A high temperature and high breakdown resistant polycarbonate and fluorene polyester based multilayer structure composite film and its preparation method and application

Abstract

A high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film and its preparation method and application, which relate to the composite film preparation technology field. The purpose of the present invention is to solve the problem that the traditional composite film cannot operate stably in a high temperature environment due to the difference in surface energy between the filler and the matrix, resulting in filler agglomeration, and the spatial discontinuity of the dielectric constant causing local electric field distortion. In the present invention, PC as the outer layer will make it difficult for carriers to be injected into the electrode due to its excellent insulation performance, and FPE with a high glass transition temperature as the inner layer improves the high temperature resistance of the composite medium, effectively reduces the internal current density of the composite film, ensures the insulation and temperature stability of the composite film, and thus improves the breakdown strength and energy storage characteristics of the composite film. The present invention can obtain a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film and its preparation method and application.

Description

Technical Field

[0001] The invention relates to the technical field of composite film preparation, and in particular to a high-temperature-resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film, and a preparation method and application thereof. Background Art

[0002] Polymer dielectrics are key components of electrostatic capacitors in the fields of energy, transportation, military, and aerospace, with operating temperatures reaching over 120°C. However, the sharp drop in energy storage capacity caused by high temperatures severely limits the practicality of polymer dielectrics at high temperatures. Polymer dielectrics have become the material of choice for high energy density capacitors due to their high breakdown strength and excellent mechanical properties. Researchers prepare polymer nanocomposites by introducing inorganic nanofillers into polymer matrices as a common strategy to improve the high-temperature energy storage properties of dielectric polymers. However, the difference in surface energy between the filler and the matrix may cause filler agglomeration, and the spatial discontinuity of the dielectric constant may cause local electric field distortion, which will increase the probability of failure. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that the traditional composite film cannot operate stably in a high temperature environment due to the difference in surface energy between the filler and the matrix, which leads to filler agglomeration and the spatial discontinuity of the dielectric constant leads to local electric field distortion. The present invention provides a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film and its preparation method and application.

[0004] A high temperature and high breakdown resistant polycarbonate and fluorene polyester based multilayer structure composite film, comprising a fluorene polyester film and two polycarbonate films of the same thickness, wherein the fluorene polyester film is arranged between the two polycarbonate films, and the thickness ratio of each polycarbonate film layer to the fluorene polyester film is (6:3), (5:5), (4:7) or (3:9).

[0005] A method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film is carried out according to the following steps:

[0006] Step S1: preparing a polycarbonate film;

[0007] The polycarbonate particles are added to a tetrahydrofuran solution, mechanically stirred at a temperature of 15 to 25° C. until completely dissolved, and after standing, the mixed solution is evenly coated on one surface of a pretreated substrate, and then the substrate is subjected to gradient heating and heat preservation, and then cooled to room temperature, and finally the film on the substrate is peeled off to obtain a polycarbonate film;

[0008] Step S2: preparing a fluorene polyester film;

[0009] Adding fluorene polyester to methyl pyrrolidone solution, mechanically stirring for 4 to 6 hours at a temperature of 15 to 25° C., to obtain a fluorene polyester solution; uniformly coating the fluorene polyester solution on one surface of a pretreated substrate, then subjecting the substrate to gradient heating and heat preservation, cooling the substrate to room temperature, and finally peeling off the film on the substrate to obtain a fluorene polyester film;

[0010] Step S3: preparing a polycarbonate and fluorene polyester-based multilayer composite film;

[0011] The fluorene polyester film is placed between two layers of polycarbonate films, subjected to a heat pressing process, and finally cooled to obtain a high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film; the mass ratio of the polycarbonate to the fluorene polyester is (1.6-1.7): (0.4-0.5).

[0012] The invention discloses an application of a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film, and an application of the high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film in a high temperature energy storage capacitor.

