Aramid composite and its use in composite separators

Abstract

The application provides an aramid fiber composite and application thereof in a composite diaphragm, and relates to the technical field of battery diaphragms. The aramid fiber composite is prepared by the following method: dissolving a cosolvent and a dispersing agent in a high-temperature solvent, adding diamine and phthaloyl chloride in sequence under the conditions of nitrogen and low temperature, and reacting under high-speed stirring; stopping the reaction, diluting by using a solvent, and obtaining aramid nanofibers after filtration and washing; immersing the aramid nanofibers in a diisocyanate ethanol solution, washing and drying after stirring reaction, and obtaining diisocyanate-wrapped aramid fibers; immersing the diisocyanate-wrapped aramid fibers in a polyethyleneimine aqueous solution, and obtaining the aramid fiber composite after stirring reaction, washing and drying. The aramid nanocomposite with a specific structure is modified, the functional group adsorption and interface regulation principle are combined, a high-performance composite diaphragm with strong interface combination, ion management capability, thermodynamic stability and controllable moisture absorption is obtained, and the high-performance composite diaphragm is significantly superior to a traditional inorganic coating diaphragm or a single ANF modified diaphragm.

Description

Technical Field

[0001] This application relates to the field of battery separator technology, and more specifically, to an aramid composite and its application in composite separators. Background Technology

[0002] In various battery devices such as lithium-ion batteries and energy storage batteries, the separator, as one of the core components, plays a crucial role in isolating the positive and negative electrodes, preventing short circuits, and ensuring smooth ion transport. Its comprehensive performance directly determines the battery's cycle stability, safety, and lifespan. With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage, the market's requirements for battery energy density, cycle life, and safety performance are constantly increasing. The technical shortcomings of traditional battery separators are becoming increasingly prominent, and have become a core bottleneck restricting battery performance upgrades.

[0003] Battery separators widely used in existing technologies generally suffer from numerous performance defects. Among these, poor interfacial compatibility is the primary problem. The interaction between the separator and the electrolyte and electrode materials is weak, which easily leads to increased interfacial impedance, causing abnormal growth of the solid electrolyte interphase (SEI) film and accelerating battery capacity decay. Simultaneously, the surface coating of the separator often employs a simple coating process, resulting in insufficient adhesion between the coating and the base film. Under the mechanical stress of battery charge-discharge cycles and the corrosive effects of electrolyte, the coating is prone to peeling and powdering, further deteriorating interfacial stability and even causing potential internal short circuits.

[0004] Furthermore, existing separators have low ion adsorption and regulation capabilities, failing to effectively adjust ion transport rates and distribution uniformity. This leads to an imbalance in lithium-ion flux, affecting battery charge and discharge efficiency and inducing lithium dendrite growth, threatening battery safety. Traditional separators also exhibit significant deficiencies in mechanical and heat resistance. Their poor mechanical strength makes them unable to withstand tensile and puncture stresses during battery assembly and cycling, making them prone to breakage. Poor heat resistance causes pore collapse and dimensional shrinkage under high-temperature conditions, leading to short circuits at the positive and negative electrodes, and in severe cases, even inducing thermal runaway.

[0005] These defects, when combined, lead to shortened battery cycle life and increased safety hazards, making it difficult to meet the demands of high-end batteries. Therefore, developing a separator material that can significantly improve interfacial compatibility, solve the coating peeling problem, and simultaneously impart excellent ion adsorption control capabilities, synergistically enhance mechanical properties and heat resistance, achieving a balance between separator stability and ion transport performance, and optimizing overall battery performance, has become a pressing technical problem in the current battery field. This also provides an urgent practical need and technological direction for the development of the composite material in this application. Summary of the Invention

[0006] The purpose of this application is to provide an aramid composite that enriches the surface with amino and urea bonds through HDI and PEI grafting, which can effectively adsorb lithium ions and transition metal ions, inhibit dendrite growth, and significantly enhance the interfacial bonding with coatings and membrane substrates.

