Preparation technology of a high-temperature resistant epoxy energy storage film based on liquid crystal ordered structure

Abstract

The present invention discloses a preparation technique for a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, comprising the following steps: S1. Mix a liquid crystal biphenyl-type epoxy monomer, a bisphenol A-type epoxy monomer, and a curing agent in proportion, and simultaneously perform magnetic stirring and oil bath heating and melting treatment to obtain a mixed molten liquid; S2. Subject the mixed molten liquid obtained in S1 to degassing treatment, and then pour it into a mold; perform heat pressing and curing treatment to obtain an epoxy film. By introducing high-polarity carbon-fluorine bonds into the liquid crystal molecule-modified epoxy film, the present invention using the above-mentioned preparation technique for a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure improves the energy storage density of the epoxy film, can maintain a relatively high glass transition temperature, enhances the high-temperature energy storage characteristics of the epoxy film, and at the same time, the cured epoxy film has a liquid crystal ordered structure, realizing a synchronous increase in thermal conductivity, providing a new idea for the development of high-performance epoxy materials for the field of dielectric energy storage.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric energy storage, and particularly to a preparation technology of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure. Background Art

[0002] Power devices such as high-voltage insulated gate bipolar transistors (IGBTs) are widely used in ultra-high voltage (UHV) polymer dielectrics, which have the advantages of high dielectric constant, low dielectric loss, high power density, high charge-discharge efficiency, large working voltage / current, high reliability, and low cost. They are widely used as energy storage materials for capacitors in high-power rapid regulation of smart grids and AC-DC conversion of electric vehicles. When decentralized new energy generation is incorporated into the power system, the load of the distributed power grid increases, and the supply-demand control becomes complicated. Therefore, to achieve high-power rapid regulation of smart grids, capacitors with high energy storage density and low dielectric loss are required.

[0003] Biaxially oriented polypropylene (BOPP) is widely used as a commercial energy storage dielectric due to its extremely low dielectric loss (tanδ≈4.0×10 -4 ), high dielectric strength, and excellent tensile properties. However, due to its low dielectric constant (ε r = 2.2 at 1 kHz), at a working electric field strength of 200 kV / mm, the energy storage density (E w ) of BOPP is only 0.5 J / cm 3 , and in practical applications, it is often necessary to increase the amount of material to meet the capacity requirements. At the same time, the volume of the capacitor will increase due to the increase in the amount of material, and it is becoming increasingly difficult to meet the growing capacity requirements of power inverters in a limited space.

[0004] In the prior art, the dielectric constant and dielectric strength of dielectric materials are in a contradictory relationship. Increasing the dielectric constant of dielectric materials will cause an increase in dielectric loss of the materials, resulting in an increase in leakage current, which will in turn have a negative impact on the dielectric strength. How to synergistically improve the dielectric constant and dielectric strength of dielectric materials or improve the dielectric constant without affecting the dielectric strength has become the focus of research on polymer energy storage dielectric materials. In addition, in AC-DC conversion applications, affected by the high degree of integration, miniaturization of power units, and difficult heat dissipation, the working temperature of electronic devices is constantly rising, and the heat resistance requirements for capacitors are getting higher and higher. For example, the working environment temperature of power inverters in electric vehicles has reached 110 - 120°C. Currently, the working temperature of commercial BOPP is relatively low. When the ambient temperature is higher than 85°C, its dielectric loss and charge-discharge efficiency (η) will deteriorate severely, and additional space is required to install a cooling device, which further limits the application of BOPP in electric vehicle power inverters and smart grids. Therefore, it is urgent to develop energy storage dielectric materials with high working temperature and high energy storage density. Summary of the Invention

[0005] The object of the present invention is to provide a preparation technique for a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, improve the high-temperature energy storage characteristics of the epoxy film, solve the problem of the sharp decline in the energy storage performance of commercial dielectric films, and provide a new idea for developing high-performance epoxy materials for the field of dielectric energy storage.

[0006] To achieve the above object, the present invention provides a preparation technique for a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, including the following steps:

[0007] S1. In proportion, mix a liquid crystal biphenyl-type epoxy monomer (TMBP), a bisphenol A-type epoxy monomer (EP-828), and a curing agent, and simultaneously perform magnetic stirring and oil bath heating and melting treatment to obtain a mixed molten liquid;

[0008] S2. Perform degassing treatment on the mixed molten liquid obtained in S1, and then pour it into a mold; use a hot pressing method for heating and curing treatment to obtain an epoxy film.

[0009] Preferably, in S1, the curing agent includes 2,3,4-trifluoroaniline (TFAn) and 4,4-diaminodiphenylmethane (DDM).

[0010] Preferably, in S1, the liquid crystal biphenyl-type epoxy monomer can be selected as 3,3,5,5-tetramethylbiphenyl bisphenol diglycidyl ether (TMBP). The liquid crystal ordered structure of TMBP helps to improve the breakdown field strength E b , thermal conductivity, and heat resistance characteristics.

[0011] Preferably, in S1, the sum of the molar amounts of the bisphenol A-type epoxy monomer and the liquid crystal biphenyl-type epoxy monomer: the curing agent = 3:2.

[0012] Preferably, in S1, the magnetic stirring and oil bath heating and melting treatment are specifically:

[0013] Add a magnetic stir bar, and use a magnetic stirrer to place the mixture in an oil bath for heating and melting while performing magnetic stirring.

[0014] Preferably, the temperature of the oil bath heating is 105 °C, the stirring rate is 150 - 250 r / min, and the stirring time is 10 min.

[0015] Preferably, in S2, the degassing treatment is specifically:

[0016] Place the mixed molten liquid in a vacuum drying oven and perform it in a way of heating and refluxing until no bubbles are generated.

[0017] Considering that bubbles may be generated during the mixing of the molten liquid, resulting in uneven components in the obtained mixed molten liquid and a reduction in breakdown due to a large number of bubble defects, before curing, the mixed molten liquid is degassed to eliminate the bubbles in the mixed molten liquid, thereby reducing the probability of insulation failure.

[0018] Preferably, the temperature of the degassing treatment is 105 - 110 °C, and the degassing time is 3 - 5 min.

