Separator, secondary battery and electric device

Abstract

Disclosed are a separator, a secondary battery and an electric device. The separator comprises: a substrate and a coating, wherein the coating is formed on at least one side of the substrate, and comprises acrylate polymer particles. In a three-dimensional imaging spectrogram, the value of an effective abscissa in a scan spectrum across the centers of the acrylate polymer particles is 5-150 um. The separator can be bonded to an electrode sheet by means of cold pressing, and the bonding force between the electrode sheet and the separator is suitable, thereby improving the cycle performance of a battery.

Description

Separating membrane, secondary battery and electrical device

[0001] Priority information

[0002] This application claims priority and benefit to patent application 202411216469.9, filed with the China National Intellectual Property Administration on August 30, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of batteries, specifically relating to a separator, a secondary battery, and an electrical device. Background Technology

[0004] In recent years, with the rapid growth of portable electronic devices, electric vehicles, and other technologies, the demand for power batteries has also been increasing. Among these, the electrochemical performance of batteries has received increasing attention.

[0005] Currently, polyvinylidene fluoride (PVDF) is used as the adhesive for the separator in batteries. PVDF is coated onto the separator, wound with the electrode sheets, and then heated and pressed together to bond the electrode sheets to the separator, increasing cell rigidity and maintaining consistent cell thickness. Without this hot-pressing process, gaps would exist between the separator and the electrode sheets, leading to openings in the cell and wrinkles in the separator. However, excessive adhesion between the electrode sheets and the separator after hot pressing can cause the positive and / or negative electrode sheets to easily detach during battery cycling, thus reducing the battery's cycle performance. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a separator membrane, which aims to achieve cold pressing bonding between the separator membrane and the electrode sheet, thereby improving the cycle performance of the battery.

[0007] To achieve the above objectives, one aspect of this application provides a separating membrane, the separating membrane comprising:

[0008] Substrate;

[0009] A coating formed on at least one side of the substrate, the coating comprising acrylate polymer particles, wherein the effective abscissa value in the scanning spectrum along the center of the acrylate polymer particles in a three-dimensional imaging spectrum is 5 μm-150 μm.

[0010] This application includes at least the following beneficial effects: the separator and the electrode can be cold-pressed together, and the adhesion between the electrode and the separator is appropriate, thereby improving the cycle performance of the battery.

[0011] In some embodiments, the vertical axis of the scanning spectrum along the center of the acrylate polymer particles in the three-dimensional imaging spectrum is set between 5 μm and 25 μm. This ensures suitable adhesion between the electrode and the separator.

[0012] In some embodiments, the acrylate polymer particles form protrusions on the coating surface.

[0013] In some embodiments, the height of the protrusion on both sides is 2μm-100μm.

[0014] In some embodiments, the volume average particle size distribution Dv50 of the acrylate polymer particles is 2 μm-25 μm, optionally 5 μm-15 μm, and / or the volume average particle size distribution Dv99 of the acrylate polymer particles is 4 μm-50 μm, optionally 15 μm-40 μm. This reduces the risk of clogging the pores of the separator and improves the permeability of the separator to active ions.

[0015] In some embodiments, the acrylate polymer particles comprise a first organic polymer and a second organic polymer. The first organic polymer has monomers comprising a first monomer, a second monomer, a third monomer, and a fourth monomer. The second organic polymer has monomers comprising a first monomer, a second monomer, a third monomer, a fourth monomer, and a fifth monomer. The structure of the first monomer includes:

[0016] Wherein, R1 includes a hydrogen atom or an alkyl group with 1-18 carbon atoms, and R2 includes an alkyl group with 1-18 carbon atoms.

[0017] The structure of the second polymer monomer includes:

[0018] R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms;

[0019] The structure of the third polymeric monomer includes:

[0020] R4 includes a hydrogen atom or an alkyl group with 1-6 carbon atoms, and R5 includes a hydrogen atom, a hydroxyl-substituted alkyl group with 1-6 carbon atoms, or an alkoxy group with 1-6 carbon atoms.

[0021] The structure of the fourth polymeric monomer includes:

[0022] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms;

[0023] The structure of the fifth polymeric monomer includes:

[0024] R7 and R8 are alkyl groups, and the total number of carbon atoms in R7 and R8 is 2-10. This allows for cold-press bonding between the separator and the electrode, and the adhesion between the electrode and the separator is appropriate, thereby improving the cycle performance of the battery.

[0025] In some implementations, the total number of carbon atoms in R7 and R8 is 5-8.

[0026] In some embodiments, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10). This not only facilitates the winding and unwinding of the separator, but also improves the cold-pressing adhesion between the separator and the positive and negative electrode sheets, thereby enhancing the cycle performance of the battery.

[0027] In some embodiments, the mass ratio of the first polymer monomer, the second polymer monomer, the third polymer monomer, and the fourth polymer monomer in the first organic polymer is 1:0.01-0.25:0.01-0.1:0.01-0.2. This improves the cold-pressing adhesion between the separator and the positive and negative electrode sheets.

[0028] In some embodiments, the mass ratio of the first, second, third, fourth, and fifth monomers in the second organic polymer is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.15. This improves the cold-pressing adhesion between the separator and the positive and negative electrode sheets.

[0029] In some embodiments, the first polymeric monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. This improves the cold-press adhesion between the separator and the positive and negative electrode sheets.

[0030] In some embodiments, the second polymeric monomer includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. This improves the cold-press adhesion between the separator and the positive and negative electrode sheets.

[0031] In some embodiments, the third polymerizing monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide. This can improve the cold-press adhesion between the separator and the positive and negative electrode sheets.

[0032] In some embodiments, the fourth polymeric monomer includes at least one of acrylonitrile, methacrylonitrile, or ethyl acrylonitrile. This can improve the cold-press adhesion between the separator and the positive and negative electrode sheets.

[0033] In some embodiments, the fifth polymeric monomer includes At least one of the following. This can improve the cold-pressing adhesion between the separator and the positive and negative electrode sheets.

[0034] In some embodiments, the coating further includes a second type of organic polymer particles, comprising at least one of the following: polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinylidene fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorinated alkenyl monomer units and vinyl monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylic monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylate monomer units, and modified compound particles of the above homopolymers or copolymers. The second type of organic polymer particles and the acrylate polymer particles form the protrusions on the coating surface. This improves the cycle performance and safety performance of the battery.

[0035] In some embodiments, the mass ratio of the acrylate polymer particles to the second organic polymer particles is (20-90):(0-70), and optionally (45-90):(0-45).

[0036] In some embodiments, the volume average particle size distribution Dv50 of the second organic polymer particles is 2μm-25μm, optionally 5μm-15μm, and / or the volume average particle size distribution Dv99 of the second organic polymer particles is 4μm-50μm, optionally 15μm-40μm. This allows for improved safety and cycle performance while reducing battery costs.

[0037] The second aspect of this application provides a secondary battery, which includes the separator membrane described in the first aspect of this application.

[0038] A third aspect of this application discloses an electrical device comprising the secondary battery described in the second aspect of this application. Therefore, this electrical device exhibits excellent cycle performance and safety performance.

[0039] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0040] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0041] Figure 1 is a schematic diagram of the structure of the isolation membrane in one embodiment of this application.

[0042] Figure 2 is a three-dimensional spectrum of acrylate polymer particles on the isolation membrane in one embodiment of this application.

[0043] Figure 3 is a schematic diagram of the winding of the battery cell after the separator is stacked with the positive and negative electrode sheets in one embodiment of this application.

[0044] Figure 4 is a schematic diagram of a battery according to one embodiment of this application.

[0045] Figure 5 is an exploded view of the battery according to one embodiment of this application, as shown in Figure 4.

[0046] Figure 6 is a schematic diagram of a battery module according to one embodiment of this application.

[0047] Figure 7 is a schematic diagram of a battery pack according to one embodiment of this application.

[0048] Figure 8 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 7.

[0049] Figure 9 is a schematic diagram of an electrical device in which a battery is used as a power source according to an embodiment of this application.

