A separator coating material rapidly bonded with pole pieces, and a preparation method and application thereof

Abstract

The application provides a separator coating material for rapid adhesion of pole pieces and a preparation method and application thereof, and belongs to the technical field of film preparation. The film comprises modified PVDF 1-20 parts, acrylonitrile multi-copolymer 1-15 parts, dispersant 1-5 parts, water-based polymer binder 2-10 parts, wetting agent 0.1-1 part and deionized water 55-185 parts by mass. The preparation method comprises the following steps: uniformly mixing the acrylonitrile multi-copolymer, the dispersant, the deionized water and the modified PVDF, grinding, heating while stirring, then adding the water-based polymer binder, continuously heating and stirring, adding the wetting agent after the temperature is reduced to room temperature, and obtaining the coating material. The coating material can be used for surface coating of a polyolefin-based film or a coated film. The application coats the pretreated PVDF with the water-based polymer binder, optimizes the expansion rate and the adhesion strength, realizes rapid adhesion, can be used for rapid production of laminated batteries, greatly improves the battery production efficiency and the qualified rate, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of thin film preparation technology, and in particular to a diaphragm coating material that can be rapidly bonded to electrodes, its preparation method, and its application. Background Technology

[0002] With the widespread adoption of electronic devices and the rise of the electric vehicle market, the demand and performance requirements for lithium-ion batteries are constantly increasing. The separator in a lithium-ion battery is crucial; it separates the positive and negative electrodes, prevents short circuits, and provides pathways for lithium-ion migration. Its performance affects the battery's charge-discharge performance, cycle life, and safety. A high-quality separator ensures interface stability, low internal resistance, and the ability to close micropores during abnormal temperature rises to prevent thermal runaway, which is key to the efficient and safe operation of lithium batteries.

[0003] Lithium-ion batteries are mainly manufactured using two methods: wound and stacked. Wound batteries offer advantages such as mature technology, high production efficiency, regular shape for easy installation, relatively low equipment cost, and strong product consistency. However, their energy density is limited, internal structural stability is poor, they are prone to wavy deformation at corners, have poor heat dissipation, and are unsuitable for irregularly shaped batteries. Stacked batteries, on the other hand, have high energy density, stable internal structure, long cycle life, are suitable for large-size and irregularly shaped batteries, and have good charge-discharge performance. However, their production efficiency is lower, equipment investment is large, the process is more complex, requiring high precision in equipment and skilled operators, and the yield rate is lower. In the production of stacked batteries, the separator and electrodes need to be precisely and firmly bonded together. With the continuous improvement of stacked battery processing technology and the increasing production speed, higher requirements are placed on the bonding strength and speed between the battery separator and electrodes.

[0004] Currently, the mainstream coating technologies for lithium-ion battery separators can be divided into three major systems: inorganic coating, organic coating, and composite coating. Inorganic coatings primarily utilize inorganic ceramic materials such as alumina and boehmite (e.g., CN118712657B). By constructing a high-temperature resistant protective layer, they significantly improve the separator's thermal stability and puncture resistance. While enhancing battery safety, their unique microporous labyrinth structure effectively extends the lithium-ion migration path, thereby reducing the battery's self-discharge rate. Organic coating systems are represented by polymer materials such as polyvinylidene fluoride (PVDF) (e.g., CN202310349038.9), polymethyl methacrylate (PMMA) (e.g., CN202411169892.8), and aramid fibers. These coatings significantly enhance the interfacial adhesion between the separator and the electrode sheets, which is beneficial for improving battery cycle life. However, due to limitations of traditional processes, the aforementioned organic materials can only achieve effective bonding at the interface under high temperature and high pressure conditions, which cannot meet the process requirements of rapid bonding. This leads to the phenomenon of relative displacement between the electrode and the separator during the production of stacked batteries. This technical bottleneck seriously restricts the production efficiency of the stacking process.

[0005] While some companies in the market have attempted to improve the battery by increasing the proportion of adhesive in the coating or adding other types of adhesives, there is a lack of targeted development for rapid bonding between the battery separator and the electrode. Increasing the amount of adhesive has minimal effect and can actually lead to a loss of separator permeability, increasing battery internal resistance and consequently affecting battery energy density, which is detrimental to the rate discharge and cycle performance of lithium-ion batteries.

[0006] In summary, the main defects of the existing technology include: 1) slow bonding speed and low bonding ability, which cannot meet the high-speed production requirements of stacked batteries; 2) excessive adhesive in order to ensure bonding, which leads to a decrease in the permeability of the separator; 3) lack of design adaptability to negative electrode materials, and the interface is prone to failure due to volume expansion.