[0019] Preferably, in S2, the heat pressing method for heating and curing treatment is specifically as follows:

[0020] First, the mold is preheated. Then, a PET release film is placed under the mold. The degassed mixed molten liquid is poured into a copper foil mold with a thickness of 10 μm. Then, another PET release film is covered on the top of the mold, and it is placed between mirror - level smooth stainless - steel plates and put into a hot press for step - by - step heating and curing treatment.

[0021] Considering that the mixed molten liquid is prone to low - temperature crystallization when it comes into contact with low temperatures, resulting in incomplete curing reaction. To avoid this situation, in the present invention, the mold is preheated to the curing temperature first, and then the degassed mixed solution is poured into it, and then the curing treatment is carried out. The pouring method is used for pouring, and the temperature of the mixed molten liquid during pouring is the temperature after degassing treatment, 105 °C.

[0022] Preferably, the temperature of the preheating treatment is 100 - 110 °C, the temperature of the heating and curing treatment is 105 - 200 °C, and the curing time is 10 h.

[0023] During the curing process, the present invention takes into account that the curing process of the liquid crystal biphenyl type epoxy monomer consists of early line segment extension, branching, and cross-linking reactions. The curing temperature has a great influence on the linear segment extension of the biphenyl liquid crystal unit, which is important for the π-π stacking interaction of the biphenyl liquid crystal unit. Therefore, in order to enable the liquid crystal biphenyl type epoxy monomer to have sufficient time to achieve effective line segment extension, form liquid crystal domains, with a more complete curing degree and a higher cross-linking degree, the present invention preferably adopts a stepwise temperature increase curing process for curing treatment. And the preferred curing process of the present invention is: first, in a hot press, cure at a curing temperature of 110°C for 4 hours, then cure at a curing temperature of 160°C for 4 hours, and finally cure at a curing temperature of 200°C for 2 hours. It is divided into three stages for stepwise temperature increase. The treatment temperature in the first stage is lower than the curing temperature of the liquid crystal biphenyl type epoxy monomer and the curing agent used. In this stage, the biphenyl liquid crystal unit can produce a π-π stacking effect, which helps these units self-assemble and orient to form liquid crystal domains, and form a 20-μm thin film under a pressure of 200 kPa. Then continue to cure at 160°C for 4 hours and at 200°C for 2 hours to ensure complete branching and cross-linking.

[0024] Therefore, the present invention adopts the above-mentioned preparation technology of a high-temperature resistant epoxy energy storage thin film based on a liquid crystal ordered structure, and the beneficial effects are as follows:

[0025] The present invention uses a liquid crystal biphenyl type epoxy monomer (TMBP) and a bisphenol A type epoxy monomer (EP) as the matrix, regulates the structure of the intrinsic curing agent (TFAn and DDM) and the curing temperature, and introduces high-polarity carbon-fluorine bonds into the liquid crystal molecule-modified epoxy thin film to prepare a new type of high-temperature resistant epoxy energy storage thin film based on a liquid crystal ordered structure, characterized its electrical and thermal properties, and proved that this method can prepare an energy storage dielectric material with a high working temperature and a high energy storage density.

[0026] The present invention introduces a liquid crystal biphenyl type epoxy monomer as a rigid group, which can not only improve the heat resistance of the polymer dielectric, but also reduce its dielectric loss and improve the charge-discharge efficiency. Compared with traditional filled epoxy resins, the biphenyl structure in its molecular structure has greater rigidity, which further enhances the resistance to the internal rotation of the bond and the molecular chain. Therefore, the introduction of the liquid crystal biphenyl structure can effectively enhance the heat resistance of the epoxy thin film, and the liquid crystal molecule has excellent electrical insulation performance. Introducing liquid crystal molecules into the epoxy thin film can effectively improve the heat resistance, thermal conductivity, and mechanical properties of the thin film.

[0027] Introducing liquid crystal molecules into the epoxy thin film cross-linked network (TMBP / DDM) of the present invention can effectively enhance the rigidity of molecular chain segments. However, the improvement in the rigidity of the molecular chain cross-linked structure will limit the generation of molecular chain segment polarization, resulting in a relatively low dielectric constant of the epoxy thin film and insufficient energy storage density. To address the problem of insufficient dielectric constant, introducing highly polar carbon-fluorine bonds into the cross-linked system of liquid crystal molecule-modified epoxy resin (TMBP / EP11) can effectively improve the dielectric constant and energy storage density of the epoxy thin film. Introducing TFAn with an amine group at one end can also adjust the cross-linking degree of the epoxy thin film to achieve control of film-forming ability and mechanical properties.

[0028] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0029] Figure 1 It is the infrared spectrogram of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0030] Figure 2 It is the SEM images of the cross-sectional structure and planar structure of the epoxy thin films prepared in Examples 1, 3, and 5 of the present invention. Among them, (a) is the SEM observation cross-sectional morphology of Example 1, (b) is the SEM observation cross-sectional morphology of Example 3, (c) is the SEM observation cross-sectional morphology of Example 5, (d) is the SEM observation surface morphology of Example 1, (e) is the SEM observation surface morphology of Example 3, and (f) is the SEM observation surface morphology of Example 5;

[0031] Figure 3 It is the DSC test results of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0032] Figure 4 It is the tensile property test results of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0033] Figure 5 It is the axial thermal conductivity test results of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0034] Figure 6 It is the planar thermal conductivity test results of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0035] Figure 7 It is the dielectric property test results of the epoxy thin films prepared in Examples 1 to 5 of the present invention;

[0036] Figure 8 It is the electric dipole moment results of the molecules obtained by quantum chemical calculation in Examples 1, 3, and 5 of the present invention. Among them, (a) is Example 1, (b) is Example 3, and (c) is Example 5;

[0037] Figure 9 Dielectric spectroscopy test results of the epoxy films prepared in Examples 1 to 5 of the present invention at different temperatures, where (a) is Example 1, (b) is Example 3, (c) is Example 5, and (d) is the comparison of dielectric losses of the three films at 10 Hz and different temperatures;

[0038] Figure 10 Comparison of the DC dielectric strength of the epoxy films prepared in Examples 1 to 5 of the present invention;

[0039] Figure 11 Calculation results of the electrostatic potential distribution on the isosurface of the electronic charge density based on the density functional theory for Examples 1, 3, and 5 of the present invention, where (a) is Example 1, (b) is Example 3, and (c) is Example 5;

