High-temperature energy storage fluorine-containing aromatic polyamide dielectric film and preparation method thereof

Abstract

The application discloses a high-temperature energy storage fluorine-containing aromatic polyamide dielectric film and a preparation method thereof. The preparation method comprises the following steps in sequence: S1. condensation of diacyl chloride monomers and fluorine-containing diamine monomers to obtain fluorine-containing aromatic polyamide raw materials; S2. the fluorine-containing aromatic polyamide raw materials are sequentially dissolved in a polar solvent and a Lewis acid to obtain a uniform fluorine-containing aromatic polyamide solution; and S3. the uniform fluorine-containing aromatic polyamide solution is subjected to film coating and high-temperature heat treatment, and the high-temperature energy storage fluorine-containing aromatic polyamide dielectric film is obtained. The preparation method is suitable for preparing the high-temperature energy storage fluorine-containing aromatic polyamide dielectric film, and the prepared film has no breakdown weak point, high breakdown strength, high energy storage density and excellent energy storage performance under high-temperature conditions.

Description

Technical Field

[0001] This invention belongs to the field of capacitor film technology, and relates to a polyamide dielectric film, specifically a high-temperature energy storage fluorinated aromatic polyamide dielectric film and its preparation method. Background Technology

[0002] Polymer thin film materials are widely used in electrostatic capacitors due to their advantages such as fast charge and discharge rates, high power density, high breakdown strength, self-healing and good processability. Application fields such as new energy vehicles, photovoltaic grid connection, oil and gas exploration, and aerospace have put forward higher requirements for the energy storage performance of polymer thin films at high temperatures (≥150℃).

[0003] Biaxially oriented polypropylene (BOPP) is one of the most commercially successful capacitor film materials, but its mechanical properties and heat resistance are significantly insufficient. It loses its mechanical stability above the glass transition temperature (Tg), so the maximum operating temperature of BOPP film in short-term operation is <105℃, and in long-term operation it is ≤85℃. When the temperature rises above 85℃, BOPP film will show significant conductivity loss, and the discharge efficiency and energy density will drop sharply.

[0004] Para-aramid has excellent high-temperature resistance, but its precursor is difficult to dissolve directly in organic solvents such as DMAC, resulting in poor film-forming processability. Therefore, aramid paper made from short aramid fibers is currently widely used. However, due to the many pores and defects inside aramid paper, its breakdown strength is greatly reduced, generally only about 200kV / mm, making it difficult to use in energy storage capacitors.

[0005] Patent CN111004507A discloses a method for preparing and using a cross-linked polyetherimide-based dielectric composite film. It mainly uses functionalized nano-ceramic particles to undergo a cross-linking reaction with a polyetherimide matrix. The film exhibits excellent dielectric properties, such as high dielectric constant and low dielectric loss, at both room temperature and high temperature. However, the high dielectric constant of the ceramic particles often reduces the breakdown strength of the composite material or makes it difficult to significantly improve the breakdown strength, thus it does not have good energy storage performance. Furthermore, the cross-linking between molecules can significantly damage the toughness of the film, further limiting its application. Patent CN112789326A discloses a high-temperature energy storage hybrid polyetherimide dielectric film, its preparation method, and its application. By introducing nanoscale inorganic particles in situ into the polyetherimide-based dielectric composite film, the dispersion problem of nanomaterials is effectively solved, and ultra-high density deep traps are introduced, resulting in excellent energy storage performance at high temperatures. However, its breakdown strength is still not high, and further enhancement is urgently needed to significantly increase the energy storage density. Furthermore, the inorganic nanoparticles are not covalently fixed to the macromolecular chains, and long-term use may lead to migration and aggregation, affecting energy storage performance. Additionally, its preparation process is relatively complex and costly, making mass production difficult. Patent CN113980312A discloses a high-temperature resistant, high-breakdown-strength intrinsic aramid film and its preparation method. However, its macromolecular chains are difficult to disperse at the molecular level, and the lack of high-temperature kinetic control in the later stages ultimately results in low orientation and crystallinity, poor high-temperature energy storage performance and long-term stability, making direct application in film capacitors difficult. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature energy storage fluorinated aromatic polyamide dielectric film and its preparation method, so as to solve the problems of low breakdown strength, low energy storage density and poor high-temperature resistance of polymer films in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film includes the following steps performed sequentially:

[0009] S1. Polycondense diacyl chloride monomer and fluorinated diamine monomer to obtain fluorinated aromatic polyamide raw material;

[0010] S2. Fluorinated aromatic polyamide raw material is dissolved by sequentially adding a polar solvent and a Lewis acid to obtain a homogeneous solution of fluorinated aromatic polyamide;

[0011] S3. The fluorinated aromatic polyamide uniform solution is coated and subjected to high-temperature heat treatment to obtain the high-temperature energy storage fluorinated aromatic polyamide dielectric film.

