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

Isolation film and preparation method thereof, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority benefit of Chinese patent application No. 202410271123.2 filed on March 8, 2024, and incorporates the entirety of the application into this document. Technical Field

[0003] The present application belongs to the field of batteries, and specifically relates to an isolation membrane and a preparation method thereof, a battery and an electrical device. Background Art

[0004] In recent years, with the rapid growth of portable electronic devices and electric vehicles, the demand for power batteries has also continued to grow. Among them, the electrochemical performance of batteries has also attracted more and more attention.

[0005] Currently, the separator adhesive in batteries uses polyvinylidene fluoride. The separator is coated with polyvinylidene fluoride, which is then wound around the electrode and then heated and pressed to bond the electrode to the separator. Without a hot pressing process, the separator and electrode will not be sufficiently bonded, and the bare cell will not be hard enough, which may cause difficulty in robot transfer and even cause the inner separator to fold and the positive and negative electrodes to come into contact. However, after hot pressing, the adhesion between the electrode and the separator is too strong, causing the positive and / or negative electrode to easily release from the mold during the battery cycle, thereby reducing the battery's cycle performance.

[0006] Summary of the Invention

[0007] In view of the technical problems existing in the background technology, the present application provides an isolation membrane, which aims to achieve cold pressing bonding between the isolation membrane and the electrode, thereby improving the cycle performance of the battery.

[0008] In order to achieve the above-mentioned object, the present application provides an isolation membrane in one aspect, wherein the isolation membrane comprises:

[0009] substrate;

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

[0011] The present application includes at least the following beneficial effects: the isolation membrane of the present application can be cold-pressed and bonded to the pole piece, and the bonding force between the pole piece and the isolation membrane is appropriate, which can improve the efficiency of cell shaping, and at the same time, isolation membrane clogging is not likely to occur, thereby improving the cycle performance of the battery.

[0012] In some embodiments of the present application, the acrylic polymer particles have an AFM Young's modulus of 30 MPa-70 MPa, optionally 40 MPa-60 MPa, thereby ensuring appropriate bonding strength between the electrode and the isolation film.

[0013] In some embodiments of the present application, the acrylic polymer particles form protrusions on the surface of the coating, thereby ensuring appropriate adhesion between the electrode and the isolation film.

[0014] In some embodiments of the present application, the double-sided height of the protrusion is 2 μm-100 μm, optionally 10 μm-55 μm, and more preferably 25 μm-35 μm. This ensures proper adhesion between the electrode and the separator, while effectively alleviating cell safety issues caused by current collector fracture due to excessive corner stress in the wound structure.

[0015] In some embodiments of the present application, the volume average particle size Dv50 of the acrylic polymer particles is 2μm-25μm, optionally 5μm-15μm, and / or the particle size distribution Dv90 of the acrylic polymer particles is 4μm-50μm, optionally 15μm-40μm, and / or the particle size distribution Dv99 of the acrylic polymer particles is less than or equal to 50μm, and / or the number particle size distribution Dv10 of the acrylic polymer particles is 1μm-5μm, optionally 1μm-3μm. In this way, the risk of clogging the pores of the separator can be reduced, the active ion permeability of the separator can be improved, the risk of lithium deposition at corners can be reduced, and the safety problem of the battery cell caused by the current collector rupture due to excessive corner stress in the winding structure can be effectively alleviated.

[0016] In some embodiments of the present application, the acrylic polymer particles include a first organic polymer and a second organic polymer, the polymeric substance of the first organic polymer includes a first substance, a second substance, a third substance, a fourth substance, and a fifth substance, and the polymeric substance of the second organic polymer includes 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 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, and R2 comprises an alkyl group of 1 to 18 carbon atoms;

[0019] The structure of the second substance includes:

[0020] wherein R3 comprises a hydrogen atom, a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms;

[0021] The structure of the third substance includes:

[0022] wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms;

[0023] The structure of the fourth substance includes:

[0024] wherein R6 comprises a hydrogen atom or an alkyl group of 1 to 8 carbon atoms;

[0025] The structure of the fifth substance includes:

[0026] Wherein, n=3-10;

[0027] The structure of the sixth substance includes:

[0028] Wherein, m=1-10.

[0029] Thus, the AFM adhesion of the acrylic polymer particles can be adjusted to the above range, cold pressing bonding between the isolation membrane and the pole piece can be achieved, and the bonding force between the pole piece and the isolation membrane is appropriate, thereby improving the cycle performance of the battery.

[0030] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10), and can optionally be 1:(0.5-3). This not only facilitates the winding and unwinding of the separator, but also improves the cold-pressed bonding strength between the separator and the positive and negative electrode sheets, thereby enhancing the battery's cycling performance.

[0031] In some embodiments of the present application, in the polymeric substance 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, and can be optionally 1:0.02-0.25:0.02-0.1:0.02-0.2:0.03-0.1. Thus, the present application can adjust the AFM adhesion of the first organic polymer by controlling the first substance, the second substance, the third substance, the fourth substance and the fifth substance in the preparation of the first organic polymer to be within the above-mentioned mixing ratio. At the same time, the carboxyl group contained in the second substance can form a binding force with the functional groups on the electrode and the isolation membrane material, thereby improving the bonding effect between the electrode and the isolation membrane.

[0032] In some embodiments of the present application, in the polymeric substance 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, and optionally 1:0.05-0.25:0.1-0.3:0.02-0.2:0.03-0.1:0.03-0.1. Thus, by controlling the mixing ratio of the first substance, the second substance, the third substance, the fourth substance, and the fifth substance used to prepare the second organic polymer within the above-mentioned range, the AFM adhesion of the second organic polymer can be adjusted, and the ionic conductivity and bonding properties of the second organic polymer can be improved.

[0033] In some embodiments of the present 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. Thus, the use of the first substance can adjust the AFM adhesion of the acrylic polymer particles and improve the anti-swelling ability of the acrylic polymer particles.

[0034] In some embodiments of the present application, the second substance includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Thus, using this second substance can adjust the AFM adhesion of the acrylic polymer particles. Using these acrylic polymer particles on a separator can improve the cold-press adhesion between the separator and the electrode, thereby enhancing the battery's cycling performance.

[0035] In some embodiments of the present application, the third substance includes at least one of acrylamide, N-methylol acrylamide, or N-butoxymethyl acrylamide. Thus, using the third substance can adjust the molecular weight of the first organic polymer and the second organic polymer, thereby improving the cold-pressed adhesion between the separator and the electrode, and enhancing the battery's cycling performance.

[0036] In some embodiments of the present application, the fourth substance includes at least one of acrylonitrile or methacrylonitrile. Thus, the fourth substance can improve the adhesion and ionic conductivity of the acrylic polymer particles. Using the acrylic polymer particles in a separator can enhance the cold-pressed adhesion between the separator and the electrode, reduce battery resistance, and thus improve battery cycling performance.

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

[0038] In some embodiments of the present application, the sixth substance includes at least one of malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide or sebacic acid dihydrazide.

[0039] In some embodiments of the present application, the acrylic polymer particles have a first glass transition temperature and a second glass transition temperature, 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 the present application, the acrylic polymer particles have a first glass transition temperature and a second glass transition temperature, the first glass transition temperature is -80°C to 25°C, and the second glass transition temperature is in the range of 26°C to 100°C.

[0041] In some embodiments of the present application, the coating further comprises a second organic polymer particle, wherein the second organic polymer particle comprises polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinyl fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorine-containing alkenyl monomer units and vinyl monomer units, copolymer particles of fluorine-containing alkenyl monomer units and acrylic acid monomer units, copolymer particles of fluorine-containing alkenyl monomer units and acrylate monomer units, and at least one of particles of modified compounds of the above homopolymers or copolymers, and the second organic polymer particles and the acrylate polymer particles form the protrusions on the surface of the coating. Thus, the cycle performance and safety performance of the battery can be improved.

[0042] In some embodiments of the present application, the mass ratio of the acrylic polymer particles to the second organic polymer particles is (20-90):(0-70), or optionally (45-90):(0-45). This can reduce battery cost while improving safety and cycle performance.

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

[0044] A second aspect of the present application provides a method for preparing an isolation membrane, comprising:

[0045] providing a substrate;

[0046] A coating is formed on at least one side of the substrate, wherein the coating comprises acrylic polymer particles, and the acrylic polymer particles have an AFM adhesion force of 2nN-3nN.