[0040] Figure 12 Schematic diagrams of the cross-linking structures of the molecular chains of Examples 1, 3, and 5 of the present invention, where (d) is Example 1, (e) is Example 3, and (f) is Example 5;

[0041] Figure 13 Calculation results of the free volume ratios of the three cross-linking systems based on the Forcite module for Examples 1, 3, and 5 of the present invention, where (g) is Example 1, (h) is Example 3, and (i) is Example 5;

[0042] Figure 14 DC breakdown test results of the epoxy films prepared in Examples 1, 3, and 5 of the present invention at different temperatures, where (a) is Example 1, (b) is Example 3, and (c) is Example 5;

[0043] Figure 15 Partial discharge test results of the epoxy films prepared in Examples 1, 3, and 5 of the present invention, where (a) is Example 1, (b) is Example 3, (c) is Example 5, and (d) is the average partial discharge quantity;

[0044] Figure 16 Results of the thermally stimulated current analysis of the epoxy films prepared in Examples 1 and 3 of the present invention, where (a) is the thermally stimulated current, (b) is the peak fitting of the TMBP / EP11 system, and (c) is the peak fitting of the 3F@TMBP / EP11 system;

[0045] Figure 17 High-temperature conductivity test results of the epoxy films prepared in Examples 1 and 3 of the present invention;

[0046] Figure 18Results of the polarization hysteresis loops of the epoxy films prepared in Examples 1 to 5 of the present invention under different electric field strengths and different test temperatures, where (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, (e) is Example 5, (f) is under the condition of the same electric field strength, (g) is Example 1 under different test temperature conditions, (h) is Example 3 under different test temperature conditions, and (i) is Example 5 under different test temperature conditions;

[0047] Figure 19 Results of the comparison of the energy storage performance of the epoxy films prepared in Examples 1 to 5 of the present invention, where (a) is at room temperature, (b) is under different temperature conditions, (c) is the comparison of the energy storage density of this study with other studies or commercial films at room temperature and a charge-discharge efficiency greater than 90%, and (d) is the comparison of the charge-discharge efficiency of this study with other studies or commercial films at 140 °C and 200 kV / mm;

[0048] Figure 20 Results of the high-temperature energy storage cycling performance test of the epoxy film prepared in Example 3 of the present invention at 200 kV / mm and different temperatures;

[0049] Figure 21 Schematic diagram of the self-healing process of the metallized film of the present invention;

[0050] Figure 22 Test results of the comparison of the morphology and energy storage performance of the epoxy film prepared in Example 3 of the present invention before and after breakdown, where (a) is the scanning electron microscope image before breakdown, (b) is the energy dispersive spectrometer analysis before breakdown, (c) is the polarized light microscope image after breakdown, (d) is the scanning electron microscope image after breakdown, (e) is the energy dispersive spectrometer analysis after breakdown, and (f) is the comparison of the energy storage performance before and after breakdown. Detailed implementation manners

[0051] The technical solutions of the present invention will be further described below with reference to the drawings and examples.

[0052] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs.

[0053] Example 1

[0054] This example provides a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, and its preparation technology is as follows:

[0055] Mix 0.5 g of TMBP, 0.5 g of EP, and 0.272 g of DDM, and place a magnetic stir bar into it. Use a magnetic stirrer to heat and melt the mixture in an oil bath at 105 °C and perform magnetic stirring for 10 min. After stirring is completed, use a magnet to remove the magnetic stir bar. Subsequently, place the obtained mixed molten liquid in a vacuum drying oven at 90 °C to degas until no bubbles are generated. Place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 20 μm, and finally cover another PET release film on the mold. Place it in the middle of a mirror-level smooth stainless steel plate and cure it in a hot press at a curing temperature of 110 °C for 4 h, then cure it at a curing temperature of 160 °C for 4 h, and finally cure it at a curing temperature of 200 °C for 2 h. An epoxy film with both heat resistance and energy storage performance is obtained and named TMBP / EP11.

[0056] Example 2

[0057] This example provides a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, and its preparation technology is as follows:

[0058] Mix 0.5 g of TMBP, 0.5 g of EP, 0.265 g of DDM, and 0.015 g of TFAn, and place a magnetic stir bar into it. Use a magnetic stirrer to heat and melt the mixture in an oil bath at 105 °C and perform magnetic stirring for 10 min. After stirring is completed, use a magnet to remove the magnetic stir bar. Subsequently, place the obtained mixed molten liquid in a vacuum drying oven at 90 °C to degas until no bubbles are generated. Place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 20 μm, and finally cover another PET release film on the mold. Place it in the middle of a mirror-level smooth stainless steel plate and cure it in a hot press at a curing temperature of 110 °C for 4 h, then cure it at a curing temperature of 160 °C for 4 h, and finally cure it at a curing temperature of 200 °C for 2 h. An epoxy film with both heat resistance and energy storage performance is obtained and named 1F@TMBP / EP11.

[0059] Example 3

[0060] This example provides a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, and its preparation technology is as follows:

[0061] Mix 0.5 g of TMBP, 0.5 g of EP, 0.247 g of DDM and 0.04 g of TFAn, and put in a magnetic stir bar. Use a magnetic stirrer to place the mixture in an oil bath at 105 °C to heat and melt it, and carry out magnetic stirring for 10 min. After stirring is completed, use a magnet to suck out the magnetic stir bar. Subsequently, place the obtained mixed molten liquid in a vacuum drying oven at 90 °C to degas until no bubbles are generated. Place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 20 μm. Finally, cover the mold with another PET release film, place it in the middle of a mirror-level smooth stainless steel plate, and cure it in a hot press at a curing temperature of 110 °C for 4 h, then cure it at a curing temperature of 160 °C for 4 h, and finally cure it at a curing temperature of 200 °C for 2 h. An epoxy film with both heat resistance and energy storage performance is obtained, and it is named 3F@TMBP / EP11.

