High-temperature energy storage sandwich structure composite material and preparation method thereof

Abstract

The application discloses a high-temperature energy storage sandwich structure composite material and a preparation method thereof. A polyamide acid precursor solution A with dispersed oxide aerogel is used as insulating layer slurry, a polyamide acid precursor solution B with dispersed BBC is used as polarization layer slurry, the polarization layer and the insulating layer are sequentially and layer by layer cast by adjusting the height of a doctor blade and drying conditions, a sandwich structure is prepared, and after gradient temperature imidization, the sandwich structure is placed in a hot press to make the interlayer polymers undergo thermal fusion by accurately controlling the temperature and time, so that a seamless and thickness-stable sandwich structure is formed.

Description

Technical Field

[0001] This invention belongs to the field of polymer-based dielectric material preparation technology, specifically relating to a high-temperature energy storage sandwich structure composite material and its preparation method. Background Technology

[0002] Electrostatic capacitors, compared to other energy storage devices, offer advantages such as high power density, high discharge speed, low cost, and good stability, leading to their widespread application in numerous fields. However, with the development of lightweight and integrated technologies and growing concerns about safety, ceramic and electrolytic capacitors are no longer suitable for long-term operation under high voltage. Compared to ceramic capacitors, polymer-based dielectric materials, with their high breakdown strength, ease of processing, good safety, and lightweight properties, are considered an ideal choice for achieving high energy density energy storage. However, polymer materials face significant challenges across a wide temperature range: at low temperatures, material embrittlement and increased local discharge at defects hinder energy storage; at high temperatures, conduction losses and Joule heating caused by exponentially increasing leakage current significantly reduce energy storage efficiency and can easily lead to thermal runaway, thus limiting their energy storage density and application limits. Currently, the commercially available benchmark material—biaxially oriented polypropylene (BOPP)—has an energy storage density of less than 4 J / cm³. 3 Furthermore, the maximum operating temperature does not exceed 105℃, which is no longer sufficient to meet the needs of cutting-edge technologies.

[0003] To improve high-temperature performance, polymers with high glass transition temperatures (Tg), such as polyetherimide (PEI) and polyimide (PI), have been extensively studied. However, a high Tg only signifies good thermal stability and does not directly translate into excellent high-temperature energy storage performance. Under high temperature and high field conditions, these polymers also face the problem of a sharp increase in electrical conductivity, leading to significant energy loss and a decrease in energy storage efficiency. In recent years, introducing inorganic fillers into the polymer matrix to suppress conduction losses and improve high-temperature performance has become an effective strategy. Among them, ferroelectric ceramic fillers can significantly improve the dielectric constant of composite materials, but their dielectric properties differ greatly from those of the polymer matrix, resulting in poor compatibility and a tendency to cause filler agglomeration and interface defects. These microscopic defects can become the initiation point of breakdown under high pressure and temperature stress, severely impairing the reliability and lifespan of the material.

[0004] To fundamentally address the inherent limitations of single-structure composite materials, the "sandwich" multi-layer structure design concept emerged and has demonstrated immense potential. This structure, through ingenious hierarchical design, combines materials with different functions, aiming to synergistically leverage the advantages of each layer.

[0005] Therefore, developing a novel polymer-based composite dielectric material based on a sandwich structure, and achieving high energy density and high efficiency over a wide temperature range (especially high temperature) through optimized design and synergistic coupling of each functional layer, has become a key direction for breaking through current technological bottlenecks and meeting the needs of next-generation high-performance electronic devices. It has significant scientific research value and broad industrialization prospects. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for preparing a high-temperature energy storage sandwich structure composite material. The preparation method of this invention uses a polyamic acid precursor solution A containing dispersed oxide aerogel as the insulating layer slurry and a polyamic acid precursor solution B containing dispersed BBC as the polarization layer slurry. The polarization layer and insulating layer are sequentially cast by adjusting the doctor blade height and drying conditions to prepare a sandwich structure. After gradient heating and imidization, the structure is placed in a hot press. By precisely controlling the temperature and time, the interlayer polymers undergo thermal fusion, forming a seamless and thickness-stable sandwich structure.

