Battery cells, battery devices and power-consuming devices

Abstract

The present application provides a battery cell, a battery device, and an electrical device, belonging to the field of battery technology. The battery cell provided in the present application includes a positive electrode plate, the positive electrode plate includes a positive electrode current collector, a positive electrode film layer provided on at least one side of the positive electrode current collector, and an undercoat layer provided between the positive electrode current 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; the tensile strength of the positive electrode current collector is 220MPa-330MPa; and the volume distribution particle size Dv99 of the particles in the undercoat layer is less than or equal to 20μm. The battery cell provided in the present application 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 systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. However, the market's pursuit of superior electrical performance in battery cells has increased the difficulty of processing them, leading to a decrease in yield. This has resulted in battery safety and service life failing to meet expectations, limiting further applications. Striking a balance between these two issues has become a pressing challenge 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, which 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 a primer 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 primer 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 embodiments of the present application is greater than or equal to 20μm to increase the compaction density of the electrode and improve the energy density of the battery cell. In order to improve the compaction density of the electrode, it is necessary to increase the proportion of large particles in the electrode film layer to achieve a dense stacking of the film layer through gradation theory. However, during the slicing process, the cutter squeezes the large particles, causing the large particles to squeeze the current collector, causing the current collector to undergo extrusion deformation and fracture rather than shear fracture, 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 primer layer is 2-8.5, and can be optionally 2-6.

[0008] In the embodiment 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 reducing the generation of electrode burrs while further improving the energy density of the battery.

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

[0010] Polycrystalline particles are formed by the agglomeration of small-diameter single-crystal particles. Using polycrystalline particles in the undercoat layer, with a particle size within the above range, can not only maintain high electrode density while reducing the probability of burrs, 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 battery's dynamic performance. It also facilitates the utilization of the specific capacity of the battery cell, further improving the energy density of the battery cell.

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

[0012] In any embodiment, the Dv99 of the single crystal particles in the primer layer is 6 μm-15 μm, optionally 6 μm-10 μm; and / or the Dv50 of the single crystal particles in the primer 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 gradation 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 primer layer 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 conducive to further improving the compaction density of the pole piece, reducing the generation of burrs while improving the high energy density of the battery, improving the yield rate of the pole piece, and meeting 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 bimodal peak position is located at 2 μm-5.5 μm; and the second peak of the bimodal 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, 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 improving the compaction density of the electrode sheet, thereby improving 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 conducive to further improving 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 active materials, it is beneficial to the utilization 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, and the molar proportion of nickel 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 percentage of nickel of 80%-96% has a high gram capacity, which is conducive to further improving the energy density of battery cells. However, the lithium-containing transition metal oxide with a high nickel content also has high particle hardness, which increases the degree of compression of the current collector by large particles in the positive electrode film layer, making it easy to generate burrs during the cutting of the positive electrode sheets. The technical solution in the embodiments of the present application is particularly suitable for such positive electrode sheets, further improving the high energy density of the battery while increasing the yield rate during the sheet cutting process, meeting performance and efficiency requirements.

[0029] In any embodiment, the second lithium-containing transition metal oxide includes nickel, and the molar proportion of 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.

[0030] The base coating 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 active material of the electrode 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] Providing 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, reducing the probability of burrs on the electrode during slicing. However, the addition of the primer takes up space in the positive electrode film layer, which has a negative impact on the battery's 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 ranges can, on the one hand, effectively reduce the contact between large particles of the positive electrode active material and the current collector, reducing the probability of burrs on the electrode during slicing, and further improving the safety performance of the battery cell. On the other hand, it can also reduce the battery capacity loss caused by the addition of the primer, allowing the battery cell to still have 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] Reducing the thickness of the positive electrode film helps reduce the diffusion path of lithium ions and improve the dynamic performance of battery cells. However, as the thickness of the positive electrode film decreases, the compaction density of the electrode sheet is further increased to achieve high energy density. This increases the pressure on the current collector from large particles during slicing, increasing the probability of burrs. Furthermore, as the thickness of the positive electrode film and the electrode sheet decreases, the control of burrs on large-sized products becomes increasingly stringent, making burrs more likely to protrude from the edge of the positive electrode film, exacerbating the safety risks posed by burrs.

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

[0036] When the thickness of the single-sided primer coating 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 electrode during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the deterioration of the electrode compaction and battery capacity loss caused by the addition of the primer 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 optionally 7 μm-15 μm.

[0038] The positive electrode current collector does not contribute to battery capacity, so reducing its thickness helps free up space for the positive electrode active material, thereby increasing the energy density of the battery cell. However, this thinning reduces its ability to withstand large particle extrusion during the slitting process, exacerbating burring. Maintaining the positive electrode current collector thickness within the above range helps improve the yield rate during the electrode sheet cutting process while maintaining high battery cell energy density, thereby meeting 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 performance and efficiency requirements.