[0007] In view of the above, this application is hereby submitted. Summary of the Invention

[0008] The purpose of this invention is to provide a separator coating material that can be rapidly bonded to the electrode, its preparation method and application. By coating pretreated PVDF with an aqueous polymer binder, the expansion rate and bonding strength are optimized to achieve rapid bonding. This material can be used for the rapid production of stacked batteries, which greatly improves battery production efficiency and yield, and has broad application prospects.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a diaphragm coating material for rapid adhesion to electrode sheets: by weight, it comprises 1-20 parts of modified PVDF, 1-15 parts of acrylonitrile multi-polymer copolymer, 1-5 parts of dispersant, 2-10 parts of waterborne polymer binder, 0.1-1 parts of wetting agent, and 55-185 parts of deionized water.

[0011] Secondly, the present invention also provides a method for preparing the diaphragm coating material that rapidly adheres to the electrode sheet, wherein acrylonitrile multi-component copolymer, dispersant, deionized water and modified PVDF are mixed evenly according to the stated mass parts and then ground. The obtained modified PVDF dispersion is heated while stirring, and then an aqueous polymer binder is added. The heating and stirring are continued to effectively knead and coat the PVDF. After cooling to room temperature, a wetting agent is added to obtain the coating material.

[0012] Optionally, the acrylonitrile multi-component copolymer includes one or more of acrylonitrile-acrylamide-acrylate copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, or acrylonitrile-methacrylate copolymer.

[0013] Optionally, the dispersant includes one or more of the following: nonionic dispersant, fluorinated aqueous dispersant, polyurethane dispersant, or polyester dispersant.

[0014] Optionally, the aqueous polymer binder includes one or more of PAA (polyacrylic acid), PMMA (polymethyl methacrylate), PAM (polyacrylamide), SBR (styrene-butadiene rubber), and WPU (waterborne polyurethane). This aqueous polymer binder exhibits high bonding strength, a certain degree of toughness, and a relatively fast curing speed, enabling effective coating of PVDF. It allows for rapid bonding of the separator and electrode while providing high bonding strength, resulting in a tight fit between the separator and the electrode. This improves the production speed and yield of stacked batteries, significantly reducing manufacturing costs.

[0015] Optionally, the wetting agent includes one or more of the following: organosilicon-modified wetting agents, polyether wetting agents, alkynyl alcohol wetting agents, or alcohol wetting agents.

[0016] PVDF, as a traditional binder, is the most widely used binder in the manufacture of positive electrodes for commercial lithium-ion batteries. PVDF possesses excellent electrochemical stability, mechanical properties, processability, and the oxidation and corrosion resistance of its high-energy CF bonds. Within lithium-ion batteries, PVDF provides tight adhesion between the electrode and separator, and facilitates ion transport. While PVDF itself does not conduct lithium ions, it expands with electrolyte absorption to facilitate ion transport; however, this expansion reduces its adhesive properties. Using an aqueous polymer binder to effectively coat PVDF allows for optimal expansion at a specific coating ratio. The aqueous polymer binder provides initial adhesion to the positive and negative electrodes of the lithium-ion battery, ensuring that the electrodes and separator do not shift during battery production. After hot pressing, it adheres tightly to the separator and electrodes together with the PVDF. This excellent adhesion reduces internal voids in the battery, improving energy density and cycle life.

[0017] Preferably, the modified PVDF is obtained by soaking PVDF in an alkaline solution at a certain temperature and then washing it with deionized water.

[0018] Furthermore, the concentration of the alkaline solution is 1-6 mol / L.

[0019] Furthermore, the soaking temperature is 25-80℃, and the soaking time is 5-30 minutes. Preferably, the soaking temperature is 45-80℃.

[0020] It can be inferred that treatment with an alkaline solution at the stated temperature triggers the dehydrofluorination (HDF) reaction of the PVDF molecular chains, forming a carbon-carbon double bond structure. This process partially disrupts the original fluorocarbon bond network, resulting in conjugated double bonds and some oxygen-containing groups on the material surface. This increases the surface polarity of the material, leading to better and more uniform dispersion in water, smaller particle size, and increased chemical activity. It also enhances the material's ability to subsequently bind with different polymer materials, improves the coating effect, and makes it suitable for various coating processes.

[0021] Optionally, the alkaline solution includes one or more of the following: sodium hydroxide, potassium hydroxide, ammonia, barium hydroxide, sodium bicarbonate, ammonium bicarbonate, ammonium carbonate, or an aqueous solution of sodium carbonate.

[0022] Furthermore, the heating and continued heating temperatures are both 40-80°C.