[0007] Another objective of this application is to provide an application of aramid composite in battery separators, which employs a double-layer coating of inorganic ceramic and aramid composite to achieve coating non-detachment, controllable ion transport, moderate balance of hygroscopicity, and synergistic improvement of mechanical and heat resistance, thereby significantly improving battery cycle performance and safety.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows: On the one hand, this application provides an aramid composite, which is prepared by the following method: S1. Dissolve the solubilizing salt and dispersant in a high-temperature solvent, and under nitrogen and low-temperature conditions, add diamine and phthaloyl chloride in sequence, and react under high-speed stirring; S2. When the Weissenberg effect occurs, the reaction is stopped. The solution is diluted with solvent and then filtered and washed to obtain aramid nanofibers. S3. Immerse aramid nanofibers in a diisocyanate ethanol solution, stir and react, then wash and dry to obtain diisocyanate-coated aramid. S4. The above-mentioned diisocyanate-coated aramid is immersed in a polyethyleneimine aqueous solution, and after stirring, washing, and drying, the aramid composite is obtained.

[0009] On the other hand, this application provides an application of aramid composite in composite separators. The composite separator uses PP, PE, BOPP, PET, PI film, aramid film, PA film, PPS film, PVDF film or PES film as substrate. The aramid composite, binder and inorganic ceramic particles are dispersed in water to obtain a slurry. The slurry is coated on one or both sides of the substrate and dried to obtain the composite separator.

[0010] Compared with the prior art, the embodiments of this application have at least the following advantages or beneficial effects: This application obtains highly dispersible aramid nanofibers with a high aspect ratio through an optimized ANF preparation process; further, the aramid fibers are surface-grafted with diisocyanate and polyethyleneimine to obtain an ANF composite, the surface of which is enriched with a large number of amino groups (…). The compound contains amino and urea bonds (-NH-CO-NH-). This compound is then combined with an inorganic ceramic slurry and coated onto the surface of a PE separator to form a double-layer coating structure. In this application, the amino and urea functional groups in the composite can effectively adsorb and complex lithium ions and transition metal ions during battery cycling, inhibiting the formation of "dead lithium" and metal dendrites, while simultaneously regulating the interfacial ion distribution and transport kinetics. The strong hydrophilicity of the amino group and the hydrogen bond network of the urea bond work synergistically to moderately regulate the hygroscopicity of the coating, avoiding interfacial side reactions caused by excessive water absorption, while simultaneously enhancing the interfacial adhesion between the coating and the PE substrate.

[0011] Therefore, based on experimental data, this application significantly improves the interfacial compatibility between the inorganic ceramic coating and the PE separator, fundamentally solving the problem of coating easy detachment and powder shedding during long-term cycling or bending processing; it endows the separator with active ion adsorption and regulation capabilities, effectively stabilizing lithium ion flow and suppressing concentration polarization, thereby significantly improving the cycle life and rate performance of the battery; it rationally controls hygroscopicity, ensuring good electrolyte wetting to reduce interfacial impedance, while avoiding the decrease in separator dimensional stability due to excessive hygroscopicity, achieving a hydrophilic / hydrophobic balance of the separator; through the nanofiber bridging effect of the ANF composite and interfacial hydrogen bond crosslinking, it synergistically improves the mechanical strength (such as peel strength) and heat shrinkage resistance (significantly reduced heat shrinkage rate) of the coating, ensuring the safety of the separator under high temperature or abuse conditions. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a SEM image of the aramid composite obtained in Example 1 of this application; Figure 2 This is a photograph of the diaphragm after a heat resistance test at 220 °C in Example 1 of this application. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to specific embodiments.

[0016] An aramid composite, said aramid composite being prepared by the following method: S1. Dissolve the solubilizing salt and dispersant in a high-temperature solvent, and under nitrogen and low-temperature conditions, add diamine and phthaloyl chloride in sequence, and react under high-speed stirring; S2. When the Weissenberg effect occurs, the reaction is stopped. The solution is diluted with solvent and then filtered and washed to obtain aramid nanofibers. S3. Immerse aramid nanofibers in a diisocyanate ethanol solution, stir and react, then wash and dry to obtain diisocyanate-coated aramid. S4. The above-mentioned diisocyanate-coated aramid is immersed in a polyethyleneimine aqueous solution, and after stirring, washing, and drying, the aramid composite is obtained.

