High-temperature-resistant energy-storage all-organic polyimide film and preparation method thereof

Abstract

According to the high-temperature-resistant energy-storage all-organic polyimide film and the preparation method thereof, donor units and acceptor units which are connected through chemical bonds are introduced into small organic molecules, so that strong electrostatic interaction can be generated in the molecules, and the thermal stability and the structural reliability of doped small molecules are remarkably improved through connection of the chemical bonds; the preparation method comprises the following steps: dissolving dianhydride and diamine, uniformly mixing to form a polyurethane solution, dissolving high-polarity small molecules in the solution, adding the polyurethane solution, uniformly mixing, spin-coating a glass sheet with the obtained mixed solution, and carrying out thermal imidization treatment to finally obtain a film; the mechanical property, the dielectric constant and the high-temperature energy storage performance of the film are evaluated, and the result shows that the high-temperature energy storage performance of the polyimide film added with the high-polarity small molecules is remarkably improved on the basis of keeping excellent mechanical property, and the application of the polyimide film in a high-temperature dielectric medium scene is developed.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature energy storage thin films, and particularly relates to a high-temperature resistant energy storage all-organic polyimide thin film and a preparation method thereof. Background Art

[0002] With the increasing demand for miniaturization and lightweight of devices and the emergence of harsh application scenarios, the electrostatic energy storage technology faces higher requirements. However, the currently commercial biaxially oriented polypropylene film capacitors have poor heat resistance, and the long-term stable working temperature is only 85°C, which is difficult to meet the requirements of high-temperature application scenarios. Among polymer films, polyimide (PI) is known as the top of the material pyramid because of the special imide ring in its molecular chain, which has excellent insulation and mechanical properties. Therefore, PI is often used as the matrix material for high-voltage polymer dielectrics. However, the relative dielectric constant of pure PI polymers is relatively low, and the energy density at 150°C is small, which is difficult to meet the requirements of miniaturization and lightweight of high-temperature capacitor energy storage. Therefore, it is necessary to develop polyimide polymer materials with good flexibility, easy processing and high energy storage performance. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention designs a doping system with strong intramolecular charge transfer ability by introducing donor and acceptor units connected by chemical bonds into organic small molecules. The donor-acceptor structure can not only generate strong electrostatic interaction inside the molecule, but also significantly improve the thermal stability and structural reliability of the doped small molecules through chemical bond connection.

[0004] To achieve the above technology, the present invention provides a high-temperature resistant energy storage all-organic polyimide thin film and a preparation method thereof. The preparation method is as follows:

[0005] (1) First, dissolve the dianhydride in a solvent to obtain a mixed solution 1, and dissolve the diamine in a solvent to obtain a mixed solution 2;

[0006] (2) Further mix and stir the mixed solution 1 and the mixed solution 2 for 12 hours to obtain a mixed solution 3;

[0007] (3) Then, dissolve the high-polarity small molecule DADQ in a solvent and stir for 2 hours to obtain a mixed solution 4;

[0008] (4) Subsequently, gradually add the mixed solution 4 to the mixed solution 3 to obtain a mixed solution 5, and the mixed solution 5 is subjected to ultrasonic treatment for 2 hours after stirring for 30 minutes;

[0009] (5) Then, the obtained mixed solution 5 is evenly drop-coated on a clean glass slide;

[0010] (6) Then, perform thermal imidization treatment on the mixed solution 5 on the glass slide;

[0011] (7) After the thermal imidization is completed, the mixed solution 5 is formed into a film on a glass slide. The glass slide is immersed in deionized water, and the film is peeled off from the glass slide.

[0012] (8) The film is dried in a vacuum oven to completely remove the residual moisture, and a film is obtained.

[0013] Further, the dianhydride is 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) (BPADA), which is stored in a desiccator; the diamine is 4,4'-diaminodiphenylmethane (MDA), which is stored in a refrigerator.

