High temperature resistant acrylic separator and method of making same

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a high-temperature-resistant acrylic diaphragm glue and a preparation method thereof.The high-temperature-resistant acrylic diaphragm glue comprises a base film and high-temperature-resistant acrylic paste coated on both sides of the base film; the base film is a polyolefin film; the raw materials of the high-temperature-resistant acrylic paste comprise, by mass fraction, 50-100 parts of n-butyl acrylate, 1-10 parts of 2-hydroxyethyl acrylate, 50-100 parts of nano ceramic powder, 50-80 parts of urea, 5-15 parts of graphene oxide, 1-4 parts of a first crosslinking agent, 1-2 parts of a second crosslinking agent, 0.01-0.1 parts of an initiator, 5-15 parts of polyvinylidene fluoride, 5-15 parts of aluminum hydroxide and 50-65 parts of polysiloxane.The present application has the characteristics of low shrinkage and high safety of ceramic paste at high temperature, high conductivity at room temperature, can withstand high temperature of 180-200 DEG C, and is conducive to the cycle stability of the electrode.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a high-temperature resistant acrylic separator and its preparation method. Background Technology

[0002] Lithium-ion batteries are widely used in power, consumer, and energy storage applications due to their advantages such as high specific energy, high specific power, high voltage platform, low self-discharge, long cycle life, low environmental pollution, and no memory effect.

[0003] In lithium-ion batteries, the separator separates the positive and negative electrodes and absorbs the electrolyte, allowing lithium ions to pass through. However, with the continuous development of electric vehicles, the requirements for lithium-ion batteries in terms of safety, charge-discharge performance, cycle performance, and rate capability are becoming increasingly stringent. To improve the surface properties of the separator, the main method currently used is to coat the separator surface with a layer of ceramic slurry. Ceramic-coated separators are currently the most effective way to improve the safety of lithium-ion batteries. After coating the separator with ceramic slurry, the heat shrinkage resistance, safety, thermal stability, and mechanical strength of the separator can be effectively improved, thereby extending the service life of the separator.

[0004] As a crucial material in lithium-ion batteries, the ceramic separator's performance determines the battery's interface structure and internal resistance, directly affecting its capacity, cycle life, and safety. A high-performance separator is essential for improving the overall performance of the battery. Polyolefin separators are widely used in lithium batteries due to their high chemical stability. However, polyolefin separators have poor heat resistance. While ceramic coating can improve their heat resistance to some extent, they are prone to cracking when the temperature exceeds 150℃. Furthermore, the ceramic coating increases the internal resistance of the separator, hindering ion conduction during battery cycling, a problem that urgently needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-temperature resistant acrylic diaphragm and its preparation method.

[0006] A high-temperature resistant acrylic membrane includes: a base membrane and a high-temperature resistant acrylic slurry coated on both sides of the base membrane; wherein the base membrane is a polyolefin film; the raw materials of the high-temperature resistant acrylic slurry include, by weight, 50-100 parts of n-butyl acrylate, 1-10 parts of 2-hydroxyethyl acrylate, 50-100 parts of nano-sized ceramic powder, 50-80 parts of urea, 5-15 parts of graphene oxide, 1-4 parts of a first crosslinking agent, 1-2 parts of a second crosslinking agent, 0.01-0.1 parts of an initiator, 5-15 parts of polyvinylidene fluoride, 5-15 parts of aluminum hydroxide, and 50-65 parts of polysiloxane.

[0007] Preferably, the base film is a polypropylene film with a thickness of 10-20 μm and a porosity of 35-45%.

[0008] Preferably, the first crosslinking agent includes glutaraldehyde and resorcinol.

[0009] More preferably, the mass ratio of glutaraldehyde to resorcinol is 4-8:2-5.

[0010] Preferably, the second crosslinking agent is phthalimide diisocyanate.

[0011] Preferably, the initiator is a peroxide initiator, and more preferably at least one of benzoyl peroxide, tert-butyl peroxide, and methyl ethyl ketone peroxide.

