Lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a lithium battery diaphragm and a preparation method thereof, the lithium battery diaphragm comprises a base membrane and a coating coated on the base membrane, the coating comprises ceramic powder, a silane coupling agent and a fatty acid polymer, the fatty acid polymer is a high-molecular compound formed by a polymerization reaction of a fatty acid monomer, and the silane coupling agent is a silane coupling agent. The carbon atom number of the fatty acid polymer is less than or equal to 6. The hydrophobic slurry comprises the silane coupling agent and the fatty acid polymer, and can be cross-linked with the ceramic powder to form a hydrophobic space structure, so that the water content in the diaphragm is effectively reduced, and free water in the slurry is separated out; the invention aims to form a macromolecular filling space structure through the synergistic effect of the granular ceramic powder, the silane coupling agent and the fatty acid polymer, so that the hydrophobic capacity is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to a lithium battery separator and a preparation method thereof. Background Art

[0002] Lithium-ion secondary batteries have the characteristics of high energy density, long cycle life, no memory effect, and are safe, environmentally friendly, reliable, and can be charged and discharged quickly. Therefore, they have become a hot spot in energy storage technology research in recent years and are widely used in portable electronic products such as mobile phones, laptops, digital cameras, and will surely become the preferred energy storage equipment for hybrid vehicles and electric vehicles. In recent years, with the continuous development of electrochemistry and emerging battery chemistry, battery technology has made great progress. Among them, lithium-ion batteries have the highest energy density and meet the current requirements for large power capacity, lightness, and thinness of portable electronic products. Therefore, the lithium-ion battery market is expanding year by year. The research on lithium-ion battery materials, especially power lithium-ion battery materials, has received more and more attention.

[0003] Lithium battery separators are crucial in lithium batteries. Conventional single-sided boehmite-coated separators are generally light and hydrophobic, and cannot meet the above requirements. Summary of the invention

[0004] In view of the deficiencies of the prior art, an object of the present invention is to provide a lithium battery separator.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned lithium battery separator.

[0006] Another object of the present invention is to provide a hydrophobic slurry.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned hydrophobic slurry.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A lithium battery separator comprises: a base film and a coating coated on the base film, wherein the coating comprises: ceramic powder, a silane coupling agent and a fatty acid polymer, wherein the ratio of the ceramic powder, the silane coupling agent and the fatty acid polymer is (10-15): (0.05-0.22): (0.02-0.45) by mass, wherein the fatty acid polymer is a high molecular compound formed by polymerization of fatty acid monomers, and the number of carbon atoms in the fatty acid polymer is ≤6.

[0010] In the above technical solution, the fatty acid monomer is one or a mixture of several of acetic acid, propionic acid, butyric acid, isobutyric acid, n-butyric acid, valeric acid and isovaleric acid.

[0011] In the above technical solution, the viscosity of the fatty acid polymer at 25° C. is 48 to 52 mPa·s, the pH is 6 to 8, and the density is 1.00 to 2.05 g / mL.

[0012] In the above technical solution, the silane coupling agent is one or a mixture of vinyl triethyl silane, vinyl trimethoxy silane, trimethyl methoxy silane, aminopropyl trimethoxy silane, methacryloxy silane and ureidopropyl triethoxy silane.

[0013] In the above technical solution, the coating comprises stripes which are parallel to each other and arranged at intervals, the distance between adjacent stripes is 1 to 2 mm, and the width of each stripe is 4 to 5 mm.

[0014] The method for preparing the lithium battery separator comprises: coating a hydrophobic slurry on a base film by an anilox roller, and drying the base film to obtain the lithium battery separator.

[0015] In the above technical solution, the surface of the anilox roller is provided with strip-shaped protrusions.

[0016] In the above technical solution, during coating, the axial angle between each stripe and the anilox roller is 45°, and the protrusion depth is 1 to 6 μm.

[0017] A hydrophobic slurry comprises: ceramic powder, silane coupling agent and fatty acid polymer, wherein the ratio of ceramic powder, silane coupling agent and fatty acid polymer is (10-15): (0.05-0.3): (0.02-0.5) by weight.

