Preparation method of giant dielectric constant ceramic / PVDF composite material

Abstract

The invention relates to a preparation method of a giant dielectric constant ceramic / PVDF composite material, which comprises the following steps: preparing CCTO powder by a solid phase method or a sol-gel method, carrying out SiO2 coating modification by a stber method, and compounding with a PVDF matrix by different volume fractions (0.5-4%) by a solution tape casting method to prepare a thick film. Experimental results show that the composite material effectively combines the high dielectric property of CCTO and the excellent mechanical property of PVDF, the comprehensive performance is optimal when the volume fraction of CCTO is 2%, the energy storage density reaches 4.39 J / cm < 3 > when SiO2 is not coated, and is increased to 5.91 J / cm < 3 > after SiO2 coating, meanwhile, the composite material has the advantages of high dielectric constant and low dielectric loss, the problem that the energy storage performance of a single material is insufficient is effectively solved, and the composite material is suitable for industrial production. And a practical reference is provided for the development of the dielectric energy storage field.

Description

Technical Field

[0001] This invention relates to the field of energy storage materials technology, specifically disclosing a method for preparing a giant dielectric constant ceramic / PVDF composite material with high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density as the core performance objectives, to meet the stringent application requirements of miniaturization, lightweighting and high energy storage of electronic devices. Background Technology

[0002] Currently, dielectric energy storage materials are mainly classified into three categories: ceramic materials, polymer materials, and polymer-based composite materials. While ceramic materials possess high dielectric constants, they suffer from poor processability and insufficient flexibility. Polymer materials, such as polyvinylidene fluoride (PVDF), exhibit good mechanical properties and processability, but their relatively low dielectric constant makes them unsuitable for high-energy storage requirements when used alone. Combining ceramic fillers with polymer matrices can achieve complementary advantages.

[0003] CaCu3Ti4O 12 CCTO is a typical giant dielectric material with a dielectric constant as high as 10 at room temperature. 4 -10 5 Furthermore, CCTO exhibits stable performance over a wide temperature range, making it an ideal composite filler. However, the preparation of CCTO / PVDF composites suffers from problems such as uneven dispersion of CCTO powder, poor interfacial compatibility with the PVDF matrix, high dielectric loss, and insufficient breakdown field strength, hindering significant improvements in the energy storage performance of the composites. Therefore, developing a method for preparing CCTO / PVDF composites that achieves synergistic optimization of high dielectric constant, low dielectric loss, high breakdown field strength, and high energy storage density has significant practical implications and application value. Summary of the Invention

[0004] The core objective of this invention is to provide a method for preparing a giant dielectric constant ceramic / PVDF composite material, overcoming the defects of poor CCTO powder dispersion, poor interfacial compatibility, and insufficient performance synergy in traditional processes. This method achieves synergistic optimization of high dielectric constant, low dielectric loss, high breakdown field strength, and high energy storage density in the composite material, providing an efficient and feasible technical solution for the preparation of high-performance energy storage capacitors.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A giant dielectric constant ceramic / PVDF composite material is characterized by being composed of giant dielectric constant CCTO ceramic powder as filler and PVDF as polymer matrix. The volume fraction of CCTO ceramic powder in the composite material is 0.5%-4%, and the surface of the CCTO ceramic powder is modified by SiO2 coating. This composite material combines the high dielectric properties of CCTO with the excellent mechanical properties of PVDF. Its core advantage lies in simultaneously possessing high dielectric constant, low dielectric loss, high breakdown field strength, and high energy storage density, making it suitable for various high-energy-storage capacitor applications.

[0006] Furthermore, the preparation method of the aforementioned giant dielectric constant ceramic / PVDF composite material includes the following steps: Step 1: Pure phase CCTO powder was prepared using the sol-gel method. The specific process was as follows: Solution A was prepared with Ti(OC4H9)4, C2H5OH, and CH3COOH, and Solution B was prepared with Cu(NO3)2·H2O, Ca(NO3)3·4H2O, H2O, and C2H5OH. Solution A was added to Solution B at a rate of 1 drop / 2 seconds while stirring. After aging for 24-48 h, a gel was obtained. The gel was dried and ground at 60-90 ℃ and calcined at 750-950 ℃ for 10-15 h to obtain nano-sized CCTO powder.

