Separator, secondary battery cell and electrical apparatus

Abstract

Provided in the present application are a separator, a secondary battery cell, and an electrical apparatus. The separator comprises a substrate and a coating layer arranged on at least one side of the substrate; the coating layer comprises first inorganic particles and second inorganic particles, the average particle size of the second inorganic particles being greater than the average particle size of the first inorganic particles; the first inorganic particles form a main body portion of the coating layer, and the second inorganic particles are embedded in the main body portion and form a protrusion portion on the surface of the coating layer; the first inorganic particles exhibit block-shaped or flake-shaped morphology, and the second inorganic particles exhibit spherical, quasi-spherical or ellipsoidal morphology. The separator has excellent pressure resistance and high structural stability, and can provide a sufficient buffer space for the expansion of electrode sheets in a cycle process, thereby helping to construct stable electrolyte infiltration channels, and improving the cycle life of secondary battery cells.

Description

Separator membrane, secondary battery cells and electrical devices Cross-references to related applications This application claims priority to Chinese Patent Application No. 202510123754.4, filed on January 26, 2025, entitled “Separator, Secondary Battery Cell and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0001] This application relates to the field of battery technology, and in particular to a separator, a secondary battery cell, and an electrical device. Background Technology

[0002] Currently, improving energy density is the primary goal of rechargeable battery research and development. To further promote the widespread application of high-energy-density rechargeable batteries, it is necessary to comprehensively consider their energy density, power performance, cycle life, and safety performance. In the later stages of charge-discharge cycles, rechargeable batteries inevitably experience volume expansion and contraction, leading to continuous stress accumulation within the electrode components. This reduces the structural stability of the electrode components and hinders the electrolyte from fully wetting the electrodes and separator, negatively impacting the cycle performance of the rechargeable battery. These problems are even more pronounced in high-energy-density rechargeable batteries.

[0003] For example, to meet the demand for high energy density, the diameter of cylindrical secondary battery cells is gradually increased. The internal expansion force of the battery during cycling increases accordingly. In the later stages of cycling, the central hole of the cylindrical secondary battery cell is prone to collapse, the internal hydraulic balance of the battery is disrupted, the electrolyte wetting channel is blocked, and the electrolyte cannot fully wet the separator, resulting in a deterioration of cycle life. Summary of the Invention

[0004] This application provides a separator, a secondary battery cell, and an electrical device to alleviate the problem of deterioration in the cycle performance of a secondary battery cell due to expansion.

[0005] The first aspect of this application provides a separating membrane, including a substrate and a coating disposed on at least one side of the substrate. The coating includes first inorganic particles and second inorganic particles, wherein the average particle size of the second inorganic particles is greater than the average particle size of the first inorganic particles, the first inorganic particles form the main body of the coating, the second inorganic particles are embedded in the main body and form protrusions on the surface of the coating, and the first inorganic particles have a blocky or sheet-like morphology, and the second inorganic particles have a spherical, near-spherical or ellipsoidal morphology.

[0006] In the aforementioned isolation membrane coating configuration, the first inorganic particles have a blocky or sheet-like morphology with a small average particle size, forming the main body of the coating. The second inorganic particles have a spherical, near-spherical, or ellipsoidal morphology with a larger average particle size, embedded within the main body formed by the smaller-diameter first inorganic material, and forming protrusions on the coating surface. The blocky or sheet-like morphology of the first inorganic particles allows for smaller interparticle gaps in three-dimensional space, which, on the one hand, improves the packing density of the main body and prevents missed coating during the coating process; on the other hand, it has better pressure resistance, which helps to strengthen the support of the main body for the protrusions. The spherical, near-spherical, or ellipsoidal morphology of the second inorganic particles results in a uniform stress distribution when subjected to external stress, making it less prone to stress concentration and breakage. Furthermore, the protrusions exhibit good structural stability under expansion forces, effectively resisting the collapse of the central hole.

[0007] Therefore, the separator provided in this application exhibits superior compressive strength and high structural stability, providing ample buffer space for electrode expansion during cycling. This facilitates the construction of stable electrolyte wetting channels and enhances the cycle life of the secondary battery cell. Specifically, the separator provided in this application effectively supports the electrode assembly when the cylindrical secondary battery cell is subjected to high internal expansion forces, slowing down the shrinkage of the central hole diameter and reducing the probability of central hole collapse, thereby improving the cycle performance of the secondary battery cell.

[0008] In any embodiment of the first aspect, the ratio of the average particle size of the second inorganic particles to the average particle size of the first inorganic particles is greater than or equal to 6:1, and can be selected as 7:1 to 11.5:1. This can comprehensively improve the active ion transport performance and enhance the stability of the separator under high temperature and / or high mechanical stress conditions.

[0009] In any embodiment of the first aspect, the average particle size of the first inorganic particles is less than 1 μm, and can be selected from 200 nm to 500 nm. This can reduce the probability of incomplete coating, which is beneficial for further improving the heat resistance and oxidation resistance of the separator, while also helping to control the pore size of the main body of the coating, improving the wettability of the electrolyte to the coating, and increasing the active ion transport efficiency.

[0010] In any embodiment of the first aspect, the average particle size of the second inorganic particles is 2.2 μm to 5 μm, optionally 2.2 μm to 4 μm, and further optionally 2.5 μm to 3.2 μm, which can enhance the pressure resistance of the separator and increase the electrolyte absorption rate of the separator.

[0011] In any embodiment of the first aspect, the mass content of the second inorganic particles in the coating is less than the mass content of the first inorganic particles; optionally, the mass ratio of the first inorganic particles to the second inorganic particles in the coating is 1:(0.09-0.15), which is beneficial to construct a more stable gap between the separator and the electrode, enhance the separator's resistance to deformation and its liquid retention capacity, and improve the group margin and cycle performance of the secondary battery cell.

[0012] In any embodiment of the first aspect, the mass content of the second inorganic particles in the coating is 7%-15%, optionally 8.5%-12%, to further improve the heat resistance and oxidation resistance of the separator.

[0013] In any embodiment of the first aspect, at least a portion of the first inorganic particles and / or at least a portion of the second inorganic particles are primary particles. Primary particles have higher strength, enabling them to better perform their supporting role in the coating, reducing the amount of binder required, and improving the heat resistance and electrolyte wettability of the separator.

[0014] In any embodiment of the first aspect, the sphericity of the second inorganic particles is between 0.6 and 1.0, thereby exhibiting good isotropy, being able to withstand greater pressure, not easily crushed, and being able to construct more stable protrusions.

