Dielectric composite material containing metal / ceramic nanosheets and preparation method thereof

Abstract

The invention belongs to the technical field of polymer energy storage materials, and particularly relates to a dielectric composite material containing metal / ceramic nanosheets and a preparation method of the dielectric composite material. The preparation method comprises the following steps: synthesizing uniformly dispersed aluminum oxide nanosheets anchored by silver nanoparticles through a one-step method, splitting an imide ring on the surface of PI (Polyimide) by alkaline water, loading metal ions to the tail end of a molecular chain, carrying out sequential ion exchange and post-heat treatment to remove a PI substrate, and simultaneously obtaining the aluminum oxide nanosheets anchored by the silver nanoparticles through one step. The method can prevent premature reduction of nanoparticles and formation of a mixture, while overcoming the problem of agglomeration. Dispersing the silver nanoparticle-loaded aluminum oxide nanosheets in an organic solvent, performing ultrasonic treatment to uniformly disperse the silver nanoparticle-loaded aluminum oxide nanosheets, adding polyetherimide particles, stirring, casting, drying, cooling, and drying again to obtain the dielectric composite material containing the metal / ceramic nanosheets. Many equivalent micro-capacitors are formed between the silver nanoparticles and the polymer, and meanwhile, the dielectric constant and the breakdown strength are remarkably improved through the charge scattering effect of the aluminum oxide nanosheets and the coulomb blocking effect of the silver nanoparticles.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer energy storage materials, and in particular relates to a dielectric composite material containing metal / ceramic nanosheets and a preparation method thereof. Background Art

[0002] Polymer dielectrics have attracted considerable attention due to their widespread applications in advanced electronics and power systems. Their inherent flexibility, lightweight properties, and scalable processability make them promising candidates for applications such as high-voltage pulse capacitors, sensors, and printed circuits. While these materials exhibit excellent electrical insulation properties, their poor temperature stability significantly limits their application in high-temperature environments. Their practical application at high temperatures is severely hampered by the dramatic decrease in breakdown strength and energy storage capacity.

[0003] Incorporating ceramic nanofillers into polymers has been shown to be an effective strategy to improve high-temperature energy storage performance, using the inherent thermal stability of ceramics to compensate for the limitations of polymers at high temperatures. Two-dimensional ceramic nanosheets have shown great application potential in the field of dielectric energy storage materials due to their unique structure, significant surface effects, and excellent thermal conductivity and dielectric properties. For example, Yang et al. prepared phosphotungstic acid sub-nanosheets (PWNS) of different morphologies by hydrothermal synthesis and then modified their surfaces with oleylamine. These functionalized nanostructures were then incorporated into high-temperature dielectric polymers to form polymer nanocomposites. The discharge energy density (U d ) is 7.27 J cm -3 , the efficiency (η) is 90%. It is worth noting that even at a high temperature of 200 ° C, the U d Also maintained at 4.54 J cm -3 (η=90%). Meanwhile, the PI system exhibits excellent high temperature performance. d90 The value reaches 8.1 J cm at 150 °C. -3 , reaching 7.2Jcm at 200℃ -3 At the same time, the Coulomb blockade effect induced by metal nanoparticles has considerable potential in improving energy storage performance. For example, when aluminum nanoparticles and gold nanoparticles are anchored on titanium dioxide fibers to form a multilayer core-shell nanocomposite and incorporated into polyetherimide, a 11.3 J cm-2 energy storage capacity can be achieved at high temperatures of 150 °C and 200 °C. -3 and 9.7 J cm -3The results show that the high energy storage density of the two-dimensional ceramic nanosheets is 300% and 353% higher than that of the original polyetherimide, respectively. Compared with zero-dimensional and one-dimensional nanofillers, two-dimensional nanofillers have a higher specific surface area and can accommodate more Coulomb blockade units. Therefore, the introduction of two-dimensional ceramic nanosheets anchored with metal nanoparticles is a very promising method to improve the energy storage density. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a dielectric composite material containing metal / ceramic nanosheets and a method for preparing the same. By introducing metal / ceramic composite nanosheets into a polymer to form the dielectric composite, the dielectric constant is significantly improved due to the numerous equivalent microcapacitors formed between the metal nanoparticles and the polymer. The Coulomb blockade effect caused by the metal nanoparticles and the inherent high insulating properties of alumina significantly enhance the breakdown strength. Ultimately, the dielectric composite material achieves a significant increase in high-temperature energy storage density.