[0018] In the above technical solution, the hydrophobic slurry also includes: an adhesive and water. In terms of mass fractions, the ratio of the fatty acid polymer, water and adhesive is (0.02-0.5): (75-79.2): (1-5).

[0019] The method for preparing the above-mentioned hydrophobic slurry comprises the following steps:

[0020] Step 1, mixing ceramic powder and silane coupling agent, stirring at room temperature for 25 to 30 minutes, filter pressing, drying, crushing, and sieving to obtain a first powder;

[0021] In step 1, the drying is performed until the moisture content is 0.6-0.8% (mass fraction).

[0022] In step 1, the ceramic powder is granular boehmite and / or alumina.

[0023] In step 1, the particle size of the ceramic powder is 400-500 nm.

[0024] In step 1, a first powder with a particle size of 400 to 500 nm is obtained by sieving.

[0025] Step 2, mixing the first powder and water until uniformly to obtain a first solution, mixing the first solution, fatty acid polymer and adhesive until uniformly, grinding, and obtaining a hydrophobic slurry, wherein the ratio of the fatty acid polymer, silane coupling agent, water, ceramic powder and adhesive is (0.02-0.5): (0.05-0.3): (75-79.2): (10-15): (1-5) by mass.

[0026] In step 2, the adhesive is polyacrylate.

[0027] In step 2, the first powder and water are mixed, first stirred at a rotation speed of 3100 to 3600 r / min and a revolution speed of 10 to 20 r / min for 10 to 15 min, and then ultrasonicated at a frequency of 5 to 7 kHz for 10 to 30 min until uniform, to obtain a first solution.

[0028] In step 2, the first solution, the fatty acid polymer and the adhesive are mixed, first stirred at a rotation speed of 1000-1500 r / min and a revolution speed of 10-20 r / min for 5-10 min, and then ultrasonicated at a frequency of 5-7 kHz for 10-30 min until uniform.

[0029] In step 2, grinding is performed at a rotation speed of 300 to 400 r / min for 10 to 15 minutes to obtain a hydrophobic slurry.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The hydrophobic slurry of the present invention includes a silane coupling agent and a fatty acid polymer, which can be cross-linked with the ceramic powder to form a hydrophobic space structure, effectively reduce the water content in the diaphragm, and precipitate free water in the slurry, aiming to further enhance the hydrophobic ability by forming a polymer-filled space structure through the synergistic effect of granular ceramic powder, silane coupling agent and fatty acid polymer, and reduce the probability of active material loss caused by the reaction between lithium ions and free water in the lithium battery, thereby causing a decrease in the capacity of the lithium ion battery;

[0032] 2. The present invention uses an anilox roller with intermittent oblique lines similar to zebra patterns to coat the surface of the base film, so that the obtained diaphragm has intermittent oblique lines, which effectively reduces the surface density of the diaphragm and thus reduces the quality of the lithium-ion battery;

[0033] 3. The present invention uses a zebra-like anilox roller to coat the hydrophobic slurry, which synergistically improves the performance of the diaphragm, thereby improving the durability of the battery and the endurance of new energy electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The electron microscope image of the diaphragm prepared from the hydrophobic slurry of Example 1;

[0035] Figure 2 The electron microscope image of the diaphragm prepared from the surface-modified slurry of Comparative Example 1;

[0036] Figure 3 The electron microscope image of the diaphragm prepared from the conventional ceramic lithium battery diaphragm slurry without surface modification of Comparative Example 2;

[0037] Figure 4 This is the appearance of the separator prepared from the hydrophobic slurry of Example 1. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0039] The raw material information involved in the following examples is as follows:

[0040] Boehmite, with the molecular formula of γ-AlOOH (hydrated boehmite), was purchased from Wuhan Kemik Biopharmaceutical Technology Co., Ltd.

[0041] Fatty acid polymers are high molecular weight compounds formed by polymerization of fatty acid monomers. They were purchased from Nantong Zhonghe Chemical New Materials Co., Ltd.

[0042] The molecular structure of the silane coupling agent is YR-Si(OR)3 (where Y is an organic functional group and SiOR is a silaneoxy group). The silaneoxy group is reactive to inorganic substances, and the organic functional group is reactive or compatible to organic substances. It was purchased from Nanjing Xuanhao New Materials Co., Ltd.

