Battery unit, battery device, power-consuming device and energy storage device

Abstract

Battery unit comprising a laminated battery cell, wherein the laminated battery cell comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises lithium-containing transition metal phosphate particles with a carbon material arranged at least partially on surfaces of the lithium-containing transition metal phosphate particles; the packing density of the positive electrode plate in a fully charged state of the battery unit is between 2.3 g / cm² 3 and 2.6 g / cm³ 3 lies; where the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2lies, with the one-sided areal density of the positive electrode film layer optionally between 0.3 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2 and optionally between 0.35 g / 1540.25 mm 2 and 0.4 g / 1540.25 mm 2 lies; wherein, with reference to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is between 12% and 50%, preferably between 12% and 37%; wherein the uniformity of the distribution of the particles with particle size R1, which satisfies R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is less than or equal to 5%, optionally between 0.2% and 2%, and further optionally between 0.2% and 0.9%.

Description

Technical field

[0001] The present application relates to a battery unit, a battery device, a power-consuming device and an energy storage device. State of the art

[0002] Battery units are not only used in energy storage and power supply systems such as hydroelectric, thermal, wind and solar power plants, but are also widely used in electric transport vehicles such as electric bicycles, electric motorcycles and electric vehicles, as well as in military equipment, aerospace and other fields.

[0003] As the market strives for longer battery life and operating time, higher demands are being placed on battery capacity and cycle performance. However, with existing technologies, it is difficult to improve both battery capacity and cycle performance simultaneously. The question of how to reconcile these two aspects has become a pressing technical challenge. Summary

[0004] The present application addresses the aforementioned problems and aims to provide a battery unit that has both high capacity and good cycle performance.

[0005] The first aspect of the present application relates to a battery unit. The battery unit comprises a laminated battery cell, which in turn comprises a positive electrode plate and a negative electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector. The positive electrode film layer comprises lithium-containing transition metal phosphate particles with a carbon material arranged on at least a portion of the surface of the lithium-containing transition metal phosphate particles. In a fully charged state of the battery unit, the packing density of the positive electrode plate is between 2.3 g / cm³. 3 and 2.6 g / cm³ 3 ; the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2With respect to the total surface area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm lies between 12% and 50%. The uniformity of the distribution of particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm is less than or equal to 5% in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate.

[0006] Compared to ternary materials, lithium-containing transition metal phosphates exhibit a more stable structure and are less prone to fracture under high pressure. During the electrode plate compaction process, these lithium-containing transition metal phosphates must withstand higher pressures to increase the packing density. However, studies have shown that when the battery unit is fully charged, the electrode plate becomes overloaded if the packing density of the positive electrode plate exceeds 2.6 g / cm³. 3 This results in a high voltage concentration, which can easily lead to the positive electrode plate detaching during the cycle. In a fully discharged battery unit, the particles of the positive electrode film layer are not firmly bonded if the packing density of the positive electrode plate is below 2.3 g / cm³. 3This increases the internal resistance of the battery and reduces the energy density of the battery unit. The one-sided areal density of the positive electrode film layer is less than 0.25 g / 1540.25 mm². 2 The content of positive electrode active material in the battery unit is low, which does not effectively improve the battery's energy density. The one-sided areal density of the positive electrode film layer is greater than 0.45 g / 1540.25 mm². 2 This causes the positive electrode film layer to become too thick. The stress distribution of the positive electrode film layer is uneven during the compaction process, and a local stress concentration can lead to film delamination. By controlling the packing density of the positive electrode plate to 2.3 g / cm², this can be prevented. 3 and 2.6 g / cm³ 3 and the one-sided areal density of the positive electrode film layer to 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2The energy density can be improved while simultaneously reducing the risk of detachment of the positive electrode film layer.

[0007] The applicant also noted that the expansion volume of a thick-coated electrode plate increases considerably during battery charging and discharging, making film delamination a likely occurrence in the later stages of long cycles. Large particles in the coating are likely the starting point for this delamination. Studies have shown that large particles tend to develop stress concentrations and cracks during the film compaction process. However, if the content of large particles in the positive electrode film layer is too low, the increase in the packing density of the positive electrode film layer is limited. Investigations have shown that the packing density of the positive electrode plate can be reduced to 2.3 g / cm³. 3up to 2.6 g / cm³ 3 and the one-sided areal density of the positive electrode film layer to 0.25 g / 1540.25 mm² 2 up to 0.45 g / 1540.25 mm 2This can be regulated. If, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is less than 12%, the energy density of the battery is reduced; if, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is more than 50%, stress concentration can easily occur during the film compaction process, and uneven expansion can occur during the cycle, leading to loss of film powder or even film detachment.In the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the uniformity of the distribution of particles with particle size R1, which meets R1 ≥ 1000 nm, is greater than 5%, which increases the stress concentration during the compaction process of the film layer, further increases the uneven expansion during the cycle and increases the risk of film powder loss and detachment.

[0008] The battery unit comprises a laminated battery cell. When fully charged, the packing density of the positive electrode plate is between 2.3 g / cm³. 3 and 2.6 g / cm³ 3 , and the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2With respect to the total surface area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size of R1 (R1 ≥ 1000 nm) lies between 12% and 50%. In the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the uniformity of the distribution of particles with a particle size of R1 (R1 ≥ 1000 nm) is at most 5%. Firstly, laminated battery cells, compared to wound cells, have no corner areas, which can effectively improve the battery's space utilization and thus increase the volume energy density. The absence of corner areas also helps to reduce voltage concentration, decrease the probability of film delamination, and reduce the risk of battery capacity loss.Secondly, controlling the packing density and the one-sided coating area density within the aforementioned range is not only advantageous for increasing the loading quantity of the positive electrode active material, but also for controlling the porosity of the positive electrode film layer within a suitable range. This increases the electrolyte infiltration rate, allowing the gram capacity of the active material to be fully utilized and further improving the volume energy density of the battery. Furthermore, the embodiments of the present application contribute to increasing the loading quantity of the positive electrode active material and improving the voltage distribution by controlling the content of large particles in the positive electrode film layer and their uniformity of distribution.This mitigates the negative effects of voltage concentration, making it easier to consider the battery's capacity and cycle stability, and reducing the risk of battery capacity loss.

[0009] In summary, the battery units provided by the embodiments of the present application exhibit both high capacity and pronounced capacity cycle stability.

[0010] In each embodiment, the one-sided coating area density of the positive electrode film layer is between 0.3 g / 1540.25 mm². 2 and 0.45 g / 1540.25 mm 2 .

[0011] In each embodiment, the one-sided coating area density of the positive electrode film layer is between 0.35 g / 1540.25 mm². 2 and 0.4 g / 1540.25 mm 2 .

[0012] The one-sided coating area density of the positive electrode film layer remains within the aforementioned range, which helps to further improve the battery's capacity with regard to cycle performance.

[0013] In each embodiment, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm, relative to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, lies between 12% and 37%.

[0014] Large particles with a particle size R1 ≥ 1000 nm contribute to increasing the packing density of the positive electrode plate and thus increasing the volume energy density of the battery unit. However, researchers have found that these large particles tend to cause voltage concentration, increasing the risk of positive electrode film delamination. Therefore, the surface area fraction of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate remains in the range of 12% to 37%.This can not only improve the packing density of the electrode plate, but also prevent the probability of film delamination from increasing too much, thereby improving the energy density of thick-coated lithium-containing transition metal phosphate batteries, while reducing capacity loss and taking into account the battery's cycle life.

[0015] In each embodiment, the uniformity of the distribution of particles with a particle size R1 that meets R1 ≥ 1000 nm lies in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate between 0.2% and 2%.

[0016] In each embodiment, the uniformity of the distribution of particles with a particle size R1 that meets R1 ≥ 1000 nm lies in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate between 0.2% and 0.9%.

[0017] The uniformity of particle distribution, with a particle size R1 ≥ 1000 nm, across the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is between 0.2% and 2%, preferably between 0.2% and 0.9%. This effectively reduces the stress concentration in local areas of the film layer, allowing the stress to be distributed uniformly across the entire surface of the film layer during the film compaction process. This increases the battery's energy density while simultaneously reducing the likelihood of film delamination, minimizing capacity loss in thick-coated lithium-containing transition metal phosphate batteries, and improving the battery's cycle life.

[0018] In each embodiment, the one-sided thickness H of the positive electrode film layer is between 70 µm and 120 µm.

[0019] In each embodiment, the one-sided thickness H of the positive electrode film layer is between 90 µm and 120 µm.

[0020] If the thickness of the positive electrode film layer on one side is within the range mentioned above, this helps to increase the amount of charge on the positive electrode active material of the battery and thereby increase the battery's capacity.

[0021] In each embodiment, the one-sided thickness H of the positive electrode film layer is between 100 µm and 120 µm.

[0022] Increasing the thickness of the positive electrode film layer contributes to increasing the amount of charge on the positive electrode active material and thus increasing the battery's capacity. However, the applicant found that with a one-sided thickness of at least 100 µm of the positive electrode film layer during the battery cycle, the volume expansion of the positive electrode film layer is greater, resulting in a higher voltage and a more pronounced voltage concentration phenomenon in the positive electrode film layer. This increases the risk of film delamination, which impairs the battery's cycle performance. In the embodiments of the present application, the battery's capacity is increased by increasing the thickness of the positive electrode film layer.Simultaneously, the area fraction of particles with particle size R1, which fulfills R1 ≥ 1000 nm, is controlled in relation to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, as well as the uniformity of the distribution of particles with particle size R1 (R1 ≥ 1000 nm) in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, which controls the content of large particles in the positive electrode film layer within a reasonable range, improves the uniformity of their distribution, and mitigates the voltage concentration phenomenon on the large particles, thereby improving the battery capacity with regard to the cycle performance of the battery.

[0023] In each embodiment, the median value L lies in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate. R1A50the sphericity in a cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, between 0.6 and 0.8.

[0024] In the embodiments of the present application, the cross-section of the positive electrode film layer lies along the thickness direction of the electrode plate L. R1A50The particles have a particle size R1 that meets the criteria of ≥ 1000 nm within the aforementioned range. These particles exhibit high roundness, which improves particle sliding within the positive electrode film layer, reduces stress concentration during the compaction of the thickly coated film layer, and decreases the likelihood of film delamination due to local stress concentration during extended cycles of the positive electrode film layer. This further improves the volumetric energy density of the lithium transition metal phosphate battery, mitigates the problem of battery cell capacity degradation, and extends the cycle life.

[0025] In each embodiment, the median value L R1A50the sphericity in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate in the cumulative area distribution curve of the sphericity of particles with particle size R1, which satisfies R1 ≥ 1000 nm, between 0.65 and 0.75.

[0026] In each embodiment, the median value L R1A50 the sphericity in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate in the cumulative area distribution curve of the sphericity of particles with particle size R1, which satisfies R1 ≥ 1000 nm, between 0.67 and 0.75.

[0027] In the cross-section of the positive electrode film layer along the thickness direction of the electrode plate lies the median value L R1A50The sphericity in the cumulative area distribution curve of the sphericity of particles with particle size R1, which meets the requirement R1 ≥ 1000 nm, is in the range of 0.65 to 0.75, preferably in the range of 0.67 to 0.75. This setting further increases the cycle life of the thick-coated lithium transition metal phosphate battery.

[0028] In each embodiment, the median value is C 50 The degree of graphitization (C-value) of the positive electrode film layer is shown in a cumulative distribution curve, where the C-value is obtained in a surface scanning mode of a laser microconfocal Raman spectrometer. The degree of graphitization (C-value) is I G / I D , where I G a G-peak intensity of the Raman spectrum at 1580 ± 100 cm⁻¹ -1 and I D a D peak intensity of the Raman spectrum at 1350 ± 100 cm -1represents.

[0029] The higher the degree of graphitization of the carbon on the surface of the positive electrode active material, the higher the proportion of carbon with graphite structure in the positive electrode film layer and the easier the particles can slide in the coating layer with the help of the highly graphitized carbon structure, thereby reducing the stress concentration in the electrode plate.

[0030] In the embodiments of the present application, the median value C 50of the graphitization degree within the aforementioned range, which helps to improve the sliding of particles in the positive electrode film layer, reduce the stress concentration during the compaction of the thickly coated film layer, and reduce the probability of film detachment due to local stress concentration during long cycles of the positive electrode film layer, thereby further mitigating the problem of battery cell capacity degradation while simultaneously improving the battery cycle life and the energy density of the battery volume.

[0031] In each embodiment, the median value is B 50 of the coating value in the cumulative distribution curve of the coating value B of the positive electrode film layer, which is obtained in the surface scanning mode of the laser microconfocal Raman spectrometer, between 0.30 and 0.60, where the coating value BI P / I Dis, where I P the peak P intensity of the Raman spectrum at 948 ± 100 cm -1 and I D the D peak intensity of the Raman spectrum at 1350 ± 100 cm -1 is.

[0032] If the median value B 50If the coating value of the positive electrode film layer lies within the above range, this means that the carbon material layer of the positive electrode active material is relatively dense and uniform. This has a positive effect on the uniformity of the sliding of the positive electrode film layer during rolling and reduces the stress concentration phenomenon in the thick positive electrode film layer. Furthermore, the dense and uniform carbon material layer allows the large particles in the positive electrode film layer to slide more easily during the compaction process, thereby reducing the stress concentration phenomenon on the large particles in the thick positive electrode film layer, decreasing the probability of the positive electrode film layer detaching, and thus increasing the battery's cycle life while simultaneously reducing capacity loss.

[0033] In each embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise components that are represented by the following general formula: Li m Fe x P y O j Q q Formula 1 where Q comprises one or more of the following elements: Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl and Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4 and 0 ≤ q ≤ 0.1.

[0034] In each embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise one or more of the following materials: lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadium phosphate, lithium manganese iron phosphate and modified materials thereof.

[0035] In each embodiment, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise one or more of the materials lithium iron phosphate and its doping and coating modification materials.

[0036] In each embodiment, the iron leaching rate of the positive electrode material lies between 658 ppm and 1921 ppm.

[0037] In each embodiment, the iron leaching rate of the positive electrode material is between 658 ppm and 1485 ppm.

[0038] The iron dissolved in the positive electrode material originates primarily from the lithium-containing transition metal phosphate particles within the positive electrode active material. The iron leaching rate depends on the number of lattice defects in the lithium-containing transition metal phosphate and on the integrity and density of the carbon material layer on the surface of the positive electrode active material. The lower the iron leaching rate, the fewer lattice defects the lithium-containing transition metal phosphate exhibits, which positively reduces lattice corrosion in a weakly acidic environment. Conversely, the more complete and dense the carbon material layer on the surface of the positive electrode active material, the more effectively the leaching of iron ions is inhibited in a weakly acidic environment.The positive electrode material with an iron leaching ridge within the aforementioned area exhibits relatively few lattice defects and a complete and dense carbon material layer, which has a beneficial effect on improving the compressive strength and sliding behavior in the positive electrode film layer under high rolling pressure, increases the packing density of the positive electrode film layer and reduces the stress concentration in the positive electrode film layer, thereby improving the energy density of the battery and reducing the capacity loss of the battery.

[0039] In each embodiment, the mass content of titanium relative to the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer is between 500 ppm and 8000 ppm.

[0040] In each embodiment, the mass content of titanium relative to the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer is between 1000 ppm and 3000 ppm.

[0041] The introduction of titanium into lithium-containing transition metal phosphate particles requires the addition of a titanium source during the fabrication of the positive electrode active material. Titanium sources are often inert materials, and their adhesion to the surface of lithium-containing transition metal phosphate feedstocks can decrease reactivity and reduce particle size growth. Increasing the graphitization degree of the positive electrode active material often necessitates a higher sintering temperature or a longer sintering time. However, this also increases the particle size in the positive electrode film layer, raises the stress concentration of the positive electrode film layer, and causes the positive electrode film layer to degrade.In the embodiments of the present application, a high titanium content is added to the lithium-containing transition metal phosphate particles, thus reducing the reactivity of the starting materials for the synthesis of the positive electrode active material. This allows the proportion of large particles to be controlled while maintaining a high degree of graphitization of the positive electrode active material, reducing the voltage concentration in the positive electrode film layer and the probability of film detachment of the positive electrode film layer, thereby improving the energy density of the battery with regard to the battery's cycle life.

[0042] Simultaneously, doping the positive electrode active material with titanium is advantageous because it causes lattice distortion, reduces the Li-O bond energy, increases the lithium-ion transfer rate, and improves the battery's kinetic performance. Lithium-ion diffusion in the thick-coated film layer is uneven and often accompanied by a significant lithium-ion concentration gradient. The embodiments of the present application can improve the solid-phase transfer rate of the positive electrode active material by adding a high titanium content to the lithium-containing transition metal phosphate particles and reduce the kinetic problems of batteries with thick electrode plates.

[0043] In each embodiment, the mass content of vanadium relative to the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer is between 500 ppm and 5000 ppm.

[0044] In each embodiment, the mass content of vanadium relative to the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer is between 500 ppm and 3000 ppm.

[0045] The vanadium in the positive electrode film layer can have several valence states. Among these, vanadium with a valence of +5 (V 5+ ) at the position of the phosphorus element. Due to its large radius, it can cause lattice distortions and widen the diffusion channel of lithium ions, thereby increasing the ionic conductivity of the positive electrode active material and boosting the kinetic performance of the battery. Vanadium with a valence of +3 (V 3+The transition metal can be doped to create lithium vacancies through charge balancing, thereby improving the electronic conductivity of the positive electrode active material. Furthermore, the improved uniformity of vanadium distribution within the lithium-containing transition metal phosphate particles contributes to further enhancing the kinetic performance and reaction homogeneity of the positive electrode film layer, thereby further improving the kinetic and cycle performance of the battery unit.

[0046] The vanadium mass content in the aforementioned area is beneficial for improving the kinetic performance of the positive electrode plate and the kinetic performance of the thick-coated lithium-containing transition metal phosphate battery. Simultaneously, the synergistic effect of titanium, vanadium, and carbon nanotubes in the positive electrode film layer promotes the formation of a stable three-dimensional network that enhances both electronic and ionic conductivity, thereby further increasing the kinetic performance of the thick-coated lithium-containing transition metal phosphate batteries.

[0047] In each embodiment, the positive electrode film layer also comprises a conductive medium, and with respect to the total area of ​​the cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of the agglomerated region of the conductive medium is between 0.5% and 2.5%.