[0005] The technical solutions adopted are:

[0006] A method for preparing a dielectric composite material containing metal / ceramic nanosheets comprises the following steps:

[0007] (1) Pretreatment of polyimide (PI) film;

[0008] (2) The pretreated polyimide film is immersed in a sodium hydroxide solution to react, so that the imide ring on the polyimide surface is opened and the Na + The polyimide film is then washed with deionized water until it is neutral, and then immersed in a silver nitrate solution for the first ion exchange, that is, the exchange of sodium ions with silver ions; after the ion exchange is completed, the film is washed with deionized water to wash away the silver nitrate solution on the surface of the film, and then immersed in an aluminum chloride solution for the second ion exchange, that is, the exchange of sodium ions with aluminum ions, to introduce silver ions and aluminum ions to the surface of the polyimide film;

[0009] (3) washing the aluminum chloride solution on the surface of the polyimide film with deionized water, drying, and then heating from room temperature to 600-700° C. for preservation to generate aluminum oxide nanosheets loaded with silver nanoparticles while removing the base polyimide film;

[0010] (4) Alumina nanosheets loaded with silver nanoparticles are dispersed in an organic solvent and ultrasonically treated to uniformly disperse them. After completion, polyetherimide particles are added, and the mixture is vigorously stirred under heating and then slowly stirred at room temperature overnight to obtain a casting solution; the solution is cast on a glass substrate, dried, cooled, and then dried again to obtain a dielectric composite material containing metal / ceramic nanosheets.

[0011] Preferably, in step (1), the method of pretreatment is to cut the 0.015-0.03 micron thick polyimide film into square pieces, and then clean the film with alcohol and deionized water to remove the oil and impurities on the surface of the film.

[0012] Preferably, in step (2), the concentration of sodium hydroxide is 1-2.5 mol / L, and the immersion time is 1-5 hours. As a further preference, the concentration of sodium hydroxide is 2-2.5 mol / L, and the immersion time is 2 hours.

[0013] Preferably, in step (2), the concentration of silver nitrate solution is 1.5-3×10 -4 mol / L, and the first ion exchange time is 1-10 minutes; the concentration of aluminum chloride solution is 0.1-0.5 mol / L, and the second ion exchange time is 0.5-2 hours. As a further preference, the concentration of silver nitrate is 2.5-3×10 -4 mol / L, and the immersion time is 5 minutes.

[0014] Preferably, in step (3), the temperature is raised at a rate of 2℃ / min after drying, and the holding time is 10-60 minutes.

[0015] Preferably, in step (4), the organic solvent is any one of 1-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and chloroalkane; preferably, it is 1-methyl-2-pyrrolidone; and the ultrasonic treatment time is 0.5-1 hour.

[0016] Preferably, in step (4), the mixture is stirred vigorously at 75-80℃ for 2-8 hours, and then slowly stirred at room temperature overnight to obtain a casting solution. As a further preference, the mixture is stirred vigorously for 4-6 hours.

[0017] Preferably, in step (4), the solution is cast on a glass substrate, dried in an oven at 100℃ for 1-4 hours, and then further dried at 200℃ for 1-10 minutes. As a further preference, the solution is first dried in an oven at 100℃ for 4 hours. The cooling is rapid cooling with ice water, and finally dried in an oven at 40℃ for 10-20 hours.

[0018] Preferably, in step (4), the silver nanoparticle-loaded alumina nanosheet accounts for 0.05-0.3 wt% of the total mass of the polymer particles.

