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

Abstract

The application provides a battery monomer, a battery device, a power consumption device and an energy storage device. The battery monomer comprises a laminated core, a positive electrode film layer comprises lithium-containing transition metal phosphate particles with carbon materials arranged on at least part of the surface; the compaction density of the positive electrode sheet of the battery monomer in a full discharge state is 2.3g / cm 3 -2.6g / cm 3 ; the single-sided surface density of the positive electrode film layer is 0.25g / 15 40.25mm 2 -0.45g / 15 40.25mm 2 ; based on the total area of the particles in the section of the positive electrode film layer along the thickness direction of the sheet, the area proportion of the particles with a particle size R1 satisfying R1>=1000nm is 12%-50%; in the section of the positive electrode film layer along the thickness direction of the sheet, the distribution uniformity of the particles with a particle size R1 satisfying R1>=1000nm is less than or equal to 5%. The battery monomer provided by the application has high capacity and good cycle performance.

Description

Technical Field

[0001] 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

[0002] 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.

[0003] 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

[0004] 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.

[0005] The first aspect of this application provides a battery cell comprising a stacked cell, the stacked cell comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film comprising lithium transition metal phosphate particles of carbon material disposed on at least a portion of its surface; the battery cell, in its 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 Based on the total area of ​​particles in the cross section along the thickness direction of the positive electrode film, the area ratio of particles with particle size R1 satisfying R1≥1000nm is 12%-50%; the distribution uniformity of particles with particle size R1 satisfying R1≥1000nm in the cross section along the thickness direction of the positive electrode film is less than or equal to 5%.

[0006] Compared to ternary materials, lithium-containing transition metal phosphates have a more stable structure and are less prone to breakage under high pressure. Lithium-containing transition metal phosphates require higher pressure during electrode compaction to achieve higher compaction density. However, research shows that the compaction density of the positive electrode sheet in a fully discharged battery cell is greater than 2.6 g / cm³. 3 This can cause overvoltage on the electrode, resulting in large stress concentrations, which can easily lead to the shedding of the positive electrode film during cycling; the compaction density of the positive electrode sheet in a fully discharged state is less than 2.3 g / cm³. 3This results in loose bonding between the positive electrode film particles, increasing the battery's internal resistance and reducing the energy density of the individual cells. The single-sided density of the positive electrode film is less than 0.25g / 1540.25mm. 2 The low content of positive electrode active material in the battery cell fails to effectively improve the battery's energy density. The single-sided density of the positive electrode film is greater than 0.45 g / 1540.25 mm. 2 This would result in an excessively thick positive electrode film, leading to uneven stress distribution during compaction and localized stress concentrations that could cause film detachment. The compaction density of the positive electrode sheet should be controlled at 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 It can improve energy density while maintaining a low risk of positive electrode film shedding.

[0007] The applicant further discovered that the expansion volume of thick-coated electrodes significantly increases during battery charging and discharging, making them prone to film detachment in the later stages of long-cycle operation. Large particles within the film are particularly susceptible to becoming the initiation points for detachment. Studies show that large particles easily cause stress concentration and cracking during film compaction; however, if the content of large particles in the positive electrode film is too low, it limits the improvement of the positive electrode film compaction density. Research indicates that the optimal compaction density for the positive electrode 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 Based on the total area of ​​particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, if the area ratio of particles with a particle size R1 satisfying R1≥1000nm is less than 12%, it will reduce the energy density of the battery. Based on the total area of ​​particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, if the area ratio of particles with a particle size R1 satisfying R1≥1000nm is greater than 50%, it will easily cause stress concentration during the film compaction process and uneven expansion during cycling, which will lead to film powder shedding or even detachment. If the distribution uniformity 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 is greater than 5%, it will increase the stress concentration during the film compaction process, further increase the uneven expansion during cycling, and increase the risk of film powder shedding or detachment.

[0008] The battery cell includes stacked cells. When fully discharged, the compaction density of the positive electrode is 2.3 g / cm³. 3 -2.6g / cm 3The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area ratio of particles with a particle size R1 ≥ 1000 nm is 12%-50%, and the distribution uniformity of particles with a particle size R1 ≥ 1000 nm in the cross-section along the thickness direction of the positive electrode film is less than or equal to 5%. Firstly, compared to wound cells, stacked cells have no corner areas, which effectively improves the space utilization of the battery, thereby increasing the volumetric energy density. Furthermore, the absence of corner areas helps reduce stress concentration, decreases the probability of film peeling, and reduces the risk of a significant drop in battery capacity. Secondly, by controlling the compaction density and single-sided coating density within the aforementioned ranges, it is not only beneficial to increase the loading of the positive electrode active material but also to control the porosity of the positive electrode film within a suitable range, thereby increasing the electrolyte wetting rate and allowing the specific capacity of the active material to be fully utilized, further improving the volumetric energy density of the battery. Furthermore, by controlling the content and uniformity of large particles in the positive electrode film, this embodiment of the application helps to increase the loading of positive electrode active material and improve stress distribution, thereby mitigating the negative impact of stress concentration. This helps to balance battery capacity and cycle stability, and reduce the risk of battery capacity drop.

[0009] In summary, the battery cells provided in this application embodiment have both good capacity and good capacity cycle stability.

[0010] 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 .

[0011] 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 .

[0012] 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.

[0013] 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%-37%.

[0014] 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 detachment. 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 further reduced to within the range of 12%-37%. This can improve the compaction density of the electrode without making the probability of film detachment too high. This improves the energy density of thickly coated lithium transition metal phosphate batteries while alleviating the capacity drop problem and taking into account the cycle life of the battery.

[0015] 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%.

[0016] 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%-0.9%.

[0017] The uniformity of particle distribution with a particle size R1 of ≥1000nm in the cross-section of the positive electrode film along the thickness direction is 0.2%-2%, and further within the range of 0.2%-0.9%. This can effectively reduce the stress concentration in local areas of the film, allowing the stress during the film compaction process to be uniformly distributed throughout the entire film area. This further improves the battery energy density while reducing the probability of film peeling, alleviating the capacity drop problem of thickly coated lithium transition metal phosphate batteries, and improving battery cycle life.

[0018] In any embodiment, the thickness H of the positive electrode film on one side is 70 μm-120 μm.

[0019] In any embodiment, the thickness H of the positive electrode film on one side is 90 μm-120 μm.

[0020] 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.

[0021] In any embodiment, the thickness H of the positive electrode film on one side is 100μm-120μm.

[0022] 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. Simultaneously, the application controls the proportion of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the electrode thickness direction, ensuring the uniformity of particle distribution with a particle size R1 ≥ 1000 nm. This controls the content of large particles in the positive electrode film within a reasonable range and improves their uniformity of distribution, mitigating stress concentration at large particles. Therefore, the application improves both battery capacity and cycle performance.

[0023] In any embodiment, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.6-0.8.

[0024] In the embodiments of this application, in the cross-section of the positive electrode film along the electrode thickness direction, the particle size R1 of the particles satisfies R1≥1000nm. R1A 50 Within the above range, particles with a particle size R1 satisfying R1≥1000nm have higher roundness, which helps to improve the slippage of particles in the positive electrode film, reduce stress concentration during the compaction of thick coating film, and reduce the probability of film peeling caused by local stress concentration during long cycle. This further improves the volumetric energy density of lithium transition metal phosphate batteries, while also improving the capacity drop problem of battery cells and increasing cycle life.

[0025] In any embodiment, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.65-0.75.

[0026] In any embodiment, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.67-0.75.

