Separator and preparation method therefor, battery, and electric device

Abstract

Disclosed in the present application are a separator and a preparation method therefor, a 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 acrylic ester polymer particles, the acrylic polymer ester particles having an AFM adhesive force of 2-3 nN.

Description

Separating membranes and their preparation methods, batteries and electrical devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application No. 202410271123.2, filed on March 8, 2024, the entirety of which is incorporated herein by reference. Technical Field

[0003] This application belongs to the field of batteries, specifically relating to a separator and its preparation method, a 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 around the electrode sheets, and then heated and pressed to bond the electrodes to the separator. Without this hot-pressing process, insufficient adhesion between the separator and the electrode sheets results in inadequate rigidity of the bare cell, potentially causing difficulties in robotic transfer and even leading to folding of the inner separator and contact between the positive and negative electrodes. 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.

[0006] Summary of the Invention

[0007] 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.

[0008] To achieve the above objectives, one aspect of this application provides a separating membrane, the separating membrane comprising:

[0009] Substrate;

[0010] A coating formed on at least one side of the substrate, the coating comprising acrylate polymer particles having an AFM adhesion force of 2nN-3nN.

[0011] This application includes at least the following beneficial effects: the separator of this application can be cold-pressed and bonded to the electrode, and the adhesion between the electrode and the separator is appropriate, which can improve the cell shaping efficiency and at the same time prevent separator clogging, thereby improving the cycle performance of the battery.

[0012] In some embodiments of this application, the AFM Young's modulus of the acrylate polymer particles is 30 MPa-70 MPa, optionally 40 MPa-60 MPa. This results in suitable adhesion between the electrode and the separator.

[0013] In some embodiments of this application, the acrylate polymer particles form protrusions on the coating surface. This results in suitable adhesion between the electrode and the separator.

[0014] In some embodiments of this application, the height of the protrusion on both sides is 2μm-100μm, optionally 10μm-55μm, and more preferably 25μm-35μm. This ensures appropriate adhesion between the electrode and the separator, while effectively mitigating cell safety issues caused by current collector breakage due to excessive corner stress in the wound structure.

[0015] In some embodiments of this application, the volume average particle size Dv50 of the acrylate polymer particles is 2μm-25μm, optionally 5μm-15μm, and / or the particle size distribution Dv90 of the acrylate polymer particles is 4μm-50μm, optionally 15μm-40μm, and / or the particle size distribution Dv99 of the acrylate polymer particles is less than or equal to 50μm, and / or the number particle size distribution Dv10 of the acrylate polymer particles is 1μm-5μm, optionally 1μm-3μm. This reduces the risk of clogging the pores of the separator, improves the permeability of the separator's active ions, reduces the risk of lithium plating at corners, and effectively alleviates the cell safety problem caused by current collector breakage due to excessive corner stress in the wound structure.

[0016] In some embodiments of this application, the acrylate polymer particles comprise a first organic polymer and a second organic polymer. The polymeric components of the first organic polymer include a first substance, a second substance, a third substance, a fourth substance, and a fifth substance. The polymeric components of the second organic polymer include a first substance, a second substance, a third substance, a fourth substance, a fifth substance, and a sixth substance.

[0017] The structure of the first substance includes:

[0018] Wherein, R1 includes a hydrogen atom or an alkyl group of 1-18 carbon atoms, and R2 includes an alkyl group of 1-18 carbon atoms;

[0019] The structure of the second substance includes:

[0020] R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms;

[0021] The structure of the third substance includes:

[0022] 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.

[0023] The structure of the fourth substance includes:

[0024] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms;

[0025] The structure of the fifth substance includes:

[0026] Where n = 3 - 10;

[0027] The structure of the sixth substance includes:

[0028] Where m = 1 - 10.

[0029] Therefore, the AFM adhesion of acrylate polymer particles can be adjusted to the above range, which can achieve cold pressing 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.

[0030] In some embodiments of this application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10), optionally 1:(0.5-3). 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.

[0031] In some embodiments of this application, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, and the fifth substance in the polymeric material of the first organic polymer is 1:0.01-0.25:0.01-0.1:0.01-0.2:0.02-0.15, or optionally 1:0.02-0.25:0.02-0.1:0.02-0.2:0.03-0.1. Therefore, by controlling the mixing ratio of the first, second, third, fourth, and fifth substances in the preparation of the first organic polymer to the above-mentioned mixing ratio, this application can adjust the AFM adhesion of the first organic polymer. Simultaneously, the carboxyl groups contained in the second substance can form a binding force with the functional groups on the electrode and separator materials, improving the adhesion effect between the electrode and the separator.

[0032] In some embodiments of this application, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance in the polymeric material of the second organic polymer is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.15:0.02-0.15, or optionally 1:0.05-0.25:0.1-0.3:0.02-0.2:0.03-0.1:0.03-0.1. Therefore, by controlling the mixing ratio of the first, second, third, fourth, and fifth substances in the preparation of the second organic polymer within the above-mentioned range, this application can adjust the AFM adhesion of the second organic polymer and improve its ionic conductivity and adhesiveness.

[0033] In some embodiments of this application, the first substance 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 above-mentioned first substance, the AFM adhesion of acrylate polymer particles can be adjusted, and the anti-swelling ability of acrylate polymer particles can be improved.

[0034] In some embodiments of this application, the second substance includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Therefore, by using the aforementioned second substance, the AFM adhesion of the acrylate polymer particles can be adjusted. Applying these acrylate polymer particles to the separator can improve the cold-press adhesion between the separator and the electrode, thereby improving the cycle performance of the battery.

[0035] In some embodiments of this application, the third substance includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide. Therefore, by using the aforementioned third substance, the molecular weights of the first and second organic polymers can be adjusted, thereby improving the cold-pressing adhesion between the separator and the electrode, and enhancing the cycle performance of the battery.

[0036] In some embodiments of this application, the fourth substance includes at least one of acrylonitrile or methacrylonitrile. Therefore, by using the aforementioned fourth substance, the adhesion and ionic conductivity of the acrylate polymer particles can be improved. Using these acrylate polymer particles on a separator can improve the cold-pressing adhesion between the separator and the electrode and reduce battery resistance, thereby improving the battery's cycle performance.

[0037] In some embodiments of this application, the fifth substance includes at least one of PEG-200, PEG-300, PEG-400, or PEG-500.

[0038] In some embodiments of this application, the sixth substance includes at least one of malondihydrazide, succinic dihydrazide, adipic dihydrazide, octanoic dihydrazide, azelaic dihydrazide, or sebacate dihydrazide.

[0039] In some embodiments of this application, the acrylate polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is less than or equal to 25°C and the second glass transition temperature is greater than 25°C.

[0040] In some embodiments of this application, the acrylate polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is from -80°C to 25°C and the second glass transition temperature is from 26°C to 100°C.

[0041] In some embodiments of this application, the coating further includes a second type of organic polymer particles, which 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 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.

[0042] In some embodiments of this application, the mass ratio of the acrylate polymer particles to the second type of organic polymer particles is (20-90):(0-70), optionally (45-90):(0-45). This allows for improved safety and cycle performance while reducing battery costs.

[0043] In some embodiments of this application, the volume average particle size Dv50 of the second organic polymer particles is 2μm-25μm, optionally 5μm-15μm, and / or the particle size distribution Dv90 of the second organic polymer particles is 4μm-50μm, optionally 15μm-40μm, and / or the particle size distribution Dv99 of the second organic polymer particles is less than or equal to 50μm, and / or the particle size distribution Dv10 of the second organic polymer particles is 1μm-5μm, optionally 1μm-3μm.

