Battery monomer, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device, and belongs to the technical field of batteries. The battery monomer provided by the invention comprises a positive pole piece, and the positive pole piece comprises a positive current collector, a positive film layer arranged on at least one side of the positive current collector, and a bottom coating layer arranged between the positive current collector and the positive film layer on at least one side, the volume distribution particle size Dv90 of particles in the positive electrode film layer is greater than or equal to 20 microns; the tensile strength of the positive electrode current collector is 220 MPa to 330 MPa; the volume distribution particle size Dv99 of particles in the bottom coating is smaller than or equal to 20 micrometers. The battery monomer provided by the invention has excellent energy density, safety performance and power performance.

Description

Technical Field

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

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As the market pursues the electrical performance of battery cells, the processing difficulty of battery cells increases and the yield rate decreases, resulting in the safety performance and service life of battery cells failing to meet expectations, limiting the further application of batteries. How to take both into account at the same time has become an urgent problem to be solved in this field. Summary of the invention

[0003] The present application is made in view of the above-mentioned problems, and its object is to provide a battery cell, a battery device and an electric device, wherein the battery cell has excellent energy density, safety performance and power performance.

[0004] An embodiment of the first aspect of the present application provides a battery cell, wherein the battery cell includes a positive electrode plate, the positive electrode plate includes a positive electrode collector, a positive electrode film layer arranged on at least one side of the positive electrode collector, and an undercoat layer arranged between the positive electrode collector and the positive electrode film layer on at least one side, wherein the volume distribution particle size Dv90 of the particles in the positive electrode film layer is greater than or equal to 20μm, and can be optionally 20μm-28μm; the tensile strength of the positive electrode collector is 220MPa-330MPa, and can be optionally 280MPa-330MPa; the volume distribution particle size Dv99 of the particles in the undercoat layer is less than or equal to 20μm, and can be optionally 6μm-18μm.

[0005] The volume distribution particle size Dv90 of the particles in the positive electrode film layer of the battery cell provided in the embodiment of the present application is greater than or equal to 20 μm to increase the compaction density of the pole piece and improve the energy density of the battery cell. In order to increase the compaction density of the pole piece, it is necessary to increase the proportion of large particles in the pole piece film layer to achieve a dense stacking of the film layer through the grading theory. However, during the slicing process, the cutter squeezes the large particles, which will cause the large particles to squeeze the current collector, causing the current collector to be squeezed and deformed and fractured instead of cut off, thereby generating burrs and affecting the safety performance of the battery.

[0006] Providing a bottom coating layer with a small particle size can effectively reduce the squeezing of large particles in the positive electrode film layer on the current collector and improve the burr phenomenon. However, due to the lack of large particles in the bottom coating layer, the compaction density of the positive electrode sheet will be sacrificed. Properly increasing the proportion of large particles in the bottom coating layer can alleviate the decrease in compaction density, but it will still cause burr problems. The battery cell provided in the embodiment of the present application is provided with a bottom coating layer with a particle size Dv99 less than or equal to 20μm between the positive electrode film layer and the positive electrode current collector, and is used in combination with a current collector with a tensile strength of 220MPa-330MPa. By improving the ability of the current collector to resist extrusion, while taking into account the compaction density of the positive electrode sheet, the probability of the current collector generating burrs under the squeezing of large particles in the bottom coating layer and the positive electrode film layer is reduced, thereby improving the yield rate during the electrode sheet cutting process and meeting performance and efficiency requirements.

[0007] In any embodiment, the particle size distribution value (Dv90-Dv10) / Dv50 of the particles in the base coating is 2-8.5, and can be 2-6.

[0008] In the embodiments of the present application, a material whose particle size distribution width satisfies the above range is used, and particle grading is used to further improve the compaction density of the electrode, thereby further improving the energy density of the battery while reducing the generation of electrode burrs.

[0009] In any embodiment, the undercoat layer comprises polycrystalline particles, and the Dv99 of the polycrystalline particles in the undercoat layer is 6 μm-20 μm.

[0010] Polycrystalline particles are formed by the aggregation of small-diameter single-crystal particles. When polycrystalline particles are used in the bottom coating and the particle size of the polycrystalline particles is within the above range, it can not only reduce the probability of burrs while maintaining the high pressure density of the pole piece, but also effectively shorten the lithium ion transmission path, reduce concentration polarization, increase the diffusion coefficient of lithium ions in the positive pole piece, and improve the dynamic performance of the battery. At the same time, it is beneficial to the performance of the gram capacity of the battery cell, and further improve the energy density of the battery cell.

[0011] In any embodiment, the base coating layer further comprises single crystal particles.

[0012] In any embodiment, the Dv99 of the single crystal particles in the undercoat layer is 6 μm-15 μm, optionally 6 μm-10 μm; and / or the Dv50 of the single crystal particles in the undercoat layer is 2 μm-6 μm, optionally 3 μm-5 μm.

[0013] The use of single crystal particles that meet the above-mentioned particle size range in the base coating is conducive to forming a graded distribution with the polycrystalline particles, improving the particle size distribution value of the pole piece, increasing the compaction density of the pole piece, and reducing the negative impact on the battery energy density, thereby further improving the battery energy density on the basis of improving the burr problem.

[0014] In any embodiment, the mass ratio of polycrystalline particles to single crystal particles in the base coating is 5:5-9:1, and can be optionally 6:4-8:2.

[0015] Controlling the mass ratio of polycrystalline particles and single crystal particles in the base coating to meet the above range is beneficial to further improve the compaction density of the pole piece, reduce the generation of burrs while improving the high energy density of the battery, improve the yield rate of the pole piece, and meet performance and efficiency requirements.

[0016] In any embodiment, the volume distribution curve of the particles in the positive electrode film layer presents a bimodal distribution, and the peak position difference is greater than or equal to 2 μm.

[0017] In any embodiment, in the volume distribution curve of the particles in the positive electrode film layer, the first peak of the double peak position is located at 2 μm-5.5 μm; the second peak of the double peak position is located at 6 μm-11 μm.

[0018] The volume distribution curve of the particles in the positive electrode film layer presents a bimodal distribution, indicating that the positive electrode film layer includes large particles and small particles of different sizes. Filling the gaps between large particles with small particles is beneficial to improving the compaction density of the electrode sheet, thereby further improving the energy density of the battery.

[0019] In any embodiment, the particles in the positive electrode film layer include polycrystalline particles and single crystal particles.

[0020] In any embodiment, the volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20μm-30μm, optionally 20μm-28μm; and / or, the volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer is 6μm-14μm, optionally 6μm-12μm.

[0021] In any embodiment, the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6μm-15μm, optionally 6μm-13μm; and / or, the volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer is 2μm-6μm, optionally 2μm-5.5μm.

[0022] The combination of polycrystalline particles and single crystal particles that meet the above-mentioned particle size range in the positive electrode film layer is beneficial to improving the particle grading, achieving close stacking of particles in the positive electrode film layer, and further increasing the compaction density of the electrode sheet, thereby increasing the energy density of the battery.

[0023] In any embodiment, the mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer is 5:5-9:1, and can be optionally 6:4-8:2.

[0024] Controlling the mass ratio of polycrystalline particles and single crystal particles in the positive electrode film layer to meet the above range is beneficial to further improve the compaction density of the electrode sheet, so that the battery has excellent energy density.

[0025] In any embodiment, the undercoat layer comprises a first lithium-containing transition metal oxide, the positive electrode film layer comprises a second lithium-containing transition metal oxide, and the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide each independently comprise Li a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 , wherein M1 includes one or more of Mn and Al, and M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K; 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0026] Lithium-containing transition metal oxides have high capacity and are the preferred material for high energy density batteries. When the positive electrode film layer and the bottom coating layer include the above-mentioned types of active materials, it is beneficial to the performance of their specific capacity, thereby further improving the energy density of the battery cell.

[0027] In any embodiment, the first lithium-containing transition metal oxide includes nickel element, and the molar ratio of the nickel element in the first lithium-containing transition metal oxide is 80%-96% based on the total molar number of transition metals in the first lithium-containing transition metal oxide.