[0019] The dielectric composite material containing metal / ceramic nanosheets prepared by the preparation method of the present application.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present invention synthesizes uniformly dispersed silver nanoparticle-anchored alumina nanosheets through a one-step process. Alkaline water decomposes the imide ring on the PI surface, and metal ions are loaded onto the end of the molecular chain. Sequential ion exchange is then performed, and finally heat treatment is performed to remove the PI substrate, thereby obtaining alumina nanosheets anchoring silver nanoparticles in one step. This method can prevent the premature reduction of nanoparticles and the formation of mixtures, while overcoming the agglomeration problem. The field of dielectric energy storage is one of the main application areas of two-dimensional nanosheets. Metal-ceramic composite nanosheets are introduced into polymers to form dielectric composite materials. Due to the formation of many equivalent microcapacitors between the silver nanoparticles and the polymer, the dielectric constant is significantly improved; the Coulomb blockade effect caused by the silver nanoparticles and the inherent high insulation of alumina achieve a significant enhancement in the breakdown strength; ultimately, a significant improvement in the high-temperature energy storage density of the dielectric composite material is achieved.

[0022] The present invention introduces Al2O3 nanosheets loaded with Ag nanoparticles as fillers into polymers to form nanocomposite films. The breakdown strength of the composite films at high temperatures (150°C and 200°C) is significantly improved, reaching 756.0 MV m -1 and 693.1MV m -1 , which are approximately 145.5% and 144.5% of pure PEI.

[0023] This invention produces high-purity silver nanoparticle-loaded alumina ceramic nanosheets through a simple process involving sequential ion exchange and heat treatment. These nanosheets are then introduced as fillers into a polyetherimide dielectric, achieving a synergistic improvement in dielectric constant and breakdown strength. The technical principles and production process are relatively simple, with controllable content and ease of operation. The resulting nanosheets are of stable quality, facilitating mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the preparation method of Example 1 of the present invention;

[0025] Figure 2 The scanning electron microscope image and corresponding EDX element distribution spectrum of Al2O3 nanosheets loaded with Ag nanoparticles (AgNPs@AONSs) prepared in Example 1;

[0026] Figure 3 Atomic force microscopy (3a), transmission electron microscopy (3b), X-ray diffraction (3c), and selected area electron diffraction (3d) images of Al2O3 nanosheets loaded with Ag nanoparticles (AgNPs@AONSs) prepared in Example 1;

[0027] Figure 4The infrared spectrum (4a) and SEM images (4b, 4c) of the cross-section of the film prepared in Example 1, the Al2O3 nanosheets loaded with Ag nanoparticles (hereinafter referred to as AgNPs@AONSs / PEI) are shown. Figure 4 Element distribution diagram of c;

[0028] Figure 5 The frequency stability diagram (5a) and temperature stability diagram (5b) of the dielectric constant and dielectric loss of the prepared AgNPs@AONSs / PEI composite material;

[0029] Figure 6 The breakdown strength (6a) at 150°C, the breakdown strength (6b) at 200°C, and the tensile properties (6c) of the AgNPs@AONSs / PEI composite film prepared in the present invention;

[0030] Figure 7 The electric displacement-electric field loop (7a) and discharge energy density (7b) of the AgNPs@AONSs / PEI composite film prepared by the present invention at 150°C and the electric displacement-electric field loop (7c) and discharge energy density (7d) at 200°C;

[0031] Figure 8 The power density (8a), cycle charge-discharge performance (8b), and leakage current density (8c) of the AgNPs@AONSs / PEI composite film prepared in the present invention at 200°C are shown. DETAILED DESCRIPTION

[0032] The figures are for illustrative purposes only; some well-known structures and their descriptions may be omitted from the figures for those skilled in the art and should not be construed as limiting the present invention. Unless otherwise specified, the chemicals or testing methods used in the present invention can be implemented using conventional methods.