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

[0042] Although the undercoat particle Dv99 is too small, which helps reduce burrs, it requires significantly higher rolling pressure to achieve the same compaction density for the pole piece. This, in turn, increases the elongation of the current collector, making the pole piece susceptible to breakage during preparation and cycling, and deteriorating safety performance. The battery cell provided in the embodiments of the present application achieves high pole piece density while maintaining a low cold pressing elongation, which is conducive to further improving the pole piece compaction density and battery cell energy density.

[0043] In any embodiment, the gram capacity of the positive electrode sheet 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 in 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 components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0050] Figure 1 This is a cross-sectional polishing electron microscope image of the positive electrode sheet along the thickness direction in one embodiment of the present application;

[0051] Figure 2 This is a cross-sectional polishing electron microscope morphology image of the positive electrode sheet along the thickness direction in the comparative example of the present application;

[0052] 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;

[0053] Figure 4 This is a cross-sectional morphology diagram of a positive electrode sheet cut along the thickness direction in one embodiment of the present application;

[0054] Figure 5 This is a comparison chart of the Li ion diffusion coefficient of the positive electrode sheet in one embodiment of the present application;

[0055] Figure 6 is the positive electrode elongation ratio contrast ratio in one embodiment of the present application;

[0056] Figure 7 This is a comparison chart of the gram capacity of the positive electrode sheet in one embodiment of the present application;

[0057] Figure 8 is a schematic diagram of a battery cell according to one embodiment of the present application;

[0058] Figure 9 yes Figure 8 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0059] Figure 10 is a schematic diagram of a battery module according to one embodiment of the present application;

[0060] Figure 11 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0061] Figure 12 yes Figure 11 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0062] Figure 13 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0063] Description of reference numerals:

[0064] 11 positive electrode sheet; 111 positive electrode current collector; 112 base coating; 113 positive electrode film layer

[0065] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0066] Below, the battery cells, methods for preparing battery cells, polymers, and embodiments of the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0067] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and 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 special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this 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 all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0068] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0069] 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.

[0070] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0071] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0072] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0073] As the market demands for the endurance of electrical devices increase, increasing the volumetric energy density of battery cells has become a common pursuit in the industry. Increasing the volumetric energy density of battery cells often requires increasing the compaction density of the electrode sheets to increase the active material loading per unit volume. However, researchers have found that high-compaction-density electrode sheets are prone to burrs during the cutting process. Burred electrode sheets can easily penetrate the separator after assembly of the electrode assembly, causing abnormal self-discharge of the battery cell and even leading to short-circuit failure of the battery cell, thereby affecting the safety performance and lifespan of the battery and failing to meet the use requirements of the battery cells.

[0074] Based on the above problems, the embodiment of the first aspect of the present application provides a battery cell. Figure 1As shown, the battery cell includes a positive electrode plate 11, 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 a primer 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 primer layer is less than or equal to 20μm, and can be optionally 6μm-15μm.

[0075] 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.

[0076] In some embodiments, the tensile strength of the positive electrode current collector is 220 MPa-330 MPa. In some embodiments, the tensile strength of the positive electrode current collector is 280 MPa-330 MPa. In some embodiments, the tensile strength of the positive electrode current collector is 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, 310 MPa, 320 MPa, 330 MPa, or any range between any two of the foregoing values.

[0077] 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 between 6 μm and 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.

[0078] As 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.

[0079] When used in this article, the term "tensile strength" refers to the maximum tensile force that a current collector can withstand per unit cross-sectional area during the stretching process, reflecting the material's ability 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 of 2cm×5cm size, place the cut current collector aluminum foil on a tensile testing machine and stretch it until the aluminum foil breaks, and use 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.

[0080] 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, they 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).

[0081] 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 measured by any method known in the art. As an example, powder can be scraped from the positive electrode film layer or the undercoat layer and measured using the method described above.

[0082] 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 electrode and improve the energy density of the battery cell. In order to increase the compaction density of the electrode, it is necessary to increase the proportion of large particles in the electrode 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.

[0083] Studies have shown that Figure 2 As shown in Figure 1, setting a layer of small particle size undercoat layer can effectively reduce the squeezing of large particles in the positive electrode film on the current collector and improve the burr phenomenon. However, due to the lack of large particles in the undercoat layer, 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 the figure can alleviate the decrease of compaction density by appropriately increasing the proportion of large particles in the base coat, but it will still cause burr problems, such as Figure 3As shown. The battery cell provided in the embodiment of the present application is provided with an undercoat layer having 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 having 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 compression of large particles in the undercoat layer and the positive electrode film layer is reduced while taking into account the compaction density of the positive electrode sheet. Figure 4 As shown, the yield rate in the electrode cutting process is improved to meet performance and efficiency requirements.