[0043] In the following examples, the base film is a 12 μm PE film.

[0044] Example 1

[0045] A method for preparing a hydrophobic slurry comprises the following steps:

[0046] Step 1, in a reaction kettle, mixing a ceramic powder and a silane coupling agent, stirring at 25° C. for 30 min, filtering by pressure, drying to a moisture content of 0.8% (mass fraction), crushing, and sieving to obtain a first powder with an average particle size of 400 nm, wherein the ceramic powder is granular boehmite, the particle size of the ceramic powder is 400-500 nm, the silane coupling agent is vinyl triethyl silane, the fatty acid polymer is a polymer compound formed by polymerization of fatty acid monomers, the fatty acid polymer is a short-chain fatty acid with a carbon number of ≤6, the fatty acid monomer is butyric acid, the appearance of the fatty acid polymer is a light yellow transparent liquid, the viscosity of the fatty acid polymer at 25° C. is 50.69 mPa·s, the pH is 6, and the density is 1.15 g / mL (the fatty acid polymer is miscible with water, ethanol, and isopropanol in any proportion);

[0047] Step 2, mixing the first powder and water, stirring for 10 minutes at a rotation speed of 3600r / min and a revolution speed of 20r / min in a planetary stirring device, and then ultrasonicating for 30 minutes at a frequency of 7kHz in an ultrasonic device until uniform, to obtain a first solution, mixing the first solution, the fatty acid polymer and the adhesive, stirring for 10 minutes at a rotation speed of 1000r / min and a revolution speed of 20r / min in a planetary stirring device, and then ultrasonicating for 30 minutes at a frequency of 7kHz in an ultrasonic device until uniform, putting into a sand mill, grinding at a speed of 400r / min for 10 minutes, to obtain a hydrophobic slurry, in which the ratio of fatty acid polymer, silane coupling agent, water, ceramic powder and adhesive is 0.5:0.3:79.2:15:5 by mass, and the adhesive is polyacrylate, and the polyacrylate specifically uses polymethyl acrylate.

[0048] Example 2

[0049] A method for preparing a hydrophobic slurry is basically the same as Example 1 "A method for preparing a hydrophobic slurry", with the only difference being that in this example, the silane coupling agent is vinyltrimethoxysilane and the fatty acid monomer is isovaleric acid.

[0050] In Example 2, the fatty acid polymer has an appearance of a colorless viscous liquid, a viscosity of 48.6 mPa·s at 25° C., a pH of 6.2, and a density of 1.31 g / mL (the fatty acid polymer is miscible with water, ethanol, and isopropanol in any proportion).

[0051] Example 3

[0052] A method for preparing a hydrophobic slurry is basically the same as Example 1 "A method for preparing a hydrophobic slurry", with the only difference being that in this example, the silane coupling agent is methacryloxysilane and the fatty acid monomer is isobutyric acid.

[0053] In Example 3, the fatty acid polymer has an appearance of a colorless liquid, a viscosity of 51.2 mPa·s at 25° C., a pH of 6.4, and a density of 1.06 g / mL (the fatty acid polymer is miscible with water, ethanol, and isopropanol in any proportion).

[0054] Comparative Example 1

[0055] A method for preparing a surface-modified slurry comprises the following steps:

[0056] Step 1, in a reaction kettle, mixing granular boehmite and a silane coupling agent, stirring at 25° C. for 30 minutes, filtering, drying to a moisture content of 0.8% (mass fraction), crushing, and sieving to obtain powder A, wherein the silane coupling agent is aminopropyltriethoxysilane, and the ratio of boehmite to the silane coupling agent is 30:1 by mass;

[0057] Step 2, mixing the dispersant, water and A powder, stirring for 10 minutes at a rotation speed of 3600r / min and a revolution speed of 20r / min in a planetary stirring device, and then ultrasonicating for 30 minutes at 7kHz in an ultrasonic device, adding an adhesive, stirring for 10 minutes at a rotation speed of 1000r / min and a revolution speed of 20r / min in a planetary stirring device, and then ultrasonicating for 30 minutes at a frequency of 7kHz in an ultrasonic device until uniform, putting into a sand mill, grinding at a speed of 400r / min for 10 minutes, and obtaining a surface-modified slurry, wherein the ratio of dispersant, water, boehmite and adhesive is 0.2:79.8:15:5 by mass, the dispersant is an ammonium salt dispersant (ammonium polyacrylate), and the adhesive is polyacrylate (methyl polyacrylate).