[0027] 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 a particle size R1 satisfying R1≥1000nm, the median L of spheroidality is... R1A50Further within the range of 0.65-0.75, and even further within the range of 0.67-0.75, it helps to further improve the cycle life of thick-coated lithium transition metal phosphate batteries.

[0028] 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 Greater than or equal to 0.95 and less than or equal to 1.2; wherein 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 the D peak at that location.

[0029] 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.

[0030] In the embodiments of this application, the median C of the degree of graphitization 50 Within the aforementioned range, it helps to improve the slippage of particles in the positive electrode film, reduce stress concentration during the compaction of thick coating film, and lower the probability of film peeling due to local stress concentration during long cycles. This further improves the capacity drop of individual cells and increases the cycle life of the battery while increasing the volumetric energy density of the battery.

[0031] 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... 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.

[0032] The median B of the coating value of the positive electrode film 50Within 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 during the rolling process and reducing stress concentration in the thick-coated positive electrode film. Furthermore, thanks to the dense and uniform carbon material layer, large particles in the positive electrode film are more likely to slip during the compaction process, thereby reducing stress concentration at large particles in the thick-coated positive electrode film, reducing the probability of positive electrode film detachment, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0033] In any embodiment, the lithium transition metal phosphate particles in the positive electrode film layer comprise components represented by the following general formula:

[0034] Li m Fe x P y O j Q q Formula I,

[0035] 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.

[0036] 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.

[0037] 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.

[0038] In any embodiment, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1921ppm.

[0039] In any embodiment, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1485ppm.

[0040] The iron dissolved in the cathode material mainly originates from the lithium transition metal phosphate in the cathode active material. The iron dissolution rate depends on the number of lattice defects in the lithium transition metal phosphate and the integrity and density of the carbon material layer on the surface of the cathode active material. A lower iron dissolution rate means fewer lattice defects in the lithium transition metal phosphate, which helps reduce lattice corrosion in weak acid environments. Furthermore, a more complete and dense carbon material 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 material layer. This is beneficial for improving the compressive strength and slippage of particles in the cathode film under high rolling pressure, increasing the compaction density of thick-coated cathode films, reducing stress concentration in the cathode film, improving battery energy density, and addressing issues such as capacity drops and cycle life.

[0041] In any embodiment, the lithium transition metal phosphate particles include titanium, and the mass content of titanium is 500ppm-8000ppm based on the total mass of the lithium transition metal phosphate particles in the positive electrode film.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] In any embodiment, the lithium-containing transition metal phosphate particles include vanadium, and the vanadium content is 500ppm-5000ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film.

[0046] In any embodiment, the vanadium content is 500ppm-3000ppm based on the total mass of lithium transition metal phosphate particles in the positive electrode film.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Meanwhile, research shows that large-sized particles in lithium transition metal phosphate particles are prone to rebound. When the agglomeration area of ​​the conductive agent is within the above range, the uniform distribution of the conductive agent can suppress the rebound of lithium transition metal phosphate particles, form mechanical constraints on the particles and even the film layer, improve the cohesion of the film layer, reduce the phenomenon of film layer powder shedding and shedding, and improve the cycle life of the battery.

[0052] 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 1.5%-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.

[0053] The fact that the area of ​​the agglomerated region of the conductive agent is within the above range indicates that the conductive agent is more evenly distributed in the positive electrode film and has a lower content. This not only improves the dynamic performance of the positive electrode film but also 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.

[0054] 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.

[0055] 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.

[0056] In any embodiment, the conductive agent also includes conductive carbon black.

[0057] 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.

[0058] In any embodiment, the agglomeration regions of the conductive agent include carbon nanotubes and conductive carbon black.

[0059] 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 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, 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 agglomeration 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 blockage of the local ion transport path in the agglomerated area of the conductive agent. 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.

[0060] In any embodiment, based on the mass of the positive electrode film layer, the mass content C1 of carbon nanotubes satisfies: 0 < C1 ≤ 2.5%, and the mass content C2 of conductive carbon black satisfies: 0 < C2 ≤ 2.5%.

[0061] 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, taking into account the problem of capacity drop, and improving the cycle life of the battery.

[0062] In any embodiment, the positive electrode film layer further includes a dispersant, and the dispersant includes hydrogenated nitrile rubber (HNBR).

[0063] HNBR is obtained by hydrogenating the double bonds of nitrile rubber. Its highly saturated main chain structure endows it with excellent oil resistance, heat resistance, and aging resistance, etc. This enables it to remain stable in different environments and systems when used as a dispersant, and is not prone to degradation or deterioration, thereby 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 be well extended and dispersed in non-polar or weakly polar media, enabling the particles to be evenly dispersed in the medium.

[0064] 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.

[0065] In any embodiment, based on the mass of the positive electrode film, the mass content of the dispersant is 0.5%-2%.

[0066] 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.

[0067] In any embodiment, the porosity of the positive electrode film is 14%-28%.

[0068] When the porosity of the 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 electrodes 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.

[0069] 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.

[0070] 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 at least one 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.

[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] 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.

[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 vinylidene fluoride polymers.

[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 L1 of the housing satisfies: 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 L1 of the housing satisfies: 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 105Ah-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;

[0095] Figure 2 This is a schematic diagram of a diaphragm using existing technology;

[0096] Figure 3 This is a schematic diagram of the surface morphology of the adhesive layer according to an embodiment of this application;

[0097] Figure 4 This is a schematic diagram of a pouch cell battery according to this application;

[0098] Figure 5 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0099] Explanation of reference numerals in the attached figures:

[0100] 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

[0101] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0107] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] A single battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging.

[0116] 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.

[0117] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0118] 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.

[0119] 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.

[0120] A single battery cell includes electrode components and an electrolyte.

[0121] 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.

[0122] Lithium-containing transition metal phosphates, as positive electrode active materials, offer advantages such as high safety, long cycle life, low cost, and high high-temperature stability. However, their intrinsic specific capacity is significantly lower than that of ternary materials. To compensate for this energy density shortcoming, the applicant discovered that employing a thick coating strategy (i.e., increasing the content of active material per unit area, often resulting in a larger film thickness) can increase the loading of positive electrode active material in the battery, thereby improving the battery's energy density. However, during long-term battery cycling, thick-coated cells experience greater volume expansion, leading to increased internal stress and making the electrode prone to film shedding or even detachment in the later stages of long-term cycling. Film detachment results in the loss of positive electrode active material, causing rapid capacity decay (capacity plunge). Furthermore, it creates an "island" effect, where isolated regions form between some active material particles or between particles and the conductive agent, preventing good electrical contact and effective electron transport. Consequently, these particles cannot participate in the battery's charge and discharge reactions. Simultaneously, these materials affect ion transport, increasing internal resistance, leading to localized overheating and increasing the risk of thermal runaway, severely impacting battery lifespan. Therefore, how to improve battery energy density while maintaining stable battery capacity over the long term remains a pressing technical problem that needs to be solved.

[0123] The first aspect of this application provides a battery cell comprising a stacked cell, the stacked cell comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film comprising lithium transition metal phosphate particles of carbon material disposed on at least a portion of its surface; the battery cell, in its 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 Based on the total area of ​​particles in the cross section along the thickness direction of the positive electrode film, the area ratio of particles with particle size R1 satisfying R1≥1000nm is 12%-50%; the distribution uniformity of particles with particle size R1 satisfying R1≥1000nm in the cross section along the thickness direction of the positive electrode film is less than or equal to 5%.