[0084] In some embodiments, the particle size distribution value of the particles in the primer layer is (Dv90-Dv10) / Dv50 of 2-8.5. In some embodiments, the particle size distribution value of the particles in the primer layer is (Dv90-Dv10) / Dv50 of 2-6.

[0085] In some embodiments, the particle size distribution value (Dv90-Dv10) / Dv50 of the particles in the primer layer can be selected as 2, 3, 4, 5, 6, 7, 8, 8.5, or any range between any two of the aforementioned values.

[0086] As used herein, the term "particle size distribution (Dv90 - Dv10) / Dv50" has a well-known meaning in the art, referring to the width of the particle size distribution, reflecting the uniformity or dispersion of particle sizes. This can be measured using methods known in the art, such as the volume-based particle size distribution plot of the sample, and the particle size distribution value calculated using the formula (Dv90 - Dv10) / Dv50.

[0087] In the embodiment 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 reducing the generation of electrode burrs while further improving the energy density of the battery.

[0088] In some embodiments, the undercoat layer comprises polycrystalline particles, and the polycrystalline particles in the undercoat layer have a Dv99 of 6-20 μm.

[0089] In some embodiments, the Dv99 of the polycrystalline particles in the base coating can be selected as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any range between any two of the foregoing values.

[0090] 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.

[0091] 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 at a certain observation scale, it is impossible to define smaller particles inside the single crystal through grain boundaries.

[0092] Polycrystalline particles are formed by the aggregation of small-sized single crystal 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.

[0093] In some embodiments, the base coating further comprises single crystal particles.

[0094] In some embodiments, the Dv99 of the single crystal particles in the undercoat layer is between 6 μm and 15 μm. In some embodiments, the Dv99 of the single crystal particles in the undercoat layer is between 6 μm and 10 μm. In some embodiments, the Dv99 of the single crystal particles in the undercoat layer 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.

[0095] In some embodiments, the Dv50 of the single crystal particles in the undercoat layer is between 2 μm and 6 μm. In some embodiments, the Dv50 of the single crystal particles in the undercoat layer is between 3 μm and 5 μm. In some embodiments, the Dv50 of the single crystal particles in the undercoat layer 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.

[0096] The use of single crystal particles that meet the above-mentioned particle size range in the base coating is conducive to forming a gradation 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.

[0097] In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the primer layer is 5:5-9:1. In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the primer layer is 6:4-8:2. In some embodiments, the mass ratio of polycrystalline particles to single crystal particles in the primer layer can be 5:5, 6:4, 7:3, 8:2, 9:1, or any range between any two of the foregoing values.

[0098] When used in this article, the mass ratio of polycrystalline particles and single crystal particles in the base coating can be determined by the following method: take a prepared positive electrode sheet, or a positive electrode sheet disassembled from a battery, and perform CP-SEM testing. Randomly select a number of points for photography, 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 photographed picture 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.

[0099] Controlling the mass ratio of polycrystalline particles and single crystal particles in the base coating to meet the above range is conducive to further improving the compaction density of the pole piece, reducing the generation of burrs while improving the high energy density of the battery, improving the yield rate of the pole piece, and meeting performance and efficiency requirements.

[0100] 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.

[0101] 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.

[0102] In some embodiments, in the volume distribution curve of the particles in the positive electrode film layer, the first peak in the bimodal peak position is located at 2 μm-5.5 μm; the second peak in the bimodal peak position is located at 6 μm-11 μm.

[0103] In some embodiments, in the volume distribution curve of the particles in the positive electrode film layer, the first peak in the bimodal peak position 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 in the bimodal peak position is located at 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, or a range between any two of the aforementioned values.

[0104] The volume distribution curve of particles in the positive electrode film can be determined by referring to GB / T19077-2016 and using the test method described above. The bimodal distribution curve indicates that the positive electrode film contains large and small particles of varying sizes. Filling the gaps between large particles with small particles helps increase the electrode packing density, thereby further improving the battery's energy density.

[0105] In some embodiments, the particles in the positive electrode film layer include polycrystalline particles and single crystal particles.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the positive electrode film layer can be selected as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or any range between any two of the aforementioned values.

[0110] 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.

[0111] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the positive electrode film layer can be selected as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any range between any two of the aforementioned values.

[0112] 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.

[0113] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the positive electrode film layer can be selected as 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, or any range between any two of the aforementioned values.

[0114] 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 improving the compaction density of the electrode sheet, thereby improving the energy density of the battery.