[0007] Step 2: CCTO powder was modified with SiO2 coating using the Stöber method to obtain CCTO@SiO2 filler with excellent dispersibility and interfacial compatibility. The specific process is as follows: 300-400 mesh CCTO powder was dispersed in a mixed solution of isopropanol and deionized water. 30% ammonium hydroxide was added to adjust the pH. Tetraethyl orthosilicate (TEOS) was added dropwise at a rate of 0.5-3 μl / min, followed by 0.5-5 min of ultrasonic dispersion and 1-5 min of stirring after each addition. After aging for 5-10 h, the mixture was centrifuged, washed with water until pH=7, and dried at 80-120 ℃ to obtain the CCTO@SiO2 filler.

[0008] Step 3: Dissolve 0.5-2 g of PVDF in 5-20 ml of DMF and stir for 4 h until completely dissolved. Add 0.5-4% (v / v) of CCTO@SiO2 filler, stir for 30-60 min, and then ultrasonically disperse for 30-60 min. Repeat this process 3-6 times and let stand for 10-15 h to eliminate air bubbles and obtain a uniform composite slurry.

[0009] Step 4: The composite slurry is made into a thick film using the solution casting method, dried in an airless oven at 80-120 ℃, and then vacuum heated in a vacuum drying oven at 180-240 ℃ for 5-10 min. After removal, it is annealed in ice water and peeled off to obtain a high-performance CCTO@SiO2 / PVDF composite thick film material with a large dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density.

[0010] 1. This invention employs two processes, solid-state method and sol-gel method, to prepare CCTO powder. The appropriate preparation method can be selected according to actual needs. The powder prepared by solid-state method has fewer impurities and higher crystallinity, while the powder prepared by sol-gel method has smaller particle size (nanoscale) and better dispersibility. Through SiO2 coating modification treatment, the interfacial compatibility between CCTO powder and PVDF matrix is ​​effectively improved, interfacial defects are reduced, dielectric loss is lowered, and the breakdown field strength of the composite material is improved.

[0011] 2. This invention, by optimizing the volume fraction of CCTO powder, found that when the CCTO volume fraction is 2%, the composite material exhibits the best overall performance, with a storage density of 4.39 J / cm³ without SiO₂ coating. 3 After being coated with SiO2, the energy storage density was further increased to 5.91 J / cm³. 3 The resulting composite thick film exhibits significantly better energy storage performance than traditional composite materials, while maintaining low dielectric loss and high dielectric constant. This composite thick film combines excellent dielectric and energy storage properties, meeting the demands for miniaturization and high energy storage in electronic devices, and has broad application prospects in communications, transportation, and aerospace. Attached Figure Description

[0012] Figure 1 XRD patterns of CCTO ceramic powder prepared by the sol-gel method; Figure 2 XRD patterns of CCTO ceramic powder prepared by SiO2-coated sol-gel method; Figure 3 SEM image of CCTO powder prepared by sol-gel method; Figure 4 The relative permittivity of CCTO@SiO2 / PVDF composite thick film varies with frequency; Figure 5 CCTO@SiO2 / PVDF composite thick film P - E curve. Detailed Implementation Example 1

[0013] CCTO@SiO2 / PVDF material with a filler volume fraction of 0.5%.

[0014] (1) CCTO powder was prepared by the sol-gel method, specifically: solution A (Ti(OC4H9)4, C2H5OH, CH3COOH) and solution B (Cu(NO3)2·H2O, Ca(NO3)2·4H2O, H2O, C2H5OH) were prepared. Solution A was added dropwise to solution B and aged for 36 h. The gel was dried at 80 ℃ and calcined at 800 ℃ for 12 h to obtain CCTO powder by the sol-gel method.

