A double-layer structure PEI-based full-organic composite film and a preparation method thereof

Abstract

The application provides a PEI-based full-organic composite film with a double-layer structure and a preparation method thereof. r The application selects high-epsilon PVDF and high-eta PEI, designs the PEI-based full-organic composite film with the double-layer structure, the bottom layer is pure PEI, the PEI-based full-organic composite film is provided with high eta, and high epsilon is ensured. b The top layer is a PVDF / PEI blending layer, the epsilon of the composite material is jointly enhanced by the PVDF and the micro-interface polarization existing in the blending layer. r The double-layer structure can effectively combine the advantages of different layers, meanwhile, high dielectric constant, high breakdown field strength and low dielectric loss are obtained, high energy storage density and high energy storage efficiency are obtained, and the double-layer structure can be applied to various application fields.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer energy storage technology, and particularly relates to a double-layer structure polyetherimide (PEI) based full-organic composite film and a preparation method thereof. BACKGROUND

[0002] With the rapid development of modern science and technology, there is an urgent need for dielectric materials with more excellent performance in the field of power electronics system. Due to the fast charging and discharging speed and the ultra-high power density, the dielectric capacitor has a wide application and prospect in the fields of hybrid electric vehicles, 5g communication and pulse power equipment. Among them, microelectronic devices including gate dielectric, high energy storage density capacitor and electroactive material require that the nanocomposite material has high dielectric constant and dielectric strength, and still has low dielectric loss, high breakdown field strength and good toughness. However, the relatively low energy density of the dielectric makes it unable to meet the requirements of miniaturization and light weight of advanced electronic devices. Therefore, it is urgent to develop a dielectric material with high energy density and low dielectric loss. Traditional polymer materials such as polyimide (PI), polymethyl methacrylate (PMMA) and epoxy resin have the characteristics of small volume and easy processing, but the dielectric constant is very low, which is difficult to meet the actual use requirements.

[0003] In order to further improve the electric displacement and energy storage density of the polymer material, the nanoceramic particles with high dielectric constant are selected as fillers to be added to the polymer matrix, so as to form a ceramic / polymer composite material. By selecting high dielectric constant ceramic as filler, the dielectric constant of the composite material can be effectively improved, and on the other hand, the polymer matrix retains its high breakdown field strength, so as to realize the significant improvement of the energy storage density. At present, the ceramic fillers commonly used for preparing polyvinylidene fluoride (PVDF) based composite materials mainly include barium titanate (BaTiO3), titanium dioxide (TiO2) and lead zirconate titanate (PbZrTiO3). However, with the development of ceramic / polymer energy storage composite materials, researchers found that although the addition of ceramic can effectively improve the dielectric constant of the polymer, the great difference in surface energy between the inorganic filler and the organic matrix and the agglomeration problem of the inorganic filler will form defects and reduce the breakdown voltage of the composite material. Therefore, it is urgent to develop a full-organic dielectric film with excellent energy storage performance. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a double-layer structure PEI based full-organic composite film and a preparation method thereof, so as to solve the problem of low energy storage density of the composite material prepared by blending ceramic and polymer. The double-layer structure full-organic PEI based full-organic composite film prepared by the present application has high breakdown field strength and high energy storage density, can be quickly charged and discharged, and has excellent cycle stability.

[0005] The application is realized by the following technical scheme:

[0006] The PEI-based full-organic composite film with a double-layer structure comprises a PEI layer and a PVDF / PEI blending layer arranged in layers.

[0007] Preferably, in the PVDF / PEI blending layer, the PVDF accounts for 10% to 75% of the volume of the PEI.

[0008] Preferably, the thickness of the PEI layer is 3 to 6 microns, and the thickness of the PVDF / PEI blending layer is 6 to 10 microns.

[0009] Preferably, the energy storage density of the PEI-based full-organic composite film with a double-layer structure is between 13.93 to 20.16 J·cm -3 .

[0010] The preparation method of the PEI-based full-organic composite film with a double-layer structure comprises the following steps:

[0011] S1, dispersing PEI in a first solvent to obtain solution A; dispersing PVDF and PEI in a second solvent to obtain suspension X;

[0012] S2, once casting solution A on a substrate and drying into a film to form a PEI layer; twice casting suspension X on the PEI layer and drying into a film to form a PVDF / PEI blending layer; drying the obtained sample to obtain a preliminary sample;

[0013] S3, quenching the preliminary sample to obtain a PEI-based full-organic composite film with a double-layer structure.

[0014] Preferably, in S1, the first solvent is NMP, and the second solvent is NMP.

[0015] Preferably, in S1, dispersing PVDF and PEI in a second solvent to obtain suspension X, specifically: dosing PVDF powder and PEI particles so that the PVDF powder accounts for 10% to 75% of the volume of the PEI particles to obtain mixture A; adding mixture A into the second solvent, stirring, and ultrasonicating to obtain suspension X.

[0016] Preferably, S2 specifically comprises: once casting solution A on a substrate and drying into a film at 85 to 125℃ under vacuum for 35 to 45 minutes to form a PEI layer; then, twice casting suspension X on the PEI layer and drying into a film at 75 to 95℃ under vacuum for 25 to 35 minutes to form a PVDF / PEI blending layer; and drying the obtained sample at 55 to 75℃ under vacuum for 10 to 14 hours to obtain a preliminary sample.

