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

Abstract

The invention provides a battery monomer, a battery device, a power utilization device and an energy storage device. The single battery comprises a laminated battery cell, the laminated battery cell comprises a positive pole piece and a negative pole piece, and the compaction density of the positive pole piece is 2.3 g / cm < 3 >-2.6 g / cm < 3 >; the density of the single side surface of the positive electrode film layer is 0.25 g / 1540.25 mm < 2 > to 0.45 g / 1540.25 mm < 2 >; in the tangent plane of the positive electrode film layer along the thickness direction of the positive electrode plate, LR1A50 is 0.6-0.8 in a sphericity-like area cumulative distribution curve of particles of which the particle size R1 is greater than or equal to 1000nm; the median C50 of the graphitization degree is 0.95-1.20 in a cumulative distribution curve of the graphitization degree C value obtained by the positive electrode film layer in a surface scanning mode of a laser microscopic confocal Raman spectrometer. The battery monomer provided by the invention has high capacity and good cycle performance.

Description

[0001] This application is a divisional application of Chinese patent application entitled “Battery cell, battery device, power supply device and energy storage device”, filed on June 20, 2025, with application number “202510829320.6”. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, battery device, power consumption device, and energy storage device. Background Technology

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

[0004] As the market demands longer driving range and longer battery life, higher requirements are being placed on battery capacity and cycle performance. However, current technologies struggle to simultaneously improve these performance aspects, making it crucial to address this critical technical challenge. Summary of the Invention

[0005] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell that has both high capacity and good cycle performance.

[0006] The first aspect of this application provides a battery cell comprising a stacked cell, the stacked cell including a positive electrode and a negative electrode, the positive electrode including a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film including lithium transition metal phosphate particles of carbon material disposed on at least a portion of its surface; the battery cell, in a fully discharged state, has a compaction density of 2.3 g / cm³ for the positive electrode. 3 -2.6g / cm 3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 The value is 0.6-0.8; in the cumulative distribution curve of graphitization degree C obtained by laser microscopy confocal Raman spectroscopy in the instrument scanning mode, the median C of graphitization degree is 0.6-0.8. 50 The value ranges from 0.95 to 1.20; among which, the degree of graphitization C is I. G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at ID This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0007] Studies have shown that stress concentration areas in the film layer are prone to cracking under cyclic expansion, becoming the starting point for film delamination, which is more pronounced in thick-coated cells. Compared to ternary materials, lithium-containing transition metal phosphate structures are more stable and less prone to breakage under high pressure. Lithium-containing transition metal phosphates require higher pressure during electrode compaction to achieve higher compaction density. However, under full-discharge conditions, the compaction density of the positive electrode in a single battery cell exceeds 2.6 g / cm³. 3 This can lead to overpressure on the electrode, increased stress concentration, and a higher risk of film shedding during cycling; while the compaction density of the positive electrode is less than 2.3 g / cm³. 3 This will result in insufficient contact between the positive electrode film particles, leading to increased internal resistance of the battery and affecting the energy density of the individual cells; the single-sided density of the positive electrode film is less than 0.25g / 1540.25mm. 2 This cannot meet the requirements for high energy density; the single-sided density of the positive electrode film is higher than 0.45 g / 1540.25 mm. 2 If the positive electrode film is too thick, the volume expansion during cycling will be significant and the stress concentration will be aggravated, increasing the risk of film shedding.

[0008] Stacked cells are beneficial for improving the space utilization of batteries, thereby further increasing the volumetric energy density and capacity of individual cells. The applicant found that in thick-coated stacked cells, stress concentration usually originates from localized stress generated during compaction. On the one hand, during compaction, particles with low sphericity have sharp stress surfaces and increased sliding friction, making them more prone to stress concentration; on the other hand, lithium-containing transition metal phosphate particles often require high-temperature sintering, which, along with grain boundary melting and particle growth, reduces the sphericity of the particles, with the median sphericity often not exceeding 0.8. When the positive electrode film layer is truncated along the thickness direction of the positive electrode sheet, the cumulative distribution curve of the sphericity area of ​​particles with a particle size R1 satisfying R1≥1000nm, L... R1A50 When the value is less than 0.6, significant local stress will form during particle compaction, significantly increasing the risk of film detachment during cycling; on the other hand, the median C of graphitization degree... 50 Reflecting the degree of order in carbon material layers, a graphitization degree higher than 1.2 indicates lower concentration. Therefore, considering material uniformity, the graphitization degree of carbon material layers is typically not higher than 1.2. 50 When the value is less than 0.95, the slipability of the carbon layer structure decreases, resulting in high friction between particles during compaction and difficulty in slippage. This further increases the stress during the compaction process, thereby increasing the probability of film detachment during the cycle.

[0009] The battery cell provided in this application adopts a thick coating and stacked cell process, and controls the compaction density of the positive electrode sheet to be 2.3 g / cm³ when the battery cell is fully discharged. 3 -2.6g / cm 3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 While increasing battery capacity, this also alleviates stress concentration, reduces the probability of film peeling, and improves battery cycle life. Furthermore, by controlling the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction, L... R1A50 The graphitization degree C is 0.6-0.8, and the median C of the graphitization degree C is found in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode. 50 The concentration is 0.95-1.20, which improves the spheroidal nature of large particles in the positive electrode film and the graphitization degree of the positive electrode film, improves the local stress generated during the compaction process, thereby further reducing the probability of film peeling and improving the cycle life of the battery.

[0010] In summary, the battery cell of this application improves the problem of capacity drop while maintaining good capacity, and takes into account the cycle life of the battery.

[0011] In any embodiment, the surface density of the positive electrode film coating on one side is 0.3 g / 1540.25 mm. 2 - 0.45g / 1540.25mm 2 .

[0012] In any embodiment, the areal density of the positive electrode film layer on one side is 0.35 g / 1540.25 mm. 2 - 0.4g / 1540.25mm 2 .

[0013] The single-sided coating density of the positive electrode film is further within the above range, which helps to further improve the battery capacity while taking into account cycle performance.

[0014] In any embodiment, the median C of the graphitization degree C value in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 1.01-1.13.

[0015] If the graphitization degree of the positive electrode film is further within the above range, it will help to further improve the slippage of particles in the positive electrode film, reduce stress concentration in the positive electrode film, and thus further improve the long-cycle stability of the battery cell.

[0016] In any embodiment, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.65-0.75.

[0017] In any embodiment, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.67-0.72.

[0018] In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 Within the range of 0.65-0.75, and further within the range of 0.67-0.72, it is beneficial to further reduce the stress concentration at large particles in the positive electrode film layer of the thick-coated laminated cell, thereby reducing the probability of film layer peeling and improving the cycle life of the battery.

[0019] In any embodiment, the thickness H of the positive electrode film on one side is 70 μm - 120 μm.

[0020] In any embodiment, the thickness H of the positive electrode film on one side is 90 μm - 120 μm.

[0021] A single-sided thickness of the positive electrode film within the above-mentioned range helps to increase the loading of positive electrode active materials in the battery, thereby increasing the battery capacity.

[0022] In any embodiment, the thickness H of the positive electrode film on one side is 100μm-120μm.

[0023] Increasing the thickness of the positive electrode film helps to increase the loading of the positive electrode active material and thus improves the battery capacity. However, the applicant has found that when the thickness of the positive electrode film on one side is greater than or equal to 100 μm, the volume expansion of the positive electrode film is more significant during battery cycling, resulting in greater stress. This leads to more pronounced stress concentration in the positive electrode film, increasing the risk of film detachment and consequently affecting the battery's cycle performance. The embodiments of this application increase the battery capacity by increasing the thickness of the positive electrode film, while simultaneously controlling the particle size R1 in the cross-section along the thickness direction of the positive electrode sheet to be spherical, satisfying R1≥1000nm. Furthermore, the cumulative distribution curve of the graphitization degree C value obtained in the laser confocal Raman spectroscopy instrument scanning mode shows the median C of the graphitization degree. 50Improving the slippage between particles in the positive electrode film layer and reducing stress concentration during electrode compaction improves battery capacity while maintaining good cycle performance. In any embodiment, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the electrode thickness direction, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-50%.

[0024] In any implementation, based on the total area of ​​particles in the cross section of the positive electrode film along the thickness direction of the electrode sheet, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-40%.

[0025] Large particles with a particle size R1 ≥ 1000 nm help improve the compaction density of the positive electrode, thereby increasing the volumetric energy density of the battery cell. However, researchers have found that these large particles are prone to stress concentration, increasing the risk of positive electrode film delamination. Therefore, the area ratio of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the thickness direction should be in the range of 12%-50%, and further in the range of 12%-40%. This can improve the compaction density of the electrode without making the film delamination probability too high. This improves the energy density of thick-coated lithium transition metal phosphate batteries while alleviating the capacity drop problem and taking into account the cycle life of the battery.

[0026] In any embodiment, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm in the cross section of the positive electrode film along the electrode thickness direction is less than or equal to 5%.

[0027] In any embodiment, the uniformity of particle distribution with particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is 0.2%-2.5%.

[0028] In any embodiment, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is 0.2%-2%.

[0029] If the uniformity of particle distribution with particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the thickness direction of the electrode sheet is within the above range, it can effectively reduce the stress concentration in local areas of the film layer, so that the stress during the film layer compaction process can be uniformly distributed throughout the entire area of ​​the film layer. This can improve the battery energy density while reducing the probability of film layer peeling, alleviate the capacity drop problem of thick-coated lithium transition metal phosphate batteries, and improve the battery cycle life.

[0030] In any embodiment, the median B of the coating value B obtained in the cumulative distribution curve of the positive electrode film layer under laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50The value is 0.30-0.60, where the coating value B is I. P / I D , where I P This indicates that the Raman spectrum is at 948±100 cm⁻¹ -1 The intensity of the P peak at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0031] The median B of the coating value of the positive electrode film 50 Within the aforementioned range, it is evident that the carbon material layer of the positive electrode active material is relatively dense and uniform, which is beneficial for improving the slip uniformity of the positive electrode film layer during the rolling process and reducing stress concentration in the thick-coated positive electrode film layer. In addition, thanks to the dense and uniform carbon material layer, large particles in the positive electrode film layer are more likely to slip during the compaction process, thereby reducing stress concentration at large particles in the thick-coated positive electrode film layer, reducing the probability of positive electrode film layer detachment, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0032] In any embodiment, the lithium transition metal phosphate particles in the positive electrode film layer comprise 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, and Br, with 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0≤q≤0.1.

[0033] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorinated vanadium phosphate, lithium manganese iron phosphate, and their modified materials.

[0034] In any embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer include one or more of lithium iron phosphate and its doped and modified materials, and coating and modified materials.

[0035] In any embodiment, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1921ppm.

[0036] In any embodiment, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1485ppm.

[0037] In any embodiment, the mass content of titanium is 500ppm-8000ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0038] In any embodiment, the mass content of titanium is 1000ppm-3000ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0039] Introducing titanium into lithium transition metal phosphate particles requires adding a titanium source during the preparation of the cathode active material. Titanium sources are often inert materials, and their adhesion to the surface of the lithium transition metal phosphate raw material reduces reactivity and particle size growth. Increasing the graphitization degree of the cathode active material often requires higher sintering temperatures or longer sintering times, but this also increases the particle size in the cathode film, increasing stress concentration and potentially causing film detachment. In this embodiment, by adding a high content of titanium to the lithium transition metal phosphate particles, the reactivity of the raw materials for synthesizing the cathode active material is reduced. This allows the cathode active material to achieve a high degree of graphitization while controlling the proportion of large particles, reducing stress concentration in the cathode film, lowering the probability of film detachment, and improving both battery energy density and cycle life.

[0040] Meanwhile, the doping of titanium in the positive electrode active material is beneficial for inducing lattice distortion, reducing Li-O bond energy, increasing lithium-ion transport rate, and improving the kinetic performance of the battery. In thick coated films, lithium-ion diffusion is uneven, often accompanied by a significant lithium-ion concentration gradient. This application's embodiments improve the solid-phase transport rate of the positive electrode active material by adding a high content of titanium to lithium-containing transition metal phosphate particles, thus addressing the kinetic problems of thick electrode batteries.

[0041] In any embodiment, the vanadium content is 500 ppm to 5000 ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0042] In any embodiment, the vanadium content is 500 ppm to 3000 ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0043] Vanadium in the positive electrode film can be in multiple valence states, including +5 vanadium (V5). 5+ Vanadium (V+3) can be doped into phosphorus sites. Due to its large radius, it can cause lattice distortion, 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 (V+3) 3+Vanadium can be doped into transition metal sites, generating lithium vacancies through charge compensation, thereby improving the electronic conductivity of the positive electrode active material. Furthermore, the increased uniformity of vanadium distribution in lithium-containing transition metal phosphate particles helps to further improve the kinetic performance and reaction uniformity of the positive electrode film, thus further enhancing the kinetic and cycle performance of the battery cell.

[0044] Vanadium content within the aforementioned range helps improve the kinetic performance of the positive electrode and the kinetic performance of thick-coated lithium transition metal phosphate batteries. Simultaneously, the synergistic effect of titanium, vanadium, and carbon nanotubes in the positive electrode film helps form a good three-dimensional network, further improving the electronic and ionic conductivity of the positive electrode film, thereby further enhancing the kinetic performance of thick-coated lithium transition metal phosphate batteries.

[0045] In any embodiment, the porosity of the positive electrode film is 14%-28%.