[0015] (2) Disperse 300-400 mesh CCTO powder in a mixed solution of isopropanol and deionized water, add 30% ammonium hydroxide to adjust the pH value, add tetraethyl orthosilicate (TEOS) dropwise at a rate of 0.5-3 μl / min, and perform ultrasonic dispersion for 0.5-5 min and stirring for 1-5 min after each drop. After aging for 5-10 h, centrifuge and wash with water until pH=7, and dry at 80-120 ℃ to obtain CCTO@SiO2 filler.

[0016] (3) Take 0.5-2 g of PVDF and dissolve it in 5-20 ml of DMF. Stir for 4 hours until completely dissolved. Add 0.5% volume fraction of CCTO@SiO2 filler. Stir for 30-60 min and then ultrasonically disperse for 30-60 min. Repeat this process 3-6 times. Let stand for 10-15 hours to eliminate air bubbles and obtain a uniform composite slurry.

[0017] (4) The composite slurry is made into a thick film by solution casting method, dried in an airless oven at 80-120 ℃, and then vacuum heated in a vacuum drying oven at 180-240 ℃ for 5-10 min. After being taken out, it is annealed in ice water and peeled off to obtain a high-performance CCTO@SiO2 / PVDF composite thick film material with a large dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density. Example 2

[0018] In this embodiment, the CCTO@SiO2 / PVDF material has a filler volume fraction of 1%, and other conditions are the same as in Example 1. Example 3

[0019] In this embodiment, the CCTO@SiO2 / PVDF material has a filler volume fraction of 2%, and other conditions are the same as in Example 1. Example 4

[0020] In this embodiment, the CCTO@SiO2 / PVDF material has a filler volume fraction of 3%, and other conditions are the same as in Example 1. Example 5

[0021] XRD tests were performed on the CCTO ceramic powder filler in Examples 1-4 to obtain... Figure 1As a result, X-ray diffraction peaks with high diffraction intensity were found on the (211), (220), (013), (222), (321), (400), (422), and (440) crystal planes. Moreover, the positions of the diffraction peaks of the main crystal phase were consistent with the CCTO standard PDF card (PDF#715-1149), indicating that the CCTO powder prepared by the solid-state method and the sol-gel method had good crystallization.

[0022] XRD tests were performed on the CCTO@SiO2 ceramic powder used in Examples 1-4 to obtain... Figure 3 As shown in the figure, the smoothness of the XRD pattern of CCTO coated with SiO2 is reduced compared with that of uncoated CCTO. This is because the addition of the SiO2 phase leads to the appearance of trace impurities in the CCTO phase. High diffraction peaks with high diffraction intensity are present on the (220), (400), and (422) crystal planes. At the same time, the positions of the main phase diffraction peaks are consistent with the standard PDF card. The presence of the SiO2 phase near the (220) and (422) crystal planes indicates that the SiO2 successfully coated the CCTO with good coating effect.

[0023] SEM images of the CCTO ceramic powder filler used in Examples 1-4 were taken to obtain... Figure 3 result. Figure 3 (ac) is a magnified view of a part, showing that the CCTO powder has a uniform particle size distribution and no agglomeration or clumping is observed; Figure 3 (d) Particle size distribution of CCTO powder prepared by solid-state firing measured using Nanomesure software. The figure shows that the particle size of the powder is concentrated between 250-550 nm, with an average particle size of 380 nm.

[0024] Dielectric property tests were conducted on Examples 1-4, and the relative permittivity of the CCTO@SiO2 / PVDF composite thick film as a function of frequency was obtained. The graphs show that the permittivity decreases with increasing frequency, reaching a maximum of 17 at a 2% addition level, and then begins to decrease. This is because at low frequencies, electronic displacement polarization, ionic displacement polarization, dipole orientation polarization, thermionic relaxation polarization, and space charge polarization generally occur simultaneously in the dielectric, resulting in a higher permittivity. However, as the frequency increases, the changes in these polarization modes lag behind the frequency change, and only electronic displacement polarization and ionic displacement polarization are effective. Therefore, at high frequencies, the permittivity of the composite material decreases. The permittivity of the film coated with SiO2 is also lower than that of the uncoated film.