[0048] With respect to the total cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of the agglomerated region of the conductive medium lies within the above range, indicating that the conductive medium is uniformly distributed in the positive electrode film layer and can easily form a uniform conductive network. This particularly helps to reduce the problem of kinetic degradation caused by the enlargement of the ion transfer path in the thick coating film layer, to reduce local polarization and even lithium plating problems caused by the battery during the cycling process, and to improve the battery's cycle life.

[0049] Simultaneously, studies have shown that large particles in lithium-containing transition metal phosphate particles tend to rebound. The agglomerated area of ​​the conductive agent within the aforementioned region can suppress the rebound of the lithium-containing transition metal phosphate particles by means of the uniform distribution of the conductive agent, generate mechanical constraints on the particles and even the film layer, improve the cohesion of the film layer, reduce powder loss and film layer delamination, and extend the battery's cycle life.

[0050] In each embodiment, the positive electrode film layer also comprises a conductive medium, and with respect to the total area of ​​the cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of the agglomerated region of the conductive medium is between 1.5% and 2.5%.

[0051] In the embodiments of the present application, the area fraction of the agglomerated region of the conductive material lies further within the range mentioned above, indicating that the conductive material is distributed more uniformly in the positive electrode film layer and that the conductive material content remains relatively low. This not only improves the kinetic performance of the positive electrode film layer but also helps to reduce the space occupied by excess conductive material in the positive electrode active material. This further increases the volume energy density of the battery and simultaneously improves its kinetic performance.

[0052] In each embodiment, the conducting medium comprises carbon nanotubes comprising one or more of the following types: single-walled carbon nanotubes, thin-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0053] Since carbon nanotubes have a one-dimensional structure, they can form a network structure within the positive electrode film layer. On the one hand, the high elastic modulus of carbon nanotubes allows their network structure to not only act as a bridge for voltage propagation but also to have a binding effect on the thickly coated positive electrode film layer. This prevents the rebound of lithium-containing transition metal phosphate particles, effectively mitigates the voltage concentration, reduces the risk of film delamination, and thus minimizes capacitance loss. On the other hand, the excellent conductivity of carbon nanotubes makes their network structure an efficient electron transfer channel.Even in the event of local film detachment, the thick electrode plate can still maintain a high electron transfer efficiency in the in-plane direction and thickness direction, thereby delaying the onset of capacity loss and further increasing the dynamic performance and cycle life of the battery.

[0054] In each embodiment, the conducting medium also comprises conductive carbon black.

[0055] The conductive carbon black has a high specific surface area and therefore good fluid retention capacity. The thick electrode plate exhibits a large expansion force during the cycle, which can easily force the electrolyte out. The distribution of the conductive carbon black in the positive electrode film layer helps to improve the fluid retention capacity of the thick electrode plate, further mitigating the phenomenon of battery capacity saturation during the cycle and improving the battery's cycle life.

[0056] In each embodiment, the agglomerated region of the conductive medium comprises carbon nanotubes and conductive carbon black.

[0057] Researchers discovered that carbon nanotubes, due to their high surface energy, tend to agglomerate, leading to an uneven distribution within the positive electrode film layer and an inability to form an effective carbon nanotube network structure. The surface energies of conductive carbon black and carbon nanotubes are relatively close and can be adsorbed onto the surface of carbon nanotubes to form a physical barrier. This increases resistance to carbon nanotube agglomeration, reduces direct contact between carbon nanotubes, and thus prevents agglomeration and improves the uniformity of carbon nanotube distribution within the positive electrode film layer. This, in turn, contributes to improving the conductivity of the thick positive electrode film layer and increasing the dynamic performance of the battery.On the other hand, it contributes to the binding effect of carbon nanotubes on the positive electrode film layer, reducing the risk of delamination of the thick positive electrode film layer and further improving the dynamic performance and cycle life of the battery. Furthermore, the agglomeration of carbon nanotubes in the agglomerated region of the conductor also leads to the blocking of local ion transfer pathways in this region. The combination with conductive carbon black can improve the lithium-ion transfer capacity of this region, reduce local polarization, and further enhance the cycle stability of the battery.

[0058] In each embodiment, the mass fraction C1 of the carbon nanotubes satisfies, relative to the mass of the positive electrode film layer, 0 < C1 ≤ 2.5%, and the mass fraction C2 of the conductive carbon black satisfies 0 < C2 ≤ 2.5%.

[0059] The mass fraction of carbon nanotubes and conductive carbon black lies within the aforementioned range, which effectively mitigates the agglomeration of carbon nanotubes and forms a good conductive network structure, thereby effectively reducing the voltage concentration of the positive electrode film layer and improving the fluid retention rate of the positive electrode plate during long cycles, further reducing the risk of film delamination and the degree of polarization, thus improving the kinetic performance of the battery, taking into account the capacity loss problem, and improving the cycle life of the battery.

[0060] In each embodiment, the positive electrode film layer also comprises a dispersing agent comprising hydrogenated nitrile rubber (HNBR).

[0061] HNBR is obtained by hydrogenating the double bonds of nitrile rubber. Its highly saturated main-chain structure gives it excellent oil resistance, heat resistance, and aging resistance. This allows it to remain stable when used as a dispersant in various environments and systems, making it less likely to degrade or decompose and thus enabling it to effectively exert its dispersing effect. The HNBR molecular chain contains both polar nitrile groups and nonpolar hydrocarbon segments. The polar nitrile group can interact with some polar substances or particle surfaces, for example, by adsorption onto the surface of dispersed particles through hydrogen bonding, electrostatic effects, etc.; the nonpolar hydrocarbon chain segments exhibit good lipophilicity and can stretch and disperse well in nonpolar or weakly polar media, so that the particles are dispersed uniformly in the medium.

[0062] When HNBR is adsorbed onto the surface of particles in the slurry, its long-chain molecules form a physical barrier around the particles, preventing them from approaching and aggregating. This allows the particles to remain relatively independent and dispersed within the system. Simultaneously, HNBR can reduce the surface tension between the dispersion medium and the dispersed particles, facilitating wetting and promoting particle dispersion. It can also reduce the interfacial energy between particles, thereby decreasing interfacial energy-driven particle aggregation.Furthermore, the elastic network structure of HNBR can mitigate the shrinkage stress caused by solvent volatilization during the drying of the slurry into a film, reduce the reaggregation of the conductor caused by capillary force in this process, decrease the area ratio of the agglomerated region of the conductor, and improve the dynamic performance and cycle life of the battery.

[0063] In each embodiment, the mass content of the dispersing agent, relative to the total weight of the positive electrode film layer, is between 0.5% and 2%.

[0064] The mass content of the dispersant is within the aforementioned range, which allows for a uniform dispersion of the particles in the positive electrode film layer, while simultaneously maintaining a high charge capacity of the positive electrode film layer, reducing the voltage concentration in the thickly coated positive electrode film layer made of lithium transition metal phosphate, and effectively reducing the capacity loss.

[0065] In each embodiment, the porosity of the positive electrode film layer is between 14% and 28%.

[0066] The porosity of the positive electrode film layer lies within the aforementioned range, and the positive electrode film layer exhibits good electrolyte wettability and tortuosity, which promotes lithium ion diffusion in the liquid and solid phases, contributes to reducing concentration polarization of the thick electrode plate, and improves the battery's dynamic performance. Simultaneously, it helps to reduce the volume expansion of the thick-coated electrode plate during cycling, decrease the mechanical stress on the film layer, and reduce voltage concentration, thereby lowering the risk of film delamination of the thick-coated electrode plate.

[0067] Particularly in thick-coated pouch packaging batteries, the distance between the casing and the electrode plate is small, the volume coverage of the film layer is large, the electrolyte retention volume is reduced, and the porosity of the positive electrode film layer is within the aforementioned range, which helps to improve the liquid retention rate of the battery cell and improve the dynamic performance of the battery.

[0068] In each embodiment, the battery unit further comprises a separator arranged between the positive electrode plate and the negative electrode plate, wherein the separator comprises a base film and a ceramic layer arranged on at least one side of the base film, and a bonding layer arranged on at least one side of the ceramic layer facing away from the base film, wherein the bonding layer is a continuous layer with a porous structure and the bonding layer comprises a vinylidene fluoride polymer.

[0069] In each embodiment, the battery unit also includes the separator, which is arranged between the positive electrode plate and the negative electrode plate, wherein the separator comprises a base film, ceramic layers arranged on both sides of the base film and a connecting layer arranged on at least one side of the ceramic layers, facing away from the base film.

[0070] In each embodiment, the battery unit further comprises a separator arranged between the positive electrode plate and the negative electrode plate, the separator comprising a base film, ceramic layers arranged on both sides of the base film, and connecting layers arranged on both sides of the ceramic layers, facing away from the base film.

[0071] In each embodiment, the vinylidene fluoride polymer comprises one or more of the following materials: polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0072] In each embodiment, the vinylidene fluoride polymer comprises polyvinylidene fluoride (PVDF).

[0073] In the prior art, water-based PVDF is typically used for the separator's interconnect layer, exhibiting an island-like structure within the separator. This allows for the provision of gaps for battery cell expansion and is also easy to manufacture. However, the contact area between the interconnect layer of such a separator and the electrode plate is small, and the bonding force is weak.

[0074] The separator used in the present application employs a continuous layer with a porous structure as the bonding layer. This porous structure provides space for the expansion of the thick-coated battery cell, thereby improving its stability. Simultaneously, the contact area with the electrode plate is larger compared to conventional bonding layers, resulting in a stronger and more uniform connection between the separator and the electrode plate. Furthermore, when the positive electrode film layer rebounds, the contact between the separator and the positive electrode film layer is maintained, thus reducing the likelihood of film detachment.

[0075] In contrast to a wound battery cell, the extrusion between the separator and the electrode plate is lower in a laminated battery cell, and the separator and electrode plate tend to shift relative to each other. This disturbs the film layer, making it susceptible to powder loss or delamination. Furthermore, it can cause the positive and negative electrodes to overlap, increasing the risk of an internal short circuit in the battery cell. Therefore, the separator provided in the embodiments of the present application is particularly well suited for the laminated battery cell. The increased bond strength between the porous bonding layer and the electrode plate helps to improve the bond strength between the separator and the electrode plate and to reduce the relative shift between them.This helps to reduce disturbance of the positive electrode film layer and the likelihood of film detachment, and also helps to reduce the risk of overlap of the positive and negative electrode plates, which could cause a short circuit of the battery cell.

[0076] In summary, the selection of the vinylidene fluoride polymer in the bonding layer of the embodiments of the present application from the aforementioned materials contributes to the formation of a continuous and uniform porous bonding layer. Firstly, the bonding strength between the bonding layer and the electrode plates is improved and uniformly distributed, which helps to reduce the stress concentration in the thickly coated positive electrode film layer of lithium-containing transition metal phosphate and to reduce the risk of film delamination, thereby further improving the cycle life of the battery.Secondly, the compound layer is stably bonded to the positive or negative electrode plate, which helps to reduce direct contact between the positive and negative electrode plates due to the relative displacement of the electrode plate and separator, thus decreasing the risk of an internal short circuit and improving the battery's safety performance. Thirdly, the porous compound layer helps to maintain the separator's porosity, allowing space for battery cell expansion and further improving the battery's cycle life.

[0077] Ceramic particles are flame-retardant and have a high hardness value. They are difficult to deform under heat and therefore exhibit excellent dimensional stability. The low thermal conductivity of ceramic materials can also prevent specific thermal leakage points in the battery from developing into a general thermal leakage, thus improving the safety performance of the battery unit.

[0078] In each embodiment, the thickness of the base film in the separator is between 7 µm and 9 µm.

[0079] In each embodiment, the one-sided thickness of the ceramic layer in the separator is between 2 µm and 4 µm.

[0080] In each embodiment, the one-sided thickness of the bonding layer in the separator is between 1 µm and 5 µm.

[0081] The thickness of the compound layer is too small, the cavity in the separator is too small, and the bonding force between the separator and the electrode plate is insufficient. On the one hand, the voltage increases after the film layer expands, and the probability of the film layer delaminating increases, which affects the battery's cycle life. On the other hand, the probability of a short circuit between the positive and negative electrodes increases, which in turn impairs the battery's safety performance. If the thickness of the compound layer is too large, it occupies a significant amount of space in the battery, thereby negatively impacting the battery's volumetric energy density. In the embodiments of the present application, the thickness of the compound layer is within the aforementioned range, which helps to optimize the battery's cycle life, safety performance, and volumetric energy density.

[0082] In each embodiment, the positive electrode film layer in the lower region near the positive electrode current collector is provided with a primer layer, wherein the primer layer comprises a conductive agent and a binder, wherein the conductive agent comprises carbon nanotubes and conductive carbon black and the binder comprises a vinylidene fluoride polymer.

[0083] In each embodiment, the primer layer has a thickness of 0.5 µm to 5 µm.

[0084] The primer layer provided in the embodiments of the present application contributes to improving the bonding strength between the positive electrode film layer and the positive electrode current collector and to mitigating the voltage concentration phenomenon in the presence of large particles, thereby reducing the probability of detachment of the positive electrode film layer and improving the cycle stability of the battery. At the same time, compared to direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the primer layer and the positive electrode film layer is increased, which contributes to increasing the electron transfer area between the positive electrode current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode plate and improving the dynamic performance of the battery.

[0085] In each embodiment, the battery unit comprises a casing, and the laminated battery cell is housed within the casing. The dimension of the casing along the longitudinal direction is L1, the dimension of the casing along the width direction is W1, and the dimension of the casing along the thickness direction is H1, where 450 mm ≤ L1 ≤ 1300 mm, 100 mm ≤ W1 ≤ 150 mm, and 14 mm ≤ H1 ≤ 22 mm.

[0086] In each embodiment, the dimension of the shell along the longitudinal direction is L1, and 450 mm ≤ L1 ≤ 650 mm.

[0087] If the longitudinal dimension L1 of the casing meets the criteria of 450 mm ≤ L1 ≤ 650 mm, the battery unit length is shorter. This helps to shorten the current diffusion path and reduce the internal resistance of the electrode plate, thereby reducing heat generation and improving the battery's dynamic performance. Furthermore, the shorter casing length contributes to shortening the electrolyte diffusion path during the infiltration process, improving the infiltration rate and electrolyte uniformity, further promoting the uniformity of lithium ion insertion and extraction during the cycle, reducing voltage concentrations, decreasing the risk of film delamination, and improving the cycle stability of the battery unit.

[0088] In each embodiment, the dimension of the shell along the longitudinal direction L1 900 mm ≤ L1 ≤ 1300 mm.

[0089] If the dimension L1 of the casing along the longitudinal direction meets the condition 900 mm ≤ L1 ≤ 1300 mm, the battery unit is longer, which helps to reduce the volume ratio of the casing within the battery unit and increase the charge ratio of the active material. Simultaneously, a longer battery unit can reduce the number of batteries required in the battery module, simplify the structural design of the battery module, decrease the number and complexity of structural components within the battery module, and thus improve the space utilization of the battery pack and further contribute to improving the volume energy density of the battery unit.

[0090] In each embodiment, the material of the casing is a pouch packaging material comprising an aluminum-plastic composite film.

[0091] In each embodiment, the material of the casing comprises a composite film made of aluminum and one or more of the following materials: polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET), and polyethylene (PE).

[0092] The pouch packaging material has a high degree of elongation, allowing for a thinner and softer shell. This contributes to better space utilization within the battery unit and thus increases its energy density. Furthermore, the high barrier properties of aluminum effectively reduce the ingress of water and oxygen into the battery, minimizing electrolyte degradation and electrode material oxidation, thereby extending the battery's lifespan.

[0093] In each embodiment, the capacity of the battery unit at 25 °C is between 105 Ah and 300 Ah.

[0094] In each embodiment, the capacity of the battery unit at 25 °C is between 150 Ah and 190 Ah.

[0095] A second aspect of the present application relates to a battery device comprising the battery unit provided by the first aspect of the present application.

[0096] In a third aspect of the present application, a power-consuming device is provided, comprising the battery device provided in the second aspect, and the battery device is used to provide electrical energy.

[0097] In a fourth aspect of the present application, an energy storage device is provided, comprising the battery device provided in the second aspect, and the battery device is used to store electrical energy. Brief description of the drawings Fig.is a schematic diagram of a separator according to an embodiment of the present application; Fig. is a schematic diagram of a separator in the prior art; Fig. a schematic structure diagram of a connection layer according to an embodiment of the present application; Fig. a schematic diagram of a laminated pouch packaging battery according to the present application; Fig. is a schematic diagram of the structure of a power-consuming device according to the present application. Explanation of reference symbols:

[0098] 5 Battery unit; 50 Casing; 20 Separator; 201 Base film; 202 Ceramic layer; 203 Bonding layer; X Longitudinal direction; Y Width direction; Z Thickness direction. Detailed descriptions

[0099] The following describes in detail embodiments of a battery unit, a battery device, a power-consuming device, and an energy storage device specifically disclosed in the present application, possibly with reference to the drawings. However, an unnecessarily detailed description can be omitted. For example, a detailed description of known facts and a repeated description of essentially the same structure can be omitted.

[0100] This is intended to prevent the following description from becoming unnecessarily long and to facilitate understanding for the person skilled in the art. Furthermore, the drawings and the following description serve to enable the person skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0101] The “ranges” disclosed in this application are defined in the form of lower and upper limits. A specific range is defined by selecting a lower and an upper limit. The selected lower and upper limits define the boundaries of the respective range. The range thus defined can include or exclude the end values ​​and can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also considered. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are listed, all of the following ranges are considered: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5.In this application, unless otherwise specified, a range of numbers “a to b” represents an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the range of numbers “0 to 5” means that all real numbers between “0 and 5” have been listed in this article, and “0 to 5” is simply an abbreviation for these combinations of numbers. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0102] Unless expressly stated otherwise, all embodiments and all optional embodiments of the present application can be combined to form new technical solutions, and such technical solutions are deemed to be included in the disclosure of the present application.

[0103] Unless expressly stated otherwise, all embodiments and all optional embodiments of the present application can be combined to form new technical solutions, and such technical solutions are deemed to be included in the disclosure of the present application.

[0104] Unless otherwise stated, all steps of the present application may be carried out successively or in any order, but preferably consecutively. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out consecutively, or that the method may include steps (b) and (a) carried out consecutively. For example, this means that the method may also include step (c), that step (c) may be added in any order, and the method may, for example, include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0105] In this application, the terms "multiple" and "multiple" refer to two or more.