[0028] The first lithium-containing transition metal oxide with a molar proportion of nickel of 80%-96% has a high gram capacity, which is conducive to further improving the energy density of the battery cell, but the lithium-containing transition metal oxide with a high nickel proportion also has a high particle hardness, which increases the degree of squeezing of the large particles in the positive electrode film layer on the current collector, making it easy to generate burrs during the cutting process of the positive electrode sheet. The technical solution in the embodiment of the present application is particularly suitable for the positive electrode sheet, which further improves the high energy density of the battery while improving the yield rate during the cutting process of the electrode sheet, meeting the performance and efficiency requirements.

[0029] In any embodiment, the second lithium-containing transition metal oxide includes nickel element, and the molar ratio of the nickel element in the second lithium-containing transition metal oxide is 80%-96% based on the total molar number of transition metals in the second lithium-containing transition metal oxide.

[0030] The undercoat layer includes a second lithium-containing transition metal oxide with a nickel content of 80%-96%, which can reduce the generation of burrs while reducing the negative impact of energy density caused by occupying the positive electrode film layer, which is beneficial to the utilization of the gram capacity of the electrode active material and further improves the energy density of the battery.

[0031] In any embodiment, the thickness L1 of the positive electrode film layer on one side and the thickness L2 of the primer layer on one side satisfy the following formula I: .

[0032] Setting a primer between the positive electrode film layer and the positive electrode current collector can effectively reduce the contact between the active material and the current collector, and reduce the probability of burrs on the pole piece during cutting. However, since the addition of the primer takes up the space of the positive electrode film layer, it has a negative impact on the battery energy density. Controlling the thickness of the primer on one side and the thickness of the positive electrode film on one side to meet the above range can effectively reduce the contact between large particles of the positive electrode active material and the current collector, reduce the probability of burrs on the pole piece during cutting, and further improve the safety performance of the battery cell; on the other hand, it can also reduce the battery capacity loss caused by adding the primer, so that the battery cell still has a high energy density.

[0033] In any embodiment, the thickness L1 of the positive electrode film layer on one side is 30 μm-60 μm.

[0034] The thinning of the positive electrode film layer is conducive to reducing the diffusion path of lithium ions and improving the dynamic performance of battery cells; however, with the thinning of the positive electrode film layer, in order to make the battery have a high energy density, the compaction density of the pole piece is further increased, which makes the current collector more severely squeezed by large particles during slicing, and the probability of burrs is higher. At the same time, with the thinning of the positive electrode film layer and the positive electrode sheet, the burr control level of large-size specifications is tightened simultaneously, and the burrs are more likely to protrude from the edge of the positive electrode film layer, exacerbating the safety hazards of the burr problem.

[0035] In any embodiment, the thickness L2 of the primer layer on one side is 10 μm-30 μm.

[0036] When the thickness of the bottom coating on one side is within the above range, it can reduce the contact between large particles of the positive electrode active material and the current collector, reduce the probability of large-sized burrs on the pole piece during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the deterioration of pole piece compression and battery capacity loss caused by adding the bottom coating, so that the battery cell still has a high energy density.

[0037] In any embodiment, the thickness of the positive electrode current collector is 5 μm-20 μm, and can be 7 μm-15 μm.

[0038] The positive electrode current collector does not contribute to the capacity of the battery, and its thinning is conducive to making room for the positive electrode active material and improving the energy density of the battery cell. However, the thinning of the positive electrode current collector reduces its ability to withstand large particle extrusion during the slitting process, and the burr phenomenon is more serious. The thickness of the positive electrode current collector within the above range is conducive to improving the yield rate during the electrode cutting process while maintaining the high energy density of the battery cell, meeting the performance and efficiency requirements.

[0039] In any embodiment, when the battery cell is fully charged, the compaction density of the positive electrode sheet is 3.4 g / cm 3 -3.7g / cm 3 .

[0040] The compaction density of the positive electrode sheet within the above range is beneficial to maintaining the high energy density of the battery cell while improving the yield rate in the electrode sheet cutting process, thereby meeting the performance and efficiency requirements.

[0041] In any embodiment, the positive electrode sheet is 3.65g / cm 3 The elongation at the cold pressed compaction density is 0.3%-1.0%.

[0042] Although the particle Dv99 in the bottom coating is too small, it is helpful to reduce the generation of burrs, but in order to achieve the same compaction density of the pole piece, the rolling pressure needs to be greatly increased, which leads to an increase in the extension of the current collector, and the pole piece is prone to breaking during the preparation and circulation process, which deteriorates the safety performance. The battery cell provided by the embodiment of the present application achieves high pressure density of the pole piece while maintaining a low cold pressing extension rate, which is conducive to further improving the compaction density of the pole piece and the energy density of the battery cell.

[0043] In any embodiment, the gram capacity of the positive electrode plate is 210 mAh / g-240 mAh / g.

[0044] In any embodiment, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the proportion of positive electrode sheets with burrs among at least 2000 positive electrode sheets is 0%-2%.

[0045] In any embodiment, the volume energy density of the battery cell is 650Wh / L-700Wh / L, and can be optionally 670Wh / L-690Wh / L.

[0046] An embodiment of a second aspect of the present application provides a battery device, which includes the battery cell in the above embodiment.

[0047] An embodiment of the third aspect of the present application provides an electrical device, which includes the battery cell in the above embodiment or the battery device provided by the second aspect of the present application, and the battery cell is used to provide electrical energy.

[0048] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0050] Figure 1 This is a cross-sectional polishing electron microscope morphology image of a positive electrode sheet along the thickness direction in one embodiment of the present application; Figure 2 This is a cross-sectional polishing electron microscope morphology image of the positive electrode sheet in the comparative example of the present application along the thickness direction; Figure 3 This is a cross-sectional morphology diagram of a positive electrode sheet cut along the thickness direction in the comparative example of the present application; Figure 4 is a cross-sectional morphology diagram of a positive electrode sheet cut along the thickness direction in one embodiment of the present application; Figure 5 This is a comparison diagram of Li ion diffusion coefficients of the positive electrode sheet in one embodiment of the present application; Figure 6 is the positive electrode sheet elongation ratio contrast ratio in one embodiment of the present application; Figure 7 This is a comparison chart of the gram capacity of the positive electrode sheet in one embodiment of the present application; Figure 8 is a schematic diagram of a battery cell according to an embodiment of the present application; Fig. 9 yes Figure 8 An exploded view of a battery cell according to an embodiment of the present application is shown; Fig.10 is a schematic diagram of a battery module according to an embodiment of the present application; Fig.11 is a schematic diagram of a battery pack according to an embodiment of the present application; Fig.12 yes Fig.11 An exploded view of a battery pack according to an embodiment of the present application is shown; Fig.13 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0051] Description of reference numerals: 11 positive electrode sheet; 111 positive electrode current collector; 112 bottom coating; 113 positive electrode film layer 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0052] Hereinafter, the battery cell, the method for preparing the battery cell, the polymer and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same 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 descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0053] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0055] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0056] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0057] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0058] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0059] As the market demands for the endurance of electrical devices increase, increasing the volume energy density of battery cells has become a common pursuit in the industry. The increase in the volume energy density of battery cells often requires an increase in the compaction density of the pole pieces to increase the load of active materials per unit volume. However, researchers have found that pole pieces with high compaction density are prone to burrs during the cutting process. Pole pieces with burrs can easily penetrate the diaphragm after the electrode assembly, causing abnormal self-discharge of the battery cell, and even causing short circuit failure of the battery cell, thereby affecting the safety performance and life of the battery, and failing to meet the use requirements of the battery cell.

[0060] Based on the above problems, the first embodiment of the present application provides a battery cell. Figure 1 As shown, the battery cell includes a positive electrode plate 11, and the positive electrode plate includes a positive electrode collector 111, a positive electrode film layer 113 arranged on at least one side of the positive electrode collector, and an undercoat layer 112 arranged between the positive electrode collector and the positive electrode film layer on at least one side, wherein the volume distribution particle size Dv90 of the particles in the positive electrode film layer is greater than or equal to 20μm, and can be optionally 20μm-28μm; the tensile strength of the positive electrode collector is 220MPa-330MPa, and can be optionally 280MPa-330MPa; the volume distribution particle size Dv99 of the particles in the undercoat layer is less than or equal to 20μm, and can be optionally 6μm-15μm.

[0061] In some embodiments, the volume distribution particle size Dv90 of the particles in the positive electrode film layer is greater than or equal to 20 μm. In some embodiments, the volume distribution particle size Dv90 of the particles in the positive electrode film layer is 20 μm-28 μm. In some embodiments, the volume distribution particle size Dv90 of the particles in the positive electrode film layer is 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, or any range between any two of the foregoing values. It can be understood that the particles in the positive electrode film layer mainly come from the positive electrode active material particles.