[0012] Preferably, the polysiloxane is at least one of polydimethylsiloxane, cyclomethylsiloxane, aminosiloxane, and polymethylphenylsiloxane.

[0013] Preferably, the high-temperature resistant acrylic slurry is prepared using the following steps:

[0014] S1. Add nano-sized ceramic powder to an ethanol aqueous solution and sonicate for 1-2 hours. Add 50-80 parts of urea and ball mill for 10-20 hours. Filter, wash, and vacuum dry to obtain aminated ceramic.

[0015] S2. Add the aminated ceramic and graphene oxide to water and stir for 1-2 hours. Add the first crosslinking agent and stir at 60-80°C for 2-5 hours. Directional freeze for 1-3 hours and freeze dry to obtain pretreated nano-sized ceramic powder.

[0016] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and the second crosslinking agent, and stir at 70-90℃ for 1-2 hours. Add pretreated nano-sized ceramic powder, initiator, and dimethylacetamide, and continue stirring for 1-3 hours. Cool down to 50-60℃, add polyvinylidene fluoride, aluminum hydroxide, and polysiloxane, and stir for 10-30 minutes. Cool down to room temperature.

[0017] More preferably, in S2, during the directional freezing process, the cold source is at the bottom, and the freezing temperature is -30 to -50°C.

[0018] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 50-80℃ for 5-10 min, drying, placing it in an aqueous solution containing ammonia and vitamin C, reducing it at 120-140℃ for 2-4 h, drying, and obtaining a coating thickness of 2-6 μm.

[0019] Preferably, in the above-mentioned aqueous solution containing ammonia and vitamin C, the ammonia concentration is 12-18% and the vitamin C concentration is 0.5-1 g / mL.

[0020] Beneficial effects:

[0021] This invention uses urea as an ammonia source to blend and modify nanoscale ceramic powder, thereby incorporating amino groups into the ceramic structure. After cross-linking with graphene oxide, the graphene oxide and ceramic powder are tightly bonded together, exhibiting extremely high stability. Subsequently, a regular aerogel structure is formed through directional freezing, which not only has a higher thermal conductivity and better high-temperature stability, but also excellent dispersion and compatibility with acrylic resin, significantly enhancing the high-temperature strength of acrylic resin. At the same time, the directional and regular graphene oxide sheet structure forms ion conduction pathways, effectively improving ion conduction performance.

[0022] This invention combines the low shrinkage and high safety of ceramic slurry at high temperatures with high conductivity at room temperature. It can significantly improve the charging speed and specific energy of lithium-ion batteries. Moreover, the ceramic particles and acrylic resin form a good network structure that can withstand high temperatures of 180-200℃, effectively solving the problem of membrane shrinkage or melting caused by high temperatures. At the same time, the network structure can effectively prevent nanoparticles from moving during cycling, maintain the stability of the electrode structure, and promote the cycling stability of the electrode.

[0023] This invention provides a relatively efficient process, in which the coating method is simple, low-cost, and has stable performance. When applied to lithium-ion batteries used in electric vehicles, it can withstand high temperatures, and the membrane shrinkage rate is significantly reduced compared to existing ceramic-coated membranes, making it suitable for large-scale application. Attached Figure Description

[0024] Figure 1 This is a comparison chart of the tensile strength of the products obtained in Example 5 and Comparative Examples 1-3.

[0025] Figure 2 This is a comparison chart of the heat shrinkage rates of the products obtained in Example 5 and Comparative Examples 1-3.

[0026] Figure 3 This is a comparison chart of the liquid absorption rate and ionic conductivity of the products obtained in Example 5 and Comparative Examples 1-3.

[0027] Figure 4 The graph shows a comparison of the capacity retention rates of button batteries made using the products obtained in Example 5 and Comparative Examples 1-3. Detailed Implementation

[0028] The present invention will be further explained below with reference to specific embodiments.

[0029] The polypropylene film was purchased from Wenzhou Moutai New Materials Co., Ltd., with a thickness of 16 μm and a porosity of 40%. The nano-sized ceramic powder was purchased from Hangzhou Moukang New Materials Co., Ltd., with alumina as its main component, an average particle size of 0.5 μm, and a purity of 99.9%.