[0023] Preferably, the heating temperature is 65-80℃; the further heating temperature is 50-65℃.

[0024] Further, preferably, the mass ratio of the modified PVDF to the waterborne polymer binder is 6:1-2:1; preferably, the mass ratio of the modified PVDF to the waterborne polymer binder is 4:1-3:1.

[0025] Thirdly, the present invention also provides a lithium-ion battery separator, the separator comprising a polyolefin-based film or a coated film, wherein at least one side of the separator is coated with the coating material or the coating material prepared by the preparation method described above.

[0026] Optionally, the coating can be one of micro-grooving roller coating, spin-jet coating or dot matrix coating, with a single-sided coating thickness of 0.5-5 μm, and after drying, a lithium-ion battery separator with a coating that can be quickly bonded to the electrode sheet is obtained.

[0027] Compared with existing technologies, this invention uses a water-based polymer binder to coat PVDF, which solves the contradiction between expansion rate and bonding strength. While meeting the bonding strength with the electrode material, it also improves the bonding speed, achieving rapid bonding with the battery electrode. It can firmly bond with the battery electrode in a short time, greatly improving battery production efficiency, adapting to the needs of modern rapid battery production, reducing bonding time and processes in the stacking equipment production, and significantly saving battery manufacturing costs.

[0028] The product of this invention has high adaptability, enabling rapid bonding not only to battery positive electrode materials but also to battery negative electrode materials. It is well known that battery positive electrode materials have higher surface energy and activity, making rapid bonding easier, while negative electrode materials have smoother surfaces, making bonding more difficult. Furthermore, during battery charging and discharging, the volume change of negative electrode materials is relatively large, with expansion and contraction during lithium insertion and extraction, which can easily damage the bonding interface. This invention uses a water-based polymer binder to coat pretreated PVDF, solving the problems of slow and weak bonding between the separator and the negative electrode.

[0029] Meanwhile, the water-based coating method results in low raw material and equipment costs, is environmentally friendly and safe, avoids clogging of membrane gaps, and has a fast drying speed, making it suitable for industrial production. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The coating materials prepared in Examples 1-5 and Comparative Examples 1-2 of this invention are used to compare the peel strength with that of the negative electrode material after hot pressing;

[0032] Figure 2 The coating materials prepared in Examples 1-5 and Comparative Examples 1-2 of this invention are used to compare the peel strength with that of the positive electrode material after hot pressing. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] As used in this article:

[0035] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0036] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0037] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0038] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0039] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0040] The test methods for hot-press peel strength in the following examples and comparative examples are as follows:

[0041] (1) Cut the positive and negative plates into strips of fixed width (20*200mm), place the strips on an electric roller press and compact them twice to make plate samples for later use.

[0042] (2) Cut the coated film sample into strips (30*200mm) that are slightly wider than the electrode sample.

[0043] (3) Place the prepared electrode sample flat on the cut membrane sample in the center, and then place both on the hot pressing machine. Hot pressing machine settings: hot pressing temperature 80℃, pressure 1Mpa, hot pressing time 5s. Start the equipment to prepare the sample, and remove the sample after hot pressing is completed.

[0044] (4) Replace the peel strength test fixture on the testing machine and adjust the fixture so that the distance between the fixtures (the lower edge of the upper fixture and the upper edge of the lower fixture) is 30mm. Fix the hot-pressed sample to be tested on the fixture. One end of the fixture clamps the electrode plate and the other end clamps the coated film sample. Tighten the fixture to fix the sample.

[0045] (5) Clear all force and displacement values ​​to zero, click the start button to start the test, test stroke 100mm, after the test, measure the average peel force of the test stroke, and finally obtain the peel strength of the hot-pressed sample under the specified hot-pressing conditions (80℃, 1Mpa, 5s) = peel force / electrode width, unit N / m.

[0046] Hot-press peel strength is greatly affected by the initial hot-pressing conditions. Under constant hot-pressing temperature and pressure, the shorter the hot-pressing time, the lower the hot-press peel strength. Higher hot-press peel strength indicates stronger adhesion between the coating and the electrode.

[0047] Example 1

[0048] (1) PVDF was soaked in 2 mol / L NaOH aqueous solution at 60℃ for 15 min, and then washed with deionized water to obtain modified PVDF.

[0049] (2) 10g of acrylonitrile-acrylamide-ammonium acrylate copolymer and 2g of fluorinated water-based dispersant hexafluorobutyl acrylate were added to 163g of deionized water to form an aqueous solution. Then, 20g of modified PVDF was added and stirred rapidly for 90min. After mixing evenly, the mixture was ground using a sand mill to obtain a uniform modified PVDF dispersion. The dispersion was then heated to 70℃ and stirred slowly for 2h. Then, 5g of water-based PMMA binder was added and the mixture was heated and stirred at 70℃ for 1h to effectively coat the modified PVDF. After cooling to room temperature, 0.2g of wetting agent polyether modified siloxane was added and mixed evenly to obtain the coating slurry.