[0017] In some embodiments of this application, the solubilizing salt in step S1 above includes one or more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, aluminum chloride, sodium acetate, potassium acetate, zinc acetate, lithium bromide, lithium iodide, methyltri-n-butylammonium chloride, and tetraethylammonium chloride, and the mass concentration of the solubilizing salt in the system is 3-10%; the dispersant is 5-15% of the mass of diamine and phthaloyl chloride, and the molar ratio of diamine to phthaloyl chloride is 1:(1.01-1.3).

[0018] In some embodiments of this application, the dispersant in step S1 above includes any one or more of the following: methoxy polyethylene glycol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, Tween 80, Span 80, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium polyacrylate, and naphthalene sulfonate dispersants. The solvent includes any one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, 1,3-dimethylimidazolinone, dimethyl sulfoxide, sulfolane, pyridine, N-ethylpyrrolidone, N-butylpyrrolidone, tetrahydrofuran, and dichloromethane; The phthaloyl chloride includes isophthaloyl chloride, terephthaloyl chloride, and o-phthaloyl chloride; the diamine includes any one or more of the following: diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]propane, bis(trifluoromethyl)-4,4'-diaminobiphenyl, bis(4-aminophenoxy)benzene, bis(3-aminophenoxy)benzene, diaminocyclohexylmethane, isophorone diamine, cyclohexane diamine, diaminodicyclohexylbenzene, ethylenediamine, hexamethylenediamine, diaminobenzoic acid, butanediamine, and phenylenediamine.

[0019] In some embodiments of this application, the high temperature in step S1 is 80-100 ℃, and the low temperature is 0-10 ℃.

[0020] In some embodiments of this application, the diisocyanate in step S3 above includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, terephthalic diisocyanate, 1,6-hexamethylene diisocyanate, phenylenediamine diisocyanate, and tetramethylphenylenediamine diisocyanate.

[0021] In some embodiments of this application, the molar ratio of aramid to diisocyanate and polyethyleneimine in steps S3 and S4 above is 1:(0.01-0.05):(0.03-0.1).

[0022] In some embodiments of this application, the stirring reaction in step S4 above is carried out at a temperature of 40-60 °C, a rotation speed of 200-500 r / min, and a time of 3-6 h; washing is performed by rinsing with anhydrous ethanol and deionized water in sequence; drying is performed by vacuum drying at 60-80 °C to constant weight.

[0023] In some embodiments of this application, the stirring reaction in step S5 above is carried out at a temperature of 40-60 °C, a rotation speed of 200-500 r / min, and a time of 4-8 h; washing is performed by repeated rinsing with deionized water; and drying is performed by vacuum drying at 60-80 °C to constant weight.

[0024] An application of an aramid composite in a composite separator, wherein the composite separator uses PP, PE, BOPP, PET, PI film, aramid film, PA film, PPS film, PVDF film or PES film as substrate, the aramid composite, binder and inorganic ceramic particles are dispersed in water to obtain a slurry, the slurry is coated on one or both sides of the substrate, and the composite separator is obtained after drying.

[0025] In some embodiments of this application, by mass ratio, the inorganic ceramic slurry comprises 80-90%, the aramid composite 5-10%, and the binder 5-10%; the solid content of the slurry is 10-30%; the inorganic ceramic particles include boehmite, The substrate comprises one or more of the following: silica, magnesium oxide, boron nitride, titanium dioxide, LATP, LZTP, and LLZO; the binder comprises one or more of the following: polyacrylic acid, polyacrylate, styrene-butadiene rubber latex, low molecular weight polyvinylidene fluoride, polymethyl methacrylate, polyvinyl alcohol, polyurethane, and polyacrylamide; the substrate thickness is 3-9 μm, and the thickness of the single-layer coating is 1-3 μm.

