Battery cell, battery device, and electric device

Abstract

The invention provides a single battery, a battery device and a power utilization device, the single battery comprises a laminated electrode assembly, the laminated electrode assembly comprises a positive pole piece, an isolating membrane and a negative pole piece which are laminated, the negative pole piece comprises a negative current collector and a negative membrane layer arranged on at least one side of the negative current collector, the positive pole piece comprises a positive pole current collector and a positive pole film layer arranged on at least one side of the positive pole current collector, the positive pole film layer comprises a positive pole active material, the positive pole active material comprises lithium-containing transition metal phosphate particles, the compaction density of the positive pole piece is 2.25-2.65 g / cm < 3 >, and the lithium-containing transition metal phosphate particles are uniformly distributed on the positive pole piece. In a particle roughness area cumulative distribution curve obtained by the tangent plane of the positive electrode film layer along the thickness direction of the pole piece, the roughness RA50 is 0.90-0.98, and the roughness RA90 is more than 0.93. The battery monomer can give consideration to both energy density and cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular, to a battery cell, a battery device, and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application scope of secondary batteries, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, and aerospace. Among them, lithium iron phosphate system batteries have attracted more and more attention in recent years due to their excellent safety performance.

[0003] With the rapid development of lithium iron phosphate system batteries, higher requirements have also been put forward for their cycle performance and energy density. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device, and an electrical device, and the battery cell of the present application can balance energy density and cycle performance.

[0005] To achieve the above object, a first aspect of the present application provides a battery cell, characterized in that it includes a stacked electrode assembly, the stacked electrode assembly includes a positive electrode tab, a separator, and a negative electrode tab stacked, the negative electrode tab includes a negative current collector and a negative electrode film layer provided on at least one side of the negative current collector, the positive electrode tab includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector, the positive electrode film layer includes a positive active material, the positive active material includes lithium-containing transition metal phosphate particles, and the tap density of the positive electrode tab is 2.25 g / cm 3 -2.65 g / cm 3 , in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the tab, the roughness R A50 is 0.90 - 0.98, the roughness R A90 is 0.93 or more, R A50 represents the roughness corresponding to the cumulative area ratio of 50% of the cumulative area on the vertical axis in the roughness cumulative distribution curve, and R A90 represents the roughness corresponding to the cumulative area ratio of 90% of the cumulative area on the vertical axis in the roughness cumulative distribution curve. The battery cell of the present application can balance energy density and the cycle performance of the battery.

[0006] In some embodiments, in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the tab, the roughness R A90 is 0.93 - 0.995, R A90It represents the roughness corresponding to when the cumulative area ratio of the vertical axis in the roughness cumulative distribution curve is 90%. In some embodiments, in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the R of the roughness A10 is 0.85 - 0.90, and R A10 represents the roughness corresponding to when the cumulative area ratio of the vertical axis in the roughness cumulative distribution curve is 10%. The R of the roughness A10 and R A90 Within the above range, it indicates that the surface of the particles in the positive electrode film layer is highly smooth and is prone to slip under external forces.

[0007] In some embodiments, in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the concentration of the roughness (R A90 -R A10 ) / R A50 is 0.085 - 0.105. A small concentration of the roughness of the positive electrode film layer indicates that the width of the roughness distribution of the particles in the positive electrode film layer is narrow and the concentration is good.

[0008] In some embodiments, the tap density of the positive electrode sheet is 2.35 g / cm 3 -2.45 g / cm 3 . Thus, it is beneficial to enable the battery cell to obtain a high energy density.

[0009] In some embodiments, the single-sided coating weight of the positive electrode film layer is 0.33 g / 1540.25 mm 2 ~0.43 g / 1540.25 mm 2 . In some embodiments, the single-sided coating weight of the positive electrode film layer is 0.36 g / 1540.25 mm 2 ~0.40 g / 1540.25 mm 2 . Thus, it is beneficial to enable the battery to obtain a relatively high energy density.

[0010] In some embodiments, the porosity of the positive electrode sheet is 23% - 32%. A porosity within this range can simultaneously ensure that the battery has a relatively high tap density and good wettability, thereby ensuring that the battery has a high energy density and good cycling performance.

[0011] In some embodiments, the lithium-containing transition metal phosphate particles include a lithium-containing transition metal phosphate matrix and a coating layer located on at least a part of the surface of the lithium-containing transition metal phosphate matrix, and the coating layer contains carbon. Carbon has excellent electrical conductivity and is beneficial to the transmission of electrons. The setting of the carbon coating layer can significantly improve the electronic conductivity of the lithium-containing transition metal phosphate material.

[0012] In some embodiments, the chemical formula of the lithium-containing transition metal phosphate matrix is represented as Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 , where 0.5 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, N, and P; Y includes one or more of O and F. In some embodiments, the lithium-containing transition metal phosphate includes lithium iron phosphate.

[0013] In some embodiments, the lithium-containing transition metal phosphate contains Ti element. Based on the mass of the lithium-containing transition metal phosphate, the mass content of the Ti element is 0.05% - 0.2%. By including the Ti element, the transport barrier of lithium ions can be reduced, the diffusion rate of lithium ions can be increased, thereby improving the kinetic performance of the battery and enhancing the cycling performance.

[0014] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the D of the lithium-containing transition metal phosphate particles A50 is 100 nm - 2.5 μm, and D A50 represents the particle size value corresponding to the cumulative area ratio of 50% on the vertical axis in the area cumulative distribution curve. The design of using a combination of large and small particles for the positive electrode can increase the tap density of the positive electrode, thereby enhancing the energy density of the battery.

[0015] In some embodiments, the thickness of the positive electrode current collector is 12 μm - 20 μm. Using a thicker current collector can improve the overall strength and support of the laminated battery, and at the same time reduce the risk of the electrode sheet wrinkling or breaking during high-pressure rolling.

[0016] In some embodiments, the tap density of the negative electrode sheet is 1.3 g / cm 3 -1.55 g / cm 3 . In some embodiments, the tap density of the negative electrode sheet is 1.40 g / cm 3-1.50 g / cm 3 By keeping the compaction density within the above range, it is beneficial to improve the energy density of the battery.

[0017] In some embodiments, the single-sided coating weight of the negative electrode film layer is 0.15 g / 1540.25 mm 2 ~0.207 g / 1540.25 mm 2 In some embodiments, the single-sided coating weight of the negative electrode film layer is 0.17 g / 1540.25 mm 2 ~0.2 g / 1540.25 mm 2 Thus, it is beneficial to ensure that the battery has a high energy density.

[0018] In some embodiments, the porosity of the negative electrode plate is 23% - 32%. This can ensure that the battery has a high energy density and good cycling performance.

[0019] In some embodiments, the thickness of the negative electrode current collector is 6 μm - 12 μm. This can improve the overall strength and support of the stacked battery, and at the same time avoid the risk of the electrode plate wrinkling or breaking during high-pressure rolling.

[0020] In some embodiments, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and the volume average particle size Dv50 of the graphite is 13 μm - 22 μm. In some embodiments, the volume average particle size Dv50 of the graphite is 14.5 μm - 20 μm. By using graphite with a particle size in the above range, it is beneficial to increase the compaction density of the electrode plate, thereby increasing the volume energy density of the battery; at the same time, it can ensure that the transmission path of lithium ions in the graphite is appropriate, reducing the risk of adverse effects on battery performance due to too long a path.

[0021] In some embodiments, the separator includes a base film and coatings provided on both sides of the base film, the coatings include a bonding layer, the bonding layer is a continuous layer with a porous structure, and the bonding layer includes a fluoropolymer. Thus, it has good adhesion, thereby obtaining a battery cell with a high energy density and a stable structure.

[0022] In some embodiments, the fluoropolymer includes one or more of polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-chlorotrifluoroethylene-tetrafluoroethylene-hexafluoropropylene copolymer. These polymers can dissolve in oily solvents, opening the molecular chains to form a relatively uniform slurry. Thus, an overall porous network structure is formed during coating, significantly improving the adhesion to the electrode plate.

[0023] In some embodiments, the unilateral thickness of the adhesive layer is 0.5 μm - 2 μm. Within this thickness range, the bonding strength between the separator film and the electrode sheet is within a suitable range, which is beneficial to the cycling performance and safety performance of the battery cell.

[0024] In some embodiments, the coating further includes a ceramic layer disposed between the base film and the adhesive layer. The provision of a ceramic layer between the base film and the adhesive layer can improve the wettability of the electrolyte to the separator, promote the flow of the electrolyte, and is beneficial to further improving the performance deterioration problem caused by insufficient electrolyte wetting of the battery core, thereby being more beneficial to improving the cycling performance of the battery cell.

[0025] In some embodiments, the ceramic layer includes one or more ceramic particles such as alumina, boehmite, silica, magnesia, titania, stannic oxide, calcium oxide, zirconia, yttria, zinc oxide, silicon carbide, magnesium fluoride, barium sulfate, barium titanate, aluminum hydroxide, magnesium hydroxide, or calcium hydroxide.

[0026] In some embodiments, the unilateral thickness of the ceramic layer is 0.5 μm - 4 μm. Within this thickness range, the wettability and liquid retention of the electrolyte can be improved, which is beneficial to the cycling performance and safety performance of the battery cell.

[0027] In some embodiments, the thickness of the base film is 7 μm - 9 μm.

[0028] In some embodiments, the battery cell contains an electrolyte, and the electrolyte includes a chain carbonate solvent. Based on the total mass of the electrolyte, the mass content of the chain carbonate solvent is 43% - 71%. As a solvent for the electrolyte, the chain carbonate has a lower viscosity than the cyclic carbonate. When the electrolyte includes 43% - 71% of the chain carbonate, the viscosity of the electrolyte is effectively reduced, and the wetting of the electrode assembly is improved.

[0029] In some embodiments, the chain carbonate includes one or both of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). When DMC and EMC are used in combination, it can not only effectively reduce the viscosity of the electrolyte and improve the wettability of the electrolyte, but also will not cause a decrease in the low-temperature performance of the battery.