[0012] As a limitation, the diacyl chloride monomer includes at least one of terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylate, and 4,4-chloroformylphenyl ether.

[0013] As another limitation, the fluorinated diamine monomer is prepared by fluorination of a diamine monomer;

[0014] The diamine monomer includes at least one selected from p-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzoxazole, biphenyl diamine, 4,4'-diaminobenzoylaniline, 2,2'-dimethyl-1,1'-diaminebiphenyl, 2,2'-dimethyl-1,1'-biphenyl-4,4'-diamine, 4-aminophenyl-4-aminobenzoate, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2'-p-phenyl-bisbenzimidazole diamine, 2-(3-aminophenyl)-5-aminobenzimidazole, 5-methyl-1,3-diaminobenzene, 1,4-bis(4-amino-2-methylphenoxy)benzene, and 4,4'-diaminobiphenyl.

[0015] As a third limitation, the polar solvent includes at least one of N-methylpyrrolidone, N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethyl sulfoxide, acetone, and tetrahydrofuran.

[0016] As a fourth limitation, the Lewis acid includes at least one of calcium chloride, ferric chloride, copper chloride, lithium chloride, calcium bromide, lithium bromide, and sodium acetate.

[0017] As a fifth limitation, the molar ratio of the diacyl chloride monomer to the fluorinated diamine monomer is 1:1.

[0018] As a sixth limitation, the sum of the amounts of the polar solvent and the Lewis acid accounts for 85% to 95% of the mass of the homogeneous solution of the fluorinated aromatic polyamide; the mass ratio of the Lewis acid to the polar solvent is 1:10 to 50.

[0019] As a seventh limitation, the coating is made by coating a glass plate with a uniform solution of fluorinated aromatic polyamide, drying it at 80°C for 1 to 4 hours, and then soaking it in deionized water at 80°C for 1 to 5 hours to remove Lewis acid.

[0020] As an eighth limitation, the high-temperature heat treatment is to hold at 60–150°C for 10–60 min, at 150–250°C for 10–60 min, at 360°C for 10–150 min, or at 390–420°C for 10–150 min.

[0021] The present invention also provides a high-temperature energy storage fluorinated aromatic polyamide dielectric film prepared by the above preparation method.

[0022] By adopting the above technical solution, the technical progress achieved by this invention compared with the prior art is as follows:

[0023] ① The present invention provides a high-temperature energy storage fluorinated aromatic polyamide dielectric film. The aromatic polyamide fluorinated groups generate strong electrostatic interactions with Lewis acids, which completely destroy the hydrogen bond interactions between macromolecular chains, so that the macromolecular chains form molecular-level dispersion in the solvent. During the later film formation process, the molecular-level dispersed macromolecular chains can be tightly packed, so that there are no breakdown weak points in the film and the high-temperature energy storage performance is excellent.

[0024] ② The high-temperature energy storage fluorinated aromatic polyamide dielectric film provided by this invention has a breakdown strength of 700 kV / mm at high temperature (150℃) and an energy storage density of 10 J / cm³. 3 It has a mechanical strength of up to 400MPa and excellent overall performance, which is superior to existing high-temperature energy storage polymer films.

[0025] ③ The present invention provides a method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film. First, the fluorinated aromatic polyamide raw material is dissolved in a polar solvent to obtain a preliminary macroscopic dispersion. Second, by adjusting the content of Lewis acid, the Lewis acid forms a strong electrostatic interaction with the fluorinated groups on the aromatic polyamide and promotes the formation of single coordination of the macromolecular chain, thereby destroying the interaction of inter-chain hydrogen bonds, so that the fluorinated aromatic polyamide reaches the single-chain molecular level dispersion and obtains a uniform solution of fluorinated aromatic polyamide.

[0026] ④ The present invention provides a method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film, which controls the orientation and crystallization kinetics of the fluorinated aromatic polyamide by adjusting the temperature of the heat treatment, thereby preparing a film with high orientation and high crystallinity.

[0027] ⑤ The present invention provides a method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film, which has a simple preparation process, low cost, and is suitable for industrial production.