[0025] Hysteresis loop tests were performed on Examples 1-4 to obtain CCTO@SiO2 / PVDF composite thick films. P- E The curve shows that the energy storage density of the CCTO@SiO2 / PVDF composite thick film reaches a maximum of 5.91 J / cm² at 2 vol%. 3 This is because the insulating SiO2 coating reduces its leakage conductivity, increases its breakdown strength, and thus increases its energy storage density.

Claims

1. A giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material, characterized in that, Using PVDF as the polymer matrix, SiO2-coated modified CaCu3Ti4O 12 CCTO is used as the filler, with a volume fraction of 0.5% to 4%.

2. A method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material, characterized in that, Includes the following steps: (1) Pure phase CCTO powder was prepared by sol-gel method, and CCTO powder was modified by SiO2 coating by Stöber method to obtain CCTO@SiO2 filler with excellent dispersibility and interfacial compatibility. (2) Weigh PVDF and N,N-dimethylformamide (DMF) according to the proportion, stir until PVDF is completely dissolved, add CCTO@SiO2 filler with different volume fractions, and after stirring-ultrasonic dispersion treatment, let stand to obtain a uniform composite slurry; (3) The composite slurry is made into a thick film by solution casting method, and then dried, vacuum heated, ice water annealed and peeled to finally obtain a high-performance ceramic / PVDF composite material with a large dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density.

3. The method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to claim 2, characterized in that, The specific process for preparing CCTO powder by sol-gel method in step (1) is as follows: Solution A is prepared with Ti(OC4H9)4, C2H5OH and CH3COOH, and Solution B is prepared with Cu(NO3)2·H2O, Ca(NO3)3·4H2O, H2O and C2H5OH. Solution A is added to Solution B at a rate of 1 drop / 2 seconds and stirred. After aging for 24-48 h, a gel is obtained. The gel is dried and ground at 60-90 ℃ and calcined at 750-950 ℃ for 10-15 h to obtain nano-sized CCTO powder.

4. The method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to claim 2, characterized in that, The specific process of SiO2 coating modification in step (1) is as follows: 300-400 mesh CCTO powder is dispersed in a mixed solution of isopropanol and deionized water, 30% ammonium hydroxide is added to adjust the pH value, tetraethyl orthosilicate (TEOS) is added dropwise at a rate of 0.5-3 μl / min, and ultrasonic dispersion and stirring are performed for 0.5-5 min and 1-5 min respectively after each drop is added. After aging for 5-10 h, the mixture is centrifuged and washed with water until pH=7, and then dried at 80-120 ℃ to obtain CCTO@SiO2 filler.

5. The method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to claim 2, characterized in that, The preparation parameters of the composite slurry in step (2) are as follows: 0.5-2 g PVDF is dissolved in 5-20 ml DMF and stirred for 4 h until completely dissolved. 0.5-4% volume fraction of CCTO@SiO2 filler is added, stirred for 30-60 min and then ultrasonically dispersed for 30-60 min. This process is repeated 3-6 times and allowed to stand for 10-15 h to eliminate air bubbles.

6. The method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to claim 2, characterized in that, The preparation process parameters of the thick film in step (3) are as follows: after film formation by casting, it is dried in an airless oven at 80-120 ℃, placed in a vacuum drying oven at 180-240 ℃ and vacuum heated for 5-10 min, then taken out and annealed in ice water, and peeled off to obtain CCTO / PVDF composite thick film.

7. The method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to claim 2, characterized in that, When the volume fraction of CCTO is 2%, the composite material exhibits the best overall performance, with a storage density of 4.39 J / cm³ without SiO₂ coating. 3 After being coated with SiO2, the energy storage density increased to 5.91 J / cm³. 3 At room temperature and 50 Hz, the dielectric constant can reach a maximum of 17, and the dielectric loss remains at a low level.

8. The ceramic / PVDF composite material prepared by the method for preparing a giant dielectric constant ceramic / polyvinylidene fluoride (PVDF) composite material according to any one of claims 2 to 7, characterized in that, Its core performance highlights are a large dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density synergistically meeting the development needs of miniaturization, lightweighting and high energy storage of electronic devices, and providing high-performance material solutions for the field of dielectric energy storage.

Images