[0047] Therefore, the above-mentioned isolation membrane can be obtained by adopting this method. The isolation membrane can be cold-pressed and bonded to the pole piece, and the bonding force between the pole piece and the isolation membrane is appropriate, which can improve the efficiency of battery cell shaping. At the same time, the isolation membrane is not prone to clogging, thereby improving the cycle performance of the battery.

[0048] The third aspect of the present application provides a battery, comprising the separator described in the first aspect of the present application or the separator obtained by the method of the second aspect, thereby having excellent cycle performance.

[0049] The fourth aspect of the present application provides an electrical device, which includes the battery described in the third aspect of the present application. As a result, the electrical device has excellent cycle performance and safety performance.

[0050] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0052] FIG1 is a Thermal Tune interface diagram during AFM adhesion and AFM Young's modulus testing of acrylic polymer particles;

[0053] FIG2 is a parameter interface diagram during the AFM adhesion and AFM Young's modulus testing of acrylic polymer particles;

[0054] FIG3 is a diagram of the parameter setting interface during the AFM adhesion and AFM Young's modulus testing of acrylic polymer particles;

[0055] FIG4 is a force curve during AFM adhesion and AFM Young's modulus testing of acrylic polymer particles;

[0056] FIG5 is a force curve during AFM adhesion and AFM Young's modulus testing of acrylic polymer particles;

[0057] FIG6 is a fitting curve of the FD curve during the AFM adhesion and AFM Young's modulus tests of acrylic polymer particles;

[0058] FIG7 is a SEM image of the isolation membrane;

[0059] FIG8 is a schematic diagram of the winding of a battery cell after the separator, the positive electrode sheet, and the negative electrode sheet are stacked in one embodiment of the present application.

[0060] FIG9 is a schematic diagram of a battery according to an embodiment of the present application.

[0061] FIG. 10 is an exploded view of the battery shown in FIG. 9 according to an embodiment of the present application.

[0062] FIG11 is a schematic diagram of a battery module according to an embodiment of the present application.

[0063] FIG12 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0064] FIG13 is an exploded view of the battery pack shown in FIG12 according to an embodiment of the present application.

[0065] FIG14 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0066] Description of reference numerals:

[0067] 1 battery cell; 11 shell; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper box; 32 lower box. DETAILED DESCRIPTION

[0068] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0069] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0070] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0072] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0073] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0074] Currently, market developments indicate that secondary batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As the application of secondary batteries continues to expand, market demand is also growing.

[0075] The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell has a certain hardness. That is, because the positive and negative electrode sheets and the separator are bonded together and support each other, a structure with a certain thickness is formed. A structure with a certain thickness has a certain hardness. The negative electrode will expand during the charge and discharge process. If the bonding force is weak, a gap will form between the positive and negative electrode sheets and the separator. The positive and negative electrode sheets and the separator cannot adhere to each other and support each other, causing the battery cell to become loose and the hardness to decrease. At this point, the battery's cycle performance deteriorates, which directly leads to a shortened battery life. Electric vehicles need to frequently replace batteries, and consumers' costs for electric vehicles increase.

[0076] The isolation membrane and the electrode are tightly fitted, which can improve the discharge capacity of the battery, reduce internal resistance, reduce polarization loss, extend the cycle life of the battery, and improve the utilization rate of the secondary battery. The commonly used binder on the existing isolation membrane is polyvinylidene fluoride, which requires a hot pressing process (heating during the pressing process after the isolation membrane and the electrode are stacked) to make the isolation membrane and the electrode tightly bonded. However, after the hot pressing process, the adhesion between the isolation membrane and the positive and negative electrode sheets is too strong. During the battery cycle, excessive expansion of the negative electrode will cause the positive electrode active material in the positive electrode sheet or the negative electrode active material in the negative electrode sheet to be torn off, that is, the positive and negative electrode sheets are demolded, thereby reducing the cycle performance of the battery.

[0077] The coating of the isolation membrane of the present application includes acrylic polymer particles, and the AFM adhesion force of the acrylic polymer particles is 2nN-3nN. The acrylic polymer particles with AFM adhesion can be bonded to the pole piece during the cold pressing process (no heating is performed during the pressing process after the isolation membrane and the pole piece are stacked), and the isolation membrane is not prone to clogging, thereby achieving cold pressing bonding between the isolation membrane and the pole piece, and the bonding force between the pole piece and the isolation membrane is appropriate, thereby improving the cycle performance of the battery.

[0078] The isolation membrane disclosed in the embodiments of the present application is suitable for use in batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or 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, battery-powered vehicles, electric vehicles, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0079] In a first aspect, the present application proposes an isolation film, which includes a substrate and a coating, wherein the coating is formed on at least one side of the substrate, and the coating includes acrylic polymer particles. The AFM adhesion force of the acrylic polymer particles is 2nN-3nN, for example, 2.2nN-2.8nN, 2.4nN-2.6nN, 2.4nN-2.5nN, etc.

[0080] The present application adopts acrylic polymer particles with an AFM adhesion of 2nN-3nN on the coating of the isolation membrane. The acrylic polymer particles with AFM adhesion can be bonded to the pole piece during the cold pressing process, and the isolation membrane is not prone to clogging, thereby achieving cold pressing bonding between the isolation membrane and the pole piece, and the bonding force between the pole piece and the isolation membrane is appropriate, thereby improving the cycle performance of the battery.

[0081] The process by which the above-mentioned acrylic polymer particles exert their properties is speculated as follows: the AFM adhesion force of the acrylic polymer particles is too large (greater than 3nN), the cohesive energy itself becomes larger, the interaction force between the polymer particles is small, and the particles are easily spread out during the cold pressing process, resulting in a large contact area with the positive and negative electrodes, which may cause the isolation membrane to have excessive adhesion to the positive and negative electrodes, and the isolation membrane is prone to clogging, reducing the ion transmission channel; the AFM adhesion force of the acrylic polymer particles is too small (less than 2nN), and the polymer is easily broken up by high-speed shearing during the pulping process, resulting in smaller particles, and no protrusions can be formed on the surface of the isolation membrane, which makes the corners of the wound battery cell more likely to break due to stress accumulation, worsening the safety performance of the battery cell, and the reduction in height may cause the gap between the electrode and the isolation membrane to decrease, which is not conducive to the infiltration of the electrolyte into the battery cell structure, worsening the battery cell cycle performance and affecting production efficiency. Therefore, the present application uses acrylic polymer particles with an AFM adhesion force of 2nN-3nN on the coating of the isolation membrane. The acrylic polymer particles with an AFM adhesion force can be bonded to the electrode during the cold pressing process, and the isolation membrane is not prone to clogging, thereby achieving cold pressing bonding between the isolation membrane and the electrode, and the bonding force between the electrode and the isolation membrane 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 acrylic polymer particles can be obtained by scanning with an atomic force microscope (AFM).

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

[0084] As an example, the AFM adhesion and AFM Young's modulus of the acrylic polymer particles can be measured by the following method: using an atomic force microscope (Bruker Dimension ICON) with a silicon tip on nitride lever as the probe;

[0085] First step, obtain the force curve on the hard surface:

[0086] a. Select a hard surface, such as sapphire, silicon wafer, etc., and scan with the needle in Contact mode.

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

[0088] c. Set the Ramp parameters: In the parameter interface of the force curve test, there are Trigger Mode options, namely "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 the scanning state.

[0091] The second step is to calculate the Deflection Sensitivity:

[0092] a. Move the cursor to the coordinate on the left side of the force curve window. Click the left mouse button and move the mouse to create a red dotted line. Repeat this process to create another dotted line. Move each dotted line to the right end of the diagonal portion of the force curve.

[0093] b. Click icon, the software will automatically calculate Deflection Sensitivity. Click OK in the dialog box that pops up, 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] Sader's method can usually be used to calculate k for rectangular cantilevers. The formula is:

[0096] From this formula, we can see that as long as we know the length L, width w, resonant frequency f0, and quality factor Q of the cantilever beam, we can calculate the elastic coefficient k.

[0097] The following describes the method for obtaining the parameters of the cantilever beam, including length L, width w, resonance frequency f0, and quality factor Q.

[0098] The test steps are as follows:

[0099] a. Determine the cantilever length L and width w: Use a standard grating as a ruler and read directly from an optical microscope.

[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 according to Figure 1.