[0046] When the porosity of the positive electrode film is within the aforementioned range, the positive electrode film exhibits good electrolyte wettability and tortuosity, which facilitates the diffusion of lithium ions in both the liquid and solid phases. This helps reduce concentration polarization in thick electrode sheets and improves the battery's kinetic performance. Simultaneously, it helps alleviate volume expansion of thick-coated electrodes during cycling, reduces mechanical stress in the film, and minimizes stress concentration, thereby reducing the risk of film detachment from thick-coated electrodes.

[0047] Especially in thick-coated soft-pack batteries, the gap between the casing and the electrode is small, the volume occupancy of the film is large, the electrolyte capacity is reduced, and the porosity of the positive electrode film is within the above range, which helps to improve the liquid retention rate of the cell and improve the battery dynamic performance.

[0048] In any embodiment, the positive electrode film layer further includes a conductive agent, and the area ratio of the agglomerated region of the conductive agent is 0.5%-2.5% based on the total area of ​​the cross section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0049] Based on the total area of ​​the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is within the above range, indicating that the conductive agent in the positive electrode film is uniformly dispersed and it is easy to form a uniform conductive network. This is especially beneficial to reduce the problem of kinetic decline caused by the growth of ion transport paths in thick coating films, reduce local polarization and even lithium plating problems generated during battery cycling, and improve the cycle life of the battery.

[0050] Meanwhile, research shows that the first large-sized particles in lithium transition metal phosphate particles are prone to rebound. The agglomeration area of ​​the conductive agent within the above range can suppress the rebound of lithium transition metal phosphate particles by means of the uniform distribution of the conductive agent, forming mechanical constraints on the particles and even the film layer, improving the cohesion of the film layer, reducing the phenomenon of film layer powder shedding and shedding, and improving the cycle life of the battery.

[0051] In any embodiment, the positive electrode film layer further includes a conductive agent, and the area ratio of the agglomerated region of the conductive agent is 0.5%-1.7% based on the total area of ​​the cross section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0052] In this embodiment, the area ratio of the agglomerated region of the conductive agent is further within the above-mentioned range, indicating that the conductive agent is more uniformly distributed in the positive electrode film layer and the content of the conductive agent is low. While improving the dynamic performance of the positive electrode film layer, it helps to reduce the space occupied by the excessive conductive agent on the positive electrode active material, thereby improving the battery's dynamic performance and further increasing the battery's volumetric energy density.

[0053] In any embodiment, the conductive agent includes carbon nanotubes, which include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0054] Because carbon nanotubes have a one-dimensional structure, they can form a network structure in the positive electrode film. On the one hand, the high elastic modulus of carbon nanotubes enables their network structure to not only act as a bridge for stress propagation but also to bind the thickly coated positive electrode film, suppressing the rebound of lithium-containing transition metal phosphate particles, effectively alleviating stress concentration, reducing the risk of film shedding, and thus improving the problem of battery capacity drop. On the other hand, the excellent conductivity of carbon nanotubes makes their network structure a highly efficient electron transport channel. Even if there is local film shedding, the thick electrode can still maintain high electron transport efficiency in the in-plane and thickness directions, thereby delaying the occurrence of capacity drop and further improving the battery's dynamic performance and cycle life.

[0055] In any embodiment, the conductive agent also includes conductive carbon black.

[0056] Conductive carbon black has a high specific surface area, thus exhibiting excellent electrolyte retention capacity. Thick electrodes experience greater expansion force during cycling, making it easier for electrolyte to be squeezed out. The distribution of conductive carbon black in the positive electrode film layer helps improve the electrolyte retention capacity of thick electrodes, further mitigating the phenomenon of capacity drop during battery cycling and improving battery cycle life.

[0057] In any embodiment, the agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

[0058] Researchers found that due to their high surface energy, carbon nanotubes are prone to agglomeration, resulting in uneven dispersion in the positive electrode film layer and unable to form an effective carbon nanotube network structure. The surface energy of conductive carbon black 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 thick-coated positive electrode film layer and enhance 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 thick-coated 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 area of the conductive agent will also cause local ion transport pathways in the agglomerated area of the conductive agent to be blocked. The combination of conductive carbon black can improve the lithium ion transport ability in this area, reduce local polarization, and further improve the cycle stability of the battery.

[0059] In any implementation, 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 < C2 ≤ 2.5%.

[0060] 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 sheet during long-term cycling, further reducing the risk of film layer shedding and polarization degree of the electrode sheet, improving the kinetic performance of the battery and taking into account the problem of capacity drop, and improving the cycle life of the battery.

[0061] In any implementation, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber (HNBR).

[0062] HNBR is obtained by hydrogenating the double bonds of nitrile rubber. Its highly saturated main chain structure gives it excellent oil resistance, heat resistance, and aging resistance, etc. This enables it to remain stable in different environments and systems when used as a dispersant, and is not prone to degradation or deterioration, thus effectively exerting the dispersing effect. The HNBR molecular chain contains both polar nitrile groups and non-polar hydrocarbon segments. The polar nitrile groups can interact with the surfaces of some polar substances or particles, such as adsorbing on the surface of the dispersed particles through hydrogen bonds, electrostatic interactions, etc.; the non-polar hydrocarbon segments have good lipophilicity and can stretch and disperse well in non-polar or weakly polar media, enabling the particles to be evenly dispersed in the medium.

[0063] When HNBR adsorbs onto the surface of particles in the slurry, its long-chain molecules form a physical barrier around the particles, preventing them from approaching each other and agglomerating, thus maintaining a relatively independent dispersion. Simultaneously, HNBR reduces the surface tension between the dispersion medium and the dispersed particles, making the particles easier to wet and promoting dispersion. It also reduces the interfacial energy between particles, minimizing aggregation driven by interfacial energy. Furthermore, during slurry drying and film formation, the elastic network structure of HNBR buffers the shrinkage stress caused by solvent evaporation, reducing the re-agglomeration of conductive agents due to capillary forces, lowering the area of ​​agglomerated regions, and improving the battery's kinetic performance and cycle life.

[0064] In any embodiment, based on the mass of the positive electrode film, the mass content of the dispersant is 0.5%-2%.

[0065] When the mass content of the dispersant is within the above range, it can achieve uniform dispersion of particles in the positive electrode film while maintaining a high loading capacity, reduce stress concentration in the thick-coated lithium transition metal phosphate positive electrode film, and effectively alleviate the problem of battery capacity drop.

[0066] In any embodiment, the battery cell further includes a separator disposed between the positive electrode and the negative electrode. The separator includes a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on the side of the ceramic layer away from the base film. The adhesive layer is a continuous layer with a porous structure and includes a vinylidene fluoride polymer.

[0067] In any embodiment, the battery cell further includes a separator disposed between the positive electrode and the negative electrode. The separator includes a base film, ceramic layers disposed on both sides of the base film, and an adhesive layer disposed on the side of the ceramic layers away from the base film.

[0068] In any embodiment, the vinylidene fluoride polymer includes one or more of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0069] In any embodiment, the vinylidene fluoride polymer includes polyvinylidene fluoride (PVDF).

[0070] In the prior art, the adhesive layer of the separator usually uses aqueous PVDF, which presents an island-like structure in the separator. This is beneficial for providing gaps for cell expansion and is also convenient for manufacturing. However, such a separator adhesive layer has a small contact area with the electrode and weak adhesion.

[0071] The separator provided in this application uses a continuous porous layer as the adhesive layer. Its porous structure provides space for the expansion of the thick-coated cell, improving its stability. At the same time, compared with the adhesive layer in the prior art, it has a larger bonding area with the electrode, which makes the bonding between the separator and the electrode more firm and uniform. Furthermore, when the positive electrode film layer rebounds, it helps to maintain the interfacial contact between the separator and the positive electrode film layer, reducing the probability of film layer detachment.

[0072] Compared to wound cells, laminated cells have less compression between the separator and the electrode, making them more prone to relative displacement. This displacement can disturb the membrane layer, leading to powder shedding or detachment. Furthermore, it can cause the positive and negative electrodes to overlap, increasing the risk of internal short circuits within the cell. Therefore, the separator provided in this application is particularly suitable for laminated cells. Increased adhesion between the porous adhesive layer and the electrode helps improve the bond between the separator and the electrode, reducing relative displacement. This helps reduce disturbance to the positive electrode membrane layer, lowering the probability of membrane detachment, and also reduces the risk of short circuits caused by positive and negative electrode overlap.

[0073] In summary, when the vinylidene fluoride polymer in the adhesive layer of this application is selected from the above-mentioned materials, it helps to form a continuous and uniform porous adhesive layer. First, the adhesion between the adhesive layer and the electrode is improved and uniformly distributed, which helps to reduce stress concentration in the thick-coated lithium transition metal phosphate positive electrode film, reducing the risk of film detachment and thus helping to further improve the cycle life of the battery. Second, the stable adhesion between the adhesive layer and the positive or negative electrode helps to reduce the direct contact between the positive and negative electrode due to the relative displacement between the electrode and the separator, reducing the risk of internal short circuit and helping to improve battery safety performance. Third, the porous adhesive layer helps to maintain the porosity of the separator, reserving space for cell expansion and further improving the cycle life of the battery.

[0074] In any embodiment, the thickness of the base film in the diaphragm is 7μm-9μm.

[0075] In any embodiment, the thickness of the ceramic layer on one side of the diaphragm is 2μm-4μm.

[0076] In any embodiment, the thickness of the adhesive layer on one side of the diaphragm is 1 μm-5 μm.

[0077] If the adhesive layer is too thin, the void space in the separator is small and the adhesion between the separator and the electrode is weak. On the one hand, the stress increases after the membrane expands, increasing the probability of membrane detachment and affecting the cycle life of the battery; on the other hand, the probability of a short circuit between the positive and negative electrodes increases, thus affecting the battery's safety performance. If the adhesive layer is too thick, it occupies a large amount of space in the battery, thus affecting the battery's volumetric energy density. In the embodiments of this application, the thickness of the adhesive layer is within the above-mentioned range, which helps to balance the battery's cycle life, safety performance, and volumetric energy density.

[0078] In any embodiment, the positive electrode film layer has a base coating layer in the bottom region near the positive electrode current collector. The base coating layer includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes polyvinylidene fluoride (PVDF).

[0079] In any embodiment, the thickness of the base coating is 0.5 μm to 5 μm.

[0080] The undercoating layer provided in this application helps improve the adhesion between the positive electrode film and the positive electrode current collector and alleviates stress concentration at large particles, thereby reducing the probability of positive electrode film detachment and improving the cycle stability of the battery. Simultaneously, compared to direct contact between the positive electrode current collector and the positive electrode film, the increased contact area between the undercoating layer and the positive electrode film helps increase the area for electron transport between the current collector and the positive electrode film, thereby reducing the internal resistance of the electrode and improving the battery's dynamic performance.

[0081] In any embodiment, the battery cell includes a housing, and the stacked cells are housed within the housing. The housing has a length dimension of L1, a width dimension of W1, and a thickness dimension of H1, wherein 450mm≤L1≤1300mm, 100mm≤W1≤150mm, and 14mm≤H1≤22mm.

[0082] In any embodiment, the length dimension of the housing is L1, where 450mm≤L1≤650mm.

[0083] When the length dimension L1 of the casing satisfies 450mm≤L1≤650mm, the length of the battery cell is shorter, which helps to shorten the current diffusion path, reduce the internal resistance of the electrode, thereby reducing the heat generation of the battery and improving its dynamic performance. In addition, the shorter casing length helps to shorten the diffusion path of the electrolyte during the wetting process, improve the wetting rate and uniformity of the electrolyte, further promote the uniformity of lithium ion insertion and extraction during cycling, alleviate stress concentration, reduce the risk of film peeling, and improve the cycle stability of the battery cell.

[0084] In any embodiment, the length dimension of the housing is L1, where 900mm≤L1≤1300mm.

[0085] When the length dimension L1 of the casing satisfies 900mm≤L1≤1300mm, the battery cell is relatively long, which helps to reduce the volume ratio of the casing in the battery cell and increase the load ratio of active materials. At the same time, a longer battery cell can reduce the number of batteries required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of structural components in the module, thereby improving the space utilization of the battery pack and thus helping to improve the volumetric energy density of the battery cell.

[0086] In any embodiment, the shell is made of a soft-pack material, which includes an aluminum-plastic composite film.

[0087] In any embodiment, the material of the housing includes one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) forming a composite film with aluminum.

[0088] Soft-pack materials have high elongation, resulting in thinner and more flexible casings that improve space utilization of individual battery cells, thereby increasing their energy density. Furthermore, aluminum's high barrier properties effectively reduce the penetration of water and oxygen into the battery, decreasing electrolyte decomposition and electrode material oxidation, thus extending battery life.

[0089] In any embodiment, at 25°C, the capacity of the battery cell is 95Ah-300Ah.

[0090] In any embodiment, at 25°C, the capacity of the battery cell is 150Ah-190Ah.

[0091] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0092] A third aspect of this application provides an electrical device, which includes the battery device provided in the second aspect, the battery device being used to provide electrical energy.