[0106] Unless otherwise stated, the terms used in this application have the general meanings which are usually understood by those skilled in the art.

[0107] Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods specified in the examples of this application. Unless otherwise specified, the test temperature for all parameters is 25 °C.

[0108] A battery device can contain one or more battery components to provide voltage and capacity. A battery component can comprise a variety of pouch-packed battery units, which may be connected in series, parallel, or a hybrid configuration via a busbar component. For example, the battery component can be a battery module, and the battery module consists of a variety of pouch-packed battery units arranged and secured to form an independent module. For example, a battery module can be formed by bundling multiple battery units together with cable ties.

[0109] The battery device can be a battery pack comprising a case and one or more battery components, with the battery components housed within the case. For example, the battery component can also be a battery module; it can be accommodated within the case by securing the battery module within the case. Alternatively, the battery component can be accommodated within the case by directly securing multiple pouch-packed battery units within the case.

[0110] In the embodiments of the present application, the box can comprise a first box and a second box. The top cover and the bottom plate are each connected to the frame, creating an enclosed space inside the box for housing the battery components. "Enclosed" here means "covered" or "enclosed" and can be sealed or unsealed. The first box part can be a top cover or a bottom plate. For example, the box can comprise a top cover, a frame, and a bottom plate. The top cover and the bottom plate are each connected to the frame, creating an enclosed space inside the box for housing the battery components.

[0111] In the embodiments of the present application, the box can be part of the chassis structure of the vehicle. For example, part of the box can become at least part of the floor of the vehicle, or part of the box can become at least part of the cross member and the longitudinal member of the vehicle.

[0112] In the embodiments of the present application, the battery unit can be a secondary battery that can be used continuously by activating active materials through charging after discharging. The battery unit can be a lithium-ion battery. The battery unit can have a flat design.

[0113] The battery mentioned in the embodiments of the present application can be a single physical module comprising one or more battery units to provide a higher voltage and capacity. For example, the battery mentioned in this application can comprise a battery unit, a battery module, or a battery set.

[0114] The battery unit is the smallest unit that makes up a battery and can independently perform the charging and discharging functions.

[0115] If multiple battery units are present, the battery cells can be connected in series, parallel, or in a hybrid configuration via a busbar component. In some embodiments, the battery can be a battery module. If multiple battery units are present, the multiple battery units are arranged and secured to form a battery module. In some embodiments, the battery can be a battery pack comprising a housing and battery units, with the battery units or battery module being housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, part of the housing can become at least part of the vehicle's floor, or part of the housing can become at least part of the vehicle's crossmember and longitudinal member.

[0116] In some embodiments, the battery can be an energy storage device. The energy storage device includes energy storage containers and energy storage cabinets.

[0117] In some embodiments, the battery units can be assembled into a battery module. A battery module can comprise multiple battery units, and the exact number can be adjusted depending on the application and the capacity of the battery module.

[0118] 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 depending on the application and capacity of the battery pack.

[0119] A battery unit comprises an electrode array and an electrolyte.

[0120] The electrode arrangement typically consists of a positive electrode plate and a negative electrode plate. The negative electrode plate is the electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode plate is the electrode that releases or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0121] Lithium-containing transition metal phosphates as positive electrode active materials offer advantages such as high safety, long lifespan, low cost, and high high-temperature stability. However, their intrinsic gram capacity is significantly lower than that of ternary materials. To compensate for this lack of energy density, the applicant found that by employing a thick coating strategy (i.e., a strategy to increase the active material content per unit area, often associated with a greater film thickness), the charge on the positive electrode active material in the battery can be increased, thereby improving the battery's energy density. However, during the battery's long cycle, the thick-coated battery cell generates greater volume expansion, leading to increased internal stress, which can cause the electrode plate to easily lose film powder or even detach later in the long cycle.Film delamination leads, on the one hand, to the loss of the positive electrode active material involved in the charging and discharging process, resulting in a rapid loss of battery capacity (capacity drop). On the other hand, an "island effect" occurs, meaning that isolated areas form between some active material particles or between the particles and the conductive medium. These areas cannot establish good electrical contact and therefore cannot participate in the battery's charging and discharging process. Simultaneously, this material impairs ion conductivity, increases the battery's internal resistance, leads to localized overheating, and increases the risk of thermal runaway, significantly reducing the battery's lifespan.Therefore, the question of how to achieve long-term stable maintenance of battery capacity while simultaneously improving the battery's energy density remains a technical problem that urgently needs to be solved.

[0122] The first aspect of the present application relates to a battery unit. The battery unit comprises a laminated battery cell, which in turn comprises a positive electrode plate and a negative electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector. The positive electrode film layer comprises lithium-containing transition metal phosphate particles with a carbon material arranged on at least a portion of the surface of the lithium-containing transition metal phosphate particles. In a fully charged state of the battery unit, the packing density of the positive electrode plate is between 2.3 g / cm³. 3 and 2.6 g / cm³ 3 ; the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2With respect to the total surface area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm lies between 12% and 50%. The uniformity of the distribution of particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm is less than or equal to 5% in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate.

[0123] Compared to ternary materials, lithium-containing transition metal phosphates exhibit a more stable structure and are less prone to fracture under high pressure. During the electrode plate compaction process, these lithium-containing transition metal phosphates must withstand higher pressures to increase the packing density. However, studies have shown that when the battery unit is fully charged, the electrode plate becomes overloaded if the packing density of the positive electrode plate exceeds 2.6 g / cm³. 3 This results in a high voltage concentration, which can easily lead to the positive electrode plate detaching during the cycle. In the fully discharged state of the battery unit, the particles of the positive electrode film layer are not firmly bonded if the packing density of the positive electrode plate is below 2.3 g / cm³. 3This increases the battery's internal resistance and reduces the battery unit's energy density. The one-sided areal density of the positive electrode film layer is less than 0.25 g / 1540.25 mm². 2 The content of positive electrode active material in the battery unit is low, which does not effectively improve the battery's energy density. The one-sided areal density of the positive electrode film layer is greater than 0.45 g / 1540.25 mm². 2 This causes the positive electrode film layer to become too thick. The stress distribution of the positive electrode film layer is uneven during the compaction process, and a local stress concentration can lead to film delamination. By controlling the packing density of the positive electrode plate to 2.3 g / cm², this can be prevented. 3 and 2.6 g / cm³ 3 and the one-sided areal density of the positive electrode film layer to 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2The energy density can be improved while simultaneously reducing the risk of detachment of the positive electrode plate.

[0124] The applicant also noted that the expansion volume of a thick-coated electrode plate increases considerably during battery charging and discharging, making film delamination a likely occurrence in the later stages of long cycles. Large particles in the coating are likely the starting point for this delamination. Studies have shown that large particles tend to develop stress concentrations and cracks during the film compaction process. However, if the content of large particles in the positive electrode film layer is too low, the increase in the packing density of the positive electrode film layer is limited. Studies have shown that the packing density of the positive electrode plate can be reduced to 2.3 g / cm³. 3 up to 2.6 g / cm³3 and the one-sided areal density of the positive electrode film layer to 0.25 g / 1540.25 mm² 2 up to 0.45 g / 1540.25 mm 2This can be regulated. If, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is less than 12%, the energy density of the battery is reduced; if, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is more than 50%, stress concentration can easily occur during the film compaction process, and uneven expansion can occur during the cycle, leading to loss of film powder or even film detachment.In the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the uniformity of the distribution of particles with particle size R1, which meets R1 ≥ 1000 nm, is greater than 5%, which increases the stress concentration during the compaction process of the film layer, further increases the uneven expansion during the cycle and increases the risk of film powder loss and detachment.

[0125] In the embodiments of the present application, the battery unit comprises a laminated battery cell, the packing density of the positive electrode plate in the fully charged state of the battery unit is between 2.3 g / cm³. 3 and 2.6 g / cm³ 3 , the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2Based on the total particle area in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets the criteria of R1 ≥ 1000 nm is between 12% and 50%. The uniformity of the distribution of particles with a particle size R1 that meets the criteria of R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is less than or equal to 5%. Firstly, laminated battery cells, compared to wound cells, have no corner areas, which can effectively improve the battery's space utilization and thus increase its volume energy density. The absence of corner areas also helps to reduce voltage concentration, decrease the likelihood of film delamination, and reduce the risk of battery capacity loss.Secondly, controlling the packing density and the one-sided coating area density within the aforementioned range is not only advantageous for increasing the loading quantity of the positive electrode active material, but also for controlling the porosity of the positive electrode film layer within a suitable range. This increases the electrolyte infiltration rate, allowing the gram capacity of the active material to be fully utilized and further improving the volume energy density of the battery. Furthermore, the embodiments of the present application contribute to increasing the loading quantity of the positive electrode active material and improving the voltage distribution by controlling the content of large particles in the positive electrode film layer and their uniformity of distribution.This mitigates the negative effects of voltage concentration, making it easier to consider the battery's capacity and cycle stability, and reducing the risk of battery capacity loss.

[0126] In summary, the battery units provided by the embodiments of the present application exhibit both high capacity and pronounced capacity cycle stability.

[0127] In this application, a laminated battery cell refers to a battery cell formed by stacking a positive electrode plate, a separator, and a negative electrode plate.

[0128] In the present application, the positive electrode film layer comprises lithium-containing transition metal phosphate particles. However, the term "positive electrode film layer" does not refer solely to the positive electrode active material layer. Other film layers, which are difficult to distinguish, such as the primer layer, the liquid retention layer, etc., and which are associated with the "positive electrode film layer," are also collectively referred to as the positive electrode film layer.

[0129] In the present application, lithium-containing transition metal phosphate refers to a phosphate material containing lithium and a transition metal element, which can be detected by all methods known in the art. For example, it can be detected by combining an X-ray diffractometer (XRD) with an energy-dispersive spectrometer and an inductively coupled plasma mass spectrometer.

[0130] In the present application, the carbon material deposited on at least a portion of the surface of the lithium-containing transition metal phosphate particles can be detected by any method known in the art. For example, by characterizing the lithium-containing transition metal phosphate particles using a transmission electron microscope and an energy-dispersive spectrometer, it is possible to observe the carbon material deposited on at least a portion of the surface of the lithium-containing transition metal phosphate particles.

[0131] In this application, the fully discharged state refers to the state after the battery has been placed in an oven at an ambient temperature of 25 °C, left to rest for two hours while maintaining a constant battery temperature of 25 °C, and then discharged first with a constant current of 1 / 3 C to 2.5 V and subsequently further discharged with a constant current of 0.1 C to 2.0 V.

[0132] In the present application, the packing density of the positive electrode plate can be determined using methods known in the art. For example, the battery is placed in an oven at 25 °C and left to stand for two hours. While maintaining the battery temperature at 25 °C, the battery is discharged to 2.5 V with a constant current of 1 / 3 C and then discharged to 2.0 V with a constant current of 0.1 C. The battery is disassembled to obtain the positive electrode plate. The remaining electrolyte is treated with dimethyl carbonate solvent, the electrode plate is dried, and cut into small slices with an area of ​​S. The mass is determined as W1, and the thickness T1 of the positive electrode plate is measured with a micrometer.Then the positive electrode film layer of the weighed electrode plate is wiped off, the mass of the current collector is weighed and recorded as W2, and the thickness T2 of the current collector is measured with a micrometer. The packing density PD of the positive electrode plate is (W1 - W2) / [(T1 - T2) × S].

[0133] In some embodiments, the packing density of the positive electrode film layer in the fully charged state of the battery unit can be 2.3 g / cm². 3 , 2.31 g / cm³ 3 , 2.32 g / cm³ 3 , 2.33 g / cm³ 3 , 2.34 g / cm³ 3 , 2.35 g / cm³ 3 , 2.36 g / cm³ 3 , 2.37 g / cm³ 3 , 2.38 g / cm³ 3 , 2.39 g / cm³ 3 , 2.40 g / cm³ 3 , 2.41 g / cm³ 3 , 2.42 g / cm³ 3 , 2.43 g / cm³ 3 , 2.44 g / cm³ 3 , 2.45 g / cm³ 3 , 2.46 g / cm³ 3 , 2.47 g / cm³ 3 , 2.48 g / cm³ 3 , 2.49 g / cm³ 3 , 2.50 g / cm³ 3 , 2.55 g / cm³ 3, 2.60 g / cm³ 3 , or lie within a range formed by any two of these values.

[0134] In the present application, the one-sided coating area density of the positive electrode film layer has a well-known meaning in the art and can be determined using methods known in the art. The present application provides a method for testing the coating weight of the positive electrode film layer: Disassembling a battery cell to obtain a positive electrode plate, for example, removing a one-sided coated positive electrode plate (in the case of double-sided coating, the positive electrode film layer can first be removed from one side) – and punching out a small disc with area S1, subsequently weighing and recording it as M1. Then, the positive electrode film layer of the weighed positive electrode plate is wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0. The one-sided coating area density of the positive electrode film layer = (M1 - M0) / S1.To ensure the accuracy of the test results, several groups (e.g., 10 groups) of test samples can be tested, and the average value calculated as the test result. The higher the one-sided coating area density of the positive electrode film layer, the greater the load per unit area, which contributes to increasing the volume energy density of the battery unit.

[0135] In some embodiments, the one-sided coating area density of the positive electrode film layer can be selected as follows: 0.25 g / 1540 mm² 2 , 0.26 g / 1540 mm 2 , 0.27 g / 1540 mm 2 , 0.28 g / 1540 mm 2 , 0.29 g / 1540 mm 2 , 0.30 g / 1540 mm 2 , 0.31 g / 1540 mm 2 , 0.32 g / 1540 mm 2 , 0.33 g / 1540 mm 2 , 0.34 g / 1540 mm 2 , 0.35 g / 1540 mm 2 , 0.36 g / 1540 mm 2 , 0.37 g / 1540 mm 2 , 0.38 g / 1540 mm 2 , 0.39 g / 1540 mm 2, 0.40 g / 1540 mm 2 , 0.41 g / 1540 mm 2 , 0.42 g / 1540 mm 2 , 0.43 g / 1540 mm 2 , 0.44 g / 1540 mm 2 , or 0.45 g / 1540 mm 2 , or in a range formed by any two of these values.

[0136] In some embodiments, the one-sided coating area density of the positive electrode film layer is between 0.3 g / 1540.25 mm². 2 and 0.45 g / 1540.25 mm 2 .

[0137] In some embodiments, the one-sided coating area density of the positive electrode film layer is between 0.35 g / 1540.25 mm². 2 and 0.4 g / 1540.25 mm 2 .

[0138] The one-sided coating area density of the positive electrode film layer remains within the aforementioned range, which helps to further improve the battery's capacity with regard to cycle performance.

[0139] In this application, the term "particle" refers to particles whose complete boundaries are visible in the field of view of the positive electrode film layer at a specific magnification, for example, 10,000x. Defects and scratches may be present within the particles, but complete boundaries sufficient to separate the particles are not visible within them. In this application, the positive electrode film layer can be either a newly produced positive electrode film layer or one obtained by disassembling a battery.

[0140] In this application, the following procedure is used to identify particles: The positive electrode film layer is cut with an argon ion beam along the thickness direction of the electrode plate (example: instrument model: Leica EMTIC3XCP, operating voltage: 6 kV, operating time: 6 h). After the cross-section is exposed, a scanning electron microscope (example: instrument model: Hitachi SU8230, operating voltage: 3 kV, beam current: high, probe model: U (LA100), working distance: < 5 mm) is used to observe the cross-section of the positive electrode film layer along the thickness direction of the electrode plate. Using field emission scanning electron microscopy, images are acquired in secondary electron mode at non-edge positions in the cross-section of the positive electrode film layer (after observing the edge of the electrode plate under the scanning electron microscope, the field of view is adjusted to the center of the sample).The electron microscope images are acquired at a magnification of 10,000x, and the particles in the electron microscope images are analyzed using ImageJ software (1.46r, Win64 version). The specific procedure for using the ImageJ software is as follows: loading the scanning electron microscope images to be analyzed, using the Cellpose plug-in software to identify the particles and performing manual corrections based on the results, and using ImageJ to read and calculate statistical data. The specific procedure for identifying particles with the Cellpose plug-in software is as follows: setting the segmentation diameter parameter (diameter in the segmentation module) to 15 pixels, clicking "runcyto3" to perform particle identification, and manually marking the particles in the image that are not detected, not fully detected, or incorrectly identified by the software.The particles in the image that are not detected, not detected completely, or detected incorrectly by the software mainly include the following types: 1. The particles are too large or have scratches on their surface, preventing or preventing detection. 2. Scratches are created on the particle surface during sectioning with the argon ion beam. During the detection process, the software may incorrectly interpret these scratches as particle boundaries, leading to detection errors. 3. The particles are too small for successful detection. 4. The particles are located at the edge of the electron microscope's field of view, and the edge penetrates the particle's interior, preventing a complete representation of its morphology and resulting in only a portion being detected instead of the whole, leading to detection errors.The aforementioned particles that cannot be identified or exhibit identification errors are manually calibrated. The exact procedure is as follows: Large particles at the edges of the scanning electron microscope that cannot be fully displayed are deleted. It is then checked whether gap scratches are present in other particles that cannot be identified or exhibit identification errors. If no gap scratches are present, the particles are identified as a single particle and manually labeled based on the manually observed particle boundaries. If gap scratches are present, it is determined whether the gap scratches penetrate the particles. If not, the particles are identified as a single particle and manually labeled. If the gap scratches penetrate the particles, it is determined whether they are linear or irregular.If the gap scratches are irregular, they are identified as a boundary between particles, and the particles are divided along this boundary. If the gap scratches are linear, a contrast comparison is performed. If the contrast is unclear and without visible cracks, it is identified as a scratch and classified as a single particle. If the contrast is strong and with visible cracks, it is identified as a boundary between particles and marked as two particles. After manual marking, the information irrelevant to the particles is deleted in the automatic image processing, thus completing the determination and identification of the particles in the image.

[0141] In the cross-section of the positive electrode plate along its thickness direction, the area fraction of particles with a particle size R1 that satisfies R1 ≥ 1000 nm can intuitively reflect the proportional area relationship between some particles in this particle size segment and all particles, and represent the area of ​​the particles in this particle size segment. It is evident that the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, especially those with a particle size greater than 50 nm, originate mainly from the positive electrode active material.Therefore, the embodiments of the present application can accurately and objectively reproduce the distribution of the lithium-containing transition metal phosphate particles in the positive electrode film layer by observing and counting the particle area in the cross-section of the positive electrode plate along the thickness direction of the electrode plate.