[0062] In some embodiments, the tensile strength of the positive current collector is 220MPa-330MPa. In some embodiments, the tensile strength of the positive current collector is 280MPa-330MPa. In some embodiments, the tensile strength of the positive current collector is 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300MPa, 310MPa, 320MPa, 330MPa, or any range between any two of the foregoing values.

[0063] In some embodiments, the volume distribution particle size Dv99 of the particles in the primer layer is less than or equal to 20 μm. In some embodiments, the volume distribution particle size Dv99 of the particles in the primer layer is 6 μm-18 μm. In some embodiments, the volume distribution particle size Dv99 of the particles in the primer layer is 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, or any range between any two of the foregoing values.

[0064] When used in this article, the term "burr" refers to a metal protrusion or protrusion extending outward from the current collector in accordance with the IEEE1725 battery cell safety performance review and testing standard; the extension direction can be in any direction, such as the thickness direction or the pole piece plane direction, and the causes of its occurrence include but are not limited to cutting, tearing, etc.

[0065] When used in this article, the term "tensile strength" refers to the maximum tensile force that the current collector can withstand per unit cross-sectional area during the stretching process, reflecting the ability of the material to resist fracture. Its value can be measured by instruments or methods known in the art. As an example, it can be measured by the following method: take a current collector, or disassemble the current collector from a battery cell, cut the current collector into a test sample with a size of 2cm×5cm, place the cut current collector aluminum foil on a tensile testing machine and stretch it until the aluminum foil breaks, and take the maximum tensile stress N1 of the sample during the current collector stretching and fracture process as the tensile strength of the sample, in MPa.

[0066] When used in this article, the terms "volume distribution particle size Dv99, Dv90, Dv50, Dv10" refer to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 99%, 90%, 50%, and 10%, respectively. The numerical values ​​can be measured using conventional instruments and methods in the field. For example, it can be measured with reference to GB / T19077-2016 using an instrument that uses a particle size distribution laser diffraction method (such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK).

[0067] The volume distribution particle size Dv90 of the particles in the positive electrode film layer and the volume distribution particle size Dv99 of the particles in the undercoat layer can be tested by any known method in the art. As an example, powder is scraped from the positive electrode film layer or the undercoat layer and tested in the manner described above.

[0068] The volume distribution particle size Dv90 of the particles in the positive electrode film layer of the battery cell provided in the embodiment of the present application is greater than or equal to 20 μm to increase the compaction density of the pole piece and improve the energy density of the battery cell. In order to increase the compaction density of the pole piece, it is necessary to increase the proportion of large particles in the pole piece film layer to achieve a dense stacking of the film layer through the grading theory. However, during the slicing process, the cutter squeezes the large particles, which will cause the large particles to squeeze the current collector, causing the current collector to be squeezed and deformed and fractured instead of cut off, thereby generating burrs, such as Figure 3 As shown, it affects the safety performance of the battery.

[0069] Studies have shown that if Figure 2 As shown in the figure, setting a layer of small particle size bottom coating can effectively reduce the squeezing of large particles in the positive electrode film layer on the current collector and improve the burr phenomenon. However, due to the lack of large particles in the bottom coating, the compaction density of the positive electrode sheet will be sacrificed. Please continue to refer to Figure 1 , compared to Figure 2 The technical solution shown in FIG. 1 can alleviate the decrease in compaction density by appropriately increasing the proportion of large particles in the base coating, but it will still cause burr problems, such as Figure 3 The battery cell provided in the embodiment of the present application is provided with a base coating layer with a particle size Dv99 less than or equal to 20 μm between the positive electrode film layer and the positive electrode current collector, and is used in combination with a current collector with a tensile strength of 220 MPa-330 MPa. By improving the anti-extrusion ability of the current collector, the probability of the current collector generating burrs under the extrusion of large particles in the base coating layer and the positive electrode film layer is reduced while taking into account the compaction density of the positive electrode sheet, as shown in FIG. Figure 4 As shown, the yield rate in the electrode cutting process is improved to meet performance and efficiency requirements.

[0070] In some embodiments, the particle size distribution value of the particles in the primer layer (Dv90-Dv10) / Dv50 is 2-8.5. In some embodiments, the particle size distribution value of the particles in the primer layer (Dv90-Dv10) / Dv50 is 2-6.

[0071] In some embodiments, the particle size distribution value (Dv90-Dv10) / Dv50 of the particles in the base coating layer can be selected as 2, 3, 4, 5, 6, 7, 8, 8.5, or any range between any two of the aforementioned values.

[0072] In this article, the term "particle size distribution value (Dv90-Dv10) / Dv50" has a well-known meaning in the art, which refers to the parameter of the particle size distribution width, reflecting the uniformity or dispersion of the particle size. The test can be performed using methods known in the art, such as the particle size distribution diagram of the sample based on the volume distribution, and the particle size distribution value is calculated using the formula (Dv90-Dv10) / Dv50.

[0073] In the embodiments of the present application, a material whose particle size distribution width satisfies the above range is used, and particle grading is used to further improve the compaction density of the electrode, thereby further improving the energy density of the battery while reducing the generation of electrode burrs.

[0074] In some embodiments, the base coating layer includes polycrystalline particles, and the Dv99 of the polycrystalline particles in the base coating layer is 6-20 μm.

[0075] In some embodiments, the Dv99 of the polycrystalline particles in the base coating can be selected to be 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any range between any two of the aforementioned values.

[0076] When used in this article, the term "polycrystalline particles" refers to agglomerates of single crystal particles. The agglomeration here is a hard agglomeration caused by chemical bonding of single crystal particles, which makes the polycrystalline particles have more clear grain boundaries and inconsistent atomic arrangement orientation. After cutting the cross section of the polycrystalline particles, it can be seen that the particles are formed by the agglomeration of many primary particles.

[0077] When used in this article, the term "single crystal particle" refers to the smallest unit of a particle within a certain observation range. The interior of a single crystal particle may include defects of any form, but it is impossible to define smaller particles therein. It can be understood that the single crystal particle described in this article does not necessarily mean that there are no grain boundaries inside the single crystal, and it is a continuous and consistent periodic arrangement of atoms, molecules or ions in three-dimensional space, but it means that on a certain observation scale, it is impossible to define smaller particles inside the single crystal through grain boundaries.

[0078] Polycrystalline particles are formed by the aggregation of small-sized single-crystalline particles. Figure 5 and Figure 7 As shown, when polycrystalline particles are used in the bottom coating and the particle size of the polycrystalline particles is within the above range, it can not only reduce the probability of burrs while maintaining the high pressure density of the electrode, but also effectively shorten the lithium ion transmission path, reduce concentration polarization, increase the diffusion coefficient of lithium ions in the positive electrode, and enhance the dynamic performance of the battery. At the same time, it is beneficial to the performance of the battery cell's gram capacity and further improve the energy density of the battery cell.

[0079] In some embodiments, the base coating further comprises single crystal particles.

[0080] In some embodiments, the Dv99 of the single crystal particles in the bottom coating is 6 μm-15 μm. In some embodiments, the Dv99 of the single crystal particles in the bottom coating is 6 μm-10 μm. In some embodiments, the Dv99 of the single crystal particles in the bottom coating can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any range between any two of the foregoing values.

[0081] In some embodiments, the Dv50 of the single crystal particles in the bottom coating is 2 μm-6 μm. In some embodiments, the Dv50 of the single crystal particles in the bottom coating is 3 μm-5 μm. In some embodiments, the Dv50 of the single crystal particles in the bottom coating can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any range between any two of the foregoing values.

[0082] The use of single crystal particles that meet the above-mentioned particle size range in the base coating is conducive to forming a graded distribution with the polycrystalline particles, improving the particle size distribution value of the pole piece, increasing the compaction density of the pole piece, and reducing the negative impact on the battery energy density, thereby further improving the battery energy density on the basis of improving the burr problem.

[0083] In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the bottom coating is 5:5-9:1. In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the bottom coating is 6:4-8:2. In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the bottom coating can be 5:5, 6:4, 7:3, 8:2, 9:1, or any range between any two of the foregoing values.