[0030] In some embodiments, the electrolyte further includes a cyclic carbonate. The cyclic carbonate is beneficial to the dissociation of the lithium salt and improves the conductivity of the electrolyte. In addition, the cyclic carbonate can also form a stable SEI film on the surface of the negative electrode, which is thus beneficial to the improvement of the cycling stability and safety of the battery.

[0031] In some embodiments, based on the total mass of the electrolyte, the mass content of the cyclic carbonate is 14% - 42%. When the mass content of the cyclic carbonate is within the above range, it is beneficial to improve the conductivity of the electrolyte and does not affect the wettability of the electrolyte on the electrode assembly.

[0032] The second aspect of the present application provides a battery device, which includes the battery cell of the first aspect of the present application.

[0033] The third aspect of the present application provides an electrical device, which includes the battery device of the second aspect of the present application. Description of the Drawings

[0034] Figure 1 is a scanning electron microscope image of a cross-section of the positive electrode film layer along the thickness direction of the electrode in an embodiment of the present application; Figure 2 is a schematic diagram of a battery cell in an embodiment of the present application; Figure 3 is Figure 2 the exploded view of the battery cell shown in an embodiment of the present application; Figure 4 is a schematic diagram of a battery module in an embodiment of the present application; Figure 5 is a schematic diagram of a battery pack in an embodiment of the present application; Figure 6 is Figure 5 the exploded view of the battery pack shown in an embodiment of the present application; Figure 7 is a schematic diagram of an electrical device powered by a secondary battery in an embodiment of the present application.

[0035] Description of the Reference Numerals 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Embodiments

[0036] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the present application.

[0037] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are understood to be contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0039] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0040] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, if a method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0041] If there is no special instruction, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0042] If there is no special instruction, the numerical values of the various parameters mentioned in this application can be determined by various commonly used testing methods in the art. For example, they can be determined according to the testing methods given in this application.

[0043] At present, lithium iron phosphate system batteries (the positive electrode active material includes lithium-containing transition metal phosphates) have attracted more and more attention due to their better safety performance than ternary system batteries. However, compared with ternary system batteries, the energy density of lithium iron phosphate system batteries is lower. Therefore, in the prior art, the energy density is usually increased by increasing the compaction density of the electrode sheet.

[0044] However, the inventors found that when the compaction density of the positive electrode film layer is large, the stress release in the film layer in the later stage of cycling will cause the electrode sheet to deform and wrinkle, which will further cause poor contact between the positive electrode film layer and the separator and between the positive electrode film layer and the current collector, resulting in an increase in the interface resistance and having an adverse effect on the cycling performance of the battery.

[0045] Based on this, the present application provides a new battery cell, battery device and electrical device, which can obtain excellent cycling performance while having a high energy density. The following will describe the present application and optional implementation manners in more detail.

[0046] Battery cell In the first aspect of the present application, a battery cell is provided, which is characterized in that it includes a stacked electrode assembly. The stacked electrode assembly includes a stacked positive electrode sheet, a separator and a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative electrode film layer provided on at least one side of the negative current collector. The positive electrode sheet includes a positive current collector and a positive electrode film layer provided on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes lithium-containing transition metal phosphate particles. The compaction density of the positive electrode sheet is 2.25 g / cm 3 -2.65 g / cm 3 , in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the R A50 of the roughness is 0.90 - 0.98, and the R A90 of the roughness is 0.93 or more. R A50 represents the roughness corresponding to the cumulative area ratio of 50% of the cumulative area of the vertical axis in the roughness cumulative distribution curve, and R A90 represents the roughness corresponding to the cumulative area ratio of 90% of the cumulative area of the vertical axis in the roughness cumulative distribution curve.

[0047] In the present application, by making the compaction density of the positive electrode sheet be 2.25 g / cm 3 -2.65 g / cm 3 , the battery cell obtains a high energy density. In addition, by adopting a stacked structure and a high compaction density design, the energy density of the battery can be further improved, and the problem that the electrode sheet is prone to cracking at the corners in the winding structure can be avoided. Furthermore, by making the RA50 and R A90 Within the above range, it indicates that the surface of the particles is relatively smooth, and the frictional force between the particles is relatively small, which can improve the ease of slippage between the lithium-containing transition metal phosphate particles. The stress generated during the lithium deintercalation and intercalation processes of the electrode can be released through the slippage between the particles, thereby alleviating the damage to the electrode structure caused by the stress release of the electrode, reducing the risk of poor contact between the positive electrode film layer and the separator and between the positive electrode film layer and the current collector, reducing the increase in internal resistance, and improving the cycling performance of the battery.

[0048] In the present application, the tap density of the positive electrode is the tap density under the condition of 0% SOC (State of Charge). Exemplarily, the tap density under the condition of 0% SOC is 2.25 g / cm 3 、2.26 g / cm 3 、2.27 g / cm 3 、2.28 g / cm 3 、2.29 g / cm 3 、2.30 g / cm 3 、2.35 g / cm 3 、2.40 g / cm 3 、2.45 g / cm 3 、2.50 g / cm 3 、2.55 g / cm 3 、2.60 g / cm 3 2.65 g / cm 3 Or it is a range between any two values. In some embodiments, the tap density of the positive electrode under the condition of 0% SOC is 2.35 g / cm 3 -2.45 g / cm 3 。

[0049] In the present application, the term "particle" refers to a particle with a recognizable complete boundary in the field of view of the positive electrode film layer at a certain magnification, such as 10,000 times. There may be defects and scratches inside the particle, but no complete boundary sufficient to divide the particle can be recognized inside the particle.

[0050] The method for identifying particles is as follows: Cut the positive electrode film layer along the thickness direction of the electrode plate by an argon ion beam. After exposing the cut surface, use a scanning electron microscope to observe the cut surface of the positive electrode film layer along the thickness direction of the electrode plate. Use a field emission scanning electron microscope to collect images in the secondary electron mode at a non-edge position (after observing the edge of the electrode plate under the scanning electron microscope, adjust the field of view to the central part of the sample) on the cut surface of the positive electrode film layer, take an electron micrograph at a magnification of 10,000 times, and analyze the particles in the electron micrograph using ImageJ software (version 1.46r, win64). The specific method of using ImageJ software is as follows: Load the scanning electron micrograph to be analyzed, as Figure 1 shown; Use the Cellpose plug-in software in it to identify particles, and perform manual correction on this basis; Use Image J to read and count data. The specific method of using the Cellpose plug-in software to identify particles is as follows: Set the segmentation diameter parameter (diameter in the Segmantation module) to 15 pixels. After clicking "run cyto3" to identify particles, manually mark the particles in the image that are not recognized by the software, not fully recognized by the software, or have recognition errors. The particles in the image that are not recognized by the software, not fully recognized by the software, or have recognition errors mainly include the following types: 1. Due to the particle being too large or having scratches on the particle surface, the particle cannot be recognized or cannot be fully recognized; 2. During the argon ion beam cutting process, scratches will be generated on the particle surface, and the software may misjudge the scratches as the particle boundary during the recognition process, resulting in recognition errors; 3. Due to the particle being too small, it fails to be recognized successfully; 4. The particle is located at the edge of the electron microscope field of view, and the interior of the particle is penetrated by the edge, and the morphology cannot be fully displayed, and the local part is recognized instead of the whole, resulting in recognition errors. For the above unrecognized or misrecognized particles, manual calibration is carried out. The specific process is as follows: Delete the large particles that are located at the four edges of the scanning electron microscope and cannot be fully displayed; Judge whether there are gap scratches inside other unrecognized or misrecognized particles. If there are no gap scratches inside the particle, judge it as a single particle, and manually mark it according to the particle boundary observed manually; In response to the presence of gap scratches inside the particle, judge whether the gap scratches penetrate the particle. If they do not penetrate the particle, judge it as a single particle and perform manual marking; In response to the gap scratches penetrating the particle, judge whether the gap scratches are linear or irregular; In response to the gap scratches being irregular, judge it as the boundary between particles and divide the particles along this boundary; In response to the gap scratches being linear, perform contrast of contrast; In response to the contrast being not obvious and there being no sense of crack, judge it as a scratch and mark it as a single particle; In response to the contrast being strong and there being a sense of crack, judge it as the boundary between particles and mark it as two particles. After manual marking, delete the information unrelated to the particles during the automatic image processing process, and the determination and marking of the particles in the picture are completed.

[0051] The cross-sectional morphology diagram of the positive electrode film layer along the thickness direction of the electrode sheet is as follows Figure 1 shown. Different from the state of the positive electrode active material in the Malvern laser scattering method and also different from the state of the positive electrode active material when directly observing the positive electrode active material by scanning electron microscopy. Under the action of the roll pressure, the particles in the positive electrode film layer show a good dispersion state. Observing the positive electrode film layer is beneficial to effectively characterize the objective conditions of the particle size, particle area and quantity of the particles in the positive electrode film layer.

[0052] It can be understood that the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, especially the particles with a size of more than 50 nm, mainly come from the positive electrode active material. Therefore, by observing and counting the particle size of the particles in the cross-section of the positive electrode film layer in this application, the distribution of the lithium-containing transition metal phosphate particles in the positive electrode film layer in the electrode sheet can be accurately and objectively reflected.

[0053] In the prior art, the particle size of the positive electrode active material is usually statistically analyzed by the Malvern laser diffraction method. However, the inventor's research shows that due to the easy agglomeration of lithium phosphate, the test results obtained by the Malvern laser diffraction method based on the laser scattering principle often measure the particle size of its particle agglomerates, and cannot truly reflect the particle size of the particles in the positive electrode active material, let alone reflect the dispersion state of the positive electrode active material in the film layer, because the dispersion degree of the positive electrode active material in the film layer will increase during the film-forming roll pressing process. The test results obtained by the Malvern laser diffraction method are closely related to the particle size, specific surface area and agglomeration degree of the positive electrode active material. Therefore, the particle size obtained by the Malvern laser diffraction method test cannot be equated or analogized to the particle size statistically obtained in this application.