[0093] The fourth aspect of this application provides an energy storage device, which includes the battery device provided in the second aspect, the battery device being used to store electrical energy. Attached Figure Description

[0094] Figure 1 This is a schematic diagram of the diaphragm according to one embodiment of this application; Figure 2 This is a schematic diagram of a diaphragm using existing technology; Figure 3 This is a schematic diagram of the surface morphology of the adhesive layer according to an embodiment of this application; Figure 4This is a schematic diagram of a pouch cell battery according to this application; Figure 5 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0095] Explanation of reference numerals in the attached figures: 5. Battery cell; 50. Casing; 20. Separator; 201. Base film; 202. Ceramic layer; 203. Adhesive layer; X. Length direction; Y. Width direction; Z. Thickness direction. Detailed Implementation

[0096] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the lithium-ion secondary battery, battery device, power consumption device, and energy storage device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0097] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0098] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0099] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0100] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0101] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0102] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0103] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0104] In embodiments of this application, the battery device may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple pouch cell batteries connected in series, parallel, or a combination of these pouch cell batteries via a busbar. For example, a battery cell assembly is typically formed by arranging multiple pouch cell batteries; a battery cell assembly may also be a battery module, which is formed by arranging and fixing multiple pouch cell batteries into a single module. As an example, a battery module may be formed by bundling multiple battery cells together with cable ties.

[0105] The battery device can be a battery pack, which includes a housing and one or more individual battery cells housed within the housing. The individual battery cells can be battery modules, which can be housed within the housing by fixing the battery modules to the housing; alternatively, multiple pouch battery cells can be directly fixed to the housing and housed within the housing.

[0106] In embodiments of this application, the housing may include a first housing and a second housing. The first housing and the second housing are fastened together to form a closed space inside the housing for housing individual battery cells. Here, "closed" refers to covering or shutting down; it can be sealed or unsealed. The first housing may be a top cover or a bottom plate. For example, the housing may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, forming a closed space inside the housing for housing individual battery cells.

[0107] In embodiments of this application, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least a part of the vehicle's floor, or a portion of the housing can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0108] In this embodiment, the battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used; the battery cell can be a lithium-ion battery. The battery cell can be flat.

[0109] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0110] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging.

[0111] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0112] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0113] In some implementations, individual battery cells can be assembled into a battery module, and the number of individual battery cells contained in the battery module can be multiple, with the specific number adjustable according to the application and capacity of the battery module.

[0114] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0115] A single battery cell includes electrode components and an electrolyte.

[0116] Electrode assemblies typically include positive and negative electrodes. The negative electrode is the electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode is the electrode that absorbs or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0117] While lithium-containing transition metal phosphates offer significant advantages in cycle stability as positive electrode active materials, their intrinsic specific capacity is significantly lower than that of ternary materials. The applicant has found that using a thick coating process in electrode fabrication is an effective way to compensate for the low capacity of lithium-containing phosphates. However, this process improvement also brings new technical challenges: thicker electrodes experience greater volume expansion during long-term cycling, leading to increased internal stress. This stress makes the film layer prone to partial or complete detachment from the electrode. Film detachment results in the loss of positive electrode active material participating in the charge-discharge reaction and creates an "island" effect, where isolated regions form between active material particles or between particles and the conductive agent, preventing proper electrical contact and thus hindering their participation in the battery's charge-discharge reaction, causing a sharp drop in battery capacity. Simultaneously, this material affects ion transport, increases internal resistance, leads to localized overheating, and increases the risk of thermal runaway, severely impacting battery lifespan. Therefore, how to improve energy density while maintaining stable battery capacity during cycling remains a pressing technical problem that needs to be solved.

[0118] The first aspect of this application provides a battery cell comprising a stacked cell, the stacked cell including a positive electrode and a negative electrode, the positive electrode including a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film including lithium transition metal phosphate particles of carbon material disposed on at least a portion of its surface; the battery cell, in a fully discharged state, has a compaction density of 2.3 g / cm³ for the positive electrode. 3 -2.6g / cm 3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 The value is 0.6-0.8; in the cumulative distribution curve of graphitization degree C obtained by laser microscopy confocal Raman spectroscopy in the instrument scanning mode, the median C of graphitization degree is 0.6-0.8. 50 The value ranges from 0.95 to 1.20; among which, the degree of graphitization C is I. G / ID I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0119] Studies have shown that stress concentration areas in the film layer are prone to cracking under cyclic expansion, becoming the starting point for film delamination, which is more pronounced in thick-coated cells. Compared to ternary materials, lithium-containing transition metal phosphate structures are more stable and less prone to breakage under high pressure. Lithium-containing transition metal phosphates require higher pressure during electrode compaction to achieve higher compaction density. However, under full-discharge conditions, the compaction density of the positive electrode in a single battery cell exceeds 2.6 g / cm³. 3 This can lead to overpressure on the electrode, increased stress concentration, and a higher risk of film shedding during cycling; while the compaction density of the positive electrode is less than 2.3 g / cm³. 3 This will result in insufficient contact between the positive electrode film particles, leading to increased internal resistance of the battery and affecting the energy density of the individual cells; the single-sided density of the positive electrode film is less than 0.25g / 1540.25mm. 2 This cannot meet the requirements for high energy density; the single-sided density of the positive electrode film is higher than 0.45 g / 1540.25 mm. 2 If the positive electrode film is too thick, the volume expansion during cycling will be significant and the stress concentration will be aggravated, increasing the risk of film shedding.

[0120] Stacked cells are beneficial for improving the space utilization of batteries, thereby further increasing the volumetric energy density and capacity of individual cells. The applicant discovered that in thick-coated stacked cells, stress concentration typically originates from localized stress generated during compaction. On the one hand, during compaction, particles with low sphericity have sharp stress surfaces and are less prone to slippage; under stress, the mutual obstruction between particles easily leads to stress concentration. When the positive electrode film layer is truncated along the thickness direction of the positive electrode sheet, the cumulative distribution curve of the sphericity area of ​​particles with a diameter R1 satisfying R1≥1000nm, L... R1A50 When the value is less than 0.6, significant local stress will form during particle compaction, significantly increasing the risk of film detachment during cycling; on the other hand, the median C of graphitization degree... 50 Reflecting the degree of order in carbon material layers, when C 50When the value is less than 0.95, the slipability of the carbon layer structure decreases, resulting in high inter-particle friction during compaction and difficulty in slippage. This further increases the stress during compaction, thereby increasing the probability of film delamination during cycling. Lithium-containing transition metal phosphate particles often require high-temperature sintering. With the increase of sintering temperature or time, particle grain boundaries melt, particles grow, and graphitization increases, but the sphericity of the particles decreases. In order to balance the sphericity and graphitization of particles in the film and reduce the short-board effect of stress concentration during compaction caused by either, the median sphericity of particles with a particle size R1 satisfying R1≥1000nm usually does not exceed 0.8; and the median C of the graphitization of the cathode film is... 50 It is usually not higher than 1.2.

[0121] The battery cell provided in this application adopts a thick coating and stacked cell process, and controls the compaction density of the positive electrode sheet to be 2.3 g / cm³ when the battery cell is fully discharged. 3 -2.6g / cm 3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 While increasing battery capacity, this also alleviates stress concentration, reduces the probability of film peeling, and improves battery cycle life. Furthermore, by controlling the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction, L... R1A50 The graphitization degree C is 0.6-0.8, and the median C of the graphitization degree C is found in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode. 50 The concentration is 0.95-1.20, which improves the spheroidal nature of large particles in the positive electrode film and the graphitization degree of the positive electrode film, improves the local stress generated during the compaction process, thereby further reducing the probability of film peeling and improving the cycle life of the battery.

[0122] In summary, the battery cell of this application improves the problem of capacity drop while having high capacity, and takes into account the cycle life of the battery.

[0123] In this application, a laminated cell refers to a cell formed by stacking a positive electrode, a separator, and a negative electrode together.

[0124] In this application, the positive electrode film layer contains lithium transition metal phosphate, but the positive electrode film layer does not refer to the positive electrode active material layer alone. Other film layers that are connected to the positive electrode active material layer and are difficult to distinguish, such as the undercoat layer and the liquid retention layer, are all collectively referred to as the positive electrode film layer.

[0125] In this application, lithium-containing transition metal phosphates refer to phosphate materials containing lithium and transition metal elements, which can be detected by any method known in the art. For example, they can be detected by combining X-ray diffraction (XRD) with energy dispersive spectroscopy (EDS) or inductively coupled plasma mass spectrometry (ICP-MS).

[0126] In this application, the carbon material disposed on at least a portion of the surface of lithium-containing transition metal phosphate particles can be detected by any method known in the art. As an example, the carbon material disposed on at least a portion of the surface of lithium-containing transition metal phosphate particles can be observed by characterizing the particles using a combination of transmission electron microscopy and energy dispersive spectroscopy.

[0127] In this application, the fully discharged state refers to the state after the battery is placed in a 25°C oven environment, left to stand for 2 hours, and the battery temperature is maintained at 25°C, and then discharged at a constant current of 1 / 3C to 2.5V and then discharged at a constant current of 0.1C to 2.0V.

[0128] In this application, the compaction density of the positive electrode sheet can be tested using methods known in the art. As an example, the battery is placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V, then discharged at a constant current of 0.1C to 2.0V. The battery is then disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S, obtaining a mass of W1. The thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed electrode sheet is wiped off, and the mass of the current collector is weighed and recorded as W2. The thickness T2 of the current collector is measured using a micrometer. The compaction density PD of the positive electrode sheet is then calculated as follows: (W1...) W2) / [(T1-T2)×S。

[0129] In some embodiments, the compaction density of the positive electrode sheet of the battery cell in its fully discharged state can be selected as 2.3 g / cm³. 3 2.31 g / cm 3 2.32 g / cm 3 2.33 g / cm 3 2.34 g / cm 3 2.35g / cm 3 2.36 g / cm 3 2.37 g / cm 3 2.38g / 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 32.44 g / cm 3 2.45g / cm 3 2.46 g / cm 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.50g / cm 3 2.52g / cm 3 2.55g / cm 3 2.60g / cm 3 Or the range of values ​​between any two.

[0130] In this application, the single-sided coating surface density of the positive electrode film has a well-known meaning in the art and can be tested using methods known in the art. For example, take a single-sided coated and cold-pressed positive electrode sheet (if it is a double-sided coated positive electrode sheet, the positive electrode film layer on one side can be wiped off first), cut it into a small circular piece with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive electrode film layer of the weighed positive electrode sheet, weigh the current collector, and record it as M0. The single-sided surface density of the positive electrode film layer = (M1-M0) / S1. To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples can be tested, and the average value can be calculated as the test result. A higher single-sided coating surface density of the positive electrode film layer indicates an increase in its load per unit area, which helps to improve the volumetric energy density of the battery cell.

[0131] In some embodiments, the surface density of the coating on one side of the positive electrode film can be selected as 0.25 g / 1540 mm. 2 0.26g / 1540mm 2 0.27g / 1540mm 2 0.28g / 1540mm 2 0.29g / 1540mm 2 0.3 g / 1540 mm 2 0.31 g / 1540mm 2 0.32 g / 1540mm 2 0.33 g / 1540mm 2 0.34g / 1540mm 2 0.35g / 1540mm 2 0.36g / 1540mm 2 0.37g / 1540mm 2 0.38g / 1540mm 2 0.39g / 1540mm 2 0.40g / 1540mm 20.41g / 1540mm 2 0.42g / 1540mm 2 0.43g / 1540mm 2 0.44g / 1540mm 2 0.45g / 1540mm 2 Or the range of values ​​between any two.

[0132] In some embodiments, the areal density of the positive electrode film coating on one side is 0.3 g / 1540.25 mm. 2 - 0.45g / 1540.25mm 2 .

[0133] In some embodiments, the areal density of the positive electrode film layer on one side is 0.35 g / 1540.25 mm. 2 - 0.4g / 1540.25mm 2 .

[0134] The single-sided coating density of the positive electrode film is further within the above range, which helps to further improve the battery capacity while taking into account cycle performance.

[0135] In this application, the term "particle" refers to a particle in the positive electrode film layer that has a identifiable complete boundary in the field of view at a certain magnification, such as 10,000x. Defects and scratches may exist inside the particle, but a complete boundary sufficient to divide the particle cannot be identified within it. The positive electrode film layer in this application can be a freshly prepared positive electrode film layer or a positive electrode film layer obtained from disassembly of a battery.

[0136] In this application, the particle identification method is as follows: The positive electrode film layer is cut along the thickness direction of the electrode sheet using an argon ion beam (for example, a Leica EMTIC3XCP device can be used, operating voltage: 6kV, operating time: 6h). After exposing the cut surface, a scanning electron microscope (for example, a Hitachi SU8230 device can be used, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) is used to observe the cut surface of the positive electrode film layer along the thickness direction of the electrode sheet. Images are acquired using a field emission scanning electron microscope at a non-edge location in the cut surface of the positive electrode film layer (after observing the electrode edge under the scanning electron microscope, the field of view is adjusted to the center of the sample) in secondary electron mode. Electron micrographs are taken at 10kx magnification, and the particles in the electron micrographs are analyzed using ImageJ software (1.46r, win64 version). The specific steps for using ImageJ software are as follows: Load the scanning electron microscope (SEM) image to be analyzed; use the Cellpose plugin to identify particles, and then perform manual corrections; use ImageJ to read and analyze data. The specific method for using the Cellpose plugin to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "runcyto3" to identify particles; manually mark particles in the image that were not identified by the software, were not fully identified, or were identified incorrectly. Particles that were not identified by the software, were not fully identified, or were identified incorrectly mainly include the following: 1. Particles that are too large or have scratches on their surface, making them unidentifiable or incompletely identifiable; 2. During argon ion beam cutting, scratches may be generated on the particle surface, and the software may misinterpret these scratches as particle boundaries, leading to identification errors; 3. Particles that are too small and were not successfully identified; 4. Particles located at the edge of the SEM field of view, with the particle's interior penetrated by the edge, preventing a complete view of the morphology, resulting in identification errors due to partial identification replacing the whole.For the unidentified or misidentified particles mentioned above, manual calibration is performed. The specific process is as follows: 1. Delete large particles located around the edges of the scanning electron microscope that are not fully displayed. 2. Determine if any unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, classify it as a single particle and manually mark it based on the observed particle boundary. 3. If cracks or scratches are found inside the particle, determine if they penetrate the particle. If not, classify it as a single particle and manually mark it. 4. If cracks or scratches penetrate the particle, determine if they are linear or irregular. 5. If the cracks or scratches are irregular, classify them as the boundary between particles and divide the particles along this boundary. 6. If the cracks or scratches are linear, perform contrast comparison. 7. If the contrast is not obvious and there is no crack-like appearance, classify it as a scratch and mark it as a single particle. 8. If the contrast is strong and there is a crack-like appearance, classify it as the boundary between particles and mark it as two particles. After manual marking, delete information irrelevant to the particles from the automatic image processing, thus completing the particle identification and marking in the image.