[0050] (3) The prepared coating slurry was coated onto both sides of the polyolefin-based film using a spin-jet coating machine. The coating thickness on one side was 2 μm. After drying, sample 1 was obtained. The performance test results are shown in Table 1. The peel strength of the positive and negative electrodes is compared. Figure 1 and Figure 2 .

[0051] Example 2

[0052] (1) PVDF was soaked in 2 mol / L NaOH aqueous solution at 60℃ for 15 min, and then washed with deionized water to obtain modified PVDF.

[0053] (2) 10g of acrylonitrile-acrylamide-ammonium acrylate copolymer and 2g of fluorinated water-based dispersant hexafluorobutyl acrylate were added to 163g of deionized water to form an aqueous solution. Then, 20g of modified PVDF was added and stirred rapidly for 90min. After mixing evenly, the mixture was ground using a sand mill to obtain a uniform modified PVDF dispersion. The dispersion was then heated to 70℃ and stirred slowly for 2h. Then, 5g of water-based SBR binder was added and the mixture was heated and stirred at 55℃ for 1h to effectively coat the modified PVDF. After cooling to room temperature, 0.2g of wetting agent polyether modified siloxane was added and mixed evenly to obtain the coating slurry.

[0054] (3) The prepared coating slurry was coated onto both sides of the polyolefin-based film using a spin-jet coating machine. The coating thickness on one side was 2 μm. After drying, sample 2 was obtained. The performance test results are shown in Table 1. The peel strength of the positive and negative electrodes is compared. Figure 1 and Figure 2 .

[0055] Example 3

[0056] (1) PVDF was soaked in 2 mol / L NaOH aqueous solution at 60℃ for 15 min, and then washed with deionized water to obtain modified PVDF.

[0057] (2) 10g of acrylonitrile-acrylamide-ammonium acrylate copolymer and 3g of nonionic dispersant polyethylene glycol were added to 162g of deionized water to form an aqueous solution. Then, 20g of modified PVDF was added and stirred rapidly for 90min. After mixing evenly, the mixture was ground with a sand mill to obtain a uniform modified PVDF dispersion. The dispersion was then heated to 70℃ and stirred slowly for 2h. Then, 5g of water-based PAA binder was added and the mixture was heated and stirred at 70℃ for 1h to effectively coat the modified PVDF. After cooling to room temperature, 0.2g of wetting agent polyether modified siloxane was added and mixed evenly to obtain the coating slurry.

[0058] (3) The prepared coating slurry was coated onto both sides of the polyolefin-based film using a spin-jet coating machine. The coating thickness on one side was 2 μm. After drying, sample 3 was obtained. The performance test results are shown in Table 1. The peel strength of the positive and negative electrodes is compared. Figure 1 and Figure 2 .

[0059] Example 4

[0060] (1) PVDF was soaked in 2 mol / L NaOH aqueous solution at 60℃ for 15 min, and then washed with deionized water to obtain modified PVDF.

[0061] (2) 10g of acrylonitrile-butadiene copolymer and 3g of nonionic dispersant polyacrylate were added to 162g of deionized water to form an aqueous solution. Then, 20g of modified PVDF was added and stirred rapidly for 90min. After mixing evenly, the mixture was ground with a sand mill to obtain a uniform modified PVDF dispersion. The dispersion was then heated to 70℃ and stirred slowly for 2h. Then, 5g of water-based PAM binder was added and the mixture was heated and stirred at 55℃ for 1h to effectively coat the modified PVDF. After cooling to room temperature, 0.2g of wetting agent polyether modified siloxane was added and mixed evenly to obtain the coating slurry.

[0062] (3) The prepared coating slurry was coated onto both sides of the polyolefin-based film using a spin-jet coating machine. The coating thickness on one side was 2 μm. After drying, sample 4 was obtained. The performance test results are shown in Table 1. The peel strength of the positive and negative electrodes is compared. Figure 1 and Figure 2 .

[0063] Example 5

[0064] (1) PVDF was soaked in 2 mol / L NaOH aqueous solution at 60℃ for 15 min, and then washed with deionized water to obtain modified PVDF.