[0013] Principle of the present invention:

[0014] The present invention constructs a PC-FPE-based multilayer structure composite film with two layers of polycarbonate and one layer of fluorene polyester. PC as an outer layer makes it difficult for carriers to be injected into the electrode due to its excellent insulation performance. FPE has a high glass transition temperature and is used as an inner layer to improve the high temperature resistance of the composite medium. Under the synergistic effect of the two mechanisms, the internal current density of the composite film can be effectively reduced, and the insulation and temperature stability of the composite film can be further guaranteed, thereby improving the breakdown strength and energy storage characteristics of the composite film.

[0015] Beneficial effects of the present invention:

[0016] (1) The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester-based multilayer composite film of the present invention uses PC as an insulating layer and FPE as a heat-resistant layer, and is prepared by a hot pressing method, wherein PC with a low dielectric constant and a high breakdown field strength withstands a higher applied voltage. In addition, in the multilayer composite film, the macroscopic interface between the layers hinders the growth of the breakdown path. The redistribution of the electric field in the composite material and the obstruction of the macroscopic interface to the breakdown path make the multilayer composite film have a higher breakdown field strength than pure PC and FPE. Ultimately, the multilayer composite film greatly improves the breakdown performance, and the excellent breakdown strength enables it to have an ultra-high energy density. In addition, PC has an extremely high charge and discharge efficiency due to its own low leakage current.

[0017] (2) The high temperature resistant and high breakdown polycarbonate and fluorene polyester-based multilayer structure composite film prepared by the process of the present invention has excellent dielectric properties, breakdown properties, energy storage properties and heat resistance, providing new materials for high-performance supercapacitors, and can be widely used in key components of electrostatic capacitors in the fields of energy, transportation, military and aerospace. The preparation equipment of the present invention has a simple process, is easy to implement, is low in cost and is environmentally friendly and pollution-free, providing a good strategy for the development of advanced polymer capacitors.

[0018] The invention can obtain a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film and a preparation method and application thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The cross-sectional scanning electron microscope image of the polycarbonate and fluorene polyester-based multilayer structure composite film with a FPE film thickness of 5 μm in Example 2 is shown, A represents the PC film, and B represents the FPE film;

[0020] Figure 2 The Fourier transform infrared spectra of the polycarbonate and fluorene polyester-based multilayer structure composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, a represents the PC film in Comparative Example 1, b represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 1, c represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, d represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, e represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4, and f represents the FPE film in Comparative Example 1;

[0021] Figure 3 The Fourier transform infrared spectra of the polycarbonate and fluorene polyester-based multilayer structure composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, a represents the PC film in Comparative Example 1, b represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 1, c represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, d represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, e represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4, and f represents the FPE film in Comparative Example 1;

[0022] Figure 4 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and △ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4;

[0023] Figure 5 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and ▲ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4;

[0024] Figure 6 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and ▲ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4. DETAILED DESCRIPTION

[0025] Specific implementation method 1: This implementation method is a high temperature and high breakdown resistant polycarbonate and fluorene polyester based multilayer structure composite film, which is composed of a layer of fluorene polyester film and two layers of polycarbonate film with the same thickness. The fluorene polyester film is arranged between the two layers of polycarbonate film, and the thickness ratio of each layer of polycarbonate film to the fluorene polyester film is (6:3), (5:5), (4:7) or (3:9).

[0026] Specific implementation method 2: This implementation method is a method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film, which is carried out according to the following steps:

[0027] Step S1: preparing a polycarbonate film;

[0028] The polycarbonate particles are added to a tetrahydrofuran solution, mechanically stirred at a temperature of 15 to 25° C. until completely dissolved, and after standing, the mixed solution is evenly coated on one surface of a pretreated substrate, and then the substrate is subjected to gradient heating and heat preservation, and then cooled to room temperature, and finally the film on the substrate is peeled off to obtain a polycarbonate film;

[0029] Step S2: preparing a fluorene polyester film;