[0015] In any embodiment of the first aspect, the height of the protrusion is 3μm-8μm. This facilitates the creation of a suitable gap between the positive and negative electrode plates, effectively buffering the internal expansion forces of the secondary battery cell during cycling.

[0016] In any embodiment of the first aspect, the first inorganic particle and the second inorganic particle each independently comprise at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, strontium titanate, barium titanate, and magnesium fluoride.

[0017] In any embodiment of the first aspect, the first inorganic particles and the second inorganic particles comprise alumina, optionally comprising an α-crystal form, which can significantly improve the compressive strength and heat resistance of the coating.

[0018] In any embodiment of the first aspect, the coating surface density is 2.0 g / m². 2 -4.0g / m 2 Further reducing the impact of separator thickness on the energy density of secondary battery cells allows for more balanced electrical performance in the secondary battery cells.

[0019] In any embodiment of the first aspect, the thickness of the main body is 0.5μm-2μm, which provides higher structural stability, more sufficient electrolyte wetting channels in the later stages of cycling, and effectively improves the cycle life of the secondary battery cell.

[0020] In any embodiment of the first aspect, the thickness of the substrate is 3 μm-7 μm. The coating with the above-described configuration can significantly improve the thermal safety and cycle performance of the separator, thus allowing for the use of a thinner substrate, thereby increasing the energy density of the secondary battery cell.

[0021] In any embodiment of the first aspect, the above-mentioned separator membrane satisfies one or more of the following characteristics: (1) the wetting velocity K of the separator membrane is 0.52 cm / s. 0.5 -0.56cm / s 0.5 (2) At 25℃, a compressive stress of 5MPa is applied to the separator along the thickness direction, and the incompressible ratio of the separator is 75%-80%; (3) At 65℃, a compressive stress of 5MPa is applied to the separator along the thickness direction, and the incompressible ratio of the separator is 60%-70%. The two types of inorganic particles with large differences in particle size are intercalated in the coating to obtain a main body with high packing density and a more stable pore structure. Therefore, the separator not only has good wettability and liquid retention of electrolyte, but also has excellent compressive strength and heat and oxidation resistance.

[0022] The second aspect of this application provides a secondary battery cell, including an electrode assembly, which includes a positive electrode, a negative electrode, and any of the separators described in the first aspect, wherein the separator is disposed between the positive electrode and the negative electrode.

[0023] In any embodiment of the second aspect, the secondary battery cell is a cylindrical secondary battery cell, which includes a central hole. The diameter of the central hole when the cylindrical secondary battery cell is in a 0% SOC state within 600 cycles is denoted as D1, and the diameter of the central hole when the cylindrical secondary battery cell is in a 100% SOC state within 600 cycles is denoted as D2. D1-D2≤0.5mm, and optionally D1-D2≤0.2mm.

[0024] In any embodiment of the second aspect, the diameter of the cylindrical secondary battery cell is greater than or equal to 40 mm, and D1 satisfies 4 mm ≤ D1 ≤ 6 mm.

[0025] In any embodiment of the second aspect, the positive electrode of the secondary battery cell includes a positive current collector and a positive electrode film, the positive electrode film including a positive electrode active material, and the positive electrode active material including a layered lithium-containing transition metal oxide.

[0026] In any embodiment of the second aspect, the negative electrode sheet of the secondary battery cell includes a negative current collector and a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material; optionally, the silicon-based material includes one or more of silicon-oxygen materials and silicon-carbon composite materials.

[0027] A third aspect of this application provides an electrical device comprising any of the secondary battery cells of the second aspect. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0029] Figure 1 is a schematic diagram of a battery pack according to one embodiment of this application;

[0030] Figure 2 is an exploded view of the battery pack in one embodiment of this application shown in Figure 1;

[0031] Figure 3 is a schematic diagram of a battery module with a cylindrical secondary battery cell in one embodiment of this application;

[0032] Figure 4 is a schematic diagram of the structure of the cylindrical secondary battery cell shown in Figure 3;

[0033] Figure 5 is a schematic diagram of an electrical device in which a secondary battery cell is used as a power source according to an embodiment of this application.

[0034] The accompanying drawings are not drawn to scale.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Battery pack; 2. Upper housing; 3. Lower housing; 4. Battery module; 6. Battery module of cylindrical secondary battery cell; 7. Cylindrical secondary battery cell; 7a. First electrode lead-out part; 7b. Second electrode lead-out part; 21. Housing; 211. End wall; 212. Side wall; 30. Electrode terminal; Z. Axial direction. Detailed Implementation

[0037] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0038] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the separator, secondary battery cell, and power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0039] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0045] Typically, a secondary battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is placed between the positive and negative electrodes to prevent short circuits between the positive and negative electrodes, while allowing active ions to pass freely to form a circuit.

[0046] [Isolation membrane]

[0047] As described in the background section, the energy density requirements for secondary battery cells are becoming increasingly stringent. However, as the energy density of secondary battery cells increases, it is more likely to cause an increase in volume expansion force, which can damage the structural stability of the secondary battery cells and thus deteriorate their cycle performance.

[0048] Taking a cylindrical secondary battery cell as an example, during the cyclic charging and discharging process, the negative electrode plate will expand due to the insertion of ions. As the diameter of the cylindrical secondary battery cell increases, the expansion of the negative electrode plate accumulates and may generate greater expansion force. This will increase the pressure between the positive and negative electrode plates, causing the electrolyte in the pores inside the positive electrode film layer of the positive electrode plate and the electrolyte in the pores inside the negative electrode film layer of the negative electrode plate to be squeezed out. In the later stages of the cycle, the central hole may also collapse, affecting the cycle performance of the cylindrical secondary battery cell.

[0049] To address the aforementioned problems, a first embodiment of this application provides a separating membrane, comprising a substrate and a coating disposed on at least one side of the substrate. The coating comprises first inorganic particles and second inorganic particles, wherein the average particle size of the second inorganic particles is greater than the average particle size of the first inorganic particles, the first inorganic particles form the main body of the coating, the second inorganic particles are embedded in the main body and form protrusions on the surface of the coating, and the first inorganic particles have a blocky or sheet-like morphology, while the second inorganic particles have a spherical, near-spherical, or ellipsoidal morphology.

[0050] It should be noted that in this application, "quasi-spherical" means that the shape of inorganic particles is visually close to that of a sphere and satisfies the following: (1) the size is roughly equal in all directions, showing good symmetry; (2) the surface is relatively smooth, and there may be slight bumps or irregular shape changes, but usually it will not affect its overall spherical characteristics; (3) it has dispersibility and fluidity similar to that of a sphere.