[0028] The preparation method of the present invention is applicable to the preparation of high-temperature energy storage fluorinated aromatic polyamide dielectric films. The prepared films have no breakdown weak points, high breakdown strength, high energy storage density, and excellent energy storage performance under high temperature conditions. Attached Figure Description

[0029] Figure 1 An optical microscope image of the fluorinated aromatic polyamide dielectric film α1 in Example 1;

[0030] Figure 2 An optical microscope image of the fluorinated aromatic polyamide dielectric film β1 in Example 1;

[0031] Figure 3The combined dielectric properties test results of α1 and β1 of the fluorinated aromatic polyamide dielectric film in Example 1 are shown.

[0032] Figure 4 The images show the XRD patterns of α1 and β1 of the fluorinated aromatic polyamide dielectric film in Example 1, where... Figure 4 a is the XRD pattern of β1. Figure 4 b is the XRD pattern of α1;

[0033] Figure 5 The results show the combined dielectric properties of the fluorinated aromatic polyamide dielectric films α1 and β2 in Example 1. Detailed Implementation

[0034] The present invention will be further described in detail below through specific embodiments. It should be understood that the described embodiments are only for explaining the present invention and do not limit the present invention.

[0035] Example 1: A high-temperature energy storage fluorinated aromatic polyamide dielectric film and related experiments

[0036] This embodiment prepared a high-temperature energy storage fluorinated aromatic polyamide dielectric film, and comparative experiments were conducted to verify the effects of adding Lewis acid and high-temperature heat treatment, specifically including the following steps performed sequentially:

[0037] I. Sample Preparation

[0038] ① Sample 1 was prepared through the following steps:

[0039] S1. Preparation of fluorinated aromatic polyamide raw materials

[0040] Under a nitrogen atmosphere, 10g of 2,2'-bis(trifluoromethyl)-1,1'-biphenyl-4,4'-diamine (prepared by fluorination of 2,2'-dimethyl-1,1'-biphenyl-4,4'-diamine, with the structural formula […]) was first prepared. Add 400g of NMP (N-methylpyrrolidone) and stir to disperse evenly. Gradually add 6.3g of terephthaloyl chloride (2,2'-bis(trifluoromethyl)-1,1'-biphenyl-4,4'-diamine to terephthaloyl chloride in a molar ratio of 1:1). Stir until the gel is clear. After the reaction is complete, wash thoroughly with deionized water to remove HCl and other impurities generated during the reaction. Precipitate to obtain 16g of fluorinated aromatic polyamide raw material.

[0041] S2. Preparation of nascent fluorinated aromatic polyamide films

[0042] Fluorinated aromatic polyamide raw material was added to 298g of DMAC (N,N'-dimethylacetamide) and stirred to initially dissolve and disperse the macromolecular chains of fluorinated aromatic polyamide. Then, 3% (w / w) of LiCl (dMAC by mass) was added to the system and stirred thoroughly to achieve a homogeneous solution of fluorinated aromatic polyamide with monodisperse molecular chains (the sum of the added polar solvent and Lewis acid accounted for 95% of the mass of the homogeneous solution of fluorinated aromatic polyamide). The adhesive was slowly and evenly coated onto a clean glass plate using a coating machine. After film formation, the film was dried at 80℃ for 1h and then further soaked in deionized water at 80℃ for 1h to remove Lewis acid, thus preparing a nascent fluorinated aromatic polyamide film.

[0043] S3. Heat treatment kinetics control for the preparation of fluorinated aromatic polyamide dielectric films.

[0044] The obtained fluorinated aromatic polyamide nascent film was kept at 80℃ for 10 min, at 200℃ for 10 min, at 360℃ for 30 min, and at 400℃ for 10 min to prepare the fluorinated aromatic polyamide dielectric film α1.

[0045] ②Sample 2 was prepared through the following steps:

[0046] The preparation steps of Sample 2 are basically the same as those of Sample 1 in this embodiment for preparing the fluorinated aromatic polyamide dielectric film α1, except that LiCl was not added in step S2, and the fluorinated aromatic polyamide dielectric film prepared is β1.

[0047] ③ Sample 3 was prepared through the following steps:

[0048] The preparation steps of sample 3 are basically the same as steps S1 to S3 of sample 1 in this embodiment for preparing the fluorinated aromatic polyamide dielectric film α1. The only difference is that the heat treatment at 400°C for 10 min was not performed in step S3. The fluorinated aromatic polyamide dielectric film prepared is β2.