[0115] In some embodiments, the mass ratio of polycrystalline particles in the positive electrode film to single crystal particles in the positive electrode film is 5:5-9:1. In some embodiments, the mass ratio of polycrystalline particles in the positive electrode film to single crystal particles in the positive electrode film is 6:4-8:2.

[0116] 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.

[0117] It can be understood that the mass ratio of polycrystalline particles and single crystal particles in the positive electrode film layer can be tested using 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 picture to the size of the positive electrode film layer.

[0118] Controlling the mass ratio of polycrystalline particles and single crystal particles in the positive electrode film layer to meet the above range is conducive to further improving the compaction density of the electrode sheet, so that the battery has excellent energy density.

[0119] In some embodiments, 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 M2w1 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.

[0120] It is 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.

[0121] In some embodiments, a1 can be selected from 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 from 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 from 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 from 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 0, 0.02, 0.04, 0.06, 0.08, 0.1, or any range between any two of the aforementioned values. In some embodiments, b1 can be -0.1, -0.05, 0, 0.05, 0.1, or any range between any two of the aforementioned values.

[0122] 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 active materials, it is beneficial to the utilization of their specific capacity, thereby further improving the energy density of the battery cell.

[0123] In some embodiments, the first lithium-containing transition metal oxide includes nickel, and the molar proportion of nickel 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.

[0124] In some embodiments, based on the total molar number of transition metal in the first lithium-containing transition metal oxide, the molar proportion of nickel 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.

[0125] As used herein, 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, the following method can be used for measurement: scrape 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 at a digestion temperature of 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. The molar ratio of nickel in the first lithium-containing transition metal oxide is calculated by dividing the molar number of nickel by the total molar number of transition metal elements based on the total molar number of transition metals in the first lithium-containing transition metal oxide.

[0126] The first lithium-containing transition metal oxide with a molar percentage of nickel of 80%-96% has a high gram capacity, which is conducive to further improving the energy density of battery cells. However, the lithium-containing transition metal oxide with a high nickel content also has high particle hardness, which increases the degree of compression of the current collector by large particles in the positive electrode film layer, making it easy to generate burrs during the cutting of the positive electrode sheets. The technical solution in the embodiments of the present application is particularly suitable for such positive electrode sheets, further improving the high energy density of the battery while increasing the yield rate during the sheet cutting process, meeting performance and efficiency requirements.

[0127] In some embodiments, the second lithium-containing transition metal oxide includes nickel, and the molar proportion of 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.

[0128] In some embodiments, based on the total molar number of transition metal in the second lithium-containing transition metal oxide, the molar proportion of nickel in the second lithium-containing transition metal oxide can be selected as 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, or any range between any two of the foregoing values.

[0129] As used herein, the molar fraction of the transition metal element in the second lithium-containing transition metal oxide is determined using instruments and methods known in the art. For example, powder is scraped from the undercoat layer and measured using the same method as described above for determining the molar fraction of the transition metal element in the first lithium-containing transition metal oxide.

[0130] The base coating 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 active material of the electrode and further improves the energy density of the battery.

[0131] 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:

[0132] .

[0133] 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.

[0134] When used in this article, the thickness of the positive electrode film layer on one side and the thickness of the primer layer on one side can be observed and measured by scanning electron microscopy on the interface of the positive electrode sheet.

[0135] Providing 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, reducing the probability of burrs on the electrode during slicing. However, the addition of the primer takes up space in the positive electrode film layer, which has a negative impact on the battery's 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 ranges can, on the one hand, effectively reduce the contact between large particles of the positive electrode active material and the current collector, reducing the probability of burrs on the electrode during slicing, and further improving the safety performance of the battery cell. On the other hand, it can also reduce the battery capacity loss caused by the addition of the primer, allowing the battery cell to still have a high energy density.

[0136] 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.

[0137] Reducing the thickness of the positive electrode film helps reduce the diffusion path of lithium ions and improve the dynamic performance of battery cells. However, as the thickness of the positive electrode film decreases, the compaction density of the electrode sheet is further increased to achieve high energy density. This increases the pressure on the current collector from large particles during slicing, increasing the probability of burrs. Furthermore, as the thickness of the positive electrode film and the electrode sheet decreases, the control of burrs on large-sized products becomes increasingly stringent, making burrs more likely to protrude from the edge of the positive electrode film, exacerbating the safety risks posed by burrs.

[0138] 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.

[0139] When the thickness of the single-sided primer coating 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 electrode during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the deterioration of the electrode compaction and battery capacity loss caused by the addition of the primer coating, so that the battery cell still has a high energy density.

[0140] In some embodiments, the thickness of the positive electrode current collector is 5 μm to 20 μm. In some embodiments, the thickness of the positive electrode current collector is 7 μm to 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.