[0007] The second objective of this invention is to provide a high-temperature energy storage sandwich composite material prepared by the above-described preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention discloses a method for preparing a high-temperature energy storage sandwich structure composite material. A polyamic acid precursor solution A, containing dispersed oxide aerogel, is cast onto a substrate and dried to form a bottom insulating film layer. Then, a polyamic acid precursor solution B, containing dispersed BBC, is cast onto the bottom insulating film layer and dried to form a middle polarized film layer. Next, a polyamic acid precursor solution A, containing dispersed oxide aerogel, is cast onto the middle polarized film layer and dried to form a top insulating film layer. Finally, the sandwich structure composite film composed of the bottom insulating film layer, the middle polarized film layer, and the top insulating film layer is subjected to imidization treatment and then hot-pressed to obtain the sandwich structure composite material.

[0010] The chemical formula of the BBC is 0.85(0.8BaTiO3-0.2(Bi) 0.5 Na 0.5 TiO3)-0.15CaZrO3.

[0011] The preparation method of the present invention involves introducing trace amounts of oxide aerogel as an insulating layer and a small amount of 0.85 (0.8BaTiO3-0.2 (Bi)) into a polymer matrix. 0.5 Na 0.5TiO3-0.15CaZrO3 (BBC) serves as the polarization layer, constructing a multilayer structure with synergistic functions: The insulating layer, relying on the three-dimensional nanonetwork and ultra-high specific surface area of ​​the oxide aerogel, forms numerous interfacial traps with the polymer, effectively binding charge carriers and suppressing conductivity migration, thereby significantly improving breakdown strength and insulation stability under high temperature and high field conditions. The polarization layer, leveraging the high dielectric constant of the relaxor ferroelectric ceramic BBC, enhances the overall polarization capability of the material, increasing energy storage density. Furthermore, the oxide aerogel, as a highly efficient thermal insulation unit, can significantly extend the heat flow path, extending... The slow accumulation of heat in the material ensures its performance reliability under extreme temperature environments. At the same time, since SiO2 aerogel is a wide-bandgap material, it can reduce external charge injection. In this invention, the inner layer adopts a relaxor ferroelectric material with high electron affinity, which can further restrict and bind the migration of charges already injected into the interior. This synergistic effect of outer layer insulation and inner binding of charge migration can effectively reduce leakage current density and loss and improve the breakdown strength of the material. Through the synergy of the above insulation, polarization and heat insulation, the composite material has both high energy storage performance and excellent stability in a wide temperature range.

[0012] Experiments revealed that only BBC and oxide aerogels achieved the optimal synergistic effect. During the actual exploration process, combinations of 0.9 (0.8 BaTiO3-0.2 (Bi)) were tried. 0.5 Na 0.5 (TiO3)-0.1CaZrO3 and 0.8(0.8BaTiO3-0.2(Bi) 0.5 Na 0.5 Other relaxor ferroelectric ceramics such as 0.85(0.8BaTiO3-0.2CaZrO3) do not perform as well as those using BBC. This is because 0.85(0.8BaTiO3-0.2(Bi) 0.5 Na 0.5 TiO3-0.15CaZrO3 ceramics exhibit a moderate relative permittivity of about 750, which can not only effectively delay polarization saturation, but also reduce the probability of electromechanical breakdown due to weak electrostriction. On the other hand, compared with other samples, this ceramic has the lowest loss from room temperature to 150°C, and its low tanδ can be maintained below 0.02 over a wide frequency range.

[0013] In this invention, the oxide aerogel cannot be hydrophobically treated. Experiments have shown that dispersing the aerogel to make it more uniformly dispersed in the insulating layer actually reduces the overall performance. However, without dispersing, the aerogel has better synergy with the polarization layer. The performance improvement brought about by this sandwich structure leads to an increase in overall performance.

[0014] Furthermore, if the top and bottom layers are replaced with polarization layers and the middle layer is replaced with an insulating layer, the synergistic effect will decrease, resulting in a reduction in overall performance.

[0015] In a preferred embodiment, when the polyamic acid precursor solution A containing dispersed oxide aerogel is cast onto the substrate, the doctor blade height is controlled to be 25-50 μm; when the polyamic acid precursor solution B containing dispersed BBC is cast onto the bottom insulating film layer, the doctor blade height is controlled to be 75-200 μm, preferably 75-100 μm; and when the polyamic acid precursor solution A containing dispersed oxide aerogel is cast onto the middle polarized film layer, the doctor blade height is controlled to be 25-100 μm, preferably 50-100 μm.