[0062] Example 4

[0063] This example provides a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, and its preparation technology is as follows:

[0064] Mix 0.5 g of TMBP, 0.5 g of EP, 0.22 g of DDM and 0.08 g of TFAn, and put in a magnetic stir bar. Use a magnetic stirrer to place the mixture in an oil bath at 105 °C to heat and melt it, and carry out magnetic stirring for 10 min. After stirring is completed, use a magnet to suck out the magnetic stir bar. Subsequently, place the obtained mixed molten liquid in a vacuum drying oven at 90 °C to degas until no bubbles are generated. Place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 20 μm. Finally, cover the mold with another PET release film, place it in the middle of a mirror-level smooth stainless steel plate, and cure it in a hot press at a curing temperature of 110 °C for 4 h, then cure it at a curing temperature of 160 °C for 4 h, and finally cure it at a curing temperature of 200 °C for 2 h. An epoxy film with both heat resistance and energy storage performance is obtained, and it is named 6F@TMBP / EP11.

[0065] Example 5

[0066] This example provides a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, and its preparation technology is as follows:

[0067] Mix 0.5 g of TMBP, 0.5 g of EP, 0.183 g of DDM and 0.13 g of TFAn, and place a magnetic stir bar. Use a magnetic stirrer to heat and melt the mixture in an oil bath at 105 °C and perform magnetic stirring for 10 min. After stirring, use a magnet to suck out the magnetic stir bar. Subsequently, place the obtained mixed molten liquid in a vacuum drying oven at 90 °C to degas until no bubbles are generated. Place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 20 μm. Finally, cover another PET release film on the mold, place it in the middle of a mirror-level smooth stainless steel plate, and cure it in a hot press at a curing temperature of 110 °C for 4 h, then cure it at a curing temperature of 160 °C for 4 h, and finally cure it at a curing temperature of 200 °C for 2 h. A new energy storage epoxy film with a liquid crystal ordered structure, high heat resistance and high thermal conductivity is obtained, and it is named 10F@TMBP / EP11.

[0068] Experimental tests

[0069] (I) Molecular structure characterization

[0070] As Figure 1 shown, the infrared spectra of the epoxy films prepared in Examples 1 to 5 and the standard TMBP after normalization for different crosslinking and curing systems. In the figure, the stretching of hydroxyl groups is at 3200 - 3600 cm -1 , the stretching of alkyl groups is at 2800 - 3100 cm -1 , the stretching of aromatic hydrocarbons is at 1450 - 1600 cm -1 , and the stretching of carbon-oxygen bonds is at 1000 - 1200 cm -1 . The characteristic peak of secondary amino groups (brown shadow) is at 3200 - 3400 cm -1 , and the characteristic peak of epoxy groups (blue shadow) is at 913 cm -1 . No obvious characteristic peaks are found in the above two places, indicating that both epoxy resins and curing agents have reacted completely. The characteristic peak of carbon-fluorine bonds is at 1220 - 1245 cm -1 . When carbon-fluorine bonds are introduced into the crosslinking system, a gradient change in the peak value of the five systems can be clearly observed in this range, indicating that the four carbon-fluorine bond modified systems have successfully grafted carbon-fluorine bonds.

[0071] (II) Morphology characterization

[0072] Use a field emission electron microscope (SEM, Zeiss GeminiSEM 500) to perform morphology tests on the epoxy films prepared in Examples 1, 3 and 5. The test results are as Figure 2As shown in the figure. It can be observed that as the amount of carbon-fluorine bond introduced increases, the cross-section and section of the film become smoother and smoother. There are many serrated patterns on the cross-section of the TMBP / EP11 cross-linked system, the serrated patterns on the cross-section of the 3F@TMBP / EP11 cross-linked system are significantly reduced, and almost no obvious patterns can be observed on the cross-section of the 10F@TMBP / EP11 cross-linked system. This is because when TFAn is used as a curing agent, it can only link two epoxy molecular chains, while DDM can link four epoxy molecular chains. Therefore, the cross-linking degree of the cross-linked structure will decrease as the amount of carbon-fluorine bond introduced increases. The decrease in cross-linking degree can effectively reduce the restriction on the movement of molecular segments, thereby enhancing the flexibility of the cross-linked system, which is beneficial to its application in the roll-to-roll process of metal film capacitors.

[0073] (III) DSC Test

[0074] As Figure 3 shown, it can be seen from the Tg curve of the epoxy film that as the amount of TFAn introduced increases, the glass transition temperature of the epoxy film decreases significantly. The results show that the glass transition process of the polymer material corresponds to the static-dynamic transition process of the cross-linked structure segments. The overlapping of the electron clouds of the polymer forms an asymmetric large π bond, making the internal rotation of the molecular chain more difficult. Polymers containing conjugated double bonds such as benzene rings have greater rigidity and excellent heat resistance. Although TFAn contains an aromatic ring structure, the introduction of TFAn will cause a decrease in the cross-linking degree of the molecular segment cross-linked system, and the decrease in cross-linking degree will cause a reduction in the constraint on the movement of the segments, so it will cause a decrease in the glass transition temperature. However, compared with ordinary epoxy resins, the Tg after the introduction of TFAn is still relatively high. The Tg value of 10F@TMBP / EP11 with the worst heat resistance can still reach 135 °C, which can basically meet the application of power inverters in general high-temperature working environments. The mechanical properties of the epoxy film are of great significance for its practical application.

[0075] (IV) Tensile Property Test

[0076] As Figure 4 shown, tensile tests were carried out on five kinds of epoxy films. Among them, the tensile fracture strength of the TMBP / EP11 system without the introduction of TFAn is 64.22 Mpa. After the introduction of 1wt%, 3wt%, 6wt% and 10wt% TFAn respectively, the tensile fracture strength decreased by 8.3%, 8.5%, 27% and 38% respectively. It can be found that after the introduction of TFAn, the tensile fracture strength decreased to varying degrees as a whole. When the introduction amount is small (<3wt%), the decrease is not obvious. When the introduction amount exceeds 6wt%, the tensile fracture strength drops sharply. The elongation at break will be significantly improved when the introduction amount is small. At this time, the flexibility of the polymer matrix can be effectively improved. When the introduction amount exceeds a certain degree, the cross-linking degree decreases significantly. At this time, the elongation at break is affected by the fracture strength and also drops sharply.