[0044] A second aspect of this application provides a method for preparing a separator membrane, comprising:

[0045] Provide base materials;

[0046] A coating is formed on at least one side of the substrate, the coating comprising acrylate polymer particles having an AFM adhesion force of 2nN-3nN.

[0047] Therefore, the above-mentioned separator can be obtained by using this method. The separator can be cold-pressed and bonded to the electrode, and the adhesion between the electrode and the separator is appropriate, which can improve the cell shaping efficiency and prevent separator clogging, thereby improving the cycle performance of the battery.

[0048] A third aspect of this application discloses a battery comprising the separator described in the first aspect of this application or a separator obtained using the method of the second aspect. Therefore, the battery exhibits excellent cycle performance.

[0049] A fourth aspect of this application discloses an electrical device comprising the battery described in the third aspect of this application. Therefore, this electrical device exhibits excellent cycle performance and safety performance.

[0050] 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

[0051] 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:

[0052] Figure 1 shows the Thermal Tune interface during the AFM adhesion and AFM Young's modulus tests of acrylate polymer particles.

[0053] Figure 2 is a parameter interface diagram during the AFM adhesion force and AFM Young's modulus test of acrylate polymer particles;

[0054] Figure 3 shows the parameter setting interface during the AFM adhesion force and AFM Young's modulus test of acrylate polymer particles.

[0055] Figure 4 shows the force curves during the AFM adhesion force and AFM Young's modulus test of acrylate polymer particles;

[0056] Figure 5 shows the force curves during the AFM adhesion force and AFM Young's modulus tests of acrylate polymer particles.

[0057] Figure 6 shows the fitting curves of the FD curves during the AFM adhesion force and AFM Young's modulus tests of acrylate polymer particles.

[0058] Figure 7 is a SEM image of the separator;

[0059] Figure 8 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.

[0060] Figure 9 is a schematic diagram of a battery according to one embodiment of this application.

[0061] Figure 10 is an exploded view of a battery according to an embodiment of this application, as shown in Figure 9.

[0062] Figure 11 is a schematic diagram of a battery module according to one embodiment of this application.

[0063] Figure 12 is a schematic diagram of a battery pack according to one embodiment of this application.

[0064] Figure 13 is an exploded view of a battery pack according to an embodiment of this application, as shown in Figure 12.

[0065] Figure 14 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.

[0066] Explanation of reference numerals in the attached figures:

[0067] 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Battery module; 3. Battery pack; 31. Upper casing; 32. Lower casing. Detailed Implementation

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0072] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] A tight bond between the separator and the electrode improves battery 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 separators, requiring a hot-pressing process (heating during the pressing process after stacking the separator and electrode) to achieve a tight bond. However, after hot pressing, the adhesion between the separator and the positive and negative electrodes becomes too strong. 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, resulting in electrode demolding and reduced battery cycle performance.

[0077] The coating of the separator in this application includes acrylate polymer particles. The acrylate polymer particles have an AFM adhesion strength of 2nN-3nN. The acrylate polymer particles with this AFM adhesion strength can bond to the electrode during the cold pressing process (without heating during the pressing process after stacking the separator and the electrode), and are less prone to clogging of the separator pores. This allows the separator to be cold-pressed to bond with the electrode, and the adhesion strength between the electrode and the separator is appropriate, thereby improving the cycle performance of the battery.

[0078] The separator disclosed in this application is applicable to batteries, and the battery 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.

[0079] The first aspect of this application discloses a release membrane comprising a substrate and a coating, the coating being formed on at least one side of the substrate, the coating comprising acrylate polymer particles having an AFM adhesion force of 2nN-3nN, such as 2.2nN-2.8nN, 2.4nN-2.6nN, 2.4nN-2.5nN, etc.

[0080] This application uses acrylate polymer particles with an AFM adhesion strength of 2nN-3nN on the coating of the separator. These acrylate polymer particles with AFM adhesion strength can bond to the electrode during the cold pressing process, and are less likely to cause separator pore blockage. This allows the separator to be cold-pressed to bond with the electrode, and the adhesion strength between the electrode and the separator is appropriate, thereby improving the cycle performance of the battery.

[0081] The process by which the aforementioned acrylate polymer particles exert their performance is speculated as follows: If the AFM adhesion of the acrylate polymer particles is too high (greater than 3nN), their cohesive energy increases, and the interparticle force is weak. The particles are prone to spreading out during cold pressing, resulting in an excessively large contact area with the positive and negative electrodes. This may lead to excessive adhesion between the separator and the electrodes, and the separator is prone to clogging, reducing ion transport channels. Conversely, if the AFM adhesion of the acrylate polymer particles is too low (less than 2nN), the polymer is easily dispersed during the high-speed shearing process in the slurry preparation, resulting in smaller particles. The separator surface cannot form protrusions, making the corners of the wound cell more prone to breakage due to stress accumulation, thus deteriorating the cell's safety performance. Furthermore, the reduced height may decrease the gap between the electrodes and the separator, hindering electrolyte wetting of the cell structure, worsening cell cycle performance, and affecting production efficiency. Therefore, this application uses acrylate polymer particles with an AFM adhesion strength of 2nN-3nN on the coating of the separator. These acrylate polymer particles with AFM adhesion strength can bond to the electrode during the cold pressing process and are less likely to cause separator pore blockage. This allows the separator to be cold-pressed to bond with the electrode, and the adhesion strength between the electrode and the separator is appropriate, thereby improving the cycle performance of the battery.

[0082] It should be noted that the AFM adhesion force and AFM Young's modulus of the acrylate polymer particles can be obtained by atomic force microscopy (AFM).

[0083] In some embodiments of this application, the AFM Young's modulus of the acrylate polymer particles is 30 MPa-70 MPa, for example, 35 MPa-65 MPa, 40 MPa-60 MPa, 45 MPa-55 MPa, 45 MPa-50 MPa, etc. Therefore, acrylate polymer particles with an AFM Young's modulus of 30 MPa-70 MPa have moderate hardness. When applied to the separator, the acrylate polymer particles can be appropriately deformed during bare cell shaping, resulting in a suitable contact area between the separator and the positive and negative electrodes. This leads to appropriate adhesion between the separator and the positive and negative electrodes, thereby improving the battery's kinetic and cycle performance. In other embodiments of this application, the AFM Young's modulus of the acrylate polymer particles is 40 MPa-60 MPa.

[0084] As an example, the AFM adhesion force and AFM Young's modulus of the acrylate polymer particles can be obtained by testing them using an atomic force microscope (Bruker Dimension ICON) with a silicon tip on a nitride lever.

[0085] The first step is to obtain the force curve on a hard surface:

[0086] a. Select a hard surface, such as sapphire or silicon, and scan with a probe in Contact mode.

[0087] b. Click the Ramp button. The system will stop scanning and the probe will move to the center of the scanned image. At the same time, the Ramp parameter interface will appear in the software.

[0088] c. Set Ramp parameters: In the parameter interface of the force curve test, there are Trigger Mode options: “Off”, “Absolute”, and “Relative”. Select “Relative”.

[0089] d. Click “Capture” to save the force curve.

[0090] e. Click “Scan” and the system will return to scanning mode.

[0091] The second step is to calculate the deflection sensitivity:

[0092] a. Move the cursor to the coordinates on the left side of the force curve window. Click the left mouse button and move the mouse to get a red dashed line. Repeat this process to get another dashed line. Move both dashed lines to the right-hand diagonal section of the force curve.

[0093] b. Click The software will automatically calculate Deflection Sensitivity. Click OK in the dialog box that appears, and the system will update this parameter and display it in the parameter menu.