[0124] Compared to ternary materials, lithium-containing transition metal phosphates have a more stable structure and are less prone to breakage under high pressure. Lithium-containing transition metal phosphate particles require higher pressure during electrode compaction to achieve higher compaction density. However, research shows that the compaction density of the positive electrode sheet in a fully discharged state is greater than 2.6 g / cm³. 3 This can cause overvoltage on the electrode, resulting in large stress concentrations, which can easily lead to the shedding of the positive electrode film during cycling; the compaction density of the positive electrode sheet in a fully discharged state is less than 2.3 g / cm³.3 This results in loose bonding between the positive electrode film particles, increasing the battery's internal resistance and reducing the energy density of the individual cells. The single-sided density of the positive electrode film is less than 0.25g / 1540.25mm. 2 The low content of positive electrode active material in the battery cell fails to effectively improve the battery's energy density. The single-sided density of the positive electrode film is greater than 0.45 g / 1540.25 mm. 2 This would result in an excessively thick positive electrode film, leading to uneven stress distribution during compaction and localized stress concentrations that could cause film detachment. The compaction density of the positive electrode sheet should be controlled at 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 It can improve energy density while maintaining a low risk of positive electrode film shedding.

[0125] The applicant further discovered that the expansion volume of thick-coated electrodes significantly increases during battery charging and discharging, making them prone to film detachment in the later stages of long-cycle operation. Large particles within the film are particularly susceptible to becoming the initiation points for detachment. Studies show that large particles easily cause stress concentration and cracking during film compaction; however, if the content of large particles in the positive electrode film is too low, it limits the improvement of the positive electrode film compaction density. Research indicates that the optimal compaction density for the positive electrode 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 Based on the total area of ​​particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, if the area ratio of particles with a particle size R1 satisfying R1≥1000nm is less than 12%, it will reduce the energy density of the battery. Based on the total area of ​​particles in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, if the area ratio of particles with a particle size R1 satisfying R1≥1000nm is greater than 50%, it will easily cause stress concentration during the film compaction process and uneven expansion during cycling, which will lead to film powder shedding or even detachment. If the distribution uniformity 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 is greater than 5%, it will increase the stress concentration during the film compaction process, further increase the uneven expansion during cycling, and increase the risk of film powder shedding or detachment.

[0126] In this embodiment, the battery cell includes stacked cells, and the compaction density of the positive electrode sheet in the fully discharged state is 2.3 g / cm³. 3 -2.6g / cm3 The single-sided density of the positive electrode film is 0.25 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area ratio of particles with a particle size R1 ≥ 1000 nm is 12%-50%, and the distribution uniformity of particles with a particle size R1 ≥ 1000 nm in the cross-section along the thickness direction of the positive electrode film is less than or equal to 5%. Firstly, compared to wound cells, stacked cells have no corner areas, which effectively improves the space utilization of the battery, thereby increasing the volumetric energy density. Furthermore, the absence of corner areas helps reduce stress concentration, decreases the probability of film peeling, and reduces the risk of a significant drop in battery capacity. Secondly, by controlling the compaction density and single-sided coating density within the aforementioned ranges, it is not only beneficial to increase the loading of the positive electrode active material but also to control the porosity of the positive electrode film within a suitable range, thereby increasing the electrolyte wetting rate and allowing the specific capacity of the active material to be fully utilized, further improving the volumetric energy density of the battery. Furthermore, by controlling the content and uniformity of large particles in the positive electrode film, this embodiment of the application helps to increase the loading of positive electrode active material and improve stress distribution, thereby mitigating the negative impact of stress concentration. This helps to balance battery capacity and cycle stability, and reduce the risk of battery capacity drop.

[0127] In summary, the battery cells provided in this application embodiment have both good capacity and good capacity cycle stability.

[0128] In this application, a laminated cell refers to a cell formed by stacking a positive electrode, a separator, and a negative electrode together.

[0129] In this application, the positive electrode film layer contains lithium transition metal phosphate particles. However, the positive electrode film layer does not refer solely to the positive electrode active material layer. Other film layers that are connected to the positive electrode active material layer and are difficult to distinguish, such as the undercoat layer and the liquid retention layer, are collectively referred to as the positive electrode film layer.

[0130] 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).

[0131] 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.

[0132] 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.

[0133] 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 environment and left to stand for 2 hours. After the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.5V and then discharged at a constant current of 0.1C to 2.0V. The battery is disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S. The mass of the circular pieces is obtained as W1, and the thickness of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the above-weighed electrode sheet is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness of the current collector is measured using a micrometer. Then, the compaction density of the positive electrode sheet is PD = (W1-W2) / [(T1-T2)×S].

[0134] 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 3 2.44 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 2.55g / cm 3 2.60g / cm 3 Or the range of values ​​between any two.

[0135] In this application, the unilateral coating surface density of the positive electrode film layer has a well-known meaning in the art and can be tested using methods known in the art. For example, take a positive electrode sheet that has been coated on one side and cold-pressed (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 above-weighed positive electrode sheet, weigh the current collector, and record it as M0. The unilateral 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 test samples can be tested, and the average value can be calculated as the test result. A higher unilateral 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.

[0136] 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 2 0.41g / 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.

[0137] 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 .

[0138] 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 .

[0139] 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.

[0140] 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.

[0141] 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.

[0142] In the cross-section of the positive electrode sheet along the thickness direction, the area ratio of particles with a particle size R1 satisfying R1≥1000nm can intuitively reflect the ratio of the area of ​​some particles in that particle size range to the total particle area, reflecting the size of the particles in that particle size range. It is understood that the particles in the cross-section of the positive electrode film along the thickness direction, especially those larger than 50nm, mainly originate from the positive electrode active material. Therefore, the embodiments of this application, through the observation and statistical analysis of the particle area in the cross-section of the positive electrode sheet along the thickness direction, can accurately and objectively reflect the distribution of lithium transition metal phosphate particles in the positive electrode film.

[0143] 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.

[0144] 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.

[0145] 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 percentage of particles with a particle size R1 satisfying R1≥1000nm can be selected as 12%, 12.11%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 34.88%, 34.89%, 34.93%, 34.97%, 35%, 36%, 36.71%, 36.73%, 36.75%, 36.83%, 36.87%, 36.92%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 49.99%, 50%, or any value range between the two.

[0146] 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%-37%.

[0147] 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 detachment. 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 further reduced to within the range of 12%-37%. This can improve the compaction density of the electrode without making the probability of film detachment too high. This improves the energy density of thickly coated lithium transition metal phosphate batteries while alleviating the capacity drop problem and taking into account the cycle life of the battery.

[0148] 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.

[0149] In some embodiments, 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 selected as 0.01%, 0.1%, 0.2%, 0.24%, 0.3%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.99%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.47%, 1.5%, 1.6%, 1.7%, 1.8%, 1.81%, 1.82%, 1.85%, 1.9%, 1.94%, 1.95%, 1.98%. 1.99%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.45%, 2.5%, 2.6%, 2.7%, 2.8%, 2.81%, 2.82%, 2.83%, 2.85%, 2.9%, 2.94%, 2.98%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 4.91%, 5%, or any range of two.

[0150] 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%.

[0151] 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%-0.9%.

[0152] The uniformity of particle distribution with a particle size R1 of ≥1000nm in the cross-section of the positive electrode film along the thickness direction is 0.2%-2%, and further within the range of 0.2%-0.9%. This can effectively reduce the stress concentration in local areas of the film, allowing the stress during the film compaction process to be uniformly distributed throughout the entire film area. This further improves the battery energy density while reducing the probability of film peeling, alleviating the capacity drop problem of thickly coated lithium transition metal phosphate batteries, and improving battery cycle life.

[0153] In some embodiments, the thickness H of the positive electrode film on one side is 70 μm-120 μm.

[0154] In some embodiments, the thickness H of the positive electrode film on one side is 90 μm-120 μm.