[0014] Further, the structural formula and chemical reaction equation of the high-polarity small molecule DADQ are as follows:

[0015]

[0016] The preparation process of the high-polarity small molecule DADQ is as follows:

[0017] 1) Dissolve 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile, heat and stir evenly.

[0018] 2) Then add pyrrolidine all at once, and at this time the color of the solution changes from green to purple.

[0019] 3) Stir the solution in step 2) at 70 °C for 4 hours, then cool to room temperature and store it at low temperature for 3 days to form PTCNQ precipitate.

[0020] 4) Separate and obtain PTCNQ by filtration, and wash it with cold acetonitrile to obtain long and thin purple needle-shaped crystals.

[0021] 5) Dissolve PTCNQ in acetonitrile to obtain a solution and preheat it to 40 °C. Add ethylenediamine to the PTCNQ acetonitrile solution, and the mixed solution quickly changes from dark green to yellow.

[0022] 6) Stir the mixed solution in step 5) at 70 °C for 4 hours. After cooling to room temperature, filter to obtain DADQ precipitate, and wash it with cold acetonitrile to finally obtain fine granular yellow powder.

[0023] Further, the molar ratio range of 7,7,8,8-tetracyanoquinodimethane (TCNQ) to pyrrolidine is 1.2 - 1.5.

[0024] Further, the molar ratio range of pyrrolidine to ethylenediamine is 2 - 2.5.

[0025] Further, the solvent in step (1) is N-methyl-2-pyrrolidone (NMP).

[0026] Furthermore, the molar ratio of the dianhydride to the diamine monomer is 1:1.

[0027] Furthermore, the solid content of the highly polar small molecule DADQ in the mixed solution 4 is 30 - 80%, and the amount of the mixed solution 4 added is 0.1 - 1.0% of the volume ratio of the mixed solution 3.

[0028] Furthermore, the thermal imidization process is as follows: first, dry at 80 °C for 12 hours to completely remove the solvent; then heat at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure that the polymer is fully imidized.

[0029] Furthermore, the film thickness is controlled between 10 - 12 μm.

[0030] Furthermore, a high-temperature resistant energy storage all-organic polyimide film.

[0031] The beneficial effects of the present invention are as follows: The present invention proposes an innovative and general modification method to optimize the capacitive energy storage performance of polyimide-based composites in high-temperature environments. By incorporating highly polar small molecules, the energy disorder of the polyimide matrix is significantly enhanced. Experimental results combined with computational simulations show that the increase in energy disorder broadens the energy level gap between transport states, reduces the mobility of effective carriers in the direction of the applied electric field, thereby suppressing charge transport. This mechanism provides a new perspective and important insights for the study of charge dynamics in disordered dielectric materials. Under the condition of 200 °C, the polyimide composite material added with highly polar small molecules exhibits excellent capacitive energy storage performance, achieving a discharge energy density of 6.45 J / cm 3 ³. The dual improvement of this all-organic composite material in terms of high energy density and high efficiency lays a solid foundation for the stable operation of thin film capacitors in harsh environments such as high temperature and high electric field. Specific Embodiments

[0032] Comparative Example 1

[0033] A polyimide film and its preparation method are as follows:

[0034] (1) First, dissolve 0.1 mmol of 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) in 5 mL of N-methyl-2-pyrrolidone (NMP) respectively. The molar ratio of the dianhydride to the diamine monomer is 1:1, and the total monomer mass is 300 mg;

[0035] (2) After the two monomers are completely dissolved, mix the solutions and stir for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution;

[0036] (3) Then, the obtained mixed solution was evenly drop-coated on a clean glass slide to prevent the introduction of impurities from interfering with the film-forming process;

[0037] (4) Then, the polymer on the glass slide was subjected to thermal imidization treatment according to the procedure: first, it was dried at 80 °C for 12 hours to completely remove the N-methyl-2-pyrrolidone (NMP) solvent; then, it was heated at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure that the polymer was fully imidized;

[0038] (5) After the thermal imidization was completed, the film was soaked in deionized water, peeled off from the glass slide, and then dried in a vacuum oven at 100 °C to completely remove the residual moisture. The final thickness of the film used for electrical characterization was 10 μm.