[0137] In this application, the method for testing the sphericity of particles with a diameter R1 satisfying R1≥1000nm in a cross-section of the positive electrode film along the thickness direction of the positive electrode sheet is as follows: Particles in the cross-section of the positive electrode film are identified using the method described above. The morphology of the particles in the cross-section along the thickness direction of the positive electrode sheet is analyzed using the "Shape Description" analysis function in ImageJ. According to the software manual (ImageJ User Guide IJ 1.46r), the "Round" parameter obtained from the analysis represents the ratio of the pixel area of ​​the particle to the area of ​​a circle with the fitted major axis as its diameter, which can be used to characterize the sphericity of the particle. The closer the particle is to a sphere, the closer the ratio of the pixel area to the area of ​​the circle with the fitted major axis as its diameter is to 1. Therefore, the "Round" parameter of the particle obtained from the analysis is used to characterize the sphericity of the particle. The sphericity of at least 1000 particles with a particle size R1 satisfying R1≥1000nm was arranged in ascending order. The cumulative sphericity distribution curve of particles with a particle size R1 satisfying R1≥1000nm within the positive electrode film was obtained by plotting sphericity on the horizontal axis and the cumulative area percentage on the vertical axis. R1A1 50 is the sphericity L value corresponding to the cumulative area ratio of the vertical axis in the cumulative distribution curve of the sphericity L value of particles with particle size R1 satisfying R1≥1000nm.

[0138] In some embodiments, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50The value can be selected from 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.705, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, or any value range between the two.

[0139] Those skilled in the art can control the sphericity of particles using any known process. For example, the sphericity of particles can be adjusted through processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, and adding surfactants, as well as by adjusting the parameters of each process.

[0140] In this application, the cumulative distribution curve of graphitization degree C value refers to the curve obtained by arranging at least 100 C values ​​in ascending order, with graphitization degree as the horizontal axis and the cumulative percentage as the vertical axis. 50 This represents the C value corresponding to a cumulative percentage of 50% on the vertical axis of the cumulative distribution curve for graphitization degree C. The median C value for graphitization degree. 50 Compared to point values, it can reflect the overall graphitization degree of particles in the positive electrode film, i.e., the degree of slippage; compared to the mean value, it can reduce the influence of extreme values ​​during the test and improve the confidence of the test results.

[0141] The graphitization degree (C-value) of the positive electrode film can be obtained using a laser confocal Raman spectroscopy (LCS) surface scanning mode. Specifically, a high-precision Renishaw laser confocal Raman spectroscopy system is used, with an excitation wavelength of 532 nm. A suitable amount of the positive electrode film is scanned on its surface or along a section of the electrode thickness. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, with grid vertices as test points, a step size of 5 μm, and a total of 100 scan points. This yields the C-values ​​at different sites and the cumulative distribution curve of the C-values ​​in the surface scan area. The positive electrode film in this application can be either freshly prepared or obtained from disassembly from a battery. Positive electrode films obtained from disassembly inevitably have residual electrolyte salt particles on their surface. To improve testing accuracy, it is preferable to perform a surface scan on a section of the positive electrode film along the electrode thickness direction to characterize the graphitization degree of the positive electrode film.

[0142] The graphitization degree C of the positive electrode film was obtained by the ratio of the peak intensities of the G-band and D-band peaks in the Raman spectrum. The position of the G-band peak was 1580±100 cm. -1 Its characterization of carbon sp 2 Hybrid structure; D peak position is 1350±100 cm⁻¹ -1It characterizes a disordered structure, where disorder refers to the irregular arrangement of carbon atoms within the structure. In graphite crystals, carbon atoms in the same layer arrange themselves in an sp... 2 Hybridization forms covalent bonds, while interlayer bonding is facilitated by van der Waals forces, making the carbon in the graphite structure prone to slip. Therefore, the C value can characterize the degree of graphitization in the cathode film. It is understandable that the degree of graphitization in the cathode film mainly originates from the graphitized carbon material within the cathode film, i.e., the carbon material layer of the cathode active material. Although rich in sp... 2 Hybridized carbon nanotube conductive agents also have relatively high I0 G / I D However, due to its low content and small tube diameter, its addition to the positive electrode film results in an extreme value in the Raman surface scan test of the positive electrode film, and does not affect the graphitization degree C in the positive electrode film. 50 This has an impact. Therefore, the degree of graphitization of the positive electrode film can also be used to characterize the degree of graphitization of the positive electrode active material.

[0143] Those skilled in the art can control the degree of graphitization of active material particles using any known process. For example, adjusting the carbon source, sintering temperature, sintering time, sintering pressure, and sintering atmosphere can all achieve adjustments to the degree of graphitization of active material particles.

[0144] The higher the degree of graphitization of carbon on the surface of the positive electrode active material, the higher the proportion of graphite-structured carbon in the positive electrode film layer, and the easier it is for particles to slip by means of the highly graphitized carbon structure in the coating layer, thus reducing stress concentration in the electrode.

[0145] In some embodiments, the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value can be selected from 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, or any value range between the two.

[0146] In some embodiments, the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 1.01-1.13.

[0147] If the graphitization degree of the positive electrode film is further within the above range, it will help to further improve the slippage of particles in the positive electrode film, reduce stress concentration in the positive electrode film, and thus further improve the long-cycle stability of the battery cell.

[0148] In some embodiments, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.65-0.75.

[0149] In some embodiments, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.67-0.72.

[0150] In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 Within the range of 0.65-0.75, and further within the range of 0.67-0.72, it is beneficial to further reduce the stress concentration at large particles in the positive electrode film layer of the thick-coated laminated cell, thereby reducing the probability of film layer peeling and improving the cycle life of the battery.

[0151] In some embodiments, the thickness H of the positive electrode film on one side is 70 μm - 120 μm.

[0152] In some embodiments, the thickness H of the positive electrode film on one side is 90 μm - 120 μm.

[0153] The thickness of the positive electrode film can be measured using any method known in the art. As an example, the thickness of the positive electrode film in a cross-section along the thickness direction of the positive electrode sheet is measured using a scanning electron microscope.

[0154] In some embodiments, the single-sided thickness H of the positive electrode film can be selected as 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 83 μm, 84 μm, 85 μm, 86 μm, 87 μm, 88 μm, 89 μm, 90 μm, 91 μm, 92 μm, 93 μm, 94 μm, 95 μm, 96 μm, etc. μm, 97μm, 98μm, 99μm, 100μm, 101μm, 102μm, 103μm, 104μm, 105μm, 106μm, 107μm, 108μm, 109μm , 110μm, 111μm, 112μm, 113μm, 114μm, 115μm, 116μm, 117μm, 118μm, 119μm, 120μm or any numerical range between the two.

[0155] A single-sided thickness of the positive electrode film within the above-mentioned range helps to increase the loading of positive electrode active materials in the battery, thereby increasing the battery capacity.

[0156] In some embodiments, the thickness H of the positive electrode film on one side is 100 μm-120 μm.

[0157] Increasing the thickness of the positive electrode film helps to increase the loading of the positive electrode active material and thus improves the battery capacity. However, the applicant has found that when the thickness of the positive electrode film on one side is greater than or equal to 100 μm, the volume expansion of the positive electrode film is more significant during battery cycling, resulting in greater stress. This leads to more pronounced stress concentration in the positive electrode film, increasing the risk of film detachment and consequently affecting the battery's cycle performance. The embodiments of this application increase the battery capacity by increasing the thickness of the positive electrode film, while simultaneously controlling the particle size R1 in the cross-section along the thickness direction of the positive electrode sheet to be spherical, satisfying R1≥1000nm. The median C of the graphitization degree C value in the cumulative distribution curve of the positive electrode film obtained under laser microscopy confocal Raman spectroscopy surface scanning mode is also considered. 50 This improves the slippage between particles in the positive electrode film and reduces stress concentration during electrode compaction, thereby increasing battery capacity while maintaining battery cycle performance.

[0158] In some implementations, based on the total area of ​​particles in the cross section of the positive electrode film along the thickness direction of the electrode, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-50%.

[0159] It is understandable that the particles in the cross-section of the positive electrode film along the thickness direction, especially those larger than 50 nm, mainly originate from the positive electrode active material. Therefore, the embodiments of this application can accurately and objectively reflect the distribution of lithium transition metal phosphate particles in the positive electrode film by observing and statistically analyzing the particle area in the cross-section of the positive electrode along the thickness direction.

[0160] In existing technologies, laser particle size analyzers are typically used to statistically analyze the particle size of positive electrode active materials using Malvern laser diffraction. However, the applicant's research indicates that because lithium-containing transition metal phosphate particles are prone to agglomeration, the test results obtained by Malvern laser diffraction based on the principle of laser scattering often only reflect the particle size of the agglomerates, and cannot accurately reflect the particle size of the positive electrode active material, let alone its dispersion state in the film layer. This is because the dispersion of the positive electrode active material in the film layer increases during slurry preparation and film forming rolling. The test results obtained by Malvern laser diffraction are affected by the particle size, specific surface area, and degree of agglomeration of the positive electrode active material. Compared to the actual dispersion 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 Malvern laser diffraction cannot be equated with or analogized to the particle size statistically obtained in the embodiments of this application.

[0161] The specific method for testing the area ratio of particles with a diameter R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is as follows: Particles in the positive electrode film are identified using the method described above in this application. The images after particle identification and labeling are imported into ImageJ software for analysis. A scale is set based on the scanning electron microscope image. The particle diameter, area, sphericity, and roughness of the particles in the cross-section along the electrode thickness direction are statistically analyzed using the "Feret diameter," "Area," "Round," and "Solidity" analysis functions. According to the software manual (ImageJ User Guide IJ 1.46r), the obtained "Feret" parameter represents the maximum spacing between all parallel lines in the two-dimensional projection of the particle, thus characterizing the particle diameter; the obtained "Area" parameter represents the pixel area of ​​the particle. Because particles smaller than 50nm are prone to significant errors during statistical analysis and are difficult to accurately identify, and because the particle size of conductive agents is generally smaller than 50nm, which can also introduce large errors into the statistical results, particles smaller than 50nm are not counted in the particle size statistics of this application, and the statistical data of particles whose AR, Round, or Solidity is displayed as "NaN" are deleted. The sum of the "Area" parameters of particles with a particle size R1 satisfying R1≥1000nm and the sum of the "Area" parameters of all particles are calculated, and these are respectively used as the area of ​​particles with a particle size R1 satisfying R1≥1000nm and the total area of ​​the counted particles. The sum of the areas of particles with a particle size R1 satisfying R1≥1000nm divided by the total area of ​​the counted particles is used as the proportion of the area of ​​particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the thickness direction of the electrode sheet.

[0162] In some implementations, based on the total area of ​​particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the area ratio of particles with a particle size R1 satisfying R1≥1000nm can be selected as 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any value range between the two.

[0163] In some implementations, based on the total area of ​​particles in the cross section of the positive electrode film along the thickness direction of the electrode, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-40%.

[0164] Large particles with a particle size R1 ≥ 1000 nm help improve the compaction density of the positive electrode, thereby increasing the volumetric energy density of the battery cell. However, researchers have found that these large particles are prone to stress concentration, increasing the risk of positive electrode film delamination. Therefore, the area ratio of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the thickness direction should be in the range of 12%-50%, and further in the range of 12%-40%. This can improve the compaction density of the electrode without making the film delamination probability too high. This improves the energy density of thick-coated lithium transition metal phosphate batteries while alleviating the capacity drop problem and taking into account the cycle life of the battery.

[0165] In some embodiments, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm in the cross section of the positive electrode film along the electrode thickness direction is less than or equal to 5%.