[0054] In this application, the method for testing the roughness of particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet is as follows: Identify the particles in the cross-section of the positive electrode film layer according to the method described above. Import the image after the particles are judged and marked into the ImageJ software for analysis. Set the scale according to the scanning electron microscope image. Analyze the Feret diameter and Area of the particle cross-section in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet through the analysis functions of "Feret diameter", "Area", "Round", and "Solidity". According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained by analysis represents the maximum distance between all parallel lines of the outer contour of the particle cross-section, which characterizes the particle size; the "Area" parameter obtained represents the pixel area of the particle. Since particles with a particle size less than 50 nm have large errors in the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50 nm, which will cause large errors in the statistical results. Therefore, in the particle size statistics process of this application, particles with a particle size less than 50 nm are not counted, and the particle statistical data corresponding to "Area" or "Round" or "Solidity" displayed as "NaN" are deleted. Use the "Shape Descriptor" analysis function in ImageJ to analyze the morphology of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet. According to the software manual (ImageJ User Guide IJ 1.46r), the "Solidity" parameter obtained by analysis represents the ratio of the pixel area of the particle to the convex area. Therefore, the roughness of the particle is characterized by the "Solidity" parameter of the obtained particle. According to the definition, the closer the roughness is to 1, the smoother the particle. Arrange the roughnesses of at least 5000 obtained particles in ascending order. Use the roughness as the horizontal axis and the cumulative area ratio as the vertical axis to obtain the roughness cumulative distribution curve of the particles in the positive electrode film layer. R A50 is the roughness R value corresponding to the cumulative area ratio of 50% on the vertical axis in the roughness R value cumulative distribution curve.

[0055] The R of the roughness A50 Compared with the point value, it can reflect the overall roughness of the particles in the positive electrode film layer; compared with the mean value, it can reduce the influence of extreme values in the test process and improve the confidence level of the test results.

[0056] In this application, in the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the R of the roughness of the particles A50 is 0.90, 091, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or the numerical range between any two of them.

[0057] In the present application, in the cumulative area distribution curve of the particle roughness obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the R of the roughness A90 is 0.93 or more, optionally 0.93 - 0.995. Exemplarily, the R of the roughness A90 is 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 0.995, 0.999 or the numerical range between any two of them. The R of the roughness A90 within the above range indicates that the positive electrode film layer has a high roughness at different sites, indicating a high degree of smoothness of the particle surface and being prone to slip under an external force.

[0058] In some embodiments, in the cumulative area distribution curve of the roughness of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the concentration degree of the roughness is 0.085 - 0.105, and the concentration degree = (R A90 - R A10 ) / R A50 . Exemplarily, (R A90 - R A10 ) / R A50 can be optionally 0.085, 0.088, 0.090, 0.091, 0.092, 0.093, 0.094, 0.095, 0.096, 0.097, 0.098, 0.099, 0.100, 0.101, 0.102, 0.103, 0.104, 0.105 or the numerical range between any two of them.

[0059] In the cumulative area distribution curve of the roughness of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the specific method for testing the concentration degree of the roughness is as follows: Referring to the roughness testing method described above in the present application, by analogy, R A90 is the R value corresponding to the cumulative area ratio of 90% of the cumulative area of the vertical axis in the cumulative distribution curve of the roughness R value, and R A10 is the R value corresponding to the cumulative area ratio of 10% of the cumulative area of the vertical axis in the cumulative distribution curve of the roughness R value. The concentration degree of the roughness is represented by (R A90 - R A10 ) / R A50 . (R A90 - R A10 ) / R A50 can not only reflect the roughness size of most particles, be unaffected by extreme values, but also reflect the width of the particle roughness distribution in the positive electrode film layer. A small concentration degree of the roughness R value of the positive electrode film layer indicates a narrow width of the particle roughness distribution and good concentration in the positive electrode film layer.

[0060] In some embodiments, in the cumulative area distribution curve of particle roughness obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode, the R of the roughness A10 is 0.85 - 0.90. Exemplarily, the R of the roughness A10 is 0.85, 0.86, 0.87, 0.88, 0.89, 0.90 or the numerical range between any two of them. When the R of the roughness A10 is within the above range, it indicates that different sites in the positive electrode film layer have relatively high roughness, indicating a high degree of smoothness on the particle surface and being prone to slip under external force.

[0061] In some embodiments, the single-sided coating weight of the positive electrode film layer is 0.33 g / 1540.25mm 2 ~0.43 g / 1540.25mm 2 . Exemplarily, the single-sided coating weight is 0.33 g / 1540.25mm 2 , 0.34 g / 1540.25mm 2 , 0.35 g / 1540.25mm 2 , 0.36 g / 1540.25mm 2 , 0.37 g / 1540.25mm 2 , 0.38 g / 1540.25mm 2 , 0.39 g / 1540.25mm 2 , 0.40 g / 1540.25mm 2 , 0.41 g / 1540.25mm 2 , 0.42 g / 1540.25mm 2 , 0.43 g / 1540.25mm 2 or the numerical range between any two of them. In some embodiments, the single-sided coating weight of the positive electrode film layer is 0.36 g / 1540.25mm 2 ~0.40 g / 1540.25mm 2 . Thus, it is beneficial to enable the battery to obtain a relatively high energy density.

[0062] In some embodiments, the porosity of the positive electrode is 23% - 32%. Exemplarily, the porosity of the positive electrode is 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32% or the numerical range between any two of them. When the porosity is within this range, it can ensure that the battery has a relatively high tap density and good wettability, thereby ensuring that the battery has a high energy density and good cycling performance.

[0063] In this application, the porosity is tested by the gas displacement method with reference to GB / T 24586-2009. After the electrode sheet / separator is impregnated in DMC and cleaned and dried, it is tested using a true density meter AccuPyc Ⅱ1340. Among them, the percentage of the pore volume in the electrode sheet to the total volume of the electrode sheet is the porosity of the electrode sheet, and the calculation formula is: porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0064] In some embodiments, the lithium-containing transition metal phosphate particles include a lithium-containing transition metal phosphate matrix and a coating layer located on at least a part of the surface of the lithium-containing transition metal phosphate matrix, and the coating layer contains carbon elements. Carbon has excellent electrical conductivity and is beneficial to the transmission of electrons. The setting of the carbon coating layer can significantly improve the electronic conductivity of the lithium-containing transition metal phosphate material and make up for the defect of poor electronic conduction performance of the lithium-containing transition metal phosphate material.

[0065] The carbon coating layer provided on at least a part of the surface of the lithium-containing transition metal phosphate can be detected by any well-known method in the art. As an example, the carbon coating layer provided on at least a part of the surface of the lithium-containing transition metal phosphate can be observed by characterizing the lithium-containing transition metal phosphate by combining a transmission electron microscope and an energy spectrum analyzer. It should be noted that the elements in the carbon coating layer are not limited to carbon elements, and there may also be other non-carbon elements. The carbon coating layer is not limited to a film shape, and also includes an island shape, an irregular shape or a discontinuous coating layer.

[0066] In some embodiments, the chemical formula of the lithium-containing transition metal phosphate matrix is expressed as Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 , where 0.5 ≤ x1 ≤ 0.8, 0 ≤ y1 ≤ 1.3, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N, P; Y includes one or more of O, F. In some embodiments, the lithium-containing transition metal phosphate includes lithium iron phosphate.

[0067] The lithium-containing transition metal phosphate contains Ti. For example, lithium iron phosphate contains Ti. Additionally, based on the mass of the lithium-containing transition metal phosphate, the mass content of the Ti element is 0.05% to 0.2%. Exemplarily, the mass content of the Ti element is 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2% or any value range between any two of them. By including the Ti element, the transport barrier of lithium ions can be reduced, the diffusion rate of lithium ions can be increased, thereby improving the kinetic performance of the battery and enhancing the cycling performance.

[0068] In some embodiments, in the cross-section of the positive electrode film layer along the thickness direction of the electrode, the D of the lithium-containing transition metal phosphate particles A50 is 100 nm to 2.5 μm. The positive electrode adopts a design with a combination of large and small particles, which can improve the tap density of the positive electrode, thereby enhancing the energy density of the battery. Exemplarily, D A50 is 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm or any value range between any two of them.

[0069] In this application, as the D A50 test method, it can be carried out as follows: In the cross-section of the positive electrode film layer along the thickness direction of the electrode, the D of the particles A50The calculation method is as follows. The image after particle determination and identification is imported into ImageJ software for analysis according to the method described above. The scale is set according to the scanning electron microscope image, and the particle size and area of the particles in the cross-section of the positive electrode film layer along the thickness direction of the electrode are analyzed through the analysis functions of "Feret diameter", "Area", "Round" and "Solidity". According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained by analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which characterizes the particle size of the particle; and the "Area" parameter obtained represents the pixel area of the particle. Since particles with a particle size less than 50 nm have large errors in the statistical process and are difficult to accurately identify, and the particle size of the conductive agent is generally less than 50 nm, which will cause large errors in the statistical results. Therefore, particles with a particle size less than 50 nm are not statistically counted in the particle size statistics process of this application, and the corresponding particle statistical data with "NaN" displayed in AR or Round or Solidity are deleted. According to the above method, to meet the sample number with statistical significance, at least 10 non-overlapping scanning electron microscope images are collected for each electrode, and the particle sizes of at least 5000 particles are counted. The particle sizes of at least 5000 obtained particles are arranged in ascending order. With the particle size as the horizontal axis and the cumulative area ratio calculated by the "Area" of the particles as the vertical axis, the area cumulative distribution curve of the particles in the positive electrode film layer is obtained. D A50 It is the particle size value corresponding to when the cumulative area ratio on the vertical axis in the area cumulative distribution curve is 50%.

[0070] In some embodiments, the thickness of the positive current collector is 12 μm to 20 μm. Exemplarily, the thickness of the positive current collector is 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or any numerical range between any two of them. Using a thicker current collector can improve the overall strength and support of the stacked battery, and at the same time reduce the risk of wrinkles or fractures occurring in the electrode during high-pressure rolling.