[0026] The features and performance of this application will be further described in detail below with reference to the embodiments. Example 1

[0027] S1, Take 5 g 0.36 g of PEG was added and dissolved in 100 mL of N-methylpyrrolidone (NMP) in a reactor under a nitrogen atmosphere at 100 °C. The reaction system was then cooled to 5 °C using an ice-water bath, and p-phenylenediamine (10 mmol) and diaminophthalic acid (10 mmol) were added at low temperature and dissolved in the NMP solution with stirring. 20.14 mmol of terephthaloyl chloride (TPC) was added, and the reaction was initiated with high-speed stirring. The reaction was stopped when the Weissenberg effect occurred, and the solution was diluted with excess NMP. Subsequently, the diluent was slowly added to a large volume of deionized water, and the mixture was filtered and washed to obtain aramid nanofibers (ANF).

[0028] The above-mentioned aramid nanofibers were soaked in anhydrous ethanol for 3.5 h, then rinsed three times successively with deionized water and anhydrous ethanol, and dried under vacuum at 60 ℃ for 8 h to constant weight. 0.5 g of the dried aramid was immersed in 50 mL of 1,6-hexamethylene diisocyanate ethanol solution, stirred at 42 ℃ and 200 r / min for 3 h, rinsed successively with anhydrous ethanol and deionized water, and dried under vacuum at 60 ℃ to constant weight to obtain hexamethylene diisocyanate-coated aramid. 0.3 g of hexamethylene diisocyanate-coated aramid was weighed and immersed in 50 mL of polyethyleneimine (PEI) aqueous solution, stirred at 50 ℃ and 200 r / min for 5 h, rinsed repeatedly with deionized water, and dried under vacuum at 60 ℃ to constant weight to complete the grafting, obtaining the aramid composite. In this example, ANF:HDI:PEI = 1:0.02:0.04. The SEM morphology of the aramid composite product in this example is shown below. Figure 1 As shown.

[0029] S2. Mix 82 parts of inorganic particles (silica), 10 parts of aramid composite and 8 parts of PI and disperse them evenly in an aqueous solvent to obtain a coating slurry with a solid content of 25%. Apply the coating slurry to both sides of a PE film with a thickness of 7 μm using a doctor blade. The coating thickness on one side is 2 μm. After drying at 80 ℃ for 1.5 h, a coating layer is formed, and finally a composite membrane is obtained. Example 2

[0030] S1. 5 g LiCl and 0.36 g PEG were added and dissolved in 100 ml N-methylpyrrolidone (NMP) in a reactor under a nitrogen atmosphere at 100 °C. The reaction system was then cooled to 5 °C using an ice-water bath. 15 mmol of pyromellitic diamine and 5 mmol of 1,6-hexanediamine were added and dissolved in the NMP solution with stirring. 20.10 mmol of terephthaloyl chloride (TPC) was added, followed by pyridine after 1 min, and the reaction was initiated with high-speed stirring. The reaction was stopped when the Weissenberg effect occurred. After gelation, excess NMP was used for dilution. Subsequently, the diluent was slowly added to a large amount of deionized water, and the mixture was filtered and washed to obtain aramid nanofibers (ANF).

[0031] The above-mentioned aramid nanofibers were soaked in anhydrous ethanol for 4 h, then rinsed sequentially with deionized water and anhydrous ethanol, and dried under vacuum at 60 °C to constant weight. 0.5 g of the dried aramid was immersed in 50 mL of terephthalic diisocyanate ethanol solution, stirred at 42 °C and 200 r / min for 3 h, rinsed sequentially with anhydrous ethanol and deionized water, and dried under vacuum at 60 °C to constant weight to obtain terephthalic diisocyanate-coated aramid. 0.3 g of terephthalic diisocyanate-coated aramid was weighed and immersed in 50 mL of polyethyleneimine (PEI) aqueous solution, stirred at 50 °C and 200 r / min for 5 h, rinsed repeatedly with deionized water, and dried under vacuum at 60 °C to constant weight to complete the grafting process, obtaining the aramid composite. In this example, ANF:terephthalic diisocyanate:PEI = 1:0.025:0.04.