[0016] In a preferred embodiment, a polyamic acid precursor solution A containing dispersed oxide aerogel is cast onto a substrate and dried at 65-75°C for 10-15 minutes to form a bottom insulating film layer. Then, a polyamic acid precursor solution B containing dispersed BBC is cast onto the bottom insulating film layer and dried at 75-85°C for 15-20 minutes to form a middle polarized film layer. Finally, a polyamic acid precursor solution A containing dispersed oxide aerogel is cast onto the middle polarized film layer and dried at 65-75°C for 2-3 hours to form a top insulating film layer.

[0017] In this invention, by controlling the height of the scraper and coordinating the drying temperature and drying time of each layer after casting, the required thickness of each layer can be obtained in a controllable manner. Experiments have shown that the upper and lower layers require a lower temperature for drying, and if the temperature is too high, it will easily cause defects such as holes. However, for the middle layer, due to its compact structure, the temperature can be slightly higher for drying.

[0018] In a preferred embodiment, the thickness ratio of the bottom insulating film layer, the middle polarization film layer, and the top insulating film layer is 0.8-1.2:0.8-3:0.8-1.2, more preferably 0.8-1.2:0.8-1.2:0.8-1.2. Experiments have shown that controlling the thickness within the range of this invention yields optimal performance; otherwise, it will lead to a decrease in breakdown performance and difficulty in achieving the desired overall material polarization and dielectric constant.

[0019] In a preferred embodiment, the polyamic acid precursor solution A containing dispersed oxide aerogel is selected from one of SiO2 aerogel, Al2O3 aerogel, and ZrO2 aerogel, preferably SiO2 aerogel.

[0020] In a preferred embodiment, the process of obtaining the polyamic acid precursor solution A containing the oxide aerogel is as follows: the oxide aerogel is dispersed in a solvent to obtain a dispersion, and a diamine monomer and an anhydride monomer are added sequentially to the dispersion and reacted under stirring to obtain the product.

[0021] In a further preferred embodiment, the diamine monomer is selected from 1,3-phenylenediamine.

[0022] In a further preferred embodiment, the anhydride monomer is selected from bisphenol A type diether dianhydride.

[0023] In a further preferred embodiment, the molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; preferably 1:1.

[0024] In a further preferred embodiment, during the reaction under stirring, the stirring speed is controlled at 200-400 rpm, and the reaction time is 12-24 h. In actual operation, the mixed solution obtained by sequentially adding diamine monomer and acid anhydride monomer to the dispersion is placed on a stirring table and stirred at room temperature to ensure a complete reaction and the formation of a polyamic acid (PAA) precursor solution with uniform viscosity and uniform filler distribution.

[0025] In a preferred embodiment, the process of obtaining the polyamic acid precursor solution B containing BBC is as follows: BBC is dispersed in a solvent to obtain a dispersion, and a diamine monomer and an anhydride monomer are added sequentially to the dispersion, and the mixture is reacted under stirring to obtain the desired product.

[0026] In a preferred embodiment, the particle size of the BBC is ≤1μm. Experiments have shown that the particle size cannot be too large, as this can easily lead to localized electric field concentration.

[0027] In a further preferred embodiment, the diamine monomer is selected from 1,3-phenylenediamine.

[0028] In a further preferred embodiment, the anhydride monomer is selected from bisphenol A type diether dianhydride.

[0029] In a further preferred embodiment, the molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; preferably 1:1.

[0030] In a further preferred embodiment, during the reaction under stirring, the stirring speed is controlled at 200-400 rpm, and the time is 12-24 h.

[0031] In a preferred embodiment, the imidization process is as follows: sequentially holding at 70-80℃ for 1-2 hours, 90-100℃ for 1-2 hours, 130-150℃ for 1-2 hours, 180-200℃ for 1-2 hours, 230-250℃ for 1-2 hours, and 280-300℃ for 1-2 hours. Then, the temperature is slowly lowered to room temperature under vacuum.