[0142] In the prior art, a laser particle size analyzer is generally used to measure the particle size of the positive electrode active material using the Malvern laser diffraction method. However, the applicant's research shows that lithium-containing transition metal phosphate particles tend to agglomerate, and the test results obtained with the laser scattering-based Malvern laser diffraction method often measure the particle size of the particle agglomerates, which cannot reflect the actual particle size of the particles in the positive electrode active material. Furthermore, they can hardly reflect the dispersion state of the positive electrode active material in the film layer, as the degree of dispersion of the positive electrode active material in the film layer increases during the slurry and film rolling process.The test results obtained using the Malvern laser diffraction method are influenced 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 plate, the number of large particles detected in the test is lower than the actual value, while the number of small particles is higher than the actual value. Therefore, the particle size determined using the Malvern laser diffraction method cannot correspond to or be compared with the particle size statistically determined in the embodiments of the present application.

[0143] The specific test method for the area ratio of particles with a particle size R1, satisfying R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is as follows: Referring to the method described above in this application for identifying the particles in the positive electrode film layer, importing the images after identification and labeling of the particles into the ImageJ software for analysis, scaling according to the scanning electron microscope images, using the analysis functions "Feret Diameter (Feret)," "Area (Area)," "Roundness (Round)," and "Solidity" to perform a statistical analysis of the particle size, area, sphericity, and roughness of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate. According to the software manual (ImageJUserGuideIJ 1.46r), the parameter “Feret” obtained through the analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which characterizes the particle size; the parameter “Area” obtained represents the pixel area of ​​the particle. Since particles smaller than 50 nm exhibit large errors in the statistical process and are difficult to identify accurately, and since the particle size of the conducting medium is generally smaller than 50 nm, leading to large errors in the statistical results, particles smaller than 50 nm are not counted in the particle size statistics process of the present application, and the particle statistics data displayed as “NaN”, corresponding to AR, Round, or Solidity, are deleted.The sum of the parameter "Area" of particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm, and the sum of the parameter "Area" of all particles, are calculated as the area of ​​particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm, or the total area of ​​the statistical particles. The sum of the areas of the particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm, divided by the total area of ​​the counted particles, is defined as the area ratio of the particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate.

[0144] In some embodiments, the area fraction of particles whose particle size R1 ≥ 1000 nm, based on the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, can be selected as follows: 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 range of numbers in between.

[0145] In some embodiments, the area fraction of particles with particle size R1, which meets R1 ≥ 1000 nm, relative to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, is between 12% and 37%.

[0146] Large particles with a particle size R1 ≥ 1000 nm contribute to increasing the packing density of the positive electrode plate and thereby increasing the volume energy density of the battery unit. However, researchers have found that these large particles tend to cause voltage concentration, which increases the risk of delamination of the positive electrode film layer. Therefore, the surface area fraction of particles with a particle size R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is preferably in the range of 12% to 37%.This can not only improve the packing density of the electrode plate, but also prevent the probability of film delamination from increasing too much, thereby improving the energy density of thick-coated lithium-containing transition metal phosphate batteries, while reducing capacity loss and taking into account the battery's cycle life.

[0147] The uniformity of the distribution of particles with a particle size R1, satisfying R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate can be determined using methods known in the art. For example, the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is divided into three layers of equal thickness along the thickness direction of the electrode plate (if the surface of the positive electrode current collector is coated with a primer layer and then with a layer of the positive electrode active material,In cross-section, the area of ​​the positive electrode film layer extending 5 µm from the positive electrode current collector to the surface of the positive electrode film layer away from the positive electrode current collector is divided into three layers of equal thickness along the thickness direction of the electrode plate: the lower layer near the positive electrode current collector, the upper layer away from the positive electrode current collector, and the middle layer between the upper and lower layers. For each of these three layers (lower, middle, and upper), ten non-overlapping fields of view are randomly selected, and scanning electron microscope images are acquired at a magnification of 10,000x. The ten scanning electron microscope images acquired from each layer are then used to create a new set of images.The images are imported into the ImageJ software for analysis, and according to the aforementioned "test method for the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate," the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is determined in the 10 images corresponding to the top, middle, and bottom layers, resulting in a total of 3 values. The range of these three values ​​for the top, middle, and bottom layers represents the uniformity of the distribution of particles with a particle size R1 that meets R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate. This range corresponds to the difference between the maximum and minimum values ​​of the three determined values. The lower the uniformity of the distribution of particles with a particle size R1,The more the particle size R1 ≥ 1000 nm is met in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the more uniform the distribution of large particles with a particle size R1 that meets R1 ≥ 1000 nm is in the positive electrode film layer. This helps to reduce the voltage concentration phenomenon on the large particles in the positive electrode film layer, reduce the probability of film delamination and peeling, and improve the cycle performance of the battery.

[0148] In some embodiments, the uniformity of the particle distribution with a particle size R1 that meets R1 ≥ 1000 nm in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate can optionally be adjusted to 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 in between.

[0149] In some embodiments, the uniformity of the distribution of particles with a particle size R1 that meets R1 ≥ 1000 nm lies between 0.2% and 2% in the cross-section of the positive electrode film layer along the thickness direction.

[0150] In some embodiments, the uniformity of the distribution of particles with a particle size R1 that meets R1 ≥ 1000 nm lies between 0.2% and 0.9% in the cross-section of the positive electrode film layer along the thickness direction.

[0151] The uniformity of particle distribution, with a particle size R1 ≥ 1000 nm, lies between 0.2% and 2% in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, and between 0.2% and 0.9% in the other regions. This effectively reduces the stress concentration in local areas of the film layer, allowing the stress to be distributed uniformly across the entire surface of the film layer during the film compaction process. This increases the battery's energy density, reduces the likelihood of film delamination, minimizes capacity loss in thick-coated lithium-containing transition metal phosphate batteries, and improves the battery's cycle life.

[0152] In some embodiments, the one-sided thickness H of the positive electrode film layer is between 70 µm and 120 µm.

[0153] In some embodiments, the one-sided thickness H of the positive electrode film layer is between 90 µm and 120 µm.

[0154] The thickness of the positive electrode film layer can be determined using all methods known in the prior art. For example, the thickness of the positive electrode film layer in the cross-section of the positive electrode plate is measured along the thickness direction using a scanning electron microscope.

[0155] In some embodiments, the one-sided thickness H of the positive electrode film layer can be selected as follows: 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, 97 µm, 98 µm, 99 µm, 100 µm, 101 µm, 102 µm, 103 µm, 104 µm, 105 µm, 106 µm, 107 µm, 108 µm, 109 µm, 110 µm, 111 µm, 112 µm, 113 µm, 114 µm, 115 µm, 116 µm, 117 µm, 118 µm, 119 µm, 120 µm, or any range in between.

[0156] If the thickness of the positive electrode film layer on one side is within the range mentioned above, this helps to increase the amount of charge of the positive electrode active material in the battery and thereby increase the battery's capacity.

[0157] In some embodiments, the one-sided thickness H of the positive electrode film layer is between 100 µm and 120 µm.

[0158] Increasing the thickness of the positive electrode film layer contributes to increasing the amount of charge on the positive electrode active material and thus increasing the battery's capacity. However, the applicant found that with a one-sided thickness of at least 100 µm of the positive electrode film layer during the battery cycle, the volume expansion of the positive electrode film layer is greater, resulting in a higher voltage and a more pronounced voltage concentration phenomenon in the positive electrode film layer. This increases the risk of film delamination, which impairs the battery's cycle performance. In the embodiments of the present application, the battery's capacity is increased by increasing the thickness of the positive electrode film layer.Simultaneously, the area fraction of particles with particle size R1, which fulfills R1 ≥ 1000 nm, is controlled in relation to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, as well as the uniformity of the distribution of particles with particle size R1 (R1 ≥ 1000 nm) in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, which controls the content of large particles in the positive electrode film layer within a reasonable range, improves the uniformity of their distribution, and mitigates the voltage concentration phenomenon on the large particles, thereby improving the battery capacity with regard to the cycle performance of the battery.

[0159] In some embodiments, the median value L R1A50the sphericity in the cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate between 0.6 and 0.8.

[0160] The specific test method for the sphericity of particles with particle size R1, satisfying R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, is as follows: Referring to the method described above in this application for identifying the particles in the positive electrode film layer, importing the images after identification and labeling of the particles into the ImageJ software for analysis, scaling according to the scanning electron microscope images, and using the analysis functions "Feret Diameter (Feret)" and "Roundness (Round)" to perform a statistical analysis of the particle size and sphericity of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate. According to the software manual (ImageJUserGuideIJ 1.46r), the "Feret" parameter obtained through analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, characterizing the particle size; according to the software manual (ImageJUserGuideIJ 1.46r), the "Round" parameter obtained through analysis represents the ratio of the particle's pixel area to the area of ​​a circle with the adjusted major diameter as its diameter, which can be used to characterize the particle's sphericity. The closer the particle is to a sphere, the closer the ratio of the pixel area to the area of ​​the circle whose diameter corresponds to the adjusted major diameter is to 1. Therefore, the "Round" parameter of the particle obtained through analysis is used to characterize the particle's sphericity.The sphericity of at least 1000 particles with a particle size R1 that meets the criterion R1 ≥ 1000 nm is arranged in ascending order, with the sphericity as the horizontal axis and the cumulative area fraction as the vertical axis, in order to obtain a cumulative area distribution curve of the sphericity of particles in the positive electrode film layer. L. R1A50 is the L-value of the sphericity at which the cumulative area fraction reaches 50% of the vertical axis in the cumulative area distribution curve of the sphericity of particles with particle size R1, which satisfies R1 ≥ 1000 nm.

[0161] The sphericity of the particles can be adjusted by a person skilled in the art using all known methods. For example, the sphericity of the particles can be adjusted by processes such as grinding, polishing, chemical etching, mechanical stirring, extrusion, coating, granulation, addition of surfactants, and adjustment of the parameters of each process.

[0162] It is understandable that lithium-containing transition metal phosphate particles often need to be sintered at high temperatures. As the grain boundaries melt and the particles grow, the particle sphericity decreases. If the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm, relative to the total particle area in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, is between 12% and 50%, the median particle sphericity is often not above 0.8.

[0163] In some embodiments, the cross-section of the positive electrode film layer along the thickness direction of the electrode plate can be defined in the cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, L R1A50The value can be chosen as 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, 0.8 or any value in the intermediate range.

[0164] In the embodiments of the present application, the cross-section of the positive electrode film layer lies along the thickness direction of the electrode plate L. R1A50 of the particles have a particle size R1 that meets the requirement of ≥ 1000 nm within the aforementioned range. These particles exhibit high roundness, which improves particle sliding within the positive electrode film layer, reduces stress concentration during the compaction of the thickly coated film layer, and decreases the likelihood of film delamination due to local stress concentration during long cycles of the positive electrode film layer. This further improves the volumetric energy density of the lithium transition metal phosphate battery, mitigates the problem of battery cell capacity degradation, and extends the cycle life.

[0165] In some embodiments, the median value L R1A50the sphericity in the cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate between 0.65 and 0.75.

[0166] In some embodiments, the median value L R1A50 the sphericity in the cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate between 0.67 and 0.75.

[0167] In the cross-section of the positive electrode film layer along the thickness direction of the electrode plate lies the median value L R1A50the sphericity in the cumulative area distribution curve of the sphericity of particles with particle size R1, which fulfills R1 ≥ 1000 nm, in the range of 0.65 and 0.75 and further in the range of 0.67 and 0.75, which helps to further improve the cycle life of thick-coated lithium transition metal phosphate batteries.

[0168] In some embodiments, the median value is C 50 The degree of graphitization (C-value) in the cumulative distribution curve of the degree of graphitization of the positive electrode film layer is greater than or equal to 0.95 and less than or equal to 1.2, where the cumulative distribution curve of the degree of graphitization (C-value) is obtained in a surface scanning mode of a laser microconfocal Raman spectrometer. The degree of graphitization (C-value) is I G / I D , where I G a G-peak intensity of the Raman spectrum at 1580 ± 100 cm⁻¹ -1 and I Da D peak intensity of the Raman spectrum at 1350 ± 100 cm -1 represents.

[0169] In the present application, the cumulative distribution curve of the degree of graphitization (C-value) refers to a curve obtained by arranging at least 100 obtained C-values ​​in ascending order, with the degree of graphitization being the horizontal axis and the cumulative percentage being the vertical axis. 50 The C-value corresponds to the point where the cumulative number on the vertical axis of the cumulative distribution curve of the degree of graphitization is 50%. Compared to the point value, the median C-value can be... 50The graphitization degree reflects the overall graphitization degree of the particles in the positive electrode film layer, i.e., the degree of slippage. Compared to the mean value, it can reduce the influence of extreme values ​​during the test process and improve the reliability of the test results.

[0170] The graphitization degree (C-value) of the positive electrode film layer can be determined using the surface scanning mode of a laser microconfocal Raman spectrometer. As an example, a laser microconfocal Raman spectrometer (high-precision Renishaw laser microconfocal Raman spectrometer) is used, an excitation wavelength of 532 nm is selected, and a suitable amount of the positive electrode film layer is extracted to perform an area scan of its surface or a cross-section along the thickness direction of the electrode plate. The scanning area is 45 µm × 45 µm and is divided into 10 × 10 grids, with the grid vertices used as test points. The step size is 5 µm, and the total number of test points is 100. In this way, the C-values ​​at various locations and the cumulative distribution curve of the C-value in the surface scanning area are determined.In the present application, the positive electrode film layer can be either a freshly produced positive electrode film layer or one obtained from dismantling a battery. The surface of the positive electrode film layer obtained from dismantling a battery necessarily contains electrolyte salt particles. To improve test accuracy, an area scan of the cross-section of the positive electrode film layer is preferably performed along the thickness direction of the electrode plate to determine the degree of graphitization of the positive electrode film layer.

[0171] The graphitization degree (C-value) of the positive electrode film layer is determined by the ratio of the peak intensities of the G-tip (G-band) and the D-tip (D-band) in the Raman spectrum. The position of the G-tip is at 1580 ± 100 cm⁻¹. -1 and identifies the carbon sp2 -Hybrid structure. The position of the D-tip is at 1350±100 cm. -1 and denotes the disordered structure, where disorder means that the carbon atoms in the structure do not have a regular arrangement. In graphite crystals, carbon atoms in the same layer form sp 2 Hybridization involves covalent bonds, and the interlayer is bound by van der Waals forces, allowing the carbon to easily slide within the graphite structure. Therefore, the C value can characterize the degree of graphitization of the positive electrode film layer. It is understood that the degree of graphitization in the positive electrode film layer primarily stems from the carbon material within the positive electrode film layer undergoing graphitization treatment, i.e., the carbon material layer of the positive electrode active material. Although conductive carbon nanotubes with a high sp 2-Hybrid structure also has a relatively high I G / I D Due to its low additive content and small tube diameter, its addition to the positive electrode film layer shows an extreme value in the Raman area scanning test of the positive electrode film layer and has no influence on the degree of graphitization C. 50 in the positive electrode film layer. Therefore, the degree of graphitization of the positive electrode film layer can also be used to characterize the degree of graphitization of the positive electrode active material.

[0172] A person skilled in the art can adjust the degree of graphitization of the active material particles using any method known to them. For example, the degree of graphitization of the active material particles can be adjusted by regulating the carbon source, the sintering temperature, the sintering time, the sintering pressure, and the sintering atmosphere.

[0173] The higher the degree of graphitization of the carbon on the surface of the positive electrode active material, the higher the proportion of carbon with graphite structure in the positive electrode film layer and the easier the particles can slide in the coating layer with the help of the highly graphitized carbon structure, thereby reducing the stress concentration in the electrode plate.

[0174] In some embodiments, the median value C 50 The graphitization degree of the positive electrode film layer in the cumulative distribution curve of the graphitization degree C value, obtained by the surface scanning mode of the laser microconfocal Raman spectrometer, can be selected as 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 range of numbers in between.

[0175] In the embodiments of the present application, the median value C 50 of the graphitization degree within the aforementioned range, which helps to improve the sliding of particles in the positive electrode film layer, reduce the stress concentration during the compaction of the thickly coated film layer, and reduce the probability of film detachment due to local stress concentration during long cycles of the positive electrode film layer, thereby further mitigating the problem of battery cell capacity degradation while simultaneously improving the battery cycle life and the energy density of the battery volume.

[0176] In some embodiments, the median value is B 50of the coating value in the cumulative distribution curve of the coating value B of the positive electrode film layer between 0.30 and 0.60, wherein the cumulative distribution curve of the coating value B is obtained in the surface scanning mode of the laser microconfocal Raman spectrometer, wherein the coating value BI P / I D is, where I P the peak P intensity of the Raman spectrum at 948 ± 100 cm -1 and I D the D peak intensity of the Raman spectrum at 1350 ± 100 cm -1 represents.

[0177] The cumulative distribution curve of the coating value B is obtained by sorting at least 100 determined B-values ​​in ascending order; the coating B-value is plotted on the abscissa and the cumulative fraction on the ordinate. To reduce the influence of the extreme coating value, caused by the particle-free area in the positive electrode film layer, on the test results, the median value B is 50 The coating value is used to evaluate the density of the carbon material layer on the positive electrode active material. B 50 is the B-value, which corresponds to the 50% cumulative quantity share on the ordinate in the cumulative distribution curve of the coating value B.

[0178] In the present application, the coating value B of the positive electrode film layer can be determined by scanning with a laser microconfocal Raman spectrometer. As an example, a high-resolution Renishaw laser microscope confocal Raman spectrometer with an excitation wavelength of 532 nm is used. A representative sample of the positive electrode film layer is applied to its surface or to the cross-section along the thickness direction of the electrode plate. The area is scanned over a 45 µm × 45 µm region, which is subdivided into a grid of 10 × 10 sub-areas. The measurement points are located at the grid nodes with a step size of 5 µm, resulting in a total of 100 individual points. From the Raman spectra thus obtained, the B values ​​at each location as well as the cumulative distribution curve of the B values ​​over the entire scanned area are obtained.In the present application, the positive electrode film layer can be either a freshly produced positive electrode film layer or one obtained by dismantling a battery. The positive electrode film layer removed from a battery inevitably has electrolyte salt residues on its surface. To increase measurement accuracy, it is therefore recommended to perform an area scan in a cross-section of the positive electrode film layer along the thickness direction of the electrode plate to determine the coating value of the positive electrode film layer.