[0050] Explanation of reference numerals in the attached drawings: 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Battery module; 3. Battery pack; 31. Upper housing; 32. Lower housing; 100. Separator; 101. Coating; 102. Substrate. Detailed Implementation

[0051] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0052] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0053] 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.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0056] 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.

[0057] Currently, the application of rechargeable batteries is becoming increasingly widespread, judging from market trends. They are not only used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of rechargeable battery applications, market demand is also constantly increasing.

[0058] A battery cell consists of a positive electrode, a negative electrode, and a separator. The cell possesses a certain degree of rigidity; that is, the positive and negative electrodes and the separator, bonded together, adhere and support each other, forming a structure of a certain thickness, which in turn provides rigidity. During charging and discharging, the negative electrode expands. If the adhesion is weak, gaps will form between the positive and negative electrodes and the separator, preventing them from adhering and supporting each other. This results in a loose cell with reduced rigidity. Consequently, the battery's cycle performance deteriorates, directly shortening its lifespan. Electric vehicles require frequent battery replacements, increasing costs for consumers.

[0059] A tight bond between the separator and the electrode improves the battery's discharge capacity, reduces internal resistance, minimizes polarization loss, extends cycle life, and increases the utilization rate of rechargeable batteries. Currently, polyvinylidene fluoride (PVDF) is commonly used as the adhesive on the separator in existing rechargeable batteries. A hot-pressing process (heating during the pressing process after stacking the separator and electrode) is typically required to achieve a tight bond. However, this hot-pressing process leads to several drawbacks. First, it reduces battery manufacturing efficiency. Second, the temperature difference between the inner and outer rings of the cell after hot pressing results in uneven bonding. During the shaping process, the outer ring is heated for a longer period, resulting in greater adhesion, while the inner ring is heated for a shorter period, resulting in weaker adhesion. This leads to a significant difference in bonding between the inner and outer rings of the cell. During battery cycling, excessive expansion of the negative electrode can cause the positive active material in the positive electrode or the negative active material in the negative electrode to be torn off, i.e., the positive and negative electrodes become detached, thus reducing the battery's cycle performance.

[0060] The separator of this application includes a substrate and a coating. The coating includes acrylate polymer particles. In the three-dimensional imaging spectrum, the effective abscissa value along the center of the acrylate polymer particles is 5μm-150μm. The acrylate polymer particles can be bonded to the electrode during the cold pressing process, thereby realizing that the separator can be cold-pressed to the electrode. The adhesion between the electrode and the separator is appropriate, which can improve the cycle performance of the battery.

[0061] The separator disclosed in this application can be used in batteries, and the batteries disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0062] The first aspect of this application discloses a barrier membrane. Referring to FIG1, the barrier membrane 100 includes a substrate 102 and a coating 101. The coating 101 is formed on at least a portion of the surface of the substrate 11. The coating 101 includes acrylate polymer particles. In a three-dimensional imaging spectrum, the effective abscissa value along the center of the acrylate polymer particles is 5μm-150μm, for example, 10μm-140μm, 20μm-130μm, 30μm-120μm, 40μm-110μm, 50μm-100μm, 60μm-90μm, 70μm-80μm, etc.

[0063] This application employs a coating of the aforementioned acrylate polymer particles on the separator membrane. These acrylate polymer particles can adhere to the electrode during the cold pressing process, thereby achieving cold pressing adhesion between the separator membrane and the electrode, and ensuring suitable adhesion between the electrode and the separator membrane, which in turn improves the cycle performance of the battery.

[0064] The process by which the aforementioned acrylate polymer particles exert their performance is hypothesized as follows: The coating on the separator is formed into a ring-like structure, with the acrylate polymer particles mainly distributed on the ring. Simultaneously, some acrylate polymer particles are also present in the central region of the ring. Starting from the side of the coating containing acrylate polymer particles closest to the substrate, a three-dimensional scan of the coating is performed along the direction away from the substrate, resulting in a three-dimensional height spectrum. From this three-dimensional height spectrum, a two-dimensional scan spectrum (i.e., a scan spectrum along the center of the acrylate polymer particles) can be obtained. The horizontal axis in this two-dimensional spectrum represents the diameter of the near-circular shape formed by the acrylate polymer particle coating. Furthermore, the effective horizontal axis in the two-dimensional spectrum along the center of the acrylate polymer particles refers to the location where the vertical axis value in the corresponding two-dimensional spectrum is not zero. The effective horizontal axis value in the two-dimensional spectrum along the center of the acrylate polymer particles is the sum of the lengths of all effective horizontal axes in the two-dimensional spectrum along the center of the acrylate polymer particles. The larger this value, the larger the ring area of ​​the acrylate polymer particles. When the effective abscissa value is too small (below 5μm), the adhesion force decreases significantly, affecting the shaping process. Insufficient protrusions also limit the corner space of the cell, causing safety issues. Conversely, if the effective abscissa value is too large (greater than 150μm), excessive adhesion worsens wetting, leading to overcharging and lithium plating, resulting in capacity loss and safety risks. In the three-dimensional imaging spectrum of this application, the effective abscissa value along the center of the acrylate polymer particles ranges from 5μm to 150μm. The ring-like structure formed by the cold pressing of the acrylate polymer particles on the coating has a suitable area, facilitating adhesion to the electrode. This achieves a reasonable cold-pressed adhesion between the separator and the electrode, improving shaping efficiency, reducing energy consumption, increasing winding speed, and enhancing battery cycle performance. It also has a reasonable gap-forming capability, improving battery cycle life.

[0065] In some embodiments of this application, in the three-dimensional imaging spectrum, the vertical axis value of the scanning spectrum along the center of the acrylate polymer particles is 5μm-25μm, for example, 7μm-23μm, 10μm-20μm, 12μm-18μm, 15μm-17μm, etc. Specifically, in the three-dimensional imaging spectrum, the vertical axis value of the scanning spectrum along the center of the acrylate polymer particles, i.e., the two-dimensional spectrum, is the maximum value of the vertical axis in the two-dimensional spectrum, which represents the height of the protrusion formed by the acrylate polymer particles on the coating surface. This application controls the height of the acrylate polymer particles to meet the above range. When the battery experiences thermal runaway and generates high temperatures, the protrusions formed by the acrylate polymer particles can form a large-area film structure to reduce or block electron transport channels, delay the thermal propagation of the battery, and thus effectively improve the battery's cycle performance and safety performance at high temperatures.

[0066] In this application, the method for testing the effective abscissa and ordinate in the scanning spectrum along the center of the acrylate polymer particles includes:

[0067] Equipment used: Olympus OLS5100-SAF

[0068] Test process:

[0069] 1. Sample preparation

[0070] (1) Disassemble the battery and cut the area on the separator that is not in contact with the positive and negative electrode plates (including corner areas, the innermost ring of the cell or the outermost ring of the cell) to prepare a separator sample of at least 10cm*10cm in size. The separator surface should be free of foreign objects, damage or other appearance defects.

[0071] (2) Place the isolation membrane sample into the test fixture and clamp it to ensure that the area to be tested is within the observation range and that no wrinkles are generated on the surface of the isolation membrane during the clamping process;

[0072] (3) Confirm that the eyepiece is in 5X lens observation mode.

[0073] 2. Data Collection

[0074] (1) Adjust the focus using autofocus or the mouse wheel until the image is clear;

[0075] (2) Adjust the field of view by dragging the mouse or using the joystick;

[0076] (3) By switching lenses, the best observation image can be obtained;

[0077] (4) Observation was performed using a 50x lens, which is consistent with the size and data accuracy of PCS (polymer particles). Observation magnification: 1133X, observation range: 257μm×257μm;

[0078] (5) Use the mouse wheel to focus on the lowest position of the sample (the lowest position is the side of the coating containing acrylate polymer particles that is close to the substrate), and click "3D Acquisition - Start" in the lower right corner. During the test, ensure that there is no vibration in the environment to ensure the test accuracy.