[0051] The isolation membrane provided in this application includes a specially designed coating. The first inorganic particles have a blocky or sheet-like morphology with a small average particle size, forming the main body of the coating. The second inorganic particles have a spherical, near-spherical, or ellipsoidal morphology with a larger average particle size, embedded within the main body formed by the smaller-diameter first inorganic material, and forming protrusions on the coating surface. The blocky or sheet-like morphology of the first inorganic particles allows for smaller interparticle gaps in three-dimensional space. This improves the packing density of the main body, preventing missed coating during application; it also provides better pressure resistance, enhancing the support of the main body for the protrusions. The spherical, near-spherical, or ellipsoidal morphology of the second inorganic particles ensures uniform stress distribution under applied stress, reducing the likelihood of stress concentration and breakage. Furthermore, the protrusions exhibit good structural stability under expansion forces, effectively resisting the collapse of the central hole.

[0052] Compared to existing technologies that use organic particles embedded in the main body to form protrusions on the coating surface, using inorganic particles provides improved wettability. The particle morphology, size, and distribution are easily controlled, and they are less prone to agglomeration during preparation. More importantly, the protrusions formed by the second inorganic particles exhibit superior compressive strength and high structural stability, providing ample buffer space for electrode expansion during cycling. This facilitates the construction of stable electrolyte wetting channels and improves the cycle life of the secondary battery cell. Specifically, the separator provided in this application effectively supports the electrode assembly when the cylindrical secondary battery cell is subjected to high internal expansion forces, slowing down the shrinkage of the central hole diameter and reducing the probability of central hole collapse, thereby improving the cycle performance of the secondary battery cell.

[0053] Unwilling to be limited by any theory, the inventors, through extensive experimental exploration, discovered that by adjusting the particle size ratio of the first inorganic particles to the second inorganic particles within a certain range, a more suitable height difference can be formed between the particles, thereby creating pore sizes and distributions more conducive to the migration of active ions. Simultaneously, the particle size matching achieves stable support for the pores formed by the second inorganic particles from the smaller-sized first inorganic particles. Therefore, in some embodiments, the ratio of the average particle size of the second inorganic particles to the average particle size of the first inorganic particles is greater than or equal to 6:1, optionally from 7:1 to 11.5:1, and further optionally from 7:1 to 9.5:1. Through the synergistic cooperation of two types of inorganic particles with different particle sizes and morphologies, the active ion transport performance can be comprehensively improved, and the stability of the separator under high temperature and / or high mechanical stress conditions can be enhanced.

[0054] In some embodiments, the average particle size of the first inorganic particles is less than 1 μm, which can effectively control the packing density of the main body and further improve the strength and stability of the coating.

[0055] In some embodiments, the average particle size of the first inorganic particles is 200 nm to 500 nm, optionally 200 nm-350 nm or 300 nm-450 nm. An average particle size within this range reduces the likelihood of incomplete coating due to insufficient dispersion of the first inorganic particles caused by excessively large particle sizes. This is beneficial for further improving the heat resistance and oxidation resistance of the separator, while also helping to control the pore size of the coating's main body, improving the wettability of the electrolyte to the coating, and increasing the active ion transport efficiency. This, in turn, is more conducive to the capacity utilization and cycle performance of the secondary battery cells.

[0056] In some embodiments, the average particle size of the second inorganic particles is 2.2 μm to 5 μm, optionally 2.2 μm to 4.0 μm, and further optionally 2.5 μm to 3.2 μm. When the average particle size of the second inorganic particles is within the above range, protrusions with excellent compressive strength can be formed on the surface of the main body, making the separator more pressure-bearing and increasing the electrolyte absorption rate of the separator. Therefore, when the internal expansion force of the secondary battery cell is large, the structural stability and cycle life of the secondary battery cell can be effectively improved.

[0057] In this application, the "average particle size" of inorganic particles (e.g., the first inorganic particle, the second inorganic particle) refers to the arithmetic mean of the particle sizes of inorganic particles calculated after measuring the particle sizes of multiple inorganic particles in the separator coating. Generally, the distance between the two farthest points on an inorganic particle is taken as the particle size of that inorganic particle.

[0058] The average particle size of inorganic particles can be determined using instruments and methods known in the art. For example, a scanning electron microscope (SEM) can be used to obtain a cross-sectional image of the separator along its thickness direction. Specifically, a high vacuum mode is selected, with an operating voltage of 1-3 kV. A test sample of 50 mm × 100 mm is randomly selected on the separator. Multiple test areas (e.g., more than 5, with an area of ​​5 mm × 5 mm) are randomly selected within the test sample. The particle size of inorganic particles in each test area is read at a certain magnification (e.g., 5000-6000 times). The number and particle size of inorganic particles in each test area are counted, and the arithmetic mean of the particle sizes in each test area is taken as the average particle size. To ensure the accuracy of the test results, multiple (e.g., 10) test samples can be used for the above test, and the average value of each test sample is taken as the final test result.

[0059] In some embodiments, the mass content of the second inorganic particles in the coating is less than the mass content of the first inorganic particles; optionally, the mass ratio of the first inorganic particles to the second inorganic particles in the coating is 1:(0.09-0.15). When the mass ratio is within the above range, the first inorganic particles form a main body of suitable and uniform thickness, providing stable support for the second inorganic particles. The second inorganic particles can be relatively uniformly and firmly embedded in the main body, creating a more stable gap between the separator and the electrode, enhancing the separator's resistance to deformation and its liquid retention capacity, and improving the cell margin and cycle performance of the secondary battery.

[0060] In some embodiments, the mass content of the second inorganic particles in the coating is 7%-15%, optionally 8.5%-12%. When the mass content of the second inorganic particles is within the above range, the main body of the formed coating can provide better protection to the substrate and improve the heat resistance and oxidation resistance of the release film.

[0061] In some embodiments, at least some of the first inorganic particles and / or at least some of the second inorganic particles are primary particles. Primary particles have higher strength, enabling them to better perform their supporting role in the coating, reducing the amount of binder required, and improving the heat resistance and electrolyte wettability of the separator. By observing the coating cross-section using a scanning electron microscope, it can be determined whether the morphology of the first and second inorganic particles is that of primary or secondary particles.

[0062] In some embodiments, the sphericity of the second inorganic particles is between 0.6 and 1.0. Second inorganic particles with higher sphericity have better isotropy, thus they can withstand greater pressure, are less likely to be crushed, and can form more stable protrusions.

[0063] The above sphericity is calculated using the formula S = dn / a is calculated, where d n Let d be the diameter of the sphere equivalent to the volume of the second inorganic particle. n = (6V / π) 1 / 3 V represents the volume of the second inorganic particle, and a is the length of the major axis of the second inorganic particle. When the second inorganic particle is used as a protrusion in the isolation film coating, multiple cross-sectional dimensions of the second inorganic particle can be measured using a scanning electron microscope, followed by approximate solution and statistical averaging.

