Preparation method and application of flexible hydroxyl modified BNT-CBZ-OH ceramic particle / polymer composite membrane

Abstract

The invention provides a preparation method and application of a flexible hydroxyl modified BNT-CBZ-OH ceramic particle / polymer composite membrane, and relates to the technical field of flexible energy storage capacitors. The preparation process of the composite film comprises the following steps: firstly, texturing a sodium bismuth titanate (BNT) seed crystal template; the highly-oriented lead-free BNT-CBZ textured ceramic is prepared by adopting solid-phase sintering and template grain growth technologies; carrying out surface hydroxylation on the ceramic particles; preparing P (VDF-TrFE) transparent slurry, and mixing and ball-milling the P (VDF-TrFE) transparent slurry and the hydroxylated ceramic powder; the energy storage capacitor prepared by adopting the composite film prepared by the invention is good in ductility and high in output performance, and can be widely applied to the fields of electronic circuits, energy collection, intelligent power grids, pulse power systems and the like.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage capacitors, and in particular to a preparation method and application of a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite film. Background Art

[0002] Dielectric energy storage materials play an important role in modern technology, especially in the fields of flexible electronics and energy storage. However, traditional dielectric ceramic materials have many limitations. Conventional dielectric ceramics have high hardness and low maximum tolerable electric field, i.e. breakdown electric field, which limits their use in flexible applications and also limits their use under high voltage conditions. On the other hand, although pure flexible polymer energy storage materials have good flexibility and processability, their output performance is low and it is difficult to meet the needs of practical applications. Therefore, how to improve the output performance of dielectric energy storage materials while maintaining flexibility has become an urgent problem to be solved.

[0003] In order to solve the above problems, researchers have tried to combine traditional dielectric ceramics with flexible polymers to prepare composite materials. However, this composite material still faces many challenges in practical applications. First, the physical and chemical properties between the organic polymer matrix and the inorganic ceramic filler are quite different, resulting in poor compatibility between the two. Nano-ceramic fillers with high surface energy are very easy to agglomerate in the polymer matrix, thereby forming a large number of pores inside the composite material, significantly reducing the breakdown electric field of the composite dielectric material. In addition, the low breakdown electric field of traditional energy storage ceramics further limits its application in the field of high-voltage energy storage. These problems seriously restrict the performance improvement and practical application of composite piezoelectric materials. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite film and its application, which utilizes template textured ceramics to improve the breakdown field strength of energy storage ceramics, and hydroxyl-modified ceramic particles to improve their compatibility with polymers, thereby improving the breakdown field strength of composite dielectric materials in many aspects. The prepared hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite film is applied to energy storage capacitors, meeting the requirements of flexible applications and high-voltage occasions, and having high output performance.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite membrane, the preparation method comprising the following steps: S1. Preparation of Bi 0.5 Na 0.5 TiO 3 (BNT) Template grains: S1-1: Using Bi 2 O 3 and TiO 2 Prepared Bi 4 Ti 3 O 12 Precursor; S1-2, Bi 4 Ti 3 O 12 Precursor and TiO 2 、Na 2 CO 3 After mixing, ball milling and sintering, Na 0.5 Bi 4.5 Ti 4 O 15 Plate-like crystallites; S1-3, Na 0.5 Bi 4.5 Ti 4 O 15 Flake-like microcrystalline mixed Na 2 CO 3 Ball milling and sintering to remove Bi from the product 2 O 3 , get Bi 0.5 Na 0.5 TiO 3 The template crystal is a BNT seed crystal template; S2, template texture BNT-CBZ ceramic powder: according to 0.7 (Bi 0.5 Na 0.5 )TiO 3 -0.3Ca 0.85 Bi 0.1 ZrO 3 The raw materials are weighed and mixed, ball-milled, and then pre-sintered at a high temperature, and then mixed with a BNT seed crystal template, ball-milled, and sintered to obtain a BNT-CBZ textured ceramic powder; S3, surface hydroxylation of ceramic powder: dispersing BNT-CBZ textured ceramic powder into hydrogen peroxide solution for surface hydroxylation to obtain BNT-CBZ-OH ceramic particles; S4, preparation of ceramic particle / P(VDF-TrFE) mixed slurry: dissolving P(VDF-TrFE) in N,N-dimethylformamide, and then adding BNT-CBZ-OH ceramic particles to obtain ceramic particle / P(VDF-TrFE) mixed slurry; S5. Casting film: casting the mixed slurry on a substrate in a casting machine to solidify it to form a composite film.