[0079] 3. Data Analysis

[0080] (1) Noise removal and tilt correction are performed in "automatic" mode;

[0081] (2) Select the “Area / Volume” analysis interface, move the profile observation line to the area without PCS (polymer particles), and move the baseline to the substrate plane;

[0082] (3) Move the outline back to the PCS (polymer particle) area and move it to the position corresponding to the longest axis of the acrylate polymer particle;

[0083] (4) Adjust the size of the calculation region to 50μm. 2 ;

[0084] (5) Click “Create Report” to obtain the three-dimensional and two-dimensional spectra of the acrylate polymer particles.

[0085] 4. End of measurement

[0086] (1) Click "File", "Data", "Excel Data", name the file, and save it to the corresponding folder;

[0087] (2) From the three-dimensional spectrum of the near-circular acrylate polymer particle coating obtained by scanning (as shown in Figure 2), the scanning spectrum along the center of the acrylate polymer particles is a two-dimensional spectrum. The horizontal axis of this two-dimensional spectrum represents the diameter of the near-circular shape formed by the acrylate polymer particle coating. The effective horizontal axis in the two-dimensional spectrum along the center of the acrylate polymer particles refers to the location where the vertical axis value in the corresponding two-dimensional spectrum is not 0. The effective horizontal axis value in the two-dimensional spectrum along the center of the acrylate polymer particles is the sum of the lengths of all effective horizontal axes in the two-dimensional spectrum along the center of the acrylate polymer particles. The larger this value, the larger the area of ​​the acrylate polymer ring. The vertical axis value in the two-dimensional spectrum along the center of the acrylate polymer particles is the maximum value of the vertical axis in the two-dimensional spectrum.

[0088] Select at least 10 different samples and repeat steps 1-4 to obtain at least 10 sets of effective abscissa and ordinate values. Then, use the average of the at least 10 sets of effective abscissa values ​​as the effective abscissa value in the scanning spectrum along the center of the acrylate polymer particles, and use the average of the at least 10 sets of ordinate values ​​as the ordinate value in the scanning spectrum along the center of the acrylate polymer particles.

[0089] There are no particular restrictions on the type of substrate in this application; any known porous substrate with good chemical and mechanical stability can be selected.

[0090] In some embodiments of this application, the substrate may be a porous membrane or porous nonwoven mesh comprising one or more of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinylnaphthalene. In other embodiments, the substrate is a porous membrane or porous nonwoven mesh comprising polyethylene and / or polypropylene. By selecting the above-mentioned substrates to prepare the separator membrane, it is advantageous for the substrate to bond with the coating through an adhesive, forming a moderately dense, porous separator membrane capable of conducting active ions.

[0091] In some embodiments of this application, the acrylate polymer particles form protrusions on the coating surface. Therefore, when thermal runaway of the battery generates high temperatures, the protrusions formed by the acrylate polymer particles on the coating surface can form a large-area film structure to reduce or block electron transport channels, delaying the thermal propagation of the battery, thereby effectively improving the battery's cycle performance and safety performance at high temperatures.

[0092] It should be noted that the separator can be scanned using a scanning electron microscope (SEM), and the SEM image can show that the acrylate polymer particles form protrusions on the coating surface.

[0093] In some other embodiments of this application, the protrusions formed by acrylate polymer particles on the coating surface can be tested using methods known in the art. As an example, this can be achieved using a ZEISS Sigma300 scanning electron microscope, following these steps: First, cut the isolation membrane to be tested into a 6mm × 6mm sample. Clamp the sample between two conductive and thermally conductive copper foils, and secure the sample to the copper foils with double-sided tape. Press the sample with a 400g flat iron block for 1 hour to minimize the gap between the sample and the copper foils. Then, trim the edges with scissors and attach the sample to a sample stage with conductive adhesive, ensuring the sample slightly protrudes from the edge of the sample stage. Next, mount the sample stage onto the sample holder and lock it in place. Turn on the power to the IB-19500CP argon ion cross-section polisher and evacuate to 10Pa. -4 Pa, set the argon flow rate to 0.15 MPa and the voltage to 8 kV, and the polishing time to 2 hours. Adjust the sample stage to the swing mode to start polishing. After polishing, use a ZEISS Sigma300 scanning electron microscope to obtain the ion polished cross-sectional morphology (CP) image of the sample to be tested. From the CP image, the protrusion information formed by the acrylate polymer particles on the coating surface can be obtained.

[0094] In some embodiments of this application, the surface of the separator coating has raised areas with a double-sided height of 2μm-100μm, such as 5μm-95μm, 10μm-90μm, 15μm-85μm, 20μm-80μm, 25μm-75μm, 30μm-70μm, 35μm-65μm, 40μm-60μm, 45μm-55μm, 45μm-50μm, etc. This height range of raised areas provides adequate space between the separator and the electrode to release stress, preventing breakage during electrode winding and improving safety. Furthermore, it allows for suitable gaps between the separator and the electrode, facilitating electrolyte flow and wetting, and improving the cycle performance of the battery cell. In some embodiments of this application, the double-sided height of the raised areas is 10μm-55μm, more preferably 25μm-35μm.

[0095] In this application, coatings are formed on both opposite surfaces of the substrate. The sum of the heights of the protrusions on both sides of the coating is the double-sided height of the protrusion, and the double-sided height of the protrusion can be tested using methods known in the art. As an example, it can be tested by the following method: Referring to Figure 3, the negative electrode sheet, separator, and positive electrode sheet are first stacked sequentially to form a battery cell and then wound up (the outermost layer of the battery cell ends with the convex surface of the positive electrode sheet). Then, a CT device (ZEISS-1500) is used to scan the position 15±1mm below the edge of the negative electrode sheet at the corner of the wound battery cell. Samples are taken along the horizontal and oblique angles (30-45°) in the obtained CT image, and lines are drawn in the direction of the maximum gap. The sampling position for the inner 5 folds is from the convex surface of the innermost positive electrode sheet to the convex surface of the 5th positive electrode sheet, and the average value of 4 folds is taken. After 6 folds, the sampling position is from the convex surface of the inner positive electrode sheet to the convex surface of the outer positive electrode sheet, and the value is taken every 5 folds.

[0096] Average gap between inner 5 layers = [CT measurement distance - 4 * thickness of negative electrode sheet after cold pressing * (1 + negative electrode sheet rebound rate) - 4 * thickness of positive electrode sheet after cold pressing * (1 + positive electrode sheet rebound rate) - 8 * separator thickness] / 8

[0097] Average gap after 6-10 inner layers = [CT measurement distance - 5 * thickness of negative electrode sheet after cold pressing * (1 + negative electrode sheet rebound rate) - 5 * thickness of positive electrode sheet after cold pressing * (1 + positive electrode sheet rebound rate) - 10 * separator thickness] / 10

[0098] Wherein, negative electrode rebound rate = (thickness of negative electrode before entering the casing - thickness of negative electrode after cold pressing) / thickness of negative electrode after cold pressing;

[0099] Positive electrode rebound rate = (positive electrode thickness before casing - positive electrode thickness after cold pressing) / positive electrode thickness after cold pressing;

[0100] The height of the double-sided protrusion of the separator membrane = (average gap of the inner 5 layers + average gap after the inner 6th to 10th layers) / 2.

[0101] In some embodiments of this application, the volume average particle size Dv50 of the acrylate polymer particles is 2μm-25μm, for example, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 23μm, 23μm, 24μm, 25μm, etc. In other embodiments of this application, the volume average particle size Dv50 of the acrylate polymer particles is 5μm-15μm.

[0102] In some embodiments of this application, the volumetric particle size distribution Dv99 of the acrylate polymer particles is 4μm-50μm, such as 5μm-50μm, 8μm-45μm, 10μm-42μm, 15μm-40μm, 20μm-38μm, 25μm-35μm, 27μm-32μm, 30μm-32μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv99 of the acrylate polymer particles is 15μm-40μm.

