A polyvinyl diaphragm coated with a porphyrin molecular self-polymer and a ceramic material and a preparation method and application thereof

Abstract

This invention relates to the field of lithium-ion batteries, specifically to a polyethylene separator co-coated with a porphyrin self-polymer and a ceramic material. The separator comprises a polyethylene base film with a thickness of 7-10 μm, a 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer with a thickness of 0.1-1 μm, and an alumina ceramic layer with a thickness of 1-5 μm. In the porphyrin self-polymer, the methoxycarbonyl polar groups bind to neighboring molecules through dipole-dipole interactions and hydrogen bonds, enhancing the inter-chain bonding force and mitigating deformation caused by localized stress concentration. Simultaneously, the rigid planar structure of the porphyrin macrocycle forms an ordered layered arrangement through π-π stacking, suppressing free rotation and vibration of the molecular chains and reducing thermal damage to the material structure. Combined with the ceramic layer as a rigid framework, multi-level synergistic support is achieved, significantly improving the thermal stability and mechanical strength of the separator. This invention also discloses the preparation method and application of this separator.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to a polyethylene separator coated with porphyrin self-polymer and ceramic material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, and stable cycling, leading to their widespread application in electronic devices, new energy vehicles, and satellites. However, currently available lithium-ion batteries still suffer from poor thermal stability, and their safety remains a significant challenge. The separator is a core component of the battery, its function being to facilitate rapid lithium-ion migration through its porous structure while simultaneously isolating the positive and negative electrodes to prevent short circuits. Therefore, the performance and safety of the separator are crucial factors in ensuring the efficient, safe, and stable operation of lithium-ion batteries. Polyolefins are widely recognized as the industry benchmark for lithium-ion battery separator materials due to their ease of processing and low cost. However, the poor thermal stability, low porosity, and insufficient wettability of polyolefin separators remain significant drawbacks, severely impacting battery stability and efficiency.

[0003] To overcome the shortcomings of polyolefin membrane materials, the industry mainly focuses on exploring polyolefin modification technologies. Currently, technologies to improve the thermal stability of polyolefin membranes primarily include inorganic particle coating, organic modification, and composite material modification. While modification with inorganic materials, organic polymers, and composite materials can improve the thermal stability of polyolefin membranes to some extent, some problems and defects remain. For example, the large difference between inorganic particle coatings and the polyolefin substrate surface results in weak interfacial bonding, leading to coating peeling and pore blockage during long-term operation, causing a decline in electrochemical performance. Furthermore, inorganic particles are prone to agglomeration, affecting the uniformity of the modified coating. Organic modification technology relies on deposition, but the lack of chemical bonds between the organic material and the polyolefin substrate can cause interfacial separation at high temperatures. Currently, the industry still lacks organic coating modification technologies with high adhesion or the ability to form strong covalent bonds. This problem directly leads to the inability of organically modified separators to meet the long-term reliability requirements of high-capacity, high-rate batteries. The seemingly improved wettability or thermal stability at room temperature will gradually worsen under high temperature or long-term cycling conditions due to the gradual separation of the interface between the organic coating and the polyolefin substrate. This can result in decreased membrane porosity and reduced ionic conductivity, or even cause the tiny particles formed by coating peeling to clog electrode pores and potentially lead to internal short circuits and other safety hazards.

[0004] Therefore, there is an urgent need to develop an organic-inorganic composite coating technology that can form strong covalent bonds on the surface of polyolefin substrates and has excellent thermal stability. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a polyethylene separator co-coated with a porphyrin self-polymer and a ceramic material. In this separator, the methoxycarbonyl group of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin molecule synergistically enhances the mechanical strength and thermal stability of the separator, and forms a multi-level synergy with the alumina ceramic layer, further strengthening the thermal stability of the separator.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a polyethylene separator co-coated with a porphyrin self-polymer and a ceramic material, comprising a polyethylene base film with a thickness of 7-12 μm, a 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer with a thickness of 0.1-1 μm, and an alumina ceramic layer with a thickness of 1-5 μm.

[0007] Preferably, the porosity of the polyethylene-based film is 35% to 55%.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned diaphragm, the method comprising the following steps: coating a 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin solution onto the surface of a pretreated polyethylene membrane, and crosslinking it in a vacuum environment at 70~80°C for 20~26 h; coating an alumina ceramic slurry onto the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer and placing it in a vacuum drying oven, raising the temperature to 70~80°C, and drying for 20~26 h to obtain the diaphragm.