[0064] In some embodiments, the height of the protrusion is 3μm-8μm. The height of the protrusion is the vertical distance between the apex of the protrusion and the surface of the main body away from the substrate. When the height of the protrusion is within the above range, the coating exhibits excellent compressive and heat resistance properties, and is conducive to creating a suitable gap between the positive and negative electrode sheets, effectively buffering the internal expansion force of the secondary battery cell during cycling, and further reducing the probability of central hole collapse.

[0065] In some embodiments, the first inorganic particle and the second inorganic particle each independently comprise at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, strontium titanate, barium titanate, and magnesium fluoride.

[0066] In some implementations, the first inorganic particle and the second inorganic particle are made of the same material.

[0067] In some embodiments, the first and second inorganic particles comprise alumina, and the alumina crystal form includes α-crystal, θ-crystal, γ-crystal, and η-crystal forms. Among these, α-crystal alumina possesses advantages such as high hardness, low dielectric constant, high true density, and good heat resistance; θ-crystal alumina has moderate specific surface area and hardness; and both γ-crystal and η-crystal forms have large specific surface areas. Further, in some embodiments, the alumina crystal form includes α-crystal. Using α-crystal alumina as the inorganic particle can significantly improve the compressive strength and heat resistance of the coating.

[0068] When the first or second inorganic particle contains alumina, the crystal form of the alumina can be identified by X-ray diffraction (e.g., a Bruker D8 DISCOVER X-ray diffractometer). Specifically: α-crystal alumina exhibits diffraction peaks at 2θ of 57.48°±0.2° and 42.34°±0.2° in the X-ray diffraction pattern. θ-crystal alumina exhibits diffraction peaks at 2θ of 36.68°±0.2° and 31.21°±0.2° in the X-ray diffraction pattern. γ-crystal alumina exhibits diffraction peaks at 2θ of 66.95°±0.2° and 45.91°±0.2° in the X-ray diffraction pattern. η-crystal alumina exhibits diffraction peaks at 2θ of 31.89°±0.2° and 19.37°±0.2° in the X-ray diffraction pattern. When using an X-ray diffractometer, a Cu target can be used. Tube voltage 40kV, tube current 40mA, continuous scanning range 5°-80°.

[0069] In some embodiments, the coating surface density is 2.0 g / m². 2 -4.0g / m 2 By controlling the weight of the single-sided coating on the separator per unit area within the aforementioned range, the impact of separator thickness on the energy density of the secondary battery cells can be further reduced while fully improving the cycle performance and safety performance of the cells.

[0070] In some embodiments, the thickness of the main body is 0.5 μm-2 μm. For example, the thickness of the main body can be 0.5 μm-0.8 μm, 0.5 μm-1.0 μm, 1.0 μm-1.2 μm, 1.2 μm-1.4 μm, 1.5 μm-1.8 μm, 1.6 μm-2 μm, 1 μm-2 μm, or 0.5 μm-1.5 μm, but is not limited to these. When the thickness of the main body is within the above range, the structural stability is higher, a stable micron-level gap can be provided between the electrodes, and a more sufficient electrolyte wetting channel can be provided in the later stages of cycling, effectively improving the cycle life of the secondary battery cell.

[0071] The thickness of the aforementioned protrusion and main body can be determined in the following way, taking the main body as an example: using an argon ion cross-section polisher (e.g., IB-19500CP) under vacuum conditions of -120℃ to 80℃, setting the argon flow rate (e.g., 1.0-1.5MPa), voltage (e.g., 7.0-7.5kV), and polishing time (e.g., 2.0-2.5 hours), the qualified isolation membrane sample is polished using the swing mode; after polishing, the ion polished cross-sectional morphology (CP) image of the test sample is obtained using a scanning electron microscope (e.g., ZEISS Sigma 300), with a working voltage of 1-3kV and a magnification of 5000-6000; the thickness of the main body at multiple locations (e.g., 12 locations) within the field of view is marked, and the average value of multiple measured thicknesses is calculated as the thickness of the main body.

[0072] In some embodiments, the thickness of the substrate is 3μm-7μm. The coating provided in this application can significantly improve the thermal safety and cycle performance of the separator, thus allowing for the use of thinner substrates, thereby increasing the energy density of the secondary battery cells.

[0073] This application does not impose any special restrictions on the coating method. For example, the prepared coating slurry can be sequentially applied to both surfaces of the substrate using a coating machine. In some embodiments, the coating surface density is 2.0 g / m². 2 -4.0g / m 2 .

[0074] Without being confined to any particular theory, it is known that rechargeable battery cells undergo varying degrees of volume expansion during cycling. In particular, cylindrical rechargeable battery cells contain a central hole, so during the later stages of cycling, volume expansion creates an inward expansion force along the radial direction of the cylinder. This force increases with the diameter of the cylindrical rechargeable battery cell, reaching as high as 3 MPa to 5 MPa, inducing central hole collapse. Once central hole collapse occurs, the electrolyte wetting channels become blocked, the separator dries out and fails, the battery's internal resistance increases, making charging and discharging difficult, and causing the capacity of the cylindrical rechargeable battery cell to rapidly decay.

[0075] In the coating provided in this application, two types of inorganic particles with significantly different particle sizes are intercalated, resulting in a bulk matrix with high packing density and a more stable pore structure, which is beneficial for simultaneously improving the compressive strength and wettability of the separator. In some embodiments, the separator meets one or more of the following characteristics: 1) The wetting velocity K of the separator is 0.52 cm / s. 0.5 -0.56cm / s 0.52) At 25℃, a compressive stress of 5MPa is applied to the separator along its thickness direction, and the incompressibility of the separator is 75%-80%; 3) At 65℃, a compressive stress of 5MPa is applied to the separator along its thickness direction, and the incompressibility of the separator is 60%-70%. The separator not only has good wettability and electrolyte retention, which helps improve the ion conductivity of the separator, but also has excellent compressive strength, heat resistance, and oxidation resistance, which can optimize the cycle performance and safety performance of secondary battery cells.