[0103] In this application, acrylate polymer particles that meet the above-mentioned volume particle size distribution are used on the separator membrane. This not only reduces the risk of acrylate polymer particles clogging the separator membrane pores and improves the permeability of active ions in the separator membrane, but also reduces the risk of corner breakage. At the same time, it effectively alleviates the cell safety problem caused by the current collector breakage due to excessive corner stress in the wound structure.

[0104] It should be noted that, in the embodiments of this application, the volume average particle size Dv50 of the acrylate polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 50%, and the volume particle size distribution Dv99 of the acrylate polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 99%. The above-mentioned volume particle size distribution of the acrylate polymer particles can be tested using methods known in the art. As an example, the test method is as follows:

[0105] The particle size distribution was determined using laser diffraction, in accordance with GB / T 19077-2016 / ISO 13320:2009. A laser particle size analyzer (Malvin 3000, MasterSizer 3000) was used, with a helium-neon red light source as the main light source. 1g of the sample (refractive index 1.58) was added to a clean small beaker, along with one drop of surfactant and 20ml of deionized water (ensuring a light-blocking degree of 8-12%). The sample was sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer was then turned on, and the optical path system was cleaned before automatically testing the background. The sonicated sample solution was stirred to ensure uniform dispersion, then placed into the sample cell as required, and particle size measurement began. The measurement results can be read from the instrument.

[0106] In some embodiments of this application, the acrylate polymer particles comprise: a first organic polymer and a second organic polymer, wherein the polymer monomers of the first organic polymer include a first polymer monomer, a second polymer monomer, a third polymer monomer, and a fourth polymer monomer, and the polymer monomers of the second organic polymer include a first polymer monomer, a second polymer monomer, a third polymer monomer, a fourth polymer monomer, and a fifth polymer monomer, and the structure of the first polymer monomer includes:

[0107] Wherein, R1 includes a hydrogen atom or an alkyl group with 1-18 carbon atoms, and R2 includes an alkyl group with 1-18 carbon atoms.

[0108] The structure of the second polymer monomer includes:

[0109] R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms;

[0110] The structure of the third polymeric monomer includes:

[0111] R4 includes a hydrogen atom or an alkyl group with 1-6 carbon atoms, and R5 includes a hydrogen atom, a hydroxyl-substituted alkyl group with 1-6 carbon atoms, or an alkoxy group with 1-6 carbon atoms.

[0112] The structure of the fourth polymeric monomer includes:

[0113] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms;

[0114] The structure of the fifth polymeric monomer includes: R7 and R8 are alkyl groups and the total number of carbon atoms in R7 and R8 is 2-10. Optionally, the total number of carbon atoms in R7 and R8 is 5-8.

[0115] The acrylate polymer particles described in this application include a first organic polymer and a second organic polymer. The first organic polymer comprises a first polymer, a second polymer, a third polymer, and a fourth polymer. The first polymer comprises an unsaturated ester group, the second polymer comprises an unsaturated carboxyl group, the third polymer comprises an unsaturated amide group, and the fourth polymer comprises an unsaturated cyano group. The first organic polymer is prepared by polymerizing the first, second, third, and fourth polymers. After the coating slurry is transferred to the substrate, the friction between the slurry and the release membrane increases during the solvent evaporation process of the slurry spreading and drying on the substrate. This means that the first organic polymer diffuses from a dot-like shape to a near-ring-like shape, thereby improving the effective abscissa of the scanning spectrum of the center of the acrylate polymer particles. The second organic polymer comprises the first, second, third, fourth, and fifth monomers. The fifth monomer contains unsaturated ester groups. The second organic polymer is prepared by polymerizing the first, second, third, fourth, and fifth monomers. During the coating spreading process, acrylate polymer particles tend to move towards the edge of the ring, thereby reducing the effective abscissa of the scanning spectrum of the center of the acrylate polymer particles and reducing the protrusion height, further reducing adhesion.

[0116] The acrylate polymer particles, which are compounded with a first organic polymer prepared using a first polymerizing monomer, a second polymerizing monomer, a third polymerizing monomer, and a fourth polymerizing monomer, and a second organic polymer prepared using the same first polymerizing monomer, a second polymerizing monomer, a third polymerizing monomer, a fourth polymerizing monomer, and a fifth polymerizing monomer, are used on a separator membrane. The acrylate polymer particles can adhere to the electrode during the cold pressing process and are less likely to cause pore blockage in the separator membrane. This allows the separator membrane to be cold-pressed and bonded to the electrode, and the adhesion between the electrode and the separator membrane is appropriate, thereby improving the cycle performance of the battery.

[0117] In some embodiments of this application, the structure of the first polymeric monomer includes:

[0118] R1 includes hydrogen atoms or alkyl groups with 1-18 carbon atoms, and R2 includes alkyl groups with 1-18 carbon atoms. The first polymerizing monomer includes unsaturated ester groups, which is beneficial to the polymerization of the monomer and can improve the swelling resistance of the polymer. As a flexible monomer segment in the molecular chain, it helps to reduce the hydrophilicity of acrylate polymer particles and facilitates the adjustment of the effective abscissa in the scanning spectrum of the center of acrylate polymer particles within the above range. It can also improve the adhesion of acrylate polymer particles.

[0119] As an example, alkyl groups with 1-18 carbon atoms can be understood as alkyl groups with 1-18 carbon atoms, such as methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), n-hexyl (-CH2CH2CH2CH2CH2CH3), etc.

[0120] In some embodiments of this application, the first polymeric monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. Therefore, by using the first polymeric monomer described above, the effective abscissa of the center scanning spectrum of the acrylate polymer particles in the three-dimensional imaging spectrum can be adjusted to the aforementioned range. When used in a separator, it enables cold-press bonding between the separator and the positive and negative electrodes.

[0121] In some embodiments of this application, the structure of the second polymeric monomer includes:

[0122] R3 includes hydrogen atoms and alkyl groups with 1-18 carbon atoms, either substituted or unsubstituted. Therefore, the inclusion of unsaturated carboxyl groups in the second monomer facilitates monomer polymerization. Using a second monomer containing carboxyl groups during the preparation of the first organic polymer allows the carboxyl groups to bond with functional groups on the electrode and separator materials during the cold-pressing process, thus improving adhesion.

[0123] It should be noted that the substituted alkyl group with 1-18 carbon atoms can be understood as a group in which at least one hydrogen atom on an alkyl group with 1-18 carbon atoms is replaced by another group, such as -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc.

[0124] In some embodiments of this application, the second polymeric monomer includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Therefore, by using the second polymeric monomer described above, the adhesive properties of the first organic polymer can be adjusted.

[0125] In some embodiments of this application, the structure of the third polymeric monomer includes:

[0126] R4 comprises a hydrogen atom or an alkyl group with 1-6 carbon atoms, and R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group with 1-6 carbon atoms, or an alkoxy group with 1-6 carbon atoms. Thus, the third polymerizing monomer includes an unsaturated amide group, which is beneficial for monomer polymerization, and this type of monomer can adjust the molecular weight of the first organic polymer, thereby improving the adhesion of the acrylate polymer particles.

[0127] It should be noted that hydroxyl-substituted alkyl groups with 1-6 carbon atoms can be understood as groups in which at least one hydrogen atom of an alkyl group with 1-6 carbon atoms is replaced by a hydroxyl group, such as -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc. Similarly, hydroxyl-substituted alkoxy groups with 1-6 carbon atoms can be understood as groups in which at least one hydrogen atom of an alkoxy group with 1-6 carbon atoms is replaced by a hydroxyl group, such as methoxy (HOCH2O-), ethoxy (OHCH2CH2O-), propoxy (OHCH2CH2CH2O-), etc.

[0128] In some embodiments of this application, the third polymerizing monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide. Therefore, by using the aforementioned third polymerizing monomer, the molecular weight of the acrylate polymer particles can be adjusted, thereby improving the adhesiveness of the acrylate polymer particles.

[0129] In some embodiments of this application, the structure of the fourth polymeric monomer includes:

[0130] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms. Therefore, the fourth polymerizing monomer includes an unsaturated cyano group, which is beneficial for monomer polymerization and improves the ionic conductivity and adhesiveness of the second organic polymer.