[0009] Preferably, the above method further includes the following steps: placing the polyethylene film in a mixed solution of ethanol and deionized water, ultrasonically cleaning it for 30-60 minutes, and then vacuum drying it in a vacuum drying oven at 70-80°C for 5-10 hours to obtain a pretreated polyethylene film.

[0010] More preferably, the volume ratio of ethanol to deionized water is 1:1 to 1.5.

[0011] Preferably, the 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin solution is prepared by dissolving the 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer in 1,2-dichloroethane, followed by adding dimethoxymethane and AlCl3 and dispersing to obtain the solution.

[0012] More preferably, the mass ratio of 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin, 1,2-dichloroethane, dimethoxymethane, and AlCl3 is 0.5~2:10~20:0.25~1.

[0013] Preferably, the alumina ceramic slurry is prepared by dispersing Al2O3 powder in deionized water, adding ammonium polyacrylate dispersant and polyvinylidene fluoride binder, and mixing evenly to obtain the ceramic slurry.

[0014] More preferably, the mass ratio of Al2O3 powder, deionized water, ammonium polyacrylate and polyvinylidene fluoride is 1~5:100~200:0.01~0.05:0.01~0.05.

[0015] More preferably, the particle size of the Al2O3 powder is 80~120nm.

[0016] Meanwhile, the present invention also discloses the application of the above-mentioned separator in lithium-ion batteries.

[0017] Beneficial effects:

[0018] In methoxycarbonylphenyl porphyrin self-polymers, the polar methoxycarbonyl group can form dipole-dipole interactions and hydrogen bonds with neighboring molecules, increasing the bonding force between molecular chains and reducing deformation caused by local stress concentration. Simultaneously, the rigid planar structure of the porphyrin macrocycle forms a tightly ordered layered arrangement through π-π stacking, restricting the free rotation and vibration of the molecular chains and reducing the damage to the material structure caused by thermal motion. Combined with a ceramic layer as a rigid framework, this achieves multi-level synergistic support, significantly improving the thermal stability and mechanical strength of the membrane. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0020] Figure 1 This is a schematic diagram illustrating the preparation of a polyethylene diaphragm co-coated with porphyrin self-polymer and ceramic material. Detailed Implementation

[0021] To better illustrate the purpose, technical solution, and advantages of this invention, the following will further explain the invention in conjunction with specific experiments. It should be noted that in this invention, unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0022] Example 1: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material.

[0023] Step 1: Take a polyethylene film (7μm thick, 40% porosity), cut it to 100mm×100mm, place it in a 1:1 mixture of ethanol and deionized water, ultrasonically clean it for 30min, and then vacuum dry it in a vacuum drying oven at 80℃ for 5h to obtain a pretreated polyethylene film.

[0024] Step 2: Add 1g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 10mL of anhydrous 1,2-dichloroethane. After dissolving, add 0.3g of dimethoxymethane and 0.5g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0025] Step 3: The methoxycarbonylphenyl porphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum environment at 75°C and kept at that temperature for 24 hours for crosslinking. The thickness of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer is 1 μm.

[0026] Step 4: Take 1g of Al2O3 powder (particle size 80~120nm), add it to 100mL of deionized water, then add 0.01g of ammonium polyacrylate and 0.01g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0027] Step 5: The Al2O3 ceramic slurry was coated onto a 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin polymer layer and placed in a vacuum drying oven at 70°C for 26 hours to cure, yielding a polyethylene membrane co-coated with porphyrin self-polymer and ceramic material; the thickness of the Al2O3 ceramic layer was 2 μm. The preparation process is described in [reference needed]. Figure 1 .

[0028] Example 2: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material.

[0029] Step 1: Take a polyethylene film (thickness 9μm, porosity 35%), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.5, ultrasonically clean it for 60min, and then vacuum dry it in a vacuum drying oven at 70℃ for 10h to obtain a pretreated polyethylene film.

[0030] Step 2: Add 3g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 30mL of anhydrous 1,2-dichloroethane. After dissolving, add 0.8g of dimethoxymethane and 0.25g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0031] Step 3: The methoxycarbonylphenylporphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum drying oven at 80°C and kept for 20 hours. The thickness of the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer is 0.3 μm.

[0032] Step 4: Take 3g of Al2O3 powder (particle size 80~120nm), add it to 150mL of deionized water, then add 0.03g of ammonium polyacrylate and 0.03g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0033] Step 5: Coat the Al2O3 ceramic slurry onto the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer, and place it in a vacuum drying oven. Raise the temperature to 80℃ and dry and cure for 20 hours to obtain a polyethylene diaphragm co-coated with porphyrin self-polymer and ceramic material. The thickness of the Al2O3 ceramic layer is 1 μm.