[0032] S2. Mix 85 parts of inorganic particles (silica), 8 parts of aramid composite and 7 parts of PI and disperse them evenly in an aqueous solvent to obtain a coating slurry with a solid content of 25%. Apply the coating slurry to both sides of a PE film with a thickness of 7 μm using a doctor blade. The coating thickness on one side is 2 μm. After drying at 80 ℃ for 1.5 h, a coating layer is formed, and finally a composite membrane is obtained. Example 3

[0033] S1, Take 5 g 0.36 g of PEG was added and dissolved in 100 mL of N-methylpyrrolidone (NMP) in a reactor under a nitrogen atmosphere at 100 °C. The reaction system was then cooled to 5 °C using an ice-water bath, and p-phenylenediamine (10 mmol) and 1,6-hexanediamine (10 mmol) were added at low temperature and dissolved in the NMP solution with stirring. 20.14 mmol of terephthaloyl chloride (TPC) was added, and the reaction was initiated with high-speed stirring. The reaction was stopped when the Weissenberg effect occurred, and the solution was diluted with excess NMP. Subsequently, the diluent was slowly added to a large volume of deionized water, and the mixture was filtered and washed to obtain aramid nanofibers (ANF).

[0034] The above-mentioned aramid nanofibers were soaked in anhydrous ethanol for 3.5 h, then rinsed three times successively with deionized water and anhydrous ethanol, and dried under vacuum at 60 ℃ for 8 h to constant weight. 0.5 g of the dried aramid was immersed in 50 mL of 1,6-hexamethylene diisocyanate ethanol solution, stirred at 42 ℃ and 200 r / min for 3 h, rinsed successively with anhydrous ethanol and deionized water, and dried under vacuum at 60 ℃ to constant weight to obtain 1,6-hexamethylene diisocyanate-coated aramid. 0.3 g of 1,6-hexamethylene diisocyanate-coated aramid was weighed and immersed in 50 mL of polyethyleneimine (PEI) aqueous solution, stirred at 50 ℃ and 200 r / min for 5 h, rinsed repeatedly with deionized water, and dried under vacuum at 60 ℃ to constant weight to complete the grafting and obtain the aramid composite. In this example, ANF:1,6-hexamethylene diisocyanate:PEI = 1:0.02:0.04.

[0035] S2. Mix 83 parts of silica, 7 parts of aramid composite, 7 parts of PI, and 3 parts of PVDF evenly and disperse them in an aqueous solvent to obtain a coating slurry with a solid content of 25%. Apply the coating slurry to both sides of a PE film with a thickness of 7 μm using a doctor blade, with a coating thickness of 2 μm on each side. After drying at 80 ℃ for 1.5 h, a coating layer is formed, and finally a composite membrane is obtained.

[0036] Comparative Example 1

[0037] Take 5 g 0.36 g of PEG was added and dissolved in 100 mL of N-methylpyrrolidone (NMP) in a reactor under a nitrogen atmosphere at 100 °C. The reaction system was then cooled to 5 °C using an ice-water bath, and p-phenylenediamine (10 mmol) and diaminophthalic acid (10 mmol) were added at low temperature and dissolved in the NMP solution with stirring. 20.14 mmol of terephthaloyl chloride (TPC) was added, and the reaction was initiated with high-speed stirring. The reaction was stopped when the Weissenberg effect occurred, and the solution was diluted with excess NMP. Subsequently, the diluent was slowly added to a large volume of deionized water, and the mixture was filtered and washed to obtain aramid nanofibers (ANF).

[0038] 82 parts of silica, 10 parts of aramid and 8 parts of PI were mixed and dispersed evenly in an aqueous solvent to obtain a coating slurry with a solid content of 25%. The coating slurry was coated on both sides of a PE film with a thickness of 7 μm using a doctor blade, with a coating thickness of 2 μm on each side. After drying at 80 °C for 1.5 h, a coating layer was formed.

[0039] Comparative Example 2

[0040] 90 parts of silica and 10 parts of PI were mixed and dispersed evenly in an aqueous solvent to obtain a coating slurry with a solid content of 25%. The coating slurry was then coated onto both sides of a PE film with a thickness of 7 μm using a doctor blade, with a coating thickness of 2 μm on each side. After drying at 80℃ for 1.5 h, a coating layer was formed.