[0094] The third step is to calculate the cantilever elastic coefficient k.

[0095] The Sader method is commonly used to calculate k for rectangular cantilever beams. Its formula is:

[0096] As can be seen from this formula, as long as the length L, width w, resonant frequency f0, and quality factor Q of the cantilever beam are known, the elastic coefficient k can be obtained.

[0097] The following describes how to obtain the parameters of a cantilever beam, including its length L, width w, resonant frequency f0, and quality factor Q.

[0098] The testing steps are as follows:

[0099] a. Determine the length L and width w of the cantilever: read them directly from the optical microscope using a standard grating as a scale.

[0100] b. Determine the quality factor Q and natural frequency f0: Open the Thermal Tune interface, select Simple Harmonic Oscillator (Fluid), and set the relevant parameters as shown in Figure 1.

[0101] c. Select “Acquire Data”. After the peak appears, use Ctrl+left click to zoom in on the peak, and then click “Fit Data” to fit the peak.

[0102] d. After the fitting is complete, the software will display the resonance frequency f0 and the quality factor Q.

[0103] e. Calculate the k value: Open the website http: / / www.ampc.ms.unimelb.edu.au / afm / calibration.html#normal, where there is a ready-made calculation program. Enter the obtained length L, width w, resonant frequency f0, and quality factor Q, and click "Calculate" to easily obtain the k value.

[0104] Step 4, force curve test:

[0105] a. As shown in Figure 2, simply change Plot Unit to Force in the parameter interface, and set the relevant parameters as shown in Figure 3.

[0106] b. Interpretation of the force curve:

[0107] The force curve directly measures the relationship between force and scanner extension (FZ curve). However, the force-sample distance relationship (FD curve) obtained after conversion provides a more intuitive reflection of the material's mechanical properties.

[0108] [Corrected according to Rule 91, 11.12.2024] The FZ and FD curves have the same shape before the probe contacts the sample. The difference lies in the fact that after the probe contacts the sample, the extension of the scanner in the Z direction is equivalent to the sum of the bending of the cantilever beam and the deformation of the sample. At this time, the distance D between the probe and the sample is equivalent to the deformation of the sample. The FD curve can intuitively show the relationship between force and sample deformation. In the software, the FD curve is usually displayed as a Force-Separation relationship. The viscosity (adhesion) of the sample can be reflected by the difference between the lowest point of the Retract portion (curve 1) of the force curve (FZ or FD curve) and the baseline, as shown in Figure 4. This lowest point represents the situation where the probe experiences the maximum gravitational force during the process of withdrawing from the sample. After this point, the probe can overcome the gravitational force and the force curve reaches the baseline position.

[0109] From the formula

[0110] It can be seen that integrating the product of the force and velocity of the cantilever beam over time represents the energy dissipation during that time interval. In the force curve, this is represented by the shaded area in Figure 5. Energy dissipation primarily reflects the inelastic deformation of the cantilever beam, and this information is related to the viscoelasticity of the sample.

[0111] [Corrected according to Rule 91, 11.12.2024] The relationship between force and sample deformation in the FD curve can be used to calculate the Young's modulus of the sample's AFM through fitting. For example, curve segment AB in Figure 6 below can be used for fitting calculation of the Young's modulus of the DMT model. The AFM adhesion force is F in Figure 6. adh .

[0112] 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.

[0113] 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.

[0114] 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.

[0115] It should be noted that the isolation membrane can be scanned using a scanning electron microscope (SEM). Referring to Figure 7, the SEM image shows that the acrylate polymer particles form protrusions on the coating surface.

[0116] In 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 10°C. -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.

[0117] 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. In some embodiments of this application, the height of the protrusion on both sides is 25μm-35μm.

[0118] 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 8, 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.

[0119] 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

[0120] 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

[0121] 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;

[0122] Positive electrode rebound rate = (positive electrode thickness before casing - positive electrode thickness after cold pressing) / positive electrode thickness after cold pressing;

[0123] 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.

[0124] 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.

[0125] In some embodiments of this application, the volumetric particle size distribution Dv90 of the acrylate polymer particles is 4μm-50μm, such as 5μm-48μm, 7μm-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 Dv90 of the acrylate polymer particles is 15μm-40μm.

[0126] In some embodiments of this application, the volumetric particle size distribution Dv99 of the acrylate polymer particles is less than or equal to 50 μm, such as 5 μm-50 μm, 8 μm-45 μm, 10 μm-42 μm, 15 μm-40 μm, 20 μm-38 μm, 25 μm-35 μm, 30 μm-32 μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv99 of the acrylate polymer particles is 30 μm-45 μm.

[0127] In some embodiments of this application, the volumetric particle size distribution Dv10 of the acrylate polymer particles is 1μm-5μm, such as 1μm, 2μm, 3μm, 4μm, 5μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv10 of the acrylate polymer particles is 1μm-3μm.

[0128] In this application, acrylate polymer particles with the aforementioned volumetric particle size distribution are used on the separator. This not only mitigates the risk of acrylate polymer particles clogging the separator's pores but also addresses the issue of thick coatings that negatively impact the energy density of the battery. Furthermore, it reduces lithium plating caused by uneven current density distribution at the corners of the wound cell and effectively reduces corner anode breakage and separator puncture due to expansion during later cycling stages. Additionally, it effectively reduces capacity loss such as circular lithium plating caused by corner stress compression due to insufficient corner space. Therefore, using these acrylate polymer particles on the separator improves the pore clogging of the separator, enhances the active ion permeability of the separator, and mitigates the problem of thick polymer coatings that negatively impact the energy density of the battery.

[0129] 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%, the volume particle size distribution Dv90 of the acrylate polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 90%, 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%, and the volume particle size distribution Dv10 of the acrylate polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 10%. The above-mentioned volume particle size distributions of the acrylate polymer particles can be tested using methods known in the art. As an example, the test method is as follows:

[0130] The particle size distribution was determined using laser diffraction, in accordance with standard 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 to be tested 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 after cleaning the optical path system, the background was automatically measured. The sonicated 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.

[0131] In some embodiments of this application, the acrylate polymer particles comprise: a first organic polymer and a second organic polymer, wherein the polymeric components of the first organic polymer include a first substance, a second substance, a third substance, a fourth substance, and a fifth substance, and the polymeric components of the second organic polymer include a first substance, a second substance, a third substance, a fourth substance, a fifth substance, and a sixth substance.

[0132] The structure of the first substance includes:

[0133] 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.

[0134] The structure of the second substance includes:

[0135] R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms;

[0136] The structure of the third substance includes:

[0137] 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.

[0138] The structure of the fourth substance includes:

[0139] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms;

[0140] The structure of the fifth substance includes:

[0141] Where n = 3 - 10;

[0142] The structure of the sixth substance includes:

[0143] Where m = 1 - 10.

[0144] The acrylate polymer particles of this application include a first organic polymer and a second organic polymer. The polymeric components of the first organic polymer include a first substance, a second substance, a third substance, a fourth substance, and a fifth substance. The first substance includes unsaturated ester groups, the second substance includes unsaturated carboxyl groups, the third substance includes unsaturated amide groups, the fourth substance includes unsaturated cyano groups, and the fifth substance includes hydroxyl groups. The first organic polymer is prepared by polymerizing the first substance, the second substance, the third substance, the fourth substance, and the fifth substance. The resulting first organic polymer has high AFM adhesion and low AFM Young's modulus, thereby improving the adhesion between the separator and the electrode. The polymeric material of the second organic polymer includes the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance. The sixth substance includes an acylhydrazine group in its structure. The second organic polymer is prepared by polymerizing the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance. The resulting second organic polymer has a low AFM adhesion force and a high AFM Young's modulus, which can improve the adhesion between acrylate polymer particles and the electrode sheet and ensure that the separator membranes do not interact with each other, thus affecting the coating, storage, and transportation of the separator membranes.