[0006] Preferably, the specific process in step S1-1 is to add Bi in a molar ratio of 2:3 2 O3 and TiO 2 Mix into reaction powder, then add the same mass of mixed powder of reactant powder, put into ball mill, add ethanol and mill for 10-12h, the speed of ball mill is 250-300r / min, take out, dry and sieve, put into crucible and keep at 1080℃ for 1h, then rinse off the salt with deionized water repeatedly to obtain Bi 4 Ti 3 O 12 Precursor; and the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:1.

[0007] Preferably, the specific process in step S1-2 is to convert Bi 4 Ti 3 O 12 Precursor and TiO 2 、Na 2 CO 3 The reactant powder was mixed in a molar ratio of 9:2:5, and the mixed powder of the same mass as the reactant powder was added, ball milled for 10-12 h, taken out, dried and sieved, placed in a crucible and kept at 1080 ° C for 1 h, and then repeatedly rinsed with deionized water to remove the salt to obtain Na 0.5 Bi 4.5 Ti 4 O 15 Flaky microcrystals; wherein the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:1.

[0008] Preferably, the specific steps in step S1-3 are to convert Na 0.5 Bi 4.5 Ti 4 O 15 Plate-like crystallites and Na 2 CO 3 The mixture was mixed in a molar ratio of 4:3 to obtain a powder, and the mixed powder of the same mass as the reactant powder was added, ball milled for 10-12 h, taken out, dried and sieved, placed in a crucible and kept at 1060 ° C for 3 h, and then repeatedly rinsed with deionized water to remove the salt, and the generated Bi was removed with 6 mol / L HCl. 2 O 3 , get Bi 0.5 Na 0.5 TiO 3 Template crystal; wherein the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:1.

[0009] Preferably, the raw material in step S2 is TiO 2 、Bi 2 O 3 、Na 2 CO 3 、CaO、ZrO2 The purity of each raw material is >98%, and the raw materials are dried at 80-100°C for more than 3h before use.

[0010] Preferably, the specific steps in step S2 are: S2-1, placing the weighed raw materials in a nylon ball mill containing zirconium oxide grinding balls, adding anhydrous ethanol and ball milling for 10-24 hours, then heating to 800-900°C and pre-calcining for 2-3 hours to obtain pre-calcined powder; S2-2, ball-milling the calcined powder and the BNT seed crystal template in a mass ratio of 1-3:10-50, continuing the ball milling for 10-20 hours, and then drying and passing through an 80-mesh sieve to obtain a mixed powder; S2-3. Sinter the mixed powder at 1050-1150° C. for 2-3 hours to obtain BNT-CBZ textured ceramic powder.

[0011] Preferably, the specific operation of surface hydroxylation in step S3 is to disperse the BNT-CBZ textured ceramic powder in a 35% hydrogen peroxide solution at a ratio of 1 g:10 ml, and to fully react by magnetic stirring at 80-100°C and 500-800 r / min for 3 hours; after the reaction, centrifuge at 3000 rpm for 8-10 minutes to obtain a precipitate; wash the precipitate with distilled water and ethanol, and then keep it warm in a vacuum drying oven at 70-100°C for 8-12 hours to obtain BNT-CBZ-OH ceramic particles.

[0012] Preferably, in step S4, the ratio of P(VDF-TrFE) powder dissolved in N,N-dimethylformamide is 1g:20ml; and the content of BNT-CBZ-OH ceramic particles in the mixed slurry is 2wt%-10wt%. After mixing, high-energy ball milling is performed at a speed of 300-500rmp / min for 20-30min and then degassing in a vacuum mixer for 3h.