[0034] Example 3: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material

[0035] Step 1: Take a polyethylene film (12μm thick, 45% porosity), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.4, ultrasonically clean it for 50min, and then vacuum dry it in a vacuum drying oven at 75℃ for 8h to obtain a pretreated polyethylene film.

[0036] Step 2: Add 5g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 50mL of anhydrous 1,2-dichloroethane. After dissolving, add 1.5g of dimethoxymethane and 0.4g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0037] Step 3: The methoxycarbonylphenylporphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum drying oven at 70°C and kept for 26 hours. The thickness of the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer is 0.5 μm.

[0038] Step 4: Take 5g of Al2O3 powder (particle size 80~120nm), add it to 200mL of deionized water, then add 0.05g of ammonium polyacrylate and 0.05g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0039] Step 5: Coat the Al2O3 ceramic slurry onto the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer, and place it in a vacuum drying oven. Raise the temperature to 75°C and dry and cure for 24 hours to obtain a polyethylene membrane co-coated with porphyrin self-polymer and ceramic material; wherein the thickness of the Al2O3 ceramic layer is 5μm.

[0040] Example 4: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material.

[0041] Step 1: Take a polyethylene film (12μm thick, 55% porosity), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.4, ultrasonically clean it for 50min, and then vacuum dry it in a vacuum drying oven at 75℃ for 8h to obtain a pretreated polyethylene film.

[0042] Step 2: Add 2g of 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 50mL of anhydrous 1,2-dichloroethane. After dissolving, add 1g of dimethoxymethane and 0.5g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0043] Step 3: The methoxycarbonylphenylporphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum drying oven at 70°C and kept for 26 hours. The thickness of the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer is 0.4 μm.

[0044] Step 4: Take 2g of Al2O3 powder (particle size 80~120nm), add it to 200mL of deionized water, then add 0.02g of ammonium polyacrylate and 0.02g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0045] Step 5: Coat the Al2O3 ceramic slurry onto the 5,10,15,20-tetra(4-methoxyphenyl)porphyrin polymer layer, and place it in a vacuum drying oven. Raise the temperature to 75°C and dry and cure for 24 hours to obtain a polyethylene membrane co-coated with porphyrin self-polymer and ceramic material; wherein the thickness of the Al2O3 ceramic layer is 4μm.

[0046] Example 5: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material.

[0047] Step 1: Take a polyethylene film (thickness 9μm, porosity 40%), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.3, ultrasonically clean it for 30min, and then vacuum dry it in a vacuum drying oven at 80℃ for 5h to obtain a pretreated polyethylene film.

[0048] Step 2: Add 4g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 20mL of anhydrous 1,2-dichloroethane. After dissolving, add 1.2g of dimethoxymethane and 0.3g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0049] Step 3: The methoxycarbonylphenyl porphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum environment at 75°C and kept at this temperature for crosslinking for 24 hours. The thickness of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer is 0.1 μm.

[0050] Step 4: Take 4g of Al2O3 powder (particle size 80~120nm), add it to 130mL of deionized water, then add 0.04g of ammonium polyacrylate and 0.02g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0051] Step 5: Coat the Al2O3 ceramic slurry onto the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer, and place it in a vacuum drying oven. Raise the temperature to 70°C and dry and cure for 26 hours to obtain a polyethylene membrane co-coated with porphyrin self-polymer and ceramic material; wherein the thickness of the Al2O3 ceramic layer is 3μm.

[0052] Example 6: A polyethylene separator co-coated with porphyrin self-polymer and ceramic material.

[0053] Step 1: Take a polyethylene film (7μm thick, 45% porosity), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.2, ultrasonically clean it for 30min, and then vacuum dry it in a vacuum drying oven at 80℃ for 5h to obtain a pretreated polyethylene film.

[0054] Step 2: Add 2g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 40mL of anhydrous 1,2-dichloroethane. After dissolving, add 0.6g of dimethoxymethane and 0.45g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0055] Step 3: The methoxycarbonylphenyl porphyrin coating solution is uniformly coated onto the pretreated polyethylene film. After coating, the film is transferred to a vacuum environment at 75°C and kept at this temperature for crosslinking for 24 hours. The thickness of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer is 0.8 μm.

[0056] Step 4: Take 2g of Al2O3 powder (particle size 80~120nm), add it to 180mL of deionized water, then add 0.02g of ammonium polyacrylate and 0.03g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0057] Step 5: Coat the Al2O3 ceramic slurry onto the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer, and place it in a vacuum drying oven. Raise the temperature to 70°C and dry and cure for 26 hours to obtain a polyethylene membrane co-coated with porphyrin self-polymer and ceramic material; wherein the thickness of the Al2O3 ceramic layer is 4μm.