[0166] The uniformity of particle distribution with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction can be tested using methods known in the art. As an example, the cross-section of the positive electrode film along the electrode thickness direction is divided into three layers of equal thickness (when the positive electrode current collector surface is coated with a base coating and then the positive electrode active material layer is coated, the area from 5μm away from the positive electrode current collector to the surface of the positive electrode film away from the positive electrode current collector in the cross-section along the electrode thickness direction is divided into three layers of equal thickness): a lower layer close to the positive electrode current collector, an upper layer away from the positive electrode current collector, and a middle layer placed between the upper and lower layers; [The text abruptly ends here, likely due to an incomplete translation or a missing section.] Ten non-overlapping fields of view were randomly selected from each of the upper, middle, and lower layers, and scanning electron microscope (SEM) images were captured at 10kx magnification. The ten SEM images from each layer were imported into ImageJ software for analysis. Based on the aforementioned "test method for the area proportion of particles with a particle size R1 satisfying R1≥1000nm in the cross-section along the electrode thickness direction of the positive electrode film layer," the area proportion of particles with a particle size R1 satisfying R1≥1000nm was obtained from the ten images corresponding to the upper, middle, and lower layers, resulting in three values. The range of these three values ​​for the upper, middle, and lower layers represents the uniformity of particle distribution with a particle size R1 satisfying R1≥1000nm in the cross-section along the electrode thickness direction of the positive electrode film layer. The range is the difference between the maximum and minimum values ​​among the three values ​​for the upper, middle, and lower layers. The smaller the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the more uniform the distribution of large particles with a particle size R1 satisfying R1≥1000nm in the positive electrode film layer. This helps to reduce stress concentration at large particles in the positive electrode film layer, reduce the probability of delamination and desquamation, and improve the cycle performance of the battery.

[0167] In some embodiments, the uniformity of particle distribution with particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction can be selected as 0.01%, 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%, 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%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or any value range between the two.

[0168] In some embodiments, the uniformity of particle distribution with particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is 0.2%-2.5%.

[0169] In some embodiments, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is 0.2%-2%.

[0170] If the uniformity of particle distribution with particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the thickness direction of the electrode sheet is within the above range, it can effectively reduce the stress concentration in local areas of the film layer, so that the stress during the film layer compaction process can be uniformly distributed throughout the entire area of ​​the film layer. This can improve the battery energy density while reducing the probability of film layer peeling, alleviate the capacity drop problem of thick-coated lithium transition metal phosphate batteries, and improve the battery cycle life.

[0171] In some embodiments, the median B of the coating value B obtained in the cumulative distribution curve of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value is 0.30-0.60, where the coating value B is I. P / I D , where I P This indicates that the Raman spectrum is at 948±100 cm⁻¹ -1 The intensity of the P peak at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

[0172] The cumulative distribution curve of the coating value (B-value) is obtained by arranging at least 100 B-values ​​in ascending order, with the coating value on the horizontal axis and the cumulative percentage on the vertical axis. To reduce the influence of extreme coating values ​​caused by non-particle regions in the positive electrode film on the test results, the median coating value (B-value) is used. 50 Evaluate the density of the carbon material layer on the positive electrode active material. B 50 The B value is the value corresponding to the cumulative number of values ​​on the vertical axis of the cumulative distribution curve of the coverage value B value when the cumulative number accounts for 50%.

[0173] In this application, the coating value (B-value) of the positive electrode film can be obtained by scanning with a laser confocal microscopy (LCM) spectrometer. Specifically, a high-precision Renishaw laser confocal microscopy (LCM) spectrometer is used, with an excitation wavelength of 532 nm. An appropriate amount of the positive electrode film is scanned on its surface or along a section of the electrode thickness. The scanning area is 45 μm × 45 μm, divided into 10 × 10 grids, with grid vertices as test points, a step size of 5 μm, and a total of 100 scan points. This yields the B-values ​​at different locations and the cumulative distribution curve of the B-values ​​in the scanned area. The positive electrode film in this application can be either freshly prepared or obtained from disassembly from a battery. Positive electrode films obtained from disassembly inevitably have residual electrolyte salt particles on their surface. To improve testing accuracy, it is preferable to perform a surface scan of the positive electrode film along the electrode thickness to characterize the coating value.

[0174] The coating value B of the positive electrode film was obtained by the ratio of the peak intensities of the P-band and D-band in the Raman spectrum, with the P-band located at 948±100 cm⁻¹. -1 Its characterization of phosphate PO4 3- Structure; D peak position is 1350±100cm -1 The characterization of the structure is based on disorder, where disorder refers to the irregular arrangement of carbon atoms within the structure. During the testing process, an excitation wavelength of 532 nm was selected, resulting in a shallow testing depth. Consequently, in the test results obtained using laser microscopy confocal Raman spectroscopy in surface scanning mode, the carbon structure peak exhibited a higher intensity compared to the phosphate structure peak.

[0175] Those skilled in the art can control the coating value of active material particles using any known process. For example, adjusting the carbon source type, carbon source addition amount, sintering temperature, sintering time, sintering pressure, and sintering atmosphere can all achieve adjustments to the coating value of the active material particles. The coating value (B-value) reflects the density of the carbon material layer on the surface of lithium transition metal phosphate particles. The denser the carbon material layer, the lower the relative intensity of the phosphate structure detected in the Raman spectrum, and the smaller the coating value (B-value) of the cathode film.

[0176] In some embodiments, the positive electrode film further includes a coating layer disposed on at least a portion of the surface of the lithium-containing transition metal phosphate particles, wherein the median B of the coating value B in the cumulative distribution curve of the positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 The value can be selected from 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, or any value range between the two.

[0177] The median B of the coating value of the positive electrode film 50 Within the aforementioned range, it is evident that the carbon material layer of the positive electrode active material is relatively dense and uniform, which is beneficial for improving the slip uniformity of the positive electrode film layer during the rolling process and reducing stress concentration in the thick-coated positive electrode film layer. In addition, thanks to the dense and uniform carbon material layer, large particles in the positive electrode film layer are more likely to slip during the compaction process, thereby reducing stress concentration at large particles in the thick-coated positive electrode film layer, reducing the probability of positive electrode film layer detachment, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0178] In some embodiments, the lithium transition metal phosphate particles in the positive electrode film layer comprise 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, and Br, with 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0≤q≤0.1.

[0179] In some implementations, m can be selected as 0.8, 0.85, 0.9, 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, or any value range between two of these; x can be selected as 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or any value range between two of these. y can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.00 or any value between two of these; j can be 3.5, 3.6, 3.7, 3.8, 3.9, 4 or any value between two of these; q can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or any value between two of these.

[0180] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorinated vanadium phosphate, lithium manganese iron phosphate, and their modified materials.

[0181] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film include one or more of lithium iron phosphate and its doped and modified materials, and coating and modified materials.

[0182] In some embodiments, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1921ppm.

[0183] The iron dissolution rate of the positive electrode material in the positive electrode film layer can be tested using methods known in the art. As an example, 7.5g of positive electrode material powder obtained by scraping powder from the positive electrode film layer sample is weighed and added to 100.3g of 0.3% ascorbic acid solution (solvent is ultrapure water). After stirring at 500 rpm for 305 minutes, the solution is quickly aspirated using a 5mL syringe and filtered into a test tube using a 0.45μm pore size filter. 1mL of the supernatant is aspirated with a pipette and added to a glass volumetric flask for 50-fold dilution. The iron concentration in the solution is obtained by testing with an inductively coupled plasma mass spectrometer (ICP-OES). The iron dissolution rate of the positive electrode material in the positive electrode film layer is calculated using the formula: (ICP test iron concentration × solution volume / mass of the solution used for volume adjustment) × 100.3g / mass of positive electrode material powder. The solution volume is 50mL and the mass of the solution used for volume adjustment is 1g.

[0184] In some embodiments, the iron dissolution rate of the positive electrode material in the positive electrode film layer can be 658ppm, 700ppm, 800ppm, 890pm, 900ppm, 1000ppm, 1058pm, 1076pm, 1100ppm, 1143pm, 1200ppm, 1236pm, 1300ppm, 1311pm, 1384pm, 1349pm, 1400ppm, 1485pm, 1500ppm, 1531pm, 1600ppm, 1700ppm, 1800ppm, 1921ppm, or any value between the two.

[0185] In some embodiments, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1485ppm.

[0186] The iron dissolved in the cathode material mainly originates from the lithium transition metal phosphate (LMT) of the cathode active material. The iron dissolution rate depends on both the number of lattice defects in the LMT and the integrity and density of the carbon layer on the surface of the cathode active material. A lower iron dissolution rate means fewer lattice defects in the LMT, which helps reduce lattice corrosion in weak acid environments. Furthermore, a more complete and dense carbon layer on the surface of the cathode active material inhibits the dissolution of iron ions in weak acid environments. Cathode materials with iron dissolution rates within the above range have relatively few lattice defects and a complete and dense carbon layer. This improves the compressibility and slippage of particles in the cathode film under high rolling pressure, increases the compaction density of the cathode film, reduces stress concentration in the cathode film, improves the energy density of the battery, and also addresses the issue of battery capacity drops.

[0187] In some implementations, the mass content of titanium is 500ppm-8000ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0188] The types and contents of elements in lithium transition metal phosphate particles in the positive electrode film can be tested using any method known in the art. As an example, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to test the titanium content, referring to Appendix C of GB / T 33822-2017.

[0189] In some embodiments, based on the total mass of lithium transition metal phosphate particles in the positive electrode film, the mass content of titanium can be selected as 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm, 7000ppm, 7500ppm, 8000ppm, or any value range between the two.

[0190] In some embodiments, the mass content of titanium is 1000ppm-3000ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0191] Introducing titanium into lithium transition metal phosphate particles requires adding a titanium source during the preparation of the cathode active material. Titanium sources are often inert materials, and their adhesion to the surface of the lithium transition metal phosphate raw material reduces reactivity and particle size growth. Increasing the graphitization degree of the cathode active material often requires higher sintering temperatures or longer sintering times, but this also increases the particle size in the cathode film, increasing stress concentration and potentially causing film detachment. In this embodiment, by adding a high content of titanium to the lithium transition metal phosphate particles, the reactivity of the raw materials for synthesizing the cathode active material is reduced. This allows the cathode active material to achieve a high degree of graphitization while controlling the proportion of large particles, reducing stress concentration in the cathode film, lowering the probability of film detachment, and improving both battery energy density and cycle life.

[0192] Meanwhile, the doping of titanium in the positive electrode active material is beneficial for inducing lattice distortion, reducing Li-O bond energy, increasing lithium-ion transport rate, and improving the kinetic performance of the battery. In thick coated films, lithium-ion diffusion is uneven, often accompanied by a significant lithium-ion concentration gradient. This application's embodiments improve the solid-phase transport rate of the positive electrode active material by adding a high content of titanium to lithium-containing transition metal phosphate particles, thus addressing the kinetic problems of thick electrode batteries.

[0193] In some implementations, the vanadium content is 500 ppm to 5000 ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0194] The types and contents of elements in lithium transition metal phosphate particles in the positive electrode film can be tested using any method known in the art. As an example, inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to test the vanadium content, referring to Appendix C of GB / T 33822-2017.

[0195] In some embodiments, the vanadium content can be selected as 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, or 5000ppm, based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0196] In some implementations, the vanadium content is 500 ppm to 3000 ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0197] Vanadium in the positive electrode film can be in multiple valence states, including +5 vanadium (V5). 5+ Vanadium (V+3) can be doped into phosphorus sites. Due to its large radius, it can cause lattice distortion, 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 (V+3) 3+ Vanadium can be doped into transition metal sites, generating lithium vacancies through charge compensation, thereby improving the electronic conductivity of the positive electrode active material. Furthermore, the increased uniformity of vanadium distribution in lithium-containing transition metal phosphate particles helps to further improve the kinetic performance and reaction uniformity of the positive electrode film, thus further enhancing the kinetic and cycle performance of the battery cell.

[0198] Vanadium content within the aforementioned range helps improve the kinetic performance of the positive electrode and the kinetic performance of thick-coated lithium transition metal phosphate batteries. Simultaneously, the synergistic effect of titanium, vanadium, and carbon nanotubes in the positive electrode film helps form a good three-dimensional network, further improving the electronic and ionic conductivity of the positive electrode film, thereby further enhancing the kinetic performance of thick-coated lithium transition metal phosphate batteries.

[0199] In some implementations, the porosity of the positive electrode film is 14%-28%.

[0200] In this application, the porosity of the positive electrode film layer can be tested in the following way. Import the cross-sectional scanning electron microscope (SEM) image of the positive electrode film layer along the electrode thickness direction obtained as described above into ImageJ software. Select the line tool and use a line to mark the length of the scale bar in the image. Click "Analyze Set Scale" and set the scale parameters in the software according to the scale bar length in the image. Select the rectangle tool and select the part of the image outside the scale bar area. Use "Image Duplicate" to copy the selected area and use "Image Type 8 bit" to adjust the image format. Select "Analyze Set Measurements" and choose the following five options: "Area", "Mean gray value", "Area Fraction", "Limit tothreshold", and "Feret's diameter". Select 3 for "Decimal places". Then, select "Image" - "Adjust" - "Threshold" sequentially, and set 0 and 100 respectively in the "Threshold" selection box. The pore data from the cross-sectional SEM image can then be exported using the Analyze-Measure function. Export using "Image" - "Overlay" - "Flatten" to obtain a pore image; click "Apply" in "Threshold", then click "Analyze" - "Analyze Particles", check the four columns on the left to obtain pore statistics.

[0201] It is understood that in this embodiment, "pores" in the cross-section of the positive electrode film are identified through image color difference and threshold. These "pores" are not the pore data obtained from the degassing test, but are mainly used to characterize the gaps between particles in the cross-section of the positive electrode film. This method is superior to the degassing method because the porosity obtained by the degassing method is related to the pores between particles and the pores in the carbon material layer on the particle surface, and cannot objectively reflect the pores between particles.