[0017] Preferably, S3 specifically involves heating the preliminary sample at 195–205°C for 8–10 minutes and then quenching it in ice water at -3–4°C to obtain a double-layer PEI-based all-organic composite film.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention selects high ε r A bilayer PEI-based all-organic composite film was designed using PVDF and PEI with a high η value. The bottom layer is pure PEI, which provides a high η value for the PEI-based all-organic composite film and ensures high ET. b The top layer is a PVDF / PEI blend layer, where the PVDF and the microscopic interfacial polarization within the blend layer jointly enhance the ε of the composite material. r This invention introduces a dual-layer structure design into an all-organic composite material. Pure PEI serves as the bottom layer to improve breakdown strength and reduce dielectric loss, while a PVDF / PEI blend layer serves as the top layer to increase the dielectric constant, acting as a high-dielectric layer. This dual-layer structure effectively combines the advantages of each layer, achieving high dielectric constant, high breakdown field strength, and low dielectric loss, resulting in high energy storage density and high energy storage efficiency, suitable for various applications. The energy storage density of the PEI-based all-organic composite film with the dual-layer structure is 13.93–20.16 J·cm⁻¹. -3 The energy storage efficiency is 91.97–94.58%.

[0020] Furthermore, by controlling the volume fraction of PVDF incorporated into the PEI matrix in the blend layer, the dielectric constant of the layer can be controlled, thereby controlling the energy storage density and obtaining a series of pure organic dielectric PEI-based all-organic composite films with excellent energy storage performance. When the PVDF content in the blend layer is 50 vol%, the optimal comprehensive energy storage characteristics are obtained, achieving a breakdown electric field strength of 640 MV·m. -1 At that time, the energy storage density was 20.16 J·cm³. -3 The energy storage efficiency is 94.58%.

[0021] This invention prepares composite films by casting and heat treatment of the films, including quenching in ice water, which improves the ferroelectricity of the films and reduces leakage current. The resulting PEI-based all-organic composite films have smooth surfaces with no obvious cracks, and the top and bottom layers are perfectly connected. The entire film is dense and compact, without obvious pores or defects. The preparation process of this invention is simple and stable, and suitable for industrial production.

[0022] Furthermore, during the preparation of suspension X, alternating stirring and sonication can ensure thorough mixing of components, uniform distribution of raw materials, and reduce the occurrence of defects. Attached Figure Description

[0023] Figure 1 Cross-sectional SEM image of the double-layered PEI-based all-organic composite thin film material prepared in Example 1 of the present application;

[0024] Figure 2 Dielectric constant as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 1 of the present application;

[0025] Figure 3 Dielectric loss as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 1 of the present application;

[0026] Figure 4 Electric hysteresis loop of the double-layered PEI-based all-organic composite thin film material prepared in Example 1 of the present application (test frequency: 10 Hz);

[0027] Figure 5 Cross-sectional SEM image of the double-layered PEI-based all-organic composite thin film material prepared in Example 2 of the present application;

[0028] Figure 6 Dielectric constant as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 2 of the present application;

[0029] Figure 7 Dielectric loss as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 2 of the present application;

[0030] Figure 8 Electric hysteresis loop of the double-layered PEI-based all-organic composite thin film material prepared in Example 2 of the present application (test frequency: 10 Hz);

[0031] Figure 9 Cross-sectional SEM image of the double-layered PEI-based all-organic composite thin film material prepared in Example 3 of the present application;

[0032] Figure 10 Dielectric constant as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 3 of the present application;

[0033] Figure 11 Dielectric loss as a function of frequency of the double-layered PEI-based all-organic composite thin film material prepared in Example 3 of the present application;

[0034] Figure 12 Electric hysteresis loop of the double-layered PEI-based all-organic composite thin film material prepared in Example 3 of the present application (test frequency: 10 Hz);

[0035] Figure 13 SEM image of cross-section of the PEI-based full-organic composite film material with double-layer structure prepared in Example 4 of the present application;

[0036] Figure 14 Diagram of dielectric constant changing with frequency of the PEI-based full-organic composite film material with double-layer structure prepared in Example 4 of the present application;

[0037] Figure 15 Diagram of dielectric loss changing with frequency of the PEI-based full-organic composite film material with double-layer structure prepared in Example 4 of the present application;

[0038] Figure 16 Diagram of electric hysteresis loop of the PEI-based full-organic composite film material with double-layer structure prepared in Example 4 of the present application (the test frequency is 10 Hz).

[0039] Figure 17 Diagram of electric hysteresis loop of the PEI-based full-organic composite film material with double-layer structure prepared in Example 3 of the present application, and comparison diagram of electric hysteresis loop of the single-layer pure PEI film material prepared in Comparative Example 1 and the double-layer composite film material formed by the pure PEI film and the pure PVDF film prepared in Comparative Example 2 (the test frequency is 10 Hz). DETAILED DESCRIPTION

[0040] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the personnel in the field without making creative efforts should belong to the protection scope of the present application.