[0058] Comparative Example 2

[0059] A method for preparing a conventional ceramic lithium battery diaphragm slurry without surface modification comprises: mixing granular boehmite, a dispersant and water, stirring for 10 minutes at a rotation speed of 3600 r / min and a revolution speed of 20 r / min in a planetary stirring device, ultrasonically treating the mixture at a frequency of 7 kHz for 30 minutes in an ultrasonic device until the mixture is uniform, adding an adhesive, stirring for 10 minutes at a rotation speed of 1000 r / min and a revolution speed of 20 r / min in the planetary stirring device, ultrasonically treating the mixture at a frequency of 7 kHz for 30 minutes in an ultrasonic device until the mixture is uniform, beating the mixture into a sand mill, and grinding the mixture at a rotation speed of 400 r / min for 10 minutes to obtain the conventional ceramic lithium battery diaphragm slurry without surface modification, wherein the ratio of the dispersant, water, boehmite and adhesive is 0.2:79.8:15:5 by mass, the adhesive is polyacrylate (polymethyl acrylate), and the dispersant is an ammonium salt dispersant (ammonium polyacrylate).

[0060] Examples 4 to 6 and Comparative Examples 3 to 4

[0061] A lithium ion battery comprises: a positive electrode, a negative electrode, a separator and an electrolyte, and is wound to obtain a 606090-type lithium ion battery with a capacity of 4000mAh and a nominal voltage of 3.7V. The positive electrode is prepared by mixing N-methylpyrrolidone, a ternary material (NCM523), a positive electrode conductive agent (conductive carbon black) and a positive electrode binder (polyvinylidene fluoride), wherein the ratio of N-methylpyrrolidone, the ternary material, the positive electrode conductive agent and the positive electrode binder is 10:8:1:1 by mass, and after mixing, the mixture is stirred at a rotation speed of 1500r / min and a revolution speed of 20r / min, and then ultrasonicated at a frequency of 7kHz for 30min to obtain a positive electrode slurry, and 1.5g of the positive electrode slurry is coated on a copper foil substrate (91.5mm*1m ), dried in a constant temperature oven to form a positive electrode coating, and then firmly pressed by roller pressing to obtain a positive electrode; the method for preparing a negative electrode is: N-methylpyrrolidone, graphite, a negative electrode conductive agent (carbon powder) and a negative electrode binder (polyacrylate), the ratio of N-methylpyrrolidone, graphite, negative electrode conductive agent and negative electrode binder is 10:8:0.8:1.2 by mass, after mixing, it is stirred at a rotation speed of 1500r / min and a revolution speed of 20r / min, and then ultrasonicated at a frequency of 7kHz for 30min to obtain a negative electrode slurry, 1.5g of the negative electrode slurry is coated on a copper foil substrate (91.5mm*1.2m), dried in a constant temperature oven to form a negative electrode coating, and then firmly pressed by roller pressing to obtain a negative electrode. The electrolyte is a mixture of an electrolyte and a solvent, the electrolyte in the electrolyte is lithium tetrafluoroborate, the solvent is a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), the ratio of EC to DMC is 1:1 by mass, and the concentration of the electrolyte in the electrolyte is 1 mol / L. The method for preparing the diaphragm comprises: coating the slurry on a single side of a base film using an anilox roller, drying at 50° C. for 10 min, obtaining a coating on the base film, and obtaining a diaphragm. The slurry is one of the hydrophobic slurry prepared in Examples 1 to 3, the surface-modified slurry prepared in Comparative Example 1, and the conventional ceramic lithium battery diaphragm slurry without surface modification prepared in Comparative Example 2.

[0062] The surface of the anilox roller is provided with strip-shaped protrusions so that the upper part of the coating is formed with parallel and spaced stripes, wherein the distance between adjacent stripes is 1.2 mm, the width of each stripe is 4.5 mm, and during coating, the axial angle of each stripe to the anilox roller is 45°, and the protrusion depth is 4 μm.