[0155] 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.

[0156] 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.

[0157] 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.

[0158] In some embodiments, the thickness H of the positive electrode film on one side is 100 μm-120 μm.

[0159] 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. Simultaneously, the application controls the proportion of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film along the electrode thickness direction, ensuring the uniformity of particle distribution with a particle size R1 ≥ 1000 nm. This controls the content of large particles in the positive electrode film within a reasonable range and improves their uniformity of distribution, mitigating stress concentration at large particles. Therefore, the application improves both battery capacity and cycle performance.

[0160] In some embodiments, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the spheroidality area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.6-0.8.

[0161] In this application, the method for testing the sphericity 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. 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 and sphericity of the particles in the cross-section along the electrode thickness direction are statistically analyzed using the "Feret diameter" and "Round" analysis functions. According to the software manual (ImageJUserGuideIJ 1.46r), the "Feret" parameter obtained from the analysis represents the maximum spacing between all parallel lines in the two-dimensional projection of the particle, thus characterizing the particle diameter. According to the software manual (ImageJUserGuideIJ 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 obtained particles is used to characterize the sphericity of the particles. The sphericity of at least 1000 particles with a particle size R1 satisfying R1≥1000nm is arranged in ascending order, and the cumulative sphericity distribution curve of the positive electrode film particles is obtained with sphericity as the horizontal axis and cumulative area ratio as the vertical axis. R1A50 The cumulative distribution curve of the sphericity L value for particles with particle size R1 satisfying R1≥1000nm is the sphericity L value corresponding to the cumulative area ratio of the vertical axis being 50%.

[0162] 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.

[0163] Understandably, lithium-containing transition metal phosphate particles often require high-temperature sintering, which leads to a decrease in sphericity due to grain boundary melting and particle growth. Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, when the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-50%, the median sphericity of the particles usually does not exceed 0.8.

[0164] In some embodiments, 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 a particle size R1 satisfying R1≥1000nm, L R1A50 can be selected as a value range between any two of the following: 0.6, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.7, 0.72, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, and 0.8.

[0165] In the embodiments of this application, in the cross-section of the positive electrode film along the electrode thickness direction, the particle size R1 of the particles satisfies R1≥1000nm. R1A 50 Within the above range, particles with a particle size R1 satisfying R1≥1000nm have higher roundness, which helps to improve the slippage of particles in the positive electrode film, reduce stress concentration during the compaction of thick coating film, and reduce the probability of film peeling caused by local stress concentration during long cycle. This further improves the volumetric energy density of lithium transition metal phosphate batteries, while also improving the capacity drop problem of battery cells and increasing cycle life.

[0166] In some embodiments, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the spheroidality area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.65-0.75.

[0167] In some embodiments, in the cross-section of the positive electrode film along the electrode thickness direction, the median L of the spheroidality in the cumulative distribution curve of the spheroidality area of ​​particles with a particle size R1 satisfying R1≥1000nm is... R1A50 It is 0.67-0.75.

[0168] 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 a particle size R1 satisfying R1≥1000nm, the median L of spheroidality is... R1A50 Further within the range of 0.65-0.75, and even further within the range of 0.67-0.75, it helps to further improve the cycle life of thick-coated lithium transition metal phosphate batteries.

[0169] In some embodiments, the median C of the graphitization degree C in the cumulative distribution curve of the positive electrode film obtained in laser microscopy confocal Raman spectroscopy instrument scanning mode is... 50 Greater than or equal to 0.95 and less than or equal to 1.2; wherein 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 the D peak at that location.

[0170] 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.

[0171] 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.

[0172] 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 -1 It 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 DHowever, 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.

[0173] 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.

[0174] 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.

[0175] In some embodiments, 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 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.

[0176] In the embodiments of this application, the median C of the degree of graphitization 50 Within the aforementioned range, it helps to improve the slippage of particles in the positive electrode film, reduce stress concentration during the compaction of thick coating film, and lower the probability of film peeling due to local stress concentration during long cycles. This further improves the capacity drop of individual cells and increases the cycle life of the battery while increasing the volumetric energy density of the battery.

[0177] 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.

[0178] 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%.

[0179] 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.

[0180] 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 , is one of the characteristic peaks of carbon materials, and its characterization of sp 2 Defects or disordered structures in the hybrid carbon atom lattice. During the testing process, an excitation wavelength of 532 nm was selected, resulting in a shallower testing depth. Consequently, in the test results obtained using laser microscopy confocal Raman spectroscopy in surface scanning mode, the carbon structure peaks exhibited higher intensity compared to the phosphate structure peaks.

[0181] 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.

[0182] 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.

[0183] 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 during the rolling process and reducing stress concentration in the thick-coated positive electrode film. Furthermore, thanks to the dense and uniform carbon material layer, large particles in the positive electrode film are more likely to slip during the compaction process, thereby reducing stress concentration at large particles in the thick-coated positive electrode film, reducing the probability of positive electrode film detachment, improving the problem of battery capacity drop, and increasing the cycle life of the battery.

[0184] In some embodiments, the lithium transition metal phosphate particles in the positive electrode film layer comprise components represented by the following general formula:

[0185] Li m Fe x P y O j Q q Formula I,

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] In some embodiments, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1921ppm.

[0191] The iron dissolution rate of the cathode material can be tested using methods known in the art. As an example, 7.5g of cathode material powder obtained by scraping from the cathode film 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 using a pipette and added to a glass volumetric flask for 50-fold dilution. The iron concentration in the solution is measured using inductively coupled plasma mass spectrometry (ICP-OES). The iron dissolution rate of the cathode material is calculated using the formula: (ICP test iron concentration × solution volume / mass of the solution used for volume adjustment) × 100.3g / mass of cathode material powder, where the solution volume is 50mL and the mass of the solution used for volume adjustment is 1g.

[0192] 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.

[0193] In some embodiments, the iron dissolution rate of the positive electrode material in the positive electrode film layer is 658ppm-1485ppm.

[0194] The iron dissolved in the cathode material mainly originates from lithium transition metal phosphate particles in the cathode active material. The iron dissolution rate depends on the number of lattice defects in the lithium transition metal phosphate and the integrity and density of the carbon material layer on the surface of the cathode active material. A lower iron dissolution rate means fewer lattice defects in the lithium transition metal phosphate, which helps reduce lattice corrosion in weak acid environments. Furthermore, a more complete and dense carbon material 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 material layer. This is beneficial for improving the compressive strength and slippage of particles in the cathode film under high rolling pressure, increasing the compaction density of thick-coated cathode films, reducing stress concentration in the cathode film, improving battery energy density, and addressing issues such as capacity drops and cycle life.

[0195] In some embodiments, the lithium transition metal phosphate particles include titanium, and the titanium content is 500ppm-8000ppm based on the total mass of the lithium transition metal phosphate particles in the positive electrode film.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] In some embodiments, the lithium transition metal phosphate particles include vanadium, and the vanadium content is 500ppm-3000ppm based on the total mass of the lithium transition metal phosphate particles in the cathode film.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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."

[0209] In some embodiments, the positive electrode film layer further includes a conductive agent, and the area ratio of the agglomerated region of the conductive agent can be selected from 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.68%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.41%, 2.5%, or any value range between the two, based on the total area of ​​the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet.

[0210] 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.

[0211] Meanwhile, research shows that large-sized particles in lithium transition metal phosphate particles are prone to rebound. When the agglomeration area of ​​the conductive agent is within the above range, the uniform distribution of the conductive agent can suppress the rebound of lithium transition metal phosphate particles, form mechanical constraints on the particles and even the film layer, improve the cohesion of the film layer, reduce the phenomenon of film layer powder shedding and shedding, and improve the cycle life of the battery.