[0032] This invention achieves a highly efficient synergy between the stable evaporation of solvent residue and the cyclization reaction of polyamic acid to polyetherimide (PEI) through a precisely controlled stepwise heating imidization process. This process greatly avoids defects such as bubbles, pores and microcracks caused by thermal stress.

[0033] In a preferred embodiment, the hot pressing temperature is 230-250℃, and the hot pressing time is 15-30 minutes. This invention also provides a high-temperature energy storage sandwich structure composite material prepared by the above method.

[0034] In a preferred embodiment, the sandwich structure composite material consists of a bottom insulating layer, a polarization layer, and a top insulating layer, wherein both the bottom insulating layer and the top insulating layer are composed of a PEI matrix and an oxide aerogel dispersed in the PEI matrix; the oxide aerogel is selected from one of SiO2 aerogel, Al2O3 aerogel, and ZrO2 aerogel, preferably SiO2 aerogel.

[0035] The polarization layer consists of a PEI matrix and BBC dispersed in the PEI matrix.

[0036] In a further preferred embodiment, the mass fraction of oxide aerogel in the bottom insulating layer and the top insulating layer is 0.1~3wt%, preferably 0.75wt%.

[0037] In a further preferred embodiment, the mass fraction of BBC in the polarization layer is 0.25~1wt%, preferably 0.5wt%.

[0038] The beneficial effects of this invention are:

[0039] This invention, through rational structural design and precise manufacturing process, successfully obtained a high-temperature energy storage sandwich composite material with excellent comprehensive performance. Its core advantage stems from the synergistic construction and functional complementarity of the insulating layer and polarization layer.

[0040] 1. The insulating layer provides dual protection against electrons and heat: The insulating layer, composed of trace oxide aerogels, introduces numerous deep-level interface traps into the polymer matrix through its continuous three-dimensional nanonetwork and extremely high specific surface area. These traps effectively confine and significantly suppress carrier migration, greatly reducing conductivity loss and leakage current, thus providing the material with extremely high breakdown strength under high temperature and high field conditions. Simultaneously, the aerogel itself, as a highly efficient thermal insulation unit, can significantly lengthen and distort heat flow paths, effectively blocking external heat from entering and diffusing into the material, ensuring the long-term stable operation of the composite material at high temperatures.

[0041] 2. Synergistic effect of high polarization and internal trapping in the polarization layer: The polarization layer composed of BBC relaxor ferroelectric ceramics effectively enhances the overall polarization intensity of the composite material by utilizing its high dielectric constant, thereby significantly improving the energy storage density. More importantly, the BBC nanoparticles themselves can also serve as effective trap centers, further confining the charge carriers inside the polarization layer. Together with the insulating layer, they form a multi-layered space charge defense system that runs through the entire sandwich structure, synergistically reducing energy loss during charging and discharging.

[0042] 3. Synergistic Effect and Final Performance of the Sandwich Structure: The "sandwich" structure constructed by layer-by-layer casting of the insulating and polarization layers achieves optimized configuration and performance superposition of each functional layer. The insulating layer focuses on isolating electrons and heat, while the polarization layer focuses on enhancing polarization and internal confinement. The synergistic effect of the two ultimately enables the composite material to simultaneously possess high breakdown strength, low loss, high energy storage efficiency, and excellent high-temperature stability under extreme temperature environments, effectively meeting the urgent needs of modern electronic power systems for high-temperature, high-energy, and highly reliable dielectric materials. Attached Figure Description

[0043] Figure 1 Cross-sectional SEM and EDS images of the SA-BBC-SA / PEI thin film prepared by the method in Example 1.

[0044] Figure 2 The dielectric spectrum and dielectric temperature spectrum of the sandwich composite material prepared by the method in Example 1 are shown below. Figure 2 In the image, (a) represents the dielectric spectrum of the sandwich composite material. Figure 2 (b) in the figure is the dielectric temperature spectrum of the sandwich structure composite material.

[0045] Figure 3 The load-displacement curves and Young's modulus variation diagrams of the sandwich composite material prepared by the method in Example 1 are shown below. Figure 3 In the figure, (a) is the load-displacement curve of the sandwich composite material. Figure 3 (b) in the figure shows the variation of Young's modulus of the sandwich composite material.