[0077] (V) Thermal Conductivity Test

[0078] Figure 5 and Figure 6 are the axial and planar thermal conductivity test results of different crosslinking systems respectively. Both tests show the same trend, that is, when the crosslinking degree of the crosslinking system decreases, there is a strong scattering effect on phonon transport, resulting in a decrease in the mean free path of phonon transport, which is not conducive to the formation of thermal conduction paths and the diffusion of heat. Compared with TMBP / EP11, the axial thermal conductivities of epoxy films with 1wt%, 3wt%, 6wt% and 10wt% TFAn introduced decrease by 4.1% (0.322 W / mK), 8.9% (0.306 W / mK), 19.3% (0.271 W / mK) and 28% (0.242 W / mK) respectively, and the axial thermal conductivity of TMBP / EP11 is 0.336 W / mK; the planar thermal conductivities decrease by 10% (0.99 W / mK), 20% (0.88 W / mK), 34% (0.725 W / mK) and 32% (0.753 W / mK) respectively, and the planar thermal conductivity of TMBP / EP11 is 1.1 W / mK. It can be found that similar to the trend of the tensile test results, when a small amount of TFAn is introduced, the decrease in the thermal conductivity of the epoxy film is relatively small. When the introduction amount is greater than 6wt%, due to the large decrease in the crosslinking degree, the thermal conductivity also decreases significantly.

[0079] (VI) Dielectric Property Characterization

[0080] 1) Research on the Influence Mechanism of the Introduction Amount of Carbon-Fluorine Bonds on the Dielectric Properties of Epoxy Films

[0081] Figure 7Dielectric properties of different epoxy films at room temperature (25 °C). Before introducing TFAn, the dielectric constant of TMBP / EP11 was relatively low, 4.36 at 10 Hz. After introducing TFAn, the dielectric constants at 10 Hz were 4.76 (1F@TMBP / EP11), 5.09 (3F@TMBP / EP11), 5.25 (6F@TMBP / EP11), and 5.69 (10F@TMBP / EP11) respectively. The strong polar carbon-fluorine bond shows the same trend as the change in the content of TFAn in the system for the improvement of the dielectric constant. There are mainly two reasons. First, after introducing the high-polar carbon-fluorine bond, the polarization performance of the molecular chain segments is greatly improved. Second, the introduction of the carbon-fluorine bond is realized by adding TFAn to the curing system. Different from the curing agent DDM that can link four epoxy molecular chains, there is only one secondary amino group in the TFAn molecule, which can only link two epoxy molecular chains. Therefore, the crosslinking density of the crosslinked system will decrease, and the restriction of the molecular chain segment movement is reduced, which is beneficial for the molecular chain segments to move directionally under the action of an external electric field. To verify this theory, molecular simulation and simulation calculations were carried out. The Dmol3 module in Material Studio was used to optimize the calculation of the smallest repeating unit of the crosslinked structure. The electric dipole moment of the molecule was obtained through quantum chemical calculations, as shown in Table 1.

[0082] Table 1 Dipole moment vector direction and magnitude

[0083] Curing system x y z Dipole magnitude / a.u. TMBP / EP11 0.360839 0.336043 1.839466 4.8406 3F@TMBP / EP11 2.044803 1.418162 1.351327 7.1975 10F@TMBP / EP11 -2.307237 1.445727 2.528565 9.4447

[0084] As Figure 8 It can be seen from Table 1 that compared with the TMBP / EP11 system, 3F@TMBP / EP11 and 10F@TMBP / EP11 show higher dipole moments and stronger molecular polarities. More precisely, the mean square dipole moment of the 3F@TMBP / EP11 system was calculated to be 7.1945 Debye, nearly 1.48 times that of the TMBP / EP11 system (4.8406 Debye), and the mean square dipole moment of the 10F@TMBP / EP11 system was 9.4447 Debye, nearly 1.95 times that of the TMBP / EP11 system (as shown in Table 1). The high dipole moments of the 3F@TMBP / EP11 and 10F@TMBP / EP11 systems may be contributed by two parts. First, due to the tight binding of chemical bonds, the decrease in the crosslinking degree of the crosslinked network contributes to the dipole moment. Second, the highly polar C-F bond plays an important role in enhancing the dipole moment.

[0085] 2) Research on the influence mechanism of temperature on the dielectric properties of epoxy films

[0086] As Figure 9As shown in the DSC test results, TMBP / EP11 has the best high-temperature stability among the five systems, and its dielectric loss remains stable even at 160 °C. The dielectric loss of the system of Example 5 with the worst high-temperature resistance performance can also remain relatively stable at 140 °C. The above results indicate that on the premise of having less influence on the high-temperature resistance performance, introducing high-polarity carbon-fluorine bonds can effectively improve the dielectric constant of the epoxy film without affecting the dielectric loss.

[0087] (VII) Dielectric Strength Characterization

[0088] 1) Research on the Influence Mechanism of the Introduction Amount of Carbon-Fluorine Bonds on the Dielectric Strength of Epoxy Films

[0089] Figure 10 The dielectric strength of epoxy films modified by liquid crystal molecules with different TFAn contents, and the film thickness is 10 (±1) μm. The Weibull distribution function was used to process the test results, and the dielectric strength of the epoxy films modified by carbon-fluorine bonds and liquid crystal molecules was obtained. The dielectric strength of the epoxy film before introducing TFAn was 569.8 kV / mm, and the dielectric strengths of the epoxy films after introducing TFAn were 500.3 kV / mm (1 wt%), 490 kV / mm (3 wt%), 451.9 kV / mm (6 wt%), and 442.9 kV / mm (10 wt%), respectively. It can be found that as the introduction amount of TFAn increases, the dielectric strength of the crosslinked system at room temperature gradually decreases. There are mainly two reasons. First, as the introduction amount of TFAn increases, the content of the highly rigid curing agent DDM in the system gradually decreases, the highly rigid phenyl structure relatively decreases, the restriction on the movement of free electrons decreases, and the ability of the crosslinked structure to withstand the impact of free electrons also decreases. Second, the crosslinking degree of the crosslinked system will decrease with the increase in the content of TFAn, that is, the rotational energy barrier of the molecular chain segments decreases, and it is easier to undergo movements such as turning and displacement. The mean free path of free electrons increases, and free electrons can obtain greater kinetic energy to impact the crosslinked structure. To verify this theory, the electrostatic potential distribution on the electron charge density isosurface was calculated based on density functional theory. As Figure 11 shown, red and blue represent positive and negative potentials respectively. It can be observed that the electrostatic potential of TMBP / EP11 is higher than that of 3F@TMBP / EP11 and 10F@TMBP / EP11. These results indicate that TMBP / EP11 has a stronger repulsion or attraction to free electrons, can effectively reduce the activity ability of free electrons, and reduce the kinetic energy and collision ionization of free electrons. Since there is relatively more DDM and relatively more phenyl structures in the TMBP / EP11 curing system, stronger electrostatic forces can be generated to repel or attract carriers. Stronger electrostatic forces and the restriction on the migration of current carriers will lead to a more obvious trapping effect, which can reduce the mean free path and energy of free electrons in the electric field. The calculation results show that due to stronger electrostatic forces and a more obvious trapping effect, TMBP / EP11 should have a higher Eb In addition to the electrostatic potential, the mobility of molecular chain segments is another important factor determining the dielectric breakdown strength of the crosslinked system.