[0084] When used in this article, the mass proportion of polycrystalline particles and single crystal particles in the base coating can be determined by the following method: take a prepared positive electrode plate, or a positive electrode plate disassembled from a battery, and perform a CP-SEM test. Randomly select a number of points for shooting, and the number of points is ≥10, which can be 10, 20, 50, 100, etc. The area ratio of the polycrystalline particles and single crystal particles in the captured image to the size of the base coating is calculated, and the average value is obtained. The area ratio between the polycrystalline particles and the single crystal particles in the base coating can be equivalent to the mass ratio of the polycrystalline particles to the single crystal particles in the base coating.

[0085] Controlling the mass ratio of polycrystalline particles and single crystal particles in the base coating to meet the above range is beneficial to further improve the compaction density of the pole piece, reduce the generation of burrs while improving the high energy density of the battery, improve the yield rate of the pole piece, and meet performance and efficiency requirements.

[0086] In some embodiments, the volume distribution curve of the particles in the positive electrode film layer presents a bimodal distribution, and the peak position difference is greater than or equal to 2 μm.

[0087] In some embodiments, the volume distribution curve of the particles in the positive electrode film layer presents a bimodal distribution, and the peak position difference is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or a range between any two of the aforementioned values.

[0088] In some embodiments, in the volume distribution curve of the particles in the positive electrode film layer, the first peak of the double peak position is located at 2 μm-5.5 μm; the second peak of the double peak position is located at 6 μm-11 μm.

[0089] In some embodiments, in the volume distribution curve of particles in the positive electrode film layer, the first peak of the bimodal peak is located at 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, or a range between any two of the aforementioned values; the second peak of the bimodal peak is located at 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, or a range between any two of the aforementioned values.

[0090] The volume distribution curve of particles in the positive electrode film layer can refer to GB / T19077-2016 and be tested using the test method described above. The volume distribution curve of particles in the positive electrode film layer presents a bimodal distribution, indicating that the positive electrode film layer includes large particles and small particles of different sizes. Filling the gaps between large particles with small particles is beneficial to improving the compaction density of the pole piece, thereby further improving the energy density of the battery.

[0091] In some embodiments, the particles in the positive electrode film layer include polycrystalline particles and single crystal particles.

[0092] In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20 μm-30 μm. In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20 μm-28 μm.

[0093] In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer can be selected as 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, or any range between any two of the aforementioned values.

[0094] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer is 6 μm-14 μm. In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer is 6 μm-12 μm.

[0095] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer can be selected to be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or any range between any two of the aforementioned values.

[0096] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6 μm-15 μm. In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6 μm-13 μm.

[0097] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer can be selected to be 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any range between any two of the aforementioned values.

[0098] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer is 2 μm-6 μm, and can be optionally 2 μm-5.5 μm.

[0099] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer can be selected to be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, or any range between any two of the aforementioned values.

[0100] The combination of polycrystalline particles and single crystal particles that meet the above-mentioned particle size range in the positive electrode film layer is beneficial to improving the particle grading, achieving close stacking of particles in the positive electrode film layer, and further increasing the compaction density of the electrode sheet, thereby increasing the energy density of the battery.

[0101] In some embodiments, the mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer is 5:5-9:1. In some embodiments, the mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer is 6:4-8:2.

[0102] In some embodiments, the mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer can be selected as 5:5, 6:4, 7:3, 8:2, 9:1, or any range between any two of the aforementioned values.

[0103] It can be understood that the mass ratio of polycrystalline particles and single crystal particles in the positive electrode film layer can be tested by the method for determining the mass ratio of polycrystalline particles and single crystal particles in the base coating layer described above. The difference lies in the calculation of the area ratio of the polycrystalline particles and single crystal particles in the image to the size of the positive electrode film layer.

[0104] Controlling the mass ratio of polycrystalline particles and single crystal particles in the positive electrode film layer to meet the above range is beneficial to further improve the compaction density of the electrode sheet, so that the battery has excellent energy density.

[0105] In some embodiments, the undercoat layer includes a first lithium-containing transition metal oxide, the positive electrode film layer includes a second lithium-containing transition metal oxide, and the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide each independently include Li a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 , wherein M1 includes one or more of Mn and Al, and M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K; 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0106] It can be understood that the chemical components of the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide may be the same or different.

[0107] In some embodiments, a1 can be selected as 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, or any range between any two of the aforementioned values. In some embodiments, x1 can be selected as 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or any range between any two of the aforementioned values. In some embodiments, y1 can be selected as 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or any range between any two of the aforementioned values. In some embodiments, z1 can be selected as 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or any range between any two of the aforementioned values. In some embodiments, w1 can be selected as 0, 0.02, 0.04, 0.06, 0.08, 0.1, or any range between any two of the above values. In some embodiments, b1 can be selected as -0.1, -0.05, 0, 0.05, 0.1, or any range between any two of the above values.

[0108] Lithium-containing transition metal oxides have high capacity and are the preferred material for high energy density batteries. When the positive electrode film layer and the bottom coating layer include the above-mentioned types of active materials, it is beneficial to the performance of their specific capacity, thereby further improving the energy density of the battery cell.

[0109] In some embodiments, the first lithium-containing transition metal oxide includes nickel element, and the molar ratio of nickel element in the first lithium-containing transition metal oxide is 80%-96% based on the total molar number of transition metal in the first lithium-containing transition metal oxide.

[0110] In some embodiments, based on the total molar number of transition metal in the first lithium-containing transition metal oxide, the molar ratio of nickel element in the first lithium-containing transition metal oxide can be selected to be 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, or any range between any two of the foregoing values.

[0111] When used in this article, the molar ratio of the transition metal element in the first lithium-containing transition metal oxide can be determined by instruments and methods known in the art. As an example, it can be measured by the following method: scrape the powder from the positive electrode film layer, take 0.5g of the material to be tested, soak it in 100mL of aqua regia solution for digestion, the digestion temperature is 50°C, and then take the completely dissolved solution for inductively coupled plasma (ICP) testing to detect the content of transition metals (such as Ni, Co, Mn ions) in the solution, and divide the molar number of nickel elements by the total molar number of transition metal elements as the molar ratio of nickel elements in the first lithium-containing transition metal oxide based on the total molar number of transition metals in the first lithium-containing transition metal oxide.

[0112] The first lithium-containing transition metal oxide with a molar proportion of nickel of 80%-96% has a high gram capacity, which is conducive to further improving the energy density of the battery cell, but the lithium-containing transition metal oxide with a high nickel proportion also has a high particle hardness, which increases the degree of squeezing of the large particles in the positive electrode film layer on the current collector, making it easy to generate burrs during the cutting process of the positive electrode sheet. The technical solution in the embodiment of the present application is particularly suitable for the positive electrode sheet, which further improves the high energy density of the battery while improving the yield rate during the cutting process of the electrode sheet, meeting the performance and efficiency requirements.

[0113] In some embodiments, the second lithium-containing transition metal oxide includes nickel, and the molar ratio of the nickel in the second lithium-containing transition metal oxide is 80%-96% based on the total molar number of transition metals in the second lithium-containing transition metal oxide.

[0114] In some embodiments, based on the total molar number of transition metal in the second lithium-containing transition metal oxide, the molar ratio of nickel element in the second lithium-containing transition metal oxide can be selected to be 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, or any range between any two of the foregoing values.

[0115] As used herein, the molar ratio of the transition metal element in the second lithium-containing transition metal oxide is determined by instruments and methods known in the art. As an example, powder is scraped from the bottom coating and tested using the test method for the molar ratio of the transition metal element in the first lithium-containing transition metal oxide as described above.

[0116] The undercoat layer includes a second lithium-containing transition metal oxide with a nickel content of 80%-96%, which can reduce the generation of burrs while reducing the negative impact of energy density caused by occupying the positive electrode film layer, which is beneficial to the utilization of the gram capacity of the electrode active material and further improves the energy density of the battery.

[0117] In some embodiments, the coating thickness L1 of the positive electrode film layer on one side and the coating thickness L2 of the primer layer on one side satisfy the following formula I: .

[0118] In some embodiments, the coating thickness L1 of the positive electrode film layer on one side and the coating thickness L2 of the primer layer on one side satisfy the value of L2 / (L1+L2) of 10%, 20%, 30%, 40%, 50%, or a range between any two of the aforementioned values.