[0202] In some embodiments, the porosity of the positive electrode film can be selected as 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, or any value range between the two.

[0203] When the porosity of the positive electrode film is within the aforementioned range, the positive electrode film exhibits good electrolyte wettability and tortuosity, which facilitates the diffusion of lithium ions in both the liquid and solid phases. This helps reduce concentration polarization in thick electrode sheets and improves the battery's kinetic performance. Simultaneously, it helps alleviate volume expansion of thick-coated electrodes during cycling, reduces mechanical stress in the film, and minimizes stress concentration, thereby reducing the risk of film detachment from thick-coated electrodes.

[0204] Especially in thick-coated soft-pack batteries, the gap between the casing and the electrode is small, the volume occupancy of the film is large, the electrolyte capacity is reduced, and the porosity of the positive electrode film is within the above range, which helps to improve the liquid retention rate of the cell and improve the battery dynamic performance.

[0205] In some embodiments, the positive electrode film layer further includes a conductive agent, and the area of ​​the agglomerated region of the conductive agent accounts for 0.5%-2.5% based on the total area of ​​the cross section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0206] In this application, the area ratio of the conductive agent agglomeration region, based on the total area of ​​the cross-section of the positive electrode film layer along the electrode thickness direction, can be tested using the following method. A similar method to that described above is used to observe the cross-section of the positive electrode film layer along the electrode thickness direction using a scanning electron microscope (SEM), and the area of ​​the conductive agent agglomeration region in the SEM image is measured at 3kx magnification. Since the conductive agent is generally a carbon-based material, such as conductive carbon black or carbon nanotubes, aggregated conductive agent can be seen under high magnification in the SEM. The conductive agent agglomeration region often appears black and agglomerated compared to other areas in the positive electrode film layer. Using image analysis software, the conductive agent agglomeration region refers to the area in the SEM image where the conductive agent is clearly aggregated and appears black. Specifically, the scanning electron microscope (SEM) image at 3kx magnification is imported into ImageJ. Black conductive agent agglomeration regions with a Feret value greater than or equal to 2μm are selected, and the sum of the areas of these selected regions is recorded as the area of ​​the conductive agent agglomeration region. The area ratio of the conductive agent agglomeration region is the ratio of its area to the total area of ​​the imported SEM image. Three randomly selected, non-overlapping SEM images are used, and the average of these ratios is calculated as the "area ratio of the conductive agent agglomeration region based on the total area of ​​the cross-section along the electrode thickness direction of the positive electrode film."

[0207] In some embodiments, the positive electrode film layer further includes a conductive agent. Based on the total area of ​​the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomerated region of the conductive agent 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%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any value range between the two.

[0208] Based on the total area of ​​the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is within the above range, indicating that the conductive agent in the positive electrode film is uniformly dispersed and it is easy to form a uniform conductive network. This is especially beneficial to reduce the problem of kinetic decline caused by the growth of ion transport paths in thick coating films, reduce local polarization and even lithium plating problems generated during battery cycling, and improve the cycle life of the battery.

[0209] Meanwhile, research shows that the first large-sized particles in lithium transition metal phosphate particles are prone to rebound. The agglomeration area of ​​the conductive agent within the above range can suppress the rebound of lithium transition metal phosphate particles by means of the uniform distribution of the conductive agent, forming mechanical constraints on the particles and even the film layer, improving the cohesion of the film layer, reducing the phenomenon of film layer powder shedding and shedding, and improving the cycle life of the battery.

[0210] In some embodiments, the positive electrode film layer further includes a conductive agent, and the area of ​​the agglomerated region of the conductive agent accounts for 0.5%-1.7% based on the total area of ​​the cross section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0211] In this embodiment, the area ratio of the agglomerated region of the conductive agent is further within the above-mentioned range, indicating that the conductive agent is more uniformly distributed in the positive electrode film layer and the content of the conductive agent is low. While improving the dynamic performance of the positive electrode film layer, it helps to reduce the space occupied by the excessive conductive agent on the positive electrode active material, thereby improving the battery's dynamic performance and further increasing the battery's volumetric energy density.

[0212] In some embodiments, the conductive agent includes carbon nanotubes, which include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0213] In this application, the term "carbon nanotube" refers to a structure composed of carbon atoms arranged in sp... 2Graphene sheets, formed by hybrid bonding, are rolled up to form nanomaterials with several to dozens of coaxial hollow cylindrical layers. Their diameters typically range from several to tens of nanometers, while their lengths can vary from micrometers to centimeters, exhibiting a high aspect ratio. Based on the number of layers, graphene sheets can be classified into: single-walled carbon nanotubes (SWCNTs), few-walled carbon nanotubes (FWCNTs), and multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes possess excellent electrical conductivity and high elastic modulus.

[0214] Because carbon nanotubes have a one-dimensional structure, they can form a network structure in the positive electrode film. On the one hand, the high elastic modulus of carbon nanotubes enables their network structure to not only act as a bridge for stress propagation but also to bind the thickly coated positive electrode film, suppressing the rebound of lithium-containing transition metal phosphate particles, effectively alleviating stress concentration, reducing the risk of film shedding, and thus improving the problem of battery capacity drop. On the other hand, the excellent conductivity of carbon nanotubes makes their network structure a highly efficient electron transport channel. Even if there is local film shedding, the thick electrode can still maintain high electron transport efficiency in the in-plane and thickness directions, thereby delaying the occurrence of capacity drop and further improving the battery's dynamic performance and cycle life.

[0215] In some embodiments, the conductive agent also includes conductive carbon black.

[0216] Conductive carbon black has a high specific surface area, thus exhibiting excellent electrolyte retention capacity. Thick electrodes experience greater expansion force during cycling, making it easier for electrolyte to be squeezed out. The distribution of conductive carbon black in the positive electrode film layer helps improve the electrolyte retention capacity of thick electrodes, further mitigating the phenomenon of capacity drop during battery cycling and improving battery cycle life.

[0217] In some embodiments, the agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

[0218] Researchers have found that due to their high surface energy, carbon nanotubes are prone to agglomeration, resulting in uneven dispersion in the positive electrode film layer and the inability to form an effective carbon nanotube network structure. The surface energy of conductive carbon black is relatively close to that of carbon nanotubes, which can adsorb on the surface of carbon nanotubes to form a physical barrier, increasing the resistance to carbon nanotube agglomeration, reducing the direct contact between carbon nanotubes, thereby inhibiting agglomeration and improving the uniformity of carbon nanotube distribution in the positive electrode film layer. On the one hand, this helps to improve the conductivity of the thick-coated positive electrode film layer and enhance 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 thick-coated 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 agglomeration area of the conductive agent will also cause local blockage of the ion transport path in the conductive agent agglomeration area, and the combination of conductive carbon black can improve the lithium ion transport ability in this area, reduce local polarization, and further improve the cycle stability of the battery.

[0219] 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 < C2 ≤ 2.5%.

[0220] 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.

[0221] In some embodiments, based on the mass of the positive electrode film layer, the mass content C2 of conductive carbon black can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% or the numerical range between any two of them.

[0222] 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, improving the liquid retention rate of the positive electrode plate 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 taking into account the problem of capacity drop, and improving the cycle life of the battery.

[0223] In some embodiments, the positive electrode film layer further includes a dispersant, including hydrogenated nitrile butadiene rubber (HNBR).

[0224] HNBR is obtained by hydrogenating and saturating the double bonds of nitrile rubber. Its highly saturated main chain structure gives it excellent oil resistance, heat resistance, and aging resistance. This allows it to remain stable in different environments and systems when used as a dispersant, without easily degrading or deteriorating, thus effectively exerting its dispersing effect. The HNBR molecular chain contains both polar nitrile groups and non-polar hydrocarbon segments. The polar nitrile groups can interact with some polar substances or particle surfaces, such as through hydrogen bonding or electrostatic interactions, and adsorb onto the surface of the dispersed particles; the non-polar hydrocarbon segments have good oleophilicity and can extend and disperse well in non-polar or weakly polar media, so that the particles are uniformly dispersed in the medium.

[0225] When HNBR adsorbs onto the surface of particles in the slurry, its long-chain molecules form a physical barrier around the particles, preventing them from approaching each other and agglomerating, thus maintaining a relatively independent dispersion. Simultaneously, HNBR reduces the surface tension between the dispersion medium and the dispersed particles, making the particles easier to wet and promoting dispersion. It also reduces the interfacial energy between particles, minimizing aggregation driven by interfacial energy. Furthermore, during slurry drying and film formation, the elastic network structure of HNBR buffers the shrinkage stress caused by solvent evaporation, reducing the re-agglomeration of conductive agents due to capillary forces, lowering the area of ​​agglomerated regions, and improving the battery's kinetic performance and cycle life.

[0226] In some implementations, the mass content of the dispersant is 0.5%-2% based on the mass of the positive electrode film.

[0227] In some implementations, based on the mass of the positive electrode film, the mass content of the dispersant can be selected as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, or any value range between the two.

[0228] When the mass content of the dispersant is within the above range, it can achieve uniform dispersion of particles in the positive electrode film while maintaining a high loading capacity, reduce stress concentration in the thick-coated lithium transition metal phosphate positive electrode film, and effectively alleviate the problem of battery capacity drop.

[0229] In some embodiments, the battery cell further includes a separator 20 disposed between the positive electrode and the negative electrode. The separator 20 includes a base film 201, a ceramic layer 202 disposed on at least one side of the base film 201, and an adhesive layer 203 disposed on the side of the ceramic layer 202 away from the base film 201. The adhesive layer 203 is a continuous layer with a porous structure and includes a vinylidene fluoride polymer.

[0230] In some embodiments, the battery cell further includes a separator disposed between the positive electrode and the negative electrode. The separator includes a base film, ceramic layers disposed on both sides of the base film, and an adhesive layer disposed on both sides of the ceramic layers away from the base film.

[0231] In some embodiments, the vinylidene fluoride polymer includes one or more of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0232] In some embodiments, vinylidene fluoride polymers include polyvinylidene fluoride (PVDF).

[0233] In existing technologies, the adhesive layer of the diaphragm typically uses aqueous PVDF, which exhibits an island-like structure within the diaphragm, such as... Figure 2 As shown, this is beneficial for providing a gap for cell expansion and also facilitates manufacturing; however, the contact area between such a separator adhesive layer and the electrode is small, and the adhesion is weak.

[0234] The diaphragm provided in this application uses a continuous porous layer as the adhesive layer, such as... Figure 1 and Figure 3 As shown, its porous structure provides space for the expansion of the thick-coated cell, improving its stability; at the same time, compared with the adhesive layer in the prior art, it has a larger bonding area with the electrode, thus making the bonding between the separator and the electrode more firm and uniform; furthermore, when the positive electrode film rebounds, it helps to maintain the interfacial contact between the separator and the positive electrode film, reducing the probability of film detachment.

[0235] It is understandable that a continuous adhesive layer may break and deform into a blocky structure during electrode manufacturing or cycling due to contact with or compression of the positive or negative electrode. The continuous structure referred to in this application means that, at the microscopic level, such as under a scanning electron microscope or optical microscope, the adhesive layer of the separator is continuous. To reflect the true morphology of the separator, during sampling, it is preferable to sample in areas of the battery where the separator's adhesive layer is not bonded to the positive or negative electrode. For example, sampling can be performed at locations beyond the positive and negative electrode; or sampling can be performed near the surface of the electrode assembly. This sampling area has less adhesion to the positive or negative electrode, providing a better reflection of the separator's true state.

[0236] Compared to wound cells, laminated cells have less compression between the separator and the electrode, making them more prone to relative displacement. This displacement can disturb the membrane layer, leading to powder shedding or detachment. Furthermore, it can cause the positive and negative electrodes to overlap, increasing the risk of internal short circuits within the cell. Therefore, the separator provided in this application is particularly suitable for laminated cells. Increased adhesion between the porous adhesive layer and the electrode helps improve the bond between the separator and the electrode, reducing relative displacement. This helps reduce disturbance to the positive electrode membrane layer, lowering the probability of membrane detachment, and also reduces the risk of short circuits caused by positive and negative electrode overlap.

[0237] In summary, when the vinylidene fluoride polymer in the adhesive layer of this application is selected from the above-mentioned materials, it helps to form a continuous and uniform porous adhesive layer. First, the adhesion between the adhesive layer and the electrode is improved and uniformly distributed, which helps to reduce stress concentration in the thick-coated lithium transition metal phosphate positive electrode film, reducing the risk of film detachment and thus helping to further improve the cycle life of the battery. Second, the stable adhesion between the adhesive layer and the positive or negative electrode helps to reduce the direct contact between the positive and negative electrode due to the relative displacement between the electrode and the separator, reducing the risk of internal short circuit and helping to improve battery safety performance. Third, the porous adhesive layer helps to maintain the porosity of the separator, reserving space for cell expansion and further improving the cycle life of the battery.

[0238] In some embodiments, the base film may be made of one or more of the following materials, including but not limited to glass fiber, nonwoven fabric, polyethylene (PE), and polypropylene (PP).

[0239] In some embodiments, the ceramic layer includes one or more of alumina (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), silicon oxide (SiO2), and boron nitride (BN).

[0240] Ceramic particles possess flame retardancy and high hardness, making them resistant to deformation under heat and exhibiting excellent dimensional stability. The low thermal conductivity of ceramic materials further prevents certain thermal runaway points in the battery from expanding into overall thermal runaway, thereby improving the safety performance of individual battery cells.