[0071] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector. In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0072] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode active material in the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Li will change.

[0073] In the listing of the positive electrode active material in the present application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0074] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0075] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In the present application, the lithium-containing transition metal phosphate particles of the positive electrode active material can be prepared by the following method, which includes the following steps.

[0077] S1: Obtain a mixed raw material including a carbon source, a lithium source, an iron source, and a phosphorus source.

[0078] S2: Add a solvent to the above mixed raw material, and obtain a mixed slurry after grinding.

[0079] S3: Obtain a precursor powder after drying the mixed slurry.

[0080] S4: Sinter the precursor powder to obtain the cathode active material, including: sinter the precursor powder for the first time to obtain a first sintered product, mix the first sintered product and a carbon source to obtain an intermediate raw material, divide the intermediate raw material into two groups, and grind them respectively to obtain a first group of ground products and a second group of ground products. The D V50 of the first group of ground products is 0.8 μm - 1.2 μm, and the D V50 of the second group of ground products is 0.29 μm - 0.50 μm. Mix the first group of ground products and the second group of ground products to obtain a mixed intermediate product, and then sinter the mixed intermediate product for the second time.

[0081] For small particles relative to large particles, the proportion of surface atoms is relatively high, the surface energy is large, the surface atoms have high activity, and the surface area per unit volume is larger. Therefore, the surface diffusion rate is faster, which makes small particles prone to relatively intense surface rearrangement during sintering, promoting the evolution of particles into a smooth morphology. Therefore, controlling the grinding particle size to a smaller value, including the grinding of the mixed slurry and the intermediate raw material, is beneficial for the formation of a product with a smoother and flatter surface during the subsequent sintering process. At the same time, particles with a smaller grinding particle size are more easily coated, improving the coating integrity.

[0082] In some embodiments, the iron source is an iron-containing compound. In some embodiments, the iron source includes at least one of iron hydroxide, ferrous chloride, iron(III) oxide, iron phosphate, ferric pyrophosphate, ferrous oxalate, iron powder, iron nitrate, magnetite, and iron oxyhydroxide.

[0083] In some embodiments, the phosphorus source is a phosphoric acid compound. In some embodiments, the phosphorus source includes at least one of phosphoric acid, iron phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0084] In some embodiments, the iron source and the phosphorus source can be the same substance. In some embodiments, iron phosphate is used as both the iron source and the phosphorus source.

[0085] In some embodiments, the lithium source includes one or more of lithium carbonate, lithium dihydrogen phosphate, lithium oxalate, lithium oxide, lithium hydroxide, and lithium acetate.

[0086] In some embodiments, the lithium source includes lithium carbonate.

[0087] In some embodiments, the carbon source includes one or more of glucose, polyethylene glycol, citric acid, sucrose, starch, fructose, lactose, polyaniline, polyacrylonitrile, and polyvinylpyrrolidone.

[0088] In some embodiments, the carbon source includes glucose and polyethylene glycol.

[0089] In some embodiments, based on the total mass of the carbon source, the mass content of polyethylene glycol is 20% - 75%.

[0090] In some embodiments, the slurry further includes a titanium source. Optionally, the titanium source includes one or more of titanium dioxide, tetrabutyl titanate, titanium nitrate, and titanic acid.

[0091] In some embodiments, the atomic molar ratio of iron element to phosphorus element in the iron source and the phosphorus source is 0.95 - 1.

[0092] In some embodiments, the atomic molar ratio of iron element to phosphorus element in the lithium source and the iron source can be optionally 0.95, 0.955, 0.96, 0.965, 0.97, 0.975, 0.98, 0.985, 0.99, 0.995, 1, or a numerical range between any two of them.

[0093] In some embodiments, based on the total mass of the mixed raw materials, the mass proportion of the carbon source in the mixed raw materials is 5% - 7%.

[0094] By controlling the lithium content of the carbon source within the above range, the conductivity of the material can be enhanced, and the negative impact on the specific capacity of the positive electrode sheet and the battery energy density can be reduced. An overly thick carbon layer not only occupies the effective active material space but may also cause the instability of the material structure.

[0095] In some embodiments, the solvent includes water and its mixtures.

[0096] In some embodiments, the mixed raw materials including a carbon source, a lithium source, an iron source, and a phosphorus source are obtained by: adding the carbon source, the lithium source, the phosphorus source, the iron source, and the carbon source into a solvent and mixing and stirring, and the rotation speed of the stirring is 1400 rpm - 2200 rpm.

[0097] In some embodiments, the mixed slurry obtained after grinding includes primary grinding, and the primary grinding satisfies one or more of the following conditions.

[0098] (1) The grinding balls for the primary grinding are one or more of zirconia balls, silicon nitride zirconia balls, and ceramic zirconia balls.

[0099] (2) The diameter of the grinding balls for the primary grinding is 0.5 - 0.7 mm.

[0100] (3) The rotation speed of the primary grinding is 450 rpm - 550 rpm.

[0101] (4) The time of the primary grinding is 0.5 h - 1.5 h.

[0102] (5) The pressure in the grinding chamber for the first grinding is 0.01 MPa - 0.3 MPa.

[0103] In some embodiments, the mixed slurry obtained after grinding includes performing a second grinding after the first grinding, and the second grinding satisfies one or more of the following conditions.

[0104] (1) The grinding balls for the second grinding are one or more of zirconia balls, silicon zirconitride balls, and ceramic zirconia balls.

[0105] (2) The diameter of the grinding balls for the second grinding is 0.25 mm - 0.35 mm.

[0106] (3) The rotation speed for the second grinding is 470 rpm - 530 rpm.

[0107] (4) The time for the second grinding is 3.0 h - 5.0 h.

[0108] (5) The pressure in the grinding chamber for the second grinding is 0.01 - 0.3 MPa.

[0109] In some embodiments, the particle size D of the mixed slurry V50 is 0.29 - 0.5.

[0110] In step S2, performing at least two grindings is beneficial for controlling the temperature and viscosity of the slurry, reducing the excessive viscosity of the slurry caused by too high temperature and the resulting raw material agglomeration, improving the uniformity of the particle size in the product, reducing the generation of oversize particles, and facilitating the control of the particle roughness in the positive electrode film layer. The first grinding can handle large particle materials, and the second grinding further refines the materials and adjusts the particle size distribution. In this way, the non-uniformity of the particle size caused during the grinding process can be effectively reduced, the agglomeration phenomenon between particles can be reduced, the conductivity and cycle stability of the battery can be improved, and at the same time, the overall production efficiency can be improved while meeting the performance of the final product.

[0111] In some embodiments, in step S3, obtaining the precursor powder by drying the mixed slurry includes obtaining the precursor powder by spray-drying the mixed slurry.

[0112] In the present application, in step S4, sintering the precursor powder to obtain the positive electrode active material includes at least two sinterings. In some embodiments, the first sintering satisfies one or more of the following conditions: (1) The heating rate is 2 °C / min - 10 °C / min; (2) The holding temperature is 720 °C - 790 °C; (3) The holding time is 5 h - 12 h. In some embodiments, the carbon sources added in mixing the first sintering product and the carbon source to obtain the intermediate raw material include glucose and polyethylene glycol.

[0113] In some embodiments, based on the mass of the first sintered product, the mass content of glucose in the intermediate raw material is 1%-2%, and the mass content of polyethylene glycol in the intermediate raw material is 2%-5%.

[0114] In some embodiments, the grinding conditions of the first group of ground products satisfy one or more of the following conditions: (1) the rotation speed is 550 rpm ± 50 rpm; (2) the grinding time is 0.5 h - 1.5 h.

[0115] In some embodiments, the grinding conditions of the second group of ground products satisfy one or more of the following conditions: (1) the rotation speed is 500 rpm ± 50 rpm; (2) the grinding time is 3 h - 5 h.

[0116] In some embodiments, the mass ratio of the first group of ground products to the second group of ground products is (60:40) - (80:20).

[0117] By adjusting the mass ratio of the first group of ground products to the second group of ground products, cathode active materials with different grading ratios can be obtained, thereby finely adjusting the area ratio of particles of each particle size and obtaining the required packing structure.

[0118] In some embodiments, the mixed intermediate product is subjected to a second sintering.

[0119] In some embodiments, the second sintering satisfies one or more of the following conditions: (1) the holding temperature is 770°C - 830°C; (2) the holding time is 5 h - 12 h; (3) the heating rate is 2°C / min - 10°C / min.

[0120] The two - sintering process can effectively shorten the sintering time in the high - temperature range, thereby reducing the risk and probability of magnetic substances appearing during high - temperature sintering. By adjusting the particle sizes of the two groups of grinding during the second sintering, the activity of the particles can be controlled, so that the cathode active material has large particles with a certain area ratio. While improving the compaction density of the electrode sheet and the energy density of the battery cell, the battery cell also has a low self - discharge level, enabling the energy density of the battery cell to be maintained for a long time during the storage and cycling of the battery cell.

[0121] By controlling the sintering temperature in the first sintering and second sintering processes, the rate of sintering diffusion can be controlled. At high temperatures, the diffusion on the particle surface increases, the defects in the particles are repaired, and the lattice rearrangement occurs. Through recrystallization, the defects on the particle surface are eliminated, the grain structure of the particles becomes more orderly, the size of the particles gradually increases, and it helps to smooth the particle surface. The sintering temperature also affects the graphitization rate of the carbon source. Kinetically, carbon atoms gain more energy and can overcome the original energy barrier, causing them to rearrange more violently in the lattice. The sintering time affects the extent of the reaction. If the sintering time is too short, the diffusion and rearrangement of the lithium-containing transition metal phosphate and the carbon source are not completely completed; if the sintering time is too long, the particles will grow abnormally, the grains inside the particles will coarsen, the material structure tends to be unstable, the bonding force between the particles increases, and agglomeration occurs.

[0122] In some embodiments, after sintering the precursor, the product is subjected to air jet milling to obtain the positive electrode active material.