[0039] Example 1

[0040] A high-temperature resistant energy storage all-organic polyimide film and its preparation method are as follows:

[0041] (1) First, 0.1 mmol of 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) were respectively dissolved in 5 mL of N-methyl-2-pyrrolidone (NMP). The molar ratio of the dianhydride to the diamine monomer was 1:1, and the total monomer mass was 300 mg;

[0042] (2) After the two monomers were completely dissolved, the mixed solution was stirred for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution;

[0043] (3) Then, the high-polarity small molecule DADQ was dissolved in N-methyl-2-pyrrolidone (NMP), and the solid content was maintained at 50%. It was stirred for 2 hours to ensure its complete dissolution and form a stable dispersion;

[0044] (4) Subsequently, the solution in step (3) was gradually added to the polyamic acid solution according to a volume ratio of 0.1%. To ensure the uniform distribution of the dopant in the polymer matrix, the mixed solution was ultrasonically treated for 2 hours after stirring for 30 minutes;

[0045] (5) Then, the obtained mixed solution was evenly drop-coated on a clean glass slide to prevent the introduction of impurities from interfering with the film-forming process;

[0046] (6) Then, the polymer on the glass slide was subjected to thermal imidization treatment according to the procedure: first, it was dried at 80 °C for 12 hours to completely remove the dimethylformamide solvent; then, it was heated at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure that the polymer was fully imidized;

[0047] After the thermal imidization is completed, the film is immersed in deionized water, peeled off from the glass sheet, and then dried in a vacuum oven at 100 °C to completely remove the residual moisture. The final film thickness for electrical characterization is 10 μm.

[0048] The preparation process of the highly polar small molecule DADQ is as follows: Dissolve 1.22 mmol of 7,7,8,8 - tetracyano - p - benzoquinodimethane (TCNQ) in 20 mL of acetonitrile, heat and stir, and then add 0.98 mmol of pyrrole all at once. At this time, the color of the solution changes from green to purple. The mixed solution is stirred at 70 °C for 4 hours, then cooled to room temperature and stored in the refrigerator for 3 days; the obtained PTCNQ precipitate is separated by filtration and washed with cold acetonitrile to obtain slender purple needle - shaped crystals; then add PTCNQ to 10 mL of acetonitrile solution and preheat to 40 °C, then add 0.44 mmol of ethylenediamine, and the solution quickly changes from dark green to yellow; the mixed solution is stirred at 70 °C for 4 hours, cooled to room temperature, filtered to obtain the DADQ precipitate, and washed with cold acetonitrile. Finally, fine granular DADQ yellow powder is obtained.

[0049] Example 2

[0050] A high - temperature - resistant energy - storage all - organic polyimide film and its preparation method are as follows:

[0051] (1) First, dissolve 0.1 mmol of 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) in 5 mL of N - methyl - 2 - pyrrolidone (NMP) respectively. The molar ratio of dianhydride to diamine monomer is 1:1, and the total monomer mass is 300 mg.

[0052] (2) After the two monomers are completely dissolved, mix the solutions and stir for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution.

[0053] (3) Then, dissolve the highly polar small molecule DADQ in N - methyl - 2 - pyrrolidone (NMP) to keep the solid content at 50%, and stir for 2 hours to ensure its complete dissolution and form a stable dispersion.

[0054] (4) Subsequently, add the solution in step (3) to the polyamic acid solution step by step according to a volume ratio of 0.3%. To ensure the uniform distribution of the dopant in the polymer matrix, the mixed solution is ultrasonically treated for 2 hours after stirring for 30 minutes.

[0055] (5) Then, evenly drop - coat the obtained mixed solution on a clean glass sheet to prevent the interference of impurity introduction on the film - forming process.