[0013] Preferably, in the step S5, the distance between the scraper and the casting base is set to 20-100 μm, the scraper travel speed is 20-50 cm / min, and it is dried to a thick film at 40-80°C, then heated to 50-90°C in a vacuum drying oven, cured for 5-10 hours, and then heated to 130°C and kept warm for 2-3 hours to obtain a BNT-CBZ-OH / polymer composite film.

[0014] The composite film is used to prepare energy storage capacitors. The application method is to use ITO transparent conductive film as a substrate, cast a BNT-CBZ-OH / polymer composite film on the ITO transparent conductive film, and then sputter a gold electrode on the top mask.

[0015] The present invention provides a method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite membrane and its application, which has the advantages of: The present invention selects 0.7 (Bi 0.5 Na 0.5 )TiO 3 -0.3Ca 0.85 Bi 0.1 ZrO 3 Energy storage ceramic formula, preparation of BNT template and textured BNT-CBZ ceramic powder. The lattice matching degree of BNT template and BNT-CBZ ceramic is consistent, which is one of the ideal templates for textured BNT-based ceramics and can induce oriented growth of grains. After the introduction of hydroxyl groups on the surface of BNT-CBZ ceramic powder, the hydroxyl groups combine with the fluorine atoms in the PVDF molecules to form hydrogen bonds. This effect greatly improves the dispersion effect of nanofillers in the polymer matrix and significantly reduces defects such as pores inside the composite material. At the same time, the BNT-CBZ ceramic particles are mixed with P(VDF-TrFE) polymer for ball milling. During the high-energy ball milling process, the "drag effect" produced causes the α crystal phase in the PVDF polymer to transform into the β crystal phase with higher piezoelectric properties, so that the prepared slurry exhibits better piezoelectric properties. The tape casting process can make the arrangement of BNT-CBZ ceramic grains more regular, thereby optimizing its piezoelectric properties. Finally, the material exhibits a higher breakdown field strength and the energy storage density reaches 13.8 J / cm 3 , the breakdown electric field reaches 480 kV / mm; the composite film prepared by the present invention is used to prepare energy storage capacitors, which have good ductility and high output performance, and can be widely used in electronic circuits, energy collection, smart grids, pulse power systems and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The surface grain morphology characteristics of the BNT-CBZ textured ceramics in Examples 3, 4 and 5 of the present invention; Figure 2 The schematic diagram of the structure of the polymer composite film energy storage capacitor of the present invention, and the enlarged diagram shows the surface morphology characteristics of the BNT-CBZ-OH / polymer composite film; Figure 3 This is a photo of the polymer composite film prepared in Example 3 of the present invention; Figure 4 The dielectric spectra of polymer composite film energy storage capacitors prepared in various embodiments of the present invention are shown in Figure (a) as the dielectric constant spectrum and Figure (b) as the dielectric loss spectrum; Figure 5 Comparison of breakdown electric fields of polymer composite film energy storage capacitors prepared in various embodiments of the present invention; Figure 6Comparison of the single - pole hysteresis loops of the polymer composite film energy - storage capacitors prepared in each embodiment of the present invention; Figure 7 Comparison of the effective energy - storage densities of the polymer composite film energy - storage capacitors prepared in each embodiment of the present invention; Figure 2 In the figure: 1. Sputtered gold electrode; 2. BNT - CBZ - OH / polymer composite film; 3. Bottom ITO transparent conductive film. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] All the following raw materials are purchased from Shanghai Macklin Biochemical Co., Ltd. and Sinopharm Chemical Reagent Co., Ltd., and the purity requirement is above analytical pure (content > 98%).