[0058] Comparative Example 1

[0059] Except for the use of tetraphenylporphyrin instead of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin monomer, the other conditions were the same as in Example 1.

[0060] Comparative Example 2

[0061] Except for the use of tetraphenylmethane instead of 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin monomer, the other conditions were the same as in Example 1.

[0062] Comparative Example 3

[0063] Except for replacing the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin monomer with tetra(4-methoxycarbonylphenyl)methane, the other conditions were the same as in Example 1.

[0064] Comparative Example 4

[0065] The performance was tested using a polyethylene-based film.

[0066] Comparative Example 5

[0067] Only the polyethylene-based film was coated with alumina ceramic material, and all other conditions remained the same as in Example 1.

[0068] Comparative Example 6

[0069] Step 1: Take a polyethylene film (7μm thick, 40% porosity), cut it to 100mm×100mm, place it in a mixed solution of ethanol and deionized water with a volume ratio of 1:1.2, ultrasonically clean it for 30min, and then vacuum dry it in a vacuum drying oven at 80℃ for 5h to obtain a pretreated polyethylene film.

[0070] Step 2: Take 1g of Al2O3 powder (particle size 80~120nm), add it to 100mL of deionized water, then add 0.01g of ammonium polyacrylate and 0.01g of polyvinylidene fluoride, and disperse evenly to obtain Al2O3 ceramic slurry.

[0071] Step 3: Coat the vinyl ester membrane with Al2O3 ceramic slurry and place it in a vacuum drying oven. Raise the temperature to 70°C and dry and cure for 26 hours to obtain a ceramic-coated polyethylene membrane; wherein the thickness of the Al2O3 ceramic layer is 1 μm.

[0072] Step 4: Add 1g of 5,10,15,20-tetratetra(4-methoxycarbonylphenyl)porphyrin monomer powder to a flask containing 40mL of anhydrous 1,2-dichloroethane. After dissolving, add 0.3g of dimethoxymethane and 0.3g of anhydrous AlCl3 and mix well to obtain a methoxycarbonylphenylporphyrin coating solution.

[0073] Step 3: The methoxycarbonylphenyl porphyrin coating solution is uniformly coated onto the ceramic polyethylene separator. After coating, it is transferred to a vacuum environment at 75°C and kept at this temperature for crosslinking for 24 hours to obtain a polyethylene separator co-coated with porphyrin self-polymer and ceramic material; wherein, the thickness of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer is 0.6 μm.

[0074] Performance testing

[0075] The membranes prepared in the above embodiments and comparative examples were tested for air permeability, heat shrinkage rate, tensile strength, and needle puncture resistance. The test results are shown in Table 1. The specific operation of the tests is as follows:

[0076] 1. Air permeability: Gurley air permeability meter. Characterizes the porosity of the diaphragm and the electrolyte wetting rate; the lower the test value, the better the air permeability of the diaphragm.

[0077] 2. Heat shrinkage rate: Take a diaphragm sample, put it in an oven with a set temperature and keep it for 60 minutes. Take out the sample, cool it and measure the dimensional change. Heat shrinkage rate = [(original length - shrinkage length) / original length] × 100%.

[0078] 3. Puncture resistance: Tensile test with a puncture probe. Place the diaphragm under the probe and puncture downwards with force, recording the maximum force with which the probe punctures the diaphragm.

[0079] Table 1 Test Results

[0080] Example 1 180 2.3 516.56 Example 2 196 3.5 573.16 Example 3 226 4.5 691.92 Example 4 242 5 702.33 Example 5 201 3.2 564.45 Example 6 178 2.4 530.12 Comparative Example 1 194 14 488.35 Comparative Example 2 182 28 475.15 Comparative Example 3 178 20 480.35 Comparative Example 4 163 80 460.32 Comparative Example 5 212 35 488.22 Comparative Example 6 201 13 493.64

[0081] Results Analysis

[0082] According to Table 1, a comprehensive comparison between Examples 1-6 and Comparative Examples 1-6 shows that the introduction of 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin systematically improves the thermal stability and mechanical properties of the membrane. The key performance indicators in the examples are superior to those in the comparative examples, and the air permeability remains within a reasonable range, verifying the synergistic effect of the methoxycarbonylphenyl porphyrin self-polymer and ceramic co-coating of the polyethylene membrane.