[0145] The first organic polymer prepared using the first, second, third, fourth, and fifth substances has different AFM adhesion strength and AFM Young's modulus compared to the second organic polymer prepared using the first, second, third, fourth, fifth, and sixth substances. The acrylate polymer particles obtained by mixing the first and second organic polymers have suitable AFM adhesion strength and AFM Young's modulus, which facilitates the bonding of the acrylate polymer particles to the electrode during the cold pressing process. At the same time, it is less likely to cause pore blockage of the separator, thus achieving cold pressing bonding between the separator and the electrode. Furthermore, the adhesion strength between the electrode and the separator is suitable, improving the cycle performance of the battery. Meanwhile, the glass transition temperature of the first organic polymer is lower than that of the second organic polymer. When the acrylate polymer particles are at a temperature between the glass transition temperatures of the first and second organic polymers, without applying pressure, the second organic polymer structure is in a glassy state, possessing a large AFM Young's modulus and low AFM adhesion, and can serve as the skeletal structure of the acrylate polymer particle powder, making the acrylate polymer particles non-sticky and able to meet the requirements of separator winding and unwinding. At this temperature, the first organic polymer structure is in a rubbery state, possessing a relatively large AFM adhesion, and can exhibit a certain degree of "flowability" after applying a certain pressure. The structure of the first organic polymer in the acrylate polymer particles can fully penetrate into the pores of the positive and negative electrode plates and the separator, increasing the mechanical interlocking effect, fully utilizing its bonding performance, and thus helping to improve the cycle performance of the battery.

[0146] In some embodiments of this application, the structure of the first substance includes:

[0147] R1 includes hydrogen atoms or alkyl groups of 1-18 carbon atoms, and R2 includes alkyl groups of 1-18 carbon atoms. The first substance includes unsaturated ester groups, which is beneficial to the polymerization of monomers and can improve the swelling resistance of polymers. It can also adjust the AFM adhesion and Young's modulus of the first organic polymer and the second organic polymer to a suitable range.

[0148] 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.

[0149] In some embodiments of this application, the first substance 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 substance described above, the AFM adhesion strength and Young's modulus of the first and second organic polymers can be adjusted to a suitable range, thereby enabling cold-press bonding of the separator to the positive and negative electrode sheets when used in a separator.

[0150] In some embodiments of this application, the structure of the second substance includes:

[0151] 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 substance is beneficial for monomer polymerization. Using a second substance containing carboxyl groups during the preparation of the first and second organic polymers can improve the AFM adhesion and Young's modulus of both polymers. Furthermore, during the cold pressing process for the separator and electrode, the carboxyl groups can form bonding forces with the functional groups on the electrode and separator materials, thus enhancing the adhesion effect.

[0152] 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.

[0153] In some embodiments of this application, the second substance includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Therefore, by using the second substance described above, the AFM adhesion and Young's modulus of the first and second organic polymers can be adjusted, while simultaneously improving the adhesion between the electrode and the separator during cold pressing.

[0154] In some embodiments of this application, the structure of the third substance includes:

[0155] 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 substance includes unsaturated amide groups in its structure, which is beneficial for monomer polymerization. Furthermore, these monomers can adjust the molecular weight of the first and second organic polymers, thereby improving the adhesiveness of the acrylate polymer particles.

[0156] 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.

[0157] In some embodiments of this application, the third substance includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide. Therefore, by using the aforementioned third substance, the molecular weight of the first organic polymer and the second organic polymer can be adjusted, thereby improving the adhesiveness of the acrylate polymer particles.

[0158] In some embodiments of this application, the structure of the fourth substance includes:

[0159] R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms. Therefore, the fourth substance includes an unsaturated cyano group in its structure, which is beneficial for monomer polymerization and can improve the ionic conductivity and adhesiveness of the first and second organic polymers.

[0160] In some embodiments of this application, the fourth substance includes at least one of acrylonitrile, methacrylonitrile, or ethyl acrylonitrile. Therefore, by using the aforementioned fourth substance, the ionic conductivity and adhesiveness of the acrylate polymer particles can be improved.

[0161] In some embodiments of this application, the structure of the fifth substance includes:

[0162] Where n = 3-10. Therefore, the fifth substance with this composition can improve the hydrophilicity of the first and second organic polymers while adjusting their adhesion to AFM, enhance the stability of the coating slurry, and also improve the wettability of the coating slurry to the substrate, thus reducing powdering.

[0163] In some embodiments of this application, the fifth substance includes at least one of PEG-200, PEG-300, PEG-400, or PEG-500.

[0164] It should be noted that the number after PEG represents its average molecular weight. For example, PEG-200 means polyethylene glycol with an average molecular weight of 200.

[0165] The structure of the sixth substance includes:

[0166] Where m = 1-10. Therefore, by adding the sixth substance of this composition during the polymerization process of the second organic polymer, the AFM Young's modulus of the second organic polymer can be increased, thereby enhancing the cohesiveness and adhesion of the acrylate polymer particles, and simultaneously improving their wetting of the base film.

[0167] In some embodiments of this application, the sixth substance includes at least one of malondihydrazide, succinic dihydrazide, adipic dihydrazide, octanoic dihydrazide, azelaic dihydrazide, or sebacate dihydrazide.

[0168] 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.

[0169] In this application, because the first organic polymer and the second organic polymer have different AFM adhesive forces and AFM Young's moduli, the mass ratio of the first organic polymer to the second organic polymer is set within the aforementioned range. The resulting acrylate polymer particles possess suitable AFM adhesive forces and AFM Young's moduli, which facilitates adhesion between the acrylate polymer particles and the electrode during cold pressing. Simultaneously, it reduces the likelihood of separator pore blockage, achieving cold pressing adhesion between the separator and the electrode. Furthermore, the adhesion between the electrode and the separator is appropriate, improving the battery's cycle performance. Simultaneously, the glass transition temperature of the first organic polymer is lower than that of the second organic polymer. When the acrylate polymer particles are at a temperature between the glass transition temperatures of the first and second organic polymers, without applying pressure, the second organic polymer structure is in a glassy state, possessing a larger AFM Young's modulus and lower AFM adhesive forces. This allows it to serve as the skeletal structure of the acrylate polymer particle powder, making the acrylate polymer particles non-adhesive and satisfying the requirements for separator winding and unwinding. At this temperature, the first organic polymer structure is in a rubbery state, possessing a relatively large AFM adhesion force. Under certain pressure, it exhibits a certain degree of "flowability." The structure of the first organic polymer within the acrylate polymer particles can fully penetrate the pores of the positive and negative electrode sheets and the separator, increasing the mechanical interlocking effect and fully utilizing its bonding performance, thereby contributing to improved battery cycle performance. In other embodiments of this application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.5-3).