[0063] Table 1

[0064] Examples and Comparative Examples Slurry for preparing diaphragm Example 4 Example 1 Example 5 Example 2 Example 6 Example 3 Comparative Example 3 Comparative Example 1 Comparative Example 4 Comparative Example 2

[0065] Comparative Example 5

[0066] A lithium ion battery is basically the same as the lithium ion battery of Example 4, the only difference being that the diaphragm is different: the method for preparing the diaphragm of Comparative Example 5 is: using a conventional plate roller to coat the slurry on one side of a base film, drying it at 50°C for 10 minutes, obtaining a coating on the base film, and obtaining a diaphragm, and the slurry is the hydrophobic slurry prepared in Example 1.

[0067] Figure 1 This is an electron microscope image of the diaphragm prepared from the hydrophobic slurry of Example 1. Figure 2 This is an electron microscope image of the diaphragm prepared from the surface-modified slurry of Comparative Example 1. Figure 3 This is an electron microscope image of the separator prepared from the conventional ceramic lithium battery separator slurry without surface modification of Comparative Example 2. Figure 4 The appearance of the diaphragm prepared from the hydrophobic slurry of Example 1. Figure 4 It can be seen that the diaphragm obtained after the hydrophobic slurry of Example 1 is coated by anilox roller is in the shape of intermittent stripes.

[0068] The hydrophobic slurry prepared in Example 1, the surface-modified slurry prepared in Comparative Example 1, and the conventional ceramic lithium battery separator slurry without surface modification prepared in Comparative Example 2 were tested. The test conditions were all carried out under standard atmospheric conditions: temperature: 20°C to 30°C; relative humidity: 55% to 60%; atmospheric pressure: 94 kPa to 100 kPa. The test results are shown in Table 2.

[0069] Table 2

[0070] Examples and Comparative Examples D10(μm) D50(μm) D90(μm) D99(μm) Example 1 0.579 1.141 2.432 3.135 Comparative Example 1 0.586 1.131 1.998 2.901 Comparative Example 2 0.487 0.897 2.117 2.986

[0071] As shown in Table 2, the particle size D90 of the conventional ceramic lithium battery separator slurry without surface modification prepared in Comparative Example 2 is 2.117 μm; the particle size D90 of the surface modified slurry prepared in Comparative Example 1 is 1.998 μm; and the particle size D90 of the hydrophobic slurry prepared in Example 1 of the present invention is 2.432 μm. It can be seen that the boehmite particles modified by aminopropyltriethoxysilane and the boehmite particles without silane coupling agent modification will cause the powder structure to be destroyed, resulting in a decrease in the slurry particle size. The hydrophobic slurry (polymer slurry) prepared by surface modification of granular boehmite and the silane coupling agent and fatty acid polymer of Examples 1 to 3 of the present invention has a more stable structure and a good degree of dispersion, so that when coated on the base film, a hydrophobic structure will be formed, the coating is uniform, the surface is flat, and no vertical scratches will appear. Moreover, the particles are not prone to precipitation and agglomeration during storage, and the storage stability is good.

[0072] Table 3

[0073]

[0074] It can be seen from Table 3 that the water content of the diaphragm prepared by Comparative Example 2 is 1273 Ppm; while the water content of the diaphragm prepared by the hydrophobic slurry of Example 1 is within 400 ppm, and it has better hydrophobic ability. Examples 1 to 3 of the present invention further enhance the hydrophobic ability by forming a polymer-filled space structure through the synergistic effect of granular boehmite, fatty acid polymer and silane coupling agent.

[0075] The test data of the lithium ion batteries prepared in Examples 4 to 6 and Comparative Examples 3 to 4 are shown in the following table.

[0076] Table 4

[0077]

[0078] It can be clearly seen from Table 4 that the "diaphragm mass" of the diaphragm prepared by the hydrophobic slurry of Examples 1 to 3 is smaller than that of the comparative example. For example, the "diaphragm mass" in Example 4 is reduced by 0.4751 g compared with the "diaphragm mass" in Comparative Example 5, thereby reducing the mass of the lithium-ion battery. Through the synergistic effect of the silane coupling agent and the fatty acid polymer, and the anilox roller coating with intermittent oblique lines similar to zebra stripes, the coating mass is reduced without affecting the performance, which greatly reduces the production cost and improves the production efficiency. It can not only well reduce the mass of the lithium-ion battery, but also form a stable material interface, thereby improving the battery life of the lithium battery.

