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

Abstract

The preparation method comprises the following steps: taking a polyamide acid precursor solution A dispersed with oxide aerogel as insulating layer slurry, and taking a polyamide acid precursor solution B dispersed with BBC as polarization layer slurry; the height of a scraper and drying conditions are adjusted, a polarization layer and an insulating layer are subjected to layer-by-layer tape casting in sequence, a sandwich structure is prepared, the sandwich structure is placed in a hot press after gradient heating imidization, interlayer polymers are subjected to heat fusion by accurately controlling the temperature and time, and the sandwich structure which is seamlessly combined and stable in thickness 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 new type of polymer-based composite dielectric material based on sandwich structure, through the optimization design and synergistic coupling of each functional layer, realizing high energy storage density and high efficiency in a wide temperature range (especially high temperature), becomes the key direction to break through the current technical bottleneck and meet the demand of next generation high-performance electronic devices, has important scientific research value and broad industrialization prospect. SUMMARY

[0006] In view of the shortcomings of the prior art, a first object of the present application is to provide a preparation method of a sandwich structure composite material for high temperature energy storage. In the preparation method, the polyamide acid precursor solution A dispersed with oxide aerogel is used as the insulating layer slurry, the polyamide acid precursor solution B dispersed with BBC is used as the polarization layer slurry, the polarization layer and the insulating layer are cast in sequence layer by layer by adjusting the doctor blade height and drying conditions, a sandwich structure is prepared, and after gradient 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 stable thickness sandwich structure is formed.

[0007] A second object of the present application is to provide a sandwich structure composite material for high temperature energy storage prepared by the above preparation method.

[0008] In order to achieve the above object, the present application adopts the following technical scheme:

[0009] The preparation method of the sandwich structure composite material for high temperature energy storage of the present application is that the polyamide acid precursor solution A dispersed with oxide aerogel is cast on a substrate to form a bottom insulating film layer after 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 after 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 after drying, and 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 chemical formula of the BBC is 0.85(0.8BaTiO3-0.2(Bi 0.5 Na 0.5 )TiO3)-0.15CaZrO3.

[0010] The preparation method of the present application respectively introduces trace oxide aerogel as an insulating layer and a small amount of 0.85(0.8BaTiO3-0.2(Bi 0.5 Na 0.5)TiO3)-0.15CaZrO3(BBC) as the polarization layer, a multi-layer structure with synergistic function is constructed: the insulation layer relies on the three-dimensional nanometer network and ultra-high specific surface area of the oxide aerogel to form a large number of interface traps with the polymer, effectively binding carriers and inhibiting conductive migration, thereby significantly improving the breakdown strength and insulation stability at high temperature and high field; and the polarization layer enhances the overall polarization ability of the material by means of the high dielectric constant of the relaxor ferroelectric ceramic BBC, thereby improving the energy storage density; in addition, the oxide aerogel as an efficient thermal insulation unit can greatly extend the heat flow path and delay the accumulation of heat in the material, thereby ensuring the performance reliability of the material in extreme temperature environments; at the same time, since the SiO2 aerogel is a wide band gap material, it can reduce the injection of external charges; in the present application, the inner layer adopts a relaxor ferroelectric material with high electron affinity, which can further limit and bind the migration of charges injected into the interior; the synergistic effect of the outer layer insulation and the internal bound charge migration can effectively reduce the leakage current density and loss and improve the breakdown strength of the material; through the synergy of the above insulation, polarization and thermal insulation, the composite material has high energy storage performance and excellent stability in a wide temperature range.

[0011] It is found through experiments that only BBC and oxide aerogel can obtain the optimal synergistic effect; in the actual exploration process, other relaxor ferroelectric ceramics such as 0.9(0.8BaTiO3-0.2(Bi 0.5 Na 0.5 )TiO3)-0.1CaZrO3 and 0.8(0.8BaTiO3-0.2(Bi 0.5 Na 0.5 )TiO3)-0.2CaZrO3 are tried, and the performance is not as good as that of BBC; this is because the 0.85(0.8BaTiO3-0.2(Bi 0.5 Na 0.5 )TiO3)-0.15CaZrO3 ceramic has a medium relative dielectric constant of about 750, which can effectively delay polarization saturation and reduce the probability of electromechanical breakdown due to weak electrostrictive effect; on the other hand, compared with other samples, the loss of the ceramic from room temperature to 150 DEG C is the smallest, and the low tan delta can be maintained below 0.02 in a relatively wide frequency range.