[0170] In this application, it should be noted that since acrylate polymer particles are composed of a stack of first and second organic polymer particles, and only one particle can be detected at a time during AFM adhesion and AFM Young's modulus testing—that is, either the first or second organic polymer particle—it is stipulated that when the ratio of the first to the second organic polymer particles is a:b (if a and b are integers, then a first organic polymer particles and b second organic polymer particles are taken respectively; if a and b are not integers, they are converted to integers, for example, a:b = 1:0.5, then it is converted to a:b = 2:1, that is, two first organic polymer particles and one second organic polymer particle are taken, and the Dv50 difference between each first and second organic polymer particle does not exceed 5nm), then a first organic polymer particles and b second organic polymer particles are taken, and the AFM adhesion of a first organic polymer particles is measured sequentially, denoted as A1, ... A. a-1 A aThe AFM adhesion forces of b second organic polymer particles were measured sequentially and denoted as B1, ... B. b-1 B b A a B represents the AFM adhesion force of the a-th first organic polymer particle. b This represents the AFM adhesion force of the b-th second organic polymer particle; then according to (If a ≥ 3, b ≥ 3; if a = 1, b = 1, then calculate the AFM adhesive force of the acrylate polymer particles according to (A1 + B1) / 2; similarly, if a = 1, b = 2, then calculate the AFM adhesive force of the acrylate polymer particles according to (A1 + B1 + B2) / 3); simultaneously measure the AFM Young's modulus of a first organic polymer particles in sequence, and record them as C1, ... C a-1 C a And the AFM Young's modulus of b second organic polymer particles were measured sequentially, denoted as D1, ... D b-1 D b C a D represents the AFM Young's modulus of the a-th first organic polymer particle. b This represents the AFM Young's modulus of the b-th second organic polymer particle; then according to (a≥3, b≥3; if a=1, b=1, then the AFM Young's modulus of the acrylate polymer particles is calculated according to (C1+D1) / 2; similarly, if a=1, b=2, then the AFM Young's modulus of the acrylate polymer particles is calculated according to (C1+D1+D2) / 3). In some embodiments of this application, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, and the fifth substance in the polymeric mass of the first organic polymer is 1:0.01-0.25:0.01-0.1:0.01-0.2:0.02-0.15, for example 1:0.02-0.25:0.01-0.1:0.01-0.2:0.02-0.15, 1:0.05-0.2:0.01-0.1:0.01-0.2:0.02-0.1 5, 1: 0.1-0.15: 0.01-0.1: 0.01-0.2: 0.02-0.15, 1: 0.1-0.12: 0.01-0.1: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.03-0.1: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.05-0.1: 0.01-0.2: 0.02-0.15, 1: 0.01-0.25: 0.08-0.1: 0.01- 0.2: 0.02-0.15, 1: 0.01-0.25: 0.01-0.1: 0.03-0.2: 0.02-0.15, 1: 0.01-0.25: 0.01-0.1: 0.05-0.2: 0.02-0.15, 1: 0.01-0.25: 0.01-0.1: 0.08-0.2: 0.02-0.15, 1: 0.01-0.25: 0.01-0.1: 0.1-0.2: 0.02-0.15, 1: 0.01-0.25: 0 .01-0.1: 0.15-0.2: 0.02-0.15, 1: 0.01-0.25: 0.01-0.1: 0.01-0.2: 0.05-0.15, 1: 0.01-0.25: 0.01-0.1: 0.01-0.2: 0.08-0.15, 1: 0.01-0.25: 0.01-0.1: 0.01-0.2: 0.1-0.15, 1: 0.01-0.25: 0.01-0.1: 0.01-0.2: 0.12-0.15, etc.Therefore, by controlling the first, second, third, fourth, and fifth substances in the preparation of the first organic polymer at the above-mentioned mixing ratio, the resulting first organic polymer has a high AFM adhesion force and a low AFM Young's modulus, thereby improving the bonding effect between the separator and the electrode. At the same time, the first organic polymer has a low glass transition temperature. When the acrylate polymer particles are at a temperature higher than the glass transition temperature of the first organic polymer, the structure of the first organic polymer is in a rubber state. When a certain pressure is applied to the acrylate polymer particles containing the first organic polymer, they can have a certain "fluidity". The structure of the acrylate polymer particles including the first organic polymer can fully penetrate into the pores of the positive and negative electrode sheets and the separator, increasing the mechanical interlocking effect and fully exerting its bonding performance, thereby helping to improve the cycle performance of the battery.

[0171] In some other embodiments of this application, the mass ratio of the first substance, the second substance, the third substance, the fourth substance and the fifth substance in the polymeric mass of the first organic polymer is 1:0.02-0.25:0.02-0.1:0.02-0.2:0.03-0.1.

[0172] In some embodiments of this application, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance in the polymeric material of the second organic polymer is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.15:0.02-0.15, for example 1:0.05-0.2:0.05-0.3:0.01-0.2:0.02-0.15:0.02-0.15, 1:0.08-0.18:0.05-0. .3: 0.01-0.2: 0.02-0.15: 0.02-0.15, 1: 0.1-0.15: 0.05-0.3: 0.01-0.2: 0.02-0.15: 0.02-0.15, 1: 0.01-0.25: 0.1-0.25: 0.01-0.25: 0.02-0.15: 0.02-0.15, 1: 0.01-0.25: 0.15-0.2: 0.01-0.25: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.05-0.2: 0.02-0.15: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.08-0.15: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.1-0.15: 0.02-0.15: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.05-0.12: 0.02-0.15, 1: 0.0 1-0.25: 0.05-0.3: 0.01-0.2: 0.08-0.1: 0.02-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.02-0.15: 0.05-0.15, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.02-0.15: 0.08-0.12, 1: 0.01-0.25: 0.05-0.3: 0.01-0.2: 0.02-0.15: 0.1-0.12, etc.

[0173] This application controls the mixing ratio of the first, second, third, fourth, fifth, and sixth substances in the preparation of the second organic polymer to the above-mentioned mixing ratio. The resulting second organic polymer has a high AFM Young's modulus and a low AFM adhesion force. The acrylate polymer particles obtained by mixing the first and second organic polymers have suitable AFM adhesion force and AFM Young's modulus, which is beneficial for the acrylate polymer particles to bond to the electrode during the cold pressing process. At the same time, it is not easy for the separator to become clogged, thus realizing the cold pressing bonding between the separator and the electrode. Furthermore, the adhesion force between the electrode and the separator is suitable, improving the cycle performance of the battery. Meanwhile, the second organic polymer has a higher glass transition temperature (its glass transition temperature is higher than that of the first organic polymer). When the acrylate polymer particles are at a temperature between the glass transition temperatures of the first and second organic polymers, without applying pressure to the acrylate polymer particles, the second organic polymer structure is in a glassy state, possessing a large AFM Young's modulus and low AFM adhesion. It can serve as the skeletal structure of the acrylate polymer particle powder, making the acrylate polymer particles non-sticky and capable of satisfying the winding and unwinding of the release film. In other embodiments of this application, the mass ratio of the first, second, third, fourth, fifth, and sixth substances in the polymeric composition of the second organic polymer is 1:0.05-0.25:0.1-0.3:0.02-0.2:0.03-0.1:0.03-0.1.

[0174] In some embodiments of this application, the acrylate polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is less than or equal to 25°C, and the second glass transition temperature is greater than 25°C. Specifically, the first organic polymer of this application corresponds to the first glass transition temperature, and the second organic polymer corresponds to the second glass transition temperature.

[0175] The glass transition temperature (Tg) is the temperature at which a polymer transitions from a rubbery state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the amorphous portion of crystalline polymers) from a glassy state to a rubbery state, or vice versa. It is the lowest temperature at which the macromolecular chains of an amorphous polymer can move freely, and is usually represented by Tg. Above the glass transition temperature, the polymer exhibits elasticity; below the glass transition temperature, the polymer exhibits brittleness. The glass transition temperature can be measured using methods commonly used in the art, such as differential scanning calorimetry as described in GB / T 19466.2.