[0101] c. Select "Acquire Data". When a peak appears, use Ctrl+left key to enlarge the peak and click "Fit Data" to fit the peak.

[0102] d. After the fitting is complete, the software will display the resonant 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 for a ready-made calculation program. Enter the length L, width w, resonant frequency f0, and quality factor Q, and click "Calculate" to easily calculate the k value.

[0104] Step 4: Force curve test:

[0105] a. See 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 force curve:

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

[0108] [Corrected 11.12.2024 according to Rule 91] The FZ curve and the FD curve have the same curve shape before the probe contacts the sample. The difference is that after the probe contacts the sample, the extension of the scanner in the Z direction is equivalent to the sum of the bending amount 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 give the relationship between the force and the 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 part (curve 1) of the force curve (FZ or FD curve) and the baseline, as shown in Figure 4. This lowest point represents the situation when the gravitational force exerted on the probe in the process of withdrawing from the sample is the largest. After this point, the probe can get rid of the gravitational force and make the force curve reach the baseline position.

[0109] By the formula

[0110] As can be seen, the product of the cantilever's force and velocity, integrated over time, represents the energy dissipation during that time period. In the force curve, this is represented by the shaded area in Figure 5. Energy dissipation primarily reflects the cantilever's inelastic deformation, which is related to the sample's viscoelastic properties.

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

[0112] There is no particular limitation on the type of substrate in the present application, and any known porous substrate with good chemical stability and mechanical stability can be selected.

[0113] In some embodiments of the present application, the substrate may be a porous membrane or porous nonwoven web 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 oxide, cyclic olefin copolymer, polyphenylene sulfide and polyethylene naphthalene. In other embodiments, the substrate is a porous membrane or porous nonwoven web comprising polyethylene and / or polypropylene. By selecting the above-mentioned substrates to prepare the isolation membrane, it is beneficial for the substrate to be combined with the coating through an adhesive to form an isolation membrane that is moderately dense, porous and can conduct active ions.

[0114] In some embodiments of the present application, the acrylic polymer particles form protrusions on the coating surface. Therefore, when the battery experiences thermal runaway and generates high temperatures, the protrusions formed by the acrylic polymer particles on the coating surface can form a large-area adhesive film structure to reduce or block the transmission path of insulators, slowing the spread of heat in the battery, thereby effectively improving the battery's cycling performance and safety performance at high temperatures.

[0115] It should be noted that the isolation film can be scanned using a scanning electron microscope (SEM). Referring to FIG. 7 , it can be seen from the SEM image that the acrylic polymer particles form protrusions on the coating surface.

[0116] In other embodiments of the present application, the acrylate polymer particles forming protrusions on the coating surface can be tested using methods well known in the art. As an example, the following method can be used for testing: Use a ZEISS Sigma300 scanning electron microscope for testing, and follow the following steps to test: First, cut the isolation film to be tested into 6mm×6mm test samples, clamp the test samples with two pieces of conductive and heat-conductive copper foil, and fix the test samples and the copper foils with double-sided tape. Press with a 400g flat iron block for 1 hour to make the gap between the test sample and the copper foil as small as possible, then trim the edges with scissors and stick them on a sample table with conductive glue, with the sample slightly protruding from the edge of the sample table. Then put the sample table into the sample holder, lock it, turn on the power of the IB-19500CP argon ion cross-section polisher and evacuate to 10 -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 rocking mode and start polishing. After polishing, use a ZEISS Sigma300 scanning electron microscope to obtain an ion polishing cross-sectional morphology (CP) image of the sample to be tested. From the CP image, information about the protrusions formed by the acrylic polymer particles on the coating surface can be obtained.

[0117] In some embodiments of the present application, a protrusion is formed on the surface of the separator coating of the present application, and the double-sided height of the protrusion is 2μm-100μm, for example, 5μm-95μm, 10μm-90μm, 15μm-85μm, 20μm-80μm, 25μm-75μm, 30μm-70μm, 35μm-65μm, 40μm-60μm, 45μm-55μm, 45μm-50μm, etc. As a result, the protrusions in this height range can, on the one hand, provide appropriate space between the separator and the pole piece to release stress, prevent the pole piece from breaking during the winding process, and improve safety; on the other hand, a suitable gap is left between the separator and the pole piece to facilitate electrolyte flow and infiltration, thereby improving the cycle performance of the battery cell. In some embodiments of the present application, the double-sided height of the protrusion is 10μm-55μm. In some embodiments of the present application, the double-sided height of the protrusion is 25 μm-35 μm.

[0118] In the present application, coatings are formed on both opposite surfaces of the substrate, and the sum of the heights of the protrusions on the coatings on both sides is the double-sided height of the protrusion, and the double-sided height of the protrusion can be tested by methods known in the art. As an example, it can be tested by the following method: Referring to Figure 8, the negative electrode sheet, the separator and the positive electrode sheet are first stacked in sequence to form a battery cell and then rolled up (the outermost layer of the battery cell ends with the convex surface of the positive electrode sheet), and 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. In the resulting CT image, samples are taken along the horizontal and oblique angles (30-45°), and the direction with the largest gap is marked; the inner 5-fold sampling position is from the convex surface of the innermost positive electrode sheet to the convex surface of the fifth positive electrode sheet, and the average of 4 folds is taken; the sampling position after 6 folds 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 + rebound rate of negative electrode sheet) - 4 * thickness of positive electrode sheet after cold pressing (1 + rebound rate of positive electrode sheet) - 8 * thickness of separator] / 8

[0120] Average gap value after inner 6-10 layers = [CT measurement distance - 5 * thickness of negative electrode sheet after cold pressing * (1 + rebound rate of negative electrode sheet) - 5 * thickness of positive electrode sheet after cold pressing (1 + rebound rate of positive electrode sheet) - 10 * thickness of separator] / 10

[0121] Among them, the rebound rate of the negative electrode sheet = (the thickness of the negative electrode sheet before entering the shell - the thickness of the negative electrode sheet after cold pressing) / the thickness of the negative electrode sheet after cold pressing;

[0122] Positive electrode sheet rebound rate = (positive electrode sheet thickness before entering the shell - positive electrode sheet thickness after cold pressing) / positive electrode sheet thickness after cold pressing;

[0123] The double-sided height of the isolation film protrusion = (the average gap between the inner 5 layers + the average gap between the inner 6-10 layers) / 2.

[0124] In some embodiments of the present application, the volume average particle size Dv50 of the acrylic polymer particles is 2 μm-25 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 23 μm, 23 μm, 24 μm, 25 μm, etc. In other embodiments of the present application, the volume average particle size Dv50 of the acrylic polymer particles is 5 μm-15 μm.

[0125] In some embodiments of the present application, the volume particle size distribution Dv90 of the acrylic polymer particles is 4μm-50μm, for example, 5μm-48μm, 7μm-45μm, 10μm-42μm, 15μm-40μm, 20μm-38μm, 25μm-35μm, 27μm-32μm, 30μm-32μm, etc. In other embodiments of the present application, the volume particle size distribution Dv90 of the acrylic polymer particles is 15μm-40μm.

[0126] In some embodiments of the present application, the volume particle size distribution Dv99 of the acrylic polymer particles is less than or equal to 50 μm, for example, 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 the present application, the volume particle size distribution Dv99 of the acrylic polymer particles is 30 μm-45 μm.

[0127] In some embodiments of the present application, the volume particle size distribution Dv10 of the acrylic polymer particles is 1 μm-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. In other embodiments of the present application, the volume particle size distribution Dv10 of the acrylic polymer particles is 1 μm-3 μm.

[0128] In the present application, acrylic polymer particles that meet the above-mentioned volume particle size distribution are used on the separator, which can not only improve the risk of acrylic polymer particles clogging the pores of the separator, but also improve the problem that acrylic polymer particles are coated on the separator to form a thicker coating, which affects the energy density of the battery prepared later. At the same time, it can also reduce the lithium precipitation caused by the uneven current density distribution at the corners of the wound battery cell, and can effectively reduce the problems such as the corner anode rupture and puncture of the diaphragm caused by expansion in the late cycle. In addition, it can also effectively reduce the capacity loss such as circular spot lithium precipitation caused by corner stress extrusion caused by insufficient corner space. Therefore, when the acrylic polymer particles are used on the separator, it can improve the pores of the separator that the acrylic polymer particles clog, improve the active ion permeability of the separator, and improve the problem that the polymer is coated on the separator to form a thicker coating, which affects the low energy density of the battery prepared later.