[0090] The free volume fractions of three crosslinked systems were calculated based on the Forcite module. First, the crosslinked structures of the molecular chains were optimized and annealed to obtain more stable or lower-energy structures, as Figure 12 shown. Subsequently, molecular dynamics simulations were performed on the processed crosslinked structures to obtain their free volumes, as Figure 13 shown by the blue part in. Free volume refers to the defects and voids of atomic size generated by the random packing of atoms. According to the dielectric breakdown theory, free volume can provide space for the migration of free electrons. The calculation results show that the free volume of TMBP / EP11 is larger than that of 3F@TMBP / EP11 and 10F@TMBP / EP11. The calculation results of the free volume ratio are shown in Table 2.

[0091] Table 2 Free volume ratios of different crosslinked systems

[0092]

[0093] Combined with the electrostatic potential distribution in Table 2, it can be seen that with the introduction of carbon-fluorine bonds, the dielectric strength of the epoxy film decreases, which is consistent with the test results.

[0094] 2) Research on the influence mechanism of temperature on the dielectric strength of epoxy films

[0095] DC breakdown tests were carried out on three different crosslinked structures (TMBP / EP11, 3F@TMBP / EP11, 10F@TMBP / EP11) at different temperatures, and the test results are as Figure 14 shown. When the temperature gradually increases, the mobility of molecular chain segments is further enhanced. At this time, the mean free path of free electrons further increases, and the kinetic energy obtained by free electrons increases. Therefore, the dielectric strength of each crosslinked system decreases with the increase of temperature. When the temperature rises to the glass transition temperature, the molecular chain segments begin to transform from the glassy state to the high elastic state. At this time, the mobility of molecular chain segments reaches the peak. When the temperature continues to rise, the glassy state-high elastic state transition is completely completed. At this time, the dielectric strength of the crosslinked system will drop sharply.

[0096] To verify the repulsive and attractive effects of specific structures on free electrons, partial discharge tests were carried out, as Figure 15 shown. It was found that when TFAn was introduced, the partial discharge amount increased significantly, which was caused by the lack of specific structural restrictions on the movement of free electrons in some molecular chain segments, further verifying that the high-rigidity curing agent can effectively inhibit the movement of free electrons and play a positive role in improving the dielectric strength of the system.

[0097] The trap distribution of the epoxy film was obtained by thermally stimulated current analysis, as Figure 16 shown in (a). The trap energy levels and trap charge amounts of the two crosslinked systems were calculated by the full width at half maximum method, as shown in Table 3.

[0098] Table 3 Trap energy levels and trap charge amounts of different epoxy films

[0099]

[0100] After introducing the carbon-fluorine bond, the trap energy levels and trap charge amounts of the crosslinked system decreased significantly. This is because the decrease in the crosslinking density of the crosslinked structure results in fewer deep traps in the polymer. At this time, the restriction of the crosslinked structure on free electrons decreases, and free electrons can obtain greater kinetic energy to impact the crosslinked structure. Therefore, the dielectric strength of the epoxy film decreased.

[0101] To further verify the influence of the introduction of the carbon-fluorine bond and temperature on the voltage withstand performance of the material, the conductivities of the epoxy films modified by the carbon-fluorine bond and liquid crystal molecules at different temperatures were tested. The test results are as Figure 17 shown. The conductivity test results of TMBP / EP11 and 3F@TMBP / EP11 at different temperatures show the same results as the breakdown performance and thermally stimulated current tests. That is, with the introduction of the carbon-fluorine bond, the rigid structure of the molecular chain segments relatively decreases, and the crosslinking density of the crosslinked structure decreases, resulting in fewer deep traps in the polymer. At this time, the restriction of the crosslinked structure on free electrons decreases, so the conductivity increases. Comparing the conductivity test results of the same system at different temperatures, since the carrier density increases after the temperature rises, the conductivity also tends to increase.

[0102] (VIII) Research on the energy storage characteristics of epoxy films modified by highly polar carbon-fluorine bonds and liquid crystal molecules

[0103] 1) Research on the polarization performance of epoxy films modified by carbon-fluorine bonds and liquid crystal molecules

[0104] Figure 18 are the polarization hysteresis loops of the epoxy films at different electric field strengths and different test temperatures. The polarization intensity of the film increases with the increase of the electric field strength. Combining with the dielectric spectroscopy test results, due to the extremely low dielectric loss of the epoxy film, all films show very small magnetic hysteresis losses and very narrow polarization hysteresis loops at room temperature, which provides an important guarantee for improving the charge-discharge efficiency.

[0105] Generally speaking, under the same electric field conditions, the electric displacement of the TMBP / EP11 system is the lowest. After introducing the carbon-fluorine bond, the electric displacement begins to gradually increase, which is due to the increase in the dielectric constant of the epoxy film after the introduction of the carbon-fluorine bond. The highly polar carbon-fluorine bond can effectively promote the polarization enhancement of the crosslinked system. To study the influence of temperature change on the polarization performance of the crosslinked system, the electric field intensity of 200 kV / mm was selected, and the polarization hysteresis loop test was carried out under different temperature conditions. When the ambient temperature is less than 120 °C, the three kinds of films tested can maintain their performance at room temperature. When the temperature rises to 140 °C, the polarization hysteresis loops of the TMBP / EP11 system and 3F@TMBP / EP11 can still maintain a narrow spacing between the charge and discharge curves, which mainly benefits from their high glass transition temperature. When the ambient temperature is within the glass transition temperature, their dielectric loss can remain stable. The glass transition temperature of the epoxy film of the 10F@TMBP / EP11 system is only 135 °C. At this time, the ambient temperature is higher than its glass transition temperature, so its dielectric loss increases, resulting in an increase in the spacing between the charge and discharge curves of the polarization hysteresis loop. After the ambient temperature further rises to 160 °C, the spacing between the charge and discharge curves of the 10F@TMBP / EP11 system polarization hysteresis loop further increases. Different from the 10F@TMBP / EP11 system, under the influence of the high glass transition temperature, TMBP / EP11 can still maintain low dielectric loss and a narrow polarization hysteresis loop at 160 °C.