[0049] II. Verification Experiment of the Effect of Adding Lewis Acid

[0050] Optical microscopy images were taken of α1 and β1 of the fluorinated aromatic polyamide dielectric films of samples 1 and 2, respectively, and the results are as follows: Figure 1 and Figure 2 As shown;

[0051] Depend on Figure 1 and Figure 2The comparison shows that the transmittance of the fluorinated aromatic polyamide dielectric film β1 is significantly lower than that of α1. This is because in sample 1, the Lewis acid forms a strong electrostatic interaction with the fluorinated groups on the molecular chain, which effectively breaks the hydrogen bond interaction between the macromolecular chains and achieves molecular-level dispersion of the macromolecular chains in the solution. Therefore, the macromolecular chains can self-assemble and stack tightly during the film formation process. In contrast, sample 2 does not have Lewis acid to assist in dispersion, which makes it difficult for the molecular chains to stack tightly. The increased gaps in the samples result in light scattering, leading to a significant decrease in transmittance.

[0052] The comprehensive dielectric properties (including breakdown strength and energy storage density) of the fluorinated aromatic polyamide dielectric films α1 and β1 of Sample 1 and Sample 2 were tested respectively, and the results are as follows: Figure 3 As shown;

[0053] Breakdown strength test method: DC voltage, boost rate of 400V / s, test temperature of 150℃. The sample is clamped between two spherical electrodes, which are then immersed in insulating oil. The sample thickness is controlled between 8 and 15 μm. At least 10 sets of valid data must be collected for each type of film test. Data analysis is based on the following formula.

[0054]

[0055] Where P(E) is the cumulative failure probability; E is the measured breakdown field strength; Eb is the Weibull breakdown strength, which is the field strength when the cumulative failure probability is 63.2%; and β is the shape parameter that determines the data dispersion.

[0056] Energy density testing method: The instrument used was a Sawyer-Tower ferroelectric analyzer from Polyk Inc. (USA) and a Trek 610C power amplifier. The AC voltage was used at a frequency of 100Hz. The sample was coated with gold on both sides (4mm in diameter) between two cylindrical electrodes, and the sample thickness was controlled to be approximately 10μm.

[0057] Depend on Figure 3 It can be seen that the overall dielectric properties of the fluorinated aromatic polyamide dielectric film α1 are significantly better than those of β1. The reason is that after the Lewis acid in sample 1 forms a strong electrostatic interaction with the fluorinated groups on the molecular chain, it effectively breaks the hydrogen bond interaction between the macromolecular chains, realizes the molecular-level dispersion of the macromolecular chains in the solution, and can self-assemble and stack tightly during the film formation process, so there are basically no weak points of breakdown, thus having high breakdown strength and energy storage density.

[0058] III. Verification Experiment of the Effect of High Temperature Treatment

[0059] X-ray diffraction experiments were performed on α1 and β2 of the fluorinated aromatic polyamide dielectric films of samples 1 and 3, respectively, and the results are as follows: Figure 4 As shown;

[0060] Depend on Figure 4It can be seen that the crystallinity of the fluorinated aromatic polyamide dielectric film α1 is 40%, and the crystallinity of the fluorinated aromatic polyamide dielectric film β2 is 16%. The reason is that the high temperature of 400℃ can induce the crystallization of the fluorinated aromatic polyamide film, thereby preparing a fluorinated aromatic polyamide dielectric film with high orientation and high crystallinity.

[0061] The comprehensive dielectric properties (including breakdown strength and energy storage density) of the fluorinated aromatic polyamide dielectric films α1 and β2 of samples 1 and 3 were tested respectively, and the results are as follows: Figure 5 As shown;

[0062] Depend on Figure 5 It can be seen that the overall dielectric properties of the fluorinated aromatic polyamide dielectric film α1 are significantly better than those of β2. This is because the high temperature of 400℃ can induce the fluorinated aromatic polyamide film to crystallize, thereby preparing a fluorinated aromatic polyamide dielectric film with high orientation and high crystallinity. Its molecular chains are further tightly packed without any weak points of breakdown, thus having high breakdown strength and high energy storage density.

[0063] Examples 2-12: High-Temperature Energy Storage Fluorinated Aromatic Polyamide Dielectric Films and Energy Storage Density Testing

[0064] In this embodiment, high-temperature energy storage fluorinated aromatic polyamide dielectric films α2-α11 and β3 were prepared. Their preparation steps were basically the same as steps S1-S3 of the preparation of high-temperature energy storage fluorinated aromatic polyamide dielectric film α1 in Example 1, with the only differences being the amount of Lewis acid and the heat treatment process parameters. The other parts of Examples 2-12 were the same as in Example 1. The energy storage density of the prepared fluorinated aromatic polyamide dielectric films was then tested. Specific process parameters and test results are shown in Table 1.