[0179] The coating value B of the positive electrode film layer is determined from the intensity ratio of the P-tip (P-band) and the D-tip (D-band) in the Raman spectrum, where the position of the P-tip is at 948 ± 100 cm⁻¹ -1 and identifies the PO4 3-Structure, with the position of the D-tip at 1350 ± 100 cm -1 lies and is a characteristic peak of the carbon material, which represents lattice defects or disordered structures in sp 2 -hybridized carbon atoms. During the test, an excitation wavelength of 532 nm is selected and the test depth is shallow. Therefore, in the test results of the positive electrode film layer obtained in the surface scanning mode of the laser microconfocal Raman spectrometer, the tip of the carbon structure showed a higher intensity than the tip of the phosphate structure.

[0180] Any method known to the art for adjusting the coating value of the active material particles is available to those skilled in the art. For example, the coating value can be adjusted by selectively choosing and varying the following parameters: the type of carbon source, the amount of carbon source added, sintering temperature, sintering time, sintering pressure, and sintering atmosphere. The coating value (B-value) can reflect the density of the carbon material layer on the surface of the lithium-containing transition metal phosphate particles. The denser the carbon material layer, the lower the phosphate structure strength detected in the Raman spectrum and the lower the coating value (B-value) of the positive electrode film layer.

[0181] In some embodiments, the positive electrode film layer also comprises a coating layer arranged on at least a portion of the surface of the lithium-containing transition metal phosphate particles. In the cumulative distribution curve of the coating value B obtained by the positive electrode film layer in the surface scanning mode of the laser microconfocal Raman spectrometer, the median value B can be determined. 50 The coating value can be selected as 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 numerical range in between.

[0182] If the median value B 50If the coating value of the positive electrode film layer lies within the above range, this means that the carbon material layer of the positive electrode active material is relatively dense and uniform. This has a positive effect on the uniformity of the sliding of the positive electrode film layer during rolling and reduces the stress concentration phenomenon in the thick positive electrode film layer. Furthermore, the dense and uniform carbon material layer allows the large particles in the positive electrode film layer to slide more easily during the compaction process, thereby reducing the stress concentration phenomenon on the large particles in the thick positive electrode film layer, decreasing the probability of the positive electrode film layer detaching, reducing battery capacity loss, and increasing the battery's cycle life.

[0183] In some embodiments, the lithium-containing transition metal phosphate particles comprise a compound represented by the formula: Li m Fe x P y O j Q q Formula 1 where Q comprises one or more of the following elements: Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl and Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4 and 0 ≤ q ≤ 0.1.

[0184] In some embodiments, m can be selected from the values ​​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 range in between; x can be selected from the values ​​0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or any range in between; y can be selected from the values ​​0.95, 0.96, 0.97, 0.98, 0.99, 1.00, or any numerical range in between; j can be selected from the values ​​3.5, 3.6, 3.7, 3.8, 3.9, 4, or any range of numbers in between; q can be selected from the values ​​0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range in between.

[0185] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise one or more from the group consisting of lithium iron phosphate, lithium manganese phosphate, fluorovantyllithium phosphate, lithium iron manganese phosphate and their modified materials.

[0186] In some embodiments, the lithium-containing transition metal phosphate particles in the positive electrode film layer comprise one or more from the group consisting of: lithium iron phosphate, their doped modified materials, and their coated modified materials.

[0187] In some embodiments, the iron leaching rate of the positive electrode material is between 658 ppm and 1921 ppm.

[0188] The iron leaching levels of the positive electrode material can be tested using a known technical procedure. For example, 7.5 g of powder of the positive electrode material, obtained by scraping a sample of the positive electrode film layer, are weighed out and added to 100.3 g of ascorbic acid solution with a mass concentration of 0.3% (the solvent is ultrapure water). After stirring for 305 minutes at 500 rpm, the solution is rapidly aspirated with a 5 mL syringe and filtered through a 0.45 µm pore filter into a test tube. 1 mL of the supernatant is aspirated with a pipette, transferred to a glass volumetric flask, and diluted 50-fold. The solution is then tested using an inductively coupled plasma mass spectrometer (ICP-OES) to determine the iron concentration.The iron leaching rate of the positive electrode material is calculated using the following formula: (ICP test iron concentration x solution volume / the mass of the solution involved in the volume determination) x 100.3 g / the mass of the powder of the positive electrode material, where the solution volume is 50 mL and the mass of the solution involved in the volume determination is 1 g.

[0189] In some embodiments, the iron leaching rate of the positive electrode material can be 658 ppm, 700 ppm, 800 ppm, 890 ppm, 900 ppm, 1000 ppm, 1058 ppm, 1076 ppm, 1100 ppm, 1143 ppm, 1200 ppm, 1236 ppm, 1300 ppm, 1311 ppm, 1384 ppm, 1349 ppm, 1400 ppm, 1485 ppm, 1500 ppm, 1531 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1921 ppm or any range of numbers in between.

[0190] In some embodiments, the iron leaching rate of the positive electrode material is between 658 ppm and 1485 ppm.

[0191] The iron dissolved in the positive electrode material originates primarily from the lithium-containing transition metal phosphate present in the positive electrode active material. The iron leaching rate depends on the number of lattice defects in the lithium-containing transition metal phosphate and on the integrity and density of the carbon material layer on the surface of the positive electrode active material. The lower the iron leaching rate, the fewer lattice defects the lithium-containing transition metal phosphate exhibits, which positively influences the reduction of lattice corrosion in a weakly acidic environment. The more complete and dense the carbon material layer on the surface of the positive electrode active material, the more strongly the leaching of iron ions is inhibited in a weakly acidic environment.The positive electrode material with an iron leaching ridge within the aforementioned area exhibits relatively few lattice defects and a complete and dense carbon material layer, which has a beneficial effect on improving the compressive strength and sliding behavior in the positive electrode film layer under high rolling pressure, increases the packing density of the positive electrode film layer and reduces the stress concentration in the positive electrode film layer, thereby improving the energy density of the battery and reducing the capacity loss of the battery.

[0192] In some embodiments, the mass content of titanium is between 500 ppm and 8000 ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0193] In some embodiments, the mass content of titanium is between 1000 ppm and 3000 ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0194] The types and concentrations of elements in the lithium-containing transition metal phosphate particles in the positive electrode film layer can be tested using all methods known in the art. For example, titanium and its concentration are tested by inductively coupled plasma optical emission spectrometry according to Annex C of GB / T 33822-2017.

[0195] In some embodiments, the mass fraction of titanium, based on the total mass of the lithium transition metal phosphate particles in the positive electrode film layer, can be selected as follows: 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm. 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm or any value in any of these ranges.

[0196] The introduction of titanium into lithium-containing transition metal phosphate particles requires the addition of a titanium source during the fabrication of the positive electrode active material. Titanium sources are often inert materials, and their adhesion to the surface of lithium-containing transition metal phosphate feedstocks can decrease reactivity and reduce particle size growth. Increasing the graphitization degree of the positive electrode active material often necessitates a higher sintering temperature or a longer sintering time. However, this also increases the particle size in the positive electrode film layer, raises the stress concentration of the positive electrode film layer, and causes the positive electrode film layer to degrade.In the embodiments of the present application, a high titanium content is added to the lithium-containing transition metal phosphate particles, thus reducing the reactivity of the starting materials for the synthesis of the positive electrode active material. This allows the proportion of large particles to be controlled while maintaining a high degree of graphitization of the positive electrode active material, reducing the voltage concentration in the positive electrode film layer and the probability of film detachment of the positive electrode film layer, thereby improving the energy density of the battery with regard to the battery's cycle life.

[0197] Simultaneously, doping the positive electrode active material with titanium is advantageous because it causes lattice distortion, reduces the Li-O bond energy, increases the lithium-ion transfer rate, and improves the battery's kinetic performance. Lithium-ion diffusion in the thick-coated film layer is uneven and often accompanied by a significant lithium-ion concentration gradient. The embodiments of the present application can improve the solid-phase transfer rate of the positive electrode active material by adding a high titanium content to the lithium-containing transition metal phosphate particles and reduce the kinetic problems of the battery with the thick electrode plate.

[0198] In some embodiments, the mass content of vanadium is between 500 ppm and 5000 ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0199] The types and concentrations of elements in the lithium-containing transition metal phosphate particles in the positive electrode film layer can be tested using all methods known in the art. For example, vanadium and its concentration are tested by inductively coupled plasma optical emission spectrometry according to Annex C of GB / T 33822-2017.

[0200] In some embodiments, the mass fraction of vanadium, based on the total mass of the lithium transition metal phosphate particles in the positive electrode film layer, can be selected as follows: 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, or any value within this range. Area.

[0201] In some embodiments, the mass content of vanadium is between 500 ppm and 3000 ppm based on the total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer.

[0202] The vanadium in the positive electrode film layer can exhibit various valence states. Among these, vanadium with a valence of +5 (V 5+ ) at the position of the phosphorus element. Due to its large radius, it can cause lattice distortions and widen the diffusion channel of lithium ions, thereby improving the ionic conductivity of the positive electrode active material and increasing the kinetic performance of the battery. Vanadium with a valence of +3 (V 3+The transition metal can be doped to create lithium vacancies through charge balancing, thereby improving the electronic conductivity of the positive electrode active material. Furthermore, the improved uniformity of the vanadium distribution within the lithium-containing transition metal phosphate particles contributes to further enhancing the kinetic performance and reaction uniformity of the positive electrode film layer, thereby improving the kinetic and cycle performance of the battery unit.

[0203] The vanadium mass content in the aforementioned area is beneficial for improving the kinetic performance of the positive electrode plate and the kinetic performance of the thick-coated lithium-containing transition metal phosphate battery. Simultaneously, the synergistic effect of titanium, vanadium, and carbon nanotubes in the positive electrode film layer promotes the formation of a stable three-dimensional network that enhances both electronic and ionic conductivity, thereby further increasing the kinetic performance of the thick-coated lithium-containing transition metal phosphate batteries.

[0204] In some embodiments, the positive electrode film layer further comprises a conductive medium, and the area fraction of an agglomerated region of the conductive medium is between 0.5% and 2.5%, based on the total area of ​​the cross-sectional area of ​​the positive electrode film layer along the thickness direction of the positive electrode plate.

[0205] In the present application, the area fraction of the agglomerated region of the conductive medium, relative to the total cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate, can be determined using the following method. A method similar to that described above is used to observe the cross-section of the positive electrode film layer along the thickness direction of the electrode plate through a scanning electron microscope, and the area of ​​the agglomerated region of the conductive medium in the scanning electron microscope image is measured at a magnification of 3000x. Since the conductive medium is generally carbon-based materials such as conductive carbon black or carbon nanotubes, it is visible under the high magnification of a scanning electron microscope.The agglomerated area of ​​the conductive material often appears as black agglomerates compared to other areas of the positive electrode film layer. Using image analysis software, the agglomerated area of ​​the conductive material is defined as the region in the scanning electron microscope image where the conductive material is clearly aggregated and appears black. Specifically, the scanning electron microscope image is imported into ImageJ at 3000x magnification, and the black agglomerated area of ​​the conductive material is masked out using a Feret value greater than or equal to 2 µm. The sum of the masked areas is counted and recorded as the area of ​​the agglomerated area of ​​the conductive material. The area fraction of the agglomerated area of ​​the conductive material corresponds to the ratio of the area of ​​the agglomerated area of ​​the conductive material to the total area of ​​the imported scanning electron microscope image.Three scanning electron microscope images are randomly selected whose areas do not overlap. The average area fraction of the agglomerated region of the conductive medium is calculated as 'area fraction of the agglomerated region of the conductive medium, relative to the total cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate'.

[0206] In some embodiments, the positive electrode film layer further comprises a conductive medium; the area fraction of the agglomerated region of the conductive medium, relative to the total area of ​​the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, can be set to a value such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.68%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.41%, 2.5%, or a value in any range between these values.

[0207] With respect to the total cross-sectional area of ​​the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of the agglomerated region of the conductive medium lies within the above range, indicating that the conductive medium is uniformly distributed in the positive electrode film layer and can easily form a uniform conductive network. This particularly helps to reduce the problem of kinetic degradation caused by the enlargement of the ion transfer path in the thickly coated film layer, to reduce local polarization and even lithium plating problems caused by the battery during the cycling process, and to improve the battery's cycle life.

[0208] Simultaneously, studies have shown that large particles in lithium-containing transition metal phosphate particles tend to rebound. The agglomerated area of ​​the conductive agent within the aforementioned region can suppress the rebound of the lithium-containing transition metal phosphate particles by means of the uniform distribution of the conductive agent, generate mechanical constraints on the particles and even the film layer, improve the cohesion of the film layer, reduce powder loss and film layer delamination, and extend the battery's cycle life.

[0209] In some embodiments, the positive electrode film layer further comprises a conductive medium, and the area fraction of an agglomerated region of the conductive medium is between 1.5% and 2.5%, based on the total area of ​​the cross-sectional area of ​​the positive electrode film layer along the thickness direction of the positive electrode plate.

[0210] In the embodiments of the present application, the area fraction of the agglomerated region of the conductive material lies further within the above range, indicating that the conductive material is more uniformly distributed in the positive electrode film layer and that its concentration is relatively low. This not only improves the kinetic performance of the positive electrode film layer but also helps to reduce the space occupied by excess conductive material in the positive electrode active material. This further improves the volume energy density of the battery and simultaneously enhances its kinetic performance.

[0211] In some embodiments, the conductor comprises carbon nanotubes, which are single-walled, thin-walled, and multi-walled carbon nanotubes.

[0212] In the present application, the term "carbon nanotube" refers to a nanomaterial with several to dozens of coaxial hollow tubes formed by coiling graphene layers connected by sp 2 Carbon nanotubes are formed by hybrid bonds between carbon atoms. Their diameter is typically in the range of a few to several tens of nanometers, and their length can range from micrometers to centimeters, indicating a high aspect ratio. Depending on the number of graphene layers, they can be classified as single-walled carbon nanotubes (SWCNTs), few-walled carbon nanotubes (FWCNTs), and multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes exhibit excellent electrical conductivity and a high modulus of elasticity.

[0213] Since carbon nanotubes have a one-dimensional structure, they can form a network structure within the positive electrode film layer. On the one hand, the high elastic modulus of carbon nanotubes allows their network structure to not only act as a bridge for voltage propagation but also to have a binding effect on the thickly coated positive electrode film layer. This prevents the rebound of lithium-containing transition metal phosphate particles, effectively mitigates the voltage concentration, reduces the risk of film delamination, and thus minimizes battery capacity loss. On the other hand, the excellent conductivity of carbon nanotubes makes their network structure an efficient electron transfer channel.Even in the event of local film detachment, the thick electrode plate can still maintain a high electron transfer efficiency in the in-plane direction and thickness direction, thereby delaying the onset of capacity loss and further improving the dynamic performance and cycle life of the battery.

[0214] In some embodiments, the positive electrode film layer can optionally also include the conductive carbon black.

[0215] The conductive carbon black has a high specific surface area and therefore good fluid retention capacity. The thick electrode plate exhibits a large expansion force during the cycle, which can easily force the electrolyte out. The distribution of the conductive carbon black in the positive electrode film layer helps to improve the fluid retention capacity of the thick electrode plate, further mitigating the phenomenon of battery capacity drop during the cycle and improving the battery's cycle life.

[0216] In some embodiments, the agglomerated region of the conductive medium comprises carbon nanotubes and the conductive carbon black.

[0217] Researchers discovered that carbon nanotubes, due to their high surface energy, tend to agglomerate, leading to an uneven distribution within the positive electrode film layer and an inability to form an effective carbon nanotube network structure. The surface energies of conductive carbon black and carbon nanotubes are relatively close and can be adsorbed onto the surface of carbon nanotubes to form a physical barrier. This increases resistance to carbon nanotube agglomeration, reduces direct contact between carbon nanotubes, and thus prevents agglomeration and improves the uniformity of carbon nanotube distribution within the positive electrode film layer. This, in turn, contributes to improving the conductivity of the thick positive electrode film layer and increasing the dynamic performance of the battery.On the other hand, it contributes to the binding effect of carbon nanotubes on the positive electrode film layer, reducing the risk of delamination of the thick positive electrode film layer and further improving the dynamic performance and cycle life of the battery. Furthermore, the agglomeration of carbon nanotubes in the agglomerated region of the conductor also leads to the blocking of local ion transfer pathways in this region. The combination with conductive carbon black can improve the lithium-ion transfer capacity of this region, reduce local polarization, and further enhance the cycle stability of the battery.

[0218] In some embodiments, the mass fraction C1 of the carbon nanotubes is 0 < C1 ≤ 2.5 % and the mass fraction C2 of the conductive carbon black is 0 < C2 ≤ 2.5 % based on the mass of the positive electrode film layer.

[0219] In some embodiments, the mass fraction C1 of the carbon nanotubes, based on the mass of the positive electrode film layer, is optionally 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%, or 2.5%, or in a range formed by any two of these values.

[0220] In some embodiments, the mass fraction C2 of the conductive carbon black, based on the mass of the positive electrode film layer, is optionally 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%, or 2.5%, or in a range formed by any two of these values.

[0221] The mass fraction of carbon nanotubes and conductive carbon black lies within the aforementioned range, which effectively mitigates the agglomeration of carbon nanotubes and forms a good conductive network structure, thereby effectively reducing the voltage concentration of the positive electrode film layer and improving the fluid retention rate of the positive electrode film layer during long cycles, further reducing the risk of film delamination and the degree of polarization, thus improving the kinetic performance of the battery, taking into account the capacity loss problem, and improving the cycle life of the battery.

[0222] In some embodiments, the positive electrode film layer further comprises a dispersing agent comprising hydrogenated nitrile butadiene rubber (HNBR).

[0223] HNBR is obtained by hydrogenating the double bonds of nitrile rubber. Its highly saturated main-chain structure gives it excellent oil resistance, heat resistance, and aging resistance. This allows it to remain stable when used as a dispersant in various environments and systems, making it less likely to degrade or decompose and thus enabling it to effectively exert its dispersing effect. The HNBR molecular chain contains both polar nitrile groups and nonpolar hydrocarbon segments. The polar nitrile group can interact with some polar substances or particle surfaces, for example, by adsorption onto the surface of dispersed particles through hydrogen bonding, electrostatic effects, etc.; the nonpolar hydrocarbon chain segments exhibit good lipophilicity and can stretch and disperse well in nonpolar or weakly polar media, so that the particles are dispersed uniformly in the medium.