[0176] It is understood that if the first glass transition temperature is less than or equal to 25°C, and above the first glass transition temperature, the structure of the first organic polymer in the acrylate polymer particles is in a rubber state; if the second glass transition temperature is greater than 25°C, and below the second glass transition temperature, the structure of the second organic polymer in the acrylate polymer particles is in a glass state.

[0177] For example, if the first glass transition temperature is lower than room temperature and the second glass transition temperature is higher than room temperature, at room temperature, without applying pressure to the separator, and the second glass transition temperature is higher than room temperature, the structure of the second organic polymer in the acrylate polymer particles on the separator is in a glassy state, which is relatively hard and can serve as the skeleton structure of the acrylate polymer particle powder, making the acrylate polymer particles non-sticky. At room temperature, if the first glass transition temperature is lower than room temperature, the structure of the first organic polymer in the acrylate polymer particles is in a rubbery state, which can have a certain "flowability" after applying a certain pressure. The structure of the first organic polymer in the acrylate polymer particles can fully penetrate into the pores of the positive and negative electrode plates and the separator, increasing the mechanical interlocking effect, which can fully exert its bonding performance, thereby helping to improve the cycle performance of the battery.

[0178] It is understandable that when the temperature is above the first glass transition temperature, the structure of the acrylate polymer particles, including the first organic polymer, is in a soft state and can be deformed by extrusion pressure. The structure of the separator and the electrode has pores. As the extrusion pressure is applied to the acrylate polymer particles, part of the structure of the first organic polymer can penetrate into the pores of the separator and the electrode, bonding the separator and the electrode together, achieving a mechanical interlocking effect and realizing the bonding function.

[0179] Because the glass transition temperatures of the first and second organic polymers in the acrylate polymer particles differ significantly, when cold-pressed at a temperature between the first and second glass transition temperatures, the structure of the first organic polymer in the acrylate polymer particles is in a rubbery state, while the structure of the second organic polymer in the acrylate polymer particles is in a glassy state, giving the acrylate polymer particles a "soft yet hard" characteristic. When coated onto a separator, at a temperature between the first and second glass transition temperatures and without applied pressure, the acrylate polymer particles are non-adhesive, satisfying the requirements for winding and unwinding the separator. When a certain pressure is applied, the acrylate polymer particles exhibit pressure sensitivity and good adhesion, meeting the adhesion strength requirements between the separator and the positive and negative electrode sheets.

[0180] Therefore, the acrylate polymer particles used in the separator of this application are non-adhesive at temperatures between the first and second glass transition temperatures during separator coating, facilitating separator winding and unwinding. However, after being wound with the positive and negative electrode sheets and subjected to a cold pressing process, the acrylate polymer particles exhibit superior adhesion, ensuring a tight bond between the positive and negative electrode sheets and the separator. Thus, using these acrylate polymer particles on the separator can improve the cold pressing adhesion between the separator and the positive and negative electrode sheets, thereby enhancing the cell's rigidity and battery cycle performance.

[0181] In some embodiments of this application, the first glass transition temperature can be any value such as -100℃, -90℃, -80℃, -70℃, -50℃, -30℃, -10℃, 10℃, 20℃, 24℃, 25℃, etc., or a range between any two of the above values, without any specific limitation.

[0182] In some embodiments of this application, the second glass transition temperature can be any value such as 26°C, 30°C, 50°C, 80°C, 100°C, 200°C, or any range between any two of the above values, without any specific limitation.

[0183] In some embodiments of this application, the first glass transition temperature ranges from -80°C to 25°C. In some embodiments of this application, the first glass transition temperature ranges from -60°C to 25°C.

[0184] Within the aforementioned range, the acrylate polymer particles, including those with a first glass transition temperature, are in a rubbery state above the first glass transition temperature. This is beneficial for their adhesive properties during cold pressing, and also improves the adhesion between the separator and the electrode after cold pressing, thereby enhancing battery performance.

[0185] The values ​​in the range of -80℃ to 25℃ include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 25℃, etc., as well as the range values ​​between any two of the above point values.

[0186] The values ​​in the range of -60℃ to 25℃ include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and -60℃, -50℃, -40℃, -30℃, -20℃, -10℃, 0℃, 10℃, 20℃, 25℃, etc., as well as the range values ​​between any two of the above point values.

[0187] In some embodiments of this application, the second glass transition temperature ranges from 26°C to 100°C. In some embodiments of this application, the second glass transition temperature ranges from 26°C to 90°C.

[0188] Within the aforementioned range, the structure in the acrylate polymer particles that includes a second glass transition temperature is in a glassy state below the second glass transition temperature. This is beneficial for serving as the skeletal structure of the acrylate polymer particles at temperatures between the first and second glass transition temperatures, making the acrylate polymer particles non-sticky and facilitating the winding and unwinding steps of the release film at a certain temperature.

[0189] The values ​​in the range of 26℃ to 100℃ include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 26℃, 28℃, 30℃, 50℃, 80℃, 90℃, 100℃, etc., and the range values ​​between any two of the above point values.

[0190] The values ​​in the range of 26°C to 90°C include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, etc., and the range values ​​between any two of the above point values.

[0191] It should be noted that the first substance used in the polymeric material for preparing the first organic polymer in this application may be the same as or different from the first substance used in the polymeric material for preparing the second organic polymer. Similarly, the second, third, fourth, and fifth substances used in the polymeric material for preparing the first organic polymer may be the same as or different from the second, third, fourth, and fifth substances used in the polymeric material for preparing the second organic polymer. Those skilled in the art can make selections according to actual needs.

[0192] In some embodiments of this application, the method for preparing the acrylate polymer particles includes:

[0193] Water, emulsifier, initiator, first substance, second substance, third substance, fourth substance and fifth substance are blended to obtain the first polymer emulsion;

[0194] Water, emulsifier, initiator, first substance, second substance, third substance, fourth substance, fifth substance and sixth substance are blended to obtain a second polymer emulsion;

[0195] The first polymer emulsion and the second polymer emulsion are mixed to obtain the acrylate polymer particles.

[0196] The first organic polymer is prepared by emulsion polymerization of the first, second, third, fourth, and fifth substances, and the second organic polymer is prepared by emulsion polymerization of the first, second, third, fourth, fifth, and sixth substances.

[0197] This application obtains a first polymer emulsion and a second polymer emulsion through emulsion polymerization, and then obtains the acrylate polymer particles by spray drying. That is, the acrylate polymer particles comprise a first organic polymer and a second organic polymer.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] Acrylic polymer particles consisting of a first organic polymer and a second organic polymer are obtained through a spray drying process.

[0204] In some embodiments of this application, the step of mixing and stirring the first polymer emulsion and the second polymer emulsion, followed by 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 ranges from 1:(0.1-10). In some embodiments, the mass ratio of the first organic polymer to the second organic polymer in the mixed emulsion ranges from 1:(0.5-3).

[0205] 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.

[0206] 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.

[0207] 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.

[0208] In some embodiments of this application, the volumetric particle size distribution 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 volumetric particle size distribution Dv50 of the second type of organic polymer particles is 5μm-15μm.

[0209] In some embodiments of this application, the volumetric particle size distribution Dv90 of the second type of organic polymer particles is 4μm-50μm, such as 5μm-48μm, 7μm-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 Dv90 of the second type of organic polymer particles is 15μm-40μm.

[0210] In some embodiments of this application, the volumetric particle size distribution Dv99 of the second type of organic polymer particles is less than or equal to 50 μm, such as 5 μm-50 μm, 8 μm-45 μm, 10 μm-42 μm, 15 μm-40 μm, 20 μm-38 μm, 25 μm-35 μm, 30 μm-32 μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv99 of the second type of organic polymer particles is 30 μm-45 μm.