[0019] Example 1: Preparation of P(VDF - TrFE) polymer film (1) Preparation of P(VDF - TrFE) slurry Dissolve 2 grams of poly(vinylidene fluoride - co - trifluoroethylene) (P(VDF - TrFE)) powder in 40 ml of N,N - dimethylformamide (DMF), and magnetically stir at 50 °C for 4 h until completely dissolved to obtain a transparent solution. Subsequently, put the solution into a vacuum mixer for defoaming for 3 h to ensure that there are no bubbles in the solution, and obtain the P(VDF - TrFE) slurry.

[0020] (2) Casting film formation Using the ITO transparent conductive film as the substrate, cast the P(VDF - TrFE) slurry in a casting machine. Set the distance between the doctor blade and the casting belt to 40 μm, and the traveling speed of the doctor blade to 30 cm / min. Finally, cast the uniform slurry into a film strip with a thickness of 40 μm, and dry it into a thick film at 60 °C; then heat the sample in a vacuum drying oven, select the temperature to be 80 °C, heat for 10 h for curing, and then raise the temperature to 130 °C and keep it warm for 2 h to obtain the P(VDF - TrFE) polymer film. Cut the composite film into a shape of 15 mm × 15 mm, with a thickness of about 15 μm, and sputter a gold electrode with a diameter of 2 mm and a thickness of 40 nm on the top mask to obtain the polymer composite film energy - storage capacitor.

[0021] Example 2: Preparation of BNT-CBZ ceramic particles / polymer composite membrane: 1. Preparation of BNT-CBZ ceramic powder BNT-CBZ textured ceramics were prepared by conventional solid phase sintering method, the steps are as follows: (1) Selection of raw material TiO 2 、Bi 2 O 3 、Na 2 CO 3 、CaO、ZrO 2 (The purity of all raw materials is >98%); dry the raw powder at 100℃ for 3h.

[0022] (2) According to 0.7(Bi 0.5 Na 0.5 )TiO 3 -0.3Ca 0.85 Bi 0.1 ZrO 3 The ingredients of the chemical stoichiometric ratio of the formula (referred to as BNT-CBZ) were weighed (with an accuracy of 0.0001 g), placed in a nylon ball mill containing zirconium oxide grinding balls, and ball milled for 21 h with anhydrous ethanol.

[0023] (3) After the slurry is dried, it is sieved and pre-calcined at 840°C for 3 hours to obtain pre-calcined powder.

[0024] (4) Perform secondary ball milling for 20 h, dry and sieve through an 80-mesh sieve to obtain composite powder. Sinter the ceramic powder at 1120 °C for 2 h to obtain BNT-CBZ ceramic particles.

[0025] 2. Preparation of ceramic particles / P (VDF-TrFE) mixed slurry 2 grams of P(VDF-TrFE) powder was dissolved in 40 ml of N,N-dimethylformamide (DMF) and magnetically stirred at 50°C for 4 hours until it was completely dissolved to obtain a transparent solution. BNT-CBZ ceramic particles were added to the above P(VDF-TrFE) transparent solution to prepare a PVDF / BNT-CBZ mixed solution (the content of BNT-CBZ ceramic particles in the mixed solution was 2wt%), and then the mixed solvent was placed in an agate ball mill and high-energy ball milled at a speed of 500 rpm / min for 30 minutes to obtain a mixed slurry; the solution was then placed in a vacuum mixer for degassing for 3 hours to ensure that there were no bubbles in the solution.

[0026] 3. Cast film With ITO transparent conductive film as the substrate, the mixed slurry was cast in a casting machine, the distance between the scraper and the casting base was set to 40μm, the scraper travel rate was 30cm / min, and finally the uniform slurry was cast into a film strip with a thickness of 40μm, and dried at 60℃ to form a thick film; then the sample was heated in a vacuum drying oven at 80℃ for 10h for curing, and then heated to 130℃ for 2h to obtain a BNT-CBZ / polymer composite film. After cooling, the composite film was cut into a shape of 15 mm×15mm with a thickness of about 15μm, and a gold electrode with a diameter of 2mm and a thickness of 40nm was sputtered on the top mask to obtain a polymer composite film energy storage capacitor.