[0046] Figure 4 The graphs show the leakage current density of the sandwich composite material prepared by the method in Example 1 at 150°C and 200°C. Figure 4 (a) Figure 4 (b) in the figure is the leakage current density curve of the sandwich composite material at 150℃, where Figure 4 (c) Figure 4 (d) in the figure is the leakage current density curve of the sandwich structure composite material at 200℃.

[0047] Figure 5 The graph shows the energy storage performance of the sandwich composite material prepared by the method in Example 1 at 150°C and 200°C; whereby... Figure 5 (a) shows the energy storage performance of the sandwich composite material at 150℃. Figure 5 (b) in the figure shows the energy storage performance of the sandwich structure composite material at 200℃. Detailed Implementation

[0048] Example 1

[0049] A SiO2 aerogel with a specific surface area greater than 600 m² / g and a three-dimensional framework structure was selected, with a framework pore size distribution of 5-20 nm and a SiO2 nanoparticle size of 5-10 nm. A relaxor ferroelectric filler BBC prepared by a conventional solid-state reaction method was selected. This BBC filler has extremely low remanent polarization due to its polar nano-microregions effectively limiting losses.

[0050] Weigh 2.63 mg of SiO2 aerogel and add it to N-methylpyrrolidone (NMP) solvent. Disperse the mixture using an ultrasonic machine for 5 min to form a preliminarily dispersed insulating slurry.

[0051] Weigh 1.75 mg of BBC relaxor ferroelectric ceramics and add them to NMP solvent. Disperse the mixture using an ultrasonic machine for 30 min to form a preliminarily dispersed polarization layer slurry.

[0052] In the well-dispersed insulating layer slurry and polarization layer slurry, 0.06 g of 1,3-phenylenediamine (MPD) and 0.29 g of bisphenol A diether dianhydride (BPADA) were added sequentially, with the molar ratio of the two monomers controlled at 1.0. The mixture was magnetically stirred at a constant speed of 300 rpm for 12 hours at room temperature to obtain the insulating layer PAA and the polarization layer PAA. During this process, the polymerization reaction of polyamic acid (PAA) occurred directly around the dispersed SiO2 aerogel framework and BCC, achieving filler dispersion and strong interfacial interaction. The polymerized viscous insulating layer PAA solution was cast onto a clean glass substrate using a 50 μm high scraper as the bottom insulating layer. After drying in a 70°C forced-air drying oven for 15 min to evaporate most of the solvent from the bottom layer, the polymerized viscous polarization layer PAA solution was then cast onto the bottom of the insulating layer using a 75 μm high scraper as the intermediate polarization layer. The mixture was then dried in an 80°C forced-air drying oven for 20 minutes to evaporate most of the solvent in the intermediate layer and ensure a tight bond between the bottom intermediate layer and the top layer. Finally, the viscous PAA solution for the insulating layer obtained from polymerization was transferred to a 70°C forced-air drying oven for 2 hours using a 100μm high doctor blade, and then cast onto the intermediate polarization layer as the top insulating layer. This low-temperature, slow-drying process ensured stable solvent evaporation, avoided internal stress accumulation and film defects caused by excessively rapid surface skinning, and controlled the interlayer thickness by varying the doctor blade height, drying temperature, and time. The dried sandwich-structured PAA composite film was placed in a vacuum oven and subjected to the following precise gradient heat treatment procedure under continuous vacuum: the temperature was increased to 80°C at a rate of 2°C / min and held for 2 hours; subsequently, the temperature was sequentially increased to 100°C and held for 1 hour, 150°C and held for 1 hour, 200°C and held for 1 hour, 250°C and held for 1 hour, and 300°C and held for 1 hour, with each temperature stage held for a specified time. After treatment, the film was cooled to room temperature in the oven. This procedure ensures a thorough and complete imidization reaction from PAA to PEI. Simultaneously, the vacuum environment effectively eliminates small molecules of reaction byproducts and prevents oxidative degradation of the material at high temperatures, ultimately yielding a high-performance sandwich-structured PEI composite material. The prepared three-layer film is aligned and placed in a hot press, where it is hot-pressed at 250°C for 20 minutes to form a seamlessly bonded and thickness-stable sandwich structure between the polymer layers.