[0041] It should be noted that the terms "comprising" and "having" and any variations thereof in the present application are intended to cover the non-exclusive inclusion, for example, the process, method, system, product or equipment including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units which are not clearly listed or inherent to these processes, methods, products or equipment.

[0042] The PEI-based full-organic composite film with double-layer structure in the present application comprises a PEI layer and a PVDF / PEI blending layer which are arranged in layers.

[0043] In the embodiments of the present application, the PVDF accounts for 10% to 75% of the volume of the PEI in the PVDF / PEI blending layer.

[0044] In the embodiment of the present application, the thickness of the PEI layer is 3-6 μm, and the thickness of the PVDF / PEI blend layer is 6-10 μm.

[0045] The preparation method of the PEI-based full-organic composite film is as follows: first, PVDF powder is mixed with PEI, and the obtained mixture is dispersed in solvent NMP to obtain a PVDF / PEI mixture; and then a PEI-based full-organic high-energy-density PEI-based full-organic composite film with a double-layer structure, in which the top layer is a PVDF / PEI blend layer and the bottom layer is a pure PEI layer, is prepared by a flow casting method.

[0046] Specifically, the method comprises the following steps:

[0047] (1) Analytically pure PVDF powder and PEI particles are proportioned according to a certain ratio so that PVDF accounts for 10%-75% of the volume of PEI to obtain a mixture A; NMP is used as a solvent, and the mixture A and NMP are mixed according to a mass ratio of 1:(6.25-10) and then added to a beaker with a rotor.

[0048] (2) The mixed solution obtained in step (1) is sealed with a preservative film, and then placed on a magnetic stirrer for stirring and dispersion; first, stirring is performed at a speed of 450-600 r·min -1 and a temperature of 30-70℃ for 12-14 h for dissolution, then stirring is performed at a speed of 450-600 r·min -1 and a temperature of 20-35℃ for 1-3 h for cooling, and then ultrasonic treatment is performed for 25-45 min; stirring and ultrasonic treatment are alternated for 4-8 times; and finally, stirring is performed at a temperature of 25℃ for 1-3 h to obtain a room-temperature suspension X of uniformly blended PVDF and PEI.

[0049] (3) NMP is used as a solvent, and the solvent is added to a beaker with a rotor; at the same time, only PEI solid particles are added, and the mass ratio of the PEI particles to the NMP solvent is 1:(6.25-8.33); stirring is performed at a speed of 500-650 r·min -1 and a temperature of 40-80℃ for 12-14 h for dissolution, then stirring is performed at a speed of 500-650 r·min -1 and a temperature of 20-35℃ for 1-3 h for cooling to obtain a solution A.

[0050] (4) Set the temperature of the casting machine to 180-200°C, control the height of the doctor blade to 15-25 μm, cast the solution A prepared in step (3) on a glass plate for the first time, vacuum dry at 85-125°C for 35-45 min to form a film, then cast the suspension X prepared in step (2) on the glass plate with the first film for the second time, vacuum dry at 75-95°C for 25-35 min to form a film, finally obtain a PEI-based full-organic composite film with a double-layer structure of PEI layer at the bottom and PVDF / PEI blend layer at the top. Finally, vacuum dry the PEI-based full-organic composite film with a double-layer structure prepared as the preliminary sample at 55-75°C for 10-14 h to volatilize the solvent, and obtain the preliminary sample.

[0051] (5) Heat the PEI-based full-organic composite film with a double-layer structure prepared as the preliminary sample at 195-205°C for 8-10 min, then immediately quench in ice water at -3-4°C. The surface of the PEI-based full-organic composite film with a double-layer structure after quenching is smooth and no obvious cracks appear, and a dense PEI-based full-organic composite film with a double-layer structure is obtained, i.e. the perfect connection of the bottom layer (pure PEI layer with high breakdown strength and low dielectric loss) and the top layer (PVDF / PEI blend layer) is achieved, and the whole film is dense and compact without obvious pores and defects.

[0052] Performance test:

[0053] Cut the PEI-based full-organic composite film with a double-layer structure prepared into a rectangle of 10 mm x 15 mm, then prepare a film for testing, plate a gold electrode with a diameter of 6 mm, and then test the dielectric properties at room temperature.

[0054] Cut the PEI-based full-organic composite film with a double-layer structure prepared into a rectangle of 10 mm x 15 mm, then prepare a film for testing, plate a gold electrode with a diameter of 2 mm, and then test the ferroelectric properties at a frequency of 10 Hz at room temperature, and calculate the energy storage characteristics, the calculation formula of the energy storage density (W1) and the energy loss density (W2) is:

[0055]

[0056]

[0057] wherein W1 and W2 represent the energy storage density and the energy loss density respectively, P max represents the maximum polarization intensity, P r represents the remanent polarization intensity, E represents the electric field intensity, and P represents the polarization intensity.

[0058] The energy storage density W1 of the PEI-based full-organic composite film material with a double-layer structure is 13.93-20.16 J·cm -3 .

[0059] The application will be described in further detail below with reference to the drawings.