[0027] Embodiment 3:

[0028] Preparation of flexible hydroxyl modified BNT-CBZ-OH ceramic particles / polymer composite film energy storage capacitor: 1. Preparation of Bi 0.5 Na 0.5 TiO 3 (BNT) Template grains: The preparation method adopts the molten salt method, which is to mix the reactants and salts in a certain proportion, heat the salt to melt it, and then react the reactants in the molten salt to generate the target product. The steps are: (1) Weigh Bi according to the molar ratio of 2:3 2 O 3 and TiO 2 , add NaCl and KCl mixed powder of the same mass as the reactant powder (the molar ratio of NaCl to KCl is 1:1), put the mixture into a ball mill, add ethanol and ball mill for 12 hours at a speed of 280r / min, take out, dry and sieve, put into a crucible and keep it at 1080℃ for 1 hour, and then repeatedly rinse off the salt with deionized water to obtain Bi 4 Ti 3 O 12 Precursor; (2) Change Bi 4 Ti 3 O 12 Precursor and TiO 2 、Na 2 CO 3 Mix them in a molar ratio of 9:2:5. Similarly, add NaCl and KCl (the molar ratio of NaCl and KCl is 1:1) with the same mass as the reactant powder, ball mill for 12 h, take out, dry and sieve, put into a crucible and keep it at 1080℃ for 1 h, and then repeatedly rinse off the salt with deionized water to obtain Na 0.5 Bi 4.5 Ti 4 O 15 Plate-like crystallites; (3) Put Na0.5 Bi 4.5 Ti 4 O 15 Plate-like crystallites and Na 2 CO 3 Mix according to the molar ratio of 4:3, add the same mass of NaCl and KCl mixed powder as the reactant powder (the molar ratio of NaCl and KCl is 1:1), ball mill for 12 h, take out, dry and sieve, put into a crucible and keep it at 1060℃ for 3 h, then rinse the salt repeatedly with deionized water, and remove the generated Bi with 6 mol / L HCl. 2 O 3 , AgNO 3 Solution test: No Cl ions exist in the solution. Finally, Bi 0.5 Na 0.5 TiO 3 Template crystals.

[0029] 2. Template textured BNT-CBZ ceramic powder BNT-CBZ textured ceramics were prepared by conventional solid phase sintering method, the steps are as follows: (1) Selection of raw material TiO 2 、Bi 2 O 3 、Na 2 CO 3 、CaO、ZrO 2 (The purity of all raw materials was >98%), and the raw powder was dried at 100 °C for 3 h.

[0030] (2) According to 0.7(Bi 0.5 Na 0.5 )TiO 3 -0.3Ca 0.85 Bi 0.1 ZrO 3 The ingredients of the chemical stoichiometric ratio of the formula (referred to as BNT-CBZ) were weighed (with an accuracy of 0.0001 g), placed in a nylon ball mill containing zirconium oxide grinding balls, and ball milled for 21 h with anhydrous ethanol.

[0031] (3) After the slurry is dried, it is sieved and pre-calcined at 850°C for 3 h to obtain pre-calcined powder.

[0032] (4) The pre-burned powder was mixed with the BNT seed crystal template prepared in the previous step and subjected to secondary ball milling (the mass ratio of the BNT seed crystal template to the pre-burned powder was 1:20). The secondary ball milling time was 20 h. After drying, the mixture was sieved through an 80-mesh sieve to obtain a mixed powder.

[0033] (5) The mixed ceramic powder is sintered at 1120°C for 2 hours. During the sintering, the ceramic powder grows under the action of the template grains to obtain a BNT-CBZ textured ceramic powder with a relatively consistent lattice orientation.

