Polyetherimide-based high-temperature energy storage composite dielectric material and preparation method thereof

Abstract

The application discloses a kind of polyetherimide-based high-temperature energy storage composite dielectric materials and preparation method thereof, including preparation silicon carbide surface coating silica nano core-shell particles, obtain nano core-shell particle turbid liquid;Preparation polyetherimide solution and ferroelectric polymer solution;In nano core-shell particle turbid liquid join polyetherimide solution and ferroelectric polymer solution, preparation composite dielectric solution;Composite dielectric solution is coated on glass substrate, after series temperature drying, peeling, obtain composite dielectric thin film.The nano core-shell filler in the application has the advantage of wide band gap, enhances the insulating properties of the material, and the micron and nanoscale phase separation structure formed enhances the mechanical properties of the material, improves the breakdown field strength under high temperature conditions;Polarization response ability of composite dielectric is enhanced by interface effect between core-shell filler and polyetherimide matrix.

Description

Technical Field

[0001] This invention belongs to the field of dielectric capacitors and can be used in high-temperature environments. It is a polyetherimide-based composite dielectric material with added ferroelectric polymer and nano-core-shell particles, and its preparation method. Background Technology

[0002] Polymer-based dielectric capacitors have broad application prospects in fields such as smart grids, distributed energy, and hybrid vehicles due to their excellent properties such as high power density, fast charge and discharge efficiency, and long cycle life.

[0003] However, current mainstream polymer-based materials have several major problems: 1. Low dielectric breakdown strength, which limits the upper limit of their operating voltage and energy density; 2. High dielectric loss at high frequencies, which leads to reduced energy conversion efficiency and heat generation; 3. Limited dielectric constant, which directly affects the energy storage capacity per unit volume; 4. The dielectric properties of polymer materials are relatively sensitive to temperature, fluctuating with temperature changes, which is not conducive to maintaining stable performance over a wide temperature range and reduces their applicability under extreme environmental conditions.

[0004] Therefore, mitigating electrical breakdown failure caused by carrier migration while enhancing the polarization response of the polymer matrix, reducing dielectric loss, and improving temperature stability has become one of the hot topics and key areas of research on high-temperature polymer-based dielectric capacitors.

[0005] Polyetherimide (PEI) has a high glass transition temperature ( T g Within the temperature range of room temperature to 150 °C, due to its unique structure, it is superior to other high-temperature resistant materials. T g Dielectric polymers exhibit better thermal stability, superior breakdown strength, and lower dielectric loss. However, pure PEI has a relatively low dielectric constant. Many studies have improved the dielectric constant of composite materials by adding nano-inorganic fillers with high dielectric constants to PEI. For example, the Chinese patent document "A core-shell structure filler and its preparation method and its application in polyetherimide-based energy storage composite films" (publication number CN117757147A) describes an invention that prepared a filler with high breakdown strength (485.0 kV / mm) at 150 °C and a dielectric constant in the range of (10~10). 6 The dielectric composite material exhibits characteristics almost independent of frequency (Hz) and has good frequency stability. However, due to the dielectric difference at the interface between the nano-inorganic filler and the polymer composite, the breakdown strength of the nanocomposite dielectric decreases. Therefore, improving energy storage performance while avoiding charge accumulation at the interface between the inorganic filler and the polymer is one of the current challenges to be solved. Summary of the Invention

[0006] To address the aforementioned deficiencies in the existing technology, the present invention aims to provide a polyetherimide-based high-temperature energy storage composite dielectric material and its preparation method. By introducing ferroelectric polymers and inorganic nano-core-shell particles into the polyetherimide matrix, a composite dielectric film is prepared, which improves the high-temperature breakdown field strength and polarization response of the energy storage dielectric, reduces dielectric loss, and achieves high energy storage density and energy storage efficiency under high-temperature conditions.

[0007] The present invention is achieved through the following technical solution.

[0008] One aspect of the present invention provides a method for preparing a polyetherimide-based high-temperature energy storage composite dielectric material, comprising the following steps:

[0009] 1) Add nano-core-shell particle filler to N-methylpyrrolidone solvent at a mass ratio of 100:(3~12), and sonicate to obtain nano-core-shell particle turbid liquid;

[0010] 2) Add polyetherimide solution and ferroelectric polymer solution to the nano-core-shell particle turbid liquid at a mass ratio of 100:(1~4):(96~99), mix evenly, and obtain composite dielectric solution;

[0011] 3) The obtained composite dielectric solution is coated onto a cleaned glass substrate, dried at a series of temperatures, and then peeled off to obtain a composite dielectric film.