[0129] It should be noted that in the embodiments of the present application, the volume average particle size Dv50 of the acrylic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage of the particles reaches 50%, the volume particle size distribution Dv90 of the acrylic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage of the particles reaches 90%, the volume particle size distribution Dv99 of the acrylic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage of the particles reaches 99%, and the volume particle size distribution Dv10 of the acrylic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage of the particles reaches 10%. The above-mentioned volume particle size distribution of the acrylic polymer particles can be tested using methods known in the art. As an example, the test method is:

[0130] Reference standard GB / T 19077-2016 / ISO 13320:2009 particle size distribution laser diffraction method. Use a laser particle size analyzer (Malvern 3000, MasterSizer 3000) for testing, and use a helium-neon red light source as the main light source. Take a clean small beaker and add 1g of the sample to be tested, add a drop of surfactant, add 20ml of deionized water (the sample concentration ensures that the light shielding is 8-12%), and ultrasonicate at 53KHz / 120W for 5 minutes to ensure that the sample is completely dispersed. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the ultrasonicated test solution to make it evenly dispersed, place it in the sample cell as required, and start measuring the particle size. The measurement results can be read from the instrument.

[0131] In some embodiments of the present application, the acrylic polymer particles include: a first organic polymer and a second organic polymer, the polymeric substance of the first organic polymer includes a first substance, a second substance, a third substance, a fourth substance, and a fifth substance, and the polymeric substance of the second organic polymer includes 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 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, and R2 comprises an alkyl group of 1 to 18 carbon atoms,

[0134] The structure of the second substance includes:

[0135] wherein R3 comprises a hydrogen atom, a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms;

[0136] The structure of the third substance includes:

[0137] wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms;

[0138] The structure of the fourth substance includes:

[0139] wherein R6 comprises a hydrogen atom or an alkyl group of 1 to 8 carbon atoms;

[0140] The structure of the fifth substance includes:

[0141] Wherein, n=3-10;

[0142] The structure of the sixth substance includes:

[0143] Wherein, m=1-10.

[0144] The acrylic polymer particles of the present application include a first organic polymer and a second organic polymer, and the polymeric substances 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 an unsaturated ester group, the second substance includes an unsaturated carboxyl group, the structure of the third substance includes an unsaturated amide group, the structure of the fourth substance includes an unsaturated cyano group, and the fifth substance includes a hydroxyl group. 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 obtained first organic polymer has a higher AFM adhesion force and a lower AFM Young's modulus, thereby improving the bonding effect between the isolation membrane and the electrode. The polymeric substances of the second organic polymer include the first substance, the second substance, the third substance, the fourth substance, the fifth substance and the sixth substance, and the structure of the sixth substance includes a hydrazide group. 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 obtained second organic polymer has a lower AFM adhesion force and a higher AFM Young's modulus, which can improve the adhesion between the acrylic polymer particles and the electrode, and ensure that the isolation membranes do not interact with each other and affect the spraying, storage and transportation of the isolation membranes.

[0145] The first organic polymer prepared by using the first substance, the second substance, the third substance, the fourth substance and the fifth substance has different AFM adhesion force and AFM Young's modulus from the second organic polymer prepared by using the first substance, the second substance, the third substance, the fourth substance, the fifth substance and the sixth substance. The acrylic polymer particles obtained by mixing the first organic polymer and the second organic polymer have suitable AFM adhesion force and AFM Young's modulus, which is conducive to the acrylic polymer particles being able to bond with the pole piece during the cold pressing process. At the same time, the isolation membrane is not prone to clogging, thereby achieving cold pressing bonding between the isolation membrane and the pole piece, and the bonding force between the pole piece and the isolation membrane is suitable, thereby improving the cycle performance of the battery. At the same time, the glass transition temperature of the first organic polymer is lower than that of the second organic polymer. When the acrylic polymer particles are at a temperature between the glass transition temperatures of the first and second organic polymers, and no pressure is applied to the acrylic polymer particles, the second organic polymer structure is in a glassy state, exhibiting a large AFM Young's modulus and low AFM adhesion. This serves as the skeleton structure of the acrylic polymer particle powder, rendering the acrylic polymer particles non-sticky and enabling the winding and unwinding of the separator. At this temperature, the first organic polymer structure is in a rubbery state, exhibiting a relatively large AFM adhesion. Upon application of a certain pressure, it exhibits a certain degree of "fluidity." The structure of the acrylic polymer particles, including the first organic polymer, can fully penetrate the pores of the positive and negative electrode sheets and the separator, enhancing the mechanical interlocking effect and fully utilizing its bonding properties, thereby helping to improve the battery's cycling performance.

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

[0147] Among them, R1 includes a hydrogen atom or an alkyl group with 1-18 carbon atoms, R2 includes an alkyl group with 1-18 carbon atoms, and the first substance includes an unsaturated ester group, which is beneficial to the polymerization of the monomer and can improve the anti-swelling ability of the polymer. The AFM adhesion and Young's modulus of the first organic polymer and the second organic polymer can be adjusted to an appropriate range.

[0148] As an example, an alkyl group with 1-18 carbon atoms can be understood as an alkyl group 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 the present 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. Thus, by using the first substance described above, the AFM adhesion and Young's modulus of the first organic polymer and the second organic polymer can be adjusted to a suitable range, so that when used in a separator, cold-press bonding of the separator to the positive and negative electrode sheets can be achieved.

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

[0151] Wherein, R3 comprises a hydrogen atom, or a substituted or unsubstituted alkyl group of 1-18 carbon atoms. Thus, the unsaturated carboxyl group in the second substance facilitates the polymerization of the monomers. Using the second substance containing the carboxyl group in the preparation of the first and second organic polymers can improve the AFM adhesion and Young's modulus of the first and second organic polymers. Furthermore, during the cold pressing process of the isolation membrane and the electrode, the carboxyl group can form a binding force with the functional groups on the electrode and isolation membrane materials, thereby improving the bonding effect.

[0152] It should be noted that the substituted alkyl group of 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 other groups, such as -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc.

[0153] In some embodiments of the present application, the second substance includes at least one of acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Thus, using the second substance described herein can adjust the AFM adhesion and Young's modulus of the first and second organic polymers, while also improving the bonding between the electrode and the isolation film during the cold pressing process.

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

[0155] R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms. Thus, the structure of the third substance includes an unsaturated amide group, which facilitates polymerization of the monomers. Furthermore, this type of monomer can adjust the molecular weight of the first organic polymer and the second organic polymer, thereby improving the adhesiveness of the acrylic polymer particles.

[0156] It should be noted that the alkyl group of 1-6 carbon atoms substituted by hydroxyl groups can be understood as a group in which at least one hydrogen atom on an alkyl group with 1-6 carbon atoms is replaced by a hydroxyl group, for example -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc. At the same time, the alkoxy group of 1-6 carbon atoms substituted by hydroxyl groups can be understood as a group in which at least one hydrogen atom on an alkoxy group with 1-6 carbon atoms is replaced by a hydroxyl group, for example, methoxy (HOCH2O-), ethoxy (OHCH2CH2O-), propoxy (OHCH2CH2CH2O-), etc.

[0157] In some embodiments of the present application, the third substance includes at least one of acrylamide, N-methylol acrylamide, or N-butoxymethyl acrylamide. Thus, the molecular weights of the first organic polymer and the second organic polymer can be adjusted using the third substance, thereby improving the adhesion of the acrylic polymer particles.

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

[0159] Wherein, R6 includes a hydrogen atom or an alkyl group with 1 to 8 carbon atoms. Thus, the structure of the fourth substance includes an unsaturated cyano group, which is beneficial to the polymerization of the monomer and can improve the ionic conductivity and adhesion of the first organic polymer and the second organic polymer.

[0160] In some embodiments of the present application, the fourth substance includes at least one of acrylonitrile, methacrylonitrile, or ethacrylonitrile. Thus, the use of the fourth substance can improve the ionic conductivity and adhesion of the acrylic polymer particles.

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

[0162] Here, n = 3-10. Thus, the fifth material of this composition can adjust the AFM adhesion of the first organic polymer and the second organic polymer while improving their hydrophilicity, enhancing the stability of the coating slurry, and also improving the wettability of the coating slurry with the substrate, thereby reducing powder loss.