[0076] In this application, the wetting speed of the separator has a meaning known in the art and can be measured using methods known in the art. Exemplarily, the wetting speed of the separator can be determined as follows: the separator is cut into samples with a width of 5 mm and a length of 100 mm, and the two ends of the sample are fixed and placed horizontally; 100 mL of electrolyte is dropped onto the center of the flat separator sample using a pipette, and the length of electrolyte diffusion (i.e., wetting length) within a specified time (2 min in this application) is captured using a high-speed camera, thereby obtaining the wetting speed. To ensure the accuracy of the test results, multiple (e.g., 5 to 10) separator samples can be tested, and the test results are obtained by calculating the average value. The composition of the electrolyte used for testing is as follows: the solvent is an organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 3:5:2, and the electrolyte salt is LiPF6 with a concentration of 1 mol / L.

[0077] The incompressibility ratio of the separator film can be determined as follows: Take 10 layers of separator film, stack them in a fresh state, and roll them three times with a 3kg self-weight roller. Then, use a Mahr Millimar C1216M film thickness gauge to test the Mahr thickness, which is recorded as h0. Take another 10 layers of separator film, stack them in a fresh state, and apply a 5MPa compressive stress at 25℃ and 65℃ respectively using a hot press, and hold for 10s-15s for shaping. Then, use a Mahr Millimar C1216M film thickness gauge to test the Mahr thickness, which is recorded as h1. The incompressibility ratio k of the separator film can be calculated by the following formula: k=1-(h0-h1) / h0.

[0078] The separator provided in this application does not have any particular restrictions on the material of the substrate; any known substrate with good chemical and mechanical stability can be selected. For example, at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but not limited to these. The substrate can be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer can be the same or different.

[0079] In some embodiments, the coating may also include organic compounds, such as polymers that improve heat resistance (referred to as "heat-resistant adhesives"), dispersants, wetting agents, and other types of binders. All of the above-mentioned organic compounds are non-particulate substances in the coating. This application does not impose any particular limitation on the types of organic compounds mentioned above; any known material with good improving properties can be selected.

[0080] In some implementations, the air permeability of the separator is 160 sec / 100cc to 260 sec / 100cc.

[0081] In some embodiments, the transverse tensile strength of the separator is 3000 kg / cm². 2 -4000kg / cm 2 .

[0082] In some embodiments, the longitudinal tensile strength of the separator is 2000 kg / cm². 2 -3000kg / cm 2 .

[0083] In some embodiments, the transverse elongation at break of the separator is 60%-140%.

[0084] In some embodiments, the longitudinal elongation at break of the separator is 100%-180%.

[0085] In this application, the air permeability, tensile strength, and elongation at break of the separator all have meanings known in the art and can be measured using methods known in the art. For example, they can all be tested with reference to the standard GB / T 36363-2018.

[0086] It should be noted that the coating parameters (such as areal density and thickness) of the aforementioned separator are coating parameters for one side of the separator substrate. When the coating is applied to both sides of the substrate, if the coating parameters on either side meet the requirements of this application, it is considered to fall within the protection scope of this application.

[0087] [Secondary battery cell]

[0088] The second embodiment of this application provides a secondary battery cell, which includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and any one of the separators in the first embodiment. The separator is disposed between the positive electrode and the negative electrode.

[0089] For example, the secondary battery cell can be a cylindrical secondary battery cell, a prismatic secondary battery cell, a pouch secondary battery cell, or a secondary battery cell of other shapes. Prismatic secondary battery cells include square secondary battery cells, blade-shaped secondary battery cells, and multi-prismatic secondary battery cells, such as hexagonal prismatic secondary battery cells.

[0090] In some embodiments, the secondary battery cell is a cylindrical secondary battery cell, which includes a central hole. The diameter of the central hole when the cylindrical secondary battery cell is in a 0% SOC state within 600 cycles is denoted as D1, and the diameter of the central hole when the cylindrical secondary battery cell is in a 100% SOC state within 600 cycles is denoted as D2. D1-D2≤0.5mm, and optionally D1-D2≤0.2mm.

[0091] In some implementations, the diameter of the cylindrical secondary battery cell is greater than or equal to 40 mm, and D1 satisfies 4 mm ≤ D1 ≤ 6 mm.

[0092] [Positive electrode plate]

[0093] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film, the positive electrode film including a positive active material, the positive active material including a layered lithium-containing transition metal oxide.

[0094] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0095] In some embodiments, the positive 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, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for use in batteries.

[0097] When the secondary battery cell is a lithium-ion secondary battery, as an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0098] When the secondary battery cell is a sodium-ion secondary battery, as an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion secondary batteries may also be used.

[0099] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0100] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0101] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0102] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0103] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0104] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0105] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0106] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0108] [Negative electrode plate]

[0109] In some embodiments, the negative electrode includes a negative current collector and a negative electrode film, the negative electrode film including a negative electrode active material, the negative electrode active material including a silicon-based material.

[0110] In some embodiments, the silicon-based material may further include at least one of elemental silicon, silicon-nitrogen composites, silicon-oxygen materials, silicon-carbon composites, and silicon alloys. In some embodiments, the silicon-based material includes one or more of silicon-oxygen materials and silicon-carbon composites.

[0111] The negative electrode active material can also be other negative electrode active materials known in the art for use in batteries. 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, tin-based materials, and lithium titanate, etc. Tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used.

[0112] The aforementioned negative electrode active materials can be used alone or in combination of two or more.

[0113] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, 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).

[0114] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0116] As an example, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0117] In some embodiments, the negative electrode sheet may include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0118] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0119] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0120] In some implementations, the negative electrode can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode, the surface of the foamed metal may or may not contain a negative electrode active material.

[0121] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0122] Electrolyte

[0123] In some embodiments, the secondary battery cell also includes an electrolyte, which comprises an electrolyte salt and a solvent, and serves to conduct ions between the positive and negative electrodes.

[0124] 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0125] In some embodiments, the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium perchlorate, sodium hexafluoroarsenate, sodium difluorosulfonylimide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorodioxalate phosphate, and sodium tetrafluorooxalate phosphate.

[0126] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0127] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the secondary battery cell, such as additives that improve the overcharge / fast charge performance of the secondary battery cell, additives that improve the high-temperature performance of the secondary battery cell, and additives that improve the low-temperature performance of the secondary battery cell.

[0128] [shell]

[0129] In some embodiments, the secondary battery cell includes a casing. The casing can be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc.

[0130] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0131] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0132] In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, it serves to protect the electrode assembly, and a sealing bag is included between the housing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag can be a bag-shaped insulating component or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0133] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the secondary battery cell.

[0134] As an example, when the internal pressure or temperature of a single secondary battery cell reaches a predetermined threshold, it is actuated to release the internal pressure or temperature. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the secondary battery cell.