[0083] As shown in Examples 1-6 and Comparative Example 4, coating the polyolefin membrane with 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer resulted in a decrease in the membrane's permeability after coating. The permeability ranged from 178 to 242 s, remaining within a reasonable range. This indicates that the synergistic coating of the porphyrin polymer layer and the ceramic layer did not significantly hinder the ion transport channels, ensuring the basic permeability of the membrane and facilitating the permeation of gas or electrolyte.

[0084] According to the data from Examples 1-6, the thermal shrinkage rate of the diaphragm remained stable in the range of 2.3% to 5%, and the puncture resistance reached 516.56 to 702.33 gf, significantly better than the comparative examples, confirming its excellent thermal stability and mechanical properties. Comparative experiments showed that when tetraphenylporphyrin, tetraphenylmethane, or tetra(4-methoxycarbonylphenyl)methane was used instead of tetra(4-methoxycarbonylphenyl)porphyrin (Examples 1 and Comparative Examples 1-3), or when only an alumina ceramic coating was used (Examples 1 and Comparative Example 5), even adjustments to the mechanical properties and thermal stability of the diaphragm resulted in a significant decrease.

[0085] Mechanistic analysis shows that the polar methoxycarbonyl groups in the methoxycarbonylphenyl porphyrin self-polymer can enhance the inter-chain bonding force through dipole interactions and hydrogen bonds, effectively dispersing local stress. Simultaneously, the rigid planar structure of the porphyrin macrocycle forms an ordered layered arrangement through π-π stacking, suppressing the thermal motion of the molecular chains. This molecular structure forms a multi-level synergistic mechanism with the ceramic layer: the ceramic layer, as a rigid framework, together with the chemical interaction of the porphyrin molecules, constitutes a synergistic support system. Through the "ceramic-methoxycarbonylphenyl porphyrin polymer-polyethylene" sandwich structure, multi-level support is achieved, ensuring the membrane maintains a compact structure at high temperatures; while maintaining basic porosity and permeability, significant improvements in thermal shrinkage performance and mechanical strength are achieved.

[0086] In summary, this invention effectively improves the thermal stability and mechanical strength of polyethylene separators by synergistic coating of porphyrin self-polymers and ceramic materials, while maintaining good air permeability, providing a feasible solution for optimizing the performance of lithium-ion battery separators.

Claims

1. A method for preparing a polyethylene separator co-coated with a porphyrin self-polymer and a ceramic material, characterized in that, The method includes the following steps: coating a 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin solution onto the surface of a pretreated polyethylene film, and crosslinking it in a vacuum environment at 70-80°C for 20-26 hours; coating an alumina ceramic slurry onto the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin polymer layer and placing it in a vacuum drying oven, raising the temperature to 70-80°C, and drying for 20-26 hours to obtain a diaphragm; The preparation method of the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin solution is as follows: 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin monomer is dissolved in 1,2-dichloroethane, followed by the addition of dimethoxymethane and AlCl3 and dispersion to obtain the 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin solution; the mass ratio of 5,10,15,20-tetra(4-methoxycarbonylphenyl)porphyrin, 1,2-dichloroethane, dimethoxymethane, and AlCl3 is 1~5:12.56~62.8:0.3~1.5:0.25~0.5; The alumina ceramic slurry is prepared by dispersing Al2O3 powder in deionized water, adding ammonium polyacrylate dispersant and polyvinylidene fluoride binder, and mixing them evenly to obtain the ceramic slurry. The diaphragm comprises a polyethylene base film with a thickness of 7-10 μm, a 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin polymer layer with a thickness of 0.1-1 μm, and an alumina ceramic layer with a thickness of 1-5 μm.

2. The preparation method according to claim 1, characterized in that, The porosity of the polyethylene-based film is 35% to 45%.

3. The preparation method according to claim 1, characterized in that, The method further includes the following steps: placing the polyethylene film in a mixed solution of ethanol and deionized water, ultrasonically cleaning it for 30-60 minutes, and then vacuum drying it in a vacuum drying oven at 70-80°C for 5-10 hours to obtain a pretreated polyethylene film.

4. The preparation method according to claim 3, characterized in that, The volume ratio of ethanol to deionized water is 1:1 to 1.

5.

5. The preparation method according to claim 4, characterized in that, The mass ratio of Al2O3 powder, deionized water, ammonium polyacrylate and polyvinylidene fluoride is 1~5:100~200:0.01~0.05:0.01~0.

05.

6. A polyethylene separator co-coated with a porphyrin self-polymer and a ceramic material, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. The application of the separator as described in claim 6 in lithium-ion batteries.

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