[0123] In some embodiments, the classification frequency of the air jet milling is 20 Hz - 30 Hz, and the milling pressure is 0.45 MPa - 0.55 MPa.

[0124] The classification frequency in air jet milling refers to the working frequency of the classification device in air jet milling, which is usually related to the classification efficiency and particle size distribution of the particles. A higher classification frequency will screen the particles in the air flow more times, so that larger particles are screened out and smaller particles are left. And a higher classification frequency may increase the number of particle collisions, causing irregular particles to be further impacted and making the particle surface smoother.

[0125] A high air pressure will cause the particles to receive a greater impact force, and the collisions between the particles will be more violent, resulting in a stronger impact and wear on the particle surface. It can crush large particles into small particles, the collisions between the particles are more violent, and the surface is more easily trimmed, improving the surface flatness of the particles.

[0126] However, too high a classification frequency and milling pressure will cause the agglomerated particles to disperse into primary particles and then further crack and break, affecting the predetermined particle size distribution, making the carbon coating layer incomplete, manifested as an increase in iron dissolution, having a negative impact on the slip of the particles during rolling, and increasing the contact and reaction between the lithium-containing transition metal phosphate and external factors such as the electrolyte, which is not conducive to maintaining the cycle performance and life of the battery. Therefore, it is necessary to control the classification frequency and milling pressure of the air jet milling within a suitable range.

[0127] In some embodiments, the positive electrode plate can be prepared in the following manner: the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode paste; the positive electrode paste is coated on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0128] Negative electrode plate In the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0129] In some embodiments, the tap density of the negative electrode plate is 1.3 g / cm 3 -1.55 g / cm 3 . Exemplarily, the tap density is 1.30 g / cm 3 , 1.35 g / cm 3 , 1.40 g / cm 3 , 1.41 g / cm 3 , 1.42 g / cm 3 , 1.43 g / cm 3 , 1.44 g / cm 3 , 1.45 g / cm 3 , 1.46 g / cm 3 , 1.47 g / cm 3 , 1.48 g / cm 3 , 1.49 g / cm 3 , 1.50 g / cm 3 , 1.51 g / cm 3 , 1.52 g / cm 3 , 1.53 g / cm 3 , 1.54 g / cm 3 , 1.55 g / cm 3 or any value range between any two of them. Optionally, the tap density of the negative electrode plate is 1.40 g / cm 3 -1.50 g / cm 3 . By making the tap density within the above range, it is beneficial to improve the energy density of the battery. The tap density of the negative electrode plate in the present application is the tap density measured under the condition of 0% SOC (State of Charge).

[0130] In some embodiments, the single-sided coating weight of the negative electrode film layer is 0.150 g / 1540.25 mm 2 ~0.207 g / 1540.25 mm 2 . Exemplarily, the single-sided coating weight is 0.150 g / 1540.25 mm 2 , 0.155 g / 1540.25 mm 2 , 0.160 g / 1540.25 mm 2 , 0.165 g / 1540.25 mm 2 , 0.170 g / 1540.25 mm 2 , 0.175 g / 1540.25 mm 2 , 0.180 g / 1540.25 mm 2 , 0.185 g / 1540.25 mm 2 , 0.190 g / 1540.25 mm 2 , 0.195 g / 1540.25 mm 2 , 0.200 g / 1540.25 mm 2 , 0.207 g / 1540.25 mm 2 or a numerical range between any two of them. Optionally, the single-sided coating weight of the negative electrode film layer is 0.170 g / 1540.25 mm 2 ~0.200 g / 1540.25 mm 2 . By making the single-sided coating weight of the negative electrode film layer within the above range, it can ensure that the battery has a high energy density.

[0131] In some embodiments, the porosity of the negative electrode sheet is 23% - 32%. Exemplarily, the porosity of the negative electrode sheet is 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32% or a numerical range between any two of them. The porosity within this range can ensure that the battery has a high tap density and good wettability, thereby ensuring that the battery has a high energy density and good cycling performance.

[0132] In some embodiments, the thickness of the negative electrode current collector is 6 μm - 12 μm. Exemplarily, the thickness of the negative electrode current collector is 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm or a numerical range between any two of them. Using a thicker current collector can improve the overall strength and support of the laminated battery, and at the same time can also avoid the risk of the electrode sheet wrinkling or breaking during high-pressure rolling.

[0133] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0134] The negative electrode active material may be a negative electrode active material for batteries well-known in the art. In some embodiments, the negative electrode active material includes graphite, and the volume average particle size Dv50 of the graphite is 13 μm to 22 μm. Exemplarily, the volume average particle size Dv50 is 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm or the numerical range between any two of them. Optionally, the volume average particle size Dv50 of the graphite is 14.5 μm to 20 μm. By using graphite with a particle size in the above range, it is beneficial to improve the compaction density of the electrode sheet, and thus improve the volume energy density of the battery; at the same time, it can ensure that the transmission path of lithium ions in the graphite is appropriate, and reduce the risk of adverse effects on the battery performance due to too long a path.

[0135] However, as the negative electrode active material, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. As an example, the negative electrode active material may further include soft carbon and / or hard carbon.

[0136] In some embodiments, the negative electrode film layer may optionally further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0137] In some embodiments, the negative electrode film layer may optionally further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0138] In some embodiments, the negative electrode film layer may optionally further include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0139] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0140] Separator The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0141] In some embodiments, the separator includes a base film and coatings provided on both sides of the base film, the coating includes a bonding layer, the bonding layer is a continuous layer with a porous structure, and the bonding layer includes a fluoropolymer.

[0142] The bonding layer is a porous continuous layer structure, which is mainly constructed by an oil-based binder, that is, the binder is dispersed in an organic solvent and then coated into a film. The resulting bonding layer is a continuous structure. Such a structure is different from the bonding layer constructed by a traditional water-based binder, which mainly disperses the binder in an aqueous solvent and then coats it into a film, thereby forming an island-like structure of the bonding layer. Although the island-like structure of the bonding layer is convenient for manufacturing, the bonding area is small and the bonding force is weak. This problem is particularly obvious in the laminated battery, which will cause the misalignment of the laminated battery electrode sheets, thereby affecting the cycle performance. Therefore, the battery cell of the present invention adopts a laminated electrode assembly and at the same time adopts a separator with the above-mentioned porous continuous bonding layers on both sides, so that there is a good bonding force between the electrode sheet and the separator, thereby obtaining a battery cell with a high energy density and a stable cell structure. For the bonding layer, on the one hand, the continuous film layer enables the bonding layer to have a larger area in contact with the electrode sheet, enhancing the bonding force between the separator and the electrode sheet; on the other hand, the porous structure enables the active ions in the electrolyte to be more easily transported between the separators.

[0143] The morphology of the continuous layer with a porous structure of the bonding layers on both sides of the separator can be observed by an electron microscope. For example, the separator can be disassembled from the battery cell, and after cleaning the surface, it can be observed under, for example, a scanning electron microscope. In order to reflect the true morphology of the separator, during the sampling process, it is preferably sampled in the area where the bonding layer of the separator in the battery does not bond with the positive electrode sheet or the negative electrode sheet. As an example, it is sampled at the position of the separator where the projection exceeds the positive electrode sheet and the negative electrode sheet; or it is sampled at the separator near the surface of the electrode assembly. In these sampling areas, the bonding between the separator and the positive electrode sheet or the negative electrode sheet is less, and the true state of the separator can be better reflected.

[0144] In addition, it is understood that the continuous structure may become a block due to contact with the positive electrode sheet or the negative electrode sheet or force compression during the manufacturing or circulation process of the electrode sheet. The continuous structure referred to in this application does not mean that the bonding layer is continuous in the entire battery. Instead, it means that at the microscopic level, such as when observed under an electron microscope, it is a mesh-like continuous layer with a porous structure, rather than an island structure.

[0145] The present application has no particular restrictions on the type of basement membrane, and any known porous structure basement membrane with good chemical stability and mechanical stability can be selected. In some embodiments, the material of the basement membrane includes one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The basement membrane can be a single-layer film or a multi-layer composite film, without particular restrictions. When the basement membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions. Optionally, the basement membrane is polyethylene.

[0146] In some embodiments, the thickness of the base film is 7 μm to 9 μm, which is conducive to improving the safety performance of the battery cell. Exemplarily, the thickness of the base film is any value among 7 μm, 8 μm, 9 μm, or a value between any two values.

[0147] The coating is located on both sides of the base film, including a bonding layer, and the bonding layer is a continuous layer of a porous structure. In some embodiments, the bonding layer is arranged on the surface of the base film and contacts the base film. In other embodiments, there are other layers interposed between the bonding layer and the base film, for example, a ceramic layer described in detail below.

[0148] The bonding layer includes a fluorine-containing polymer. The fluorine-containing polymer includes one or more of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluorochloroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride-trifluorochloroethylene-tetrafluoroethylene-hexafluoropropylene copolymer. Optionally, the fluorine-containing polymer includes polyvinylidene fluoride PVDF. This type of polymer can be dissolved in an oily solvent, so that the molecular chain opens to form a more uniform slurry. Thereby, an overall porous mesh structure is formed during coating, which significantly improves the bonding force between the pole piece.

[0149] In some embodiments, the thickness of the adhesive layer on one side is 0.5 μm-2 μm. Within this thickness range, the bonding strength between the separator and the pole piece is in a suitable range, which is beneficial to the cycle performance and safety performance of the battery cell. Exemplarily, the thickness of the adhesive layer on one side is any value among 0.15 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a value between any two values.

[0150] The "unilateral thickness of the adhesive layer" mentioned in this application refers to the average thickness of the film layer where the adhesive material exists, without counting the part of the pores in the film layer where the adhesive material does not exist.

[0151] In some embodiments, the coating further includes a ceramic layer disposed between the base film and the adhesive layer. The ceramic layer includes one or more ceramic particles such as alumina, boehmite, silica, magnesia, titania, stannic oxide, calcium oxide, zirconia, barium sulfate, yttria, zinc oxide, silicon carbide, magnesium fluoride, barium titanate, aluminum hydroxide, magnesium hydroxide, or calcium hydroxide. Optionally, the ceramic layer includes alumina and / or boehmite.