[0056] (6) Then, perform thermal imidization on the polymer on the glass slide according to the procedure: first, dry it at 80 °C for 12 hours to completely remove the dimethylformamide solvent; then, heat it at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure that the polymer is fully imidized;

[0057] (7) After the thermal imidization is completed, soak the film in deionized water, peel the film from the glass slide, and then dry it in a vacuum oven at 100 °C to completely remove the residual moisture. The final thickness of the film used for electrical characterization is 10 μm.

[0058] The preparation process of the highly polar small molecule DADQ is as follows: Dissolve 1.22 mmol of 7,7,8,8 - tetracyano - p - benzoquinodimethane (TCNQ) in 20 mL of acetonitrile, heat and stir, and then add 0.98 mmol of pyrrole at one time. At this time, the color of the solution changes from green to purple. Stir the mixed solution at 70 °C for 4 hours, then cool it to room temperature and store it in the refrigerator for 3 days; The obtained PTCNQ precipitate is separated by filtration and washed with cold acetonitrile to obtain long and thin purple needle - shaped crystals; Then add PTCNQ to 10 mL of acetonitrile solution and preheat it to 40 °C, then add 0.44 mmol of ethylenediamine. The solution quickly changes from dark green to yellow; Stir the mixed solution at 70 °C for 4 hours, cool it to room temperature, filter to obtain the DADQ precipitate, and wash it with cold acetonitrile to finally obtain fine granular DADQ yellow powder;

[0059] Example 3

[0060] A high - temperature - resistant energy - storage all - organic polyimide film and its preparation method are as follows:

[0061] (1) First, dissolve 0.1 mmol of 4,4'-(4,4'-isopropyl diphenoxy) bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) in 5 mL of N - methyl - 2 - pyrrolidone (NMP) respectively. The molar ratio of the dianhydride to the diamine monomer is 1:1, and the total monomer mass is 300 mg;

[0062] (2) After the two monomers are completely dissolved, mix the solutions and stir for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution;

[0063] (3) Then, dissolve the highly polar small molecule DADQ in N - methyl - 2 - pyrrolidone (NMP), keep the solid content at 50%, and stir for 2 hours to ensure its complete dissolution and form a stable dispersion;

[0064] (4) Subsequently, the solution in step (3) was gradually added to the polyamic acid solution at a volume ratio of 0.5%, and to ensure the uniform distribution of the dopant in the polymer matrix, the mixed solution was ultrasonically treated for 2 hours after stirring for 30 minutes;

[0065] (5) Then, the obtained mixed solution was uniformly drop-coated on a clean glass slide to prevent the interference of impurity introduction on the film-forming process;

[0066] (6) Then, the polymer on the glass slide was subjected to thermal imidization treatment according to the procedure: first dried at 80 °C for 12 hours to completely remove the N,N-dimethylformamide solvent; then heated at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure the full imidization of the polymer;

[0067] (7) After the thermal imidization was completed, the film was soaked in deionized water, the film was peeled off from the glass slide, and then dried in a vacuum oven at 100 °C to completely remove the residual moisture. The final thickness of the film used for electrical characterization was 10 μm.

[0068] The preparation process of the highly polar small molecule DADQ is as follows: 1.22 mmol of 7,7,8,8-tetracyanoquinodimethane (TCNQ) was dissolved in 20 mL of acetonitrile, heated and stirred, and then 0.98 mmol of pyrrole was added at one time. At this time, the color of the solution changed from green to purple. The mixed solution was stirred at 70 °C for 4 hours, then cooled to room temperature and stored in the refrigerator for 3 days; the obtained PTCNQ precipitate was separated by filtration and washed with cold acetonitrile to obtain slender purple needle-like crystals; then PTCNQ was added to 10 mL of acetonitrile solution and preheated to 40 °C, and then 0.44 mmol of ethylenediamine was added. The solution quickly changed from dark green to yellow; the mixed solution was stirred at 70 °C for 4 hours, cooled to room temperature, filtered to obtain the DADQ precipitate, and washed with cold acetonitrile to finally obtain fine granular DADQ yellow powder;