[0241] In some embodiments, the thickness of the base film in the diaphragm is 7 μm-9 μm.

[0242] In some embodiments, the thickness of the base film in the diaphragm can be selected as 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or any value range between the two.

[0243] In some embodiments, the thickness of the ceramic layer on one side of the diaphragm is 2 μm-4 μm.

[0244] In some embodiments, the thickness of the ceramic layer on one side of the diaphragm can be selected as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or any value range between the two.

[0245] In some embodiments, the thickness of the adhesive layer on one side of the diaphragm is 1 μm-5 μm.

[0246] In some embodiments, the thickness of the adhesive layer on one side of the diaphragm can be selected as 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any value range between the two.

[0247] In this application, "thickness" has a meaning known in the art and can be measured using methods and instruments known in the art. As an example, it can be measured using a high-precision micrometer (e.g., a Mitutoyo 293-100 model with an accuracy of 0.1 μm).

[0248] If the adhesive layer is too thin, the void space in the separator is small and the adhesion between the separator and the electrode is weak. On the one hand, the stress increases after the membrane expands, increasing the probability of membrane detachment and affecting the cycle life of the battery; on the other hand, the probability of a short circuit between the positive and negative electrodes increases, thus affecting the battery's safety performance. If the adhesive layer is too thick, it occupies a large amount of space in the battery, thus affecting the battery's volumetric energy density. In the embodiments of this application, the thickness of the adhesive layer is within the above-mentioned range, which helps to balance the battery's cycle life, safety performance, and volumetric energy density.

[0249] In some embodiments, the positive electrode film layer has an undercoat layer in the bottom region near the positive electrode current collector. The undercoat layer includes a conductive agent and a binder. The conductive agent includes carbon nanotubes and conductive carbon black, and the binder includes polyvinylidene fluoride (PVDF).

[0250] In some embodiments, the thickness of the base coating is 0.5 μm to 5 μm.

[0251] In some embodiments, the thickness of the base 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 any value range between the two.

[0252] The undercoating layer provided in this application helps improve the adhesion between the positive electrode film and the positive electrode current collector and alleviates stress concentration at large particles, thereby reducing the probability of positive electrode film detachment and improving the cycle stability of the battery. Simultaneously, compared to direct contact between the positive electrode current collector and the positive electrode film, the increased contact area between the undercoating layer and the positive electrode film helps increase the area for electron transport between the current collector and the positive electrode film, thereby reducing the internal resistance of the electrode and improving the battery's dynamic performance.

[0253] In some implementations, such as Figure 4 As shown, the battery cell 5 includes a housing 50, and the stacked cells are housed inside the housing 50. The housing 50 has a length dimension of L1 in the X direction, a width dimension of W1 in the Y direction, and a thickness dimension of H1 in the Z direction. Wherein, 450mm≤L1≤1300mm, 100mm≤W1≤150mm, and 14mm≤H1≤22mm.

[0254] In some implementations, L1 can be selected as 450mm, 480mm, 490mm, 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 600mm, 610mm, 620mm, 630mm, 640mm, 650mm, 660mm, 670mm, 680mm, 690mm, 700mm, 710mm, 720mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm, 1250mm, 1300mm, or any value range between the two.

[0255] In some implementations, W1 can be selected as 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or any value range between the two.

[0256] In some implementations, H1 can be selected as 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm or any value range between the two.

[0257] In some embodiments, the length dimension of the housing is L1, where 450mm ≤ L1 ≤ 650mm.

[0258] When the length dimension L1 of the casing satisfies 450mm≤L1≤650mm, the length of the battery cell is shorter, which helps to shorten the current diffusion path, reduce the internal resistance of the electrode, thereby reducing the heat generation of the battery and improving its dynamic performance. In addition, the shorter casing length helps to shorten the diffusion path of the electrolyte during the wetting process, improve the wetting rate and uniformity of the electrolyte, further promote the uniformity of lithium ion insertion and extraction during cycling, alleviate stress concentration, reduce the risk of film peeling, and improve the cycle stability of the battery cell.

[0259] In some embodiments, the length dimension of the housing is L1, where 900mm ≤ L1 ≤ 1300mm.

[0260] When the length dimension L1 of the casing satisfies 900mm≤L1≤1300mm, the battery cell is relatively long, which helps to reduce the volume ratio of the casing in the battery cell and increase the load ratio of active materials. At the same time, a longer battery cell can reduce the number of batteries required in the battery module, simplify the structural design of the battery module, reduce the number and complexity of structural components in the module, thereby improving the space utilization of the battery pack and thus helping to improve the volumetric energy density of the battery cell.

[0261] In some implementations, such as Figure 4 As shown, the material of the shell 50 is a soft-pack material, which includes an aluminum-plastic composite film.

[0262] In some embodiments, the shell material includes one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) forming a composite film with aluminum.

[0263] Soft-pack materials have high elongation, resulting in thinner and more flexible casings that improve space utilization of individual battery cells, thereby increasing their energy density. Furthermore, aluminum's high barrier properties effectively reduce the penetration of water and oxygen into the battery, decreasing electrolyte decomposition and electrode material oxidation, thus extending battery life.

[0264] In some embodiments, the capacity of the battery cell is 95Ah-300Ah at 25°C.

[0265] In some embodiments, the capacity of the battery cell is 150Ah-190Ah at 25°C.

[0266] In this application, the capacity of a single battery cell has a meaning known in the art and can be tested using methods known in the art. As an example, at 25°C, the battery is charged to 3.65V at a charging rate of 0.5C, then charged at a constant voltage of 3.65V to 0.05C, left to stand for 10 minutes, and then discharged at a discharging rate of 1C to 2.5V. The discharge capacity of the battery cell is taken as the capacity of the battery cell.

[0267] In some embodiments, at 25°C, the capacity of the battery cell can be selected as 95Ah, 100Ah, 105Ah, 110Ah, 115Ah, 120Ah, 125Ah, 130Ah, 135Ah, 140Ah, 145Ah, 150Ah, 155Ah, 158Ah, 159Ah, 160Ah, 161Ah, 165Ah, 170Ah, 175Ah, 178Ah, 180Ah, 185Ah, 190Ah, 200Ah, 210Ah, 220Ah, 230Ah, 240Ah, 250Ah, 270Ah, 280Ah, 290Ah, 300Ah, or any value range between the two.

[0268] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0269] The battery device disclosed in this application can be used in electrical devices that use the battery device as a power source or in various energy storage systems that use the battery device as an energy storage element. Besides vehicles, the battery device can also be used in, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0270] A third aspect of this application provides an electrical device that uses a battery as a power source, the electrical device including at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The battery cell, battery module, or battery pack can be selected as the electrical device according to its usage requirements.

[0271] Figure 5 This is an example of an electrical device. The electrical device disclosed in this application can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device is installed inside the vehicle, and the battery device can be located at the bottom, front, or rear of the vehicle. The battery device can be used to power the vehicle; for example, the battery device can serve as the vehicle's operating power source. The vehicle may also include a controller and a motor. The controller is used to control the battery device to supply power to the motor, for example, for the vehicle's starting, navigation, and operating power needs. In some embodiments of this application, the battery device can not only serve as the vehicle's operating power source but also as the vehicle's drive power source, replacing or partially replacing gasoline or natural gas to provide driving power for the vehicle.

[0272] The fourth aspect of this application provides an energy storage device that uses a battery device as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0273] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0274] Example 1 (1) Preparation of positive electrode active material Lithium dihydrogen phosphate, ferrous oxalate, carbon source, titanium dioxide, and vanadium pentoxide were mixed evenly in methanol and ground to obtain a mixed raw material. The ratio of lithium dihydrogen phosphate to ferrous oxalate was such that the molar ratio of lithium to iron was 1.025:1.0. The carbon source consisted of polyethylene glycol with a weight average molecular weight of 500, polyethylene glycol with a weight average molecular weight of 2000, and polyethylene glycol with a weight average molecular weight of 4000, all in a mass ratio of 2:6:2. The particle size D of the ferrous oxalate was... 10 With a particle size of 6.5 μm and a diameter D 50 62μm, particle size D 90 The thickness is 108 μm, and the mass content of Fe in ferrous oxalate is 30.5%, while the mass content of ferric iron is 0.03%.

[0275] The mixed raw materials are ball-milled multiple times and demagnetized in a ball mill to obtain a mixed slurry. The number of grinding cycles and time are controlled, and the particle size Dv of the resulting mixed slurry is determined. 50 It is 3.15μm.

[0276] The spray-dried slurry yields a dried precursor powder, which is light yellow in appearance and uniform in color.

[0277] The precursor powder was placed in a sintering furnace and heated from 25°C to 360°C at a rate of 2°C / min under a nitrogen atmosphere, and held at that temperature for 3.5 h. Then, the temperature was increased to a second temperature of 785°C at a rate of 5°C / min and held at that temperature for 10 h, followed by cooling. The total mass content of Ti was 1050 ppm and the mass content of V was 950 ppm, based on the total mass of the positive electrode active material.

[0278] The obtained material was crushed using an airflow pulverization method with a grading frequency of 21 Hz and a pulverizing airflow of 0.54 MPa to obtain lithium iron phosphate cathode active material with carbon material on its surface.

[0279] The D10, D50, D90, and Dv50 mentioned above refer to the data obtained by testing using the Malvern laser scattering method.

[0280] (2) Preparation of positive electrode sheet The above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride were mixed in a mass ratio of 94.1:1.9:3 in the solvent N-methylpyrrolidone. Then, 1% (by mass) of dispersant HNBR was added, and the mixture was thoroughly mixed, stirred, and dispersed in a stirring tank to form a positive electrode slurry. The stirring process included pre-stirring and main stirring. The stirring speed of pre-stirring was lower than that of main stirring. The pre-stirring had an orbital speed of 25 rpm, a rotational speed of 500 rpm, and a pre-stirring time of 15 minutes. After the stirring process, the positive electrode slurry was conveyed to the coating process. The conductive agent consisted of conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 0.9:1. The specific surface area of ​​the conductive carbon black was 80 m². 2 / g, oil absorption value of 180mL / 100g, average length of carbon nanotubes of 20μm, specific surface area of ​​280m². 2 / g; The positive electrode slurry was transferred and coated onto aluminum foil, dried, and then hot-pressed to obtain a positive electrode film with a single-sided density of 0.38 g / 1540.25 mm. 2 The compacted density is 2.36 g / cm³. 3 The positive electrode sheet. Here, compaction density refers to the compaction density of a single battery cell under full discharge conditions.

[0281] The hot pressing process includes three hot roller pressing processes, with the hot roller pressing pressure increasing sequentially to 35 tons, 55 tons, and 75 tons. The hot roller temperature is 65°C. Before the first entry into the hot roller for compaction, the electrode sheet is heated to 50°C.

[0282] The positive electrode sheets are slit and punched into specified shapes, and then the punched positive electrode sheets are sorted by weight using a weighing and sorting machine for stacking by a stacking machine.

[0283] Among them, in the cross-section of the positive electrode film along the electrode thickness direction, in the cumulative distribution curve of the spheroidal area of ​​particles with particle size R1 satisfying R1≥1000nm, the median L of spheroidality is... R1A50 The median C of the graphitization degree of the positive electrode film is 0.721. 50The value is 1.11; based on the total area of ​​particles in the cross-section of the positive electrode film along the electrode thickness direction, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 35.28%; the distribution uniformity of particles with a particle size R1 satisfying R1≥1000nm in the cross-section of the positive electrode film along the electrode thickness direction is 1.97%; the median value B of the positive electrode film coating value B is... 50 The value is 0.441; the iron dissolution rate of the positive electrode material is 976 ppm; based on the total area of ​​the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is 1.91%; the porosity of the positive electrode film is 15.06%.

[0284] (3) Preparation of negative electrode sheet A mixture of artificial graphite and natural graphite (by weight 1:1), conductive carbon black (as a conductive agent), styrene-butadiene rubber (SBR) (as a binder), and sodium carboxymethyl cellulose (CMC) (as a thickener) are mixed evenly in a weight percentage of 96:0.5:2.0:1.5. Deionized water is then added, and the mixture is stirred and dispersed to obtain a negative electrode slurry. The negative electrode slurry is then coated onto a copper foil substrate, and after drying, compaction, slitting, and sheet forming, a negative electrode sheet is obtained.

[0285] The negative electrode sheets are slit and punched into specified shapes, and then the punched negative electrode sheets are sorted by weight using a weighing and sorting machine for stacking by a stacking machine.

[0286] (4) Diaphragm Polyvinylidene fluoride (PVDF) was dissolved in N-methylpyrrolidone (NMP) and stirred until homogeneous. Polyethylene glycol (PEG) was then added as a pore-forming agent and thoroughly mixed to obtain an adhesive layer solution. This adhesive layer solution was applied to the aforementioned base membrane with ceramic layers on both sides. After pre-evaporation at 80°C and drying at 110°C, the membrane was immersed in deionized water to dissolve the PEG, resulting in a membrane with a porous adhesive layer.

[0287] 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 adhesive layer is 1 μm.

[0288] (5) Electrolyte In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed evenly.

[0289] Lithium hexafluorophosphate was then added and dissolved in an organic solvent to make the concentration of lithium hexafluorophosphate in the electrolyte 1.05 mol / L. Ethylene carbonate (VC) was then added and stirred until homogeneous to obtain the electrolyte of Example 1.

[0290] 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%.