[0079] The air permeability of the diaphragm prepared from the hydrophobic slurry of Example 2 is 238 Sec / 100 ml, and the air permeability of the diaphragm prepared from the surface-modified slurry of Comparative Example 1 is 252 Sec / 100 ml.

[0080] Comparative Example 5 is a diaphragm obtained by coating the hydrophobic slurry of Example 1 with a conventional plate roller. The surface density of the diaphragm in Comparative Example 5 is 14.38 g / ㎡, which is greater than the surface density of the diaphragm obtained by coating the hydrophobic slurry of Example 1 with an anilox roller with zebra patterns. It can be seen that the performance of the diaphragm can be further improved by coating with an anilox roller with zebra patterns.

[0081] Parameters of the resulting membrane prepared from the hydrophobic slurry of Example 1.

[0082]

[0083]

[0084] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A lithium battery separator, comprising: A base film and a coating applied on the base film, characterized in that the coating comprises: ceramic powder, silane coupling agent and fatty acid polymer, and the ratio of ceramic powder, silane coupling agent and fatty acid polymer is (10-15): (0.05-0.22): (0.02-0.45) by mass, wherein the fatty acid polymer is a high molecular compound formed by polymerization reaction of fatty acid monomers, and the number of carbon atoms of the fatty acid polymer is ≤6.

2. The lithium battery separator according to claim 1, characterized in that: The fatty acid monomer is one or a mixture of acetic acid, propionic acid, butyric acid, isobutyric acid, n-butyric acid, valeric acid and isovaleric acid.

3. The lithium battery separator according to claim 1, characterized in that The silane coupling agent is one or a mixture of vinyl triethyl silane, vinyl trimethoxy silane, trimethyl methoxy silane, aminopropyl trimethoxy silane, methacryloxy silane and ureidopropyl triethoxy silane.

4. The lithium battery separator according to claim 1, characterized in that The fatty acid polymer has a viscosity of 48 to 52 mPa·s at 25° C., a pH of 6 to 8, and a density of 1 to 2.05 g / mL.

5. A hydrophobic slurry, characterized in that: include: The ceramic powder, the silane coupling agent and the fatty acid polymer are in a ratio of (10-15): (0.05-0.3): (0.02-0.5) by weight.

6. A method for preparing the hydrophobic slurry according to claim 5, comprising the following steps: Step 1, mixing ceramic powder and silane coupling agent, stirring at room temperature for 25 to 30 minutes, filter pressing, drying, crushing, and sieving to obtain a first powder; Step 2, mixing the first powder and water until uniformly to obtain a first solution, mixing the first solution, fatty acid polymer and adhesive until uniformly, grinding, and obtaining a hydrophobic slurry, wherein the ratio of the fatty acid polymer, silane coupling agent, water, ceramic powder and adhesive is (0.02-0.5): (0.05-0.3): (75-79.2): (10-15): (1-5) by mass.

7. A method for preparing a lithium battery separator, characterized in that: include: The hydrophobic slurry according to claim 5 is coated on the base film by using an anilox roller and dried to obtain a lithium battery separator.

8. Application of ceramic powder, silane coupling agent and fatty acid polymer to synergistically reduce the water content of the diaphragm.

9. The use according to claim 8, characterized in that: The fatty acid polymer is a high molecular compound formed by polymerization of fatty acid monomers, the carbon number of the fatty acid polymer is ≤6, and the fatty acid monomer is one or a mixture of several of acetic acid, propionic acid, butyric acid, isobutyric acid, n-butyric acid, valeric acid and isovaleric acid.

10. The use according to claim 8, characterized in that: The silane coupling agent is one or a mixture of vinyl triethyl silane, vinyl trimethoxy silane, trimethyl methoxy silane, aminopropyl trimethoxy silane, methacryloxy silane and ureidopropyl triethoxy silane.

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