[0060] Example 1

[0061] A group of PEI-based full organic composite films with double-layer structure were prepared by solution layer-by-layer casting process in this example. The PEI-based full organic composite film can be simplified as 0-X model, wherein 0 represents the pure PEI of the bottom layer, and X represents the volume fraction of PVDF in the PEI of the top layer. In this example, the PEI-based full organic composite film can be simplified as 0-10 model, wherein the bottom layer is a pure PEI film, and the top layer is a PVDF / PEI blend layer with a volume fraction of PVDF in PEI of 10%.

[0062] The above-mentioned method for preparing the PEI-based full organic composite film with double-layer structure comprises the following steps:

[0063] (1) A certain amount of 0.1308 g of PVDF powder and 1.0 g of PEI particles of analytical purity were mixed according to a certain proportion, so that the volume fraction of PVDF in PEI was 10%, to obtain a mixture A. 10 ml of NMP was measured as a solvent, and the mixture A was mixed with NMP and added to a beaker with a rotor.

[0064] (2) The solution obtained in step (1) was sealed with a preservative film, and was placed on a magnetic stirrer for stirring and dispersion. First, stirring was carried out at a speed of 500 r·min -1 and a temperature of 40℃ for 13 h for dissolution, then stirring was carried out at a speed of 500 r·min -1 and a temperature of 25℃ for 2 h, followed by ultrasonic treatment for 45 min, and the stirring and ultrasonic treatment were alternated for 6 times; stirring was carried out at a temperature of 25℃ for 3 h to obtain a uniform PVDF and PEI blend suspension X 10 at room temperature.

[0065] (3) 10 ml of NMP solution was measured and added to the beaker containing the rotor, and only PEI solid particles were added. Stirring was carried out at a speed of 550 r·min -1 and a temperature of 55℃ for 12 h for dissolution, then stirring was carried out at a speed of 550 r·min -1 and a temperature of 25℃ for 3 h for cooling, to obtain solution A0.

[0066] (4) The temperature of the casting machine was set to 190℃, and the height of the doctor blade was controlled to be 15 μm. The solution A0 prepared in step (3) was cast on a glass plate once, and the film was formed by vacuum drying at 105℃ for 30 min, and then the suspension X 10The double-layer structure PEI-based all-organic composite film with PEI layer as the bottom layer and PVDF / PEI blend layer as the top layer was obtained by secondary flow casting on the glass plate with once film forming, vacuum drying at 95℃ for 30 min, and finally vacuum drying at 60℃ for 12 h to obtain the preliminary sample.

[0067] (5) The double-layer structure PEI-based all-organic composite film preliminary sample prepared was heated at 200℃ for 9 min and then immediately quenched in ice water to obtain the dense double-layer structure PEI-based all-organic composite film with model 0-10.

[0068] The interface of the double-layer structure PEI-based all-organic composite film material prepared in Example 1 was tested by SEM, as shown in Figure 1 The SEM image shows that the double-layer structure PEI-based all-organic composite film prepared is tightly combined without obvious defects, the thickness of the PEI layer is 5 μm, and the thickness of the PVDF / PEI blend layer is 8 μm.

[0069] The double-layer structure PEI-based all-organic composite film prepared in Example 1 was cut into a rectangle of 10 mm x 15 mm to prepare a film, gold electrodes with a diameter of 6 mm were plated, and then the dielectric constant performance test was carried out at room temperature, as shown in The dielectric constant of the PEI-based all-organic composite film prepared in this example gradually decreases with the increase of frequency. When the frequency is 10 kHz, the dielectric constant of the PEI-based all-organic composite film prepared in this example is 3.58.

[0070] Figure 3 The double-layer structure PEI-based all-organic composite film prepared in Example 1 was cut into a rectangle of 10 mm x 15 mm to prepare a film, gold electrodes with a diameter of 6 mm were plated, and then the dielectric loss performance test was carried out at room temperature, as shown in The dielectric loss of the PEI-based all-organic composite film prepared in this example gradually increases with the increase of frequency. When the frequency is 10 kHz, the dielectric loss of the PEI-based all-organic composite film prepared in this example is 0.014.

[0071] Figure 4 The double-layer structure PEI-based all-organic composite film prepared in Example 1 was cut into a rectangle of 10 mm x 15 mm to prepare a film, gold electrodes with a diameter of 2 mm were plated, and then the ferroelectric performance test was carried out at room temperature at a frequency of 10 Hz, and the energy storage characteristic calculation was carried out. As shown in The hysteresis loop of the double-layer structure PEI-based all-organic composite film material in this example measured at room temperature is shown. Based on the hysteresis loop, the effective energy storage density of the double-layer structure PEI-based all-organic composite film material in this example is as high as 14.02 J·cm -1 at an electric field intensity of 560 MV·m-3 Table 1 is the energy storage properties of the PEI-based all-organic composite thin film material of the double-layer structure of the present embodiment at room temperature.

[0072] Example 2

[0073] A group of PEI-based all-organic composite thin films of double-layer structure were prepared by the solution layer-by-layer casting process in the present embodiment. The PEI-based all-organic composite thin film can be simplified as a 0-X model, wherein 0 represents the pure PEI of the bottom layer, and X represents the volume fraction of PVDF in the PEI of the top layer. In the present embodiment, the PEI-based all-organic composite thin film can be simplified as a 0-25 model, wherein the bottom layer is a pure PEI film, and the top layer is a PVDF / PEI blend layer with a volume fraction of PVDF in PEI of 25%.