[0012] In the present application, the oxide aerogel cannot be subjected to hydrophobic treatment; it is found through experiments that dispersing treatment makes the oxide aerogel more uniformly dispersed in the insulation layer, but the overall performance is actually reduced; on the contrary, without dispersing treatment, the synergistic effect with the polarization layer is better; the performance improvement brought by the sandwich structure makes the overall performance higher.

[0013] In addition, if the upper and lower layers are changed to polarization layers and the middle layer is changed to an insulation layer, the synergistic ability will decrease, and the overall performance will decrease.

[0014] Preferably, the polyamic acid precursor solution A dispersed with oxide aerogel is cast on the substrate with the doctor blade height controlled at 25-50 μm, the polyamic acid precursor solution B dispersed with BBC is cast on the bottom insulating film layer with the doctor blade height controlled at 75-200 μm, preferably 75-100 μm, and the polyamic acid precursor solution A dispersed with oxide aerogel is cast on the middle polarization film layer with the doctor blade height controlled at 25-100 μm, preferably 50-100 μm.

[0015] Preferably, the polyamic acid precursor solution A dispersed with oxide aerogel is cast on the substrate to form the bottom insulating film layer after drying at 65-75 °C for 10-15 min, then the polyamic acid precursor solution B dispersed with BBC is cast on the bottom insulating film layer to form the middle polarization film layer after drying at 75-85 °C for 15-20 min, and the polyamic acid precursor solution A dispersed with oxide aerogel is cast on the middle polarization film layer to form the top insulating film layer after drying at 65-75 °C for 2-3 h.

[0016] In the present application, the thickness of each layer can be controlled by the doctor blade height, and the drying temperature and drying time after casting each layer. It is found that the upper and lower layers need to be dried at a lower temperature, otherwise defects such as holes are likely to occur. The middle layer can be dried at a slightly higher temperature due to its compact structure.

[0017] Preferably, 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, preferably 0.8-1.2:0.8-1.2:0.8-1.2. It is found that the final performance is optimal when the thickness is controlled within the range of the present application. If it is not reasonable, the breakdown performance will decrease and the overall polarization and dielectric constant of the material will be difficult to reach the desired value.

[0018] Preferably, the oxide aerogel in the polyamic acid precursor solution A dispersed with oxide aerogel is selected from one of SiO2 aerogel, Al2O3 aerogel, and ZrO2 aerogel, preferably SiO2 aerogel.

[0019] Preferably, the polyamic acid precursor solution A dispersed with oxide aerogel is obtained by dispersing the oxide aerogel into a solvent to obtain a dispersion, and then adding diamine monomers and acid anhydride monomers into the dispersion under stirring.

[0020] Further preferably, the diamine monomers are selected from 1,3-phenylenediamine.

[0021] Further preferably, the acid anhydride monomer is selected from bisphenol A type diether dianhydride.

[0022] Further preferably, the molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; preferably 1:1.

[0023] Further preferably, the stirring speed is controlled to be 200-400 rpm during the reaction under stirring, and the reaction time is 12-24 h.

[0024] Preferably, the polyamic acid precursor solution B with dispersed BBC is obtained by dispersing the BBC into a solvent to obtain a dispersion, and then adding the diamine monomer and the acid anhydride monomer into the dispersion under stirring to react.

[0025] Preferably, the particle size of the BBC is ≤1 μm.

[0026] Further preferably, the diamine monomer is selected from 1,3-phenylenediamine.

[0027] Further preferably, the acid anhydride monomer is selected from bisphenol A type diether dianhydride.

[0028] Further preferably, the molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; preferably 1:1.

[0029] Further preferably, the stirring speed is controlled to be 200-400 rpm during the reaction under stirring, and the reaction time is 12-24 h.

[0030] Preferably, the imidization treatment is performed by sequentially maintaining at 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, and then slowly cooling to room temperature under vacuum.

[0031] By the gradual temperature increasing imidization process controlled accurately, the present application realizes the stable evaporation of solvent residues and the efficient cooperation of the polyamic acid to polyetherimide (PEI) cyclization reaction, which greatly avoids the defects such as bubble holes and micro-cracks caused by thermal stress.

[0032] Preferably, the hot-pressing temperature is 230-250℃, and the hot-pressing time is 15-30min. The application also provides the high-temperature energy storage sandwich structure composite prepared by the preparation method.