[0141] The positive electrode current collector does not contribute to battery capacity, so reducing its thickness helps free up space for the positive electrode active material, thereby increasing the energy density of the battery cell. However, this thinning reduces its ability to withstand large particle extrusion during the slitting process, exacerbating burring. Maintaining the positive electrode current collector thickness within the above range helps improve the yield rate during the electrode sheet cutting process while maintaining high battery cell energy density, thereby meeting performance and efficiency requirements.

[0142] In some embodiments, the cold pressed density of the positive electrode is 3.1 g / cm 3 -3.8g / cm 3 In some embodiments, the cold pressed density of the positive electrode is 3.55 g / cm 3 -3.75g / cm 3 In some embodiments, the cold pressed density of the positive electrode sheet can 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 above values.

[0143] As used herein, the compacted density of the positive electrode sheet after cold pressing 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 a test sample of the sheet with an area of ​​S, and record the weight as W. Then, the thickness T of the sheet is measured (it can be measured using an instrument that can measure the thickness of a sheet in the art, including but not limited to instruments such as micrometers). After the positive electrode sheet is cold pressed, the compacted density of the positive electrode sheet can be calculated using the formula W / (T×S).

[0144] 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 above values.

[0145] As used herein, when the battery cell is fully discharged, the compacted 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 2 hours. After the battery temperature is maintained at 25°C, discharge the battery at a constant current of 1 / 3C to 2.8V, let it stand for 30 minutes, and then 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 then dry the plate. Then, use the aforementioned positive electrode plate compacted density measurement method to measure the compacted density of the positive electrode plate of the battery cell after full discharge.

[0146] 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 performance and efficiency requirements.

[0147] In some embodiments, the positive electrode sheet is at 3.65 g / cm 3 The cold pressing elongation at the cold pressing 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.

[0148] When used in this article, the term "cold pressing elongation of the positive electrode sheet" has the meaning commonly 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, it can be measured by the following method: before the sheet is cold pressed, take a section of the positive electrode sheet with a length of L, and then roll the positive electrode sheet from small to large according to the target pressure of different cold pressing compaction densities, 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%.

[0149] 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 by the embodiment of the present application achieves high density of the pole piece while maintaining a low cold pressing elongation, which is beneficial to further improve the compaction density of the pole piece and the energy density of the battery cell.

[0150] In some embodiments, the gram capacity of the positive electrode sheet is 210 mAh / g to 240 mAh / g. In some embodiments, the gram capacity of the positive electrode sheet is 210 mAh / g, 215 mAh / g, 220 mAh / g, 225 mAh / g, 230 mAh / g, 235 mAh / g, 240 mAh / g, or any range between any two of the foregoing values.

[0151] 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.

[0152] As used herein, a positive electrode sheet with burrs refers to a sheet with burrs on it that has been calibrated after slitting. Sheets with a burr size greater than or equal to 40% of the thickness of the positive electrode sheet are included in the statistical range and are calibrated as having burrs. The proportion of positive electrode sheets with burrs can be tested using methods known in the art. As an example, the following method can be used to test: a certain number of slid sheets are observed through a microscope (including but not limited to a CCD), and the frequency K1 of the sheets with burrs is counted. The proportion of sheets with burrs is calculated as K1 / total number of sheets × 100%.

[0153] 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: observe the burrs after slicing using a CCD instrument (such as Keyence 600), the test temperature is 25°C, the test electrode size is 80mm×60mm, the magnification is 300x, the light input opening is 30%, and the burr size is calibrated, such as Figure 3 shown.

[0154] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0155] In some embodiments, the positive electrode film layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0156] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0157] In some embodiments, the positive electrode plate can be prepared by the following method: the components for preparing the above-mentioned primer layer, 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 primer layer 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 layer slurry; the primer layer slurry is first coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode film layer slurry is then coated on the surface of the primer layer, and after drying, cold pressing and other processes, the positive electrode plate can be obtained.

[0158] [Negative electrode]

[0159] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.

[0160] 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 either or both of the two opposite surfaces of the negative electrode current collector.

[0161] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer 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) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0162] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well 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 oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, 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.

[0163] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0164] 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.

[0165] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0166] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0167] [Electrolytes]

[0168] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0169] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0170] In some embodiments, the electrolyte salt may 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.

[0171] 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, methylpropyl carbonate, ethylpropyl 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, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0172] In some embodiments, the electrolyte may further include additives. For example, the additives may include 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, and additives that improve battery high or low temperature performance.

[0173] [Isolation film]

[0174] 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 and mechanical stability can be selected.

[0175] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0176] [Battery Cell]

[0177] 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.

[0178] 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.