[0211] In some embodiments of this application, the volumetric particle size distribution Dv10 of the second type of organic polymer particles is 1μm-5μm, such as 1μm, 2μm, 3μm, 4μm, 5μm, etc. In other embodiments of this application, the volumetric particle size distribution Dv10 of the second type of organic polymer particles is 1μm-3μm.

[0212] 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.

[0213] 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%; the volume particle size distribution Dv90 of the second type of organic polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 90%; 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%; and the volume particle size distribution Dv10 of the second type of organic polymer particles is the particle size corresponding to a cumulative particle size volume distribution percentage of 10%. The above-mentioned volume particle size distributions 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:

[0214] The particle size distribution was determined using laser diffraction, in accordance with standard 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 to be tested 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 after cleaning the optical path system, the background was automatically measured. The sonicated 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.

[0215] A second aspect of this application also provides a method for preparing a separating membrane, comprising the following steps:

[0216] (1) Provide the substrate;

[0217] (2) A coating comprising acrylate polymer particles is formed on at least one side of the substrate, wherein the acrylate polymer particles have an AFM adhesion force of 2nN-3nN.

[0218] Specifically, the substrate and acrylate polymer particles are the same as described above, and will not be repeated here.

[0219] In some embodiments of this application, the separator includes a substrate and a coating, the coating being disposed on only one surface of the substrate.

[0220] In some embodiments of this application, the separator includes a substrate and a coating, the coating being disposed on both surfaces of the substrate.

[0221] In some embodiments of this application, step (2) may be performed by the following steps: (2-1) providing a coating slurry, the coating slurry comprising acrylate polymer particles and an organic solvent; (2-2) applying the coating slurry to at least one side of a substrate and drying it to obtain a release film.

[0222] In some embodiments of this application, in step (2-1), the solvent in the coating slurry can be water, such as deionized water.

[0223] In some embodiments of this application, in step (2-1), the coating slurry may further include other organic compounds, such as polymers that improve heat resistance, dispersants, wetting agents, and emulsion-like binders. These other organic compounds are non-particulate in the dried coating.

[0224] In some embodiments of this application, in step (2-1), the coating slurry may further include a second type of organic polymer particles, which together with the acrylate polymer particles form the protrusions on the coating surface. The second type of organic polymer particles includes 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.

[0225] In some embodiments of this application, in step (2-2), the coating is performed using a coating machine.

[0226] In this embodiment of the application, there are no special restrictions on the model of the coating machine, and commercially available coating machines can be used.

[0227] In some embodiments of this application, in step (2-2), the coating may be applied using processes such as transfer coating, spin coating, or dip coating; for example, the coating may be applied using transfer coating.

[0228] In some embodiments of this application, the coating machine includes a gravure roller for transferring coating slurry onto a substrate.

[0229] By controlling the above process parameters within the given range, the performance of the separator membrane of this application can be further improved. Those skilled in the art can selectively adjust one or more of the above process parameters according to actual production conditions.

[0230] A third aspect of this application provides a battery comprising the separator described in the first aspect or a separator obtained by the method described in the second aspect.

[0231] A battery is a device that can be recharged after being discharged, allowing its active materials to be reactivated and continue to be used.

[0232] 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, located between the positive and negative electrodes, conducts ions.

[0233] 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.

[0234] 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.

[0235] In some embodiments of this application, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer 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.).

[0236] 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.

[0237] As an example, when the positive electrode sheet is used in a lithium-ion battery, the positive electrode active material can be a known positive electrode active material 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.

[0238] 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.

[0239] Examples of the aforementioned layered transition metal oxides include:

[0240] 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;

[0241] 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;

[0242] 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。

[0243] Examples of the aforementioned polyanionic compounds include:

[0244] 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;

[0245] 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;

[0246] 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;

[0247] 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.

[0248] As an example of the above Prussian blue analogues, for example, the following can be listed:

[0249] 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 include 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 include at least cations of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn or W.

[0250] 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.

[0251] In some embodiments of this application, 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 after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] 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.).

[0256] 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.

[0257] 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.

[0258] 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)).

[0259] 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.

[0260] 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.

[0261] 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.

[0262] In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0263] 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.

[0264] 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.

[0265] 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.

[0266] 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.

[0267] The batteries described in this application may be in the form of individual battery cells, battery modules, or battery packs.

[0268] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0269] 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.

[0270] 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.

[0271] 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 9 shows a square battery cell 1 as an example.

[0272] In some embodiments, referring to FIG10, 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.

[0273] 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.

[0274] Figure 11 shows a battery module 2 as an example. Referring to Figure 11, 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 arbitrary way. Furthermore, the multiple batteries 1 can be fixed in place by fasteners.

[0275] Optionally, the battery module 2 may also include a housing with a receiving space in which a plurality of batteries 1 are received.

[0276] 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.

[0277] Figures 12 and 13 show an example battery pack 3. Referring to Figures 12 and 13, 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.

[0278] 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.

[0279] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0280] Figure 14 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.

[0281] 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.

[0282] 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.

[0283] Preparation of the first organic polymer emulsion

[0284] Preparation Example A1

[0285] Weigh out the following components separately: methyl acrylate (substance 1), acrylic acid (substance 2), acrylamide (substance 3), acrylonitrile (substance 4), and PEG-400 (substance 5) in a mass ratio of 1:0.1:0.03:0.05:0.05. 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. Obtain the first organic polymer emulsion A1.

[0286] Preparation Examples A2 to A21, and Preparation Examples A2-A21, were prepared by adjusting the types and mass ratios of substances based on Preparation Example A1 to obtain the first organic polymer emulsions A2-A21, as detailed in Table 1.

[0287] Table 1

[0288] Preparation of the first organic polymer emulsion

[0289] Preparation Example B1

[0290] Weigh out the following components separately: methyl acrylate (substance 1), acrylic acid (substance 2), acrylamide (substance 3), acrylonitrile (substance 4), PEG-400 (substance 5), and adipic acid dihydrazide (substance 6) (mass ratio of 1:0.1:0.25:0.1:0.05:0.05), and mix 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.

[0291] Preparation Examples B2 to B21, and Preparation Examples B2-B21, were prepared by adjusting the monomer types and mass ratios based on Preparation Example B1 to obtain the second organic polymer emulsions B2-B21, as detailed in Table 2.

[0292] Table 2

[0293] Example 1

[0294] (1) Preparation of acrylate polymer particles

[0295] According to the weight percentage of the first organic polymer and the second organic polymer, the first organic polymer emulsion A1 and the second organic polymer emulsion B2 are weighed in a 1:1 ratio, stirred and mixed evenly, and then spray-dried to obtain acrylate polymer particles. The spray-drying conditions are: inlet air temperature 110℃, outlet air temperature 50℃, and air pressure 0.5kPa.

[0296] (2) Preparation of the separating membrane

[0297] A commercially available PE microporous film (7 μm thick, 80 nm average pore size from Zhuogao Electronics Technology Co., Ltd.) 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 (20% solid content). The slurry was sprayed onto both surfaces of the base film, dried to remove the solvent, and the coating density of the composition on the substrate was 1.5 g / m². 2 An isolation membrane is obtained.

[0298] (3) Preparation of positive electrode sheet

[0299] 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 .

[0300] (4) Preparation of negative electrode sheet

[0301] 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 .

[0302] (5) Preparation of electrolyte

[0303] 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.

[0304] (6) Preparation of secondary batteries

[0305] 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.

[0306] The preparation methods of the lithium-ion batteries in Examples 2 to 45 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 the polymers of Examples 2 to 45 and Comparative Examples 1 to 4, as detailed in Table 3.