[0033] Preferably, the sandwich structure composite 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, and are preferably SiO2 aerogels.

[0034] The polarization layer is composed of a PEI matrix and BBC dispersed in the PEI matrix.

[0035] Further preferably, in the bottom insulating layer and the top insulating layer, the mass fraction of the oxide aerogels is 0.1-3wt%, and is preferably 0.75wt%.

[0036] Further preferably, in the polarization layer, the mass fraction of the BBC is 0.25-1wt%, and is preferably 0.5wt%.

[0037] The application has the following advantages:

[0038] The application successfully obtains a high-temperature energy storage sandwich structure composite with excellent comprehensive performance through reasonable structural design and precise preparation process. The core advantage comes from the synergistic construction and functional complementation of the insulating layer and the polarization layer.

[0039] 1. The insulating layer realizes double insulation of electrons and heat: the insulating layer composed of trace oxide aerogels introduces a large number of deep-level interface traps in the polymer matrix by virtue of its continuous three-dimensional nanometer network and extremely high specific surface area. These traps can effectively bind and significantly inhibit the migration of carriers, greatly reducing the conductance loss and leakage current, thereby providing the material with extremely high breakdown strength under high temperature and high field. At the same time, the aerogel itself as a high-efficiency heat insulation unit can greatly extend and distort the heat flow path, effectively block the injection and diffusion of external heat into the material, and provide protection for the long-term stable operation of the composite material at high temperature.

[0040] 2. The polarization layer realizes the synergy of high polarization and internal traps: the polarization layer composed of BBC relaxor ferroelectric ceramics effectively improves the overall polarization strength of the composite material by using its high dielectric constant, thereby significantly improving the energy storage density. More importantly, the BBC nanoparticles themselves can also act as effective trap centers, further binding the carriers inside the polarization layer, and together with the insulating layer, building a multi-level space charge defense system throughout the sandwich structure, thereby synergistically reducing the energy loss during charging and discharging.

[0041] 3. Synergistic effect and final performance of sandwich structure: The above-mentioned "sandwich" structure of insulation layer and polarization layer is built by layer-by-layer flow casting, which realizes the optimal configuration and performance superposition of each functional layer. The insulation layer focuses on isolating electrons and heat, and the polarization layer focuses on improving polarization and internal binding. The synergistic effect of the two ultimately enables the composite material to have high breakdown strength, low loss, high energy storage efficiency and excellent high-temperature stability under extreme temperature environment, which well meets the urgent needs of modern electronic and power systems for high-temperature, high-energy and high-reliability dielectric materials. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Cross-sectional SEM and EDS images of SA-BBC-SA / PEI film prepared by the method in Example 1.

[0043] Figure 2 Dielectric spectrum and dielectric temperature spectrum of the sandwich structure composite material prepared by the method in Example 1, wherein Figure 2 (a) in FIG. 1 is the dielectric spectrum of the sandwich structure composite material, Figure 2 (b) in FIG. 1 is the dielectric temperature spectrum of the sandwich structure composite material.

[0044] Figure 3 Load-displacement curve and Young's modulus change diagram of the sandwich structure composite material prepared by the method in Example 1, wherein Figure 3 (a) in FIG. 2 is the load-displacement curve of the sandwich structure composite material, Figure 3 (b) in FIG. 2 is the Young's modulus change diagram of the sandwich structure composite material.

[0045] Figure 4 Leakage current density curve diagram of the sandwich structure composite material prepared by the method in Example 1 at 150°C and 200°C, wherein Figure 4 (a) in FIG. 3, Figure 4 (b) in FIG. 3 is the leakage current density curve diagram of the sandwich structure composite material at 150°C, wherein Figure 4 (c) in FIG. 3, Figure 4 (d) in FIG. 3 is the leakage current density curve diagram of the sandwich structure composite material at 200°C.

[0046] Figure 5 Energy storage performance diagram of the sandwich structure composite material prepared by the method in Example 1 at 150°C and 200°C; wherein Figure 5 (a) in FIG. 4 is the energy storage performance diagram of the sandwich structure composite material at 150°C, Figure 5 (b) in FIG. 4 is the energy storage performance diagram of the sandwich structure composite material at 200°C. DETAILED DESCRIPTION

[0047] Example 1

[0048] SiO2 aerogel with three-dimensional skeleton structure having a specific surface area higher than 600 m2 / g, skeleton pore size distribution in the range of 5-20 nm, SiO2 nanoparticles in it having a size of 5-10 nm. Relaxor ferroelectric filler BBC prepared by a conventional solid-phase method, which effectively limits losses due to its polar nanoregions, has a very low remanence.