[0212] 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 1.5%-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.

[0213] 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.

[0214] 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.

[0215] In this application, the term "carbon nanotube" refers to a structure composed of carbon atoms arranged in sp... 2 Graphene 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.

[0216] Due to the one-dimensional structure of carbon nanotubes, a network structure can be formed in the positive electrode film layer. On the one hand, the high elastic modulus of carbon nanotubes enables their network structure to not only serve as a bridge for stress propagation but also have a binding effect on the thick-coated positive electrode film layer, inhibiting the rebound of lithium-containing transition metal phosphate particles, effectively alleviating stress concentration, reducing the risk of film layer detachment, and thereby improving the problem of battery capacity plunge. On the other hand, the excellent electrical conductivity of carbon nanotubes makes their network structure an efficient electron transport channel. Even if there is local film layer detachment, the thick electrode can still maintain high electron transport efficiency in the in-plane direction and thickness direction, thus delaying the occurrence of capacity plunge and further improving the battery's kinetic performance and cycle life.

[0217] In some embodiments, the conductive agent further includes conductive carbon black.

[0218] Conductive carbon black has a relatively high specific surface area and thus has good liquid retention ability. The thick electrode has a large expansion force during cycling, making the electrolyte easy to be extruded. The distribution of conductive carbon black in the positive electrode film layer is beneficial to improving the liquid retention ability of the thick electrode, further alleviating the phenomenon of capacity plunge during battery cycling, and improving the cycle life of the battery.

[0219] In some embodiments, the agglomeration region of the conductive agent includes carbon nanotubes and conductive carbon black.

[0220] Researchers found that due to its high surface energy, carbon nanotubes are prone to agglomeration, resulting in uneven dispersion in the positive electrode film layer and unable to form an effective carbon nanotube network structure. The surface energies of conductive carbon black and carbon nanotubes are relatively close, and it can adsorb on the surface of carbon nanotubes to form a physical barrier, increasing the resistance to carbon nanotube agglomeration, reducing the direct contact between carbon nanotubes, and thus inhibiting the agglomeration phenomenon and improving the distribution uniformity of carbon nanotubes in the positive electrode film layer. On the one hand, this helps to improve the electrical conductivity of the thick-coated positive electrode film layer and the kinetic performance of the battery; on the other hand, it helps to exert the binding effect of carbon nanotubes on the positive electrode film layer, reducing the risk of detachment of the thick-coated positive electrode film layer, and further improving the kinetic performance and cycle life of the battery. In addition, the agglomeration of carbon nanotubes in the agglomeration region of the conductive agent will also cause local blockage of the ion transport path in the agglomeration region of the conductive agent. The combination of conductive carbon black can improve the lithium ion transport ability in this region, reduce local polarization, and further improve the cycle stability of the battery.

[0221] 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%.

[0222] In some embodiments, based on the mass meter of the positive electrode film, the mass content C1 of carbon nanotubes can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any value range between the two.

[0223] In some embodiments, based on the mass of the positive electrode film, the mass content C2 of conductive carbon black can be selected as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, or any value range between the two.

[0224] When the mass content of carbon nanotubes and conductive carbon black is within the above range, it can effectively alleviate the aggregation of carbon nanotubes and form a good conductive network structure, thereby effectively reducing the stress concentration of the positive electrode film and improving the liquid retention rate of the positive electrode during long-term cycling. This further reduces the risk of electrode film shedding and polarization, improves the dynamic performance of the battery, and also addresses the capacity drop problem and improves the cycle life of the battery.

[0225] In some embodiments, the positive electrode film layer further includes a dispersant, including hydrogenated nitrile butadiene rubber (HNBR).

[0226] 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.

[0227] 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.

[0228] In some implementations, the mass content of the dispersant is 0.5%-2% based on the mass of the positive electrode film.

[0229] 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.

[0230] 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.

[0231] In some implementations, the porosity of the positive electrode film is 14%-28%.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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, helps reduce concentration polarization in thick electrodes, and improves the battery's kinetic performance. Simultaneously, it helps alleviate the 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.

[0236] 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.

[0237] 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.

[0238] 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 at least one side of the ceramic layer away from the base film.

[0239] Placing ceramic layers on both sides of the base film helps improve the rigidity of the pouch cell and reduces local stress concentration.

[0240] 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 the ceramic layers on the sides away from the base film.

[0241] In some embodiments, the vinylidene fluoride polymer includes one or more of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0242] In some embodiments, vinylidene fluoride polymers include polyvinylidene fluoride (PVDF).

[0243] 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.

[0244] The diaphragm provided in this application uses a continuous porous layer as the adhesive layer, such as... Figure 1 and Figure 3 As shown, compared to 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.

[0245] 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.

[0246] 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.

[0247] 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 increased and uniformly distributed adhesion between the adhesive layer and the electrode helps to reduce stress concentration in the thick-coated lithium transition metal phosphate positive electrode film, reducing the risk of film detachment and thus further improving the cycle life of the battery. Second, the stable adhesion between the adhesive layer and the positive or negative electrode helps to reduce 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 improving 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.

[0248] 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).

[0249] 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).

[0250] 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.

[0251] In some embodiments, the thickness of the base film in the diaphragm is 7 μm-9 μm.

[0252] 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.

[0253] In some embodiments, the thickness of the ceramic layer on one side of the diaphragm is 2 μm-4 μm.

[0254] 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.

[0255] In some embodiments, the thickness of the adhesive layer on one side of the diaphragm is 1 μm-5 μm.

[0256] 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.

[0257] 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.

[0258] 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 vinylidene fluoride polymers.

[0259] In some embodiments, the thickness of the base coating is 0.5 μm to 5 μm.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] In some implementations, L1 can be selected as 450mm, 460mm, 470mm, 480mm, 490mm, 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 600mm, 610mm, 620mm, 630mm, 640mm, 650mm, 660mm, 670mm, 680mm, 690mm, 700mm, 710mm, 720mm, 750mm, 800mm, 850mm, 900mm, 950mm, 1000mm, 1050mm, 1100mm, 1150mm, 1200mm, 1250mm, 1300mm, or any value range between the two.

[0264] In some implementations, W1 can be selected as 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or any value range between the two.

[0265] In some implementations, H1 can be selected as 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm or any value range between the two.

[0266] In some embodiments, the length dimension L1 of the housing satisfies: 450mm≤L1≤650mm.

[0267] 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.

[0268] In some embodiments, the length dimension L1 of the housing satisfies: 900mm≤L1≤1300mm.

[0269] 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.

[0270] 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.

[0271] 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.

[0272] 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.

[0273] In some embodiments, the capacity of the battery cell is 105Ah-300Ah at 25°C.

[0274] In some embodiments, the capacity of the battery cell is 150Ah-190Ah at 25°C.

[0275] 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, the battery cell is charged to 3.65V at a charging rate of 0.5C, then charged to 0.05C at a constant voltage of 3.65V, left to stand for 10 minutes, and then discharged to 2.5V at a discharging rate of 1C. The discharge capacity of the battery cell is taken as the capacity of the battery cell.

[0276] In some embodiments, at 25°C, the capacity of the battery cell can be selected as 105Ah, 107Ah, 110Ah, 115Ah, 120Ah, 125Ah, 130Ah, 135Ah, 140Ah, 145Ah, 150Ah, 155Ah, 160Ah, 161Ah, 162Ah, 163Ah, 164Ah, 165Ah, 170Ah, 175Ah, 180Ah, 182Ah, 185Ah, 190Ah, 200Ah, 210Ah, 220Ah, 230Ah, 240Ah, 250Ah, 270Ah, 280Ah, 290Ah, 300Ah, or any value range between the two.