[0030] Example 1

[0031] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0032] The raw materials for the high-temperature resistant acrylic slurry include: 50g of n-butyl acrylate, 1g of 2-hydroxyethyl acrylate, 50g of nano-grade ceramic powder, 50g of urea, 5g of graphene oxide, 1g of the first crosslinking agent, 1g of phthalimide diisocyanate, 0.01g of tert-butyl peroxide, 5g of polyvinylidene fluoride, 5g of aluminum hydroxide, and 50g of cyclomethylsiloxane.

[0033] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 4:2.

[0034] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0035] S1. Nano-sized ceramic powder was added to 100g of 40% ethanol aqueous solution and ultrasonically treated for 1h at a frequency of 5kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 10h at a revolution speed of 500r / min and a rotation speed of 200r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0036] S2. Add the aminated ceramic and graphene oxide to 200g of water, stir at 1000r / min for 1h, add the first crosslinking agent, stir at 60℃ for 2h, directional freeze for 1h (the cold source is at the bottom, and the freezing temperature is -30℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0037] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 70°C for 1 hour. Add pretreated nano-sized ceramic powder, tert-butyl peroxide, and 200g of dimethylacetamide and continue stirring for 1 hour. Cool down to 50°C, add polyvinylidene fluoride, aluminum hydroxide, and cyclomethylsiloxane, and stir for 10 minutes at a stirring speed of 1000r / min. Cool down to room temperature.

[0038] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 50°C for 5 min, drying, placing it in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 12% and vitamin C concentration of 0.5 g / mL), reducing it at 120°C for 2 h, drying, and obtaining a coating thickness of 2 μm.

[0039] Example 2

[0040] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0041] The raw materials for the high-temperature resistant acrylic slurry include: 100g of n-butyl acrylate, 10g of 2-hydroxyethyl acrylate, 100g of nano-grade ceramic powder, 80g of urea, 15g of graphene oxide, 4g of the first crosslinking agent, 2g of phthaloyl diisocyanate, 0.1g of methyl ethyl ketone peroxide, 15g of polyvinylidene fluoride, 15g of aluminum hydroxide, and 65g of aminosiloxane.

[0042] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 8:5.

[0043] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0044] S1. Nano-sized ceramic powder was added to 150g of 60% ethanol aqueous solution and ultrasonically treated for 2h at a frequency of 12kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 20h at a revolution speed of 800r / min and a rotation speed of 400r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0045] S2. Add the aminated ceramic and graphene oxide to 400g of water, stir at 2000r / min for 2h, add the first crosslinking agent, stir at 80℃ for 5h, directional freeze for 3h (the cold source is at the bottom, and the freezing temperature is -50℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0046] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 90°C for 2 hours. Add pretreated nano-sized ceramic powder, methyl ethyl ketone peroxide, and 400g of dimethylacetamide and continue stirring for 3 hours. Cool down to 60°C, add polyvinylidene fluoride, aluminum hydroxide, and aminosiloxane, and stir for 30 minutes at a stirring speed of 3000r / min. Cool down to room temperature.

[0047] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 80°C for 10 min, drying, placing in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 18% and vitamin C concentration of 1 g / mL), reducing at 140°C for 4 h, drying, and obtaining a coating thickness of 6 μm.

[0048] Example 3

[0049] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0050] The raw materials for the high-temperature resistant acrylic slurry include: 70g of n-butyl acrylate, 7g of 2-hydroxyethyl acrylate, 70g of nano-grade ceramic powder, 70g of urea, 8g of graphene oxide, 3g of the first crosslinking agent, 1.3g of phthalimide diisocyanate, 0.08g of tert-butyl peroxide, 8g of polyvinylidene fluoride, 12g of aluminum hydroxide, and 55g of polymethylphenylsiloxane.

[0051] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 7:3.