[0224] When HNBR is adsorbed onto the surface of particles in the slurry, its long-chain molecules form a physical barrier around the particles, preventing them from approaching and aggregating. This allows the particles to remain relatively independent and dispersed within the system. Simultaneously, HNBR can reduce the surface tension between the dispersion medium and the dispersed particles, facilitating wetting and promoting particle dispersion. It can also reduce the interfacial energy between particles, thereby decreasing interfacial energy-driven particle aggregation.Furthermore, the elastic network structure of HNBR can mitigate the shrinkage stress caused by solvent volatilization during the drying of the slurry into a film, reduce the reaggregation of the conductor caused by capillary force in this process, decrease the area ratio of the agglomerated region of the conductor, and improve the dynamic performance and cycle life of the battery.

[0225] In some embodiments, the mass content of the dispersing agent, relative to the mass of the positive electrode film layer, is between 0.5% and 2%.

[0226] In some embodiments, the mass fraction of the dispersant relative to the mass of the positive electrode film layer is optionally 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5% or 2%, or a range formed by any two of these values.

[0227] The mass content of the dispersant is within the aforementioned range, which allows for a uniform dispersion of the particles in the positive electrode film layer, while simultaneously maintaining a high charge capacity of the positive electrode film layer, reducing the voltage concentration in the thickly coated positive electrode film layer made of lithium transition metal phosphate, and effectively alleviating the problem of battery capacity loss.

[0228] In some embodiments, the porosity of the positive electrode film layer is between 14% and 28%.

[0229] In the present application, the porosity of the positive electrode film layer can be tested as follows. The scanning electron microscope images of the positive electrode film layer, obtained as described above along the thickness direction of the electrode plate, are imported into the ImageJ software. The scale length contained in the image is marked using the line tool. Then, "Analyze Set Scale" is clicked, and the scale parameters are set in the software according to the scale length specified in the image. The rectangle tool is selected, and the image area outside the scale mark is selected. The selected area is copied using "Image Duplicate." The image format is converted using "Image Type 8-bit." "Analyze Set Measurements" is opened; the following five options are activated: "Area," "Mean gray value," "Area fraction," "Limit to threshold," and "Feret's diameter." The "Decimal places" value is set to 3.Next, select "Image" - "Adjust" - "Threshold" in sequence, and in the "Threshold" dialog, set the threshold values ​​to 0 and 100. Finally, export the pore data from the cross-sectional electron microscope images using the "Analyze-Measure" function. Use "Image" - "Overlay" - "Flatten" to export the pore image. Then, click "Apply" in "Threshold". Next, click "Analyze" - "Analyze Particles" and activate the first four columns on the left to obtain the pore statistics data.

[0230] It is understandable that in the embodiments of the present application, the "pores" in the cross-section of the positive electrode film layer are identified by using image color differences and threshold values. This "pore" is not the pore data obtained in the exhaust gas test, but is primarily used to characterize the distance between particles in the cross-section of the positive electrode film layer. This method is superior to the extraction method because the porosity obtained by the extraction method is related to the pores between the particles and the pores in the carbon material layer on the surface of the particles, and cannot objectively reflect the pores between the particles.

[0231] In some embodiments, the porosity of the positive electrode film layer can be set to 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or any range in between.

[0232] The porosity of the positive electrode film layer lies within the aforementioned range, and the positive electrode film layer exhibits good electrolyte wettability and tortuosity, which promotes the diffusion of lithium ions in the liquid and solid phases, contributes to reducing the concentration polarization of the thick electrode plate, and improves the battery's dynamic performance. Simultaneously, it helps to reduce the volume expansion of the thick-coated electrode plate during the cycle, decrease the mechanical stress on the film layer, and reduce the voltage concentration, thereby lowering the risk of film delamination of the thick-coated electrode plate.

[0233] Particularly in thick-coated pouch packaging batteries, the distance between the casing and the electrode plate is small, the volume coverage of the film layer is large, the electrolyte retention volume is reduced, and the porosity of the positive electrode film layer is within the aforementioned range, which helps to improve the liquid retention rate of the battery cell and improve the dynamic performance of the battery.

[0234] In some embodiments, the battery unit further comprises a separator 20 arranged between the positive electrode plate and the negative electrode plate. The separator 20 comprises a base film 201, a ceramic layer 202 arranged on at least one side of the base film 201, and a compound layer 203 arranged on the side of the ceramic layer 202 facing away from the base film 201. The compound layer 203 forms a continuous layer with a porous structure and comprises a vinylidene fluoride polymer.

[0235] In some embodiments, the battery unit further comprises the separator, which is arranged between the positive electrode plate and the negative electrode plate; the separator comprises a base film and a ceramic layer arranged on both sides of the base film, as well as a connecting layer arranged on at least one side of the ceramic layer facing away from the base film.

[0236] The ceramic layers arranged on both sides of the base film help to improve the stiffness of the pouch packaging battery and reduce local stress concentration.

[0237] In some embodiments, the battery unit further comprises the separator, which is arranged between the positive electrode plate and the negative electrode plate; the separator comprises the base film, the ceramic layer, which is arranged on both sides of the base film, and the bonding layer, which is arranged on both sides of the ceramic layer facing away from the base film.

[0238] In some embodiments, the vinylidene fluoride polymer comprises one or more of the following materials: polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).

[0239] In some embodiments, the vinylidene fluoride polymer comprises polyvinylidene fluoride (PVDF).

[0240] In the prior art, the separator's bonding layer is typically made with water-based PVDF, which has an island-like structure (see...). Fig.While this morphology offers space for the expansion of the battery cell and simplifies manufacturing, it leads to a smaller contact area between the separator's bonding layer and the electrode plate, and thus to a reduced adhesive force.

[0241] The embodiments of the present application provide a separator whose connecting layer is designed as a continuous layer with a porous structure (see Fig. and Fig. In comparison to the bonding layer in the prior art, the bonding layer has a significantly larger contact area with the electrode plate, resulting in a more uniform and stronger bond between the separator and the electrode plate. Furthermore, the contact area between the separator and the positive electrode film layer is maintained even upon rebound of the positive electrode film layer, thus significantly reducing the probability of film detachment.

[0242] It is understandable that the continuous compound layer can break and deform into a block structure due to contact or extrusion with the positive or negative electrode plate during the electrode plate manufacturing or circulation process. The continuous structure referred to in the present application means that the separator's compound layer is continuous at the microscopic level, for example, when viewed under a scanning electron microscope or an optical microscope. To reflect the true morphology of the separator, the sampling process preferably focuses on the area where the separator's compound layer is not in contact with the positive or negative electrode plate within the battery.For example, sampling is performed at a position on the separator behind the positive and negative electrode plates; or sampling is performed on the separator near the surface of the electrode array. The sampling area of ​​the separator exhibits less adhesion to the positive or negative electrode plate and can better reflect the actual condition of the separator.

[0243] Compared to wound battery cells, the extrusion between the separator and the electrode plates in the laminated battery cell is lower, and the separator and the electrode plate tend to shift relative to each other. This disturbs the film layer and makes it susceptible to powder loss or delamination. Furthermore, it can cause the positive and negative electrodes to overlap, increasing the risk of an internal short circuit in the battery cell. Therefore, the separator provided in the embodiments of the present application is particularly well suited for the laminated battery cell. The increased bond strength between the porous compound layer and the electrode plate helps to improve the bond strength between the separator and the electrode plates and to reduce the relative shift between them.This helps to reduce disturbance of the positive electrode film layer and the likelihood of film detachment, and also helps to reduce the risk of overlap of the positive and negative electrodes, which could cause a short circuit of the battery cell.

[0244] In summary, the selection of the vinylidene fluoride polymer in the compound layer of the embodiments of the present application from the aforementioned materials contributes to the formation of a continuous and uniform porous compound layer. Firstly, the bonding force between the compound layer and the electrode plate is improved and uniformly distributed, which helps to reduce the stress concentration in the thickly coated positive electrode film layer of the lithium-containing transition metal phosphate and to reduce the risk of film delamination, thereby further extending the cycle life of the battery.Secondly, the bonding layer is stably connected to the positive or negative electrode plate, which helps to reduce direct contact between the positive and negative electrode plates due to the relative displacement of the electrode film layer and the separator, thus decreasing the risk of an internal short circuit and improving the battery's safety performance. Thirdly, the porous bonding layer helps to maintain the separator's porosity, providing space for battery cell expansion and further extending the battery's lifespan.

[0245] In some embodiments, the base film material can be selected from at least one of the following materials: fiberglass, nonwoven fabric, polyethylene (PE) and polypropylene (PP).

[0246] In some embodiments, the ceramic layer comprises one or more of the following materials: aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), silicon oxide (SiO2) and boron nitride (BN).

[0247] Ceramic particles are flame-retardant and have a high hardness value. They are difficult to deform under heat and therefore exhibit excellent dimensional stability. The low thermal conductivity of ceramic materials can also prevent specific thermal leakage points in the battery from developing into a general thermal leakage, thus improving the safety performance of the battery unit.

[0248] In some embodiments, the thickness of the base film in the separator is between 7 µm and 9 µm.

[0249] In some embodiments, the thickness of the base film in the separator can be set to 7 µm, 7.5 µm, 8 µm, 8.5 µm, 9 µm or any range in between.

[0250] In some embodiments, the thickness of the ceramic layer on one side of the separator is between 2 µm and 4 µm.

[0251] In some embodiments, the one-sided thickness of the ceramic layer in the separator is optionally 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm or any value between these values.

[0252] In some embodiments, the one-sided thickness of the bonding layer in the separator is between 1 µm and 5 µm.

[0253] In some embodiments, the one-sided thickness of the compound layer in the separator is optionally 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 in a range formed by any two of these values.

[0254] The thickness of the compound layer is too thin, the cavity in the separator is small, and the bonding force between the separator and the electrode plate is low. On the one hand, the voltage increases after the film layer expands, increasing the probability of film delamination, which negatively impacts the battery's cycle life. On the other hand, the probability of a short circuit between the positive and negative electrodes increases, which in turn impairs the battery's safety performance. If the thickness of the compound layer is too great, it occupies a lot of space in the battery, thereby reducing the battery's volumetric energy density. In the embodiments of the present application, the thickness of the compound layer is within the aforementioned range, which helps to simultaneously improve the battery's cycle life, safety performance, and volumetric energy density.

[0255] In some embodiments, a base coating is provided in the lower region of the positive electrode film layer – near the positive electrode current collector. This base coating comprises a conductive agent and a binder, wherein the conductive agent comprises carbon nanotubes and conductive carbon black, and the binder comprises a vinylidene fluoride polymer.

[0256] In some embodiments, the thickness of the base coating is between 0.5 µm and 5 µm.

[0257] In some embodiments, the thickness of the base coating is 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 within a range formed by any two of these values.

[0258] The primer layer provided in the embodiments of the present application contributes to improving the bonding strength between the positive electrode film layer and the positive electrode current collector and to mitigating the voltage concentration phenomenon in the presence of large particles, thereby reducing the probability of detachment of the positive electrode film layer and improving the cycle stability of the battery. At the same time, compared to direct contact between the positive electrode current collector and the positive electrode film layer, the contact area between the primer layer and the positive electrode film layer is increased, which contributes to increasing the electron transfer area between the current collector and the positive electrode film layer, thereby reducing the internal resistance of the electrode plate and improving the dynamic performance of the battery.

[0259] In some embodiments, such as in Fig. As shown, the battery unit 5 comprises a casing 50, the laminated battery cell is housed in the casing 50, the casing 50 has the dimension along the longitudinal direction X L1, the dimension along the transverse direction Y W1 and the dimension along the thickness direction Z H1, where 450 mm ≤ L1 ≤ 1300 mm, 100 mm ≤ W1 ≤ 150 mm, 14 mm ≤ H1 ≤ 22 mm.

[0260] In some embodiments, L1 can optionally be 450 mm, 460 mm, 470 mm, 480 mm, 490 mm, 500 mm, 510 mm, 520 mm, 530 mm, 540 mm, 550 mm, 560 mm, 570 mm, 580 mm, 590 mm, 600 mm, 610 mm, 620 mm, 630 mm, 640 mm, 650 mm, 660 mm, 670 mm, 680 mm, 690 mm, 700 mm, 710 mm, 720 mm, 750 mm, 800 mm, 850 mm, 900 mm, 950 mm, 1000 mm, 1050 mm, 1100 mm, 1150 mm, 1200 mm, 1250 mm mm, 1300 mm, or any value range in between can be selected.

[0261] In some embodiments, W1 can be selected as 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm, or any range of values ​​in between.

[0262] In some embodiments, H1 can be selected as 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, or any range of values ​​in between.

[0263] In some embodiments, the dimension L1 of the shell along the longitudinal direction satisfies 450 mm ≤ L1 ≤ 650 mm.

[0264] If the longitudinal dimension L1 of the casing meets the criteria of 450 mm ≤ L1 ≤ 650 mm, the battery unit length is shorter. This helps to shorten the current diffusion path and reduce the internal resistance of the electrode plate, thereby reducing heat generation and improving the battery's dynamic performance. Furthermore, the shorter casing length contributes to shortening the electrolyte diffusion path during the infiltration process, improving the infiltration rate and electrolyte uniformity, further promoting the uniformity of lithium ion insertion and extraction during the cycle, reducing voltage concentrations, decreasing the risk of film delamination, and improving the cycle stability of the battery unit.

[0265] In some embodiments, the dimension L1 of the shell along the longitudinal direction satisfies 900 mm ≤ L1 ≤ 1300 mm.

[0266] If the dimension L1 of the casing along the longitudinal direction meets the condition 900 mm ≤ L1 ≤ 1300 mm, the battery unit length is longer, which helps to reduce the volume ratio of the casing within the battery and increase the charge ratio of the active material. Simultaneously, a longer battery unit can reduce the number of batteries required in the battery module, simplify the structural design of the battery module, decrease the number and complexity of structural components within the module, and thus improve the space utilization of the battery pack and further contribute to improving the volume energy density of the battery unit.

[0267] In some embodiments, such as in Fig. shown, the sleeve 50 consists of a pouch packaging material comprising an aluminum-plastic composite foil.

[0268] In some embodiments, the material of the casing comprises a composite film formed from aluminum and one or more of the following materials: polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET) and polyethylene (PE).

[0269] The pouch packaging material has a high degree of elongation, allowing its casing to be thinner and softer. This contributes to better space utilization within the battery unit and thus increases the battery's energy density. Furthermore, the high barrier properties of aluminum effectively reduce the ingress of water and oxygen into the battery, decrease electrolyte degradation and the oxidation level of the electrode material, and thus extend the battery's lifespan.

[0270] In some embodiments, the battery unit capacity at 25 °C is between 105 Ah and 300 Ah. In some embodiments, the battery unit capacity at 25 °C is between 150 Ah and 190 Ah.

[0271] Within the scope of this application, the capacity of the battery unit corresponds to the generally accepted term in the field; it can be determined using methods known from the technical literature. Example: The battery unit is charged to 3.65 V at a charging rate of 0.5 C, then charged to 0.05 C at a constant voltage of 3.65 V, allowed to rest for 10 minutes, and then discharged to 2.5 V at a discharge rate of 1 C. The discharge capacity of the battery unit is used as the capacity of the battery unit.

[0272] In some embodiments, the capacity of the battery cell at 25 °C can be 105 Ah, 107 Ah, 110 Ah, 115 Ah, 120 Ah, 125 Ah, 130 Ah, 135 Ah, 140 Ah, 145 Ah, 150 Ah, 155 Ah, 160 Ah, 161 Ah, 162 Ah, 163 Ah, 164 Ah, 165 Ah, 170 Ah, 175 Ah, 180 Ah, 182 Ah, 185 Ah, 190 Ah, 200 Ah, 210 Ah, 220 Ah, 230 Ah, 240 Ah, 250 Ah, 270 Ah, 280 Ah, 290 Ah, 300 Ah or any range in between.

[0273] A second aspect of the present application relates to a battery device comprising the battery unit provided by the first aspect of the present application.

[0274] The battery device provided for in the present application can be used in power-consuming devices that utilize the battery device as a power source, or in various energy storage systems that use the battery device as an energy storage element. Vehicles include, among others, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, ships, spacecraft, etc. Electric toys include, among others, stationary or mobile electric toys such as game consoles, electric toy cars, electric toy ships, and electric toy airplanes. Spacecraft include, among others, airplanes, rockets, space shuttles, and spacecraft.

[0275] A third aspect of the present application relates to a power-consuming device comprising at least one of the following: a battery unit, a battery module, and a battery pack. The battery unit, battery module, or battery pack can be used as a power source for the power-consuming device and also as an energy storage unit for the power-consuming device. The power-consuming device can be selected as a battery unit, battery module, or battery pack according to its usage requirements.

[0276] Fig.Figure 1 shows an example of a power-consuming device. The power-consuming device disclosed in the embodiments of the present application can be a fuel-powered vehicle, a gas-powered vehicle, or a vehicle powered by alternative energy. The alternative energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. A battery device is arranged inside the power-consuming device, and the battery device can be located at the bottom, the top, or the end of the power-consuming device. The battery device can be used to power a vehicle. For example, the battery device can serve as the operating current source for the vehicle.The power-consuming device may further comprise a regulator and a motor, the regulator being used to control the battery device in order to supply power to the motor, for example, to meet the power requirements of the power-consuming device during starting, navigation, and driving. In some embodiments of the present application, the battery device may serve not only as the operating power source of the vehicle but also as the propulsion power source of the vehicle, replacing fuel or natural gas wholly or partially to provide propulsion power for the vehicle.

[0277] A fourth aspect of the present application relates to an energy storage device that uses a battery device as a power source. The energy storage device may be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power plant, an energy storage battery pack, or a portable energy storage system. Examples of implementation

[0278] The embodiments described below are exemplary and serve only to illustrate the present application; they should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the technical literature or product instructions should be followed. All reagents and instruments used without manufacturer information are commercially available, conventional products. Exemplary embodiment 1(1) Preparation of the positive electrode active material

[0279] Lithium carbonate, iron phosphate, titanium dioxide, vanadium pentoxide, sucrose, glucose, and polyethylene glycol are dissolved in deionized water and mixed in a premixing tank. The molar ratio of lithium carbonate to iron phosphate is 1.025 : 1.0. Based on the total mass of the mixed raw materials, the mass content of sucrose is 2%, the mass content of glucose is 4%, and the mass content of polyethylene glycol is 5%. After homogeneous mixing, a mixed raw material with a solids content of 38% is obtained.