[0033] Example 1

[0034] like Figure 1 As shown, a method for preparing a dielectric composite material containing metal / ceramic nanosheets comprises the following steps:

[0035] (1) Cut a 0.025 μm thick polyimide (PI) film into square pieces and wash them with alcohol and deionized water to remove oil and impurities on the film surface;

[0036] (2) Immerse the PI film in a 2.5 mol / L sodium hydroxide (NaOH) solution for 2 hours to open the imide ring on the polyimide surface and + The PI film was then washed with deionized water until it was neutral and then immersed in a 2.8×10-4 mol / L silver nitrate (AgNO3) solution for 5 minutes for the first ion exchange (Na + →Ag + ). Wash repeatedly with deionized water to remove the AgNO3 solution on the surface of the film and then immerse it in 0.5 mol / L aluminum chloride (AlCl3) solution for 1 hour for the second ion exchange (Na + →Al 3+ ), Ag+ and Al 3+ Introduced into the surface of PI film;

[0037] (3) The AlCl3 solution on the surface of the film was washed off with deionized water, and after drying, the temperature was raised from room temperature to 600°C at a rate of 2°C / min and kept for 30 minutes to generate aluminum oxide nanosheets loaded with silver nanoparticles while removing the substrate PI film.

[0038] (4) Alumina nanosheets loaded with silver nanoparticles were dispersed in 1-methyl-2-pyrrolidone (NMP) solvent and ultrasonically treated for 1 hour to uniformly disperse them. After completion, polyetherimide (PEI) particles were added and the mixture was vigorously stirred at 75°C for 5 hours and then slowly stirred at room temperature overnight to obtain a casting solution. The solution was cast on a glass substrate, dried in an oven at 100°C for 4 hours, and then further dried at 200°C for 5 minutes. The glass substrate and the film were then quickly cooled with ice water, separated from the glass substrate, and finally dried in an oven at 40°C for 16 hours to obtain a dielectric composite material containing metal / ceramic nanosheets. Among them, the alumina nanosheets loaded with silver nanoparticles accounted for 0.2wt% of the total mass of the polymer particles.

[0039] like Figure 2 As shown, the scanning electron microscope image and EDX spectrum of Ag-loaded Al2O3 nanosheets (AgNPs@AONSs) are shown. Figure 3 a is the atomic force microscopy image of AgNPs@AONSs, Figure 3 b is a transmission electron microscope image. Figure 2 , 3a, 3b, it can be seen that the silver ions are evenly anchored on the alumina nanosheets, and the silver particles are quasi-spherical with a diameter of less than 5 nm. Figure 3 c is the result of X-ray diffraction of AgNPs@AONSs. Its crystal plane is (111)(200)(220)(311), and the results of the control standard card confirm the successful synthesis of silver nanoparticles. The results of selected area electron diffraction ( Figure 3 d) It shows diffuse light spots and a few inconspicuous light spots around it, indicating that the aluminum oxide generated at a lower temperature is amorphous, so the selected area electron diffraction shows an amorphous result as a whole.

[0040] Figure 4 a is a comparison of the infrared spectra of pure PEI and 0.3wt% AgNPs@AONSs / PEI nanocomposite. It can be seen that the introduction of inorganic nanofillers has no effect on the molecular chain structure. Figure 4 b, 4c are scanning electron microscope images of thin film cross sections, combined with Figure 4 The element distribution of d–4f indicates the successful formation of nanocomposites.

[0041] Example 2

[0042] In the dielectric composite material containing metal / ceramic nanosheets prepared by the present invention, the aluminum oxide nanosheets loaded with silver nanoparticles account for 0.05 wt% of the total mass of the polymer particles.

[0043] Other unmentioned places are the same as those in Example 1.

[0044] Example 3

[0045] In the dielectric composite material containing metal / ceramic nanosheets prepared by the present invention, the aluminum oxide nanosheets loaded with silver nanoparticles account for 0.1 wt% of the total mass of the polymer particles.

