-methylpyrrolidone, and then add 1.1% by mass of the dispersant HNBR, and mix well in the stirring tank, stir and disperse to make the cathode slurry; after completing the stirring process, transfer the cathode slurry to the coating process; among them, the mass ratios of the cathode active material, conductive agent, binder and dispersant are calculated based on the total mass of the solids in the cathode slurry; the conductive agent includes 1.33% by mass of conductive carbon black and 0.67% by mass of single-walled carbon nanotubes, the specific surface area of the conductive carbon black is 85 m 2 / g, the oil absorption value is 200 ml / 100 g, the average length of the single-walled carbon nanotubes is 30 μm, the specific surface area is 300 m 2 / g, and the mass content of metal impurities in the single-walled carbon nanotubes < 1 wt%; Transfer and coat the cathode slurry onto the current collector aluminum foil and dry it. After hot pressing, the single-sided thickness of the cathode film layer is 106.21 μm, and the compaction density is 2.37 g / cm 3 of the cathode electrode. Among them, the drying temperature is 95 °C and the speed is 2.0 m / min.

[0299] The hot pressing process includes three hot roll pressing processes, and the hot roll pressing pressure increases in turn. The hot roll pressures are 35 tons, 55 tons, and 75 tons in turn; the hot roll temperature is 65 °C. Before entering the hot roll compaction for the first time, the electrode is heated, and the heating temperature is 50 °C. Here, the compaction density refers to the compaction density in the fully discharged state of the battery cell, and its test method is as follows.

[0300] Cut the cathode electrode into strips and punch it into a specified shape, and divide the punched cathode electrodes into grades by weight through a weighing and sorting machine for the laminator to stack.

[0301] Example 4 The preparation method of Example 4 is basically the same as that of Example 1, except that there are slight differences in the preparation process of the cathode active material and the hot pressing process of the cathode electrode. The specific differences include: (1) The carbon sources in the mixed raw materials are sucrose and glucose. The mass of sucrose is 2 wt% compared to the mass of iron phosphate, and the mass of glucose is 4 wt% compared to the mass of iron phosphate. (2) The processes of heating and sintering are different. The precursor powder is sintered at least twice in a nitrogen atmosphere. The first sintering temperature is 765 °C and the holding time is 8 hours to obtain a preliminarily sintered product.

[0302] Add 1.5 wt% (based on the mass of the preliminarily sintered product) of glucose, 3.0 wt% (based on the mass of the preliminarily sintered product) of polyethylene glycol, titanium dioxide, and vanadium pentoxide to the preliminarily sintered product. After grinding evenly, divide it into two groups for secondary grinding. The grinding parameters of the two groups are different, and control the D V 50 of the particles after grinding in the first group to be 2.2 μm, and the D V 50 of the particles after grinding in the second group to be 0.4 μm. Mix the particles after grinding in the first group and the second group according to a mass ratio of 30:70, and spray dry and conduct the second sintering. The temperature of the second sintering is 815 °C and the holding time is 10 hours.

[0303] Based on the total mass of the positive electrode active material, the mass content of Ti element is 1050 ppm, and the mass content of V element is 950 ppm.

[0304] (3) Transfer and coat the positive electrode slurry onto the current collector aluminum foil and dry it. After hot pressing, a positive electrode sheet with a single-side thickness of 106.34 μm and a compaction density of 2.37 g / cm 3 is obtained. Among them, the drying temperature is 95 °C and the speed is 2.0 m / min.

[0305] The hot pressing process includes three hot roll pressing processes. The hot roll pressing pressure increases successively, and the hot roll pressures are 35 tons, 55 tons, and 70 tons in sequence; the hot roll temperature is 65 °C. Before entering the hot roll compaction for the first time, heat the electrode sheet, and the heating temperature is 50 °C. Here, the compaction density refers to the compaction density in the fully discharged state of the battery monomer, and its test method is as follows.