[0179] As used herein, the volumetric energy density of a battery cell can be measured using instruments and methods known in the art. For example, the following method can be used: The weight M of all active materials per unit area of ​​the positive electrode sheet in each battery cell is measured, with the cell volume V. Each battery is charged at room temperature at a 0.33C rate to a voltage of 4.25V, and then discharged at a 0.33C rate to a voltage of 2.8V, to obtain the discharge energy S0. Battery mass energy density = S0 / M; cell volume energy density = S0 / V.

[0180] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0181] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0182] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 8 The battery cell 5 is a square structure as an example.

[0183] In some embodiments, reference Figure 9 , the outer packaging may include a shell 51 and a cover plate 53. 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.

[0184] [Battery device]

[0185] The present application also provides a battery device, which includes 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.

[0186] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0187] Figure 10 4 is an example of a battery module. Figure 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. The plurality of battery cells 5 may further be fixed by fasteners.

[0188] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0189] 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 based on the application and capacity of the battery pack.

[0190] Figure 11 and Figure 12 The battery pack 1 is used as an example. Figure 11 and Figure 12 The battery pack 1 may include a battery box and multiple 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 an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0191] [Electrical devices]

[0192] In addition, the present application also provides an electrical 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 electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0193] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0194] Figure 13 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells in this device, a battery pack or battery module can be used.

[0195] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0196] Example

[0197] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0198] 1. Preparation method

[0199] Example 1

[0200] 1) Preparation of positive electrode sheet

[0201] Preparation of base coating slurry: ternary active material LiNi with Dv99 of 15μm 0.92 Co 0.04 Mn 0.04 O2 polycrystalline particles and LiNi with Dv99 of 7μm and Dv50 of 2.5μm 0.92 Co 0.04 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. The mixture is stirred in a vacuum mixer until the system becomes uniform to obtain a primer slurry.

[0202] 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, Dv99 of 12μm, Dv50 of 5μm single crystal ternary active material LiNi 0.92 Co 0.04 Mn 0.04 A mixture of O2 (polycrystalline particles: single crystal particles with a mass ratio of 7:3), conductive carbon, and binder PVDF are mixed in a mass ratio of 98:1:1, and solvent NMP is added. The mixture is stirred in a vacuum mixer until the system becomes uniform to obtain a positive electrode film slurry.

[0203] Take a positive electrode current collector aluminum foil with a tensile strength of 300 MPa, apply the primer slurry evenly on both sides of the positive electrode current collector and dry it to form a primer layer, where 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-side 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 ;

[0204] Pole sheet slitting (one out of two): the positive electrode sheet is cut 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;

[0205] Pole piece cutting: The slit pole pieces are wound and cut, with a winding speed of 0.6m / s, a core length of 3m, a steel blade as the cutting blade, and a negative pressure of -10Kpa inside the winding machine.

[0206] 2) Preparation of negative electrode sheet

[0207] 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 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.

[0208] 3) Preparation of diaphragm

[0209] A polyethylene film with a thickness of 13 μm was used as the separator.

[0210] 4) Preparation of electrolyte

[0211] 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.

[0212] 5) Battery assembly

[0213] The cells are arranged in the order of "diaphragm - negative electrode sheet - separator - positive electrode sheet". One end of the positive electrode sheet, negative electrode sheet, and two separators are fixed to the discharge roller, and the other end is fixed to the winding shaft after being stacked together. A motor rotates the winding shaft, winding the positive electrode sheet, negative electrode sheet, and two separators to form a wound bare cell. The bare cell is placed in an outer packaging, injected with the above-mentioned electrolyte, and encapsulated to form a battery cell.

[0214] Among them, the volume distribution particle size Dv99 of the particles in the positive electrode bottom coating is 15μm, and the volume distribution curve of the positive electrode film particles shows a bimodal distribution, with the peak positions of 5μm and 9μm respectively, and the peak position difference is 4μm;

[0215] The particle size distribution value (Dv90-Dv10) / Dv50 in the primer layer is 4.8; the mass ratio of polycrystalline particles to single crystal particles in the primer layer is 7:3; the thickness L2 of the primer layer on one side is 10μm; the thickness L1 of the positive electrode film on one side is 40μm; the thickness relationship L2 / (L1+L2) between the primer layer and the positive electrode film on one side is 20%;

[0216] 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.

[0217] Comparative Example 1

[0218] 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 requirement of 220 MPa-330 MPa. Specific preparation parameters are shown in Table 1.

[0219] Comparative Example 2

[0220] The preparation method of the battery cell of Comparative Example 2 is similar to that of the battery cell of Example 1, except that the volume distribution particle size of the undercoat particles in the battery cell of Comparative Example 2 does not meet Dv99 less than or equal to 20 μm. Specific preparation parameters are shown in Table 1.