[0277] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0278] 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.

[0279] 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.

[0280] Figure 5This 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.

[0281] 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.

[0282] Example

[0283] 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.

[0284] Example 1

[0285] (1) Preparation of positive electrode active material

[0286] Lithium carbonate, iron phosphate, titanium dioxide, vanadium pentoxide, sucrose, glucose, and polyethylene glycol were added to deionized water and mixed in a premixing tank. The ratio of lithium carbonate to iron phosphate was such that the molar ratio of lithium to iron was 1.025:1.0. Based on the total mass of the mixed raw materials, the mass content of sucrose was 2%, the mass content of glucose was 4%, and the mass content of polyethylene glycol was 5%. After uniform mixing, a mixed raw material with a solid content of 38% was obtained.

[0287] Among them, the particle size D of lithium carbonate V50 The particle size is 6 μm; the morphology of the iron phosphate particles is spherical; both titanium dioxide and vanadium pentoxide are nanoparticles; the purity of sucrose is ≥98%; the moisture content of glucose is <0.5%; and the weight average molecular weight of polyethylene glycol is 1500.

[0288] The mixed raw materials were ground twice in a sand mill: coarse grinding for 1 hour, followed by fine grinding. During the grinding process, the slurry temperature was controlled below 40℃ to obtain a mixed slurry. The particle size D of the solid particles in the mixed slurry was... V50 The particle size was 0.45 μm. Spray drying was performed to obtain a dried precursor powder. After drying, its particle size D... 50 It is 55.55 μm.

[0289] The precursor powder was subjected to a two-stage heating sintering process in a nitrogen atmosphere to obtain the positive electrode active material: the temperature was increased from 25℃ to 450℃ at a heating rate of 2℃ / min (first heating stage), and held for 3 hours; the temperature was then increased from 450℃ to 780℃ at a heating rate of 5℃ / min (second heating stage), and held for 12 hours. The air volume in the heating stage was greater than that in the isothermal stage, with a ratio of 1.5:1, and the total air volume was 1350 cm³. 3 / h, after which cooling is completed; particle size D is obtained by airflow pulverization. V50 The positive electrode active material of lithium iron phosphate has carbon material on its 1.65μm surface. Based on the total mass of the positive electrode active material, the mass content of Ti element is 1050ppm and the mass content of V element is 950ppm.

[0290] The above D 50 D V50 D V90 This refers to data obtained through the Malvern laser scattering method.

[0291] (2) Preparation of positive electrode sheet

[0292] The above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride were mixed in a solvent N-methylpyrrolidone at a mass ratio of 95:2:3. The mixture was thoroughly mixed, stirred, and dispersed in a stirring tank to form a positive electrode slurry. After the stirring process, the positive electrode slurry was transported to the coating process. The conductive agent consisted of conductive carbon black and multi-walled carbon nanotubes at a mass ratio of 1:1, with the conductive carbon black having a specific surface area of ​​80 m². 2 / g, oil absorption value of 180mL / 100g, average length of carbon nanotubes of 20μm, specific surface area of ​​280m². 2 / g.

[0293] 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 2.35 g / cm³. 3The positive electrode sheet. The compaction density here refers to the compaction density of the battery cell under full discharge conditions. The transfer coating speed is 20 m / min. The hot pressing process includes three hot rolling processes, with the hot rolling pressure increasing sequentially to 40 tons, 60 tons, and 80 tons; the hot rolling temperature is 60℃. Before the first hot rolling compaction, the electrode sheet is heated to 40℃.

[0294] 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.

[0295] 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 0.689. 50 The median value of the positive electrode film coating, B, is 1.009. 50 The value is 0.46; the iron dissolution rate of the positive electrode material in the positive electrode film is 974 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 1.68%; the porosity of the positive electrode film is 16.03%.

[0296] (3) Preparation of negative electrode sheet

[0297] A mixture of artificial graphite and natural graphite (mass ratio 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, and deionized water is added. After stirring and dispersing, a negative electrode slurry is obtained. The negative electrode slurry is coated on a copper foil substrate, and after drying, compaction, slitting, and sheet forming, a negative electrode sheet is obtained.

[0298] 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.

[0299] (4) Diaphragm

[0300] 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.

[0301] 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.

[0302] (5) Electrolyte

[0303] 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.

[0304] 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.

[0305] 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%.

[0306] (6) Battery preparation

[0307] 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.

[0308] The preparation methods of Examples 2-5 are basically the same as those of Example 1, except that the preparation method of the positive electrode active material is adjusted:

[0309] Example 2

[0310] (1) Preparation of positive electrode active material

[0311] Lithium dihydrogen phosphate, ferrous oxalate, polyethylene glycol with a weight average molecular weight of 1000, polyethylene glycol with a weight average molecular weight of 1600, 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 resulted in a lithium to iron molar ratio of 1.025:1.0. The ferrous oxalate had a particle size D10 of 6.5 μm, a particle size D50 of 62 μm, and a particle size D90 of 108 μm. The ferrous oxalate contained 30.5% Fe by mass and 0.03% ferric iron by mass.

[0312] 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 D of the resulting mixed slurry is determined. V 50 is 3.15μm.

[0313] The spray-dried slurry yields a dried precursor powder, which is light yellow in appearance and uniform in color.

[0314] 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 780°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 vanadium was 950 ppm, based on the total mass of the positive electrode active material.

[0315] 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.

[0316] The D10, D50, D90, and Dv50 mentioned above refer to the data obtained by testing using the Malvern laser scattering method.

[0317] (2) Preparation of positive electrode sheet

[0318] The above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are mixed in a mass ratio of 95:2:3 with N-methylpyrrolidone as solvent. The mixture is thoroughly mixed, stirred, and dispersed in a stirring tank to form a positive electrode slurry. After the stirring process, the positive electrode slurry is conveyed to the coating process. The stirring includes pre-stirring and main stirring. The stirring speed of pre-stirring is lower than that of main stirring. The pre-stirring has an orbital speed of 25 rpm, a rotational speed of 500 rpm, and a pre-stirring time of 15 minutes. The conductive agent includes conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 1:1. The specific surface area of ​​the conductive carbon black is 80 m². 2 / g, oil absorption value of 180mL / 100g, average length of carbon nanotubes of 20μm, specific surface area of ​​280m².2 / g.

[0319] 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 2.35 g / cm³. 3 The positive electrode sheet. Here, compaction density refers to the compaction density of a single battery cell under full discharge conditions.

[0320] 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.

[0321] 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.

[0322] Example 3

[0323] (1) Preparation of positive electrode active material

[0324] Lithium carbonate, ferric phosphate, sucrose, glucose, titanium dioxide, and vanadium pentoxide were added to water and mixed in a premixing tank at 1800 rpm. The ratio of lithium carbonate to ferric phosphate resulted in a molar ratio of iron to phosphorus of 0.97. The mass content of glucose relative to ferric phosphate was 3.8%, and the mass content of sucrose relative to ferric phosphate was 1.9%.

[0325] The mixed raw materials were ground twice in a sand mill. The first grinding was performed using 0.6 mm diameter zirconia balls at 500 rpm for 1 hour, with a grinding chamber pressure of less than 0.3 MPa. The second grinding was then performed to obtain a mixed slurry. The particle size D of the mixed slurry was... V 50 is 0.435μm;

[0326] The mixed slurry is spray-dried to obtain precursor powder.