[0052] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0053] S1. Nano-sized ceramic powder was added to 130g of 45% ethanol aqueous solution and ultrasonically treated for 100min at a frequency of 6kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 18h at a revolution speed of 600r / min and a rotation speed of 340r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0054] S2. Add the aminated ceramic and graphene oxide to 250g of water, stir at 1800r / min for 80min, add the first crosslinking agent, stir at 75℃ for 3h, directional freeze for 2.5h (the cold source is at the bottom, and the freezing temperature is -30℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0055] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 85°C for 80 min. Add pretreated nano-sized ceramic powder, tert-butyl peroxide, and 360 g of dimethylacetamide and continue stirring for 1.5 h. Cool down to 58°C, add polyvinylidene fluoride, aluminum hydroxide, and polymethylphenylsiloxane, and stir for 10 min at a stirring speed of 2500 r / min. Cool down to room temperature.

[0056] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 60°C for 9 min, drying, placing in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 14% and vitamin C concentration of 0.9 g / mL), reducing at 125°C for 3.5 h, drying, and obtaining a coating thickness of 3 μm.

[0057] Example 4

[0058] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0059] The raw materials for the high-temperature resistant acrylic slurry include: 90g of n-butyl acrylate, 3g of 2-hydroxyethyl acrylate, 90g of nano-grade ceramic powder, 60g of urea, 12g of graphene oxide, 2g of the first crosslinking agent, 1.7g of phthaloyl diisocyanate, 0.02g of benzoyl peroxide, 12g of polyvinylidene fluoride, 8g of aluminum hydroxide, and 60g of polydimethylsiloxane.

[0060] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 5:4.

[0061] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0062] S1. Nano-sized ceramic powder was added to 110g of 55% ethanol aqueous solution and ultrasonically treated for 80min at a frequency of 9kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 12h at a revolution speed of 700r / min and a rotation speed of 260r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0063] S2. Add the aminated ceramic and graphene oxide to 350g of water, stir at 1200r / min for 100min, add the first crosslinking agent, stir at 65℃ for 4h, directional freeze for 1.5h (the cold source is at the bottom, and the freezing temperature is -50℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0064] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 75°C for 100 min. Add pretreated nano-sized ceramic powder, benzoyl peroxide, and 240 g of dimethylacetamide and continue stirring for 2.5 h. Cool down to 52°C, add polyvinylidene fluoride, aluminum hydroxide, and polydimethylsiloxane, and stir for 30 min at a stirring speed of 1500 r / min. Cool down to room temperature.

[0065] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 70°C for 7 min, drying, placing in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 16% and vitamin C concentration of 0.7 g / mL), reducing at 135°C for 2.5 h, drying, and obtaining a coating thickness of 5 μm.

[0066] Example 5

[0067] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0068] The raw materials for the high-temperature resistant acrylic slurry include: 80g of n-butyl acrylate, 5g of 2-hydroxyethyl acrylate, 80g of nano-grade ceramic powder, 65g of urea, 10g of graphene oxide, 2.5g of the first crosslinking agent, 1.5g of phthalimide diisocyanate, 0.05g of benzoyl peroxide, 10g of polyvinylidene fluoride, 10g of aluminum hydroxide, and 58g of polydimethylsiloxane.

[0069] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 6:3.5.

[0070] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0071] S1. Nano-sized ceramic powder was added to 120g of 50% ethanol aqueous solution and ultrasonically treated for 90min at a frequency of 7.5kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 15h at a revolution speed of 650r / min and a rotation speed of 300r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0072] S2. Add the aminated ceramic and graphene oxide to 300g of water, stir at 1500r / min for 90min, add the first crosslinking agent, stir at 70℃ for 3.5h, directional freeze for 2h (the cold source is at the bottom, and the freezing temperature is -40℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0073] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 80℃ for 90 min. Add pretreated nano-sized ceramic powder, benzoyl peroxide, and 300 g of dimethylacetamide and continue stirring for 2 h. Cool down to 55℃, add polyvinylidene fluoride, aluminum hydroxide, and polydimethylsiloxane, and stir for 20 min at a stirring speed of 2000 r / min. Cool down to room temperature.