[0012] Preferably, the nano-core-shell filler is prepared according to the following method:

[0013] Silicon carbide nanoparticles were sintered in a high-temperature furnace at 900~1100 ℃ for 5~6 h to obtain nano-core-shell particle fillers uniformly coated with silicon dioxide.

[0014] Preferably, the silicon carbide nanoparticles have a particle size range of 50-100 nm and a shell silica thickness of 5-10 nm.

[0015] Preferably, the polyetherimide solution is an N-methylpyrrolidone solution with a mass concentration of 100~150 mg / mL.

[0016] Preferably, the ferroelectric polymer is polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (VDF-HFP), or Kramar terpolymer (VDF-TrFE-CFE).

[0017] Preferably, the ferroelectric polymer solution is prepared according to the following method:

[0018] To add the ferroelectric polymer to the N-methylpyrrolidone solvent, the mixture was stirred at 50-80 °C for 8-10 h to obtain a ferroelectric polymer solution with a concentration of 180-210 mg / mL.

[0019] Preferably, the process involves adding nano-core-shell fillers to an N-methylpyrrolidone solvent and then performing ultrasonic treatment using advanced ultrasonic equipment with an ultrasonic power of 600-700W and an ultrasonic time of 10-15 hours.

[0020] Preferably, the composite dielectric film preparation includes uniformly coating a composite dielectric solution onto a glass substrate by casting, preheating it in an oven at 70 °C for 12-15 h, then heating it to 100-120 °C and holding it for 5-8 h, and then holding it at 150-160 °C and 200-210 °C for 12-15 h respectively to obtain the composite dielectric film.

[0021] In another aspect, the present invention provides a polyetherimide-based high-temperature energy storage composite dielectric material prepared by the method described above.

[0022] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0023] 1. This invention utilizes inorganic nanoparticles to prepare core-shell structured fillers. A certain amount of silicon carbide particles are directly oxidized on their surface through high-temperature sintering to generate a silica shell, resulting in wide-bandgap SiC@SiO2 particles. These particles, along with a ferroelectric polymer, are then introduced into a polyetherimide matrix. Utilizing the unique high glass transition temperature and low dielectric loss of polyetherimide, combined with the wide bandgap advantage of the silica shell material in the core-shell nanoparticles, the energy required for charge carriers to cross the energy barrier is increased, thereby enhancing the insulation performance of the material. Simultaneously, the nano- and micron-scale phase separation structures generated by the ferroelectric polymer within the polyetherimide matrix improve the mechanical properties of the composite material, thereby increasing the breakdown field strength of polyetherimide at high temperatures.

[0024] 2. The polarization response capability of the composite dielectric is enhanced by the interfacial effect between the core and shell of the core-shell filler and between the filler and the polymer matrix.

[0025] 3. Under the formulation of this invention, high energy storage density and high energy storage efficiency can be simultaneously obtained at 150 °C. The high energy storage efficiency effectively reduces the release of stored energy as heat, extending the material's lifespan. Results show that the prepared composite dielectric film can achieve an energy storage density exceeding 5 J / cm³ at 150 °C. 3 The energy storage efficiency exceeds 90%.

[0026] 4. The polyetherimide-based composite dielectric of this invention has a simple preparation process, good stability, and can meet the needs of different applications. The raw materials involved are inexpensive, the technology is mature, and it is suitable for industrial production. It can be widely used in high-temperature polymer materials for smart grids, distributed energy, and hybrid vehicles. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 (a) and (b) in the figures are transmission electron microscope (TEM) images of the 5nm and 20nm core-shell SiC@SiO2 particles prepared in the embodiments of the present invention.

[0029] Figure 2 (a) and (b) are comparison images of the polyetherimide-based composite dielectric film prepared in Example 2 of the present invention and the polyetherimide dielectric film prepared in the comparative example, respectively, using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

[0030] Figure 3 The composite dielectric films prepared in Examples 1-4 of this invention and the comparative examples prepared at room temperature T R (a) Curves showing the changes in dielectric constant and dielectric loss with frequency at 150℃; (b) Curves showing the changes in dielectric constant and dielectric loss with frequency.

[0031] Figure 4 The composite dielectric films prepared in Examples 1-4 of this invention and the comparative examples prepared at room temperature T R The Weibull distribution and breakdown field strength diagrams at 150℃ are shown in (a) and (c), which are Weibull distribution diagrams, and (b) and (d), which are breakdown field strength diagrams.