[0221] Comparative Example 3

[0222] 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.

[0223] Examples 2-4

[0224] 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.

[0225] Example 5

[0226] 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 sheet is adjusted. Specific preparation parameters are shown in Table 1.

[0227] Examples 6-8

[0228] 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 sizes Dv99 and Dv50 of the second single crystal particles in the bottom coating layer of the positive electrode sheet 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.

[0229] Examples 9-10

[0230] 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.

[0231] Examples 11-13

[0232] 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 ratios of the first polycrystalline particles and the first single crystal particles in the positive electrode film layer of the positive electrode sheet are adjusted. Specific preparation parameters are shown in Table 1.

[0233] Examples 14-15

[0234] 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 primer layer on one side of the positive electrode sheet and the thickness of the positive electrode film on one side are adjusted. Specific preparation parameters are shown in Table 1.

[0235] Example 16

[0236] The preparation method of the battery cell of Example 16 is similar to that of the battery cell of Example 1, except that the bottom coating in the battery cell of Example 16 only includes polycrystalline particles and does not include single crystal particles. Specific preparation parameters are shown in Table 1.

[0237] Table 1

[0238]

[0239] 2. Performance Testing

[0240] 1. Test method for tensile strength of positive electrode current collector

[0241] Take a current collector, or disassemble the current collector from the battery cell, cut the current collector into 2cm×5cm lengths, 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.

[0242] 2. CP-SEM characterization method of the cross section of the positive electrode

[0243] The sample to be characterized was prepared as follows: First, the positive electrode sheet was cut into 2 cm × 2 cm specimens and secured to the sample stage with paraffin wax. The sample stage was then placed in the sample holder and locked securely. The argon ion cross-section polisher IB-19500CP was powered on and vacuumed. The argon flow rate was set to 0.15 MPa, the control voltage to 8 kV, and the polishing time to 2 hours. The sample stage was then set to rocking mode and polishing began. After polishing, the sample to be characterized was obtained.

[0244] Micromorphology Characterization: Samples were characterized using a ZEISS Sigma300 scanning electron microscope. Sample testing can refer to JY / T010-1996. To ensure the accuracy of the test results, multiple randomly selected areas of the sample were scanned and cross-sectional morphology images were captured at a fixed magnification of 5kx.

[0245] 3. Test method of material particle size

[0246] The battery cells were disassembled, and the powder to be tested was scraped out from the positive electrode film layer and the undercoat layer. The materials were poured into a wind dispersion tank filled with ethanol and ultrasonically dispersed for 5 minutes. Sodium dodecyl sulfate (SDS) was added as a dispersant. The materials were then 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 undercoat layer.

[0247] 4. Characterization method of burr test on the cross section of positive electrode

[0248] An ultra-depth-of-field microscope (Keyence 600) was used to characterize the cut electrode. The test temperature was 25°C, the test electrode size was 80mm×60mm, the magnification was 300x, the light aperture was 30%, and the burr characterization and size calibration were performed on the cut cross-section of the electrode.

[0249] Burr size statistics: 2000 cut electrodes were observed by CCD, and the frequency of electrodes with burrs, K1, was counted. The burr ratio was calculated to be K1 / 2000×100%.

[0250] 5. Test method for Li ion diffusion coefficient of positive electrode

[0251] The coated electrodes were assembled into a semi-electric Vs Li, and the assembled buckle was 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.

[0252] Calculation: According to the GIIT formula The Li ion diffusion coefficient of the positive electrode sheet is calculated by dividing the voltage rise after one cycle (pulse + relaxation) by the voltage rise during the pulse process and filling in the diffusion coefficient formula. The Li ion diffusion coefficient in the embodiment of the present application and the comparative example is as follows: Figure 5 shown.

[0253] 6. Test method for elongation of positive electrode

[0254] Before the electrode is cold pressed, take a section of positive electrode sheet with a length of L, and then roll the positive electrode sheet in order according to the target pressure of different compaction densities, from small to large, and record the length L1 of the electrode 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%. The comparison of the elongation of the positive electrode sheet in an embodiment of the present application and the comparative example is shown in the figure below. Figure 6 shown.

[0255] 7. Test method for gram capacity of positive electrode

[0256] The active material on one side of the positive electrode was washed with NMP, and the washed single-sided positive electrode was assembled into a button battery. It was activated for 3 cycles at 0.1C / 0.1C, and then its gram capacity was measured at 0.1C / 0.1C. The voltage window was 2.8-4.3V. Figure 7 shown.

[0257] 8. Battery internal resistance DCR test method

[0258] At room temperature, the above battery cells were charged at a rate of 1 / 3C to the upper limit voltage, that is, 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.