[0065] Table 1. Summary of Raw Material Consumption, Process Parameters, and Energy Storage Density

[0066]

[0067] As shown in Table 1, compared with fluorinated aromatic polyamide dielectric films β1-β3, the high-temperature energy storage performance of fluorinated aromatic polyamide dielectric films α1-α12 after Lewis acid-assisted dissolution treatment is significantly improved, and the optimal mass dispersion of Lewis acid addition is 3%. Furthermore, by inducing macromolecular chain orientation through 360℃ heat treatment, the high-temperature energy storage performance of the fluorinated aromatic polyamide dielectric films is further improved, and the optimal duration of 360℃ heat treatment is 30 min. Finally, by controlling the crystallization kinetics at higher temperatures, the highest crystallinity is achieved at 400℃ heat treatment. Ultimately, the high-temperature energy storage performance of the fluorinated aromatic polyamide dielectric film α1 reaches the optimal value and is superior to the energy storage performance reported in most literature.

[0068] Examples 13-17 High-Temperature Energy Storage Fluorinated Aromatic Polyamide Dielectric Films

[0069] In this embodiment, high-temperature energy storage fluorinated aromatic polyamide dielectric films α13 to α17 were prepared. The preparation steps were basically the same as steps S1 to S3 of the preparation of high-temperature energy storage fluorinated aromatic polyamide dielectric film α1 in Example 1. The only difference was the amount of raw materials and the process parameters. For details, please refer to Table 2.

[0070] Table 2. Summary of Raw Materials and Process Parameters

[0071]

[0072]

[0073] The contents of Examples 13-17 are the same as those of Example 1, and the high-temperature energy storage fluorinated aromatic polyamide dielectric films obtained are α13-α17.

Claims

1. A method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film, comprising the following steps performed sequentially: S1. Polycondense diacyl chloride monomer and fluorinated diamine monomer to obtain fluorinated aromatic polyamide raw material. After the reaction is completed, wash with deionized water to remove HCl and other impurities generated during the reaction. S2. Fluorinated aromatic polyamide raw material is dissolved by sequentially adding a polar solvent and a Lewis acid to obtain a homogeneous solution of fluorinated aromatic polyamide; S3. The fluorinated aromatic polyamide uniform solution is coated and subjected to high-temperature heat treatment to obtain the high-temperature energy storage fluorinated aromatic polyamide dielectric film; The diacyl chloride monomer includes at least one of terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylate, and 4,4-chloroformylphenyl ether; The fluorinated diamine monomer is prepared by fluorination of a diamine monomer; the diamine monomer includes at least one of p-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzoxazole, biphenyl diamine, 4,4'-diaminobenzoylaniline, 2,2'-dimethyl-1,1'-biphenyl-4,4'-diamine, 4-aminophenyl-4-aminobenzoate, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2'-p-phenyl-bisbenzimidazole diamine, 2-(3-aminophenyl)-5-aminobenzimidazole, 5-methyl-1,3-diaminobenzene, 1,4-bis(4-amino-2-methylphenoxy)benzene, and 4,4'-diaminobiphenyl. The high-temperature heat treatment is to hold at 60-150℃ for 10-60 min, at 150-250℃ for 10-60 min, at 360℃ for 10-150 min, and at 390-420℃ for 10-150 min. The Lewis acid includes at least one of calcium chloride, ferric chloride, copper chloride, lithium chloride, calcium bromide, lithium bromide, and sodium acetate; The sum of the amounts of the polar solvent and the Lewis acid added accounts for 85% to 95% of the mass of the homogeneous solution of fluorinated aromatic polyamide; the mass ratio of Lewis acid to polar solvent is 1:10 to 50.

2. The method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film according to claim 1, characterized in that, The polar solvent includes at least one of N-methylpyrrolidone, N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethyl sulfoxide, acetone, and tetrahydrofuran.

3. The method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film according to claim 1, characterized in that, The molar ratio of the diacyl chloride monomer to the fluorinated diamine monomer is 1:

1.

4. The method for preparing a high-temperature energy storage fluorinated aromatic polyamide dielectric film according to claim 1, characterized in that, The coating is made by uniformly coating a glass plate with a fluorinated aromatic polyamide solution, drying it at 80°C for 1-4 hours, and then soaking it in deionized water at 80°C for 1-5 hours to remove Lewis acid.

5. The high-temperature energy storage fluorinated aromatic polyamide dielectric film prepared by the preparation method according to any one of claims 1 to 4.

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