[0280] The particle size D V50 The particle size of lithium carbonate is 6 µm, the morphology of iron phosphate particles is spherical, titanium dioxide and vanadium pentoxide are both nanoparticles; the purity of sucrose is at least 98%, the water content of glucose is less than 0.5%, and the weight average molecular weight of polyethylene glycol is 1500.

[0281] The mixed raw materials are milled twice in a sand mill: first coarsely for one hour and then finely. During the milling process, the temperature of the slurry is regulated to below 40 °C to obtain a mixed slurry. The particle size D V50 The solid particle size in the mixed slurry is 0.45 µm. The mixed slurry is spray-dried to obtain a dry precursor powder. After drying, the particle size D is... 50 55.55 µm.

[0282] The precursor powder is subjected to a two-stage temperature-increase sintering process in a nitrogen atmosphere to obtain the positive electrode active material: first temperature increase: 2 °C / min from 25 °C to 450 °C, holding time 3 hours, and second temperature increase: 5 °C / min from 450 °C to 780 °C, holding time 12 hours, whereby the aeration volume in the heating stage was larger than in the constant temperature stage (in a ratio of 1.5 : 1) and the total aeration volume was 1350 cm³ 3 The throughput is / h, and the temperature is lowered after completion. Air jet milling results in a particle size D. V50 of the positive electrode active material made of lithium iron phosphate with the carbon material on the surface is achieved at 1.65 µm, with the mass content of Ti being 1050 ppm and the mass content of V being 950 ppm, based on the total mass of the positive electrode active material.

[0283] The above values ​​D 50 , D V50and D V90 refer to the data obtained using the Malvern laser scattering method. (2) Preparation of the positive electrode plate

[0284] The above-mentioned positive electrode active material, the conducting agent and the binder polyvinylidene fluoride are mixed in a solvent (N-methylpyrrolidone) in a mass ratio of 95 : 2 : 3 and thoroughly mixed, stirred and dispersed in a stirred tank to form a positive electrode slurry.

[0285] After the stirring process is complete, the positive electrode slurry is fed into the coating process. The conductive medium consists of conductive carbon black and multi-walled carbon nanotubes in a 1:1 ratio. The specific surface area of ​​the conductive carbon black is 80 m². 2The oil absorption of conductive carbon black is 180 mL / 100 g. The carbon nanotubes have an average length of 20 µm and a specific surface area of ​​280 m². 2 / G.

[0286] The positive electrode slurry is applied to an aluminum foil, dried and hot-pressed to form a positive electrode plate with a one-sided areal density of the positive electrode film layer of 0.38 g / 1540.25 mm². 2 and a packing density of 2.35 g / cm³ 3to obtain. The packing density here refers to that of the battery unit in its fully discharged state. The transfer coating speed is 20 m / min. The hot pressing process comprises three hot rolling operations, with the hot rolling pressure increasing successively to 40 tons, 60 tons, and 80 tons respectively; the hot rolling temperature is 60 °C, and the electrode plate is heated to 40 °C before the first entry into the hot rolling compaction.

[0287] The positive electrode plate is first cut into strips and then punched into the specified shape; the positive electrode plates punched in this way are then divided into groups according to their weight using a weighing and sorting system in order to be provided to the stacking robot for layering.

[0288] In the cross-section of the positive electrode film layer, along the thickness direction of the electrode plate, the cumulative area distribution curve of the sphericity of the particles with a particle size R1 that satisfies R1 ≥ 1000 nm shows the median value L R1A50 the sphericity of 0.689; the median value C 50 The degree of graphitization of the positive electrode film layer is 1.009; the median value B 50 The coating value B of the positive electrode film layer is 0.46; the iron dissolution rate of the positive electrode material is 974 ppm; 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 fraction of the agglomerated region of the conductive medium is 1.68%; and the porosity of the positive electrode film layer is 16.03%. (3) Preparation of the negative electrode plate

[0289] A mixture of synthetic and natural graphite (in a 1:1 weight ratio), conductive carbon black as a conductor, styrene-butadiene rubber (SBR) as a binder, and sodium carboxymethylcellulose (CMC) as a thickener is mixed uniformly in a ratio of 96:0.5:2.0:1.5 and mixed with deionized water. After stirring and dispersion, a negative electrode slurry is formed, which is then applied to a copper foil. After drying, compacting, cutting, and shaping the foil, a negative electrode plate is obtained.

[0290] The negative electrode plate is first cut into strips and then punched into the specified shape; the negative electrode plates punched in this way are then divided into groups according to their weight using a weighing and sorting system in order to be provided to the stacking robot for layering. (4) Separator

[0291] Polyvinylidene fluoride (PVDF) is dissolved in N-methylpyrrolidone (NMP), stirred thoroughly, and polyethylene glycol (PEG) is added as a pore-forming agent. The mixture is stirred and mixed thoroughly to obtain a solution of the bonding layer. This solution is applied to the base film with the ceramic layer on both sides, pre-evaporated at 80 °C, dried at 110 °C, and then immersed in deionized water to dissolve the PEG, resulting in a separator with a porous bonding layer.

[0292] The thickness of the base film is 8 µm, the thickness of the ceramic layer on one side is 3 µm, and the thickness of the bonding layer on one side is 1 µm. (5) Electrolyte

[0293] The organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed uniformly in a glove box with an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm).

[0294] Lithium hexafluorophosphate is then added and dissolved in an organic solvent to adjust the concentration of lithium hexafluorophosphate in the electrolyte to 1.05 mol / L. Vinylene carbonate (VC) is then added and stirred uniformly to obtain the electrolyte solution according to embodiment 1.

[0295] The mass fraction of the individual components relative to the total mass of the electrolyte is: Dimethyl carbonate 26%, Ethyl methyl carbonate 43.3%, Ethylene carbonate 17.3% and Vinylene carbonate 0.9%. (6) Preparing the battery

[0296] The positive electrode plate, the separator, and the negative electrode plate are stacked sequentially using a stacking machine. The separator must be able to insulate the positive and negative electrodes to create a laminated battery cell. The laminated battery cell is then glued to create a secure encapsulation. The laminated battery cell is then encased with adhesive in an outer packaging made of an aluminum-plastic foil pouch. This pouch consists of an inner layer of polypropylene, a middle layer of aluminum foil, and an outer layer of nylon. The outer packaging is die-cut from the aluminum-plastic foil and then formed and cut to the desired shape and size using a forming machine.The aluminum-plastic foil is then heat-sealed to ensure a minimum packaging tension of 25 N / 8 mm. The battery is vacuum-dried and allowed to settle, the electrolyte is injected using a flat-head needle, and then the battery is packaged. The pouch-packed battery is then incubated at 45 °C for 2 minutes at 90 kg / cm. 2 hot-pressed at 25 °C, 2 minutes and 90 kg / cm² 2 Cold-pressed. After the forming, vacuum extraction, and trimming processes, a battery unit is obtained. The battery unit has a longitudinal dimension of 600 mm, a width dimension of 125 mm, and a thickness dimension of 20 mm.

[0297] The manufacturing processes of embodiments 2-5 are basically the same as those of embodiment 1, with the exception that the manufacturing process of the positive electrode active material is adapted. Exemplary embodiment 2(1) Preparation of the positive electrode active material

[0298] Lithium dihydrogen phosphate, iron 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 are uniformly mixed in methanol and milled to obtain a blended raw material. The ratio of lithium dihydrogen phosphate to iron oxalate is such that the molar ratio of lithium to iron is 1.025:1.0. The particle size D10 of the iron oxalate is 6.5 µm, the particle size D50 is 62 µm, and the particle size D90 is 108 µm. The iron content by mass in the iron oxalate is 30.5%, and the content of the trivalent iron is 0.03% by mass.

[0299] The mixed raw materials are repeatedly ball-milled and demagnetized in a ball mill to obtain a mixed slurry. The milling time and number of milling passes are controlled to determine the particle size D. V50% of the mixed slurry should be ground to 3.15 µm.

[0300] The mixed slurry is spray-dried to obtain a dry precursor powder material, and the dry precursor powder material has a light yellow appearance and a uniform color.

[0301] The precursor powder is placed in a sintering furnace and heated under a nitrogen atmosphere from 25 °C to 360 °C at a rate of 2 °C / min, maintaining this temperature for 3.5 hours. The temperature is then increased to 780 °C at a rate of 5 °C / min and held at this temperature for 10 hours. The temperature is then reduced and the material is cooled. The titanium content is 1050 ppm and the vanadium content is 950 ppm, based on the total mass of the positive electrode active material.

[0302] The material obtained is crushed by air jet milling with a classification frequency of 21 Hz and a milling pressure of 0.54 MPa to obtain a positive electrode active material made of lithium iron phosphate with a carbon material provided on the surface.

[0303] The values ​​D10, D50, D90 and Dv50 mentioned above refer to the data obtained using the Malvern laser scattering method. (2) Preparation of the positive electrode plate

[0304] The aforementioned positive electrode active material, the conductive agent, and polyvinylidene fluoride as a binder are mixed in the solvent N-methylpyrrolidone in a mass ratio of 95:2:3 and thoroughly blended, stirred, and dispersed in a stirred tank to form a positive electrode slurry. After completion of the stirring process, the positive electrode slurry is fed into the coating process. The stirring process includes a pre-stirring and a main stirring stage, with the stirring speed being lower at 25 rpm during pre-stirring and 500 rpm during main stirring. The pre-stirring time is 15 minutes. The conductive agent consists of conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 1:1. The conductive carbon black has a specific surface area of ​​80 m². 2 / g and an oil absorption value of 180 mL / 100 g. The carbon nanotubes have an average length of 20 µm and a specific surface area of ​​280 m². 2 / G.

[0305] The positive electrode slurry is applied to an aluminum foil, dried and hot-pressed to form a positive electrode plate with a one-sided areal density of the positive electrode film layer of 0.38 g / 1540.25 mm². 2 and a packing density of 2.35g / cm³ 3 to obtain. The packing density here refers to that of the battery unit in its fully discharged state.

[0306] The hot pressing process comprises three hot rolling pressing operations, and the hot rolling pressure increases successively to 35 tons, 55 tons and 75 tons respectively; the hot rolling temperature is 65 °C, and before the first entry into the hot rolling compaction, the electrode plate is heated to 50 °C.

[0307] The positive electrode plate is first cut into strips and then punched into the specified shape; the positive electrode plates punched in this way are then divided into groups according to their weight using a weighing and sorting system in order to be provided to the stacking robot for layering. Exemplary embodiment 3(1) Preparation of the positive electrode active material

[0308] Lithium carbonate, iron phosphate, sucrose, glucose, titanium dioxide and vanadium pentoxide are introduced into water and mixed in a premixing tank at a speed of 1800 rpm, the ratio of lithium carbonate and iron phosphate being chosen such that the molar ratio of iron to phosphorus is 0.97, the mass content of glucose is 3.8% based on iron phosphate and the mass content of sucrose is 1.9% based on iron phosphate.

[0309] The mixed raw materials are milled twice in a sand mill, the first milling being carried out using zirconium dioxide spheres with a diameter of 0.6 mm at a rotational speed of 500 rpm for 1 hour and a milling chamber pressure of less than 0.3 MPa, and the second milling being carried out to obtain a mixed slurry, with a particle size D V 50 of the mixed slurry is 0.435 µm.

[0310] The mixed slurry is spray-dried to obtain a precursor powder.

[0311] The precursor powder is sintered to obtain a positive electrode material made of lithium iron phosphate. The sintering process includes: First sintering: The precursor powder is sintered in a nitrogen atmosphere, heated from 25 °C to 765 °C at a heating rate of 5 °C / min, held at this temperature for 10 hours and then cooled to obtain the first sintered product. Grinding and mixing: To the first sintered product, 0.5% sucrose, 1% glucose, and 3.0% polyethylene glycol—each based on the total mass of the first sintered product—are added. The mixed material is then divided into two groups and subjected to a third grinding stage, which is stopped when the D V50 the particle size in the first group reaches 1.02 µm (grinding conditions: 550 rpm with a grinding time of 1 hour) to obtain a first group of ground products, and as the D V50The particle size in the second group is reduced to 0.42 µm (grinding conditions: 500 rpm with a grinding time of 4 hours) to obtain a second group of ground products. The second group of ground products and the first group of ground products are mixed in a mass ratio of 70:30 to obtain the intermediate product, which is then spray-dried. Second sintering: The dried mixed intermediate product is sintered in a nitrogen atmosphere, heated from 25 °C to 800 °C at a heating rate of 5 °C / min and held at this temperature for 10 hours. After cooling, a second sintered product is obtained.

[0312] After sintering, the second sintered product is cooled to below 100 °C and comminuted by air jet milling to obtain a positive electrode active material made of lithium iron phosphate with a carbon material applied to the surface. Air jet milling is performed at a classification frequency of 23 Hz and a milling pressure of 0.55 MPa. The titanium dioxide (Ti) content is 1050 ppm and the vanadium (V) content is 950 ppm by mass, based on the total mass of the positive electrode active material. (2) Preparation of the positive electrode plate

[0313] The aforementioned positive electrode active material, the conductive agent, and polyvinylidene fluoride as a binder are mixed in the solvent N-methylpyrrolidone in a mass ratio of 95:2:3 and thoroughly blended, stirred, and dispersed in a stirred tank to form a positive electrode slurry. After completion of the stirring process, the positive electrode slurry is fed into the coating process. The stirring process includes a pre-stirring and a main stirring stage, with the stirring speed being lower at 25 rpm during pre-stirring and 500 rpm during main stirring. The pre-stirring time is 15 minutes. The conductive agent consists of conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 1:1. The conductive carbon black has a specific surface area of ​​80 m². 2 / g and an oil absorption value of 180 mL / 100 g. The carbon nanotubes have an average length of 20 µm and a specific surface area of ​​280 m². 2 / G.

[0314] The positive electrode slurry is applied to an aluminum foil, dried and hot-pressed to form a positive electrode plate with a one-sided areal density of the positive electrode film layer of 0.39 g / 1540.25 mm². 2 and a packing density of 2.36 g / cm³ 3 to obtain. The packing density here refers to that of the battery unit in its fully discharged state. Drying takes place at a temperature of 95 °C and a speed of 2.0 m / min.

[0315] The hot pressing process comprises three hot rolling pressing operations, and the hot rolling pressure increases successively to 35 tons, 55 tons and 75 tons respectively; the hot rolling temperature is 65 °C, and before the first entry into the hot rolling compaction, the electrode plate is heated to 50 °C.

[0316] The positive electrode plate is first cut into strips and then punched into the specified shape; the positive electrode plates punched in this way are then divided into groups according to their weight using a weighing and sorting system in order to be provided to the stacking robot for layering. Example 4

[0317] The manufacturing process of embodiment 4 is essentially the same as that of embodiment 1. The difference from embodiment 1 is that the manufacturing process of the positive electrode active material differs slightly. The specific differences include: (1) The carbon sources in the mixed raw material are sucrose and glucose. The mass of sucrose is 2 wt% compared to the mass of iron phosphate and the mass of glucose is 5.7 wt% compared to the mass of iron phosphate. (2) The heating and sintering process differs. The precursor powder is sintered at least twice in a nitrogen atmosphere, with the first sintering temperature being 750 °C and the holding time being 8 hours, in order to obtain a primary sintered product.

[0318] To the primary calcined product, 1.5 wt% (based on the mass of the primary calcined product) of glucose, 3.0 wt% (based on the mass of the primary calcined product) of polyethylene glycol, titanium dioxide, and vanadium pentoxide are added. After uniform milling, the product is divided into two groups for secondary milling. The milling parameters of the two groups are different. V50 The particle size is adjusted to 2.0 µm after grinding the first group, and D V50The particle size is adjusted to 0.35 µm after milling the second group. The milled particles from the first and second groups are mixed in a mass ratio of 30:70, spray-dried, and sintered a second time. The second sintering temperature is 800 °C and is maintained at this temperature for 10 hours.

[0319] The mass content of titanium is 1050 ppm and the mass content of vanadium is 950 ppm, based on the total mass of the positive electrode active material.

[0320] (3) The positive electrode slurry is applied to an aluminium foil, dried and hot-pressed to form a positive electrode plate with a one-sided areal density of the positive electrode film layer of 0.39 g / 1540.25 mm² 2 and a packing density of 2.36 g / cm³ 3to obtain. Packing density here refers to the packing density in the fully discharged state of the battery unit. Drying takes place at a temperature of 95 °C and a speed of 2.0 m / min.

[0321] The hot pressing process comprises three hot rolling pressing operations, and the hot rolling pressure increases successively, reaching 35 tons, 55 tons and 70 tons respectively; the hot rolling temperature is 65 °C, and before the first entry into the hot rolling compaction, the electrode plate is heated to 50 °C. Example 5

[0322] The manufacturing process of embodiment 5 is essentially the same as that of embodiment 1. The difference from embodiment 1 lies in the fact that the sintering process of the positive electrode active material and the hot pressing process of the positive electrode plate are different. In detail: (1) The precursor powder is subjected to a two-stage temperature-increase sintering process in a nitrogen atmosphere to obtain the positive electrode active material: first temperature increase: 2 °C / min from 25 °C to 440 °C, holding time 2.5 hours, and second temperature increase: 5 °C / min from 440 °C to 760 °C, holding time 11 hours. The particle size Dv is reduced by air jet milling. 50 The surface thickness of the positive electrode active material, lithium iron phosphate, with the carbon material on the surface, is 1.6 µm. Air jet milling then takes place below this surface at a classification frequency of 25 Hz and a milling pressure of 0.55 MPa. (2) The positive electrode slurry is applied to an aluminium foil, dried and hot-pressed to form a positive electrode plate with a one-sided areal density of the positive electrode film layer of 0.39 g / 1540.25 mm² 2 and a packing density of 2.35 g / cm³ 3to obtain. Packing density here refers to the packing density in the fully discharged state of the battery unit. The transfer coating speed is 20 m / min.