[0053] Example 2

[0054] Other conditions are the same as in Example 1, with the first layer of the scraper having a thickness of 25 μm, the second layer having a thickness of 100 μm, and the third layer having a thickness of 50 μm.

[0055] Example 3

[0056] Other conditions are the same as in Example 1, with the first layer of the scraper having a thickness of 50 μm, the second layer having a thickness of 100 μm, and the third layer having a thickness of 50 μm.

[0057] Example 4

[0058] Other conditions are the same as in Example 1, with the first layer of the scraper having a thickness of 25 μm, the second layer having a thickness of 200 μm, and the third layer having a thickness of 25 μm.

[0059] Performance testing

[0060] Figure 1 Cross-sectional SEM and EDS images of the SA-BBC-SA / PEI thin film prepared by the method in Example 1, wherein... Figure 1 The cross-sectional SEM images of the SA-BBC-SA / PEI film show that the SA and BBC fillers have good interfacial compatibility with the polymer, with no obvious defects and no obvious agglomeration. Figure 1 The cross-sectional EDS elemental mapping diagram of the SA-BBC-SA / PEI thin film shows that the film has a three-layer structure, with the upper and lower insulating layers being SA / PEI and the middle polarization layer being BBC / PEI. The total thickness is 12 μm, and the thickness ratio between each layer is approximately 1:1:1.

[0061] Figure 2 The dielectric spectrum and dielectric temperature spectrum of the composite materials prepared by the methods in Examples 1 and Comparative Examples 1-4 are shown. As can be seen from the figures, all composite materials exhibit excellent temperature stability in terms of dielectric constant and dielectric loss. Furthermore, BBC can significantly improve the overall dielectric constant of the nanocomposite. Therefore, the dielectric constant of Example 1 is significantly higher than that of Comparative Examples 1 and 2.

[0062] Figure 3 The load-displacement curves and Young's modulus variation graphs of the composite materials prepared by the methods in Example 1 and Comparative Examples 1-4 are shown. It can be seen from the graphs that the Young's modulus of the composites after adding fillers is greater than that of pure PEI. Furthermore, the sandwich structure SA-BBC-SA / PEI prepared in Example 1 has the highest Young's modulus. The intrinsic modulus of the SiO2 aerogel framework is much higher than that of the polymer matrix, constraining the movement of the PEI molecular chains in the matrix through a stress transfer mechanism, thus improving the overall stiffness of the material. Each layer uses PEI as the matrix, resulting in good interlayer compatibility, effective stress transfer, and prevention of interfacial slippage. Moreover, the intrinsic moduli of both the BBC and SiO2 aerogel framework are much higher than those of the polymer matrix, constraining the movement of the PEI molecular chains in the matrix through a stress transfer mechanism, thereby improving the overall stiffness of the material.

[0063] Figure 4The graphs show the leakage current density of the composite materials prepared by the methods in Example 1 and Comparative Examples 1-4 at 150°C and 200°C. SiO2 aerogel, with its wide bandgap of up to 9 eV and excellent insulation properties, can effectively trap charge, reduce leakage current density, and improve the breakdown strength of the nanocomposite. BBC, with its high electron affinity (3.8 eV), can effectively trap carrier movement, reducing leakage current density. The sandwich structure SA-BBC-SA / PEI prepared in Example 1 has the lowest leakage current density. On the one hand, the outer insulating layer can reduce external charge injection; on the other hand, the BBC in the middle polarized layer can act as a trap to trap carrier movement. Therefore, the sandwich structure SA-BBC-SA / PEI has a lower leakage current density and a smaller jump distance compared to other structures.

[0064] Figure 5 The graph shows the energy storage performance of the composite materials prepared by the methods in Example 1 and Comparative Examples 1-4 at 150°C and 200°C.

[0065] As can be seen from the figure, at 150°C, the U of the sandwich structure SA-BBC-SA / PEI in Example 1... 90% The energy density (at an efficiency higher than 90%) can reach 8.03 J / cm³. 3 Compared to pure PEI (3.37 J / cm³), 3 The concentration of U in pure PEI increased by approximately 138%. As the temperature gradually increased to 200℃, the U... 90% Only 2.54 J / cm 3 However, the sandwich structure SA-BBC-SA / PEI, with its unique structure, still allows U 90% Achieve 6.94 J / cm 3 This represents an improvement of approximately 173%. Overall, the sandwich structure SA-BBC-SA / PEI possesses significantly higher breakdown strength and energy density than pure PEI.