[0306] Example 5 The preparation method of Example 5 is basically the same as that of Example 1, except that there are differences in the sintering process of the positive electrode active material and the hot pressing process of the positive electrode sheet. Specifically: (1) Perform two-stage heating and sintering on the precursor powder in a nitrogen atmosphere to obtain the positive electrode active material: heat from 25 °C to 440 °C at a heating rate of 2 °C / min (the first heating stage), and hold for 2.5 h; heat from 440 °C to 760 °C at a heating rate of 5 °C / min (the second heating stage), and hold for 11 h; then increase the airflow pulverization intensity to obtain a lithium iron phosphate positive electrode active material with carbon material on the surface.

[0307] (2) Transfer and coat the positive electrode slurry onto the current collector aluminum foil and dry it. After hot pressing, a positive electrode sheet with a single-sided thickness of 105.65 μm and a compaction density of 2.36 g / cm 3 is obtained. Among them, the transfer coating speed is 20 m / min.

[0308] The hot pressing process includes three hot roll pressing processes, and the hot roll pressing pressure increases successively. The hot roll pressures are 45 tons, 60 tons, and 80 tons in sequence; the hot roll temperature is 60 °C. Before the first entry into the hot roll compaction, the electrode sheet is heated, and the heating temperature is 40 °C.

[0309] The preparation methods of Examples 6 - 11 are basically the same as that of Example 1, except that the preparation method of the positive electrode sheet is adjusted, specifically as follows: Example 6 Transfer and coat the positive electrode slurry of Example 1 onto the current collector aluminum foil and dry it. By adjusting the pressure, rolling speed, roll gap, pressure holding time, rolling times in the hot pressing process, and controlling the coating surface density, a positive electrode sheet with a single-sided thickness of 91.88 μm of the positive electrode film layer is obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is referred to below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0310] Example 7 Transfer and coat the positive electrode slurry of Example 1 onto the current collector aluminum foil and dry it. By adjusting the pressure, rolling speed, roll gap, pressure holding time, rolling times in the hot pressing process, and controlling the coating surface density, a positive electrode sheet with a single-sided thickness of 116.09 μm of the positive electrode film layer is obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is referred to below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0311] Example 8 Transfer and coat the positive electrode slurry of Example 1 onto the current collector aluminum foil and dry it. By adjusting the pressure, rolling speed, roll gap, pressure holding time, rolling times in the hot pressing process, and controlling the coating surface density, a positive electrode sheet with a single-sided thickness of 72.34 μm of the positive electrode film layer is obtained by hot pressing; the compaction density of the positive electrode sheet is 2.36 g / cm 3 . Here, the compaction density refers to the compaction density under the fully discharged state of the battery cell, and its test method is referred to below. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0312] Example 9 The positive electrode slurry of Example 1 was transferred and coated onto a current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes in the hot pressing process, and controlling the coating areal density, a positive electrode plate with a single-sided thickness of 83.91 μm for the positive electrode film layer was obtained by hot pressing; the tap density of the positive electrode plate was 2.36 g / cm 3 . Here, the tap density refers to the tap density under the fully discharged state of the battery cell, and its test method is as follows. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0313] Example 10 The positive electrode slurry of Example 1 was transferred and coated onto a current collector aluminum foil and dried. By adjusting the pressure, rolling speed, roll gap, pressure holding time, number of rolling passes in the hot pressing process, and controlling the coating areal density, a positive electrode plate with a single-sided thickness of 98.93 μm for the positive electrode film layer was obtained by hot pressing; the tap density of the positive electrode plate was 2.52 g / cm 3 . Here, the tap density refers to the tap density under the fully discharged state of the battery cell, and its test method is as follows. Keep the number of stacked layers unchanged, and adaptively adjust the thickness of the battery cell according to the thickness of the positive electrode film layer.