[0135] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0136] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0137] The term "actuation" as used in this application refers to the pressure relief mechanism being activated or undergoing a certain state, thereby releasing the internal pressure and temperature of the secondary battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is actuated, the high-temperature, high-pressure substances inside the secondary battery cell are discharged as waste from the actuated portion. This method allows for pressure and temperature relief of the secondary battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0138] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0139] The emissions from secondary battery cells mentioned in this application include, but are not limited to: electrolytes, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0140] [Battery Device]

[0141] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple secondary battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0142] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0143] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or shutting down; it can be sealed or not sealed. The first enclosure may be a top cover or a bottom plate. The enclosure may also include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, forming a closed space inside the enclosure to house the individual battery cells.

[0144] As an example, the housing can be part of the vehicle's chassis structure. For instance, a portion of the housing can be at least a part of the vehicle's floor, or a portion of the housing can be at least a part of the vehicle's crossbeams and longitudinal beams.

[0145] Figures 1 and 2 show a battery pack 1 as an example. Referring to Figures 1 and 2, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box. To improve the sealing performance after the upper box 2 and lower box 3 are connected, a sealing element, such as sealant or a sealing ring, may be provided between the upper box 2 and lower box 3.

[0146] In some embodiments, a battery cell assembly is typically formed by arranging multiple secondary battery cells.

[0147] In some embodiments, the battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As an example, a battery module can be formed by bundling multiple secondary battery cells together with cable ties.

[0148] As an example, a battery cell assembly can be housed in a housing by fixing the battery module to the housing, or by directly fixing multiple secondary battery cells to the housing.

[0149] In some embodiments, the battery pack 1 is used to house cylindrical secondary battery cells, which can be one or more. If there are multiple cylindrical secondary battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that the multiple cylindrical secondary battery cells are connected in both series and parallel. The multiple cylindrical secondary battery cells can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of the multiple cylindrical secondary battery cells is housed within the battery pack housing. Alternatively, as shown in Figure 3, there are multiple cylindrical secondary battery cells 7, which are first connected in series, parallel, or in a mixed configuration to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or in a mixed configuration to form a whole, and housed within the battery pack housing.

[0150] Multiple cylindrical secondary battery cells 7 in the battery module 6 can be electrically connected through a busbar to achieve parallel, series, or mixed connection of the multiple cylindrical secondary battery cells 7 in the battery module 6. There can be one or more busbars, and each busbar is used to electrically connect at least two cylindrical secondary battery cells 7.

[0151] Figure 4 is a schematic diagram of the structure of a cylindrical secondary battery cell in some embodiments of this application. Exemplarily, the cylindrical secondary battery cell 7 can be a lithium-ion secondary battery cell, a sodium-ion secondary battery cell, a sodium-lithium-ion secondary battery cell, a lithium metal secondary battery cell, a sodium metal secondary battery cell, a lithium-sulfur secondary battery cell, a magnesium-ion secondary battery cell, a nickel-metal hydride secondary battery cell, a nickel-cadmium secondary battery cell, or a lead-acid secondary battery cell, but is not limited thereto.

[0152] In some embodiments, the cylindrical secondary battery cell 7 includes an electrode assembly and a housing 21. The housing 21 includes an end wall 211 and a side wall 212. Electrode terminals 30 are disposed on the end wall 211. Each electrode terminal 30 includes a first electrode lead-out 7a and a second electrode lead-out 7b. The first electrode lead-out 7a is electrically connected to a first tab, and the second electrode lead-out 7b is electrically connected to a second tab. The first electrode lead-out 7a and the second electrode lead-out 7b are insulated from each other. The first electrode lead-out 7a and the second electrode lead-out 7b are used to connect to an external circuit to realize the charging or discharging of the cylindrical secondary battery cell 7.

[0153] In some embodiments, the first electrode lead-out portion 7a and the second electrode lead-out portion 7b are located on the same side of the electrode assembly 10 along the axial direction Z of the cylindrical secondary battery cell 7.

[0154] For example, when multiple cylindrical secondary battery cells 7 are assembled into a group, the first electrode lead-out portion 7a and the second electrode lead-out portion 7b are used to connect to the busbar component.

[0155] For example, when multiple cylindrical secondary battery cells 7 are assembled into a group, the first electrode lead-out portion 7a and the second electrode lead-out portion 7b of the multiple cylindrical secondary battery cells 7 can be arranged on the same side, which facilitates the connection between the current collector and the first electrode lead-out portion 7a and the second electrode lead-out portion 7b, and simplifies the battery structure.

[0156] The technical solutions described in this application are applicable to various electrical devices that use individual rechargeable battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft. As for the aforementioned electrical devices, individual rechargeable battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0157] Figure 5 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery cells in this device, a battery pack or battery module can be used.

[0158] [Example]

[0159] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0160] Example 1

[0161] Preparation of the separating membrane:

[0162] (1) Provide a porous PE substrate with a thickness of 5μm and a porosity of 40%;

[0163] (2) Preparation of coating slurry: The first inorganic particles α-Al2O3, the second inorganic particles α-Al2O3, and the water-soluble non-particulate binder polyacrylate are mixed evenly in an appropriate amount of deionized water at a dry weight ratio of 85:10:5 to obtain a coating slurry with a solid content of 30% (by weight).

[0164] The first inorganic particle is a blocky particle with an average particle size of 350 nm; the second inorganic particle is a spherical particle with an average particle size of 2.8 μm and a sphericity of not less than 0.6; in addition, it can be observed by SEM that both the first and second inorganic particles are mixtures of primary and secondary particles.

[0165] (3) The coating slurry prepared in (2) is coated on the two surfaces of the PE substrate using a coating machine, and a release film is obtained through drying, slitting and other processes.

[0166] The coating speed was 120 m / min, the linear velocity ratio was 1.0, the drying temperature was 65℃, and the drying time was 10 s; the areal density of the single-sided coating on the release liner was 2.5 g / m³. 2 .

[0167] Preparation of the positive electrode: The positive electrode active material LiNi... 0.9 Co 0.05 Mn 0.05 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry is coated onto a positive electrode current collector aluminum foil, and then subjected to drying, cold pressing, slitting, and cutting processes to obtain the positive electrode sheet. The areal density of the positive electrode sheet is 0.207 mg / mm². 2 The compacted density is 3.5 g / cm³. 3 .

[0168] Preparation of the negative electrode sheet: Artificial graphite (negative electrode active material), silicon-carbon composite material (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) are mixed evenly in a suitable amount of deionized water at a mass ratio of 91.7:4.8:0.6:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry is coated onto copper foil (negative electrode current collector), and the negative electrode sheet is obtained through drying, cold pressing, slitting, and cutting. The areal density of the negative electrode sheet is 0.126 mg / mm². 2 The compacted density is 1.7 g / cm³. 3 .