[0291] (6) Battery preparation The positive electrode, separator, and negative electrode are stacked sequentially using a stacking machine. The separator must effectively isolate the positive and negative electrodes to obtain a stacked battery cell. The stacked battery cell is then coated with adhesive to ensure tight containment. The coated stacked battery cell is placed in an outer packaging material, an aluminum-plastic film, which is composed of an inner polypropylene layer, a middle aluminum foil layer, and an outer nylon composite layer. The aluminum-plastic film outer packaging is then formed and trimmed using a punching machine to achieve the desired shape and size. The aluminum-plastic film is then heat-sealed to ensure a sealing tensile strength ≥25N / 8mm. The battery undergoes vacuum baking and settling, electrolyte is injected using a flat-head needle, and then it is sealed. Finally, the soft-pack battery undergoes hot and cold pressing operations. The hot pressing temperature is 45℃, the time is 2 minutes, and the pressure is 90kg / cm². 2 The cold pressing temperature was 25℃, the time was 2 minutes, and the pressure was 90 kg / cm². 2 Finally, after processes such as formation, vacuum degassing, and edge trimming, the battery cell is obtained. The battery cell has a length of 600mm, a width of 125mm, and a thickness of 20mm.

[0292] The preparation methods of Examples 2-10 are basically the same as those of Example 1, except that the preparation method of the positive electrode active material is adjusted, as follows: Example 2 The preparation method of Example 2 is basically the same as that of Example 1, except that the second temperature is adjusted to 765°C in the preparation of the positive electrode active material.

[0293] Example 3 The preparation method of Example 3 is basically the same as that of Example 1, except that the second temperature is adjusted to 735°C in the preparation of the positive electrode active material.

[0294] Example 4 The preparation method of Example 4 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a molecular weight of 500 and polyethylene glycol with a molecular weight of 2000 in a mass ratio of 2:8.

[0295] Example 5 The preparation method of Example 5 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a molecular weight of 500.

[0296] Example 6 The preparation method of Example 6 is basically the same as that of Example 1, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol with a molecular weight of 2000.

[0297] Example 7 The preparation method of Example 7 is basically the same as that of Example 3, except that in the preparation of the positive electrode active material, the carbon source is replaced with polyethylene glycol and glucose with a molecular weight of 500 in a mass ratio of 2:8.

[0298] Example 8 The preparation method of Example 8 is basically the same as that of Example 1, except that the coating weight is adjusted during the preparation of the positive electrode sheet, and parameters such as the hot roller pressure, hot roller temperature, transfer coating speed, and heating temperature before the first compaction by the hot roller are adjusted accordingly, so that the single-sided density of the positive electrode film layer obtained by cold pressing is 0.43 g / 1540.25 mm. 2 The thickness of the battery should be adjusted appropriately while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0299] Example 9 The preparation method of Example 9 is basically the same as that of Example 1, except that during the preparation of the positive electrode sheet, the coating weight is adjusted, and parameters such as the hot roller pressure, hot roller temperature, transfer coating speed, and heating temperature before the first compaction by the hot roller are adaptively adjusted so that the single-sided density of the positive electrode film layer obtained by cold pressing is 0.26 g / 1540.25 mm. 2 The thickness of the battery should be adjusted appropriately while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0300] Example 10 The preparation method of Example 10 is basically the same as that of Example 1, except that parameters such as the hot roller pressure, hot roller temperature, transfer coating speed, and heating temperature before the first compaction by the hot roller are adjusted to obtain a single-sided density of 0.41 g / 1540.25 mm. 2 The compacted density is 2.52 g / cm³. 3 The positive electrode sheet. Here, compaction density refers to the compaction density of a fully charged battery cell. The battery thickness is adjusted appropriately while maintaining the same number of positive electrode sheets, separator, and negative electrode sheets.

[0301] Comparative Example 1 The preparation method of Comparative Example 1 is basically the same as that of Example 3, except that the carbon source is replaced with glucose in the preparation of the positive electrode active material.

[0302] Comparative Example 2 The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the coating weight is adjusted during the preparation of the positive electrode sheet, and parameters such as the hot roller pressure, hot roller temperature, transfer coating speed, and heating temperature before the first compaction by the hot roller are adjusted accordingly, so that the single-sided density of the positive electrode film layer obtained by cold pressing is 0.24 g / 1540.25 mm. 2 The thickness of the battery should be adjusted appropriately while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0303] Test methods 1. Capacity of a single battery cell At 25℃, charge the battery cell to 3.65V at a charging rate of 0.5C (the nominal capacity of the single cell), then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, and then discharge it to 2.5V at a discharge rate of 1C, let it stand for 10 minutes. Calculate the capacity C during the discharge process using the formula C=I×t, with the unit being Ah.

[0304] 2. Number of cycles corresponding to 80% capacity decay At 25°C, charge the battery cell to 3.65V at a charging rate of 0.5C (the nominal capacity of the single cell), then charge it to 0.05C at 3.65V, let it stand for 10 minutes, and then discharge it to 2.5V at a discharging rate of 1C, let it stand for 10 minutes. One charge-discharge cycle is one cycle. Continue the test until the battery capacity decreases to 80% of the nominal capacity. This number of cycles is recorded as 80%SOH.

[0305] Test Results The test results of the above embodiments and comparative examples are shown in Table 1.

[0306] Table 1

[0307] As can be seen from the comparison of the embodiments and comparative examples, the battery cell includes a stacked cell, which includes a positive electrode and a negative electrode. The positive electrode 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 transition metal phosphate particles containing carbon material disposed on at least a portion of its surface. In the fully discharged state, the compaction density of the positive electrode in the battery cell is 2.3 g / cm³. 3 -2.6g / cm 3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative area distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50The median C50 of the graphitization degree of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode is 0.95-1.20, which helps to improve the cycle stability of the battery during long-term cycling while maintaining good capacity.

[0308] As can be seen from the comparison of Examples 1-3, in the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with particle size R1 satisfying R1≥1000nm, L R1A50 With a value of 0.65-0.75 and a value of 0.67-0.72, the battery cells exhibit good long-term cycle stability.

[0309] A comparison of Examples 1, 3-6, and 7 shows that the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode is the highest. 50 Further, the value can be optionally set to 1.01-1.13, which helps to further improve the long-cycle stability of the battery cells.

[0310] As can be seen from the comparison between Example 1 and Examples 8-10, the single-sided coating surface density of the positive electrode film is further improved to 0.35 g / 1540.25 mm. 2 - 0.4g / 1540.25mm 2 Within this range, it helps to further balance battery capacity and long-cycle stability.

[0311] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes a stacked cell, the stacked cell includes a positive electrode and a negative electrode, the positive electrode 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 transition metal phosphate particles of carbon material disposed on at least part of its surface; When the battery cell is fully discharged, the compaction density of the positive electrode sheet is 2.3 g / cm³. 3 -2.6g / cm 3 ; The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 ; In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.6-0.8; In the cumulative distribution curve of the graphitization degree C value of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode, the median C of the graphitization degree is... 50 The value ranges from 0.95 to 1.20; among which, the degree of graphitization C is I. G / I D I G This indicates that the Raman spectrum is at 1580±100 cm⁻¹ -1 The intensity of peak G at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

2. The battery cell according to claim 1, characterized in that, The single-sided density of the positive electrode film is 0.3 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 .

3. The battery cell according to claim 1 or 2, characterized in that, In the cumulative distribution curve of the graphitization degree C value of the positive electrode film obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode, the median C of the graphitization degree is... 50 The value is 1.01-1.

13.

4. The battery cell according to any one of claims 1-3, characterized in that, The single-sided density of the positive electrode film is 0.35 g / 1540.25 mm. 2 -0.4g / 1540.25mm 2 .

5. The battery cell according to any one of claims 1-4, characterized in that, In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.65-0.

75.

6. The battery cell according to any one of claims 1-4, characterized in that, In the cross-section of the positive electrode film along the thickness direction of the positive electrode sheet, in the cumulative distribution curve of the spheroidal area of ​​particles with a particle size R1 satisfying R1≥1000nm, L R1A50 It is 0.67-0.

72.

7. The battery cell according to any one of claims 1-6, characterized in that, The thickness H of the positive electrode film on one side is 70μm-120μm.

8. The battery cell according to any one of claims 1-6, characterized in that, The thickness H of the positive electrode film on one side is 90μm-120μm.

9. The battery cell according to any one of claims 1-6, characterized in that, The thickness H of the positive electrode film on one side is 100μm-120μm.

10. The battery cell according to any one of claims 1-9, characterized in that, Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area proportion of particles with a particle size R1 satisfying R1≥1000nm is 12%-50%; and / or, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm is less than or equal to 5%.

11. The battery cell according to any one of claims 1-9, characterized in that, Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area proportion of particles with a particle size R1 satisfying R1≥1000nm is 12%-40%; and / or, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm is 0.2%-2.5%.

12. The battery cell according to any one of claims 1-9, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm is 0.2%-2%.

13. The battery cell according to any one of claims 1-12, characterized in that, In the cumulative distribution curve of the coating value B obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the median B of the coating value is... 50 The value is 0.30-0.60, where the coating value B is I. P / I D , where I P This indicates that the Raman spectrum is at 948±100 cm⁻¹ -1 The intensity of the P peak at I D This indicates that the Raman spectrum is at 1350±100 cm⁻¹ -1 The intensity of peak D at that location.

14. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal phosphate particles in the positive electrode film layer comprise 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, and Br, with 0.8≤m≤1.15, 0.9≤x≤1, 0.95≤y≤1, 3.5≤j≤4, and 0≤q≤0.

1.

15. The battery cell according to claim 14, characterized in that, The iron dissolution rate of the positive electrode material in the positive electrode film is 658ppm-1921ppm.

16. The battery cell according to claim 14, characterized in that, The iron dissolution rate of the positive electrode material in the positive electrode film is 658ppm-1485ppm.

17. The battery cell according to claim 14, characterized in that, The lithium-containing transition metal phosphate particles include titanium, and the mass content of titanium is 500ppm-8000ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film.

18. The battery cell according to claim 14, characterized in that, The lithium-containing transition metal phosphate particles include titanium, and the mass content of titanium is 1000ppm-3000ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film.

19. The battery cell according to claim 14, characterized in that, The lithium-containing transition metal phosphate particles include vanadium, and the mass content of the vanadium is 500ppm-5000ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film.

20. The battery cell according to claim 14, characterized in that, The lithium-containing transition metal phosphate particles include vanadium, and the mass content of vanadium is 500ppm-3000ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film.

21. The battery cell according to any one of claims 1-20, characterized in that, The porosity of the positive electrode film is 14%-28%.

22. The battery cell according to any one of claims 1-21, characterized in that, The positive electrode film layer further includes a conductive agent. Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the area ratio of the agglomeration region of the conductive agent is 0.5% - 2.5%.

23. The battery cell according to claim 22, characterized in that, The area ratio of the agglomeration region of the conductive agent is 0.5% - 1.7%.

24. The battery cell according to claim 22 or 23, 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 any one of claims 22-24, characterized in that, The conductive agent further includes conductive carbon black.

26. The battery cell according to claim 22 or 23, characterized in that, The agglomeration region of the conductive agent further includes carbon nanotubes and conductive carbon black.

27. The battery cell according to any one of claims 22-26, characterized in that, Based on the mass of the positive electrode film layer, the mass content C1 of the carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of the conductive carbon black satisfies: 0 < C2 ≤ 2.5%.

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 any one of claims 1-29, characterized in that, The battery cell further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, ceramic layers disposed on both sides of the base film, and a bonding layer disposed on the side of at least one of the ceramic layers away from the base film. The bonding layer is a continuous layer with a porous structure, and the bonding layer includes a vinylidene fluoride-based polymer.

31. The battery cell according to claim 30, characterized in that, The separator satisfies at least one of the following conditions: (1) The thickness of the base film is 7μm - 9μm; (2) The thickness of the ceramic layer on one side is 2μm - 4μm; (3) The thickness of the bonding layer on one side is 1μm - 5μm.

32. The battery cell according to any one of claims 1-31, characterized in that, The positive electrode film layer is provided with a bottom coating in the bottom region close to the positive electrode current collector. 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 polyvinylidene fluoride (PVDF); (2) The thickness of the bottom coating is 0.5μm - 5μm.

33. The battery cell according to any one of claims 1-32, 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 L1, the dimension of the housing in the width direction is W1, and the dimension of the housing in the thickness direction is H1. Among them, 450mm ≤ L1 ≤ 1300mm, 100mm ≤ W1 ≤ 150mm; 14mm ≤ H1 ≤ 22mm.

34. The battery cell according to claim 33, characterized in that, The dimension of the housing in the length direction is L1, 450mm ≤ L1 ≤ 650mm.

35. The battery cell according to claim 33, characterized in that, The dimension of the housing in the length direction is L1, 900mm ≤ L1 ≤ 1300mm.

36. The battery cell according to any one of claims 33-35, characterized in that, The material of the housing is a soft package material, and the soft package material includes an aluminum-plastic composite film. The aluminum-plastic composite film includes a composite film formed by one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE) and aluminum.

37. The battery cell according to any one of claims 1-36, characterized in that, At 25°C, the capacity of the battery cell is 95Ah - 300Ah.

38. The battery cell according to any one of claims 1-37, characterized in that, At 39. A battery device, characterized in that, ​ 40. An electrical device, characterized in that, The electrical device includes the battery device as described in claim 39, the battery device being used to provide electrical energy.

41. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 39, the battery device being used to store electrical energy.

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