[0032] Figure 5 The composite dielectric films prepared in Examples 1-4 of this invention and the comparative examples prepared at room temperature T R (a) Energy storage density diagram at 150°C (b). Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0034] This invention provides a method for preparing a polyetherimide-based high-temperature energy storage composite dielectric material, comprising the following steps:

[0035] Step 1, prepare the nano-core-shell particle suspension:

[0036] Silicon carbide nanoparticles with a particle size range of 50-100 nm and a silica shell thickness of 5-10 nm were sintered in a high-temperature furnace at 900-1100 °C for 5-6 h to obtain nano-core-shell particle fillers uniformly coated with silica.

[0037] The nano-core-shell particles were added to the N-methylpyrrolidone solvent at a mass ratio of 100:(3~12) and ultrasonically treated at a power of 600~700W for 10~15 h to obtain a nano-core-shell particle turbid liquid.

[0038] Step 2, prepare the composite dielectric solution:

[0039] Polyetherimide was added to N-methylpyrrolidone solvent to obtain a polyetherimide solution with a mass concentration of 100~200 mg / mL.

[0040] Ferroelectric polymers (polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP), or Kramar terpolymer P (VDF-TrFE-CFE)) were added to N-methylpyrrolidone solvent and stirred at 50-80 °C for 8-10 h to obtain a ferroelectric polymer solution with a concentration of 180-210 mg / mL.

[0041] Polyetherimide solution and ferroelectric polymer solution were added to the nano-core-shell particle turbid liquid at a mass ratio of 100:(1~4):(96~99), and then stirred for 12 hours to mix the three evenly to obtain a composite dielectric solution.

[0042] Step 3, Preparation of composite dielectric thin film:

[0043] The obtained composite dielectric solution was coated onto a cleaned glass substrate and kept at a preheated oven at 70 °C for 12–15 h. Then, the temperature was raised to 100–120 °C and kept at 150–160 °C and 200–210 °C for 12–15 h respectively. After drying, the substrate was peeled off to obtain the composite dielectric film.

[0044] The present invention will be further illustrated by the following examples.

[0045] Example 1

[0046] The preparation method of the polyetherimide-based energy storage composite dielectric thin film with excellent high-temperature energy storage characteristics in this embodiment includes the following steps:

[0047] 1) Preparation of core-shell structured SiC@SiO2 particle turbidity:

[0048] Weigh 0.1 g of silicon carbide nanoparticles and place them in a crucible. Set the high-temperature furnace temperature to 900 °C and keep it at that temperature for 6 h in an air atmosphere to obtain a silicon dioxide shell with a thickness of 6 nm, denoted as SiC@SiO2.

[0049] SiC@SiO2 particles were added to N-methylpyrrolidone solvent at a mass ratio of 100:6, and ultrasonic treatment was performed using advanced ultrasonic equipment to uniformly disperse the filler in the solvent. The ultrasonic treatment was carried out at a power of 600W for 15 h to obtain a turbid liquid of nano-core-shell particles.

[0050] 2) Preparation of polyetherimide solution:

[0051] 200 mg of polyetherimide was added to 1 mL of N-methylpyrrolidone solvent and stirred at 60 °C for 8 h to obtain a polyetherimide solution with a concentration of 200 mg / mL.

[0052] 3) Preparation of ferroelectric polymer polyvinylidene fluoride (PVDF) solution:

[0053] 200 mg of ferroelectric polymer polyvinylidene fluoride particles were added to 1 mL of N-methylpyrrolidone solvent and stirred at 60 °C for 8 h to obtain a polyvinylidene fluoride solution with a concentration of 200 mg / mL.

[0054] 4) Preparation of composite dielectric solutions

[0055] A polyetherimide solution and a ferroelectric polymer solution were added to the nano-core-shell particle turbidity at a mass ratio of 100:1:99 and mixed evenly to obtain a composite dielectric solution.

[0056] 5) Preparation of composite dielectric thin films:

[0057] Using a glass slide as a substrate, 200 μL of composite dielectric solution was measured with a pipette and uniformly coated onto the glass slide using a casting method. The glass slide containing the composite dielectric solution was then transferred to an oven preheated to 70 °C and kept at that temperature for 12 h. The temperature was then raised to 100 °C and kept at that temperature for 6 h, followed by holding at 150 °C and 200 °C for 14 h each, to obtain a composite dielectric film with a thickness of 4–6 μm, denoted as 0.30SiC@SiO2 / 1PVDF / 99PEI, or simply 1-99.