[0152] Disposing a ceramic layer between the base film and the adhesive layer can improve the wettability of the electrolyte to the separator, promote the flow of the electrolyte, and is beneficial to further improving the performance deterioration problem caused by insufficient electrolyte infiltration in the battery cell, thereby being more conducive to improving the cycle performance of the battery cell.

[0153] In some embodiments, the average particle size of the ceramic material is 0.2 μm to 2.5 μm; optionally, it is 0.5 μm to 1.5 μm. Controlling the average particle size of the ceramic material within the above range is beneficial to improving the liquid retention capacity of the separator membrane, thereby being beneficial to further improving the lithium deposition situation, and further being beneficial to improving the cycle performance and safety performance of the battery cell. Exemplarily, the average particle size of the ceramic material is any value among 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 2.5 μm or a value within the range composed of any two numerical values.

[0154] In some embodiments, the unilateral thickness of the ceramic layer is 0.5 μm - 4 μm. Within this thickness range, the wettability and liquid retention property of the electrolyte can be improved, which is beneficial to the cycle performance and safety performance of the battery cell. Exemplarily, the thickness of the unilateral ceramic layer is any value among 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or a value within the range composed of any two numerical values.

[0155] The presence of the adhesive layer and the optional ceramic layer in the separator membrane disassembled from the electrode assembly can be observed under a scanning electron microscope (SEM).

[0156] In some embodiments, the thickness of the base film is 7 μm - 9 μm. Exemplarily, the thickness of the base film is 7 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, 8.0 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9 μm or any value range between any two of them.

[0157] In some embodiments, the porosity of the separator is 28% - 50%. Exemplarily, the porosity is 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or any value range between any two of them. Optionally, the porosity of the separator is 31% - 40%. By making the porosity of the separator within the above range, it is possible to reduce the influence on the migration rate of lithium ions between the positive and negative electrodes while enabling the separator to have appropriate mechanical strength.

[0158] The present application does not particularly limit the preparation method of the separator. Exemplarily, it can be prepared according to the following method.

[0159] For the separator with a ceramic layer, the ceramic layer is first coated. Ceramic particles and a binder (for example, with a mass ratio of 5:1, and a thickener if any) for forming the ceramic layer are dispersed in a solvent (such as N-methylpyrrolidone NMP) to form a ceramic layer slurry. The ceramic layer slurry is coated on both sides of the base film, and after drying to remove the solvent, a separator with ceramic layers on both sides of the base film is obtained.

[0160] Next, the adhesive layer is coated. A fluoropolymer (such as PVDF, with a final mass content of 20%) is dissolved in an organic solvent (such as NMP), and then a pore-forming agent (such as PEG, with a final mass content of 15%) is added and mixed evenly to obtain an adhesive layer solution. The liquid is coated on the surface of the ceramic layer (for those without a ceramic layer, it can be directly coated on the surface of the base film), and part of the solvent is pre-evaporated at 80 °C, and then dried at 110 °C. The dried separator is immersed in deionized water to dissolve and wash away PEG, thereby forming a porous adhesive layer.

[0161] Electrolyte The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application does not specifically limit the type of the electrolyte, and it can be selected according to requirements.

[0162] In some embodiments, the electrolyte includes a chain carbonate solvent. Based on the total mass of the electrolyte, the mass content of the chain carbonate solvent is 43% - 71%. Exemplarily, based on the total mass of the electrolyte, the mass content of the chain carbonate solvent is any value among 43%, 45%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 65%, 70%, 71% or a value within the range composed of any two of these values. Optionally, based on the total mass of the electrolyte, the mass content of the chain carbonate solvent is 52% - 62%. As a solvent of the electrolyte, the chain carbonate has a lower viscosity than the cyclic carbonate. When the electrolyte contains 43% - 71% of the chain carbonate, the viscosity of the electrolyte is effectively reduced, and the wetting of the electrode assembly is improved.

[0163] In some embodiments, the chain carbonate includes one or both of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). Optionally, the chain carbonate solvent includes DMC and EMC. Further optionally, the chain carbonate is DMC and EMC.

[0164] DMC has a lower viscosity than EMC and can play a greater role in reducing the viscosity of the electrolyte. However, the crystallization temperature of DMC is relatively high, so its low-temperature performance is relatively poor and it is prone to crystallization at low temperatures. When DMC is used in combination with EMC, it can not only effectively reduce the viscosity of the electrolyte and improve the wettability of the electrolyte, but also will not cause a decline in the low-temperature performance of the battery.

[0165] This application does not particularly limit the ratio of DMC to EMC, which can be adjusted as needed. In some embodiments, based on the total mass of the electrolyte, the mass content of DMC is 8% - 43%. Exemplarily, based on the total mass of the electrolyte, the mass content of DMC is any value among 8%, 10%, 12%, 15%, 17%, 20%, 122%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 43% or a value within the range composed of any two of these values. When the content of DMC in the electrolyte is within the above range, it can fully play its role in reducing the viscosity of the electrolyte without affecting the low-temperature performance of the battery.

[0166] In some embodiments, the electrolyte further includes a cyclic carbonate. The cyclic carbonate is beneficial to the dissociation of the lithium salt and improves the conductivity of the electrolyte. In addition, the cyclic carbonate can also form a stable SEI film on the surface of the negative electrode, thus contributing to the improvement of the cycle stability and safety of the battery.

[0167] In some embodiments, the cyclic carbonate may include ethylene carbonate (EC) and / or propylene carbonate (PC).

[0168] In some embodiments, based on the total mass of the electrolyte, the mass content of the cyclic carbonate is 14% - 42%. Exemplarily, based on the total mass of the electrolyte, the mass content of the cyclic carbonate is any value among 14%, 17%, 20%, 23%, 24%, 26%, 28%, 30%, 32%, 33%, 36%, 39%, 42% or a value within the range composed of any two of these numerical values. Optionally, based on the total mass of the electrolyte, the mass content of the cyclic carbonate is 23% - 33%. When the mass content of the cyclic carbonate is within the above range, it is beneficial to improve the conductivity of the electrolyte while not affecting the wettability of the electrolyte to the electrode assembly.

[0169] This application places no particular restrictions on the electrolyte salt. In some embodiments, the electrolyte salt includes a lithium salt. The lithium salt includes one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro-bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate. Optionally, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorophosphate, and lithium bis(fluorosulfonyl)imide.

[0170] In some embodiments, based on the total mass of the electrolyte, the mass content of the electrolyte salt is 8% - 18%, optionally 11% - 15%.

[0171] In some embodiments, the electrolyte may further include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc. Exemplarily, the additives include one or more of vinylene carbonate, fluoroethylene carbonate, and fluorobenzene. Based on the total mass of the electrolyte, the mass content of the additives is 0.4% - 5%, optionally 0.7% - 3%. Exemplarily, in the electrolyte, the mass content of the additives is any value among 0.5%, 0.7%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a value within the range composed of any two of these numerical values.

[0172] In this application, the battery cell includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0173] In some embodiments, a battery cell may include an outer package. The outer package may be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0174] In some embodiments, the outer package of the battery cell may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the battery cell may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic, and examples of the plastic may include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0175] The present application has no particular limitation on the shape of the battery cell, and it may be cylindrical, square, or any other shape. For example, Figure 2 is a battery cell 5 with a square structure as an example.

[0176] In some embodiments, referring to Figure 3 , the outer package may include a housing 51 and a top cover assembly 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator are formed into an electrode assembly 52 through a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 may be one or more, and those skilled in the art can select according to specific actual needs.

[0177] Battery device The second aspect of the present application provides a battery device. The battery device (Battery Apparatus) of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly (Battery CellAssembly) may include a plurality of the battery cells provided in the first aspect above, and the plurality of battery cells are connected in series, in parallel, or in a hybrid connection through a current collecting component.

[0178] In some embodiments, the battery cell assembly (Battery Cell Assembly) is generally formed by arranging a plurality of battery cells.

[0179] As an example, the battery cell assembly may be a battery module (Battery Module), and the battery module is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module may be formed by bundling a plurality of battery cells with a tie strap.

[0180] As an example, the battery cell assembly may also be accommodated in a box by directly fixing a plurality of battery cells to the box.

[0181] As an example, the housing may include a first housing and a second housing. The first housing and the second housing are snapped together so that a closed space is formed inside the housing to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first housing can be a top cover or a bottom plate.

[0182] As an example, the housing may include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the housing to accommodate the battery cell assembly.

[0183] In some embodiments, the housing can be part of the chassis structure of a vehicle. For example, part of the housing can become at least part of the floor of the vehicle, or part of the housing can become at least part of the cross member and longitudinal member of the vehicle.

[0184] In some embodiments, the battery device can be a battery pack, and the battery pack includes a housing and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the housing.

[0185] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, vehicles, ships, and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles, and spaceships, etc.

[0186] Figure 4 is a battery module 4 as an example. Refer to Figure 4 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0187] Optionally, the battery module 4 can further include a housing having an accommodation space, and a plurality of battery cells 5 are accommodated in the accommodation space.

[0188] Figure 5 and Figure 6 is a battery pack 1 as an example. Refer to Figure 5 and Figure 6 , in the battery pack 1, it can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes a first housing 2 and a second housing 3, and the first housing 2 can cover the second housing 3 and form a closed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0189] Power consumption device The third aspect of the embodiments of the present application further provides an electrical device. The electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0190] The electrical device mentioned in the embodiments of the present application includes the battery device provided in the second aspect of the present application. The battery device can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0191] Figure 7 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack or a battery module can be used.

[0192] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinning, and a battery cell can be used as the power source.