[0066] Furthermore, the sandwich structure SA-BBC-SA / PEI obtained in Example 2 has a thickness of 10.6 μm and a thickness ratio of approximately 1:1:1. At 150°C, its U90% can reach 6.69 J / cm². 3 Compared to pure PEI (3.37 J / cm³), 3 The concentration of PEI increased by approximately 98.5%. However, as the temperature gradually increased to 200℃, the U90% of pure PEI was only 2.54 J / cm³. 3 However, Example 2 still allows U90% to achieve 6.41 J / cm³. 3 ;

[0067] Example 3 yielded a sandwich structure SA-BBC-SA / PEI with a thickness of 11.4 μm and a thickness ratio of approximately 1:1:1. At 150°C, its U90% concentration reached 6.74 J / cm². 3 Compared to pure PEI (3.37 J / cm³), 3 The concentration of PEI increases by approximately 100%. However, as the temperature gradually increases to 200℃, the U90% of pure PEI is only 2.54 J / cm³. 3 However, Example 3 still allows U90% to achieve 6.44 J / cm². 3 ;

[0068] Example 4 yielded a sandwich structure SA-BBC-SA / PEI with a thickness of 12.2 μm and a thickness ratio of approximately 1:2.5:1. At 150°C, its U90% concentration reached 5.58 J / cm². 3 Compared to pure PEI (3.37 J / cm³), 3 The concentration of PEI increased by approximately 65.6%. However, as the temperature gradually increased to 200℃, the U90% of pure PEI was only 2.54 J / cm³. 3 However, in Example 3, U90% can still achieve 4.73 J / cm³. 3 .

[0069] This example demonstrates that a suitable sandwich structure can effectively improve the energy storage performance of PEI-based polymers at high temperatures and effectively extend the effective operating temperature range of the composite material.

[0070] The sandwich-structured SA-BBC-SA / PEI composite material prepared in this invention utilizes the unique three-dimensional framework structure, high specific surface area, wide bandgap, and excellent thermal insulation properties of SiO2 aerogel, enabling the insulating layer to effectively reduce the injection of external charges. Furthermore, the high dielectric constant and high electron affinity of BBC allow the polarization layer to improve the overall polarization level of the material and effectively hinder the transport and migration of internal charge carriers. Compared to pure PEI, this significantly improves Young's modulus, reduces leakage current density, and decreases conduction losses, ultimately achieving excellent energy storage performance even at high temperatures.

[0071] Comparative Example 1

[0072] Other conditions were the same as in Example 1, except that no filler was added to prepare a single-layer pure PEI film.

[0073] Comparative Example 2

[0074] Other conditions were the same as in Example 1, except that SiO2 aerogel was added as a filler to prepare a single-layer SiO2 aerogel / PEI film.

[0075] Comparative Example 3

[0076] Other conditions were the same as in Example 1, except that ceramic filler BT-BNT-CZ was added as filler to prepare a single-layer BT-BNT-CZ / PEI film.

[0077] Comparative Example 4

[0078] The other conditions are the same as in Example 1, except that the top and bottom layers are replaced with polarization layers and the middle layer is replaced with an insulating layer to prepare a three-layer BBC-SA-BBC / PEI thin film.

[0079] Comparative Example 5

[0080] Other conditions were the same as in Example 1, except that ceramic filler BaTiO3 was added as filler to prepare a single-layer BT / PEI film.

Claims

1. A method for preparing a high temperature energy storage sandwich structure composite material, characterized in that: The polyamide acid precursor solution A dispersed with oxide aerogel is cast on a substrate to form a bottom insulating film layer by drying, then the polyamide acid precursor solution B dispersed with BBC is cast on the bottom insulating film layer to form a middle polarization film layer by drying, then the polyamide acid precursor solution A dispersed with oxide aerogel is cast on the middle polarization film layer to form a top insulating film layer by drying, finally the sandwich structure composite film composed of the bottom insulating film layer, the middle polarization film layer and the top insulating film layer is subjected to imidization treatment and then hot-pressed to obtain the sandwich structure composite material; The BBC has a chemical formula of 0.85 (0.8 BaTiO3- 0.2 (Bi 0.5 Na 0.5 )TiO3)- 0.15 CaZrO3.