[0074] The above method for preparing the high-energy-density PEI-based all-organic composite thin film material of double-layer structure comprises the following steps:

[0075] (1) A certain amount of 0.3269 g of PVDF powder and 1.0 g of PEI particles of analytical purity were mixed to make the volume fraction of PVDF in PEI 25%, obtaining a mixture A. 10 ml of NMP was measured as a solvent, and the mixture A was mixed with NMP and added to a beaker with a rotor.

[0076] (2) The solution obtained in step (1) was sealed with a preservative film and placed on a magnetic stirrer for stirring and dispersion. First, stirring was carried out at a speed of 500 r·min -1 and a temperature of 40℃ for 13 h, then stirring was carried out at a speed of 500 r·min -1 and a temperature of 25℃ for 2 h, followed by ultrasonic treatment for 45 min, and the stirring and ultrasonic treatment were alternated for 6 times. Stirring was carried out at a temperature of 25℃ for 3 h, obtaining a uniform PVDF and PEI blend suspension X 25 at room temperature.

[0077] (3) 10 ml of NMP solution was measured and added to the beaker containing the rotor, and only PEI solid particles were added. Stirring was carried out at a speed of 550 r·min -1 and a temperature of 55℃ for 12 h for dissolution, and then stirring was carried out at a speed of 550 r·min -1 and a temperature of 25℃ for 3 h for cooling, obtaining solution A0.

[0078] (4) The temperature of the casting machine was set to 190℃, and the height of the doctor blade was controlled to 15 μm. The solution A0 prepared in step (3) was cast on a glass plate once, and the film was dried in a vacuum at 105℃ for 30 min, and then the suspension X 25The prepared double-layer structure PEI-based all-organic composite film preliminary sample is heated at 200℃ for 9min and then immediately quenched in ice water to obtain a dense double-layer structure PEI-based all-organic composite film, and the model is 0-25.

[0079] (5) The prepared double-layer structure PEI-based all-organic composite film preliminary sample is heated at 200℃ for 9min and then immediately quenched in ice water to obtain a dense double-layer structure PEI-based all-organic composite film, and the model is 0-25.

[0080] The interface of the prepared double-layer structure PEI-based all-organic composite film material is subjected to SEM test, as shown in Figure 5 It can be seen from the SEM diagram that the prepared double-layer structure film is tightly combined and has no obvious defects.

[0081] The prepared double-layer structure PEI-based all-organic composite film is cut into a rectangle of 10mmx15mm to form a film, a gold electrode with a diameter of 6mm is plated, and then the dielectric constant performance test is carried out at room temperature, as shown in Figure 6 The PEI-based all-organic composite film prepared in this embodiment gradually decreases in dielectric constant with the increase of frequency. When the frequency is 10kHz, the dielectric constant of the PEI-based all-organic composite film prepared in this embodiment is 3.89.

[0082] The prepared double-layer structure PEI-based all-organic composite film is cut into a rectangle of 10mmx15mm to form a film, a gold electrode with a diameter of 6mm is plated, and then the dielectric loss performance test is carried out at room temperature, as shown in Figure 7 The PEI-based all-organic composite film prepared in this embodiment gradually increases in dielectric loss with the increase of frequency. When the frequency is 10kHz, the dielectric loss of the PEI-based all-organic composite film prepared in this embodiment is 0.013.

[0083] The prepared double-layer structure PEI-based all-organic composite film is cut into a rectangle of 10mmx15mm to form a film, a gold electrode with a diameter of 2mm is plated, and then the ferroelectric performance is tested at a frequency of 10Hz at room temperature, and the energy storage characteristic calculation is carried out. As shown in Figure 8 The hysteresis loop of the double-layer structure PEI-based all-organic composite film material in this embodiment measured at room temperature is shown, and based on the hysteresis loop, the effective energy storage density of the double-layer structure PEI-based all-organic composite film material in this embodiment is as high as 16.37J·cm -1 -2 at an electric field intensity of 590MV·m -3 -2. Table 1 is the energy storage characteristics of the prepared double-layer structure PEI-based all-organic composite film material at room temperature in this embodiment.

[0084] Example 3

[0085] A group of PEI-based all-organic composite films with double-layer structure were prepared by solution layer-by-layer casting process. The PEI-based all-organic composite films can be simplified as 0-X model, where 0 represents the pure PEI of the bottom layer, and X represents the volume fraction of PVDF in PEI of the top layer. In this embodiment, the PEI-based all-organic composite films can be simplified as 0-50 model, where the bottom layer is a pure PEI film, and the top layer is a PVDF / PEI blend layer with a volume fraction of PVDF in PEI of 50%.

[0086] The above-mentioned method for preparing PEI-based all-organic composite films with double-layer structure comprises the following steps:

[0087] (1) A certain amount of 0.6538g of PVDF powder and 1.0g of PEI particles were mixed according to a certain proportion, so that the volume fraction of PVDF in PEI was 50%, to obtain a mixture A. 10ml of NMP was measured as a solvent, and the mixture A was mixed with NMP and added to a beaker with a rotor.