[0193] Examples Hereinafter, examples of the present application will be described. The examples described below are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. For those not specified in the examples in terms of specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0194] Example 1 (1) Preparation method of the positive electrode material S1. Lithium carbonate, iron phosphate, glucose, and titanium dioxide are added to water and mixed in a premixing tank at a rotation speed of 1800 rpm, and demagnetization is carried out through a demagnetizing rod with a magnetic field strength of 8000 - 12000 Gs. Among them, the ratio of lithium carbonate and iron phosphate is controlled so that the molar ratio of iron and phosphorus is 0.975, and the mass content of glucose is 5.7% relative to the total amount of iron phosphate. By doping titanium dioxide, the mass content of doped titanium in the carbon-coated lithium iron phosphate positive electrode active material is 1000 ppm.

[0195] S2, subject the mixed raw materials to two grinding-demagnetization cycles in a sand mill. Conduct the first grinding under the conditions of using zirconia balls with a diameter of 0.6 mm and a rotation speed of 500 rpm for 1 h, with the pressure in the grinding chamber less than 0.3 MPa. Demagnetize the raw materials after the first grinding using a permanent magnet demagnetizer, with the demagnetization intensity being greater than or equal to 8000 Gs. Then conduct the second grinding on the demagnetized raw materials to obtain a mixed slurry, where the particle size D V50 is 0.40 μm ± 0.10 μm.

[0196] S3, spray-dry the mixed slurry to obtain a precursor powder.

[0197] S4, sinter the precursor powder to obtain a lithium iron phosphate cathode material. The sintering process includes the following steps.

[0198] First sintering: Sinter the precursor powder in a nitrogen atmosphere, raise the temperature from 25 °C to 760 °C at a heating rate of 5 °C / min, and hold for 10 h. After cooling, obtain the first sintering product.

[0199] Grinding and mixing: Add 1.5% glucose and 3.0% polyethylene glycol based on the total mass of the first sintering product to the first sintering product. Divide it into two groups for grinding (the third grinding). Stop grinding when the particle size D V50 in the first group reaches 1.0 μm (grinding conditions: 550 rpm ± 50 rpm, grinding time 1 h) to obtain the first group of grinding products; stop grinding when the particle size D V50 in the second group reaches 0.31 μm (grinding conditions: 500 rpm ± 50 rpm, grinding time 4 h) to obtain the second group of grinding products; mix the first group of grinding products and the second group of grinding products according to a mass ratio of 70:30 to obtain a mixed intermediate product; spray-dry the mixed intermediate product.

[0200] Second sintering: Sinter the dried mixed intermediate product in a nitrogen atmosphere, raise the temperature from 25 °C to 800 °C at a heating rate of 5 °C / min, and hold for 10 h. After cooling, obtain the second sintering product.

[0201] S5, after sintering, cool to below 100 °C, and crush the second sintering product using airflow crushing to obtain a carbon-coated lithium iron phosphate cathode active material. Among them, the classification frequency of airflow crushing is 25 Hz, and the crushing air pressure is 0.55 MPa.

[0202] (2) Preparation of the positive electrode sheet The positive electrode active material prepared in the above (1) (chemical formula LiFePO4; D A50Mix lithium iron phosphate (the volume average particle size Dv50 is 720 nm), polyvinylidene fluoride, conductive carbon black, and carboxymethyl cellulose in a weight ratio of 97:2:1, then add them to the solvent N-methylpyrrolidone and stir evenly to form the positive electrode slurry; coat the positive electrode slurry on the positive electrode current collector aluminum foil (thickness 15 um) to form a positive electrode film layer (the single-sided coating weight is 0.38 g / 1540.25 mm 2 ), and after drying, perform cold pressing of the electrode sheet under the condition of a roll pressure of 55 tons to obtain a positive electrode sheet (the single-sided coating thickness is 102.8 μm, and the porosity is 28%).

[0203] (3) Preparation of the negative electrode sheet Mix the negative electrode material graphite (the volume average particle size Dv50 is 15 μm), the conductive agent Super-P, the dispersant CMC, and the binder SBR in a mass ratio of 96.4:0.4:1.0:2.2 in an appropriate amount of deionized water and stir well to form the negative electrode slurry; coat the negative electrode slurry on the copper foil (8 um) to form a negative electrode film layer (the single-sided coating weight of the negative electrode film layer is 0.185 g / 1540.25 mm 2 , and the single-sided coating thickness is 82 μm), and after drying and cold pressing, obtain a negative electrode sheet (the porosity is 29%).

[0204] (4) Preparation of the electrolyte In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), mix the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) evenly. Then add lithium hexafluorophosphate and dissolve it in the organic solvent so that the concentration of lithium hexafluorophosphate in the electrolyte is 1.05 mol / L, and add vinylene carbonate (VC) and stir evenly to obtain the electrolyte of Example 1.

[0205] Among them, based on the total mass of the electrolyte, the mass content of dimethyl carbonate is 27.2%, the mass content of ethyl methyl carbonate is 29.9%, the mass content of ethylene carbonate is 28.1%, and the mass content of vinylene carbonate is 2.6%.

[0206] (5) Separator A 7-μm polyethylene film is used as the base film. Alumina powder (particle size 1 μm) of ceramic material and polyvinylidene fluoride (PVDF) as the binder are added to the solvent N-methylpyrrolidone (mass ratio of alumina:PVDF: solvent is 5:1:10) and mixed evenly to form a ceramic layer slurry. The ceramic layer slurry is coated on both sides of the base film and dried to form a ceramic layer. Polyvinylidene fluoride (PVDF) is added to the solvent N-methylpyrrolidone and mixed evenly, and then polyethylene glycol (PEG) as a pore-forming agent is added to make a binder layer solution, where the mass content of PVDF is 20% and the mass content of PEG is 10%. The binder layer solution is coated on the ceramic layer, pre-volatilized at 80 °C and dried at 110 °C, and then immersed in deionized water to dissolve polyethylene glycol, obtaining a separator membrane. The single-sided thickness of the ceramic layer of the obtained separator membrane is measured to be 1.6 μm, the single-sided thickness of the binder layer is 0.65 μm, and the porosity of the separator membrane is 35% according to the following method.

[0207] (6)Preparation of battery cell Stack the above-mentioned positive electrode sheet, separator membrane, and negative electrode sheet in sequence, with the separator membrane placed between the positive electrode sheet and the negative electrode sheet to play a role in isolation, and then form an electrode assembly through the lamination process. Place the electrode assembly in the outer package, inject the above-mentioned electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, forming, and shaping.

[0208] Performance test of electrode sheet (1)Compaction density of electrode sheet The compaction density of the electrode sheet is determined by measuring the single-sided coating weight (g / cm 2 ) of the electrode sheet per unit area and the thickness (cm) of the single-sided coating on the electrode sheet (the number of sampling points > 10). Among them, the compaction density PD of the negative electrode sheet = the single-sided coating weight (g / cm 2 ) of the electrode sheet per unit area / the thickness (cm) of the single-sided coating on the electrode sheet.

[0209] Testing method for single-sided coating weight of electrode sheet After the battery cell is fully discharged (0% SOC) and disassembled, an appropriate amount of electrode sheet is taken, soaked in DME for 1 h and then taken out and dried. Cut 10 electrode sheets of the same size, weigh their weights, and record the average weight of the 10 electrode sheets as m1; then wipe off the active material coatings on both sides of the 10 electrode sheets and weigh the weight of the substrate, and record the average weight of the 10 substrates as m2; then the single-sided coating weight of the electrode sheet = (m2 - m1) / 2.

[0210] Measuring method for thickness of single-sided coating on electrode sheet After the full discharge of the battery cell, disassemble it, take an appropriate amount of the electrode sheet in the double-sided coating area, soak it in DME for 1 h, and then take it out and dry it. Use a micrometer to measure the total thickness of the electrode sheet at 15 different positions, and take the average value as t1; then measure the thickness of the substrate of the electrode sheet at 15 different positions, and take the average value as t2; then the thickness of the single-sided coating of the electrode sheet = (t1 - t2) / 2.

[0211] (2)Measurement of roughness R A10 , R A50 , R A90 measurement Measure according to the specific test method described above. Among them, R A50 is the roughness R value corresponding to the proportion of the cumulative area of the vertical axis in the cumulative distribution curve of the roughness R value being 50%; R A10 is the roughness R value corresponding to the proportion of the cumulative area of the vertical axis in the cumulative distribution curve of the roughness R value being 10%; R A90 is the roughness R value corresponding to the proportion of the cumulative area of the vertical axis in the cumulative distribution curve of the roughness R value being 90%.

[0212] Separator characteristic test (1)Coating thickness Use an argon ion cross-section polisher (such as the IB-09010 CP type argon ion cross-section polisher of JEOL Company, Japan) to polish the separator along the thickness direction (argon gas flow rate 0.12 MPa, polishing time 90 min) to obtain the cross-section of the separator along the thickness direction. Observe that the base film, ceramic layer and adhesive layer are present in the field of view under a field emission scanning electron microscope. In 5 different fields of view, select 5 sites respectively, measure the thickness of the ceramic layer and adhesive layer on the side of the base film, and calculate the average value.

[0213] (2)Separator porosity Determine the porosity of the separator according to the standard GB / T 24586-2009.

[0214] Performance test of battery cell (1)Volume energy density test At 25 °C, charge the battery cell at a constant current of 0.33C to the cut-off voltage of 3.65V, and then charge it at a constant voltage of 3.65V until the current is 0.05C. At this time, the secondary battery is in a fully charged state. After standing the fully charged secondary battery for 5 min, discharge it at a constant current of 0.33C to the cut-off voltage of 2.5V, and record the discharge energy as Q0.

[0215] Measure the length, width and thickness of the battery cell, and then calculate the volume of the battery cell as V; then the volume energy density of the battery = Q0 / V, unit: Wh / L.

[0216] (2)DCR Growth Rate Test Method At 25°C, it is charged at a constant current of 0.33C until 3.65V, then charged at a constant voltage until the current reaches 0.05C, then discharged at 1 / 3C to 50% SOC, left standing for 5 minutes, then discharged with a 3C pulse for 30 seconds, left standing for 40 seconds, then charged with a 3C current for 40 seconds, and left standing for 10 minutes.