[0163] In some embodiments of the present 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 the above-mentioned 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] Here, m = 1-10. Thus, by adding the sixth substance of the composition during the polymerization of the second organic polymer, the AFM Young's modulus of the second organic polymer can be increased, thereby enhancing the cohesion and adhesion of the acrylic polymer particles and improving their wetting into the base film.

[0167] In some embodiments of the present application, the sixth substance includes at least one of malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide or sebacic acid dihydrazide.

[0168] In some embodiments of the present 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 the present application, since the first organic polymer and the second organic polymer have different AFM adhesion and AFM Young's modulus, the mass ratio of the first organic polymer to the second organic polymer is set within the above range, and the resulting acrylic polymer particles have suitable AFM adhesion and AFM Young's modulus, thereby facilitating the acrylic polymer particles to adhere to the electrode during the cold pressing process, while also preventing the separator from clogging holes, achieving cold pressing bonding between the separator and the electrode, and providing suitable adhesion between the electrode and the separator, thereby improving the battery's cycle performance. At the same time, the glass transition temperature of the first organic polymer is lower than the glass transition temperature of the second organic polymer. When the acrylic polymer particles are at a temperature between the glass transition temperature of the first organic polymer and the glass transition temperature of the second organic polymer, when no pressure is applied to the acrylic polymer particles, the second organic polymer structure is in a glassy state, has a larger AFM Young's modulus and a lower AFM adhesion, and can serve as the skeleton structure of the acrylic polymer particle powder, making the acrylic 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, exhibiting a relatively large AFM adhesion force and exhibiting a certain degree of "fluidity" upon application of a certain pressure. The acrylic polymer particles, including the first organic polymer, are able to fully penetrate the pores of the positive and negative electrode sheets and the separator, enhancing the mechanical interlocking effect and fully utilizing their bonding properties, thereby helping to improve the battery's cycling performance. In other embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.5-3).

[0170] In the present application, it should be noted that, since the acrylic polymer particles are formed by the accumulation of the first organic polymer particles and the second organic polymer particles, and during the AFM adhesion and AFM Young's modulus tests, only one of the particles can be detected at a time, that is, either the first organic polymer particles or the second organic polymer particles are detected, it is stipulated that when the ratio of the first organic polymer particles to the second organic polymer particles is a:b (if a and b are integers, a first organic polymer particles and b second organic polymer particles are taken respectively; if a and b are not integers, they are converted into integers, for example, a:b=1:0.5, then it is converted into 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 organic polymer particle and the second organic polymer particle does not exceed 5 nm), then a first organic polymer particles and b second organic polymer particles are taken, and the AFM adhesion of a first organic polymer particle is measured in sequence, and recorded as A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A110, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A39, A40, A39, A41, A39, A42, A39, A43, A39, A44, A39, A45, A46, A47, A48, A49, A49, A49, A50, A51, A52, A53, A54, A55, A69, A69, A70, A71, A a-1 、A a, and measure the AFM adhesion of b second organic polymer particles in sequence, which are respectively recorded as B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15, B16, B17, B18, B19, B20, B21, B22, B23, B24, B25, B26, B27, B28, B2 b-1 、B b , where A a represents the AFM adhesion force of the a-th first organic polymer particle, B b represents the AFM adhesion force of the bth second organic polymer particle; then according to (a≥3, b≥3, if a is 1 and b is 1, the AFM adhesion force of the acrylic polymer particles is calculated according to (A1+B1) / 2. Similarly, if a is 1 and b is 2, the AFM adhesion force of the acrylic polymer particles is calculated according to (A1+B1+B2) / 3); at the same time, the AFM Young's modulus of a first organic polymer particle is measured in sequence and recorded as C1, C... a-1 、C a , and measure the AFM Young's modulus of b second organic polymer particles in sequence, which are respectively recorded as D1, D b-1 、D b , where C a represents the AFM Young's modulus of the ath first organic polymer particle, D b represents the AFM Young's modulus of the bth second organic polymer particle; then according to (a≥3, b≥3, if a is 1 and b is 1, the AFM Young's modulus of the acrylic polymer particles is calculated according to (C1+D1) / 2. Similarly, if a is 1 and b is 2, the AFM Young's modulus of the acrylic polymer particles is calculated according to (C1+D1+D2) / 3). In some embodiments of the present application, in the polymer substance 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, 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, the present application controls the first substance, second substance, third substance, fourth substance and fifth substance for preparing the first organic polymer to be within the above-mentioned mixing ratio, and the obtained first organic polymer has a higher AFM adhesion force and a lower AFM Young's modulus, thereby improving the bonding effect between the isolation membrane and the electrode. At the same time, the first organic polymer has a lower glass transition temperature. When the acrylic polymer particles are at a temperature higher than the glass transition temperature of the first organic polymer, the first organic polymer structure is in a rubbery state. After a certain pressure is applied to the acrylic polymer particles containing the first organic polymer, it can have a certain "fluidity". The structure including the first organic polymer in the acrylic polymer particles can fully penetrate into the pores of the positive and negative electrode sheets and the isolation membrane, thereby increasing the mechanical interlocking effect, and can fully exert its bonding performance, thereby helping to improve the cycle performance of the battery.

[0171] In other embodiments of the present application, in the polymer substance 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.

[0172] In some embodiments of the present application, in the polymeric substance 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, 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: 0.01-0.2: 0.02-0.15: 0.02-0.15, 1: 0.01-0.25: 0.15-0.2: 0.01-0.2: 0.02-0.15: 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] In the present application, the first substance, the second substance, the third substance, the fourth substance, the fifth substance and the sixth substance for preparing the second organic polymer are controlled within the above-mentioned mixing ratio, so that the obtained second organic polymer has a higher AFM Young's modulus and a lower AFM adhesion force. The acrylic polymer particles obtained by mixing the first organic polymer and the second organic polymer have suitable AFM adhesion force and AFM Young's modulus, which is conducive to the adhesion of the acrylic polymer particles to the electrode during the cold pressing process, and at the same time, it is not easy for the isolation membrane to be blocked, thereby achieving cold pressing bonding between the isolation membrane and the electrode, and the bonding force between the electrode and the isolation membrane is suitable, thereby improving the cycle performance of the battery. At the same time, the second organic polymer has a relatively high glass transition temperature (its glass transition temperature is higher than that of the first organic polymer). When the acrylic polymer particles are at a temperature between the glass transition temperature of the first organic polymer and the glass transition temperature of the second organic polymer, and when no pressure is applied to the acrylic polymer particles, the second organic polymer structure is in a glassy state, has a relatively large AFM Young's modulus and a relatively low AFM adhesion force, and can serve as the skeleton structure of the acrylic polymer particle powder, making the acrylic polymer particles non-sticky and capable of meeting the requirements of the winding and unwinding of the isolation film. In other embodiments of the present application, among the polymeric substances 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.

[0174] In some embodiments of the present application, the acrylic 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 the present 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 changes from an elastic state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from the glassy state to the elastic state, or vice versa. It is the lowest temperature at which the macromolecular segments of an amorphous polymer can move freely, and is usually denoted by Tg. Above the Tg, a polymer exhibits elasticity; below the Tg, it exhibits brittleness. The Tg can be measured using methods commonly used in the art, such as differential scanning calorimetry (DSC) as described in GB / T 19466.2.

[0176] It can be understood that the first glass transition temperature is less than or equal to 25°C, above which the structure of the first organic polymer in the acrylic polymer particles is in a rubbery state, and the second glass transition temperature is greater than 25°C, below which the structure of the second organic polymer in the acrylic polymer particles is in a glassy state.

[0177] For example, the first glass transition temperature is lower than room temperature, and the second glass transition temperature is higher than room temperature. At room temperature, when no pressure is applied to the isolation membrane, the second glass transition temperature is higher than room temperature. The structure of the second organic polymer in the acrylic polymer particles on the isolation membrane is in a glassy state, which is relatively hard and can serve as the skeleton structure of the acrylic polymer particle powder, so that the acrylic polymer particles are non-sticky. At room temperature, the first glass transition temperature is lower than room temperature, and the structure of the first organic polymer in the acrylic polymer particles is in a rubbery state. After applying a certain pressure, it can have a certain "fluidity". The structure of the first organic polymer in the acrylic polymer particles can fully penetrate into the pores of the positive and negative pole pieces and the isolation membrane, thereby increasing the mechanical interlocking effect and fully exerting its bonding performance, thereby helping to improve the cycle performance of the battery.