[0119] When used in this article, the thickness of the positive electrode film layer on one side and the thickness of the undercoat layer on one side can be observed and measured by scanning electron microscopy on the interface of the positive electrode plate.

[0120] Setting a primer between the positive electrode film layer and the positive electrode current collector can effectively reduce the contact between the active material and the current collector, and reduce the probability of burrs on the pole piece during cutting. However, since the addition of the primer takes up the space of the positive electrode film layer, it has a negative impact on the battery energy density. Controlling the thickness of the primer on one side and the thickness of the positive electrode film on one side to meet the above range can effectively reduce the contact between large particles of the positive electrode active material and the current collector, reduce the probability of burrs on the pole piece during cutting, and further improve the safety performance of the battery cell; on the other hand, it can also reduce the battery capacity loss caused by adding the primer, so that the battery cell still has a high energy density.

[0121] In some embodiments, the thickness L1 of the positive electrode film layer on one side is 30 μm-60 μm. In some embodiments, the thickness L1 of the positive electrode film layer on one side is 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, or any range between any two of the foregoing values.

[0122] The thinning of the positive electrode film layer is conducive to reducing the diffusion path of lithium ions and improving the dynamic performance of battery cells; however, with the thinning of the positive electrode film layer, in order to make the battery have a high energy density, the compaction density of the pole piece is further increased, which makes the current collector more severely squeezed by large particles during slicing, and the probability of burrs is higher. At the same time, with the thinning of the positive electrode film layer and the positive electrode sheet, the burr control level of large-size specifications is tightened simultaneously, and the burrs are more likely to protrude from the edge of the positive electrode film layer, exacerbating the safety hazards of the burr problem.

[0123] In some embodiments, the thickness L2 of the primer layer on one side is 10 μm-30 μm. In some embodiments, the thickness L2 of the primer layer on one side is 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, or any range between any two of the foregoing values.

[0124] When the thickness of the bottom coating on one side is within the above range, it can reduce the contact between large particles of the positive electrode active material and the current collector, reduce the probability of large-sized burrs on the pole piece during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the deterioration of pole piece compression and battery capacity loss caused by adding the bottom coating, so that the battery cell still has a high energy density.

[0125] In some embodiments, the thickness of the positive electrode current collector is 5 μm-20 μm. In some embodiments, the thickness of the positive electrode current collector is 7 μm-15 μm. In some embodiments, the thickness of the positive electrode current collector is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or any range between any two of the foregoing values.

[0126] The positive electrode current collector does not contribute to the capacity of the battery, and its thinning is conducive to making room for the positive electrode active material and improving the energy density of the battery cell. However, the thinning of the positive electrode current collector reduces its ability to withstand large particle extrusion during the slitting process, and the burr phenomenon is more serious. The thickness of the positive electrode current collector within the above range is conducive to improving the yield rate during the electrode cutting process while maintaining the high energy density of the battery cell, meeting the performance and efficiency requirements.

[0127] In some embodiments, the cold pressed density of the positive electrode plate is 3.1 g / cm 3 -3.8g / cm 3 In some embodiments, the cold pressed density of the positive electrode plate is 3.55 g / cm 3 -3.75g / cm 3 In some embodiments, the cold pressed density of the positive electrode sheet may be 3.1 g / cm 3 、3.2g / cm 3 、3.3g / cm 3 、3.4g / cm 3 、3.5g / cm 3 、3.6g / cm 3 、3.7g / cm 3 、3.8g / cm 3 , or any range between any two of the aforementioned values.

[0128] When used in this article, after the positive electrode sheet is cold pressed, the compaction density of the positive electrode sheet can be measured using instruments and methods known in the art. As an example, the following method can be used for testing: take a positive electrode sheet prepared after cold pressing, use an electronic balance to weigh the electrode sheet test sample with an area of ​​S, and record the weight as W, and then measure the thickness T of the electrode sheet (it can be measured using an instrument that can measure the thickness of the electrode sheet in the art, including but not limited to instruments such as micrometers), and after the positive electrode sheet is cold pressed, the compaction density of the positive electrode sheet can be calculated by the formula W / (T×S).

[0129] In some embodiments, when the battery cell is fully charged, the compaction density of the positive electrode sheet is 3.4 g / cm 3 -3.7g / cm 3 In some embodiments, when the battery cell is fully charged, the compaction density of the positive electrode sheet can be 3.4 g / cm 3 、3.45g / cm 3 、3.5g / cm 3 、3.55g / cm 3 、3.6g / cm 3 、3.65g / cm 3 、3.7g / cm 3 , or any range between any two of the aforementioned values.

[0130] When used in this article, when the battery cell is fully discharged, the compaction density of the positive electrode plate can be measured using instruments and methods known in the art. As an example, the following method can be used for testing: place the battery cell at 25°C and let it stand for 2h. When the battery temperature is maintained at 25°C, discharge the battery at a constant current of 1 / 3C to 2.8V and then let it stand for 30min. Discharge it at a constant current of 0.04C to 2.8V, disassemble the fully discharged plate, clean the residual electrolyte with an organic solvent (the organic solvent can be a conventional solvent in the art that can clean the electrolyte, including but not limited to dimethyl carbonate, etc.), remove the residual electrolyte and dry the plate, and then use the aforementioned positive electrode plate compaction density measurement method to measure the compaction density of the positive electrode plate of the battery cell after full discharge.

[0131] The compaction density of the positive electrode sheet within the above range is beneficial to maintaining the high energy density of the battery cell while improving the yield rate in the electrode sheet cutting process, thereby meeting the performance and efficiency requirements.

[0132] In some embodiments, the positive electrode sheet is 3.65 g / cm 3 The cold pressing elongation at the cold pressing compaction density is 0.3%-1.0%. In some embodiments, the positive electrode sheet is 3.65g / cm 3The cold pressing elongation at the cold pressing compaction density is 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any range between any two of the foregoing values.

[0133] When used in this article, the term "cold pressing elongation of the positive electrode sheet" has a meaning well known in the art, which represents the ability of the sheet to undergo plastic deformation before and after cold pressing, and can be measured by instruments and methods known in the art. As an example, the following method can be used for measurement: before the sheet is cold pressed, take a section of positive electrode sheet with a length of L, and then roll the positive electrode sheet from small to large according to target pressures of cold pressing compaction densities of different sizes, and record the length L1 of the sheet after each rolling. The elongation of the positive electrode sheet at the corresponding compaction density can be calculated using the formula (L1-L) / L×100%.

[0134] Although the Dv99 of the particles in the base coating is too small, it is helpful to reduce the generation of burrs. However, in order to achieve the same compaction density of the pole piece, the rolling pressure needs to be greatly increased, which leads to increased elongation of the current collector. The pole piece is prone to breakage during the preparation and circulation process, which deteriorates the safety performance. Figure 6 As shown, the battery cell provided in the embodiment of the present application achieves high pressure density of the pole piece while maintaining a low cold pressing elongation rate, which is beneficial to further improve the compaction density of the pole piece and the energy density of the battery cell.

[0135] In some embodiments, the gram capacity of the positive electrode sheet is 210mAh / g-240mAh / g. In some embodiments, the gram capacity of the positive electrode sheet is 210mAh / g, 215mAh / g, 220mAh / g, 225mAh / g, 230mAh / g, 235mAh / g, 240mAh / g, or any range between any two of the foregoing values.

[0136] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the proportion of positive electrode sheets with burrs among 2000 positive electrode sheets is 0%-2%. In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the proportion of positive electrode sheets with burrs among 2000 positive electrode sheets is 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any range between any two of the foregoing values.

[0137] As used herein, a positive electrode sheet with burrs refers to a positive electrode sheet with a burr size calibrated after the positive electrode sheet is cut. The size is greater than or equal to 40% of the thickness of the positive electrode sheet and is included in the statistical range, and is calibrated as a positive electrode sheet with burrs. The proportion of positive electrode sheets with burrs can be tested by methods known in the art. As an example, the following method can be used for testing: observe a certain number of cut electrode sheets through a microscope (including but not limited to CCD), count the frequency K1 of electrode sheets with burrs, and calculate the proportion of electrode sheets with burrs as K1 / total number of electrode sheets × 100%.