[0058] Example 2

[0059] 1) Preparation of core-shell structured SiC@SiO2 particle turbidity:

[0060] Weigh 0.1 g of silicon carbide nanoparticles and place them in a crucible. Set the high-temperature furnace temperature to 1000 °C and keep it at that temperature for 5 h in an air atmosphere to obtain a silicon dioxide shell with a thickness of 8 nm, denoted as SiC@SiO2.

[0061] SiC@SiO2 particles were added to N-methylpyrrolidone solvent at a mass ratio of 100:10, and ultrasonic treatment was performed using advanced ultrasonic equipment to uniformly disperse the filler in the solvent. The ultrasonic treatment was carried out at a power of 650W for 10 h to obtain a turbid liquid of nano-core-shell particles.

[0062] 2) Preparation of polyetherimide solution:

[0063] 150 mg of polyetherimide was added to 1 mL of N-methylpyrrolidone solvent and stirred at 70 °C for 9 h to obtain a polyetherimide solution with a concentration of 150 mg / mL.

[0064] 3) Preparation of ferroelectric polymer polyvinylidene fluoride-co-hexafluoropropylene P (VDF-HFP) solution:

[0065] 180 mg of ferroelectric polymer polyvinylidene fluoride-co-hexafluoropropylene particles were added to 1 mL of N-methylpyrrolidone solvent and stirred at 70 °C for 9 h to obtain a polyvinylidene fluoride-co-hexafluoropropylene solution with a concentration of 180 mg / mL.

[0066] 4) Preparation of composite dielectric solutions

[0067] A polyetherimide solution and a ferroelectric polymer solution were added to the nano-core-shell particle turbidity at a mass ratio of 100:2:98 and mixed evenly to obtain a composite dielectric solution.

[0068] 5) Preparation of composite dielectric thin films:

[0069] Using a glass slide as a substrate, 200 μL of composite dielectric solution was measured with a pipette and uniformly coated onto the glass slide using a casting method. The glass slide containing the composite dielectric solution was then transferred to an oven preheated to 70 °C and kept at that temperature for 15 h. The temperature was then raised to 120 °C and kept at that temperature for 5 h, followed by holding at 160 °C and 210 °C for 12 h each. The resulting polyetherimide-based composite dielectric film was denoted as 0.30SiC@SiO2 / 2 P(VDF-HFP) / 98PEI, or simply 2-98.

[0070] Example 3

[0071] 1) Preparation of core-shell structured SiC@SiO2 particle turbidity:

[0072] Weigh 0.1 g of silicon carbide nanoparticles and place them in a crucible. Set the high-temperature furnace temperature to 1100 °C and keep it at that temperature for 5.5 h in an air atmosphere to obtain a silicon dioxide shell with a thickness of 10 nm, denoted as SiC@SiO2.

[0073] SiC@SiO2 particles were added to N-methylpyrrolidone solvent at a mass ratio of 100:12, and ultrasonic treatment was performed using advanced ultrasonic equipment to uniformly disperse the filler in the solvent. The ultrasonic treatment was carried out at a power of 700W for 13 h to obtain a turbid liquid of nano-core-shell particles.

[0074] 2) Preparation of polyetherimide solution:

[0075] 150 mg of polyetherimide was added to 1 mL of N-methylpyrrolidone solvent and stirred at 80 °C for 7 h to obtain a polyetherimide solution with a concentration of 100 mg / mL.

[0076] 3) Preparation of the ferroelectric polymer Kramar terpolymer P(VDF-TrFE-CFE) solution:

[0077] 190 mg of the ferroelectric polymer Kramer terpolymer particles were added to 1 mL of N-methylpyrrolidone solvent and stirred at 70 °C for 9 h to obtain a Kramer terpolymer solution with a concentration of 190 mg / mL.

[0078] 4) Preparation of composite dielectric solutions

[0079] A polyetherimide solution and a ferroelectric polymer solution were added to the nano-core-shell particle turbidity at a mass ratio of 100:3:97 and mixed evenly to obtain a composite dielectric solution.