[0307] Table 3

[0308] The glass transition temperatures of the first organic polymers A1-A21 and the second organic polymers B1-B21 were characterized. The AFM adhesion force and AFM Young's modulus of the acrylate polymer particles obtained in Examples 1-45 and Comparative Examples 1-4 were also characterized, as well as the cold-pressing adhesion force between the electrode and the separator in the obtained batteries and the cycle performance of the batteries. The characterization results are shown in Table 4.

[0309] Performance testing

[0310] (1) Glass transition temperature test

[0311] 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.

[0312] (2) AFM adhesion and AFM Young's modulus tests of acrylate polymer particles

[0313] See the previous text.

[0314] (3) Cold pressing bonding performance test of the release liner

[0315] The testing process is as follows:

[0316] 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.

[0317] 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.

[0318] 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.

[0319] 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.

[0320] 5. Cut the cold-pressed sample into strips of 72.5mm*15mm using a die and a punch.

[0321] 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.

[0322] 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.

[0323] 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.

[0324] 9. Click on the stretching operation interface on the computer desktop, clear the force and displacement to zero, and then click "Start" to perform a pre-stretch of about 5mm; after the pre-stretch, clear the force and displacement to zero again, start the test, and after the test is completed, export and save the complete data.

[0325] 10. For each group, at least 5 test samples must be measured, and the repeatability of the adhesion test curves for the 5 test samples must be good before proceeding to the next group of tests. Otherwise, the tests need to be repeated until the repeatability of the 5 test samples is good.

[0326] 11. After the test is completed, plot the bond strength (N / m)-displacement curve and calculate the bond force.

[0327] (4) Battery cycle performance test procedure

[0328] 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.

[0329] Table 4

[0330] Conclusion: As shown in Table 4, the AFM adhesion of the acrylate polymer particles in Examples 1-45 is 2nN-3nN, while that in Comparative Example 1 is 1.8nN, 1.3nN, 3.5nN, and 0.9nN. The cold-pressing adhesion between the separator and the negative electrode sheet in Examples 1-45 and the capacity retention rate of the battery are both higher than those in Comparative Examples 1-4. This indicates that when the acrylate polymer particles with an AFM adhesion of 2nN-3nN of this application are used as separators, cold-pressing adhesion between the separator and the electrode sheet can be achieved, and the adhesion force is suitable, thereby improving the cycle performance of the battery.

[0331] 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. An isolation film, wherein, include: Substrate; A coating formed on at least one side of the substrate, the coating comprising acrylate polymer particles having an AFM adhesion force of 2nN-3nN.

2. The separator film according to claim 1, wherein The AFM Young's modulus of the acrylate polymer particles is 30 MPa-70 MPa.

3. The separator film according to claim 1 or 2, wherein The AFM Young's modulus of the acrylate polymer particles is 40 MPa-60 MPa.

4. The separator film according to any one of claims 1 to 3, wherein The acrylate polymer particles form protrusions on the coating surface.

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

6. The separator film according to any one of claims 1 to 5, wherein The volume average particle size Dv50 of the acrylate polymer particles is 2μm-25μm, and / or The acrylate polymer particles have a volumetric particle size distribution Dv90 of 4 μm-50 μm, and / or The volumetric particle size distribution Dv99 of the acrylate polymer particles is less than or equal to 50 μm, and / or The volumetric particle size distribution Dv10 of the acrylate polymer particles is 1μm-5μm.

7. The separator film according to any one of claims 1 to 6, wherein The acrylate polymer particles comprise a first organic polymer and a second organic polymer. The polymeric components of the first organic polymer include a first substance, a second substance, a third substance, a fourth substance, and a fifth substance. The polymeric components of the second organic polymer include a first substance, a second substance, a third substance, a fourth substance, a fifth substance, and a sixth substance. The structure of the first substance comprises: Wherein, R1 includes a hydrogen atom or an alkyl group of 1-18 carbon atoms, and R2 includes an alkyl group of 1-18 carbon atoms; The structure of the second substance comprises: R3 includes hydrogen atoms, substituted or unsubstituted alkyl groups with 1 to 18 carbon atoms; The structure of the third substance comprises: 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 substance includes: R6 includes a hydrogen atom or an alkyl group with 1-8 carbon atoms; The structure of the fifth substance includes: Where n = 3 - 10; The structure of the sixth substance comprises: Where m = 1 - 10.

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

9. The separator film according to claim 7 or 8, wherein In the polymeric material of the first organic polymer, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, and the fifth substance is 1:0.01-0.25:0.01-0.1:0.01-0.2:0.02-0.

15.

10. The separator film according to any one of claims 7 to 9, wherein In the polymeric material of the first organic polymer, the mass ratio of the first substance, the second substance, the third substance, the fourth substance and the fifth substance is 1:0.02-0.25:0.02-0.1:0.02-0.2:0.03-0.

1.

11. The separator film according to any one of claims 7 to 10, wherein In the polymeric material of the second organic polymer, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance is 1:0.01-0.25:0.05-0.3:0.01-0.2:0.02-0.15:0.02-0.

15.

12. The separator film according to any one of claims 7 to 11, wherein In the polymeric material of the second organic polymer, the mass ratio of the first substance, the second substance, the third substance, the fourth substance, the fifth substance, and the sixth substance is 1:0.05-0.25:0.1-0.3:0.02-0.2:0.03-0.1:0.03-0.

1.

13. The separator membrane according to any one of claims 7-12, wherein, The first substance 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.

14. The separator membrane according to any one of claims 7-13, wherein, The second substance includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptaenoic acid.

15. The separator membrane according to any one of claims 7-14, wherein, The third substance includes at least one of acrylamide, N-hydroxymethylacrylamide, or N-butoxymethylacrylamide.

16. The separator membrane according to any one of claims 7-15, wherein, The fourth substance includes at least one of acrylonitrile, methacrylonitrile, or ethyl acrylonitrile.

17. The separator membrane according to any one of claims 7-16, wherein, The fifth substance includes at least one of PEG-200, PEG-300, PEG-400 or PEG-500.

18. The separator membrane according to any one of claims 7-17, wherein, The sixth substance includes at least one of malondihydrazide, succinic dihydrazide, adipic dihydrazide, octanoic dihydrazide, azelaic dihydrazide, or sebacate dihydrazide.

19. The separator membrane of any one of claims 1-18, wherein, The acrylate polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is less than or equal to 25°C and the second glass transition temperature is greater than 25°C.

20. The separator membrane of any one of claims 1-19, wherein, The acrylate polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is from -80°C to 25°C and the second glass transition temperature is from 26°C to 100°C.

21. The separator membrane of any one of claims 4-20, 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.

22. The separator film according to claim 21, wherein The mass ratio of the acrylate polymer particles to the second type of organic polymer particles is (20-90):(0-70).

23. The separator film according to claim 21 or 22, wherein The volume average particle size distribution Dv50 of the second type of organic polymer particles is 2μm-25μm, and / or The particle size distribution Dv90 of the second type of organic polymer particles is 4μm-50μm, and / or The particle size distribution Dv99 of the second type of organic polymer particles is less than or equal to 50 μm, and / or The particle size distribution Dv10 of the second type of organic polymer particles is 1μm-5μm.

24. A method of making a separator film, wherein, include: Provide base materials; A coating is formed on at least one side of the substrate, the coating comprising acrylate polymer particles having an AFM adhesion force of 2nN-3nN.

25. A battery, wherein, The separator includes any one of claims 1-23 or a separator obtained by the method of claim 24.

26. An electrical device, comprising: Includes the battery as described in claim 25.

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