[0138] As used herein, the term "burr size" refers to the absolute length of the burr (not limited to the vertical distance). The burr size can be tested using instruments and methods known in the art. For example, the following method can be used to test: use a CCD instrument to observe the burrs after cutting (such as Keyence 600), the test temperature is 25°C, the test electrode size is 80mm×60mm, the magnification is 300x, the light intake opening is 30%, and the burr size is calibrated, such as Figure 3 shown.

[0139] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (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.).

[0140] 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 fluorine-containing acrylate resin.

[0141] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0142] In some embodiments, the positive electrode plate can be prepared in the following manner: the components for preparing the base coating, such as the first lithium-containing transition metal oxide, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a base coating slurry; the second lithium-containing transition metal oxide, the conductive agent, the binder and other components are dispersed in a solvent to form a positive electrode film slurry; the base coating slurry is first coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode film slurry is then coated on the surface of the base coating, and after drying, cold pressing and other processes, the positive electrode plate can be obtained.

[0143] [Negative electrode] The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.

[0144] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0145] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper 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 substrate. The composite current collector may be formed by forming a metal material (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.).

[0146] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0147] In some embodiments, the negative electrode film layer may further include a binder, which 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).

[0148] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0149] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0150] 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0151] [Electrolytes] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0152] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0153] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0154] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0155] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0156] [Isolation film] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0157] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0158] [Battery Cell] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0159] In some embodiments, the volumetric energy density of the battery cell is 650Wh / L-700Wh / L. In some embodiments, the volumetric energy density of the battery cell is 670Wh / L-690Wh / L. In some embodiments, the volumetric energy density of the battery cell is 650Wh / L, 655Wh / L, 660Wh / L, 665Wh / L, 670Wh / L, 675Wh / L, 680Wh / L, 685Wh / L, 690Wh / L, 695Wh / L, 700Wh / L, or any range between any two of the foregoing values.

[0160] When used herein, the volume energy density of a battery cell can be measured by instruments and methods known in the art. For example, the following method can be used for measurement: the weight M of all active materials loaded per unit area of ​​the positive electrode sheet in the battery cell is measured respectively, and the cell volume is V; each battery is charged at a rate of 0.33C at room temperature to a voltage equal to 4.25V, and then discharged at a rate of 0.33C to a voltage equal to 2.8V, and the discharge energy S0 is measured. Battery mass energy density = S0 / M; cell volume energy density = S0 / V.

[0161] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0162] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0163] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 8 The battery cell 5 is a square structure as an example.

[0164] In some embodiments, reference Fig. 9 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or 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 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0165] [Battery device] The present application also provides a battery device, the battery device comprising the battery cell provided in the present application. In some embodiments, the battery device is one or more of a battery module, a battery pack, and an energy storage device.

[0166] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0167] Fig.10 4 is an example of a battery module. Fig.10 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0168] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0169] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0170] Fig.11 and Fig.12 1 is a battery pack 1 as an example. Fig.11 and Fig.12The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0171] [Electrical devices] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may 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 and satellites, energy storage systems, etc., but are not limited thereto.

[0172] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0173] Fig.13 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0174] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0175] Example Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0176] 1. Preparation method Example 1 1) Preparation of positive electrode Preparation of base coating slurry: LiNi ternary active material with Dv99 of 15 μm 0.92 Co 0.04 Mn 0.04 O2 polycrystalline particles and LiNi with Dv99 of 7μm and Dv50 of 2.5μm 0.92 Co0.04 Mn 0.04 A mixture of O2 single crystal particles (polycrystalline particles: single crystal particles is 7:3), conductive carbon, and binder PVDF are mixed in a mass ratio of 98.3:0.8:0.9, and a solvent N-methyl-2-pyrrolidone (NMP) is added, and the mixture is stirred under a vacuum stirrer until the system is uniform, thereby obtaining a primer slurry; Preparation of positive electrode film slurry: Polycrystalline ternary active material LiNi with Dv99 of 25μm and Dv50 of 9μm 0.92 Co 0.04 Mn 0.04 O2, single crystal ternary active material LiNi with Dv99 of 12μm and Dv50 of 5μm 0.92 Co 0.04 Mn 0.04 A mixture of O2 (the mass ratio of polycrystalline particles: single crystal particles is 7:3), conductive carbon, and binder PVDF are mixed in a mass ratio of 98:1:1, and a solvent NMP is added. The mixture is stirred under the action of a vacuum stirrer until the system is uniform, thereby obtaining a positive electrode film slurry; Take a positive electrode current collector aluminum foil with a tensile strength of 300 MPa, evenly apply the primer slurry on both sides of the positive electrode current collector and dry it to form a primer layer, wherein the coating weight on one side is 40 mg / 1540.25 mm 2 ; The positive electrode film slurry is evenly coated on the surface of the base coating away from the positive electrode current collector, and the single-sided coating weight is 160mg / 1540.25mm 2 After drying at room temperature, the film was transferred to an oven for further drying, and then cold pressed to obtain a positive electrode sheet. After cold pressing, the thickness of the bottom coating on one side was 10 μm, the thickness of the positive electrode film on one side was 40 μm, and the compaction density of the positive electrode film was 3.65 g / cm 3 ; Pole sheet slitting (one out of two): the positive electrode sheet is slitting on the slitting machine, the slitting speed is 0.5m / s, the slitting knife is made of steel, and the negative pressure of the slitting machine is -10Kpa; Pole piece cutting: The slit pole pieces are wound and cut, with a winding speed of 0.6m / s, each winding core length of 3m, the cutting knife is made of steel, and the negative pressure in the winding machine is -10Kpa.

[0177] 2) Preparation of negative electrode sheet The negative electrode material hard carbon, binder polyvinyl alcohol, and conductive agent SP-Li were fully mixed and ball-milled in a deionized water solvent system at a mass ratio of 90:5:5 to obtain a negative electrode slurry. The negative electrode slurry was mixed at a mass ratio of 155 mg / 1540.25 mm 2 The single-sided coating weight of the film was double-sided coated on the surface of the copper foil and vacuum dried overnight at a temperature of 110° C. to obtain a negative electrode sheet.

[0178] 3) Preparation of diaphragm A polyethylene film with a thickness of 13 μm was used as the separator.

[0179] 4) Preparation of electrolyte Lithium hexafluorophosphate (LiPF6) was dissolved in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to form a uniform solution, thereby obtaining an electrolyte with a LiPF6 concentration of 1 mol / L.

[0180] 5) Battery assembly Place them in the order of "diaphragm-negative electrode sheet-diaphragm-positive electrode sheet", fix one end of the positive electrode sheet, negative electrode sheet and two separators to the discharge roller, and fix the other end to the winding shaft after stacking together. Use a motor to rotate the winding shaft, wind up the positive electrode sheet, negative electrode sheet and two separators, and obtain a wound bare cell. Place the bare cell in an outer package, inject the above-mentioned electrolyte and package it to obtain a battery cell.

[0181] Among them, the volume distribution particle size Dv99 of the particles in the bottom coating of the positive electrode sheet is 15μm, and the volume distribution curve of the particles in the positive electrode film layer shows a bimodal distribution, with the peak positions of 5μm and 9μm respectively, and the peak position difference is 4μm; The particle size distribution value of the bottom coating (Dv90-Dv10) / Dv50 is 4.8; the mass ratio of polycrystalline particles to single crystal particles in the bottom coating is 7:3; the thickness of the bottom coating on one side L2 is 10μm; the thickness of the positive electrode film on one side L1 is 40μm; the thickness relationship between the bottom coating on one side and the positive electrode film L2 / (L1+L2) is 20%; The thickness of the positive electrode sheet is 113μm; the cold pressed density of the positive electrode sheet is 3.65g / cm 3 ;The volume energy density of the battery cell is 695Wh / L.

[0182] Comparative Example 1 The preparation method of the battery cell of Comparative Example 1 is similar to that of the battery cell of Example 1, except that the positive electrode current collector of the battery cell of Comparative Example 1 does not meet the tensile strength of 220 MPa-330 MPa. Specific preparation parameters are shown in Table 1.

[0183] Comparative Example 2 The preparation method of the battery monomer of Comparative Example 2 is similar to that of the battery monomer of Example 1, except that the volume distribution particle size of the bottom coating particles in the battery monomer of Comparative Example 2 does not satisfy Dv99 less than or equal to 20 μm. Specific preparation parameters are shown in Table 1.