[0046] Other unmentioned places are the same as those in Example 1.

[0047] Example 4

[0048] In the dielectric composite material containing metal / ceramic nanosheets prepared by the present invention, the aluminum oxide nanosheets loaded with silver nanoparticles account for 0.3 wt% of the total mass of the polymer particles.

[0049] Before the dielectric performance test, the LCR precision analyzer (E4980A) was open / short compensated. The frequency stability of the dielectric performance was measured in the range of 100Hz-1MHz, and the temperature stability was measured in the range of 40-200℃ at 1000Hz. Using the following formula (ε r =tC / Aε) to calculate the dielectric constant of the material, where t represents the sample thickness, A represents the electrode area, C represents the parallel capacitance, and ε0 represents the absolute dielectric constant of free space, which is generally 8.85×10 -12 F / m. Figure 5a, 5b show the changes in the dielectric constant and dielectric loss of the composite film with frequency and temperature, respectively. Compared with pure PEI film, the dielectric constant of the composite film gradually increases with the increase of AgNPs@AONSs content. Although only a very small amount of 0.3wt% AgNPs@AONSs was added, the dielectric constant of the composite film was still increased by about 38%. This is mainly attributed to two points: one is that the dielectric constant of alumina is relatively high (about 10), and the other is that many equivalent micro-capacitors are formed between silver nanoparticles and polymers, which increases the polarization of the film, so the dielectric constant is also significantly improved. In the temperature range of 40 to 200 ° C, 0.1wt% AgNPs@AONSs / PEI nanocomposite materials exhibit excellent temperature stability (ε r The change of is less than 3%), which ensures the stability of energy storage performance in a wide temperature range.

[0050] like Figure 6 As shown in the figure, the breakdown strength test was conducted using a ferroelectric tester (PK-CPE1801). The voltage ramp rate was set to 500V / s, and the breakdown strength analyzed using a two-parameter Weibull distribution is also a determining factor for the working voltage and energy storage density of dielectric materials. b A scaling parameter, β, indicates a breakdown probability of 63.2% for the tested sample and can be considered the characteristic breakdown strength of the dielectric. The shape parameter β of the Weibull analysis is positively correlated with the stability of the test results. These results demonstrate that AgNPs@AONS effectively enhance the breakdown strength of the nanocomposite at elevated temperatures. Figure 6 a, 6b show that 0.1 wt% AgNPs@AONSs / PEI nanocomposites can reach 756.0 MV m at 150 °C and 200 °C. -1 and 693.1MV m -1 , which are approximately 145.5% and 144.5% of pure PEI, respectively. In addition, the shape parameter (β) increased significantly from 19.6 and 14.1 of PEI to 34.8 and 27.6 of 0.1wt%, indicating that the 0.1wt% AgNPs@AONSs / PEI nanocomposite has high structural integrity and reliability at high temperatures. The significant improvement in breakdown performance can be attributed to the Schottky barrier formed between silver nanoparticles and polymer, as well as the Coulomb blockade barrier of silver nanoparticles. At the same time, alumina nanosheets are generated on the surface of PI. During the heat treatment to remove PI, PI will produce thermal shrinkage, resulting in a corrugated structure of alumina. This structure enhances the scattering effect of charges and effectively dissipates the electrostatic energy under high electric field, thereby improving the breakdown strength. Figure 6 c is the stress-strain curve of the nanocomposite and pure PEI, among which 0.1wt% AgNPs@AONSs / PEI nanocomposite exhibits the highest tensile strength and Young's modulus, which is consistent with the breakdown strength results.

[0051] As shown in Figure 7 , the hysteresis loop of the material was obtained by using a ferroelectric tester (PK-CPE1801, poly-k Technologies), and the charge and discharge energy density and efficiency were obtained from the hysteresis loop. It can be seen intuitively from Figure 7 that the high-temperature energy storage performance is improved. At 150℃ and 200℃, the area enclosed by the AgNPs@AONSs / PEI nanocomposite loop and the Y-axis is significantly larger than that of PEI. The 0.1wt% AgNPs@AONSs / PEI nanocomposite obtains a high energy density of 10.2J cm -3 at 150℃, and the energy density still remains at 7.9J cm -3 at 200℃. At the same time, the discharge efficiency is also improved.