[0074] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 65°C for 8 min, drying, placing it in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 15% and vitamin C concentration of 0.8 g / mL), reducing it at 130°C for 3 h, drying, and obtaining a coating thickness of 4 μm.

[0075] Comparative Example 1

[0076] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0077] The raw materials for the high-temperature resistant acrylic slurry include: 80g of n-butyl acrylate, 5g of 2-hydroxyethyl acrylate, 80g of nano-grade ceramic powder, 10g of graphene oxide, 2.5g of the first crosslinking agent, 1.5g of phthalimide diisocyanate, 0.05g of benzoyl peroxide, 10g of polyvinylidene fluoride, 10g of aluminum hydroxide, and 58g of polydimethylsiloxane.

[0078] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 6:3.5.

[0079] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0080] S1. Add nano-sized ceramic powder and graphene oxide to 300g of water, stir at 1500r / min for 90min, add the first crosslinking agent, stir at 70℃ for 3.5h, directional freeze for 2h (the cold source is at the bottom, and the freezing temperature is -40℃), and freeze dry to obtain pretreated nano-sized ceramic powder.

[0081] S2. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 80℃ for 90 min. Add pretreated nano-sized ceramic powder, benzoyl peroxide, and 300 g of dimethylacetamide and continue stirring for 2 h. Cool down to 55℃, add polyvinylidene fluoride, aluminum hydroxide, and polydimethylsiloxane, and stir for 20 min at a stirring speed of 2000 r / min. Cool down to room temperature.

[0082] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 65°C for 8 min, drying, placing it in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 15% and vitamin C concentration of 0.8 g / mL), reducing it at 130°C for 3 h, drying, and obtaining a coating thickness of 4 μm.

[0083] Comparative Example 2

[0084] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0085] The raw materials for the high-temperature resistant acrylic slurry include: 80g of n-butyl acrylate, 5g of 2-hydroxyethyl acrylate, 80g of nano-grade ceramic powder, 65g of urea, 10g of graphene oxide, 2.5g of the first crosslinking agent, 1.5g of phthalimide diisocyanate, 0.05g of benzoyl peroxide, 10g of polyvinylidene fluoride, 10g of aluminum hydroxide, and 58g of polydimethylsiloxane.

[0086] The first crosslinking agent is composed of glutaraldehyde and resorcinol in a mass ratio of 6:3.5.

[0087] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0088] S1. Nano-sized ceramic powder was added to 120g of 50% ethanol aqueous solution and ultrasonically treated for 90min at a frequency of 7.5kHz. Urea was added and the mixture was then fed into a planetary ball mill and ball-milled for 15h at a revolution speed of 650r / min and a rotation speed of 300r / min. The mixture was then filtered, washed, and vacuum-dried to obtain aminated ceramic.

[0089] S2. Add the aminated ceramic and graphene oxide to 300g of water, stir at 1500r / min for 90min, add the first crosslinking agent, stir at 70℃ for 3.5h, freeze at -40℃ for 2h (with the cold source around the perimeter), and freeze-dry to obtain pretreated nano-sized ceramic powder.

[0090] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 80℃ for 90 min. Add pretreated nano-sized ceramic powder, benzoyl peroxide, and 300 g of dimethylacetamide and continue stirring for 2 h. Cool down to 55℃, add polyvinylidene fluoride, aluminum hydroxide, and polydimethylsiloxane, and stir for 20 min at a stirring speed of 2000 r / min. Cool down to room temperature.

[0091] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 65°C for 8 min, drying, placing it in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 15% and vitamin C concentration of 0.8 g / mL), reducing it at 130°C for 3 h, drying, and obtaining a coating thickness of 4 μm.

[0092] Comparative Example 3

[0093] A high-temperature resistant acrylic membrane includes: a polypropylene film and a high-temperature resistant acrylic slurry coated on both sides of the polypropylene film.