[0106] 2) Based on the test results of the polarization hysteresis loop, the energy storage density and charge-discharge efficiency of each crosslinked system at different electric field intensities and different temperatures were obtained by calculating the area integral. As Figure 19 (a) shows, it is the comparison of the energy storage performance of the epoxy film modified by highly polar carbon-fluorine bonds and liquid crystal molecules at room temperature. As the amount of introduced carbon-fluorine bonds increases, the energy storage density of the epoxy film under the same electric field shows an upward trend. For example, at room temperature and 400 kV / mm, the energy storage densities of the five kinds of epoxy films are 3.28 J / cm 3 (TMBP / EP11), 3.49 J / cm 3 (1F@TMBP / EP11), 4.49 J / cm 3 (3F@TMBP / EP11), 4.75 J / cm 3 (6F@TMBP / EP11), 5.07 J / cm 3(10F@TMBP / EP11). Due to having the highest dielectric constant, under the condition of the same electric field strength, 10F@TMBP / EP11 has the highest energy storage density. And for the five systems at room temperature, they can still maintain a high charge-discharge efficiency of over 90% until electrical breakdown occurs. The lowest is the 1F@TMBP / EP11 system, whose charge-discharge efficiency is 90.9% at room temperature and 540 kV / mm. The low energy loss is beneficial for this research to be applied to high-frequency charge-discharge equipment.

[0107] As Figure 19 (b) shows the comparison of the energy storage performance of the highly polarized carbon-fluorine bond and liquid crystal molecule modified epoxy film at different temperatures. Consistent with the results of the high-temperature dielectric spectroscopy test, due to the sharp rise in dielectric loss, the charge-discharge efficiency of the 10F@TMBP / EP11 system decreased sharply after the test temperature exceeded 140 °C. At 140 °C and 200 kV / mm, it could still maintain an energy storage performance of 0.95 J / cm 3 and 88.3%. When the temperature increased to 160 °C, its energy storage density decreased to 0.62 J / cm 3 , and the charge-discharge efficiency decreased to 47.2%. The 3F@TMBP / EP11 system showed stable and excellent energy storage performance under both room temperature and high-temperature conditions. At room temperature and 500 kV / mm, the energy storage density and charge-discharge efficiency could reach 7.1 J / cm 3 and 91.5% respectively. At 140 °C and 200 kV / mm, the energy storage density and charge-discharge efficiency could reach 1.01 J / cm 3 and 94.3% respectively. At 160 °C and 200 kV / mm, the energy storage density and charge-discharge efficiency could reach 0.83 J / cm°C and 81.5% respectively.

[0108] As Figure 19(c) shows the comparison of the energy storage density of the 3F@TMBP / EP11 film with other research or commercial films at a charge-discharge efficiency greater than 90% at room temperature. Under the conditions of room temperature and 500 kV / mm, the energy storage density and charge-discharge efficiency of the 3F@TMBP / EP11 film are 7.1 J / cm3 and 91.5% respectively. Although linear dielectric materials such as polypropylene, polyimide, and polyetherimide have extremely high charge-discharge efficiencies, their low dielectric constants (<3.5) make it difficult to improve their energy storage densities. Epoxy resin is a typical thermosetting polymer with linear polarization characteristics, and its dense cross-linked network gives it extremely high charge-discharge efficiency. The polar C-N bonds in the cured epoxy resin result in a relatively high dielectric constant (>4), and the further introduction of highly polar carbon-fluorine bonds further increases the dielectric constant, reaching 5.1 at 10 Hz. These factors ensure that the epoxy film has a relatively high energy storage density on the premise that the charge-discharge efficiency is greater than 90%. As Figure 19 (d) shows the comparison of the charge-discharge efficiency of the 3F@TMBP / EP11 film in this study with other research or commercial films under the conditions of 140 °C and 200 kV / mm. Under these conditions, the energy storage density and charge-discharge efficiency of the 3F@TMBP / EP11 film are 1.02 J / cm3 and 94.3% respectively. For example, materials such as polycarbonate and polyetherimide are typical high-temperature-resistant dielectric materials, and the high-rigidity groups in the molecular structure of the materials ensure their high charge-discharge efficiency at high temperatures. Compared with common high-temperature-resistant dielectric materials, the heat resistance of ordinary epoxy is far from sufficient. In this invention, a liquid crystal molecule structure is introduced through the curing reaction of epoxy groups and amine groups to construct a highly rigid cross-linked structure, achieving the purpose of improving its heat resistance.

[0109] Based on the above results, the cyclic performance of the 3F@TMBP / EP11 film in a high-temperature environment was tested to evaluate the stability of the film during long-term use at high temperatures. As Figure 20 shown, the high-temperature energy storage cyclic performance of the 3F@TMBP / EP11 film was tested at 200 kV / mm and different temperatures. After 10,000 cycles at 80 °C and 140 °C, the energy storage density and charge-discharge efficiency hardly changed, indicating that the epoxy film has excellent reliability when used under the conditions of 140 °C and 200 kV / mm. The commercial BOPP film breaks down under the conditions of 120 °C, 200 kV / mm, and 10,000 cycles, and the energy storage density decreases by 16%. Compared with BOPP, the 3F@TMBP / EP11 film has much better stability during long-term use at high temperatures.