[0080] 5) Preparation of composite dielectric thin films:

[0081] Using a glass slide as a substrate, 200 μL of composite dielectric solution was measured with a pipette and uniformly coated onto the glass slide using a casting method. The glass slide containing the composite dielectric solution was then transferred to an oven preheated to 70 °C and kept at that temperature for 14 h. The temperature was then raised to 110 °C and kept at that temperature for 8 h, followed by holding at 160 °C and 205 °C for 13 h each. The resulting polyetherimide-based composite dielectric film was denoted as 0.30SiC@SiO2 / 3P(VDF-TrFE-CFE) / 97PEI, or simply 3-97.

[0082] Example 4

[0083] 1) Preparation of core-shell structured SiC@SiO2 particle turbidity:

[0084] Weigh 0.1 g of silicon carbide nanoparticles and place them in a crucible. Set the high-temperature furnace temperature to 1050 °C and keep it at that temperature for 6 h in an air atmosphere to obtain a silicon dioxide shell with a thickness of 6 nm, denoted as SiC@SiO2.

[0085] SiC@SiO2 particles were added to N-methylpyrrolidone solvent at a mass ratio of 100:3, and ultrasonic treatment was performed using advanced ultrasonic equipment to uniformly disperse the filler in the solvent. The ultrasonic treatment was carried out at a power of 600W for 12 h to obtain a turbid liquid of nano-core-shell particles.

[0086] 2) Preparation of polyetherimide solution:

[0087] 210 mg of polyetherimide was added to 1 mL of N-methylpyrrolidone solvent and stirred at 65 °C for 10 h to obtain a polyetherimide solution with a concentration of 210 mg / mL.

[0088] 3) Preparation of ferroelectric polymer polyvinylidene fluoride (PVDF) solution:

[0089] 210 mg of ferroelectric polymer polyvinylidene fluoride particles were added to 1 mL of N-methylpyrrolidone solvent and stirred at 65 °C for 10 h to obtain a polyvinylidene fluoride solution with a concentration of 210 mg / mL.

[0090] 4) Preparation of composite dielectric solutions

[0091] A polyetherimide solution and a ferroelectric polymer solution were added to the nano-core-shell particle turbidity at a mass ratio of 100:4:96 and mixed evenly to obtain a composite dielectric solution.

[0092] 5) Preparation of composite dielectric thin films:

[0093] Using a glass slide as a substrate, 200 μL of composite dielectric solution was measured with a pipette and uniformly coated onto the glass slide using a casting method. The glass slide containing the composite dielectric solution was then transferred to an oven preheated to 70 ℃ and kept at that temperature for 13 h. The temperature was then raised to 105 ℃ and kept at that temperature for 7 h, followed by holding at 155 ℃ and 200 ℃ for 15 h each, to obtain a composite dielectric film with a thickness of 4~6 μm, denoted as 0.30SiC@SiO2 / 4PVDF / 96PEI, or simply 4-96.

[0094] Comparative Example

[0095] The difference between this comparative example and Example 1 is that only steps (2) and (5) are performed: 200 mg of polyetherimide is weighed and added to 2 mL of N-methylpyrrolidone solvent, and stirred at 60 °C for 8 h to obtain a 100 mg / mL pure polyetherimide solution. The pure polyetherimide solution is then cast on a glass slide, and the same drying steps are performed to obtain a polyetherimide dielectric film, abbreviated as P-PEI.

[0096] Figure 1 (a) and (b) are TEM images of the 5 nm and 20 nm core-shell structured SiC@SiO2 particles prepared in Examples 1-4, respectively, forming a complete core-shell structure with a silicon dioxide shell thickness of 6 nm.

[0097] Figure 2 (a) and (b) are surface SEM and EDS comparison images of the preferred embodiment 2 and the comparative example of the present invention, respectively. The uniform distribution of Si, C, O, F and N elements in the composite dielectric indicates that SiC@SiO2 was successfully introduced. The ferroelectric polymer polyvinylidene fluoride forms a phase separation structure at the nanoscale and microscale inside the polyetherimide. SiC@SiO2 tends to be distributed inside the micron-sized polyvinylidene fluoride (white circle represents the micron-level phase separation structure, and black circle represents the nanoscale phase separation structure).

[0098] Figure 3 Examples 1-4 and the comparative example were tested at (a) room temperature T. R (b) The curves showing the changes in dielectric constant and dielectric loss with frequency at 150 °C demonstrate that the dielectric constant of all composite dielectrics exhibits good frequency stability within the tested frequency range (100-1 MHz). Furthermore, the interface effect between the filler and the polymer matrix enhances the polarization response of the composite dielectric, which helps to improve the dielectric constant.