[0094] The raw materials for the high-temperature resistant acrylic slurry include: 80g of n-butyl acrylate, 5g of 2-hydroxyethyl acrylate, 80g of nano-grade ceramic powder, 10g of graphene oxide, 1.5g of dimethyl diisocyanate, 0.05g of benzoyl peroxide, 10g of polyvinylidene fluoride, 10g of aluminum hydroxide, and 58g of polydimethylsiloxane.

[0095] The above-mentioned high-temperature resistant acrylic slurry is prepared using the following steps:

[0096] S1. Add nano-sized ceramic powder and graphene oxide to 300g of water, stir at 1500r / min for 90min, and freeze dry to obtain pretreated nano-sized ceramic powder.

[0097] S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and dimethyl diisocyanate, and stir at 80℃ for 90 min. Add pretreated nano-sized ceramic powder, benzoyl peroxide, and 300 g of dimethylacetamide and continue stirring for 2 h. Cool down to 55℃, add polyvinylidene fluoride, aluminum hydroxide, and polydimethylsiloxane, and stir for 20 min at a stirring speed of 2000 r / min. Cool down to room temperature.

[0098] The preparation method of the above-mentioned high-temperature resistant acrylic diaphragm includes the following steps: coating the two sides of the base membrane with high-temperature resistant acrylic slurry, curing at 65°C for 8 min, drying, placing it in an aqueous solution containing ammonia and vitamin C (ammonia concentration of 15% and vitamin C concentration of 0.8 g / mL), reducing it at 130°C for 3 h, drying, and obtaining a coating thickness of 4 μm.

[0099] The products obtained in Examples 1-5 and Comparative Examples 1-3 were cut into 15mm × 200mm pieces and stretched under constant tension using a tensile testing machine at a speed of 50mm / min until the diaphragm broke.

[0100] like Figure 1 As shown, the tensile strength of the product obtained in Example 5 was the highest, which was better than that of Comparative Example 1 and Comparative Example 3 (P < 0.05), but there was no significant difference compared with Examples 1-4 and Comparative Example 2 (P > 0.05).

[0101] The products obtained in Examples 1-5 and Comparative Examples 1-3 were cut into 100mm × 100mm pieces and then subjected to heat shrinkage tests. The heat shrinkage test conditions were 200℃ × 1h.

[0102] like Figure 2 As shown, the thermal shrinkage rate of the products obtained in Example 5 was the lowest, which was better than that of Comparative Examples 1-3 (P<0.05), but there was no significant difference from Examples 1-4 (P>0.05).

[0103] The products obtained in Examples 1-5 and Comparative Examples 1-3 were subjected to absorption tests in a membrane electrolyte (EC:PC:EMC:EP = 1:1:1:1). The sample size was 50mm × 100mm, and the weight was recorded as M0. After soaking in the electrolyte for 24 hours, the weight was recorded as M1.

[0104] Liquid absorption rate = (M1 - M0) ÷ M0 × 100%.

[0105] The products obtained in Examples 1-5 and Comparative Examples 1-3 were used to form button cells with ternary positive electrode sheets and graphite negative electrode sheets, respectively. The ionic conductivity was tested at room temperature (25°C) with a frequency of 0-100000Hz and a perturbation voltage of 5mV.

[0106] like Figure 3 As shown, the product obtained in Example 5 had the highest liquid absorption rate and ionic conductivity, which was better than that of Comparative Examples 1-3 (P < 0.05), but there was no significant difference compared with Examples 1-4 (P > 0.05).

[0107] The above-mentioned button cell batteries were subjected to discharge rate testing as follows: The button cell batteries were charged at a constant current and constant voltage (0.5C) to 4.35V, then charged at a constant voltage until the current dropped to 0.05C (cutoff). They were then discharged to 3.0V at currents of 0.2C, 1.0C, and 2.0C, respectively, and the discharge capacity at different discharge rates was recorded. The discharge capacity at 0.2C was taken as 100%, and the corresponding battery capacity retention rate was calculated.

[0108] like Figure 4 As shown, the button cell made from the product of Example 5 had the highest capacity retention rate, which was better than that of Comparative Examples 1-3 (P<0.05), but there was no significant difference from Examples 1-4 (P>0.05).