[0041] Experimental Example

[0042] 1. The membranes obtained in Examples 1-3 and Comparative Examples 1-2 were cut into multiple groups of 10×10cm and dried at 220℃ for 1 h. Their heat resistance was tested, and their shrinkage rate after heating is shown in Table 1. The photograph of the membrane of Example 1 after the heat resistance test at 220℃ is shown in Table 1. Figure 2 As shown.

[0043] Table 1

[0044] As can be seen from Table 1, after heat treatment at 220 °C for 1 h, the composite membranes prepared in Examples 1-3 had a longitudinal thermal shrinkage rate DL≤2.1% and a transverse thermal shrinkage rate DW≤2.3%, which were much lower than those in Comparative Example 1 (DL=12.3%, DW=11.2%) and Comparative Example 2 (DL=15.0%, DW=15.2%). This indicates that after aramid nanofibers (ANF) were modified by grafting with diisocyanate and PEI, a rigid three-dimensional cross-linked network was formed in the coating. It constructed a composite structure of "fiber skeleton-particle filling-bonding cross-linking" with silica particles and PI binder. At a high temperature of 220 °C, it effectively suppressed the thermal deformation and slippage of the PE base film and the coating, and improved the high-temperature dimensional stability of the membrane.

[0045] 2. Cut the films obtained in Examples 1-3 and Comparative Examples 1-2 into samples of the same size and measure their peel strength. The data obtained are shown in Table 2.

[0046] Table 2

[0047] As shown in Table 2, the peel strength of the examples was 0.62-0.68 MPa, while that of Comparative Example 1 was only 0.45 MPa, and that of Comparative Example 2 was 0.32 MPa. This indicates that the isocyanate-PEI segments grafted onto the aramid surface form hydrogen bonds and covalent bonds with the silica particles, and react with the active sites on the PI binder and PE base film surface, significantly improving the interfacial adhesion between the coating and the base film, as well as within the coating itself, thus preventing coating detachment during cycling. In contrast, the unmodified aramid and binder are only physically entangled, resulting in weak interfacial adhesion, and long-term cycling easily leads to coating cracking and detachment. The pure PI binder has poor interfacial affinity with the PE base film, resulting in insufficient coating adhesion and easy peeling failure.

[0048] 3. Cut the membranes obtained in Examples 1-3 and Comparative Examples 1-2 into separator sizes, assemble them into batteries, and measure their impedance. The data obtained are shown in Table 3.

[0049] Table 3

[0050] As shown in Table 3, the impedance of the examples is 2.05-2.18 Ω / cm², the impedance of Comparative Example 1 is 2.55 Ω / cm², and the impedance of Comparative Example 2 is 2.85 Ω / cm². This indicates that the aramid composite modification optimizes the pore structure of the coating, resulting in higher interconnected porosity between the fiber skeleton and inorganic particles, better electrolyte wettability, and lower ion transport resistance. Simultaneously, the stable interface structure prevents pore collapse at high temperatures, ensuring the integrity of the ion transport channels. In contrast, unmodified aramid is prone to agglomeration, leading to uneven pore distribution in the coating, local pore blockage, and increased ion transport resistance. Pure PI coatings are prone to microcracks or low porosity due to uneven stress during coating, resulting in discontinuous ion transport channels and a significant increase in impedance.

[0051] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An aramid composite, characterized in that, The aramid composite is prepared by the following method: S1. Dissolve the solubilizing salt and dispersant in a high-temperature solvent, and under nitrogen and low-temperature conditions, add diamine and phthaloyl chloride in sequence, and react under high-speed stirring; S2. When the Weissenberg effect occurs, the reaction is stopped. The solution is diluted with solvent and then filtered and washed to obtain aramid nanofibers. S3. Immerse aramid nanofibers in a diisocyanate ethanol solution, stir and react, then wash and dry to obtain diisocyanate-coated aramid. S4. The above-mentioned diisocyanate-coated aramid is immersed in a polyethyleneimine aqueous solution, and after stirring, washing, and drying, the aramid composite is obtained.