[0049] 2.63 mg of SiO2 aerogel was weighed out and added to the N-methylpyrrolidone (NMP) solvent, dispersed using an ultrasonic machine for 5 min, forming a preliminary dispersion of the insulating layer slurry.

[0050] 1.75 mg of BBC relaxor ferroelectric ceramic was weighed out and added to the NMP solvent, dispersed using an ultrasonic machine for 30 min, forming a preliminary dispersion of the polarizing layer slurry.

[0051] In the well-dispersed insulating layer slurry and the polarization layer slurry, 0.06 g of 1,3-phenylenediamine (MPD) and 0.29 g of bisphenol A diether dianhydride (BPADA) were added in strict order, respectively, and the molar ratio of the two monomers was controlled to be 1.0. The insulating layer PAA and the polarization layer PAA were obtained by magnetic stirring at a constant speed of 300 rpm for 12 hours at room temperature. In this process, the polymerization of polyamic acid (PAA) was directly carried out around the dispersed SiO2 aerogel skeleton and BCC, realizing the dispersion of fillers and strong interfacial interaction. The viscous insulating layer PAA solution obtained by polymerization was cast on a clean glass substrate as the bottom insulating layer by a doctor blade with a height of 50 pm. The sample was transferred to a 70°C air drying oven for drying for 15 min to volatilize most of the solvent in the bottom layer. Then, the viscous polarization layer PAA solution obtained by polymerization was cast on the bottom insulating layer as the intermediate polarization layer by a doctor blade with a height of 75 pm. The sample was transferred to an 80°C air drying oven for drying for 20 min to volatilize most of the solvent in the intermediate layer and make the bottom layer and the intermediate layer tightly combined. Finally, the viscous insulating layer PAA solution obtained by polymerization was cast on the intermediate polarization layer as the top insulating layer by a doctor blade with a height of 100 pm and transferred to a 70°C air drying oven for drying for 2 h. This low-temperature slow drying process ensures the stable volatilization of the solvent, avoids the accumulation of internal stress and film defects caused by too fast skinning on the surface, and controls the thickness between layers by controlling the height of the doctor blade, the drying temperature and time. The dried sandwich structure PAA composite film was placed in a vacuum oven, and the following precise gradient heat treatment program was performed in a continuous vacuum environment: the temperature was raised to 80°C at a rate of 2°C / min and kept for 2 h; then the temperature was raised to 100°C, 150°C, 200°C, 250°C and 300°C in turn and kept for 1 h at each temperature. After the treatment, the sample was cooled to room temperature in the oven. This program ensures that the imidization reaction of PAA to PEI is sufficient and complete, and the vacuum environment effectively removes the small molecules of the reaction byproducts and prevents the oxidation degradation of the material at high temperature, finally obtaining a high-performance sandwich structure PEI composite material. The prepared three-layer film was aligned and placed in a hot press at 250°C for 20 min to make the interlayer polymers form a seamless combination and stable sandwich structure.

[0052] Example 2

[0053] The other conditions were the same as in Example 1, the first layer doctor blade had a thickness of 25 pm, the second layer doctor blade had a thickness of 100 pm, and the third layer doctor blade had a thickness of 50 pm.

[0054] Example 3

[0055] 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.

[0056] Example 4

[0057] 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.

[0058] Performance testing

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 ;

[0066] The sandwich structure SA-BBC-SA / PEI obtained in Example 3 has a thickness of 11.4 μm, and the thickness ratio is about 1:1:1. The U90% at 150℃ can reach 6.74 J / cm 3 . Compared with pure PEI (3.37 J / cm 3 ), it is increased by about 100%. As the temperature gradually increases to 200℃, the U90% of pure PEI is only 2.54 J / cm 3 , while the U90% of Example 3 can still reach 6.44 J / cm 3 .

[0067] The sandwich structure SA-BBC-SA / PEI obtained in Example 4 has a thickness of 12.2 μm, and the thickness ratio is about 1:2.5:1. The U90% at 150℃ can reach 5.58 J / cm 3 . Compared with pure PEI (3.37 J / cm 3 ), it is increased by about 65.6%. As the temperature gradually increases to 200℃, the U90% of pure PEI is only 2.54 J / cm 3 , while the U90% of Example 3 can still reach 4.73 J / cm 3 .