[0069] Example 4

[0070] A high-temperature resistant energy storage all-organic polyimide film and its preparation method are as follows:

[0071] (1) First, 0.1 mmol of 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) were respectively dissolved in 5 mL of N-methyl-2-pyrrolidone (NMP). The molar ratio of the dianhydride to the diamine monomer was 1:1, and the total monomer mass was 300 mg;

[0072] (2) After the two monomers were completely dissolved, the mixed solution was stirred for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution;

[0073] (3) Then, dissolve the high-polarity small molecule DADQ in N-methyl-2-pyrrolidone (NMP), keeping the solid content at 50%, and stir for 2 hours to ensure its complete dissolution and form a stable dispersion;

[0074] (4) Subsequently, gradually add the solution from step (3) to the polyamic acid solution according to a volume ratio of 0.8%. To ensure the uniform distribution of the dopant in the polymer matrix, the mixed solution is subjected to ultrasonic treatment for 2 hours after stirring for 30 minutes;

[0075] (5) Then, evenly drop the obtained mixed solution onto a clean glass slide to prevent the introduction of impurities from interfering with the film-forming process;

[0076] (6) Then, perform thermal imidization treatment on the polymer on the glass slide according to the procedure: first dry it at 80 °C for 12 hours to thoroughly remove the dimethylformamide solvent; then heat it at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure the full imidization of the polymer;

[0077] (7) After the thermal imidization is completed, immerse the film in deionized water, peel the film from the glass slide, and then dry it in a vacuum oven at 100 °C to completely remove the residual moisture. The final thickness of the film for electrical characterization is 10 μm.

[0078] The preparation process of the high-polarity small molecule DADQ is as follows: Dissolve 1.22 mmol of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in 20 mL of acetonitrile, heat and stir, and then add 0.98 mmol of pyrrole at once. At this time, the color of the solution changes from green to purple. Stir the mixed solution at 70 °C for 4 hours, then cool it to room temperature and store it in the refrigerator for 3 days; the obtained PTCNQ precipitate is separated by filtration and washed with cold acetonitrile to obtain slender purple needle-like crystals; then add PTCNQ to 10 mL of acetonitrile solution and preheat it to 40 °C, then add 0.44 mmol of ethylenediamine, and the solution quickly changes from dark green to yellow; stir the mixed solution at 70 °C for 4 hours, cool it to room temperature, filter to obtain the DADQ precipitate, and wash it with cold acetonitrile to finally obtain fine granular DADQ yellow powder;

[0079] Example 5

[0080] A high-temperature resistant energy storage all-organic polyimide film and its preparation method are as follows:

[0081] (1) First, 0.1 mmol of 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) and 4,4'-diaminodiphenylmethane (MDA) were separately dissolved in 5 mL of N-methyl-2-pyrrolidone (NMP). The molar ratio of the dianhydride to the diamine monomer was 1:1, and the total monomer mass was 300 mg;

[0082] (2) After the two monomers were completely dissolved, the mixed solution was stirred for 12 hours to promote the full reaction of the monomers to form a polyamic acid solution;

[0083] (3) Then, the high-polarity small molecule DADQ was dissolved in N-methyl-2-pyrrolidone (NMP), maintaining a solid content of 50%, and stirred for 2 hours to ensure its complete dissolution and form a stable dispersion;

[0084] (4) Subsequently, the solution from step (3) was gradually added to the polyamic acid solution at a volume ratio of 1.0%. To ensure the uniform distribution of the dopant in the polymer matrix, the mixed solution was ultrasonically treated for 2 hours after stirring for 30 minutes;

[0085] (5) Then, the obtained mixed solution was evenly drop-coated on a clean glass slide to prevent the introduction of impurities from interfering with the film-forming process;

[0086] (6) Then, the polymer on the glass slide was subjected to thermal imidization treatment according to the procedure: first dried at 80 °C for 12 hours to thoroughly remove the dimethylformamide solvent; then heated at 150 °C, 200 °C, and 250 °C for 1 hour each to ensure the full imidization of the polymer;

[0087] (7) After the thermal imidization was completed, the film was soaked in deionized water, the film was peeled off from the glass slide, and then dried in a vacuum oven at 100 °C to completely remove the residual moisture. The final film thickness for electrical characterization was 10 μm.