[0178] It can be understood that when the temperature is above the first glass transition temperature, the structure of the acrylic polymer particles including the first organic polymer is in a soft state and can be deformed with the extrusion force, while the structure of the isolation membrane and the electrode has pores. As the extrusion force acts on the acrylic polymer particles, part of the structure of the first organic polymer can penetrate into the pores of the isolation membrane and the electrode, bonding the isolation membrane and the electrode together, achieving a mechanical interlocking effect and realizing the bonding function.

[0179] Due to the significant difference in glass transition temperatures between the first and second organic polymers in the acrylic polymer particles, when cold-pressed at a temperature between the first and second glass transition temperatures, the first organic polymer in the acrylic polymer particles is in a rubbery state, while the second organic polymer in the acrylic polymer particles is in a glassy state, giving the acrylic polymer particles the properties of being both soft and hard. When coated on a separator, at a temperature between the first and second glass transition temperatures and without applied pressure, the acrylic polymer particles are non-sticky, allowing the separator to be wound and unwound. When a certain pressure is applied, the acrylic polymer particles exhibit pressure sensitivity and excellent adhesion, meeting the bonding requirements between the separator and the positive and negative electrodes.

[0180] Therefore, the acrylic polymer particles used on the separator of the present application are non-sticky at temperatures between the first and second glass transition temperatures when the separator is coated, facilitating winding and unwinding of the separator. However, after being wound with the positive and negative electrode sheets and subjected to a cold pressing process, the acrylic polymer particles exhibit excellent adhesion, allowing the positive and negative electrode sheets to adhere tightly to the separator. Therefore, using these acrylic polymer particles on the separator can improve the cold pressing adhesion between the separator and the positive and negative electrode sheets, thereby improving the hardness of the battery cell and the battery cycle performance.

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

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

[0183] In some embodiments of the present application, the first glass transition temperature range is -80°C to 25°C. In some embodiments of the present application, the first glass transition temperature range is -60°C to 25°C.

[0184] Within the above range, the acrylic polymer particles include a structure with a first glass transition temperature and are in a rubbery state above the first glass transition temperature, which is beneficial for exerting their adhesiveness during the cold pressing process, and is beneficial for the adhesion between the isolation membrane and the electrode after cold pressing, thereby improving the performance of the battery.

[0185] In the above-mentioned range of -80℃ to 25℃, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such 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-mentioned point values.

[0186] In the above-mentioned range of -60℃ to 25℃, the values ​​include the minimum and maximum values ​​of the range, as well as every value between such 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-mentioned point values.

[0187] In some embodiments of the present application, the second glass transition temperature range is 26°C to 100°C. In some embodiments of the present application, the second glass transition temperature range is 26°C to 90°C.

[0188] Within the above range, the structure including the second glass transition temperature in the acrylic polymer particles is in a glassy state below the second glass transition temperature, which is beneficial to serve as the skeleton structure of the acrylic polymer particles at a temperature between the first glass transition temperature and the second glass transition temperature, making the acrylic polymer particles non-sticky and facilitating the operation of the winding and unwinding steps of the isolation film at a certain temperature.

[0189] In the above-mentioned 26°C to 100°C, the values ​​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 and 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, 100°C, etc., as well as the range values ​​between any two of the above-mentioned point values.

[0190] In the above-mentioned 26°C to 90°C, the values ​​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 and 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, etc., as well as the range values ​​between any two of the above-mentioned point values.

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

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

[0193] blending water, an emulsifier, an initiator, a first substance, a second substance, a third substance, a fourth substance, and a fifth substance to obtain a first polymer emulsion;

[0194] blending water, an emulsifier, an initiator, a first substance, a second substance, a third substance, a fourth substance, a fifth substance, and a sixth substance to obtain a second polymer emulsion;

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

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

[0197] In the present application, a first polymer emulsion and a second polymer emulsion are obtained by emulsion polymerization, and then the acrylic polymer particles are obtained by spray drying. That is, the acrylic polymer particles include the first organic polymer and the second organic polymer.

[0198] Emulsion polymerization is a process in which monomers are dispersed in water with the help of emulsifiers and mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

[0199] Emulsifiers are substances that can transform mutually incompatible oils and water into an emulsion that is difficult to separate. Emulsifiers are typically surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups. For example, the emulsifier can be at least one of sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, or sodium palmitoleate.

[0200] An initiator is a substance that can initiate polymerization 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 of olefinic and diene monomers. For example, the initiator can be at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile, dimethyl azobisisobutyrate, benzoyl peroxide, or dioctanoyl peroxide.

[0201] Water, emulsifier, initiator, and monomers constituting the polymer are blended and stirred. The water and emulsifier are stirred and dispersed to form an emulsion, that is, the emulsifier forms micelles in the aqueous phase, and most of the micelles are solubilized with monomers. Under heating conditions, the initiator initiates polymerization of the monomers inside the micelles to obtain an emulsion.

[0202] Spray drying, through mechanical action, disperses the material to be dried (a mixture of the first polymer emulsion and the second polymer emulsion) into very fine mist-like particles (increasing the water evaporation area and accelerating the drying process), which come into contact with hot air, instantly removing most of the water and drying the solid matter in the material into powder.

[0203] Acrylate 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 the present application, the step of mixing and stirring the first polymer emulsion and the second polymer emulsion and spray drying to obtain a polymer includes: mixing and stirring the first polymer emulsion and the second polymer emulsion to obtain a mixed emulsion, wherein the mass ratio of the first organic polymer to the second organic polymer in the mixed emulsion is in the range of 1:(0.1-10). In some embodiments, the mass ratio of the first organic polymer to the second organic polymer in the mixed emulsion is in the range of 1:(0.5-3).

[0205] In some embodiments of the present application, the separator coating of the present application may further include a second type of organic polymer particles, that is, the separator coating includes acrylic polymer particles and a second type of organic polymer particles, wherein the organic particles include polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinyl fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorine-containing olefin monomer units and vinyl monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylic monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylic monomer units, and copolymer particles of fluorine-containing olefin monomer units and acrylic ester monomer units, as well as at least one of particles of modified compounds of the above homopolymers or copolymers, and the organic particles and the acrylic ester polymer particles form the protrusions on the surface of the coating. This can improve the cycle performance and safety performance of the battery.

[0206] In some embodiments of the present application, the mass ratio of the acrylic polymer particles to the second organic polymer particles is (20-90):(0-70), for example, the mass ratio of the acrylic 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 can improve the wettability and uniformity of the electrolyte, enhance the battery's high-temperature storage performance, and enhance battery safety and cycling performance. In other embodiments, the mass ratio of the acrylic polymer particles to the second organic polymer particles is (45-90):(0-45). This can improve battery safety and cycling performance.

[0207] In some embodiments of the present application, the coating may further include other organic compounds, such as polymers that improve heat resistance, dispersants, wetting agents, and other types of adhesives. These other organic compounds are all non-granular substances in the coating. This application does not specifically limit the type of these other organic compounds; any known material with good performance improvement properties may be selected.

[0208] In some embodiments of the present application, the volume particle size distribution Dv50 of the second organic polymer particles is 2 μm-25 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 23 μm, 23 μm, 24 μm, 25 μm, etc. In other embodiments of the present application, the volume particle size distribution Dv50 of the second organic polymer particles is 5 μm-15 μm.

[0209] In some embodiments of the present application, the volume particle size distribution Dv90 of the second organic polymer particles is 4μm-50μm, for example, 5μm-48μm, 7μm-45μm, 10μm-42μm, 15μm-40μm, 20μm-38μm, 25μm-35μm, 27μm-32μm, 30μm-32μm, etc. In other embodiments of the present application, the volume particle size distribution Dv90 of the second organic polymer particles is 15μm-40μm.

[0210] In some embodiments of the present application, the volume particle size distribution Dv99 of the second organic polymer particles is less than or equal to 50 μm, for example, 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 the present application, the volume particle size distribution Dv99 of the second organic polymer particles is 30 μm-45 μm.

[0211] In some embodiments of the present application, the volume particle size distribution Dv10 of the second organic polymer particles is 1 μm-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. In other embodiments of the present application, the volume particle size distribution Dv10 of the second organic polymer particles is 1 μm-3 μm.