2. The aramid composite according to claim 1, characterized in that, In step S1, the co-solubilizing salt includes one or more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, aluminum chloride, sodium acetate, potassium acetate, zinc acetate, lithium bromide, lithium iodide, methyltri-n-butylammonium chloride, and tetraethylammonium chloride, and the mass concentration of the co-solubilizing salt in the system is 3-10%; the dispersant is 5-15% of the mass of diamine and phthaloyl chloride, and the molar ratio of diamine to phthaloyl chloride is 1:(1.01-1.3).

3. The aramid composite according to claim 2, characterized in that, The dispersant in step S1 includes any one or more of the following: methoxy polyethylene glycol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, Tween 80, Span 80, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium polyacrylate, and naphthalene sulfonate dispersants. The solvent includes any one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, 1,3-dimethylimidazolinone, dimethyl sulfoxide, sulfolane, pyridine, N-ethylpyrrolidone, N-butylpyrrolidone, tetrahydrofuran, and dichloromethane; The phthaloyl chloride includes isophthaloyl chloride, terephthaloyl chloride, and o-phthaloyl chloride; the diamine includes any one or more of the following: diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]propane, bis(trifluoromethyl)-4,4'-diaminobiphenyl, bis(4-aminophenoxy)benzene, bis(3-aminophenoxy)benzene, diaminocyclohexylmethane, isophorone diamine, cyclohexane diamine, diaminodicyclohexylbenzene, ethylenediamine, hexamethylenediamine, diaminobenzoic acid, butanediamine, and phenylenediamine.

4. An aramid composite according to claim 1, characterized in that, In step S1, the high temperature is 80-100 ℃, and the low temperature is 0-10 ℃.

5. An aramid composite according to claim 1, characterized in that, The diisocyanate in step S3 includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, terephthalic diisocyanate, 1,6-hexamethylene diisocyanate, phenylenediamine diisocyanate, and tetramethylphenylenediamine diisocyanate.

6. The aramid composite according to claim 1, characterized in that, In steps S3 and S4, the molar ratio of aramid to diisocyanate and polyethyleneimine is 1:(0.01-0.05):(0.03-0.1).

7. An aramid composite according to claim 1, characterized in that, In step S4, the stirring temperature is 40-60 °C, the stirring speed is 200-500 r / min, and the time is 3-6 h; washing is performed by rinsing with anhydrous ethanol and deionized water in sequence; drying is performed by vacuum drying at 60-80 °C to constant weight.

8. An aramid composite according to claim 1, characterized in that, In step S5, the stirring reaction is carried out at a temperature of 40-60 ℃, a rotation speed of 200-500 r / min, and a time of 4-8 h; washing is performed by repeated rinsing with deionized water; drying is performed by vacuum drying at 60-80 ℃ to constant weight.

9. The application of the aramid composite according to any one of claims 1-8 in a composite separator, characterized in that, The composite diaphragm uses PP, PE, BOPP, PET, PI film, aramid film, PA film, PPS film, PVDF film or PES film as the substrate. The aramid composite, binder and inorganic ceramic particles are dispersed in water to obtain a slurry. The slurry is coated on one or both sides of the substrate and dried to obtain the composite diaphragm.

10. The application of the aramid composite according to claim 9 in a composite separator, characterized in that, By mass ratio, the slurry contains 80-90% inorganic ceramic particles, 5-10% aramid composite, and 5-10% binder; the solid content of the slurry is 10-30%; the inorganic ceramic particles include boehmite, The substrate comprises one or more of the following: silica, magnesium oxide, boron nitride, titanium dioxide, LATP, LZTP, and LLZO; the binder comprises one or more of the following: polyacrylic acid, polyacrylate, styrene-butadiene rubber latex, low molecular weight polyvinylidene fluoride, polymethyl methacrylate, polyvinyl alcohol, polyurethane, and polyacrylamide; the substrate thickness is 3-9 μm, and the thickness of the single-layer coating is 1-3 μm.

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