[0034] 3. Hydroxylation of ceramic powder surface Weigh 5 grams of BNT-CBZ textured ceramic powder and disperse it in 50 ml of 35% hydrogen peroxide solution for surface hydroxylation. Stir magnetically for 3 hours at 90°C for full reaction at a speed of 700 r / min. Then centrifuge for 10 minutes to obtain a precipitate at a centrifugal speed of 3000 rpm. Wash with distilled water and ethanol, and keep warm in a vacuum drying oven at 70°C for 8 hours to obtain surface hydroxylated BNT-CBZ nanoparticles (BNT-CBZ-OH).

[0035] 4. Preparation of ceramic particles / P (VDF-TrFE) mixed slurry 2 grams of P(VDF-TrFE) powder was dissolved in 40 ml of N,N-dimethylformamide (DMF) and magnetically stirred at 50°C for 4 hours until it was completely dissolved to obtain a transparent solution. Surface hydroxylated BNT-CBZ nanoparticles were added to the above P(VDF-TrFE) transparent solution to prepare a PVDF / BNT-CBZ mixed solution (the content of BNT-CBZ-OH ceramic particles in the mixed solution was 2 wt%), and then the mixed solvent was placed in an agate ball mill and high-energy ball milled at a speed of 500 rpm / min for 30 minutes to obtain a mixed slurry; the solution was then placed in a vacuum mixer for degassing for 3 hours to ensure that there were no bubbles in the solution.

[0036] 5. Cast film With ITO transparent conductive film as the substrate, the slurry was cast in a casting machine, the distance between the scraper and the casting base was set to 40μm, the scraper travel rate was 30cm / min, and finally the uniform slurry was cast into a film strip with a thickness of 40μm, and dried at 60℃ to form a thick film; then the sample was heated in a vacuum drying oven at 80℃ for 10h for curing, and then heated to 130℃ for 2h to obtain a BNT-CBZ-OH / polymer composite film. After cooling, the composite film was cut into a shape of 15 mm×15mm with a thickness of about 15μm, and a gold electrode with a diameter of 2mm and a thickness of about 40nm was sputtered on the top mask to obtain a polymer composite film energy storage capacitor.

[0037] Embodiment 4:

[0038] A method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite film energy storage capacitor, wherein the specific preparation process is the same as that of the above-mentioned Example 3, except that during the preparation of the ceramic particle / P(VDF-TrFE) mixed slurry, the content of BNT-CBZ-OH ceramic particles in the mixed solution is 5wt%.

[0039] Embodiment 5:

[0040] A method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite film energy storage capacitor, wherein the specific preparation process is the same as that of the above-mentioned Example 3, except that during the preparation of the ceramic particle / P(VDF-TrFE) mixed slurry, the content of BNT-CBZ-OH ceramic particles in the mixed solution is 10wt%.

[0041] Detection: The electrical performance tests of the polymer composite film energy storage capacitors of Examples 1-5 were carried out: 1. Dielectric performance test: The dielectric response test was performed using a high and low temperature dielectric test system (GWJDN-600) and a precision LCR meter (Agilent E4980A); The dielectric spectrum results are as follows Figure 4 As shown in (a), the dielectric constant of Example 1 without adding ceramic particle filler is the lowest. With the addition of ceramic particles, the dielectric constant of the composite membrane energy storage capacitor corresponding to Example 2 increases. After the BNT-CBZ ceramic particles are treated with texturing and hydroxylation, the dielectric constant increases significantly. As shown in Figure #3, when the content of BNT-CBZ-OH ceramic particles in the mixed solution is 10wt%, the dielectric constant is the largest, reaching 12.53. In addition, from Figure 4 From the dielectric loss spectrum of (b), we can see that with the increase of BNT-CBZ-OH ceramic content, the dielectric loss increases, but it is less than 0.2, showing good insulation performance.

[0042] See Table 1 below for details: Table 1

[0043] 2. The composite film energy storage capacitors prepared in Examples 1-5 were tested for maximum withstand field strength (breakdown field strength). The test method was to immerse the samples in silicone oil and use a ferroelectric test system with a high-voltage power supply (TREK-610E) to measure at 1 Hz.