[0259] 9. Battery energy density test method

[0260] The weight M of all active materials loaded per unit area of ​​the positive electrode sheet of the battery cell was measured respectively, and the volume of the battery cell was V. Each battery was 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 was measured, and the volume energy density of the battery cell was obtained as S0 / V.

[0261] 3. Analysis of test results of various embodiments and comparative examples

[0262] 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 table below.

[0263] Table 2

[0264]

[0265] It can be seen from the results of the examples 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 enables the battery cell to have a high energy density, which is conducive to further improvement of the comprehensive performance of the battery cell.

[0266] Table 3

[0267]

[0268] From the comparison of Examples 1 and 6-8 in Table 3, it can be seen that the battery cell base coat includes polycrystalline particles, the Dv99 of the polycrystalline particles in the base coat is 6-20 μm, and the particle size distribution value (Dv90-Dv10) / Dv50 of the particles in the base coat is 2-8.5, so that the battery cell has high energy density, low burr generation probability, and high dynamic performance.

[0269] 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. 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 further improve the energy density of the battery cell while reducing the probability of burr generation.

[0270] 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 improving the compaction density of the positive electrode sheet and further improving the energy density of the battery cell.

[0271] 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 primer 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 primer layer on one side is 10μm-30μm, which can not only reduce the probability of burrs on the electrode during cutting, but also reduce the battery capacity loss, so that the battery cell has excellent energy density.

[0272] Depend on Figure 5 and Figure 7From the comparison between Example 1 and Example 16, it can be seen that the polycrystalline particles included in the bottom coating of the battery cell 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 sheet, and is also beneficial to the performance of the gram capacity of the positive electrode sheet, thereby further improving the dynamic performance and energy density of the battery cell.

[0273] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine 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 20 μm-28 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 6 μm-18 μm.

2. The battery cell according to claim 1, wherein: The tensile strength of the positive electrode current collector is 280 MPa-330 MPa.

3. The battery cell according to claim 1, wherein: The particle size distribution value of the particles in the primer layer is (Dv90-Dv10) / Dv50 of 2-8.

5.

4. The battery cell according to claim 3, characterized in that The particle size distribution value of the particles in the primer layer is (Dv90-Dv10) / Dv50 of 2-6.

5. The battery cell according to claim 1, characterized in that The undercoat layer includes polycrystalline particles.

6. The battery cell according to claim 5, characterized in that The undercoat layer also includes single crystal particles.

7. The battery cell according to claim 6, 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.

8. The battery cell according to claim 7, 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.

9. The battery cell according to claim 6, characterized in that: The mass ratio of polycrystalline particles to single crystal particles in the primer layer is 5:5-9:

1.

10. The battery cell according to claim 9, characterized in that The mass ratio of polycrystalline particles to single crystal particles in the undercoat layer is 6:4-8:

2.

11. The battery cell according to claim 1, wherein 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.

12. The battery cell according to claim 11, 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.

13. 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.

14. The battery cell according to claim 13, 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.

15. The battery cell according to claim 14, 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.

16. The battery cell according to claim 13, 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.

17. The battery cell according to claim 16, 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.

18. The battery cell according to claim 13, 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.

19. The battery cell according to claim 18, 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.

20. The battery cell according to claim 1, characterized in that The bottom coating 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, -0.1≤b1≤0.

1.

21. The battery cell according to claim 20, characterized in that The first lithium-containing transition metal oxide includes nickel. Based on the total molar number of transition metals in the first lithium-containing transition metal oxide, the molar proportion of nickel in the first lithium-containing transition metal oxide is 80%-96%.

22. The battery cell according to claim 20, characterized in that The second lithium-containing transition metal oxide includes nickel. Based on the total molar number of transition metals in the second lithium-containing transition metal oxide, the molar proportion of nickel in the second lithium-containing transition metal oxide is 80%-96%.

23. 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: 。 24. The battery cell according to claim 23, characterized in that The thickness L1 of the positive electrode film layer on one side is 30 μm-60 μm.

25. The battery cell according to claim 23, characterized in that The thickness L2 of the primer layer on one side is 10 μm to 30 μm.

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

27. The battery cell according to claim 26, characterized in that The thickness of the positive electrode current collector is 7 μm-15 μm.

28. 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 .

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

30. 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.

31. 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 in at least 2000 positive electrode sheets is 0%-2%.

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

33. The battery cell according to claim 32, characterized in that The volume energy density of the battery cell is 670Wh / L-690Wh / L.

34. A battery device, characterized in that: The battery device comprises the battery cell according to any one of claims 1 to 33, and the battery device is one or more of a battery module, a battery pack, and an energy storage device.

35. An electrical device, characterized in that: The electrical device comprises the battery cell according to any one of claims 1 to 33 or the battery device according to claim 34.

Images