[0327] The precursor powder is sintered to obtain lithium iron phosphate cathode material. The sintering process includes:

[0328] First sintering: The precursor powder is sintered in a nitrogen atmosphere, heated from 25°C to 765°C at a heating rate of 5°C / min, and held at that temperature for 10 hours. After cooling, the first sintered product is obtained.

[0329] Grinding and mixing: Add 0.5% sucrose, 1% glucose, and 3.0% polyethylene glycol (by weight of the first sintered product) to the first sintered product; divide into two groups and grind (third grinding), wherein the particle size D in the first group is... V50 Grinding was stopped when the particle size reached 1.02 μm (grinding conditions: 550 rpm, grinding time 1 h), yielding the first group of grinding products; the particle size D of the second group... V50 Grinding was stopped when the particle size reached 0.42 μm (grinding conditions: 500 rpm, grinding time 4 h), and a second set of grinding products was obtained; the first set of grinding products and the second set of grinding products were mixed at a mass ratio of 70:30 to obtain a mixed intermediate product; the mixed intermediate product was spray-dried.

[0330] Second sintering: The dried mixed intermediate product is sintered in a nitrogen atmosphere, heated from 25°C to 800°C at a heating rate of 5°C / min, and held at that temperature for 10 hours. After cooling, the second sintered product is obtained.

[0331] After sintering, the material is cooled to below 100 °C, and the second sintering product is crushed using air jet milling to obtain lithium iron phosphate cathode active material with carbon material on its surface. The air jet milling stage frequency is 23 Hz, and the milling pressure is 0.55 MPa. Based on the total mass of the cathode active material, the mass content of Ti is 1050 ppm, and the mass content of V is 950 ppm.

[0332] (2) Preparation of positive electrode sheet

[0333] The above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are mixed in a mass ratio of 95:2:3 with N-methylpyrrolidone as solvent. The mixture is thoroughly mixed, stirred, and dispersed in a stirring tank to form a positive electrode slurry. After the stirring process, the positive electrode slurry is conveyed to the coating process. The stirring includes pre-stirring and main stirring. The stirring speed of pre-stirring is lower than that of main stirring. The pre-stirring has an orbital speed of 25 rpm, a rotational speed of 500 rpm, and a pre-stirring time of 15 minutes. The conductive agent includes conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 1:1. The specific surface area of ​​the conductive carbon black is 80 m². 2 / g, oil absorption value of 180mL / 100g, average length of carbon nanotubes of 20μm, specific surface area of ​​280m². 2 / g.

[0334] 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 0.39 g / 1540.25 mm. 2 The compacted density is 2.36 g / cm³. 3The positive electrode sheet. The compaction density here refers to the compaction density of the battery cell under full discharge conditions. The drying temperature is 95°C, and the drying speed is 2.0 m / min.

[0335] 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.

[0336] 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.

[0337] Example 4

[0338] The preparation method of the positive electrode active material in Example 4 is basically the same as that in Example 1, except that the preparation process of the positive electrode active material is slightly different. The specific differences include:

[0339] (1) The carbon sources in the mixed raw materials are sucrose and glucose. The mass of sucrose is 2 wt% relative to the mass of ferric phosphate, and the mass of glucose is 5.7 wt% relative to the mass of ferric phosphate.

[0340] (2) The heating and sintering processes are different. The precursor powder is sintered at least twice in a nitrogen atmosphere. The first sintering temperature is 750℃ and the holding time is 8 hours to obtain the initial sintered product.

[0341] 1.5 wt% (based on the mass of the initial calcination product) of glucose, 3.0 wt% (based on the mass of the initial calcination product) of polyethylene glycol, titanium dioxide, and vanadium pentoxide were added to the initial calcination product. After grinding evenly, the mixture was divided into two groups for secondary grinding. The grinding parameters for the two groups were different, and the particle size distribution (D) of the particles after the first group of grinding was controlled. V50 The particle size (D) of the second group of milled particles is 2.0 μm. V50 The particle size was 0.35 μm. The ground particles from the first and second groups were mixed at a mass ratio of 30:70, spray-dried, and then subjected to a second sintering. The second sintering temperature was 800℃, and the temperature was maintained for 10 hours.

[0342] Based on the total mass of the positive electrode active material, the mass percentage of titanium is 1050 ppm and the mass percentage of vanadium is 950 ppm.

[0343] (3) The positive electrode slurry was transferred and coated onto aluminum foil, dried, and hot-pressed to obtain a positive electrode film with a single-sided density of 0.39 g / 1540.25 mm. 2 The compacted density is 2.36 g / cm³. 3The positive electrode sheet. The compaction density here refers to the compaction density of the battery cell under full discharge conditions. The drying temperature is 95°C, and the drying speed is 2.0 m / min.

[0344] The hot pressing process includes three hot roller pressing processes, with the hot roller pressing pressure increasing sequentially to 35 tons, 55 tons, and 70 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.

[0345] Example 5

[0346] The preparation method of Example 5 is basically the same as that of Example 1, except that the sintering process of the positive electrode active material and the hot pressing process of the positive electrode sheet are different. Specifically:

[0347] (1) The precursor powder was subjected to a two-stage heating sintering process in a nitrogen atmosphere to obtain the positive electrode active material: the temperature was increased from 25℃ to 440℃ at a heating rate of 2℃ / min (first heating stage) and held for 2.5h; the temperature was increased from 440℃ to 760℃ at a heating rate of 5℃ / min (second heating stage) and held for 11h; the particle size Dv was obtained by air jet milling. 50 The active cathode material is a lithium iron phosphate cathode with a carbon material on its 1.6 μm surface. The air jet milling stage frequency is 25 Hz, and the milling pressure is 0.55 MPa.

[0348] (2) The positive electrode slurry was transferred and coated onto aluminum foil, dried, and hot-pressed to obtain a positive electrode film with a single-sided density of 0.39 g / 1540.25 mm. 2 The compacted density is 2.35 g / cm³. 3 The positive electrode sheet. The compaction density here refers to the compaction density of the battery cell under full discharge conditions. The transfer coating speed is 20 m / min.

[0349] The hot pressing process includes three hot roller pressing processes, with the hot roller pressing pressure increasing sequentially to 45 tons, 60 tons, and 80 tons. The hot roller temperature is 60°C. Before the first hot roller compaction, the electrode sheet is heated to 40°C.

[0350] Example 6

[0351] The preparation method of Example 6 is similar to that of Example 2, except that in the preparation of the positive electrode sheet, the above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are uniformly mixed in the solvent N-methylpyrrolidone at a mass ratio of 94.52:1.99:2.99. Based on the total mass of the positive electrode active material, conductive agent, binder polyvinylidene fluoride and dispersant, 0.5% of the dispersant HNBR is added. The mixture is thoroughly mixed in a stirring tank, stirred, and dispersed to prepare the positive electrode slurry, as detailed in Table 1.

[0352] Example 7

[0353] The preparation method of Example 7 is similar to that of Example 6, except that in the preparation of the positive electrode sheet, the above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are uniformly mixed in the solvent N-methylpyrrolidone at a mass ratio of 93.57:1.97:2.96. Based on the total mass of the positive electrode active material, conductive agent, binder polyvinylidene fluoride and dispersant, a dispersant of 1.5% by mass is added, as detailed in Table 1.