[0068] This example shows that a suitable sandwich structure can effectively improve the energy storage performance of PEI-based polymers at high temperatures, and effectively expand the effective working temperature range of the composite material.

[0069] The sandwich structure SA-BBC-SA / PEI composite material prepared in the application utilizes the unique three-dimensional skeleton structure, high specific surface area, wide band gap, excellent heat insulation performance and other characteristics of SiO2 aerogel, so that the insulating layer can effectively reduce the injection of external charges. And by using the high dielectric constant and high electron affinity energy of BBC, the polarization layer can improve the overall polarization level of the material and effectively hinder the transport and migration of internal carriers. Compared with pure PEI, the Young's modulus is effectively improved, the leakage current density is reduced, and the conduction loss is reduced, and finally excellent energy storage performance can still be obtained at high temperatures.

[0070] Comparative Example 1

[0071] Other conditions are the same as those in Example 1, except that no filler is added to prepare a single-layer pure PEI film.

[0072] Comparative Example 2

[0073] Other conditions are the same as those in Example 1, except that SiO2 aerogel is added as a filler to prepare a single-layer SiO2 aerogel / PEI film.

[0074] Comparative Example 3

[0075] Other conditions are the same as example 1, only ceramic filler BT-BNT-CZ is added as filler to prepare single layer BT-BNT-CZ / PEI film.

[0076] Comparative example 4

[0077] Other conditions are the same as example 1, only the upper and lower layers are changed to polarization layer, the middle layer is changed to insulating layer, to prepare three layer BBC-SA-BBC / PEI film.

[0078] Comparative example 5

[0079] Other conditions are the same as example 1, only ceramic filler BaTiO3 is added as filler to prepare single layer BT / PEI film.

Claims

1. A method for preparing a high-temperature energy storage sandwich structure composite material, characterized in that: 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. The chemical formula of the BBC is 0.85(0.8BaTiO3-0.2(Bi) 0.5 Na 0.5 TiO3)-0.15CaZrO3.

2. The method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1, characterized in that: When polyamic acid precursor solution A with dispersed oxide aerogel is cast onto the substrate, the doctor blade height is controlled at 25-50 μm. When polyamic acid precursor solution B with dispersed BBC is cast onto the bottom insulating film layer, the doctor blade height is controlled at 75-200 μm. When polyamic acid precursor solution A with dispersed oxide aerogel is cast onto the middle polarized film layer, the doctor blade height is controlled at 25-100 μm. 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.

3. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: The thickness ratio of the bottom insulating film layer, the middle polarized film layer, and the top insulating film layer is 0.8-1.2:0.8-3:0.8-1.

2.

4. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: In the polyamic acid precursor solution A containing dispersed oxide aerogel, the oxide aerogel is selected from one of SiO2 aerogel, Al2O3 aerogel and ZrO2 aerogel.

5. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: The process for 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 to the dispersion in sequence, and the mixture is reacted under stirring to obtain the product. The diamine monomer is selected from 1,3-phenylenediamine; The anhydride monomer is selected from bisphenol A type diether dianhydride; The molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; During the reaction under stirring, the stirring speed is controlled at 200-400 rpm, and the time is 12-24 hours.

6. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: The process for obtaining the polyamic acid precursor solution B containing BBC is as follows: BBC is dispersed in a solvent to obtain a dispersion, and diamine monomer and acid anhydride monomer are added to the dispersion in sequence, and the reaction is carried out under stirring to obtain the product. The particle size of the BBC is ≤1μm; The diamine monomer is selected from 1,3-phenylenediamine; The anhydride monomer is selected from bisphenol A type diether dianhydride; The molar ratio of the diamine monomer to the acid anhydride monomer is 0.8-1.2:1; During the reaction under stirring, the stirring speed is controlled at 200-400 rpm, and the time is 12-24 hours.

7. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: The imidization process is as follows: sequentially heat treatment at 70-80℃ for 1-2 hours, at 90-100℃ for 1-2 hours, at 130-150℃ for 1-2 hours, at 180-200℃ for 1-2 hours, at 230-250℃ for 1-2 hours, and at 280-300℃ for 1-2 hours.

8. A method for preparing a high-temperature energy storage sandwich structure composite material according to claim 1 or 2, characterized in that: The hot pressing temperature is 230-250℃, and the hot pressing time is 15-30 minutes.

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

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

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