[0314] Example 11 Mix 93.9% by mass of the above positive electrode active material, 2% by mass of the conductive agent, and 3% by mass of the binder polyvinylidene fluoride in the solvent N-methylpyrrolidone, and then add 1.1% by mass of the dispersant HNBR, and mix well in a stirring tank. Stirring includes a first stirring and a second stirring, where the stirring speed of the first stirring is 400 rpm and the stirring time is 15 min, and the stirring speed of the second stirring is 1200 rpm and the stirring time is 150 min. After dispersion, a positive electrode slurry is prepared; after completing the stirring process, the positive electrode slurry is transported to the coating process.

[0315] 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, specifically as follows: Comparative Example 1 The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that there are differences in the sintering process of the positive electrode active material. Specifically: The precursor powder was subjected to two-stage temperature-raising sintering in a nitrogen atmosphere to obtain the positive electrode active material: heated from 25 °C to 500 °C at a heating rate of 2 °C / min (the first heating stage) and held for 3.5 h; heated from 500 °C to 800 °C at a heating rate of 5 °C / min (the second heating stage) and held for 13 h; then, after reducing the air flow pulverization intensity, a lithium iron phosphate positive electrode active material with a carbon material on the surface was obtained.

[0316] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the preparation method of the separator is adjusted as follows: Polyvinylidene fluoride (PVDF) and a dispersant were added to deionized water and stirred evenly; a thickening agent and an aqueous binder were added to the above-mentioned stirred solution, and the mixture was stirred evenly in a sand mill to obtain a binder layer slurry; the binder layer slurry was sprayed onto a base film with double-sided ceramic layers, and after pre-volatilization at 80 °C and drying at 90 °C, a separator with an island-shaped binder layer was obtained.

[0317] Among them, the thickness of the base film is 8 μm, the thickness of a single-sided ceramic layer is 3 μm, and the thickness of a single-sided binder layer is 1 μm.

[0318] Test method: 1. Capacity of the battery cell At 25 °C, it was charged to 3.65 V at a charging rate of 0.5C of the nominal capacity of the battery cell, then charged at a constant voltage of 3.65 V to 0.05C, left standing for 10 min, and then discharged at a discharge rate of 1C to 2.5 V, left standing for 10 min. The capacity C during the discharge process was calculated by the formula C = I * t, and the unit was Ah.

[0319] 2. Number of cycles corresponding to the capacity decay to 90% At 25 °C, it was charged to 3.65 V at a charging rate of 0.5C of the nominal capacity of the battery cell, then charged at a constant voltage of 3.65 V to 0.05C, left standing for 10 min, and then discharged at a discharge rate of 1C to 2.5 V, left standing for 10 min. The above one charge and discharge was regarded as one cycle, and the test was stopped until the battery capacity decayed to 90% of the nominal capacity, and it was recorded as the number of cycles @90% SOH.

[0320] Table 1

[0321] Table 2

[0322] As can be seen from Table 1 and Table 2, through the comparison of the examples and the comparative examples, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the particles with a particle size greater than or equal to 1 μm is 12% - 50%, and the binder layer of the separator is a continuous layer with a porous structure. When the binder layer includes a polyvinylidene fluoride polymer, while maintaining a good capacity of the battery cell, the risk of the mutual extrusion between the positive and negative electrode sheets in the thickness direction during the rebound of the battery core evolving into a horizontal misalignment is reduced, and the probability of the positive and negative electrodes overlapping and thus causing a short circuit is reduced, improving the cycle performance of the battery.

[0323] From the comparison between Example 4 and Examples 1-3 and 5, it can be seen that in the cross-section of the positive electrode film layer along the thickness direction of the electrode piece, the area of particles with a particle size greater than or equal to 1 μm accounts for 12%-40%, which is beneficial for the battery to further improve the electrode piece rebound phenomenon caused by stress concentration caused by large particles in the electrode piece while maintaining high capacity, reduce the probability of contact between the negative electrode film layer and the positive electrode film layer of the electrode piece and short circuit, and further improve the cycle performance of the battery.