[0169] In this embodiment, the electrolyte includes lithium salt and solvent. The solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 30:70. The concentration of lithium salt LiPF6 in the electrolyte is 1.0 mol / L.

[0170] Preparation of a secondary battery cell: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The positive electrode, separator, and negative electrode are then wound to obtain an electrode assembly. The electrode assembly is placed in a cylindrical shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a cylindrical secondary battery cell is obtained. The electrode assembly and the shell are both cylindrical, comprising a housing and end caps. The housing includes integrally formed sidewalls and end walls. The sidewalls surround the electrode assembly, and the end caps and end walls are axially opposite each other. The cylindrical secondary battery cell has a diameter of 46 mm and a height of 95 mm. The initial diameter of the central hole in the formed cylindrical secondary battery cell is 6 mm.

[0171] Example 2

[0172] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0173] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 1.5 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0174] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0175] Example 3

[0176] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0177] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 2.2 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0178] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0179] Example 4

[0180] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0181] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 2.5 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0182] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0183] Example 5

[0184] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0185] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 3.2 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0186] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0187] Example 6

[0188] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0189] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 4.0 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0190] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0191] Example 7

[0192] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0193] The second inorganic particle used in this embodiment is a spherical particle with an average particle size of 5.0 μm and a sphericity of not less than 0.64. The other settings are the same as in Example 1.

[0194] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0195] Example 8

[0196] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0197] When preparing the coating slurry, the first inorganic particles α-Al2O3, the second inorganic particles α-Al2O3, and the water-soluble non-particulate binder polyacrylate are mixed evenly in an appropriate amount of deionized water according to a dry weight ratio of 88:7:5 to obtain a coating slurry with a solid content of 30% (by weight). The remaining settings are consistent with those in Example 1.

[0198] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0199] Example 9

[0200] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0201] When preparing the coating slurry, the first inorganic particles α-Al2O3, the second inorganic particles α-Al2O3, and the water-soluble non-particulate binder polyacrylate are mixed evenly in an appropriate amount of deionized water according to a dry weight ratio of 83:12:5 to obtain a coating slurry with a solid content of 30% (by weight). The remaining settings are consistent with those in Example 1.

[0202] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0203] Example 10

[0204] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0205] When preparing the coating slurry, the first inorganic particles α-Al2O3, the second inorganic particles α-Al2O3, and the water-soluble non-particulate binder polyacrylate are mixed evenly in an appropriate amount of deionized water at a dry weight ratio of 80:15:5 to obtain a coating slurry with a solid content of 30% (by weight). The remaining settings are consistent with those in Example 1.

[0206] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0207] Example 11

[0208] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0209] The first inorganic particle α-Al2O3 used in this embodiment is a block particle with an average particle size of 200nm, and the rest of the settings are the same as in Example 1;

[0210] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0211] Example 12

[0212] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0213] The first inorganic particle α-Al2O3 used in this embodiment is a block particle with an average particle size of 300nm, and the rest of the settings are the same as in Example 1;

[0214] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0215] Example 13

[0216] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0217] The first inorganic particle α-Al2O3 used in this embodiment is a block particle with an average particle size of 450nm, and the rest of the settings are the same as in Example 1;

[0218] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0219] Example 14

[0220] The only difference between this embodiment and Embodiment 1 is the preparation process of the separator:

[0221] The first inorganic particle α-Al2O3 used in this embodiment is a block particle with an average particle size of 500nm, and the rest of the settings are the same as in Example 1;

[0222] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0223] Comparative Example 1

[0224] The only difference between this comparative example and Example 1 is the preparation of the separating membrane; no second inorganic particles are used. Specifically, in the preparation of the coating slurry:

[0225] The first inorganic particles α-Al2O3 and the water-soluble non-particulate binder polyacrylate were mixed evenly in an appropriate amount of deionized water at a dry weight ratio of 95:5 to obtain a coating slurry with a solid content of 30% (by weight); the rest of the settings were the same as in Example 1.

[0226] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0227] Comparative Example 2

[0228] The only difference between this comparative example and Example 1 is the preparation of the separator. Polyacrylate copolymer organic particles are used instead of the second inorganic particles. Specifically, in the preparation of the coating slurry:

[0229] According to the dry weight ratio of 82:7:11, the first inorganic particles α-Al2O3, polyacrylate copolymer organic particles, and water-soluble non-particulate binder polyacrylate are mixed evenly in an appropriate amount of deionized water to obtain a coating slurry with a solid content of 25% (by weight).

[0230] The polyacrylate copolymer organic particles are spherical particles with an average particle size of 2.8 μm, the glass transition temperature of the polyacrylate copolymer is 52 °C, and the other settings are the same as in Example 1.

[0231] The preparation of the positive and negative electrode sheets, the composition of the electrolyte, and the preparation of the secondary battery cells are all the same as in Example 1.

[0232] [Test Characterization Methods]

[0233] The methods described above can be used to test the average particle size, morphology of inorganic particles, thickness of the main body, height of the protrusions, incompressibility of the separator, wettability, etc. in the coating, which will not be elaborated here.

[0234] The shrinkage of the central hole after 600 charge-discharge cycles of a cylindrical secondary battery cell was used as an evaluation index for its structural stability. The specific test method is as follows:

[0235] The cylindrical secondary battery cells prepared in the above embodiments and comparative examples all have an initial central hole diameter of a0 = 6 mm. After the cylindrical secondary battery cells are left to stand at 25°C for 30 minutes, they are charged at a constant current rate of 1C to the charging cutoff voltage of 4.2V. Then, they are charged at a constant voltage until the current is no greater than 0.05C, left to stand for 30 minutes, and then discharged at a constant current rate of 0.33C to the discharge cutoff voltage of 2.8V. After standing for 30 minutes, the battery capacity C0 is recorded. This method is repeated for 600 charge-discharge cycles. The current central hole diameter a1 is measured using a CCD vision inspection device. The central hole shrinkage Δa = a0 – a1, in mm.

[0236] The capacity retention rate of a cylindrical secondary battery cell after 900 charge-discharge cycles at 65℃ was used as the evaluation index for its high-temperature cycling performance. The specific test method is as follows:

[0237] The cylindrical secondary battery cells prepared in the above embodiments and comparative examples were placed in an environment at 65°C and left to stand for 30 minutes. Then, they were charged at a constant current rate of 1C to the charging cutoff voltage of 4.2V, followed by constant voltage charging until the current was no greater than 0.05C. After standing for 30 minutes, they were discharged at a constant current rate of 0.33C to the discharge cutoff voltage of 2.8V. After standing for 30 minutes, the battery capacity C0 was recorded. The secondary battery cells were subjected to 900 charge-discharge cycles in this manner, and the battery capacity after 900 cycles was recorded as C1. The capacity retention rate after 900 charge-discharge cycles was R = C1 / C0 × 100%.