[0109] The applicant believes that the above results are due to the following: This invention uses urea as an ammonia source to blend and modify nanoscale ceramic powder, thereby modifying the ceramic structure with amino groups. After cross-linking with graphene oxide, the graphene oxide and ceramic powder are tightly bonded together, resulting in extremely high stability. Subsequently, a regular aerogel structure is formed through directional freezing, which not only has a higher thermal conductivity and better high-temperature stability, but also excellent dispersion and compatibility with acrylic resin, significantly enhancing the high-temperature strength of acrylic resin. At the same time, the directional and regular graphene oxide sheet structure forms ion conduction pathways, effectively improving ion conduction performance.

[0110] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant acrylic diaphragm, characterized in that, include: Base film and high-temperature resistant acrylic slurry coated on both sides of the base film; The base film is a polyolefin film; the raw materials of the high-temperature resistant acrylic slurry include, by weight, 50-100 parts of n-butyl acrylate, 1-10 parts of 2-hydroxyethyl acrylate, 50-100 parts of nano-grade ceramic powder, 50-80 parts of urea, 5-15 parts of graphene oxide, 1-4 parts of the first crosslinking agent, 1-2 parts of the second crosslinking agent, 0.01-0.1 parts of initiator, 5-15 parts of polyvinylidene fluoride, 5-15 parts of aluminum hydroxide, and 50-65 parts of polysiloxane. The first crosslinking agent includes glutaraldehyde and resorcinol; the second crosslinking agent is dimethyl diisocyanate.

2. The high-temperature resistant acrylic diaphragm according to claim 1, characterized in that, The base film is a polypropylene film with a thickness of 10-20 μm and a porosity of 35-45%.

3. The high-temperature resistant acrylic diaphragm according to claim 1, characterized in that, The mass ratio of glutaraldehyde to resorcinol is 4-8:2-5.

4. The high-temperature resistant acrylic diaphragm according to claim 1, characterized in that, The initiator is a peroxide initiator.

5. The high-temperature resistant acrylic diaphragm according to claim 1, characterized in that, High-temperature resistant acrylic slurry is prepared using the following steps: S1. Add nano-sized ceramic powder to an ethanol aqueous solution and sonicate for 1-2 hours. Add 50-80 parts of urea and ball mill for 10-20 hours. Filter, wash, and vacuum dry to obtain aminated ceramic. S2. Add the aminated ceramic and graphene oxide to water and stir for 1-2 hours. Add the first crosslinking agent and stir at 60-80°C for 2-5 hours. Directional freeze for 1-3 hours and freeze dry to obtain pretreated nano-sized ceramic powder. S3. Mix n-butyl acrylate, 2-hydroxyethyl acrylate, and the second crosslinking agent, and stir at 70-90℃ for 1-2 hours. Add pretreated nano-sized ceramic powder, initiator, and dimethylacetamide, and continue stirring for 1-3 hours. Cool down to 50-60℃, add polyvinylidene fluoride, aluminum hydroxide, and polysiloxane, and stir for 10-30 minutes. Cool down to room temperature.

6. The high-temperature resistant acrylic diaphragm according to claim 5, characterized in that, In S2, during the directional freezing process, the cold source is at the bottom, and the freezing temperature is -30 to -50℃.

7. A method for preparing a high-temperature resistant acrylic diaphragm as described in any one of claims 1-6, characterized in that, The process includes the following steps: coating both sides of the base film with high-temperature resistant acrylic slurry, curing at 50-80℃ for 5-10 minutes, drying, placing it in an aqueous solution containing ammonia and vitamin C, reducing it at 120-140℃ for 2-4 hours, drying, and obtaining a coating thickness of 2-6 μm.

8. The method for preparing the high-temperature resistant acrylic membrane according to claim 7, characterized in that, In an aqueous solution containing ammonia and vitamin C, the ammonia concentration is 12-18% and the vitamin C concentration is 0.5-1 g / mL.

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