[0030] Adding fluorene polyester to methyl pyrrolidone solution, mechanically stirring for 4 to 6 hours at a temperature of 15 to 25° C., to obtain a fluorene polyester solution; uniformly coating the fluorene polyester solution on one surface of a pretreated substrate, then subjecting the substrate to gradient heating and heat preservation, cooling the substrate to room temperature, and finally peeling off the film on the substrate to obtain a fluorene polyester film;

[0031] Step S3: preparing a polycarbonate and fluorene polyester-based multilayer composite film;

[0032] The fluorene polyester film is placed between two layers of polycarbonate films, subjected to a heat pressing process, and finally cooled to obtain a high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film; the mass ratio of the polycarbonate to the fluorene polyester is (1.6-1.7): (0.4-0.5).

[0033] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that: the ratio of the mass of the polycarbonate particles described in step S1 to the volume of the tetrahydrofuran solution is (1.6-1.7) g: (1-1.1) mL.

[0034] The other steps are the same as those in the second specific implementation method.

[0035] Specific implementation method four: The difference between this implementation method and specific implementation method two or three is that the pretreated substrates in step S1 and step S2 are processed according to the following steps: first, the substrate is cleaned with clean water for 3 to 5 times, then rinsed with deionized water for 3 to 5 times, and then cleaned with anhydrous ethanol for 3 to 5 times, and finally dried at a temperature of 75 to 80°C for 12 to 15 hours to obtain a pretreated substrate, which is a glass plate.

[0036] The other steps are the same as those in the second or third embodiment.

[0037] Specific implementation mode 5: The difference between this implementation mode and specific implementation modes 2 to 4 is that the mechanical stirring in step S1 and step S2 adopts a magnetic stirrer, and the stirring speed is 150-300 r / min.

[0038] The other steps are the same as those in Specific Embodiments 2 to 4.

[0039] Specific embodiment six: The difference between this embodiment and specific embodiments two to five is: the gradient heating and heat preservation steps in step S1 and step S2: first heat the substrate to 60-80°C, and keep it at 60-80°C for 6-12h; after the heat preservation is completed, heat it to 80-120°C, and continue to keep it at 80-120°C for 8-12h.

[0040] The other steps are the same as those in Specific Embodiments 2 to 5.

[0041] Specific embodiment 7: The difference between this embodiment and any one of specific embodiments 2 to 6 is that the ratio of the mass of the fluorene polyester described in step S2 to the volume of the methyl pyrrolidone solution is (0.4-0.5) g: (3.5-4) mL.

[0042] The other steps are the same as those in Specific Embodiments 2 to 6.

[0043] Specific embodiment eight: The difference between this embodiment and specific embodiments two to seven is: the step of hot pressing process in step S3: after placing the fluorene polyester film between two layers of polycarbonate film, and then placing it between two layers of iron plates, and then placing the iron plate in a flat vulcanizer, and keeping it warm at a temperature of 160-170°C for 0.5-1h; after the insulation is completed, hot pressing is performed at a pressure of 10-15MPa for 1-2h, and cooling is performed after the hot pressing is completed to obtain a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film.

[0044] The other steps are the same as those in Specific Embodiments 2 to 7.

[0045] Specific embodiment nine: The difference between this embodiment and any one of specific embodiments two to eight is that the thickness ratio of each layer of polycarbonate film to fluorene polyester film in the high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film described in step S3 is (6:3), (5:5), (4:7) or (3:9).

[0046] The other steps are the same as those in Specific Embodiments 2 to 8.

[0047] Specific implementation method ten: This implementation method is an application of a high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film, and the application of the high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film in high-temperature energy storage capacitors.