[0212] In the present application, the second organic polymer particles meeting the above-mentioned particle size distribution are used in combination with the acrylic polymer particles on the isolation membrane. This can not only improve the risk of the second organic polymer particles and the acrylic polymer particles clogging the pores of the isolation membrane, but also improve the problem of the second organic polymer particles and the acrylic polymer particles being coated on the isolation membrane to form a thicker coating, thereby affecting the energy density of the battery prepared later.

[0213] It should be noted that, in the embodiments of the present application, the volume average particle size Dv50 of the second organic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 50%, the volume particle size distribution Dv90 of the second organic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 90%, the volume particle size distribution Dv99 of the second organic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 99%, and the volume particle size distribution Dv10 of the second organic polymer particles is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 10%. The above-mentioned volume particle size distribution of the second organic polymer particles can be tested using methods known in the art. As an example, the test method is:

[0214] Reference standard GB / T 19077-2016 / ISO 13320:2009 particle size distribution laser diffraction method. Use a laser particle size analyzer (Malvern 3000, MasterSizer 3000) for testing, and use a helium-neon red light source as the main light source. Take a clean small beaker and add 1g of the sample to be tested, add a drop of surfactant, add 20ml of deionized water (the sample concentration ensures that the light shielding is 8-12%), and ultrasonicate at 53KHz / 120W for 5 minutes to ensure that the sample is completely dispersed. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the ultrasonicated test solution to make it evenly dispersed, place it in the sample cell as required, and start measuring the particle size. The measurement results can be read from the instrument.

[0215] A second aspect of the present application further provides a method for preparing an isolation film, comprising the following steps:

[0216] (1) providing a substrate;

[0217] (2) forming a coating layer comprising acrylic polymer particles on at least one side of the substrate, wherein the acrylic polymer particles have an AFM adhesion force of 2nN to 3nN.

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

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

[0220] In some embodiments of the present application, the isolation film includes a substrate and a coating, and the coating is disposed on both surfaces of the substrate.

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

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

[0223] In some embodiments of the present application, in step (2-1), the coating slurry may further include other organic compounds, for example, a polymer to improve heat resistance, a dispersant, a wetting agent, and an emulsion-like adhesive. The other organic compounds are all non-granular in the dried coating.

[0224] In some embodiments of the present application, in step (2-1), the coating slurry may further include a second organic polymer particle, and the second organic polymer particle and the acrylic polymer particle together form the protrusions on the coating surface, and the second organic polymer particle includes polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinyl fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorine-containing olefin monomer units and vinyl monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylic monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylic monomer units, and at least one of the modified compound particles of the above homopolymers or copolymers.

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

[0226] In the embodiments of the present application, there is no special restriction on the model of the coating machine, and a commercially available coating machine can be used.

[0227] In some embodiments of the present application, in step (2-2), the coating may be performed by transfer coating, spin spray coating, dip coating, or the like; for example, the coating may be performed by transfer coating.

[0228] In some embodiments of the present application, the coater includes a gravure roller; the gravure roller is used to transfer the coating slurry to the substrate.

[0229] By controlling the above process parameters within the given ranges, the performance of the isolation membrane of the present 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 the present application provides a battery, which includes the isolation membrane of the first aspect or the isolation membrane obtained by the method of the second aspect.

[0231] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0232] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0233] In a battery, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0234] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0235] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. 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 the present application, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0237] As an example, when the positive electrode plate is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries 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 may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.

[0238] For example, when the positive electrode plate 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. For example, the positive electrode active material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

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

[0240] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where 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 polyanionic compound include:

[0244] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 including at least one of H, Li, Na, K or NH4, M 3 Contains at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu or Zn, X 1 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, and 0 < q ≤ 2;

[0247] Na s Mn t Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, and 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 [[ID=4,7]]each independently include at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, and 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 the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0251] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0252] In some embodiments of the present application, based on the total mass of the positive electrode active material layer, the binder accounts for 1% to 3% by mass in the positive electrode sheet, for example, 1.2% to 2.8%, 1.5% to 2.5%, 1.8% to 2.2%, 2% to 2.2%, etc. This can reduce the shedding of the positive electrode sheet, thereby improving the cycle performance of the battery containing the binder.

[0253] In a battery, the negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0254] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0255] In some embodiments of the present 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0256] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, or tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0257] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0258] In some embodiments of the present application, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0259] In some embodiments of the present application, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, and the binder, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0260] In some embodiments of the present application, based on the total mass of the negative electrode active material layer, the binder accounts for 1%-3% by mass in the negative electrode sheet, for example, 1.2%-2.8%, 1.5%-2.5%, 1.8%-2.2%, 2%-2.2%, etc. This can reduce the shedding of the negative electrode sheet, thereby improving the cycle performance of the battery containing the binder.

[0261] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0262] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0263] In some embodiments of the present 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, or lithium tetrafluorooxalatophosphate.

[0264] In some embodiments of the present application, when the battery is a sodium ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0265] In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone or diethyl sulfone.

[0266] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0267] The battery of the present application may include a battery cell form, a battery module form, and a battery pack form.

[0268] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0269] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0270] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0271] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG9 shows a battery cell 1 with a square structure as an example.

[0272] In some embodiments, referring to Figure 10, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0273] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0274] Figure 11 shows an example battery module 2. Referring to Figure 11 , within the battery module 2, multiple batteries 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple batteries 1 may be secured together using fasteners.

[0275] Optionally, the battery module 2 may further include a housing having a receiving space, and the plurality of batteries 1 are received in the receiving space.

[0276] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0277] Figures 12 and 13 illustrate 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 comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed 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, the present application also provides an electrical device, which includes the battery provided in the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0279] As the electrical device, a 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 electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0281] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0282] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0283] Preparation of the first organic polymer emulsion

[0284] Preparation Example A1

[0285] Weigh methyl acrylate (first substance), acrylic acid (second substance), acrylamide (third substance), acrylonitrile (fourth substance), and PEG-400 (fifth substance) (mass ratio of 1:0.1:0.03:0.05:0.05) and mix thoroughly. Add 1000g of the mixture, 30g of sodium lauryl sulfate (emulsifier), 10g of ammonium persulfate (initiator), and 1200g of deionized water to a 5000mL four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Emulsify at high speed for 30 minutes. Under nitrogen, heat to 75°C, react for 4 hours, cool to below 40°C, adjust the pH to neutral, and filter. This yields the first organic polymer emulsion A1.

[0286] Preparation Examples A2 to A21, Preparation Examples A2-A21, based on Preparation Example A1, adjusted the types of substances and mass ratios to obtain the first organic polymer emulsions A2-A21, see Table 1 for details.

[0287] Table 1

[0288] Preparation of the first organic polymer emulsion

[0289] Preparation Example B1

[0290] Weigh methyl acrylate (first substance), acrylic acid (second substance), acrylamide (third substance), acrylonitrile (fourth substance), PEG-400 (fifth substance), and adipic acid dihydrazide (sixth substance) in a mass ratio of 1:0.1:0.25:0.1:0.05:0.05). Mix thoroughly. Add 200 g of the mixture, 6 g of sodium lauryl sulfate (emulsifier), 2 g of ammonium persulfate (initiator), and 300 g of deionized water to a 1000 mL four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Emulsify at high speed for 30 minutes. Under nitrogen, heat to 75°C, react for 4 hours, cool to below 40°C, adjust the pH to neutral, and filter. This yields the second organic polymer emulsion B1.

[0291] Preparation Example B2 to Preparation Example B21, Preparation Example B2-B21, based on Preparation Example B1, the monomer types and mass ratios were adjusted to obtain the second organic polymer emulsion B2-B21, see Table 2 for details.

[0292] Table 2

[0293] Example 1

[0294] (1) Preparation of acrylic polymer particles

[0295] The first organic polymer emulsion A1 and the second organic polymer emulsion B2 were weighed according to a weight percentage of the first organic polymer and the second organic polymer of 1:1, stirred and mixed evenly, and then spray-dried to obtain acrylic polymer particles. The conditions of the spray-drying process were: an inlet air temperature of 110°C, an outlet air temperature of 50°C, and an air pressure of 0.5 kPa.

[0296] (2) Preparation of isolation membrane

[0297] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuo Gao Electronic Technology Co., Ltd.) was used as the base film. The acrylic polymer particles prepared above and the second organic polymer were stirred and mixed uniformly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed onto both surfaces of the base film and dried to remove the solvent. The coating density of the coating composition on the substrate was 1.5 g / m 2 , and obtain an isolation film.