[0217] Record the voltage before and after the pulse discharge. The formula for calculating DCR is DCR = (voltage before the pulse discharge after the standing ends - voltage before the standing after the pulse discharge) / pulse current.

[0218] The DCR before the cycle is tested according to the above process and denoted as R0, and the DCR after 2000 cycles is denoted as R1. Then the growth rate of DCR after 2000 cycles = (R1 - R0) / R0 * 100%.

[0219] Cycle Test Method At 25°C, the lithium-ion secondary battery is charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V until the current reaches 0.05C; left standing for 10 minutes; then discharged at a constant current of 0.33C to 2.5V; the above steps are cycled 2000 times.

[0220] Examples 2 - 5 The preparation methods of Examples 2 - 5 are similar to that of Example 1, except that the preparation methods of the positive electrode material and the positive electrode plate are adjusted as shown in Table 1.

[0221] Examples 6 - 10 The preparation methods of Examples 6 - 10 are similar to that of Example 1, except that the compaction density of the electrode plate is adjusted by adjusting the roll pressure during cold pressing of the electrode plate.

[0222] Comparative Example 1 The preparation method of Comparative Example 1 is similar to that of Example 6, except that in step S4, for the first group, the grinding is stopped when the D of the particles V50 reaches 1.50μm; for the second group, the grinding is stopped when the D of the particles V50 reaches 0.45μm.

[0223] Comparative Example 2 The preparation method of Comparative Example 2 is similar to that of Example 1, except that the compaction density of the electrode plate is adjusted by adjusting the roll pressure during cold pressing of the electrode plate to 65 tons.

[0224] According to the same test method as in Example 1, the performances of the battery monomers prepared in Examples 2 to 9 and Comparative Examples 1 and 2 are measured, and the specific results are shown in Table 1.

[0225] Table 1

[0226] As can be seen from Table 1, in Examples 1 to 5, when the compaction density of the positive electrode is the same, with the increase of the lithium iron phosphate particles R A50 it is beneficial to improve the growth of DCR during the battery cycle. The growth of DCR during the cycle is related to problems such as the wrinkling and deformation of the electrode caused by stress concentration during the electrode cycle. The deformation of the electrode will affect the interfacial contact between the electrode and the separator, affecting the normal insertion and extraction of lithium ions, thus leading to an increase in the internal resistance of the battery. Using lithium iron particles with higher roughness can release the stress generated during the insertion and extraction of lithium in the electrode through the slip between the particles, thereby alleviating the damage of the electrode stress concentration to the electrode structure and improving the battery performance.

[0227] In Examples 6 to 10, when using lithium iron particles with the same roughness, as the compaction of the positive electrode increases, the volumetric energy density of the battery increases accordingly.

[0228] Compared with Example 6, in Comparative Example 1, it has the same compaction density, but since R A50 is outside the scope of this application, the DCR growth rate increases significantly, and it is impossible to balance the energy density and cycle performance.

[0229] In addition, compared with Examples 1 to 10, in Comparative Example 2, the compaction density is higher and the energy density is increased, but the DCR growth rate increases significantly, and it is impossible to balance the energy density and cycle performance. If the compaction density is too high, the contact pressure between the particles increases, which may cause particle deformation or rupture, resulting in an increase in side reactions and impedance during charge and discharge; on the other hand, the residual stress of the electrode is higher after high-pressure rolling, and the insertion and extraction of lithium ions during the charge and discharge process will further exacerbate the stress concentration, leading to particle contact failure and electrode structure degradation, forming local "dead zones" and increasing the interfacial impedance. Therefore, in this application, by making the compaction density within a specific range, the high energy density and excellent cycle performance of the battery are balanced.

[0230] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of this application are included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various deformations that those skilled in the art can think of applied to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes a laminated electrode assembly, and the laminated electrode assembly includes a positive electrode tab, a separator, and a negative electrode tab which are stacked. The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector. The positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes lithium-containing transition metal phosphate particles. The compaction density of the positive electrode sheet is 2.25 g / cm 3 - 2.65 g / cm 3 , In the cumulative distribution curve of the roughness area of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the R of the roughness A50 is 0.90 to 0.98, and the R of the roughness A90 is 0.93 or more. R A50 represents the roughness corresponding to the case where the cumulative area ratio of the vertical axis in the roughness cumulative distribution curve is 50%, R A90 represents the roughness corresponding to the case where the cumulative area ratio of the vertical axis in the roughness cumulative distribution curve is 90%.

2. The battery cell according to claim 1, wherein, In the cumulative distribution curve of the roughness area of the particles obtained from the cross-section of the positive electrode film layer in the thickness direction of the electrode sheet, the R of the roughness A90 is 0.93 - 0.

995.

3. The battery cell according to claim 1 or 2, characterized in that, In the roughness area cumulative distribution curve of the particles obtained from the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, the roughness R A10 is 0.85 - 0.90, and R A10 represents the roughness corresponding to the cumulative area ratio of 10% of the cumulative area of the vertical axis in the roughness cumulative distribution curve.

4. The battery cell according to claim 1 or 2, characterized in that, In the cumulative distribution curve of the roughness area of the particles obtained from the cross-section of the positive electrode film layer in the thickness direction of the electrode sheet, the concentration of roughness (R A90 -R A10 ) / R A50 is 0.085 - 0.

105.

5. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the positive electrode sheet is 2.35 g / cm 3 - 2.45 g / cm 3 .

6. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the positive electrode film layer is 0.33 g / 1540.25 mm 2 ~0.43 g / 1540.25 mm 2 .

7. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the positive electrode film layer is 0.36 g / 1540.25 mm 2 ~0.40 g / 1540.25 mm 2 .

8. The battery cell according to claim 1 or 2, characterized in that, The porosity of the positive electrode tab is 23% - 32%.

9. The battery cell according to claim 1 or 2, characterized in that, The lithium-containing transition metal phosphate particles include a lithium-containing transition metal phosphate matrix and a coating layer located on at least part of the surface of the lithium-containing transition metal phosphate matrix. The coating layer contains carbon elements.

10. The battery cell according to claim 9, wherein, The chemical formula of the lithium-containing transition metal phosphate matrix is expressed as Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 , Wherein, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 0.8, 0.9 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N, P; Y includes one or more of O, F.

11. The battery cell according to claim 9, characterized in that, The lithium-containing transition metal phosphate includes lithium iron phosphate.

12. The battery cell according to claim 9, wherein, The lithium-containing transition metal phosphate contains Ti element. Based on the mass of the lithium-containing transition metal phosphate, the mass content of the Ti element is 0.05% - 0.2%.

13. The battery cell according to claim 1 or 2, characterized in that, In the cross-section of the positive electrode film layer along the thickness direction of the electrode sheet, D of the lithium-containing transition metal phosphate particles A50 is 100 nm to 2.5 μm, and D A50 represents the particle size value corresponding to the cumulative area ratio of 50% of the cumulative area on the vertical axis in the area cumulative distribution curve.

14. The battery cell according to claim 1 or 2, characterized in that, The thickness of the positive electrode current collector is 12μm - 20μm.

15. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the negative electrode plate is 1.3 g / cm 3 - 1.55 g / cm 3 .

16. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the negative electrode sheet is 1.40 g / cm 3 - 1.50 g / cm 3 .

17. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the negative electrode film layer is 0.15 g / 1540.25mm 2 ~0.207 g / 1540.25mm 2 .

18. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the negative electrode film layer is 0.17 g / 1540.25 mm 2 ~0.2 g / 1540.25 mm 2 .

19. The battery cell according to claim 1 or 2, characterized in that, The porosity of the negative electrode tab is 23% - 32%.

20. The battery cell according to claim 1 or 2, characterized in that, The thickness of the negative electrode current collector is 6μm - 12μm.

21. The battery cell according to claim 1 or 2, characterized in that, The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite. The volume average particle size Dv50 of the graphite is 13μm - 22μm.

22. The battery cell according to claim 21, wherein The volume average particle size Dv50 of the graphite is 14.5μm - 20μm.

23. The battery cell according to claim 1 or 2, characterized in that, The separator includes a base film and coating layers disposed on both sides of the base film. The coating layers include a bonding layer, and the bonding layer is a continuous layer with a porous structure. The bonding layer includes a fluoropolymer.

24. The battery cell according to claim 23, characterized in that, The fluoropolymer includes one or more of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluorochloroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-trifluorochloroethylene-tetrafluoroethylene-hexafluoropropylene copolymer.

25. The battery cell according to claim 24, wherein The thickness of one side of the bonding layer is 0.15μm - 2μm.

26. The battery cell according to claim 24, characterized in that, The coating layer further includes a ceramic layer disposed between the base film and the bonding layer.

27. The battery cell according to claim 26, wherein, The ceramic layer comprises one or more ceramic particles of alumina, boehmite, silicon oxide, magnesium oxide, titanium oxide, tin oxide, calcium oxide, zirconium oxide, barium sulfate, yttrium oxide, zinc oxide, silicon carbide, magnesium fluoride, barium titanate, aluminum hydroxide, magnesium hydroxide or calcium hydroxide.

28. The battery cell according to claim 26, wherein The single-side thickness of the ceramic layer is 0.5 μm - 4 μm.

29. The battery cell according to claim 23, characterized in that, The thickness of the base film is 7 μm - 9 μm.

30. The battery cell according to claim 1 or 2, characterized in that, The battery cell contains an electrolyte, and the electrolyte includes a chain carbonate solvent. Based on the total mass of the electrolyte, the mass content of the chain carbonate solvent is 43% - 71%.

31. The battery cell according to claim 30, characterized in that, The chain carbonate includes one or both of dimethyl carbonate and ethyl methyl carbonate.

32. The battery cell according to claim 30, characterized in that, The electrolyte further includes a cyclic carbonate.

33. The battery cell according to claim 32, wherein, Based on the total mass of the electrolyte, the mass content of the cyclic carbonate is 14% - 42%.

34. A battery device, characterized in that, Comprising the battery cell according to any one of claims 1 to 33.

35. An electrical device, characterized in that, Comprising the battery device according to claim 34.

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