[0048] The following examples are used to verify the beneficial effects of the present invention:

[0049] Example 1: A method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film, which is carried out according to the following steps:

[0050] Step S1: preparing a polycarbonate film;

[0051] 1.7 g of polycarbonate (PC) particles were added to 10 mL of tetrahydrofuran solution, mechanically stirred at 25° C. for 6 h (until completely dissolved), and the mixed solution was evenly coated on one surface of the pretreated substrate after standing, and then the substrate was first heated to 60° C. and kept at 60° C. for 6 h; after the insulation was completed, it was heated to 80° C. and then kept at 80° C. for 8 h, and after the insulation was completed, it was cooled to room temperature, and finally the film on the substrate was peeled off to obtain a polycarbonate film with a thickness of 6 μm;

[0052] Step S2: preparing a fluorene polyester film;

[0053] 0.4 g of fluorene polyester (FPE) was added to 3.5 mL of methyl pyrrolidone solution, and mechanically stirred for 6 hours at a temperature of 25° C. to obtain a fluorene polyester solution; the fluorene polyester solution was uniformly coated on one surface of the pretreated substrate, and then the substrate was heated to 80° C. and kept at 80° C. for 12 hours; after the insulation, it was heated to 120° C., and then kept at 120° C. for 12 hours, and after the insulation, it was cooled to room temperature, and finally the film on the substrate was peeled off to obtain a fluorene polyester film with a thickness of 3 μm;

[0054] The substrates pretreated in step S1 and step S2 are treated according to the following steps: first, the substrate is washed with clean water for 5 times, then rinsed with deionized water for 5 times, then washed with anhydrous ethanol for 5 times, and finally dried at 80° C. for 12 hours to obtain a pretreated substrate, wherein the substrate is a glass plate;

[0055] In step S1 and step S2, the mechanical stirring is performed using a magnetic stirrer, and the stirring speed is 210 r / min;

[0056] Step S3: preparing a polycarbonate and fluorene polyester-based multilayer composite film;

[0057] The fluorene polyester film is placed between two layers of polycarbonate film, and then between two layers of iron plates, and then the iron plates are placed in a flat vulcanizer and kept warm at 170°C for 0.5 hours; after the heat preservation, it is hot-pressed at a pressure of 15MPa for 1 hour, and then cooled after the hot pressing to obtain a high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film;

[0058] Example 2: In this example, the thickness of each PC film layer is 5 μm, and the thickness of the FPE film is 5 μm; other experimental conditions are the same as those in Example 1.

[0059] Example 3: In this example, the thickness of each PC film layer is 4 μm, and the thickness of the FPE film is 7 μm; other experimental conditions are the same as those in Example 1.

[0060] Example 4: In this example, the thickness of each PC film layer is 3 μm, and the thickness of the FPE film is 9 μm; other experimental conditions are the same as those in Example 1.

[0061] Comparative Example 1: Preparation of PC and FPE films;

[0062] Step 1: taking PC and tetrahydrofuran solution respectively according to the ratio of the mass of polycarbonate to the volume of tetrahydrofuran solution of 1.7 g:10 mL; adding PC to the tetrahydrofuran solution, mechanically stirring for 6 hours at a temperature of 25° C. to obtain a PC solution, then standing the solution, uniformly coating the PC solution on one surface of the pretreated substrate, then heating the substrate to 60° C. and keeping it at 60° C. for 6 hours, then heating the substrate to 80° C. and keeping it at 60° C. for 8 hours, finally cooling to room temperature, peeling off the film on the substrate to obtain a PC film;

[0063] Step 2: FPE and methyl pyrrolidone solution are taken respectively according to the ratio of the mass of FPE to the volume of the methyl pyrrolidone solution of 0.4 g:3.5 mL; FPE is added to the methyl pyrrolidone solution, and mechanically stirred at a temperature of 25° C. for 6 hours to obtain an FPE solution, and the FPE solution is evenly coated on one surface of the pretreated substrate, and then the substrate is heated to 80° C. and kept at 80° C. for 12 hours, and then the substrate is heated to 120° C. and kept at 12 hours, and finally cooled to room temperature, and the film on the substrate is peeled off to obtain an FPE film;

[0064] Step 3: The PC film and the FPE film are respectively subjected to a hot pressing process to obtain a hot pressed PC film and a FPE film.