[0044] For specific results, see Figure 5As shown in Table 2 below, the breakdown field strength of the pure P(VDF-TrFE) polymer film corresponding to Example 1 is the smallest, which is 310 kV / mm. The breakdown field strength is improved after adding ceramic particles, and the breakdown field strength is even greater after texturing and hydroxylation. When the content of hydroxylated BNT-CBZ-OH ceramic particles is 5wt%, the breakdown field strength reaches the maximum, which is 480 kV / mm. Higher content, such as Example 5, leads to a decrease in the breakdown field strength.

[0045] Table 2

[0046] 3. Comparison of unipolar hysteresis loops of the composite film energy storage capacitors prepared in Examples 1-5; Specific results such as Figure 6 As shown in Table 3 below, the applied electric field is the maximum tolerable field strength of each embodiment. It can be seen that the polarization intensity value of embodiment 4 is the largest, which is 10.1 mC / cm 2 , indicating that the performance is best when the content of hydroxylated BNT-CBZ-OH ceramic particles is 5wt%.

[0047] Table 3

[0048] The effective energy storage density of each embodiment can be calculated based on the hysteresis loop. Figure 7 The following Table 4 lists the effective energy storage density values ​​corresponding to the polymer composite membrane energy storage capacitors of each embodiment. It can be seen that the ceramic particle composite can significantly improve the energy storage density, and the performance is best when the hydroxylated BNT-CBZ-OH ceramic particle content is 5wt%, that is, the effective energy storage density of Example 4 reaches 13.8 J / cm 3 higher level.

[0049] Table 4

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a flexible hydroxyl-modified BNT-CBZ-OH ceramic particle / polymer composite membrane, characterized in that: The preparation method comprises the following steps: S1. Preparation of Bi 0.5 Na 0.5 TiO3(BNT) template grains: S1-1: Bi4Ti3O prepared from Bi2O3 and TiO2 12 Precursor; S1-2, Bi4Ti3O 12 The precursor was mixed with TiO2 and Na2CO3, ball-milled and sintered to obtain Na 0.5 Bi 4.5 Ti4O 15 Plate-like crystallites; S1-3, Na 0.5 Bi 4.5 Ti4O 15 The flaky microcrystals are mixed with Na2CO3 and then ball-milled and sintered, and then Bi2O3 in the product is removed to obtain Bi 0.5 Na 0.5 The TiO3 template crystal is the BNT seed crystal template; S2, template texture BNT-CBZ ceramic powder: according to 0.7 (Bi 0.5 Na 0.5 )TiO3-0.3Ca 0.85 Bi 0.1 The raw materials of ZrO3 formula are weighed and mixed and ball-milled, then pre-sintered at elevated temperature, and then mixed with BNT seed crystal template and ball-milled and sintered to obtain BNT-CBZ textured ceramic powder; S3, surface hydroxylation of ceramic powder: dispersing BNT-CBZ textured ceramic powder into hydrogen peroxide solution for surface hydroxylation to obtain BNT-CBZ-OH ceramic particles; S4, preparation of ceramic particle / P(VDF-TrFE) mixed slurry: dissolving P(VDF-TrFE) in N,N-dimethylformamide, and then adding BNT-CBZ-OH ceramic particles to obtain ceramic particle / P(VDF-TrFE) mixed slurry; S5. Casting film: casting the mixed slurry on a substrate in a casting machine to solidify it to form a composite film.

2. The preparation method according to claim 1, characterized in that: The specific process of step S1-1 is to mix Bi2O3 and TiO2 in a molar ratio of 2:3 into a reaction powder, then add a mixed powder of the same mass of the reactant powder, put it into a ball mill, add ethanol and ball mill for 10-12 hours, the ball mill speed is 250-300r / min, take it out, dry it and sieve it, put it into a crucible and keep it at 1080℃ for 1 hour, and then repeatedly rinse it with deionized water to remove the salt to obtain Bi4Ti3O 12 Precursor; and the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:

1.