[0131] In some embodiments of this application, the fourth polymerizing monomer includes at least one selected from acrylonitrile, methacrylonitrile, or ethyl acrylonitrile. Therefore, using the aforementioned fourth polymerizing monomer can improve the ionic conductivity and adhesiveness of the acrylate polymer particles.

[0132] In some embodiments of this application, the structure of the fifth polymeric monomer includes:

[0133] R7 and R8 are alkyl groups, and the total number of carbon atoms in R7 and R8 is 2-10, for example, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Therefore, the fifth monomer can increase the glass transition temperature of the second organic polymer while reducing its hydrophilicity, causing the acrylate polymer particles to migrate more quickly to the ring edge during water evaporation, thereby reducing the effective abscissa of the acrylate polymer particle center in the scanning spectrum. In other embodiments of this application, the total number of carbon atoms in R7 and R8 is 5-8.

[0134] In some embodiments of this application, the fifth polymeric monomer includes At least one of the following. In some embodiments of this application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10), for example 1:(0.5-9.5), 1:(1-9), 1:(1.5-8.5), 1:(2-8), 1:(2.5-7.5), 1:(3-7), 1:(3.5-6.5), 1:(4-6), 1:(4.5-5.5), 1:(5-5.5), etc.

[0135] The acrylate polymer particles described in this application are secondary particles formed by the agglomeration of primary particles of a first organic polymer and primary particles of a second organic polymer. Both primary particles of the first and second organic polymers have the opportunity to be exposed on the surface of the secondary particles. By adjusting the mass ratio of the first and second organic polymers, the opportunity for the first organic polymer to be exposed on the surface of the secondary particles is controlled, thereby adjusting the adhesiveness of the acrylate polymer particles. Thus, by setting the mass ratio of the first and second organic polymers within the aforementioned range, at a certain temperature, the acrylate polymer particles can simultaneously possess both a rubbery and a glassy state. The glassy structure is relatively rigid, and when no pressure is applied to the acrylate polymer particles, the glassy structure can act as the skeletal structure of the acrylate polymer particle powder, making the acrylate polymer particles non-sticky and able to meet the requirements of the release film winding and unwinding. The polymer structure, being in a rubber-like state, exhibits a certain degree of "fluidity" under pressure. The rubber-like structure within the acrylate polymer particles allows it to fully penetrate the pores of the positive and negative electrode sheets and the separator, increasing the mechanical interlocking effect and fully utilizing its adhesive properties, thereby improving the battery's cycle performance. Simultaneously, the composition is not too rigid to affect the adhesion between the separator and the electrode sheets. In other embodiments of this application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.5-3).

[0136] In some embodiments of this application, the mass ratio of the first polymeric monomer, the second polymeric monomer, the third polymeric monomer, and the fourth polymeric monomer in the first organic polymer is 1:0.01-0.25:0.01-0.1:0.01-0.2, for example 1:0.02-0.25:0.01-0.1:0.01-0.2, 1:0.05-0.25:0.01-0.1:0.01-0.2, 1:0.1-0.25:0.01-0.1:0.01-0.2, 1:0.15-0.2:0.01-0.1:0.01-0.2, 1:0.17-0.2:0.01-0.1:0.01-0.2, 1:0.01-0.25 : 0.02-0.1: 0.01-0.2, 1: 0.01-0.25: 0.05-0.1: 0.01-0.2, 1: 0.01-0.25: 0.08-0.1: 0.01-0.2, 1: 0.01-0.25: 0.01-0.1: 0.02-0.2, 1: 0.01-0.25: 0.01-0.1 The mixing ratios are as follows: 0.05-0.2, 1:0.01-0.25:0.01-0.1:0.08-0.2, 1:0.01-0.25:0.01-0.1:0.1-0.2, 1:0.01-0.25:0.01-0.1:0.15-0.2, 1:0.01-0.25:0.01-0.1:0.18-0.2, etc. Therefore, by controlling the mixing ratios of the first, second, third, and fourth monomers in the preparation of the first organic polymer to the above-mentioned mixing ratios, this application helps to lower the glass transition temperature of the first organic polymer. Simultaneously, the carboxyl groups contained in the second monomer can form bonding forces with the functional groups on the electrode and separator materials, improving the adhesion between the electrode and the separator.

[0137] In some embodiments of this application, the mass ratio of the first, second, third, fourth, and fifth monomers in the polymerizing monomers of the second organic polymer is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.15, for example 1:0.02-0.25:0.05-0.3:0.01-0.2:0.02-0.15, 1:0.05-0.2:0.05-0.3:0.01-0.2:0.02-0.15, 1 : 0.07-0.2: 0.05-0.3: 0.01-0.2: 0.02-0.15, 1: 0.1-0.2: 0.05-0.3: 0.01-0.2: 0.02-0.15, 1: 0.15-0.2: 0.05-0.3: 0.01-0.2: 0.02-0.15, 1: 0.18-0.2: 0.05-0.3: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.25: 0.01-0.2: 0.02-0.15, 1: 0 .01-0.25: 0.1-0.25: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.15-0.2: 0.01-0.2: 0.02-0.15, 1: 0.17-0.2: 0.1-0.25: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.02-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.05-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.1-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.15-0.18: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.05-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.07-0.13, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.1-0.13, etc. Therefore, by controlling the mixing ratio of the first, second, third, fourth, and fifth polymerizing monomers in the preparation of the second organic polymer to the above-mentioned mixing ratio, this application not only helps to adjust the effective abscissa and ordinate of the center scanning spectrum of the acrylate polymer particles in the three-dimensional imaging spectrum to the above-mentioned range, but also improves the ionic conductivity and adhesion of the second organic polymer.

[0138] It should be noted that the first polymerizing monomer used in preparing the first organic polymer and the first polymerizing monomer used in preparing the second organic polymer may be the same or different. Similarly, the second polymerizing monomer used in preparing the first organic polymer and the second polymerizing monomer used in preparing the second organic polymer may be the same or different. The third polymerizing monomer used in preparing the first organic polymer and the third polymerizing monomer used in preparing the second organic polymer may be the same or different. The fourth polymerizing monomer used in preparing the first organic polymer and the fourth polymerizing monomer used in preparing the second organic polymer may be the same or different. Those skilled in the art can make the selection according to actual needs.

[0139] In some embodiments of this application, the method for preparing the acrylate polymer particles includes:

[0140] Water, emulsifier, initiator, first polymer monomer, second polymer monomer, third polymer monomer and fourth polymer monomer are blended to obtain a first polymer emulsion;

[0141] Water, emulsifier, initiator, first polymer monomer, second polymer monomer, third polymer monomer, fourth polymer monomer and fifth polymer monomer are blended to obtain a second polymer emulsion;

[0142] The first polymer emulsion and the second polymer emulsion are mixed to obtain the acrylate polymer particles.

[0143] The first organic polymer is prepared by emulsion polymerization of a first, second, third, and fourth monomer, and the second organic polymer is prepared by emulsion polymerization of the same monomers. The first and second organic polymers prepared using the above monomers possess suitable first and second glass transition temperatures. Coating these acrylate polymer particles onto a separator ensures that the acrylate polymer particles are non-adhesive at room temperature while maintaining good adhesion between the separator and the positive and negative electrode sheets during cold pressing. This improves the cell's rigidity and addresses issues such as cell opening and soft cells. Furthermore, the application of these acrylate polymer particles coated onto the separator to the battery ensures suitable adhesion between the separator and the positive and negative electrode sheets, thereby improving the battery's cycle performance and kinetic performance.

[0144] This application obtains a first polymer emulsion and a second polymer emulsion through emulsion polymerization, and then obtains the acrylate polymer particles through spray drying. That is, the acrylate polymer particles comprise a first organic polymer and a second organic polymer.

[0145] Emulsion polymerization is a process in which monomers are dispersed in water to form an emulsion using emulsifiers and mechanical stirring, and then an initiator is added to initiate the polymerization of the monomers.