[0065] Figure 1 The cross-sectional scanning electron micrograph of the polycarbonate and fluorene polyester-based multilayer structure composite film having a FPE film thickness of 5 μm in Example 2 is shown, where A represents the PC film and B represents the FPE film; Figure 1 As shown, the film structures of PC and FPE are complete and the layered structures are obvious.

[0066] Figure 2 The Fourier transform infrared spectra of the polycarbonate and fluorene polyester-based multilayer structure composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, a represents the PC film in Comparative Example 1, b represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 1, c represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, d represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, e represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4, and f represents the FPE film in Comparative Example 1;

[0067] like Figure 2As shown, from the FTIR spectrum, at 1504 cm -1 and 1776cm -1 There are two strong transmission peaks at 1742 cm-1, which are derived from the stretching vibration of the aromatic ring of PC and C=O. -1 In addition, no new absorption peaks appeared in the FTIR spectrum of the composite film, proving that the composite film only underwent simple physical recombination and no new substances were produced.

[0068] Figure 3 The Fourier transform infrared spectra of the polycarbonate and fluorene polyester-based multilayer structure composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, a represents the PC film in Comparative Example 1, b represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 1, c represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, d represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, e represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4, and f represents the FPE film in Comparative Example 1;

[0069] like Figure 3 As shown in the figure, since FPE has a glass transition temperature of up to 330°C, FPE shows a smooth curve within the temperature range of this DSC test. The glass transition temperature of PC is 150°C. As the thickness of the FPE layer increases, the glass transition temperature of the composite film gradually increases, which proves that the presence of the FPE layer increases the glass transition temperature of the composite film, making the composite film have excellent heat resistance, providing conditions for subsequent high-temperature energy storage tests.

[0070] Figure 4 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and ▲ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4;

[0071] like Figure 4As shown in the figure, at 150°C, the breakdown results of the multilayer composite film are better than those of the single-layer FPE film and PC film. Since PC has excellent insulation properties, the composite medium in the area near the upper electrode can effectively suppress carrier injection, and FPE has excellent heat resistance, so that the multilayer structure can perform excellent performance at high temperatures. In addition, the interlayer interface effectively prevents the growth of electrical dendrites and improves the breakdown strength of the composite medium. Among them, when the FPE layer thickness is 5μm, the breakdown field strength of the PC and FPE-based multilayer composite film can reach 535.0kV / mm, which is 30% higher than that of the pure FPE film.

[0072] Figure 5 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and ▲ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4;

[0073] like Figure 5 As shown in the figure, the dielectric constant of the composite dielectric increases with the increase of FPE content, which can be attributed to the fact that the dielectric constant of FPE is higher than that of PC. The interface polarization between PC and FPE in the multilayer structure is also one of the reasons why the dielectric constant of the composite material is better than that of pure PC. 0 -10 6 The dielectric loss in the Hz range is very low, less than 0.01, which is conducive to improving the energy storage efficiency under high temperature and high field in the future.

[0074] Figure 6 The DC breakdown Weibull distribution diagrams of the polycarbonate and fluorene polyester-based multilayer composite films prepared in Examples 1-4 and the PC film and FPE film prepared in Comparative Example 1 are shown, where ● represents the FPE film in Comparative Example 1, and ■ represents the PC film in Comparative Example 1. It represents the polycarbonate and fluorene polyester based multilayer structure composite film in Example 1, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 2, ▼ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 3, and ▲ represents the polycarbonate and fluorene polyester-based multilayer structure composite film in Example 4.

[0075] like Figure 6As shown in Figure 2, at 150 °C, the energy storage density and energy storage efficiency also increase with the increase of PC layer thickness. When the PC layer thickness is 5 μm, the energy storage density and energy storage efficiency of the composite film reach 1.31 J / cm 3 and 89.7% higher performance, which is 2.42 times the energy storage density of pure PC (0.54J / cm 3 ), the energy storage density is greatly improved, which is mainly due to the excellent insulation properties of PC, which greatly reduces the injection of charges at the electrode.