[0088] The preparation process of the high-polarity small molecule DADQ is as follows: 1.22 mmol of 7,7,8,8-tetracyano-p-benzoquinodimethane (TCNQ) was dissolved in 20 mL of acetonitrile, heated and stirred, and then 0.98 mmol of pyrrole was added all at once. At this time, the color of the solution changed from green to purple. The mixed solution was stirred at 70 °C for 4 hours, then cooled to room temperature and stored in the refrigerator for 3 days; the obtained PTCNQ precipitate was separated by filtration and washed with cold acetonitrile to obtain slender purple needle-like crystals; then PTCNQ was added to 10 mL of acetonitrile solution and preheated to 40 °C, and then 0.44 mmol of ethylenediamine was added. The solution quickly changed from dark green to yellow; the mixed solution was stirred at 70 °C for 4 hours, cooled to room temperature, filtered to obtain the DADQ precipitate, and washed with cold acetonitrile to finally obtain fine granular DADQ yellow powder;

[0089] The above comparative examples and examples were tested, and the test results are shown in Tables 1 and 2 as follows:

[0090] 1. The glass transition temperature (Tg) of the test samples was measured by a DSC-Q8000 differential scanning calorimeter (DSC) from TA Instruments. The test process included three heating and cooling cycles, with a temperature change rate of 10 °C / min. To eliminate the thermal history of the samples, the data from the third thermal cycle was used to calculate the Tg of the samples.

[0091] 2. The energy band structure of the samples was characterized by ultraviolet-visible spectroscopy (UV-vis) using a Hitachi U-3010 spectrophotometer in the wavelength range of 200 - 700 nm, and the wavelength accuracy of the test was ±0.3 nm.

[0092] 3. The Young's modulus of the samples was tested using an Instron 34SC-1 bench-top tensile testing machine. The test samples were long strip-like films with a thickness of 10 μm and a width of 10 mm.

[0093] 4. The steps for testing the dielectric properties of the samples were as follows: First, gold electrodes with a diameter of 10 mm and a thickness of 60 nm were sputtered on both sides of the film. Subsequently, a broadband dielectric spectrometer (Novocontrol Concept 80) and a Quatro-Cryosystem temperature control system were used to test the dielectric spectra of the samples at 10 2 ~10 6 Hz, and at the same time, by precisely controlling the oven temperature in the range of 25 - 250 °C, the dielectric constant and dielectric loss of the samples were obtained.

[0094] 5. To evaluate the effect of the samples in terms of high-temperature insulation performance, a TREK 610C amplifier was used to measure the breakdown field strength of the samples, that is, a voltage was applied to the samples at a DC boost rate of 500 V / s until electrical breakdown occurred. To ensure the reliability of the results, each sample was tested at least 20 times. The test results were analyzed using the two-parameter Weibull statistical method to determine the high-temperature breakdown strength (Eb) of the samples and obtain the shape parameter β indicating the breakdown stability of the y samples. Higher Eb and β values mean that the dielectric polymer has higher breakdown strength and stability, which means that the samples have higher breakdown reliability at high temperatures and can maintain stable insulation performance even under extreme conditions.

[0095] 6. To prove the high-temperature energy storage performance of the samples, the samples were subjected to an electric displacement - electric field intensity cycling test at a temperature of 200 °C, a frequency of 100 Hz, and an electric field of 650 MV / m. The discharge energy density of the samples was obtained by integrating the electric hysteresis loop of the samples. The higher the discharge energy density, the better the high-temperature energy storage performance.