[0146] Emulsifiers are substances that can transform immiscible oils and water into emulsions that are difficult to separate. Emulsifiers are typically surfactants that combine the properties of both hydrophilic polar groups and hydrophobic (lipophilic) nonpolar groups. For example, emulsifiers can be at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, or sodium palmitate.

[0147] An initiator is a substance that can initiate a polymerization reaction of monomers. For example, a free radical initiator refers to a class of compounds that readily decompose into free radicals (i.e., primary free radicals) upon heating, and can be used to initiate free radical polymerization and copolymerization reactions of olefins and dienes. For instance, an initiator can be at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile, dimethyl azobisisobutyrate, benzoyl peroxide, or dioctanoyl peroxide.

[0148] Water, emulsifier, initiator, and the constituent monomers of the polymer are blended and stirred. After the water and emulsifier are dispersed by stirring, an emulsion is formed. That is, the emulsifier forms micelles in the aqueous phase. Most of the micelles contain solubilized monomers. Under heating conditions, the initiator initiates the polymerization of monomers inside the micelles to obtain the emulsion.

[0149] Spray drying uses mechanical action to disperse the material to be dried (a mixture of a first polymer emulsion and a second polymer emulsion) into very fine, mist-like particles (increasing the surface area for water evaporation and accelerating the drying process). These particles then come into contact with hot air, instantly removing most of the moisture and drying the solid matter in the material into powder.

[0150] The acrylate polymer particles, comprising a first organic polymer and a second organic polymer, are obtained by spray drying.

[0151] In some embodiments of this application, the step of mixing and stirring the first polymer emulsion and the second polymer emulsion and then spray drying to obtain a polymer includes: mixing and stirring the first polymer emulsion and the second polymer emulsion to obtain a mixed emulsion, wherein the mass ratio of the first organic polymer to the second organic polymer in the mixed emulsion is in the range of 1:(0.1-10), preferably 1:(0.5-3).

[0152] In some embodiments of this application, the separator coating may further include a second type of organic polymer particles. Specifically, the separator coating comprises acrylate polymer particles and a second type of organic polymer particles. These organic particles include at least one of the following: polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinylidene fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorinated alkenyl monomer units and vinyl monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylic monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylate monomer units, and modified compound particles of the aforementioned homopolymers or copolymers. The organic particles and the acrylate polymer particles form the protrusions on the coating surface. This improves the cycle performance and safety performance of the battery.

[0153] In some embodiments of this application, the mass ratio of the acrylate polymer particles to the second organic polymer particles is (20-90):(0-70), for example, the mass ratio of the acrylate polymer particles to the second organic polymer particles is (20-90):(5-65), (20-90):(10-60), (20-90):(20-50), (20-90):(30-40), (30-80):(0-70), (40-70):(0-70), (50-60):(0-70), (30-80):(5-65), (40-65):(10-55), (45-60):(20-45), (55-60):(30-45). This improves the wettability and distribution uniformity of the electrolyte, enhances the battery's high-temperature storage performance, and improves battery safety and cycle performance. In other embodiments, the mass ratio of the acrylate polymer particles to the second organic polymer particles is (45-90):(0-45). This further improves battery safety and cycle performance.

[0154] In some embodiments of this application, the coating may further include other organic compounds, such as polymers that improve heat resistance, dispersants, wetting agents, and other types of adhesives. All of the aforementioned other organic compounds are non-particulate substances in the coating. This application does not impose any particular limitation on the types of these other organic compounds; any known material with good improving properties can be selected.

[0155] In some embodiments of this application, the volume average particle size Dv50 of the second type of organic polymer particles is 2μm-25μm, for example, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 23μm, 23μm, 24μm, 25μm, etc. In other embodiments of this application, the volume average particle size Dv50 of the second type of organic polymer particles is 5μm-15μm.

[0156] In some embodiments of this application, the volumetric particle size distribution Dv99 of the second type of organic polymer particles is 4μm-50μm, such as 5μm-50μm, 8μm-45μm, 10μm-42μm, 15μm-40μm, 20μm-38μm, 25μm-35μm, 27μm-32μm, 30μm-32μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv99 of the second type of organic polymer particles is 15μm-40μm.

[0157] In this application, a second type of organic polymer particles that meet the above-mentioned particle size distribution are used in combination with the acrylate polymer particles on the separator membrane. This not only reduces the risk of the second type of organic polymer particles and the acrylate polymer particles clogging the pores of the separator membrane, but also improves the problem that the second type of organic polymer particles and the acrylate polymer particles forming a thick coating on the separator membrane would affect the energy density of the battery in the later manufacturing process.

[0158] It should be noted that, in the embodiments of this application, the volume average particle size Dv50 of the second type of organic polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 50%, and the volume particle size distribution Dv99 of the second type of organic polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 99%. The aforementioned volume particle size distribution of the second type of organic polymer particles can be tested using methods known in the art. As an example, the test method is as follows:

[0159] The particle size distribution was determined using laser diffraction, in accordance with GB / T 19077-2016 / ISO 13320:2009. A laser particle size analyzer (Malvin 3000, MasterSizer 3000) was used, with a helium-neon red light source as the main light source. 1g of the sample (refractive index 1.58) was added to a clean small beaker, along with one drop of surfactant and 20ml of deionized water (ensuring a light-blocking degree of 8-12%). The sample was sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer was then turned on, and the optical path system was cleaned before automatically testing the background. The sonicated sample solution was stirred to ensure uniform dispersion, then placed into the sample cell as required, and particle size measurement began. The measurement results can be read from the instrument.

[0160] The second aspect of this application discloses a secondary battery, which includes the separator membrane described in the first aspect of this application.

[0161] A rechargeable battery is a battery that can be recharged after being discharged, allowing the active materials to be activated and the battery to continue to be used.

[0162] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The separator, positioned between the positive and negative electrodes, serves as a barrier. The electrolyte, acting as a conductor of ions, lies between the positive and negative electrodes.

[0163] In a battery, the positive electrode typically includes a positive current collector and a positive active material layer disposed on the positive current collector, wherein the positive active material layer includes a positive active material.

[0164] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0165] In some embodiments of this application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0166] In some embodiments of this application, the positive electrode active material may be a positive electrode active material known in the art for use in batteries.

[0167] As an example, when the positive electrode sheet is used in a lithium-ion battery, the positive electrode active material can be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, 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 transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNiO2). 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) or its modified compounds. Examples of lithium phosphates with an olivine structure may 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 manganese iron phosphate, or lithium manganese iron phosphate and carbon composites.

[0168] As an example, when the positive electrode sheet is used in a sodium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material may include, but is not limited to, at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0169] Examples of the aforementioned layered transition metal oxides include:

[0170] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 Including at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, or Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0171] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 Including at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, or Ba, 0 <z≤0.1;

[0172] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0173] Examples of the aforementioned polyanionic compounds include:

[0174] A 1 f M 3 g (PO4) i O j X 1 3-j A 1 Including at least one of H, Li, Na, K or NH4, M 3 Including at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, or Zn, X 1 It is at least one of F, Cl or Br, 0 <f≤4,0<g≤2,1≤i≤3,0≤j≤2;

[0175] Na n M 4 PO4X2 , where M 4 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, and X 2 is at least one of F, Cl or Br, and 0 < n ≤ 2;

[0176] Na p M 5 q (SO4)3, where M 5 includes at least one of Mn, Fe, Co, Ni, Cu or Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0177] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2 or 3.

[0178] As an example of the above-mentioned Prussian blue analogues, for example, the following can be listed:

[0179] A u M 6 v [M 7 (CN)6] w ·xH2O, where A includes H + , NH4 + , at least one of alkali metal cations or alkaline earth metal cations, M 6 and M 7 each independently includes at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ or Ra 2+ , at least one of them, M 6 and M 7 each independently includes at least cations of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn or W.

[0180] In some embodiments of this application, the positive electrode active material layer 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, or carbon nanofibers.

[0181] 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.