[0099] Figure 4 Examples 1-4 and the comparative examples were tested at room temperature T. R The Weibull distribution and breakdown field strength diagrams at 150 °C are shown in Figures (a) and (c), and Figures (b) and (d), respectively. Figure 4 It can be seen that the breakdown strength of the composite dielectric prepared in Example 2 is 658.57 MV / m at room temperature, and the breakdown strength is improved to 718.21 MV / m at 150 °C. This is due to the wide bandgap advantage of the shell material in the nano core-shell particles and the enhancement of the mechanical properties of the composite dielectric by the ferroelectric polymer, thereby improving the breakdown strength of the composite dielectric.

[0100] Figure 5 Examples 1-4 and the comparative example of the present invention were tested at room temperature T. R (a) and (b) plots of energy storage density and efficiency at 150 °C, from Figure 5 It can be seen that the composite dielectric prepared in Example 2 has a discharge energy density of 7.24 J / cm² at room temperature and 625 MV / m. 3 At that time, the efficiency reached 94.6%; under the conditions of 150 ℃ and 700 MV / m, the energy storage density reached 10 J / cm³. 3 At this point, the efficiency is 93.3%. This is mainly due to the improved breakdown strength, and the enhanced polarization response capability of the composite dielectric is achieved through the interfacial effects between the core and shell of the core-shell packing and between the packing and the polymer matrix, thereby improving the energy storage density and energy storage efficiency.

[0101] The core-shell nanoparticles with a wide bandgap prepared in this invention effectively increase the energy barrier for carrier migration through the silica shell, and enhance the mechanical properties of polyetherimide by adding ferroelectric polymers to generate nano- and micro-scale phase separation structures inside the matrix, effectively improving the breakdown strength of polyetherimide at high temperatures; at the same time, the polarization response is significantly enhanced by the interfacial polarization mechanism between the filler and the matrix, thus obtaining a polyetherimide-based composite dielectric with high energy storage density and energy storage efficiency under high temperature conditions.

[0102] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for preparing a polyetherimide-based high-temperature energy storage composite dielectric material, characterized in that, Includes the following steps: 1) Add nano-core-shell particle filler to N-methylpyrrolidone solvent at a mass ratio of 100:(3~12), and sonicate to obtain nano-core-shell particle turbid liquid; The nano-core-shell particle filler was prepared according to the following method: Silicon carbide nanoparticles were sintered in a high-temperature furnace at 900~1100 ℃ for 5~6 h to obtain nano core-shell particle fillers uniformly coated with silica. 2) Add ferroelectric polymer solution and polyetherimide solution to the nano-core-shell particle turbid liquid at a mass ratio of 100:(1~4):(96~99), mix evenly, and obtain composite dielectric solution; 3) The obtained composite dielectric solution is coated onto a cleaned glass substrate, dried at a series of temperatures, and then peeled off to obtain a composite dielectric film.

2. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, The silicon carbide nanoparticles have a particle size range of 50-100 nm and a shell silica thickness of 5-10 nm.

3. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, The polyetherimide solution is an N-methylpyrrolidone solution with a mass concentration of 100~150 mg / mL.

4. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, The ferroelectric polymer is polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (VDF-HFP), or Kramar terpolymer (VDF-TrFE-CFE).

5. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, The ferroelectric polymer solution is prepared according to the following method: To add the ferroelectric polymer to the N-methylpyrrolidone solvent, the mixture was stirred at 50-80 °C for 8-10 h to obtain a ferroelectric polymer solution with a concentration of 180-210 mg / mL.

6. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, Nano-core-shell particles were added to N-methylpyrrolidone solvent and ultrasonically treated using advanced ultrasonic equipment with an ultrasonic power of 600-700W and an ultrasonic time of 10-15 h.

7. The method for preparing the polyetherimide-based high-temperature energy storage composite dielectric material according to claim 1, characterized in that, The composite dielectric film preparation process includes uniformly coating a composite dielectric solution onto a glass substrate by casting, preheating it in an oven at 70 °C for 12-15 h, then raising the temperature to 100-120 °C and holding it for 5-8 h, and then holding it at 150-160 °C and 200-210 °C for 12-15 h respectively to obtain the composite dielectric film.

8. A polyetherimide-based high-temperature energy storage composite dielectric material prepared by the method according to any one of claims 1-7.

9. The application of the polyetherimide-based high-temperature energy storage composite dielectric material as described in claim 8 in high-temperature polymer materials for smart grids, distributed energy, and hybrid vehicles.

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