Claims

1. A high temperature and high breakdown resistant polycarbonate and fluorene polyester based multilayer structure composite film, characterized in that The polycarbonate and fluorene polyester-based multilayer structure composite film consists of a layer of fluorene polyester film and two layers of polycarbonate films of the same thickness. The fluorene polyester film is arranged between the two layers of polycarbonate films. The thickness ratio of each layer of polycarbonate film to the fluorene polyester film is (6:3), (5:5), (4:7) or (3:9).

2. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film as claimed in claim 1, characterized in that The preparation method is carried out according to the following steps: Step S1: preparing a polycarbonate film; The polycarbonate particles are added to a tetrahydrofuran solution, mechanically stirred at a temperature of 15 to 25° C. until completely dissolved, and after standing, the mixed solution is evenly coated on one surface of a pretreated substrate, and then the substrate is subjected to gradient heating and heat preservation, and then cooled to room temperature, and finally the film on the substrate is peeled off to obtain a polycarbonate film; Step S2: preparing a fluorene polyester film; Adding fluorene polyester to methyl pyrrolidone solution, mechanically stirring for 4 to 6 hours at a temperature of 15 to 25° C., to obtain a fluorene polyester solution; uniformly coating the fluorene polyester solution on one surface of a pretreated substrate, then subjecting the substrate to gradient heating and heat preservation, cooling the substrate to room temperature, and finally peeling off the film on the substrate to obtain a fluorene polyester film; Step S3: preparing a polycarbonate and fluorene polyester-based multilayer composite film; The fluorene polyester film is placed between two layers of polycarbonate films, subjected to a heat pressing process, and finally cooled to obtain a high-temperature resistant and high-breakdown polycarbonate and fluorene polyester-based multilayer structure composite film; the mass ratio of the polycarbonate to the fluorene polyester is (1.6-1.7): (0.4-0.5).

3. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The ratio of the mass of the polycarbonate particles to the volume of the tetrahydrofuran solution in step S1 is (1.6-1.7) g: (1-1.1) mL.

4. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The pretreated substrates in step S1 and step S2 are treated according to the following steps: first, the substrate is cleaned with clean water for 3 to 5 times, then rinsed with deionized water for 3 to 5 times, then cleaned with anhydrous ethanol for 3 to 5 times, and finally dried at a temperature of 75 to 80° C. for 12 to 15 hours to obtain a pretreated substrate, wherein the substrate is a glass plate.

5. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that In step S1 and step S2, the mechanical stirring is performed by a magnetic stirrer, and the stirring speed is 150-300 r / min.

6. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The steps of gradient heating and heat preservation in step S1 and step S2 are as follows: firstly, the substrate is heated to 60-80°C and kept at 60-80°C for 6-12h; after the heat preservation, the substrate is heated to 80-120°C and kept at 80-120°C for 8-12h.

7. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The ratio of the mass of the fluorene polyester described in step S2 to the volume of the methyl pyrrolidone solution is (0.4-0.5) g: (3.5-4) mL.

8. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The steps of hot pressing process in step S3 are as follows: placing the fluorene polyester film between two layers of polycarbonate film, and then placing it between two layers of iron plates, and then placing the iron plates in a flat vulcanizer and keeping it warm at 160-170°C for 0.5-1h; after the insulation, hot pressing is performed at a pressure of 10-15MPa for 1-2h, and cooling is performed after the hot pressing is completed to obtain a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film.

9. The method for preparing a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film according to claim 2, characterized in that The thickness ratio of each layer of polycarbonate film to fluorene polyester film in the high temperature and high breakdown resistant polycarbonate and fluorene polyester based multilayer structure composite film described in step S3 is (6:3), (5:5), (4:7) or (3:9).

10. The use of a high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film as claimed in claim 1, characterized in that The application of the high temperature resistant and high breakdown polycarbonate and fluorene polyester based multilayer structure composite film in high temperature energy storage capacitors.

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