[0052] Figure 8 a, 8b are the power density diagram and the charge and discharge cycle stability diagram of the composite film, respectively. The power density of the composite film at 200℃ is as high as 1.01MW cm -3 , and it remains stable after 100,000 cycles of charge and discharge under an electric field of 300MV m -1 . Figure 8 c is the leakage current density of the composite film at 200℃. Due to the coulomb blockade effect of silver nanoparticles and the blocking and scattering effect of aluminum oxide on electron transport, the leakage current density of the composite film is also significantly reduced.

[0053] Of course, the above description is not a limitation on the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A method for preparing a dielectric composite material containing metal / ceramic nanosheets, characterized in that: The steps include: (1) Pre-treating the polyimide film; (2) immersing the pretreated polyimide film in a sodium hydroxide solution for reaction, then washing the polyimide film with deionized water until neutral, and then immersing it in a silver nitrate solution for the first ion exchange, i.e., the exchange of sodium ions with silver ions; after the ion exchange, washing it with deionized water to wash off the silver nitrate solution on the surface of the film, and then immersing it in an aluminum chloride solution for the second ion exchange, i.e., the exchange of sodium ions with aluminum ions, thereby introducing silver ions and aluminum ions onto the surface of the polyimide film; (3) washing the aluminum chloride solution on the surface of the polyimide film with deionized water, drying, and then heating from room temperature to 400-600° C. for preservation to generate aluminum oxide nanosheets loaded with silver nanoparticles while removing the base polyimide film; (4) Alumina nanosheets loaded with silver nanoparticles are dispersed in an organic solvent and ultrasonically treated to uniformly disperse them. After completion, polyetherimide particles are added, and the mixture is vigorously stirred under heating and then slowly stirred at room temperature overnight to obtain a casting solution; the solution is cast on a glass substrate, dried, cooled, and then dried again to obtain a dielectric composite material containing metal / ceramic nanosheets.

2. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (1), the pretreatment method is to cut the polyimide film with a thickness of 0.015 to 0.03 microns into square pieces, and wash them with alcohol and deionized water in sequence to remove oil and impurities on the surface of the film.

3. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (2), the concentration of sodium hydroxide is 1 to 2.5 mol / L, and the immersion time is 1 to 5 hours.

4. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (2), the concentration of the silver nitrate solution is 1.5 to 3 × 10 -4 mol / L, the time for the first ion exchange is 1 to 10 minutes; the concentration of aluminum chloride solution is 0.1 to 0.5 mol / L, and the time for the second ion exchange is 0.5 to 2 hours.

5. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (3), after drying, the temperature is increased at a rate of 2°C / min, and the heat preservation time is 10 to 60 minutes.

6. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (4), the organic solvent is any one of 1-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and chloroethane; and the ultrasonic treatment time is 0.5 to 1 hour.

7. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (4), the mixture is vigorously stirred at 75-80° C. for 2-8 hours, and then slowly stirred at room temperature overnight to obtain a casting solution.

8. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (4), the solution is cast on a glass substrate, first dried in an oven at 100°C for 1 to 4 hours, then further dried at 200°C for 1 to 10 minutes; cooled rapidly with ice water, and finally dried in an oven at 40°C for 10 to 20 hours.

9. The method for preparing a dielectric composite material containing metal / ceramic nanosheets according to claim 1, characterized in that: In the step (4), the aluminum oxide nanosheets loaded with silver nanoparticles account for 0.05 to 0.3 wt% of the total mass of the polymer particles.

10. A dielectric composite material containing metal / ceramic nanosheets prepared by the preparation method according to any one of claims 1 to 9.

Images