[0324] From the comparison between Examples 8 and 9 and Examples 6 and 7, it can be seen that the single-side thickness H of the positive electrode film layer is 90 μm-120 μm, which is beneficial to further improve the capacity of the battery.

[0325] From the comparison between Example 7 and Examples 1-6, 8-10, it can be seen that in the cross section of the positive electrode film along the thickness direction of the electrode sheet, in the cumulative distribution curve of the sphericity area 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, which can further improve the stress concentration of large particles, reduce the rebound of the pole piece caused by stress release during the cycle process, and further improve the cycle life of the battery cell.

[0326] Table 3

[0327] From the comparison between Example 11 and Example 1, it can be seen that when the distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region is 0.2%-3.5%, it is beneficial to reduce the risk of increased peripheral current density and easy lithium precipitation caused by local excessive extrusion and local blockage of lithium ion transmission pathways due to uneven distribution of large particles, thereby further improving the cycle performance of the battery on the basis of good capacity.

[0328] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that, It includes a laminated battery cell, and the laminated battery cell includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate; The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes lithium-containing transition metal phosphate particles, and at least part of the surface of the lithium-containing transition metal phosphate particles is provided with a carbon material; in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of particles with a particle size greater than or equal to 1 μm is 12%-50%; The separator includes a base film, a ceramic layer disposed on both sides of the base film, and an adhesive layer disposed on the side of the ceramic layer away from the base film at least close to the positive electrode plate side. The adhesive layer is a continuous layer with a porous structure, and the adhesive layer includes a polyvinylidene fluoride polymer.

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 electrode plate, the area ratio of particles with a particle size of 1 μm - 5 μm is 12%-50%.

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

4. The battery cell according to claim 1, characterized in that, The polyvinylidene fluoride polymer includes one or more of a polyvinylidene fluoride homopolymer and a copolymer of polyvinylidene fluoride and hexafluoropropylene.

5. The battery cell according to claim 1, wherein The single-sided thickness of the positive electrode film layer is 70 μm - 120 μm.

6. The battery cell according to claim 5, wherein The single-sided thickness of the positive electrode film layer is 90 μm - 120 μm.

7. The battery cell according to claim 6, characterized in that, The single-sided thickness of the positive electrode film layer is 100 μm - 120 μm.

8. The battery cell according to claim 1, wherein The positive electrode film layer includes a first region, which is located at the top of the positive electrode film layer away from the positive electrode current collector. The distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region is 0.2%-5%.

9. The battery cell according to claim 8, wherein, The distribution uniformity of particles with a particle size greater than or equal to 1 μm in the first region is 0.2%-3.5%.

10. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, in the cumulative area distribution curve of the sphericity of particles with a particle size greater than or equal to 1 μm, the median sphericity L A50 is 0.6 - 0.

8.

11. The battery cell according to claim 10, wherein, Median L of sphericity A50 is 0.65 - 0.

75.

12. The battery cell according to claim 11, wherein, Median L of sphericity A50 is 0.67 - 0.

75.

13. The battery cell according to claim 1, characterized in that, In the cumulative distribution curve of the graphitization degree C value obtained in the surface scanning mode of the laser confocal Raman spectrometer for the said positive electrode film layer, the median C of the graphitization degree 50 is greater than or equal to 0.95 and less than or equal to 1.20; wherein, the graphitization degree C value is I G / I D , I G represents the intensity of the G peak of the Raman spectrum at 1580 ± 100 cm -1 , and I D represents the intensity of the D peak of the Raman spectrum at 1350 ± 100 cm -1 .

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

15. The battery cell according to claim 1, wherein, The iron dissolution rate of the positive electrode material is 658 ppm - 1921 ppm.

16. The battery cell according to claim 15, wherein, The iron dissolution rate of the positive electrode material is 658 ppm - 1485 ppm.

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

1.

18. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal phosphate particles include titanium element. Based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of titanium element is 500 ppm - 8000 ppm.

19. The battery cell according to claim 18, wherein, The mass content of titanium element is 1000 ppm - 3000 ppm.

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

21. The battery cell according to claim 20, wherein, The mass content of vanadium element is 500 ppm - 3000 ppm.

22. The battery cell according to claim 1, wherein, The positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the total area ratio of the agglomeration regions of the conductive agent is 0.2% - 6%.

23. The battery cell according to claim 22, wherein, The total area ratio of the agglomeration regions of the conductive agent is 1.5% - 5%.

24. The battery cell according to claim 22, 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.

25. The battery cell according to claim 23, wherein, The conductive agent further includes conductive carbon black.

26. The battery cell according to any one of claims 22-25, characterized in that, The agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

27. The battery cell according to claim 26, wherein Based on the mass of the positive electrode film layer, the mass content C1 of the carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of the conductive carbon black satisfies: 0 < C1 ≤ 2.5%.

28. The battery cell according to claim 1, characterized in that, The positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber HNBR.

29. The battery cell according to claim 28, characterized in that, Based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

30. The battery cell according to claim 1, characterized in that, When the battery cell is in a fully discharged state, the compaction density of the positive electrode plate is 2.3 g / cm 3 - 2.6 g / cm 3 .

31. The battery cell according to claim 1, wherein, The porosity of the positive electrode film layer is 14% - 28%.

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

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

34. The battery cell according to claim 1, characterized in that, The battery cell includes a housing, the stacked electrode core is accommodated in the housing. The dimension of the housing in the length direction is L0, the dimension of the housing in the width direction is W0, and the dimension of the housing in the thickness direction is H0. 450 mm ≤ L0 ≤ 1300 mm, 100 mm ≤ W0 ≤ 150 mm, 14 mm ≤ H0 ≤ 22 mm.

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

36. The battery cell according to claim 34, wherein, The dimension L0 of the housing in the length direction satisfies: 900 mm ≤ L0 ≤ 1300 mm.

37. The battery cell according to claim 34, characterized in that, The housing satisfies at least one of the following conditions: (1) The material of the housing is a soft package material, and the soft package material includes an aluminum-plastic composite film; (2) The housing includes a first sealing area, and the first sealing area is provided at at least one end of the stacked electrode core extending in the width direction; the first sealing area includes a folded edge structure extending in the length direction, and a packaging adhesive is provided on the folded edge structure. The packaging adhesive is continuously provided in the length direction and fixes the folded edge structure; (3) The housing includes at least one second sealing area, and the second sealing area is provided at at least one end of the stacked electrode core extending in the length direction of the housing, and the second sealing area is provided on the tab side of the stacked electrode core.

38. The battery cell according to claim 37, wherein, The soft package material includes a composite film formed by one or more of polypropylene, polybutylene terephthalate, polybutylene succinate, nylon, polyethylene terephthalate, polyethylene and aluminum.

39. The battery cell according to claim 1, wherein, A plurality of rubber rings surrounding along the width direction are arranged on the outer periphery of the laminated battery cell, and the rubber rings surrounding along the width direction are arranged at intervals along the length direction.

40. The battery cell according to claim 1, characterized in that, At 25 °C, the capacity of the battery cell is 100 Ah - 300 Ah.

41. The battery cell according to claim 40, wherein, At 25 °C, the capacity of the battery cell is 110 Ah - 190 Ah.

42. The battery cell according to claim 41, characterized in that, At 25 °C, the capacity of the battery cell is 125 Ah - 180 Ah.

43. A battery device, characterized in that, It includes the battery cell according to any one of claims 1 - 42.

44. An electrical device, characterized in that, The electrical device includes the battery device according to claim 43, and the battery device is used to provide electrical energy.

45. A energy storage device, characterized in that, The energy storage device includes the battery device according to claim 43, and the battery device is used to store electrical energy.

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