[0096] Table 1

[0097]

[0098] Table 2

[0099]

[0100] According to the comparative data of the comparative examples and the examples, it can be seen that adding a certain content of high-polarity small molecules to the polyimide has little effect on the glass transition temperature and mechanical properties of the polyimide. While maintaining excellent mechanical properties, the polyimide has an increased dielectric constant, improved high-temperature energy storage performance, and improved high-temperature insulation performance, so as to expand the application of polyimide as a high-temperature dielectric material.

Claims

1. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof, characterized in that: The preparation method is as follows: (1) firstly dissolving dianhydride in a solvent to obtain a mixed solution 1, and dissolving diamine in a solvent to obtain a mixed solution 2; (2) further mixing the mixed solution 1 and the mixed solution 2 and stirring for 12 hours to obtain a mixed solution 3; (3) Then, the highly polar small molecule DADQ was dissolved in the solvent and stirred for 2 hours to obtain a mixed solution 4; (4) Then, the mixed solution 4 was gradually added to the mixed solution 3 to obtain a mixed solution 5, and the mixed solution 5 was subjected to ultrasonic treatment for 2 hours after being stirred for 30 minutes; (5) Then, the obtained mixed solution 5 is evenly dropped onto a clean glass sheet; (6) then subjecting the mixed solution 5 on the glass sheet to thermal imidization treatment; (7) After the thermal imidization is completed, the mixed solution 5 forms a film on the glass sheet, the glass sheet is immersed in deionized water, and the film is peeled off from the glass sheet; (8) The film is dried in a vacuum oven to completely remove residual moisture to obtain a film.

2. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 1, characterized in that: The dianhydride is 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) (BPADA), which is stored in a desiccator; the diamine is 4,4'-diaminodiphenylmethane (MDA), which is stored in a refrigerator.

3. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 2, characterized in that: The structural formula and chemical reaction equation of the highly polar small molecule DADQ are as follows:

4. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 3, characterized in that: The preparation process of the highly polar small molecule DADQ is as follows: 1) dissolving 7,7,8,8-tetracyano-p-benzoquinodimethane (TCNQ) in acetonitrile, heating and stirring evenly; 2) Then add pyrrolidine all at once, and the color of the solution changes from green to purple; 3) stirring the solution in 2) at 70° C. for 4 hours, then cooling to room temperature, and storing at low temperature for 3 days to generate PTCNQ precipitate; 4) PTCNQ was separated by filtration and washed with cold acetonitrile to obtain elongated purple needle-shaped crystals; 5) Dissolve PTCNQ in acetonitrile to obtain a solution and preheat it to 40° C. Add ethylenediamine to the PTCNQ acetonitrile solution, and the mixed solution quickly changes from dark green to yellow; 6) The mixed solution in 5) was stirred at 70° C. for 4 hours, cooled to room temperature, filtered to obtain DADQ precipitate, and washed with cold acetonitrile to finally obtain fine granular yellow powder.

5. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 4, characterized in that: The molar ratio of 7,7,8,8-tetracyanoquinodimethane (TCNQ) to pyrrolidine is in the range of 1.2-1.

5.

6. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 4, characterized in that: The molar ratio of pyrrolidine to ethylenediamine is in the range of 2-2.

5.

7. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 1, characterized in that: The solvent in step (1) is N-methyl-2-pyrrolidone (NMP), and the molar ratio of the dianhydride to the diamine monomer is 1:

1.

8. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 1, characterized in that: The solid content of the high polarity small molecule DADQ in the mixed solution 4 is 30-80%, and the amount of the mixed solution 4 added is 0.1-1.0% by volume of the mixed solution 3.

9. A high temperature resistant energy storage all-organic polyimide film and a preparation method thereof according to claim 1, characterized in that: The thermal imidization process is: first drying at 80°C for 12 hours to completely remove the solvent; then heating at 150°C, 200°C and 250°C for 1 hour each to ensure that the polymer is fully imidized, and the film thickness is controlled between 10-12um.

10. A high temperature resistant energy storage all-organic polyimide film according to claim 1.

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