2. The method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1, characterized in that: When the polyamide acid precursor solution A dispersed with oxide aerogel is cast on a substrate, the doctor blade height is controlled to be 25-50 μm, when the polyamide acid precursor solution B dispersed with BBC is cast on the bottom insulating film layer, the doctor blade height is controlled to be 75-200 μm, and when the polyamide acid precursor solution A dispersed with oxide aerogel is cast on the middle polarization film layer, the doctor blade height is controlled to be 25-100 μm; The polyamide acid precursor solution A dispersed with oxide aerogel is cast on a substrate to form a bottom insulating film layer by drying at 65-75 ℃ for 10-15 min, then the polyamide acid precursor solution B dispersed with BBC is cast on the bottom insulating film layer to form a middle polarization film layer by drying at 75-85 ℃ for 15-20 min, then the polyamide acid precursor solution A dispersed with oxide aerogel is cast on the middle polarization film layer to form a top insulating film layer by drying at 65-75 ℃ for 2-3 h.

3. The method of claim 1 or 2, wherein the method further comprises: The thickness ratio of the bottom insulating film layer, the middle polarization film layer and the top insulating film layer is 0.8-1.2:0.8-3:0.8-1.

2.

4. The method of claim 1 or 2, wherein the method further comprises: The oxide aerogel in the polyamide acid precursor solution A dispersed with oxide aerogel is selected from one of SiO2 aerogel, Al2O3 aerogel and ZrO2 aerogel.

5. The method of claim 1 or 2, wherein the method further comprises: The polyamide acid precursor solution A dispersed with oxide aerogel is obtained by dispersing oxide aerogel into solvent to obtain a dispersion, then adding diamine monomer and acid anhydride monomer into the dispersion in sequence and reacting under stirring; The diamine monomer is selected from 1,3-phenylenediamine; The acid anhydride monomer is selected from bisphenol A type diether dianhydride; The substance amount ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; The stirring speed is controlled to be 200-400 rpm and the stirring time is controlled to be 12-24 h.

6. The preparation method of the sandwich structure composite material with high temperature energy storage according to claim 1 or 2, characterized in that: The polyamide acid precursor solution B dispersed with BBC is obtained by dispersing BBC into solvent to obtain a dispersion, then adding diamine monomer and acid anhydride monomer into the dispersion in sequence and reacting under stirring; The particle size of the BBC is ≤1 μm; The diamine monomer is selected from 1,3-phenylenediamine; The acid anhydride monomer is selected from bisphenol A type diether dianhydride; The substance amount ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; The stirring speed is 200-400 rpm and the stirring time is 12-24 h.

7. The method of claim 1 or 2, wherein the method further comprises: The imidization process is: 70-80℃ for 1-2 h, 90-100℃ for 1-2 h, 130-150℃ for 1-2 h, 180-200℃ for 1-2 h, 230-250℃ for 1-2 h, and 280-300℃ for 1-2 h.

8. The method of claim 1 or 2, wherein the method further comprises: The hot-pressing temperature is 230-250℃ and the hot-pressing time is 15-30 min.

9. The high-temperature energy storage sandwich structure composite material prepared by the preparation method according to any one of claims 1-8, characterized in that: The sandwich structure composite material is composed of a bottom insulating layer, a polarization layer, and a top insulating layer, wherein the bottom insulating layer and the top insulating layer are both composed of a PEI matrix and oxide aerogels dispersed in the PEI matrix; the oxide aerogels are selected from one of SiO2 aerogels, Al2O3 aerogels, and ZrO2 aerogels, The polarization layer is composed of a PEI matrix and BBC dispersed in the PEI matrix.

10. The high-temperature energy storage sandwich structure composite material according to claim 9, characterized in that: In the bottom insulating layer and the top insulating layer, the mass fraction of the oxide aerogels is 0.1-3 wt%; In the polarization layer, the mass fraction of the BBC is 0.25-1 wt%.

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