[0354] Example 8

[0355] The preparation method of Example 8 is similar to 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 to achieve a single-sided density of 0.43 g / 1540.25 mm² for the cold-pressed positive electrode film. 2 The thickness of the battery is adjusted appropriately, while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0356] Example 9

[0357] The preparation method of Example 9 is similar to 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 to achieve a single-sided density of 0.26 g / 1540.25 mm² for the positive electrode film obtained by cold pressing. 2 The thickness of the battery is adjusted appropriately, while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0358] Example 10

[0359] The preparation method of Example 10 is similar to that of Example 1, except that the above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are mixed in the solvent N-methylpyrrolidone at a mass ratio of 95.48:1.5:3.02, and thoroughly mixed, stirred, and dispersed in a stirring tank to form a positive electrode slurry. After the stirring process is completed, the positive electrode slurry is transported to the coating process. The conductive agent includes conductive carbon black and multi-walled carbon nanotubes at a mass ratio of 0.5:1.

[0360] Example 11

[0361] The preparation method of Example 11 is similar to 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 0.38 g / 1540.25 mm. 2 The compacted density is 2.55 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.

[0362] Comparative Example 1

[0363] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the sintering process of the positive electrode active material is different, specifically:

[0364] The precursor powder was subjected to a two-stage heating and sintering process in a nitrogen atmosphere to obtain the positive electrode active material: the temperature was increased from 25℃ to 500℃ at a heating rate of 2℃ / min (first heating stage), and held for 3.5h; the temperature was increased from 500℃ to 800℃ at a heating rate of 5℃ / min (second heating stage), and held for 13h; the material was then subjected to air jet milling to obtain a lithium iron phosphate positive electrode active material with a particle size Dv50 of 1.6μm and a carbon material on its surface. The air jet milling stage frequency was 25Hz, and the milling pressure was 0.55MPa.

[0365] Comparative Example 2

[0366] The preparation method of Comparative Example 2 is similar to that of Comparative Example 1. The difference is that, in the preparation of the positive electrode sheet, the above-mentioned positive electrode active material, conductive agent, and binder polyvinylidene fluoride are uniformly mixed in the solvent N-methylpyrrolidone at a mass ratio of 93.57:1.97:2.96. Based on the total mass of the positive electrode active material, conductive agent, binder polyvinylidene fluoride and dispersant, a dispersant of 1.5% by mass is added.

[0367] Comparative Example 3

[0368] The preparation method of Comparative Example 3 is similar to that of Example 1, except that the coating weight is adjusted during the preparation of the positive electrode sheet so that the single-sided density of the positive electrode film obtained by cold pressing is 0.24 g / 1540.25 mm. 2 The thickness of the battery is adjusted appropriately, while keeping the number of positive electrode plates, separators, and negative electrode plates constant.

[0369] Test methods

[0370] 1. Capacity of a single battery cell

[0371] 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.

[0372] 2. Number of cycles corresponding to 80% capacity decay

[0373] 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.

[0374] Test Results

[0375] The test results of the above embodiments and comparative examples are shown in Tables 1-2.

[0376] Table 1

[0377]

[0378] 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 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%-50%; in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the distribution uniformity of particles with a particle size R1 satisfying R1≥1000nm is less than or equal to 5%, which helps to improve the cycle stability of the battery during long-term cycling while maintaining good capacity.

[0379] As can be seen from the comparison between Examples 1-3 and Examples 4-5, in terms of the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is further within the range of 12%-37%, which helps to further improve the battery capacity and long-cycle stability.

[0380] As can be seen from the comparison between Examples 4 and Examples 1-3, 5-11, and Examples 2 and Examples 6-7, in the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the uniformity of the distribution of particles with a particle size R1 satisfying R1≥1000nm is in the range of 0.2%-2%, and further in the range of 0.2%-0.9%, which helps to further improve the long-cycle stability of the battery.

[0381] As can be seen from the comparison between Example 1 and Examples 8-9, the single-sided coating surface density of the positive electrode film is further improved to 0.3 g / 1540.25 mm. 2 -0.45g / 1540.25mm 2 Within this range, it further reaches 0.35g / 1540.25mm. 2 -0.4g / 1540.25mm 2 Within this range, it helps to further balance battery capacity and long-cycle stability.

[0382] Table 2

[0383]

[0384] As can be seen from the comparison between Example 1 and Example 10, 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 in the range of 0.5%-2.5%, and further in the range of 1.5%-2.5%, which helps to further improve the long-cycle stability of the battery.

[0385] 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 ; Based on the total area of ​​particles in the cross-section along the thickness direction of the positive electrode film, the area ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-50%; 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%; 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 Greater than or equal to 0.95 and less than or equal to 1.2; wherein 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; 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 the spheroidality is... R1A50 It is 0.6-0.8; 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 at least one 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.

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, 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 .

4. The battery cell according to claim 1, 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 ratio of particles with a particle size R1 satisfying R1≥1000nm is 12%-37%.

5. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode film 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%.

6. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode film along the thickness direction of the electrode sheet, the uniformity of particle distribution with particle size R1 satisfying R1≥1000nm is 0.2%-0.9%.

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

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

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

10. The battery cell according to claim 1, characterized in that, 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 the spheroidality is... R1A50 It is 0.65-0.

75.

11. The battery cell according to claim 1, characterized in that, 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 the spheroidality is... R1A50 It is 0.67-0.

75.

12. The battery cell according to claim 1, 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 B 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.

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

14. The battery cell according to claim 13, characterized in that, The iron dissolution rate of the positive electrode material in the positive electrode film is 658ppm-1921ppm.

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

16. The battery cell according to claim 13, characterized in that, The lithium-containing transition metal phosphate includes 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.

17. The battery cell according to claim 16, characterized in that, Based on the total mass of lithium transition metal phosphate particles in the positive electrode film, the mass content of titanium is 1000ppm-3000ppm.

18. The battery cell according to claim 13, characterized in that, The lithium-containing transition metal phosphate includes vanadium, and the vanadium content is 500ppm-5000ppm 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 18, characterized in that, Based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, the mass content of vanadium element is 500 ppm - 3000 ppm.

20. The battery cell according to claim 1, 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 plate, the area ratio of the agglomeration region of the conductive agent is 0.5% - 2.5%.

21. The battery cell according to claim 20, characterized in that, Based on the total area of the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area ratio of the agglomeration region of the conductive agent is 1.5% - 2.5%.

22. The battery cell according to claim 21, 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.

23. The battery cell according to claim 22, characterized in that, The conductive agent further includes conductive carbon black.

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

25. The battery cell according to claim 24, characterized in that, 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%.

26. 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 butadiene rubber (HNBR).

27. The battery cell according to claim 26, characterized in that, Based on the mass of the positive electrode film layer, the mass content of the dispersant is 0.5% - 2%.

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

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

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

31. The battery cell according to claim 1, characterized in that, The battery cell includes a housing, the laminated battery 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, where 450 mm ≤ L1 ≤ 1300 mm, 100 mm ≤ W1 ≤ 150 mm; 14 mm ≤ H1 ≤ 22 mm.

32. The battery cell according to claim 31, characterized in that, The dimension L1 of the housing in the length direction satisfies: 450 mm ≤ L1 ≤ 650 mm.

33. The battery cell according to claim 31, characterized in that, The dimension L1 of the housing in the length direction satisfies: 900 mm ≤ L1 ≤ 1300 mm.

34. The battery cell according to claim 31, characterized in that, The material of the housing is a soft package material, and the soft package material includes an aluminum-plastic composite film.

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

36. The battery cell according to claim 1, characterized in that, At 25 °C, the capacity of the battery cell is 105 Ah - 300 Ah.

37. The battery cell according to claim 1, characterized in that, At 25 °C, the capacity of the battery cell is 150 Ah - 190 Ah.

38. A battery device, characterized in that, Including the battery cell according to any one of claims 1 - 37.

39. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 38, the battery device being used to provide electrical energy.

40. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 38, the battery device being used to store electrical energy.

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