[0088] (2) The solution obtained in step (1) was sealed with plastic wrap and placed on a magnetic stirrer for stirring and dispersion. First, stirring was carried out at a speed of 500r·min -1 and a temperature of 40℃ for 13h, then stirring was carried out at a speed of 500r·min -1 and a temperature of 25℃ for 2h, followed by ultrasonic treatment for 45min, and the stirring and ultrasonic treatment were alternated for 6 times. Finally, stirring was carried out at a temperature of 25℃ for 3h to obtain a uniform PVDF and PEI blend suspension X 50 at room temperature.

[0089] (3) 10ml of NMP solution was measured and added to a beaker containing a rotor, and only PEI solid particles were added. Stirring was carried out at a speed of 550r·min -1 and a temperature of 55℃ for 12h to dissolve, and then stirring was carried out at a speed of 550r·min -1 and a temperature of 25℃ for 3h to cool down, to obtain solution A0.

[0090] (4) The temperature of the casting machine was set to 190℃, and the height of the doctor blade was controlled to be 15μm. The solution A0 prepared in step (3) was cast on a glass plate once, and the film was dried in a vacuum oven at 105℃ for 30min, and then the suspension X 50A secondary casting process was performed on a glass plate with a primary film, followed by vacuum drying at 95°C for 30 min to obtain a bilayer PEI-based all-organic composite film with a PEI bottom layer and a PVDF / PEI blend top layer. Finally, the prepared bilayer PEI-based all-organic composite film was vacuum dried at 60°C for 12 h to obtain a preliminary sample.

[0091] (5) The prepared bilayer PEI-based all-organic composite film sample was heated at 200℃ for 9 min and then immediately placed in ice water for quenching to obtain a dense bilayer PEI-based all-organic composite film with a model of 0-50.

[0092] The interface of the prepared bilayer PEI-based all-organic composite thin film material was subjected to SEM testing, such as... Figure 9 The SEM images show that the fabricated bilayer film is tightly bonded and has no obvious defects.

[0093] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament, and a 6mm diameter gold electrode was deposited on it. Then, the dielectric constant was tested at room temperature. Figure 10 In this embodiment, the dielectric constant of the PEI-based all-organic composite film gradually decreases with increasing frequency. At a frequency of 10 kHz, the dielectric constant of the PEI-based all-organic composite film prepared in this embodiment is 4.19.

[0094] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament film, and then a 6mm diameter gold electrode was deposited. Dielectric loss performance was then tested at room temperature. Figure 11 In this embodiment, the dielectric loss of the PEI-based all-organic composite film gradually increases with increasing frequency. At a frequency of 10 kHz, the dielectric loss of the PEI-based all-organic composite film prepared in this embodiment is 0.012.

[0095] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament film. A 2mm diameter gold electrode was deposited on the film, and its ferroelectric properties were tested at 10Hz at room temperature. Energy storage characteristics were then calculated. Figure 12 The figure shows the hysteresis loop of the bilayer PEI-based all-organic composite thin film material of this embodiment, measured at room temperature. Based on the hysteresis loop, the energy storage characteristics can be calculated, and the effective energy storage density of the bilayer PEI-based all-organic composite thin film material of this embodiment is at an electric field strength of 640 MV·m. -1 Up to 20.16 J·cm -3 Table 1 shows the energy storage characteristics of the PEI-based all-organic composite thin film material with a double-layer structure in this embodiment at room temperature.

[0096] Example 4

[0097] This example prepares a group of PEI-based full organic composite films with a double-layer structure by a solution layer-by-layer casting process. The PEI-based full organic composite film can be simplified as a 0-X model, where 0 represents the pure PEI of the bottom layer, and X represents the volume fraction of PVDF in PEI of the top layer. In this example, the PEI-based full organic composite film can be simplified as a 0-75 model, where the bottom layer is a pure PEI film, and the top layer is a PVDF / PEI blend layer with a volume fraction of PVDF in PEI of 75%.

[0098] The above method for preparing a PEI-based full organic composite film with a double-layer structure includes the following steps:

[0099] (1) According to a certain proportion, 0.9808 g of analytical pure PVDF powder and 1.0 g of PEI particles are dosed so that the volume fraction of PVDF in PEI is 75%, obtaining a mixture A. 10 ml of NMP is measured as a solvent, and the mixture A is mixed with NMP and added to a beaker with a rotor.

[0100] (2) The solution obtained in step (1) is sealed with a preservative film, and is placed on a magnetic stirrer for stirring and dispersion. First, stirring is carried out at a speed of 500 r·min -1 and a temperature of 40℃ for 13 h, then stirring is carried out at a speed of 500 r·min -1 and a temperature of 25℃ for 2 h, then ultrasonic is used for 45 min, and stirring and ultrasonic are alternated for 6 times; stirring is carried out at a temperature of 25℃ for 3 h, obtaining a uniform PVDF and PEI blend suspension X 75 at room temperature.