[0182] In some embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the binder in the positive electrode sheet is 1%-3%, for example, 1.2%-2.8%, 1.5%-2.5%, 1.8%-2.2%, 2%-2.2%, etc. This reduces the loss of material from the positive electrode sheet, thereby improving the cycle performance of the battery containing it.

[0183] In a battery, the negative electrode typically includes a negative current collector and a negative active material layer disposed on the negative current collector, wherein the negative active material layer includes a negative active material.

[0184] 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 layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0185] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (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.).

[0186] In some embodiments of this application, the negative electrode active material may be a negative electrode active material 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, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, or 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. These negative electrode active materials may be used alone or in combination of two or more.

[0187] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0188] In some embodiments of this application, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0189] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, and binder, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes.

[0190] In some embodiments of this application, based on the total mass of the negative electrode active material layer, the mass percentage of the binder in the negative electrode sheet is 1%-3%, for example, 1.2%-2.8%, 1.5%-2.5%, 1.8%-2.2%, 2%-2.2%, etc. This reduces the loss of material from the negative electrode sheet, thereby improving the cycle performance of the battery containing it.

[0191] This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0192] In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0193] In some embodiments of this application, when the battery is a lithium-ion battery, the electrolyte salt may include 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, or lithium tetrafluorooxalate phosphate.

[0194] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0195] In some embodiments of this application, the solvent may include at least one selected from 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, or diethyl sulfone.

[0196] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0197] The batteries described in this application may be in the form of individual battery cells, battery modules, or battery packs.

[0198] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0199] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0200] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0201] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 shows a square battery cell 1 as an example.

[0202] In some embodiments, referring to FIG5, the outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0203] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0204] Figure 6 shows a battery module 2 as an example. Referring to Figure 6, in battery module 2, multiple batteries 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other manner. Furthermore, the multiple batteries 1 can be fixed in place using fasteners.

[0205] Optionally, the battery module 2 may also include a housing with a receiving space in which a plurality of batteries 1 are received.

[0206] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0207] Figures 7 and 8 show a battery pack 3 as an example. Referring to Figures 7 and 8, the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0208] In addition, this application also provides an electrical device, which includes the battery provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0209] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0210] Figure 9 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 this device, a battery pack or battery module can be used.

[0211] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0212] 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.

[0213] 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.

[0214] Preparation of the first organic polymer emulsion

[0215] Preparation Example A1

[0216] Weigh out the first monomer methyl acrylate, the second monomer acrylic acid, the third monomer acrylamide, and the fourth monomer acrylonitrile (the mass ratio of the first, second, third, and fourth monomers is 1:0.01:0.1:0.1:0.1), and mix them thoroughly. Add 1000g of the mixture, 30g of sodium dodecyl sulfate emulsifier, 10g of ammonium persulfate initiator, and 1200g of deionized water to a 5000mL four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. Emulsify at high speed for 30 minutes. Under nitrogen protection, heat to 75℃ and react for 4 hours, then cool to below 40℃, adjust the pH to neutral, and filter. The resulting organic polymer emulsion is A1.

[0217] Preparation Examples A2 to A15 were prepared by adjusting the types and mass ratios of substances in Preparation Example A1 to obtain the first organic polymer emulsions A2-A15, as detailed in Table 1.

[0218] Table 1

[0219] Preparation of the second organic polymer emulsion

[0220] Preparation Example B15

[0221] Weigh out the following monomers separately: methyl acrylate (first monomer), acrylic acid (second monomer), acrylamide (third monomer), acrylonitrile (fourth monomer), and monomer 3 (fifth monomer, formula 3) (mass ratio of first monomer, second monomer, third monomer, fourth monomer, and fifth monomer is 1:0.01:0.15:0.1:0.1), and mix them thoroughly. Add 200g of the mixture, 6g of sodium dodecyl sulfate emulsifier, 2g of ammonium persulfate initiator, and 300g of deionized water to a 1000mL four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. Emulsify at high speed for 30 minutes. Under nitrogen protection, heat to 75℃ and react for 4 hours, then cool to below 40℃, adjust the pH to neutral, and filter. This yields the second organic polymer emulsion, B1.

[0222] Preparation Examples B2 to B17, and Preparation Examples B2-B17, were prepared by adjusting the monomer types and mass ratios based on Preparation Example B1 to obtain the second organic polymer emulsions B2-B17, as detailed in Table 2.

[0223] Table 2

[0224] Example 1

[0225] (1) Preparation of acrylate polymer particles

[0226] According to the weight percentage of the first organic polymer and the second organic polymer, the first organic polymer emulsion A3 and the second organic polymer emulsion B1 were weighed in a 1:1 ratio, stirred and mixed evenly, and then the acrylate polymer particles were obtained by spray drying. The conditions of the spray drying process were: inlet air temperature 110℃, outlet air temperature 50℃, and air pressure 0.5kPa.

[0227] (2) Preparation of the separating membrane

[0228] A commercially available PE microporous film (from Zhuogao Electronics Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 80 nm was used as the base film. The acrylate polymer particles prepared as described above and a second organic polymer were mixed evenly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed onto both surfaces of the base film, dried to remove the solvent, and the coating density of the coating composition on the substrate was 1.5 g / m². 2 An isolation membrane is obtained.

[0229] (3) Preparation of positive electrode sheet

[0230] Lithium iron phosphate (LiFePO4), carbon black (Super P), and polyvinylidene fluoride (PVDF) binder were mixed uniformly in an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry was then coated onto aluminum foil used as a positive electrode current collector. The positive electrode sheet was obtained through drying, cold pressing, slitting, and cutting processes. The areal density of the positive electrode was 0.207 mg / mm². 2 The compacted density is 3.5 g / cm³. 3 .

[0231] (4) Preparation of negative electrode sheet

[0232] Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) were mixed evenly in a suitable amount of deionized water at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. This slurry was then coated onto copper foil (negative electrode current collector). The negative electrode sheet was obtained through drying, cold pressing, slitting, and cutting processes. The areal density of the negative electrode was 0.126 mg / mm². 2 The compacted density is 1.7 g / cm³. 3 .

[0233] (5) Preparation of electrolyte

[0234] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. LiPF6 is then dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0235] (6) Preparation of secondary batteries

[0236] The positive electrode, separator, and negative electrode are stacked, wound, and cold-pressed in sequence to obtain a battery cell (during which the separator is bonded to the electrode). The battery cell is placed in an outer package, the electrolyte prepared above is added, and after processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0237] The preparation methods of lithium-ion batteries in Examples 2 to 31 and Comparative Examples 1 to 4 are the same as those in the examples, except that, based on Example 1, the types and mass ratios of the first organic polymer emulsion and the second organic polymer emulsion are adjusted to obtain acrylate polymer particles in Examples 2 to 31 and Comparative Examples 1 to 4, as detailed in Table 3.

[0238] Table 3

[0239] The glass transition temperatures of the first organic polymers A1-A15 and the second organic polymers B1-B17 were characterized. The effective abscissa and ordinate values ​​of the acrylate polymer particles obtained in Examples 1-31 and Comparative Examples 1-4 along their center scan spectra, as well as the cold pressing adhesion between the electrode and the separator in the obtained batteries and the cycle performance of the batteries, were characterized. The characterization results are shown in Table 4.

[0240] Performance testing

[0241] (1) Glass transition temperature test

[0242] Weigh 6 ± 0.05 mg of sample into an Al crucible, level it, and cover it. Test the sample using a Netzsch DSC 3500Sirius measuring instrument. The nitrogen atmosphere was used with a purge gas rate of 50 mL / min and a protective gas rate of 100 mL / min. The heating conditions were as follows: heating rate of 10 °C / min and temperature range of -70 to 200 °C.

[0243] (2) Testing the effective x and y coordinates in the scanning spectrum along the center of acrylate polymer particles

[0244] See the previous text.

[0245] (3) Cold pressing bonding performance test of the release liner

[0246] The testing process is as follows:

[0247] 1. Select a separator membrane with a length of 300 mm and a width of 100 mm, and the above-prepared positive and negative electrode sheets.

[0248] 2. Wrap the release liner with paper on both sides and use a die and a punch to cut it into samples of 54.2mm*72.5mm.