[0323] The hot pressing process comprises three hot rolling pressing operations, and the hot rolling pressure increases successively to 45 tons, 60 tons and 80 tons respectively; the hot rolling temperature is 60°C, and before the first entry into the hot rolling compaction, the electrode plate is heated to 40°C. Example 6

[0324] The manufacturing process of embodiment 6 is essentially the same as that of embodiment 2. The difference from embodiment 2 is that, in preparing the positive electrode plate, the aforementioned positive electrode active material, the conducting agent, and the binder polyvinylidene fluoride are uniformly mixed in the solvent, N-methylpyrrolidone, in a mass ratio of 94.52 : 1.99 : 2.99. Subsequently, 0.5% by mass of the dispersing agent HNBR is added, based on the total mass of the positive electrode active material, the conducting agent, the binder polyvinylidene fluoride, and the dispersing agent. The mixture is thoroughly mixed, stirred, and dispersed in a stirred tank to form a positive electrode slurry, as shown in Table 1 for details. Example 7

[0325] The manufacturing process of embodiment 7 is essentially the same as that of embodiment 6. The difference from embodiment 6 is that, in preparing the positive electrode plate, the aforementioned positive electrode active material, the conductive agent, and the binder polyvinylidene fluoride are first uniformly mixed in N-methylpyrrolidone as a solvent in a mass ratio of 93.57 : 1.97 : 2.96. Subsequently, 1.5% by mass of the dispersant HNBR is added, based on the total mass of the positive electrode active material, the conductive agent, the binder polyvinylidene fluoride, and the dispersant, as shown in Table 1 for details. Example 8

[0326] The manufacturing process of embodiment 8 is essentially the same as that of embodiment 1. The difference from embodiment 1 is that during the preparation of the positive electrode plate, the coating weight is adjusted and the parameters such as hot rolling pressure, hot rolling temperature, speed of the transfer coating and the heating temperature before the first hot rolling compaction are adaptively adjusted so that the one-sided areal density of the positive electrode film layer obtained by cold pressing is 0.43 g / 1540.25 mm². 2 The thickness of the battery is adjusted accordingly, while the number of positive electrode plates, separators, and negative electrode plates remains unchanged. Example 9

[0327] The manufacturing process of embodiment 9 is essentially the same as that of embodiment 1. The difference from embodiment 1 is that during the preparation of the positive electrode plate, the coating weight is adjusted and the parameters such as hot rolling pressure, hot rolling temperature, speed of the transfer coating and the heating temperature before the first hot rolling compaction are adaptively adjusted so that the one-sided areal density of the positive electrode film layer obtained by cold pressing is 0.26 g / 1540.25 mm². 2 The thickness of the battery is adjusted accordingly, while the number of positive electrode plates, separators, and negative electrode plates remains unchanged. Example 10

[0328] The manufacturing process of embodiment 10 is essentially the same as that of embodiment 1. The difference from embodiment 1 is that the aforementioned positive electrode active material, the conductive agent, and the binder polyvinylidene fluoride are mixed in a mass ratio of 95.48 : 1.5 : 3.02 in N-methylpyrrolidone as a solvent and thoroughly mixed, stirred, and dispersed in a stirred tank to form a positive electrode slurry. After completion of the stirring process, the positive electrode slurry is fed to the coating process. The conductive agent comprises conductive carbon black and multi-walled carbon nanotubes in a mass ratio of 0.5 : 1. Example 11

[0329] The manufacturing process of embodiment 11 is essentially the same as that of embodiment 1. The difference from embodiment 1 is that the parameters such as hot rolling pressure, hot rolling temperature, speed of the transfer coating and heating temperature are adjusted before the first hot rolling compaction in order to produce the positive electrode plate with a one-sided areal density of 0.38 g / 1540.25 mm². 2 and a packing density of 2.55 g / cm³ 3 to obtain. Here, packing density refers to the packing density in the fully discharged state of the battery unit. The thickness of the battery is specifically adjusted, while the number of positive electrode plates, separators, and negative electrode plates remains unchanged. Comparative example 1

[0330] The manufacturing process of comparative example 1 is fundamentally the same as that of embodiment 1. The difference lies in the sintering process of the positive electrode active material. Specifically: The precursor powder is sintered in a nitrogen atmosphere using a two-stage temperature program to obtain the positive electrode active material: heating from 25 °C to 500 °C at 2 °C / min, holding time 3.5 hours (first heating phase), and heating from 500 °C to 800 °C at 5 °C / min, holding time 13 hours (second heating phase). Air jet milling achieves a particle size Dv50 of 1.6 µm for the positive electrode active material, which consists of lithium iron phosphate with the carbon material on the surface. This air jet milling is performed at a classification frequency of 25 Hz and a milling pressure of 0.55 MPa. Comparative example 2

[0331] The manufacturing process of Comparative Example 2 is essentially the same as that of Comparative Example 1. The difference from Comparative Example 1 lies in the preparation of the positive electrode plate: the aforementioned positive electrode active material, the conductive agent, and the binder polyvinylidene fluoride are first homogeneously dispersed in N-methylpyrrolidone as a solvent in a mass ratio of 93.57 : 1.97 : 2.96. Subsequently, hydrogenated nitrile butadiene rubber (HNBR) is added as a dispersant at a mass fraction of 1.5%, based on the total mass of the positive electrode active material, conductive agent, polyvinylidene fluoride, and dispersant. Comparative example 3

[0332] The manufacturing process of Comparative Example 3 is essentially the same as that of Comparative Example 1. The difference from Comparative Example 1 is that, during the preparation of the positive electrode plate, the coating weight is adjusted so that the one-sided areal density of the positive electrode film layer obtained by cold pressing is 0.24 g / 1540.25 mm². 2 the thickness of the battery is adjusted accordingly, while the number of positive electrode plates, separators and negative electrode plates remains unchanged. Test procedure 1. Battery unit capacity

[0333] The battery unit is charged at 25 °C at 0.5 C of its nominal capacity up to 3.65 V, then recharged at a constant voltage of 3.65 V up to 0.05 C, left to rest for 10 minutes, then discharged at 1 C to 2.5 V, and left to rest for another 10 minutes. The capacity C transferred during the discharge process is determined using the formula C = I*t (in Ah). 2. Number of cycles until capacity drops to 80%

[0334] The battery unit is charged at 25°C at 0.5C of its nominal capacity up to 3.65V, then recharged at a constant voltage of 3.65V up to 0.05C, left to rest for 10 minutes, then discharged at 1C to 2.5V, and left to rest for another 10 minutes. This process constitutes one cycle. The test continues until the battery capacity drops to 80% of its nominal capacity; the corresponding number of cycles is recorded as @80% SOH. Test results

[0335] The test results of the above embodiments and comparison examples are summarized in Table 1 and Table 2. Table 1 Positive electrode film layer battery Single-sided surface density g / 1540.25 mm 2 Packing density (g / cm³) 3) Area fraction of particles with particle size R1 that meets the requirement of R1 ≥1000 nm Uniformity of the distribution of particles with particle size R1, which fulfills R1 ≥1000 nm Dispersant type Dispersant content @80%SOH(cycles) Capacity (Ah) Example 1 0,38 2,35 36,83 % 1,9 % / / 2018 162 Example 2 0,38 2,35 34,89 % 0,99 % / / 2087 163 Example 3 0,39 2,36 34,97 % 1,47 % / / 2084 164 Example 4 0,39 2,36 49,99 % 4,91 % / / 1990 163 Example 5 0,38 2,35 12,11 % 1,82 % / / 2049 161 Example 6 0,38 2,35 34,93 % 0,45 % HNBR 0,5 % 2120 162 Example 7 0,38 2,35 34,88 % 0,24 % HNBR 1,5 % 2135 161 Example 8 0,43 2,35 36,92 % 1,98 % / / 2012 182 Example 9 0,26 2,35 36,75 % 1,81 % / / 2025 107 Example 10 0,38 2,35 36,73 % 1,85 % / / 2003 162 Example 11 0,38 2,55 36,87 % 1,94 % / / 2009 161 Comparative example 1 0,39 2,36 56,75 % 5,58 % / / 1899 162 Comparative example 2 0,39 2,36 56,81 % 4,50 % HNBR 1,5 % 1908 162 Comparative example 3 0,24 2,35 36,81 % 1,87 % / / 2016 101

[0336] From the comparison between the exemplary embodiments and the comparative examples, it can be seen that the battery unit comprises a laminated battery cell, wherein the laminated battery cell comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises lithium-containing transition metal phosphate particles with a carbon material arranged at least partially on the surfaces of the lithium-containing transition metal phosphate particles. The packing density of the positive electrode plate in a fully charged state of the battery unit is between 2.3 g / cm³. 3 and 2.6 g / cm³ 3 , the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2and 0.45 g / 1540.25 mm 2 Based on the total surface area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets the criteria of R1 ≥ 1000 nm lies between 12% and 50%. Furthermore, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the uniformity of the distribution of particles with a particle size R1 that meets the criteria of R1 ≥ 1000 nm is less than or equal to 5%. This improves the long-term cycle stability of the battery while maintaining good capacity of the battery unit.

[0337] From the comparison between embodiments 1-3 and embodiments 4-5, it can be seen that, with reference to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is still in the range of 12% to 37%, which contributes to further improving the capacity and long-term cycle stability of the battery.

[0338] From the comparison between embodiment 4 and embodiments 1-3, 5-11, and between embodiment 2 and embodiments 6-7, it can be seen that in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the uniformity of the distribution of particles with a particle size R1, which fulfills R1 ≥ 1000 nm, is in the range of 0.2%-2% and further in the range of 0.2%-0.9%, which contributes to further improving the long-term cycle stability of the battery.

[0339] From the comparison between embodiment 1 and embodiments 8-9, it can be seen that the one-sided coating area density of the positive electrode film layer is further in the range of 0.3 g / 1540.25 mm². 2 up to 0.45 g / 1540.25 mm 2 and further in the range of 0.35 g / 1540.25 mm 2 up to 0.4 g / 1540.25 mm 2This helps to further balance battery capacity and long-term cycle stability. Table 2 C1 C2 Area share of the agglomerated area of ​​the guideline @80%SOH(cycles) Example 1 1 % 1 % 1,68 % 2018 Example 10 1 % 0,5 % 2,41 % 2003

[0340] From the comparison between embodiment 1 and embodiment 10, it can be seen that, with respect to the total area of ​​the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of the agglomerated region of the conductive medium is in the range of 0.5%-2.5% and further in the range of 1.5%-2.5%, which contributes to further improving the long-term cycle stability of the battery.

[0341] It should be noted that the present application is not limited to the embodiments mentioned above. The aforementioned embodiments are merely exemplary, and all embodiments that exhibit essentially the same structure and effect as the technical teaching in the sense of the present technical solution also fall within the scope of protection of the present application. Furthermore, embodiments obtained by modifications of the described embodiments, as well as by combining individual features from different embodiments, without departing from the spirit of the present application, are also included.

Claims

[1] Battery unit comprising a laminated battery cell, wherein the laminated battery cell comprises a positive electrode plate and a negative electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprising lithium-containing transition metal phosphate particles with a carbon material arranged at least partially on surfaces of the lithium-containing transition metal phosphate particles; the packing density of the positive electrode plate in a fully charged state of the battery unit is between 2.3 g / cm² 3 and 2.6 g / cm³ 3 lies; where the one-sided areal density of the positive electrode film layer is between 0.25 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2lies, with the one-sided areal density of the positive electrode film layer optionally between 0.3 g / 1540.25 mm² 2 and 0.45 g / 1540.25 mm 2 and optionally between 0.35 g / 1540.25 mm 2 and 0.4 g / 1540.25 mm 2 lies; wherein, with reference to the total area of ​​particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of particles with a particle size R1 that meets R1 ≥ 1000 nm is between 12% and 50%, preferably between 12% and 37%; wherein the uniformity of the distribution of the particles with particle size R1, which satisfies R1 ≥ 1000 nm, in the cross-section of the positive electrode film layer along the thickness direction of the electrode plate is less than or equal to 5%, optionally between 0.2% and 2%, and further optionally between 0.2% and 0.9%. [2] Battery unit according to claim 1, wherein the one-sided thickness H of the positive electrode film layer is between 70 µm and 120 µm, wherein the thickness H is optionally between 90 µm and 120 µm and further optionally between 100 µm and 120 µm. [3] Battery unit according to claim 1 or 2, wherein in a cross-section of the positive electrode film layer along the thickness direction of the electrode plate a cumulative area distribution curve of the sphericity of particles with a particle size R1 that satisfies R1 ≥ 1000 nm, the median value L R1A50 the sphericity lies between 0.6 and 0.8, optionally between 0.65 and 0.75 and further optionally between 0.67 and 0.75; and / or wherein in a cumulative distribution curve of the graphitization degree C-value of the positive electrode film layer the median value C 50the degree of graphitization is greater than or equal to 0.95 and less than or equal to 1.2, wherein the cumulative distribution curve of the degree of graphitization C-value is obtained in a surface scanning mode of a laser microconfocal Raman spectrometer, where the degree of graphitization C-value I G / I D is, where I G a G-peak intensity of the Raman spectrum at 1580 ± 100 cm⁻¹ -1 and I D a D peak intensity of the Raman spectrum at 1350 ± 100 cm -1 represents. [4] Battery unit according to one of claims 1 to 3, wherein in a cumulative distribution curve of the coating value B of the positive electrode film layer the median value B 50 of the coating value lies between 0.30 and 0.60, wherein the cumulative distribution curve of the coating value B is obtained in a surface scanning mode of a laser microconfocal Raman spectrometer, where the coating value BI P / I Dis, where I P a peak P intensity of the Raman spectrum at 948 ± 100 cm -1 and I D the D peak intensity of the Raman spectrum at 1350 ± 100 cm -1 represents. [5] Battery unit according to any one of claims 1 to 4, wherein the lithium-containing transition metal phosphate particles comprise a compound represented by the formula: Li m Fe x P y O j Q q where Q comprises one or more of the following elements: Al, Na, K, Mg, Cu, Mn, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl and Br, 0.8 ≤ m ≤ 1.15, 0.9 ≤ x ≤ 1, 0.95 ≤ y ≤ 1, 3.5 ≤ j ≤ 4 and 0 ≤ q ≤ 0.

1. Formula I, [6] Battery unit according to claim 5, wherein the iron leaching rate of the positive electrode material is between 658 ppm and 1921 ppm, optionally between 658 ppm and 1485 ppm. [7] Battery unit according to claim 5 or 6, wherein the mass content of titanium, based on a total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer, is between 500 ppm and 8000 ppm, optionally between 1000 ppm and 3000 ppm. [8] Battery unit according to one of claims 5 to 7, wherein the mass content of vanadium based on a total mass of the lithium-containing transition metal phosphate particles in the positive electrode film layer is between 500 ppm and 5000 ppm, optionally between 500 ppm and 3000 ppm. [9] Battery unit according to one of claims 1 to 8, wherein the positive electrode film layer further comprises a conductive medium, wherein, with respect to a total area of ​​the cross-section of the positive electrode film layer along the thickness direction of the electrode plate, the area fraction of an agglomerated region of the conductive medium is between 0.5% and 2.5%, optionally between 1.5% and 2.5%. [10] Battery unit according to claim 9, wherein the conductor comprises carbon nanotubes which are single-walled, thin-walled and multi-walled carbon nanotubes, wherein the conductor optionally comprises conductive carbon black. [11] Battery unit according to claim 9 or 10, wherein the agglomerated region of the conductive medium further comprises carbon nanotubes and conductive carbon black. [12] Battery unit according to claim 11, wherein, with reference to the mass of the positive electrode film layer, the mass fraction C1 of the carbon nanotubes and the mass fraction C2 of the conductive carbon black satisfy 0 < C1 ≤ 2.5 % and 0 < C2 ≤ 2.5 % respectively. [13] Battery unit according to any one of claims 1 to 12, wherein the positive electrode film layer further comprises a dispersing agent comprising hydrogenated nitrile butadiene rubber (HNBR). [14] Battery unit according to claim 13, wherein the mass content of the dispersing agent is between 0.5% and 2%, based on the mass of the positive electrode film layer. [15] Battery unit according to any one of claims 1 to 14, wherein the porosity of the positive electrode film layer is between 14% and 28%. [16] Battery unit according to any one of claims 1 to 15, wherein the battery unit further comprises a separator arranged between the positive electrode plate and the negative electrode plate, wherein the separator comprises a base film, a ceramic layer arranged on both sides of the base film, and a bonding layer arranged on at least one side of the ceramic layer facing away from the base film, wherein the bonding layer forms a continuous layer with a porous structure and comprises a vinylidene fluoride polymer. [17] Battery unit according to claim 16, wherein the separator meets at least one of the following conditions: (1) wherein the thickness of the base film is between 7 µm and 9 µm; (2) wherein the thickness of the ceramic layer on one side is between 2 µm and 4 µm; (3) wherein the thickness of the compound layer on one side is between 1 µm and 5 µm. [18] Battery unit according to any one of claims 1 to 17, wherein the positive electrode film layer in a bottom region near the positive electrode current collector is provided with a primer layer, wherein the primer layer meets at least one of the following conditions: (1) wherein the primer layer comprises a conductive agent and a binder, wherein the conductive agent comprises carbon nanotubes and conductive carbon black and the binder comprises a vinylidene fluoride polymer; (2) wherein the thickness of the primer layer is between 0.5 µm and 5 µm. [19] Battery unit according to any one of claims 1 to 18, wherein the battery unit comprises a casing, wherein the laminated battery cell is housed in the casing, wherein the casing has a dimension along the longitudinal direction L1, a dimension along the transverse direction W1 and a dimension along the thickness direction H1, wherein 450 mm ≤ L1 ≤ 1300 mm, 100 mm ≤ W1 ≤ 150 mm, and 14 mm ≤ H1 ≤ 22 mm. [20] Battery unit according to claim 19, wherein the dimension L1 of the casing along the longitudinal direction satisfies 450 mm ≤ L1 ≤ 650 mm. [21] Battery unit according to claim 19, wherein the dimension L1 of the casing along the longitudinal direction satisfies 900 mm ≤ L1 ≤ 1300 mm. [22] Battery unit according to one of claims 19 to 21, wherein the casing consists of a pouch packaging material comprising an aluminum-plastic composite film, the aluminum-plastic composite film optionally comprising a composite film formed from aluminum and one or more of the following materials: polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), nylon, polyethylene terephthalate (PET) and polyethylene (PE). [23] Battery unit according to any one of claims 1 to 22, wherein the capacity of the battery unit at 25 °C is between 105 Ah and 300 Ah, optionally between 150 Ah and 190 Ah. [24] Battery device comprising a battery unit according to any one of claims 1 to 23. [25] Power-consuming device comprising a battery device according to claim 24, wherein the battery device serves to store electrical energy. [26] Energy storage device comprising a battery device according to claim 24, wherein the battery device serves to store electrical energy.

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