[0065] (2) 10g of acrylonitrile-methacrylate copolymer and 1.5g of nonionic dispersant polyacrylate were added to 168g of deionized water to form an aqueous solution. Then, 14g of modified PVDF was added and stirred rapidly for 90min. After mixing evenly, the mixture was ground with a sand mill to obtain a uniform modified PVDF dispersion. The dispersion was then heated to 70℃ and stirred slowly for 2h. Then, 6g of water-based WPU binder was added and the mixture was heated and stirred at 70℃ for 1h to effectively coat the modified PVDF. After cooling to room temperature, 0.2g of wetting agent polyether modified siloxane was added and mixed evenly to obtain the coating slurry.

[0066] (3) The prepared coating slurry was coated onto both sides of the polyolefin-based film using a spin-jet coating machine. The coating thickness on one side was 2 μm. After drying, sample 5 was obtained. The performance test results are shown in Table 1. The peel strength of the positive and negative electrodes is compared. Figure 1 and Figure 2 .

[0067] Comparative Example 1

[0068] The difference from Example 2 is that the PVDF in step (1) was soaked in a 2 mol / L NaOH aqueous solution at 30°C.

[0069] Comparative Example 2

[0070] The difference from Example 2 is that the PVDF was not modified in step (1).

[0071] Table 1. Performance test results of the coated diaphragms in the examples and comparative examples.

[0072]

[0073] Through Table 1 and Figure 1 , 2 It can be seen that, compared with Comparative Examples 1 and 2, the coating materials prepared by modifying PVDF and coating it with water-based polymer binders in Examples 1-5 have much better hot-press peel strength for both positive and negative electrodes than those without PVDF modification or with too low a immersion temperature.

[0074] Depend on Figure 1 and 2 It is known that the hot pressing time of this application can be shortened to 5 seconds, which is much shorter than the conventional hot pressing time of 1-3 minutes in the current market, demonstrating the rapid bonding capability of the product of this invention.

[0075] As can be seen from Examples 2 and 4, the effect is better when the temperature during heating and stirring of the modified PVDF dispersion is slightly lower than that of the aqueous polymer binder.

[0076] Meanwhile, as shown in Table 1, the coating amount of the separator using the present invention is generally 10-20% lower than that of the comparative example, while maintaining the same coating thickness, it can bring stronger adhesion between the positive and negative electrodes, and can maintain relatively high adhesion strength for both the positive and negative electrodes. It is compatible with various thermal bonding and fast bonding battery devices, has no adhesion shortcomings, and fully releases the battery production rate.

[0077] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0078] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a diaphragm coating material that rapidly bonds to an electrode, characterized in that, According to the mass parts, 1-15 parts of acrylonitrile multi-component copolymer, 1-5 parts of dispersant, 55-185 parts of deionized water and 1-20 parts of modified PVDF are mixed evenly, ground, and heated while stirring. Then, 2-10 parts of water-based polymer binder are added, and heating and stirring are continued. After cooling to room temperature, 0.1-1 parts of wetting agent are added to obtain the coating material. The modified PVDF is obtained by soaking PVDF in an alkaline solution at 25-80℃ and then washing it with deionized water. The heating and further heating temperatures are both 40-80℃.

2. The preparation method according to claim 1, characterized in that, The acrylonitrile multi-component copolymer includes one or more of acrylonitrile-acrylamide-acrylate copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, or acrylonitrile-methacrylate copolymer; And / or, the dispersant includes one or more of the following: nonionic dispersants, fluorinated aqueous dispersants, polyurethane dispersants, or polyester dispersants; And / or, the waterborne polymer binder includes one or more of polyacrylic acid, polymethyl methacrylate, polyacrylamide, styrene-butadiene rubber, and waterborne polyurethane; The wetting agent includes one or more of the following: organosilicon-modified wetting agents, polyether wetting agents, alkynyl alcohol wetting agents, or alcohol wetting agents.

3. The preparation method according to claim 1, characterized in that, The concentration of the alkaline solution is 1-6 mol / L; And / or, the soaking time is 5-30 minutes.

4. The preparation method according to claim 1 or 3, characterized in that, The alkaline solution includes one or more of the following: sodium hydroxide, potassium hydroxide, ammonia, barium hydroxide, sodium bicarbonate, ammonium bicarbonate, ammonium carbonate, or sodium carbonate aqueous solution.

5. The preparation method according to claim 1, characterized in that, The heating temperature is 65-80℃; And / or, the temperature for further heating is 50-65°C.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the modified PVDF to the waterborne polymer binder is 6:1-2:

1.

7. A lithium-ion battery separator, characterized in that, The diaphragm comprises a polyolefin-based membrane or a coated film, and at least one side of the diaphragm is coated with a coating material prepared by the preparation method according to any one of claims 1-6.

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