[0249] 3. Neatly stack the cut separator sample with the positive or negative electrode sheet, making sure the separator is facing upwards. Place 130mm*130mm Teflon pads on top and bottom, place the stacked sample in the middle of a cardboard, and cover it with a 150mm*160mm cardboard.

[0250] 4. Place the stacked samples into the flatbed press and adjust the pressure. Set the air pressure to 850Kg±10KG (equivalent to approximately 2.24MPa), set T=25℃, and set the time to 15s for cold pressing.

[0251] 5. Cut the cold-pressed sample into strips of 72.5mm*15mm using a die and a punch.

[0252] 6. Secure one side of the electrode to the steel plate using double-sided tape, and attach the separator to the other side. Use double-sided tape to attach a 15mm wide strip of A4 paper to the separator, completing the test sample preparation. During testing, fix the steel plate holding the electrode in place, and use a tensile testing machine to pull the A4 paper strip upwards, separating the separator from the electrode.

[0253] 7. Turn on the high-speed rail tensile testing machine and set it in sequence as follows: adhesion force test, speed 50mm / min, and initial clamp spacing 40mm.

[0254] 8. Place the test sample between the clamps, fix the end of the steel plate to the lower clamp, and fix the A4 paper to the upper clamp. Clamp the upper and lower clamps with the fixtures respectively.

[0255] 9. Click on the stretching operation interface on the computer desktop, clear the force and displacement to zero, and then click "Start" to pre-stretch about 5mm; after pre-stretching, clear the force and displacement to zero again, start the test, and after the test is completed, export and save the complete data.

[0256] 10. For each group, at least 5 test samples must be measured, and if the adhesion test curves of the 5 test samples show good repeatability, then proceed to the next group of tests. Otherwise, the tests need to be repeated until the repeatability of the 5 test samples is good.

[0257] 11. After the test is completed, plot the bond strength (N / m)-displacement curve and calculate the bond force.

[0258] (4) Battery cycle performance test procedure

[0259] The prepared battery was charged at 60°C with a constant current of 1C to 3.65V, then charged with a constant voltage of 3.65V to a current of 0.05C, left to rest for 5 minutes, and then discharged at 1C to 2.5V. The resulting discharge capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity C of the battery after the nth cycle was recorded. n Then, the battery capacity retention rate P after each cycle n =(C n / C0)×100%. The difference in cycle performance can be reflected by the battery capacity retention rate after 1000 cycles.

[0260] Table 4

[0261] Conclusion: As shown in Table 4, the effective abscissa values ​​of the acrylate polymer particles in Examples 1-31 along the center of the acrylate polymer particles ranged from 5 μm to 150 μm, and the ordinate values ​​ranged from 5 μm to 25 μm; the effective abscissa value of the acrylate polymer particles in Comparative Example 1 along the center of the acrylate polymer particles was 155 μm, and the ordinate value was 3 μm; the effective abscissa value of the acrylate polymer particles in Comparative Example 2 along the center of the acrylate polymer particles was 4 μm, and the ordinate value was 26 μm; the effective abscissa value of the acrylate polymer particles in Comparative Example 3 along the center of the acrylate polymer particles was... The effective abscissa value is 3 μm and the ordinate value is 27 μm; the effective abscissa value of the acrylate polymer particles in Comparative Example 4 along its center scan spectrum is 159 μm and the ordinate value is 2 μm; the cold pressing adhesion between the separator and the negative electrode sheet and the capacity retention rate of the battery in Examples 1-31 are higher than those in Comparative Examples 1-4. This shows that when the acrylate polymer particles of this application that satisfy the effective abscissa and ordinate values ​​in the scan spectrum along their center are used as separators, cold pressing adhesion between the separator and the electrode sheet can be achieved, and the adhesion force is appropriate, thereby improving the cycle performance of the battery.

[0262] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A separating membrane, wherein, include: Substrate; A coating formed on at least one side of the substrate, the coating comprising acrylate polymer particles, wherein the effective abscissa value in the scanning spectrum along the center of the acrylate polymer particles in a three-dimensional imaging spectrum is 5 μm-150 μm.

2. The separator according to claim 1, wherein, In the three-dimensional imaging spectrum, the vertical coordinate of the scanning spectrum along the center of the acrylate polymer particles ranges from 5μm to 25μm.

3. The separator according to claim 1 or 2, wherein, The acrylate polymer particles form protrusions on the coating surface.

4. The separator according to claim 3, wherein, The height of the protrusion on both sides is 2μm-100μm.

5. The separator membrane according to any one of claims 1-4, wherein, The volume average particle size distribution Dv50 of the acrylate polymer particles is 2μm-25μm, and / or The volumetric particle size distribution (Dv99) of the acrylate polymer particles is 4 μm-50 μm.

6. The separator membrane according to any one of claims 1-5, wherein, The acrylate polymer particles comprise a first organic polymer and a second organic polymer. The first organic polymer comprises a first monomer, a second monomer, a third monomer, and a fourth monomer. The second organic polymer comprises a first monomer, a second monomer, a third monomer, a fourth monomer, and a fifth monomer. The structure of the first monomer includes: Wherein, R1 includes a hydrogen atom or an alkyl group with 1-18 carbon atoms, and R2 includes an alkyl group with 1-18 carbon atoms. The structure of the second polymer monomer includes: R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms; The structure of the third polymeric monomer includes: R4 includes a hydrogen atom or an alkyl group with 1-6 carbon atoms, and R5 includes a hydrogen atom, a hydroxyl-substituted alkyl group with 1-6 carbon atoms, or an alkoxy group with 1-6 carbon atoms. The structure of the fourth polymeric monomer includes: R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms; The structure of the fifth polymeric monomer includes: R7 and R8 are alkyl groups, and the total number of carbon atoms in R7 and R8 is 2-10.

7. The separator according to claim 6, wherein, The total number of carbon atoms in R7 and R8 is 5-8.

8. The separator according to claim 6 or 7, wherein, The mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10).

9. The separator membrane according to any one of claims 6-8, wherein, In the first organic polymer monomer, the mass ratio of the first monomer, the second monomer, the third monomer and the fourth monomer is 1:0.01-0.25:0.01-0.1:0.01-0.

2.

10. The separator membrane according to any one of claims 6-9, wherein, In the monomers of the second organic polymer, the mass ratio of the first monomer, the second monomer, the third monomer, the fourth monomer, and the fifth monomer is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.

15.

11. The separator membrane according to any one of claims 6-10, wherein, The first polymerizing monomer includes at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate.

12. The separator membrane according to any one of claims 6-11, wherein, The second polymerizing monomer includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid.

13. The separator membrane according to any one of claims 6-12, wherein, The third polymerizing monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide.

14. The separator membrane according to any one of claims 6-13, wherein, The fourth polymerizing monomer includes at least one of acrylonitrile, methacrylonitrile, or ethyl acrylonitrile.

15. The separator membrane according to any one of claims 6-14, wherein, The fifth polymer monomer includes At least one of them.

16. The separator membrane according to any one of claims 3-15, wherein, The coating further includes a second type of organic polymer particles, which include polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinylidene fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorinated alkenyl monomer units and vinyl monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylic monomer units, copolymer particles of fluorinated alkenyl monomer units and acrylate monomer units, and at least one of the modified compound particles of the above homopolymers or copolymers. The second type of organic polymer particles and the acrylate polymer particles form the protrusions on the surface of the coating.

17. The separator membrane according to claim 16, wherein, The mass ratio of the acrylate polymer particles to the second type of organic polymer particles is (20-90):(0-70).

18. The separator according to claim 16 or 17, wherein, The volume average particle size distribution Dv50 of the second type of organic polymer particles is 2μm-25μm, and / or The volumetric particle size distribution Dv99 of the second type of organic polymer particles is 4μm-50μm.

19. A secondary battery, wherein, The secondary battery includes any one of claims 1-18.

20. An electrical appliance, wherein, Includes the secondary battery as described in claim 19.

Images