[0110] 2) When considering the engineering applications of thin-film capacitors, the long-term operation reliability and stability should be fully taken into account. In the actual application of thin-film capacitors, a large-area dielectric polymer film is metallized, and metals are sprayed on both sides of the film as electrodes. In this structure, when a local breakdown occurs during the operation of the film, the metallization layer can act as a fuse. As Figure 21 shown, the self-healing process of the metallized film. Due to the defects in the polymer, the local electric field may increase sharply, triggering breakdown at the weak points. During the breakdown process, the ultra-high temperature (>8000K) breakdown arc rapidly destroys the electrode material, and at the same time causes the polymer to decompose, releasing various chemical residues such as CO, H2, CH4, C2H2 and graphite solids. It should be noted that the process of electrical breakdown of the material may also cause the vaporization of the metal electrode on the film surface. In particular, when the newly exposed surface area under the metal electrode is large enough to isolate the carbonized perforation and the arc is extinguished in time, the film will achieve "self-healing" in terms of insulation function, and the subsequent film can continue to work normally in capacitor applications. Otherwise, the film will completely fail after one breakdown. During the self-healing process, dielectric defects can be eliminated within <10 μs without any external operation, which helps to improve the reliability of the capacitor.

[0111] Currently, the theoretical relationship between the chemical composition of polymer dielectrics and their self-healing ability has not been clearly verified. However, some research experiences show that there is a certain relationship between the chemical composition of polymer dielectrics and their self-healing ability. For polymer dielectrics with the general formula, the larger the ratio of and, the weaker its self-healing ability. When the above ratio is small, less graphite is deposited during its self-healing process, preventing the formation of conductive graphite bridges, and finally ensuring its good self-healing performance. The ratios of PP and PET are 0.5 and 0.75 respectively, both having good self-healing behaviors. The ratio of 3F@TMBP / EP11 film in this invention is about 0.68, and its self-healing ability is between PP and PET, much lower than that of PEI (1.3), PI (1.6) and PEEK (1.33). As Figure 22 shown, the comparison of the morphology and energy storage performance of the film before and after the first breakdown.

[0112] As Figure 22As shown in (a)-(e) therein, the morphology and elemental distribution of the film before breakdown were first observed by scanning electron microscopy and energy dispersive spectroscopy. After the specimen was broken down, a hole with a diameter of 220 μm was observed by polarized light microscopy and scanning electron microscopy. This is because there may be defects at the hole position. When an external electric field is applied to both sides of the electrode, local electric field distortion occurs at the defect, eventually leading to breakdown. It can be clearly observed in the polarized light microscopy image that the silver electrode around the breakdown hole disappears. The arc generated during breakdown usually causes damage to the material and the evaporation of the surrounding silver electrode by generating intense Joule heat. The above view can also be further confirmed by the analysis results of energy dispersive spectroscopy after breakdown. As Figure 22 As shown in (f) therein, during the first charge-discharge process, after 3F@TMBP / EP11 broke down at 500 kV / mm, the 3F@TMBP / EP11 film could still complete the charge-discharge process normally under an electric field of 450 kV / mm when tested again. Before breakdown, the energy storage density and charge-discharge efficiency of 3F@TMBP / EP11 at room temperature and an electric field of 450 kV / mm were 5.583 J / cm3 and 93.5% respectively. After breakdown and measurement again, the energy storage density and charge-discharge efficiency of 3F@TMBP / EP11 under the same conditions were 5.359 J / cm3 and 89.5% respectively. Although both the energy storage density and the charge-discharge efficiency decreased slightly, it still shows that the self-repair of the 3F@TMBP / EP11 film was successful.

[0113] In summary, introducing highly polar carbon-fluorine bonds into the liquid crystal molecule-modified epoxy film can effectively improve the polarization performance of the film, thereby improving the energy storage density of the epoxy film, and still maintaining a relatively high glass transition temperature, improving the high-temperature energy storage characteristics of the epoxy film.

[0114] Therefore, the present invention adopts the above-mentioned preparation technology of a high-temperature resistant epoxy energy storage film based on liquid crystal ordered structure. By introducing highly polar carbon-fluorine bonds into the liquid crystal molecule-modified epoxy film, the polarization performance of the film is effectively improved, thereby improving the energy storage density of the epoxy film, and still maintaining a relatively high glass transition temperature, improving the high-temperature energy storage characteristics of the epoxy film, solving the problem of the sharp decline in the energy storage performance of commercial dielectric films, and providing a new idea for developing high-performance epoxy materials for the field of dielectric energy storage.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure, characterized in that, It includes the following steps: S1. Mix a liquid crystal biphenyl type epoxy monomer, a bisphenol A type epoxy monomer and a curing agent in proportion, and simultaneously carry out magnetic stirring and oil bath heating and melting treatment to obtain a mixed molten liquid; S2. Carry out degassing treatment on the mixed molten liquid obtained in S1, and then pour it into a mold; adopt a hot pressing method for heating and curing treatment to obtain an epoxy film; In S1, the curing agent includes 2,3,4-trifluoroaniline and 4,4-diaminodiphenylmethane; In S2, the specific heating and curing treatment by the hot pressing method is as follows: First, preheat the mold, then place a PET release film under the mold, pour the degassed mixed molten liquid into a copper foil mold with a thickness of 10 μm, then cover another PET release film on the top of the mold, place it in the middle of a mirror-level smooth stainless steel plate, and put it into a hot press for step-by-step temperature-rising heating and curing treatment; The temperature of the preheating treatment is 100-110°C, the temperature of the heating and curing treatment is 105-200°C, and the curing time is 10 h.

2. The preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure according to claim 1, wherein, In S1, the liquid crystal biphenyl type epoxy monomer is a tetramethyl biphenyl type epoxy monomer.

3. The preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure according to claim 1, characterized in that, In S1, the sum of the molar numbers of the bisphenol A type epoxy monomer and the liquid crystal biphenyl type epoxy monomer: the curing agent = 3:

2.

4. The preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure according to claim 1, characterized in that In S1, the specific magnetic stirring and oil bath heating and melting treatment is as follows: Add a magnetic stirrer, and use a magnetic stirrer to place the mixture in an oil bath for heating and melting while carrying out magnetic stirring.

5. The preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure according to claim 4, characterized in that The temperature of the oil bath heating is 105°C, the stirring rate is 150-250 r / min, and the stirring time is 10 min.

6. The preparation method of a high-temperature resistant epoxy energy storage film based on a liquid crystal ordered structure according to claim 1, characterized in that, In S2, the specific degassing treatment is as follows: Place the mixed molten liquid in a vacuum drying oven and carry out heating reflux until no bubbles are generated.

7. The preparation method of a high-temperature resistant epoxy energy storage thin film based on a liquid crystal ordered structure according to claim 6, characterized in that, The temperature of the degassing treatment is 105-110°C, and the degassing time is 3-5 min.

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