[0101] (3) 10 ml of NMP solution is measured and added to the beaker containing the rotor, and only PEI solid particles are added. Stirring is carried out at a speed of 550 r·min -1 and a temperature of 55℃ for 12 h for dissolution, then stirring is carried out at a speed of 550 r·min -1 and a temperature of 25℃ for 3 h for cooling, obtaining a solution A0.

[0102] (4) The temperature of the casting machine is set to 190℃, and the height of the doctor blade is controlled to be 15 μm. The solution A0 prepared in step (3) is cast on a glass plate once, and the film is formed by vacuum drying at 105℃ for 30 min. Then, the suspension X 75A secondary casting process was performed on a glass plate with a primary film, followed by vacuum drying at 95°C for 30 min to obtain a bilayer PEI-based all-organic composite film with a PEI bottom layer and a PVDF / PEI blend top layer. Finally, the prepared bilayer PEI-based all-organic composite film was vacuum dried at 60°C for 12 h to obtain a preliminary sample.

[0103] (5) The prepared bilayer PEI-based all-organic composite film sample was heated at 200℃ for 9 min and then immediately placed in ice water for quenching to obtain a dense bilayer PEI-based all-organic composite film with a model of 0-75.

[0104] The interface of the prepared bilayer PEI-based all-organic composite thin film material was subjected to SEM testing, such as... Figure 13 The SEM images show that the fabricated bilayer film has small voids, but these voids do not affect the overall integrity of the film.

[0105] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament, and a 6mm diameter gold electrode was deposited on it. Then, the dielectric constant was tested at room temperature. Figure 14 In this embodiment, the dielectric constant of the PEI-based all-organic composite film gradually decreases with increasing frequency. At a frequency of 10 kHz, the dielectric constant of the PEI-based all-organic composite film prepared in this embodiment is 4.53.

[0106] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament film, and then a 6mm diameter gold electrode was deposited. Dielectric loss performance was then tested at room temperature. Figure 15 In this embodiment, the dielectric loss of the PEI-based all-organic composite film gradually increases with increasing frequency. At a frequency of 10kHz, the dielectric loss of the PEI-based all-organic composite film prepared in this embodiment is 0.022.

[0107] The prepared bilayer PEI-based all-organic composite film was cut into 10mm × 15mm rectangles to form a filament film. A 2mm diameter gold electrode was deposited on the film, and its ferroelectric properties were tested at 10Hz at room temperature. Energy storage characteristics were then calculated. Figure 16 The figure shows the hysteresis loop of the bilayer PEI-based all-organic composite thin film material of this embodiment, measured at room temperature. Based on the hysteresis loop, the energy storage characteristics are calculated, and the effective energy storage density of the bilayer PEI-based all-organic composite thin film material of this embodiment is at an electric field strength of 520 MV·m. -1 The temperature reached as high as 13.93 J·cm. -3 Table 1 shows the energy storage characteristics of the PEI-based all-organic composite thin film material with a double-layer structure in this embodiment at room temperature.

[0108] Comparative Example 1

[0109] According to the method in Example 3, a single-layer pure PEI thin film material was prepared, including the following steps:

[0110] (1) Measure 10 ml of NMP solution and add it to a beaker containing the rotor. At the same time, add only PEI solid particles and heat at 550 r·min. -1 Dissolved by stirring at 55°C and 55°F for 12 hours, then at 550 rpm. -1 The solution A0 was obtained by stirring at a certain speed and at 25°C for 3 hours and then cooling.

[0111] (2) Set the casting machine temperature to 190℃ and control the height of the scraper to 15μm. Cast the solution A0 obtained in step (3) onto a glass plate once, vacuum dry at 105℃ for 30min to form a film, and vacuum dry at 60℃ for 12h to obtain a preliminary sample.

[0112] (5) The prepared preliminary sample was heated at 200℃ for 9 minutes and then immediately placed in ice water for quenching to obtain a single-layer pure PEI film material.

[0113] Comparative Example 2

[0114] According to the method in Example 3, a PVDF-PEI bilayer composite film material formed by a pure PEI film and a pure PVDF film was prepared, including the following steps:

[0115] (1) Take 1.2g of analytical grade PVDF powder, measure 10ml of NMP as solvent, mix the PVDF powder and NMP, and add them to a beaker with a rotor.

[0116] (2) Seal the solution obtained in step (1) with plastic wrap, place it on a magnetic stirrer and stir to disperse it at 500 r·min. -1 Dissolve by stirring for 13 hours at a speed of 100 rpm and a temperature of 40°C, then at 500 rpm. -1 The mixture was stirred at a constant speed and at 25°C for 2 hours, followed by sonication for 45 minutes. The stirring and sonication were repeated 6 times. The mixture was then stirred at 25°C for 3 hours to obtain a room-temperature PVDF suspension.

[0117] (3) Measure 10 ml of NMP solution and add it to a beaker containing the rotor. At the same time, add only PEI solid particles and heat at 550 r·min. -1 Dissolved by stirring at 55°C and 55°F for 12 hours, then at 550 rpm. -1 The solution A0 was obtained by stirring at a certain speed and at 25°C for 3 hours and then cooling.