[0184] Comparative Example 3 The preparation method of the battery cell of Comparative Example 3 is similar to that of the battery cell of Example 1, except that the volume distribution particle size of the positive electrode film layer particles in the battery cell of Comparative Example 3 does not satisfy Dv90 greater than or equal to 20 μm. Specific preparation parameters are shown in Table 1.

[0185] Embodiment 2-4 The preparation methods of the battery cells of Examples 2-4 are similar to those of the battery cells of Example 1, except that positive electrode current collector aluminum foils with different tensile strengths are used. Specific preparation parameters are shown in Table 1.

[0186] Example 5 The preparation method of the battery cell of Example 5 is similar to that of the battery cell of Example 1, except that the volume distribution particle size Dv99 of the particles in the bottom coating of the positive electrode plate is adjusted. The specific preparation parameters are shown in Table 1.

[0187] Embodiment 6-8 The preparation method of the battery cells of Examples 6-8 is similar to that of the battery cells in Example 1, except that the volume distribution particle size Dv99 of the second polycrystalline particles and the volume distribution particle size Dv99 and Dv50 of the second single crystal particles in the bottom coating layer of the positive electrode plate are adjusted, thereby changing the particle size distribution value (Dv90-Dv10) / Dv50 in the bottom coating layer. The specific preparation parameters are shown in Table 1.

[0188] Examples 9-10 The preparation method of the battery cells of Examples 9-10 is similar to that of the battery cells in Example 1, except that the volume distribution particle sizes Dv99 and Dv50 of the first polycrystalline particles and the first single crystal particles in the positive electrode film layer of the positive electrode plate are adjusted, thereby changing the volume distribution particle size Dv90 in the positive electrode film layer. The specific preparation parameters are shown in Table 1.

[0189] Examples 11-13 The preparation methods of the battery cells of Examples 11-13 are similar to those of the battery cells in Example 1, except that the mass proportions of the first polycrystalline particles and the first single crystal particles in the positive electrode film layer of the positive electrode plate are adjusted. The specific preparation parameters are shown in Table 1.

[0190] Examples 14-15 The preparation method of the battery cells of Examples 14-15 is similar to that of the battery cells in Example 1, except that the thickness of the bottom coating layer on one side of the positive electrode plate and the thickness of the positive electrode film layer on one side are adjusted. The specific preparation parameters are shown in Table 1.

[0191] Example 16 The preparation method of the battery cell of Example 16 is similar to that of the battery cell in Example 1, except that the bottom coating in the battery cell of Example 16 only includes polycrystalline particles but no single crystal particles. Specific preparation parameters are shown in Table 1.

[0192] Table 1

[0193] 2. Performance Test 1. Test method for tensile strength of positive electrode current collector Take a current collector, or disassemble the current collector from the battery cell, cut the current collector into a length of 2cm×5cm, place the cut current collector aluminum foil on a tensile testing machine and stretch it until the aluminum foil breaks. The maximum tensile stress N1 of the sample during the current collector stretching and fracture process is used as the tensile strength of the sample, in MPa.

[0194] 2. CP-SEM characterization method of positive electrode cross section The sample to be characterized was prepared as follows: first, the positive electrode sheet was cut into a sample to be tested with a size of 2 cm × 2 cm, and the sample to be tested was fixed on the sample stage by paraffin. Then, the sample stage was placed in the sample holder and locked, the power supply and vacuum of the argon ion cross-section polisher IB-19500CP were turned on, the argon gas flow rate was set to 0.15 MPa, the control voltage was set to 8 KV, and the polishing time was set to 2 hours, and the sample stage was adjusted to the swing mode to start polishing. After the polishing was completed, the sample to be characterized was obtained.

[0195] Microscopic morphology characterization: The samples were characterized using a scanning electron microscope ZEISS Sigma300. The sample test can refer to JY / T010-1996. In order to ensure the accuracy of the test results, multiple different areas can be randomly selected from the sample to be tested for scanning tests, and the cross-sectional morphology images can be taken at a fixed magnification of 5k times.

[0196] 3. Test method of material particle size The battery cells were disassembled, and the powders to be tested were scraped out from the positive electrode film layer and the bottom coating layer, respectively. The materials to be tested were poured into a wind dispersion tank filled with ethanol for ultrasonic dispersion for 5 minutes, and sodium dodecyl sulfate (SDS) was added as a dispersant. Then, the materials were transferred to a laser particle size analyzer (Malvern 2000E) for testing to obtain the volume distribution particle size of the particles in the positive electrode film layer and the bottom coating layer.

[0197] 4. Characterization method of burr test on the cross section of positive electrode An ultra-depth-of-field microscope (Keyence 600) was used to characterize the cut pole pieces. The test temperature was 25°C, the test pole piece size was 80mm×60mm, the magnification was 300x, the light opening was 30%, and the burr characterization observation and size calibration were performed from the pole piece cut section.

[0198] Burr size statistics: 2000 cut pole pieces were observed by CCD, and the frequency of pole pieces with burrs was counted K1, and the burr ratio was calculated to be K1 / 2000×100%.

[0199] 5. Test method for Li ion diffusion coefficient of positive electrode The coated electrodes were assembled into half-electric Vs Li, and the assembled button cells were activated for 3 cycles (C / D_0.1C_2.8-4.25V@25℃). After activation, a constant current intermittent titration test was performed with a pulse current of 0.2C, a pulse time of 3min, a relaxation time of 25min, and a voltage window of 2.8-4.25V. The test was performed using a Newware BTS-5V10mA test instrument.

[0200] Calculation: According to the GIIT formula , the Li ion diffusion coefficient of the positive electrode sheet is calculated by filling in the voltage rise after one cycle (pulse + relaxation) / the voltage rise during the pulse process in combination with the diffusion coefficient formula. The Li ion diffusion coefficient in one embodiment of the present application and the comparative example is as follows Figure 5 shown.

[0201] 6. Test method for elongation of positive electrode Before the electrode is cold pressed, take a section of positive electrode with a length of L, and then roll the positive electrode from small to large according to the target pressure of different compaction densities, and record the length L1 of the electrode after each rolling. The elongation of the positive electrode at the corresponding compaction density can be calculated using the formula (L1-L) / L×100%. The comparison of the elongation of the positive electrode in an embodiment of the present application and the comparative example is shown in the figure below. Figure 6 shown.

[0202] 7. Test method for gram capacity of positive electrode The active material on one side of the positive electrode sheet was washed with NMP, and the washed single-sided positive electrode sheet was assembled into a button battery, activated for 3 cycles at 0.1C / 0.1C, and then its gram capacity was measured at 0.1C / 0.1C, with a voltage window of 2.8-4.3V. Figure 7 shown.

[0203] 8. Battery internal resistance DCR test method At room temperature, the above battery cells were charged to the upper limit voltage at a rate of 1 / 3C, i.e., 100% SOC, and then the lithium-ion battery was discharged to 50% SOC. After standing for 5 minutes, it was charged at a rate of 2C for 10 seconds to obtain the charging DCR of the lithium-ion battery at 50% SOC at room temperature.

[0204] 9. Battery energy density test method The weight M of all active materials loaded per unit area of ​​the positive electrode sheet of the battery cell is measured respectively, and the volume of the battery cell is V; each battery is charged at a rate of 0.33C at room temperature to a voltage equal to 4.25V, and then discharged at a rate of 0.33C to a voltage equal to 2.8V, the discharge energy S0 is measured, and the volume energy density of the battery cell is obtained as S0 / V.

[0205] III. Analysis of test results of various embodiments and comparative examples The battery cells of each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in the following table.

[0206] Table 2

[0207] It can be seen from the results of the embodiments and comparative examples in Table 2 that the volume distribution particle size Dv90 of the particles in the positive electrode film layer in the battery cell is greater than or equal to 20 μm, the tensile strength of the positive electrode current collector is 220 MPa-330 MPa, and the volume distribution particle size Dv99 of the particles in the undercoat layer is less than or equal to 20 μm, which effectively reduces the probability of large-sized burrs on the positive electrode sheet and at the same time makes the battery cell have a high energy density, which is conducive to further improving the comprehensive performance of the battery cell.

[0208] Table 3

[0209] From the comparison of Examples 1 and 6-8 in Table 3, it can be seen that the battery monomer bottom coating includes polycrystalline particles, the Dv99 of the polycrystalline particles in the bottom coating is 6-20 μm, and the particle size distribution value (Dv90-Dv10) / Dv50 in the bottom coating is 2-8.5, so that the battery monomer has high energy density, low burr generation probability, and high dynamic performance.