[0298] (3) Preparation of positive electrode sheet

[0299] The positive electrode active material lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector aluminum foil. After drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained. The positive electrode surface density is 0.207 mg / mm 2 , compacted density is 3.5g / cm 3 .

[0300] (4) Preparation of negative electrode sheet

[0301] The negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) were mixed uniformly in a suitable amount of deionized water as a solvent at a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry. The negative electrode slurry was coated on the negative electrode current collector copper foil. After drying, cold pressing, slitting and cutting, the negative electrode sheet was obtained. The negative electrode surface density is 0.126 mg / mm 2 , compacted density is 1.7g / cm 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, and then LiPF6 is 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 sheet, separator, and negative electrode sheet are stacked in sequence, wound, and cold-pressed (during which the separator is bonded to the electrode sheet) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a secondary battery is obtained.

[0306] The preparation methods of the lithium-ion batteries of Examples 2 to 45 and Comparative Examples 1-4 are the same as those of 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 1-4, as shown in Table 3 for details.

[0307] Table 3

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

[0309] Performance Testing

[0310] (1) Glass transition temperature test

[0311] 6 ± 0.05 mg of sample was weighed into an Al crucible, shaken flat, and covered with a lid. The crucible was tested using a Netzsch DSC 3500 Sirius measuring instrument. The atmosphere was nitrogen, the purge gas rate was 50 mL / min, and the shielding gas rate was 100 mL / min. The heating conditions were: a heating rate of 10°C / min, and a temperature range of -70 to 200°C.

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

[0313] See previous article.

[0314] (3) Cold press bonding performance test of isolation film

[0315] The testing process is as follows:

[0316] 1. Select the prepared separator with a length of 300 mm and a width of 100 mm, and the positive electrode sheet and negative electrode sheet prepared above.

[0317] 2. Wrap the isolation film with paper and use a die cutter and punch to cut into 54.2mm*72.5mm samples.

[0318] 3. Stack the punched separator sample and the positive electrode or negative electrode neatly, with the separator facing upwards. Place 130mm*130mm Teflon pads on the top and bottom. Place the stacked sample in the middle of the cardboard and cover it with a 150mm*160mm cardboard.

[0319] 4. Place the folded sample into the flat press and adjust the pressure. Adjust the air pressure to 850Kg±10KG (equivalent to about 2.24MPa), set T=25℃, set the time to 15s, and perform cold pressing.

[0320] 5. Use a die cutter and a punch to cut the cold-pressed sample into small strips of 72.5mm*15mm.

[0321] 6. Secure one side of the electrode to the steel plate with double-sided tape. Adhere the isolating film to the other side. Use double-sided tape to attach a 15mm wide A4 paper strip to the isolating film to complete the test sample. During testing, hold the steel plate holding the electrode in place while the tensile testing machine pulls the A4 paper strip upward to separate the isolating film from the electrode.

[0322] 7. Turn on the high-speed rail tensile testing machine and set it to: adhesion test, speed 50mm / min, and starting 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 clamps respectively.

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

[0325] 10. Each group of test samples should be measured on at least 5 samples. If the adhesion test curves of the 5 test samples have good repeatability, then proceed to the next group of tests. Otherwise, it is necessary to test again until the repeatability of the 5 test samples is good.

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

[0327] (4) Battery cycle performance test steps

[0328] At 60 ° C, the prepared battery was charged at a constant current of 1C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left for 5 minutes, and then discharged at 1C to 2.5V. The obtained discharge capacity was recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C of the battery after the nth cycle. 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: It can be seen from Table 4 that the AFM adhesion force of the acrylic polymer particles of Examples 1-45 is 2nN-3nN, the AFM adhesion force of the acrylic polymer particles of Comparative Example 1 is 1.8nN, the AFM adhesion force of the acrylic polymer particles of Comparative Example 1 is 1.3nN, the AFM adhesion force of the acrylic polymer particles of Comparative Example 1 is 3.5nN, and the AFM adhesion force of the acrylic polymer particles of Comparative Example 1 is 0.9nN. The cold pressing adhesion force between the isolation membrane and the negative electrode plate and the capacity retention rate of the battery of Examples 1-45 are higher than those of Comparative Examples 1-4, which shows that when the acrylic polymer particles with an AFM adhesion force of 2nN-3nN of the present application are used for the isolation membrane, cold pressing bonding between the isolation membrane and the electrode can be achieved, and the adhesion force is appropriate, thereby improving the cycle performance of the battery.

[0331] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A separator, wherein: include: substrate; A coating is formed on at least one side of the substrate, the coating comprising acrylic polymer particles, and the acrylic polymer particles have an AFM adhesion force of 2nN-3nN.

2. The isolation film according to claim 1, wherein The acrylic polymer particles have an AFM Young's modulus of 30 MPa-70 MPa.

3. The separator according to claim 1 or 2, wherein: The acrylic polymer particles have an AFM Young's modulus of 40 MPa-60 MPa.

4. The isolation film according to any one of claims 1 to 3, wherein The acrylic polymer particles form protrusions on the surface of the coating. The isolation film according to claim 4 , wherein: The double-sided height of the protrusion is 2 μm-100 μm.

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

7. The isolation film according to any one of claims 1 to 6, wherein: The acrylic polymer particles include a first organic polymer and a second organic polymer, wherein the polymeric substance of the first organic polymer includes a first substance, a second substance, a third substance, a fourth substance, and a fifth substance, and the polymeric substance of the second organic polymer includes 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 includes: wherein R1 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, and R2 comprises an alkyl group of 1 to 18 carbon atoms; The structure of the second substance includes: wherein R3 comprises a hydrogen atom, a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms; The structure of the third substance includes: wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms; The structure of the fourth substance includes: wherein R6 comprises a hydrogen atom or an alkyl group of 1 to 8 carbon atoms; The structure of the fifth substance includes: Wherein, n=3-10; The structure of the sixth substance includes: Wherein, m=1-10. The isolation 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 according to claim 7 or 8, wherein: In the polymer 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 isolation film according to any one of claims 7 to 9, wherein: In the polymer substance 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 isolation film according to any one of claims 7 to 10, wherein: In the polymer substance 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 isolation film according to any one of claims 7 to 11, wherein: In the polymer substance 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 isolation film according to any one of claims 7 to 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 isolation film according to any one of claims 7 to 13, wherein: The second substance includes at least one of acrylic acid, methacrylic acid, crotonic acid, or heptenoic acid.

15. The isolation film according to any one of claims 7 to 14, wherein: The third substance includes at least one of acrylamide, N-hydroxymethyl acrylamide or N-butoxymethyl acrylamide.

16. The isolation film according to any one of claims 7 to 15, wherein: The fourth substance includes at least one of acrylonitrile, methacrylonitrile or ethacrylonitrile.

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

18. The isolation film according to any one of claims 7 to 17, wherein: The sixth substance includes at least one of malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide or sebacic acid dihydrazide.

19. The isolation film according to any one of claims 1 to 18, wherein: The acrylic 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 isolation film according to any one of claims 1 to 19, wherein The acrylic polymer particles have a first glass transition temperature and a second glass transition temperature, wherein the first glass transition temperature is in the range of -80°C to 25°C, and the second glass transition temperature is in the range of 26°C to 100°C.

21. The isolation film according to any one of claims 4 to 20, wherein: The coating also includes a second organic polymer particle, which includes polytetrafluoroethylene particles, polychlorotrifluoroethylene particles, polyvinyl fluoride particles, polyvinylidene fluoride particles, polyethylene particles, polypropylene particles, polyacrylonitrile particles, polyethylene oxide particles, copolymer particles of fluorine-containing olefin monomer units and vinyl monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylic acid monomer units, copolymer particles of fluorine-containing olefin monomer units and acrylate monomer units, and at least one of the modified compound particles of the above homopolymers or copolymers. The second organic polymer particles and the acrylate polymer particles form the protrusions on the surface of the coating.

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

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

24. A method for preparing an isolation membrane, wherein: include: providing a substrate; A coating is formed on at least one side of the substrate, wherein the coating comprises acrylic polymer particles, and the acrylic polymer particles have an AFM adhesion force of 2nN-3nN.

25. A battery, wherein: The isolation film comprises the isolation film according to any one of claims 1 to 23 or the isolation film obtained by the method according to claim 24.

26. An electrical device, wherein: Including the battery of claim 25.

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