[0118] (4) Set the temperature of the casting machine to 190°C, control the height of the doctor blade to 15 μm, and cast the solution A0 prepared in step (3) on a glass plate once, dry the film at 105°C under vacuum for 30 min, then cast the PVDF suspension prepared in step (2) on the glass plate with the once-cast film, dry the film at 95°C under vacuum for 30 min, and finally obtain a PVDF-PEI double-layer composite film material with PEI as the bottom layer and PVDF as the top layer. Finally, dry the double-layer composite film material prepared at 60°C under vacuum for 12 h to obtain a preliminary sample.

[0119] (5) Heat the preliminary sample of the double-layer composite film material prepared at 200°C for 9 min, then immediately quench in ice water, and obtain a double-layer composite film material.

[0120] Table 1 Energy storage properties of PEI-based full-organic composite film materials with a double-layer structure at room temperature

[0121]

[0122] Table 1 Energy storage properties of PEI-based full-organic composite film materials with a double-layer structure at room temperature -1 , the highest effective energy storage density is 20.16 J·cm -3 , and the energy storage efficiency is as high as 94.58%. Through the above examples, it can be found that by changing the amount of filler introduced and designing the double-layer structure of the PEI-based full-organic composite film, the maximum breakdown electric field of the PEI-based full-organic composite film is effectively increased, and thus the effective energy storage density is effectively improved. The double-layer structure PEI-based full-organic composite film material prepared is expected to replace the commercial biaxially oriented polypropylene (BOPP) to prepare a film capacitor. The energy storage density of BOPP at 640 MV·m -1 is only about 2 J·cm -3 . Film capacitors are widely used in the field of power electronics, for example, energy converters in electric vehicles, which can quickly release energy and effectively solve the problem that lithium batteries cannot release energy instantaneously.

[0123] Figure 17Figure 3 is a comparison chart of the electric hysteresis loop of the PEI-based full-organic composite film material with double-layer structure prepared in Example 3 of the present application, and the electric hysteresis loop of the single-layer pure PEI film material, and the electric hysteresis loop of the double-layer composite film material formed by the interlayer combination of the pure PEI film and the pure PVDF film. Compared with the single-layer pure PEI film, the PEI-based full-organic composite film material with double-layer structure prepared in Example 3 of the present application has a higher polarization intensity and a higher breakdown field strength, and the efficiency change is subtle, thus bringing a higher energy storage density than the single-layer pure PEI film. Compared with the double-layer composite film material formed by the interlayer combination of the pure PEI film and the pure PVDF film, the PEI-based full-organic composite film material with double-layer structure prepared in Example 3 of the present application, due to the blending composite mode, on the basis of ensuring a high polarization intensity, maximally maintains the high energy storage efficiency characteristics of PEI, thus bringing a more excellent energy storage density. Therefore, the double-layer structure composite mode proposed in the present application has superiority.

[0124] The above is only for illustrating the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A PEI-based all-organic composite film with a double-layer structure, characterized in that, It includes a PEI layer and a PVDF / PEI blend layer stacked together; in the PVDF / PEI blend layer, PVDF accounts for 10% to 75% of the PEI volume.

2. The PEI-based all-organic composite film with a double-layer structure according to claim 1, characterized in that, The thickness of the PEI layer is 3~6 μm, and the thickness of the PVDF / PEI blend layer is 6~10 μm.

3. The PEI-based all-organic composite film with a double-layer structure according to claim 1, characterized in that, The energy storage density of the bilayer PEI-based all-organic composite thin film is between 13.93 and 20.16 J·cm⁻¹. -3 between.

4. The method for preparing the bilayer PEI-based all-organic composite thin film according to any one of claims 1 to 3, characterized in that, include: S1, disperse PEI in the first solvent to obtain solution A; mix PVDF powder and PEI particles so that PVDF powder accounts for 10%~75% of the volume of PEI particles to obtain mixture A; add mixture A to the second solvent, stir, and sonicate to obtain suspension X; S2, solution A is cast onto the substrate once, dried to form a film, forming a PEI layer; suspension X is cast onto the PEI layer a second time, dried to form a film, forming a PVDF / PEI blend layer; the resulting sample is dried to obtain a preliminary sample; S3. The preliminary sample was quenched to obtain a double-layer PEI-based all-organic composite film.

5. The method for preparing the bilayer PEI-based all-organic composite thin film according to claim 4, characterized in that, In S1, the first solvent is NMP and the second solvent is NMP.

6. The method for preparing the bilayer PEI-based all-organic composite thin film according to claim 4, characterized in that, S2 specifically involves: casting solution A onto the substrate once, vacuum drying at 85-125 °C for 35-45 min to form a PEI layer; then casting suspension X onto the PEI layer a second time, vacuum drying at 75-95 °C for 25-35 min to form a PVDF / PEI blend layer; and finally vacuum drying the resulting sample at 55-75 °C for 10-14 h to obtain a preliminary sample.

7. The method for preparing the bilayer PEI-based all-organic composite thin film according to claim 4, characterized in that, S3 specifically involves heating the preliminary sample at 195~205 ℃ for 8~10 min and then quenching it in ice water at -3~4 ℃ to obtain a double-layer PEI-based all-organic composite film.

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