3. The preparation method according to claim 1, characterized in that: The specific process of step S1-2 is to add Bi4Ti3O 12 The precursor was mixed with TiO2 and Na2CO3 in a molar ratio of 9:2:5 to obtain a reactant powder, and a mixed powder of the same mass as the reactant powder was added, ball milled for 10-12 h, taken out, dried and sieved, placed in a crucible and kept at 1080 ° C for 1 h, and then repeatedly rinsed with deionized water to remove the salt to obtain Na 0.5 Bi 4.5 Ti4O 15 Flaky microcrystals; wherein the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:

1.

4. The preparation method according to claim 1, characterized in that: The specific steps in step S1-3 are to add Na 0.5 Bi 4.5 Ti4O 15 The flaky microcrystals and Na2CO3 were mixed in a molar ratio of 4:3 to obtain a powder, and a mixed powder of the same mass as the reactant powder was added, ball milled for 10-12 h, taken out, dried and sieved, placed in a crucible and kept at 1060°C for 3 h, and then repeatedly rinsed with deionized water to remove the salt, and 6 mol / L HCl was used to remove the generated Bi2O3 to obtain Bi 0.5 Na 0.5 TiO3 template crystal; wherein the mixed powder is obtained by mixing NaCl and KCl in a molar ratio of 1:

1.

5. The preparation method according to claim 1, characterized in that: In step S2, the raw materials selected are TiO2, Bi2O3, Na2CO3, CaO, and ZrO2, and the purity of each raw material is >98%, and the raw materials are dried at 80-100°C for more than 3 hours before use.

6. The preparation method according to claim 1, characterized in that: The specific steps in step S2 are: S2-1, placing the weighed raw materials in a nylon ball mill containing zirconium oxide grinding balls, adding anhydrous ethanol and ball milling for 10-24 hours, then heating to 800-900°C and pre-calcining for 2-3 hours to obtain pre-calcined powder; S2-2, ball-milling the calcined powder and the BNT seed crystal template in a mass ratio of 1-3:10-50, continuing the ball milling for 10-20 hours, and then drying and passing through an 80-mesh sieve to obtain a mixed powder; S2-3. Sinter the mixed powder at 1050-1150° C. for 2-3 hours to obtain BNT-CBZ textured ceramic powder.

7. The preparation method according to claim 1, characterized in that: The specific operation of the surface hydroxylation in step S3 is to disperse the BNT-CBZ textured ceramic powder in a 35% hydrogen peroxide solution at a ratio of 1 g:10 ml, and to fully react at 80-100° C. and 500-800 r / min for 3 hours with magnetic stirring; after the reaction is completed, centrifuge at 3000 rpm for 8-10 minutes to obtain a precipitate; wash the precipitate with distilled water and ethanol, and then keep it warm in a vacuum drying oven at 70-100° C. for 8-12 hours to obtain BNT-CBZ-OH ceramic particles.

8. The preparation method according to claim 1, characterized in that: In step S4, the ratio of P(VDF-TrFE) powder dissolved in N,N-dimethylformamide is 1g:20ml; and the content of BNT-CBZ-OH ceramic particles in the mixed slurry accounts for 2wt%-10wt%. After mixing, high-energy ball milling is performed at a speed of 300-500rmp / min for 20-30min and then degassing in a vacuum mixer for 3h.

9. The preparation method according to claim 1, characterized in that: In the step S5, the distance between the scraper and the casting base is set to 20-100 μm during casting, the scraper travel speed is 20-50 cm / min, and it is dried to a thick film at 40-80° C., then heated to 50-90° C. in a vacuum drying oven, cured for 5-10 hours, and then heated to 130° C. and kept warm for 2-3 hours to obtain a BNT-CBZ-OH / polymer composite film.

10. Use of a composite film prepared by any preparation method according to any one of claims 1 to 9 in preparing energy storage capacitors, characterized in that: The application method is to use an ITO transparent conductive film as a substrate, cast a BNT-CBZ-OH / polymer composite film on the ITO transparent conductive film, and then sputter a gold electrode on the top mask.

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