[0238] The average particle size of the first inorganic particles and the second inorganic particles (the isolation membrane of Comparative Example 1 does not contain the second inorganic particles, and the organic particles are used as a substitute in Comparative Example 2) contained in the isolation membrane of the above embodiments, the ratio of their average particle sizes, their respective mass content in the isolation membrane coating, and the ratio of their mass content in the isolation membrane coating are recorded in Table 1.

[0239] For simplicity, in Table 1, the "ratio of the average particle size of the first inorganic particles to the average particle size of the second inorganic particles" is simply referred to as the "average particle size ratio", and the "ratio of the mass content of the first inorganic particles to the second inorganic particles in the separator coating" is simply referred to as the "mass content ratio".

[0240] Table 1

[0241] The test data of the coatings, separators, and cylindrical secondary battery cells of each embodiment and comparative example are recorded in Table 2.

[0242] Table 2

[0243] Compared to the single-type inorganic particle scheme in Comparative Example 1, the scheme in this embodiment, which uses two types of inorganic particles in combination, improves the cycle performance of the cylindrical secondary battery cell. The use of highly spherical second inorganic particles to form protrusions results in uniform stress distribution, which is beneficial to the structural stability of the electrode assembly, significantly reduces the central hole shrinkage, and improves electrolyte wettability, thereby optimizing the cycle performance of the cylindrical secondary battery cell. Furthermore, compared to the method in Comparative Example 2 where organic particles are embedded in the main body and form protrusions on the coating surface, the scheme in this embodiment, which uses two types of inorganic particles in combination, provides more effective support under internal expansion forces, constructs a more stable electrolyte wetting channel, and makes the performance of the cylindrical secondary battery cell more balanced.

[0244] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A separating membrane, comprising a substrate and a coating disposed on at least one side of the substrate, the coating comprising first inorganic particles and second inorganic particles, the average particle size of the second inorganic particles being larger than the average particle size of the first inorganic particles, the first inorganic particles forming a main body portion of the coating, the second inorganic particles being embedded in the main body portion and forming protrusions on the surface of the coating, and the first inorganic particles having a blocky or sheet-like morphology, and the second inorganic particles having a spherical, near-spherical, or ellipsoidal morphology.

2. The separator membrane according to claim 1, characterized in that, The ratio of the average particle size of the second inorganic particle to the average particle size of the first inorganic particle is greater than or equal to 6:1, and can be selected from 7:1 to 11.5:

1.

3. The separator according to claim 1 or 2, characterized in that, The average particle size of the first inorganic particle is less than 1 μm, and can be selected from 200 nm to 500 nm, and further selected from 200 nm to 350 nm.

4. The separator according to claim 1 or 2, characterized in that, The average particle size of the second inorganic particles is 2.2 μm to 5.0 μm, optionally 2.2 μm to 4.0 μm, and further optionally 2.5 μm to 3.2 μm.

5. The separator membrane according to any one of claims 1 to 4, characterized in that, The mass content of the second inorganic particles in the coating is less than the mass content of the first inorganic particles; optionally, the mass ratio of the first inorganic particles to the second inorganic particles in the coating is 1:(0.09-0.15).

6. The separator according to claim 5, characterized in that, The second inorganic particles have a mass content of 7%-15% in the coating, optionally 8.5%-12%.

7. The separator membrane according to any one of claims 1 to 6, characterized in that, At least a portion of the first inorganic particles and / or at least a portion of the second inorganic particles are primary particles.

8. The separator membrane according to any one of claims 1 to 7, characterized in that, The sphericity of the second inorganic particle is between 0.6 and 1.

0.

9. The separator membrane according to any one of claims 1 to 8, characterized in that, The height of the protrusion is 3μm-8μm.

10. The separator membrane according to any one of claims 1 to 9, characterized in that, The first inorganic particle and the second inorganic particle each independently comprise at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, strontium titanate, barium titanate, and magnesium fluoride.

11. The separator membrane according to any one of claims 1 to 10, characterized in that, The first inorganic particle and the second inorganic particle comprise alumina, and optionally, the alumina comprises an α-crystal form.

12. The separator membrane according to any one of claims 1 to 11, characterized in that, The surface density of the coating is 2.0 g / m². 2 -4.0g / m 2 .

13. The separator membrane according to any one of claims 1 to 12, characterized in that, The thickness of the main body is 0.5μm-2μm; and / or the thickness of the substrate is 3μm-7μm.

14. The separator membrane according to any one of claims 1 to 13, characterized in that, The isolation membrane satisfies one or more of the following characteristics: 1) The wetting velocity K of the separating membrane is 0.52 cm / s. 0.5 -0.56cm / s 0.5 ; 2) At 25°C, a compressive stress of 5 MPa is applied to the separator along its thickness direction, and the incompressibility of the separator is 75%-80%. 3) At 65°C, a compressive stress of 5 MPa is applied to the separator along its thickness direction, and the incompressibility of the separator is 60%-70%.

15. A secondary battery cell, comprising an electrode assembly, the electrode assembly comprising a positive electrode, a negative electrode, and a separator as described in any one of claims 1 to 14, the separator being disposed between the positive electrode and the negative electrode.

16. The secondary battery cell according to claim 15, characterized in that, The secondary battery cell is a cylindrical secondary battery cell, and the cylindrical secondary battery cell includes a central hole. When the cylindrical secondary battery cell is in a 0% SOC state within 600 cycles, the diameter of the central hole is denoted as D1. When the cylindrical secondary battery cell is in a 100% SOC state within 600 cycles, the diameter of the central hole is denoted as D2. D1-D2≤0.5mm, and optionally D1-D2≤0.2mm.

17. The secondary battery cell according to claim 16, characterized in that, The diameter of the cylindrical secondary battery cell is greater than or equal to 40 mm, and D1 satisfies 4 mm ≤ D1 ≤ 6 mm.

18. The secondary battery cell according to any one of claims 15 to 17, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode film layer. The positive electrode film layer includes a positive electrode active material, which includes a layered lithium-containing transition metal oxide.

19. The secondary battery cell according to any one of claims 15 to 18, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer. The negative electrode film layer includes a negative electrode active material, which includes a silicon-based material. Optionally, the silicon-based material includes one or more of silicon-oxygen materials and silicon-carbon composite materials.

20. An electrical device comprising a plurality of secondary battery cells according to any one of claims 15 to 19.

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