[0210] From the comparison of Examples 1 and 9-10 in Table 2, it can be seen that the particles in the positive electrode film layer in the battery cell include polycrystalline particles and single crystal particles. The volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20μm-30μm, and Dv50 is 6μm-14μm, and the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6μm-15μm, and Dv50 is 2μm-6μm, which is conducive to achieving close stacking of particles in the positive electrode film layer, and can reduce the probability of burr generation while achieving further improvement in the energy density of the battery cell.

[0211] From the comparison of Examples 1 and 11-13 in Table 2, it can be seen that the mass ratio of polycrystalline particles to single crystal particles in the positive electrode film layer of the battery cell is 5:5-9:1, which is beneficial to improve the compaction density of the positive electrode sheet and further improve the energy density of the battery cell.

[0212] From the comparison of Examples 1 and 14-15 in Table 2, it can be seen that the thickness L1 of the positive electrode film layer on one side and the thickness L2 of the bottom coating layer on one side in the battery cell satisfy 10%≤L2 / (L1+L2)≤50%, the thickness L1 of the positive electrode film layer on one side is 30μm-60μm, and the thickness L2 of the bottom coating layer on one side is 10μm-30μm, which can not only reduce the probability of burrs on the electrode sheet during cutting, but also reduce the battery capacity loss at the same time, so that the battery cell has excellent energy density.

[0213] Depend on Figure 5 and Figure 7 From the comparison between Example 1 and Example 16, it can be seen that the battery cell bottom coating includes polycrystalline particles, which can not only improve the energy density, dynamic performance and burr generation probability of the battery cell, but also effectively improve the diffusion coefficient of Li ions in the positive electrode plate, and is also beneficial to the performance of the gram capacity of the positive electrode plate, so that the dynamic performance and energy density of the battery cell are further improved.

[0214] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising a positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode current collector, a positive electrode film layer disposed on at least one side of the positive electrode current collector, and a primer layer disposed between the positive electrode current collector and at least one side of the positive electrode film layer. Wherein, the volume distribution particle size Dv90 of the particles in the positive electrode film layer is greater than or equal to 20 μm; The tensile strength of the positive electrode current collector is 220MPa-330MPa; The volume distribution particle size Dv99 of the particles in the primer layer is less than or equal to 20 μm.

2. The battery cell according to claim 1, characterized in that: The volume distribution particle size Dv90 of the particles in the positive electrode film layer is 20 μm-28 μm.

3. The battery cell according to claim 1, characterized in that: The tensile strength of the positive electrode current collector is 280MPa-330MPa.

4. The battery cell according to claim 1, characterized in that: The volume distribution particle size Dv99 of the particles in the base coating is 6 μm-18 μm.

5. The battery cell according to claim 1, characterized in that: The particle size distribution value of the particles in the base coating layer is (Dv90-Dv10) / Dv50 of 2-8.

5.

6. The battery cell according to claim 5, characterized in that: The particle size distribution value of the particles in the base coating layer is (Dv90-Dv10) / Dv50 of 2-6.

7. The battery cell according to claim 1, characterized in that: The base coating layer includes polycrystalline particles, and the Dv99 of the polycrystalline particles in the base coating layer is 6 μm-20 μm.

8. The battery cell according to claim 7, characterized in that: The base coating layer also includes single crystal particles.

9. The battery cell according to claim 8, characterized in that: The Dv99 of the single crystal particles in the undercoat layer is 6 μm-15 μm; and / or, The Dv50 of the single crystal particles in the undercoat layer is 2 μm-6 μm.

10. The battery cell according to claim 9, characterized in that: The Dv99 of the single crystal particles in the undercoat layer is 6 μm-10 μm; and / or, The Dv50 of the single crystal particles in the undercoat layer is 3 μm-5 μm.

11. The battery cell according to claim 8, characterized in that: The mass ratio of polycrystalline particles to single crystal particles in the bottom coating is 5:5-9:

1.

12. The battery cell according to claim 11, characterized in that: The mass ratio of polycrystalline particles to single crystal particles in the bottom coating is 6:4-8:

2.

13. The battery cell according to claim 1, characterized in that: The volume distribution curve of the particles in the positive electrode film layer presents a bimodal distribution, and the peak position difference is greater than or equal to 2 μm.

14. The battery cell according to claim 13, characterized in that: In the volume distribution curve of the particles in the positive electrode film layer, the first peak in the double peak position is located at 2 μm-5.5 μm; the second peak in the double peak position is located at 6 μm-11 μm.

15. The battery cell according to claim 1, characterized in that: The particles in the positive electrode film layer include polycrystalline particles and single crystal particles.

16. The battery cell according to claim 15, characterized in that: The volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20 μm-30 μm; and / or, The volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer is 6 μm-14 μm.

17. The battery cell according to claim 16, characterized in that: The volume distribution particle size Dv99 of the polycrystalline particles in the positive electrode film layer is 20 μm-28 μm; and / or, The volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer is 6 μm-12 μm.

18. The battery cell according to claim 15, characterized in that: The volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6 μm-15 μm; and / or, The volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer is 2 μm-6 μm.

19. The battery cell according to claim 18, characterized in that: The volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer is 6 μm-13 μm; and / or, The volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer is 2 μm-5.5 μm.

20. The battery cell according to claim 15, characterized in that: The mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer is 5:5-9:

1.

21. The battery cell according to claim 20, characterized in that: The mass ratio of the polycrystalline particles in the positive electrode film layer to the single crystal particles in the positive electrode film layer is 6:4-8:

2.

22. The battery cell according to claim 1, characterized in that: The undercoat layer includes a first lithium-containing transition metal oxide, the positive electrode film layer includes a second lithium-containing transition metal oxide, and the first lithium-containing transition metal oxide and the second lithium-containing transition metal oxide each independently include Li a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 , wherein M1 includes one or more of Mn and Al, and M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K; 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.

1.

23. The battery cell according to claim 22, characterized in that: The first lithium-containing transition metal oxide includes nickel element. Based on the total molar number of transition metals in the first lithium-containing transition metal oxide, the molar ratio of nickel element in the first lithium-containing transition metal oxide is 80%-96%.

24. The battery cell according to claim 22, characterized in that: The second lithium-containing transition metal oxide includes nickel element. Based on the total molar number of transition metals in the second lithium-containing transition metal oxide, the molar ratio of nickel element in the second lithium-containing transition metal oxide is 80%-96%.

25. The battery cell according to claim 1, characterized in that The thickness L1 of the positive electrode film layer on one side and the thickness L2 of the primer layer on one side satisfy the following formula I: 。 26. The battery cell according to claim 25, characterized in that: The thickness L1 of the positive electrode film layer on one side is 30 μm-60 μm.

27. The battery cell according to claim 25, characterized in that: The thickness L2 of the primer layer on one side is 10 μm to 30 μm.

28. The battery cell according to claim 1, characterized in that: The thickness of the positive electrode current collector is 5 μm-20 μm.

29. The battery cell according to claim 28, characterized in that: The thickness of the positive electrode current collector is 7 μm-15 μm.

30. The battery cell according to claim 1, characterized in that When the battery cell is fully charged, the compaction density of the positive electrode sheet is 3.4 g / cm 3 -3.7g / cm 3 .

31. The battery cell according to claim 1, characterized in that The positive electrode sheet is 3.65g / cm 3 The elongation at the cold pressed compaction density is 0.3%-1.0%.

32. The battery cell according to claim 1, characterized in that The gram capacity of the positive electrode plate is 210 mAh / g-240 mAh / g.

33. The battery cell according to claim 1, characterized in that: After the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the proportion of positive electrode sheets with burrs among at least 2000 positive electrode sheets is 0%-2%.

34. The battery cell according to claim 1, characterized in that The volume energy density of the battery cell is 650Wh / L-700Wh / L.

35. The battery cell according to claim 34, characterized in that: The volume energy density of the battery cell is 670Wh / L-690Wh / L.

36. A battery device, characterized in that: The battery device comprises the battery cell according to any one of claims 1 to 35, and the battery device is one or more of a battery module, a battery pack, and an energy storage device.

37. An electrical device, characterized in that: The electrical device comprises the battery cell according to any one of claims 1 to 35 or the battery device according to claim 36.

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